Good morning California and good afternoon and good evening other parts of the world. I would like to start by inviting Professor Shirley Mung and Professor Martin Winter onto the stage to kick off the seventh event of Storage X and Posem. In the past few months you have been seen Storage X and Posem has been having amazing speakers to talk about energy storage and this event is there's no difference. We now have another two outstanding battery scientists to come here to share with us about their work. The two speakers are Professor Shirley Mung is a professor at the University of California, San Diego. All of you know Shirley. Shirley has been one of the leading scientists in many aspects of the batteries. She has been very active in developing new tools, new understanding to the very important battery problem. She is the winner of many awards. I would like to just point out a few. She's the fellow of Electrochemical Society and she's also in the battery division playing a very important role right there and as a very particular honor for me I have been working with Shirley together in the Berkeley 500 Consortium and recently I want to say congratulations to Shirley. She's a key team member. I saw the news winning the National Science Foundation, a new research center right there. There's quite a number of dollars associated with that to support the research and uses in the agro. Our second speaker, Martin Winter, he's a professor at the University of Munster or Martin of course has been a long time leader in the battery fields. If you look into his CV, I would say he has won probably all the awards possible in Electrochemical Society and also in the International Society of Electrochemistry. He's truly a leader not only scientifically but also he's leading the effort in Germany and European unions and developing the batteries for EV and he has many titles right there I will not repeat. It is my great honor today to have both of you to come to the stage to share with us about your very exciting research. Let's start from Shirley please Shirley. Thank you Yi, thank you very much for the kind introduction. I wanted to also take this opportunity to thank Stanford University for providing this wonderful platform for us to exchange ideas during this extraordinary time. So let me get started on the major content of my talk. So I believe in the audience for this audience most of the people are very familiar with the lithium-ion battery technology. We are very lucky that last year Professor Weidingham, Professor Goodenough and Dr. Yoshino won the 2019 Nobel Prize for chemistry. So the intercalation chemistry has worked extremely well in the last few decades. So I want to repeat the fundamentals of the lithium-ion batteries but just want to point out that to increase energy density has been the forever pursuit of our field and there's three major things. I think the voltage is mostly governed by thermodynamics. We know the Nernst equation where the chemical potential of the lithium in the castle than the anode materials, the differences gave the voltage and I want to remind everyone in the Nernst equation the number of electrons that transferred per ion is actually on the denominator and this is one of the reasons that many of the multivalent cations tends to have low voltage but alkaline metals like lithium, sodium, potassium has the potential of having relatively high voltage. So capacity is mostly governed by materials. When we have the intercalation compounds you can see the capacity is limited but later you're going to hear about using metallic lithium as the anode where we go away from intercalation chemistry. This is the time where the capacity can see a significant increase and I want to point out that the electrolyte research has become my latest passion because we do see quite a lot of materials that can enable high voltage operation based on thermodynamics. However, the limit on the electrolyte has delayed our progress in terms of enabling higher voltage battery materials. So the major drivers I would say you know one of the major drivers is really this holy grail quotation a lot of people use that to enable metallic lithium. In 1976 when Professor Stan Weedingham published the science paper the metallic lithium was already used in that work and the generation zero of our rechargeable battery actually do use the lithium metal. So 40, 50 years later now that we are looking at this technology again the major differences well displayed by this graph where we are going to use very very limited the lithium reservoir. Sometimes you have seen in the field people use the so-called anode free configuration because the cathode NMC already have a lot of lithium content. However, the lithium metal research still is extremely important if we want to move towards lithium free cathode such as sulfur cathode. So I think the battery 5 consortium has a very clear roadmap in terms of that our mission to enable lithium metal batteries is very critical for the future of the battery field. And at the same time again here that we have to enable higher voltage, wider voltage operation and longer cycle without the sacrifice safety and cost. So the electrolyte again become extremely important enabler for the future battery technology. So let's take a close look at the electrolyte. So of course I highly recommend you read the Dr. Kang Xu's chemical review papers. This is where I learned most of the important knowledge on the lithium ion organic electrolytes. So I want to point out that the exploration of the electrolyte also you know many pioneers have worked in this field. The components in the battery, the salt, the solvent and the lithium PF6 is absolutely not the best choice. However, it does have a very well balanced properties compared to the other types of salts. Of course, I didn't put the lithium FSI and the lithium TFSI here. As many people know, these are the salts that have been catching a lot of attentions lately. The progress of the electrolyte discovery, you can see that it started all the way back to the 1960s where I think the PC propylene carbonate was explored. And ethylene carbonate does not come into play until the late 80s. This is where the first rechargeable battery based on the graphite anode is used. However, we have been you know having different varieties of these EC ethylene carbonate based electrolytes for quite some time. And we are actually facing challenges to use the same electrolyte to enable lithium metal and especially to enable low temperature performances. So I was very fortunate that my students and the postdocs and now the CEO of the startup company South 8, Dr. Cyrus Rosmergy who came to me with a very very interesting idea. So I think I assume everybody knows but I actually have to say when he discussed with me why gas molecules can be used as electrolyte. He made a very strong case where he showed the picture of the ethylene carbonate at room temperature is actually a solid compound. So the once it mixed with the linear carbonate you know the liquid is the our version of commercial electrolyte. So when we think about electrolytes you know the reduction resistance so you don't want electrolytes to be easily reduced and you don't want them to be easily oxidized. And EC actually lies right there if you can follow my cursor. And when we did the computation exploration of the different solvent property, Cyrus showed me nicely that these gas molecules actually has extremely high electron affinity and at the same time very high ionization potential. So if you look at the ranking just based on the dielectric constant and the viscosity of course some of these gas molecules doesn't look very attractive. However if you look at the ratio of the viscosity dielectric over viscosity these small molecules can assure very very low viscosity even at extremely low temperature. The only differences between these gas molecules and those organic compounds like ethylene carbonate, diethylene carbonate is that you need to actually confine them in the container where the pressure builds up. Once the pressure builds up the self-equilibrium pressure will liquefy those gas. And that's the major idea behind liquefied gas electrolyte. And we are also very fortunate that all those new sorts, lithium TFSI, lithium FSI does dissolve in those electrolyte. So the first generation of these liquefied electrolyte displayed some very astonishingly nice physical and chemical properties for us to use as a new generation of electrolytes. So when we reported a couple years ago we enabled the lithium metal cycling. We demonstrated the minus 60 C degrees Celsius operation. I think I just want to say that it was extremely exciting for us. However we do realize there's still a lot of unresolved challenges in the liquefied gas electrolyte. For instance the operation temperature is limited to 40 C because of the super critical phase transition for the gaseous phases they actually the salt will precipitate and the conductivity will drop. And perhaps one of the most bothering factor for me is that the solubility of the salt seems to only limited to 0.1 or 0.2 molar and we can enable the lithium cycling efficiency around 97.5%. And at the same time if we look at how lithium metal behaved in these liquefied gas electrolyte we do see some encouraging aspects. For instance after very long cycling we look at the current collector the lithium metal doesn't display the kind of dendritic features like we always see in the carbonate based electrolyte even though the efficiency is low. In order to enable very long cycling lithium metal anode I think everybody understand that the efficiency has to rise possibly to three nines. And this is an extremely difficult task but I want to share with you today how we can actually increase the lithium solubility and widen the operating voltage as well as the temperature using some of the latest electrolyte design concept and the new computation and characterization tools that enable us to understand better those components in the electrolyte therefore we can actually progress towards three nines efficiencies. So we actually again you know the lithium iron field provided us some very exciting concept. I think everyone has seen a couple weeks ago the talk on the electrolytes where high concentration electrolytes or localized high concentration electrolyte introduced. What's the difference between those electrolytes is that of course in the first generation of the high concentration electrolyte the increase of these lithium salts will introduce to this very highly viscous electrolyte but most of the lithium they are bonded with the solvent molecules so there's a very few free solvents flowing around but one of the challenges to have this high concentration electrolyte is that the viscosity is so high that if we want to have this electrolyte penetrate to the porous castle we face some challenges. So later many scientists you know Professor Yamada's group Pacific Northwestern National Lab, Dr. Kang Ju, they have introduced the diluent that still can enable locally very highly concentrated electrolytes with the lithium salts and then the diluent can actually help to reduce the viscosity. So we don't face this problem in terms of high concentration but in the liquefied gas electrolyte very interestingly we can borrow the concept and think about what kind of co-solvent we can actually utilize to enable the higher concentration of salt. So if one of the examples we showed is that we can use the THF which is miscible with the fluoromethine liquefied fluoromethine and the percentage is actually very low and because of that we can increase the salt solubility by 10 times. At the same time improve the conductivity so we collaborate with Dr. Oleg Borden also in front of the research lab he very nicely used the molecular dynamics to demonstrate that because of this particular configuration we have a very similar situation as the highly concentrated electrolyte in the liquid phase where most of the TFSI will be bonded and you have actually very good ionic conductivity at the same time very little free solvents flowing around and the transference number for this liquefied gas electrolyte has the lithium transference number close to 0.8 which is extremely high among the liquefied among the liquid form of electrolyte. So I think some people know that I'm a big fan like Professor Itui that a big fan using cryogenic techniques to probe lithium metal probe SEI I think the work has demonstrated that cryogenic conditions is necessary for us to characterize lithium metal so what happened in this liquefied gas electrolyte with cycled lithium so I have three short movie to show you the first one is in the regular carbonate electrolyte and the second one will be in the ether-based electrolyte where people are awesome okay so you can see the middle one is ether the third one is actually in our liquefied gas electrolytes this particular technique with the FEI thermo-oficial scientific doer being with the cryo stage can very nicely show us that the density of the lithium metal that has been departed if you don't use a cryogenic technique the data can be a little bit misleading because there's a lot of artifacts introduced by the galleon ions lithium galleon does alloy at room temperature so this we can help us to quantify I think the quantification is the nice part of these techniques where you can actually quantify the amount of void surfaces so assuming of course there's some hypothesis in this analysis where we are assuming the less dense part occupied by the SEI or void you can see the dramatic reduction in terms of the porousities the ether-based electrolyte already way better than the carbonate base electrolyte ether-based electrolyte typically produce those granular lithium metal crystals the liquefied gas electrolyte actually shows some very very encouraging morphology for the lithium metal where you can see we are seeing less than one percent of the porousity in the liquefied gas electrolyte so another very exciting things that happened with this co-solvent idea is that we are able to now enable very high critical current density without any special three-dimensional 3d current collector this is on the flat stainless steel substrate you can actually see a very good high you know the over potential almost linearly scale with the current density increase so I also want to take this opportunity to point out that getting to three nine is already difficult but having a potential stat that has 0.1 percent aero bus is not a good design so I think that moving forward our field will need some help in the metrology development we have this plus minus 0.3 percent number variations of course you know temperature control is important but I think as we progress towards very high efficiency lithium cycling we will also have to pay attention to the hardware and the last but not least you know we are very pleased to see the low temperature operation of the lithium metal batteries this is the over potential and this is the current density and we show the different colors of the temperature so in our lab we can do minus 60c very comfortably and you can observe that of course the over potential increased very dramatically but in principle it is possible to have reasonable current critical current density at even temperature as low as minus 60c the second important progress for the liquefied gas electrolyte is since you can use thf we can also try other solvents but our search is not just by trial and error in fact in this particular case my student dan davis has been working with dr bording to look for other solvents and what they found is acetone nitrile could be a very good co-solvent if we would like to widen the operating temperature of the liquefied gas electrolyte so in the most latest reports to the open field we shown that with this new generation of the liquefied gas electrolyte the temperature operation temperature can be widened to much higher temperature above 70 degrees Celsius and still maintain an extremely good conductivity that you know this red curve here shows that a very good conductivity throughout a wide temperature range from my perspective when I actually look at you know my student yang yang took the uh minus 60 degrees Celsius departed the lithium to the cryo fib what we see is a happy surprise so here he was departing 15 micrometer lithium and we see the morphology of this lithium is extremely dense I didn't show the room temperature when the room temperature one looks even more beautiful so um with this progress I want to point out that uh uh you know these new class of electrolyte exhibit extremely exciting opportunity for us to look at some of the new uh electrolyte chemistry away from intercalation particularly for the alkyne metal now I have shown you the low temperature what about the high temperature since my talk is that saying that we have to go to the high temperature so the exciting field I think without saying people you know know that the solid electrolyte is one of the strong contender for high temperature operation so of course these cells made in my lab they are still relatively low energy density I think we made it in 2019 you know the the the progress of the solid electrolyte you know we started about eight years ago and we know at that time already our colleagues in Japan have already made a lot of progress in the past you know we are playing catch up and the enabling major factor is that we moved away from palletized cells go to podge type of cells where we can make a thin electrolyte which I will mention later how engineering wise how that can be achieved and there's a lot of chemistry involved as well and we also reported the the importance of pressure control to enable lithium metal cycling and right now we are in the stage to lower the electrolyte amount in the thick electrode loading and the progress you know a couple months ago reported by Samsung that showing that a very promising future for the solid state batteries and I do want to say that you know my perspective it that the solid state provides such a wonderful platform for us to think about what kind of new electrochemistry new characterization science we can do and that's truly exciting for us so again you know for electrolytes I show this pictures just keep reminding people the homo lumo picture of the licking iron liquid cell in the solid space polymer oxides and sulfides all have been explored and one of the reasons the oxides was so popular is because it's stability right so if you look where the metallic lithium silicon graphite and all the castles where their potential you know the voltage windows are and then you think about the electrolyte where the sei sei are located it's kind of interesting the sulfide electrolyte can ever work because obviously it has neither reductive stability nor oxidative stability and this has been demonstrated very well by both computational and experimental group but this is where I think interfacial science and interfacial engineering really shine as almost like a magic where they can enable stable cyclings because we truly understand that the sulfide stability is very limited so instead of fighting it we could think about how we can actually utilize those unique properties of the sulfides so with that I think you know the topic is very broad so today I can only mention a couple very brief examples but I want to emphasize that my take on the interfacial science in solid state batteries is it is indeed way more complicated than the liquid electrolytes so one of the major reasons that we did this review in chemical reviews is that we want to really point out that in the solid state electrolyte if we want any reasonably cost electrolytes that you know they are integrated with the cathode I think having void is inevitable also you know the cathode is still we still stay with the intercalation compound so those cathodes do have volume changes right so once the void gets generated if there's a minor volume change in the solid state and we have more numbers of interface and if we have those interface in the solid state batteries same with the liquid type you really have to think about both chemical stability because the cell is going to sit there next to the sulfide electrolyte as well as electric capability because you're going to sweep the voltage so the reactivity of the cathode is going to change because you extracted the lithium so those complexity make our research on the solid state battery extremely challenging and interesting so you know coding is one of the best strategies for us to tackle the cathode stability and I will give a short examples and I want to emphasize here that my colleague Professor Shui Bing-On has been working with us for many years and we have many candidates for the coding materials and I think lithium niobate is not the only one that can work so first let me talk about the end of the side of the interfacial story so on the negative electrode side for a very long time we have trouble enabling lithium metal cycling I think most of people know in the early days of solid state we do very strong pressing I mean this kind of pressure you know people keep telling me is impractical not practical for real cells but we do need to when we fabricate these because they are all solid state so you need a very high pressure to establish the contact because otherwise the cell impedance is just skyrocketing so you need a very high during the fabrication high pressure but when we cycle the battery I think you know the students Han who did this work very nicely demonstrated that you need to release the stress like let it go when you are cycling it and five megapascal is the critical pressure level you can do lower I think we realize you know there's a lot of people in the field working on the mechanical property of the lithium metal so below five megapascal the cells can cycle quite well even though the critical current density is still relatively low I think our cells now reach almost a thousand cycles and I think these are the things that we feel the solid state batteries provided a platform for us to learn some new science because here obviously the mechanical properties of the materials come to a critical play and using pressure as a control knob you know we have not been doing that enough okay so for the castle the example very quickly I want to point out there's a chemical stability because when you make nca or nmc next to the sulfide you put the oxides next to a sulfide there will be reactions right so that's what we call the chemical stability what's the electrochemical stability because when you sweep the voltage you take lithium out the reactivity of those nmc and nca will change so if you want to have a stable coating the coating has to be stable when the electrochemical status of the castle the change so based on both experiment and the computation we did with professor stripping on's group we can demonstrate very nicely that the coatings that they can actually significantly improve you know if you quote the nca with the niobates you can actually stabilize the castle and I want to stress here you know again lithium niobates is not the only castle that can cycle so the coatings I think you know I'm running short of time I just want to show that if it's quoted very effectively very thin coating is needed five to ten nanometer and you can have very prolonged cycling for the castle the materials so um that brings me to the message you know with these two short examples I think in the lithium ion cells I was very fortunate in the last 10 years working together with professor stan weedingham claire gray many pioneers in the field we build this very nice platform from atomic level to electrode level where the interface and the uh structure chemistry everything is properly characterized and that's where enable us you know go from the two nines to three nines in the nmc or nca type of castle the materials and liquid electrolyte now with the solid state I think the interface really presents some big challenges and we have to think about new tools we have to actually push the boundaries the buried interface is the very very difficult thing to enable uh true operando characterization because most of these solid state cells they uh contains all solid you cannot really evaporate the electrolytes so the electrolyte is part of the characterization but those electrolyte they are extremely electronically insulating they are ironically conductive but they are extremely electronically uh insulating so if we want we want to use the x-ray and the electron based the characterization techniques we are facing some challenge of course in the field uh you know both the um I think professor you can yannick has done very nice work on the in-situ xps and I think you are going to see more nmr based and CT based techniques uh to actually discover what is the dynamic nature in this uh solid solid interface and the challenge is really that you know we have to keep pushing the boundaries so that we can have a better understanding of the interface so I'm almost coming to the end of my presentation I think this one is pretty interesting now with the sulfide solid electrolyte very nice solvent has been found you need to use you know uh non-polar solvent uh where you can actually make these very nice dispersed solutions where the solid electrolyte can be a potential drop-in solution in the current processing line and my colleague Professor Zhen Cheng have helped me a lot in finding out what is the best solvent to use so to conclude the solid state apart I think that the solid electrolyte you know next a couple years we're going to see very exciting progress both academically and also in the industry side I think I hope that showed you that you know the characterization is a very important part now if we want to move to the three nine efficiencies we need a very sensitive quantifiable tools to study those electrolyte and the scalability now becoming coming to question and I do think that you know this part we will work very closely with our industry partner last but not least I want to also take the opportunity to say both the liquefied gas electrolyte as well as the solid state electrolyte at least in my research group in our campus we highly highly paying attention to the recyclability anybody who does the new battery chemistry we must think sustainability take sustainability very very seriously because we will imagine a world that there will be terawatt of terawatt hour of batteries being built so with that thank you very much I think it's my great honor to work with my colleagues who are really extremely collaborative and all the industry partners that have enabled those research so the liquefied gas electrolyte was supported by RPE because it's such a crazy idea and you know we have very good partners with LG Chem and Shell I'm very grateful for the support and for lithium metal batteries we continue like E said with the battery 500 consortium continue to push the boundaries and for all the characterization tools the basic energy science provided the huge support to enable my group to do a lot of the microscopy work with that thank you very much okay surely great talk you know you presented to us two different types of exciting electrolyte what what's the opportunity and also challenges right there there are tons of questions very interesting one piling up for you I'm glad to see that so let's start from your liquefied gas electrolyte the first question is related to low temperature and high temperature when you change the temperature this plating morphology can change so how do you explain these morphology change of lithium plating at low at high temperature they are different actually in our liquefied gas electrolyte the difference we're showing is between the different electrolyte in fact in the liquefied gas electrolyte we always get very dense lithium there's no difference between low temperature okay but between different electrolytes I think this is the part you know I think you know that in many work we do now is look at the nucleation of lithium and the field is facing a lot of the difficulties because operandum nucleation for lithium metal is still not enabled right we always departed the lithium and then we put the microscope so I think in order to truly answer the question I mean there's a lot of hypothesis of course so in the liquefied gas electrolyte please remember we don't have long carbon chain so we only have small molecules therefore the sei component are fundamentally different from the carbonate and the ether based electrolyte uh so this could be one of the major contributing factors that the certain components for the sei is missing in the liquefied gas electrolyte and that caused homophology difference yeah so surely speaking of that the sei these your liquefied electrolyte have you looked at this carefully under quail em uh what's the difference between your sei and the liquefied electrolyte electrolyte and various carbonate or either did you see big difference uh yeah so uh one of the biggest uh difference is actually we don't have any alkyl lithium oh yeah okay our molecule is cf based so uh there is really no uh certain those elements are not present but I I think with quail em you know we cannot see those uh alkyl anyway so yeah I think that uh this gave us the very good question if this is the ultimate culprit because uh uh we don't know nobody has actually shown how exactly alkyl lithium look like yeah because you have this fluorinated methane do you see more lithium fluoride in the sei uh yeah so I think that uh there's definitely a lot more lithium fluoride compared to the uh traditional low concentration carbonate electrolytes uh do we do see most of our sei component they are consistent of the lithium oxide and the lithium fluoride uh I think the part that we still need to work more on it is because in our early version of electrolyte carbon dioxide is being used as an additive uh so to make the you know uh carbonate is becoming a it's definitely there lithium carbonate but we don't know it's the chemical reaction or it's actually electrochemical formed sei okay yeah so next question Shirley what's the rationale and when you choose this cold solvent um and what's the guiding principle right there for this liquefied electrolyte maybe I can be more in detail some of the thought in my mind is you have talked about thf right you have been talking about uh also eston nitride certainly thf eston nitride these even to me when I look at that I say well it's a this solvent along it's a cathode stability uh it's not very good but in the liquefied electrolyte condition it might be different can you make a comment about the principle and I know it's wide primary window windows right there give you yeah so for thf and eston nitride we decided to release to the public because of course cyrus in south aid has many more magic formulations but the thf and the eston nitride are good learning examples so if you think about the electro affinity which is the reduction resistance and the oxidative resistance so eston nitride is bad for reduction but good for oxidation resistance so eston nitride actually is not bad for the resistance for oxidation but it's very poor for the but I think when you actually just put a small amount think about the function of thf and eston nitride is going to bind the lithium salt so they're not playing as the major solvent so the solvent the major solvent goal is still played by the fm and and I think in a couple months we will release the data on the dfm as well and those solvents because of the in highly concentrated electrolyte if you remember some of the ether they can go high voltage because concentration so we're basically borrowing the similar concept where we have each of the solvent to play its own role so the eston nitride even though the reduction potential reduction resistance is not good but we found that if you only add a very small control amount its main job is to bind the salt not to participate in the electrochemical acting so I guess your your answer to this question also partially answer another question so saying you know we saw thf right the ths must be solvated partially with lithium ion and how to explain the columbic efficiency improvement I think you kind of also related to these questions so let me move on to the next question there's a person asking this I think it's kind of interesting it's because it's fluorinated methane is that a concern you know this can be the you know global warming gas right kind of you know greenhouse gas why there is that a concern in using yeah very question so if you people go back to our 2017 publication we have been very transparent up front we actually gave all greenhouse gas index numbers to the fluorinated gas species when we first published and yeah so compared to the chlorinated version we are better right because you know that the the fluorinated version is way better than the chlorinated version but we are still not innocent okay so that's actually one of the major drivers for me to figure out the recycling of the electrolyte 100 and I tell people it's looking good because it's gas species so yeah the refrigerator industry has figured it out and I'm sure we will figure it out and it also encourage us to really think about that we need to recycle it 100% okay so let's visa of you know five more minutes let's move on to the asking the question related to uh surely related to your solar electrolyte work there's one question asking um can you comment on optimizing the cell pressure between good interface contact and then you also need to consider short circuiting and solid state batteries what are the major factors that could contribute to this so you know good interface versus the shorting and the common on the pressure effect yeah right so right now I believe that one a couple mega pasca is the optimum pressure that we have you know we are happy to share with the field I do believe that one or two mega pasca is not practical so I participated in some workshop where the OEMs are there they told me you know what atmosphere is 100 kilo pasca surely you want a 10 times more than that you know it's really kind of a bottleneck and by the way there's a difference between uniaxial pressure we call it a stack pressure and also sense on reported that these warm isostatic pressure isostatic pressure is something you know very very costly to achieve so I think the answer is still I don't have an answer I would say the lithium metal for the solid state if we can't figure out the pressure knob we will still be relatively stuck in terms of the actual commercialization I think that you know you also did a lot of the host the method for lithium metal right one of the ways to think about how you can mitigate the pressure challenge is to think about how porous materials can change the pressure distribution I think that would be a potential direction to go but I don't have a clear answer if one mega mega pasca is a possibility and then during the processing I think that people can use temperature to replace the pressure need but during the cell operation right now I don't have a better method than going to one or two mega pasca yeah one more question Shirley um there's an audience asking you about um to sulfide base solid electrolyte has smaller potential windows stability do you think it is this strong condemned contenders compared to oxide solid electrolyte yeah so uh I think uh what I shown the in uh my talk the sulfide uh the oxidative ability is no if you just use lps with the oxide it barely works right so then chlorine doping changed right so I mean we think about the face space there right so this is the part I want to highly recommend the computational method it's really really very helpful for the screening of solid electrolyte so I think sulfide uh you know um the dopant goes into the sulfide electrolyte sulfides are so friendly to any foreign elements so when they come in it will take it and that will change its stability so when we think about the coating right you think about the coating is changed on the castle so turn your mind around think about how those coating you know can you actually go the solid electrolyte to change its chemical reactivity uh I think that oxide is definitely strong uh but uh at the same time uh I used to joke about you know I put a high school students making the sulfides ball milling very easy but if llco I have to put a phd students in order to obtain very very brilliant properties so I think that's the part where uh you know um sulfides for me uh is more preferred because I want a materials that can be easily synthesized and that can be easily scaled scaled to really large uh quantity without too much difficulties um I see uh between two of you or I want to ask one question surely you talk about ceramic electrolyte interface and so on I'm so glad Martin talked about polymer electrolyte solid polymer electrolyte I really like that as well I also work on that quite a bit so um then one question is for solid state battery polymer ceramic whether it's oxide sulfide you know looking at this whole grand scheme do you want to make comments you know which one you think might be more promising and why we all understand they have these advantages and disadvantages I want you to kind of in the final panel right here giving your your will you're taking a minute for each of you to to express your view maybe surely you want to go first give Martin a break sure yeah I think for lithium metal I know the polymer still remains the extremely promising approach uh the cell architecture might require polymer plus ceramics but which ceramics I think that that's a question I cannot answer yet but I do believe that the hybrid approach will be necessary if we want to engineer a cell that lasts a very very long as well as extremely safe I think I think we cannot ignore hybrid electrolytes it's an under explored opportunity of these new materials we also should think in layers if we come to let's say layered electrodes we can use multi-layer approaches where one electrolyte is in contact with the one electrode and the other electrolyte part is in the contact with the second electrode if we go away from layered approaches that we are for example using both composite electrodes on the anode and cathode sides just remember your talk from last week where you were looking at carbon nano materials hollow carbon nano materials the interface cannot only the let's say the homogeneous interface between lithium and electrolyte or between cathode and electrolyte cannot be only electrolyte it can be also an electrode very good and my next question is uh even bigger scale uh what thing you mentioned about european union's effort and german's effort how to organize the the batteries activity forming centers you know there's uh uh battery 2030 beyond right and us right here you know surely and i participate in battery founder consortium there's also battery hub there's cesar there's efrc and we look at japan we look at china all have their own and career their own program so anything two of you you know you can see you say yeah from the past about five years or in a decade long lessons learned um and what type of investment still needed you know and how do we organize the the baffled community community to gather to address the opportunity of eeve the challenges of eeve as well as grayscale and and and many others any thought to share with the audience i'm sure there's many industry folks right here and including the perspective how do we engage industry and there could be government officials right here listening to this talk right now anything you want to say to to to really share your thought about this well this one martin has to go first martin thank you sherry thank you so if you look at the german situation i have to say that batteries in germany there's a push pull let's say motivation the industry is pulling us to find the super battery because present lisium iron is let's say not enough especially when it comes to fast charging and driving range at the same time i'm not sure whether lisium metal and solid electron light especially lisium metal in foil form will help us with fast charging by the way the academic part in germany is i'd say we have a strong materials part we also have a lot of activity on non-lysium chemistries we also have and i think this is maybe a little bit different to the situation in other continents in other countries we have a very strong engineering in germany we have big production research departments so if you consider that for example minster is a big research group with about 220 230 people this is nothing compared to the engineering departments in aachen where you have 600 700 people working on various let's say propulsion systems including fuel cell and batteries and at the moment it's very difficult to not only to bring these people together i think it's not so difficult because there's so much big money and we should work together that is one of the preconditions of the ministry so of course we cooperate when the money is waving at us at the moment but do we speak the same language do we do the engineers expect something from us which we are able to deliver honestly in the 2008 2009 year a lot of the automotive engineers especially the electrochemical part especially the electrochemical part the surface chemistry they are not aware of and then there is the other thing if i can expand on this that chemists except for the physical chemists usually we like to work in a qualitative let's say edit we like to work in a in a qualitative manner so we are saying something is better than the reference for example but engineers want to have absolute numbers from us and this is something which we have to learn so if you say what is the challenge the challenge is that the interface between material science and all the engineering when you go to production research and also to the applications that these interface is not a sharp interface a smooth interface but that's an integrated interface where the people are working closely to each other we need the people on the engineering side who have interest and understanding in material science and the other way around so i will mention about the actually what the question is really nice thank you you know there's really four points i want to say the first thing is for all the scientists around the world i really think that international cooperation and the collaboration are so important so i hope that you know despite the COVID-19 the borders closed but our you know like the fact that you're doing this platform really encourages us to exchange ideas and you know our thoughts so i want to emphasize on this thing about the data reporting among the scientists yeah i think there will there are calls among many consultants that well we need to be transparent and be doing the best practice when we are reporting the data so nothing confidential it's just you know the fact that we need to disclose the information about the data i i hope more and more scientists will join this effort in terms of what's the best way of reporting data like one thing for sure please report the amount of electrolyte yeah um the second point i want to point out for our industry colleague is that for me i think martin brought up such a good point uh actually our product my product are my students they are the people who are going to go to industry to make a difference so uh the fact you know engineers and material scientists i think it's because many companies don't have material scientists or electrochemists as part of the team members and i i hope we're in coming years we're going to see the huge changes because uh for academic institutions yes ip and the publications and things are important but for me the human capital is the best asset we are going to provide for the industry and as the martin probably know in uh germany i don't know but in us so many engineering schools stopped teaching electrochemistry there's no dedicated the course right so i think hopefully many academic institutions with the support from government and industry we will be able to do more of that i mean think about the micro electronics industry you know how many people they've educated to actually being able to do those large-scale fab and we will have to equip the all the gigawatt factories with our top scientists the material scientists and electrochemists and engineers i think the third point is really towards the fundamental science i know stan is listening uh professor stan weeding hand was one of the pioneers in the battery research field and he always always emphasized how important it is to invest in fundamental science i mean interfacial science martin i mean the the interface picture we showed i mean the work was done 40 50 years ago and they are truths they are valuable so valuable but they when these people did those interfacial science they didn't know today there will be this mega dollar industry right so i think that basic research is extremely important and there will be more investment made in terms of fundamental science fundamental electrochemistry last but not least i think investment we talk about the big dollars actually in my opinion with the scale of the climate change problems our investment is way under way way under i mean consider the cancer problems and the health problems the uh you know people are facing and then you think about the scale of the climate change i mean i have seen the values of investment coming from private sectors particularly in the philanthropy and uh you know individual donors the the contributions for us to do stem field you know solutions to provide for climate change climate crisis is actually very very little so i think all of us have to do better in terms of i mean stanford is our leading example but in many other places i think we need to do more so thank you so much sherry this is very well said i highly appreciate both of you i can see the time is up i can see three of us and with more people we can go into a even more an exciting discussion we will find a time when we meet in person by having a drink maybe we can organize a zoom drink drink sometime so so with that i think today's uh a session is well concluded thank you to both of you for the fantastic talk so at the end uh justine can you bring up the holding slide um we will continue this exciting series of symposium next week we will have professor menthiram from ut austin as well as our own professor medium chair from stanford university to speak i look forward to seeing you next week at the same time thank you so much bye now thank you well done thank you


Supercells are rotating thunderstorms that can cause tornadoes and hail. The most widely accepted theory for storm spin-up produces a pair of counter-rotating supercells. But such pairs are rarely observed in the troposphere, and a theory is needed that produces a single supercell. A new mathematical model called vertical rotating draft has been developed that includes the gross features of a supercell in highly idealized form. This new model produces a single supercell. Principal ingredients of the model include rotation about a vertical axis, horizontal convergence in the middle troposphere caused by the compression of sinking air parcels, buoyancy, and the Coriolis force. When these ingredients are used in fluid dynamic equations, the horizontal pressure gradient is found to be zero, and air parcels move along inertial circles projected on a horizontal surface. This circular motion gives the model an inertial oscillation that appears to have been overlooked in previous supercell models. The inertial oscillation consists of a long quiescent phase when the draft diameter is large and rotates anti-cyclonically, and a short intense phase when the draft diameter is small and rotates cyclonically. One cycle of mathematically driven animation represents 13 hours of quiescent phase and 5 hours of intense phase. During the intense phase of the inertial oscillation, the rotating draft resembles a supercell. Rising parcels of air expand, causing the draft to expand and rotate anti-cyclonically. The updraft changes to a downdraft, contracts, and rotation becomes cyclonic. Downdraft is driven by evaporative cooling and updraft by condensational heating. Expanding flow interacts with the Coriolis force to produce anti-cyclonic rotation during the quiescent phase. Contracting flow interacts with the Coriolis force to produce cyclonic rotation during the intense phase. Additional physical ingredients of the model include translation of the rotating draft and vertical wind shear. The rotating draft moves at a constant height above the surface of the earth. The intense phase has a small buoyant draft, cyclonic rotation, marked by a track that turns to the right. This right turn is a salient feature of actual supercells. The quiescent phase has a large negatively buoyant draft with anti-cyclonic rotation. Latent heating changes the downdraft to an updraft in the middle of the intense phase. This flow reversal interacts with the vertical wind shear to cause the right turn. The latent energy required to support this inertial oscillation is greatest during the quiescent phase when the draft diameter is large. A supercell storm that produced one and one-half centimeter hail is documented by radar echoes spaced 30 minutes apart. These echoes become increasingly stronger as the supercell builds. The track turns to the right, hail is produced, and strong echoes are recorded. The echoes then weaken as the supercell dissipates. Application of the mathematical model starts in the middle of the quiescent phase. The first weak radar echoes are in theory created by a growing updraft in a predominantly downward airflow. After the turning point, the strong echoes and hail are created in theory by a predominantly upward airflow. Data from the documented supercell storm generally support the intense phase of the model. However, the quiescent phase of the model is not supported by the storm data, possibly because the quiescent phase requires too much latent energy. The new mathematical model called vertical rotating draft has an inertial oscillation with an intense phase that resembles a single supercell. This intense phase starts with a predominantly downward flow that causes the draft to contract and spin up, partly by action of the Coriolis force. More research remains to be done. The predominantly downward flow that theoretically occurs before the turning point in a supercell track needs to be detected and measured. This down flow, if confirmed by measurements, would strongly support this new theory for the spin up of supercell storms.