 A very good morning from Stanford University. My name is Will Chu. I'm the faculty director of the StorageX Initiative and also a member of the Material Science and Engineering Department here at Stanford. It's my great pleasure to welcome everyone to the final seminar for the spring quarter. And for today's seminar, we are delighted to focus on one specific material which is critical for energy storage. Soft materials, namely polymers, are critical in today's lithium-ion battery technology. It is what the separator is made of. And it is also very important as an inactive material, for example, as binders in the electrodes of lithium-ion batteries. But their uses can be really far greater than that. Folks in academia and industry are exploring the use of soft material for things such as the solid electrolyte as active materials, for example, as electrodes and a host of other processes. Soft material has a very rich history, evolving from simple structural material all the way to complex material for electronic systems. And we're really delighted to have two of our colleagues from academia and from industry to talk about how polymers and soft materials can be used for next-generation energy storage, both for those based on lithium-ion transportation, but also based on next-generation, low-cost, long-duration storage as well. And we're delighted to have Professor Alberto Saleo from my department, and also Dr. Kevin Wojcik from Blue Current, which is a startup pioneering solid-state batteries using polymer materials. So let me get started by inviting Alberto to the stage. Alberto, as I mentioned, is my chair in my department and a great colleague and friend who has been a pioneer in the polymer field for more than 20 years. In his early work at Stanford, he really transformed the field of organic electronics by recognizing its use in biological applications and also in energy applications for solar applications. And I'm so thankful that in recent years, he has gotten interested in energy transformation as well, finding new uses for electronically conducting polymers in applications for energy storage, for electric catalysis. It's really a wonderful material that I think has been under-investigated by these fields. Alberto's extremely accomplished in addition to serving as chair of our department. He is also a fellow of MRS and has had many impacts on education, research, and so forth. His award to be too long to read, but you'll take my word that Alberto is one of the best. We've got Immaterial Science, and Alberto, I'm really delighted to have you with us this morning. And Alberto, please tell us about what other uses semiconductor polymer can have that we haven't thought of. Thank you, Will. Thanks for the kind introduction. As Will said, I come from the world of using polymers for electronics and recently we've been more and more interested in their energy applications. And so what I want to talk about today is how we're using these conjugated polymers and we're getting interested in energy storage. And in particular, I think they have advantages in the idea of having a circular economy of energy storage. So if you think of everyone wanting to have their electric vehicle and having this technology be more and more widespread, really batteries are of course a key aspect of it. And what you'd like to have is you'd like to be able to see the cost of batteries go down. The production of batteries go up and their lifetime go up maybe 10 years, 15 years or more. But no matter what, if you think of the car having a battery as sort of this standalone thing, you'll end up with a problem of having at some point a lot of dead batteries sitting somewhere. So it really is important to think of a circular economy of energy storage sort of from the ground up as we want to have more and more electricity as a source of, as a way to store energy as opposed to, as opposed to liquid fuels. So the challenges for recycling currently is that current battery technology requires organic electrolytes. These are hazardous or flammable. It doesn't mean that it can be recycled as just added costs. And in the same vein, electrodes are made with materials and binders. So if you want to recycle them, you have to separate all that. Again, this is not a fundamental obstacle but it just adds costs. And when you add costs, you wonder about adoption, right? Adoption might go down if things become too expensive. So what we are attracted by, it's the idea to having redox added materials that can be easily recycled, essentially being able to have a material that is the electrode itself without needing any binders. Also that they can be extracted using solvents very simply. It's a simple phase material. So maybe you just dissolve it and we deposit or dissolve it and reuse and purify and reuse. And also the materials that we're interested in use safe electrolytes that they can use salty water and that makes it easy for safety. Of course, the trade-off is what is the capacity and I will address that a little bit as well. But as you see, I think we are off to a really interesting start with these conjugated polymers. So like I said, I come from the world of polymers for microelectronics and in that case, you only have to transport one type of carrier and that's the electronic carrier. It turns out for historical reasons that most semiconductor polymers are good at transporting holes. So hole transporting goes along the backbone. The holes essentially move along the double bonds and the single and double bonds along the backbone and that's sort of fairly well known. And so the innovation here is not so much the fact that we have electronic charge carriers but because we're looking at electrochemical devices and in particular batteries, we also want ions to go in and out. And so now we have materials that can also carry ions. And the thing that is new here is that historically again, conjugated polymers had side chains that would repel ions or sorcery, not be sort of a comfortable home for ions but Alice Giovaniti and at the time, Ian McCulloch group is a postdoc now in my group devised a way to graph side chains that as you can see here have oxygen atoms and in this case, these can be nice homes for ions because they're polar. And if you have a whole transporter, then the ion that naturally will want to go in there to stabilize the extra positive charges and anion. So if you have a charge carrier, there are holes. So P type semiconductor backbone, you will almost automatically be able to, if the side chains can accommodate it, you will be able to accommodate an ions in the side chains and then symmetrically remember want to make a battery. So we need one electrode that carries electrons and one electrode that carries holes. So if you have your electron as a charge carrier, so it's a different type of backbone, then the side chains will accommodate pretty naturally a cat ion. So what is interesting here is sort of at a higher level is synthetic chemistry is really good at making molecules that don't exist in nature sort of almost by design. And you can see here the motif already, you have the electronic carrier as a backbone, the ionic carrier as a side chains. And so you can see how the two can almost be designed independently and you can match them to get the best performance. What's scientifically interesting here is that I simplified things greatly and reality it's not like that. There's a lot of sort of interactions to some extent you'll see and that makes the field, I think, really rich scientifically and fascinating. But let's start if you're not from the field of conjugated polymers, why do conjugated polymers behave as a semiconductor? When you see conjugated polymers, if you're not from the word of polymers, you'll see a whole bunch of different structures. They will pretty much all have this constant motif, which is an alternation of double and single bonds and maybe we'll have some hetero atoms, but really it's the alternation of double and single bonds that matters. And if I cut everything else out, the alternation of double and single bonds would be seen in polyacetylene. And what this really means is that every carbon atom is sp2 hybridized and the three sp2 orbitals are busy binding to two carbon atoms and one hydrogen atom. And then there is one electron left in a p orbital that's perpendicular to the sp2 orbitals. And now you can think of this as forming a band, right? You have all your p orbitals are lined up like this. And if they're all lined up, that they're all in phase, you get the bottom of the band. If they're all lined up, that each one of them is out of phase with its neighbor, you have the top of the band and then any other periodic combination will give you a state in between. So you can really think of this simplifying a lot as a band structure. And because the energy of the bottom of the band and the energy of the top of the band are different, you get a bandwidth and the bandwidth is really connected to the resonance integral or some extent to how much these orbitals overlap. So if you put them closer, they overlap more. If you put them further away, they overlap less. If you start contouring them, they overlap less and so on. So from the solid state physics point of view, you think of this difference in energy, the bandwidth giving rise to dispersion. So you have an effective mass and everything sort of works in the solid state physics picture. Of course it's a little bit more complicated here because as I told you, if you get some twists and turns, this overlap can change. And this is what I spend a lot of my waking hours thinking about when I think about charge transport and conjugated polymers. So this is the high level of why the backbone of, how you would design the backbone of the polymers to be electronically conducting. You need to have this alternation of double and single bonds. We're a material scientist, so we like microstructure. I showed you a molecule. What does it look like when you make a film of these materials? Well, it turns out that because of these polar side chains, these polymers swell in water, which is the electrolyte of choice for our application here. And so the ion comes in from electrolyte. The hole comes in from the electrode. If it's an ion, so it'll be compensated by a hole. But you should think of this material as a sponge for ion that also contains electronic charge carriers. So you can see now the connection to make an electrode for batteries. You can see now that the ions will be able to really penetrate the material in three dimensions. So this, I don't know if I would call it intercalation. It's more like really a penetration of electrolyte and ion. It's the swelling of the electrolyte and the polymer. And the ionic charge density will then affect the electronic charge density. So we like these materials because you get this bulk modulation of the electronic charge density and stepping back from batteries and hoping that I can convince you that these are just really interesting functional materials because if you think of, again, coming from the world of thin film electronics, there you modulate a very, very thin layer of charge carriers near an interface. Now we're actually modulating the bulk of a semiconductor. So for example, if you push ions in and out with a voltage, you can switch the semiconductor from on and off, but not just the interface, you switch the whole semiconductor. So you get a gigantic modulation of conductivity because these materials change colors when they're charged and you change a color in the bulk. You can also make displays. Electrochromic displays can be made with these materials. Fascinatingly also, when you charge these polymers, they essentially form electrostatic crosslinks so you can actuate them. You can make them more or less rigid and also because they swell with electrolyte, they change their volume so they can be used as pumps to push things around. So really interesting family of materials as well alluded to. In our case, what we're interested in is the fact that when you modulate the amount of ions, you're changing the amount of electrons so you're changing the position of the Fermi level. And so if you have two electrodes that have two different Fermi level position and you connect them, you essentially have an energy storage device. And I think you can argue semantically whether it's a battery or an electrochemical capacitor. I don't think I wanna get into that type of controversy, but the bottom line is you have a device that can store energy. And this is what I wanna talk about today. So what are the opportunities and challenges here? Here is a typical material that you'll see a lot. In this case, this is an electron conductor and I'm not gonna go into the details of the design of the molecule that make an electron conductor, but at a very simple level, you have to think of a molecule that will make electrons comfortable. So it has things on the side that are electron withdrawing so that they decrease the energy level of the electron. So when you stuff an electron in, the material doesn't become unstable. So here's one of the material that you look at and you can see this alternation of double and single bonds. This is a Naftaline diamet group here and then you have two thiophene here. And so this is called Naftaline diamet by thiophene molecule. Doesn't really matter. What matters here is that it can accept two electrons. The monomer can accept two electrons and the side chains are a polar or glycolated are sitting here. Now compare this to graphite. Typical electrode material for lithium ion batteries and you can see right away, there's a stark difference which is you need a lot of molecule to accommodate two electrons in graphite. You only need six atoms to accommodate one electron. The consequence of that is that, of course, the gravimetric capacity of these polymer electrodes is not as high as the gravimetric capacity of your typical graphite electrode. The advantages though, like we said is that a single phase electrode design, the material is both a conductor of ions and electrons. So you don't need to have a binder that does the electron conductivity or the ion conductivity with different material. And because the material swells in electrolyte, you can potentially have very fast charging rates. And in fact, we can see that. And that's something that have also been fascinated by it. These are materials that conduct ions really well. You don't need to, there's very little mechanical deformation to get the ions in and out. So they transport quite nicely. And then because the material swells in water as an electrolyte, it can operate in water as a battery electrode. So what are the strategies to design these materials? So you want balanced ionic and electronic transport properties. And again, just to simplify, you can think of the electronic transport going along the backbone and the ionic transport going along the side chain. So hey, I can graph any side chain on any backbone. I can design any material I want if I am a skilled synthetic chemist. So for the backbone design, what you need is identifying backbones that can charge, recharge reversibly without side reactions. And I'll talk a little bit about stability. But once you put an electrode, sorry, an electron on this molecule, maybe there is a chemical reaction that happens because you're also in water. So you want to avoid that and you want reversibility so you can have a lot of charging and discharging. The side chains on the other hand has to have to be tuned so that the polarity is such that they can swell, they can be swelled when they're cycled in aqueous electrolyte. So I'm showing here a side chain that wouldn't swell and here a side chain that swell. And you can imagine actually mixing and matching them to control a little bit better the properties of the material. This is a really attractive feature of synthetic semiconductors. So for our battery, we have as an annual material, like I said, for the electron side, the electron electrode, we use this polymer, we call it P7525. And the 7525 showcases an aspect that is really interesting about these materials is the fact that, like I said, I can sort of mix and match. I can make this material with alkylated side chains and we glycolated side chains. If it's fully alkylated, not good for aqueous electrolyte, it's fully glycolated. It might be very good for aqueous electrolytes but maybe charge transport is not so good. Well, it turns out that I don't have to be all or nothing. I can mix 75% monomers and 25% monomers of the other type, copolymerize them. Currently they're copolymerized in a random configuration, but you can imagine a future where you'd have them perfectly regularly copolymerized. And so you can really fine tune the level of side chain control that you have. And I'm showing here one design of side chain that's linear, but you don't have to go that way. So this is the annual material and the P7525 has a measured gravimetric capacity of about 40 a milliamp per hour program. Now on the cathode material, the other side, we have a homopolymer, we call PG3T2 for people who work in organic electronics. They'll recognize the backbone motif is sort of the fruit fly of organic electronics, poly-3-hexyl-5-gene. And all that Alex did is graft, or I'm not a synthetic chemist, it seems simple to me, is graft glycolated side chains to this motif and the material works, gravimetric capacity is a little bit lower because I think now if I remember correctly, you accept, I think it's two charges per one and a half monomer or something like that. So not quite the same charge density as the P7525. So these are solution processable and they can be used sort of additive free redox active materials are both electron and ion conductors. So that's all you need for the electrode. And we expect that they're highly stable during electrochemical cycling. I'll show you that we can cycle them for hundreds of cycles. And because they're so electrolyzed, they may have high charge and discharge rates, C rates over a hundred. So here's what the CVs look like in terms of stability. Sometimes these materials have a different cycle the very first time you charge them. I think that's what the dashed line is, but once you sort of break them in, they're pretty stable. Here's the PNDI 7525. Here's the whole side, the PG3T2. You can see that they're fairly reproducible. Some of the instability is really due to the fact that sometimes these ox ties a little bit, but it's really not something very, very fundamental. I don't think there is a lot more to say here. You can see sort of the classic CV. You put them together in electrochemical cell and this is what the charging and discharging of the cell looks like. Now in terms of retention, if you look at how well the charges retain, 91% retention after an hour, it's not bad. Again, I would say that some of that has to do with oxidation which can be avoided with better packaging. If the material that is supposed to retain electrons oxidize, it's essentially losing its charge. And so that's not desirable. In terms of where they stand, we'll compare to the competition in a ragoni plot. You can see that these materials actually compared to other carbon-based materials do quite well. They're above most of them. Sort of the envelope of the curve is above most of them. So even at a given energy density, they will have a higher power density than most of them. Lignin derived carbon being the exception there, but I believe that one actually has binders. So we were doing quite well compared to other carbon-based materials and it's fully recyclable as I will show you. To put it in the broader context of a ragoni plot, these materials also occupy a pretty interesting space. You can see that they're slightly to the right of electrochemical capacitors. So they have higher energy density with maybe a slightly lower power density and they're getting sort of close to lead acid batteries while being recyclable. So they occupy, I think you can see actually, it's sort of a void in the ragoni plot. So it's a pretty interesting space to be in. And really we just started developing these. I think there's a lot that can be done as you will see towards the end of my talk. The recycling process is as simple as advertised. You make your battery, you deposit your films from solution, we drop cast them very simply. We're not really trying to make the best battery out there, we just want to demonstrate a concept. You use it a few times, charge discharge and then you can extract the polymer by just treating the electrodes with a solvent. You have now clean carbon paper and you can re-deposit your polymers and there you go, you have your recycled battery. In real life, it looks a little bit uglier. Here's our materials in a vial. We deposit them, here's our electrodes on carbon paper, finished electrode with the current collectors. And then once you're done with charging and discharging, you put the carbon paper in a vial of solvent, this extracts the polymer, you remove the carbon paper, here's your recycled polymer, you re-deposit and you make a new battery. I want to point out we do this in small quantities so this is not really very well controlled and so I'm not convinced that we're recycling 100% of the polymers, probably some of it that's left a little bit behind. But this is the data when we do it in our lab, again, not in a very, very, very well controlled fashion. So we first make our first battery, then we scan it 500 times, charge and discharge it 500 times and we dissolve and re-deposit, we make a new battery and so on. And once we do it three times, we're left with 67% of the capacity retention. It doesn't sound that great, you've lost a third of your retention but I just want to remind you that this is done in a lab with small quantities of materials. So if you lose a little bit of it, you're actually using a large fraction of your electrode. There really just was to show the concept that you can get fairly high retention without really trying very hard. And here's a more complete data after different cycles and this shows you a few things. First of all, during the cycling, you don't lose gravimetric capacity. You can see that after 500 cycles, the battery is pretty much identical to when it started, both for the first time and the second time and the third time after you recycle it. And when you recycle, you're losing capacity and you're losing capacity mostly on the electron electrode, on the electron bearing electrode. It's this P7525. When we think that it has, you'll see a little bit later, it does have some stability issues and that's where we're losing a little bit of our material. But the interesting thing is that if you look at the chromatric efficiency after recycling, it's pretty much identical. And if you look at the gravimetric capacity versus the C-rate from the first to the third recycling cycle, sorry, the gravimetric capacity has gone down, but how it depends on C-rate is about the same and the chromatric efficiency, the chromic efficiency hasn't changed. And this tells you that when you recycle, you lose a little bit of capacity, but you're not really modifying the material fundamentally. Now, how do we know what happens after recycle it? So the polymers we work with are semi-crystalline, polycrystalline, sorry, semi-crystalline. And so if you put them in a synchrotron, they will diffract, but they also have amorphous regions. So you can look at before and after and the fraction patterns for the PG3T2. So this is the whole bearing electrode. So in this case, the X-ray diffraction patterns are pretty much identical before and after and the NMR is pretty much identical before and after. So this material actually has high chemical, electrochemical stability. On the electron side, we noticed that if we use wet solvents, so if we don't control effective is anhydrous solvents and some of the data that I showed you were used with solvents that were not perfectly anhydrous, we see new peaks showing up when we actually really control anhydrous solvents, use anhydrous solvents, those peaks disappear. And you can see without anhydrous solvents, you have new peaks appear, but if you use anhydrous solvents, the X-ray diffraction pattern stays about the same. And again, the NMR, if you're really careful of this material, it stays about the same. So if you treat it well, if you're careful about your solvents, also the N-type material is actually pretty clean when you recycle it. And this is a little bit of a light motif in organic electronics. N-type materials are always a little bit more delicate than P-type materials. So how do we study these materials? We're an academia and we like to really figure out how things work. Well, the easiest thing to do is to study them ex-situ. So you charge it, you remove the electrolyte, you stick it in the beam line. And there is essentially two families of diffraction peaks that we're interested in. The first family is a diffraction piece in what we call the high-kill direction. So it's this direction here. Remember, the ions will come in here. Here's a cartoon of it. The ions will come between these two stacks and we'll expand them. And in fact, that's what you see as you charge it. You see the diffraction peak of that direction moves to lower Q, which means that that direction is expanding. The other direction is direction between stacks, which is where some of the charge transport occur that's for the pi stacking direction. And interestingly, when you expand in one direction, you actually contract in the other. I say interestingly, because you would expect that because the volume of the unit cell should be constant, but these materials are vanavals bonded. So I actually did not necessarily expect that, but you can see it. The pi stacking peak is moving to high Q, which means that those stacks are becoming a little bit closer. The interesting thing we observe is that these changes are reversible. When you charge and discharge, we looked at the data after. So when you do the very first charging cycle, sort of break in the material a little bit. And after that, essentially everything goes back and forth very reversible. And that's a very attractive feature of these materials because it tells you you can charge them and discharge them hundreds of times without really changing the structure of the material appreciably after charging these charging cycles. We're really excited that lately we're able to do this operando. So we have a cell that fits in the beam line where we have x-rays coming in one side, the electrolyte coming in the other. And so we can do scattering as we charge and discharge the material. So we can do CV in the beam line. And here's the data where you can see as we scan the CV, we can see the fraction peaks go in and out in terms of intensity. Here's an interesting thing. This is the peak that has to do with that lamellar stacking where the ions get stuffed in and out. And you can see it changes in intensity, but not in position. So you're not changing, you're not really expanding and contracting very much. This is with a different electrolyte, with ionic liquids, but it shows you the potential of these materials to be ionic conductors without really undergoing strong structural transformations. And then I think that we can then measure charge transport as a function of charge density. And so we can see when the charge transport is optimized at what potentials. And this helps us design better materials. So how do we improve the capacity? The Achilles heel of these materials is the capacity. So remember that electron transport is the backbone, ion transport is the side chains. So if you wanna have more electrons per unit volume, what you should do is have fewer side chains. So this is one way you can go about it. So we tried for this P type material, we tried three different length side chains. And there is different things that come into play here. First of all, it's, you imagine that the capacity will go up as you make the side chain shorter because you have more volume of the material that can accommodate charges. But remember that the side chains help with solubility. And so you have to balance the fact that you want to deposit these materials from solution. You have no side chains that are essentially intractable. So here's a trade-off you're trying to, you're trying to affect. Now, one other aspect is that the side chains and the backbone, they sort of interact to form the microstructure. So it turns out that the PG2 T2, so the one with the shorter side chain is much more disordered than the PG3 T2, which is one that I've been talking about so far. And you would think like, what's the problem with disorder? The problem with disorder is electronic transport, like ordered materials. And so when we made the one with the shorter side chains, expecting to have a higher volumetric capacity, it turns out I had a lower volumetric capacity because of theoretical capacity was not reached due to the fact that we had problems putting the ions into the microstructure and the electrons in for reasons that I can explain in the Q and A, but they're really interesting. They have to do the energetics of the crystals versus the amorphous areas. So the design of the material becomes a really interesting, it's promising, synthetic chemists can make a lot of materials, but it's a very interesting fundamental science problem because it's not as obvious as you would think, just take the side chains out, you get a better material. Not only you get a material that doesn't reach a theoretical capacity, but you have a whole host of other interesting scientific issues. For example, it was very hard to recycle the PG2 T2, it wouldn't come off the electrodes. Now to improve the capacity of the anode, this is the material that I've showed you so far, these NDI T2 P75, so 75% of side chains are glycolated to accept ions, 25% aren't, and that was actually to balance electronic and ionic transport. The theoretical gravimetric capacity is about 51 and I showed you we get to about 75% of that, I think about 35 or so. So how do you try to get higher gravimetric capacity? Well, try to get rid of the side chains, remember those are for solubility, so why not dissolve the film and then get rid of the side chains, okay? Maybe that becomes a problem for recycling, but you do get an electrode that has a higher volumetric capacity. So the idea is to have some chemistry that allows you side chain cleavage, this is the monomer we're now considering, and these side chains can be cleaved off. Now actually you can accept more electrons per monomer because this unit, this benzene di-fine unit, can accept electrons as well, can in fact accept two electrons that will sit mostly on the oxygens, and so now you can actually have a theoretical capacity that's a lot higher, three times as high as that of the one that has the side chains. So this has, like I said, four electron acceptors, you can start playing with the side chains also of the NDI unit to branch them off and that allows you to make them shorter but still have good solubility. You can go even all the way to considering only the benzene di-fine unit and cleave the side chain afterwards. So this is sort of a different space where maybe recycling is less important, but you get a higher capacity by removing the side chains. So I guess the message here is that there's a lot of latitude for synthetic design to have materials that will have higher capacity and balance out this aspect of solubility versus capacity versus the ability to recycle these materials. And also we're looking at the capacity compared to lithium ion batteries, but that's not necessarily the competition. You can think of a lot of contexts where you would like a thin film battery that has an okay capacity but has other interesting aspects. For example, you could leave it out in the field without having to worry about recycling it. If you play your cards right, you might make a degradable polymer, for example. So as Will said, I think this is a very rich field that has just, I guess I shouldn't say it hasn't really been mined. 25 years ago, there was a lot of interest in redox polymers for batteries, then the field of organic electronics moved in a different direction. Now I wouldn't say we're reinventing the wheel, but we're rediscovering how interesting these materials are. And I'm very excited that we can throw all these really interesting characterization techniques in the way of understanding of these materials work in order to design better and better materials. So this is the essence of what I wanted to talk about today. I wanna thank the team that's been able to make this happen. A lot of this is a brainchild of a current, he's a postdoc in my group who really operates as an independent scientist, Alex Drivaniti. As Will mentioned, we're also looking at these materials for electric catalysis. When you look at them, if you work in that field, it becomes obvious. You have now a material that has expert electrons that are available for reaction and can bring reagents in because it swells in electrolytes, so we're looking at that. Adam Marx is our resident synthetic chemist. I've never had a synthetic chemist in my group, but now that we're trying to really understand structural property relationships in materials, we have a synthetic chemist in the group. And then a whole bunch of other students, Melissa, Tyler, Garrett, Ben is a former postdoc as well. Chris Stakaks is a staff scientist at Slack and Yile Wu is in Janan Bao's group, he's a collaborator. These are really to throw characterization techniques at these materials, understand how they work. Some of the original materials come from Ian McCulloch's group, now at Oxford. And I want to thank the funding for this work, the Tomcat Center and StorageX4C grant on recyclable batteries. So thank you everyone for your attention and I will be happy to take questions. Thank you, Alberto, for that wonderful presentation and introduction to conducting polymers. So we have a number of questions. Maybe I'll start with the high level ones, if that's okay with you, Alberto. Help us understand the context in which the polymers might be used. So I think you highlighted electrode and redox active reactions as the primary application. But as they alluded to, the energy density can be a bit limited. Are there other applications within energy storage maybe as another component of the battery that the polymers can find use for? That's a good question. I haven't really thought about it. You know, I was thinking more what type of application would benefit from the form factor and the flexibility, not so much different components of batteries. I'm thinking that part of my group works on electronic components for soft robotics. And there maybe you, really the premium comes from the fact that you could have a large area of something that ends up storing energy and because the materials are flexible, you're able to use more of an object to store energy. So the capacity per unit mass is not that great, but you have a large area that's available to you or you can fold it and do all sorts of interesting things. I never thought about other components of batteries. Do you have something in mind? You know, I'm just trying to brainstorm to see if, you know, classically inactive materials could benefit from some, you know, it's property. Yeah, so that exactly, actually, that's a very good point. I've seen proposals of using, maybe it's not part of a battery, but it's part of an object. Like the casing of an object is made of plastic. Maybe that becomes part of your energy storage. Sounds very exciting. Along those lines, in these polymer materials, what do you think is the limit of its capacity, graphometric capacity? So you highlighted pathway to get extremely attractive capacity, you know, several hundred million bars per gram. So that's already at the levels of today's battery technology. Of course, the voltage is lower compared to lithium ion, but the capacity is attractive. You know, at some point you're gonna, you know, have something that is so light as a molecule that may not work, but what does that limit look like? You think? In terms of numbers, I don't know. In terms of fundamental limit, it's going to be the stability of the materials. That's really a challenge. And then it becomes also an issue of packaging. But the electrochemical stability is the wall that will hit first, I think. Once you, what we observe when we look at these materials by spectral electrochemistry is that once you start putting a lot of charges per unit monomer, those coalesce and bipolarons and trions, all sorts of things that tend to be very reactive. It's actually, Alberta, very interesting because in organic material, there's exactly the same problems. You oxidize it too much, you reduce it too much, then the, essentially the percolations of these polarons give you a lot of problem for structure transformation. So I think it's one of the same problem. And I think I'm trying to understand how far you can go. You know, how dense of electrons can you add to the system? But it sounds like there's some room for further improvement even beyond what you have roadmap. Yeah. So your point about the electrochemical stability was the next question. You, can you give us a sense? You know, a lot of times we think about polymer as being more compatible in that aqueous environment, but this need not to be the case, right? It can also be quite compatible in non-aqueous environments. What is sort of the window of voltage that these materials live in? Gives a sense of maybe, you know, relative to hydrogen or relative to lithium where it can set comfortably. I owe a relative to hydrogen or lithium. I always think of relative to silver, silver chloride and you saw the numbers. So, yeah, sorry, I can't do it up to top of my head relative to lithium or hydrogen. Relative to silver, silver chloride, I mean, you saw that it's in the order of one and a half two volt type thing. So like you said, the voltages is intrinsically limited there compared to lithium. Right, but I think one thing that's also maybe, it's broadly appreciated in the lithium battery field is that the electrochemical stability window doesn't have to be that big for the electrodes because the electrodes only see, you know, part of the batteries environment. It is a separator that has to see the entire range. So, you know, the voltage you described, would make it quite compatible, for example, in the positive electrode of a lithium-ion battery in a negative, I think it's too reducing. So do you think there is a possibility to introduce maybe a solid state battery or some other thing in which we can really separate the two electrodes without problems and choose a polymer with a limited voltage stability and use it as a half battery and maybe pair with a inorganic material. We don't necessarily need to have an all organic battery. Right, yeah, I never thought about it. That's a really good point. Like I said, I commented from a completely different side. So these are all questions that I never considered. Graeber, maybe we have time for one last question. Can you give us a sense of the decomposition product of these polymers? Is it, could it be in the gas or is it mostly in solid or liquid states? I mean, they oxidize and so you form a small fragment that goes away and the polymer is oxidized, something like that. So they're in the liquid, they end up in the electric. The liquid state, okay. Yeah, I think in another major problem for lithium-ion batteries is outgassing. If the decomposition product is the liquid, it's actually a little easier to handle from the reliability and safety perspective. Whereas as it's a gas is a little harder to work with because it increases the pressure of the cell substantially. Let's see, I think that is all we have time for Alberto in terms of questions that will come back after Kevin's talk and then we'll discuss more polymers. Okay. Thank you very much Alberto. And now if I can ask Kevin to come to the stage as well, there you are Kevin, thank you so much. So as I introduced earlier, Kevin is representing Blue Currents, a somewhat modestly young startup that has been in stealth mode for a number of years. Kevin is the chief technology officer for Blue Current and has been spearheading the development of its core technology for solid state batteries for nearly five years, is that right Kevin? Yeah, about four and a half, four and a half years. And Kevin received his PhD from UC Berkeley working on polymer materials. And one thing that has really impressed me about Blue Current is that folks there kept their heads down, worked on the technology for many years. There's not exciting press releases. And after all this time and really something really neat comes out at the end and then Kevin is going to share that with us today. So as I mentioned, Kevin, I really appreciate you working with us to reveal some of these new exciting data on your technology and we can't wait to learn. Yeah, thank you Will. And I have to say your last questions there with Alberto were playing my hard strings a little bit. I think batteries have a pretty rich history and using soft matter and polymers. And a lot of what we're doing as a company is combining polymers with more inorganic materials. So looking forward to chatting with Alberto about that. All right, so thank you everybody. Thank you again, Will. My name is Kevin Wojcik and I'm the Q-Technology Officer at Blue Current. And I'm here today to talk to you about how Blue Current is building a completely dry solid state battery using a silicon and an active material. So Blue Current was founded in 2014. We're currently located in Hayward, California and as Will mentioned, we've been pretty quiet as a company for the past several years. We were working with our heads down. We really believe in the materials that we've been working on, but we always felt like it was really important to get the science right before kind of coming out of stealth mode and starting to scale the technology. So we recently received $30 million in funding from Koch Industries. This is to support the buildout of our company's pilot manufacturing line at our facility in Hayward. I have here the Cal logo and the Stanford logo. This is because our co-founders, Natasha Blosser and Joe DeSimone are from these two universities. In addition to developing a great battery technology, we've also been able to demonstrate that these two universities can actually collaborate together, so I'm happy to put those logos there. So what does it mean to get the science right? You know, we've had a very deep history as a company working with various electrolyte materials and active materials. Solid-state batteries are getting a ton of attention right now and we believe that there are some core challenges to getting solid-state batteries to work that really have to be solved before these technologies can be scaled. So what are those problems? Firstly, is safety. You know, a lot of what has to be done in order to get solid-state batteries back. What we've seen is that to get to the energy densities and the rate capabilities that a lot of these companies are promising, we see a lot of companies and research groups going and compromising on their technology. So the first compromise we typically see is folks adding liquid back to their cells. In an ideal world, a solid-state battery will be completely dry, but if the battery's completely dry, you have new challenges that have to be solved. Inside of a battery, you have active material particles that have to communicate with an electrolyte. Typically, an lithium-ion battery, if that electrolyte is a liquid, it's very easy to achieve transport of lithium-ions from the electrolyte to the active materials. But if you're replacing that liquid with something that's solid, it becomes really difficult to get your electrolyte to essentially wet the surface of the active materials. So in order to overcome that challenge, we see companies and research groups going and adding liquid electrolyte back to their cell. As everybody knows, liquid electrolytes are flammable. Stand-up lithium-ion batteries today have this flammable liquid electrolyte inside of them. One of the biggest driving forces for moving to solid-state is to essentially replace this liquid with something that's fully dry and inherently safe. So going and adding liquid back to our cells to achieve this ion transport is essentially taking a step back and achieving inherent safety. We also know that liquid electrolytes are generally reactive with various active materials that go into the battery. Silicone, for instance. Silicone, you know, it has this problem where during a charge and discharge, it can expand and contract. This expansion of contraction in the presence of a liquid leads to continuous reactivity that essentially depletes the battery of its lithium content. So another way around this problem of getting ion transport between the electrolyte and the active materials is to apply pressure to fully dry cells. This is sort of the second compromise we see. Pressure is applied to solid-state batteries, like I said, to achieve ion transport between the electrolyte and the active materials. It's also applied so that you can get good ion transport between the separator and the electrodes. Pressure is applied using essentially, you know, two plates that are put on either side of the cell. The plates are fastened together. They can be extremely thick, extremely heavy. The fasteners themselves can add a lot of weight. So ultimately, by applying pressure, you're reducing the overall system of energy density. So it's really critical, and we're gonna talk more about this. It's really critical that solid-state batteries companies can find a way to reduce the amount of pressure that's required for cells to operate. We also see companies compromising on temperature, and this is particularly true for polymer electrolytes. Polymer electrolytes, you're essentially taking organic polymer. You're taking a lithium salt. Lithium salts can dissolve in these polymers, which is itself magical. But in order for that polymer electrolytes to have a high ionic conductivity, you typically have to raise the electrolyte temperature up to about 60 to 80 degrees Celsius. So this is really high temperature that can essentially just limit the number of commercial applications you can have for the material. And then lastly here is scalability. There actually are solid-state batteries on the market today, but they're producing very, very small sizes. So about the size of a fingernail. It's really difficult to scale the manufacturing processes that are used to make these commercially available solid-state cells today. So we have to essentially address all four of these. And as a company, part of the reason why we've taken so long to come out of stealth mode and start to scale is because we've wanted to solve all of these problems before scaling. And I think today's conversation is really appropriate because we feel like polymers are at the core of us solving these problems. So when we think about the broader industry landscape, we've come up with a map. Here, what we're showing is essentially a four quadrant map where on the X axis, you have the anodactin material type or the electrotype. So we have lithium metal on the left and silicon on the right. And then on the Y axis, we have the electrolyte type. So on the top, we have solid electrolytes. And on the bottom, we have liquid electrolytes. A lot of battery research today is focused on the top left and the bottom right. As a company, what's sort of unique about us is that we've actually had a chance to work on three of these. So we have a really deep expertise in developing many different kinds of next generation battery technologies. We also have people on the team that have worked in the bottom right including myself. So what is probably considered to be the most ready for next generation batteries is liquid electrolytes with silicon. Silicon is an extremely energy dense material by replacing one gram of graphite with one gram of silicon. You can store 10 times more lithium. So it's extremely energy dense. As I mentioned before though, as silicon is being charged and discharged, the volume expansion of the silicon is pretty extreme. So a silicon active material particle can expand by up to 300% during charge and then it'll contract during discharge. On the surface of the silicon active material, there's an SEI layer that forms to essentially protect the active material particle from the electrolyte. The formation of that SEI layer actually consumes lithium from the liquid electrolyte. And what happens is as particles are expanding and contracting that SEI layer will actually break open during charge, during the expansion. New SEI layer will form. And then during discharge, as the particles are shrinking that SEI layer will essentially delaminate from the active material particle which then exposes new active material surface which reacts with more liquid electrolyte. And this process just happens continuously throughout cycling. Long story short, this essentially depletes the cell of its lithium content. The battery capacity will rapidly fade. So, you know, cell manufacturers want to implement as much silicon as possible into their anode but they have to overcome this fundamental challenge. As a result, state of the art cells today only have about 5% to 10% of silicon in their anode. So it would be amazing if we can go to higher silicon content in the anode. And that is essentially the approach to the current state is to use a solid electrolyte system to overcome all of those challenges that I just mentioned to have stable cycling with a high silicon content. That's what we've been able to develop. Our anodes have over three times the silicon content of liquid electrolyte lithium ion cells. I'll go into more about it in a few slides. And then on the left, we have lithium metal. You know, for a long time now, I would almost say that solid state has become synonymous with lithium metal. Lithium metal has this core problem where during charge and discharge as lithium is being passed from one side of the cell to the other, dendrites conform from one side to the other that essentially can short-circuit the cell. For a long time, solid electrolytes have been pursued as a material that can perhaps prevent dendrite both and then stop internal short-circuiting. As I mentioned before, you know, our company has had the chance to work essentially three out of these four quadrants. And in fact, we spent the first four years as a company working on lithium metal. So from 2014 to 2018, we were working with lithium metal and then it was in 2018 that we've made the pivot to silicon and we've been purely focused on silicon ever since then. So why did we make this transition and why are we working on silicon? This is a question that we get a lot and it comes down to really just a simple energy density calculation. Back in 2018, you know, we were working on all of the same problems that a lot of other research groups are, trying to prevent dendrite growth, trying to design solid electrolyte materials that can allow lithium metal to cycle stability. But it was actually more practical challenges that caused us to turn our attention to silicon and it really had to do with the thickness of the lithium metal that we could find commercially. It's really important for batteries that every component of the battery is as thin and as lightweight as possible. We were looking for, you know, commercially available lithium metal that was essentially sub-20 micrometers. Everything we could find was 30 micrometers or greater. So freestanding lithium metal, for lithium is a tricky metal. It's metal, but it's very soft. It's hard to process into really thin foil thicknesses. So really the thinnest we could find was about 30 micrometers in thickness. We could also find lithium that was deposited on copper but there, you know, the copper current collector was about 10 micrometers. The excess lithium was about 20 micrometers. So we were still kind of around this 30 micrometer network. We also knew that we could perhaps pursue some more advanced approach where maybe you are vapor depositing lithium onto a copper current collector surface. This really just seemed challenging to us and it just seemed very difficult to scale. So we took a step back and we said to ourselves, you know, we have all of these fundamental problems with lithium. It's, you know, we have dendroid formation growth. We have to solve the general reactivity problem of lithium with the electrolyte interface. Is it possible that there's another active material out there that can get us into a similar ballpark as this 30 micrometer number that I mentioned while also completely avoiding all of the challenges that I just mentioned? And the answer was yes. And, you know, the approach we took was that we had to get to a high enough silicon content in our anode to essentially be competitive to this lithium metal thickness. And what I'm showing here on the right is a graph of anode volumetric capacity versus expected anode thickness. This is for a cathode that would be, there would be three milliamp hours per centimeter squared and end of D ratio of 1.2 and a range of different silicon active materials. And this essentially became our target. We said to ourselves, you know, we have this whole spectrum of different silicon active materials we could use. They can give you all of these, this range of specific capacities. Forget the ones that are gonna give us a high silicon content and then also allow us to be competitive in energy density to lithium metal. So jumping more into the technology, starting with the anode, as I mentioned, we use a silicon based active material to be purchased this material from suppliers. We are not, you know, it's a silicon active material manufacturer. We really are an integrator. We've been able to implement over three times the silicon content of sodium and lithium ion cells. And our anode has a proprietary composite electrolyte material inside of it, which came throughout our battery. One of the unique approaches that we've taken is that when we started off as a company and when we pivoted to solid state in 2016, we believed that really there were two classes of electrolyte materials. We have polymer electrolyte materials, polymers are, they're mechanically robust, they're flexible, they're great at adhering to interfaces, they're commercially abundant, but their ionic conductivity is generally low. Then there's this other class of materials which is inorganic glass ceramic materials. They have a really high conductivity at room temperature. They have a single ion transfer in some of close to one, but they're really brittle and they're generally difficult to interface with other materials, the active materials in an electrode. So we have this belief as a company that you need to combine the two materials. So going back to what I mentioned before, combining a soft matter and inorganic electrolyte material, that really has been our approach from the past several years. In the separator, we also have a composite. We use sulfide inorganic electrolytes that we synthesize in-house. That's one of the unique things about our company is that all of the inorganic collection material we use, we can actually synthesize right here at our facility and we're in the process of scaling that material up. These separators are below 30 micrometers in thickness and it's the combination of the polymers, mechanical robustness with a high ionic conductivity of the inorganic material that allows the separator to be both high in conductivity, especially at low pressure, but also mechanically robust enough to withstand a lot of the conditions that the battery will face in commercial settings. In the cathode, we use high voltage transition metal oxide active materials, so things like NMC and NCA. And the cathode also has a high-intensity phosphorelactylite. Lastly here, one of the things our company has had to do is figure out how do you assemble a solid-state battery? It's one thing to take all of the components of the battery, sandwich them together and then apply an extremely high pressure. But as I mentioned before, high pressure is really detrimental for the energy density of the cell in a commercial setting. So we have to figure out how do you actually process a battery in a way that'll allow all the components to be thin? For instance, with the separator being sub 30 micrometers. And how do you process it in a way that'll allow for low-pressure operation? So as I mentioned before, silicon has this amazing energy density in specific capacity, but it has a lot of challenges, right? And the one I mentioned before is expansion and contraction throughout cycling. This can lead this SCI layer formation in a liquid electrolyte. And in a solid electrolyte cell, what's even more challenging is that you have to maintain a really good interface between the silicon active material and your electrolyte network while this expansion and contraction is happening. And our approach to that has been in these silicon active materials with a composite electrolyte that provides elasticity and high ionic conductivity. We refer to this combination of silicon with the composite as being a silicon elastic composite. We've pursued a number of different polymer systems as a company. We've developed polymer electrolytes. We've developed polymer systems where you are essentially cross-linking a network. And then we've also developed polymers that are functionalized to improve elasticity and improve adhesion between particles, both electrolyte particles as well as electrolyte particles with active material particles. So again, our whole approach has been to utilize polymers to maintain contact between all of the solid materials inside the solid state battery. We think this approach is particularly valuable in getting silicon active material to cycle stability in a fully dry environment. Again, we're not adding any liquid electrolyte to our cell. So it's really critical that you have some flexibility and compliance, especially within the anode so that you can have all of your materials in contact with each other. So when Blue Current was founded, we really had one vision that was to deliver a completely safe battery. In fact, we held that... For a long time, we held that higher than performance. I would say that even today, we still consider safety to be the number one priority for solid state cells. So we've gone and done a lot of safety testing. It's easy to claim that solid state batteries can be inherently safe, but it's really important that we can actually go and demonstrate that. So we've worked with an external third party to do a wide array of safety testing. We've done nail penetration, crush testing, overcharge testing, and accelerated rate calorimetry testing. All of this has been performed on multi-layer cells. We actually made, as a company, we started making multi-layer solid state cells in 2018. We were making these cells by hand, and we were really making them singularly for the purpose of doing safety testing, believe it or not. It turns out that four to 500 milliamp hours is sort of the minimum size you need in order to do accelerated rate calorimetry testing. So all of this testing has been done on roughly 500 milliamp hour pouch cells. You can see an example of test set up here for the nail penetration. And one of the things I'll mention is in all of these tests, we would measure the hydrogen sulfide gas formation during the test. The reason for that is that because we have a sulfide electrolyte inside of the cell, sulfide electrolytes, they can react with moisture and air and form hydrogen sulfide gas. And so we really want to find and characterize whether or not hydrogen sulfide gas was forming, and if so, how much of it was. You can also see a schematic for the cells we were testing. We purposely tried to double-sided coat one of our electrodes that we were minimizing the amount of current collector inside the cell. This is important in sort of replicating what energy density and you would achieve that scale. And we want the safety test to essentially represent what the cell will look like once it's scaled up to a two-hour, 10-amp hour pouch size. So just briefly looking at some of the safety testing results here, this is for nail penetration. In all of these tests, the cells were charged to 100% state charge before the abuse testing occurred. Here we would pierce the cell with a sharpened steel nail and then measure the cell voltage, the temperature, and again, the H2S, whether or not H2S was forming throughout the test. And the results here, the takeaway for the nail penetration as well as the crash and the overcharge test is that none of these tests resulted in thermal runaway. There was no venting or rejection of cell materials and there was no detection of hydrogen sulfide gas throughout the test. We consider this to be a really important and compelling takeaway. There is a lot of question with sulfide electrolyte materials whether or not they're gonna be safe in a commercial setting, but our experience has been that once the sulfide electrolytes are integrated into the electrodes and separate the components, it's actually hard for the materials to still generate hydrogen sulfide gas in a commercial setting. So this was really compelling for us. Our mission from the beginning in 2014 really was to develop a completely safe battery and it was really encouraging to go and get these results with commercially relevant cell sizes. So taking a step back and looking at the energy density for ourselves, we are projecting that for a 10 amp hour cell, our cells will have about 710 to 935 watt-hours per litre in energy density. Gravimetrically, we'll have about 270 to 335 watt-hours per kilogram. So this is of course not as high as lithium metal, right? Lithium metal is sort of the gold standard when it comes to energy density. Just based on the periodic table, it's difficult to have something that's gonna be more energy dense than lithium metal. But that's really for theoretical projections of lithium metal and it's possible that our cell's energy density ends up being very comparable to commercially viable lithium metal cells. And at the very least, we say that it's gonna be about 90% of the theoretical lithium metal energy density. And we can achieve all of this though while it being inherently safe. And what that means is that because the cells and materials are inherently safe, you'll also have energy density gains at the system level. So as I mentioned before, when we did this calculation in 2018, we recognized that it was really, really important that we can get to high silicon contents in the anode. And here what we're showing is essentially for a range of anode specific capacities and weight percentages plotted as anode volumetric capacity, what the expected cell level volumetric energy density would be. If we were stuck around five to 10% silicon content, like a lot of state of the art commercial cells are, our cell energy density would only be between four to 600 watt hours per liter. But because we can cycle stably with high silicon contents, this allows us to get some much, much higher energy densities. Currently today we're around 700 watt hours per liter, which is very comparable to partially available lithium ion cells. And we have a conservative roadmap to get to 900 plus watt hours per liter. And this is all of course, driven by the silicon content that we can achieve. But it's absolutely critical that we can achieve high silicon contents without sacrificing cycle lifetime. This is one of the things that has been really, really exciting for us has been just demonstrating and being able to see the cycle life that we can obtain with high silicon contents. So this is cycle life data for a cell that has a little over three times the silicon content of state of the art lithium ion cell. Here we're cycling the cells at about 28 degrees Celsius. They're being charged and discharged at C over five. The voltage cut offs are 2.0 to 4.2 volts and we're cycling the cells at about 2.5 megapascals, which is something that I'll come back to in a few slides. And you can see that after 1000 cycles, we have been able to retain over 85% of the cells capacity. We're comparing this to very hypothetical lines drawn here for traditional lithium ion, which can get to about 800 to 1000 cycles at 80% capacity retention, as well as cells with a very high silicon content and liquid electrolyte. They can typically get to about two to 300 cycles before hitting 80% capacity retention. So the takeaway here is that by going to high silicon content, we can drive energy density upwards and we're not sacrificing cycle lifetime. So we've been able to achieve really, really stable cycling at high silicon contents, which we feel like is extremely compelling. And I'll mention again, that the way we essentially get all of this to work is through our silicon elastic composite. So having polymer materials within the cell, they can allow silicon to expand and contract during cycling while still maintaining contact with the electrolyte network. Another critical factor in achieving high energy density is the separator. The separator in the state of the art lithium ion cell today is about eight to 10 micrometers thick. So it's incredibly important for solid state that separators are also that thin. We believe that our separator, because we're focusing on silicon as opposed to lithium metal, the overall processing, quality control and scale up, it all becomes a lot easier, right? Because we don't have to design an engineer, a separator that's going to be completely defect-free, perhaps completely high temperature center. Because we don't have to worry about dendrite formation, it makes scaling of the separator a lot easier. We also believe that taking this approach of having a composite gives you both high energy conductivity and it also gives you mechanical robustness that's necessary to get to thin thicknesses. And a lot of the work that we've had to do internally is figuring out what are the best formulations that allow you to get down to sub 20 micrometers thickness without having a separator film that's too brittle that starts to tear during the manufacturing process. You can see on the right here when I'm plotting is separator thickness versus expected volumetric energy density. A lot of solid state matter research today is kind of focused on separator thicknesses, 100 micrometers and above. A lot of solid state research uses things like pellets that are just kind of sandwiched between the anode and the cathode. But you can see how important separator thickness is. Just going from 30 micrometers to 10 micrometers, you have almost a 100 watt hour per liter gain in energy density. So it's incredibly important that the separator is thin and we feel that this approach of using composites is critical in achieving that. So just a couple of slides here on rate capability. As a company, we have always strived to get ourselves to operate at low temperatures and a room temperature. We want to have rate capabilities that are on par and that surpass what the mine cells today. Here we're looking at discharge rate capability for a cell that is identical to the one that I mentioned before. The cathode loading is about 3 milliamp hours per centimeter squared. These are, I should have meant the support, but these are small test cells. These are about 2.5 centimeter square in size. And we're going and doing a discharge rate sweep here, starting at C over five and then all the way to four C. This is all being done at 28 degrees Celsius, just a little over room temperature. So looking at our performance here at one C, we can still achieve over 90% of our C over five capacity. And when we go to four C, we can still achieve over 75% of the C over five capacity. It's really interesting that we don't see a significant drop off in the capacity that we're obtaining at these high C rates. This can be attributed to our transference number being close to unity. So again, we're lying on the ionic connectivity of the glass ceramic material, gives us this room temperature rate capability that is really compelling. And then looking at the charge rate capability data. Here we're doing a charge rate sweep. We're starting at C over five and going all the way up to two C identical cells before. And the takeaway here is that when we charge our cell at one C, we can obtain over 95% of the C over five capacity. We can charge our cells at two C and get it over 93% of the cells capacity. And another way of looking at this is that we can obtain about 80% state of charge in 20 to 25 minutes. And as a company, we're continuing to strive towards getting to this 80% SSE in 15 minute number that sort of the gold standard. So one of the last things I'll talk about here is operating pressure. I mentioned before the importance of pressure in solid state cells. Pressure can be used to essentially sandwich materials together. It helps with conductivity and getting contact between your electrolyte and active materials. But pressure has a huge impact on the system level energy. And I'll talk about that on the next slide. Well, what we've been able to do as a company is systematically reduce the amount of operating pressure required for our cells over time. So back in 2018, we were getting very compelling cycling stability over 1,000 cycles at C over 5 room temperature. But these cells were all cycling at about 40 megapascals. And we knew that this was not going to be commercially viable. So what we've been doing over time is going and just pushing that pressure lower and lower and lower. Where we are today, we have cells that have cycled again, as I mentioned before, for 1,000 plus cycles with greater than 80% capacity retention at 2.5 megapascals. And more recently, we've been able to achieve pressures at 1 megapascal and even lower. And we have cells, prototype cells, and now cycling at these low pressures. Room temperature, C over 5, that have achieved hundreds of cycles with greater than 80% capacity retention. We achieve all of this proprietary silicon elastic composite approach, where we're taking inorganic glass ceramic materials and combining them with polymers, so that we can maintain contact between silicon active material and electrolyte network during cycling. And again, we're not adding any liquid electrolyte to ourselves. So there's a big question in the solid state battery community, which is, what is an acceptable pressure that cells can operate at in a commercial setting and in an electric vehicle battery pack? So one of the things that we've done internally is try to answer that question ourselves. A lot of companies, it can be really difficult to provide an exact number of what this is. Pack design is a very tricky thing. It's within automotive companies, there are many departments that are actually involved in designing what the pack's going to look like. So it can be difficult to really provide one singular number, which is what all of we should be shooting for in solid state battery companies. So what we've tried to do internally is develop a finite element analysis model. This is some work that was led by Joseph Peterson, who was a mechanical engineer on the team, who really is just amazing. And what we're doing here is taking an industry standard with the imion module, using the same dimensions for the cells. And we're going and varying the thickness of the plates. And we're also varying the number of fasteners, because as pressure increases, here we need more and more fasteners to essentially achieve the amount of pressure. So we're varying the thickness of the plates. And then we're going and calculating the plate thickness, the plate mass, the plate volume. And then ultimately, we're calculating the system level energy density for a wide range of materials. I'm only showing one material here in the stainless steel and cell level energy densities. So what you're looking at here on the right is cell level energy density plotted against system level energy density. And this is for a range of operating pressures. So we have 0.2 megapascals all the way up to 7 megapascals. So the first thing you can see is that as cell level energy density is increasing, system level energy density is increasing, this is obvious. But the second thing is that as pressure, as operating pressure is increasing, you can see that the expected system level energy density is dropping dramatically. So if we just look at around 700 watt hours per liter or so, going from 0.2 megapascals down to 7 megapascals results in a loss of about 151 hours per liter. So you can start to see why operating pressure is so critical to system level energy density. Another way that we can think about this is that if you were to have a cell with an expected energy density of 1,000 watt hours per liter, if that cell has to operate at 7 megapascals, it's actually not going to have a higher system level energy density than a 650, 675 watt hour per liter cell that's operating at 0.2 or 0.5 megapascals. So we use this thinking to really direct our developments internally. And it's very obvious why pressure is so important. If you have to have really, really thick plates that are put on either side of the cell, the system level energy density is just not going to be much higher than state-of-the-art today. So we have here this little star that represents an industry reported system level energy density for a commercial electric vehicle. So long story short is that this problem absolutely has to be solved for fully dry solid state cells. That having a fully dry solid state cell is really the most promising way to produce energy density as well as safety. But it comes with this challenge of having to apply higher pressures. And we believe that taking this approach of using polymers and using an elastic composite can allow us to go to lower and lower pressures without sacrificing system level energy density. So lastly here, the approach we've taken is really uniquely scalable. We use all of the same lithium-ion battery manufacturing equipment that's just taken from the standard processes from nickel lithium-ion cells. These are high volume manufacturing techniques. We really aren't doing anything new or exotic when it comes to manufacturing of the cells. Solid state also has the ability to potentially eliminate. It will certainly eliminate fill. And it also has the ability to eliminate formation. So this can lead to some pretty substantial capital expenditure savings. And we believe that the approach we're taking really is fully scalable. So to summarize here, Blue Curran has been developing fully dry silicon-based solid state batteries since 2018. That really has been our singular focus for the past four years. We believe in composite material, a fully dry solid state battery cell, a fully dry electrolyte can give us inherent safety. We have been able to demonstrate that third party test facilities. This approach has been able to deliver over 1,000 cycles with greater than 80% capacity retention, really compelling rate capability. We've had some new Earth-type cells over the past year that we've been cycling at pressures below 1 megapastial, so below about 100 PSI. And one of the things that I didn't really tell since too much before, but we've really been co-designing our electrolyte materials with the process. And what I mean by that is, and coming back to the conversation's focal point today, which is polymers, you can imagine various polymers having optimal ways of being processed. And we really have co-designed the polymers to work with the processing equipment. So with that, I will thank you again, Will and E, for the chance to speak today. And I welcome any questions. Kevin, thank you so much for that great presentation. I'm always appreciate sharing technical details. And there was lots of it. Really, really appreciated, Kevin. So maybe we can begin with just some clarifying questions that we have received. So you were going a little bit quickly on the number of electrolytes, the catholite analyte used in the system. So is it one type or three types used in your cell? Yeah, that's a great question. I can't share too much about the exact polymers being used. But what I can say is that the sulfide inorganic electrolyte material we're using, we really have focused in on just one material there. It's the polymer that can kind of change between cell components. So this material is used in the composite electrodes as well on both sides, just want to clarify. That's right, yeah. Okay, so you have a single composite for your entire system. Oh, I'm sorry. No, the polymer that is within the composite varies between the cell components. Oh, okay. It's the end of the component. Okay, got it, got it. Great for that clarification. And the second clarifying question was on the first cycle inefficiency. So I think you put there about 80%. So does your energy density calculation already account for that for cycle inefficiency and the extra lithium you have to carry in the cathode? Yes, it does. Yeah, the calomic efficiency brings us down to about 160 to 165 milliamp hours per gram for the specific capacity. And that's essentially what we're using in the energy density calculation. I will also say that it's something that we are working to improve. Yeah, I think that sort of connects well to one of the final points you were making, which was the formation. So I presume this 20% expended as something to do with parasitic losses in the cell. But you mentioned that formation is not really required for yourself. So this process happened very quickly and then you're just done with it. And so it's insensitive to the time and temperature at which this happens. Yeah, I think that the truth well is that I think formation can't be completely avoided for solid state. You have to go and analyze what is the capacity of the cell and how does this cell number one compare to cell number two and cell number 1,000. That's just quality control and that can't be avoided. The expectation is that the formation that we see could, you know, that could occur during that kind of process where it's not gonna have the same extensive formation process that liquid oxides cells do, where you're kind of cycling the cell for a couple of weeks and degassing and pausing at various SOCs. Great, Kevin, but I, you know, as someone who works a little bit on formation, I can definitely resonate eliminating or shortening a substantially will definitely make your factory a lot smaller for making cells. So I think that's a great goal to work towards. Kevin, you highlighted in the sort of the beginning of your talk, the importance of safety and appreciate you sharing the nail puncture test and also for acknowledging that the cell size is a little bit on the smaller side for such a test. But I did notice that the temperature increase was very negligible, which is a little bit surprising to me as I think you were testing in the fully charged state. Can you maybe explain to us a little bit why the temperature didn't go up at all? Yeah, no, great observation, Will. I would say there's two reasons. One is that even though we're at 500 milliamp hours in capacity, we do have excess pouch material. You could probably see from the cell that we're not at the point where we're perfectly pouching materials and minimizing the total mass in the pouch yet. So there's a lot of just excess thermal mass that's there. I think the second reason and perhaps more interesting one is that during these safety tasks, you know, if the cell requires high pressure in order for lithium ions to essentially rush from one side of the cell to the other, which is what would happen during some sort of short circuit, the rate at which internal short-circuiting can happen during safety tests is effectively slower. So that can just sort of limit how fast the cell temperature is gonna rise. We are operating at low pressure, so we don't think that that's gonna significantly impact our tests, but that is something to keep in mind when looking at other solid-state battery research and safety testing. But I think that really the short answer is that we have some extra thermal mass there that's just absorbing a lot of that energy. So the cell temperature didn't rise as high as you'd expect it to. That said, I think that one really interesting thing about solid state is that you do have the mass of the solid electrolyte there. You effectively have another component inside of the cell that's there to absorb energy and effectively lower how high of a temperature the cell is gonna go to during some sort of attack. In a liquid electrolyte cell, you essentially be vaporizing and losing all of the mass of that liquid. So the temperature of the cell could rise to something like 800 degrees Celsius, at which point the aluminum current collector starts to mill. So in our cells, you have this extra thermal mass that's there to essentially absorb that energy. Kevin, yeah, I'm very excited and excited to see the testing of larger cells in the future as well. Maybe I can have one final, more of a technical question and then we can go to our discussion with Alberto. There was something that also confused me a little bit in the beginning of your talk. You were describing the journey that blue curtain has undertaken, starting with lithium metal and ended up with this composite sulfite electrolyte, polymer sulfite electrolyte. And I think you highlighted several cases in which pre-existing lithium metal is employed. So I was curious if you guys also looked at situation in which the pre-existing lithium metals very small amount or non-existent in amount as a way to not have to deal with working with lithium in the assembled state of the battery. Yeah, great question. So as a company, we have not really, our time working on with lithium metal, we really didn't pursue things like an anode-free approach or working with just a few micrometers of lithium deposit on something. I should have mentioned the energy density calculation I showed where we were kind of plotting anode thickness and talking about the impact of lithium metal thickness on the expected energy density. That really motivates the need for anode-free approaches. Having access to lithium metal really is detrimental to the expected energy density. So it's really critical for companies and research groups to pursue an anode-free approach because otherwise you're still gonna have an anode that has similar thickness to state of the art lithium ion cells today or high silicon content cells like ours. But I guess the answer question will, we didn't ourselves pursue these approaches of using just a much, much smaller non-lithium. I think we just felt like the techniques you would use to get to that thin of thickness of lithium would be generally difficult to scale. We were also just a small startup company and trying to overcome the hurdle of doing an anode-free approach because it's very challenging to do. My hats off to the folks that are pursuing us. There's been some really exciting work out there on that front. Yeah, agreed, I think the pay, they pay off is tremendous if we can get it to work, but it's also a very challenging topic indeed. So Kevin, I saved a bonus question for you because I'm not sure if you, how to what extent you can talk about it. I think this is the first time that we have heard about this polymer sulfide composite approach from Blue Current. I know that a lot of this are proprietary, but maybe you can give us a sense of, how this sort of gets the best of both worlds. One, hey, you have sulfides, on the other hand, you have a polymer electrolyte. We don't need to know the composition, but the grade we can say for a minute or two, how you landed in this and what's the property that you're aiming for that doesn't come in the end members of the polymer end or the sulfide by itself. Yeah, so I should start by saying my personal research experience, like even before joining Blue Current, I had worked with polymer electrolytes. When I was at Berkeley studying under Natasha Balsara, my PhD thesis was working with polyethylene oxide and block of polymers with styrene and lithium sulfur cell. And the challenge that everybody faces with polymer electrolytes is just the low ionic conductivity at commercially relevant temperatures. So we knew that if we wanted high rate capability, if we wanted to be able to go and do cycle life testing at C over five and C over three and one C and do that at room temperature, that polymer electrolytes themselves may be out of picture. We knew that sulfide electrolytes, though they did have high ionic conductivity and the other beautiful thing about them is that they're very processable at room temperatures. You don't have to go and center them at very high temperatures like you might have to with an oxide. So they're very malleable, they're soft, they can form good interfaces. They also have a really low density. Liquid electrolytes have a density around 1.1 to 1.2 grams per cubic centimeter. Sulfide electrolytes, they're typically around 1.8 to two grams per cubic centimeter. So you're higher in density, but you're actually not that much higher, especially compared to oxides, which are close to four to five to a cubic centimeter. So sulfides have these really compelling value proposition of being room temperature, processable, high ionic conductivity and they're generally light in weight compared to some other inorganics. But on their own, you would still have this problem where especially in the presence of active materials that are expanding and contracting, it would be really very possible to lose contact between the sulfide electrolyte and the active materials. So this combination of using polymers with the sulfide electrolyte is essentially what we use to maintain that contact. And I should just verify, or specify a little bit will, as a company, we've pursued a range of different approaches for the polymer. We've done a lot of work developing composites that have a polymer electrolyte, a sort of your organic component. We've also done a lot of work developing composites where your organic phase is cross-linked. And we've also developed composites where they're perhaps more traditional, where your organic phase is perhaps less intricate and is just there to provide adhesion and mechanical flexibility. So we really have sort of a wide range of experience with several different composite approaches. But does that help answer your question? I think it's all about balancing the properties and the capabilities of both polymers as well as the organic materials. I would say, given as a material scientist, I would love to have a magical material that does everything. But having two or more components, I think that does substantially expand the degree of freedom for optimization and engineering. So I'm very much a big fan of that. Kevin, I'm just gonna make one comment, which I didn't, you don't have to respond to it. I think just listening to your, very technically in-depth talk, and I have a sense that you're also using the composite to address the electrochemical stability window of the sulfide, solid electrolytes as well, on the cathode and anoside. And just for the audience, this is really one of the big challenges with sulfide is it's not gonna work across a four-volt window. And something has to be done to really solve that problem. And my guess is, and Kevin, I think it's getting to the heart of your technology is that your composite somehow can really make the sulfide work for a thousand cycles. It's actually impressive. With or without pressure, this reactivity's there. Actually with pressure, it's even worse. So that's very exciting. See, I don't know if Kevin wanna say anything to that extent, but that's at least my observation of the innovation. Yeah, I love that will. And the other thing that I'll mention is it makes designing the cell a little more challenging in terms of the electron microstructure, for instance, and then even the separator microstructure. If you're using a polymer, there's a battle for ion and electron transport that's occurring in the electrons. And if your polymer is not electrically conductive, then you're gonna block electrical conductivity and vice versa. So we had to think carefully about what polymers are we gonna use that'll allow for all of the mass transport to occur in the electrodes. And then in the separator, how do we optimize the mechanical robustness and the adhesion and elasticity of the separator film without, for instance, having the polymer that ends up insulating electrolyte particles from each other. Yeah, a great point, Will. Well, Kevin, I think this is a great segue to the panel discussion. I know Alberto is also very fond of mixed ionic and electronic transport and polymers. So it sounds like maybe that's something that you are deploying in your battery technology. So Kevin, thanks for that Q&A, really appreciate it and being frank and direct in addressing all these second questions, I'm sure folks really appreciate it, especially on the academic side of things. So Alberto, if I can have you up, there you are. So traditionally, we use this time to talk about sort of unifying things and broader topics in connecting the two presentations. And let me just say, what a wonderful, an hour and a half to learn about all that things polymers can do. Now I wish I have studied polymer when I was a graduate student, I feel it's too late, but maybe I'll have to take your classes, Alberto, or even working your group, maybe even be a better experience, I think. So let me start by just asking this, maybe a very scientific question. What don't we know about polymers, whether it's electronically conducting, ionically conducting or mixed conducting, what are the fundamental knowledge gaps that we still have to address today? Maybe I can ask Alberto to weigh in on this first. Yeah, so for if you said, okay, what is the holy grail question in my area of electronically or mixed conducting polymers? It's, if I'm pitching polymers to a program manager, I will say they're a synthetic semiconductor, mixed conductor, and so I can sort of make whatever molecule I want. But the question is, as long as I know what I want, and the vexing problem for us is you have the chemical structure, but that doesn't really tell you what the microstructure will look like. So I showed you quickly, I went quickly through the example of the polymer that has a shorter side chains versus a longer side chains. And if I were to ask someone which one you think is going to be more crystalline, I'd get like a 50-50 audience, a 50% would say one, 50% would say the other. And if you think about it, that's sort of the same fundamental problem of the pharma industry. You have a molecule, how will it crystallize? Because it has different structures that are all similar in energy and you can't really predict the way it's going to go. So on one hand, I will tell a synthetic chemist, I want a backbone that looks like this and side chains that look like that. And then when I cast a film, I will get a microstructure that is unpredictable and that will really dominate my properties. And that example that I showed you, I was expecting to have a higher capacity with a shorter side chain polymer. And I didn't go into the details, but the fascinating aspect of it is that it's less crystalline, so you would think it's easier for ions to go in. But then the ions are counterbalanced by an electronic charge and electronic charge lives more easily in the crystalline parts. And so somehow, because it's a more distorted structure, it actually makes it more difficult to charge, which is completely counterintuitive. So the fundamental knowledge gap there is the classical material science issue of understanding structural property relationships in materials where on top of that, sort of the theory and simulation is extremely challenging because some fundamentals are not known. And even if they're known, the energy differences between different structures are small enough that you can never assume you're at equilibrium. You don't know where you're going to be trapped. You process things five different ways, get five different microstructures. So great for academics, terrible for technology development. Thanks so much. So I think what you're saying in a nutshell is, it's not predictive quite yet in terms of our understanding of structure, property relationship. So does this mean that a lot of trial and error has to be done in order to make the target material? Yeah, absolutely. So first of all, yeah, it is not predictive, but I want to put in a plug for synthetic chemists. They actually have an amazing intuition. So it might not be synthetically predictive, but the best synthetic, sorry, may not be scientifically or quantitatively predictive, but the best synthetic chemists out there, somehow they managed to hit in the right molecules and it's not luck. It's really their skills. So often we, on the physical sciences side, we lag behind, they make a great material, like, oh, why is it working so well? Somehow, and I'm telling you, it's not luck. So there is that aspect that to me remains to be, it remains amazing. This makes me feel a little better opera. I always feel like the grass is greener and there's that coming from the inorganic material side. I always feel we don't really, we can't really predict anything. So it's good to hear that on the soft material side that there's a similar opportunity, I think, for better predictability. That's always great. Kevin, how about you? What do you think are the fundamental knowledge gap that you wish others would address? I know obviously you're really focused on getting the product out, but there are plenty of people listening here who could be working on the fundamental aspect. Yeah, I would say there's a few that come to mind. I think for polymer electrolytes, understanding ionic conductivity under compression, for instance, or under some sort of strain, I think would be really interesting to learn more about, especially as we think about electrodes where you have some sort of expansion and contraction of an active material. I think studying more about, you know, a polymer electrolyte contact with active materials, perhaps as SEI layer formation is happening and the adhesion between the materials in a fully dry environment, a lot of the work that's been done for silicon today, there's so many amazing approaches that folks are taking in designing polymers to work with silicon active materials and liquid electrolyte system. We just have to wonder how will a lot of these operate in a fully dry system? And what will the material degradation be like? Or what are the mechanical properties of the electrode and the polymer over time in a fully dry environment, as opposed to one where there's a liquid electrolyte present that's maybe wetting the polymer or... So I think that's an interesting area for research. I would also say, and this is an area where I think there is a lot of great work being done, understanding the interface between polymer materials and inorganic electrolyte materials, figuring out ways to mitigate the resistance growth that happens between polymer electrodes and inorganic electrolyte materials. I think that that really is going to be an important route to getting those two materials to synergistically work together over long length scales within battery. So I think that's another area for more on view. Thanks Kevin. I couldn't agree more about the mechanical property battery is actually, especially in your battery, it's a moving, there's moving parts in the battery. And I know Alberti, you have also been working on sort of the chemo-mechanical relationship in polymers. What kind of properties do you think will change substantially as a result of these mechanical forces, especially in a constrained cell? Like Kevin, this is, it gets even more serious. So sort of what are the unknowns here in terms of the mechanical property that you want to know? Or maybe what Alberti you're working on in terms of understanding. Yeah, I would say, you know, polymer electrolyte, the conductivity of lithium ions and of polymers is reliant on polymer chain mobility and understanding how polymer chain mobility is influenced by whether or not the polymer electrolytes under some sort of strain. I think understanding that a little bit more, perhaps you start to rely more on the hopping of lithium ions from one site to another. And you could also start to think about, you know, over, not just going and doing this on cycle number one, but thinking about how the polymer morphology and the polymer being, you know, subject to this stress and strain throughout many, many cycles. What kind of impact that has on the morphology? Yeah, does that help Will? Yeah, absolutely. No, I'm just fishing for things to work on. For us, it's, you know, the coupling between when the ions go in and out, you get these changes in the structure of the unit cell, how does that affect electronic transport? That's the one we always think about. And some of these polymers swell by amazing amounts. And so, okay, cast a film, you have this beautifully designed and engineered microstructure and then all hell breaks loose because the electrolyte streams in and what does that do to electronic transport? Right, thank you, Kevin and Alberto on that discussion about fundamental knowledge gaps. You know, maybe now, you know, we have about 15 minutes left. Maybe we can zoom out a little bit. I think both of you alluded to this importance of system level thinking, right? You know, maybe as a material scientist, I like to think about, you know, how this material does at the materials level, but, you know, in terms of the technology, it's not even the battery cell, it's the battery pack or the battery system at the end that dominates. So Alberto and Kevin, maybe you guys can give us a sense, you know, maybe there are some disadvantages at the materials level, but there are also advantages that can translate into system level performances that can be obtained anywhere else. You know, Alberto, I think, you know, you mentioned that the graphometric energy capacity is more limited in the type of polymers you presented, but I assume that, you know, the safety would be really great and probably same for Kevin as well. Love to learn a little bit about, you know, if we look at the technology at the system level, how does that change our understanding of the requirements for what the polymers must deliver instead of just looking at the, you know, the numbers for the material by itself? Because when you do it that way, sometimes it doesn't look great. I'll just give one example for our audience, you know, in the lithium-ion battery industry, you know, people have always thought you need higher energy density cathodes, right? So that's why, you know, nickel, meganese, cobalt oxide won out, but more recently people realize that lithium-ion phosphate is really safe, oxygen doesn't come out, although the energy density at the material level 30% lower, it's now found in 50% of the Tesla Model 3 vehicle. So that's a good example of how system level thinking really dominates at the end of the day. Yeah, I completely agree, Will. It's been amazing to watch sort of like the re-rise of LFP over the past couple of years. I, you know, in a lot of ways, you know, we've always had this goal of making an inherently safe cell and what's happening with LFP is what, you know, people are kind of taking, if LFP is much safer, then at a pack level and a system level, you can pack cells closer together and as a result have a system level energy density that actually is comparable to an NMC or an NCA-based cell pack. We feel similarly with fully dry solid state cells. And in some ways, that kind of gives us a platform to innovate on. If you were to take a step back and say, okay, well, maybe solid state, fully dry right now, it's only delivering 7 to 800 watt hours per liter at the cell level. Well, the truth is when you go to the system level like LFP, it can actually deliver a system level energy density that's higher than liquid electrolyte cells can achieve today because of that apparent safety. So I think that thinking that way, thinking about the end product and like the consumer's experience and safety gives you some flexibility in terms of designing, just trying to design a material set that is inherently safe and projecting that to system level energy density gains. Kevin, here's a sort of a million or a billion dollar question for you. How high do you think your volumetric utilization would be at the pack level? You know, it's about 55% now for today's lithium ion. Maybe 70% for lithium-ion phosphate based cell. I mean, if you have a truly intrinsically safe, I imagine that number can even be higher at the pack level. Yeah, that's a really great question. I am hesitant to give you any numbers because pack development is really, really a complicated thing. And I forgot to mention this earlier, but in the modules that we designed for our calculations, we didn't actually include heat transfer of thermal management system. And that's gonna have some sort of impact on the overall system level energy density. So as much as I would like to just take the numbers that I showed there and say that that's kind of what we're striving for in the truth, is I think that once you go in front of the entire pack, there's a lot of sort of components that come into place. But that said, I do think that the inherent safety and sort of like the promise of the materials at a material level will allow cells to be packed more closely together. And I think that the volumetric efficiency can be higher, but it's not the exact number. Well, Kevin, I completely agree that if you can get rid of pressure and make it intrinsically safe, I think that would translate into phenomenal pack level energy density. So very excited to see where your trajectory goes in terms of the pressure aspect. Alberto, how about in the area of low-cost energy storage, can you comment a little bit on what kind of system level consideration motivates your work and how that might map and turn into a disadvantage of a material into an advantage at the systems level? Yeah, so I'm not gonna be able to give you an answer and I'll tell you why because this has really been a desire for personal growth on my side. So I come from the world of organic electronics where we always work with materials that are less performing than the conventional counterparts. And so we're always thinking of, what is the systems level advantage when you think of an organic solar cells that could be maybe building integrated PV or something like that. And so I'm new to the world of energy storage. So I haven't put a lot of thought but if I have to give one thought that I have, it is that finding these system level advantages is actually pretty difficult to do. You have to really know the industry quite well to not say something completely stupid in that field, to go back to solar cells. When we started, I remember some people used to say, well, if the solar cell has a 3% efficiency but it's nearly free, then yeah, I will have a market that turns out to be completely wrong because you still have to install it on the roof and so on. So for me, this is a great forum. I can't say myself, what is the system level advantage of what we've been looking at? Cause like I said, it's something I'd like to understand better. So if someone actually can help me guide me in the right direction, that would be immensely helpful. Well, bro, thanks for that honest answer. Yeah, this is something I've been thinking a lot about to sort of put fundamental innovations in context of the big technology. And maybe we can segue into this final point. I would like to get your inputs and insights on is scale, right? It's agreed upon now. We need to deploy hundreds of terrolet hours of energy storage to propel us through this energy transition, which of course is motivating all of our work in academia and industry. One thing that I don't fully understand is, Kevin, you talked about the processability of the material at your factory, right? But at some point, someone has to make all the polymers to begin with as well. What does that look like? And obviously polymers a huge industry already. So certainly scaling, I think is not an issue, but how about your carbon footprint and how does one benchmark against some of the inorganic variants? And Albert, you brought up a great example of solar cells, right? So if today the performances were more similar between inorganic and organic, how does the environmental footprint compare? How does the scalability and the manufacturability starting from the mines? How does that compare? I think that's also another way of looking at the system is the entire value chain from mines and of course, including all the way to recycling as well. So I think this may be a good point for us to end on. I don't know, maybe Kevin, you wanna take a shot at that first? Yeah, well, I would start by saying that as we are starting to scale as a company, we are doing all of those calculations and making sure that as best as possible, we do this in a way that is best for the environment. What's interesting with the inorganic electrolyte materials is that it's not completely different than going and making some sort of lithium salt. I mean, it obviously depends on the composition, but a lot of the methods that you would use for making an inorganic electrolyte are have similar energy requirements compared to a prism of lithium salt. That said, I think that for the inorganic electrolytes, there's a pretty substantial difference comparing sulfides to something like an oxide in terms of what temperatures are required during the actual processing. Another reason why we are so excited about sulfide electrolytes is because, there was an interesting paper on this, I'm gonna have to find the reference. Processing a cell with a sulfide electrolyte consumes about two times less energy than if you're processing a cell with an oxide. That's because you're not going and doing high temperature centering during the manufacturing process. So we think that the sulfides are actually particularly important in having manufacturing facilities that are sustainable and comparable in energy usage to lithium ions today. But great question, Will, and that's something that we really are looking into as we're starting to scale. Kevin, I really resonate with this thermal budget problem. As a person who works with high temperature processing materials, it's really amazing to see how much energy can go into just running those big kilns for firing. And if you overlay all the announced battery factory, you can actually see kind of a emergence of your, I would say hydro belt in the North in Canada and the Nordic. And you will also, I think in the next 25 years, also see sort of the sun belts as well, where solar prevails to have that inexpensive electricity. But I think a little bit of unfortunate thing is we're turning those very valuable electricity into heat, which is maybe, you know, if you take out birds as thermodynamic classes, not your best approach, but completely agree on the thermal budget. I think that's something that I think the polymer can really tackle. Alberto, what do you think about this ability? So for us, the challenge is still figuring out what are the right materials, but people have started having these LCA considerations now in our field. And so I don't know that anyone's figured out exactly how it's gonna go, but here the positives are, people are looking at more higher yield reactions and greener ways of doing the chemistry. And then most of the materials have earth abundant elements. So there's that. And then the thermal budget that you mentioned, everything is low temperature. That was a big one for solar cells. The energy payback time for organic solar cells was calculated to be a lot, a lot lower. So that makes the proposition more attractive, even if your efficiency is not as high. So it's a field that's still in its infancy. And I agree with you, it's a great point and people are realizing it now. And so you'll see more and more proposals of people not only saying that they wanna make the highest performing material, but they want to develop the greenest chemistry as well. In fact, that's what Adam in our joint effort is trying to do. Well, this is an amazing vision, I think. Best of luck to both of you on realizing that vision. Kevin, thank you so much for sharing all the technical details and performance data. Really appreciate it. Alberto, thank you for sharing all the fundamental excitement around ionically, electronically and mixed conducting polymers. And maybe the two of you should get together to find interesting intersections. So on that note, I really like to thank both of you for getting up early in the morning today to speak to our audience and myself. Really deeply appreciate it. So this, as I mentioned, concludes our spring series of the Storage Act seminar and soon will announce the summer series as well. So please check our website periodically and for our mailing email announcements for the next set of seminars. Like to again thank everyone for joining us for this very exciting quarter. The energy storage industry is moving at a tremendous pace. And I think I hope that this forum has been a good one to give you insights of the latest and greatest both in academia and in industry. And please stay connected with us on LinkedIn on our website. If you're interested, we also have a number of excellent educational programs that you can participate at Stanford. And with that, thanks everyone and have a great summer.