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all right so today we're going to talk a
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bit about electrochemistry
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and how we use electrochemistry with
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battery
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materials at least for battery research
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and the different types of tests some of
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the different tests
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we do i do in part with my battery
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research
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um so electrochemistry it's a
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it's a pretty broad field um
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i i've only ever taken the fresh me
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freshman chemistry courses as an
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undergraduate
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so before starting my research on
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batteries i knew almost nothing about
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electrochemistry so all of this i had to
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learn on my own
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and there's not really any any good
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courses within our department that cover
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the basics
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of electrochemistry some of our classes
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do
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deal with the concepts of
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electrochemistry for example there's a
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senior level
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corrosion class dealing with the
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corrosion of
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different materials and that that
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heavily heavily relies on some of the
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concepts i'll share with you today
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and i believe there's some other uh
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metallurgy
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processing classes uh that also deal
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with these kind of reactions
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um so my definition of electrochemistry
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and i'm sure it's it's a shared
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definition is that you know it's the
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study of any chemical reactions that
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involve uh the electron transfer
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and so in other words if you have a
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metal ion or it could even be an organic
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molecule that has a change in valence
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then you can assume it's going to be an
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electrochemical reaction
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uh so the basis of electrochemistry is a
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reduction
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and oxidation reaction oh uh
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i see a chat uh could you tell professor
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mckinsley how to edit the
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video lectures sure i
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i can i can i can give them some tips i
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actually
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i'm not i'm not the best at it either
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it is definitely a skill that you have
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to practice and acquire i was just using
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the
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microsoft video editor which is a very
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basic editor editor it doesn't it's
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missing a lot of
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uh stuff like uh you can't make any
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transitions between
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cuts so but sure i can i can send them
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an email so anyways back to it
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just a reminder reduction reaction is uh
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the gain
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of electrons so for example if you have
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a metal ion
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in this case a metal two plus ion and uh
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you gain an electron that goes from
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metal two plus to metal
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one plus okay that's a reduction on the
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other hand oxidation is the opposite is
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the loss of electrons
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uh if you go from a metal two plus ion
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to metal three plus it's giving away an
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electron
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it's uh increasing its valence state so
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that's oxidation
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so in electrochemical reactions you have
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to have both
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okay so oftentimes we we only talk about
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one
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part of the reaction like a reduction or
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an oxidation separate but in
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every case you know you have to ask
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yourself where do those electrons come
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from
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if you're receiving an electron there
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has to be an opposite reaction somewhere
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else in the system that's giving away
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electrons you can't just get electrons
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from nothing
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so here's an example of a redox reaction
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is the oxidation of iron and metal into
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iron ii oxide feo
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and so the reduction half reaction of
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this uh
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this chemical reaction is the oxidation
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excuse me the reduction of oxygen
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gas all right so oxygen o2 molecule
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which a neutral molecule is giving away
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excuse me it's receiving electrons and
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becoming ionized it's becoming a o2
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minus
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ion and so the question is where does it
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receive those electrons from
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and that's the other half of the
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reaction is the oxidation reaction
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the iron metal which is a neutral
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atom is oxidizing it's giving away its
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electrons and becoming
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iron two plus and then the overall
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reaction is the iron metal is oxidized
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by oxygen
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becomes iron two oxide okay
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and of course there's this uh chemical
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reaction also depends on other factors
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like
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the oxygen content you know we can get
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different
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different iron oxides depending on how
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how much oxygen the
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oxygen there is available the
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temperature for example
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presence of water and acidity can give
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you different
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chemical compounds like different types
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of oxides so i iron three oxide iron two
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three oxide in different phases of those
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oxides um so here's a
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anti example this is not a a
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redox reaction if you remember last
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lecture
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um i was asking you guys about this this
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type of reaction we said it was a
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precipitation reaction it's not a
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it's not combustion it's not oxidation
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reaction and
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the reason i said that is because well
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we don't have any electron transfer so
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it's it's not going to be an
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electrochemical reaction
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so in this example we had a dissolved
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species of iron two plus like iron
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chloride
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ferrous chlorides for example and uh
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iron three plus like ferric chloride for
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example
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in solution and then so in solution iron
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two plus and i and three plus are at
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equilibrium they
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they have no problem being together uh
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even though there's two different
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valence states of the two ions uh but
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then we would add a base
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such as ammonium hydroxide and we're
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shifting the ph the higher
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ph where these ions are no longer
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stable they're no longer at equilibrium
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in that solution and so what happens is
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they precipitate out
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and that forms this iron 304
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also known as a spinel oxide
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this is actually let's see iron
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three plus and two plus coexist in this
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solid material and in fact the crystal
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structure is a inverse spinel
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a spinel is a type of crystal where you
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have a
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lattice of oxygen you have many
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different interstitial sites you have a
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a variety of tetrahedral interstitials
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and octahedral interstitials and so in
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this inverse
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spinel crystal the iron three plus
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occupies tetrahedral sites
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which is given by these parentheses and
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then also
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it occupies octahedral sites given by
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the brackets and then all the iron two
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plus also
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occupies the octahedral sites so that's
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an example
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of a precipitation reaction without
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electron transfer
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okay so how do we
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how do we find out what
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what material oxidizes and what material
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reduces in the given reaction
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one way to look at it is the standard
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reduction potential the
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these are empirically determined values
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of different
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species and their reduction potential
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or in other words you know what what's
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its potential to be reduced
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so on this list the the species at the
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the bottom of the list have a higher
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potential of being reduced in comparison
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to the species at the top of the list
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so like lithium plus to lithium metal
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does not have a very high
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potential compared to gold two plus the
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gold
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plus as far as reducing on the contrary
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lithium metal has a very high potential
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to become oxidized
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it's just the in the negative of this
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number um
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and so the one thing i should point out
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is that this
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standard reduction potential chart is uh
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is the reference to the she
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she is standard hydrogen electrode
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it's just a reference electrode where
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you have a hydrogen
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uh reaction h plus uh
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it turns into h2 gas it's just a
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standard
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uh potential so we we just arbitrarily
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mark that as zero if we're going to
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reference it
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uh every other reaction to that standard
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hydrogen reaction so i kind of made this
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kind of
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this diagram of different mountain peaks
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you could say
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you know so it depends on your
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perspective of where you are on the
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mountain
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you know you can either go uphill or
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downhill and then everything is relative
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to where you are so you know if we were
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to start at lithium for example
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you know everything's uphill from us as
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far as reduction
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potential and so you we could easily say
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all these numbers are referenced to
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lithium which we often do in lithium-ion
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batteries
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especially in research when we have our
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one side of the battery
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electrode is lithium metal and so you
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want to you want to measure your voltage
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compared to lithium rather than she
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so that's just an explanation of that
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okay but
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overall the species lower on the list
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have a higher potential of being reduced
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in comparison to the species above it so
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let's see
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uh here's a kind of another explanation
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of this
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you know if we had a solution of iron
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three plus
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in the solution and we wanted to measure
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the voltage
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between two electrodes platinum
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electrodes we use platinum because
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platinum is an
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inert electrode there's not going to be
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any chemical change
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with the electrode itself so what we're
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really doing is measuring the potential
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of any reaction
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on the surface of the platinum so if if
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we just have one
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uh solution with two platinum electrodes
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and try to measure
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the voltage between it like with the
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multimeter we're going to get zero volts
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right there's there's no difference in
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chemistry
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between the surface of this platinum and
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the surface of that platinum it's all
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mixed together so
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we get zero volts on the other hand if
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we were to replace one of these platinum
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electrodes with a standard hydrogen
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electrode which kind of looks like this
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it's encapsulated in its own uh it gets
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cell where this is a glass cell and then
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at the bottom
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there's this micro porous frit so it's a
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very
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very small pore porous ceramic
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which allows ionic diffusion between the
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two
290
00:09:32,000 --> 00:09:34,320
so you'll have some kind of standard
291
00:09:34,320 --> 00:09:35,120
electrolyte
292
00:09:35,120 --> 00:09:36,480
in this solution that's different than
293
00:09:36,480 --> 00:09:38,160
this iron to
294
00:09:38,160 --> 00:09:41,360
the three plus but over time if you
295
00:09:41,360 --> 00:09:43,519
leave it in here for like a couple days
296
00:09:43,519 --> 00:09:47,519
you'll have some interes some some
297
00:09:47,519 --> 00:09:49,839
exchange between ions between this fritz
298
00:09:49,839 --> 00:09:51,519
so it's not good to have it for a long
299
00:09:51,519 --> 00:09:52,000
time
300
00:09:52,000 --> 00:09:54,160
and you'll have to constantly be
301
00:09:54,160 --> 00:09:55,040
cleaning this and
302
00:09:55,040 --> 00:09:57,519
refilling it anyway so if we use a
303
00:09:57,519 --> 00:09:58,800
standard hydrogen electrode
304
00:09:58,800 --> 00:10:00,720
now we have a different chemical process
305
00:10:00,720 --> 00:10:03,519
happening at the the surface of this uh
306
00:10:03,519 --> 00:10:05,839
this uh electrode all right and that
307
00:10:05,839 --> 00:10:06,720
will
308
00:10:06,720 --> 00:10:08,800
now we can measure a potential between
309
00:10:08,800 --> 00:10:09,760
that so that we're measuring the
310
00:10:09,760 --> 00:10:10,560
potential
311
00:10:10,560 --> 00:10:12,720
of the iron three plus to be reduced to
312
00:10:12,720 --> 00:10:13,920
iron two plus
313
00:10:13,920 --> 00:10:15,519
uh i should i should make a note that
314
00:10:15,519 --> 00:10:17,360
when we measure potential like using a
315
00:10:17,360 --> 00:10:18,640
multimeter
316
00:10:18,640 --> 00:10:21,440
ideally there's no electric current
317
00:10:21,440 --> 00:10:22,480
going between
318
00:10:22,480 --> 00:10:25,519
the two electrodes if we were to short
319
00:10:25,519 --> 00:10:26,880
circuit this with a wire
320
00:10:26,880 --> 00:10:30,000
then yeah definitely the hydrogen here
321
00:10:30,000 --> 00:10:32,720
would be oxidized the h plus and the
322
00:10:32,720 --> 00:10:34,959
iron would be reduced to the
323
00:10:34,959 --> 00:10:36,959
two plus the reaction would go forward
324
00:10:36,959 --> 00:10:38,800
because there's that that thermodynamic
325
00:10:38,800 --> 00:10:39,600
driving force
326
00:10:39,600 --> 00:10:41,200
where the iron three plus has a higher
327
00:10:41,200 --> 00:10:42,720
reduction potential than the hydrogen
328
00:10:42,720 --> 00:10:43,200
gas
329
00:10:43,200 --> 00:10:45,360
being oxidized or excuse me the hydrogen
330
00:10:45,360 --> 00:10:46,640
ions being reduced
331
00:10:46,640 --> 00:10:49,600
uh but that's not good especially for a
332
00:10:49,600 --> 00:10:50,399
a hydrogen
333
00:10:50,399 --> 00:10:52,560
a standard reference electrode you don't
334
00:10:52,560 --> 00:10:54,000
want to change the chemistry because if
335
00:10:54,000 --> 00:10:55,440
you change the chemistry inside that
336
00:10:55,440 --> 00:10:56,320
reference cell
337
00:10:56,320 --> 00:10:57,519
then you're changing the reference
338
00:10:57,519 --> 00:10:58,959
potential and you'll you'll see that
339
00:10:58,959 --> 00:11:00,000
this this potential
340
00:11:00,000 --> 00:11:02,240
would change uh so ideally when you
341
00:11:02,240 --> 00:11:03,600
measure voltage across a
342
00:11:03,600 --> 00:11:05,760
use like a multimeter there's very
343
00:11:05,760 --> 00:11:07,279
little little current i
344
00:11:07,279 --> 00:11:11,200
like nominally might as well be zero
345
00:11:11,200 --> 00:11:13,680
very little current that goes through it
346
00:11:13,680 --> 00:11:15,920
that wire so it's we call this an
347
00:11:15,920 --> 00:11:19,760
open circuit voltage anyways
348
00:11:19,760 --> 00:11:21,839
so back to this uh list of standard
349
00:11:21,839 --> 00:11:23,920
reduction potentials
350
00:11:23,920 --> 00:11:26,160
so again like i was saying this is this
351
00:11:26,160 --> 00:11:27,680
is done these are measured in the
352
00:11:27,680 --> 00:11:28,240
standard
353
00:11:28,240 --> 00:11:31,760
state so it'd be like a one atmosphere
354
00:11:31,760 --> 00:11:35,440
room temperature and then you know the
355
00:11:35,440 --> 00:11:39,600
standard the activities of these are at
356
00:11:39,600 --> 00:11:42,000
equilibrium so at equilibrium the
357
00:11:42,000 --> 00:11:43,839
concentration of the reductant
358
00:11:43,839 --> 00:11:46,640
is the same as the concentration of the
359
00:11:46,640 --> 00:11:47,200
the
360
00:11:47,200 --> 00:11:49,360
oxidant okay so that's that these are
361
00:11:49,360 --> 00:11:50,959
equilibrium potentials
362
00:11:50,959 --> 00:11:52,959
in other words uh so if you change if
363
00:11:52,959 --> 00:11:54,720
you change the amount of
364
00:11:54,720 --> 00:11:56,399
reductant or oxidant you're going to
365
00:11:56,399 --> 00:11:59,600
change the voltage
366
00:12:00,000 --> 00:12:01,839
so here's an example you know what if we
367
00:12:01,839 --> 00:12:03,920
have iron three
368
00:12:03,920 --> 00:12:07,760
plus and iron two plus and zinc two plus
369
00:12:07,760 --> 00:12:09,680
and zinc metal in solution so we have
370
00:12:09,680 --> 00:12:11,360
four different species
371
00:12:11,360 --> 00:12:14,560
in the same solution i thought
372
00:12:14,560 --> 00:12:18,000
i meant for this to be just going
373
00:12:18,000 --> 00:12:19,600
so you could think about it but i guess
374
00:12:19,600 --> 00:12:21,200
i forgot to add the animations
375
00:12:21,200 --> 00:12:23,120
anyways so you have iron three plus iron
376
00:12:23,120 --> 00:12:24,959
two plus zinc two plus and zinc
377
00:12:24,959 --> 00:12:27,279
metal and the question is which one of
378
00:12:27,279 --> 00:12:29,279
these species is going to oxidize
379
00:12:29,279 --> 00:12:31,680
and which one of these species will be
380
00:12:31,680 --> 00:12:33,600
reduced in this solution
381
00:12:33,600 --> 00:12:34,959
and so if we look at the chart we see
382
00:12:34,959 --> 00:12:36,959
that iron three plus the iron two plus
383
00:12:36,959 --> 00:12:39,200
has a higher reduction potential than
384
00:12:39,200 --> 00:12:41,120
the zinc two plus the zinc metal
385
00:12:41,120 --> 00:12:43,600
so iron three plus is going to be the
386
00:12:43,600 --> 00:12:45,440
species that's reduced
387
00:12:45,440 --> 00:12:47,519
and zinc metal is going to be the
388
00:12:47,519 --> 00:12:49,360
species that's oxidized
389
00:12:49,360 --> 00:12:50,480
all right so nothing is going to happen
390
00:12:50,480 --> 00:12:51,680
in the zinc 2 plus and nothing will
391
00:12:51,680 --> 00:12:53,200
happen to the iron two plus we're just
392
00:12:53,200 --> 00:12:53,839
gonna be
393
00:12:53,839 --> 00:12:55,760
we're going to be making producing more
394
00:12:55,760 --> 00:12:56,959
iron two plus and we're gonna be
395
00:12:56,959 --> 00:12:58,560
producing more zinc two plus in our
396
00:12:58,560 --> 00:12:59,360
solution
397
00:12:59,360 --> 00:13:01,120
uh and those have their standard
398
00:13:01,120 --> 00:13:02,800
reduction potentials right for these
399
00:13:02,800 --> 00:13:03,360
different
400
00:13:03,360 --> 00:13:06,639
these uh separate redox reactions uh the
401
00:13:06,639 --> 00:13:07,839
overall reaction
402
00:13:07,839 --> 00:13:09,760
is given here the zinc metal is
403
00:13:09,760 --> 00:13:11,760
dissolving into the solution
404
00:13:11,760 --> 00:13:14,320
and the iron three plus is reducing in
405
00:13:14,320 --> 00:13:15,120
the solution
406
00:13:15,120 --> 00:13:16,880
so you're going to accumulate more zinc
407
00:13:16,880 --> 00:13:18,639
two plus and more iron two plus in
408
00:13:18,639 --> 00:13:19,279
solution
409
00:13:19,279 --> 00:13:21,920
you have an overall cell potential the
410
00:13:21,920 --> 00:13:24,160
electric potential is related to the
411
00:13:24,160 --> 00:13:26,240
gibbs free energy change of the reaction
412
00:13:26,240 --> 00:13:26,720
so
413
00:13:26,720 --> 00:13:28,320
you guys know that if you have a
414
00:13:28,320 --> 00:13:30,560
negative gibbs free energy change
415
00:13:30,560 --> 00:13:33,440
then the reaction is thermodynamically
416
00:13:33,440 --> 00:13:34,320
uh
417
00:13:34,320 --> 00:13:36,560
it will will go forward as well there's
418
00:13:36,560 --> 00:13:38,240
a thermodynamic driving force
419
00:13:38,240 --> 00:13:40,480
for the reaction to proceed so the same
420
00:13:40,480 --> 00:13:42,800
idea if you have this cell potential
421
00:13:42,800 --> 00:13:44,639
which is positive then there will be a
422
00:13:44,639 --> 00:13:46,320
thermodynamic driving force
423
00:13:46,320 --> 00:13:48,800
for this reaction to occur all right so
424
00:13:48,800 --> 00:13:50,639
it's just a simple it's negative
425
00:13:50,639 --> 00:13:52,880
z is the number of electrons i believe f
426
00:13:52,880 --> 00:13:54,560
is uh faraday's constant
427
00:13:54,560 --> 00:13:56,480
which is the number of coulombs per mole
428
00:13:56,480 --> 00:13:57,600
of electrons
429
00:13:57,600 --> 00:13:59,600
and then uh e is the the standard
430
00:13:59,600 --> 00:14:01,040
reduction potential or that we
431
00:14:01,040 --> 00:14:02,480
calculated for the reaction
432
00:14:02,480 --> 00:14:05,600
excuse me the reaction potential okay
433
00:14:05,600 --> 00:14:08,800
so let's look at this a little bit more
434
00:14:08,800 --> 00:14:11,760
so this is like the setup that we just
435
00:14:11,760 --> 00:14:13,839
described where we have a single beaker
436
00:14:13,839 --> 00:14:16,160
of solution that contains these ions and
437
00:14:16,160 --> 00:14:17,120
this metal
438
00:14:17,120 --> 00:14:19,440
and i i said well the potential the
439
00:14:19,440 --> 00:14:21,360
potential for this reaction is 1.5
440
00:14:21,360 --> 00:14:23,760
volts but you know how do you measure
441
00:14:23,760 --> 00:14:24,399
that
442
00:14:24,399 --> 00:14:25,839
physically how can you measure that in a
443
00:14:25,839 --> 00:14:27,600
single solution and the answer is
444
00:14:27,600 --> 00:14:29,440
you can't measure that it's it's the
445
00:14:29,440 --> 00:14:31,360
potential between the the surface of the
446
00:14:31,360 --> 00:14:32,079
zinc
447
00:14:32,079 --> 00:14:34,480
and the ions in solution right at the
448
00:14:34,480 --> 00:14:35,279
interface
449
00:14:35,279 --> 00:14:37,199
right so you just can't can't measure
450
00:14:37,199 --> 00:14:38,959
that and this will hap this reaction
451
00:14:38,959 --> 00:14:39,920
will proceed
452
00:14:39,920 --> 00:14:42,079
and it proceeds at the interface of the
453
00:14:42,079 --> 00:14:43,519
zinc where the zinc dissolves in the
454
00:14:43,519 --> 00:14:45,360
iron three plus at that interface
455
00:14:45,360 --> 00:14:47,680
of receive those electrons and turn into
456
00:14:47,680 --> 00:14:49,680
iron two plus
457
00:14:49,680 --> 00:14:53,360
let's see moving forward however we can
458
00:14:53,360 --> 00:14:55,199
measure this potential using like a
459
00:14:55,199 --> 00:14:56,800
multimeter
460
00:14:56,800 --> 00:14:59,920
if we separate these two cells or the
461
00:14:59,920 --> 00:15:02,959
these these two uh sets of species into
462
00:15:02,959 --> 00:15:04,240
two cells okay and
463
00:15:04,240 --> 00:15:06,560
separate electrolytes so in one cell we
464
00:15:06,560 --> 00:15:08,560
have iron two plus an iron three plus
465
00:15:08,560 --> 00:15:09,600
species
466
00:15:09,600 --> 00:15:11,440
um in the other cell we have zinc two
467
00:15:11,440 --> 00:15:12,639
plus and zinc species
468
00:15:12,639 --> 00:15:14,720
also i want to point out i have i'm not
469
00:15:14,720 --> 00:15:15,760
including any uh
470
00:15:15,760 --> 00:15:18,880
counter ions such as chlorine or or any
471
00:15:18,880 --> 00:15:20,480
whatever salt that these these
472
00:15:20,480 --> 00:15:23,600
cations came from those can also affect
473
00:15:23,600 --> 00:15:26,399
the redox potential and the activity of
474
00:15:26,399 --> 00:15:28,320
these ions but just for simplicity i'm
475
00:15:28,320 --> 00:15:30,000
leaving them out of the equation
476
00:15:30,000 --> 00:15:32,720
those ions don't won't uh change their
477
00:15:32,720 --> 00:15:33,279
valence
478
00:15:33,279 --> 00:15:35,519
j we're just kind of folk we're just
479
00:15:35,519 --> 00:15:37,839
interested in the metal ions in this
480
00:15:37,839 --> 00:15:40,880
uh these reactions and so
481
00:15:40,880 --> 00:15:42,639
here we have our iron species our zinc
482
00:15:42,639 --> 00:15:45,440
species our zinc metal as an electrode
483
00:15:45,440 --> 00:15:46,880
and we want to measure the potential
484
00:15:46,880 --> 00:15:49,199
between the two solutions we have to add
485
00:15:49,199 --> 00:15:52,880
an extra electrode for our iron
486
00:15:52,880 --> 00:15:56,160
uh or iron solution which is platinum
487
00:15:56,160 --> 00:15:57,839
again because platinum is inert and we
488
00:15:57,839 --> 00:15:58,880
don't want to
489
00:15:58,880 --> 00:16:01,199
to influence the chemistry of the
490
00:16:01,199 --> 00:16:03,120
reaction but it's acting as a catalyst
491
00:16:03,120 --> 00:16:03,680
so it's
492
00:16:03,680 --> 00:16:05,120
we're measuring the potential at the
493
00:16:05,120 --> 00:16:07,360
surface of the platinum and we also need
494
00:16:07,360 --> 00:16:09,360
to include what's called a salt bridge
495
00:16:09,360 --> 00:16:11,040
so salt bridge is just
496
00:16:11,040 --> 00:16:14,399
uh something that can balance the charge
497
00:16:14,399 --> 00:16:18,079
in both of these solutions so in
498
00:16:18,079 --> 00:16:21,120
it's it's the golden rule for all these
499
00:16:21,120 --> 00:16:22,079
systems that you
500
00:16:22,079 --> 00:16:24,880
must maintain charge neutrality if we
501
00:16:24,880 --> 00:16:26,480
take an electron away
502
00:16:26,480 --> 00:16:29,440
from one of these beakers we have to we
503
00:16:29,440 --> 00:16:30,480
have to give it
504
00:16:30,480 --> 00:16:34,000
we also have to take a a positive ion
505
00:16:34,000 --> 00:16:34,480
away
506
00:16:34,480 --> 00:16:36,560
or in other words or if we add a
507
00:16:36,560 --> 00:16:38,240
positive ion to a solution
508
00:16:38,240 --> 00:16:39,920
we also have to add an electron to the
509
00:16:39,920 --> 00:16:42,160
solution you know the overall charge
510
00:16:42,160 --> 00:16:45,440
must must maintain zero okay
511
00:16:45,440 --> 00:16:47,759
so for example if we're if we're
512
00:16:47,759 --> 00:16:49,680
reducing iron three plus to iron two
513
00:16:49,680 --> 00:16:50,000
plus
514
00:16:50,000 --> 00:16:52,880
and we're receiving an electron from the
515
00:16:52,880 --> 00:16:53,600
platinum
516
00:16:53,600 --> 00:16:55,839
okay but now our solution has just
517
00:16:55,839 --> 00:16:56,800
become
518
00:16:56,800 --> 00:16:58,800
less positive or more negative because
519
00:16:58,800 --> 00:17:01,199
we we've reduced the number of
520
00:17:01,199 --> 00:17:03,920
three plus ions so we have to balance
521
00:17:03,920 --> 00:17:04,799
that solution
522
00:17:04,799 --> 00:17:07,199
by adding in some counter ions or taking
523
00:17:07,199 --> 00:17:08,720
away counter ions
524
00:17:08,720 --> 00:17:10,720
that and that's achieved by the salt
525
00:17:10,720 --> 00:17:11,839
bridge it's just it's
526
00:17:11,839 --> 00:17:14,959
maintaining ionic continuity
527
00:17:14,959 --> 00:17:17,359
so we'll learn later that the essential
528
00:17:17,359 --> 00:17:18,640
things for a battery
529
00:17:18,640 --> 00:17:20,240
or you know the cathode anode and
530
00:17:20,240 --> 00:17:22,079
electrolyte but also we need electrical
531
00:17:22,079 --> 00:17:23,599
continuity through the circuit
532
00:17:23,599 --> 00:17:25,919
and then ionic continuity between the
533
00:17:25,919 --> 00:17:27,439
anode and cathode and this is achieved
534
00:17:27,439 --> 00:17:29,280
by the salt bridge
535
00:17:29,280 --> 00:17:31,200
anyways so at this point what we can do
536
00:17:31,200 --> 00:17:32,880
is put a voltmeter between these two
537
00:17:32,880 --> 00:17:34,559
electrodes the platinum the zinc
538
00:17:34,559 --> 00:17:36,480
and that voltmeter should read the
539
00:17:36,480 --> 00:17:38,559
standard reduction potential of our
540
00:17:38,559 --> 00:17:40,320
reaction 1.5 volts
541
00:17:40,320 --> 00:17:43,280
okay again these these two solutions by
542
00:17:43,280 --> 00:17:45,440
themselves are at equilibrium
543
00:17:45,440 --> 00:17:49,039
okay but compared to each other
544
00:17:49,039 --> 00:17:51,440
uh there's that thermodynamic driving
545
00:17:51,440 --> 00:17:53,520
force of 1.5 volts
546
00:17:53,520 --> 00:17:56,799
for them to for the zinc to to oxidize
547
00:17:56,799 --> 00:17:59,039
and for the iron 3 plus to reduce
548
00:17:59,039 --> 00:18:02,160
okay so if we were to put a wire a short
549
00:18:02,160 --> 00:18:02,640
circuit
550
00:18:02,640 --> 00:18:05,520
this reaction then this this reaction
551
00:18:05,520 --> 00:18:06,400
would go forward
552
00:18:06,400 --> 00:18:09,039
but like i said before the multimeter
553
00:18:09,039 --> 00:18:09,760
ideally
554
00:18:09,760 --> 00:18:12,000
there's no current going through the
555
00:18:12,000 --> 00:18:12,960
multimeter
556
00:18:12,960 --> 00:18:16,480
so this is an open circuit voltage
557
00:18:16,480 --> 00:18:19,760
that we're measuring and it also again i
558
00:18:19,760 --> 00:18:21,200
want to emphasize that we're measuring
559
00:18:21,200 --> 00:18:23,679
the potential at the surface of these
560
00:18:23,679 --> 00:18:24,799
electrodes right
561
00:18:24,799 --> 00:18:26,559
so these ions in the middle of the
562
00:18:26,559 --> 00:18:27,919
solution there nothing is going to
563
00:18:27,919 --> 00:18:29,120
happen to them
564
00:18:29,120 --> 00:18:30,880
right they have to be at the surface of
565
00:18:30,880 --> 00:18:33,440
the electrode in order to receive
566
00:18:33,440 --> 00:18:36,160
an electron and to be reduced and the
567
00:18:36,160 --> 00:18:37,440
same with the zinc the zinc
568
00:18:37,440 --> 00:18:40,840
at the surface is dissolving into the
569
00:18:40,840 --> 00:18:43,840
solution
570
00:18:44,880 --> 00:18:48,320
okay uh so this is a an example of like
571
00:18:48,320 --> 00:18:50,000
a two electrode cell
572
00:18:50,000 --> 00:18:53,280
um oftentimes in electrochemical work
573
00:18:53,280 --> 00:18:55,840
we use what's called a three electrode
574
00:18:55,840 --> 00:18:56,559
cell
575
00:18:56,559 --> 00:18:58,799
where we'll have a working electrode and
576
00:18:58,799 --> 00:18:59,840
that's
577
00:18:59,840 --> 00:19:01,440
that's where the reaction that we want
578
00:19:01,440 --> 00:19:03,360
to study is happening at and this is a
579
00:19:03,360 --> 00:19:04,960
half reaction remember so just
580
00:19:04,960 --> 00:19:06,480
it's only oxidation or it's only
581
00:19:06,480 --> 00:19:08,160
reduction happening at that
582
00:19:08,160 --> 00:19:10,480
interface and then we have a reference
583
00:19:10,480 --> 00:19:11,679
electrode that we're measuring the
584
00:19:11,679 --> 00:19:12,640
voltage
585
00:19:12,640 --> 00:19:15,039
against okay so like in the previous
586
00:19:15,039 --> 00:19:15,840
example
587
00:19:15,840 --> 00:19:18,480
we had uh the reference electrode right
588
00:19:18,480 --> 00:19:19,360
the voltage
589
00:19:19,360 --> 00:19:21,039
of the iron three plus the iron two plus
590
00:19:21,039 --> 00:19:22,799
reduction compared to the
591
00:19:22,799 --> 00:19:26,080
she raised 0.77 volts so that's what
592
00:19:26,080 --> 00:19:28,400
this circuit is it's just measuring
593
00:19:28,400 --> 00:19:30,080
voltage no current is going through
594
00:19:30,080 --> 00:19:30,640
there
595
00:19:30,640 --> 00:19:33,120
and then we have a counter electrode to
596
00:19:33,120 --> 00:19:34,000
provide
597
00:19:34,000 --> 00:19:36,559
the necessary electrons for this redox
598
00:19:36,559 --> 00:19:38,880
or this reduction or oxidation reaction
599
00:19:38,880 --> 00:19:40,400
either giving electrons or taking
600
00:19:40,400 --> 00:19:41,280
electrons
601
00:19:41,280 --> 00:19:43,679
away so there's another reaction that's
602
00:19:43,679 --> 00:19:44,559
happening
603
00:19:44,559 --> 00:19:46,320
at the surface of this platinum if we
604
00:19:46,320 --> 00:19:48,000
were going to proceed you know drive
605
00:19:48,000 --> 00:19:48,480
this
606
00:19:48,480 --> 00:19:52,160
this uh reaction forward or or backwards
607
00:19:52,160 --> 00:19:55,039
by changing the voltage uh there's a
608
00:19:55,039 --> 00:19:56,480
there has to be a counter
609
00:19:56,480 --> 00:19:58,559
reaction remember i said you you can't
610
00:19:58,559 --> 00:20:00,880
just get electrons from nowhere
611
00:20:00,880 --> 00:20:02,799
so there has to be a reaction happening
612
00:20:02,799 --> 00:20:04,080
at the counter electrode that's
613
00:20:04,080 --> 00:20:06,640
either providing or taking electrons but
614
00:20:06,640 --> 00:20:07,919
you don't measure the voltage
615
00:20:07,919 --> 00:20:09,679
of that reaction so you don't really you
616
00:20:09,679 --> 00:20:11,360
don't really care as long as
617
00:20:11,360 --> 00:20:14,320
your solution is large enough uh you
618
00:20:14,320 --> 00:20:15,760
have a large enough quantity of this
619
00:20:15,760 --> 00:20:16,799
electrolyte
620
00:20:16,799 --> 00:20:18,559
that whatever reaction is happening here
621
00:20:18,559 --> 00:20:20,240
does not influence
622
00:20:20,240 --> 00:20:23,520
for example the concentration or the the
623
00:20:23,520 --> 00:20:25,760
ph of the solution then it's it's it's
624
00:20:25,760 --> 00:20:28,240
fine it's negligible
625
00:20:28,240 --> 00:20:31,840
okay here's some different diagrams some
626
00:20:31,840 --> 00:20:33,440
phase diagrams are useful to
627
00:20:33,440 --> 00:20:35,039
electrochemistry one's the poor bay
628
00:20:35,039 --> 00:20:36,240
diagram
629
00:20:36,240 --> 00:20:38,320
so i've used this quite a bit kind of
630
00:20:38,320 --> 00:20:40,400
shows you what's the stable species
631
00:20:40,400 --> 00:20:42,320
at a given ph so this is this is
632
00:20:42,320 --> 00:20:43,679
primarily just for
633
00:20:43,679 --> 00:20:46,159
aqueous work so a lot of the battery
634
00:20:46,159 --> 00:20:48,159
research i do is also a non-aqueous
635
00:20:48,159 --> 00:20:51,039
battery so this is not relevant too much
636
00:20:51,039 --> 00:20:51,440
but
637
00:20:51,440 --> 00:20:54,000
you know different ph uh for different
638
00:20:54,000 --> 00:20:54,640
different
639
00:20:54,640 --> 00:20:56,799
uh species that are stable and what
640
00:20:56,799 --> 00:20:58,640
their reduction potential is
641
00:20:58,640 --> 00:21:01,679
uh and so it also useful for the you
642
00:21:01,679 --> 00:21:02,720
know
643
00:21:02,720 --> 00:21:04,960
predicting different chemical reactions
644
00:21:04,960 --> 00:21:06,720
in solution
645
00:21:06,720 --> 00:21:08,159
and then the other one is the ellingham
646
00:21:08,159 --> 00:21:09,760
diagram and i think you guys have seen
647
00:21:09,760 --> 00:21:10,960
this before it's like the first or
648
00:21:10,960 --> 00:21:13,280
second page in your kinetics textbook i
649
00:21:13,280 --> 00:21:14,000
believe
650
00:21:14,000 --> 00:21:16,480
that you've used the last quarter and
651
00:21:16,480 --> 00:21:18,159
hopefully you've done some calculations
652
00:21:18,159 --> 00:21:18,960
using that
653
00:21:18,960 --> 00:21:20,640
if not i think later this quarter when
654
00:21:20,640 --> 00:21:22,480
we do thermal properties lab
655
00:21:22,480 --> 00:21:23,840
we might take another look at this
656
00:21:23,840 --> 00:21:25,440
because we talk about the oxidation of
657
00:21:25,440 --> 00:21:26,400
different metals
658
00:21:26,400 --> 00:21:27,919
but basically you can you can use this
659
00:21:27,919 --> 00:21:30,640
diagram to show you know what species
660
00:21:30,640 --> 00:21:31,360
you would need
661
00:21:31,360 --> 00:21:34,480
to reduce uh metal oxide so it's very
662
00:21:34,480 --> 00:21:36,159
useful for
663
00:21:36,159 --> 00:21:39,200
smelting of ores or refining of of
664
00:21:39,200 --> 00:21:42,320
metal oxides right so most cases you're
665
00:21:42,320 --> 00:21:44,960
using carbon or carbon monoxide
666
00:21:44,960 --> 00:21:47,760
as a reducing agent to reduce metal
667
00:21:47,760 --> 00:21:49,919
oxide such as iron oxide or aluminum
668
00:21:49,919 --> 00:21:51,440
well aluminum oxide is a different
669
00:21:51,440 --> 00:21:53,679
process but like iron oxide
670
00:21:53,679 --> 00:21:57,280
to reduce it into iron metal
671
00:21:57,280 --> 00:22:00,799
okay so let's talk about batteries now
672
00:22:00,799 --> 00:22:02,799
um like i said before i started any
673
00:22:02,799 --> 00:22:04,080
research on batteries i had
674
00:22:04,080 --> 00:22:07,200
i knew very very little about batteries
675
00:22:07,200 --> 00:22:08,480
so i've had to learn everything on my
676
00:22:08,480 --> 00:22:09,120
own
677
00:22:09,120 --> 00:22:12,400
uh and these are kind of like the
678
00:22:12,400 --> 00:22:14,880
the basics of how batteries work and
679
00:22:14,880 --> 00:22:16,240
specifically i
680
00:22:16,240 --> 00:22:18,799
i say ion batteries but i mean all
681
00:22:18,799 --> 00:22:19,919
batteries
682
00:22:19,919 --> 00:22:22,080
need ions i at least i haven't found any
683
00:22:22,080 --> 00:22:24,400
batteries that don't use ions
684
00:22:24,400 --> 00:22:26,480
but there's three essential parts of all
685
00:22:26,480 --> 00:22:28,320
batteries and that's the cathode
686
00:22:28,320 --> 00:22:31,120
the anode and the electrolyte all right
687
00:22:31,120 --> 00:22:32,640
so there was going to be a
688
00:22:32,640 --> 00:22:35,360
a posi a potential difference between
689
00:22:35,360 --> 00:22:36,240
your
690
00:22:36,240 --> 00:22:38,400
cathode and anode just like in that cell
691
00:22:38,400 --> 00:22:39,440
we saw before
692
00:22:39,440 --> 00:22:40,559
you know there's this potential
693
00:22:40,559 --> 00:22:43,039
difference between this solution and
694
00:22:43,039 --> 00:22:44,720
this solution because of this redox
695
00:22:44,720 --> 00:22:46,400
reaction
696
00:22:46,400 --> 00:22:47,679
because of the reduction potential
697
00:22:47,679 --> 00:22:50,880
between the two okay
698
00:22:50,880 --> 00:22:53,440
and then the electrolyte is the medium
699
00:22:53,440 --> 00:22:54,480
that allows
700
00:22:54,480 --> 00:22:57,440
ions to transfer in and out of your of
701
00:22:57,440 --> 00:22:58,000
your
702
00:22:58,000 --> 00:23:01,120
electrodes um a common well i wouldn't
703
00:23:01,120 --> 00:23:02,400
say common but
704
00:23:02,400 --> 00:23:04,880
sometimes it's misconceived that you
705
00:23:04,880 --> 00:23:05,520
know
706
00:23:05,520 --> 00:23:07,840
you have an ion that's in your cathode
707
00:23:07,840 --> 00:23:08,559
and when you
708
00:23:08,559 --> 00:23:10,159
when you dis or when you charge the
709
00:23:10,159 --> 00:23:11,679
battery you're taking an ion out of your
710
00:23:11,679 --> 00:23:12,320
cathode
711
00:23:12,320 --> 00:23:14,400
and it goes into the anode and
712
00:23:14,400 --> 00:23:16,559
oftentimes i see these diagrams where it
713
00:23:16,559 --> 00:23:17,600
shows the ion
714
00:23:17,600 --> 00:23:19,919
moving all the way from the cathode all
715
00:23:19,919 --> 00:23:21,919
the way to the anode it's the same ion
716
00:23:21,919 --> 00:23:23,200
that goes back and forth
717
00:23:23,200 --> 00:23:25,360
in reality that's that's very unlikely
718
00:23:25,360 --> 00:23:26,960
that you're going to have the same ion
719
00:23:26,960 --> 00:23:29,360
go all the way to the anode in reality
720
00:23:29,360 --> 00:23:31,039
all these ions that come in and out of
721
00:23:31,039 --> 00:23:32,159
these different materials
722
00:23:32,159 --> 00:23:33,280
are probably going to be really
723
00:23:33,280 --> 00:23:35,360
relatively close to the surface and not
724
00:23:35,360 --> 00:23:36,000
travel too
725
00:23:36,000 --> 00:23:38,559
far in distance to go to all the way to
726
00:23:38,559 --> 00:23:39,440
the other side
727
00:23:39,440 --> 00:23:42,080
another misconception that i i've seen
728
00:23:42,080 --> 00:23:43,120
is that
729
00:23:43,120 --> 00:23:46,320
all lithium-ion batteries commercial
730
00:23:46,320 --> 00:23:47,679
lithium-ion batteries that are
731
00:23:47,679 --> 00:23:49,120
rechargeable like your cell phone
732
00:23:49,120 --> 00:23:50,320
battery or or
733
00:23:50,320 --> 00:23:52,799
your computer battery or the batteries
734
00:23:52,799 --> 00:23:54,320
in electric cars
735
00:23:54,320 --> 00:23:56,799
they do not contain any lithium metal
736
00:23:56,799 --> 00:23:57,440
right
737
00:23:57,440 --> 00:24:00,480
they instead for an anode they they all
738
00:24:00,480 --> 00:24:01,679
contain graphite
739
00:24:01,679 --> 00:24:04,320
okay lithium metal is just too dangerous
740
00:24:04,320 --> 00:24:06,880
of a material to be using in a lithium
741
00:24:06,880 --> 00:24:09,760
a rechargeable lithium-ion battery right
742
00:24:09,760 --> 00:24:10,880
as the more
743
00:24:10,880 --> 00:24:13,600
cycles you you charge or charge and
744
00:24:13,600 --> 00:24:14,480
recharge
745
00:24:14,480 --> 00:24:16,480
uh the lithium metal will will start
746
00:24:16,480 --> 00:24:18,000
precipitating dendrites
747
00:24:18,000 --> 00:24:19,679
and those dendrites can grow and over
748
00:24:19,679 --> 00:24:22,000
many many cycles these dendrites grow
749
00:24:22,000 --> 00:24:23,760
eventually they touch the other side and
750
00:24:23,760 --> 00:24:25,520
that's when you get a short circuit
751
00:24:25,520 --> 00:24:27,279
right so if the cathode and anode are
752
00:24:27,279 --> 00:24:28,720
touching each other
753
00:24:28,720 --> 00:24:30,320
then you're going to have a complete
754
00:24:30,320 --> 00:24:32,159
short circuit and you can't have any
755
00:24:32,159 --> 00:24:33,760
electron you won't have any electrons go
756
00:24:33,760 --> 00:24:35,120
through an external circuit
757
00:24:35,120 --> 00:24:37,600
they'll just go straight to each other
758
00:24:37,600 --> 00:24:40,080
and so that can generate a lot of heat
759
00:24:40,080 --> 00:24:41,600
it's very high current it generates a
760
00:24:41,600 --> 00:24:43,520
lot of heat and that can cause problems
761
00:24:43,520 --> 00:24:46,799
and so in order to to prevent that
762
00:24:46,799 --> 00:24:49,679
in in all batteries there's a permeable
763
00:24:49,679 --> 00:24:51,520
separator is another important part
764
00:24:51,520 --> 00:24:53,360
that's often left out of these diagrams
765
00:24:53,360 --> 00:24:56,080
the permeable separator can be uh for
766
00:24:56,080 --> 00:24:58,240
sodium ion batteries we use like a glass
767
00:24:58,240 --> 00:25:00,159
fiber so you know it allows the
768
00:25:00,159 --> 00:25:02,080
diffusion of liquids through it but
769
00:25:02,080 --> 00:25:04,880
it prevents it prevents uh the anode and
770
00:25:04,880 --> 00:25:05,760
cathode touching
771
00:25:05,760 --> 00:25:07,840
in lithium ion batteries we use a
772
00:25:07,840 --> 00:25:10,080
polymer
773
00:25:10,080 --> 00:25:13,520
porous membrane so it has a very small
774
00:25:13,520 --> 00:25:15,360
micro pores that still allow the
775
00:25:15,360 --> 00:25:17,440
liquid electrolyte to diffuse through
776
00:25:17,440 --> 00:25:18,960
and allows
777
00:25:18,960 --> 00:25:22,000
ionic continuity but no uh
778
00:25:22,000 --> 00:25:24,400
electrical continuity because when
779
00:25:24,400 --> 00:25:25,520
commercially when you make these
780
00:25:25,520 --> 00:25:26,559
materials you want to
781
00:25:26,559 --> 00:25:29,679
make them as compact as possible and so
782
00:25:29,679 --> 00:25:31,120
the anode and cathode are going to be
783
00:25:31,120 --> 00:25:32,240
very close to each other
784
00:25:32,240 --> 00:25:33,840
but you don't want them to be touching
785
00:25:33,840 --> 00:25:35,600
so there'll be a separating
786
00:25:35,600 --> 00:25:38,799
material in between and then i think for
787
00:25:38,799 --> 00:25:39,840
the
788
00:25:39,840 --> 00:25:41,919
most of the work you'll see is going to
789
00:25:41,919 --> 00:25:43,919
be for non-aqueous ion batteries but
790
00:25:43,919 --> 00:25:44,400
both
791
00:25:44,400 --> 00:25:47,120
is they're all it's the same same
792
00:25:47,120 --> 00:25:47,760
concept
793
00:25:47,760 --> 00:25:51,440
for both for aqueous and non-aqueous
794
00:25:51,440 --> 00:25:53,679
okay
795
00:25:54,720 --> 00:25:56,480
so here's some definitions before i go
796
00:25:56,480 --> 00:25:58,320
forward about uh
797
00:25:58,320 --> 00:26:00,320
you know different definitions of the
798
00:26:00,320 --> 00:26:01,840
things we use in batteries such as
799
00:26:01,840 --> 00:26:04,240
capacity of the battery so capacity is
800
00:26:04,240 --> 00:26:05,919
equivalent to
801
00:26:05,919 --> 00:26:09,039
how many electrons are transferred
802
00:26:09,039 --> 00:26:10,480
you know between the anode and the
803
00:26:10,480 --> 00:26:12,400
cathode or between the reduction and
804
00:26:12,400 --> 00:26:13,279
oxidation
805
00:26:13,279 --> 00:26:16,799
uh process it is exactly equivalent to
806
00:26:16,799 --> 00:26:20,080
the units of capacity are coulombs so
807
00:26:20,080 --> 00:26:23,440
one mole of coulombs is 96 000
808
00:26:23,440 --> 00:26:26,480
oh sorry one mole of electrons is 96 000
809
00:26:26,480 --> 00:26:29,679
coulombs and that that
810
00:26:29,679 --> 00:26:32,640
that is called a faraday's constant is
811
00:26:32,640 --> 00:26:32,960
this
812
00:26:32,960 --> 00:26:35,919
this relation however the conventional
813
00:26:35,919 --> 00:26:37,279
unit for capacity
814
00:26:37,279 --> 00:26:38,960
and you'll see this written on you know
815
00:26:38,960 --> 00:26:40,960
a lithium-ion battery
816
00:26:40,960 --> 00:26:42,159
if you have a cell phone that you can
817
00:26:42,159 --> 00:26:43,360
still take the battery out it'll
818
00:26:43,360 --> 00:26:45,279
probably say how many amp hours of
819
00:26:45,279 --> 00:26:48,159
capacity it has
820
00:26:48,880 --> 00:26:52,320
and so they use this convent this unit
821
00:26:52,320 --> 00:26:55,600
and one amp remember amp is a
822
00:26:55,600 --> 00:26:58,640
coulomb per second so one amp hour is
823
00:26:58,640 --> 00:27:00,400
one coulomb per second times
824
00:27:00,400 --> 00:27:04,799
at one hour which is 36 100 seconds
825
00:27:04,799 --> 00:27:06,960
so that's one amp hour is equivalent to
826
00:27:06,960 --> 00:27:08,720
3 600 coulombs
827
00:27:08,720 --> 00:27:10,480
okay so this is the conventional you'll
828
00:27:10,480 --> 00:27:12,720
see this written a lot amp hour milliamp
829
00:27:12,720 --> 00:27:13,279
hour
830
00:27:13,279 --> 00:27:16,880
is another that we'll use um
831
00:27:16,880 --> 00:27:18,799
so that's capacity so again how many
832
00:27:18,799 --> 00:27:20,559
electrons are being transferred
833
00:27:20,559 --> 00:27:24,880
and energy is the capacity of a battery
834
00:27:24,880 --> 00:27:27,039
times the voltage that the redox
835
00:27:27,039 --> 00:27:28,240
reaction is occurring at
836
00:27:28,240 --> 00:27:30,480
right so for like in our previous
837
00:27:30,480 --> 00:27:32,840
examples
838
00:27:32,840 --> 00:27:35,120
um
839
00:27:35,120 --> 00:27:37,360
well i'll make it simple if you if you
840
00:27:37,360 --> 00:27:39,279
have a redox reaction and it happens at
841
00:27:39,279 --> 00:27:40,240
one volt
842
00:27:40,240 --> 00:27:43,520
versus versus that zinc metal right
843
00:27:43,520 --> 00:27:47,520
um and you're you you uh
844
00:27:47,520 --> 00:27:50,559
it lasts for one hour and the current
845
00:27:50,559 --> 00:27:52,399
that you're discharging it at
846
00:27:52,399 --> 00:27:55,840
is one amp so one amp of current
847
00:27:55,840 --> 00:27:58,320
for one hour the capacity is one amp
848
00:27:58,320 --> 00:28:00,640
hour and if that redox potential was one
849
00:28:00,640 --> 00:28:01,279
volt
850
00:28:01,279 --> 00:28:03,760
then it'd be a one times one to be one
851
00:28:03,760 --> 00:28:04,720
watt hour
852
00:28:04,720 --> 00:28:07,039
of energy right so the the units of
853
00:28:07,039 --> 00:28:08,559
energy is joules but the conventional
854
00:28:08,559 --> 00:28:09,840
units that we use is watt
855
00:28:09,840 --> 00:28:12,880
hour so remember a watt is a form of
856
00:28:12,880 --> 00:28:15,600
is the unit of power which is the
857
00:28:15,600 --> 00:28:16,000
current
858
00:28:16,000 --> 00:28:17,840
times the voltage the watts are joules
859
00:28:17,840 --> 00:28:19,200
per second
860
00:28:19,200 --> 00:28:22,000
so current is coulombs per second volts
861
00:28:22,000 --> 00:28:22,880
are
862
00:28:22,880 --> 00:28:26,000
joules per coulomb okay and so that
863
00:28:26,000 --> 00:28:27,279
makes a watt so one
864
00:28:27,279 --> 00:28:29,360
watt hour is one joule per second times
865
00:28:29,360 --> 00:28:32,480
3 600 seconds it's 3 600 joules
866
00:28:32,480 --> 00:28:35,760
so that's energy okay so again energy
867
00:28:35,760 --> 00:28:38,159
has to do with voltage and capacity oh
868
00:28:38,159 --> 00:28:40,320
another another thing to watch out for
869
00:28:40,320 --> 00:28:43,760
is the term capacity versus capacitance
870
00:28:43,760 --> 00:28:46,399
capacitance is is different the units of
871
00:28:46,399 --> 00:28:48,159
capacitance is a
872
00:28:48,159 --> 00:28:51,440
ferrad i believe f ferrad and those are
873
00:28:51,440 --> 00:28:52,720
used for capacitors and i believe
874
00:28:52,720 --> 00:28:54,640
capacitance is uh
875
00:28:54,640 --> 00:28:58,000
coulombs divided by volts the
876
00:28:58,000 --> 00:29:00,640
the the i guess capacity divided by the
877
00:29:00,640 --> 00:29:01,520
voltage
878
00:29:01,520 --> 00:29:03,520
i i'm not too familiar with capacitors
879
00:29:03,520 --> 00:29:05,279
actually although capacitors are very
880
00:29:05,279 --> 00:29:06,320
similar to batteries
881
00:29:06,320 --> 00:29:08,240
in fact some supercapacitors are
882
00:29:08,240 --> 00:29:09,520
basically just batteries
883
00:29:09,520 --> 00:29:11,440
that discharge and charge at very quick
884
00:29:11,440 --> 00:29:15,520
rates is the the point of the capacitor
885
00:29:16,559 --> 00:29:19,039
um so here's an example calculation for
886
00:29:19,039 --> 00:29:19,600
uh
887
00:29:19,600 --> 00:29:21,600
the theoretical capacity so theoretical
888
00:29:21,600 --> 00:29:23,679
capacity is you know if we were to
889
00:29:23,679 --> 00:29:26,640
reduce all of the material the valence
890
00:29:26,640 --> 00:29:28,240
change the valence state of all the ions
891
00:29:28,240 --> 00:29:29,440
in this material
892
00:29:29,440 --> 00:29:31,919
you know what how much capacity would
893
00:29:31,919 --> 00:29:32,480
that be
894
00:29:32,480 --> 00:29:35,360
for that material as a battery and so
895
00:29:35,360 --> 00:29:37,120
here's the example of this material
896
00:29:37,120 --> 00:29:40,480
vanadium uh penta oxide v2o5
897
00:29:40,480 --> 00:29:42,080
so the you know the first question asked
898
00:29:42,080 --> 00:29:43,679
is what's the starting valence
899
00:29:43,679 --> 00:29:45,840
of this material all right the so the
900
00:29:45,840 --> 00:29:47,120
starting valence is a
901
00:29:47,120 --> 00:29:49,840
vanadium five plus um and the next
902
00:29:49,840 --> 00:29:51,279
question is you know how much are we
903
00:29:51,279 --> 00:29:52,240
going to
904
00:29:52,240 --> 00:29:54,720
uh reduce it by vanadium is a very
905
00:29:54,720 --> 00:29:56,159
unique material
906
00:29:56,159 --> 00:29:58,720
ion it can have multiple valence states
907
00:29:58,720 --> 00:29:59,679
that are in this
908
00:29:59,679 --> 00:30:01,679
very stable so it goes from vanadium
909
00:30:01,679 --> 00:30:04,320
five plus the name four vanadium three
910
00:30:04,320 --> 00:30:06,320
vanadium two i don't think there's a
911
00:30:06,320 --> 00:30:07,520
vanadium one is
912
00:30:07,520 --> 00:30:10,000
very stable but all those four valence
913
00:30:10,000 --> 00:30:11,279
states five to two
914
00:30:11,279 --> 00:30:14,080
are stable forms so you could you could
915
00:30:14,080 --> 00:30:14,960
reduce this
916
00:30:14,960 --> 00:30:17,279
material all the way down to two i'm not
917
00:30:17,279 --> 00:30:19,200
sure if it would retain the same crystal
918
00:30:19,200 --> 00:30:20,559
structure if you did that
919
00:30:20,559 --> 00:30:21,919
because there's only a limited number of
920
00:30:21,919 --> 00:30:24,240
space for for ions to get inside
921
00:30:24,240 --> 00:30:26,080
but anyways so in this case let's just
922
00:30:26,080 --> 00:30:27,840
say we're going from vanadium five plus
923
00:30:27,840 --> 00:30:29,600
to vanadium four plus
924
00:30:29,600 --> 00:30:31,520
okay so the first question is how many
925
00:30:31,520 --> 00:30:33,600
moles
926
00:30:33,600 --> 00:30:35,840
of electrons are transferred if we
927
00:30:35,840 --> 00:30:37,760
reduce all the vanadium 5 plus to
928
00:30:37,760 --> 00:30:40,000
vanadium 4 plus
929
00:30:40,000 --> 00:30:42,000
i'm going to go grab myself a coffee
930
00:30:42,000 --> 00:30:43,279
actually you guys
931
00:30:43,279 --> 00:30:44,720
spend the next five minutes trying to
932
00:30:44,720 --> 00:30:47,440
calculate the theoretical capacity
933
00:30:47,440 --> 00:30:50,559
in milliamps amp hours per gram
934
00:30:50,559 --> 00:30:52,240
all right when i come back we'll see if
935
00:30:52,240 --> 00:30:53,600
anyone's uh
936
00:30:53,600 --> 00:30:55,760
progressed from there i'll do the next
937
00:30:55,760 --> 00:30:56,720
slide so
938
00:30:56,720 --> 00:30:59,760
the answer here is 2. the next question
939
00:30:59,760 --> 00:31:02,399
will be 2 moles of electrons is how many
940
00:31:02,399 --> 00:31:03,440
coulombs of charge
941
00:31:03,440 --> 00:31:04,960
all right i'm gonna pause the recording
942
00:31:04,960 --> 00:31:07,600
actually and uh i'm just gonna go grab
943
00:31:07,600 --> 00:31:08,960
myself a coffee
944
00:31:08,960 --> 00:31:10,880
five minutes i'll be back let's see if
945
00:31:10,880 --> 00:31:12,960
anyone's come up with an answer
946
00:31:12,960 --> 00:31:16,080
and if not i'll get it
947
00:31:16,559 --> 00:31:18,799
did anyone come up with a uh answer for
948
00:31:18,799 --> 00:31:20,640
the theoretical capacity
949
00:31:20,640 --> 00:31:23,600
of v205 if we reduce all the vanadium
950
00:31:23,600 --> 00:31:33,840
five plus the video four plus
951
00:31:36,399 --> 00:31:41,200
okay i don't think anyone did it
952
00:31:41,200 --> 00:31:44,320
that's okay all right so hopefully you
953
00:31:44,320 --> 00:31:45,519
guys are still listening
954
00:31:45,519 --> 00:31:46,880
because i have no way of knowing if
955
00:31:46,880 --> 00:31:48,640
you're listening or not anyways
956
00:31:48,640 --> 00:31:50,880
so uh we've we've determined that
957
00:31:50,880 --> 00:31:52,159
there's going to be two moles of
958
00:31:52,159 --> 00:31:52,880
vanadium
959
00:31:52,880 --> 00:31:55,679
or two moles of electron per formula
960
00:31:55,679 --> 00:31:58,080
unit of v2o5 that are transferred for
961
00:31:58,080 --> 00:32:00,080
this reduction process
962
00:32:00,080 --> 00:32:02,159
so how many coulombs is two moles of
963
00:32:02,159 --> 00:32:03,360
electrons
964
00:32:03,360 --> 00:32:07,760
remember we use faraday's constant
965
00:32:08,480 --> 00:32:11,360
right we use uh this number here
966
00:32:11,360 --> 00:32:12,640
faraday's constant
967
00:32:12,640 --> 00:32:16,080
so one mole of electrons 96 000 coulombs
968
00:32:16,080 --> 00:32:18,480
all right so now we have the number of
969
00:32:18,480 --> 00:32:19,679
coulombs
970
00:32:19,679 --> 00:32:22,240
of charge that's been uh transferred in
971
00:32:22,240 --> 00:32:25,120
this reduction process per mole of v205
972
00:32:25,120 --> 00:32:26,799
and then we can convert that to milliamp
973
00:32:26,799 --> 00:32:28,240
hours per gram
974
00:32:28,240 --> 00:32:31,600
okay so uh one
975
00:32:31,600 --> 00:32:35,840
uh coulomb divided by
976
00:32:35,840 --> 00:32:37,679
let's see how did i do this i already
977
00:32:37,679 --> 00:32:38,960
forget
978
00:32:38,960 --> 00:32:42,080
coulombs all right so one amp
979
00:32:42,080 --> 00:32:46,240
hour of capacity is equivalent to 3 600
980
00:32:46,240 --> 00:32:47,200
coulombs
981
00:32:47,200 --> 00:32:49,360
right because 1 amp is a coulomb per
982
00:32:49,360 --> 00:32:50,399
second
983
00:32:50,399 --> 00:32:54,840
and an hour is uh 3 600 seconds
984
00:32:54,840 --> 00:32:58,320
okay and then you multiply by or the
985
00:32:58,320 --> 00:33:00,159
inverse of the molecular weight
986
00:33:00,159 --> 00:33:02,559
then that will give you actually it'll
987
00:33:02,559 --> 00:33:04,480
be in amp hours but you multiply by a
988
00:33:04,480 --> 00:33:06,720
thousand to get milliamp hours per gram
989
00:33:06,720 --> 00:33:09,760
okay so the the theoretical capacity per
990
00:33:09,760 --> 00:33:10,080
gram
991
00:33:10,080 --> 00:33:12,399
of this material for just one one
992
00:33:12,399 --> 00:33:13,600
electron
993
00:33:13,600 --> 00:33:16,880
transfer 295 milliamp hours per gram
994
00:33:16,880 --> 00:33:19,679
that has a pretty good capacity for one
995
00:33:19,679 --> 00:33:20,720
electron
996
00:33:20,720 --> 00:33:24,000
transfer for a electrode material
997
00:33:24,000 --> 00:33:28,000
anyways okay
998
00:33:28,000 --> 00:33:30,640
so one more definition is definition of
999
00:33:30,640 --> 00:33:31,120
power
1000
00:33:31,120 --> 00:33:33,279
for batteries so the power is the amount
1001
00:33:33,279 --> 00:33:35,039
of energy transferred
1002
00:33:35,039 --> 00:33:37,360
divided by how long it takes to transfer
1003
00:33:37,360 --> 00:33:38,080
that energy
1004
00:33:38,080 --> 00:33:42,320
right so we could have a battery that uh
1005
00:33:42,320 --> 00:33:44,320
the current in the battery if we're
1006
00:33:44,320 --> 00:33:45,679
drawing current for the
1007
00:33:45,679 --> 00:33:47,679
from the battery very slowly at a really
1008
00:33:47,679 --> 00:33:48,880
low current
1009
00:33:48,880 --> 00:33:51,760
so it takes a long time for that energy
1010
00:33:51,760 --> 00:33:52,000
to
1011
00:33:52,000 --> 00:33:54,000
deplete it has you could say that that's
1012
00:33:54,000 --> 00:33:55,360
a very low power
1013
00:33:55,360 --> 00:33:58,159
okay on the other hand if we take if we
1014
00:33:58,159 --> 00:33:59,200
can discharge
1015
00:33:59,200 --> 00:34:02,559
that battery in a very short amount of
1016
00:34:02,559 --> 00:34:04,640
time then it has very high power
1017
00:34:04,640 --> 00:34:07,440
the problem is as typically in battery
1018
00:34:07,440 --> 00:34:08,560
materials as we
1019
00:34:08,560 --> 00:34:11,918
increase the the current or in other
1020
00:34:11,918 --> 00:34:13,679
words if we're decreasing the amount of
1021
00:34:13,679 --> 00:34:15,280
time to discharge the battery or
1022
00:34:15,280 --> 00:34:16,560
increasing the current the
1023
00:34:16,560 --> 00:34:19,359
increasing the number of coulombs of
1024
00:34:19,359 --> 00:34:20,079
charge
1025
00:34:20,079 --> 00:34:23,280
per second uh oftentimes
1026
00:34:23,280 --> 00:34:27,199
that that the consequence is that we
1027
00:34:27,199 --> 00:34:28,079
have lower
1028
00:34:28,079 --> 00:34:31,359
voltage of the battery and then also
1029
00:34:31,359 --> 00:34:33,440
lower capacity of the battery which
1030
00:34:33,440 --> 00:34:34,639
results in lower
1031
00:34:34,639 --> 00:34:37,918
energy so as we if we try to discharge
1032
00:34:37,918 --> 00:34:39,599
the the battery faster
1033
00:34:39,599 --> 00:34:42,079
our power density tends to go down and
1034
00:34:42,079 --> 00:34:43,599
so that's a kind of a big problem with
1035
00:34:43,599 --> 00:34:45,679
with batteries and it's what separates
1036
00:34:45,679 --> 00:34:48,000
batteries from super capacitors
1037
00:34:48,000 --> 00:34:49,839
that super capacitors they might have
1038
00:34:49,839 --> 00:34:51,119
very low energy
1039
00:34:51,119 --> 00:34:53,199
but they can they can discharge and
1040
00:34:53,199 --> 00:34:54,800
charge very quickly
1041
00:34:54,800 --> 00:34:56,480
and so that they should have a higher
1042
00:34:56,480 --> 00:34:59,040
power where batteries are
1043
00:34:59,040 --> 00:35:01,119
more limited by kinetics like for
1044
00:35:01,119 --> 00:35:02,320
example the kinetics of
1045
00:35:02,320 --> 00:35:04,720
ion transport within the material you
1046
00:35:04,720 --> 00:35:06,560
know you have to rely on the diffusion
1047
00:35:06,560 --> 00:35:08,240
of ions within the solid
1048
00:35:08,240 --> 00:35:10,320
or also electrical conductivity a lot of
1049
00:35:10,320 --> 00:35:12,160
these battery materials have very poor
1050
00:35:12,160 --> 00:35:14,320
electrical conductivity not only do you
1051
00:35:14,320 --> 00:35:16,320
have to transport ions in the material
1052
00:35:16,320 --> 00:35:17,839
but you have to diffuse the electrons
1053
00:35:17,839 --> 00:35:18,640
the material
1054
00:35:18,640 --> 00:35:20,800
and so if you try to do that too quickly
1055
00:35:20,800 --> 00:35:22,880
you're going to result in
1056
00:35:22,880 --> 00:35:25,359
a higher resi higher impedance and so
1057
00:35:25,359 --> 00:35:26,640
that's going to decrease your your
1058
00:35:26,640 --> 00:35:27,520
capacity and
1059
00:35:27,520 --> 00:35:30,000
energy anyways the units of power is
1060
00:35:30,000 --> 00:35:30,960
watts of course
1061
00:35:30,960 --> 00:35:33,680
joules per second so what's nice about
1062
00:35:33,680 --> 00:35:35,680
these conventional units when we took
1063
00:35:35,680 --> 00:35:38,560
energy in watt hours and we just divide
1064
00:35:38,560 --> 00:35:40,800
it by the amount of time it takes
1065
00:35:40,800 --> 00:35:43,040
to achieve that energy then we just get
1066
00:35:43,040 --> 00:35:45,839
watts
1067
00:35:48,079 --> 00:35:50,880
so i'll i'll briefly talk about the
1068
00:35:50,880 --> 00:35:51,920
three
1069
00:35:51,920 --> 00:35:54,480
mechanisms of charge storage in a
1070
00:35:54,480 --> 00:35:56,960
battery
1071
00:35:56,960 --> 00:36:00,320
so the first uh mechanism is called
1072
00:36:00,320 --> 00:36:03,040
intercalation intercalation if you were
1073
00:36:03,040 --> 00:36:04,960
to look it up in a dictionary
1074
00:36:04,960 --> 00:36:07,040
i believe at least at least maybe 20
1075
00:36:07,040 --> 00:36:08,800
years ago it would say
1076
00:36:08,800 --> 00:36:12,400
uh something about taking a day out of
1077
00:36:12,400 --> 00:36:13,359
the calendar
1078
00:36:13,359 --> 00:36:15,760
year or putting a day into the calendar
1079
00:36:15,760 --> 00:36:17,760
year so it has to do with the calendar
1080
00:36:17,760 --> 00:36:20,800
um and particularly it's talking about
1081
00:36:20,800 --> 00:36:23,440
the february 29th a leap day year where
1082
00:36:23,440 --> 00:36:24,400
we're taking a day
1083
00:36:24,400 --> 00:36:26,320
out of the that calendar and then every
1084
00:36:26,320 --> 00:36:27,680
four years we put it back into the
1085
00:36:27,680 --> 00:36:29,599
calendar intercalate
1086
00:36:29,599 --> 00:36:32,800
um but we use it the same
1087
00:36:32,800 --> 00:36:36,079
idea for for materials
1088
00:36:36,079 --> 00:36:38,400
that we're inserting an ion into the
1089
00:36:38,400 --> 00:36:40,320
material or we're taking an ion
1090
00:36:40,320 --> 00:36:42,800
out of the material but the overall
1091
00:36:42,800 --> 00:36:43,520
structure
1092
00:36:43,520 --> 00:36:45,520
of the material the crystal structure
1093
00:36:45,520 --> 00:36:47,839
remains the same or relatively
1094
00:36:47,839 --> 00:36:50,079
unchanged uh so just like we're changing
1095
00:36:50,079 --> 00:36:50,880
the calendar
1096
00:36:50,880 --> 00:36:53,440
year the the calendar structure doesn't
1097
00:36:53,440 --> 00:36:55,520
change anyways
1098
00:36:55,520 --> 00:36:57,280
so basically we're yeah we're this
1099
00:36:57,280 --> 00:36:59,119
happens uh
1100
00:36:59,119 --> 00:37:00,800
in a lot of the different types of
1101
00:37:00,800 --> 00:37:03,280
crystal structures uh but primarily
1102
00:37:03,280 --> 00:37:06,240
layered crystal structures uh it's easy
1103
00:37:06,240 --> 00:37:07,920
to do this because you're just inserting
1104
00:37:07,920 --> 00:37:08,720
an ion
1105
00:37:08,720 --> 00:37:10,240
in between the layers for example
1106
00:37:10,240 --> 00:37:12,000
graphite which is a layered crystal
1107
00:37:12,000 --> 00:37:12,560
structure
1108
00:37:12,560 --> 00:37:15,040
you can easily in insert ions and that's
1109
00:37:15,040 --> 00:37:17,440
why why we use a graphite as a
1110
00:37:17,440 --> 00:37:19,920
anode material because the the potential
1111
00:37:19,920 --> 00:37:20,720
to insert
1112
00:37:20,720 --> 00:37:22,880
ions into like lithium ions into
1113
00:37:22,880 --> 00:37:24,800
graphite is relatively low so it makes
1114
00:37:24,800 --> 00:37:26,240
it a good anode material you want to
1115
00:37:26,240 --> 00:37:26,880
have low
1116
00:37:26,880 --> 00:37:29,359
redox potential for anode materials and
1117
00:37:29,359 --> 00:37:30,320
then metal
1118
00:37:30,320 --> 00:37:32,720
transition metal oxides that are layered
1119
00:37:32,720 --> 00:37:34,480
like vanadium oxide
1120
00:37:34,480 --> 00:37:37,520
or uh manganese oxide these these have
1121
00:37:37,520 --> 00:37:39,040
relatively higher
1122
00:37:39,040 --> 00:37:42,240
um redox potentials for these these
1123
00:37:42,240 --> 00:37:43,920
transition metal oxides so we use those
1124
00:37:43,920 --> 00:37:46,640
as cathode materials
1125
00:37:46,640 --> 00:37:48,240
so this is just an example again the
1126
00:37:48,240 --> 00:37:50,079
v2o5 if we
1127
00:37:50,079 --> 00:37:53,760
intercalate two lithiums and also we add
1128
00:37:53,760 --> 00:37:55,040
two electrons
1129
00:37:55,040 --> 00:37:58,240
then the this new formula is
1130
00:37:58,240 --> 00:38:01,280
lithium two v205 but it retains
1131
00:38:01,280 --> 00:38:03,680
more or less the same crystal structure
1132
00:38:03,680 --> 00:38:05,200
but we're just expanding
1133
00:38:05,200 --> 00:38:07,920
or and sometimes it contracts actually
1134
00:38:07,920 --> 00:38:08,240
uh
1135
00:38:08,240 --> 00:38:11,040
the inner interlayer spacing and so
1136
00:38:11,040 --> 00:38:12,800
obviously you know if you insert an ion
1137
00:38:12,800 --> 00:38:13,599
in between layers
1138
00:38:13,599 --> 00:38:15,440
you you can conceptualize why it would
1139
00:38:15,440 --> 00:38:17,119
expand right we're putting material in
1140
00:38:17,119 --> 00:38:17,680
between
1141
00:38:17,680 --> 00:38:20,400
but in some instances you'll actually
1142
00:38:20,400 --> 00:38:22,400
see a contraction of the layers and why
1143
00:38:22,400 --> 00:38:23,440
could that be
1144
00:38:23,440 --> 00:38:26,000
and the reason is that these layers are
1145
00:38:26,000 --> 00:38:27,200
are layers of
1146
00:38:27,200 --> 00:38:29,280
like vanadium and oxygen or a different
1147
00:38:29,280 --> 00:38:31,280
transition metal and oxygen the oxygen
1148
00:38:31,280 --> 00:38:33,040
is negatively charged
1149
00:38:33,040 --> 00:38:34,880
right so you have two kind of negatively
1150
00:38:34,880 --> 00:38:36,160
charged uh
1151
00:38:36,160 --> 00:38:39,200
planes uh kind of against each other
1152
00:38:39,200 --> 00:38:41,119
and then you insert a positive ion in
1153
00:38:41,119 --> 00:38:43,359
between and that the coulombic forces of
1154
00:38:43,359 --> 00:38:44,400
the positive ion
1155
00:38:44,400 --> 00:38:46,320
bring the layers closer together so they
1156
00:38:46,320 --> 00:38:47,839
actually get smaller even though you're
1157
00:38:47,839 --> 00:38:48,160
in
1158
00:38:48,160 --> 00:38:51,440
putting putting material in
1159
00:38:51,440 --> 00:38:54,320
yeah so intercalation is one of the main
1160
00:38:54,320 --> 00:38:55,599
mechanisms for
1161
00:38:55,599 --> 00:38:58,320
for lithium-ion batteries in fact the
1162
00:38:58,320 --> 00:39:00,480
nobel prize winner for
1163
00:39:00,480 --> 00:39:03,280
uh lithium-ion batteries um dr
1164
00:39:03,280 --> 00:39:04,320
whittingham
1165
00:39:04,320 --> 00:39:06,640
and amongst other others but dr
1166
00:39:06,640 --> 00:39:07,359
whittingham
1167
00:39:07,359 --> 00:39:10,240
got it because of his discovery of the
1168
00:39:10,240 --> 00:39:12,079
intercollation process for
1169
00:39:12,079 --> 00:39:15,359
the modern lithium-ion batteries
1170
00:39:15,359 --> 00:39:16,960
actually another note on that dr
1171
00:39:16,960 --> 00:39:19,359
whittingham uh
1172
00:39:19,359 --> 00:39:21,520
made this discovery while working at
1173
00:39:21,520 --> 00:39:23,200
exxon
1174
00:39:23,200 --> 00:39:25,040
the gas company so they were doing a lot
1175
00:39:25,040 --> 00:39:26,720
of research into a
1176
00:39:26,720 --> 00:39:28,560
lithium-ion batteries they're just kind
1177
00:39:28,560 --> 00:39:30,720
of kind of funny the big gas
1178
00:39:30,720 --> 00:39:33,040
it's not just gas it's a energy an
1179
00:39:33,040 --> 00:39:35,040
energy company you know is investing
1180
00:39:35,040 --> 00:39:38,320
in uh lithium-ion batteries
1181
00:39:38,320 --> 00:39:40,880
that was that was during the 70s though
1182
00:39:40,880 --> 00:39:41,599
so the
1183
00:39:41,599 --> 00:39:44,160
the next uh charge storage mechanism is
1184
00:39:44,160 --> 00:39:46,000
called conversion so this is just just
1185
00:39:46,000 --> 00:39:46,400
like
1186
00:39:46,400 --> 00:39:49,359
we're breaking down the bonds of a of a
1187
00:39:49,359 --> 00:39:50,480
material and we're
1188
00:39:50,480 --> 00:39:52,720
we're significantly changing the crystal
1189
00:39:52,720 --> 00:39:54,240
structure of that material
1190
00:39:54,240 --> 00:39:57,280
uh so for this example we have tin oxide
1191
00:39:57,280 --> 00:40:00,160
uh or any kind of metal oxide like that
1192
00:40:00,160 --> 00:40:01,520
uh adding lithium
1193
00:40:01,520 --> 00:40:04,880
and electrons and um then that
1194
00:40:04,880 --> 00:40:08,079
turns the tin oxide into tin metal so it
1195
00:40:08,079 --> 00:40:10,079
went from tin four plus to 10
1196
00:40:10,079 --> 00:40:13,280
0 or neutral metal and the lithium
1197
00:40:13,280 --> 00:40:16,960
becomes a lithium oxide a solid
1198
00:40:16,960 --> 00:40:20,720
so this this is this tends to happen
1199
00:40:20,720 --> 00:40:23,359
at lower voltages so a lot of anode
1200
00:40:23,359 --> 00:40:24,000
materials
1201
00:40:24,000 --> 00:40:26,160
that are being researched so if we go
1202
00:40:26,160 --> 00:40:27,599
back to the this uh
1203
00:40:27,599 --> 00:40:30,160
standard this standard right if we look
1204
00:40:30,160 --> 00:40:31,119
at these
1205
00:40:31,119 --> 00:40:33,839
these materials um right we're turning
1206
00:40:33,839 --> 00:40:35,119
them into metals
1207
00:40:35,119 --> 00:40:38,079
right so like uh where's the tin tin tin
1208
00:40:38,079 --> 00:40:39,359
two plus the tin metal
1209
00:40:39,359 --> 00:40:42,480
tin four plus those ten two plus um
1210
00:40:42,480 --> 00:40:45,040
so these often happen at lower voltages
1211
00:40:45,040 --> 00:40:45,599
so they're
1212
00:40:45,599 --> 00:40:47,440
they're more prevalent for anode
1213
00:40:47,440 --> 00:40:48,800
materials um
1214
00:40:48,800 --> 00:40:51,760
if i actually go back uh the highest one
1215
00:40:51,760 --> 00:40:53,520
the highest voltage would be copper so
1216
00:40:53,520 --> 00:40:54,960
there has been a bit of research of
1217
00:40:54,960 --> 00:40:56,240
trying to utilize
1218
00:40:56,240 --> 00:40:59,200
copper two plus the copper metal as part
1219
00:40:59,200 --> 00:40:59,680
of
1220
00:40:59,680 --> 00:41:01,520
different materials to help increase the
1221
00:41:01,520 --> 00:41:03,119
capacity like if we could
1222
00:41:03,119 --> 00:41:04,560
if we could make copper two plus we
1223
00:41:04,560 --> 00:41:06,720
would copper one through intercalation
1224
00:41:06,720 --> 00:41:08,240
and then copper one plus the copper
1225
00:41:08,240 --> 00:41:10,319
metal that could increase the
1226
00:41:10,319 --> 00:41:12,319
capacity even further but the problem is
1227
00:41:12,319 --> 00:41:13,760
you're just significantly
1228
00:41:13,760 --> 00:41:15,760
changing the structure of the material
1229
00:41:15,760 --> 00:41:16,880
and that's going to make it more
1230
00:41:16,880 --> 00:41:17,760
difficult
1231
00:41:17,760 --> 00:41:20,079
for a reversible reaction if we want to
1232
00:41:20,079 --> 00:41:21,440
you know we can discharge the battery
1233
00:41:21,440 --> 00:41:21,760
but
1234
00:41:21,760 --> 00:41:22,960
the question is can we charge the
1235
00:41:22,960 --> 00:41:25,040
battery and retain the same capacity
1236
00:41:25,040 --> 00:41:27,599
so oftentimes in conversion reactions
1237
00:41:27,599 --> 00:41:30,160
capacity cyclic capacity
1238
00:41:30,160 --> 00:41:31,760
over many cycles the capacity gets
1239
00:41:31,760 --> 00:41:33,040
smaller and smaller and smaller because
1240
00:41:33,040 --> 00:41:34,000
you're you're losing
1241
00:41:34,000 --> 00:41:36,640
material or the material is uh you know
1242
00:41:36,640 --> 00:41:37,760
it's
1243
00:41:37,760 --> 00:41:39,839
the you're losing continuity electrical
1244
00:41:39,839 --> 00:41:41,359
continuity for example with the
1245
00:41:41,359 --> 00:41:42,800
electrode
1246
00:41:42,800 --> 00:41:46,480
so yeah the crystal completely changes
1247
00:41:46,480 --> 00:41:48,800
and then the last form of charge storage
1248
00:41:48,800 --> 00:41:49,680
is alloying
1249
00:41:49,680 --> 00:41:51,440
so in this case you might have a metal
1250
00:41:51,440 --> 00:41:53,040
that can make an alloy
1251
00:41:53,040 --> 00:41:55,359
with lithium for example or whatever ion
1252
00:41:55,359 --> 00:41:56,079
you're using
1253
00:41:56,079 --> 00:41:59,119
so in this case again tin metal can
1254
00:41:59,119 --> 00:42:02,079
can be lithiated with lithium and so in
1255
00:42:02,079 --> 00:42:03,359
this case we're going from metal but
1256
00:42:03,359 --> 00:42:04,800
then we have lithium ions
1257
00:42:04,800 --> 00:42:06,720
the lithium ions is what's changing
1258
00:42:06,720 --> 00:42:07,839
their valence state and so
1259
00:42:07,839 --> 00:42:11,119
now just have a neutral metal this can
1260
00:42:11,119 --> 00:42:13,599
this these reactions these alloying
1261
00:42:13,599 --> 00:42:14,480
reactions
1262
00:42:14,480 --> 00:42:16,800
they can have a very high capacity and
1263
00:42:16,800 --> 00:42:18,560
also very low voltage which is
1264
00:42:18,560 --> 00:42:20,240
which is good for anode materials if you
1265
00:42:20,240 --> 00:42:21,680
want to increase the energy density of
1266
00:42:21,680 --> 00:42:23,119
your battery
1267
00:42:23,119 --> 00:42:24,880
the problem is that there's very
1268
00:42:24,880 --> 00:42:26,880
significant volume change in these
1269
00:42:26,880 --> 00:42:28,000
materials
1270
00:42:28,000 --> 00:42:30,000
tin for example has a very large volume
1271
00:42:30,000 --> 00:42:31,599
change another material
1272
00:42:31,599 --> 00:42:33,599
that has been a lot of research is a
1273
00:42:33,599 --> 00:42:35,680
silicon as an anode material because
1274
00:42:35,680 --> 00:42:36,640
silicon can
1275
00:42:36,640 --> 00:42:39,760
can absorb a lot of lithium but
1276
00:42:39,760 --> 00:42:41,599
again the volume change is very
1277
00:42:41,599 --> 00:42:43,680
significant i forget the exact number
1278
00:42:43,680 --> 00:42:44,480
but like
1279
00:42:44,480 --> 00:42:48,079
over over 500 percent change in volume
1280
00:42:48,079 --> 00:42:49,760
so you can imagine if you're changing
1281
00:42:49,760 --> 00:42:51,280
that much of your volume
1282
00:42:51,280 --> 00:42:52,800
you're gonna have a lot of mechanical
1283
00:42:52,800 --> 00:42:54,640
deformation uh and so
1284
00:42:54,640 --> 00:42:57,040
over many cycles you get significant
1285
00:42:57,040 --> 00:42:58,400
loss of capacity
1286
00:42:58,400 --> 00:43:00,400
because because of the mechanical
1287
00:43:00,400 --> 00:43:02,240
deformation that's occurring in your
1288
00:43:02,240 --> 00:43:03,839
electrode that the pieces are breaking
1289
00:43:03,839 --> 00:43:04,400
off
1290
00:43:04,400 --> 00:43:08,000
perhaps and yeah
1291
00:43:08,000 --> 00:43:09,680
so there's some some research that's
1292
00:43:09,680 --> 00:43:12,319
looking at you making very nanoscopic
1293
00:43:12,319 --> 00:43:15,440
uh particles of tint uh or of uh
1294
00:43:15,440 --> 00:43:18,000
of uh silicon or nanowires so they they
1295
00:43:18,000 --> 00:43:19,520
can they can
1296
00:43:19,520 --> 00:43:22,160
take they can have space for that volume
1297
00:43:22,160 --> 00:43:25,440
change without breaking
1298
00:43:25,599 --> 00:43:28,240
um and then another thing to consider is
1299
00:43:28,240 --> 00:43:28,960
uh
1300
00:43:28,960 --> 00:43:31,520
the selection of your electrolyte um and
1301
00:43:31,520 --> 00:43:32,400
i don't talk about
1302
00:43:32,400 --> 00:43:34,640
too much about the electrolytes and the
1303
00:43:34,640 --> 00:43:36,640
solvents that are used
1304
00:43:36,640 --> 00:43:40,000
but the electrolyte also has a
1305
00:43:40,000 --> 00:43:42,800
limit of you know if if you have a
1306
00:43:42,800 --> 00:43:44,240
cathode inside
1307
00:43:44,240 --> 00:43:46,480
your electrolyte it's going to have a
1308
00:43:46,480 --> 00:43:48,640
limit where it starts to reduce or it
1309
00:43:48,640 --> 00:43:50,800
starts to oxidize in contact with your
1310
00:43:50,800 --> 00:43:51,520
cathode or
1311
00:43:51,520 --> 00:43:54,720
anode and so it's depending on the lumo
1312
00:43:54,720 --> 00:43:55,520
the lowest
1313
00:43:55,520 --> 00:43:58,319
unoccupied molecular orbital in the homo
1314
00:43:58,319 --> 00:43:58,880
uh
1315
00:43:58,880 --> 00:44:01,359
highest occupied molecular orbital of
1316
00:44:01,359 --> 00:44:02,720
your electrolyte
1317
00:44:02,720 --> 00:44:05,839
uh solvent and so if your cathode has a
1318
00:44:05,839 --> 00:44:07,040
lower energy
1319
00:44:07,040 --> 00:44:09,359
or excuse me uh yeah lower energy than
1320
00:44:09,359 --> 00:44:11,520
the homo then you'll have a reduction
1321
00:44:11,520 --> 00:44:13,839
and if it has a higher energy than the
1322
00:44:13,839 --> 00:44:15,440
lumo the anode has higher energy than
1323
00:44:15,440 --> 00:44:16,319
luma they don't have
1324
00:44:16,319 --> 00:44:19,920
oxidation so for example for aqueous
1325
00:44:19,920 --> 00:44:22,400
batteries this severely limits
1326
00:44:22,400 --> 00:44:25,359
the selection of materials and
1327
00:44:25,359 --> 00:44:26,960
electrochemical processes for
1328
00:44:26,960 --> 00:44:28,720
aqueous batteries because you have to
1329
00:44:28,720 --> 00:44:30,560
deal with what's called the her the
1330
00:44:30,560 --> 00:44:32,560
hydrogen evolution reaction
1331
00:44:32,560 --> 00:44:34,400
that's where water breaks down into
1332
00:44:34,400 --> 00:44:36,079
hydrogen ions and the hydrogen
1333
00:44:36,079 --> 00:44:38,800
ions turn into hydrogen gas so that
1334
00:44:38,800 --> 00:44:39,599
happens
1335
00:44:39,599 --> 00:44:43,119
at a pretty a low voltage and then
1336
00:44:43,119 --> 00:44:45,280
so that's about point it also depends on
1337
00:44:45,280 --> 00:44:46,800
the the ph of the
1338
00:44:46,800 --> 00:44:49,839
the solvent as well and then on the
1339
00:44:49,839 --> 00:44:51,599
other end you have oxygen reduction
1340
00:44:51,599 --> 00:44:52,400
reaction
1341
00:44:52,400 --> 00:44:55,440
so that's when water breaks down and
1342
00:44:55,440 --> 00:44:57,280
you get oxygen ions that turn into
1343
00:44:57,280 --> 00:45:00,079
oxygen gas
1344
00:45:00,560 --> 00:45:02,960
so that's one of the limits for working
1345
00:45:02,960 --> 00:45:04,000
with aqueous ion
1346
00:45:04,000 --> 00:45:07,280
batteries and
1347
00:45:07,280 --> 00:45:10,240
also non-aqueous ion batteries so
1348
00:45:10,240 --> 00:45:12,319
there's some common electrolytes
1349
00:45:12,319 --> 00:45:15,359
for non-aqueous at least the solvents so
1350
00:45:15,359 --> 00:45:17,280
i should say the electrolyte is made out
1351
00:45:17,280 --> 00:45:19,440
of a solvent
1352
00:45:19,440 --> 00:45:22,800
and a a salt so the solvent for
1353
00:45:22,800 --> 00:45:25,200
non-aqueous electrolytes are typically
1354
00:45:25,200 --> 00:45:26,960
different types of carbonates like
1355
00:45:26,960 --> 00:45:30,839
propylene carbonate ethylene carbonate
1356
00:45:30,839 --> 00:45:34,160
dimethyl carbonate so these organic
1357
00:45:34,160 --> 00:45:36,720
materials they have a very high working
1358
00:45:36,720 --> 00:45:38,000
potential
1359
00:45:38,000 --> 00:45:40,079
so we can allow for higher voltages or
1360
00:45:40,079 --> 00:45:42,880
voltages as low as the lithium
1361
00:45:42,880 --> 00:45:45,200
without it breaking down and even even
1362
00:45:45,200 --> 00:45:47,440
then some of the materials do break down
1363
00:45:47,440 --> 00:45:49,839
and it forms what's called a electrolyte
1364
00:45:49,839 --> 00:45:50,480
interface
1365
00:45:50,480 --> 00:45:52,560
so on the surface of your material
1366
00:45:52,560 --> 00:45:53,680
you'll have a like a thin
1367
00:45:53,680 --> 00:45:57,359
layer of a byproduct of your electrolyte
1368
00:45:57,359 --> 00:45:59,359
that's broken down on the surface
1369
00:45:59,359 --> 00:46:02,240
but that that creates like a passivation
1370
00:46:02,240 --> 00:46:03,680
for further breaking down but still
1371
00:46:03,680 --> 00:46:05,520
allows ions to diffuse through that
1372
00:46:05,520 --> 00:46:06,319
layer
1373
00:46:06,319 --> 00:46:09,040
um but some cases that doesn't happen so
1374
00:46:09,040 --> 00:46:09,920
then you're you're
1375
00:46:09,920 --> 00:46:11,920
constantly breaking down the electrolyte
1376
00:46:11,920 --> 00:46:13,040
which is not good
1377
00:46:13,040 --> 00:46:15,040
and then the salt that's used is also
1378
00:46:15,040 --> 00:46:16,640
important the salt determines you know
1379
00:46:16,640 --> 00:46:17,040
what
1380
00:46:17,040 --> 00:46:20,000
what ions your ion battery is so for for
1381
00:46:20,000 --> 00:46:21,920
non-aqueous lithium ion batteries a
1382
00:46:21,920 --> 00:46:22,480
typical
1383
00:46:22,480 --> 00:46:25,680
salt is lithium hexafluorophosphate
1384
00:46:25,680 --> 00:46:28,960
it's lithium h excuse me
1385
00:46:28,960 --> 00:46:32,560
pf6 hexafluorophosphate is a common salt
1386
00:46:32,560 --> 00:46:34,319
um and then for sodium ion batteries
1387
00:46:34,319 --> 00:46:35,920
non-aqueous systems the sodium
1388
00:46:35,920 --> 00:46:37,359
perchlorate is another
1389
00:46:37,359 --> 00:46:39,839
common sodium salt so they they dissolve
1390
00:46:39,839 --> 00:46:41,599
in the electrolyte excuse me
1391
00:46:41,599 --> 00:46:43,119
they dissolve in the solvent and that's
1392
00:46:43,119 --> 00:46:45,359
what makes up the electrolyte
1393
00:46:45,359 --> 00:46:48,400
okay so some different properties of
1394
00:46:48,400 --> 00:46:50,079
these battery materials and
1395
00:46:50,079 --> 00:46:52,560
what they how they influence the
1396
00:46:52,560 --> 00:46:53,680
different performance
1397
00:46:53,680 --> 00:46:55,920
of the batteries so for the electric
1398
00:46:55,920 --> 00:46:57,760
material of course composition or in
1399
00:46:57,760 --> 00:46:59,119
other words the chemistry of the
1400
00:46:59,119 --> 00:47:00,240
material
1401
00:47:00,240 --> 00:47:02,720
that will highly affect things like the
1402
00:47:02,720 --> 00:47:04,800
electrochemical potential
1403
00:47:04,800 --> 00:47:07,040
so right you know if we're changing from
1404
00:47:07,040 --> 00:47:07,920
iron
1405
00:47:07,920 --> 00:47:10,800
ions to vanadium ions that's going to
1406
00:47:10,800 --> 00:47:12,720
change the voltage of our system
1407
00:47:12,720 --> 00:47:14,880
um you know even if we keep everything
1408
00:47:14,880 --> 00:47:16,319
the same if we just replace
1409
00:47:16,319 --> 00:47:17,680
if we have the same crystal structure
1410
00:47:17,680 --> 00:47:19,599
and we replace iron with vanadium that's
1411
00:47:19,599 --> 00:47:20,319
going to change our
1412
00:47:20,319 --> 00:47:22,240
our crystal structure i'm assuming that
1413
00:47:22,240 --> 00:47:24,400
forms the same stable complex which
1414
00:47:24,400 --> 00:47:25,440
might not
1415
00:47:25,440 --> 00:47:27,599
um and not only that but you know you
1416
00:47:27,599 --> 00:47:29,680
can have the same transition metal ion
1417
00:47:29,680 --> 00:47:31,920
like iron three plus iron two plus
1418
00:47:31,920 --> 00:47:34,480
and change its local environment you
1419
00:47:34,480 --> 00:47:36,160
know whether it's surrounded by
1420
00:47:36,160 --> 00:47:39,280
uh octahedral coordination of oxygen or
1421
00:47:39,280 --> 00:47:41,359
a tetrahedral coordination of oxygen
1422
00:47:41,359 --> 00:47:42,960
you still have the same transition metal
1423
00:47:42,960 --> 00:47:44,720
but whether it's not whether or not it's
1424
00:47:44,720 --> 00:47:46,559
octahedral or tetrahedral that will
1425
00:47:46,559 --> 00:47:48,640
change the potential of your battery as
1426
00:47:48,640 --> 00:47:49,359
well
1427
00:47:49,359 --> 00:47:51,520
and it goes even further than that it's
1428
00:47:51,520 --> 00:47:52,960
not only the nearest neighbor but
1429
00:47:52,960 --> 00:47:54,960
it could be the next nearest neighbor so
1430
00:47:54,960 --> 00:47:56,960
for example iron phosphate
1431
00:47:56,960 --> 00:47:58,559
lithium iron phosphate compared to
1432
00:47:58,559 --> 00:48:00,319
lithium iron sulfate
1433
00:48:00,319 --> 00:48:03,359
so in both cases iron is i think uh
1434
00:48:03,359 --> 00:48:05,440
i forget if it's octahedral or or
1435
00:48:05,440 --> 00:48:06,480
tetrahedral
1436
00:48:06,480 --> 00:48:09,520
but in both cases the iron is
1437
00:48:09,520 --> 00:48:12,400
surrounded by oxygen but in one the
1438
00:48:12,400 --> 00:48:15,040
oxygen is coordinated to phosphate
1439
00:48:15,040 --> 00:48:16,960
or phosphorus another one that is
1440
00:48:16,960 --> 00:48:19,040
coordinated to oxygen
1441
00:48:19,040 --> 00:48:20,480
well i say oxygen is coordinated the
1442
00:48:20,480 --> 00:48:22,800
sulfur and so just by changing those
1443
00:48:22,800 --> 00:48:24,800
next nearest neighbors you can also
1444
00:48:24,800 --> 00:48:26,880
change the electrochemical potential of
1445
00:48:26,880 --> 00:48:28,400
the battery or the discharge potential
1446
00:48:28,400 --> 00:48:29,200
of the battery
1447
00:48:29,200 --> 00:48:31,119
uh so it all has to do with the energy
1448
00:48:31,119 --> 00:48:32,559
levels of these of these
1449
00:48:32,559 --> 00:48:35,839
transition metal uh elements and how
1450
00:48:35,839 --> 00:48:38,319
near the local environment affects that
1451
00:48:38,319 --> 00:48:40,079
energy
1452
00:48:40,079 --> 00:48:42,000
and then like crystal structure can
1453
00:48:42,000 --> 00:48:43,359
affect things like uh
1454
00:48:43,359 --> 00:48:46,400
the cyclic stability right
1455
00:48:46,400 --> 00:48:49,200
like i said if you if you have um or
1456
00:48:49,200 --> 00:48:51,280
capacity is a better example
1457
00:48:51,280 --> 00:48:53,359
if you have a nice layered structure
1458
00:48:53,359 --> 00:48:55,440
lithium ions or sodium ions can diffuse
1459
00:48:55,440 --> 00:48:57,599
into the layer structure pretty easily
1460
00:48:57,599 --> 00:48:58,960
but there's other crystal structures
1461
00:48:58,960 --> 00:49:00,480
that are not layered or they don't have
1462
00:49:00,480 --> 00:49:00,960
good
1463
00:49:00,960 --> 00:49:03,040
channels for lithium-ion diffusion so
1464
00:49:03,040 --> 00:49:04,400
that can that can
1465
00:49:04,400 --> 00:49:06,480
severely affect the capacity and or like
1466
00:49:06,480 --> 00:49:08,240
things like power density because
1467
00:49:08,240 --> 00:49:11,200
uh you're the diff if your diffusion is
1468
00:49:11,200 --> 00:49:11,839
limited
1469
00:49:11,839 --> 00:49:14,160
you're eliminating you're limiting the
1470
00:49:14,160 --> 00:49:16,319
kinetics of your reaction so
1471
00:49:16,319 --> 00:49:19,040
you can't you can't just uh increase the
1472
00:49:19,040 --> 00:49:20,400
current of your battery there's going to
1473
00:49:20,400 --> 00:49:21,040
be a
1474
00:49:21,040 --> 00:49:23,280
much higher impedance to that so that's
1475
00:49:23,280 --> 00:49:24,960
going to decrease capacity and
1476
00:49:24,960 --> 00:49:28,559
power density morphology is also a big
1477
00:49:28,559 --> 00:49:29,680
factor about
1478
00:49:29,680 --> 00:49:33,280
with that like i said um kinetics is a
1479
00:49:33,280 --> 00:49:34,000
big part
1480
00:49:34,000 --> 00:49:36,800
of of the pro performance of the battery
1481
00:49:36,800 --> 00:49:38,480
you know how fast can you diffuse
1482
00:49:38,480 --> 00:49:39,119
lithium
1483
00:49:39,119 --> 00:49:40,640
and also electrons electrical
1484
00:49:40,640 --> 00:49:42,640
conductivity within your material
1485
00:49:42,640 --> 00:49:44,800
and just by changing the morphology you
1486
00:49:44,800 --> 00:49:46,319
know say you're changing it from
1487
00:49:46,319 --> 00:49:49,680
a micro particle to a nano particle
1488
00:49:49,680 --> 00:49:51,040
but you keep everything else the same
1489
00:49:51,040 --> 00:49:52,559
the crystal structure same composition
1490
00:49:52,559 --> 00:49:54,000
is the same just changing the size of
1491
00:49:54,000 --> 00:49:54,800
the particle
1492
00:49:54,800 --> 00:49:57,119
can change the capacity and the power
1493
00:49:57,119 --> 00:49:58,640
density because you're changing the
1494
00:49:58,640 --> 00:49:59,520
kinetics
1495
00:49:59,520 --> 00:50:02,720
i have an example of that next
1496
00:50:02,720 --> 00:50:04,640
the electrolyte right so what solvent
1497
00:50:04,640 --> 00:50:06,319
you choose like i said that changes uh
1498
00:50:06,319 --> 00:50:08,400
your electrochemical window
1499
00:50:08,400 --> 00:50:10,079
whether you're using water or something
1500
00:50:10,079 --> 00:50:12,079
else also some of the solvents might
1501
00:50:12,079 --> 00:50:14,319
react with the electrode material
1502
00:50:14,319 --> 00:50:17,599
um and then the ion choice also so
1503
00:50:17,599 --> 00:50:20,720
uh depending on what your ion is uh you
1504
00:50:20,720 --> 00:50:22,400
know
1505
00:50:22,400 --> 00:50:23,760
or depending on what your solvent is
1506
00:50:23,760 --> 00:50:25,520
some solvents can't dissolve certain
1507
00:50:25,520 --> 00:50:26,079
salts
1508
00:50:26,079 --> 00:50:29,359
and so on okay
1509
00:50:29,359 --> 00:50:31,280
so here's an example of changing the
1510
00:50:31,280 --> 00:50:32,640
morphology
1511
00:50:32,640 --> 00:50:35,520
uh in titanium oxide so titanium oxide
1512
00:50:35,520 --> 00:50:36,240
is not
1513
00:50:36,240 --> 00:50:38,559
a very good def uh doesn't have a very
1514
00:50:38,559 --> 00:50:39,680
high diffusion
1515
00:50:39,680 --> 00:50:42,240
of lithium ions and it doesn't it has a
1516
00:50:42,240 --> 00:50:43,520
very poor
1517
00:50:43,520 --> 00:50:45,520
electrical conductivity you know it's
1518
00:50:45,520 --> 00:50:48,880
it's a wide band gap insulator right
1519
00:50:48,880 --> 00:50:52,800
so if you you start with micro particles
1520
00:50:52,800 --> 00:50:54,720
you know you can you can reduce the
1521
00:50:54,720 --> 00:50:56,800
surface of the titanium four plus the
1522
00:50:56,800 --> 00:50:57,440
titanium
1523
00:50:57,440 --> 00:50:59,760
titanium three plus and intercalate a
1524
00:50:59,760 --> 00:51:01,040
bit of lithium
1525
00:51:01,040 --> 00:51:03,440
but it only diffuses into the surface so
1526
00:51:03,440 --> 00:51:04,400
only the surface
1527
00:51:04,400 --> 00:51:08,160
uh is is reduced um and so that severely
1528
00:51:08,160 --> 00:51:11,520
limits the specific capacity or the the
1529
00:51:11,520 --> 00:51:14,960
amount of electrons per gram of material
1530
00:51:14,960 --> 00:51:15,760
transferred
1531
00:51:15,760 --> 00:51:17,119
but if you were to take the same
1532
00:51:17,119 --> 00:51:19,520
material and make it on the nano scale
1533
00:51:19,520 --> 00:51:22,160
now you're really decreasing the excuse
1534
00:51:22,160 --> 00:51:23,119
me
1535
00:51:23,119 --> 00:51:24,960
really just decreasing the diffusion
1536
00:51:24,960 --> 00:51:26,960
distance of the lithiums the lithium has
1537
00:51:26,960 --> 00:51:28,400
no problem just diffusing a
1538
00:51:28,400 --> 00:51:31,599
few nanometers and then you can fully
1539
00:51:31,599 --> 00:51:34,000
uh achieve the the full or near
1540
00:51:34,000 --> 00:51:35,760
theoretical capacity in that case if you
1541
00:51:35,760 --> 00:51:36,000
make
1542
00:51:36,000 --> 00:51:37,839
very small materials and so there's an
1543
00:51:37,839 --> 00:51:40,640
example of this from this paper
1544
00:51:40,640 --> 00:51:43,680
and where they have titanium oxide micro
1545
00:51:43,680 --> 00:51:45,520
particles is about diameters about one
1546
00:51:45,520 --> 00:51:46,559
micron
1547
00:51:46,559 --> 00:51:48,480
and then compared it to a different type
1548
00:51:48,480 --> 00:51:50,400
of titanium oxide particle they call
1549
00:51:50,400 --> 00:51:51,760
this the the urchin
1550
00:51:51,760 --> 00:51:54,800
particle so it's basically a a sphere
1551
00:51:54,800 --> 00:51:57,599
but it's been etched away so you have a
1552
00:51:57,599 --> 00:51:58,400
very high
1553
00:51:58,400 --> 00:52:00,480
surface area they're just kind of flat
1554
00:52:00,480 --> 00:52:03,680
sheets that make up the sphere
1555
00:52:03,680 --> 00:52:06,000
and nanowires and so it has very high
1556
00:52:06,000 --> 00:52:06,800
surface area
1557
00:52:06,800 --> 00:52:08,559
and then the thickness of the the sheet
1558
00:52:08,559 --> 00:52:10,720
is very small so the diffusion distance
1559
00:52:10,720 --> 00:52:12,800
from like the lithium outside to inside
1560
00:52:12,800 --> 00:52:14,480
is very small
1561
00:52:14,480 --> 00:52:16,160
and so you see just the difference in
1562
00:52:16,160 --> 00:52:18,000
specific capacity
1563
00:52:18,000 --> 00:52:20,240
you know for the high surface area
1564
00:52:20,240 --> 00:52:22,640
urchin type titanium oxide compared to
1565
00:52:22,640 --> 00:52:24,480
just the bulk tio2
1566
00:52:24,480 --> 00:52:26,880
so just by changing the morphology
1567
00:52:26,880 --> 00:52:28,079
making it smaller
1568
00:52:28,079 --> 00:52:29,760
you're increasing the capacity also
1569
00:52:29,760 --> 00:52:31,280
you're increasing the the
1570
00:52:31,280 --> 00:52:33,200
performance i'll talk a bit about this
1571
00:52:33,200 --> 00:52:36,880
type of data a little bit later
1572
00:52:43,520 --> 00:52:46,720
so this is an example of how
1573
00:52:46,720 --> 00:52:49,839
i make batteries in my research it's a
1574
00:52:49,839 --> 00:52:51,359
bit different than like if you're making
1575
00:52:51,359 --> 00:52:52,079
batteries from
1576
00:52:52,079 --> 00:52:53,920
commercial applications obviously in
1577
00:52:53,920 --> 00:52:55,280
commercial applications
1578
00:52:55,280 --> 00:52:58,000
everything's mass produced you have
1579
00:52:58,000 --> 00:52:59,280
these printers that print out the
1580
00:52:59,280 --> 00:53:00,160
electrode material
1581
00:53:00,160 --> 00:53:03,440
very quickly right so just for research
1582
00:53:03,440 --> 00:53:06,079
we use these little button cells
1583
00:53:06,079 --> 00:53:09,520
the coin cells um so we do we start with
1584
00:53:09,520 --> 00:53:10,400
our material
1585
00:53:10,400 --> 00:53:12,319
so either a cathode material and a
1586
00:53:12,319 --> 00:53:14,079
material it's whatever our active
1587
00:53:14,079 --> 00:53:15,920
material is that we're studying
1588
00:53:15,920 --> 00:53:19,040
we mix that material by weight or these
1589
00:53:19,040 --> 00:53:21,280
numbers can change but i use 70
1590
00:53:21,280 --> 00:53:23,520
and it's fairly standard and then you
1591
00:53:23,520 --> 00:53:25,599
add carbon
1592
00:53:25,599 --> 00:53:27,520
we use a black carbon there's different
1593
00:53:27,520 --> 00:53:29,200
types of carbon that have different like
1594
00:53:29,200 --> 00:53:30,800
surface areas and
1595
00:53:30,800 --> 00:53:32,240
you could also use some people use
1596
00:53:32,240 --> 00:53:34,720
graphite that the purpose of adding
1597
00:53:34,720 --> 00:53:35,280
carbon
1598
00:53:35,280 --> 00:53:37,920
is because a lot of these materials have
1599
00:53:37,920 --> 00:53:38,559
low
1600
00:53:38,559 --> 00:53:41,520
uh electrical conductivity for example
1601
00:53:41,520 --> 00:53:44,480
my material here is a semiconductor
1602
00:53:44,480 --> 00:53:46,319
and the purpose of adding carbon is to
1603
00:53:46,319 --> 00:53:48,400
increase the electrical continuity of
1604
00:53:48,400 --> 00:53:49,760
your electrode so you can
1605
00:53:49,760 --> 00:53:51,520
help deliver the electrons throughout
1606
00:53:51,520 --> 00:53:53,599
your electrode but the carbon itself
1607
00:53:53,599 --> 00:53:55,200
does not participate
1608
00:53:55,200 --> 00:53:58,640
in the electrochemical reaction unless
1609
00:53:58,640 --> 00:54:00,319
you have graphite
1610
00:54:00,319 --> 00:54:03,359
and you're working at very low potential
1611
00:54:03,359 --> 00:54:04,480
then you could have
1612
00:54:04,480 --> 00:54:06,400
at low potentials you can have low
1613
00:54:06,400 --> 00:54:07,839
lithium intercalation but
1614
00:54:07,839 --> 00:54:09,599
for my material as a cathode i work at
1615
00:54:09,599 --> 00:54:11,520
higher potentials it's above the
1616
00:54:11,520 --> 00:54:13,280
potential for intercalation
1617
00:54:13,280 --> 00:54:15,599
so it doesn't happen so it's inert
1618
00:54:15,599 --> 00:54:16,559
basically it's just
1619
00:54:16,559 --> 00:54:18,640
added to increase cu electrical
1620
00:54:18,640 --> 00:54:20,400
continuity and then we keep it all
1621
00:54:20,400 --> 00:54:22,319
together using a binder
1622
00:54:22,319 --> 00:54:24,720
so a common binder that we use is called
1623
00:54:24,720 --> 00:54:26,000
a pvdf
1624
00:54:26,000 --> 00:54:30,800
um polyvirum bean difluorine
1625
00:54:30,800 --> 00:54:32,640
some something like that basically it's
1626
00:54:32,640 --> 00:54:34,000
a carbon chain
1627
00:54:34,000 --> 00:54:37,119
and then um you have fluorine attached
1628
00:54:37,119 --> 00:54:38,799
to each carbon and also hydrogen
1629
00:54:38,799 --> 00:54:40,240
attached to each carbon
1630
00:54:40,240 --> 00:54:42,160
so very similar to teflon which is a
1631
00:54:42,160 --> 00:54:43,440
carbon chain with
1632
00:54:43,440 --> 00:54:47,119
two fluorines attached to each carbon
1633
00:54:47,280 --> 00:54:49,200
and so it's it's also chemically inert
1634
00:54:49,200 --> 00:54:51,119
but we can dissolve it we dissolve it in
1635
00:54:51,119 --> 00:54:52,640
a solvent
1636
00:54:52,640 --> 00:54:55,920
called nmp nmp is a very it's very nasty
1637
00:54:55,920 --> 00:54:56,480
solvent
1638
00:54:56,480 --> 00:54:58,400
it's uh it eats through a lot of
1639
00:54:58,400 --> 00:55:00,559
different polymers including like
1640
00:55:00,559 --> 00:55:02,799
those the purple nitrile gloves that can
1641
00:55:02,799 --> 00:55:04,319
eat through those purple nitrile gloves
1642
00:55:04,319 --> 00:55:05,040
so we have to wear
1643
00:55:05,040 --> 00:55:08,240
special gloves when handling it and so
1644
00:55:08,240 --> 00:55:08,559
we
1645
00:55:08,559 --> 00:55:10,640
we mix that together and either like in
1646
00:55:10,640 --> 00:55:12,480
a mooring pestle like this where we
1647
00:55:12,480 --> 00:55:15,040
we kind of mix it all together or we can
1648
00:55:15,040 --> 00:55:16,640
put it into a
1649
00:55:16,640 --> 00:55:19,680
little a little container and we
1650
00:55:19,680 --> 00:55:21,760
ultrasonicate it with a very powerful
1651
00:55:21,760 --> 00:55:23,040
ultrasonic probe
1652
00:55:23,040 --> 00:55:24,480
much more powerful than a regular like
1653
00:55:24,480 --> 00:55:26,960
little container that ultrasonicates it
1654
00:55:26,960 --> 00:55:29,520
and then we spread it out the slurry
1655
00:55:29,520 --> 00:55:30,160
onto
1656
00:55:30,160 --> 00:55:31,760
the electrode or what we call the
1657
00:55:31,760 --> 00:55:33,839
current collector now depending on if
1658
00:55:33,839 --> 00:55:35,680
you're working with an anode or
1659
00:55:35,680 --> 00:55:39,359
cathode you'll either use aluminum foil
1660
00:55:39,359 --> 00:55:42,000
or copper foil as you're you're a
1661
00:55:42,000 --> 00:55:43,280
current collector
1662
00:55:43,280 --> 00:55:46,319
the reason is for for lithium-ion
1663
00:55:46,319 --> 00:55:48,000
batteries and as well as sodium ion
1664
00:55:48,000 --> 00:55:51,200
batteries if we use
1665
00:55:51,200 --> 00:55:54,640
aluminum lithium and sodium will
1666
00:55:54,640 --> 00:55:57,200
alloy with the aluminum so it's an
1667
00:55:57,200 --> 00:55:58,640
active material
1668
00:55:58,640 --> 00:56:01,280
but it alloys only at low voltages that
1669
00:56:01,280 --> 00:56:02,000
we would use
1670
00:56:02,000 --> 00:56:05,599
like for anode materials so for anodes
1671
00:56:05,599 --> 00:56:07,040
instead of aluminum we use
1672
00:56:07,040 --> 00:56:09,680
copper and lithium and sodium do not
1673
00:56:09,680 --> 00:56:11,680
alloy with copper
1674
00:56:11,680 --> 00:56:14,319
so we use copper foil for that however
1675
00:56:14,319 --> 00:56:16,720
at higher voltages copper
1676
00:56:16,720 --> 00:56:19,920
will oxidize in the copper ions so we
1677
00:56:19,920 --> 00:56:21,680
don't use copper for the cathodes we
1678
00:56:21,680 --> 00:56:23,119
only use it for the anodes
1679
00:56:23,119 --> 00:56:26,400
aluminum on the other hand aluminum also
1680
00:56:26,400 --> 00:56:28,799
oxidizes but aluminum has a passive
1681
00:56:28,799 --> 00:56:30,240
oxide layer on it
1682
00:56:30,240 --> 00:56:32,880
which passivates it from being further
1683
00:56:32,880 --> 00:56:35,040
oxidized at higher voltages
1684
00:56:35,040 --> 00:56:36,640
so that's why we use aluminum foil for
1685
00:56:36,640 --> 00:56:39,839
cathodes and a copper foil for anodes
1686
00:56:39,839 --> 00:56:43,520
anyways so we we doctor blade it onto
1687
00:56:43,520 --> 00:56:45,520
this aluminum foil i do mine just by
1688
00:56:45,520 --> 00:56:47,359
hand i take like a glass rod
1689
00:56:47,359 --> 00:56:49,280
and i just i put it onto the aluminum
1690
00:56:49,280 --> 00:56:51,440
foil and i just spread it out
1691
00:56:51,440 --> 00:56:53,440
and then i let it dry and after it's
1692
00:56:53,440 --> 00:56:55,359
dried like in this picture
1693
00:56:55,359 --> 00:56:57,839
i'll cut out little little circles with
1694
00:56:57,839 --> 00:56:58,799
a punch we have a
1695
00:56:58,799 --> 00:57:01,040
little like a lever punch that cuts out
1696
00:57:01,040 --> 00:57:02,240
these circles
1697
00:57:02,240 --> 00:57:04,400
um and then we weigh those and then
1698
00:57:04,400 --> 00:57:06,400
everything gets transferred to
1699
00:57:06,400 --> 00:57:10,160
the glove box this is a argon glove box
1700
00:57:10,160 --> 00:57:14,000
so the atmosphere is ultra pure argon in
1701
00:57:14,000 --> 00:57:17,920
fact it's 99.999 percent
1702
00:57:17,920 --> 00:57:21,040
argon and the the expensive stuff
1703
00:57:21,040 --> 00:57:24,160
and uh this glovebox also has a filter
1704
00:57:24,160 --> 00:57:26,559
system where it filters out oxygen
1705
00:57:26,559 --> 00:57:29,520
and water through if there's any leaks
1706
00:57:29,520 --> 00:57:30,720
in there
1707
00:57:30,720 --> 00:57:32,640
and so the oxygen water content of this
1708
00:57:32,640 --> 00:57:34,160
glove box is always
1709
00:57:34,160 --> 00:57:38,400
less than 0.5 parts per million
1710
00:57:38,400 --> 00:57:40,319
every now and then it will kind of bump
1711
00:57:40,319 --> 00:57:42,079
up to it'll start going up
1712
00:57:42,079 --> 00:57:44,559
over time because the the cattle there's
1713
00:57:44,559 --> 00:57:45,119
a
1714
00:57:45,119 --> 00:57:46,799
in the circulation system of the
1715
00:57:46,799 --> 00:57:49,280
glovebox there's a copper catalyst
1716
00:57:49,280 --> 00:57:52,880
the copper will will absorb the oxygen
1717
00:57:52,880 --> 00:57:56,559
and water water from the the atmosphere
1718
00:57:56,559 --> 00:57:58,400
and turn into copper oxide and then over
1719
00:57:58,400 --> 00:57:59,920
time that catalyst
1720
00:57:59,920 --> 00:58:02,319
depletes itself and it has to be
1721
00:58:02,319 --> 00:58:03,920
regenerated and then the oxygen starts
1722
00:58:03,920 --> 00:58:05,359
to go up so every every
1723
00:58:05,359 --> 00:58:07,119
two months or so we'll we'll do a
1724
00:58:07,119 --> 00:58:08,799
regeneration process
1725
00:58:08,799 --> 00:58:11,599
where we we attach the the catalyst to
1726
00:58:11,599 --> 00:58:12,079
uh
1727
00:58:12,079 --> 00:58:13,839
hydrogen so we have a five percent
1728
00:58:13,839 --> 00:58:15,760
hydrogen argon mixture
1729
00:58:15,760 --> 00:58:17,839
and we run hydrogen through the copper
1730
00:58:17,839 --> 00:58:19,680
ox which is now copper oxide
1731
00:58:19,680 --> 00:58:22,720
catalyst and the machine heats it up and
1732
00:58:22,720 --> 00:58:24,559
it reduces the copper oxide
1733
00:58:24,559 --> 00:58:27,680
back into copper and then then it's good
1734
00:58:27,680 --> 00:58:28,319
for another
1735
00:58:28,319 --> 00:58:29,839
couple months before we have to do it
1736
00:58:29,839 --> 00:58:31,839
again so
1737
00:58:31,839 --> 00:58:33,280
that's the regeneration process there's
1738
00:58:33,280 --> 00:58:34,799
a lot of upkeep that has to go on with
1739
00:58:34,799 --> 00:58:35,920
this glove box
1740
00:58:35,920 --> 00:58:37,280
another thing about the working with the
1741
00:58:37,280 --> 00:58:39,119
glove box is that it's uh
1742
00:58:39,119 --> 00:58:40,720
it's not very comfortable because it's
1743
00:58:40,720 --> 00:58:43,119
under it's under positive pressure
1744
00:58:43,119 --> 00:58:45,200
uh and so it kind of feels like you're
1745
00:58:45,200 --> 00:58:46,640
working under water
1746
00:58:46,640 --> 00:58:48,880
and also you know along with the the lab
1747
00:58:48,880 --> 00:58:50,960
coat we also wear like the purple
1748
00:58:50,960 --> 00:58:52,720
nitrile gloves and i also wear
1749
00:58:52,720 --> 00:58:54,720
like these chemical resistant sleeves
1750
00:58:54,720 --> 00:58:56,640
just to keep my lab coat on
1751
00:58:56,640 --> 00:58:58,400
and then we put that into these big
1752
00:58:58,400 --> 00:59:00,240
rubber gloves okay
1753
00:59:00,240 --> 00:59:01,680
and then on the other side inside the
1754
00:59:01,680 --> 00:59:03,920
glove box we also put on extra large
1755
00:59:03,920 --> 00:59:05,839
purple nitrile gloves
1756
00:59:05,839 --> 00:59:08,400
and so we got right already three layers
1757
00:59:08,400 --> 00:59:09,839
of gloves and you can imagine during the
1758
00:59:09,839 --> 00:59:12,240
summer it gets kind of toasty in there
1759
00:59:12,240 --> 00:59:14,720
and then additionally if if we're
1760
00:59:14,720 --> 00:59:16,160
working with sodium
1761
00:59:16,160 --> 00:59:19,599
i work with sodium a lot and the sodium
1762
00:59:19,599 --> 00:59:21,599
comes in chunks of sodium i have to
1763
00:59:21,599 --> 00:59:23,119
actually cut the sodium
1764
00:59:23,119 --> 00:59:25,920
so i use a knife and we've had instances
1765
00:59:25,920 --> 00:59:27,359
in the past where people accidentally
1766
00:59:27,359 --> 00:59:28,559
cut the glove and then
1767
00:59:28,559 --> 00:59:30,799
we start leaking argon out so now the
1768
00:59:30,799 --> 00:59:32,640
rule is we have to wear these giant
1769
00:59:32,640 --> 00:59:34,079
rubber gloves you see them in the
1770
00:59:34,079 --> 00:59:36,240
picture these uh kind of yellowy
1771
00:59:36,240 --> 00:59:38,720
pale gloves that go on top of these
1772
00:59:38,720 --> 00:59:39,520
already
1773
00:59:39,520 --> 00:59:42,160
big rubber gloves so it's it's very
1774
00:59:42,160 --> 00:59:42,880
uncomfortable
1775
00:59:42,880 --> 00:59:46,079
when we're trying to cut things and
1776
00:59:46,079 --> 00:59:48,240
and um the lithium on the other hand the
1777
00:59:48,240 --> 00:59:50,240
lithium we purchased lithium chips
1778
00:59:50,240 --> 00:59:51,520
they're already in the little cert
1779
00:59:51,520 --> 00:59:52,799
pre-cut circles
1780
00:59:52,799 --> 00:59:54,799
so it's they're very convenient to work
1781
00:59:54,799 --> 00:59:56,480
with but sodium
1782
00:59:56,480 --> 00:59:58,559
although however sodium is a much more
1783
00:59:58,559 --> 01:00:01,520
reactive metal than lithium
1784
01:00:01,520 --> 01:00:05,040
and so it oxidizes more easily
1785
01:00:05,040 --> 01:00:06,480
so there's i don't think there's a
1786
01:00:06,480 --> 01:00:09,200
manufacturing method to make the pre-cut
1787
01:00:09,200 --> 01:00:11,920
sodium to be able to ship out so we get
1788
01:00:11,920 --> 01:00:13,760
the blocks of sodium or maybe there's no
1789
01:00:13,760 --> 01:00:14,319
demand
1790
01:00:14,319 --> 01:00:16,640
as well that could also be it but we get
1791
01:00:16,640 --> 01:00:18,000
the blocks of sodium we have to
1792
01:00:18,000 --> 01:00:20,079
slice the sodium and then we have a
1793
01:00:20,079 --> 01:00:22,000
inside the glovebox we have a
1794
01:00:22,000 --> 01:00:24,640
pasta roller just like uh you know
1795
01:00:24,640 --> 01:00:25,280
making like
1796
01:00:25,280 --> 01:00:27,680
pasta from scratch rolling out the dough
1797
01:00:27,680 --> 01:00:28,640
into a sheet
1798
01:00:28,640 --> 01:00:31,839
and so we put the sodium chunk uh in the
1799
01:00:31,839 --> 01:00:33,920
pasta roller and we roll it out into a
1800
01:00:33,920 --> 01:00:35,200
flat sheet of sodium
1801
01:00:35,200 --> 01:00:37,440
and then we take a circle punch and we
1802
01:00:37,440 --> 01:00:38,480
punch out
1803
01:00:38,480 --> 01:00:41,200
the little circle chips of sodium
1804
01:00:41,200 --> 01:00:43,520
anyways so then we assemble the
1805
01:00:43,520 --> 01:00:46,160
the battery inside the glove box we have
1806
01:00:46,160 --> 01:00:47,920
the working electrode on one side that's
1807
01:00:47,920 --> 01:00:48,720
connected to
1808
01:00:48,720 --> 01:00:51,359
the top or bottom of this uh coin cell
1809
01:00:51,359 --> 01:00:53,359
the coin cell is stainless steel so you
1810
01:00:53,359 --> 01:00:54,720
need to make sure that whatever
1811
01:00:54,720 --> 01:00:56,160
electrolyte you use some of these
1812
01:00:56,160 --> 01:00:57,680
electrolytes are very corrosive
1813
01:00:57,680 --> 01:00:58,720
you want to make sure that the
1814
01:00:58,720 --> 01:01:00,160
electrolyte does not corrode the
1815
01:01:00,160 --> 01:01:01,680
stainless steel
1816
01:01:01,680 --> 01:01:03,040
and also you want to make sure that the
1817
01:01:03,040 --> 01:01:06,559
stainless steel does not react
1818
01:01:06,559 --> 01:01:08,559
with your you know when you're applying
1819
01:01:08,559 --> 01:01:09,839
a voltage to it there might be some
1820
01:01:09,839 --> 01:01:11,280
other chemical reaction happening at the
1821
01:01:11,280 --> 01:01:12,480
surface of the
1822
01:01:12,480 --> 01:01:13,680
stainless steel and that's going to
1823
01:01:13,680 --> 01:01:16,079
influence your results but the stainless
1824
01:01:16,079 --> 01:01:18,160
steel it's it you know has a chromium
1825
01:01:18,160 --> 01:01:19,200
oxide
1826
01:01:19,200 --> 01:01:21,680
passive layer so it's it's pretty
1827
01:01:21,680 --> 01:01:24,000
chemically inert
1828
01:01:24,000 --> 01:01:26,160
and then there's the separator that we
1829
01:01:26,160 --> 01:01:27,119
add
1830
01:01:27,119 --> 01:01:28,559
at this point we would add the
1831
01:01:28,559 --> 01:01:30,480
electrolyte so we have like a beaker of
1832
01:01:30,480 --> 01:01:32,720
our electrolyte some of them are
1833
01:01:32,720 --> 01:01:34,720
pre-made that we purchase
1834
01:01:34,720 --> 01:01:35,920
and then some of them we have to make
1835
01:01:35,920 --> 01:01:37,680
ourselves so we have our solvent and our
1836
01:01:37,680 --> 01:01:38,000
salt
1837
01:01:38,000 --> 01:01:39,760
and we add the salt to the solvent and
1838
01:01:39,760 --> 01:01:41,040
mix it up and then we
1839
01:01:41,040 --> 01:01:44,480
pipet it into this uh this coin cell
1840
01:01:44,480 --> 01:01:46,160
then we add the counter electrode which
1841
01:01:46,160 --> 01:01:48,000
is probably just lithium or sodium
1842
01:01:48,000 --> 01:01:50,160
and then in some of the cells we add
1843
01:01:50,160 --> 01:01:52,480
stainless steel spacers and springs
1844
01:01:52,480 --> 01:01:54,559
and then also importantly is that the
1845
01:01:54,559 --> 01:01:55,520
top of the cell
1846
01:01:55,520 --> 01:01:57,680
we you need to make sure that the the
1847
01:01:57,680 --> 01:01:59,359
counter electrode and the top cell does
1848
01:01:59,359 --> 01:02:00,319
not make any
1849
01:02:00,319 --> 01:02:02,400
electrical connection with the bottom
1850
01:02:02,400 --> 01:02:04,160
otherwise you short circuit the cell
1851
01:02:04,160 --> 01:02:08,319
so there's a a plastic plastic gasket
1852
01:02:08,319 --> 01:02:09,839
that protects the two
1853
01:02:09,839 --> 01:02:11,760
and then once you have that assembled
1854
01:02:11,760 --> 01:02:14,799
there's a device inside the glove box
1855
01:02:14,799 --> 01:02:18,079
that that's a press that crimps
1856
01:02:18,079 --> 01:02:20,319
crimps the the button cell so we put in
1857
01:02:20,319 --> 01:02:21,200
the press and we
1858
01:02:21,200 --> 01:02:24,000
we press it down and it compresses the
1859
01:02:24,000 --> 01:02:25,760
button cell so everything's
1860
01:02:25,760 --> 01:02:31,359
uh sealed in and then it can be taken
1861
01:02:32,839 --> 01:02:35,839
out
1862
01:02:40,559 --> 01:02:44,240
so i'll talk uh i'll i'm about to wrap
1863
01:02:44,240 --> 01:02:46,480
it up just a few more slides i believe
1864
01:02:46,480 --> 01:02:49,039
um actually i think i've added more so
1865
01:02:49,039 --> 01:02:50,319
we'll go through it though
1866
01:02:50,319 --> 01:02:53,440
uh some of the different tests we do for
1867
01:02:53,440 --> 01:02:54,079
batteries
1868
01:02:54,079 --> 01:02:56,559
um the machine we use is called the
1869
01:02:56,559 --> 01:03:00,079
potentiostat or galvanostat
1870
01:03:00,079 --> 01:03:02,559
and um this is an example of a
1871
01:03:02,559 --> 01:03:03,520
galvanostag
1872
01:03:03,520 --> 01:03:05,440
we have the same exact one in our lab
1873
01:03:05,440 --> 01:03:06,880
and uh so it has
1874
01:03:06,880 --> 01:03:08,240
many different channels that you can put
1875
01:03:08,240 --> 01:03:10,559
your batteries in and you program it
1876
01:03:10,559 --> 01:03:13,760
um so each channel actually has four
1877
01:03:13,760 --> 01:03:15,680
wires right like i said before for a
1878
01:03:15,680 --> 01:03:17,760
three electrode cell
1879
01:03:17,760 --> 01:03:19,599
you know you have voltage between the
1880
01:03:19,599 --> 01:03:20,880
working electrode and reference
1881
01:03:20,880 --> 01:03:21,440
electrode
1882
01:03:21,440 --> 01:03:23,359
and you have the current between the
1883
01:03:23,359 --> 01:03:24,720
working electrode and the counter
1884
01:03:24,720 --> 01:03:27,280
electrode
1885
01:03:27,680 --> 01:03:30,000
however for the two electrode cell like
1886
01:03:30,000 --> 01:03:31,200
our button cell
1887
01:03:31,200 --> 01:03:32,720
the reference electrode and counter
1888
01:03:32,720 --> 01:03:34,799
electrode will be the part of the same
1889
01:03:34,799 --> 01:03:37,200
same cell so we only have uh you know
1890
01:03:37,200 --> 01:03:39,599
two clamps
1891
01:03:39,599 --> 01:03:42,799
okay um so this is
1892
01:03:42,799 --> 01:03:45,520
one of the most common type of test
1893
01:03:45,520 --> 01:03:46,160
cyclic
1894
01:03:46,160 --> 01:03:48,640
voltometry where voltometry is uh
1895
01:03:48,640 --> 01:03:49,200
basically
1896
01:03:49,200 --> 01:03:51,599
we're we're controlling the voltage of
1897
01:03:51,599 --> 01:03:52,400
the system
1898
01:03:52,400 --> 01:03:55,599
while we measure the current response at
1899
01:03:55,599 --> 01:03:58,640
these different voltages okay
1900
01:03:58,640 --> 01:04:02,799
so this shows uh what at what voltages
1901
01:04:02,799 --> 01:04:04,880
different redox reactions happen at so
1902
01:04:04,880 --> 01:04:06,640
in this example
1903
01:04:06,640 --> 01:04:09,359
we have a sodium vanadium phosphate
1904
01:04:09,359 --> 01:04:11,440
material
1905
01:04:11,440 --> 01:04:14,160
now when you make this material more
1906
01:04:14,160 --> 01:04:16,240
very likely there will already be sodium
1907
01:04:16,240 --> 01:04:18,319
inside the material when you synthesize
1908
01:04:18,319 --> 01:04:19,599
it so
1909
01:04:19,599 --> 01:04:21,359
let's say it starts with it probably
1910
01:04:21,359 --> 01:04:22,880
starts in the vanadium
1911
01:04:22,880 --> 01:04:26,319
of let's see yeah vanadium four plus
1912
01:04:26,319 --> 01:04:28,880
is that right yeah starts out as
1913
01:04:28,880 --> 01:04:31,599
vanadium four plus with one sodium in it
1914
01:04:31,599 --> 01:04:32,480
i'd say
1915
01:04:32,480 --> 01:04:34,799
so in that case if you were to take this
1916
01:04:34,799 --> 01:04:35,920
material
1917
01:04:35,920 --> 01:04:37,839
and it's freshly made and it's inside
1918
01:04:37,839 --> 01:04:40,000
your battery and you were to measure the
1919
01:04:40,000 --> 01:04:42,480
open circuit voltage of this battery
1920
01:04:42,480 --> 01:04:44,160
this material is in the vanadium four
1921
01:04:44,160 --> 01:04:44,799
plus state
1922
01:04:44,799 --> 01:04:46,880
the open circuit voltage would say it's
1923
01:04:46,880 --> 01:04:48,000
around this this
1924
01:04:48,000 --> 01:04:50,960
would be right here so right there's no
1925
01:04:50,960 --> 01:04:52,480
current going through the battery
1926
01:04:52,480 --> 01:04:53,920
you're just measuring voltage it'd be
1927
01:04:53,920 --> 01:04:55,520
right in between here and so that's it's
1928
01:04:55,520 --> 01:04:56,400
at
1929
01:04:56,400 --> 01:05:00,240
the equilibrium state at that potential
1930
01:05:00,240 --> 01:05:02,880
okay and so what this test will do is it
1931
01:05:02,880 --> 01:05:05,119
sweeps the voltage for example let's we
1932
01:05:05,119 --> 01:05:06,160
start with
1933
01:05:06,160 --> 01:05:08,000
decreasing the voltage and as it
1934
01:05:08,000 --> 01:05:10,160
decreases the voltage you start to get
1935
01:05:10,160 --> 01:05:12,319
a reduction reaction if it's negative
1936
01:05:12,319 --> 01:05:14,240
current that's reduction
1937
01:05:14,240 --> 01:05:17,119
so we're giving electrons to the cathode
1938
01:05:17,119 --> 01:05:18,160
of this material
1939
01:05:18,160 --> 01:05:20,079
and we're taking electrons away from the
1940
01:05:20,079 --> 01:05:21,520
counter electrode so in this case the
1941
01:05:21,520 --> 01:05:22,480
counter electrode
1942
01:05:22,480 --> 01:05:25,680
our voltage is v versus sodium metal
1943
01:05:25,680 --> 01:05:27,200
so the counter electrode is just the
1944
01:05:27,200 --> 01:05:30,160
sodium redox reaction
1945
01:05:30,160 --> 01:05:31,599
so we're taking electrons away from
1946
01:05:31,599 --> 01:05:33,359
sodium sodium is dissolving
1947
01:05:33,359 --> 01:05:35,520
into the electrolyte and the vanadium
1948
01:05:35,520 --> 01:05:36,480
four plus
1949
01:05:36,480 --> 01:05:39,039
is uh reducing the vanadium three plus
1950
01:05:39,039 --> 01:05:41,280
and at the same time we're intercalating
1951
01:05:41,280 --> 01:05:44,400
sodium ions into the crystal structure
1952
01:05:44,400 --> 01:05:46,240
okay so that's what this current this
1953
01:05:46,240 --> 01:05:47,599
peak represents
1954
01:05:47,599 --> 01:05:50,079
okay and then and then after that peak
1955
01:05:50,079 --> 01:05:51,039
uh
1956
01:05:51,039 --> 01:05:53,119
we we keep on pushing the voltage and
1957
01:05:53,119 --> 01:05:55,039
there's nothing no reaction happening
1958
01:05:55,039 --> 01:05:57,200
because we haven't met that uh redox
1959
01:05:57,200 --> 01:05:58,960
potential yet for the next
1960
01:05:58,960 --> 01:06:01,280
uh reduction reaction which is an am3
1961
01:06:01,280 --> 01:06:03,359
plus and then the same thing happens so
1962
01:06:03,359 --> 01:06:04,000
we and we
1963
01:06:04,000 --> 01:06:07,200
intercalate another sodium ion into the
1964
01:06:07,200 --> 01:06:08,799
structure
1965
01:06:08,799 --> 01:06:11,440
okay and then at this point now we've
1966
01:06:11,440 --> 01:06:12,799
fully reduced
1967
01:06:12,799 --> 01:06:14,799
vanadium four plus into vanadium two
1968
01:06:14,799 --> 01:06:16,839
plus so you could say this is the
1969
01:06:16,839 --> 01:06:18,400
discharged state
1970
01:06:18,400 --> 01:06:21,119
of the battery and then we reverse the
1971
01:06:21,119 --> 01:06:22,480
voltage sweep
1972
01:06:22,480 --> 01:06:24,000
and then the opposite happens the
1973
01:06:24,000 --> 01:06:25,599
oxidation potential
1974
01:06:25,599 --> 01:06:27,440
the oxidation reaction happens on the
1975
01:06:27,440 --> 01:06:28,880
cathode
1976
01:06:28,880 --> 01:06:32,640
so now sodium is sodium ions in
1977
01:06:32,640 --> 01:06:35,039
electrolyte are plating onto the sodium
1978
01:06:35,039 --> 01:06:36,319
metal so they need to receive an
1979
01:06:36,319 --> 01:06:37,200
electron
1980
01:06:37,200 --> 01:06:40,240
and the cathode uh the sodium vanadium
1981
01:06:40,240 --> 01:06:41,119
phosphate
1982
01:06:41,119 --> 01:06:44,000
is is oxidizing it's giving away an
1983
01:06:44,000 --> 01:06:45,119
electron
1984
01:06:45,119 --> 01:06:46,880
right and that's given that's indicated
1985
01:06:46,880 --> 01:06:48,160
by the positive current
1986
01:06:48,160 --> 01:06:49,839
all right so basically what this shows
1987
01:06:49,839 --> 01:06:51,920
is which uh what potentials
1988
01:06:51,920 --> 01:06:53,760
what reactions are happening although
1989
01:06:53,760 --> 01:06:55,440
you have to have a bit of knowledge on
1990
01:06:55,440 --> 01:06:56,079
like what
1991
01:06:56,079 --> 01:06:58,960
you know what species is being reduced
1992
01:06:58,960 --> 01:07:00,480
in what species it doesn't tell you
1993
01:07:00,480 --> 01:07:01,920
obviously but it can tell you a bit of
1994
01:07:01,920 --> 01:07:03,760
information like the kinetics like how
1995
01:07:03,760 --> 01:07:06,720
how high the current is um and the
1996
01:07:06,720 --> 01:07:08,559
reversibility so this might happen over
1997
01:07:08,559 --> 01:07:10,240
many cycles and see if it's
1998
01:07:10,240 --> 01:07:12,720
repeatable or if the chemistry changes
1999
01:07:12,720 --> 01:07:14,000
you know after if you cycle
2000
01:07:14,000 --> 01:07:16,480
the battery many times perhaps the local
2001
01:07:16,480 --> 01:07:18,400
environment of the vanadium might change
2002
01:07:18,400 --> 01:07:19,680
and what you would see is that these
2003
01:07:19,680 --> 01:07:21,680
peaks begin to shift and
2004
01:07:21,680 --> 01:07:23,680
in potential you say oh it's not it's
2005
01:07:23,680 --> 01:07:25,520
not stable it's not a reversible
2006
01:07:25,520 --> 01:07:26,880
reaction because things are shifting
2007
01:07:26,880 --> 01:07:27,359
around
2008
01:07:27,359 --> 01:07:29,280
right which is not ideal for a battery
2009
01:07:29,280 --> 01:07:30,559
if you want to put in a consumer
2010
01:07:30,559 --> 01:07:32,640
electronic
2011
01:07:32,640 --> 01:07:34,000
so that's the kind of information you
2012
01:07:34,000 --> 01:07:36,559
can get so cyclic photometer again
2013
01:07:36,559 --> 01:07:39,039
controlling voltage measuring current
2014
01:07:39,039 --> 01:07:42,000
i had some examples of psychophotometry
2015
01:07:42,000 --> 01:07:44,319
i think we might skip through it because
2016
01:07:44,319 --> 01:07:47,760
uh we're a bit over time
2017
01:07:47,760 --> 01:07:50,000
on this lecture and my voice is starting
2018
01:07:50,000 --> 01:07:51,280
to go so i'll just
2019
01:07:51,280 --> 01:07:53,359
briefly introduce the second most common
2020
01:07:53,359 --> 01:07:55,680
test is galvanostatic cycling so if
2021
01:07:55,680 --> 01:07:56,720
cyclic
2022
01:07:56,720 --> 01:07:58,400
voltometry was controlling voltage and
2023
01:07:58,400 --> 01:08:01,280
measuring current galvanostatic cycling
2024
01:08:01,280 --> 01:08:04,480
is controlling current and measuring
2025
01:08:04,480 --> 01:08:05,760
voltage response
2026
01:08:05,760 --> 01:08:08,640
okay so this is the same example with a
2027
01:08:08,640 --> 01:08:11,200
sodium vanadium phosphate
2028
01:08:11,200 --> 01:08:14,319
and this this type of test you'll say
2029
01:08:14,319 --> 01:08:16,560
discharge at a certain current so for
2030
01:08:16,560 --> 01:08:17,520
example
2031
01:08:17,520 --> 01:08:20,960
uh 10 milliamps per gram all right
2032
01:08:20,960 --> 01:08:23,120
so you you know the the amount of
2033
01:08:23,120 --> 01:08:24,319
material in your
2034
01:08:24,319 --> 01:08:26,238
battery because you weighed it before
2035
01:08:26,238 --> 01:08:27,600
you assembled the battery
2036
01:08:27,600 --> 01:08:30,319
so you can calculate what 10 milliamps
2037
01:08:30,319 --> 01:08:31,520
per gram is
2038
01:08:31,520 --> 01:08:34,080
for that that battery right and give it
2039
01:08:34,080 --> 01:08:35,759
a
2040
01:08:35,759 --> 01:08:38,960
current oftentimes we use what's called
2041
01:08:38,960 --> 01:08:39,359
a c
2042
01:08:39,359 --> 01:08:42,640
rate uh so this symbol here 1c
2043
01:08:42,640 --> 01:08:47,198
1c is equivalent to the current density
2044
01:08:47,198 --> 01:08:49,759
needed to completely reach the
2045
01:08:49,759 --> 01:08:51,759
theoretical capacity of the battery in
2046
01:08:51,759 --> 01:08:53,439
one hour that's so that's one
2047
01:08:53,439 --> 01:08:56,960
c so 0.1 c or c over 10
2048
01:08:56,960 --> 01:09:00,000
would be what that'd be six minutes
2049
01:09:00,000 --> 01:09:02,719
so it that would be it would take six
2050
01:09:02,719 --> 01:09:03,359
minutes
2051
01:09:03,359 --> 01:09:06,960
to reach the theoretical capacity
2052
01:09:06,960 --> 01:09:09,520
at whatever current that is anyway so c
2053
01:09:09,520 --> 01:09:10,960
rate is often used
2054
01:09:10,960 --> 01:09:13,679
uh and the other common uh current rate
2055
01:09:13,679 --> 01:09:16,000
is milliamps per gram is also the common
2056
01:09:16,000 --> 01:09:19,198
they're they're basically equivalent
2057
01:09:19,198 --> 01:09:22,000
um so in this type of test you know
2058
01:09:22,000 --> 01:09:23,759
let's say we start with our material and
2059
01:09:23,759 --> 01:09:25,120
it's in the charge state
2060
01:09:25,120 --> 01:09:26,719
all right it's fully charged that means
2061
01:09:26,719 --> 01:09:28,238
it's fully oxidized
2062
01:09:28,238 --> 01:09:30,719
vanadium four plus so as soon as we
2063
01:09:30,719 --> 01:09:31,759
start the test
2064
01:09:31,759 --> 01:09:34,319
you know then the voltage will will
2065
01:09:34,319 --> 01:09:35,600
undergo it'll reach its
2066
01:09:35,600 --> 01:09:39,759
uh this is the the this plateau
2067
01:09:39,759 --> 01:09:41,920
the voltage of this plateau is
2068
01:09:41,920 --> 01:09:43,120
equivalent
2069
01:09:43,120 --> 01:09:46,238
to this peak this voltage
2070
01:09:46,238 --> 01:09:48,399
right so you see this is the redox
2071
01:09:48,399 --> 01:09:49,759
reaction happens at this voltage
2072
01:09:49,759 --> 01:09:50,640
vanadium four plus
2073
01:09:50,640 --> 01:09:52,880
the radium three plus that's essentially
2074
01:09:52,880 --> 01:09:55,040
the same as what this plateau is showing
2075
01:09:55,040 --> 01:09:55,520
is that
2076
01:09:55,520 --> 01:09:57,920
this is the reaction happening and then
2077
01:09:57,920 --> 01:09:58,719
capacity
2078
01:09:58,719 --> 01:10:01,440
this x-axis is essentially the same as
2079
01:10:01,440 --> 01:10:02,800
time
2080
01:10:02,800 --> 01:10:04,800
so remember we're discharging at a
2081
01:10:04,800 --> 01:10:06,400
constant current
2082
01:10:06,400 --> 01:10:09,920
and so for example uh 100 milliamps
2083
01:10:09,920 --> 01:10:12,480
and then this is just measuring the time
2084
01:10:12,480 --> 01:10:14,080
and so you just multiply by time as
2085
01:10:14,080 --> 01:10:15,679
milliamp hours and that's capacity
2086
01:10:15,679 --> 01:10:17,360
so this kind of shows how much capacity
2087
01:10:17,360 --> 01:10:18,880
there is in that material
2088
01:10:18,880 --> 01:10:20,719
and then it reaches a certain voltage
2089
01:10:20,719 --> 01:10:23,199
and uh this is a bit arbitrary we
2090
01:10:23,199 --> 01:10:25,679
we decide as a user when to stop the
2091
01:10:25,679 --> 01:10:26,320
test
2092
01:10:26,320 --> 01:10:28,560
you know say like oh this this person
2093
01:10:28,560 --> 01:10:29,920
could have stopped the test at 3 volts
2094
01:10:29,920 --> 01:10:31,520
or it could have stopped at 3.2 volts
2095
01:10:31,520 --> 01:10:32,320
and it would have been
2096
01:10:32,320 --> 01:10:35,760
more or less the same although this
2097
01:10:35,760 --> 01:10:39,040
this study didn't go to the further
2098
01:10:39,040 --> 01:10:40,640
reduction state of vanadium iii plus the
2099
01:10:40,640 --> 01:10:42,800
venem 2 plus so that's and this is the
2100
01:10:42,800 --> 01:10:44,239
fully discharged state just from
2101
01:10:44,239 --> 01:10:45,920
vanadium for the video three
2102
01:10:45,920 --> 01:10:47,440
and then what you'll do is you'll
2103
01:10:47,440 --> 01:10:49,199
reverse the current so if we this was
2104
01:10:49,199 --> 01:10:51,040
negative current to discharge
2105
01:10:51,040 --> 01:10:52,640
then you'll reverse it the positive
2106
01:10:52,640 --> 01:10:54,159
current the charge and so you'll
2107
01:10:54,159 --> 01:10:56,480
you'll go back to the origin and it'll
2108
01:10:56,480 --> 01:10:58,400
go up and this is the
2109
01:10:58,400 --> 01:11:00,560
the charge potential the plateau
2110
01:11:00,560 --> 01:11:02,159
representing the vanadium three plus the
2111
01:11:02,159 --> 01:11:04,800
m4 plus reaction and then again it's
2112
01:11:04,800 --> 01:11:07,199
arbitrary when you want to stop the
2113
01:11:07,199 --> 01:11:10,239
test so that's a galvanostatic rate
2114
01:11:10,239 --> 01:11:12,000
stability is another uh
2115
01:11:12,000 --> 01:11:14,320
very similar test where you're changing
2116
01:11:14,320 --> 01:11:16,400
the current rate that you're discharging
2117
01:11:16,400 --> 01:11:18,159
or charging battery at so that's again
2118
01:11:18,159 --> 01:11:19,120
with the c rate
2119
01:11:19,120 --> 01:11:21,199
representing the current rate so like i
2120
01:11:21,199 --> 01:11:22,159
said before
2121
01:11:22,159 --> 01:11:24,560
as you increase the current rate the
2122
01:11:24,560 --> 01:11:25,520
your your re
2123
01:11:25,520 --> 01:11:27,679
you're bumping into certain kinetic
2124
01:11:27,679 --> 01:11:28,960
limitations of this
2125
01:11:28,960 --> 01:11:31,280
uh electrochemical cell for example the
2126
01:11:31,280 --> 01:11:32,800
lithium diffusion
2127
01:11:32,800 --> 01:11:35,199
in your material or the electrical
2128
01:11:35,199 --> 01:11:37,040
conductivity of your material
2129
01:11:37,040 --> 01:11:39,600
or perhaps the the there's an energy
2130
01:11:39,600 --> 01:11:40,080
barrier
2131
01:11:40,080 --> 01:11:42,719
for electron transfer between your your
2132
01:11:42,719 --> 01:11:45,040
electrode and the material
2133
01:11:45,040 --> 01:11:49,199
so if you try to increase the current
2134
01:11:49,199 --> 01:11:51,360
higher and higher you're reaching those
2135
01:11:51,360 --> 01:11:52,960
kinetic limitations which is going to
2136
01:11:52,960 --> 01:11:53,440
start
2137
01:11:53,440 --> 01:11:55,600
dropping the voltage all right because
2138
01:11:55,600 --> 01:11:57,199
there's going to be a voltage drop if
2139
01:11:57,199 --> 01:11:58,719
you have a resistance it's essentially
2140
01:11:58,719 --> 01:12:00,239
the same as v equals ir
2141
01:12:00,239 --> 01:12:01,760
if you have a resistance and you
2142
01:12:01,760 --> 01:12:04,400
increase current the voltage
2143
01:12:04,400 --> 01:12:06,000
drop in this case a voltage drop
2144
01:12:06,000 --> 01:12:07,760
increases so if we were to take this
2145
01:12:07,760 --> 01:12:08,400
plot
2146
01:12:08,400 --> 01:12:10,320
and increase the current we would expect
2147
01:12:10,320 --> 01:12:11,920
this plateau to get smaller and smaller
2148
01:12:11,920 --> 01:12:13,199
and smaller and smaller
2149
01:12:13,199 --> 01:12:14,880
and then also the the capacity would get
2150
01:12:14,880 --> 01:12:16,400
smaller and smaller and smaller as well
2151
01:12:16,400 --> 01:12:17,760
that's what we see exactly here as we
2152
01:12:17,760 --> 01:12:19,280
increase the current our capacity is
2153
01:12:19,280 --> 01:12:21,600
getting lower and lower
2154
01:12:21,600 --> 01:12:26,239
okay um yeah i think we'll stop there
2155
01:12:26,239 --> 01:12:29,760
we covered a lot and now it's uh
2156
01:12:29,760 --> 01:12:32,080
uh some of it's a bit complex but i i
2157
01:12:32,080 --> 01:12:33,760
hope you guys kind of get a
2158
01:12:33,760 --> 01:12:37,280
broader understanding of kind of battery
2159
01:12:37,280 --> 01:12:38,640
materials energy materials and
2160
01:12:38,640 --> 01:12:41,600
electrochemistry is there any questions
2161
01:12:41,600 --> 01:12:51,840
about what we covered
2162
01:12:52,880 --> 01:12:54,560
all right if there's no questions i'll
2163
01:12:54,560 --> 01:12:56,320
see you guys thursday um i haven't
2164
01:12:56,320 --> 01:12:57,040
planned out
2165
01:12:57,040 --> 01:12:58,400
exactly what we're going to cover
2166
01:12:58,400 --> 01:12:59,520
there's a lot of slides i haven't
2167
01:12:59,520 --> 01:13:00,400
included
2168
01:13:00,400 --> 01:13:02,880
um about some of my own research in the
2169
01:13:02,880 --> 01:13:04,800
battery results
2170
01:13:04,800 --> 01:13:06,880
some of it's kind of interesting but i
2171
01:13:06,880 --> 01:13:09,840
still want to talk more about maybe the
2172
01:13:09,840 --> 01:13:13,600
the data analysis a bit so i'll find
2173
01:13:13,600 --> 01:13:16,960
something to talk about on thursday
2174
01:13:17,040 --> 01:13:19,040
and if there's no questions you guys uh
2175
01:13:19,040 --> 01:13:33,840
are good to go i'll see you on thursday
2176
01:13:47,760 --> 01:13:49,840
you
143508
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