Reinventing Batteries

Public lecture presented by Yi Cui

Batteries are needed everywhere, for consumer electronics, electric vehicles, and large-scale energy storage on the electrical grid. All of these applications are limited by the capacity, lifetime and safety of current battery technologies. This lecture discusses new chemistries and materials, now being explored in the lab, that could transform the effectiveness of batteries. The new battery materials require nanoscale engineering, and an important part of this work is the ability to observe their performance during battery operation at the scale of atoms and molecules using the X-ray beams at SLAC. These new approaches put us on a path to storing much more energy in a given volume of battery material, thus making batteries smaller, lighter and cheaper, while also increasing their safety and lifespan. 



okay so good evening and welcome to the

next installment of the slack public lectures we're very lucky to have as our

speaker today Professor each way from Stanford University from the Department

of material science and engineering the topic is batteries batteries used to

be considered some kind of irrelevant technology but today we all worry about

things like my iPhone is too heavy to stick in my back pocket my hoverboard is

going to blow up or my Tesla isn't going to make it to LA and so these are these

issues have become very relevant and professor shui is one of those people

who really has just one innovative idea after another for how we're going to

make the batteries of the future he got his undergraduate degree from the

University of Science and Technology of China from there he went to Harvard

where he got his PhD and he was a miller fellow one of these prestigious fellowships given by the University of

California at Berkeley now he's an associate professor here at Stanford has

a big lab with students who keep marching toward the future of batteries

and that's what he'll tell us about today so please welcome professor Shui

right great honor to speak in select public

lecture to I be joining stand for faculty for 11 years

this is perhaps the most prestigious lecture I'm giving looking at the audience right

here for a few high school students I can spot from their age quite a number

seniors right here also so it's really good crowd right here I know I was

making joke we so Mike I said the the lecture I'm giving only two words right

there will be inventing bare face from the non boom audience divided by the

number of words in the title I probably score the record right so so it's a

great honor absolutely from this a big crowd or audience everybody knows how

important the benefit is Mikey you know a few sentences introduction let me you

know step all the way back to the time when I was still a kid in elementary school right this is that the time use

use you saw this oh this is really big so I was thinking you know as a kid I

say what's the purpose first time seeing in Isaiah is for self-defense or something you know you carry something

like that big power you can serve the function right and then it it goes as

smaller and smaller and smaller so you look at this you say what our sorry

Kannada electronics is getting smaller we integrate more transistors on there

certainly we can make things smaller indeed a major reason to make this smaller it's not our computer chip it's

the size of the batteries right there our batteries is getting better and better right so what you will be

wondering whether this chain will go no stopping now the history actually works

right so this is what's happening so from generation 1 or iPhone why you

feel very comfortable put into your pocket tune our iPhone 6s plus it's

getting bigger bigger than what's going on so so you all know the answer it's

the belt is inside you open the phone you look at this these little is the

batteries it's occupied most of the space that actually determines how big

your phone is so this is the from your day to day life you know about this so

many exciting things are happening in the past ten years or so this is the adj

I John frying if you have it you know it's about 15 minutes right so changing

batteries is a big hassle right there Tesla I bet you got to be 10 Tesla from

these audience in the parking lot right there when I come in I actually saw a number of them 250 miles range also

that's the problem coming up go to LA not quite enough go into the supercharger station stop for half an

hour then you are ready to go so how far this can go and then station a storage

is important in California we passed the law we know we need 50 percent

renewables right if I'm solo from wind from your nuclear so in order to

integrate these into the grid they are intermittent energy sources

they fluctuate a lot so gree can not take 50 percent without energy storage

so you look at this you get all these a picture together this is the picture you

are seeing from the form the amount of energy carry in your pocket perform is

10 one hour what is power times our times time but

that's energy that's the unit remember we have a billion pieces form so every

year roughly so time together this is 10 to the 10 what our it's gigantic

well that's a roughly you know 15 to 20 billion dollars industry right now and

the Jong is a little bit bigger seven times is seventy one hour

Tesla 85 kilowatt hour so there's a lot

more assuming we want to have a million evey of Tesla idea this is 10 to the

11th one hour much bigger than the phone can consume 10 times more so you need a

lot more batteries right there there's a major motivation when alumni figure this

is a it is know in now batteries I can buy if the whole world you know production is dedicated to me

to the Tesla car so he's building the gigafactory top with a wool production

and let's look at the green so every morning you know you woke up we have

about 20 Giga watt of power right there and then climb up very fast about 30 35

or so by the time we get to 50% renewable we need to store this energy

roughly you need to be a really big bear they right there that's equivalent to

this is a million evie 10 to the 11 what our gigantic the homework can go to a

hundred times bigger than that so this huge demon right there and and

then the question you want to ask is how far the bare feet have not you can go

can really satisfy the demands application in all these areas so you

look at the relevant parameters how much energy you stop a unified away that's

kilogram and per unit volume that's lethal right there for your cell phone is probably the

leader you care the most for the car you care about a kilogram first and then

certainly the liter as well the cause is the major roadblock right now so that's what Tesla a smaller is

somewhere around 180 thousand dollars right so the the model

three claim to be $35,000 and when it comes out so the cost is a big thing in

a cycle life also for York I was three thousand for your briefs stories you

want ten thousand charging way everybody wants to do it you know plug it in and take it out it's all full everybody

wants that but it's impossible so how fast can you charge so safety is

important you have seen you know accident so what the battery can be may

ultimately safe those are the questions we try to answer and my group and many

research group are wrong they will try to answer as well so let's look at where we are right now what's really needed

lithium-ion batteries has been the most high performing batteries in the world

the the most well known chemistry let's look a little man battery is there now

in the future golf this is in a cell level when I define cell I mean those are Solander you see this individual

unit of the obra cell you see this is system level it's also referred to the

whole packaging if you have Tesla car you pack a lot of behaviors together you

do grease gear storage is the whole system cost so let's look at energy now

the cell rafi somewhere close to 200 watt hour per kilogram out of 20 what five years

development we are something wrong there we want to get to 600 why because your

car will run 750 miles that would be nice all the way to San Diego and you

can go to LA and come back still work like no charging so for the long term for the short term I will be very happy

we get 500 miles of double will be good enough

but as a research goal we might like to target and universe here let's do 600 if

we fold out before to 500 or so so to a table that's not too bad right so a

system level this Rafic held by half depending on how cool you can do your packaging the cost in the cell level we

are roughly $150 per kilowatt hour

system level is 300 to 500 because you put in all the safety system temperature

control we have a management system this will add up the cost we would like to

get to eventually system level 150 that's what the polymer energy

calculated in order to make Eevee deploy in a big scale general public can take

the cost and you need $150 per kilowatt hour for the greased gear storage is the

same number as well and that's cycle life I mentioned three thousand and then

10,000 for the grid so eventually you also want to safety to work how very

safe batteries looks like you're really working in domain is a multiple

parameters you would like to get to but let's emphasize the most important one

first that indeed a cost the cause we

still need to cut down quite a bit we wanted to get to a 70 you know in the

cell hundred fifty system so you say how do we do this we already do have been

doing lithium-ion benefits for the past 25 years our learning curve just drive down the cost so much can you feel

squeezed a lot of you know unnecessary cost to make a day of the price that

cost lower maybe getting down to 150 is hard but if you want to get to that low

looks like the most powerful norm you under tuned is the energy when the main

energy density high for the same weight same size of the where you store more energy than the

cost dollar per energy per kilowatt hour will be reduced so that becomes clear

after looking at this and say whoa let's make higher energy density berries with

the similar manufacturing cost then we can made a cost per energy lower we can

extend an actual car range and these are revolution as we are speaking is really

coming and the transportation in the grid and in also getting more renewable

into the grid so that has been the they are we really a clear focus for the past

11 years for my group but let's look at how do we get to high energy high school

physics I believe everybody understand this equation right this is the energy equals

to voltage multiplied by the amount of charge okay so I want to get more energy

what do I do right this this and it goes up high

wattage and large amount of charge and

then eventually is energy dense per way involved I want to pick the lightweight materials I can store these a charge I

want to have small model so it's the game to go into periodic table to find

what's lightweight what can you do with that so now let me come back to you know

really share with you this is the highest tag and also the easiest way to

understand how do you find a bare-faced by materials let's look at the cell

first and then we'll come back to look at it so leave your mind is used right

this is the cylinder cell this is what Tesla use 7,000 of them pack into the S

model I to to produce this amount of energy you cut it open

this is a Jerry roll inside and then if you look into that a little bit more and this

jelly roll is zooming and one of these you know two layers one is a negative

electrode also call and know the other is the positive electrode called cathode

positive electrode has this aluminum foil on the surface you have coating of

this particle called lithium cobalt oxide and the other you'll actually is a

copper foil about five to ten micron the aluminum foil similar about ten micron

also and having this practical coating and then you have a separate it's a

polymer is a nano porous has a lot of pores inside and you feel in the organic

electrolyte it's a liquid with lithium salt right you charge your battery

you're pumping in electrons it goes to the air now lithium will come in and store inside a crystal structure and

then when you use electricity you go the other way lithium will come back to lithium cobalt

oxide so this is also called rocking chair over storage leave them go in to

one side and come out and come back to the other side so in order to make this Paris to work

just a little bit science on that on that it's a material so important this

graph I particle right there labor has a carbon six this lithium cobalt oxide practical materials are important first

of all they need to move electrons electron needs to go from outside and jumping into individual of this particle

and meet with lithium ions the second is lithium ion needs to diffuse back and

forth and the liquid and also go into individual particles you also

accompanied with this a process there might be some structure change a little

bit of volume expansion and contraction because ions they all have certain diameters

they need to squeeze their way in right so and the fourth thing you need is on

each of these particle surface they are soaking into electrolyte why

for three years imagine you know I sit in water for three years what happened

you get corroded away right so the only reason this particle can survive is it

has cell passivation layer if we a mist is organic like to lie a little bit forming a very thin layer of coating

let's say a 20 nanometer to 100 nanometers also will protect its particle from a further protein away

so allow you to have this battery running for multiple years so you need

these few things now let's come back to look at this basic structure and and see how do we get high energy out of it you

increase the voltage the voltage is defined by these materials to set your

limit right there because the higher the voltage you are going to decompose your

electrolyte more and more we are now already reaching somewhere close to 4.5

what the most Republic can do is 5 so we

have about 10% we have about 10% only to go higher and then you say I want to

increase the energy what do i do as you play with charge it's the electrons you

want to store and in orders to story electron what do you need to do why do

you need lithium-ion the reason is it like to all have negative charge they

don't like each other and then you need to balance the charge these are really heavy

positive ions right there they combine they become charged no sure they are

happy you stole a lot of that by and then you know well these are ions and

electrons when they meet well they don't want to meet along I often use the idea

I say you know boy I'm going dating you cannot get them to just walk on the road right so and then they need to go to a

restaurant this is the restaurant so they need to meet gigantic very heavy so

this is your house materials and they meet right there ok judge Neil Cho fine so in order to stop

energy I want to put in a lot of electrons that's really the charge carrier during the world power your

electric car now you want to pick this M that's the ions you want a light weight

the light is Ray and periodic table is hydrogen is proton atomic weight one

leave your missile one sodium 23 magnesium 25 but remember magnesium

aluminum why here they have 2 + + 3 + charge if you put 1 irons in they can

balance 2 electrons 3 electrons so it's good but it's other consideration so

these are some of the element you see you know a letter a severe fear I we use

a lab and and also proton to coming to balance the charge however the second

consideration is is the voltage if you take proton that's a water you increase

the Walt is roughly about 1.5 while you starts to split water January hydrogen

gas so that's not good so the voltage over these a proton base

pair is not high enough but leave them most electropositive element allow you

to go to high voltage 4.5 sodium will be a little bit lower and then these will be you know even lower so you see the

reason now Veeam combined is a reasonable lightweight you know ii - proton but produce the highest voltage

why is dominating the battery technology that's because of his high wattage Pross very lightweight and now the question is

what about the cost if I pick lab so

cheap right two dollars per kilogram I pick hydrogen nearly free that's water

so if I put lithium it get up to much higher so when you look at this you say

my god this is no sustainable we'll come back to that topic I'll tell you right now one thing is lithium cause in the

bear is only less than 3% it doesn't yet it's the cobalt you put in the

gratify you put in the electrolyte you put in the subway that you put in that costs more money

lithium actually doesn't cost that it doesn't cost that much so grandpa has

been used as the negative electrode he has these are destroying is this a

carbon atom linked together to form graphite it produced this layer by layer

structure right between the layer interaction is weaker graphite snow as you know lubricant that's because of

this layer structure lithium can be charged inside these are your lithium

ions in there now so you have a negative electrode and what's the choice

beyond graphite if you look at the new material silicon was sitting in Silicon

Valley right here every time I see silicon I get excited I say well that's is that the whole valley is that know so

much about right so she silicon can still a lot more it's the lead them coming in through p4 magnets of on graph

I let him come coming in creve this is a silicon silicon bonding and for medium silicon bonding this number compared to

that number 11 times I leave the matter itself also stole a lot so we have

choices much much better choices ten times more storage so why not using this

right well let's look at the cathode then a positive electrode lithium cobalt

oxide everybody's cell phone and laptop now use lithium cobalt oxide and now

leave the manganese oxide this is and GM's the water is a lithium manganese

oxide for the electric car and lithium ion phosphate most of the Chinese the

electric car company used within Maya phosphate so they all have this crystal

structure either consists of two dimensional structure which leave them so for intercalate in and coming out or

these are three dimensional structure this yellow ball or these a one-dimensional structuralism can go any

now into this host they are stable

what's the choice for the future let's look at this solver software eight

elemental materials or molecules a of

these a soft atom forming a beautiful ring it's like a cone shape right and

then we always leave them produce lithium salt I forming a new crystal structure this is a cubic structure you

know this is lithium in a boundary solver they're completely different form

a ring to a cubic structure you want to charge up your battery and discharge back and forth now you see the problem

there are very different structures compared to this this is a two-dimensional structure never change

that much lithium just come in and out so that's a lot easier so however if you

can mainly some new materials to well I told you about silicon about lithium metal about sulfur this is a mono energy

you can stop a unit way only consider these active house material to store

lithium if you this is current I'm not using carbon combine these these

positive electric cathode when you do so I can as the negative silicon hand only

the matter and no you look at the future you say i want three times more that's

right here you can find silicon and solve a combination you can finally the

metal and sulfur that give your system more energy per unit way we do have a

barefaced chemistry that could potentially offer you get to 3x soft

ways very low cost we all know right solver is the byproduct of petroleum

refining and there's a lot of that in the mountains over solver waiting for

you to to take away so why not doing this new chemistry now let's look at a

learning curve past 25 years we live from lithium ion batteries dou square

Phi lithium cobalt oxide they can see the stable host this is what you learned

for past 25 years anything that's not stable is considered a failure for the

way f'hace however I want to stole a lot of charges I have no choice it becomes

unstable and stable from there's a chemical bond breaking from the host

atoms all those atoms solve for silicon are moving to very long distance you lose control big structure change big

volume expansion ten times more than the the materials you live on the past so

how do you handle those looks like there's no answer for that ten years ago

so from all the atomic bombing scare to nanoscale individual particle the Holly

lecture the whole packaging just look like a mess there's no way you can handle those those problem that's why I

call the inventing batteries all the thinking needs to change the period that needs to be shifted how do you design

the materials to solve this problem to enable neo chemistry for example today

I'd like to emphasize how important there are advanced tools develop for

example its lack help you to understand the challenge you can really design the

materials I will use example nanotechnology to design materials to

enable silicon nano from eleven years ago when I joined in factory knowing nothing about my office until now we

have a commercial product on the market based on silicon giving the highest energy density is also I believe from

now to future ten years silicon Anna will be driving the battery revolution

and if you look at Illamasqua announcement he also said he's going to put silicon into the gigafactory so you

might see that in the future for the greased gear storage so big new ideas is

needed how to do grease gear storage eventually bear his safety this is an

area looks like it's not much invention so we started to look into this area and try to design the bear way from the

first principle and say what do we what can we do tomato bath is

intrinsically safe so I'll tell you about four small stories look have a

look at the first one otherwise - to watch the barefaced operation so you

look at your batteries in your phone how many times have you thought about do people understand how bad is work right

the first time I work on bare face I also ask this question the answer was no no we don't understand how the battery

so it's just like a black box it's amazing it's working so x-ray is very

powerful tool so in about two weeks I need to take take my boy to to the

dentist again so this is the tiny guy well x-ray so you tu hit the beeping and

then this is the image coming out you can tell this person's teeth it's not bad healthy there's something going on

so x-ray is powerful for you to see whether this cavity where it is something bad going on you sit even

color right there why this tells you what's going on this is very small and

in a very small room you can hold this it's like why here we have a gigantic

weapon all right so that's this this is

gigantic so this is small this is about couple miles so I knew it this is like quick x-ray machine while shooting so

this is this electrons and the high vacuum going in right air traveling

giving you this you know eventually the x-ray signal so this is what extremely

bright has a high intensity or having a high spatial resolution much more than

the the dentist's x-ray having a very fast you know phantom second type of

resolution for you to study you know not just for now it's an electrons atoms

molecules so let's I biological cells and so on India dynamics so using this - let me highlight one

example you can actually do a microscopy using this x-ray using actually here and

the single channel radiates laughs that ring pattern you see this is

Mac Tony this is Johanna you know working on these using extra focus on the sample you can do the imaging you

know taking that using this CCD to to capture what's happening and in the

materials not only that you can actually in the sample you put in you can put in

a real batteries right there you are doing charging discharging during this

process watching what's happening so an example showing you right here this is

so-called tomography right 3-dimensional although particles when you believe them

going in this is 5 micron scale bar you see that kind of expand 3 dimensionally

you take lithium how you see this particle now crack so an example right

like this can tell us number one how do they crack where do they crack and

what's the smallest dimension they don't crack anymore so did teach this teach us

a lot come back to designer materials and it was the particle size we want we

want them to be small now they don't quack anymore eventually this helped you to do better

charging discharging over many cycles in combination means a technique like this

let me also highlight another tool this was a available roughly about 5 years

only the Stanford slack right here we have a one of these technique this is a

transmission electron microscope and this is a tiny hole you see right here

this is so for the sample rod in the holder you can insert it into these are

these tiny space this electron beam coming down this is the important part

you put your sample right there then you see it under electron beam and if we can

mount our sample this way if you zoom in looking at this we put a metallic pearl right there we came on our silicon you

know fausto lithium we bill a single nano structure of every

inside transmission electron microscope have a lithium cobalt oxide that's your

catheter having a little bit of electrolyte inserted right here apply water it should not start to charge and

discharge your batteries during this operation you use electron microscope to

watch what's happening to your materials not only the wires but also the particle

now let me show you one of this video now notice that this is 200 nanometer

scale bar right so now I'm going to charge up this a silicon on the a no

wires no lithium coming and you see it was bigger and bigger right diameter

increase a lot and the surface coating of copper is broken

so we learn a lot you we now know why silicon for so many years couldn't work

as a battery lecture because it just play everything surrounding it so how can you make it to work not possible and

not only that the silicon visa silicon structure when they stole leave them coming in they commit suicide let's look

at it this is a particle 800 nanometer

to establish you pull it them in you see this twisting silicon Coast ring this is a lithium silicon arrow I start forming

at the beginning all very happy going bigger and bigger as soon as it gets to certain size

if I not itself you know the stress the strain is too big so he has to commit

suicide in order to relax the strain so this is a broken so after that what

happened the barefaced die your cell phone you know no ii oh no no power anymore right so that's the consequence

because this particle broken apart they are not connected electrically anymore

so we learn a lot using this 210 they help us to guy the material design was

the critical breaking size 150 nanometer for the particles these guys too big

nano meters cannot survive nano why about 300 now knowing this we know

through small things are great they need to be small enough now let's design the materials to make

make it to work so so this is the phenomena I was describing silicon take

a lot of lithium 11 times of graphite capacity wall of expansion to four times

imagine that that's a lot right if you look at the furniture I remember when I

was a little kid you know summertime calm my mind my hometown or was very hot during summer and then wintertime it

gets cold it goes to this cycle in a Harding hole and the furniture actually cracked

that's only probably 10% you're talking about four hundred percent right here

how do you work breaking how do you build stable sort of solid electrolyte

interface remember individual particle surface soaking into a lecture life or three years for electoral car you won

ten years for greedy one twenty years how do you make it stable if this volume expansion during charging

and during this charging more in shrink so no state will interface self is right

there how do you do that so we learned a lot so let me give you up you know quicker ten years of research right into

what two slides what we use nano why there's more now they don't play and then we do Kostya is more stable and

then we do hollow you know even more stable but no stable interface and maybe do you find out the design that will

hollow structure it just keep coming now we are eleventh generation so that's my

ten ten eleven years at Stanford so that's what I did so to slice oh but let me highlight a

few to share with you the thinking what's the design principle why do we

know the volume expansion happening he breaks so small things don't break number one you need small small guys and

then there is a because a volume expansion is going to squeeze the surrounding environment in order

to break the salami and wine what do you do leave some empty space right there how do we do that we take a silica

nanoparticles 80 nanometer in diameter small enough they don't play anymore and doing a well other ones nano

material synthesis we can design empty space right there just fit exactly to a

common that it's volume expansion these are conducting carbon coating right there so make sure this expensive

don't crack your coating we packed all this particle together a hundreds of

thousands of these particles forming second or a particle like this why do we

want to do that that's because individual nanoparticle the surface area to volume ratio is too big they're going

to react with electrolyte consume too much relax your life pack into secondary secondary particle electrolyte only wet

outside we reduce the surface areas we are also having something to increase

the mass loading because we pick so many materials together efficiently on to run

a lecture so we can have more capacity to store leave them and this help dense

packing so for the charge storage capacity per unit volume can go up if

they don't pack where everywhere occupy too much volume even though individual particle can store a lot of lithium but

you won't waste a lot of space so that's not good so we designed this it's Co booming booming granite like structure

so we made this right so this is a nanoparticle packing - what about one

micron in diameter these probably have you know fifty thousand of nanoparticles

in there once you get to here these are you know a few hundreds of thousands of

particle all packing together and the electron microscope let's look at it a little bit more carefully you see the

empty space the stack space is empty is air inside this bright is the silicon

nanoparticle is each one of them having some empty space isn't that amazing

nanotechnology can do this I have a hundred thousand of these particles right here each one of them

we'll have their own space when they want to expand expand they don't track

the environment so and now you use these

to build a battery lecture you do the coding you put a lot of material onto metallic foil right you start to measure

its capacity per unit gram of silicon you see this is the capacity of silicon

and silver to is to our charging discharging speed is stable if you don't

have these a packing leave without empty space this capacity will decay fast and

also using this structure these parameters called columbic efficiency

that's this plot right here what does it mean let me explain a little bit you know when you store electrons into bare

face you put 1000 electrons in you need at least 999 electron coming out you

allow to lose only one a lot of thousand this is the one we are getting close not

in my upon a cell and you want 99.9 what does this mean this tells you if you

lose two electrons every time they've got to be psych chemical reaction happening right there if it's a 98% you

will calculate by the way is capacitor from is a capacity is 1 next likewise 90

a next psycho is 98 times 90 a next cycle is 9898 and 98% after 100 cycle

you don't have capacity anymore right so you need this hydraulic efficiency this

is the indication we can reduce our chemical reaction by packing this particle into the secondary particle

reduce the surface area effectively so we have also high capacity loading well

after this this was 2014 I've been a faculty for nine years now our

generation I up to that looks like done so we saw all the problems no not yet

not yet so all all all the way come come back - as

a cost nanoparticle we still need to learn how to make it cheap enough it's

still high cost because things are a cheaper if you take silicon right

anybody knows solar industry you know silicon was the silicon cause right now per kilogram well you're talking about

probably in the order of ten dollars or less right now polysilicon right but if

you have nanoparticle how much does cost a few years ago as the causes is as high

as gold so that doesn't work so it's now cheaper and the future public can get

cheaper for the nanoparticle but let's see if you can do one two three micron

is as cheap as graphite or cheaper it's no more charges store more energy so if

you can get my comp article to work that's a big bit before for ten years I

don't believe I have never bleep micron particle to world by the back of my mind

I always ask myself if I can make it to work it got to worth it how do how how do we

do it I was telling you big guys will play where they break into pieces the batteries die they also in encounter

ezel actual I build these so-called solid actual interface i chemical reaction compound very dry very fast

however imagine if you can come up one idea to make it to work with all these

attendees learning it's worth it so the idea come so that's this so you

have micron particle for about ten years my group learned a lot how do I build a

page they will loom for individual particle one if I can build a cage right

here this black color one is robust enough if it's micron particle Brady

brain inside they cannot fly away right this cage is electronically conducting

then I might have a chance to get it to work even they braid the brains they don't go outside so it's still my

stuff so my wall let's find the strongest page right there so to not to

be in the past 15 years where you heard about Nobel Prize of graphene graphene is very strong mechanically is

conducting electricity so if you can build Raffi multi layer graphene that's

basically guava right and then volume expansion happen you leave some empty space right there and if you don't leave

that you know even graphene cannot hold it because volume expansion is four times it will play your chemical bonding

of carbon carbon leave some space and this graphene respect they're strong

enough they're kind of how they shave you know try to keep all the silicon inside so we made this silicon micron

particle we developed synthesis doing a nickel coating get a little bit carbon

coating right there 450 degrees C not too high temperature turned out to be

this nickel is a catalyst to grow carbon into a graffiti carbon actually Nikko

leave the empty space you see now there's a page right here surrounding this black dark color of a silicon and

if you go to high resolution of transmission electron microscopy you can tell it's a graphene graphene packing

right there so let me show you up a couple well

video to tell you how amazing this graphing page can be which is all hi

what happened if you know a little bit about materials what carbon can be very

expensive one what diamond right can be very very you know cheap one is coal

somewhere in the middle is graphite and it is amorphous carbon it's all kind of carbon right there

so easily you when you make how many become a more force you can build this

amorphous carbon you know a shell its cage you can also have this graphene

cage let me show you that the difference is dramatic

somehow this video format is oh okay

show up that's good so this is the one that's graphene how you know inside

that's your microscope we use this team to push on these a graphene now you see

this a hollow shell this is really thin now banks back it's actually very resilient very flexible you push on it

it comes back you recheck the tip it comes back you can do this multiple times this may ask thing this is a plain

material function s cage if silicon play inside is kind of like silicon bonds on

to the graphene you know and push the graphene graphene doesn't play and then get contained inside but if you look at

a more first silicon or so amorphous carbon that's right here you push on

this amorphous carbon now you take it back you see it doesn't bounce back

anymore it's broken so using

graphitic having become important it's conducting so we actually use this with

your bare face right so now capacity is stable with this micron particle if we

down this case you see control sample will just capacity k very fast and not

only you have a stable capacity if you look at the electro or metallic foil

this is a cross-section and in the beginning 15.5 my copy become 17.2 only

expand a little bit in the electro level but the bare silicon particle without is

graphing cage will be broken expand a lot to 30 micron three times this is the

killer to your battery you don't want your lecture to expand if you latter expand is going to squeeze your

packaging and liquor and your packaging will be broken you look how they'll actually that's dangerous so this is now

also solve a lot your lab expansion so before my lecture there's somebody asking me

are you going to talk about commercialization I will just show one slide so this is not for the white

husband just for showing you so 2009 I found this company co-anchors

individuals have board meeting this afternoon it's looking at quite quite exciting the company's progress 2013 we

start to have a barefaced out on the market continued until now so we are

generating some of the highest energy density batteries in the world so this is a start to use silicon now I start to

get into the low become real that's why I have the confidence from now to next

10 years silicon is the driving force replace carbon prime is carbon replace

carbon eventually get your Tesla car to run not quite five hundred my apology at

do some be around 450 miles possible so this is the the materials now become

impossible so with this indeed this other chemistry so I won't have time to

talk about measure lithium metal coming in will make it even bigger this assault for coming in can make it bigger

and this what here is also full of challenges learning from silicon I think

this possibility we can make those materials to work as well you know

beyond 10 years you know lithium metal my comments off of my comment so he have a great path to we realize the high

energy you know for the transportation this is a highly highly promising let me

switch kill talk about with care storage please pay so I mentioned solar wind

integration is agree because of intermediates in meters in nature you need to smooth out a fluctuation

from second to minutes you need to be to the low shifting in hours to days you

need bear face or maybe some other technology let's look at the current technology right the most

no one the whole world actually is actually so-called pom hi Joe you pound

from you know water right here palm to a you know a lake right it's a dam right

there and then doing this is for storage storage when you use electricity you let

the water flow down and we generate electricity energy efficiency is not that high though we cannot do this in

California we don't have in our water to even do it right so so this is a very

geographic you know location dependent but indeed this is the the most popular

technology another technology only have this amount like this for 2010 so this

number now change but the scale relative skier doesn't change that much

now let's look at batteries will barely make it so you wouldn't like to connect

this I said 10 years ago where is so small everybody use with this big problem how big that is

I use I use a gigantic right here let's look at California I mentioned roughly

10 to the power in Iowa you know just roughly about 50 gigawatt hour also I want to use this number to compare the

AMIA world production of lithium ion battery as we are speaking in 2015 it's

only this number if the whole word shipped is benefit to California still

know enough yet for us to power grid right the Tesla's gigafactory what table would is capacity you know another 35

gigawatt hour in Nevada so so what does what's the scare somebody mentioned a

football stadium so this is a Stanford football stadium right so where we pay

in order to powder California imagine

Stanford Preston is willing to donate is football stadium to how the bear fees we

will need to bill over here I've a feeling from here the whole thing up to about half gigantic

battery we needed so should we think about other idea for doing battery so

here's one in order to fill a football stadium the

easiest way is actually liquid I we know uh so it is a flow Barre corridos flow

what's the idea you have this tank right here to store a liquid it's an

electrolyte inside these redox molecule can do oxidation and reduction reaction

once you have these electrochemical reaction possibility then you can store

energy this is a famous a redox couple coordinating vanadium from oxidation

state of a 5 plus 2 a 5 plus 2 or 4 plus

3 plus 2 2 plus 1 liquid is don't go in form for example this is 3 plus 2 or 2

process right here does analyze these would be here so you flow the liquid and

this is your bare face in the you store energy is thought it's liquid in order to use the energy you float it back and

that's a highly scalable method however is the cost when a diems cost the unit

is a membrane ion ion conductive membrane to be low-cost Navion is the

one use right now produced by two palm high cost and you have two liquid

flowing we serve very thin membrane if your pressure is not balanced you membrane is broken and then you need to

go in to fix it high maintenance and also the solubility of this molecule is

not that high it's about one point five molar only so if you invest a lot of

money to build this bare they building the pumping system putting the big tang that's your capital investment you want

as much energy are as possible this is only 30 watt hour per kilo similar as

your lat acid battery is too low caused by energy still very very high so we

look at this we say can be fine a new redox chemistry that has very high

solubility so that's this guy called Paul II sulfide this this really

interesting stone in my group work on sulfur your sulfur cathode the most painful

problem we are dealing with sulfur cathode is lithium sulfur we are forming so cal poly sulfide compound it's so

much solvable in to the electrolyte and then we lose materials into liquid they cost capacity decay then one day

one by still then come talk to me and then we recognize one if the solubility is so high in that liquid why

don't we use that liquid for the flow battery it's the best so that's right here you can get to 10 molar solubility

for the poly sulfide well this is 118 redox flow 1.7 molar now you see right

away if you have 1.7 I can get to 10 I have 5 times 6 times more solubility my

energy density will increase 5 to 6 times more if I do the same amount of investment on the pumping and piping and

big tang my cost per energy is reduced by you know to do 2 by 6 times right so

you take leave the metal you throw this liquid in a now into this bag if this is big tangle store this is a beautiful

thing using lithium metal you don't use to liquor you use one solid one liquid you don't have the mixing problem

anymore you don't want to liquid to mix right now solid then we have this liquid produce this yellow color it's a cell

passivation layer it stopped after a while to make this interface stable oh

it's a conducting lithium back and forth is your ionic a conducting membrane you

get it for free so you can go to low cost so we build its batteries you know

this is the stock liquid you know as soon as you put into this a flask this to real actual writer is not to work

vote for a long time run for a few thousand cycles distill some challenging

we need to solve particularly or the lithium metal surface but other than that I think this has a play hope to

impact a grayscale storage which gives the cost low enough software low cost and then I know some of you is going to

ask me what about Lisa do we have enough lithium why there is worthwhile to do all this research this is our global reserve 40

million tonne of lithium how much is the 40 million time it's very very heavy

so let's calibrate ourselves right he produced 10 billion is on leave Nissan

Leaf is 24 kilowatt hour or bare-faced 84 miles range contained four kilogram

or lithium in the barefaced so we got 10 billion it's 10 billion enough because 7

billion people in the world how many cars do we get running after 100 years

yeah we have a we have a billiard car running right there roughly right so this is good number so we have a long

way to go 2009 leaving production 22,000

ton but they can produce 23 million Nissan leave so that's great so I'm not

worried about Liam yet right so what about Tesla if I'd everybody 1s model

right if I kilowatt hour there are two red color Tesla parking outside won't belong to me

since we feel about that so big number what if we consume all this lethea what

we do we go to ocean itself ocean concentration is low 170 ppb but total

number is gigantic we need to learn how to mine lithium for my ocean I just started a project on that two weeks ago

looks like we are getting great data we can get lithium out of ocean soon if

there's a chance for the future public lecture I will show you how we can leave him out of ocean that's a standing

invitation probably so for the grayscale V film is what we consume electricity

somewhere wrong for Terra one I assume I store the homewards electricity for six

hours so that's 24 tell one hour our lithium Reserve good for 240 teller

one hour 10 times of that so we will take them multiple years I think

probably not even within my lifetime too valuable we don't have enough lithium

however we do need to be sensitive where lithium is this a job political

consideration as well that's above my pay grade to adjust this a problem so at

last let me assure you one more thing safety safety when she is very very

important so let's look at our some of the safety of safety and instance you

know about the Boeing 787 right you know about electric cars you know about

laptop this is the who about why they are just mentioned you know recently so

these all show you know saved here accident so let's come back to look at the little

man bear fit this is the basic structure I show you it got a metallic foil this

side another one this I have this particle coating which the polymer separator right there with a o'connell

actually that's a that can catch fire they can burn so what happened what's

going on with those batteries right there something is happening cause

shorting it can be external short right when you have accident something bomb

onto the bear that caused external shorting you can also have the internal shot that's due to you don't control

your charging why you overcharge you believe them damn dry shoots out from anode to cathode oh there's a defect

right there this metallic particle during manufacturing embedded inside that can easily cause shorting induce

the dendrite growth and also charging in cold weather so when you go for skiing don't charge your battery while you are

skiing using UV you all have the experience if used to code of actually yourself on turn off automatically

because it's too cold and then impedin is too high so your battery doesn't work so don't force your battery

working in the co temperature so no matter what's the reason somehow this is

something happening if you cause shorting something happening you stole a

lot of electricity and then the column will passing through this metallic foil

through this shorting you have fast release of battery electricity what happened afterwards it heats up your

bare face and then there is a few things happening when you heats up to roughly about 90 to 120 degrees C each of these

practical surface this soleal actually interface with cell decomposed it's not

stable at that temperature is XXL filming reaction release more heat right

so in this moment still know the Catching Fire yet but once you go up to

about roughly 180 degrees C now this is something you don't want your battery to

go to this is the oxide it's lithium cobalt oxide carries oxide carry a lot

of oxygen well we are we say organic luxury I like crazy and then this go

through the thermal runaway you don't have control anymore it got to catch fire and that bad things happen so now

looks lie the key thing is well let's protect our battery let's look at in the past how people do it well let me be a

little strong case oh you know Tesla needs to do that want something bomb onto my car it makes sure it doesn't

cause a you know what the battery the deformation cause shorting or internally

let me do something make sure my manufacturing is high-precision mention my balance my negative and positive

lectured the relative capacity of right they don't go down joy make sure I have a good a BM past battery management

system don't over charge with my bare face make sure I put in a fire retardant if something bad happens they don't

catch fire I put a lot of our retardant in there but these only solve the

problem to only to this level not that level yet so you still see bad his

catching fire so we have been thinking is there another way looks like if bad things

happen shouting is going on the best is heat up what if you prevent

about his heats out to the dangerous temperature then you're fine

what can we keep the temperature below this the reason is go up to desert high

temperature is because that shorting cause electricity release so let's don't release the electricity

how do we do it so we must invent something we call reversible thermal

fuse it's actually a polymer layer coating let's highlight here we only saw

metallic foil we put in a thin layer of coating this polymer these these are conducting particle because Nico neo

spikes they are connected together forming a pathway condign electricity

this polymer the blue color is insulating once you have expansion

happening due to thermal heating and it will put this particle open right it

becomes insulated if you become insulin that you have shorting right there this metallic foil is not connectivist is a

particle or battery material this electrons for electron very hard to link

into metallic foil and pass through the shot so you don't have big hole and passing through your batteries so you

don't hit it out that much so what build is nichkhun and inspire and make it stable we cover layer

graphene forming the this flexible layer now this is Keith key data

this is polypropylene polymer well-known embedded with 30% by way of nickel Neos

why you heated up 95 degree C you see the resistivity suddenly increased by a

orders of magnitude it becomes an insulator former conductor become an insulator so we test this our if you

blow the heat gun right here this become not conducting anymore these LED goes off so we build their face you know in

the regular temperature you can get capacity out once you heat it out there's no capacity coming out so you

have a thermal fuse right there it's reversible if the temperature come back to room temperature he works again so an

idea like this my Hara are solved the battery problem and a very beaver by the safety problem

let me summarize I was showing you for example there's a lot of Units to reinvent our bear face eventually

reaching this goal energy density per unit way and the cost as well because

energy is higher and we improve our material to have long cycle life we can

impact the safety let me end my talk by thanking all the heroes and my group PhD

students and postdoc they are very very talented some of them are sitting in the audience right here all these funding

support collaborators from multiple years and I would like to thank you for

your attention ever we have to take any questions you have

so this is run a little longer than our usual public lecture probably some of

you have to leave so let me just give a few moments people who have to leave to go out and then we'll take some

questions now for the questions on there are some of Professor Shui students have

microphones please wait until you have the microphone before you ask your

question so that the question can be on the videotape and we'll just take a few

but I'm sure many of you have questions so please who has a question here

thank you for the presentation Oh Chu so

I work in the solar power industry and everything's about commercialization and cost the safety as well but we

specifically with some of the inventions that you discussed whether it was

innovations and materials you mentioned briefly in your presentation that the

manufacturing for instance the the graphene container and in leaving the

gaps are you are you seeing progress in the lowering of the cost of

manufacturing of those more complex materials yeah good question we produce

those very fancy structures through a multiple step of processing indeed

there's something we need to work on in the energy scale the materials coming in

you know silica micron silicon is low cost you know carbon because it's low but we want to make sure processing cost

later is low as well this is something my startup company and empresses are

working on try to get things under control yeah you're absolutely right

from the lab into the a commercialization do so still multiple steps to to go

yes sir then thank you very much for the presentation very very excellent I do

have a question hello maybe a laptop area for example when these things are

brand new they're good to recharge for so many times in yep again you bury my

question century is this the very technology evolves I get to a point

where you have a longer charge at the

beginning of the life of the battery you can only be recharged so many times

maybe with this new graphene material

enhance that pattern so we have a very that that can be charged if you can hold

the charge for usage longer you don't have to charges many times the very last

longer that correct that's absolutely correct if you can store more energy for

given size of the pair fees indeed you don't need so many cycles because every

time you use it's going to be longer that's absolutely true yes thank you hi a fantastic lecture I

really appreciate you taking your time to present your ideas with us today I'm very interested in flexible batteries

and I'm also very concerned with the safety of batteries over time do you think that the way that flexible

batteries absorb impact will contribute positively or negatively to their safety as they permeate the market the flexible

batteries yes so flexible be referred to for some of the audience is is you can

ban you know to the degree even though it's a crazy thing like you can stretch

that do Cree a concern because of the banding motion and the materiality

material moving where it is possibility that can cause shorting or not

that's a indeed what made you think people need to take care of is to have

the flexible very not too short that's why you look at flexible very the energy density per unit way open uniform

is lower because you need to build in the SS all for protection maybe your

separator needs to get thicker and this many consideration to make things

Mayberry flexible so for many applications for transportation I don't

think you need flexible batteries you know for your cell phone you don't need it yet fractional battery might be needed is

one you have some of the available device application that's the time you

might need it it's not clear at this moment the future of flexible bear fees

I I don't think people figure that out yet so I cannot make more comment beyond

that thank you

can you sort of calibrate the difference between sort of having a really good

handle on the materials you'd like to have and use versus the young yeah we

can make this in the lab but we don't really know how to make this in any quantity all right I mean I want to

distinguish you think I really really know the right thing and if we could only make it we'd be we'd be good versus

we still don't know exactly what the right materials are well this is outstanding questions so I wish I know

you know you're asking if I know these

material this design work not only work but also can be made in a large quantity

then you're a big winner right so this is a learning curve I spend 10 years

try to learn about this for a problem like silicon and no expense so much i

beginning I never consider whether scalable or not I want to find I can

make it to work first because it's too hot so I don't want to work under the constraint of scalability yet but after

you know six seven years I slowly pull it into the constraint I want something

to be scalable so that's the sequence I learned I don't think anybody can see

that so clearly and day one I wish I could but I just can't so but it's

absolutely a good question well how do you shorten these the time of going for

make it to work and make it scalable I think the industry in University and National Lab need to talk very often

then they need to build on each other quite a bit so often time I'm excited this is

working by go out to talk to industry folks they beam it and they come back a thing I'll go out again the beam meet

again so every time I grow so this process needs to happen fast in order to

get the answers you you mentioned three more questions there to hear thank

you there's probably a lot of electric car owners here I'm one of them with a leaf

you're when you speak of charge cycles you you you do complete charge discharge

what would it be if you only went halfway and recharged or partial order

your cycle life goes up a lot so when we do the lab testing oh we are pushing our

materials the year to the extreme the habits but when you really use a lecture

car you are not going to do it right so you know when you charge your car indeed

when I charge my car I don't charge me too full actually Tesla will tell you it's banner through ninety percent fool

and don't go to 100 percent but don't empty either because when you go to the

2n that's often time its Elysium D'Angela plating coming I'll charge it to the fool if you go to the completely

empty structure change is too big and the materials level so that reduce your cycle life so if you do 50 percent you

know you go for more let's say 30 to 80 percent your battery cycle life will be

amazing once again I'd like to thank you

so much for the talk with regards to grid storage do you see more of a larger

number of smaller batteries being held by homeowners but their own personal solar networks or larger batteries and

smaller numbers of them being held by companies such as PG&E with huge solar farms so what that's interesting

question so I think for us here and

United States we have we can help both the reason is we have individual house

owners you know so many family but this doesn't work in China so what is no individual where if your individual

house owner so I was saying distributed I have a discussion with probably one or

person in the autumns sitting somewhere from the state grid from China and comparing a US and

in China model so in the US right here I will be willing to install a tesla

powerwall in my house I think this individual small sized battery has a distributed sources model will work here

combined with solar and then the bigger

scale I and here will also work you know much bigger the the baffle farm you can

have a Berry Farm as well but for countries for many European countries that if they don't they live in the city

those places doing a home and dividual alone where he will be ha you need

enough space so that's probably yet you

know I think both can exist depending on the country okay here thank you very

much for the talk my question is I was wondering if maybe

you could just say a few words about what the competition's doing it are there other other areas where where a

lot of progress is being made the let me say is different from what you're doing so I just thought we D know

the the barefaced space so I only give

you you know several examples of course you know a lot going on in the world so

this for example riskiest storage I only show you one example of a chemistry I

have two other very promising very chemistry as well working in my lab

using aqueous solution for the larger scale energy storage and then you look

at other other other chemistry as well also pushing very hard the answer is yes there are a

lot of I think friendly competition try to make different materials and

chemistry to work they all have quite a bit no promise right there as well but for the

transportation sigh I think I still strong believer is the silicon for the

coming 10 years and going to so many Bari conference right now partially

because of what we did at Stanford slack right here to show silicon is so

promising and also Empress them was the highest energy density varies in the

world so now you look at the major of every player they all start to believe in silicon to work so they all have a

huge effort to push silicon into their batteries yeah

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