 We will continue now with our afternoon event of the Purdue Engineering Distinguished Lecture Series. We go into a panel discussion and it's my distinct pleasure now to introduce the panel moderator, one of our new faculty members in the School of Mechanical Engineering. This is Professor Rebecca Cies. She is an assistant professor in mechanical engineering and also has a joint appointment with environmental and ecological engineering here at Purdue. Her research combines methods from engineering but also social science and policy and others to consider the economic and environmental impacts of energy technologies as part of a transition to a decarbonized future. Rebecca received her PhD in engineering and public policy from Carnegie Mellon in 2018 and right afterwards she was awarded an Endlinger Distinguished Bustutorial Fellowship which she conducted at Princeton's Endlinger Center for Energy and the Environment as well as Columbia's Electrochemical Energy Center. So she joined Purdue in 2020 and we're very happy to have her here. So Rebecca, I will hand it over to you. Thank you and I'm glad to have this discussion here today. For anybody who is just joining us, a quick recap of our distinguished speaker, Professor Esther Takeuchi is a SUNY Distinguished Professor and the William and Jane Knapp Chair in Energy and the Environment at SUNY Brook University. She holds a joint appointment with Brookhaven National Lab as Chief Scientist and Chair of the Interdisciplinary Science Department. Her research experience really spanned across industry, academia and the national labs and she's made transformative contributions to batteries energy storage for a variety of health and energy system applications and so we're glad to have her here. We're also joined by Dr. Marielle Patterson. She earned her Bachelor's in Chemistry from the Resleyer Polytechnic Institute and a PhD in Analytical Chemistry with a minor in Physical Chemistry from Indiana University. The subject of her thesis was the application of spectroelectrochemistry to study surface and near surface processes of corrosion and corrosion inhibition. Dr. Patterson was a postdoctoral fellow here in Michael J. Weaver's group at Purdue where she used surface enhanced ramen spectroscopy to study electrochemical catalytic processes. Dr. Patterson began her industrial career at AT&T Bell Labs where she was a subject matter expert in material processes and processes in areas like semiconductors and soldering. She was the Director of Cell Engineering R&D at Ennerdale, a manufacturer of lithium ion batteries and she is currently a Chief Engineer and Technical Product Leader in the Vehicle Electrification Systems Division at Aptiv in Westfield, Indiana. So she's interested in all aspects of energy storage from fundamental electrochemistry to the systems level. And then our final panelist today is Professor Jeffrey Greeley. He is the Charles and Nancy Davidson Professor of Chemical Engineering here at Purdue. His research focuses on enhancing society's ability to meet critical energy and environmental challenges by understanding, predicting and controlling the interactions of molecules with solid surfaces. His work on batteries is focused on implementing computational screening methods to identify and develop new battery materials and analyze reaction kinetics. He's a recipient of the Department of Energy Early Career Award and he was a university faculty scholar. Dr. Greeley received his Bachelor's in Chemical Engineering from the University of Texas at Austin and his PhD in Chemical Engineering from the University of Wisconsin-Madison. And so thank you all for joining us for this discussion today. So I guess, yeah. So this is a bit of a diverse audience and so I think at the beginning of your lecture you gave a very brief introduction to some of the different scope of batteries and perhaps it might be beneficial to sort of recap what all is encompassed when we are talking about batteries. That can mean a lot of different things to a lot of different people and so perhaps a brief recap of what that was. Sure, maybe I'll start and the other panelists can certainly jump in. Batteries have really become ubiquitous. I mean as a technology generally they're not new. Maybe batteries have been known for at least 100 years but they really serve various functions in our daily lives. Lead acid batteries are a very well known technology. They're old but on the other hand they start internal combustion engines that have been doing that effectively for decades so they meet a specific need and are very effective. We have very inexpensive batteries that we use for things like flashlights and toys and other things. Those happen to be primary batteries or single use batteries and in my mind when I talk about advanced batteries I really talk about batteries that are meeting needs of a newer set of requirements. I think in many ways the advent of lithium ion batteries was a contributor or at least an enabler of the select portable electronics revolution that we all live in today. Not to say that it couldn't have happened without lithium ion but I think lithium ion facilitated it because the energy density is so high. Other specialty batteries are for example where I used to work in implantable medical devices and then today we're really talking about big batteries. It's batteries for electric vehicles, batteries to back up the electric grid. So diversity of technology, diversity of applications. Sometimes people ask me, do I think that one universal battery will be invented that's going to solve all the world's needs? I'm not convinced. I think the applications are so diverse that different batteries need to do different things. What they do extremely well is take electricity in directly to be charged and then give electricity out that it's not changing it into something else. We're not burning something but we're using electrons to charge the battery and then we're using recovering electrons out so I think they're going to be in our future for quite a long time. This might be a good opportunity to talk a bit about what else goes into making these individual battery cells into these larger systems and perhaps Dr. Patterson can comment on all of the extra things that go into making these full systems. Sure, so there's a lot of extra things that go into making on the pathway from cell to module to pack. So if we start with the lithium ion cell, we need to group those in a configuration of series or parallel. Of course, series configuration increases the voltage. Parallel configuration increases the capacity. The cells are ganged up into a module. The module has mechanical and electrical interconnections. The mechanical interconnections are there to stabilize the module and also to help protect the module. At the module level, there's also always voltage sensing and also temperature sensing. There is usually electronics on the module and so it's kind of like a module reporting electronics. There may be fusing. There's a lot of different things that go into the module. Now we go up to the pack level. So now we arrange those modules once again in a series and parallel configuration to get the voltage that we want and of course we have enough modules to get the energy we want and hopefully the cells have good enough power capability that we get the power we want. At the pack level then, we have more components. We have contactors. Contactors are open when the pack is not in use. So if you go to measure output voltage on a lithium ion pack, when it's not in use, it'll be zero and you'll wonder what's wrong with it. Nothing's wrong, the contactors are open. There's more fusing. There's current sensors and most importantly, there is the battery management system. So it's like the executive system that takes in all that information from the modules, has the BMS hardware and software to control the battery pack within operating limits, keeping it safe. There is a low-voltage wiring harness that is for the electronics and then there's a high-voltage wiring system, interconnection to take that power and energy in or out of the pack. Also importantly is thermal management, like what we were talking about earlier. Batteries get hot when you use them. If you're talking on your cell phone long enough, it gets warm when you charge up your cell phone. It gets warm. Now imagine instead of a little cell phone battery, you've got a great big EV pack for your car or a great big grid storage system. So thermal management is also very important. So cells are where it starts. There's a system, but then there's a lot more that goes into it to create a system. Great. And so I think having these systems work across length scales and across time scales is obviously a very huge challenge and perhaps Professor Greeley, because we want these materials to be reusable and reusable for a very long period of time, perhaps you can speak to some of the challenges of what does that reusability cause in terms of difficulty for designing materials for these kinds of battery systems? Yeah, absolutely. It's... I guess when I was growing up, I think it was still primarily primary batteries that were of interest or that existed. And maybe when I became a teenager, I started hearing about rechargeable lithium ion technology. So certainly for the rechargeable batteries, the voltage, the capacity, the charge discharge rate, those are all still very important things. But the performance metrics that really come into play there are the stability, the durability, and the cyclability over ideally long periods of operation. There are a lot of mechanisms in a battery by which you can lose capacity or have other undesirable things happening. Just to name a few examples, the electrolyte in the battery. A lot of times you would have an organic electrolyte, a liquid electrolyte that can actually react with components of the battery and irreversibly decompose. Sometimes somebody had mentioned, I think during the lecture, a solid-state electrolyte. Those are great for certain things, but then you have instabilities that occur at the solid-solid interfaces. You can have also at some of the interfaces, the electrolyte... electrolyte interface, you can have a growth of dendrites. Those are basically just metal in a lithium ion battery. It's metallic lithium. You can grow and short-circuit the battery. And other things can happen. For various processes, you can have active material or charge-carrying material that loses conductivity with the rest of the cell and basically is lost. So lots and lots of things. And I think even just understanding the mechanisms by which those processes occur is a big challenge. But certainly from a design perspective, it places a lot of constraints on what you can do. It doesn't really help if you have a great capacity because the battery only lasts a few cycles. Yeah, and I think this sort of leads into the next sort of topic of discussion. So for the current chemistry, like working with what we already have today, what are some of the key knowledge gaps that are presenting challenges for applications to some of these larger-format transportation or grid storage applications? And maybe we try and work from the smallest to the largest to try and integrate some of our thinking into a coherent discussion. Okay, I'm on duck again. Yeah, so, well, I do have a little bit of a bias because some of my own research work is looking at surfaces and interfaces. So I tend to take that kind of perspective. You know, lots and lots of technical challenges as Professor Takayuchi told us very eloquently during her lecture. Maybe I'll just pick a few. So if we look at the anode of a battery, thinking just perhaps of a lithium-ion battery to take an example, there's a really interesting process that occurs there when the battery starts out, and basically the electrolyte decomposes and forms something called a solid electrolyte interface, which, you know, some people would just characterize as a layer of gunk on the electrode surface. But it actually plays a very important role because it's electrically insulating, or ideally is, but ionically conducting, and that's really the only thing that allows the battery to operate safely at all. But having said that, the structure, the molecular structure of that layer is very complex. It has inorganic components, organic components, mixed organic, inorganic components, and they really take a very complex structure. Understanding that, I think, at, again, a molecular level, ideally so that you could improve the operation, I think, is quite important because even though the SEI, as it's called, has a beneficial safety feature, it does have some undesirable features. For one thing, there are some things that could happen in the battery, for example, if the electrode expands, that layer may crack, and then you just end up decomposing more and more electrolyte. Not good. Depending on the structure of the SEI, you could have dendrites form. And it also just takes up lithium or other charge-carrying species sometimes. To give a second example, maybe switching more to the solid-solid interfaces. Partly, I think, because of these challenges, people have become very interested in solid electrolytes for a variety of battery applications. I think a lot of the safety issues are less severe with those. But at the same time, you still have a lot of these, again, I'll call them molecular-scale instabilities that can occur at the interface between the solid electrode and the solid electrolyte. And those could either be thermodynamic in nature, just due to the interfacial thermodynamics of that interface, or they could be kinetic in nature and involve reduced rates of charge transport or sort of dynamic reconstructions. So I think just kind of getting a better picture and understanding what's happening in that region could also help for a lot of future battery design efforts. And then one other thing I'll mention, just in passing, there is, I think, interest for all these reasons in having, let's say, artificial coatings on some of the electrolytes. We could call them passivating layers or protecting layers, a variety of different purposes. Ideally, those would be hopefully relatively well-ordered, so they don't have a lot of defects, which can sometimes cause problems. In the case of the solid electrolyte interface, like something that has all the good features of the naturally formed SEI but not at the bad features, that's a tall order. But one thing, and again, this is just one of my personal interests, a popular technique for making those kinds of layers is something called atomic layer deposition, which was originally developed in the microelectronics industry, but has found a lot of materials applications in the last 10, 20 years or so. But it's very interesting when you look at how that process occurs. I mean, in principle, it's very powerful, but if you take some sort of a species that you want to deposit, like, say, it's aluminum oxide, that's something people work with a lot, just as an example. But you want to go through these molecular processes to grow that aluminum oxide layer on a battery electrode. The first few cycles of that process can be very surprising and very difficult to predict, just because you have these species interacting with a foreign electrode surface. And so in some sense, I think understanding the details of those types of processes in the spirit of creating passivating layers, at least through that particular technique, might be very fruitful in the future. So those are just a few thoughts. So let me comment. You were talking about known systems. So now we're not talking about discovery, but known systems. Let me start, perhaps, with the manufacturing part. Now I'm going back to my own experience in industry, and I think one of the questions was very relevant to that. Even with trying to reproduce the same battery over and over again, the input materials are challenging to maintain to be identical. So raw feedstocks can change, vendors can change, and being very rigorous about characterizing everything and knowing what characteristics are critical is really important. It's easy to say, oh, we'll characterize everything, but financially that becomes impossible for any company that's trying to make money manufacturing. You have to know what to characterize and what features are key to make sure that you can reproduce your own batteries time after time after time. So I think that level of quality control, process control, detailed, let's say, I'll call it structure function, but it's more than just structure. It's kind of like characteristics function. Relationships are really important to understand. The second point I'll make is something that I did bring up to some extent in my presentation, where we can have a known battery, but if the usage changes, then everything changes. So I think it's very tempting to say, oh, well, my battery was rated to whatever 4.3-volt charge, but I'm just going to sneak up a little bit because if I go to 4.4 or 4.35-volt charge, I'll get a little bit extra capacity, so that's great. But I think there's a word of caution there, that if there is a known technology and it's been well-studied in one particular band of application, if the voltage range changes, if the current is higher, or quite frankly, and sometimes lower, it can also be damaging, then the understanding and the level of predictability of that battery is not what you think it is. Which leads me to my overall third comment that I'm not aware of any model today that can kind of a priori say, I can predict this battery no matter what. I mean, within a certain range and a well-defined range, I think batteries are well-understood, but if you go outside that box of knowledge, then it's like starting with a whole new system. And I'll pass it off to Dr. Patterson, but maybe I'll indulge myself by asking him a question. Because I really enjoyed hearing about the complexity of the pack design and the level of control that it's necessary, especially when I contemplate a pack that operates at like 300 volts or something, my goodness. My question is, in terms of reliability, where have you seen the greater risk? Is it cell level failure, or is it kind of maybe in a broad sense controls failure that then maybe led to cell level failure? Because it seems to me that the reliability systems of the cell manufacturing and the pack design and the pack control have to be equal or perhaps the pack design has to even exceed the cell level reliability to make the system functioning. So be interested in your thoughts on that. Sorry to divert. Right, so that is a really great question because like any engineering endeavor, if something has, let's say, a 10-year warranty, you want that item to last for 10 years in one day, right? The cells are pretty reliable. And so I haven't really seen a system fail because of a cell or I should say if something went wrong with a cell, let's say it's a little bit weaker than the other ones, right? The battery management system will find that out and will just throw a fault and shut it down. I will say that a lot of lithium-ion battery systems haven't really been out in the field long enough to fail. And so, you know, the recycling that we've all been talking about, that is just going to come in a big rush at some point, right? Now, the company I worked for did not really supply too many automotive batteries. It was mainly for buses, grid storage, and the expected lifetime on those were seven to almost 20 years. So I don't know if I'm exactly answering your question, but I will say that if something goes wrong with the cell, that will be caught in the controls. And I will say that when it comes to, you know, large manufacturing operations, there are large quality organizations, and definitely everything is specced out to automotive standards or, you know, different kinds of standards. And so everything is very thoroughly analyzed to make sure that the entire pack will last through the warranty period without anything going wrong, right? So most packs will be swapped out or scrapped out or reused when they've reached 80% capacity, right? So once again, I'm not sure I'm really answering the question. I think that does answer me. What you're saying is that spontaneous cell-level failure is pretty rare. It is. And if it's not a catastrophic failure, if it's just a failure in weakness, let's say, then that can be called out. Exactly. So that puts a lot of the reliability responsibility on the battery management system. It does. That it has to reliably do that every single time. It does. And so there's a lot of cell testing that goes into the parameters of the battery management system, both in terms of controls, like you said, voltage limits or current limits with respect to temperature, especially. And then also when it comes to just keeping track of how long has this been in service, you might do some Coulomb counting. You might report out on different lifetime parameters, a state of health. So an awful lot of responsibility lands on the battery management system to keep everything safe and to shut things down. If something looks wrong. Okay. And so I guess the sort of follow up in that, is there a lot of development of different algorithms that can better predict and go into those control systems? And is that sort of an area that's been an active part of your work? That's a huge area. So when a cell is commercialized, there's a lot of testing that is done. Some of that testing is very specific to the battery management system, to the algorithms, to current limits. Sometimes you can run a cell at a very high current, but that raises the temperature. And so you want to kind of set a current limit that will result in a reasonable temperature rise. So definitely there's so much work right now going into battery management systems and not just like local work to the cell. Also on machine learning, cloud computing. I know these are just buzzwords, but trust me, there's a lot of research going on in these areas right now. Because everybody's goal is to make that battery system last longer. Great. And I think so we've talked a lot about sort of existing chemistries and you've done a lot of work at each of you on developing sort of new battery materials. And I guess Professor Takeuchi, if you wanted to speak, what's driving a lot of this interest in new battery materials? Why, you know, beyond just having different chemistries besides lithium, are there any sort of external factors that are really incentivizing the development of new chemistries? There are and there are multiple and I think it does depend to some extent on the application. Cost is always an issue. You know, no matter what the battery application is, if we can have an alternative that's lower cost, that's better. And other is supply chain. Where are the raw materials available? Are they available in North America? Are they available in the U.S.? Do you mind in only a few locations on the planet that may or may not be politically friendly to the U.S.? So being aware of material supply chains all the way back to the ore, you know, that these materials come from, I think is something that is really gaining a lot of attention these days. And I think the other thing that's gaining attention is environmental impact. You know, especially as the battery proliferation and battery proliferation of big batteries is coming up, what's going to be the destiny of these batteries? Are we going to be able to recycle efficiently? How dangerous are these batteries after they've stopped their useful life? Not so much from a perspective of catching fire, but just from an environmental standpoint, these things are left to corrode and start leaking all over the place. How dangerous are they? So I think it's cost, I think it's supply chain, I think it's realizing that batteries are going to be more and more widespread. What's the environmental impact? So many of those things are motivating new materials. But in the vehicle space, to be honest, higher energy density is still critical. You know, people want higher energy density cells so they can use fewer of them, which saves space, saves costs. So it's not only kind of material supply and nature of materials, but it's really the functional, the performance factors that are still very much on people's minds. So I guess in the process of developing those materials, there's obviously experimental methods, Professor Greeley, you've done a lot of work on computational methods. How do you go about sort of trying to build models that can explore this vast potential of materials that could be utilized? Yeah, so one of the neat things I think about molecular level modeling is that it's very flexible, and in particular if you push that down to the level of performance, which many researchers do these days, you can make pretty useful predictions about a wide variety of different kinds of materials. And so taking advantage of really good characterization, like Professor Takuchi talked about during her talk, as sort of a basis to develop models, very important. There are some other methods that you can try to use basic thermodynamics or statistical theories to sort of predict structures and models as well. And so all of those go into the model building and prediction of properties. Just one other thing I'll mention though, I think one of the really, in addition to just the basic computational methodology, one of the really exciting things, which actually started probably around 20 years ago, but has really taken off today, is the development of data or databases. Starting, I think about 20 years ago we started to see databases, even just online of properties of bulk complex oxides or other materials that are related to battery science and other applications as well. A lot of the information in those came from various types of calculations, electronic structure, first principles, calculations, and also other information, experimental data from crystal structure databases and so forth. And so today that's all available, or much of it at least, is available online. Very, very useful tool. If you have an idea for a new material, you can usually go on there and get some idea what the phase diagram looks like. How stable is it? Or does it even make sense to look at this for certain types of conditions? I think these days a newer trend, not brand new, but still newer at least, is trying to incorporate, again, information about surfaces and interfaces in those databases. That in some sense, I guess I would argue is a bigger challenge because any given material can exhibit many, many different types of surfaces or interfaces depending on the environment that it's in. And the surfaces may also show different sensitivity to things like contaminants than the bulk material does. So in some sense it's just a much, much larger amount of data that you need to really characterize though. So that's a really significant current challenge. And I guess I would probably argue there that that is a place where calculations, at least, which is my specialty, can play a role. Because a lot of that interfacial information is very challenging to access experimentally. Probably even more so than getting information about the bulk materials. And then I guess maybe just the final point I'll make is there's a lot of talk today about machine learning and we've already had some talk about that. And I think that does have a role to play. Partly through these databases and other things, it's possible now in many systems to kind of train an algorithm on existing data and say, okay, given the structure of this material, let's get a quick estimate of the voltage or other properties. It's not a fully solved problem, but there are ways to do that. But I think one of the things that really is a very new area now is trying to invert that process in a systematic algorithmic way. So taking these machine learning trained algorithms and then reversing it and saying, okay, given a particular voltage, can we reverse these algorithms systematically to give some candidate structures that would have those? People are already doing that in a kind of brute force way. But having real algorithms that are efficiently and systematically able to reverse that process, I think that's, it's a new area in data science or at least in the materials community. And I think there's a lot of potential there as well. So I guess we've talked about all of these new materials. How do you actually get those new materials into these bigger battery systems? Is there a lot of sort of hurdles to overcome? There's obviously a lot of system design that goes into each and every one of these. Are there challenges not only just from the technical challenges associated with that, but how do you have to compete against sort of existing technologies? And have you seen sort of challenges related to that? Right, so I'll start off by saying there's only a very few commercially available lithium-ion battery materials on the market that can be purchased in like metric tons, right? There's LCO, NCA, NMCs in all the different ratios, LMO, and LFP of course. On the anode side, graphite, I'm going to throw in hard carbon, LTO, and then now silicon blended with carbon. And I'm not talking about, of course, medical implantation batteries and stuff. Those are very, very specialty. FDA regulated, et cetera. So it really is challenging to take a new material all the way through to commercialization. If you'd like to know the process for that, it's really interesting. So when we would get a new material, we would start by building half cells and half cells are cells that are made of the active material versus lithium metal. And then of course, since you have the lithium metal and also lithium ions in the electrolyte, you have your reference, it's like a quasi-reference electrode right in the cell there. That's your zero-volt limit right there. So you do a charge, a discharge. You find the initial capacity, the reversible capacity, the irreversible capacity. What does that charge and discharge curve look like? That gives you enough information then to go ahead and design a small R&D full cell. And so if that is a positive material testing, you'll probably put it against graphite. If it's a negative material that you're testing, you might put it against an NMC, for example. And we're talking about small R&D cells here. So maybe a coin cell, maybe a small pouch cell, nothing more than 100 milliamp hours, just very small cells. But with these small cells, if they're built carefully, they can be very reproducible and you can run charge and discharge testing and cycling testing. And cycling testing was really the test that we used as the gating item for if we could go to the next level and scale up that cell. And we really needed at least 1,300 cycles, that was our number, to graduate to that next level because we're not talking about commercial cells for cell phones. Nothing of only a few hundred cycles. For the applications that I'm talking about, we need thousands and thousands of cycles. Companies want warranties of seven years or nine years or 15 or 20 years. So you really need a lot of calendar life and a lot of cycle life. So if all goes well with the R&D testing, it graduates up to the large cell, the large format cell. And this is where the testing really begins. I know there was a lot of pretesting, but this is the full testing. We do a DVPNR. It's a Design Validation Plan and Report. Charge, discharge, cycling at different temperatures, different rates with different voltage limits, self-discharge, calendar life. We look at then the testing that goes into the parameters for the BMS. There are, there's United Nations 38.3 transportation testing. You cannot ship a cell unless you've passed that testing successfully. There's different safety and abuse tests. It's a lot of testing. It takes about 18 to 24 months to accomplish this testing. Maybe you could do it faster if it's a little bit of a twist on something that you've already done, but really it takes time. It takes people. It takes time. It takes equipment. There's a lot of data analysis. And of course this is when you really then commercialize that cell so you can have data sheets, proper data sheets that tell you what the current limits are, what the voltage limits are, temperature limits. And so that is how you commercialize a material into a cell. It's a long process. Great. And so I guess you touched on this a bit, that supply chains have been a challenge in recent sort of months, years. I guess in the industry experience, how has that impacted sort of your operations or what you've seen so far? And then perhaps we can talk a bit about some of the policies that have been more recently put in place to try and address those challenges. Yeah, I'll just speak shortly about supply chains. So when a company is in constant manufacturing, you have suppliers for the materials and you need to give those suppliers forecasts because not all materials are made continuously. Some are made in batches. And so you have to let them know how much you want, when, so they can deliver it to you. You'll notice that very big consumers of cells like Tesla set up really strong partnerships with cell suppliers and that is why, so that they can have that completely reliable continuous cell supply chain. I'll mention that one time that I can mention that there was a problem with supply chain was when there was a patent dispute. And this occurred back in about, I think, 2016, 2017. There was a patent dispute over NMC's. And yes, it was pretty famous patent dispute. And so for a period of time, it was actually not able, it was illegal to import a certain manufacturer's NMC in either powder form or even in finished cell form. So this really drove home and of course we were on it. We had validated a second supplier, so we had no interruption in our supply chain. But it really is important to have multiple suppliers for any given material so that you don't run into problems when things happen. Yes. And so there have been policy efforts and pushes to try and build up a domestic supply chain. I guess can any of you who want to take this question and answer, discuss sort of what has been happening recently, what that means for people who are in the battery researching space more broadly and how you see that playing out sort of in the next few years. I can comment a little bit, but I think Dr. Boudicen really is in the best position to comment on this. Manufacturing requires really a broad variety of skills. Certainly the quality control organization, as I already mentioned, but a lot of process knowledge, process design, process control, and manufacturing knowledge. And some of the challenges that we have is I think that right now that's probably a set of skill sets that maybe we need to expand and broaden and make more robust. I think on the research side of things, the United States is generally in pretty good shape. However, research and working with those tiny little batteries is a whole lot different than actually launching a new material into a process. Also, the financial reward for making that change has to be clear. What does the new material do that existing materials don't do that would warrant the expense of going through that entire qualification process? Yeah, I would just say that one of the things that I think is really interesting is in that I think it's done often in industry or lifecycle analysis or techno-economic analysis. And I guess my impression is that on some level those types of analyses are, at least for large, fairly funded programs, being almost required these days or taking a more prominent role without getting into the details. I think the reason is more or less what you just said that people recognize those are choke points or sensitive areas, however you want to refer to them, that in some way need to or should be accounted for when you're kind of planning your basic research efforts over the next 10, 20 years. Yeah, I would just add that, of course, we touched on several of these things. Earth-abundant materials are good. Local materials are good. Local processing is good. Inexpensive cost is good. But those are all ideals, right? And then there's the real world. I will say that there is a big push in all of industry to source more local materials just to lower the carbon footprint of transportation, of getting the materials to your premises. And also it avoids currency exchanges, customs, fees, things like that. So local is better if it can be done. Great. I think at this point we can open it up if there are any questions from the audience that they would like to ask. Just please remember to wait for a microphone just so that everybody who's viewing this on the recording. My question is about energy density. Professor Takayuchi mentioned about the energy density of lithium ion batteries. So before that, I want to give you a little background myself so you can understand why I'm interested in that. I'm a professor in aeronautics and astronautics. So I study chemical propulsion systems. Basically all the combustion engines that burn hydrocarbon fuels. So my question about that energy density is because for anything fly, energy density is specific energy based on volume mass matters because it increases the drug and also requirement for lift. So my question is in theory, are there any materials or battery systems that can have compatible energy density as jet fuels? So excellent question. I refer you, actually I'm a co-author on a fairly recent paper in Nature, and we tackled exactly that question. So we had people from airlines as well as battery people kind of collaborate to write this paper to understand what's possible. And broadly speaking, I think for short flights, so they talk about vertical takeoff and landing, they talk about like various flights that in the Pacific Northwest and in the East go from like island to island, you know, the short hop flights. I think electric flight is feasible. I think that the balance of the load, the energy content, the ability to charge with some frequency is viable. I think where the equation gets very challenging is when you're talking about long distance flights. You know, trans-oceanic or even transcontinental, that's pretty challenging. So I think that inroads can be made for, let me call it short hop flights, you know, where the energy content in an absolute sense is a little bit smaller and you can charge more frequently. In fact, I think there are examples. There's a company in Europe who's already making some electric planes, electric flying vehicles, I guess I'll call them, but for certain applications to think that batteries can have the energy density of jet fuel itself. Boy, that's going to take some invention or certainly not there yet, but I think there are some aeronautical applications where it is already viable, but there are some where today it is not viable and the path to get there is not yet well-defined. So, excellent question though. Hello, I am Devanjali Chatterjee. I'm a third year PhD student in mechanical engineering. So my question to you is, I have actually two questions. In your seminar you mentioned that, you mentioned about grid energy storage. So my first question to you is, what are your thoughts on the resilience of the energy grid? Like how important it is and what are the steps we can take to increase the energy resilience? And my second question to you is regarding energy justice. Like how can we make these renewable sources of energy or the electrochemical energy storage systems how they can play a part in making renewable energy more accessible to all sections of the society? Thank you. Those are two great questions. I think in terms of reliability there are several steps that can be taken. Certainly, I'll start with the United States. I think one of the challenges that we have for much of the grid is really extreme weather. Certainly on the coast, but I think it's true in the Midwest as well. When there's extreme weather, trying to have the grid be robust is really a challenge. So my view is to have a little bit more decentralization, maybe some smaller grids that can then compensate if one of them goes out can be helpful. Another thing is increasing sensor networks on the grid so it's clear where the failures and faults are. And the third thing that I think is increasing in importance is the idea of cybersecurity. More and more the grid is actually controlled by computer because the ability of humans to respond quickly enough to the dynamics of supply and demand is not really feasible anymore. So I think those are more immediate things that can be done. Energy justice, I'm actually very interested in having our moderator comment on that because I think this is really an area that she and I were discussing earlier in the day and that's something that I think we need to think about not just in the United States but in a global sense. So yes, there are obviously multiple dimensions to energy justice. There's a lot of, as we transition to this decarbonized future, thinking about how we can best mitigate some of the communities that have had to bear the burdens of our current energy system. So the places that have been impacted by air pollution the most that may not have access to the capital to install things like solar PV on residential systems or solar plus storage systems. And so I think we need to think deeply about the amount of support for providing access to all of these technologies in a way that explicitly tries to account for the fact that we have had these inequities in our current energy system. And then from a global perspective I think not only from this equity perspective that we want to increase the share of people around the world that have access to inexpensive energy but if we want to meet our carbon, our decarbonization goals like we're not going to get there unless we do that in a way that provides them with zero carbon electricity sources. And so having these technologies at a cost that can either be produced locally or transported to these places I think will be a large portion of meeting these sort of dual goals to increasing energy access and decarbonizing over the next coming decades. How much do you know about the liquid metal batteries? Ombre or DMIT? That seems like an ideal grid storage and renewable storage device. I can comment a little bit about that. Ashley, one of my former PhD students was employed there for a number of years. He's now moved on to other things. It's a very intriguing concept where they are in terms of financial viability and product ramp up. That's something you'd have to look into. I think the challenge, the technology challenge that I'm aware of was one of materials compatibility. When you have liquid alkali metals they're actually extremely reactive and from a battery perspective that's good news but the challenge is how do you contain them? In other words, literally, what do you put them into? I think the other challenge was specifically the seal. Any battery has to have some way of separating the negative terminal from the positive terminal. There has to be some kind of a seal. In some batteries the seal is ceramic and in some batteries the seal is glass, glass to metal seals. In many batteries that seal is polymeric so it's kind of a crimp with a polymeric seal but that insulating material and the stability of that insulating material is key to the lifetime of the battery. That's the technical challenge that I'm aware that they were up against. It's possible that they created a solution to that but when you have highly reactive materials and you're trying to keep them apart from each other that can be a real materials challenge. Hello, my name is Thomas. I'm an undergrad in materials science and engineering. You mentioned in your seminar that you began your research around the magnesium based on the observation that there was discrepancy in research and we all know how important observations are to quintessential inventions. My question for any of the panel members is how do you continue making these observations in a field such with so many intricacies as electrochemistry and especially as Dr. Greeley mentioned with things such as computational models becoming the basis of research moving forward? Yeah, that's a complex question and I'll invite the other panelists to comment on that as well. I think what you're really saying if I can rephrase it a little bit is it's already a crowded design space so how do you find a new niche? My comment there is really that particularly as a student to think to do is learn the fundamentals and you've got to start somewhere. I think that's really the goal of becoming part of a research group and pursuing graduate research is that you draw on the knowledge of somebody who has been in the field so they have a sense of what's new and what's already known. I will say that the sheer velocity of publications these days is pretty staggering. I mean I haven't looked but I'm sure there's thousands and thousands of papers on batteries that are being issued every year so it's certainly not possible to read all of them so I think what becomes important is to pick a place to start and become expert in that place and then once you become expert in that place you can broaden your knowledge base to look at a diversity of things so that would be my comment but I think looking in the literature is always a good place to start so press it greatly. Well first to clarify I didn't mean to imply that computations would be the default design approach going forward I think it's one tool that can help with the whole design exercise but yeah it is a complex question perhaps just a couple of thoughts I guess one is I think there's always attention if you're trying to well so one thing is just given what Dr. Takeuchi said about the sheer explosion in papers to some extent I do think you have to become a little bit more narrowly specialized or maybe a lot more narrowly specialized just to stay at the forefront of any given field but second I guess speaking to this more general topic of design or how do you find new materials I think there's always been a tension between more of a they call it an Edisonian approach where you just try a lot of things and hopefully find something that works and some of the new aspects of computational material screening or machine learning can actually fit into that category as well to some extent on the other side there's the thought that the more the deeper you understand all the physical and chemical principles that control these systems the better your intuition will be and therefore the more likely you'll be able to have intuitive leaps to come up with new materials I personally think that a combination of those two approaches is good and so in some of the work we do here at Purdue we do try to combine those in the research we do Great well I think we have to wrap it up now but I would like to take the opportunity to thank all of our panelists again for taking the time to have this discussion and thank you all for joining us for that this afternoon