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Lithium-Ion Batteries

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Have we had done that, now I will come to what I want you to teach today. Why do we prefer using lithium ion battery? Lithium ion battery has become more or less the battery of choice for all electric vehicles today. And what is the reason? So, let us look at the battery history.
The first important thing is it a one-time charged battery, you buy a battery normally we buy for a torch or pencil cell or are slightly bigger cell, once it becomes bad you throw it away. That is a one-time charge, it is actually get comes to you charged from the factory and you cannot charge it again. As opposed to that there is it those kind of cells are no use to us in electric vehicles, we want a rechargeable, even in cell phone I want a rechargeable, one-time charge once are of no use. I do not want to change cells all the time, laptop also you want a rechargeable cells.
So, the rechargeable cells are called secondary cells, one-time charge are so the primary cells, the secondary sells itself is started with nickel cadmium, 25 years back we used to have in rechargeable, we used to have a camera in which you put a rechargeable battery, if there are other devices you put a rechargeable battery and that used to nickel-cadmium, it grew to nickel metal hydride, then lead-acid became very problem. But very you useful, for example UPS in India most of them have lead acid batteries and then came lithium ion and we are starting to talk about other lithium-ion technology, lithium ion polymer, solid state lithium, ion battery, they are all variations of lithium ion batteries. Now, why did this come up? And what does it really mean? I also want to show you different kinds of battery, there is a battery pack like this, there are cells which are like a coin cells, there are different sizes and things like that.
What determines, what do you save, what is the desirable specs for the battery? What are the things that you really like to look at? Of course, since we are talking a larger battery seem a very small battery did not matter as much the cost will be one of the most important factor if I want to buy a 20 kilowatt hour battery, how much will it cost, cost per kilowatt hour is a very important parameter. And cost per kilowatt hour is very high at one time, it has gone down. There is a cell cost and there is a pack cost and the pack cost of course depends on the cell cost but pack cost is cell cost plus extra, we well get into it.
What are the parameters that makes most difference is called specific energy density, sometimes also called gravitational energy density, it is defined in terms of Watt hour per kg, why? Because almost all the items which use rechargeable are something that you carry along, your cell phone, your laptop, even your camera. So, since you carry it along question is after one charge you want to see that how long it lasts, so you want a slightly bigger cells. But the question is how much will it weigh? Will the weight in the cell phone battery become so large that I do not like it, cell phones beauty comes from its lightweight, you will say for a vehicle it matters, well it does. Because it weigh, the cells size, the battery pack is very large 20 kilowatt, 30 kilowatt hour, so weight will become very large and if the weight of the vehicle increases its usage of power increases the lie the battery you will either have to put larger battery which will again increase the weight of the vehicle or it will go smaller range.
So, weight makes a huge difference. The second reason weight makes a difference, because the weight is a reflection of weight of the materials that you use in the battery. And as I talked to you earlier, the Lithium-ion battery is the primary pair material is lithium, manganese, cobalt, nickel and graphite, these are expensive materials, if you use half as much watt hour per kg doubles you will use half as much material as you would have used when it was not doubled for a same kilowatt-hour battery. Now, half as much material uses almost will half the size, cost of battery.
So, cost of the battery is very dependent on energy density. So, this is one of the most important parameter, driving the new research in the battery, you want the cost to come down and therefore you want higher energy density, volume energy density, how much what is the size, even if weight is one part the size becomes another, you do not want your cell phone to a too bulky. Even for a two wheeler is thus size becomes too large, you cannot put it those space to put it in there. The third important parameter which had being talking right from the beginning is C rate, what is the number, sorry, life cycles are certainly C rate, at certain temperature, at certain depth of discharge, life cycle will mean not just the cost how long will this battery pack last, because after that you will have to replace it.
So, that becomes a important parameter, of course the capacity and depth of discharge usable becomes important C rate usable, safety and save disposals, so these are the parameters which defines electric vehicle. Battery of course is selected to match the vehicle requirement, you know vehicle requires 20 kilowatt hour for certain range, you to have to 20 kilowatt hour, so battery selected to match the vehicle requirement. It has to match it in two ways, one it has to match in terms of instantaneous power, if battery certainly needs say 40 kilowatt, if you have a battery which is 10 kilowatt hour it means it will require 4 C and that is not good, you have to have a minimum size the battery to be a possibly 20 kilowatt. And it is a motor guys who will tell you what is the power required.
So, power required the instantaneous power required influences the C rate and the capacity of the battery and of course weight and size becomes a very important component as I talked about, capital cost becomes very important, life cycles becomes very important, because capital cost has to be divided by life cycle, number of years that I can use, that is one, second you want to take into account the interest rate we will come to that later on. Because if you have borrowed money, it will mean that you are going to pay interest. A extremely important parameter is time to recharge the battery, I come I am have run out of battery, I go connect it to the charger, can I recharge in 10 minutes, can you charge in 5 minutes that would be ideal, I normally fill petrol in 5 minutes, I can charge in 10 minutes, well I may willing to wait, what if I cannot charge in less than 1 hour?
That becomes though, either I have to wait it for 1 hour or there is a very interesting you knew go forward and you will see a Japanese standard for a charger is called CHAdeMO, CHAdeMO, CHAdeMO is standard for the charger battery. Actually, if you look at the word you see well I put it on charger let us go to have a cup of tea and come back, CHA comes from the Japanese word CHA and Indian word chai may have be the same, deMO basically lets go for and have a cup of tea or even more, but it will take 2 hour to charge then, even tea you cannot go, can I do partial charge all those issues will come. Does it take 4 hours to charge? Remember charging in 1 hour is 1 C and I had said not the best for the battery, 0.5 C or 0.3 C would have been good for the battery, which means 3 hours charge or even 4 hours charge you have been got from the battery. But maybe you have to charge it sometime in 1 C, sometimes you have to charge faster than 1 C, 2C which means in half an hour, the questions that you will act, can the battery withstand that, what will happen to the life cycle of the battery and then of course you have to charge at higher, charge rate. So, these are the questions, we will get into depth of these things.
Let us, look at the batteries that I talked about, the historical battery. If I look at it, they will, there was a lead acid battery, still commonly used, nickel cadmium almost gone, metal hydride it used to be the their in your calculator for example, used to use this batteries a lot, rechargeable batteries. Student: Camera. Professor: Camera used to use. And then there are Lithium-ion batteries and lithium-ion also there are three kinds that I am saying there is a phosphate batteries, there is a we will get into more detail, there is a Cobalt batteries and manganese batteries. Look at the first parameter here watt hour per kg, it has been evolving and whereas it is only 30 to 40 50 watt hour per kg, which means not only it will be heavy, but also it will use lot of materials.
Nickel cadmium went a little better, nickel metal hydride did a little better, then came all this phosphate, magnesium and now Cobalt, 250 watt hour per kg, actually this is old data we have now crossed 300 watt hour per kg, 300 so this is what I am saying, we have crossed 300 watt hour per kg, extremely important, what will happen? Now, my weight of the battery reduces, if I use instead of 300 if I use 30 my battery weight would have become 10 times. So, we want to use 250, 300, these are by the way for the cells, not for the whole pack, pack maybe have some extra weight and we will figure out how much. So, it also means at 300 watt hour per kg the cost comes down, if I use for example lithium phosphate suppose it is a 100 and this is now 300 my cost will be approximately one third. And that is the reason we used to have 1000 dollar per kilowatt hour and it is gone down to almost 100 dollars per kilo watt hour, this has happened primarily the most important parameter specific energy also called gravitational energy and it is this which will drive the future battles also we will come to that, internal resistance, we want that to be low, because otherwise that much heat will get dissipated, cycle life, we want the cycle life to be close to 2000, at least 1000 2000.
So, this is not entirely correct the Cobalt NMC battery today will give you close to 2000 cycles and even 5000 cycles, there are that battery which gives you 5000 cycles. Charge time ideal is 1 to 2 hour, 2 hour, 1 hour occasionally, they impact the life of battery, there are of course other things overcharge tolerance, self-discharge, self-discharge for lithium ion battery is low 5 percent, 2 to 3 percent per month, means you have left the battery on charging, charged battery, end of the month it may be 97 percent or 95 percent, not too bad.
Of course, you can charge it, cell voltage, charge cut off all these plays important role, temperature minus 22 plus 60 degree centigrade, charging temperature 0 to 45, this play important role, maintenance-free of course we have only talked about maintenance-free battery, earlier batteries did have maintenance and the other dominant batteries that are used now. Toxicity of lithium ion battery is low compared to the earlier ones, but even then you have should recycle because material cost is high, if you recycle you get back the material. So, well cost is considered high, but it is actually falling down very rapidly (
Battery Chemistry. Most popular battery chemistry, this one I was pointing out, it is to be closed to 1000, this is 500 dollars, it was even higher, in 2010 it was 1000 dollars per kilowatt hour and if you see this is going down it has come down to a 100 dollars per kilowatt hour, its already reach 100 dollars per kilowatt hour at cell level. Lead acid battery on the other hand is reasonably expensive, well it is not as expensive as in terms of actually cost it is less, but the number of cycles that it gives is little, so it ends up being very expensive. So, lithium ion battery cells emerge somewhere here and since then it has become the dominant thing for cell phone, laptops and the cost has been coming down as the energy density keeps on going up.
This is again telling you the same thing, look at from 2011 we started with 80 watt hour per kg we have gone to 300, see the cost from 800 dollars has come to a 110 dollars. So, today we have 250 to 300 watt hour per kg, now there are promises that if I take NMC battery, but if I put graphite and silica anode in a few years, I may get to 400 watt hour per kg, 500 watt hour per kg. Volumetric energy density is already touching 500 watt hour per litre, remember these are for the cells, for the pack it depends on people like Doctor Kaushal, they are people who make it such that the pack is only 20 percent more than cells, 25 percent more than cells, the others who will make it two times the cell weight or volume then becomes a big problem. So, as I point out cost of battery is inversely proportional to energy density and it is the main driver for cost reduction, a high energy density batteries today use lithium, cobalt, nickel,1 manganese and graphite all of them are expensive material.
Let us look a little bit more at the battery. It consists of three elements cathode, anode and electrolyte in between. Cathode is a positive, anode is a negative and there is electrolyte. Ions are atoms that have lost or gained electrons these are all ions either one less then what in a neutral state it is negative charge, if there was a one more positively charged and these ions actually flow in a battery. So, there is a separator which separates out the positively charged cathode and negatively charged anode. So, in charging electrons move through separator inside the battery to cathode and then it gets positively charged. During discharge the positive current will flow from here to here, electrons will flow from here to here. So, that is what happens. This is the way electrochemical battery goes.
A lithium ion battery chemistry. It some there are a large number of lithium ion battery chemistry. It has been evolving then at least 1, 2, 3, 3 6 major chemistries. The battery called LCO lithium cobalt oxide. This is the main battery today, which is used in cell phone. It is cobalt rich and cobalt is a raw material, which is extremely expensive available only in a few countries China and there is a country called Chad in Africa or another country I am making a mistake and that has a lot of cobalt, cobalt is raw material which is not as easily found. But this is what the battery was used good density reliable battery. And then the battery came NMC lithium manganese cobalt oxide. This is the battery which is most commonly used today NMC. It gives you a good energy density and NMC itself it ask a question how much of nickel, how much of manganese and how much of cobalt oxide.
So, XYZ NMC811 basically 80 percent is nickel, 10 percent is manganese and 10 percent is cobalt dioxide. NMC111 basically means equal quantity as NMC111 moves towards NMC811 in between there is a 622, there is a 433, you will find more nickel and less of cobalt which reduces the cost and increases the energy density. Today after you have reached NMC811 there are attempt to make it they add more nickel and less cobalt that increases energy density reduces cost. The other commonly used battery is NCA. In fact, NMC and NCA are more or less similar quality we will get into it little later, but they are both more or less equal NCA is used by Tesla for its batteries, very similar behaviour NMC and NCA. Now you look at it (NM) NCA has one advantage it does not have cobalt and therefore can be less expensive.
The disadvantage is it has lower number of cycles and NMC has higher number of cycles. So Tesla still prefers it, you will say, why if it is low remember cycle why is Tesla preferring it? Because Tesla has designed a large battery which lasts 600 kilo meters, which means if it has only 1000 cycles it is a 600 1000 kilo meters. Now, vehicle is life does not go more than 300, 400, 1000 cycles. So, 1000 cycle more than enough. But if you have a 100 kilo meter range battery and if you have only 1000 cycles let us say 100 1000 cycles you have to keep on replacing maybe every alternate year. Then you want a 2000 cycles. So, that is the reason in NMC will be preferred.
There are two 1 other battery call LFPO LFP cathode, anode is graphite all these at graphite anode. It is a battery which is safer than NMC. It used to be, it was a Chinese I would do not know the Chinese invention but China dominated LFP and for a long time said this is the battery that we must use till 3, 3 and half years back. It was figured out that LFPO battery cannot go beyond 160 watt hour per kg. Remember that watt hour kg that I talked about.
So, it cannot go beyond 160 watt hour per kg which basically means at 160 watt per kg it costs, the material cost itself will be closer to 200 dollars, 250 dollars, it cannot go in this direction. When China realized that it decided to dump LFP battery saying get rid of these factories start making a NMC batteries. It started only about 2 2 and half years back but dumping can also mean that you can export the factory.
So, if India does not understand this very simple thing that LFPs life is over, it will say oh give us the factory at low-cost. Except you are taking the battery is it factory which battery will have no future because that has 150 watt hour per kg or no more, you have already reach 300 watt hour kg China has it is China, which is Chinese company CATL which has crossed 300 watt hour per kg and tomorrow it will cross 400 watt hour kg. There is 150 watt hour kg will be two and half times more expensive who will buy that. But very often in India we do not understand that, we land up into trouble. There is the other alternative there is alternative called NMCLTO it is called LTO battery. It is actually a battery which has a lower energy density but can charge discharge at a very high C rate and can withstand very high temperature. LTO battery it is called commonly it is called LTO battery. It has a, it, you can have a 10,000 cycles but almost two and a half times more expensive than NMC. Now, what do you do with 10000 cycle or 15000 cycle and costly is about two and a half three times and if you are going to put in a large upfront investment and if your interest rate is not very low you are stuck with the battery.
So the invest where the interest rate is very low. It may still have life in India it has a very limited usage. There is also LFP LTO not commonly used there is some something these are the battery. The important thing is a battery that we have to really focus on is number 1 this and number 2 this both batteries are good. If you ask me to choose I will not be able to, it depends on the application these are two batteries.
Now, comparison now just this is the same thing that I talked about if I look at NMC you can go 300 cycles, NCA also you can go 300 cycles, sorry 300 watt hour kg, 300 watt hour kg whereas LFP is 120, 150, 60 to 100, 50 to 80 this is what determines everything. This is also brings down the cost you can charge discharge at 0.5C 1C 1C 1C this you can charge discharge little faster 2C but again, what is a use you will limited by the energy density. Life cycle these had a slightly higher life cycle. But this also 2000 are there now and with silica you are looking at 8000 cycles.
So, this also fairly good. Cell temperature has to be 55 degree centigrade, LFP is safer. We must understand the why is it safer, it has less energy density, anything which is less energy density will be safer than anything with higher energy density. So you have to actually make use higher energy density because will cost low, less weight and make it safe. Cell cost of course you are seeing 100 dollars already on this. If you look at only safety, I will say NMC LTO is extremely safe. But energy density is only 80 watt hour per kg what you do cost is extremely high.
So, you must understand for what usage you are going to use what. China for example declare a policy that by 2020 all (vehicle) batteries should be 350 watt hour per kg. They are not, they are going to fall behind, they will not reach 350 but they have reached 300 that is important thing. They are saying if it is less than 350, you will not provide subsidy I think they are that modifying that, they this is the way they push technology, they declared it about three and a half years back. India declared we will use LFP which is less than 150, but did not understand at all. I will say we will keep them on power, China realize that it has to get rid of LFP and LFP cannot go above 150 everybody so used to LFP, Chinese company will dump LFP in China, they say well you will not get subsidy if you use it and since subsidy still plays a major role it has able to force Chinese company to move towards NMC and NCA. This is the way Chinese policies are done. We may have our differences with China, we may not like China but at least they are clear that they want to technologically advanced. So, now by enlarge there is a consensus in the world that has NMC NCA, but for a few years there was a lot of, lack of, the confusion.
For example, MNR in India still says you have to use only LFP battery. How this decision was taken? How did the Chinese influence them? I leave it. But the decision today is you can only use LFP we are making things solar packs with NMC battery this you cannot use it. So, what are they eight ask of a battery. (Refer Slide Time: 13:00) First as I talked of you high specific energy or gravitational energy density. Number 2 high specific power can I run at 2C, 2.5C, 3C at times discharge at least even charge at times. So, specific power, specific energy. Affordable price, very important, very important; long life can I get more number of cycles, price and life cycles have to you cope together, we want affordable price low price for reasonably good number of cycles.
Fifth is safety of course, it has to be safe, well make it safe. But you know must remember that a brand name of lithium ion is safe as opposed to lead acid and all that. When use correctly if you do a bad design it will be unsafe, when used correctly the brand name is safe. Wide operating temperature you want to be able to operate in low temperature cold temperature at 45, 48 this is a difficult one but we this is our asks I am telling you what are the ask, 6th one. Seventh one, low toxicity it is not bad but it has to disposed of well, and then fast charging fast charging is actually related to the C rate that I talked about earlier. Normally lithium battery should be charged once you are lower but can I charge occasionally fast charge. Now specific kind of battery you can, otherwise you impact the life very badly. So, these are 8 ask. Finally, a very important ask is also low self-discharge, should I charge it come back after 3 days 20 percent gone that is no good. Now fortunately lithium ion batteries have decent self-life.
There is a very interesting where things are representing a battery chemistry is represented by a kind of a six axis curve, six axis curve specific energy, specific power, safety, performance, life span and cost. Life span, number of cycles, cost, performance to some extent C rate, safety, total power that you can draw, specific energy. This so if you look at it this LCO battery used in cell phones is very good specific energy, low cost, ideal load have been lower, power moderate not very good large power, but then so C rate is low, but that does not matter because cell phone draws very little current, safety good safety, performance overall performance of the battery is good and life span is decent. If compared to this, I will look at a battery call NMC, NMC is the, if you look at it it is a more even it is all it is a moving towards hexagon.
So, the weakness of (())(16:37) it has enhanced safety, specific power has gone up, it can do better than that, cost is roughly the same, lifespan has gone up. So, overall this has is a slightly, specific energy has gone up significantly. If I look at the LMO there is another chemistry and today sometime LMO is mixed with NMC its cost is lower, specific energy, specific power, safety, life span is also lower. So, when you mix things, you have to really worry about it. LFP the specific energy is where it loses look at this. One say, this is much higher, this is bad. Cost is decent slightly higher because of the lower this thing. Power it can do better than even NMC, safety is better than an NMC, performance not that great, lifespan better than NMC but it is this is the most important parameter, this and cost related. So, this is the angle that you have to really worry about.
Look at the NCA almost similar to NMC except if you see cost is even lower. But lifespan is, life span is less should have shown up more life span is less. Safety somewhat less but it is okay. LTO on the other hand very low specific energy, very high-cost, this is, this is not cost low, sorry I think I making mistake unless cost, cost wise it is very bad this tells you how good it is, so cost is cost is so sorry even in NCA the cost is higher then, so how good it is a goodness in all this. So, this is a higher cost lifespan is good, very good, specific power also can be very good, performance can be very good, safety can be very good. So, this is a very good diagram I have taken this from a website called battery university. In fact, much of the material in this chapter has been taken from the battery university. It is a good description of these things.
So, to sum up battery chemistries for electric vehicles for some time to come is NMC graphite and NCA graphite. I will look at the future battery in a short while. Gravitational energy density is touching 300 watt hour per kg, cost is going down to 100 per hour dollar 100 per kilo watt hour. New cells will have higher energy density and therefore lower costs.
There are assignments that I am giving you, very simple assignment true or false. You have to just keep marking that and then we will come to batteries in future. Thank you.

Will now come to every day you hear news about a new battery. I will call this try to cover that in Batteries in Future. Again reasonable amount of material is been taken from battery university. The important thing is which parameter will it be better? First thing that I want to point out is there any other battery in which is expected to touch a 100 dollars per kilo watt hour? I do not see that in near future, 5-6 years. 10 years? Yes, but I still look at other batteries which are promising and may be in 5, 6, 7 years they will start touching 100 dollars per kilo watt hour. But that is the current cost and 100 dollars will fall down further. So need to compete with existing cells in terms of specific energies, costs, number of cycles and temperature range.
Cost is a very important probably the most important parameter if it does not compete in cost what will it do. Weight will matter, material ofcourse all these are related. Number of cycles matter because at the same cost if you get more number of cycles it effective cost becomes less. Temperature range this is something of immense concern. Can I get (())(02:00) in India, can I get something which will work at 50 degree centigrade better.
Ofcourse these are cells I can always make by pack work in a, even if the temperature outside is 50 degrees I can make it work at close to 25 degree centigrade by cooling. Lithium ion batteries that you get today you will see its cathode will start getting more and more nickel that is helping increase the energy density. And in anode you are adding more and more silica as I told you it started with NMC111, 433, 532, 622, 811 and now nickel-rich, so nickel rich cathode and silica-rich anode instead of graphite use more silica the problems on fusing silica it is not as easy to use helps in improving
the energy density and reducing cost. This will happen there will still be a lithium ion battery with some variation. The battery which promises quite a bit is lithium polymer, they are mostly pouch cells and I will explain what is pouch cylindrical another cells. The difference between this battery and the
currently use lithium ion battery in the currently lithium ion battery electrolyte is liquid. In this electrolyte is dry powder. It is like not powder it is more like a plastic like film it does promise
and can make things better more safer. The problem is at room temperature it has a poor conductivity you have to heat it to 60 degree centigrade.
So, that is not very desirable for which keep, in India anyway the temperature is high if it is a 10 degree centigrade heating 260 makes a huge difference, but in our India you may be a little be able to use it we keep on looking at it. There is also another thing which is gelled electrolyte instead of the liquid electrolyte or powder electrolyte plastic film like electrolyte gelled gives you slightly higher specific energy density makes a battery thinner.
So, you will see lithium polymer coming in once in a while. You will not know still lithium ion battery. They are future batteries lithium sulphur, lithium ion with solid electrolyte somewhat like this Graphene Supercapacitors, Redox-flow battery, Aluminium-graphite battery, Solid-state batteries and Hydrogen fuel cells and you will keep on hearing every day about the somebody say I have came with lithium-sulphur, somebody say it is solid electrolyte, graphene batteries supercapacitors, redox flow, aluminium graphite, solid-state batteries and hydrogen fuel cells. All of them have a, they are certainly future battery no, no doubt but all of them have serious limitations today and we look at some of that. So, as I told you these are the future batteries and let me come to look into little more detail I have again put a table of all the possible future batteries and how does it really look like.
The table was taking time I am actually putting enough data for lithium air, lithium metal, solidstate lithium, lithium sulphur and sodium ion. They are first set of 5 future batteries; solid-state lithium a lot of talk is there. Now look at it. If I could get lithium air it i