Xin Li | Director of Li Laboratory, Harvard University

What if there were a battery that would reduce the charging time of an electric car to 15 minutes and outlast existing batteries by a factor of ten?

The question drives Professor Xin Li’s research into so-called solid-state batteries at Harvard’s School of Engineering and Applied Sciences.

Listen to this conversation to learn more about Li's cutting-edge work!

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Hi, Professor Lee. Thank you so much for taking the time to speak with us today and for people listening. I think it would be great to start at the beginning, so can you please tell us a little bit about your background and what inspired your interest in energy storage technology?

Yeah, like it's, it's great to talk to you. Energy storage is a great field that excites people. Especially young people. Nowadays, when I moved to Harvard, I received the request from students almost every week asking for the courses that they can take. The spend battery is. We feel that with an industry there, there is a better industry and with commercial product. With the cell phone, laptop, electric vehicles those applications strongly integrated with this additional battery technology. That's why it's very exciting and, from my perspective, right, so I moved to MIT as a poster. That's when I started to do battery research at the beginning, right? So it's just a piece of material like sodium manganese oxide. We call it. We studied sodium ordering in the material. Try to understand how the sodium and sodium vacancy oils and how the memories charge orders and spend time in front of the microscope called transmission electron microscope to try to understand all those microstructures at that time. But that was almost ten years ago. I didn't realize that this is the field that takes power in this way nowadays. So after I moved to Harvard in 2015, right? So I try to understand whether there is a new field that I can study.Right.So beyond the conventional commercialism battery and, I started to work on starting the battery; that's the right decision that I made at that time after five-six years nowadays, less emphasized the battery, sodium-sized state battery is clearly becoming a strong competitor to the commercial salesman battery, and thus a filled with great applications.

That is very interesting, Thank you for providing that context. Just I'm curious because a lot of listeners are interested in a diverse array within the climate field and also love to hear about how opportunities for people like yourself, leaders who are doing inspiring work, how the opportunities. The rise to begin with, so could you provide some insight into how the opportunity to launch the laboratory at Harvard came about?

Yeah, yeah, yeah. So let me think about it.Right.So this is a very good question that person to think about. My personal history basically, when I was at MIT, there were several competitive energy-related research field, like the solar cell research, the fuel cell research, and also the battery research, they are related to energy conversion and energy storage at that time this one battery and beyond this land battery that includes sodium and lithium-air Et cetera.It is a relatively new field compared with the service because we know that the sort of bubbling.2008 around that time, that and few service was large at that time. But I think at a certain stage, it was kind of turned down by the DOE. So I think for young people like me, at that time to enter the field, this kind of general environment is important. If you choose a field that can keep growing in the next 5-10 twenty years, that would be great, and also, that helps my career after I moved to Harvard. It's because of my postal research. This man that we are, the third one bad way, I decided to keep doing this direction; of course, I want to distinguish my research at home when I create this laboratory from my previous post-research experience that's why I enter into a new field at that time, that's in 2015. That's called science. So what really drives me to this field of science is that way there are macrofactors, right? So the first one is something I mentioned to you. I want to enter into a new field that's the important is to enter very old field then you have to read a lot of papers, right? A lot of background new field. You have more freedom to create. You have a less boundary to limit you. Your people may have more citations, but that's just secondary. The first consideration I took at that time was that there are enough complexity in this material design, and mature scientist, by complexity means opportunity for physicians can say they want to simplify the model to as simple as possible. For example, simplify the pulpit simple inductor to a 2D square lattice or triangular. The material scientists clearly, we know that the complexity in the materials and the device, in this specific case, is the size. The better device means the opportunity to create the opportunity for advanced performance. So when I look at that way, it's complicated. You know you have the cathode material, you have the another material, you have the solid aside. You have so many solid, solid interface between the caster, between the electrolyte. But all those are new in the field of science. The battery that means a lot of activities there. For me to innovate.

Very interesting. So not only do you have to read less research papers. But there's also more opportunity that stems from the complexity of the material of solid-state batteries, which provides you with more space to innovate and also forge a unique path within this newly emerging technology. 

Exactly, So, so, but nowadays, right? So we have we have many, many sites, the battle papers I contributed many.

I did some more reading, fortunately. For all of us, I mean, I'm just attempting to put myself in your shoes back in 2015, when you were deciding to make this leap into completely new technology, and I assume that you know it's a difficult decision to make because on one hand lithium batteries and sodium, batteries had a pretty strong foundation, and their growth trajectory was pretty clear in terms of the adoption I'm just trying to get a sense of like what the decision-making process look like at the time, did you feel as if solid-state batteries could compete with lithium batteries? And how is that idea or perspective evolved since your time working in this space?

That's a very good question. So I mentioned the positive side, right? So it's an opportunity, right? It's new enough that when you. The new field like this. There are also concerns whether the size the battery can work right. So whether that's the direction for the future batteries, all those are concerns, and more specifically than at that time in 2015, 2016 when I decided that I want, I wanted to do this statically, better research was a big concern about whether my lab could assemble a science they battle and make it wrong. So that's kind of the immediate trouble I have to solve because I have never worked outside the battle before, right? So at that time, I could just read the limited literatures published by paper but by people all the papers. So you don't really know just by reading the method of the paper that you can repeat the published result, and we try to some batteries and do the better test. I can take the 1st 200 Batteries Assembly level failed, so meaning that it cannot even make one successful cycle right. Nowadays, when you make a battle, you want the battery to cycle stably for 1000 cycles, 2000 cycles, and his recent paper published this cycle for 10,000 cycles. But at that time, the 1st 102 hundred cycles. But batteries, we cannot even make successful cycle. So that's a big trouble. We have to start at the very beginning those are our concerns, but I think what drives me through this many years, right? So I think since the battery is the future compared with the commercial, it's not battery using liquid organic electrolyte, something that we were using ceramic side which is non-flammable, you see many explosion circles, EVA's. Those are all caused by the organic flammable liquid as light, but once you switch to the ceramic solid flashlight. The entire battle system becomes much safer. It's not. I think that's one big performance metric great to consider right to make the battery better. What is the direction to go and this is something that can be provided by Science day; that way, the second thing is that it goes back to the opportunity that I envisioned at that time that you have started environment science, and you can say it's all starting environment that is new enough people started with liquid, solid environment in the commercial some battery for more than 30 years and suddenly you have a new interface all solid. So these mines move from Castle directly to a solid ceramic and pass through the separator to the animal and back and forth with this outlaw new performance that is ten times better than commercial battery. So that's the thing. The point that drives me to do this science better research even I have like 200 failed batteries, and it turns out later that, yes, we could make the performance ten times better if I work with them better at that time. You have a marginal improvement of the performance. That's the difference. 

I see. Thank you so much for expanding on that.Building off that last point where you expressed. That you saw. That there's the potential to 10X the performance of the battery. So are you referring to 10 maxing the performance of the solid-state battery at the time, or are you referring to in comparison to a lithium-ion battery, you saw that you could develop a solid-state battery which performs at 10X the level of lithium batteries. Yeah, so it's ten times better than the commercialism and battery. Let's sense listeners and understanding of different metrics people look at when they're judging the performance of batteries. 

Yeah, There are several performance metrics that we have to consider when we design energy density, safety and the cycle lifetime and charging speed, and also discharging speed to explain to you why those metrics matter. Any density the commercial percent battery is on the order of 250. When I entered the field about 710 years ago, nowadays it's about 300 Watt per kilogram, and it's kind of kept there with any density increased from 150 to 200 to 250 linearly in the past 2030 years, and in recent years, it's kept at 300, but out of the kilogram, that's not surprising because if you look at the battery history, right? So like the lead acid battery and all kinds of batteries, there was this kind of linear increase in density, and then it kept there, meaning that it which the materials fundamental limit in this particular type of battery technology will need its fundamental limit and intensity will not increase unless it's you switch to a new type of battery life-size. The battery that can enable this matters anode, which is ten times the capacity of the graphite and used commercially, and then you have the opportunity to further increase the density to 3:50 or even five, and that's basically decide this performance metrics decides, for example, how long the electric vehicle can drive between two charges. If you want your electron wave to drive the same distance as your gasoline car, you fill the tank. Once and you drive 700 miles, and if you want to do that, then you have to care about this performance metric of energy density, but any density is not a metric that can be easily improved by ten times. As I mentioned, it is a linear loss, but there are other metrics that can be really improved by ten times, like the cycling lines and the commercial battery is at around 1000 like us, where you can make 2000 or 3000 cycles, but the battery could run for 10,000 cycles or even 20,000 cycles. And the second stability can be dramatically increased when you switch from liquid to study, so that's one performance metric that could be ten times better, and why this matters? Because if you use your cell phone, you have experienced that every few years, you have to switch the new phone, not because of your software is not good. It's because of the battery. So this time, the battery that's one experience that everyone has nowadays, and in addition to that.5-10 years and then sales as a used car, and people will keep using it, and the U.S. has a very large used car market, and people are many people rely on the used car, but if you have an electric vehicle with battle, that can only run for 1002 thousand cycles, and then that will change the entire car culture in the U.S., you see that you probably won't have a used car market to make this every technology more inclusive to people, I would say, right? So to people that need the used car and you want to make this better with long enough time so that the culture is not drastically changed, that's also environmental and friendly. If you have a long that way, a lifetime for like 20 years, let's say 50 years or even a century, people are talking about this if you have a better cycle for 10,020 thousand cycles. Then your battery could potentially for half a century or even a century, that will save a lot of energy for making new batteries, right? Because making less letter outside Castle, making the listen letter, and making those electric the process. It costs energy, and it takes a lot of energy, and as there might be some environmental issue, contamination also associated with, of course, you can recycle your battery people talking about this, but the recycling also costs energy, right? So that can also cause an environmental issue. If you make a battery that can run for 50 or 100 years, that would be great. Yeah, that would be great for all these considerations. That's one metric why long cycling life matters, and also, charging speed is limited to about one hour or several hours depending on you are using Level 3 or level 2 anyway. It's too slow. Just think about how you use your gasoline car. Right? If you go to the gas station right, so you feel gas time in a few minutes when you drive away, can we do this for an electric vehicle, Right? So nowadays, it's not possible, and it's partly limited by the battery technology. The battery technology nowadays cannot support such as fast enough charging, where you may say, OK, there is a Tesla supercharge that's about 30 minutes, right? So but if you do your the supercharge every day, right? So the battery will die more quickly, and we talk about like 1002 thousand because commercially nowadays. But if you do supercharge every day, right? So a better lifetime will be shortened too. I don't know, maybe a few 100 cycles. You can also heat it up when you do this supercharge, that can further shorten your charge time to, let's say, 15 minutes, but still, there's other the lifetime and also the safety issue. The fast charging may cause this penetration of expansion of the battery. So basically, we want the battery that can do 10,000 cycles and also fast enough charging speed as compared with the several hours of charging that was the ten times improvement of performance metric and we want. We drive our guests in the car. We know that we want seven minutes of charge. This will also open an entirely new application. If you can, do this fast and very frequent charge. First, you don't need a very large piece of battery. You know that you can. You want the battery to be charged. You can do it anywhere within a short period of time; then, you don't have to have a large piece of battery pack in your electric vehicle, so you have very light equal that can do a lot of times of charging every week, every day. You can think about applications like autonomous shipping and also of U.S. citizens, U.S. people they don't.Have a garage at home. So they cannot do overnight charging those people. They won't want to buy a car that needs like 10 hours of charging speed. A few million of charging speed will help these people to switch to the electric vehicle from testing more easily.

Thank you for providing all of that information as an electric vehicle driver. I definitely see a lot of benefits in terms of the performance improvements that you just mentioned. I do have a few follow-up questions. I'm curious to hear your perspective on currently. As you mentioned, it takes about 50 minutes to charge a 206. The Mile battery for the Tesla at a supercharging station, just to provide some concept of comparison, do you feel as if lithium batteries can improve in a way that reduces that 50 minutes to around 10 to 15 minutes? Have they essentially peaked from that?

From my understanding of this battery device, I'm curious why so there will be some marginal improvement of the performance right? So you know, go from 15 minutes to 10 minutes, but there will be some cost. You have to hit your battery up before you do these 10 minutes of charge because that's fundamental materials limit, and when the child speed is too fast and room temperature, you will have this interpolation to the graphite and then listen will go listen, dendrite penetrates through the separate, causing the short circuit and that explosion, at least.Right.So you will have better degradation to be faster than the slow charge as you could find ways to engineer your better device, adding the eating so cute to heat up. Do this super-fast charging, but you have to sacrifice the better lifetime and even safety, right? So then that would be a big concern; that's why I think below 10 minutes of charge speed, you have to go for a solid-state battery.

Yeah, I do see that as being a major driving contributor towards wanting to transition to a solid-state battery, the points that you mentioned as someone who drives an electric car. I mean, the 1000 to 2000 life cycles, I was thinking about that, and I feel that I still could get the current car to around a 265 to 300,000-mile life, which I mean, for my sense, I haven't really owned a car for that long of the time period, but for my sense 250 to 300,000 is a pretty reasonable amount of time to own a car. However, I think the charging time has been like a major, you know, impediment in terms of me wanting to continue to own an electric car. So I think from that angle, I see so much value.

Let me add a point. So when you do this bus charging right, the battery lifetime could be shortened by the number that you mentioned; 1002 thousand cycles could be shortened to just a few 100 cycles. If you do this super fast charging too many times for the current commercial battery, that's one issue. It's another issue is that if a battery can only run 1002 thousand cycles, that means after you sell your car. The entire battery pack has to be replaced because it is already enriched its life; then, there will be a lot of cost to recycle the battery, to disassemble it, to make new batteries. All these will add up to the cost, but the battery, and essentially to the consumer, right? So and this same price is surging, and casual material price like make and.Global are also selling, so consumer will have to pay more if the battery is with a shorter lifetime is that it can be ten times longer lifetime, so this will be reflected in the price of the battery and electric vehicle. It can make the battery and also the vehicle more affordable to people; that was actually going to be my next question to get more of a sense of the costs and the.

Economics of a solid-state versus lithium-ion, and thank you for all the information you provided so far. This has been extremely informative, and as someone who you know doesn't really know the technicalities of the battery space, but just during my work with the Department of Energy and also in these interviews have really seen that there is expected to be so much growth, for example, I was just reading about the storage futures report put out by the National Renewable Energy Laboratory in preparation for this conversation, and that was more pertinent to energy storage as it pertains to storing energy for grid services, not necessarily electric vehicles, but even on that front, they picked for there to be 500% increase in energy storage adoption over the next few decades, so I see like this space is being extremely intriguing and important to learn more about and on the economics front, could you provide some perspective in terms of how solid-state batteries compare with the lithium?

He's, yes. So he has a guideline for future batteries in the next 5-10 years or so to reach less than $100 per kWh.That's for both this man battery and the commercial liquid one, and also any new type of batteries, including solid-state battery, and we have done a calculation right, so this goal can be reached by solid-state. That way, no problem, right? So that's that something battery, as long as it's the same base. We will share the same issue with the commercialism battery about the price surge of release element, curve element, etc. So I think at a certain stage, no matter is listed on liquid electrolyte battery or listen on inside the battery, they have to give off the portion of market to new batteries with lower cost, and those new batteries could be solemnize battery, so it could be sold mine size state battery because sodium is ten times cheaper than the sum and sodium cathode can use money than iron, which is also much cheaper compared with the expensive and so all these price considerations will be important at a certain stage when the listening battery is becoming more and more expensive. Say even T.E. has a guideline for $100 per kWh. I would say that if the pure price keeps increasing, right? So at a certain stage, there's cheaper options. If you can make a battle with, for example, $80.00 or $50.00 per hour, then those batteries will become very competitive. Even the performance is a bit lower with this man badly; that's one thing. That's why I want to emphasize that the battery does not. To refer to the listener as I say badly, it could also be 30 minutes. I say battery, right? So if price is a consideration, this is the direction to go, and also, it's related to the performance I mentioned, is the battery lifetime is longer, right?

So then the after the electron. We use it for like 5-10 years, right? So the battery is still alive. We can still run for another 1020 years. You can use it for stationary energy storage, so the used battery from E.V. can be fully used for another 1020 years for grade and storage. Companies like Samsung, L.G., right so, are doing this. They buy boxes used electric vehicle batteries and to test are there any sales that are still healthy enough to be reassembled to a new pack. It's all used sales but can run for great and storage for another 5-10 years. That's another way to save the past; that we have this exercise that we could do this much better than the current commercialism.

I see. So one quick clarification for solid-state batteries, that means that only one part of the battery value chain would be changed or altered, and the lithium component can still be integrated in solid-state batteries. It's just the anode that would be altered to incorporate the solid-state element. Can you provide some insight into what exactly a solid-state battery entails and how it gets integrated into the current battery ecosystem? Sure, in addition to the biggest difference that I mentioned.

As you switch from liquid to solid electrolyte. There are many new.

In components in size, the battery, the one that you mentioned, the listen metal animal, right? So that's one big difference. People try to enable this metal in the commercial. The liquid is not battery and steel, but this could be enabled by science than the annual is ten times larger capacity, so that the density could be much higher. That's one difference. Another difference is that you have a.Environment, so you can do many things that liquid cannot do. For example, if you mix water with an air horn right, so they will just mix into a homogeneous solution. But if you have two types of solid lines, that way, you can create internal structures where you can pave. One layer of electrolyte type, and on top of it, you can paste another layer of electronic type B. All those new geometries and possibilities and complexities that can be created by all science, and the environment, we demonstrate that if you go for such a geometry design, the performance can be much improved. The ten times longer lifetime right, 10,000 cycles, 2000 cycles is partly enabled by such a design that is unique to science badly but impossible to live that way.

Very interesting social operationalize. This research it can be integrated into current supply chains, correct? It wouldn't require a complete transformation of the whole battery supply chain. Instead, it would simply require an alteration of 1 component of the current supply.

Yes and no. The current castle supply chain, we could just use it because it's the same type of castle material as the commercial battery. We also use the graphite layer right so that graphite and the supply chain we could also use it the electrolyte 1. That has to be new because they use liquid or use side, so we have to make solid effort materials, by the way. Don't make the solid enough light. It's just some standard, since it is massive, that can be easily scaled up. So many chemical companies already reached out to us to try to understand what is the material is useful for the better application, and then we can we can plan for it to make mass production in the future, right? So many chemical companies. Can you do this? So just like a few years or five years ago, there are only 2-3 companies that can provide the so-called NMC cathode material for this, not that way. But nowadays we also because I'm seeing becomes more and more important in one or two years. There are so many new such chemical material suppliers that make this mass production the same thing will happen for science. The battery once we demonstrate that, OK, this science, the battery and walk, and more and more electric vehicles will use this type of battery. They anticipate this need by the market, and they will scale up to do this mass production and same thing to this matter even with many factories, they can make this matter spoil, but they don't make it into mass. Actually, knowledge because there isn't such a big market there, but once we demonstrate that this method can work with science, the battery, and these two $100 billion of battery market, right, so that this giving up of the existing technology will happen in a year.

Yeah, once the demonstration occurs, then I assume it would be relatively easy to scale it up, and I mean, it's clear that the market will be there. What are your thoughts on the challenges to getting to that place where the demonstration projects using solid-state batteries would be implemented?

Or slightly batteries? Or is it? There are several major players in the war from the startup world, where there are common escapes and solar power energy. Conventional battery giants like L.G. and Samsung, and Panasonic, and also those carmakers like Ford, GM, BMW, and many companies in China, are trying to commercialize solidly battery. We are one of them. I would say that we started up the company in February last year. Here actually, it's earlier than that; we close the seat around in February last year, recently this year, right? So we aim to raise the iron person that's wrong. I think the challenge right through this process, I understand. I talked to our competitors. Our collaborators talk with the people in my company, and I find that the major challenge is to scale. But your battery size, while keeping the same performance that you saw at small scale battery, and also you have to control the cost, the manufacturing the processing steps have to be cheap enough. So basically, make it larger in a better world. We called it to scale up. That's the major challenge.

So the technology is there. It's competitive with the existing technology in the market. Yet has better performance metrics, and economically it's able to compete. Correct, yes. So the challenge, the key challenge is figuring out how to scale the current newly developed technology. In a way that is able to maintain those performance advantages while also keeping the costs contained.

Yeah. So, so basically, if you aim for battery for an electric vehicle and the battery has to be on the order of 50 MPR or to 100 MPR capacity, right? So or while in the university lab or in stable company, the very beginning where the battery size is on all as one.MPR or below, right? So you have to make your battery capacity battery cell capacity.100 or even 1000 times larger versus in the scaling-up process. Whether you can still keep the very nice performance metrics that you demonstrate that at small scale, right, so that's the, so that's why we think that there are different technical pathways. The best way to design a new science back with different companies will take different pathways. All these companies I mentioned we have different ways to design science the bad way. This design philosophy becomes very important because if it's not the right. At a certain stage right, you start to build the Thailand line. You want to make best production when you suddenly find OK. It's impossible to do that. You want to do mass production after IPO, for example, but then you find that no matter how much money you have in your hand, where you cannot do that, and if it's not the right tech pathway and that's, that's why we think at the very beginning, right? So this clear understanding about what is the size state battery, what is the unique advantage of size state battery from fundamental scientific perspective, right? So that's that's very important that that can help you think about. There's an engineering aspect. Different layers of engineering aspects. What is the right way to go because you know, there are so many steps there to make a better way and to scale up. There are a lot of opportunities you can make wrong decisions make wrong designs, so that's that's why we think our effort in the past five, seven years we spent at Harvard to try to understand the fundamental dynamics and kinetics electrochemistry of science batteries is super helpful. So basically, within one year, right? So guided by this design principle, we figured out this fundamental. We spend time to figure out those equations and computations to make the right prediction and make the right design that helps, and we will make very fast progress in the past 12 months when we try. To stir up.

Thank you so much, Professor Lee, for your time and all of this super insightful information. I, for one, feel like I learned so much about the state of the battery landscape and solid state. Batteries through this conversation and feel as if the potential behind this technology is immense, and look forward to seeing what the lab does and continuing to stay in touch.

Yeah, so I enjoyed this conversation. With you and you are. Very welcome to drop by. My office and I show you my laugh.

I love that. Thank you, professor.