Episode 52 | Advances and Innovation in Flow Batteries

[Music] Welcome to the battery technology podcast. My name is Ken Davis. I'm your host and this is your regular exploration of topics across the world of battery development and mobility, energy storage systems, and charging and everything else related to the transition to a greener future. Under battery technology podcast is brought to you by battery tech Europe expert Fira de Barcelona in September 2026 showcasing European innovation in battery technology. It's a new event in a rapidly developing region that focuses on the future of battery applications and it puts European innovation and the European battery technology ecosystem right at the front and center. See the show notes for more details. Episode 52 advances and innovations in flow batteries. Flow batteries are a battery technology that is coming of age and it finds particular relevance in the energy storage market which of course is a very critical growth area for everybody involved in batteries. The chemistry of flow batteries quite distinct from what we might traditionally consider certainly in the lithium ion world as a battery but they offer very unique advantages particularly in some key markets. So technology we all should know a lot more about and today is the day. I'm joined by Laura Ritzi the CEO and Fabio Difonzo, the chief scientific officer of flow nano who are based in Milan in Italy to discuss the potential flow batteries in general and some very interesting work that flow nano are doing to further expand the potential of this technology. So firstly a very warm braun giorno and then the new talk to Laura and Fabio. Thank you. Grazie mille. Buongiorno can very pleased to be here with you today. Well I'm certainly looking forward to this. So firstly Laura it might be a good idea just for us to understand a little bit more about flow nano to business the way you maybe face the market the kind of technologies you are involved with. For sure can so I'll try to give a first overview. So firstly flow nano technology is a process to produce and deposit carbon nanoparticles specifically carbon nanononions onto a target substrate. To basically decorate this target substrate this fabric with this particle to increase the the available surface, the active surface of this fabric and to boost the performance. So this is the very general overview. The technology was originally developed by Fabio within the Italian Institute of Technology years ago and then so where the technology was born and was patented originally. Then basically ex-nanon was created which is a first startup born in 2022 to start you know the path towards commercialization of the technology created within the Italian Institute of Technology. And in 23 flonano was created. Flonano was created specifically to scale up the process of carbon nanoparticles production and deposition and bring the product to the market. So this is the background. Perfect explanation. Thank you very much indeed for that Laura. Fabio I will turn to you as the inventor of this technology. But firstly to understand how flow batteries work it's a redox reaction my understanding is it's quite different really from lithium ion batteries. So I guess it would be very useful for our listeners to understand the system and the different components of the systems and also the relative importance of the different parts of that system. So, overview Fabio this will be very interesting analysis. Okay sure can. We can say the main if you look at the main difference that it's quite apparent as soon as you look at a flow battery with respect to a lithium or any ion, any ion battery is the fact that in flow batteries as the name says you store energy in liquids. And these liquids flow through the cell. And this is a very important difference between for example any flow battery there are many different chemistries in the flow battery world and a lithium ion battery. Because in lithium ion battery you store energy because into solids and in particular to the movement of lithium. So batteries discharge the lithium is in the cathode when the battery's charge you force it through the graphite anode and there you basically open the electrical circuit and there stays. But obviously this causes the fact that the lithium wants to go back to its natural position. So this means that anybody as a cell phone experience the fact that any battery lithium ion battery has self discharge. And moreover the chemistry it's so push to the limit that even if you don't use the battery the battery degrades. And obviously anybody knows that a battery has some amount of cycles typically few thousand and then it's over then it drops in capacity is quite fast. Flow batteries are completely different because first of all let's say you are in the liquid so you can store energy in tanks very simple like plastic tanks. Typically they are based with water electrolyte so that's a 90 major difference they are typically there is zero risk of fire that is very very high with lithium ion battery. And often in lithium ion battery the risk of fire and the risk of spread of fire is directly related to the election line. Absolutely and typically the more performant is a lithium ion battery like NMC cathodes with high voltage the more the higher is the risk of fire. With flow batteries based on aquaseliterally that is zero risk of fire. Absolutely zero. And this is one important difference. The other difference is that you separate the capacity of a battery and the power of the battery. So your energy and the power and these means that for example if you are connected to a PB plan then you can store that amount of power for as many hours as you want because you can just increase the size of the tanks and the amount of liquids of the electrolyte you can store energy into. One question just as occurred to me as we're talking about this presumably though because your storing electricity in a liquid the volumetric density is quite different than if you store it in solid form. So does that mean am I right you thinking that by the way and secondly does that mean that this is a technology that tends to lend itself to certain use cases rather than the other ones because of that volumetric issue? Yeah absolutely I was about to get to it and yes this is significantly lower but also in the mass basis it's gravimetric density. Energy density is much lower than lithium ion batteries and that's the reason why flow batteries are an excellent choice for stationary energy storage not for mobile application even though I have to say that there are some startups that are developing high energy liquids that obviously the dream is to be able to refuel your car like you're a fuel now with petrol that has to be a charge liquid but that's at the moment still a little bit far in the future but anyway at the moment with standard chemistries redox full batteries are for stationary applications definitely even though in this case things are not always like they appear at the first site in the sense that consider that even though you have a lithium ion battery that has something like five to ten times the energy gravity and energy density of redox flow by vanadium redox flow by the way talking about vanadium redox flow by the because they are the reference for it's 90 percent and more of the market but then when you look at the when you look at the site you want to install 100 megawatt hour megawatt hour battery supposedly you store all of the battery in containers. When you have lithium ion batteries, you have to put a distance between different containers because if one catch on fire then can spread to all of them and then obviously all the fumes, the gases that develop, they are fluorinated compounds very toxic and it's very dangerous. So you need to and you cannot you cannot extinguish a fire from a lithium ion battery because oxygen comes from the inside. So this is the problem. So the firefighter just wait that it's itself. They cannot do anything else. But it's very important that it's not you know you don't have a dominant effect that all maybe thousands of containers they catch on fire because that would become a environmental disaster. Yeah. First of all. Instead of banid, banidium or redox full battery in general based on water, since there is zero risk of fire, you can stock the container one on top of the other. You can put them underground. So at the end, if you look at the area, so per unit area of energy density or energy density, you can achieve even higher energy density, a aerial energy density, lithium ion batteries. That's really interesting because you are essentially operating in three dimensions. That's right. But all these, this is not very relevant if you are in the desert Nevada, in the desert, in Olya or in Australia. But if you are in any European environment where safety and land utilization is very critical, we think this could be definitely a differentiation between and a big heat for redox flow batteries. So these are the say the macro differences and I want you to stress this energy because everybody says, oh yeah, Liguana, it's much high energy density. That's true. But if you don't have to drive a car or you don't have to carry your pocket, your cell phone, you don't care about gravity, kinetic energy density. But if you are a company and you want to install a battery to store energy in your site, you are much more in Italy, in Northern Italy. It's a very densely populated area. You need to, every square meter has to be used at the best way possible. And most time, it's not a matter of even money, it's just a matter of that square meter. I use it for one reason or the other reason because there's no space, you know, and in London, I guess it's the same or anywhere in Europe, in the early days, because that normal, you need batteries close to what is energy's use. So where you have population, you have factories. So this is a very important point. That makes a great deal of sense. Just one thing I just want to be clear on and I think using for my audience, when we talk about lithium ion batteries, obviously everybody knows, I know cathode, electrolyte, separator, current collector. What are the elements of the system within a flow battery? So it sounds to me like you have tanks of electrolyte. Now, electrolyte is doing all the hard work in. It's presumably has been passed through this system and by pumps and piping and things like that. But it would be really interesting for me to understand a description, if you like, of the system and the various elements of it. Sure. So imagine you have these two tanks and where the liquid is. Then you have pipes that go through pump, the pump is liquid to a kind of an engine that actually looks like fuel cell. Actually, once there arrived originally from fuel cell technology, where you have a stack, that means it's, like a multi-layer cake, where you have, in this case, you don't have anode and cathode because you have the electrolyte, is the anode and cathode, light, which are the liquids. But from a hardware point of view, you have carbon electrodes, typically with filaments, carbon filaments, where all the redox reaction occur. And in between these two electrodes, you have ion selective membrane, where typically either protons or an ions pass through. And this is the same function as the separator in a lithium ion battery, basically. The difference is a very important difference because while in a lithium ion battery or sodium ion battery, you have these ions that move from a material, is detached from one material and enters in another material in the charge state and then goes back. This means that there is a stress in these materials. And this is the reason why lithium and sodium ion will have some limited capacity, lifetime. Instead, in these, in the redx flow batteries, you have only a surface reaction. So that means that you never have stress on the materials. That's why a redox flow battery typically can last for 25, 30 years on the active part, the stock. If you look at the electrolyte, if you look at the bananium electrolyte, basically is never rending, it lasts forever. Because you never have degradation, you can always recycle. And in any case, there is never an issue with risk of ability because it's very easy to precipitate bananium from the electrolyte and then maybe use for the steel industry, where actually is the main use today. It's really, really interesting. So, I think I'm getting the sense of you've got an enormous amount of scalability within this system. Because essentially, the scalability, I guess, is it just literally how much electrolyte you want to pump through the system? And I do understand it correctly. That's exactly correct. So, this is a very important point for flow batteries and the key differentiator. So, here, energy capacity and power are decapalled. So, they are physically decapalled. This means that you can size them totally independently. So, if you need six-hour duration or 12-hour hour duration, this just depends upon the amount of electrolyte that you put in your tank. That's it. Okay, so, this is another incredible benefit of flow batteries. Yeah, that makes sense. A couple of other quick things I just wanted to understand. And then I really like to understand some of the work you're doing in carbon deposition. Because one of the things I picked up from Fabio's answer a couple of minutes ago was obviously, there's a lot of work being done here at the point of which the carbon and the vanadium electrolyte are interfacing. I really want to talk about that interface. But I guess the other thing just occurred to me when we were talking there is the kind of issues we see in Lithium I about just like, dendrite formation and all those kind of things. They're just irrelevant in relation to this kind of technology. Yes, yes, correct. So, it's totally different mechanisms. And therefore, flow batteries does not suffer from, I mean, this type of problem of lithium ion. Let's talk about this interface. And you've obviously seen an opportunity to hugely improve, I guess, the surface area issues. I mean, surface area always is the issue in terms of interfaces. The greater the surface area, the better the reaction, the more efficient the reaction, the whole thing. The faster the reaction. The faster reaction, of course. So, yeah, it would be worth me understanding how you identify that opportunity and what steps, what was the journey, if you like, you took from that point to the point we reached today and all the work and the amazing things you've been able to do. Okay, that could be a long journey. We've got all day, we've got all day. Yes. So, let's first maybe point out, this is kind of an excellent point that is the first time that any of these interview have been asked to such a very fine technical detail. Imagine that with an adium, you are or any couple or typically you are in the order of between charge state, when the battery is fully charged, you have something like 1.2 volt. Okay, not as a matter. But if you 1.2, 1.3, if you put 1.2, 1.3 volt in water, even with a normal battery, as soon as you have a little metal, you will start producing hydrogen. Because you are in water and as soon as when you try to charge the state because actually the Redux reaction, why use the Vanadium is so nice and so keen for this kind of application because this was discovered something like 30 years ago in Australia, but basically you have Vanadium as full Redux state. And then the two liquids have Vanadium when the charge states are Vanadium to 1-5. the uncharch state are 3 and 4. And so when you charge a battery, you want to pass electrons for one side on the other in order to have all 1,8,5, 1,8,2. And then when you discharge, you go back in 1,8,3,1,2,4. Now, for this to happen, imagine this you have these ions in the water, and these ions in the water that do heat are electrode that can give them electrons or take from them electrons. Then to close the balance, you have protons that have to move on one side. That's why they're the role of the member. But now you imagine in order of high solubility and high conductivity, you are in a solution that is four molar sulfuric acid. So it's highly corrosive. And because of that, anything other than carbon would really suffer. Then you have to use carbon. - Because of its inertness. - Exactly. It's the most inert and cheapest material you can use in such a acidic environment. - Yeah. - Okay, that's the reason why from the early times of redux flow batteries, they start to use fels, carbon fels, made of the short fibers, carbon fibers, and typically used for example in thermal insulation, high temperature thermal insulation, or other thing. And in these, you have all these fibers, more or less carbon fiber, any carbon fiber is between five and 10 micron. You have all these fibers that where the ions arrive and exchange electrons and the redux reaction occur. Now, the problem is that when you try to, in order to drive more current through the system, you need for a given surface area, you need to increase the over potential. That means the window potential which you are operating. When you charge the battery, you are so close to the hydrogen potential that basically, if you push too hard, you want to charge too hard the battery, you start producing hydrogen. - Yeah. - Not nice, you can imagine to start, in other application, you want to produce hydrogen, but in this case in a battery, you don't want to produce hydrogen, because that will cause bubbles, we'll create, and plus, will destroy your electrolyte, because at that point, you have a physical degradation of your electrolyte. - You have a complex answer. - You are losing a lot. So, now, these, as I said, is given an area of exchange. But then, if you move around this problem, and say, okay, I cannot move the potential, but let's increase the surface area. In this way, the current that passes through the system is directly proportional. You have basically one ion that exchange, one electron, and that is the current. So, if I multiply by two times, three times, the amount of ions that can exchange electrons with the electrode, for a given voltage, I will increase the current. And increasing the current, for the same voltage, means increasing the power density of the system. - That makes perfect sense. - And that's the reason why, back in, was something like 2015, or something like that, even before that, I was, actually, I am by training, I'm a mechanical engineer, I started to study nanotechnology, nanomaterials in the US, and basically 2000. And I always, I, actually, initially my interest was more in making the machines to produce nanomaterials. But then, obviously, making a machine to produce something has to have a meaning, otherwise, there's not a purpose, otherwise, there is no reason why to make the machine. So then, and also an energy engineer. So, I always try to look for, identify, the bottleneck of an energy technology, in order to solve it. And as an energy engineer, I was training with, you know, gas turbines or steam turbines. And in that case, materials are very important. Think about gas turbines. You could not have jets, if you don't have extreme materials, but are not really the bottleneck. But when you go to any of these renewable, think about photovoltaics, batteries, materials are the key. Everything is played at level of materials. And this is the journey. So I was working in that contest, and I developed this system that is our nanoget technology, in order to produce nanoparticles, actually, of any kind in a controlled way, in a scalable way, because at that time, 25 years ago, when I started working, everybody was looking for means to produce large volumes on nanomaterials. Because it was easy to produce very few grams, but was difficult to produce a lot of large quantities. So something around 10 years ago, I developed this technology. And then I was at this technology, so at the tool, but I was looking for applications. And that's the reason why I came across this battery. I really liked it, because I thought, "Okay, this is a very promising solution for storage, or large quantities of energy, or renewables, but the issue was the cost." Again, the only issue of redux flow batteries are the cost, basically. So how can I drop the cost? I cannot do anything on the electrolyte side. That's more chemistry job. But on the stack size, then imagine if you can double triple the power density that for the same materials, because the cost is only materials. The same overall materials, I can extra, basically, the cost of the kilowatt drops by a factor of two, or three, or four. And this is our value proposition in Flonano. So basically, or today, a redux flow battery, a vanille-molex flow battery is half the electrolyte, half the stack, more or less. Now, with our technology, the cost per kilowatt of the stack drops significantly so that the overall cost of the technology goes down. Perfect. That's a brilliant explanation. I'm glad I asked that question, Malfaapier. Now, in terms of being able to succeed with that nanoparticle and deposition, I guess you have to have in your mind some kind of 3D understanding of what you're trying to create. It's not random deposition. I presume it's a very specific deposition that gives you maximized surface area. So how do you solve that part of the puzzle? - Wow, yeah, this is the very first time I've been asked this such a profound question. Thank you, Ken, because it's the first opportunity to discuss this like openly. Okay, so this is actually where the technology, our nanotechnology comes into. So imagine how it worked, first of all. We start from a mixture of argon and scatylene. So very cheap materials that we pass through an area where we have a plasma. What's a plasma? A plasma, you can say it's the same matter. State of matter you have on the sun, but actually in our case, it's more similar to some old neon lamps. I would say so it's a cold plasma, it's not hot plasma. There, basically we excite electrons and these electrons they kind of act as scissors in the catelline bonds. And once you catelline bonds, you, the carbons tend to stay with the carbon, the hydrogen with the hydrogen. So at the end, you end up with carbon particles and hydrogen. So this is an important point in our process. We have only the exhaust is hydrogen argon. So it's a very clean process. And this carbon then we control with some tricks, the way they aggregate in nanoparticles. These nanoparticles then are imaging the sources made in two separate areas. You have a high pressure area where the plasma is a reaction occur and a low pressure area where the sub-sities. And at that point is like a jet gun, let's say we shoot these nanoparticles on top of these fibers. And controlling the energy at which these particles arrive, we can control how dense they become. And as you said very properly, this is very important because the alternative, the typical usual method is to take us lorry and then just call that on the electrodes. When you do like that, you don't have any control or where your matter go. And instead in our case, we can design exactly the density of the material. When you do electrochemistry, it's not so much important the surface area. It's a bit more complex than that because you need to have what's called the roughness factor. So you need to have as much surface area as possible in a given micrometric volume. - Yeah. - On top. - Guys. has to be packed because the other problem is you have these fibers and the water has to actually the electrolyte is not really water, it's more it's denser than water and that's to pass through, you have to pump it through. So if you clog the pores, the pressure you will have an enormous amount of power, the pumping power to flow your electrolyte through. So you need to apply as much as little as possible disturbance to the hydrodynamic path of the electrode with the maximum possible surface area in that. So bottom line our electrodes typically are between two and five microns around the fibers with a very high surface area into that and given we optimize now for vanadium but we are in, so we are chemistry and mostly because we don't have any catalyst. So we just work on the surface area. So if for example we work with organics or other chemists where you need for example larger pores because you have larger molecules we can control the density of these particles and we can basically control how they diffuse inside because you have two per you have the conductive part of the flow through the electrode but then you need that last few microns whereas to diffuse and that depends critically on the size of the ions you have that they have to diffuse. So exactly as you mentioned is perfect it's a 3D micro vision I would say because you need to see in the micro and the technique we use can go typically to 300 microns of these thick pores, fibres system. We use cloth papers, nonwoven, we are optimizing also because we discovered that different battery producers for mechanical reason, manufacturing reason they want more rigid different substocks there and given so we are producing materials, optimizing materials for different applications. I could talk about this all day by the way I could listen Fabric I could listen all day I'm not going to contribute a great deal to this but I'm very much enjoying listening. We should really bring this to a conclusion what other things I'm interested in is your journey from here in terms of flow nano in terms of how does the business sit today what is the what is the next fight what does the next five years hold for flow nano in terms of the kind of market you're going to be involved in and the kind of development where it goes from here. In terms of roadmap maybe I start from where we are now so we firstly we let's say validated demonstrated this value proposition at Abundant, lab scale I would say up to 100 square centimeter within 2024 both internally and with the flow battery producer so this the the possibility to exploit our electrodes to drive much higher current and power density therefore improving the performances and ultimately reducing the cost of the technology. We then closed the first round of 1 million December 24 to run to operate the first upscale of the technology to pre industrial level and this is what we are doing this year 2025 right now scaled up the technology to 600 the square centimeter which is let's say already a industrially relevant scale because you can realize batteries flow batteries with this electrode size and we basically the milestone for this year is to demonstrate the value proposition at 600 square centimeter. Nowadays we are fundraising for the next milestone because next year we want to realize the first industrial line of production of our electrodes to then enter the market 2027 so we are we are working on a 3 million rounds to be able to create this first industrial line next year so this is let's say the next goal of the journey. Beyond this step basically the plan is to add the new production line each year in order to gradually increase the production capacity and the market penetration in the next let's say five years and this is from business and industrial perspective. On a moral let's say our endee perspective what we are also targeting to do is to let's say customize the product so the technology and the electrode for other applications. I can mention few so it could be for hydrogen production for CO2 electrochemical conversion water the contamination because let's say on one side we have already some are in the results in these fields. On the other we have already some requests from the market of nanostructure electrodes for these purposes but obviously we are start up so let's say we are trying to to be disciplined and so let's say first we want to address flow batteries market but in the next years for sure we will be able to further develop the product in order to address these other markets. That sounds eminently sensible and I wish you the very best of luck with that and by the way of course all your contact details will be on the show notes for the battery podcast so if anybody is listening to some thinking I need to get involved with these guys and I thoroughly do what you do there will be there will be opportunity to do that. That's been really fascinating. Laura I'm very grateful it's a great explanation of the work you're doing great the enthusiasm you have as well it really just comes through so loudly it's just wonderful to hear that. I wish you the very best luck with the work you're doing so now I hope to see you soon I we're running a big event in Barcelona I'm hoping you'll be you guys will be there be great if you work and I just have to say thank you very much indeed for being on the battery technology podcast. Can thank you it was it has been wonderful meeting you and this wonderful conversation together thank you for your interest for your support. A lot of beautiful and wonderful questions. Well and thank you thank you I appreciate it thank you very much and thank you can thank you about. The battery technology podcast is a copy-rises GSC media limited production. For more details for how to reach us you'll find our contact details in the show notes or at our website www.batterytechnologypodcast.com [Music]