WEBVTT
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Hello everybody, welcome to the Fire Science Show.
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We're talking batteries today, so an exciting episode coming your way.
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I had my good friend, professor Xinyan Huang from Hong Kong Polytechnic University visit us as a visiting professor at the ITB.
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We've spent a great two weeks doing research together and while his time in Poland, I could not miss an opportunity to conduct an interview with Xinyan, and he's been a guest on the podcast multiple times, mostly talking about AI and smart firefighting.
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His group is also huge on batteries and therefore we chose that the batteries would be the theme of this episode.
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And given that we are both experimentalists and we've talked a lot about the different battery hazards and battery challenges with batteries so far in the Fireside Show, I thought you know what An interesting episode could be on how do you set off a battery or ignite it where ignite is not the perfect word and you will hear the explanation in the episode how you set off a battery and experiment it's been said in a podcast by multiple guests it's quite difficult to ignite the batteries sometimes.
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Podcast by multiple guests.
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It's quite difficult to ignite the batteries sometimes, and in this episode we will talk about all different kinds of nasty stuff you can do to batteries nailing them, breaking them, dropping them, burning them, putting a coil around them, short-circuiting or overcharging.
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All of this is in this podcast episode.
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So if you're keen to learn how fire scientists, fire researchers, abuse the batteries, then you'll learn it in this episode episode.
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So if you're keen to learn how fire scientists, fire researchers, abuse the batteries, then you'll learn it in this episode, and I think this piece of information is very important.
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All of us, fire site engineers, are seeking for information about battery fires.
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All of us are dealing with some sort of battery hazards.
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And what you resort to?
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You resort to fire literature, but in the literature it's very difficult to distill the information presented and understand the information in the context of your own project.
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So in this case, knowing how exactly do scientists abuse the batteries can allow you to create better, more appropriate design scenarios for your own case.
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So I think in this case, it's critical for engineers to understand how the science is done, and that's what is in this podcast episode.
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So let's not prolong this anymore.
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Let's spin the intro and jump into the episode.
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Welcome to the Firesize Show.
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My name is Wojciech Wigrzyński and I will be your host.
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This podcast is brought to you in collaboration with Ofar Consultants, a multi-award-winning independent consultancy dedicated to addressing fire safety challenges.
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Colleagues are on a mission to continually explore the challenges that fire creates for clients and society, applying the best research experience and diligence for effective, tailored solution.
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In 2025, there will be new opportunities to work with OFR.
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Ofr will grow its team once more and is keen to hear from industry professionals who would like to collaborate on FHIR safety features this year.
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Get in touch at ofrconsultantscom.
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Hello everybody, I am joined here today by Professor Sinyan Huang from Hong Kong Polytechnic University, nice to have you here, Hi Wozniak.
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It's great to see you in person and have this interview.
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It's unusual for us to have an in-person interview, and it always makes me happy to see my guests not in the window of the computer.
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So I hope you're enjoying your stay in Poland so far.
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But let's do some serious work and let's talk about batteries, and first things first.
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You told me you like to play with batteries, so what do you have in mind saying that?
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So in general, I think a battery fire.
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From combustion point of view it's definitely a fascinating phenomenon.
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You always see new things like you have a very unconventional ignition, you have the flame, you have very different fuels sometimes generating sparks, explosions.
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So from scientific point of view, this is definitely a mystery to be solved.
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And the fun aspect the fun aspect is you always see some unexpected phenomenon.
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So from researcher point of view, if you see something unusual, you can write a new paper on that okay, yeah, that sounds like our sort of fun also, like I believe the world of batteries is.
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People would put a lot of different things into one umbrella of a battery, but there is so many chemistries, so many technologies out there, so many ways they they are used.
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Is there any specific focus you put on those?
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like the kinds of batteries that you test or their intended way of use.
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So, in general, the lithium-ion battery is definitely dominating the entire market.
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From the laptop to electric vehicle to large energy storage unit, they all use very advanced lithium-ion battery.
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Of course, there are some new battery chemistry involved, but most of them are still in the laboratory stage and not really in mass production.
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So I think everything we're talking about today is applied to the lithium-ion battery.
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I'm mostly concerned about stuff related to buildings.
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So from my perspective, I think all of it is interesting because today, an electric scooter is my design scenario for a building, electric vehicle is a design scenario for a building, a power wall in a garage is a scenario for a building.
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So yeah, all of this is relatable.
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Anyway, let's start because you're an experimentalist and you play a lot with those batteries.
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As you said, I wanted to go deep into igniting the batteries or starting the battery fires for the experiments, and I had some colleagues in the podcast.
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I had Francesco Restuccia, elena Fong, I had Professor Peter Sturm.
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Many of them shared the story that it's for them kind of hard to ignite the battery.
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I assume they were talking about, you know, devices, not just the single cell units.
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So maybe let's try and talk about how one can ignite the batteries for the purpose of research and maybe let's go from that point.
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So if you could just give me a brief overview of methods of igniting cells for experiments, thank you.
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I think you touched something very complex.
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So even when you propose, the question makes me thinking are we really using the right words to describe this process?
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For example, can we really say ignition, Because in many cases you don't see the flame?
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We usually consider you trigger some combustion reaction, then you can call it ignition.
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But in fact many cases something happens within the battery cell.
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Of course they release some flammable gas, but not every time they ignite it, and combustion or flame is not a necessary condition for the ignition of the battery and the major triggering reaction happens inside of the cell, the battery cell.
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I think we still know very little about what's really happening within the cell.
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There are different kind of theories.
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People say maybe it's some hydrogen attacked the cathode materials.
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Some people may think it's metal reactions.
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So it's definitely different from our conventional combustion fire.
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That is basically chemical reacting flow.
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We don't really have that flow inside of the battery cell.
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So that's the reason some people don't like the words of ignition.
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They use the thermal runaway.
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I think that's a reasonable description because ignition is one potential thermal runaway reaction.
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So how to trigger that ignition?
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I would say it's so different from our conventional fuel, from the gas fuel, liquid fuel, solid fuel there's no clear concept of ignition temperature here.
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Solid fuel there's no clear concept of ignition temperature here.
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So that makes us have to think a new approach to define that process, how to trigger the battery thermal runway or battery ignition, Because we don't know too much about the chemistry.
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It's different from the solid fuel, like pyrolysis dominated, so there are different stages or different steps of reaction inside the battery cell and they generate a lot of gases and these gases take some time to be released to the environment.
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Then you may have a second, the real combustion ignition in the gas phase.
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So I think what we really care, or most research conducted so far, is how to trigger the battery reaction inside.
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There are limited research talking about the ignition of the gas released from the battery.
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So perhaps, indeed, how you described it, the ignition is not the most perfect word to start, it's just a word that any fire scientist is familiar and keen to use Thermal runaway I also like that, but I think it describes two separate things.
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So one would be a thermal runaway of a cell, where it just heats up and ends up as a burned out cell, and another thing would be a thermal runaway of an entire battery pack, where we would be talking more about the propagation of the event through multiple cells.
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So I also think this would be completely two different mechanisms.
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But on one hand, you can just even though I don't have a good word for it I imagine that I have a battery in a state in which it is stable, in which it just, you know, gives me back energy, takes energy to charge itself.
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The chemical composition for it is as designed, there are no things happening with it, and suddenly I put it into a state which A it becomes unstable.
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So stuff happens to it Chemical reactions, mechanical damage, energy release.
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There are multiple phenomena which we'll definitely talk about.
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And the second thing I feel is irreversible from that point it's not that oh, I can like quickly cool it down and it's going to be back to its normal state.
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So I think it's like taking something from a stable phase into like irreversible chaotic phase but we really could use a good word for that transition.
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Yeah, I think you are touching a really good point.
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In fact, most of the combustion reaction is irreversible, especially in the solid phase, I would say.
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But there are more things that happen inside the battery.
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In fact, every time you charge it, you discharge it, you generate something new inside these battery cells, some like lithium, metal particles.
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This could be the major triggering for future more intense reactions, but I would say, every process is in general irreversible in that point of view.
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Of course, you cannot return those batteries.
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Who has went to the, or perhaps, if you find a way, you would be a very rich person.
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Yes, that's a very challenging part.
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Okay, so let's talk about how do we put those batteries into a state at which those events would come into play and they would cascade.
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I will start with one nail penetration and you go further, so let's explain.
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How do you actually?
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do it.
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So neo-channel penetration is one of the most widely used methods to trigger the battery thermal runway.
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It's reaching many different standards.
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It has its own good I would say quality or perspective, because it's relatively repeatable in that sense and it also mimics the real battery damage.
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For example, if you have two electric vehicles collide so you may have something inserted into the battery cell that triggers the thermal runway.
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So the nail test somehow mimics that kind of mechanical damage to the battery.
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But on the other hand if you put a nail into the battery, of course it will change the heat transfer process inside the battery.
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In our experiment we found if you put a very big needle you actually will cool the battery during the penetration process, especially if you use a copper one which has a very large thermal conductivity.
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So you actually cool down the battery during the nail penetration.
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So on the other side you also have the short circuit you may generate with the metal needle.
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So we also tried some non-metal needle to infer to the battery.
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You get very different phenomena.
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Really so.
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Okay, it's such a simple thing, a nail penetration, but there's so much aspects to that.
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In one of your papers I've read you also care about one, the depth at which it goes.
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Two, the velocity at which it goes.
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Three, also the battery orientation.
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So it matters if you nail it from up down or from the sides.
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I guess Now you bring more elements yes, so our original idea is for many battery jelly rolls there are multiple layers, so we want to quantify, okay, how many layers the nail breaks can trigger that some wrong way.
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Maybe there is a certain limit.
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But during the we found out it's so difficult to control that nail penetration, especially when the battery has a metal shell.
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You actually have to break that shell first and during that process it's not perfect.
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The battery may be deformed, so the jelly roll inside also deforms, so eventually it just makes us so difficult to control how much we actually break the layers of the roll.
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So finally we can only get a rough estimation.
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But definitely the penetration depths will also affect the thermal runway triggering.
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So it's not enough to just break a single sandwich of cathode anode and the separation between them in the battery.
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You have to get multiple.
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Yes, so definitely one single layer is not strong enough to trigger very intense.
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So in a wrong way, if you break more definitely, what's happening is more dramatic and you have more gas reaction.
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You start the chain reaction in a more intense way and how about nailing from a top or from the side?
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So if you nail from top, you not go that much through the layers, right, so you just squeeze them, or what?
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What happens then?
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so this is another very important point.
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So when we think about a battery, this is a three-dimensional object, so the thermal runway can also propagate in different directions inside the battery.
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Sometimes it can propagate along the Jerry Roll, sometimes it can propagate across different layers.
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The speed is actually different.
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So if you penetrate the battery from different directions you can get a very different result.
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And to bring this more into relationship with the real world.
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Does different nail penetration velocities or depths, does this reassemble some real world scenarios or is it just a way of parametrically studying it?
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So I guess every kind of standard test mimics some real situations, but during that simplification of course you ignore something, you deviate from the reality.
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But nonetheless these kind of standard tests still provide some good data for you at least to compare different batteries under different conditions.
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And we were just talking about a single cell right now, and that's also how we do it in our laboratory.
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We have a nail penetrator, a very sophisticated piece of equipment for something that really is a nail, a very large cabinet for a single nail to house.
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What if the cells are assembled into a battery and that battery is, you know, packed now within a case enclosure, and those, of course, can vary Like.
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You can have those packs that literally look like wrapped in a tin foil.
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They're very loose, something that you would put as a replacement package in whatever power bank you have.
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You could have a power bank device that you charge your phones in a plastic casing and you can have a structural floor of a car vehicle shielding those batteries.
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In the nail penetration test you only test the cell cell.
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Have you done any tests in which you would penetrate through a casing?
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And again, would that change the outcomes or so overall, this is a very challenging question.
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In fact, battery is not a material.
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It's different from like a certain plastic or like a wood, it's an assembly itself.
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It's a device, right?
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Yes, it's already a combination, even without complicated cases outside, because all the batteries they have films or case.
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It's a shell itself.
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So you have also multiple layers, different materials mixed inside, also some mechanical devices maybe to preventing or facilitating the venting.
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All these are actually really complex and of course you can go and try to measure the material property of these batteries, but that kind of experiment is very tiny, small scale, maybe some gravity analysis.
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If you only test the material, you're also not closing to the reality because there are more than 10 different materials inside a battery.
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So we don't really have a good test between the cell scale and the material scale.
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I think that's something research can be looking to it.
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We need some better test to quantify to avoid the complexity, but not just focusing on one or two materials.
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I was also asking from the perspective of the thermal runaway between the cells, because also the device is designed in a certain way to be able to take some heat away.
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Perhaps over-ventilate, over-pressure created by batteries.
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If you mechanically abuse the casing you also create new pathways in that system that perhaps change.
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But I guess that's a level of complexity we're studying.
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It will be very hard because of the numerous ways it can go.
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What do you do?
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Machine learning- so indeed, if we look at the battery like a regular fire in a room.
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So if you put a single battery cell into a battery pack or a battery energy storage container, you are like putting some fuel into the room.
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So you have to consider the built environment, ventilation, the radiation, smoke, movement, so that also creates another level of complexity.
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You have the safety of the battery itself, you have the overall environment, whether that's promoting the battery fire or kind of like stopping the battery fire.
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Yeah, very good.
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How about different mechanical abuse tests, Because the nail is not the only one.
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Are there other ways, like dropping the batteries, breaking them, half-squeezing them, hitting them?
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How do you abuse them mechanically besides nail?
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There are some standard tests where you can squeeze the battery to make it deform.
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I think some companies they also do the falling test, trying to throw the battery from a certain height and see how the battery will react.
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But these kind of tests are kind of like random.
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The repeatability is no better than flipping a coin.
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So that's the reason it's not written in many standards of these throwing tests.
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And I think the battery shape, the battery type is also not so standard.
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You have a big one, you have a small one, different chemistry inside as well.
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So I'm not sure if there will be some mechanical way to testing it.
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But to create some effects inside, those irreversible effects, whether they are like immediately, because I also know from my colleagues from other laboratories that you sometimes would abuse those batteries in different ways and they would, let's say, not go off, and then you put them in a safe space and they can go after three days, five days.
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There's famous cases of vehicle fires where the vehicle would go to a scrapyard and start going off multiple times after a very long period of time.
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So definitely some irreversible, like cascading effects are happening inside the battery, but it's not immediately.
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Perhaps the velocity of those changes is is very slow.
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I wonder, like, what mechanically has to happen inside the battery, like, do you have to break the separator?
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Do you have to physically change the condition of the cathode, anode, or or just, I don't know, squeezing layers, making them closer to each other, is is enough?
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I just wonder if, like high enough g-force acceleration on the battery, like you imagine, the vehicle is going into a crush and you just abuse this battery, but by a very rapid acceleration, but perhaps not mechanically breaking it At what point it becomes unstable and dangerous.
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Oh, that's another hard question I only have a hard question.
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Yes, I have to think more about that.
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So in general, for example, if you have a very heavy battery, if you throw it, then its impact definitely is larger.
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And internally, what's happening internally?
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That's something difficult to observe.
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Of course you can use like X-ray to scan it, but to capture a very dynamic process with the battery is moving.
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I feel that's quite challenging and I think a lot of things can be only guessed, because once you trigger the thermal runway, the battery basically burns out.
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You don't know what's going on at the beginning.
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So some better measurement mechanism is also important, but I would say, very challenging, because the battery file always destroys the device if you put anything too close.
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It's a challenging question, but I would call it a million-dollar question because we need to understand those mechanisms In this particular point of time, between the battery is abused and the battery is damaged up to a state where no diagnostics can be done.
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We need to understand that part to be able to figure out how to rule out dangerous batteries from the useful batteries.
00:23:10.127 --> 00:23:13.555
You know, because it's also from from the perspective.
00:23:13.555 --> 00:23:17.393
I mean batteries, energy, energy storage systems.
00:23:17.393 --> 00:23:21.346
This is a tool for sustainability, right that that's the reason we have them.
00:23:21.346 --> 00:23:23.528
And it's very unsustainable.
00:23:23.769 --> 00:23:56.383
If you throw out every suspicious battery and I also have a feeling that we're in Europe, in a fairly rich country, we can afford throwing those batteries, but someone will make a business out of taking those batteries that we throw away and just send them to some less fortunate place in the world where they desperately need devices like that, and we'll sell them there as a new device or as refurbished device without touching it, just taking the risk which we are not comfortable taking.
00:23:56.383 --> 00:23:57.707
So I think it's it's very.
00:23:57.707 --> 00:24:01.545
Do you know any diagnostics after mechanical abuse that you can use?
00:24:01.545 --> 00:24:05.613
Are you, if you abuse a battery and it doesn't go off, what to do with it?
00:24:06.394 --> 00:24:08.719
That's something we have trying to look into it.
00:24:08.719 --> 00:24:26.511
So if some battery, you're trying to penetrate it but it didn't go off as we expected, then maybe you can peel off and check what's inside the battery and sometimes you can see some area was triggering some reaction, some did not.
00:24:26.511 --> 00:24:33.891
You can also do some element analysis and see what kind of element increased, what chemical increased.
00:24:33.891 --> 00:24:47.698
But I feel what's really challenging is not the abusing by purpose, Because if you hit a battery, if you hit a battery, you expect it will go off.
00:24:47.698 --> 00:24:54.037
But in many cases you are driving a car, driving an electric vehicle, and suddenly self-ignite.
00:24:54.298 --> 00:24:58.190
That's something we're not really doing, the abusive condition.
00:24:58.190 --> 00:25:00.548
But still, the battery goes somewhere wrong.
00:25:00.548 --> 00:25:01.511
It goes to the fire.
00:25:01.511 --> 00:25:02.515
That's the challenge part.
00:25:02.515 --> 00:25:07.196
And something may happen inside a battery and that thing may be too small to be observed.
00:25:07.196 --> 00:25:08.461
That's the challenge part.
00:25:08.461 --> 00:25:16.345
And something may happen inside the battery and that thing may be too small to be observed by the current X-ray or like the other diagnostic method.
00:25:16.345 --> 00:25:26.775
If there are some good way can detect these small changes inside the battery, for these non-abuse conditions I would say this is a billion-dollar question.
00:25:28.405 --> 00:25:29.369
I'm interested, though.
00:25:29.369 --> 00:25:32.834
Well, I'm interested, but not for this reason.
00:25:32.834 --> 00:25:43.089
Okay, let's move into different abuses, because we just covered the mechanical abuse very widely, but there are different other abuses Electrical abuse, thermal abuse.
00:25:43.089 --> 00:25:44.454
Which would you like to follow?
00:25:45.045 --> 00:25:47.354
So I would say maybe just heat.
00:25:47.354 --> 00:25:53.958
I think heating is still the most widely used method to trigger the thermal wrong way.
00:25:53.958 --> 00:25:57.815
And when I say heating I say the external heating.
00:25:57.815 --> 00:26:01.875
And of course you can use a flame to heat the battery.
00:26:01.875 --> 00:26:05.955
You can also put some electrical coin to heat it.
00:26:05.955 --> 00:26:10.457
We also try some laser heating, trying to heat it remotely.
00:26:10.457 --> 00:26:19.076
These are all good ways to do the test, because when we do the test we want to do a repeatability check.
00:26:19.076 --> 00:26:25.815
If you have a good method of repeating the test result, that's a good method to trigger the thermal runway.
00:26:26.305 --> 00:26:37.287
Okay, but you said there's no ignition temperature, but is there a temperature at which you are fairly sure that the thermal runaway will occur in the battery when you're hitting it?
00:26:37.287 --> 00:26:46.720
Are you aiming at some specific temperature or are you noting down the temperature at which the thermal runaway did they start?
00:26:47.181 --> 00:26:55.188
I think if you really want a number, I would say 200 degree is a good number to start with and, of course, what different batteries.
