 Warm holiday greetings from Palo Alto, California. My name is Will Chu. I'm the faculty co-director of the StorageX Initiative and together with Professor Itui, we're really pleased to welcome you to the final seminar of 2022 from a Frosty Stanford campus. So for our final seminar of the quarter end of the year, we're gonna be focused on the theme of aqueous energy storage and conversion. We have covered a lot of lithium-ion batteries and beyond lithium-ion battery technologies. Aqueous energy storage is both past, present and also the future of energy storage. We are delighted to have two great speakers, Deborah Rawlison from the Naval Research Lab and Veronica Augustine, Professor of Material Science and Engineering from North Carolina State to talk about the latest in terms of academic and fundamental understanding and spending all the way to technology development and device optimization for next generation energy storage based on aqueous electrolytes. So just a few words for me on aqueous energy storage. It's a fascinating topic because this is really where the combinations of scalability, manufacturability, performance, energy density, power density can all potentially come together but yet not all of them are achieved simultaneously today. So there's huge opportunities for understanding what are the underlying design rules to improve these further and also a lot of room for technology development. And I will leave our first speaker, Deborah, to introduce this a little bit further to the state of the field. So let me ask Deborah to join us here on the screen. Unfortunately, she will not be sharing her video today. So let me start with an introduction. So Deborah, as I mentioned, is the head of the electrochemical material section of the Naval Research Lab. She is a highly distinguished electrochemist. She's the fellow of CHIP OIS, MRS, and ACS and has been a leader in aqueous electrochemistry for many decades. And she has received so many awards. I can only list a few among them as the EO Halbert Award, which is the top award offered by the Navy at the Naval Research Lab. She has received the Division of Analytical Chemistry Award from the ACS, American Chemical Society, the Riley Award from the Electro Analytical Chemistry Society and the ACS Award for the Chemistry of Material and the Hildren Prize from ACS from the Chemical Society of Washington. We are so delighted, Deborah, to have you speak to us and anchor our seminar series for 2022. And we're looking forward to hearing more about aqueous electrochemistry and its connection to energy storage technology. Deborah? Thank you so much, Will. Am I coming through? You are loud and clear. Great. Before I dive into facts and figures and graphics, I'd like to acknowledge this is very much a team effort. You'll see Jeff Long, Joe Parker, Megan Sasse, Chris Chervin, Paul Visario, all postdocs with me over the years who were hired in as staff scientist at NRL and with whom I still collaborate, we slosh around as we need to. For your faculty's information, Joe Parker is now the program manager in charge of Expeditionary Power and Energy at ONR Office and Naval Research. And today is Chris Chervin's last day at NRL because he's about to leave to head materials chemistry in basic energy sciences at DOE. And below you'll see two of our recent crop of postdocs, Travis Novak and Ryan DeBloch, whom I'm about to hire. So many moons ago, you can see the date up there, 1999. ONR ran a Grand Challenges workshop, lots of fun. They wanted out there discussions and ideas where to particularly derive energy storage. And I came up the concept that I call colors of capacitance, and I'm gonna use Yuri Gagazzi's very nice graphic to demonstrate that. So there's the one we're used to where we've got typically a liquid electrolyte. We've got an anode and a cathode. We've got a positive cathode and negative anode. There's an excess and deficit of electrons at those surfaces and the ions that are mobile come up and balance that. So it looks a lot like a dielectric capacitor. And in this way to store energy, which is again a very old science, you typically want as much electrifiable interface as you can get away with. And that's why people often are using activated carbons in commercial electrochemical capacitors, sold as supercapacitors. But there was a recognition, again, sort of in the 90s, particularly with ruthenium dioxide, Yuri's example is manganese oxide, is that there is a surface sided faraday redox reaction where there is a change in the redox state. You're not expecting the carbon to change its redox state in the EDL system. But it looks a lot like a classic capacitor, in terms of current voltage. And I'll show you that in a second. So the pseudo capacitance mechanism was recognized as another way to store energy. And then of course the classic, if you will, lithium ion battery where not only is the faraday reaction occurring, but ions have to insert into crystallographic orientations to create the stored electron ionic charge in the system. So you can consider these three, if you will, colors of capacity. That way we can store energy in a two electrode or two terminal device. But as we started working with nanoscale materials, particularly ultra porous nanoscale materials done by Veronica's PhD advisor, Bruce Dunn, Bill Smurl at Minnesota, our group, when we came into it in sort of the late 90s, is that if you can think architecturally, you're really emphasizing different colors in terms of the performance of the material in the two terminal device. So in terms of pattern recognition, looking at current on the Y, potential on the X, if you've got just the charge you're storing at the electrifiable, in this case, carbon entrance, you get this envelope, this very dull, boring, nothing's going on. Now, pseudocapacitance looks a lot like that envelope, but there's always more current, if you will, per gram after you've normalized. And you get a hint that, yeah, there might be something fair day going on at the ends and occasionally in the middle. And a true battery gives us thermodynamic peaks that relate to where is the change in the redox center in the active material. So time scales matter. There's that pattern recognition event of what the current voltage curves looks like. Supercapacitors can give you hundreds of thousands of cycles because you're not changing much physically, it's just going to the surface. The fair day reactions are involved and you have to worry about the efficiency, the coulombic recovery charge discharge. What is surface if you've got a porous system versus normally something that's tens of microns, the electrons and ions have to get into and out of. And what happens if you think in terms of nanostructuring or architectural design? And we backed into this because we were trying to understand the pseudocapacitive champ, hydrosruthenium oxide. And the fun thing about that material, RUO2, is rutile crystalline electronic conductivity approaching that of copper, not a very good pseudocapacitor. But if you start to put hydrous character into it, you can really store charge. And the odd thing was that in the 80s and 90s, people thought it was metallic, even with 2.5 moles of water in the chemical formula. That never made sense to me. So as we were studying it more as a catalyst than as a energy storage system, we did a pair distribution functional analysis in collaboration with Wojciech Damowski and Takeshi Egami. And that showed, regardless of what the water was in the chemical formula, bone dry to two point, I think we've had 2.3 moles of water, you had a network for the electrons, the crystalline rutile, which was so small, it was hard to see by standard powder x-ray diffraction. And another phase that was mapping onto those electron conductive surfaces that was protonic. So you had two transport networks in this system that was creating on its own the world's best pseudocapacitive energy storage material. I like to think of it as an analog to Diblox copolymers. So you have the classic path for the electrons, you've got a pass for the protons that's running right along that surface. And that picture, it's never been a homogeneous material, changes how you think about designing what you need to put into almost any electrochemical device. You need transport paths for electrons back to some macroscopic current collector that's gonna go through a load and then talk to the other electrode and a path for ions to move. So our way to classically make an energy storing two terminal device, regardless of what the materials are or the electrolyte is, is you've typically got an active material in red here that's not a great electron conductor. You mix it in with something that helps you move an electron so to call an ad hoc electron wire which is typically a conductive carbon powder. And to keep those powders together you often have to put in polymer binders. So as we recognize what Ruthenia as a pseudocapacitor was teaching us, we wanted to think about how do we wire electrons and ions? So we may still have a macro scale electrical contact but we want if you will a architected volume of where the current is always going to be able to go rapidly back to that macro scale contact and some kind of modification of that and they'll ultimately filling up somewhat. So you've got the active material quantity you need in terms of per gram of electrode or per square area if you're thinking of aerial and paths to move ions. So now we're thinking about I need to wire electrons. I need to wire ions. I need to wire molecules to really get current and I need a lot of area. So I've got enough, if you will, mass to store energy. Those two things need to be distinct. So if you're looking at a more bird's eye view you've got your macro scale current collector if we can't see anymore. We've got our black sort of architected current collector a redux active coating and we're talking to where the ions and electrons need to live with short distances. You notice that scale bar tens of nanometers not tens of microns as in a classic battery material. So in my view coming out of Royce Murray's group at North Carolina, we're right back to chemically modified electrodes where you had a conductive typically planar surface that you were monomolecularly modifying or putting a polymer on only you had at most a square centimeter. So we're now trying to do electro analysis in three dimensions and with hundreds to thousands of square centimeters of electrifiable area per cross-sectional footprint. So that gives you as an analytical chemist I like to have a big signal. It gives you a lot of things to understand but we still have some key questions where a lot of work needs to be done and our group can dip into this periodically we have to sell programs and sometimes they can't look too applied but we are talking to carbon for the most case in a practical battery world. And carbon is not the best electron transfer interface in terms of your heterogeneous electron transfer rate constant but we're living with carbon because it's cheap and you can do a lot of fun things with it. So if you're worried about energy and power ultimately you have to think about what is my heterogeneous electron handoff between the active material and the carbon and we're still not doing that particularly well because we're working with carbon. So I'll leave that as an open question. So if we think architecturally if we think we need to wire ions we need to wire molecules we need to wire our electrons to actually do something architecture is one way to think about it. And as we studied this more and more it became obvious once you've got that kind of control over a lot of electrifiable interface you're building in control of interfacial morphology. And that's often what trips up the long life cycling you'd like out of a practical system like a battery. And I'm gonna give you touch on some of these examples fortunately Kaylee informed me Monday I had a 30 minute talk so I threw out a lot of stuff. So touching on some of these topics will ensue. So let's talk about carbon that could be an architecture and talk back to a macro scale contact. We've come out of a lot of our understanding through aerogel science which is a whole series of talks on its own but there is a polymer an organic sol-gel process that gives you a polymer nanofoam that you can prioritize to make a reasonably conductive carbon. And rather than put it in a standard jello mold in this case of jello mold for us is carbon fiber paper. So rather than trying to span across a centimeter or a meter because sol-gel science is very scalable our mold is gonna be carbon fiber paper. So here's a carbon fiber that you can see and you can see the high quality adhesion of our pyrolyzed polymer nanofoam there. Now the fun thing about sol-gel science it gives you a way to map different pore-sized ranges that's co-continuous with that solid carbon because we're in paper we can stack at one ply, two ply, three ply we've done up to six ply. At that point it's very much a macroscopic object not even flexible whereas one ply is still flexible you've got that X, Y just because of the size of the paper you cut out and you can ply it in Z. And the important thing for us is the void is co-continuous with that solid carbon foamy network. So we've already put in the things we need to move molecules around. And let's just increase our magnification so we've gone to two to one micron we're not seeing the carbon fiber anymore here's 200 nanometers. And so what you're seeing here is a massively parallel 3D current collector. And that's kind of our starting point for a lot of what we've done over the years in terms of electrochemical capacitors and battery materials and even catalysis. And we like those cross ties and I-beams because it's much more mechanically rugged. So you're in California, you know that if you've got a lot of pillars standing up next to each other and an earthquake comes your mechanics are going to be very bad news you collapse your structure. So we think in 3D and the nice thing about this is it's ready to go into your electric. We don't make an exotic carbon and modify it and then grind it back up with carbon powder to me that is a colossal waste of time and taxpayer dollars. So we've got nanofoam filled paper which is an object itself but only so interesting because it's carbon. So we're going to dip it into an oxidant solution like aqueous permanganate. And if we've controlled what we need to control and it's usually temperature and pH what comes out looks as though it's unchanged. But if you go into your transmission electron microscope you can see the manganese oxide fibrils everywhere occasionally you catch them sort of edge on and you can see the layered MnO6 octahedra planes characteristic of burnocyte MnO2. Now the important thing about doing it this way is most manganese oxides are rocks they're not great electron conductors. And carbon is our starting point for our two terminal devices. So it's got reasonable electronic conductivity. So if you're slathering a poor electron conductor on top of a good electron conductor yeah you do have to grind it back up and mix it with carbon. But if you're painting the surface of your good conductor as we do when we electrolessly deposit the manganese oxide as the permanganate sacrificially oxidizes that carbon layer you get nanoscale deposits over your high surface area electrifiable interface. So we take something that's typically on the order of tens to a few hundred Siemens per centimeter conductor and we're just putting a really thin layer of something that's six, seven orders of magnitude less electronically conducted. So we don't have a huge omic concern in the system. And the important thing about doing it with this controls if you will painting is that you're not carpeting the boundary of the paper with thick manganese oxide. And that allows you to design in the pore structure that designs in your frequency response. And now you've added a more interesting redox flavored system on top of this carbon fiber paper. So Megan Sasson took a one-ply, two-ply, three-ply system cross section that looked at it in the microscope with manganese oxide on there. And again, we're gonna stay aqueous. So we're either going to be something like a sodium sulfate or a lithium sulfate mild electrolyte not strongly acidic or basic. And so in a sodium sulfate system you're potentially inserting sodium. And if you've got water around you always have to remember proton is often the preferred insertion ion. And so she did the voltammetry on that current voltage curve, nice envelope and normalized to 2.6 Farads of stored energy per square centimeter. Two-ply cross section. You can see the good fill factor doubled went to five. Three-ply, we're now three times that. And that told us we had good connectivity of that void across a large macroscale distance. So you can see three-ply here is over 200 microns thick. And from your pattern recognition, you can see how boring just the plain carbon nano foam paper is at a one-ply. And then we've painted it with manganese oxide, two-ply, three-ply. Our current is now the capacitance normalized to the area of the system. We can also look at it as normalized to the mass of M and O2. And as you would expect, if we've got this kind of control, the per mass comes out to the same number because we've got, if you will, three-plys, much more thickness on a program basis. You've upped it, but program, it looks identical. So particularly for aerial footprint specific applications, this is the kind of control you want. You want to build up as a skyscraper but still have control of the ions, the electrons and the molecules. But there's other fun things you can do with this lamellar bernice site-like. So we've got sodium between our layers and water. Of course, we're not showing the water. That gives us a certain milliamp hours per gram. Now I'm dividing by the total weight of the electro. That's another point that makes us growl at our laboratory because most people won't tell you what they're normalizing to. We always tell you what we normalize to. And in that sort of yellow font, this is telling you the oxidation state of the manganese. So it's not all four-plus. And typically this painting in the high surface area on a carbon surface across the literature is giving you roughly 0.3 electrons per manganese center, which is, you know, pathetic. So Megan exchanged the sodium in the inner layers for lithium, just aqueous-soak and lithium nitrate. Now we've got a lithiated system and essentially the same footprint because it really should be 29 milliamp hours per gram total electrode. We've lowered the amount of manganese four in the system a bit with the lithium, but you can see it's giving you roughly the same performance in this lithium sulfate aqueous electrolyte. But you can convert that layered manganese oxide form to something much more interesting, more like a battery material. So first they treated an argon at 300 C. And you can see we're starting to kind of roughen the surface a bit. We very much lowered the oxidation state closer to all of it being manganese three. And you start to see things that pop up that look like a Faradayke response that you'd expect for something that's probably like an MN203. But if you give it a little bit of air at a lower temperature, so you're not oxidizing the carbon, you crystallize that paint that was originally layered into a lithium spinel. And now you've got the beautiful battery response you'd expect for an intercalating system. And the reason Megan and Jeff were really focused on this is putting a lot more charge in the positive end of the spectrum. They would then pair this system with a rust painted carbon fiber paper and have its own doubly asymmetric electrochemical capacitor. And that can give you approaching two volts in an aqueous system because both electrodes are suppressing either water oxidation or water reduction. And you can see now you've upped the total milliamp hours per gram of the electrode. And this one is giving us a full electron permanganese. So this is one of the hints that carbon cares literally what the molecular atomic orbital arrangement is as you're handing off electrons. The burnocyte 0.3, if you sort of aligned where that now tall compared to the layered form skyscraper of the spinel is, now we're getting our full electron. And people have studied the lithium spinel as a battery material and in aqueous lithium sulfate. So here's one paper that came out last decade, ground it up with carbon powder. And you can see if they're going sort of, battery slow 0.3 millivolts per second, you can see some resolution of those Faraday peaks. But once you're at a millivolts per second, you've lost that resolution. And then this is a classic powder composite. But if you're doing what we do, where we've converted the burnocyte to roughly 10 nanometer thick lithium spinel, you've got that resolution even up to 25 millivolts per second. So you can be 80 times faster in terms of accessing those electrons if you take the same material and architecturally design it. So that's typically what we want in the modern era. Yes, we want energy and lots of it so we don't have to charge our battery too often, but you also want power out of it in terms of modern devices. And classic powder composites are really hard to get power out without compromising the chemo mechanical characteristics of the active material. When you're only 10 nanometers thick, you really don't have to worry about it. But there's other things you can do with burnocyte. So maybe six, seven years ago, people said, well, why don't I take out those boring sodiums or potassiums between the layers and have divalent zinc in there, the start of the zinc ion battery. So you're in a mild electrolyte off an Olivia sulfate aqueous system versus zinc foil. And you're going to try to charge and discharge that burnocyte. So we're coming in with now our burnocyte on carbon nanofoam, not the powder composite, almost everybody else in the world studies. And we wanted to play games because we knew this was a highly pseudocapacitive system. So we're going to start with our kind of Carolina blue, all zinc sulfate in the electrolyte or all sodium sulfate. So this should be acting like a battery. This should be acting like a pseudocapacitive type system. And in between, we blend the electrolytes, but we did it so we had the same ionic strength all the way through. So that wasn't a confounding variable as we studied the electrochemistry. And again, here's our pattern recognition, normalized current across the voltage versus zinc and the Carolina blue battery like all zinc sulfate, the black sodium sulfate, again our capacitive envelope and blending the sodium and zinc and the electrolyte gives us something in between. Let's look at that a little more closely. So people in the battery world for too long now have been using a deconvolution of that current voltage curve, assigning the surface sided pseudocapacitive like to a linear sweep rate, that's the K1 new, plus the more semi-infinite diffusion for ions that would have to go into the solid state as in a classic battery. And so you'll see the voltometric curve you see deconvolved to how much of its capacitive, how much of it is battery storage. So this is a very sodium rich, so it should be mostly pseudocapacitive. So, okay. Here's less sodium, more zinc, starts to look a little bit like a dinosaur. Here's 5050 and here's all battery. So yes, your response should be to shutter. We are vehemently opposed to this analysis of charge storing materials in either a half cell or a full cell, because as your eye can tell you, it's this side of ludicrous. But one of our Veronica's lap former family, Jesse Coe did his PhD with Bruce Dunn and came and joined us. And he was very imbued with that K1, K2 deconvolution. I said, no way, we're not publishing a paper with that. So he went back in the literature and found ways to look at it from impedance. And this is based off work that Brian Conway and his colleague published in the early 90s trying to understand inductive effects in corroding systems. He just flipped it and looked at the capacitive part. So if we've got pure capacitive response with our sodium electrolyte, you can see up here are slowest 0.01 Hertz frequency. We're looking at normalized capacitance. So this isn't a classic impedance plot. We're looking at it in 3D capacitance, the frequency and the potential. So we can see the nice capacitive waterfall across the entire potential window. Now we're gonna look at all sync. Here's the 0.01 Hertz. Again, you can see we're getting less in terms of real capacitance out of this system. And we get that feature that we would want to assign as a faradaic response. So it is not as, shall we say, electron communicative even at these slower rates relative to the pure capacitive response. Here's the 2 to 1 and here's our preferred one. You've got a lot of sodium and a little bit of zinc and you see how nicely you've blended in these two features. You're keeping the real capacitance high and you're putting in that faradaic response which is sort of hinted at here if you look at the capacity as a function of scan rate. The battery looks really good if you're just really slow but then it's dropping precipitously whereas the capacitor is less affected at these faster scan rates. So this is an innately hybrid material that you can access because of the ions in your electrolyte. So there are other things to do like let's go back to spinel only instead of a lithium spinel, let's make a zinc spinel because there was this recognition that the zinc wasn't really inserting into the burnocyte but there is proper insertion into the spinel form. So Megan did the same thing we'd done with the lithium, exchanged out sodium for zinc, did the atmospheric treatments to form the zinc spinel and then did an exit you study as you were in essence moving it and going to lower voltages in this case versus zinc. So she would pop in and out and see things in between. So where you're here, where you've not done any zinc out of the system if you've not discharged the battery, it looks like our classic nano foam but after we've taken it to 0.9 volts versus zinc you see all of these precipitates which is the proton insertion into the burnocyte shifting the pH very basic at that electrified interface and you precipitate the zinc hydroxy sulfite. So it's never really been a zinc insertion it's always been protonic base. And of course she did some of her exterior interior showing that yes you make all of the salt but when you come back to 1.75 you've cleared it out and she likes cross sections so you can see got that porous interior that looks like it's starting to fill but then once you've come back to 1.9 in this case it's gone away. So these are questions we can ask without a lot of the confounding implications of being in a powder composite electrode structure. And I wanna quickly finish on zinc. We're pushing batteries for energy storage because we have to find ways to take all the renewables out there and store the energy when the wind's not blowing and the sun's not shining. But if we want that for our sustainable energy future really shouldn't the batteries be sustainable as well. So Brandon Hopkins who finished his postdoc time with us about a year ago took the European Union supply risk data for elements where the EU is defined one as a low supply risk. So that's the blue line coming across here and then he plotted those numbers versus the abundance of those elements in the upper crust. And fortunately for us a lot of the low supply risk abundant things are in that green lower right quadrant. And that's important for us because we really would like our batteries to be low supply risk and sustainable as well. And then Brandon looked at the system costs. So this is dollars per kilowatt hour of the system. And yes your per cell lithium may look glorious but when you put a lot of those together you have to catastrophe management. So humans don't die and Teslas don't burn up, et cetera. And that adds weight and volume. So at that point that lithium battery pack is a lot like a fuel cell. The guts of it are only a minor fraction of the weight and volume. So if you're looking at the system you're going to say, well, gee I've lost a lot. So here's in black lithium ion. Here's some of our old favorites lead acid, nickel metal hydride. And then here's some of the things that do fall in our sustainable green area. And you can see in terms of low system cost and reasonable to great system energy and zinc's not a bad one to play with. So why zinc? Well, it's lithium ion competitive and we get zinc air to be rechargeable. You're not going to bother with lithium. In fact, I've given briefings where I've said if we had a clean sheet redesign of batteries with what we know today in the 21st century lithium would not make it on the page. So now we've got low cost non-strategic materials for an aqueous electrolyte. You've got a sweeter spot for manufacturability. You've got safer operation and the military loves zinc. In fact, they often use one shot discharge zinc airs to charge lithium batteries. But zinc systems are historically not very rechargeable. So when you bring our architected perspective and up the scale a bit now we're not tens of nanometers we might be tens of microns back in the more standard battery size. Why would we want to be spongy? Well, we've got that co-continuous ion electron path. It's scalable. You're talking to all of that surface close to open medium diffusion rates. That's a characteristic of these co-continuous four-solid networks. You've got high surface to volume ratio. So even though we've got larger zinc than we were working with with the carbon nanofone paper we're getting hundreds of square centimeters of electrochemically addressable area in the volume of the electrode per square centimeter footprint. And what that does in addition to wiring the electrons and wiring the ions, it lowers your local current density. And that's what causes a lot of problems in electrochemistry from electric deposition to electrowinning to batteries. You've got a modest electrifiable interface and you're trying to push a huge load on it. And so you push the current density to places where bad things happen. So just the physical change of our zinc from a foil or a powder has imposed morphological control because we've lowered local current density. So here's our old picture of an active material. I'm not gonna specify what it is. Grounded up with carbon powder, some kind of separator. Zinc is a powder. And as you discharge that in aqueous, the end product is zinc oxide. There's some steps in between that complicate our lives. And so that zinc oxide is not highly conductive. So you start to passivate the metallic, highly conductive zinc. And that part that isn't terribly passivated gets a lot of the local current density and that's why dendrites form. And they can be seen by eye and probably by satellite. So if you think in 3D, you're gonna take that powder and now fuse it into a sponge. So here's the cross section of the sponge. And now the zinc oxide is only going on the walls and you've always got a good metallic internal core that allows you to talk back to your macro scale current collector without any problems. So in our case, the sponge goes in, sponge comes out. And no big surprise, we've had lots of papers on that and as you'll see some patents. So we first wanted to stress test the performance of the sponge just as you would for a lithium system to see when dendrites form under which electrolyte and which loads. And it's known for zinc and alkaline that's sort of in the ballpark of, you know, pick a number, six milliamps per square, which in the old day, you typically weren't trying to push your battery torque in the modern day. Yes. So we put a zinc versus a slightly zinc oxide coated sponge and just cycled it twice the current critical current density in an alkaline electrolyte and that went on for three and a half days, took it out, rinsed it off, put it in the scanning electron microscope and you can see the exterior has this nice sort of textured everywhere. You cross section, you see the same texture. And of course, most of the electrifiable interface is inside, not at that boundary face. And there's no loss of mechanical integrity, no shape change, that core shell, zinc oxide painted wall of the zinc sponge is giving us control. If you go to a finer scale, higher mag, you can see that each of these finely textured features looks like this little spike. And that's why zinc wants to make a dendrite. If you get one of these kind of isolated from its neighbors and it's got all of the species you need to reduce to make zinc metal, you are gonna make a dendrite. And this taught us two things. You've got a confined volume in the pores. So you're going to supersaturate the soluble zincate that forms when you take divalent zinc as you discharge and it sees hydroxide in the electrolyte. That will ultimately supersaturate and spit out water and make the zinc oxide. Now, if that zinc oxide doesn't go on the zinc, you'll never talk to it again. So this was telling us that now we've got a lot of uniformity in the system, a lot of neighbors, which on their own would definitely make a dendrite, but nobody wins out. They've all got to work well and play well together. So once you've solved the zinc dendrite problem, you've got a lot of phase space to play in as this shows from single discharge zinc air to the rechargeable versus silver or nickel or manganese oxide, gold being a zinc air and ultimately an all solid state non-periodic 3D battery and even the zinc ion. And this is old work now published in Science in 2017, but we showed that versus a rechargeable cathode, in this case a commercially harvested nickel cathode, we could get greater than 90% of all the zinc in that sponge oxidized and get almost all of it back. That's just a single charge discharge. Now, of course, in the battery, you're not trying to do that. So we had a one-year program from ARPA-E where we had to demonstrate that we could eat 40% of all the zinc in the sponge as we discharge and get all of it back and do that for 100 cycles at a high load, 25 milliamps per square, and nobody's solid state electrolyte's gonna do that. And we showed that, we did it in a year. And we also showed sponge goes in, sponge comes out, but we also wanted to look at another potential application space, and that's start-stop microhybrids. And that's typically showing up in your more expensive cars, particularly in Europe, because sometimes you have to sit at stoplight for two minutes and everything shuts off. So you need an engine restart and plus all these other things you're doing while the car's running. So most people don't publish operational duty cycles, even the military, but BMW published theirs. So we scaled it to the cell we were working with, commercially harvested nickel cathodes versus our sponge and set that up and it went for four and a half months. So on the normally 20 cycles per day, that would have gone for six years. And currently those start-stop microhybrids maybe last a year, even though they're rated for two. And again, sponge goes in, sponge comes out. So often we change things. The original science work was done with 20% of the sponge being sink. And for an energy density normalization, that's not enough sink. So new postdoc from Joe Parker's original work in the science paper, Jesse Koh came in and kicked it up to 2.1 grams of zinc per CC of sponge. Joe was working with 1.4 and you just do a zinc air just to show you can eat most of the zinc. Sponge goes in, sponge comes out. Now it's coarse gray or because it's got zinc oxide. And now we're putting it versus a really homemade silver oxide because the military loves silver zinc. Silver zinc kept the Apollo 13 astronauts alive. There's some uses for it, although it's not gonna go in a car because people would be stealing batteries. So the same thing, you do a deep discharge, a deep recharge, you can see just how much you're working with. So that first generation of sponge, you've got 1.2 kilowatt hours per kilogram of zinc, 1.5 kilowatt hours per liter of zinc. And as you might expect, if you go to a per gram normalization with the higher dense sponge, that comes pretty much to the same number, but where you went out is your per liter. And although I know we're used to thinking of specific capacities and worried about weight, for most applications, it really is the energy density you want. So just that reformulated sponge is just kicked it into a new phase space. The other thing we noticed with this more dense sponge, 30% of the sponge being zinc versus the silver is we could now get a hundred cycles. And we were doing nothing to optimize the separator system and the silver cathode, which you need to do to even get tens of cycles. Our zinc Gen 1, the 1.4 grams per cc would give us 50 cycles without a problem. We were doing a hundred with the new version. And then that was sort of like the smack in the head because of course, you have to think about how uniform is the current distribution between your two terminals. And if one electrode is misbehaving like zinc is making dendrites, then the other electrode is trying to compensate for that now very irregular current distribution across the separator and the electrolyte. So if one electrode is being more uniform, you immediately take another electrode, which is willing to act up and make it more uniform. So just that physical change in the zinc started to make even an unoptimized silver system behave. And now we're denser, we're stronger, we can thin it down, we can get higher power. So this just shows when you're putting, from 15 to 500 milliamps across a square centimeter to coin cell, two terminal coin cell, you can get up to six watts per kilogram of zinc. So at this point, the system's really acting like a capacitor. And as we're making improvements in the zinc, at some point we're not gonna be able to talk about silver zinc publicly, because then we start to go on the military critical list of performance. New postdoc, new protocol, Brandon recognized that our legacy carboxymethyl cellulose that we use to make the emulsion to make the zinc wasn't working when you upped the amount of zinc in the system. So he split the functionality. He worked with resin as a porogen and he worked with the food additive, carboxymethyl cellulose powder, not a resin, to increase the viscosity. And that let him get the amount of zinc up even higher than Jesse was able to work with the 2.1 grams per CC. So now we're at 2.8 grams per CC. He put it versus a harvested nickel cathode in our coin cells. And he had designed his coin cell that he could remove the cathode part without really disrupting the separators or the zinc and replace the cathode, which he had to do because when he was starting to see any fade, he put in a fresh nickel cathode and it would kick right back up. So he did that four times. He was doing 40% of all the zinc being oxidized and recovered during the charge cycle. And it got to 150 cycles, but he had to replace that cathode four times. Whereas the zinc was just doing back strokes because it's saying, throw a better cathode at me. It could care. So in this cross section, you see, we've actually sliced one of the zinc cores and you can see how filled that is. On the map, you can see in the blue, the oxygen, you can see just how bright that is around the zinc core. And that helped verify and we've almost done tomography to show it really is that cartoon we showed. It is a core show. So here's the sort of reduced zinc. It looks very plate-like before you start 150 cycles at 40% depth of discharge. And that's theoretical. That's not a normative. Here's what I get, 40%. That's theoretical. And then here's after 150 cycles. So if you look at this on a milliamp hours per volume, in this case, cubic centimeters of zinc, you're just kicking whatever's in the literature in the teeth. And new postdoc, Ryan DeBlack, we're about to hire. He's tried to make this even faster and more scalable without, it's giving you some control on how much zinc oxide is on the surface. So now he's gotten zinc powder, salt, acetic acid, water. You could still keep the arbitrary shape construction we had with the emulsions. The heating is much shorter under nitrogen. You're getting your bridges between the zinc particles without the elaborate treatment that we described in our first paper in 2014. And then you just remove, in this case, the porgin being things like salt with water ethanol washing. So again, in that sort of nice sweet range of two to three grams per cc, so 30, 40% fill factor, getting high capacity. And this can be done without having to electro-reduce any thermal oxide on the system. So here you can see 100 square centimeters of plate zinc that could go in a pouch cell, millimeter thick, or lots of things ready to go on a coin cell, or lots of cylinders ready to go into like double A, triple A type form factors. And again, very spongy. So the anode is fine. Well, I'm sure I'm at 30 minutes plus. Just a tiny bit over. I wanna wake one more point. Now we've got to do work on the cathodes. So Brandon went back into the literature with everyone's sort of projected practical specific energy or energy density for state-of-the-art lithium ion, lithium sulfur, the approach to go to layered metal oxides versus lithium metal, the argon estimate of how the best number you might get out of lithium air and then zinc air. And of course, these orange ones are where we're caring about. It's that energy density. And of course, zinc is known for good volumetric energy and lithium is known to be very bad with respect to that. So why are we putting quite so much effort into lithium? And the fun thing about zinc air is you've got to do four electrochemical devices well. You've got to have the ability to reduce oxygen in an alkaline electrolyte. So it's like a fuel cell. You need pulse power, which typically air-breathing cathodes don't give you, but we've got ways to get around that with architected designs. You have to have the zinc not make dendrites solve that problem. And then at the end of the day, you have to evolve oxygen. So you have to have alkaline electrolyzer function. All of that's got to work in one nominal two-terminal system. So we've come back to aerogels. We've made two types of catalysts, the crypto-malane tunnel structure, polymorph of manganese oxide, and a nickel ferrite, which is known to be a reasonable oxygen evolution catalyst. Crypto-malane is better for oxygen reduction. And if you've just, we've gone to powder composite because everybody else uses that when compare results. Just the manganese oxide, you can see you've got a reasonable discharge cell voltage, but you've got to charge it well above two volts, and carbon doesn't like to go there. Whereas if you're just looking at the nickel ferrite, it's got some bifunctionality, you're perhaps not getting quite as high a initial discharge cell voltage as you like, but you keep the charge well under two volts. So put the two powders together into our carbon composite, and you get the best of both worlds. You buy back a better discharge cell voltage, you're keeping it below two volts to charge. And we're getting some of the highest power density out of a powder composite. That's, we've gotten higher power density out of an architected one, but we're still making that work with two types of catalysts in it. And this shows what happens with one alone, just the crypto-malane or the nickel ferrite, and the blue, of course, is the best of all words. You've got some of the lowest hysteresis values ever reported. And so here we are relative to what's in the literature. You know, even just the nickel ferrite alone is not bad on its own. And we never work with cobalt. All of these other ones are typically working with cobalt, and we are trying again to say low supply risk and sustainable. So be an architect. What you make may look like the dog's breakfast. It's not this periodic perfect array, but that's good for many, many reasons. And Chinese wisdom to end. It's these empty spaces that make the room livable. Well, the tangible has advantages. It is the intangible that makes it useful. So we are big fans of the importance of nothing. And I thank you for the opportunity to kind of walk you through how we view energy storage in the aqueous electrolyte world. Thank you. Deborah, thank you so much for that overview of a great body of work, spending quite a long time, really appreciate it. We're a little bit over in time. So there are two questions I wanna highlight here, Deborah. One is more on the fundamental side and one is more on the technology side. The fundamental question is, you talked about using materials like MNO2 and others without conducted additives. How tunable are these materials in terms of as electronic transport? And is that a key bottleneck as you use them for your applications? Well, that's why I point out one of the huge open questions. Carbon is not anybody's choice as a fast electron transfer surface. And we get away with what we get away with because we're so thin. So when you work with a carbon nanofoam, you're looking at four to 500 square meters per gram of electrifiable interface. So even 10 nanometer thick oxides on that surface gives you technologically relevant weight loadings. And how about just the bulk electronic transport of these materials, just to get it all the way through the thickness of the electrode? You don't have to worry about that because that 3D current collector scaffold is in good contact with the current collector. And of course, everything is happening originally at the current collector because you do have a little bit of that transmission line but it's not enough to interrupt the power in the system. So the ideal in our view would be where we're working towards, which is that 3D tricontinuous non-periodic solid state battery, which we originally proposed in the late 90s and wrote a chemical review article, the 3D battery architected paper came out. The important thing about being non-periodic is it collapses to a uniform current distribution, particularly in that filled 3D tricontinuous design. The anode and the cathode we're going to want to have at most maybe a hundred nanometers apart. And we showed with the aerogel, we could do it but we only had 20 nanometers of open space to work with. So our separator was only about seven nanometers thick and then we inter-filled with the other electrode. And that's like doing molecular electronics, so be. So if you got the right material as that original scaffold, you are always gonna have good electronic communication throughout the entire structure. And that's what the Zinc Spun shows. We have yet to make a Zinc dendrite putting an enormous amount of current on the system in the alkaline electrolyte. You have to worry about too much Zinc being in there. So we keep it sort of not much over 40% of the volume is Zinc because you run out of ions. In fact, Megan did a really nice paper on the manganese oxide coated nanofoam showing, do I want rate or do I want capacity? And there is a sweet spot in terms of the poor solid architecture. You can have too much surface area, too much active material and you don't get enough ions to it to get a real rate performance out of it. You have to go really slow. And that's what happens if the pores get too small. So you really, you know, we've been learning as we go over the last 25 years. So all those lessons are sitting in our papers over the years. Here's where we go for rate. Here's where we go for capacity. Here's how we have morphological control by a uniform. The electrochemist will tell you no electrode is truly 100% uniform. But in these approaches, it's so much more uniform than anybody else's electrode. That's why we get away with what we get away with. Thank you, Deborah. Maybe as a segue to the second question on the technology side. So, you know, in the lithium ion battery field, as you mentioned, the dominant approach has been used carbon composites, I'm saying the cathode side, in order to create the necessary electronic end ionic transport. And it's challenging from a morphology perspective. You know, 3D current collector has also been explored, but I think commercially cost has been a limiting factor. Do you also see that as a challenge for the aqueous or does the aqueous open up other doors that lithium ions do not? I think it opens doors. Plus it makes manufacturing so much less strenuous and onerous and expensive. Because once you're working with lithium and even if you're in well-behaved non-aqueous electrolytes, you've got organics. So there's that aspect of it. But if you're taking that architected approach and now it needs to be done over on the cathode side, you really are buying a lot. We're doing work now to get more than one electron out of the nickel. If you want to think about grid storage, we want to get more than one electron out of the manganese. Certainly the group at City University of New York is trying to do that because that would be a really sweet system. It would be a zinc manganese for microgrids or even larger grid scale storage. Zinc air could have a lot of implications, but that one is a lot farther away because you've got to get so many things right. But I see a way to get it right easier than with lithium air. But we've noticed once we sort of showed that we couldn't make dendrites with zinc, we saw a lot of people trying to make their lithium systems 3D to try to get around the lithium dendrite issues. So just that change of perspective, just as we had when we recognized ruthenium hydroxide was always a nanocomposite doing the two transport functions well rather than trying to make a homogeneous material do both well, buys a lot of design freedom. All right, quick and last question, volumetric energy density. You've highlighted at the materials level as you approach these porous materials, how does that play into the overall electoral level of volumetric energy density and is that a limiting factor for these electrode designs? So at the end of the day, they may be a touch thicker. So for a lot of what's getting done for EV with the company who's licensing our sponge, they still want the zinc to be about a millimeter thick because at the end of the day, you're gonna need some real mass there to have the capacity. The cathodes likely could get thinner if we can get more than one electron out of them. We're doing things that again, if you're more uniformly reactive with both electrodes because you're not making dendrites, you can get rid of some of the weight and volume that exotic separators induce. So there should be ways to buy back, I might be a little bit thicker than 50 micron foil, but I might just be a 70 micron piece of paper. Got it, so where you can maybe, you might lose some of the press density at the powder level, you're getting it because you can go with a much thicker electrode. And you've got all of that inner surface area accessible and talking back to the current collector. So the utilization is the other thing that you're getting out of this and that's gonna help with rate. The military finds that you can take the manufacturer's spec for how much energy is sitting in that packaged battery. And when you're out in the field doing stuff with it, you're not putting it on a low load and just letting it discharge. You're often asking for power out of it and in the classic powder composite, and I'm sure you guys all know this extremely well, you start to do mechanical damage to the active material if you keep trying to get power out of it so that ultimately saps how much energy you can get out of it. Cause you've lost, if you will, communication to that stress-drained active material. And that's not happening in our systems. Absolutely agreed. Deborah, thank you so much again. Let me hand things off to Yi who will introduce Veronica and then we'll come back for a panel discussion. Thank you, Deborah. Looking forward to it. Thank you. Well, thank you, Will. Well, thank you, Deborah. Let me just add a comment when you gave a great talk and also your past research, I would say has been very highly influential on me as well as the 3D architecture has been quite amazing. I learned a lot over the years from your research. Now, let me invite our next speaker, Professor Veronica Augustine to the stage. Let me do a brief introduction. Veronica is currently a associate professor of material science and engineering in North Carolina State University. She also served as the associate editor for the Journal of Materials Chemistry A and Materials Advances. She is a university faculty scholar in NC State. She has won many awards over the years, including the Department of Energy Early Career Award. And by the way, that's a very hard one to win, very prestigious, Sloan Research Fellowship. With that, Veronica, I would like to invite you to the stage and tell us about what you have been working on. Okay, thank you so much. It's really a great honor for me to be here this morning. Thank you to Will and me for the invitation and it's also a pleasure to be in the same speaking seminar slot as Dr. Deborah Rawlison. So what I'm gonna talk with you today is gonna be a little bit more on the fundamental side. Our group has been doing a lot of work in understanding proton-coupled electrochemical processes and metal oxides for energy storage and conversion. So given the 30 minute time slot, I wanted to give you kind of some short vignettes of how we look at these processes and the approaches that we take to investigate something that's very important for aqueous energy storage. A little bit more about my research group. We broadly investigate the electrochemistry of materials for energy and environmental applications. We're located at NC State University in Raleigh. This is our centennial campus, not too far away from the downtown Raleigh, showing the engineering buildings. Our group's core experimental expertise is in material synthesis, electrochemistry, as well as in situa perrondo characterization. So like many of us working in electrochemistry of materials, we really are keen to understand how these materials are behaving in their actual environments. We have a rather broad array of research topics that kind of really focus in on the fundamental aspects of materials in electrochemical systems from the proton-coupled electron transfer that's relevant for today's talks, but also we're looking at things like CO2 absorption, supraionic conductivity. A big theme is electrochemistry under confinement and I'll touch upon that just a little bit today, as well as of course porous electrodes since that's how we assemble materials for pretty much all energy and environmental applications. A little bit about material science at NC State University, especially for those students looking for graduates' research or postdoc opportunities. We have wonderful state-of-the-art materials characterization facilities from x-ray diffraction to transmission electron microscopy. We have many faculty in very diverse research topics in our department and Raleigh is a pretty nice place to live. This is our research group here on the left, so if you're interested to hear more about our group or all the other wonderful groups at NC State, please check out our website. The work that I'll share with you today is the outcome of the dissertation research of several students from my group. Shelby Pillai, who's now working at Urbix on graphite materials. James Mitchell, who's now a postdoc scholar with Shannon Betcher in Oregon. Said Said and Mike Spencer, who are graduate students and gonna be graduating in next year or two. So look for them for, if you're looking for postdocs, they would be fantastic. And Roh Tsung-Wang, who is a postdoc with Yuriko Gotsi, as well as several postdoctoral fellows. Simon Fleischman, who is now a group leader at Helmholtz Institute Own, leading his own research group in Germany. And Janelle Fortunato, who's working with us still. So, and also many collaborators, as well as funding from DOE, NSF, and Sloan Foundation. So this is our group. These are the fantastic people that I have the chance to work with each day. Okay, so the theme of my presentation is really on protons. And so to orient you with why we care about protons for energy storage, I wanted to just put up a couple of view graphs. The first is protons as charge carriers provide some unique benefits. They are obviously small. They have the smallest ionic radius of all these typical ions, anions, and cations that would be considered as charge carriers for energy systems. They're monovalent that also, and this makes them relatively mobile and easy to insert, particularly into materials. They are sustainable. This is non-metallic. And they have this unique transport mechanism via hydrogen bonding, the Grotus mechanism in liquid water, for example. All these things make them interesting as charge carriers for energy storage systems. The other relevance is obviously that they are ubiquitous in aqueous electrolytes. They can participate in multiple types of reactions, adsorption, insertion, and conversion processes. And I showed this schematic from one of the recent papers that showed that in a zinc ion containing electrolyte when you take this spinel material and you cycle it, the mechanism does not involve a multivalent cation insertion but it does involve a proton coupled reaction through a conversion type process to form something much more complex than originally thought in the research. The other reason why we're interested in proton insertion and metal oxide, specifically a beyond energy storage has to do with some kind of frontier applications of these processes. For example, in programmable resistors, tungsten oxide, the modulation of the electronic conductivity of tungsten oxide upon proton insertion as shown here can be used for these new kinds of electronic devices as well as using the proton acceptance and the proton donation capabilities of these materials to perform catalytic processes on their surfaces through proton coupled electron transfer. So there's really kind of a broad range of processes from energy storage, energy conversion towards even new applications like the ones illustrated here. So for my presentation today, we're gonna be considering kind of the array of processes that can involve protons on the surfaces of metal oxides and take a look at two specific examples. The first one is work that we've been doing in my group for a long time, which is the behavior of protons and hydrous metal oxides. The relevance of this is for energy storage. So we're looking at basically how these protons and electrons can be stored on surfaces or in the interlayers of materials. And then the second shorter story because this is a storage X series is on these processes in metal oxide electro catalysis where some of these phenomena like proton absorption or insertion appear to be influencing the surface reactions of protons. So the first story, protons and hydrous metal oxides for energy storage, it started off with our interest in understanding the role of ordered and confined water networks in crystalline tungsten oxide hydrates. So we saw in Deborah's presentation how hydrous ruthenium oxide behaves as this ideal capacitive material with very high specific capacitance, this continuous network of water molecules and conductive metal oxide particles. And so there's always an interest to find other materials perhaps that can be lower cost that would exhibit similar phenomena. And so we took this approach of looking at a material that contains structural water molecules but now it's a crystalline material. The tungsten oxide hydrates, these are the structures, the layered materials as you can see on the left here and you can go through several phase transitions within the hydrates all the way to the anhydrous tungsten oxide. All three of these phases can undergo reversible proton and cation insertion. So they are all redox active. And the hypothesis that we came in for this research was aligned with what was in the literature which is that proton insertion would be faster in this material because of the greatest transport of protons along the structural water network. This would be perhaps kind of an intuitive approach to thinking where the protons would go. And that's why we would observe fast proton insertion kinetics electrochemical. So this is work that really underpinned the dissertation research of James Mitchell. And we took a look at various form factors of hydrous tungsten oxide. Sometimes they were slurry electrodes. Sometimes they were thin films. This is the result from the thin film study. And what we always saw was that proton insertion in our hydrous materials was more reversible than in the anhydrous tungsten oxide with better capacity to retention at fast scan rates. So because of the thin film nature of these electrodes we could push them at extremely fast rates. So this is a cyclic voltamogram at 2000 millivolts per second. And we saw that at these rates the hydrous materials were performing better than the anhydrous material. This was previously observed in the literature and attributed to this quotas transport property of hydrous tungsten oxides. What we found though was something a little bit different. First, I just want to make this note that with you can, there's a strong coupling between the mechanical deformation of a material or a molecule and rate capability. So we know that electrochemical redox requires a change in bond length. So when ferrocene is oxidized to ferrocenium one way that you could characterize that is because the iron carbon bonds will lengthen. In an extended solid these electrochemical redox reactions lead to volume and or phase changes. So they're much more significant because of this extended nature of the materials. And you can consider using the rate of mechanical deformation to provide insight on the electrochemical insertion kinetics. And this is kind of that fundamental coupling between the extent of charge source the extent of volume change and the rate capability of the material. To probe this, we used operando AFM dilatometry. This is a ongoing effort with Nina Balkie who is now at NC State and Juan Yuzai who's at Oak Ridge National Laboratory where we basically performed use the AFM tip as a dilatometer. It's tracking the deformation of a drop cast electrode in the middle of this AFM cell. We're able to apply electrochemical stimulus or a bias to our electrode through our entire electrode through globally through a potential stat and then measure very locally its response. This is the cyclic voltammetry that we obtain. And so again, we see more reversible proton insertion for the hydrous materials and the anhydrous materials. This is what the surface topography looks like. And now what we're gonna do is we're gonna just land our AFM tip in the middle of these electrodes somewhere and then track how does that electrode respond when we're applying the cyclic voltammetry signal? And what we saw over and over again was that the hydrous material exhibits more reversible and smaller deformation. So the deformation magnitude for the same thickness electrodes was always smaller for the hydrous material. Very notable, there was a lack of that hysteresis. So that's what we mean by reversibility. And there's also very little dependence of the deformation on scan rate as protons are cycling in and out of the material. So right away we see that one of the big differences between these two materials has to do with how stable the structure appears during the proton insertion and the insertion process. Furthermore, to kind of go back to that initial statement that I made between the deformation of a material or a molecule and its electrochemical response, we saw a direct correlation between the current and deformation rate. So if we take the derivative of the AFM data from the previous slide, we get the solid curve here with the error bars. The dashed line is the electrochemical current coming from the entire electrode. And you can see we have extremely close agreement except in the region where we have the onset of the hydrogen evolution reaction on the electrode surface which is being measured with the potential step but which does not cause a volume change in the material and therefore does it register on the AFM tip. So we have this really nice technique to measure very locally the deformation of material and that can be applied to study, for example, the heterogeneity of the electro deformation across the spatial heterogeneity of material deformation. For our purposes here though, it showcased that there was another aspect that we could consider for why the hydrogen material showed more reversible proton insertion and it had to do with this structural response. Using operando x-ray diffraction, we were able to further correlate this response to basically a more reversible electrochemically induced phase change. This is operando x-ray diffraction performed at Slack by James Mitchell and Elisa Patterson in collaboration with Mike Tony's group. And what we observed at different scan rates is that the tungsten oxide hydrate always was showing this very reversible phase transition with proton insertion. These are the electrochemical input. This is the current response. You can see that at the redox peaks, there's this very distinct transition of the hydrate into a new crystal phase. There's no interlayer spacing change, however. So that idea that protons could be moving along these pathway, it's not really supported through the x-ray diffraction. What we can say is that we're not seeing tungsten oxygen bond distances change along that interlayer axis. On the other hand, for the anhydrous tungsten oxide, which can also accommodate protons, what we see is a very sluggish phase transition process. The material never fully transforms to its next structure. The two phases are always present. And when we push it to operate at an even faster rate, we see that the hydrous material is able to keep up with the phase transition. Whereas the anhydrous tungsten oxide that diffraction peaks appear almost static frozen and there's no structural transition at this rate. So this led us to have a revised hypothesis for what's happening with these crystalline tungsten oxide hydrates. We don't see evidence of protons transporting along these water networks here. They're more likely associated with the bridging oxygens within each of these layers. We do see evidence of structural transitions associated with the changes in the tungsten oxide bond distances within this layer. So this is a top down view on these layers. And so that makes our hypothesis more that the structural water is providing structural stability during proton insertion. So it's essentially kind of like a glue keeping these layers together and not rearranging so much as in the case of the anhydrous tungsten oxide, you have more of a floppy crystal structure, if you will, where there's no reinforcement coming from the structural water network. So this was our kind of revised hypothesis, what's happening with protons in a crystalline hydrate material. So with this work, we showed the kinetic benefit of structural water, but the capacity is very low. We not only are using tungsten here, but we also have a lot of structural water molecules. So that all kind of decreases the specific capacity. So we were on the hunt for maybe finding tungsten oxide hydrates that could have a better performance. And one route of doing this is to take high temperature solid state materials and exchange their ions, interlayer ions by protons. And one approach is to take this bismuth tungsten oxide material, expose it to acid, and you form a material that looks very similar to what you were working with before, except now the water networks are separated by basically every two tungsten oxide layers. So this is a different ways of writing this formula. You can think of it as hydrogen tungstate or W206.H2O, which shows kind of the relationship to what we were working with before. The interesting thing is that now this material shows a much more potential dependent response for proton insertion, whereas before we had this much broader response, we have a very specific potential dependence in the cyclic voltamogram. And we did achieve our goal of having about two times the specific capacity of the tungsten oxide monohydrate while maintaining very good rate capability. So that's the comparison with the blue. This material, the H2O, W207, and then the monohydrate down here. And then for the same particle size, we still see that the anhydrous material shows worse kinetics. So we were able to kind of use metastable transition metal oxides to improve the performance. Now, moving on to the next story, this is something that we've been working on for a few years. And we've had a lot of questions about this very basic kind of idea of, where does the electric double layer end and intercalation begin? So we like to work with hydrous metal oxides in our group. The tungsten oxide hydrates were saying that the protons don't appear to be moving along the structural water networks, but there are many other hydrous layered materials, for example, where they do accommodate cations inside of their structure. And so for the most part, when we think about the electric double layer, we're thinking about planar electrochemical interfaces. So when we think about processes like cation and absorption, we think about this distinction between the absorption of a fully solvated cation that would have a non-specific interaction with the surface. So in the cyclic voltamogram, for example, you would see no specific potential dependence. And then you also have specific cation and absorption where there's a chemical bond that's being formed with between the cation and the electrode surface, including either full or partial desolvation of the cation and that would have an associated potential dependence with it. And in these distinctions between these two processes, a fully solvated cation and absorption, non-specific, specific cation and absorption is essentially how we describe double layer, non-fair day capacitance and pseudo capacitance. But what happens when we have layered hydrous materials that have interlayers that either contain water molecules and cations or have a large interlayer spacing that can accommodate partially or even fully solvated cations? What happens in that in-between space between the outer surface and then the inner surface on the far right hand side, which is a clear intercalation system? We were really interested in understanding what the behavior of materials like this should be described as because there's a lot of discussion in the literature about what this is. Is this non-fair day? Is this fair day? So to look at this question, we went back to Burnisite, which we heard about in Deborah's presentation as well. It's a classic capacitive oxide material and this is the work of Shelby Ply as well as Said Said. So we made a Burnisite through electro deposition. This is the kind of perfect crystal structure of Burnisite. The interlayer contains cations as well as water molecules. The interlayer spacing is about 0.7 nanometers. And then the electrochemical responses see when we say capacitive, we mean that there's this very weak potential dependence. Most of the capacity associated with this material is coming from a potential independent process. And this material is of interest for high power energy storage, desalination as well as electro catalysis. So really broad applications and aqueous energy systems. One of the things we wanted to understand is whether most of this capacitance was just coming from outer surface processes, ion adsorption at the outer surface of this material. So what we did is this experiment that we learned from Deborah's research, which is to take the Burnisite and cycle it in a aqueous electrolyte that contained a small cation, relatively small cation like potassium, potassium as well as in a non aqueous electrolyte that contained a bulky cation like tetrabutyl ammonium and compare the capacitive response. So tetrabutyl ammonium has a ionic radius of 0.41 nanometers. It's actually used to exfoliate Burnisite. And what we observed was that the capacitance is orders of magnitude greater in an aqueous electrolyte than in this non aqueous electrolyte. So essentially what we see is that in the non aqueous electrolyte we must only have the outer surface adsorption process taking place, whereas in an aqueous electrolyte we must have outer surface adsorption as well as intercalation coming into play as well. So we would estimate based on these results that that outer surface is contributing only less than 10% to the total capacitance in the material. Another question since we were working with potassium sulfate aqueous electrolyte was whether protons are involved in the capacitive mechanism. So in this follow-up study, what we did is that we added a phosphate buffer to the electrolyte while maintaining a pH of 6.5. Now the phosphate buffer serves as a source of protons. So there has to be a proton coupled electron transfer reaction taking place at the interface. We observed that as we increased the buffer concentration there's an increase in the specific current of the electrode. However, this increase is very transient. It only occurs for the first few tens of cycles before the capacity degrades very significantly. Whereas if there's no buffer in the electrolyte you get this lower capacity but much more stable cycling. So what we observed here is that this film was basically dissolving when we had buffer present in the electrolyte. So protons did not contribute to the capacitive mechanism. This mechanism that we're talking about here when there's no buffer present in the electrolyte. Combination of experimental and computational studies led us to look at that. What is happening structurally to the material and we observed this reversible interlayer breathing of burnocyte about a 1.4% interlayer change which according to DFT simulations can be the proposed mechanism is a counter movement of potassium ions and interlayer water molecules. The structural changes that we observed are gradual and the amount of charge transfer is relatively small and it involves cations moving into the interlayer. So the question was why does this cation intercalation appear capacitive or potential independent whereas most cation intercalation does not, does have a very specific potential dependence. That is what we observe in batteries. So our hypothesis is that this has to do with the presence of those confined water molecules. These are reactive force field, grand canonical Monte Carlo simulations by our collaborators at Penn State. We understand this material as basically being very much dependent upon the nature of this interlayer environment. The cations like potassium these gray spheres are intercleaning in the middle of the hydrous interlayer and they're coordinated by other water molecules within the interlayer. Their locations are not specific so they distribute randomly in the interlayer and that's why you would see a lack of potential dependence and there's very importantly very little structural change that takes place because you have this counter movement of water molecules or water molecules that again remain as kind of pillaring molecules within the interlayer. This understanding this material has led us to write a perspective in nature energy that was led by Simon Fleischman published earlier this year where we tried to again go about this argument thinking about what happens as the interlayer spacing changes or the interaction distance between an electrolyte species and the host materials increasing and how we can think about this as kind of this continuum from outer surface absorption processes towards intercalation. Okay, now for the second part of the discussion which is how these dynamic proton processes and metal oxides could affect electro catalysts. So ion insertion can lead to dynamic changes in metal oxide materials. You can think of this as an example of how the confinement of electrolyte species is affecting electrochemical reactivity. There's also really nice work from Will's group published last year on this phenomenon in cobalt hydroxide and what we're observing here or what we decided to study in our group is to use a materials chemistry approach to see if we can trigger basically the proton insertion either on or off and see what happens to the catalytic process on the surface. So this is work done by Mike Spencer where we make these transition metal oxide organic hybrid materials. We basically have oxide layers separated by organic pillar molecules. These organic pillar molecules can take on different forms and they have some nice tunable properties. The biggest one is interlayer spacing but that can also be, you can also affect the transition metal coordination, ion transfer pathways and so on. This is what the materials look like. In particular, we used our friend the tungsten oxide monohydrate. You expose it to octalamine and heptane and there's a dissolution reassembly process. So it's not just a ion exchange but there's material actually dissolves and then reassembles with the octalamine in between the layers. And we can see that through the change in the microstructure on the SEM from the nanoscale morphology of the monohydrate to the micron scale octalamine containing material. Then you can, if you expose this material to sulfuric acid then an ion exchange process does take place and you form the dihydric form of the material but in a micron scale. So now we have several materials that we can use to probe how proton insertion affects the hydrogen evolution reaction taking place on the surface. The first thing we note is that with these octalamine containing materials we suppress proton and cation insertion. So whereas protons and small ions like lithium ions can insert into tungsten oxide monohydrate once we have octalamine in the interlayer we basically stop those from intercalating and both materials are not able to intercalate a bulky cation tetravelo ammonium. Then when we look at the hydrogen evolution reaction phenomenon we see that for the octalamine material it has the highest over potential for the HER. And we can further express this by taking the over potential at a specific current at five milliamps per square centimeter and plotting it by the number of electrons associated with each tungsten. And we see that the highest over potential is with that octalamine material. And then as we start to insert more and more protons into the structure that over potential decreases very quickly. So the open question is still exactly why proton insertion influences HER activity. One idea that's been around for a very long time is that the proton insertion changes the electronic connectivity like the work that I showed you at the very beginning from the yield is group, tungsten oxide will go from a semi-conductor to metal transition and thin film materials though we would assume that the electronic connectivity is relatively good. Another hypothesis more recent comes from our collaborators in the McCone group where they have evidence that proton insertion actually changes the absorption free energy for protons for the HER. And then something else that could potentially be taking place is if these inserted or bulk protons are actually participating in the HER and the surface active sites. So these are some hypotheses that we're testing out and still kind of to be determined for this class of materials. But we've shown definitively that the proton insertion must take place in order for the tungsten oxide surface to be catalytically active. Okay, so with that I've given you a brief overview of our group's work in proton coupled electrochemical processes and metal oxides. There's a range of phenomena that can take place from proton absorption and insertion, hydrogen evolution reaction as well as conversion or dissolution reactions. So their behavior of protons in these systems can be complex and very dynamic, but if we can harness them it can obviously make a big impact on energy and environmental applications. Like to acknowledge all the folks that have worked on this research once again in my group as well as our collaborators and then supportive of the funding agencies. And with that, I think we have time for discussion. I'm happy to take questions. Well, thank you very much Veronica. So a very nice presentation. Two directions highly correlated. I'm so glad to see these intercalations. You know, you go very deep into the proton couple of these energy storage. So one question relates to the first topic. So these are quisling water sitting between the layers. How dynamic are those water molecules? I mean, they're bounded between the layers. Once I am coming in. Right. So is there enough understanding to know how dynamics are those water molecules? They kind of just sitting in the same sites, you know. Do they change orientation? Do they kind of just having a conversation? That's a great question. In James's paper, we published in ACS Energy Letters a couple of years ago now we performed quasi-elastic neutron scattering of these materials, the hydrates in particular. And this structural water molecules and these materials is confined. There's no translational motion of water here. So you could use the term ice-like for these crystalline hydrates. This water is not very mobile. Hmm. But in other materials, we have not performed the quasi-elastic neutron scattering in bernice site, but in other materials, I would assume in bernice site I think is an example that you could see translational motion of the water, but in these particular materials, we do not. So Veronica, if water doesn't move these hypothesis of growth type of transport, would that be still happening? Or what's the thing that you're talking about here? Yeah, so the growth of transport does not require a translational motion of the water molecule, right? It just requires the movement of the proton. So when we started the work, we thought maybe we would see something like that, but I would say there's two things. Other than this slide, you do not see the word growth is transport in the remainder of my presentation because growth is transport is specifically talking about the motion of only a proton. We know in these systems, we're talking about proton coupled electrons, right? The proton and the electron are coupled. We're talking about electrochemical system. So even if water was moving through these structural water networks, which we don't have any evidence for in the tungsten oxides, I would still not call it a growth is transport mechanism because of that electron association that has to be present. So that's what we see in our work. Yeah, and the typical ways that you see in the literature of looking at for like a growth is transport mechanism is to take a pellet of the metal oxide and measure the activation energy from looking at the temperature dependence of the conductivity, right? And you can, and if your activation energy is low, you know, less than 0.4 EVs per atom or something like that, people say, well, this is a very small activation energy, therefore you must have growth is transport mechanism. But in these hydrous oxides, two issues. One is that there's a lot of water on the surface. So what you're probably measuring from those pellets is that surface, the protons transporting along the surface. And then the second thing is what I mentioned here, which is we're talking an electrochemical insertion of a proton that's coupled to an electron. And that's very different from growth is mechanism of protons and an acid electrolyte. Yeah, so maybe just a little bit for follow up on this. Do you need a little bit of motion or for water, even though it's not translational, right? So I think a proton coming in drum just kind of relay. I think it's the emotion that seems to be meant, but I haven't revealed the growth of the mechanism for a long time. Right, but there's a tiny rotation or not, yeah, yeah. Yeah, there's a slight kind of rotation of water molecules that takes place. And that could be happening within these materials. We would not be able to probe that through the quasi-elastic neutron scattering. That length scale is just very tiny. So what we know for sure is there's no translational motion. The water molecules themselves are not translating through that. It looks like the hydrogen bonding network within these crystalline tungsten oxides is basically keeping the water in relatively fixed positions. Yeah, this is fascinating. This reminds me for about a decade, my lab works on prussian blue type of open framework material. There's also crystalline water in there. So now to be sodium and potassium, all this iron going in, it's just so fast. So it allows you to do very, very fast charging. Right, right, right. Yeah, I think it is a fascinating topic and I'm sure you've seen the work from Jule, G at Oregon State, his work with prussian blues. Yeah, like from where we are right now with understanding these materials, I see we have evidence that the structural water network is playing more of a pilloring role than a proton transport network role. And that seems to be the key for the rate capability. Yeah, that's great. The second question is related to your second topic. When you have iron insertion into this layer materials, so I was thinking about what could be the reason I changed the HER activity. There could be multiple factors right there and see what's your thought. Once proton coming in first of all, the time of station state is changing slightly depending on how much proton you have. People of station state, the binding energy that will influence with the proton absorption, that's probably what you refer to in one of the paper. Yep, James MacCone's group published that work around the same time that we published our results. So it's very nice to see. Yeah, yeah. So it is an analogous material system or tungsten oxide, it's actually a moly sulfide. Moly sulfide in about a decade long. So the study is showing, if you took a lithium, for example, you change the layer spacing, you change the moly oxidation state as well. You probably change the edge size, the defect states as well, so it's very complex. That actually made the HER become so much more active after you changed that. And the other side on the OER side, something like lithium cobalt oxide, all these layer materials, you do lithium in and out. Actually my lab looked into that a while back. You'll change your OER activity as well. This is actually coupled together with certain oxidation state change, electronic structure change. So it's the, this binding energy intermediate state, it will be the main mechanism of thinking, whether there's also other things going on, it will be good to see your brain a little bit, yeah. Right, I mean, I think what's interesting in general about this research is that we have to think about it both from a very molecular level understanding, like when we talk about what's the oxidation state of the metal, but we're also talking about extended solids. So in a tungsten oxide, for example, when it's inserting protons, the electrons become delocalized, right? We're talking about a metallic conductor at that point. So it's that interplay between thinking about the molecular, like active site perspective, and then the extended solid perspective, what's important, what's the actual descriptor? I think it's very interesting in this research. I would say for what we've shown so far with our work, it's really just the first kind of definitive example that if that insertion doesn't take place, then for sure you're not gonna have a good catalyst because maybe until you can actually trigger that off, you might say, well, it might have happened anyway. You might have still had the HER take place anyway or the OER take place anyway, even without that, whatever's happening to the active material, whatever's taking place on the surface would have still happened, but now we were able to trigger that process off and we see no, it will not happen in that same manner. So that's where we are with that work. We have ongoing studies to understand the full breadth of structural transitions that are taking place in the tungsten oxide systems. There's a number of structural transitions that take place when tungsten oxide or the hydrous tungsten oxides insert protons. We're really interested in what's happening exactly at that point where the HER occurs and I don't have definitive answers for you yet on the topic, at least from the tungsten oxide perspective, but yeah, there's a lot of very interesting work showing how dynamic these materials are and how the material that you place into the electrolyte is not the activated material that you have at the point of the catalytic reaction. Yeah, okay. So Veronica, third question is not coming back to the energy storage in a proton base. So I look at the proton system, you know, once you store proton, if I compare these with lithium ion battery, lithium ion battery is a kind of rocking chair mechanism. So the electrolyte composition, the lithium concentration is fixed because the lithium coming in and then going out, so it's balanced. I myself also work on the ecosystem for a while. So oftentimes when you insert proton somewhere, it's battered, it will have a proton coming out from the opposite electrode, so you balance that. So we often face a situation of pH is changing if it's not balanced. Just pick your thought a little bit. So, and this may be for Deborah as well. I mean, this has a brainstorming like for the whole research field. How do we really design the whole full electrochemical cell that could benefit for having a fixed pH. So what will be a good pair? But that doesn't mean if pH is not balanced, it will not work less if it's absolutely this proton concentration is changing. That's why they use very high, very strong sulfuric acid to make sure the change is minimum. So it's just generally what's your thought? I mean, this question has been in my mind for a long time. When we pick a system, can we really find a great system for particularly now we talk about proton couple, like some chance for the storage. I mean, this pH change will probably start to show up. So we work in the tungsten oxides case, we're talking about 0.5 molar even one molar sulfuric acid, but from the more cell level perspective, I would love to hear Deborah's perspective because we haven't done much work in that arena. To me, we also had to think about the activity of free water in the aqueous world. And I bet it even bites us a bit in the non-aqueous world because there is always water around. I mean, the mild electrolyte case of the zinc ion is showing the problem because of the electron insertion at the cathode also is accompanied by a proton rather than the divalent zinc. You've got a huge shift in pH at that interface. And just as Yishul pointed out in lead acid, you've got high sulfuric in the alkaline systems. It's very high alkaline, but that activity of water still matters. If you bring in something that helps sop up water, like we've looked at mixed potassium, lithium high alkaline concentrations, and the lithium needs so many waters of hydration to screen its charge that you've lowered the activity of free water. You really can't corrode unless you've got a reasonably high activity of free water. So I think there are things we need to, we forget the water part of some of this. And if we really want the mild electrolyte systems to work, then some of what Veronica is teaching us with respect to buffers also needs to be brought back in. We're gonna be talking about how do you control the pH of that interface without in essence killing rate. I mean, to me, the modern energy storage system, if it's not giving you rate, its application space is very small, which is my prime concern with the solid-state electrolytes. If the best it can do is one to maybe three milliamps per square, anybody who says they're looking at it for electric vehicles really should get out of business. Highly appreciate that, Deborah. We're pleased to chime in anytime as well. This is a good delivery to our panel discussion. So yeah, Deborah, this is fantastic. I think the water one activities are very important. So you mentioned this lithium coordination with water molecule, this is a great directions to go. And also perhaps I will just add in, maybe we want to think about the kind of dilation iron that tied up the molecules, water molecules even more because the charge is high. And also perhaps the direction of water in salt that also tied up the activity of the water molecules. Yeah, I would, I just want to add one thing about the role of buffers and aqueous electrolytes, Deborah. I appreciate that you say I'm teaching you that because I'm learning a lot about this myself from the PSET field, from the proton coupled electron transfer field. The idea that you don't just need to look for a free proton in an aqueous electrolyte, but you can find proton donors from other kinds of molecules, even in non-aqueous systems, I think can be very powerful for any sorts of energy or storage or conversion reactions that we're thinking of involving protons. I always kind of came in with this idea, we're talking about hard acids, strong acids, strong bases, but it doesn't necessarily have to be the case. You can utilize other sources of protons. It does add an additional kinetic step of a proton transfer that has to occur at the interface, but that process can be faster than some of the, for example, structural transitions that might be taking place in your material subsequent to the proton donation. Yeah, where would you like to come in here for discussion? Yeah, absolutely. And Veronica, let me add my thanks to a great talk. One of the things that we constantly think about is the relative rates of surface reactions at the electrolyte interface and also bulk transport, right? And this, of course, also, as you have known in many times in your work, determines whether the materials more battery-like, more pseudo-capacitive. So in systems in which you have a lot of water insertion, like tungsten trioxide, do you have a general sense what its bulk transport properties are like? Oh, we don't, in the tungsten oxide hydrates and the anhydrous tungsten oxide, there's no water co-insertion taking place. There's no solvent co-insertion taking place whatsoever. From our investigations, the rate-limiting steps appear to be the solid-state structural transitions and not mass transport effects. That's the primary differences that we see between their responses, but we do not have a bulk diffusivity measurement for protons or lithium ions even in these systems yet. That's something that we are working on, however. Right, so, Veronica, I think what I'm trying to get at is I think a lot of these materials are somewhat nanostructure, right? So the diffusion length is short, but as you say, it doesn't seem to be limiting. So is then their potential to make them more macroscale, which could help in other respects. And I'm also trying to get a better understanding of at what scale does diffusion become a problem? Is it really so facile, or is it more the reflection that the nanostructure has prevented the material to be mass transport limited in the bulk? Yeah, that's a good question. We, in the case of the hydrates, we're not really able to play around very much with the particle size. The typical way that you would increase particle size would be through sintering or grain growth. And when we do that, the structural water will be removed. Based on estimates from the literature, and I honestly don't have that number off the top of my head for protons or lithium ions in the, in W03, for example, as you say, the diffusion length scale is much greater than the particle size. So we don't see that mass transfer limitation. I would say based on your work, as well as some other work from groups studying single particle intercalation or poor selected intercalation, it doesn't appear as a South State diffusion within a single particle is ever really a problem for lithium ions or protons. And so that's why for us, it kind of makes sense that what is the limiting factor is the structural rearrangement that has to take place. That requires more energy, that requires more time than a hopping mechanism for a small cation and a 200 nanometer particle or even smaller length scale film. Yeah, though, yeah, we definitely think diffusion is faster than most people think in the solid. It's just, it's hard to tell whether it's a reaction limited process versus diffusion. Maybe I can also shift gears a little bit since we only have 10 minutes left. Eve, Veronica and Deborah, you know, you have served roles in journal editing and so forth and myself too. And one thing I have noticed, which is very interesting is there always seem to be great performance on aqueous batteries, whether a zinc or something else. So I thought maybe you can talk a little bit about sort of tricks you can do to improve the apparent cycle life of batteries or rate capabilities because the literature reports are really all over the place. So I'm really curious for your thoughts on sort of what are some of the ways to really reveal the true properties of the material rather than be controlled by, you know, the low mass loading and so forth. I thought this might be an interesting discussion for the broader community to how to read, you know, get another 10,000, 100,000 cycle life battery. I'll have an answer. I mean, I'd love to hear Deborah's and you use response first though, they can go first. We're wasting everybody's time. And again, the research budget of the United States because we haven't imposed proper metrics either by the PI being unaware or wanting their work to look better than it is. And the journal editors are not in essence saying, I'm sorry, you're giving us something that is barely moving the needle. And that's a huge problem in almost any energy storage area. We're working on a diatribe for zinc air because with all of the various electric catalysts out there for rechargeable zinc air because no one is really pushing the aerial current per square, you have no way to say, okay, let's down select this type of electric catalyst and play with composition and structure and other things. So we're actually impeding our ability to move the needle with respect to the performance of these real systems. Same thing is true as you pointed out with respect to mass loading, many things look great on a milligram per square. But if you're in the real world, that needs to be at least an order of magnitude higher. And we're actually coming up with this, trying to improve the number of electrons out of nickel. If you're working in a powder composite system, there are so many other contributions, even in the aqueous system, to that sort of early current you see, your capacity, you can't really say, is this due to that transition metal center or not? Whereas when we're in the architecture, we start to lose all of that sort of fate. You can have rock stable response, even moving beyond a milligram per square. So part of our problem is the electrode structure is not, it's so convolved, it's hard for us to really find the right knob to turn, the right button to push. And that's what we're trying to get around, because we really need to get more than one electron out of our transition metals on the cathode side, because then there really is no reason to play with lithium at all in the standard lithium metal or lithium ion world. So yeah, I would love to see some rigorous metrics in that you'd have to have this loading or you have to have this aerial energy density or get out of here if you're holding doing, and you're not really counting all your atoms for instance. So at that point, then it's gonna be a lot cleaner on how we really improve our understanding of the materials of the electrode structure, and that will seamlessly move into better performing batteries and capacitors and electric catalysts. So, did I try both of them? That's why I resonate with you about what you're calling particularly on the power. So Will, let me just share some of my thoughts. So serving as editor for a while now, the performance done by academia, I call it general academia means it's really in the research level, not in the industry delivered at the product level. So one has to be certainly very cautious about these performance reporting, particularly that will point out the power density, particularly power density when you measure by C-ray, instead of the real column, how many milliampere centimeters square, this mass loading issue start to come up. So every time people talk about power, if I read the paper, just look at what's the mass loading, capacity loading first. But these other parameters, they're different. For example, if you look at the capacity, milliampere program or Faraday program, and the slow rate, this is more towards the intrinsic materials property. There's still value right there when you talk about performance or for capacity. But when people talk about energy density, now this comes back again, and you will measure while per kilogram in the battery field. And this highly related to your mass loading also, as well as I also see authors made a lot of mistakes. They will take the charging voltage as the energy density they could take, because charging, when you discharge, if what is hysteresis is very big, if discharge voltage is very small, your energy density is very low. This mistake right there in not just one paper, actually quite a large number of paper, particularly for the material system with the large hysteresis. And I can go on and on probably on the common of each parameters. Some parameters I would say having the value, research value for people to understand, but I agree with Deborah. There's probably some, I would say the best practice needed to recommend when people report their data, yeah, conduct the experiments. I agree, of course, with Deborah and you are saying, I'm relatively new in the role of associate editor at JMCA. I have kind of two answers. One is kind of a philosophy that I heard from Adam Heller when I was a postdoc at UT Austin, I went to talk to him a little bit about research directions and things like that. And he wrote to me something in an email that still kind of sticks to me. And I just looked up the email. So I'm gonna quote directly what he told me when I asked him about what research should I do when I'm a professor. And he said, my advice is that you contribute the best you can to uncovering new truths and keep away from the graveyards of the thousands of useless quasi-applied devices unless you are willing to persevere and carry particular device through its development and it's making into a society relevant product. And I think that kind of thinking, it was sobering for me, right? It was like, if you're just gonna make, like here I put these two things together and it lights an LED, that's not that, that's that graveyard of quasi-useless applied devices. What's the fundamental truth that you're uncovering? Or if you're gonna be making these devices, let's hope that your goal is to continue improving upon them to the point that it actually becomes a society relevant product. That's kind of on the research philosophy side. And then as an associate editor, I think that having the community rights perspectives and say, here's what we think, here's taking this dialogue and translating it into a perspective that maybe provides useful metrics of ways of thinking about is very useful, especially as the field of research grows. And we've all seen how electrochemistry has really taken off over the past 20 years, right? I remember when Bruce Dunn told me, you're gonna study electrochemistry in 2007 and I was like, what the hell is he talking about? I was gonna do biomaterials and enzyme encapsulation in his group. He told me, no, you're doing electrochemistry. And now it's, you know, the topic that makes some perfect sense for sustainable energy. So I think because we have a huge global community, we really need these. I learn a lot as an editor what people are thinking from that. Not everybody may be in a particular meeting or in a particular symposium to hear some of this, especially after the pandemic. So having that is very useful and you are welcome to submit it to JMCA anytime. Thank you Veronica. What a great note to end on. I just wanna also just maybe share my own thought on this. I think electrochemistry is a low-cost scientific field to get into. You don't need much. You don't need big vacuum chambers and you can do good electrochemistry. But as a result of that, I think less care gets into it because it's so easily initiated. So I completely agree with everything said here that the community as a whole needs to care more about benchmarking in order to have the result collectively push the field for Deborah as you pointed out. So I think this is a great message for everyone listening to your talk today. It is a really great pleasure to host you both Deborah, Veronica and E and I I wish everyone happy holidays. This will be our last seminar for the year and we'll resume middle of January. And as a reminder, all of our recordings will be posted at the end of the quarter. So these recordings from this quarter will be posted in January. So please keep up with all the content and all the great talks that we're getting from speakers participating in our symposium. And with that, happy holidays. See you all next year. Thank you, Deborah. Thank you, Veronica. Thank you, E. Happy holidays. Thank you so much. Thank you, Veronica. Happy holidays.