The Allplane Podcast #56: latest in battery tech for electric aviation, with Venkat Viswanathan
Why the aviation industry remains one of the hardest to electrify? Is Lithium-ion the best battery technology for the job? What are the most viable alternatives?
We will try to answer these questions with one of the leading experts in the field of battery science.
Venkat Viswanathan is an associate professor at Carnegie Mellon University, where he leads a research lab focusing on aviation and transportation applications of battery technology.
Venkat, who is also an advisor to several green energy firms, has recently co-authored two papers outlining the learnings of his research in this field and explaining why incremental improvement of Li-Ion batteries may not be enough for a more wide-ranging electrification of the aviation industry.
A new paradigm is needed in battery chemistry, one based on new materials and underpinned by novel research and production techniques, involving robotics and machine learning. Lithium-metal batteries and even more advanced combinations that use non-metallic elements may hold the key to the sort of energy density increases that will make the electrification of broader segments of the aviation industry feasible.
In addition to his work at the very edge of this technological frontier, Venkat is also an excellent communicator, able to explain complex scientific concepts in a straightforward and understandable way to broad non-scientific audiences.
It is because of all this that I invite you to check today’s episode out to get a grasp of the current state of battery science and its potential applications in the aviation industry!
Download this episode from:
Apple Podcasts / iTunes, Spotify, Google Podcasts or Stitcher
Things we talk about in this episode:
Venkat’s academic background and how he got interested in batteries for aviation
What is the current state of battery science & why this is a hot area of academia right now
Venkat’s two recent papers on battery technology for aviation
How battery technology used in electric cars may not be the best choice to electrify aviation
Different battery technologies: Li-Ion, Li-Metal, fluoride-based and batteries using non-metallic elements
How each of these battery technologies can fulfill different roles and serve different segments of the aviation industry
Characterization, robot-driven experimentation and machine learning: three technologies that are accelerating battery research dramatically
Resources:
Venkat at Carnegie Mellon University
Viswanathan Research Group at Carnegie Mellon University
The two articles we talk about in this episode:
“The challenges and opportunities of battery-powered flight” 22nd Jan 2022, on Nature
“The promise of energy-efficient battery-powered urban aircraft”, 9th Nov 2021, on Proceedings of the National Academy of Sciences of the United States of America
A Linkedin post with a summary of some of the findings
“La France”, the 1884 battery-powered airship
Tesla Model 3 (which uses Lithium-Ion batteries)
Two podcast episodes that we mention:
Podcast episode with Cuberg founder, Richard Wang (developing Li-Metal batteries)
Podcast episode with Pipistrel founder, Ivo Boscarol (manufacturing battery-powered aircraft)
Podcast Music: Five Armies by Kevin MacLeod
Link: https://incompetech.filmmusic.io/song/3762-five-armies
License: http://creativecommons.org/licenses/by/4.0/
Interview Transcript
(please note that, although we strive to make it as close as possible to the original recording, the transcript may not be 100% accurate)
Hello and welcome to the Allplane podcast
Here with the people that are redefining the future of commercial aviation
As usual, before I introduce today’s guest, let me remind you that you can find all the previous episodes of this podcast as well as many other aviation stories on the Allplane website: that’s allplane.tv - allplane.tv
Today we are going to touch upon a topic that is essential to any discussion about aircraft electrification: and that is the state of battery science and what can we realistically expect in this field in the coming years.
Our guest today is Venkat Viswanathan, one of the leading experts when it comes to batteries for the aviation industry.
Venkat is an associate professor at Carnegie Mellon University, in Pittsburgh, Pennsylvania, where he leads an interdisciplinary research group working on technologies with the potential to accelerate the transition to sustainable transportation and aviation.
Venkat holds a PhD from Stanford University and is also an advisor at several companies in this space, such as Quantumscape and Aionics, and previously had also been a technical advisor at Zunum Aerospace. He is also the co-founder of Chement, a startup that helps decarbonize industrial processes in the cement industry.
In the last couple of months, Venkat has co-authored a couple of papers that have been published in major journals, on Nature and on Proceedings of the National Academy of Sciences, in which he outlines the results of his work in the field of batteries for aircraft and the several possible courses of action.
But above all, Venkat is a great communicator and he has a great ability to break down complex scientific and battery chemistry concepts and explain them to a wider non-scientific audience.
So, without further ado, let’s welcome Venkat to the podcast to get the latest expert insights about batteries for aviation!
Hello Venkat, how are you?
Good. How are you doing?
Very well, where are you joining us from today?
I'm joining from Pittsburgh, Pennsylvania.
Very cool. So, first of all, let me introduce you to the audience. You are an associate professor at Carnegie Mellon University in Pittsburgh, Pennsylvania. And your area of specialty is battery science, you've been working very intensively in solving one of the major issues of aviation electrification, which is actually how can we get better batteries? How can we get batteries that provide more energy density so that we can electrify aviation further? So we're going to cover this ground now. But first of all, I will ask you to provide us a bit more of your professional and academic background. And then we can maybe move on to talk about a couple of very interesting papers that you published recently in two very prestigious journals about the science of batteries, and how the science of batteries can evolve and what we need to do in the near future to move forward in this direction?
Definitely. So I think the journey to electrification is actually one by one largely by accident. So, I was a graduate student at, at Stanford University. And I was seeing the transition to electrification of transportation. So that was when I started actually thinking about batteries largely by accident. And then I think, I have probably over 15 years in this field, and I was razor focused on trying to understand batteries for electric vehicles. And in this context, I think one, one pivotal point in my mental thinking, was a road trip I did in the summer of 2017, from Pittsburgh to Palo Alto, with my wife, and we drove in, in my 60 kilowatt hour electric vehicle. So it had about a 200-ish mile range. And of course, you know, I wouldn't say it was a cakewalk. But certainly it was not as difficult as I had originally imagined to be able to do a cross country trip in an electric vehicle. And on that trip, I realized that I'm inventing all these advanced batteries, and where are they going to go? Right? If not, for the next generation of electric vehicles, then two interesting things happened that summer. One was I got invited to attend a workshop that NASA organized, that brought together battery people and aviation people. That was the first time I met a number of folks that subsequently have played a great role in my understanding of aviation. One in particular had just then co-authored the Uber Elevate white paper, setting the stage for urban air mobility, and also folks that had thought about aviation electrification for larger aircraft. So on the road trip back, I spoke on the phone with Ashish Kumar, then co-founder and CEO of Zunum Aero, and that summer was the pivotal moment in my career, where it was clear that I had to transition to aviation, as that was a frontier where I could make better batteries, for which we will have sort of an infinite need, because whatever specific energy battery I could invent, there was a market to address. And so I think that's sort of the large context. And then a number of key things happened subsequently, once I said, I'm going to work on this, I was then signed on as a consultant at Pratt and Whitney, and I reported to Alan Epstein, who then became a co-author of one of those papers that we're going to talk about today. And it was a great period where over a period of about 12 months, I taught him all about advanced batteries. And he taught me all about aviation. So it was a good deal for both of us. And then in the summer of 2018, the Airbus Vahana team came to us and asked us to think about batteries. And that really, I think, started the journey for us in the eVTOL space. And then two people that were our project managers, Jeff Bower, who then went on to be chief engineer at Archer, and Evan Frank, who leads propulsion at Kitty Hawk. And now, and you know, with that, you know, we got our hands dirty in the aviation space. And so I think that culminated our understanding. And I think that led to these two papers in the last three months or so, which I think has really put both the battery industry and the aviation industry on alert in terms of what are the capabilities that might be possible. I think that the key goal of this work, to understand where we are today, but also to project where we might be from the lens of someone that really understands the electrochemistry of what might be possible. I think, in aviation, common trade studies will be able to project what happens in the future. And those typically run that sort of single digit percent, a couple percent, 3% per year. But the advantage in batteries is, we're just starting, I think we're just starting in this era of battery powered mobility, battery powered propulsion. So there is a long way to go. And I would say that in many ways, in terms of battery electrification, it's like back to the Wright Brothers era, so we're just at the beginning.
Yeah, actually, one of the examples with which you illustrate your paper in the Nature journal is actually from the end of the 19th century, one of the first airships powered by an electric battery, powered by an electric engine, which is a detail I was not aware of, really. And then, you mentioned that at the end of last year, you published these two papers. I'm going to post the links, of course, in the show notes, but just let me mention them. One, it's on Nature, one of the most prestigious science journals. And the title is “The challenges and opportunities of battery power flight”, it was published on the 26th of January 2022, although it was accepted in November. Sorry, I just mistook the dates. But, yeah, basically, it was published at the end of January. And then earlier on that one is, in November, you published another paper on the Proceedings of the National Academy of Sciences, the United States of America. And the title is “The promise of energy efficient battery power human aircraft”, I'm going to post links to both papers. But I'm going to ask you to go over the main findings, basically, one of the things you said…I'm not a scientist, so I'm not going to get too much into the details…is that for battery power, for electric aviation, to go forward, we need a radical change in the approach because the technologies that have been powering batteries, sorry…the batteries that have been powering electric vehicles, and on the ground electric cars, are not sufficient for the demands of electric aviation, which is something that…we could somehow suspect…we are aware of their limitations! Just to put some numbers, a Tesla Model 3 has an energy density, the battery has an energy density of 260Wh per kilogram…
Yeah.
And you said that with new approaches to battery technology it's possible to get to 600 by 2030. But eventually, we would need to get much farther than that, over 1000 to 2000 Wh per kilogram, so can you tell us basically what's the essence of these papers? And what were your findings? And what do you think, what are the limitations with the current technology? And what do you think are the most promising paths to move on to the next stage?
Yeah, definitely. So I think maybe before I sort of jump into the details, I'll just sort of set the context of how we got to this, so that the listeners get a sense of the lens through which we have approached this problem. So I co-authored this paper with six other co-authors, and three of them came from faviation and three are battery people. As I mentioned earlier, right, Alan Epstein led the aerospace section, and then I led all this value discussion. And the core approach to thinking about this problem was to take a uniquely sort of aerospace, like thinking, which is the entire system based approach…what might be feasible? And also, what are the sort of unique challenges that Aerospace has that is different from automotive? So I think this sort of larger message that you already got to was that the arc of progress in automotive batteries is not going to meet the aviation requirements. I think that's a point that, you know, many of your previous guests have made. And I think one that I think is quite clear.
Sorry, may I interrupt you here one second? So these 260 Watt hour per kilogram that we have with Tesla now, how long did it take us to get to this point?
Yeah, so that's a great question. So the earliest invention of the lithium ion battery happened in 1991, the cells there were about 150 Watt hours per kilogram. And then from there, it's taken us almost close to two and a half decades to be able to get to where we are today, cells in the range of 260 and approaching 300 Watt hours per kilogram. One important caveat is that the relevant number to use, when you want to integrate that into a device, such as an automobile or an aircraft is the pack level specific energy. So the cell has reached 60 to 300. But the pack is still in the range of about 180 to about 200 Watt hours per kilogram. So that 600 number that you mentioned, is what we think the pack will get to, we think cells will get to about 800 to 1000. So, there's what's called a packing burden from amazing cell to what you can use for variety of reasons, extra packaging that you need to be able to use in aviation propulsion…
Sorry, can you please clarify briefly for the audience who may not be familiar with the concept of cell and pack? What do they mean, in plain terms?
Yeah, let me unpack that. So the cell level specific energy is basically a cell that you might be able to buy, for example, right. So people have probably seen cylindrical cells, or lithium ion cylindrical cells that they may buy, the cell level specific energy is the energy contained inside that cell, divided by the weight of that cell. So you put that in a weighing machine, and then you get the weight, and then you get the energy content of the cell. And the energy divided by the way, is the cell level specific energy. Now, in any relevant propulsion system, that you would use these batteries, you would have many 1000s of these cells, these cells need to be connected, right, so they need to be connected electrically, they also need to be shielded from each other. So you need to package them between each other so that if one cell fails, that cell doesn't, the failure doesn't propagate to other cells. And then the final thing is, even though it has 100% of the energy, you don't use 100% of the energy, you use only maybe 90% of the energy, which is your charge from each charge, from 5% all the way to 95%. So you lose another 10% of the battery. So, pack level specific energy is the automotive battery pack, or the aviation battery pack, the energy contained inside that full pack, divided by the weight of the pack, right? So as you might expect that is lower than what you would get from the cell, because you now have to add the weight of additional components that are not providing your energy. So the packaging, the electrical wires, obviously, the window that you were limiting it to and so on. So for listeners, in Figure three of that paper, we unpack all of these different factors. And the important point we make, which I think is very interesting, is that you get a fresh cell and you only can use 45% of that fresh cell’s energy in terms of what you could use for flight. And in fact, even there, you eventually end up having to put some for reserve. So which means that, you know, you end up having a much lower fraction of the total available energy inside the cell for actual flight. And I think this is something that is not fully appreciated.
When you mentioned a fresh cell, you mean a cell that hasn't undergone any, let's say depletion of capabilities? I guess…
Exactly.
So the typical thing is that you have a computer or you have a telephone, and over time, the battery does not perform as well as when you bought it the first time, right, because there's a depletion there.
Yeah, so there's an additional aspect. It's in addition to sort of, you know, the stuff that we talked about, which is that as the battery ages, then the performance of the battery, both in terms of its ability to deliver energy, as well as the ability to deliver power, decreases. And so I think that's another factor that you need to take into account in order to decide what the available energy and available power is.
Okay. Sorry, I interrupted you earlier, just to get an idea of the pace at which the surgery science has been advancing over the last two decades. So what are the perspectives? You say that a new product may have needed to move faster. So is this due to the materials? Is this due to the way that batteries are produced? Is this due to new revolutionary approaches to technology? Tell us a bit more about how you see this thing evolving?
Yeah, so I think the pace of progress is a great way to think about it. So if you sort of took a macro view, you know, we're progressing at about 4 to 5% a year over the last 20-25 years. But if you actually look at the micro trend, which is if you look at the progress over the last five years, it's pretty incredible. If you look at what has happened with one particular technology, lithium metal, where what you do is change the anode that used today's batteries, which is usually graphite, and then maybe a little bit of silicon, you remove that graphite and then you directly use lithium in its metallic form as the anode. And it turns out that if you do that, you can now reach specific energies in the range of 400 to 500W per kilogram. This is not a new idea. This has actually been around from the 1970s. We just didn't have the tools to be able to control this, right. So this was one of the hardest problems in battery science. We call it the holy grail in battery science. And over the last five to six years there's been incredible effort in making that happen. And today, we have credible demonstrations. In fact, you have one of those great entrepreneurs, Richard Wang on the podcast…
…from Cuberg! Which is now a part of the Northvolt, which is one of the largest battery makers in Europe, well in the world, actually! And they just opened this new giga factory in the north of Sweden, they acquired Cuberg, which is an American startup working precisely on this lithium metal technology. And Cuberg is going to be, let's say, the test line for aviation oriented technologies at northvolt, and batteries for other applications as well.
Yeah
You mentioned lithium ion gets most of the press, but there are other technologies out there undergoing development.
Exactly. And, of course, I have been part of lithium metal, in other capacities, and I've been involved with quantumscape, which is also commercializing this for automotive applications. And so you ask the question, “okay, so we've solved the problem, the holy grail on the anode side, can we solve the holy grail on the cathode side?” so you can either change the anode or change the cathode. And I think, with lithium metal, the end is done right. So you are not going to do anything better than lithium metal on the anode side. So the next is to do something on the cathode side. And so figure five in that paper sets the context for this. And so the easiest way you can think about it, you probably heard these kinds of terms and NMC NCA, LFP, all kinds of terms to describe batteries. And really the core thing that you want to take away is every one of those things will have an element of metal, a transition metal NMC has nickel manganese, cobalt, NCA has nickel, cobalt, aluminum, LFP, has lithium iron phosphate. So iron, the key is for every one of those technologies. For every metal that you have you can store one lithium, if you have one iron, you can store one lithium fuel, one nickel, you can store one lithium, and this has been the cornerstone of innovation in batteries, which goes by the term insertion or intercalation. That's the core idea. Now, the paradigm that we put forward in the paper is to move beyond that one to one ratio, and store more than one lithium, for active center, whatever it is. And ideally, that active center is not a metal. The problem with metals is they come if you remember your high school chemistry, they come in the lower part of the periodic table with a second row in the lower part of the periodic table. They're heavy, right?
It's very rusty, my high school chemistry…
In fact, the rust itself, right, is the core element of modern lithium ion battery, because it's the rust, the iron, iron ore that we entered into, to find to make lithium ion phosphate. So the core idea is how do we store more than one lithium per active center. That's the core question that we went after. And we put out a number of possible options. And this goes by the larger family called Conversion instead of insertion. And in the conversion family of electrodes. The one shot on goal that we clearly to spell out is what's called CFX: Carbon, fluorine, and x here is the amount of fluorine you have. And so the beauty here is that you can now store you now have done away with all the transition metals, so there's no metal. So it's very light elements, carbon and fluorine. And you can now potentially store a lot of lithium in the system. And in fact, you might ask the question, well, you know, why is there any hope that this could get there? you can actually go out and buy a lithium CFXL. So one that has a lithium metal anodes, right, that we have talked about, and then CFX, that is 800 Watt hours per kilogram today. So you can actually go and do this, except it can only be used once. It's a primary battery. It's not a rechargeable battery that can be used for any mobility application. So this is like the single us rocket versus reusable rocket right. Obviously, the cost of the single use battery would be very high. But I think there's good reason to believe that we can make it rechargeable and we can make it achieve all of the other requirements that are needed for aviation.
But are these batteries, these technologies available? Are they available commercially? So they've got companies doing them. And for which type of applications? Is there a market for this?
So there's always a market for high energy density, single use batteries for military, defense and other other niche applications. So there are actually a number of companies that specialize in this lithium CFX battery. Eagle picture is one of them, for example. And, you know, they have been working on this technology for many years. So you can actually buy these batteries commercially. They're also sometimes used for space applications as well. So where the other metrics are not so critical, such as charging, rechargeability, right, you want you're okay with using it once, and you're happy with it. So there's a number of applications in that realm that have use for these kinds of batteries.
And in environmental terms, is there any contraindication? I mean, all these chemicals, do they have any, any secondary effects on the environment or any other things that we don't want?
Yeah, I think that I think, you know, I think that the modern lithium ion revolution has caused a strain on the metal supply chain. Right. So certainly, with nickel and cobalt, you know, the demand on nickel. And Cobalt has led to, you know, supply chain constraints. And of course, the other thing to remember is that, typically, when you make a kilowatt hour of a battery, you use up much more than a kilowatt hour of energy to be able to make that battery, which means that you have to use them substantially over the lifetime of the battery to be able to recover back the energy cost associated with that, I think with CFX in particular, some of the challenges will be on figuring out efficient ways to make the electrode. So making fluorinated materials is tricky, and will require some technological innovation. But I think none of these are showstoppers, none of these are things that we are insurmountable. We know the challenges that lie ahead. And I think there's a lot of interesting innovation on fluorination that has come in the pharma space, where people are making interesting drug-like molecules that want to make those same kinds of compounds. And so they have invented some interesting techniques. So there's that exciting cross pollination of ideas between these two communities, that might be useful, but I think in the long term, I don't think there's any significant environmental roadblock to be able to make these materials and then build batteries out of them.
So you see this as a sort of step by step ladder where you know, we have this lithium ion, then maybe lithium metal will be the next step. And then the step after that would be the fluorination technology that you mentioned. So they would be like an evolutionary ladder or they could be maybe coexisting for different types of applications. How do you see this going?
Yeah, so I think I think it will be a coexistence because I think the beauty about aviation is that there is a spectrum of needs. I think much like automotive but I think aviation even more so, I think with advanced with urban air mobility, and I think we'll get to some of that in the other paper, but in urban Air Mobility, I think current lithium ion has an important role to play current automotive grade lithium ion, then, of course, with longer range, urban Air Mobility, as well as regional mobility, I think lithium metal will play an extraordinarily important role in that segment. And then for aircrafts beyond that, where you want to fly lots of passengers, lots of distance, we will unlock new or newer markets with higher energy density cells, like the fluorinated electrodes that we just talked about.
When you say lots of passengers over long distances, can you put some figure or realistic figure on on that, because obviously, it's not the same to fly 100 passengers on a relatively short flight, a step up from the eVTOL or from the sort of very light aircraft we are seeing now. But flying intercontinental, that's a completely different, a completely different game. What sort of applications you have in mind here, when you say that this technology is going to bring a lot more range, a lot more capacity?
Yeah. So I think one one interesting way in which we close the paper, as you pointed out at the beginning, right, we start the paper with La France, which was the battery power dirigible that flew in 1884. And in fact, I also realized this as I was writing this paper, my co-author, Alan Epstein brought this up. And of course in 1909, right when the Wright Brothers delivered the first airplane to the US government, which was capable of carrying two people 1.2 kilometers, right?
1909? That's about six years after what's considered to be the first, the very first powered flight…
Yeah. And I think that's about the capability of the Pipistrel aircraft, another guest of yours…
Yes, indeed.
So, and then if you remember, in the arc of history, like in 1920, there were fueled aircraft that were carrying tens of passengers about 800 kilometers or so. I think with the kind of batteries that we're talking about here, I think we'll start to be able to do the 1920 mission, again within this period, and then I think beyond that will require a combination of innovations. So it can't be just from chemistry innovations, it has to be the integration of some chemistry innovations, with other innovations on battery packaging. And we will get to some of those things. And I think, you know, those paired together will slowly start to move to larger and larger numbers, right? And I think the numbers that we put out in that paper, and I think figure two shows the gap between the usable energy density inside a turboprop and a turbofan versus batteries, and it's on a logarithmic scale. So which means that any gap is very, very large. And so the numbers that we need, are beyond sort of the numbers that we have even identified as options for near term. I mean, I think that we've identified certainly options that eventually could get us to, you know, computer aircraft, and of course, larger aircraft to fly larger range missions, it's in the order of 1800 to 2500 Watt hours per kilogram. So another factor of two from the kind of numbers that we are talking about here, but I think you'll slowly unlock these things. Because just like what happened in electric vehicles, once you went electric, other things started to change. For example, like when you went electric, once you could redesign the vehicle, then car designers figured out other ways to make the cars more aerodynamic. Like, for example, the Model S and the model 3 have the lowest drag coefficient of vehicles in that category, including all internal combustion engine vehicles that were known. So I think, once that happens, once the unlock happens with electric propulsion, I think there are lots of other synergies that need to be exploited. And I think in the urban air mobility space, this is very clear with distributed electric propulsion, where, instead of one lot, one or two large fans right now you have many distributed either rotors, or fans that allow you much greater efficiency. And so I think if we think about what might be feasible, with just the chemistry, I think I'm fairly confident that we will be capable of flying that 1920 mission again very soon.
But let's say for example, the aircraft types now carry the bulk of passengers, like the Boeing 737 and A320, do you think these size of aircraft will be electrified in a reasonable timeframe?
I think it will require the third generation of this integration, right in the arc that we just talked about, the metal, and then fluid electrodes, and the third generation will start to unlock the 737s and the A320s. I think we need to sort of go in steps because…there's substantial hurdles to be able to manage safely, that scale of energy and be able to bring down the weight enough such that you can address the needs of those kinds of aircraft.
You touch upon the safety issue. What about the safety of all these different technologies that are not lithium ion, like lithium metal on chlorination? What's the safety profile? And what sort of precautions are going to be needed?
Yeah, so I think, aircraft and the entire aerospace industry is built on the foundation of safety as we point out in our paper, and lithium metal, certainly the reason it was abandoned in the 1970s and the 80s, actually was safety. So because what happens when you charge and recharge the battery is they form these so-called dendrites, that same kind of beautiful snow, dendrites that form that you see in winter, the very same thing happens inside the battery. It actually forms for the exact same reason that they form on snow. But in inside the battery, it's a problem because once that dendrite grows from one side to another side, then there is an electrical connection inside the battery from one electrode to another electrode that causes a short circuit, because you only want the electrons to go through the outside not to the inside. So then leads to a thermal event. And that leads to of course, fire, as popularly called. So that was one of the reasons why lithium metal was abandoned in the 70s and 80s. And that's exactly the challenge that has been addressed. Now, to be able to make them at the same safety level as lithium ion, this has been fixed. This main issue has been fixed. So the expectation is that the safety profile of lithium metal cells would be comparable to lithium ion cells. So we'll have the same kind of safety profile that we have with lithium ion cells. Now, even in lithium ion cells, the safety profile is not as good as it could be, if we could do just one thing, which is to replace the flammable electrolyte, right? The electrolyte that there is like fuel. It's an organic compound. Much like, you know, much like jet fuel, kerosene, or gasoline. And if we can find ways to replace that, or modify that, we can bring up the safety profile of current lithium ion batteries as well. And there's a lot of work going on and a lot of innovation going on there. So for lithium metal the expectation is that it will have similar safety profiles. With these chlorinated electrodes, I think it remains to be seen, because I don't think we know enough to be able to comment on the safety profile of this. But I think certainly, if you have to get anything that has to meet aviation needs, it has to be safe.
You also mentioned other advances like robotic experimentation, or machine learning driven by new material science advances. Can you elaborate a bit more on this? And what's characterization? Because that's another term that appears in the paper that I'm not I'm not sure I fully understood.
Yeah, absolutely. Let me unpack those three for you. So maybe let's do the characterization first. So in order for us to be able to make these batteries rechargeable and reversible, the lithium atoms have to move from one site to another site, and up and down back and forth every single day. That's what happens when you connect this to a power outlet or when you use it. And so in order for us to be able to control what happens, we need to be able to watch what happens, like we need to be able to really understand what is happening inside microscopically. And so what I mean by characterization is just like how we go and take a photo outside and be able to watch what happens. Or, for example, we go to a wind tunnel and make measurements in the same way here, we want to be able to take measurements and watch what happens like just like you would with a P IV for the velocity field or pressure field in a in an aviation context, we now want to be able to understand and watch what happens inside the battery. And that's what's characterization. And so the two terms we use in our paper in situ and in operando, like in operando is while the battery is operating, we want to observe what happens, right? And I think the capabilities that have been enabled in, in situ and in operando have enabled us to design better batteries faster than ever before. So if you know, and if you can watch what's happening, it's easier to fix the problem, right? So the capabilities that are there today, versus even like five years ago is incredible. I mean, there's been a step change in categorization capability. The second one there.
So we have the first first measure trend that can help support this push forward in batteries, characterization. Second one, we have robotic testing.
Yeah, exactly. And maybe I'll quickly just talk about robotic experimentation. We've been two robots, Auto and Cleo, that without any human intervention can go look for an electrolyte mix, test them, decide what to do next, right, and all of this without any human intervention. And I think what this allows us to do is search over the chemical space and bring down the amount of heuristics, bring down the amount of trial and error, which has been the way in which the battery field has been moving.
But how does it happen in practice? I mean, there's like a lab where you have a robot mixing chemicals?
Exactly. So it's a microfluidic setup. You have a bunch of different electrolyte compounds, you then mix them, send it, and send it to a test chamber. So through a microfluidic setup, you send it and then test it in an electrochemical device. So testing a battery that is sort of mimicking the true battery, and then you get the answers the answers process life. And then using that answer, there's a machine learning sort of model that decides what's the next compound to mix and test.
Okay, so it's basically it's kind of like processing feedback on the go, depending on the results keeps getting and I guess that makes it faster and more precise
Faster and it's more precise, and the beauty is you can adjust on the go if you look at human experimentation, the way we would do it is we say, Okay, I'm going to do these experiments today, right? And then I only focus on doing the experiment, I don't focus on analyzing the answer as the results are coming and deciding what to do next. Right. So usually, I just do what I planned for the day, right? And that could be that I basically, in the second experiment, I knew that everything I'm doing today is actually not useful. But if I'm not thinking, right, because I'm actually just focused on doing so, the beauty with a robotic setup is then it takes the headache away from us for doing the experiments so that we can analyze and then say, okay, oh, this tells us that this is not the right direction to go. Instead, it's this direction. And so that allows us to move to another direction.
And that takes us to the third leg is machine learning research, machine learning based research on new materials?
Yeah. And here, actually, you know, I'm involved with a company called Aionics where I'm Chief Scientist, which is commercializing these solutions to companies. And the core goal of both Aionics and this sort of vision is to be able to shrink the time taken to commercialize innovation. And if you asked Richard from Cuberg or others that have commercialized these battery innovations, the number of experiments they have done to get to their secret sauce, or the secret recipe is of the order of somewhere between 100,000 experiments to about millions of experiments.
Wow.
That's a lot of experiments, right? So we clearly have to bring that down. Right. And so the vision with machine learning is, before you even test, you already have a very good answer of whether it's going to be good or not. And with that, you can basically shrink both the number of experiments and time down. The other thing is the amount of money invested, right? So they all have invested off the order of hundreds of millions of dollars to be able to get to that secret recipe.
But sorry, Is this because it's processing the data from real life physical experiments, or because it's modeling. And it's just doing it virtually doing, let's say, theoretical experiments.
It's both, right. So it's the combination that allows this to work. It's running both modeling theoretical sort of experiments, as you described it, and real experiments. So it's extracting maximum value from the real experiments, and then combining that with what we can do with theoretical experiments. And, of course, the new innovations in machine learning that allows us to build a map between the identity of the substance to its performance. So before, we didn't have this kind of fidelity in terms of mapping the identity of the material, for example, the identity of the kind of separator being used to its function in a solid state battery. So what you had to do was to take that material, make the material, build ourselves, test, and so on. But now we are at the point where we can go from the identity to the performance quite easily. And of course, pairing all of that together, it's the package that I think is enabling rapid innovation. In this machine learning Guided Discovery, it is both using simulation and theoretical experiments, in combination with real experiments. I think it's very, very key that real experiments are a part of this loop. Because otherwise, the theoretical experiments have its deficiency in how well it can simulate reality. And so it cannot live by itself. It has to be used in conjunction with real experiments that allow us optimize these designs
Yeah, I guess it helps you narrow down a lot, the real the real life experiments. And I guess that's also why you are confident that we're going to come up soon with all these new materials…
So I think the pace of progress and the pace of innovation in the battery industry is going to be unprecedented in the coming decade. The other axes that I think is not mentioned is the excitement students feel to work on batteries. So when I started as a professor, the excitement for batteries, I would have to sort of go and say “batteries are a really important problem”. Now it's the opposite, right? Students are coming and saying, Can you teach us more battery classes? So my battery class is always oversubscribed. And so the excitement in young, innovative people working on these important problems. I think that you cannot substitute that and I think that's why, in addition to all of the other three trends that we talked about, right there is just a passion for sustainability that is there today. I think that is a key factor that will allow us to innovate much faster.
So batteries are hot. Well, they shouldn't be hot when they're on a plane right? But They are hard in the academic world. So that when it comes to the chemistry, but then you also work in the field of advanced Air Mobility and European Air Mobility, you said that you are more, let's say more optimistic about the prospects of the current lithium ion technology for human mobility, did I get it right?
Yeah, so I think in that Proceedings of the National Academy of Sciences article, we set out to answer two questions. The first question was, whether today's batteries or today or near term batteries can supply the needs of urban air mobility. So that was the first question. And the second question, which I think is an important question that every student that works in this topic asked me is, are these just sort of replacing these sort of gas guzzling versions in the air? So are these the sort of, you know, the Hummers in the air? How energy efficient are they? So the, the paper really addressed those two questions. And so what we analyze there was that we took a number of various aircraft designs, some lift plus cruise design, tiltrotor, design, tilt duct design, and then we asked the question of whether today's lithium ion cells can supply two main things cannot cannot supply the specific energy. So how much energy does it has per week, as well as specific power? And the specific power is the really important factor that is unique to UAM. And what makes it different from automotive applications?
Sorry, just parenthesis here. Can you elaborate a bit more about the difference between energy and power? Because I'm, I'm assuming this distinction for many people is not so clear.
Yeah. So how much energy is there? So if you look at your phone, right, or your car, how much energy is there? what's shown in the indicator, right at 80%? So that's, that says that I have 80% of the full energy that was there in the cell that is available. Power is how quickly you can use that energy? Right? And so, for example, you know, if you look at a car, like they give you a spec for how fast you can accelerate, right, so that's an indicator of power. So how quickly you can get the energy is power. And the actual energy contained is your is your indicator,
Can we say In plain terms is the difference between having like, let's say, stock and the flow? Things are stored and how things are used?
Yeah, exactly. So yeah, so if you if you have a tank, in that same analogy, if you have a tank, how much liquid is there, the tank tells you the energy and how quickly you take water out of the tank, tells you how much power and so for urban Air Mobility, the second one, how quickly you can get that water out of the tank, actually is as important as how much water you have in the tank to begin with
Is it because of the demands of the hovering and the vertical takeoff and many of these devices rely on?
Exactly, so it is exactly that. But it turns out that the main challenge is actually the landing segment, not the takeoff segment. Because you actually end up requiring almost the same power when you land because you have to sort of push the air to be able to land. And the problem and this I'm sure all of your listeners would have felt when they are trying to use their smartphone, when suddenly your battery's at 10%. And you try to play that YouTube video, right? It suddenly starts to freeze, and turns off right? The challenge is you need to deliver that high power at a low state of charge. So when you're when your battery pack has now gotten to let's say 30% in an eVTOL. And so actually the landing power is the failure mode currently, for batteries that are used in eVTOL applications.
So basically, when there's less energy in the battery it's more challenging to have to have this big power application.
Exactly. So the reason for that is actually quite intuitive. So I'll try and give you a simple way to think about it. So as you discharge the as you discharge the battery, right, so in the same way that you discharge water from a tank, right? When you open and try to get water from that, you now have a lower pressure head to be able to push this out. So in the same analogy, in that same water analogy, in a battery, there's less voltage to push and so as a result, you're not capable of delivering the same power.
Okay, understood. So getting back again to the lithium ion capabilities, what can be achieved with current technology or do we really do all these projects to have like your runner mobility in the near future because some of them are aiming for 2025 to 2026 launch date. Do we need some significant advances in lithium ion technology to happen in this very short period of time or with the current technology, we are already on a good track to achieve that.
So I think the punch line of that paper, much to our own sort of surprise, was that I think a number of these designs are within the reach of current or very near term lithium ion technology. So I think that was the key insight from that particular work. And that shows both the maturity of the industry, as you pointed out in terms of how they have planned their certification approaches in the mid decade, as well as the cells that will be available to them by that point. So by 2025, I think the arc of lithium ion will be able to get to high cycle life and get to the safety profile and get to the charging speeds needed for urban air mobility. And so I think the, the closing remark there, in that paper was that this technology, and of course, flying cars, right is the epitome of technological progress, may be here sooner than most people think, because of the fact that, you know, there's exceptional progress and interest in urban Air Mobility, as well as the rapid progress in lithium ion batteries, that has already gotten it to a point where these designs are approaching feasibility already today, right and think, will only get more and more feasible in the coming years. So I think by the mid decade, you know, a number of these urban Air Mobility makers have announced plans to certify and run operations. And I'm very optimistic that, at least on the battery side, right, one that I know very well, we will have the batteries ready for them to be able to fly. It's the question of whether all of the other pieces may be autonomy and certification and regulation, other challenges, noise profile, you know, lots of other aspects that need to be addressed for this to be real. But I think from an energy storage standpoint, urban Air Mobility is within striking distance. And I think what we learned there will teach us what to do in the other step changes that we talked about earlier.
To be clear, when we talk about urban air mobility, we are talking about really local movements, like you mentioned somewhere in your paper, something like less than 10 minute flight, something like that.
Yeah, I don't think it needs to be quite 10 minutes, it can be off of that order of tens of minutes…
So just to clarify that we are not talking here about 150 miles or something like that. We're talking about moving inside a very well defined European environment. Yeah. So the intent of that paper was to address the interest in the city market, not inter-city or airport, airport to city, for example, which is one of the applications
Yeah, exactly, one of the canonical use cases, Manhattan to JFK Airport or in LA, right, somewhere from downtown LA to one of the LA airports, or I think in Melbourne is the other other city being considered. So from downtown Melbourne to Melbourne Airport, I think those are some exciting markets, I think ones that today are being addressed by helicopters or other kinds of vehicles. The beauty with urban air mobility, and of course, electric is that you get better operational economics such that it can become more ubiquitous. And the hope is that, you know, with better noise profile, you can now run many more of these kinds of flights than what you could do with helicopters today. So yeah, the boundary here is those kinds of flights that would be in heavy congested urban environments, where the difference in time is significant. So traveling that same distance in the air, right, in three dimensions versus on the road, two dimensions, is significant. Those are the ones that we will see really, really a penetration in those spaces.
Exciting times. What else are you working on at the moment? You had a very productive last year in terms of papers? Are you working on any other paper that we should be waiting for in the near future?
Yeah, we are actually. So the paper that we talked about is a lot about chemistry, but now I'm going to talk about something very different, which is to estimate how much energy and power is left inside the battery. This is where it's very different from fuels, in fuels it's very easy to decide how much energy is there, you weigh how much fuel you have, right? Super easy. Unfortunately, with the battery, it's a closed system, which means that you can’t, the only thing you can do is you can observe three things, you can observe the voltage, the current and the temperature of the cell. And with that, you have to guess how it feels right?
You don't see the electrons
You don't see the electrons, right. So by observing, you have to sort of guess, you know, whether it's in a comfortable shape, whether it's happy to do the landing mission, and so on. And so this is a project that was started with the Airbus Vahana team, what we have built is a very fast and accurate way to estimate whether your battery pack is going to be capable of doing the landing mission. And of course, landing and doing the Reserve Board and reserve in aborted landing reserve mission in case you need to do that. And the key there is to be able to understand how the battery ages and we call this, we call this the battery avionics system, right? So the core vision here is that we put the battery system in the same level playing field as every other avionics systems that you have today, such that we, for a pilot, give them all of the sort of instructive information about the state of the battery: here's the amount of energy left, here's the amount of power left, here's the kind of landing mission it can do. And the most important thing is to be able to do that, as the battery ages? This is the main challenging thing, because as the battery ages, then this becomes more challenging, because an older battery cannot deliver the same amount of power. And we actually don't know when it cannot deliver the same amount of power. So these are sort of the main aspects to think about.
But what about, for example, when I got the iPhone, there's a function that tells you what the battery health is. And that's telling you some data about your battery. I mean, it's not that accurate, or it's just…
It is accurate. But aviation is different in the following way. Especially urban Air Mobility, which is the context in which we're looking at this. Health monitoring is very easy for energy, just like it's easy to see the tank and say how much energy is left. It's easy to guess the energy. Difficulty is in power. And the aviation use is actually very, very tricky. So, you can go to your iPhone and ask the question at 20%. Can I run YouTube? And okay, no, can I parallel process YouTube and then do email and then and then play something else? Right. So that's the kind of load we are putting for an eVTOL, which is, I think, from a battery physics standpoint it's really exciting for us, because it's stressing the battery in a way that causes all kinds of failure modes. So we have to understand all of that. Right. And where the title of our paper sets the context here, which is that for every challenge, there is an opportunity, right? And we love challenges, right? So, eVTOL, in that sense, is an amazing challenge for the battery designer, both from a cell engineer's perspective, but also from someone that tries to diagnose the energy and the power content of a battery.
Yeah, indeed! Well, I think we covered lots of ground. And I really appreciate your capacity to communicate all these very complex concepts in a way that I think everyone can easily understand. Because I have to admit, I'm not an expert in this topic. As I admitted earlier, my chemistry notions from high school are not very up to date. So it's been great for learning. What are the challenges in this very promising field of technology? People that want to learn more about your work, and follow the work you guys do? Where should they go? And what type of resources would you direct them to? Of course, I would put links to the papers we were mentioning all the time. But what else? Could they go?
Yeah, so I think, you know, people can look up our group website, and I'll share the link to the group website, you I am very, very active on Twitter. So people follow me. Communication, as you said, is very important. And especially in these kinds of advanced technologies, the more we communicate to the public. That's how we can reduce the barrier to adoption. So that's why I spend an enormous amount of my time trying to help communicate these ideas around these kinds of new technologies and bringing down the fear level to the adoption of these new technologies. So please do follow me on Twitter.
I do! I already do. But I recommend everyone else to do it as well.
Yeah, definitely. And I think I'll close with this parting remark. Right. I think the exciting thing for the future of aviation is interdisciplinary. And I think this has been part of aviation for decades. And actually, probably the full first century of aviation has been interdisciplinary. So in the article, we close by this comment that the way the next second century of aviation can progress rapidly, is for the two communities to come together, right? The aerospace community, and the electrochemical sciences community that thinks a lot about energy storage and energy conversion devices, that the fusion of those two is really I think, where magic happens, and I hope that through this, your listeners get excited to think a little bit more about batteries. And, and I think the future is extraordinarily bright. And I'm really excited for the second century of aviation.
I think that's an excellent concluding remark. We can leave it here for now, but I'm sure there are going to be a lot more novelties coming from the battery field. So more than welcome to come in the future and discuss it again and, and learn what's behind the scenes of all these progress we are seeing in the field of battery technology. Well, thank you very much. Thank you and all we’re looking forward to reading the new papers when they come out.
Thank you. Bye