047 - Effective pressurization of compartments with Grzegorz Sypek

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<v Wojciech Wegrzynski>Hello and welcome to the Fire Science Show episode 49.

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<v Wojciech Wegrzynski>Great to have you here again.

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<v Wojciech Wegrzynski>Over the time.

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<v Wojciech Wegrzynski>I have noticed that there are some subjects in the podcast that generate.

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<v Wojciech Wegrzynski>above the usual.

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<v Wojciech Wegrzynski>Uh, interest in my audience.

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<v Wojciech Wegrzynski>And among these topics, there's definitely battery fires.

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<v Wojciech Wegrzynski>I think lithium-ion batteries, something that touches all of us.

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<v Wojciech Wegrzynski>as engineers, because it's something new and it's something that everyone expects us to handle in a way.

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<v Wojciech Wegrzynski>Even if in your scientific or engineering career, you don't necessarily touch the topic.

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<v Wojciech Wegrzynski>Eventually you will be asked about the questions of burning electrical vehicles or is energy storage at your house safe or not.

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<v Wojciech Wegrzynski>And I think we should be ready to meet.

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<v Wojciech Wegrzynski>Answer these questions, hopefully.

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<v Wojciech Wegrzynski>Based on science and evidence.

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<v Wojciech Wegrzynski>And this is what I'm trying to get you in the podcast and also get for myself in the podcast.

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<v Wojciech Wegrzynski>By inviting world-class experts.

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<v Wojciech Wegrzynski>We had Roeland Bischop from RISE who discussed electric vehicles.

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<v Wojciech Wegrzynski>We had DK Ezekoye who discussed the battery systems.

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<v Wojciech Wegrzynski>And today and other great scientists this time, a young talent from Kings College.

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<v Wojciech Wegrzynski>Dr.

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<v Wojciech Wegrzynski>Francesco who also happens to be my good friend and whom I admire a lot because his scientific scrutiny and the way how he performs research is on another level.

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<v Wojciech Wegrzynski>All the effort he puts into quantifying uncertain.

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<v Wojciech Wegrzynski>It is understanding the first principles.

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<v Wojciech Wegrzynski>In experiments he's doing.

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<v Wojciech Wegrzynski>The way, how he designs.

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<v Wojciech Wegrzynski>This is so good.

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<v Wojciech Wegrzynski>And you will hear that.

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<v Wojciech Wegrzynski>In the public is that he's really good.

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<v Wojciech Wegrzynski>And he knows what he's talking about.

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<v Wojciech Wegrzynski>Even though every second sentence he claims he's not an expert.

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<v Wojciech Wegrzynski>He certainly is.

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<v Wojciech Wegrzynski>And with Francesco, we go deep inside the cell, the battery.

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<v Wojciech Wegrzynski>To understand what makes battery.

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<v Wojciech Wegrzynski>Dangerous.

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<v Wojciech Wegrzynski>Why batteries burn.

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<v Wojciech Wegrzynski>What evens leads to a cascading failure of battery and.

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<v Wojciech Wegrzynski>Little more about if self heating can be an issue in batteries.

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<v Wojciech Wegrzynski>And that's very interesting.

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<v Wojciech Wegrzynski>Francesco is a.

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<v Wojciech Wegrzynski>Scientists who've made a career out of investigating self-heating and I find it's really great that he applied all this knowledge.

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<v Wojciech Wegrzynski>He gained on self heating of various materials to batteries now.

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<v Wojciech Wegrzynski>And that, that looks very, very promising.

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<v Wojciech Wegrzynski>So.

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<v Wojciech Wegrzynski>It's a tough episode, but I think if we want to be prepared to deal with batteries, to talk about batteries, to provide safety.

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<v Wojciech Wegrzynski>The facilities that deal with batteries, we need to understand what happens inside the battery.

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<v Wojciech Wegrzynski>And this episode is all about it.

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<v Wojciech Wegrzynski>I hope you will enjoy it.

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<v Wojciech Wegrzynski>And one more question to ask if you do enjoy, and if you'd like the podcast.

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<v Wojciech Wegrzynski>Maybe there's a chance you could leave a five star review in your podcast app.

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<v Wojciech Wegrzynski>That would help me a lot with my search engine optimization.

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<v Wojciech Wegrzynski>The algorithms love five stars.

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<v Wojciech Wegrzynski>So if possible, and.

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<v Wojciech Wegrzynski>You can just pause for a second, jump into the review part of your podcast app and leave something nicer.

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<v Wojciech Wegrzynski>I would be very grateful for that.

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<v Wojciech Wegrzynski>And  once you've done with that, please press play and enjoy the episode.

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<v Wojciech Wegrzynski>Let's go.

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<v Wojciech Wegrzynski>Hello everybody.

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<v Wojciech Wegrzynski>I'm today here with Dr.

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<v Wojciech Wegrzynski>Francesca Restuccia of Kings College in London.

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<v Wojciech Wegrzynski>Hey, Fracnesco

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<v Francesco Restuccia>Thank you for having.

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<v Wojciech Wegrzynski>Welcome.

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<v Wojciech Wegrzynski>Welcome, man.

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<v Wojciech Wegrzynski>happy to have you here.

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<v Wojciech Wegrzynski>And another take on batteries today.

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<v Wojciech Wegrzynski>the previous episodes about batteries were really well received.

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<v Wojciech Wegrzynski>So I assume the audience in the podcast is very interested in this technology and who's not in the world of fire where, being scared about the dangers of lithium-ion batteries.

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<v Wojciech Wegrzynski>Every.

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<v Wojciech Wegrzynski>Every day and last week had a, Mike Spearpoint on the show and he also brought, uh, numerous, things to consider, not to worry about what to consider when doing a car park, uh, with this, electric vehicles.

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<v Wojciech Wegrzynski>Actually, my Mike said that the first vehicles were electric that, that, that killed me.

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<v Wojciech Wegrzynski>That's first car parks were meant for electric cars now to think about that.

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<v Wojciech Wegrzynski>Well, you have run the full circle, but Francesco.

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<v Wojciech Wegrzynski>I didn't ask you to talk about electric cars.

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<v Wojciech Wegrzynski>We can discuss, the vehicles, on some other day.

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<v Wojciech Wegrzynski>I want some hardcore chemistry, man.

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<v Wojciech Wegrzynski>I want to finally know what the hell sits in the battery that, um, makes it, so scary to everyone around.

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<v Wojciech Wegrzynski>And I've learned that I should not, poke one with the nail to see what's inside.

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<v Francesco Restuccia>Accurate?

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<v Wojciech Wegrzynski>Yeah.

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<v Francesco Restuccia>The active material inside might not like it.

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<v Wojciech Wegrzynski>Yeah.

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<v Wojciech Wegrzynski>So yeah, please tell me what kinds of devils technology lies inside the lithium-ion, uh, cell and, uh, yeah, just so let's start with the basic, like, how is god damn battery built?

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<v Wojciech Wegrzynski>I know it's from outside,

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<v Francesco Restuccia>so I'm not a chemist, so any chemist might be horrified at my explanation cause I will simplify it.

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<v Francesco Restuccia>Um, but effectively.

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<v Francesco Restuccia>You have lithium-ion batteries.

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<v Francesco Restuccia>Um, and they're named after the active material that's inside.

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<v Francesco Restuccia>So for example, when you read lithium cobalt oxide, and you read L I C O O two or LCO, you know, that just means that  the active material is lithium cobalt.

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<v Francesco Restuccia>so the material.

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<v Francesco Restuccia>The cathode is made of is lithium cobalt or the other popular one is our Alamo.

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<v Francesco Restuccia>So lithium manganese oxide.

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<v Francesco Restuccia>Um, and again, it just means that the active material, so the Capto is made up of lithium manganese, in layers.

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<v Francesco Restuccia>So they have an oxide layer.

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<v Francesco Restuccia>and the third common one is NMC.

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<v Francesco Restuccia>So the three that you usually read most about since you mentioned vehicles is NMC, which is, basically a cathode combination of nickel, manganese, cobalt.

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<v Francesco Restuccia>and so they're usually used for power cells.

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<v Francesco Restuccia>So that's why they're used a lot in electric vehicles, because for example, when you read the 18 6, 5, 0, so.

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<v Francesco Restuccia>Research papers these days I read, that tried to do a sample cell start with the 18 65 0 cell.

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<v Francesco Restuccia>and that's just a cell that can deliver, I don't know, about two to 3000 mili ampere hours.

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<v Francesco Restuccia>So four to five, um,

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<v Wojciech Wegrzynski>I have a flashlight with just one cell and it, and it lights for 12 hours.

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<v Wojciech Wegrzynski>So for me, that's 12 hours of continuous light capacity in, such a cell.

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<v Francesco Restuccia>Uh, yeah.

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<v Francesco Restuccia>And then they can charge, so they have this specific energy.

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<v Francesco Restuccia>Right.

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<v Francesco Restuccia>it could be for example, NMC is.

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<v Francesco Restuccia>between 150 to 200, what our per kilo.

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<v Francesco Restuccia>So quite high energy dense, right?

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<v Francesco Restuccia>It's, it's, it's very, very big.

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<v Francesco Restuccia>Um, or then lithium manganese oxide one, which is less powerful one, right?

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<v Francesco Restuccia>There's a hundred still, right?

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<v Francesco Restuccia>It's a hundred watt hours per kilogram.

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<v Francesco Restuccia>So these.

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<v Francesco Restuccia>Quite a lot of energy that can be stored into them.

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<v Wojciech Wegrzynski>Okay, but that that's the cathode what's what's else in there.

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<v Francesco Restuccia>So you have the anode and the electrolyte, and in fact that's where the fire comes in.

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<v Francesco Restuccia>so these batteries are made up of  and then electrolyte substance inside and the electrolyte substance, varies.

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<v Francesco Restuccia>and in fact, it's usually quite hard to find out what the electrolyte is, when writing papers, uh, again, I am not a chemist.

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<v Francesco Restuccia>So when I started looking into this.

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<v Francesco Restuccia>I was a bit confused at what the electrolyte was.

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<v Francesco Restuccia>So I asked the chemist, I asked the chemical engineer, what is the electrolyte?

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<v Francesco Restuccia>And they said, it's full of additives.

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<v Francesco Restuccia>It's really complicated.

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<v Francesco Restuccia>It varies battery from battery.

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<v Francesco Restuccia>Um, and, but you always know what the cathode is because that's what the battery is named after.

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<v Francesco Restuccia>So, and that's what really is what provides the that's the energy density

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<v Wojciech Wegrzynski>So, so let's, let's agree on calling, uh, electrolyte, the battery juice

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<v Francesco Restuccia>Exactly.

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<v Francesco Restuccia>Yeah.

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<v Francesco Restuccia>So you have the juice, you have the anode and you have the cathode,  In, uh, for a fire problems, you know, why are we interested in these materials?

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<v Francesco Restuccia>So these are the materials within a battery when you cycle a battery, so you connect it up, you make it active, then electrodes flow, right?

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<v Francesco Restuccia>So you have your electrical cycle.

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<v Francesco Restuccia>and part of the energy that's released is your electrical energy.

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<v Francesco Restuccia>And part of it is what's known as Joule heating, right?

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<v Francesco Restuccia>So it was just the electrical, the cell impedance, your cell has some resistance and it releases some heat.

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<v Francesco Restuccia>Enjoy

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<v Wojciech Wegrzynski>One one second, once the back, uh, but, the way how it is built, I was actually quite confused when I watched the video of batteries being produced.

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<v Wojciech Wegrzynski>But because when I was a young kid, I had a passion for chemistry and blowing stuff up and actually setting things on fire, which has not changed significantly.

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<v Francesco Restuccia>I was about to say now you'd basically just do that for a

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<v Wojciech Wegrzynski>Yeah, I made it into living suits, actually.

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<v Wojciech Wegrzynski>That's quite cool.

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<v Wojciech Wegrzynski>Um, and I don't go to jail for that.

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<v Wojciech Wegrzynski>That that's another benefit.

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<v Wojciech Wegrzynski>, but, uh, I I've played with batteries, uh, by playing, I mean, I've disassembled them and they, there was like a graphite core.

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<v Wojciech Wegrzynski>Uh, there was a metal encasing and there was a black, all the smelling substance in it.

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<v Wojciech Wegrzynski>and, I think.

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<v Wojciech Wegrzynski>When I then, so 30 years fast-forward, uh, how batteries made that they were like, uh, sheets of, materials spins into a cylinder.

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<v Wojciech Wegrzynski>So it's like a continuous sandwich that's just, rolled,

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<v Francesco Restuccia>Yeah.

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<v Francesco Restuccia>So, so there also, so for the.

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<v Francesco Restuccia>Cylindrical batteries.

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<v Francesco Restuccia>You're effectively you start with the powder, right?

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<v Francesco Restuccia>So you start with, some material.

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<v Francesco Restuccia>Um, you Dan make really, really, really thin sheets.

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<v Francesco Restuccia>and then you rolled them up into jelly rolls.

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<v Francesco Restuccia>So you rolled them up into really, really all these really thin sheets into a drill.

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<v Francesco Restuccia>Then you compress it into account right.

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<v Francesco Restuccia>Of metal, so that it's protected.

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<v Francesco Restuccia>and then you.

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<v Francesco Restuccia>Basically put a lid on the top, which has the plus bit so that you can connect the wire to it.

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<v Francesco Restuccia>and on the bottom you put it on node, right?

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<v Francesco Restuccia>So you put the cap on the node,

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<v Wojciech Wegrzynski>the only when I saw this, how it is made, and only when I finally understood what is inside, because I, I had this image in my head from the chatter that it's like a road of something in the middle, a substance, and, the encasing that surrounds it only when they realize it's, layers of cathodes and anodes.

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<v Wojciech Wegrzynski>all like jelly rolls together in one continuous roll.

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<v Wojciech Wegrzynski>I've realized that this.

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<v Wojciech Wegrzynski>Why these, um, mechanical failure of batteries, like why, why crushing it, or why nailing it immediately creates such an effect because essentially you're suddenly connecting the things that should be separated.

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<v Wojciech Wegrzynski>you, you create the short circuit between the cathodes and anodes.

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<v Wojciech Wegrzynski>And because they are so close together because you probably want to have the biggest surface reacting all the time.

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<v Wojciech Wegrzynski>So there's like, those ones are hundreds of these layers together.

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<v Wojciech Wegrzynski>We Pierce to them completely and suddenly you've created hundreds of short circuits

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<v . Francesco Restuccia>You, you just pointed out the item that I may stop, honestly, in the rolling, you put a really, really thin membrane, which is called the separator that separates the two.

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<v . Francesco Restuccia>Right?

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<v . Francesco Restuccia>So it almost looks like a sheet of paper.

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<v . Francesco Restuccia>Right.

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<v . Francesco Restuccia>And then you fill it with the liquid electrolyte or the juice as we called it.

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<v . Francesco Restuccia>And then you put the cap.

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<v Wojciech Wegrzynski>Yeah.

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<v Wojciech Wegrzynski>So then when these short circuits, it's just all the energy that's stored in the battery and we try to put as much energy in it because of obvious reasons is it's just released in a split of second, actually.

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<v Wojciech Wegrzynski>and th that that's really.

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<v Wojciech Wegrzynski>Interesting, but I didn't want to talk that much about mechanical failure of batteries, because, uh, you also happen to be, quite a knowledgeable person about, self-feeding processes.

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<v Wojciech Wegrzynski>And, this is something I look forward.

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<v Wojciech Wegrzynski>So you you've started mentioning, um, how, why the battery produces heat.

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<v Wojciech Wegrzynski>Maybe you can, uh, finish that thought.

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<v Francesco Restuccia>Can I add to, can I add one thing just out of curiosity?

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<v Francesco Restuccia>Cause you, you actually sparked my curiosity on, you know, that the battery manufacturing, from what I hear from the manufacturing, people that matter the battery manufacturing process is done a certain way because it was adopted from existing industries.

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<v Francesco Restuccia>Right?

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<v Francesco Restuccia>So when we used to do Kodak films, right, we already had the industry for that, which is why the.

00:12:13.158 --> 00:12:19.519
<v Francesco Restuccia>Making, from what I understand from the material scientists, the process was just on the adoption of the one from the film industry that Kodak it.

00:12:19.519 --> 00:12:27.184
<v Francesco Restuccia>So, and that's why it was done that way, because from an engineering point of view, I always thought there must be a more optimal way to do it, but they already had the industry.

00:12:27.304 --> 00:12:29.735
<v Francesco Restuccia>So, so they just adopted an existing industry.

00:12:29.825 --> 00:12:31.325
<v Francesco Restuccia>But again, I'm not a material scientist.

00:12:31.325 --> 00:12:33.215
<v Francesco Restuccia>So this is from my manufacturing colleagues.

00:12:33.245 --> 00:12:37.595
<v Francesco Restuccia>Cause I asked why I like, from an engineering perspective, there must be a more efficient way to make this.

00:12:37.774 --> 00:12:41.735
<v Francesco Restuccia>Um, and that's also why now they're always looking at future batteries and you know, there are.

00:12:42.210 --> 00:12:44.761
<v Francesco Restuccia>Materials that they're trying to think about, but yeah.

00:12:45.136 --> 00:12:47.897
<v Wojciech Wegrzynski>But there were also prismatic cells, poach cells.

00:12:47.897 --> 00:12:50.927
<v Wojciech Wegrzynski>And I guess these are done in a slightly different way.

00:12:50.927 --> 00:12:52.216
<v Wojciech Wegrzynski>I, I would guess.

00:12:52.876 --> 00:12:53.147
<v Wojciech Wegrzynski>Okay.

00:12:53.287 --> 00:12:55.956
<v Wojciech Wegrzynski>So you started mentioning why the battery heats up.

00:12:55.956 --> 00:13:00.336
<v Wojciech Wegrzynski>it it's meant to produce electricity, but it also, because it has a resistance, it's not a superconductor.

00:13:00.871 --> 00:13:04.322
<v Wojciech Wegrzynski>It must produce a heat at the same time.

00:13:04.621 --> 00:13:11.131
<v Wojciech Wegrzynski>So first, what are the rates like how much a battery heats and how much it gives back electricity?

00:13:11.557 --> 00:13:14.466
<v Francesco Restuccia>Oh, so the vast majority is electricity.

00:13:14.466 --> 00:13:18.517
<v Francesco Restuccia>So the extreme cases, the one you pointed out earlier, which is when you start having short circuits, right?

00:13:18.697 --> 00:13:22.956
<v Francesco Restuccia>Cause if you start having short circuit, then you increase that resistance of your battery massively.

00:13:23.197 --> 00:13:31.326
<v Francesco Restuccia>Or if your battery starts degrading, then that impedance internal impedance increases the higher, the internal impedance, the more Joule heating you produce.

00:13:31.596 --> 00:13:33.336
<v Francesco Restuccia>So, you know, a fresh battery, new.

00:13:34.011 --> 00:13:41.572
<v Francesco Restuccia>With no degradation with no, short-circuits probably, I would guess 99% electricity, 1% teach, right.

00:13:41.812 --> 00:13:44.782
<v Francesco Restuccia>Or maybe 2%, very, very small amount of it is heat.

00:13:45.052 --> 00:13:49.192
<v Francesco Restuccia>Um, but the more your battery degrades, the more internal impedance you create.

00:13:49.192 --> 00:13:50.721
<v Francesco Restuccia>And so the higher the heat.

00:13:50.721 --> 00:13:55.749
<v Francesco Restuccia>And so actually it's not a constant, it depends on your batteries, aging, how much it produces.

00:13:55.899 --> 00:13:56.408
<v Francesco Restuccia>And it depends.

00:13:57.075 --> 00:14:03.595
<v Francesco Restuccia>the most extreme cases when you start creating a short circuit, , because then that short circuit creates a peak of impedance, right?

00:14:03.865 --> 00:14:10.225
<v Francesco Restuccia>And so then a large portion of your energy stored becomes released in heat rather than electricity.

00:14:10.543 --> 00:14:12.479
<v Francesco Restuccia>and that's a time issue as well because.

00:14:13.169 --> 00:14:14.700
<v Francesco Restuccia>we do heat transfer for fire, right?

00:14:14.700 --> 00:14:17.610
<v Francesco Restuccia>So transfer is  a time dependent process.

00:14:17.610 --> 00:14:24.110
<v Francesco Restuccia>And so if your heat is released very slowly, over a long period of time, you go into my other area of expertise, self heating.

00:14:24.360 --> 00:14:29.850
<v Francesco Restuccia>If your heat is released very, very quickly, then you have a local peak of temperature increase.

00:14:29.940 --> 00:14:32.820
<v Francesco Restuccia>And then the rates chemistry rates are exponential.

00:14:32.820 --> 00:14:34.710
<v Francesco Restuccia>And so they go up much, much faster.

00:14:34.855 --> 00:14:42.445
<v Wojciech Wegrzynski>But, but even if it's 1%, , and let's assume you're, , car driving takes, I don't know, 30 kilowatts, 50 kilowatts, a hundred kilowatts.

00:14:42.445 --> 00:14:51.349
<v Wojciech Wegrzynski>If, if, uh, if you enjoy your life as good cars, but, it takes like, let's say 50 kilowatts, a kilo per hour.

00:14:51.708 --> 00:14:56.642
<v Wojciech Wegrzynski>And even if it's just a 1%, that's 500 Watts released into a metal tank.

00:14:56.653 --> 00:14:58.423
<v Francesco Restuccia>And even more important than the charging, right?

00:14:58.423 --> 00:15:00.583
<v Francesco Restuccia>So, you know, we always talk about fast charging.

00:15:00.864 --> 00:15:08.423
<v Francesco Restuccia>If you use all of your battery in two hours driving, but then you want to charge it in 10 minutes, you're doing the exact same electrical cycle backwards.

00:15:08.423 --> 00:15:08.634
<v Francesco Restuccia>Right.

00:15:08.874 --> 00:15:09.714
<v Francesco Restuccia>So instead of.

00:15:10.839 --> 00:15:13.479
<v Francesco Restuccia>The energy going one way, it's going the other, but you're still producing heat.

00:15:13.839 --> 00:15:17.379
<v Francesco Restuccia>The heat generation, the Joule heating is still based on that impedance.

00:15:17.379 --> 00:15:20.708
<v Francesco Restuccia>But if you want to, that's the biggest problem they have with fast charging, right?

00:15:20.739 --> 00:15:25.269
<v Francesco Restuccia>Is if you want to charge your electric vehicle in five minutes, which is impossible at the moment.

00:15:25.298 --> 00:15:30.528
<v Francesco Restuccia>But imagine you did the amount of heat that you will be producing is massive because.

00:15:31.369 --> 00:15:33.581
<v Francesco Restuccia>Kilowatts that you're putting in are huge.

00:15:33.619 --> 00:15:47.958
<v Francesco Restuccia>and so the charging rate and the discharging rate, so you're using up of your vehicle that electricity higher discharge rate means higher C number is what they call it in the battery world would mean more heat produced per unit time.

00:15:48.250 --> 00:15:52.876
<v Wojciech Wegrzynski>yeah, I was , always surprised when I saw this information about.

00:15:53.451 --> 00:16:02.509
<v Wojciech Wegrzynski>Quick chargers and people trying to connect, like I don't half megawatt charger into a truck and I'm like, I run the fire laboratory.

00:16:02.509 --> 00:16:07.072
<v Wojciech Wegrzynski>We do run a, high capacity fans in high temperatures.

00:16:07.491 --> 00:16:14.812
<v Wojciech Wegrzynski>When I have to test a hundred kilowatt fan, it adds so much to my logistics because it's like huge, huge cords.

00:16:14.812 --> 00:16:15.741
<v Wojciech Wegrzynski>It's dangerous.

00:16:15.772 --> 00:16:17.991
<v Wojciech Wegrzynski>It's a lot of electricity, man.

00:16:18.826 --> 00:16:20.027
<v Wojciech Wegrzynski>Then you just go.

00:16:20.027 --> 00:16:20.326
<v Wojciech Wegrzynski>Yeah.

00:16:20.326 --> 00:16:25.996
<v Wojciech Wegrzynski>And I will just block this half megawatts socket into my current, go for a coffee.

00:16:26.267 --> 00:16:28.226
<v Wojciech Wegrzynski>, that scares the hell out of me.

00:16:28.226 --> 00:16:37.976
<v Wojciech Wegrzynski>But I guess the, I hope they've worked, it worked it over, but again, if it's just, if it's just 1% that goes into heat, that's a considerable amount of heat

00:16:38.163 --> 00:16:40.197
<v Francesco Restuccia>And I've had this issue when designing my lab.

00:16:40.226 --> 00:16:45.027
<v Francesco Restuccia>So when I was designing my lab, I wanted to have scalability for my battery testing.

00:16:45.027 --> 00:16:54.653
<v Francesco Restuccia>So I have a nice big battery tester, but the first question I got from the health and safety team, as you know, the crazy academic who wants to put something in is how much heat will you be generating?

00:16:54.653 --> 00:16:57.057
<v Francesco Restuccia>Because this, as you've asked us to put in.

00:16:57.097 --> 00:17:00.967
<v Francesco Restuccia>A current limiter of 60 amps, 60 amps is very high.

00:17:01.148 --> 00:17:03.248
<v Francesco Restuccia>So how much heat are you going to be producing?

00:17:03.398 --> 00:17:12.708
<v Francesco Restuccia>So I had to do some back of the envelope calculations, not with 1% heat, but you know, I, I went with 10%, , just to, maximize, but yeah, it is, it is a huge concern.

00:17:12.827 --> 00:17:21.258
<v Francesco Restuccia>Um, from a research side in the lab, I can imagine from a design side when you're building the cars or building the charging stations just as big, right.

00:17:21.755 --> 00:17:24.125
<v Francesco Restuccia>Because you have more people using it, you have more chance of error.

00:17:24.125 --> 00:17:25.775
<v Francesco Restuccia>You have more risk of a failure.

00:17:26.015 --> 00:17:26.285
<v Francesco Restuccia>, Wojciech Wegrzynski: Okay.

00:17:26.285 --> 00:17:36.071
<v Francesco Restuccia>So before we go into the battery, finally igniting, we've discussed, the, the heating processes due to short circuits, uh, mechanical failure.

00:17:36.402 --> 00:17:40.884
<v Francesco Restuccia>We've briefly discussed the, charging and, and just energy consumption.

00:17:41.365 --> 00:17:49.946
<v Francesco Restuccia>And let's go into self heating, I guess if I can take it a step back in between the two, I can explain the stages maybe of the heating that might help.

00:17:50.096 --> 00:17:54.866
<v Francesco Restuccia>So in a battery, , you have reactions happening at different temperatures and you're going to get to self eating, um, with.

00:17:55.571 --> 00:18:00.731
<v Francesco Restuccia>Happy to talk about, but I guess maybe it's when your battery, it doesn't matter how your battery is heating up, right.

00:18:00.731 --> 00:18:01.932
<v Francesco Restuccia>Self-feeding or not selfie thing.

00:18:02.172 --> 00:18:08.682
<v Francesco Restuccia>, when your battery reaches a certain level of temperature and it cannot dissipate the heat, usually that's about a hundred degrees.

00:18:08.922 --> 00:18:12.192
<v Francesco Restuccia>Uh, when you get to a hundred degrees, your solid electrolyte interface.

00:18:12.521 --> 00:18:17.688
<v Francesco Restuccia>Um, so that's the thin layer, that is on your cathode.

00:18:18.462 --> 00:18:20.262
<v Francesco Restuccia>It starts to decompose.

00:18:20.292 --> 00:18:20.653
<v Francesco Restuccia>Right.

00:18:20.712 --> 00:18:26.383
<v Francesco Restuccia>Um, and so if that starts to decompose, that causes exothermic reactions and that adds its own heat.

00:18:26.712 --> 00:18:28.843
<v Francesco Restuccia>So, you know, we say it's an active material.

00:18:29.217 --> 00:18:36.836
<v Francesco Restuccia>and as an active material, as I, when I think of chemistry, the reaction rates from a combustion side always happen.

00:18:36.987 --> 00:18:39.567
<v Francesco Restuccia>Exothermic reactions always happen at different temperature ranges.

00:18:39.567 --> 00:18:39.807
<v Francesco Restuccia>Right.

00:18:40.106 --> 00:18:43.150
<v Francesco Restuccia>And so in the battery, usually you first have.

00:18:43.934 --> 00:18:56.865
<v Francesco Restuccia>Heat being created from the solid electrolyte interface decomposing, then from the electrolyte electrode decomposition at a higher temperature, and then from the electrolyte decomposition at the higher even temperature.

00:18:57.045 --> 00:19:03.285
<v Francesco Restuccia>And so you have the inner materials, those active materials they were asking about all start reacting at different temperatures.

00:19:04.170 --> 00:19:04.500
<v Wojciech Wegrzynski>Okay.

00:19:04.500 --> 00:19:07.349
<v Wojciech Wegrzynski>So can we just remove the one that reacts to the lowest temperature and

00:19:07.440 --> 00:19:07.650
<v Francesco Restuccia>Bye.

00:19:07.650 --> 00:19:12.180
<v Francesco Restuccia>You need to, you, you need you that that's what causes the battery to work.

00:19:12.930 --> 00:19:15.720
<v Wojciech Wegrzynski>Can we make a magic material that will go off at 200?

00:19:15.740 --> 00:19:16.740
<v Wojciech Wegrzynski>Not another 100.

00:19:16.813 --> 00:19:24.192
<v Francesco Restuccia>the SEI layer, so to say the solid electrolyte, the composition layer is just like a passivating layer that forms on the electrodes.

00:19:24.373 --> 00:19:28.123
<v Francesco Restuccia>And so as your battery operates, you're forming this layer.

00:19:28.242 --> 00:19:29.053
<v Francesco Restuccia>And so your.

00:19:29.501 --> 00:19:34.271
<v Francesco Restuccia>it's kind of covering the intercalated lithium, lithium in the negative electrode.

00:19:34.362 --> 00:19:42.011
<v Francesco Restuccia>Um, and so when it starts decomposing, then the intercalated lithium is exposed.

00:19:42.011 --> 00:19:42.281
<v Francesco Restuccia>Right.

00:19:42.311 --> 00:19:45.912
<v Francesco Restuccia>And so it's that exposed to the electrolyte.

00:19:45.912 --> 00:19:47.892
<v Francesco Restuccia>And so it causes even more reactions.

00:19:48.602 --> 00:20:02.877
<v Wojciech Wegrzynski>So basically you enter a path of no return and, this additional heat generated by this exothermic reaction will hit the thing more up, up to a next point where another thing will start contributing.

00:20:02.877 --> 00:20:06.261
<v Wojciech Wegrzynski>And another thing, another thing, and you end up with, this thermal runaway, I guess there's this.

00:20:06.592 --> 00:20:06.832
<v Francesco Restuccia>Yes.

00:20:07.213 --> 00:20:12.583
<v Francesco Restuccia>And actually the last material ironically, which is maybe slightly cutter, we name all the batteries from the active materials.

00:20:12.583 --> 00:20:12.792
<v Francesco Restuccia>Right.

00:20:12.792 --> 00:20:16.692
<v Francesco Restuccia>So I said, I never, but that's usually the last material that Dan starts.

00:20:17.073 --> 00:20:19.002
<v Francesco Restuccia>Cause that is the one at the most high temperature.

00:20:19.002 --> 00:20:21.762
<v Francesco Restuccia>So that's actually the last bit that starts creating heat.

00:20:21.762 --> 00:20:30.133
<v Francesco Restuccia>And do you usually, um, because normally at the higher, higher temperatures than the positive electrode can start becoming unstable and decomposed.

00:20:31.528 --> 00:20:36.867
<v Wojciech Wegrzynski>let's say, uh, the, the, all the heat released in a fire of a single cell is a hundred percent.

00:20:37.347 --> 00:20:40.887
<v Wojciech Wegrzynski>Do we know how much each of these steps contributes to this?

00:20:40.917 --> 00:20:41.307
<v Wojciech Wegrzynski>Uh,

00:20:41.662 --> 00:20:43.498
<v Francesco Restuccia>Oh uh, complicated.

00:20:43.498 --> 00:20:45.928
<v Francesco Restuccia>So it depends on the state of charge of the battery.

00:20:46.198 --> 00:20:48.867
<v Francesco Restuccia>Um, so it depends also how much energy is in the battery.

00:20:49.048 --> 00:20:51.357
<v Francesco Restuccia>Um, and it depends on what electrolyte is being used.

00:20:51.538 --> 00:20:54.837
<v Francesco Restuccia>So there are some papers that have looked at the different, contributions.

00:20:55.962 --> 00:21:06.073
<v Francesco Restuccia>And from a self-heating side, we have looked at the contribution in temperature rates of the different rates have increased, but not the individual materials.

00:21:06.343 --> 00:21:07.573
<v Francesco Restuccia>So we looked at the temperature

00:21:07.653 --> 00:21:08.042
<v Wojciech Wegrzynski>Okay.

00:21:08.042 --> 00:21:10.053
<v Wojciech Wegrzynski>So, so from this temperature to this is this

00:21:10.153 --> 00:21:10.423
<v Francesco Restuccia>yeah.

00:21:10.482 --> 00:21:10.843
<v Francesco Restuccia>Yeah.

00:21:11.113 --> 00:21:16.355
<v Francesco Restuccia>So at the macro level, rather than at the chemistry level, at the chemistry level, Quite a challenge.

00:21:16.355 --> 00:21:21.755
<v Francesco Restuccia>So because you start having, so the materials that react to start forming other materials.

00:21:21.755 --> 00:21:26.214
<v Francesco Restuccia>And in fact, if yourself, then over pressures, for example, you were talking about prismatic cells.

00:21:26.214 --> 00:21:37.384
<v Francesco Restuccia>So if we earlier, so if your personal ethics cell bursts, the safety event, and then some of this gases that are being produced inside, start reacting with the oxygen outside, then that causes even more reactions.

00:21:37.444 --> 00:21:39.471
<v Francesco Restuccia>And the gases that are being produced are.

00:21:39.703 --> 00:21:40.507
<v Francesco Restuccia>Very complicated.

00:21:40.507 --> 00:21:44.467
<v Francesco Restuccia>So there are a lot of carbohydrates, but there's also hydrochloric.

00:21:44.586 --> 00:21:47.136
<v Francesco Restuccia>Um, Gus is a hydrofluoric.

00:21:47.406 --> 00:21:52.744
<v Francesco Restuccia>Um, and so it can get, yeah, um, very complicated, very quickly.

00:21:52.859 --> 00:22:16.093
<v Wojciech Wegrzynski>well, I guess this is fundamental to understand this, Macro fires of batteries because they start like the, the ones that are from the individual cells, because obviously if the, if the car park is on fire and your battery catches fire from that heat, I guess the cell chemistry hoods not mattered that much.

00:22:16.152 --> 00:22:17.051
<v Francesco Restuccia>It just acts as a heat

00:22:17.307 --> 00:22:17.727
<v Wojciech Wegrzynski>it's as

00:22:17.892 --> 00:22:19.152
<v Francesco Restuccia>once you have a heat source.

00:22:19.211 --> 00:22:19.571
<v Francesco Restuccia>yes.

00:22:20.142 --> 00:22:21.761
<v Francesco Restuccia>It's the same with our pool fires.

00:22:21.761 --> 00:22:21.971
<v Francesco Restuccia>Right?

00:22:22.001 --> 00:22:32.182
<v Francesco Restuccia>If you have a pool fire, once your pool fire has a size, it's the heat release rate from that size, doesn't matter if you were burning,, C H C7 or C eight, right?

00:22:32.261 --> 00:22:34.961
<v Francesco Restuccia>, it's the heat that's being released from those flames.

00:22:35.021 --> 00:22:38.402
<v Francesco Restuccia>Uh, so he really straight, but you asked me earlier about modifying.

00:22:39.200 --> 00:22:40.220
<v Francesco Restuccia>Items inside.

00:22:40.789 --> 00:22:41.720
<v Francesco Restuccia>You're not far off.

00:22:41.750 --> 00:23:00.710
<v Francesco Restuccia>I actually think that is one of the solutions is, , if you can change the additives and the electrolytes to add things that maybe passively act for the duration of your battery life, but then if your temperature is above a certain temperature, they act as a suppressant or the heat remover or whatever it is that could be a solution.

00:23:00.740 --> 00:23:07.160
<v Francesco Restuccia>Um, or, you know, if you can have maybe a ceramic coated separator in between right then the.

00:23:07.930 --> 00:23:10.690
<v Francesco Restuccia>It's harder to, create short circuits from, right.

00:23:10.720 --> 00:23:11.410
<v Francesco Restuccia>Um, okay.

00:23:11.410 --> 00:23:12.250
<v Francesco Restuccia>Yeah, that's a cost.

00:23:13.924 --> 00:23:14.615
<v Francesco Restuccia>Yes, exactly.

00:23:14.615 --> 00:23:17.704
<v Francesco Restuccia>It, a cost that's a weight and weight is a big problem.

00:23:17.765 --> 00:23:19.835
<v Francesco Restuccia>Uh, but yeah, that could be what way.

00:23:19.894 --> 00:23:23.585
<v Francesco Restuccia>Um, so it's, it can start from the chemistry modification so you can change the catheter.

00:23:23.585 --> 00:23:30.244
<v Francesco Restuccia>You can change the, I know you can change the attitudes and the electrolytes, or as we are not chemist, neither myself nor you.

00:23:30.664 --> 00:23:32.734
<v Francesco Restuccia>we, we can look at the bigger size, right?

00:23:32.734 --> 00:23:34.325
<v Francesco Restuccia>So we can look at, a bigger size.

00:23:35.140 --> 00:23:39.277
<v Francesco Restuccia>Well, what can we do with a battery management system or what can we do with, separation, right?

00:23:39.517 --> 00:23:43.386
<v Francesco Restuccia>Uh, separation between batteries within a pack.

00:23:43.656 --> 00:23:45.126
<v Francesco Restuccia>Uh, what can we do with detection?

00:23:45.126 --> 00:23:47.346
<v Francesco Restuccia>What can we do with different suppression

00:23:47.366 --> 00:23:49.166
<v Wojciech Wegrzynski>I think it's a brilliant starting point.

00:23:49.166 --> 00:23:57.819
<v Wojciech Wegrzynski>And despite the, like, I'm, I'm on the edge of understanding, I understand literally up to 60% of what you said.

00:23:57.819 --> 00:24:01.869
<v Wojciech Wegrzynski>So I think, and I think I'm quite successful, but I'm going to take away.

00:24:02.109 --> 00:24:10.250
<v Wojciech Wegrzynski>The take away is, , I think there's this thought that, uh, the things happen at certain temperatures and, uh, essentially you, you, you reach a track.

00:24:10.795 --> 00:24:16.404
<v Wojciech Wegrzynski>Point which initiates a set of events that lead to failure.

00:24:16.404 --> 00:24:23.944
<v Wojciech Wegrzynski>And I think this, uh, this is a great takeaway because, it doesn't happen by, by pure magic or unicorn farts.

00:24:23.974 --> 00:24:25.904
<v Wojciech Wegrzynski>It's, chemistry that leads to that.

00:24:25.904 --> 00:24:29.775
<v Wojciech Wegrzynski>And you've already mentioned many things that influence this, thing.

00:24:30.430 --> 00:24:44.585
<v Wojciech Wegrzynski>The energy capacity of the battery, the sorry, the charging state of the battery, the processes is a charging is a discharging, the, chemistry of the electrolyte, because I think this is, this is where the confidential magic is happening.

00:24:44.913 --> 00:25:11.317
<v Wojciech Wegrzynski>if everyone is using the same cathode materials, I guess they're playing with electrolytes to differentiate and pattern some things to earn more coin on, on,  and finally, maybe not exactly, but you have a rough idea when this thing becomes dangerous, because if you don't enter this cascading, level of discuss this cascade of events leading to a major failure, you don't get a major failure.

00:25:11.731 --> 00:25:12.001
<v Francesco Restuccia>Yes.

00:25:12.071 --> 00:25:13.781
<v Francesco Restuccia>And we've talked to very generally, right?

00:25:13.781 --> 00:25:19.241
<v Francesco Restuccia>So it can also be, so I've talked about the system in charter discharge or in use, but also passive, right.

00:25:19.392 --> 00:25:20.442
<v Francesco Restuccia>That's where self-heating comes in.

00:25:20.442 --> 00:25:23.142
<v Francesco Restuccia>When you mentioned self-heating is, you know, what's a active circuit.

00:25:23.152 --> 00:25:27.231
<v Francesco Restuccia>So I said into charging or discharging rates, but batteries still react.

00:25:27.231 --> 00:25:29.932
<v Francesco Restuccia>You know, your battery is always reacting and when it's not connected, right.

00:25:29.932 --> 00:25:33.788
<v Francesco Restuccia>It's still, it's still producing heat, even in open circuit conditions.

00:25:33.847 --> 00:25:34.178
<v Francesco Restuccia>Um,

00:25:34.428 --> 00:25:34.728
<v Wojciech Wegrzynski>okay.

00:25:34.817 --> 00:25:41.557
<v Wojciech Wegrzynski>I, there was a, , Guillermo broad on Twitter, , some instruction for a laptop, which mentioned fire in so many places.

00:25:41.557 --> 00:25:47.807
<v Wojciech Wegrzynski>And I've responded showing a picture of my old laptop that two years ago, my battery has suddenly swollen.

00:25:48.637 --> 00:25:49.688
<v Wojciech Wegrzynski>Three times its size.

00:25:49.688 --> 00:25:52.778
<v Wojciech Wegrzynski>And I recall it happened literally overnight.

00:25:52.778 --> 00:25:54.548
<v Wojciech Wegrzynski>I didn't use the laptop.

00:25:54.577 --> 00:25:59.582
<v Wojciech Wegrzynski>So, when the, the device is idle, I guess there are still things, , , happening in

00:25:59.737 --> 00:26:01.866
<v Francesco Restuccia>Yeah, because mass diffusion, right.

00:26:01.896 --> 00:26:05.797
<v Francesco Restuccia>You know, you, you're always going to have some electrodes travel through.

00:26:05.880 --> 00:26:09.599
<v Francesco Restuccia>you're always going to have diffusion through your, from one side to the other.

00:26:09.599 --> 00:26:10.859
<v Francesco Restuccia>So your battery will, oh.

00:26:10.859 --> 00:26:16.589
<v Francesco Restuccia>Even when it's not connected, your internal resistance is in itself a connection.

00:26:16.589 --> 00:26:16.829
<v Francesco Restuccia>Right.

00:26:17.650 --> 00:26:21.160
<v Francesco Restuccia>so you're going to have passive resistance, not just active

00:26:21.230 --> 00:26:23.779
<v Wojciech Wegrzynski>Okay, but will it happen when the battery's discharged?

00:26:23.779 --> 00:26:25.230
<v Wojciech Wegrzynski>Like when it's a charged level?

00:26:26.545 --> 00:26:28.555
<v Francesco Restuccia>When charged double zero, that's the dust.

00:26:28.585 --> 00:26:30.444
<v Francesco Restuccia>You don't get to that condition cause that's really bad.

00:26:30.505 --> 00:26:33.714
<v Francesco Restuccia>So when everything is on one end, um, your.

00:26:34.404 --> 00:26:38.244
<v Francesco Restuccia>You're basically I've done have exposed the material.

00:26:38.244 --> 00:26:49.974
<v Francesco Restuccia>So remember I said that you're creating this SEI layer, if you've moved everything to one end, so the battery's completely at zero you're, you will have exposed that and it's not designed to be exposed.

00:26:50.244 --> 00:26:53.275
<v Francesco Restuccia>And so, in fact, I think it starts reacting even further.

00:26:53.454 --> 00:26:53.724
<v Francesco Restuccia>Uh,

00:26:53.785 --> 00:26:58.285
<v Wojciech Wegrzynski>so, so you're telling me my laptop is lying to me when it says the charge zero.

00:26:58.845 --> 00:26:59.535
<v Francesco Restuccia>Absolutely.

00:26:59.535 --> 00:27:04.335
<v Francesco Restuccia>Yeah, there is no such, yeah, you, you will never allow a device to go down to

00:27:04.555 --> 00:27:04.914
<v Wojciech Wegrzynski>Okay.

00:27:04.974 --> 00:27:05.934
<v Wojciech Wegrzynski>But what does that mean?

00:27:06.528 --> 00:27:07.008
<v Wojciech Wegrzynski>That's cool.

00:27:07.268 --> 00:27:17.984
<v Wojciech Wegrzynski>I have a laptop with one battery, but, on the factory where they produce laptop batteries, they probably have a 1 million of them stuck together.

00:27:18.224 --> 00:27:21.525
<v Wojciech Wegrzynski>Like what, what does this mean for storage of batteries?

00:27:21.625 --> 00:27:32.365
<v Wojciech Wegrzynski>Like when you produce them in, in large volume in quantities, You, you, you have a tons of devices that, and you just said that the reactions are ongoing, whether you like it or not.

00:27:32.365 --> 00:27:37.172
<v Wojciech Wegrzynski>So, so they are produced and often they are shipped as charged, batteries.

00:27:37.372 --> 00:27:38.808
<v Francesco Restuccia>and that's why they put a limit.

00:27:38.808 --> 00:27:43.458
<v Francesco Restuccia>so you have an ideal charge rate to just to think 30% from the standards now.

00:27:43.788 --> 00:27:45.587
<v Francesco Restuccia>but also colder temperatures.

00:27:45.708 --> 00:27:48.775
<v Francesco Restuccia>So that's the other thing you do is to reduce this self discharged, right?

00:27:48.954 --> 00:27:49.974
<v Francesco Restuccia>You lower the temperature.

00:27:49.974 --> 00:27:56.755
<v Francesco Restuccia>So what do I do when I store batteries in my lab is they have to be in a fridge below 10 degrees, , ideally 10 degrees.

00:27:57.095 --> 00:27:59.375
<v Francesco Restuccia>and then that is the optimal.

00:28:00.102 --> 00:28:03.372
<v Francesco Restuccia>range for them not to reduce the self discharge.

00:28:03.491 --> 00:28:05.531
<v Francesco Restuccia>So self discharge is also temperature dependent.

00:28:05.622 --> 00:28:05.981
<v Francesco Restuccia>Um,

00:28:05.981 --> 00:28:07.182
<v Wojciech Wegrzynski>Okay about the stupid question.

00:28:07.182 --> 00:28:10.468
<v Wojciech Wegrzynski>If I, myself only in winter works, uh, shorter.

00:28:10.468 --> 00:28:14.698
<v Wojciech Wegrzynski>And if I expose it to minus 20, it's going to die very soon.

00:28:14.907 --> 00:28:19.678
<v Wojciech Wegrzynski>So it loses this capability of react, which also from your perspective makes it safer.

00:28:20.132 --> 00:28:21.061
<v Francesco Restuccia>Well, uh,

00:28:21.575 --> 00:28:22.055
<v Wojciech Wegrzynski>I'm sorry.

00:28:22.055 --> 00:28:22.234
<v Wojciech Wegrzynski>I'm

00:28:22.305 --> 00:28:32.212
<v Francesco Restuccia>arise when you go to too low other problems where I So I'm not a material scientist or a chemist, but you have a sweet spot of temperatures for which the materials are designed.

00:28:32.512 --> 00:28:38.002
<v Francesco Restuccia>If you go too low in temperature, I believe you might start degrading the materials in other ways.

00:28:38.247 --> 00:28:40.257
<v Francesco Restuccia>but I'm not an expert, uh, on this.

00:28:40.797 --> 00:28:42.777
<v Francesco Restuccia>so there is a guidance on the range.

00:28:42.777 --> 00:28:44.583
<v Francesco Restuccia>You want to keep it in, for the.

00:28:45.349 --> 00:28:46.904
<v Francesco Restuccia>Battery to be healthy.

00:28:46.962 --> 00:28:49.452
<v Francesco Restuccia>and I don't know what that lower limit is.

00:28:49.637 --> 00:28:53.538
<v Wojciech Wegrzynski>matter, but but it exists that that's what matters the guidance.

00:28:53.988 --> 00:29:03.951
<v Wojciech Wegrzynski>So, , based on experience, tests, knowledge, uh, the scientists have figured out the optimal charge level where the let's say the risk would be minimum.

00:29:04.471 --> 00:29:06.061
<v Francesco Restuccia>Yeah, charge and temperature.

00:29:06.092 --> 00:29:06.902
<v Francesco Restuccia>charge and temperature.

00:29:06.902 --> 00:29:07.112
<v Francesco Restuccia>Right?

00:29:07.231 --> 00:29:12.142
<v Francesco Restuccia>So I think charge, they S they shipped them at 30%, , state of charge and temperature.

00:29:12.172 --> 00:29:15.862
<v Francesco Restuccia>I don't know, but there is an optimal temperature, which is usually your battery.

00:29:15.892 --> 00:29:20.751
<v Francesco Restuccia>The optimal temperature for a battery normally is between 10 and 25 degrees above 25 degrees.

00:29:20.872 --> 00:29:25.132
<v Francesco Restuccia>It's not good for the battery below 10 degrees might start having other issues.

00:29:25.132 --> 00:29:27.862
<v Francesco Restuccia>But for example, when I store them in the lab, it's between six and 10

00:29:28.027 --> 00:29:28.267
<v Wojciech Wegrzynski>Okay.

00:29:28.267 --> 00:29:29.666
<v Wojciech Wegrzynski>So, batteries produce heat.

00:29:29.757 --> 00:29:35.936
<v Wojciech Wegrzynski>There's an optimal, uh, temperature at which the let's call it risk being lowest.

00:29:35.967 --> 00:29:40.519
<v Wojciech Wegrzynski>Uh, maybe it's, , incorrect, but, more understandable by the fire audience.

00:29:40.849 --> 00:29:43.910
<v Wojciech Wegrzynski>So, uh, do, are we managing this heat?

00:29:44.559 --> 00:29:45.910
<v Wojciech Wegrzynski>that's something that interests me.

00:29:45.910 --> 00:30:00.156
<v Wojciech Wegrzynski>So if I have a bunch of batteries in my car, Which I don't because I don't have electric vehicle yet, but if in my hypothetical car, if I had it, would the battery management system be monitoring the heat as well?

00:30:00.156 --> 00:30:02.406
<v Wojciech Wegrzynski>Because I know it is monitoring electricity.

00:30:02.884 --> 00:30:03.664
<v Francesco Restuccia>Good question.

00:30:03.664 --> 00:30:08.209
<v Francesco Restuccia>So your battery and electric vehicle is made up of many, many cells.

00:30:08.239 --> 00:30:18.558
<v Francesco Restuccia>Thousands of cells, you for a question of cost and space, you don't monitor every single cell temperature voltage you can do by line because you can have a row.

00:30:18.798 --> 00:30:22.038
<v Francesco Restuccia>And if it's in series, you have the voltage there,

00:30:22.213 --> 00:30:25.394
<v Wojciech Wegrzynski>And the voltage you probably would like to monitor to know the charge level anyway.

00:30:25.888 --> 00:30:26.338
<v Francesco Restuccia>Correct.

00:30:26.338 --> 00:30:27.808
<v Francesco Restuccia>And you'd usually do that by row.

00:30:27.808 --> 00:30:30.959
<v Francesco Restuccia>So every six or 12 or whatever that row is.

00:30:31.199 --> 00:30:34.169
<v Francesco Restuccia>, but temperature you cannot do for each one.

00:30:34.229 --> 00:30:36.209
<v Francesco Restuccia>Um, just because it adds massive costs.

00:30:36.269 --> 00:30:45.239
<v Francesco Restuccia>And so temperature sometimes is monitored, but it would be monitored at probably a pack level, not at a cell level, but everything I've been telling you now is about a single cell.

00:30:45.239 --> 00:30:49.469
<v Francesco Restuccia>So imagine you have a cell that starts deteriorating or cell that.

00:30:49.763 --> 00:30:52.614
<v Francesco Restuccia>Goes into some kind of initial failure conditions.

00:30:53.423 --> 00:30:56.933
<v Francesco Restuccia>Usually in an electric vehicle, you're not monitoring that cells temperature.

00:30:57.269 --> 00:31:00.240
<v Francesco Restuccia>and some people say that, okay, by you're monitoring the voltage.

00:31:00.240 --> 00:31:10.109
<v Francesco Restuccia>So you will see a voltage drop, but sometimes, and we shown this, in literature, including a paper I am on, we've shown that sometimes the failure happens before the voltage drops.

00:31:10.130 --> 00:31:15.960
<v Francesco Restuccia>So in fact, I have a case in one of the papers we've written that the battery was basically on fire and the voltage was.

00:31:16.694 --> 00:31:17.204
<v Francesco Restuccia>Constant.

00:31:17.325 --> 00:31:18.884
<v Francesco Restuccia>And then it dropped 15 seconds

00:31:18.940 --> 00:31:21.490
<v Wojciech Wegrzynski>a very, very brave battery.

00:31:21.519 --> 00:31:23.890
<v Wojciech Wegrzynski>I assume it was Ukrainian fighting till the end.

00:31:24.400 --> 00:31:25.509
<v Wojciech Wegrzynski>Uh, okay.

00:31:25.759 --> 00:31:29.287
<v Wojciech Wegrzynski>and any other things you can monitor, like maybe you can measure in impendance of the cells.

00:31:29.336 --> 00:31:29.576
<v Francesco Restuccia>Yeah.

00:31:29.576 --> 00:31:36.057
<v Francesco Restuccia>So impedance is another thing they do, and they measure impedance, especially when they're trying to figure out how your battery has degraded.

00:31:36.207 --> 00:31:38.247
<v Francesco Restuccia>So imagine you want to have a second life of a battery.

00:31:38.366 --> 00:31:43.166
<v Francesco Restuccia>So the elephant in the room for batteries, my opinion is recycling, right?

00:31:43.317 --> 00:31:48.477
<v Francesco Restuccia>Just like we had for plastics is when your car or whatever system you're using reaches its end of life.

00:31:49.541 --> 00:31:57.474
<v Francesco Restuccia>You either recycled the battery and that has a lot of costs involved, or you try to redeploy it in the second life in something that requires maybe.

00:31:57.916 --> 00:31:58.933
<v Francesco Restuccia>high spec, right?

00:31:59.144 --> 00:32:00.584
<v Francesco Restuccia>Because your battery has degraded.

00:32:00.763 --> 00:32:03.703
<v Francesco Restuccia>So how do you then figure out how much your battery has degraded?

00:32:03.703 --> 00:32:06.943
<v Francesco Restuccia>So normally what they do is they then measure the impedance of the battery.

00:32:06.943 --> 00:32:15.884
<v Francesco Restuccia>So you can use impedance systems that measure what the new like internal impedance is, so that you know how much your battery has degraded.

00:32:16.153 --> 00:32:19.334
<v Francesco Restuccia>What it doesn't tell you is what conditions it was exposed to.

00:32:19.513 --> 00:32:35.759
<v Francesco Restuccia>So it doesn't tell you if it was kept in a warehouse at 40 degrees, and maybe so it doesn't tell you what has degraded, um, but yeah, battery recycling entire topic, but for me, that's the apart from the fire safety, which I find really interesting on a global scale there is what's the plan.

00:32:36.061 --> 00:32:37.622
<v Francesco Restuccia>And of life for the batteries.

00:32:37.832 --> 00:32:39.001
<v Francesco Restuccia>We have it for nuclear, right?

00:32:39.001 --> 00:32:46.112
<v Francesco Restuccia>If you have a nuclear power plant, you want to design a nuclear power plant, you are not allowed until you have presented the plan of what happens to all the spent fuel.

00:32:46.231 --> 00:32:50.372
<v Francesco Restuccia>What happens to the land, what happens to everything that goes with that, right?

00:32:50.432 --> 00:32:58.801
<v Francesco Restuccia>Um, even if you want to put a new oil rig out into the sea, you have to have an end of life plan for that platform and what happens.

00:32:59.011 --> 00:33:01.261
<v Francesco Restuccia>But with batteries, there's not much.

00:33:01.535 --> 00:33:08.662
<v Wojciech Wegrzynski>people who are listening to the podcast are, are open-minded fire engineers who wants to understand what the future brings.

00:33:08.662 --> 00:33:17.241
<v Wojciech Wegrzynski>And I think what you mentioned now, if we think we have an issue with electric vehicles or lithium-ion batteries today, which.

00:33:18.257 --> 00:33:23.557
<v Wojciech Wegrzynski>Thing is that the big issue, but let's say the, the public, would say it's a big issue today.

00:33:24.156 --> 00:33:33.156
<v Wojciech Wegrzynski>Like when you bring to the question, the, uh, out of life batteries or repurpose batteries or 30 year, all the batteries.

00:33:33.696 --> 00:33:41.586
<v Wojciech Wegrzynski>That's going to be an interesting issue we are going to have, and we better start looking for solutions, how to manage this.

00:33:42.037 --> 00:33:47.136
<v Wojciech Wegrzynski>Should we incrementally increase the fire safety regulations for the batteries?

00:33:47.166 --> 00:33:58.567
<v Wojciech Wegrzynski>If even though we don't have really good regulations at the moment, but it seems that we're struggling with something that that's not even the problem yet.

00:33:59.487 --> 00:33:59.817
<v Francesco Restuccia>Yes.

00:33:59.876 --> 00:34:02.876
<v Francesco Restuccia>And it's, I think it's going to become a problem in a couple of years, right?

00:34:02.876 --> 00:34:09.887
<v Francesco Restuccia>Once, batteries are scaling up, it's getting up and we're using more and more higher high energy density batteries once people.

00:34:10.396 --> 00:34:16.987
<v Francesco Restuccia>And there are companies that have started doing second life of batteries, you know, what are the regulations around that from a safety side, if I'm a fire.

00:34:17.179 --> 00:34:17.809
<v Francesco Restuccia>Scientists.

00:34:18.019 --> 00:34:24.139
<v Francesco Restuccia>And I care about when the system will fail and potentially cause a fire.

00:34:24.440 --> 00:34:27.409
<v Francesco Restuccia>And I have no clue of what's changed inside.

00:34:27.650 --> 00:34:31.880
<v Francesco Restuccia>I just have this battery pack, um, and I've been told the impedance has changed and that's it.

00:34:31.909 --> 00:34:33.829
<v Francesco Restuccia>I have no clue what I've exposed it to you.

00:34:34.447 --> 00:34:35.393
<v Francesco Restuccia>the history.

00:34:35.393 --> 00:34:42.563
<v Francesco Restuccia>So the history, the history of it, what's cycling, it's been exposed to what charging has been exposed to, you know, that degrades the battery.

00:34:42.563 --> 00:34:46.103
<v Francesco Restuccia>So it's from a safety side, I find it concerning,

00:34:46.364 --> 00:34:52.574
<v Wojciech Wegrzynski>And how the graded battery is more dangerous because of this increasing beadings this increased,

00:34:52.793 --> 00:34:54.594
<v Francesco Restuccia>yeah, potential short circuits.

00:34:54.594 --> 00:34:54.833
<v Francesco Restuccia>Yeah.

00:34:54.864 --> 00:34:55.884
<v Francesco Restuccia>Potential short circuits.

00:34:55.884 --> 00:34:56.094
<v Francesco Restuccia>Right.

00:34:56.094 --> 00:34:58.313
<v Francesco Restuccia>So for example, self-heating right.

00:34:58.313 --> 00:34:58.643
<v Francesco Restuccia>So

00:34:59.614 --> 00:35:00.184
<v Wojciech Wegrzynski>Yeah, go on.

00:35:00.184 --> 00:35:00.483
<v Wojciech Wegrzynski>Go,

00:35:00.653 --> 00:35:02.123
<v Francesco Restuccia>Step into self-feeding ignition.

00:35:02.514 --> 00:35:06.284
<v Francesco Restuccia>uh, so Xuanze He and Zhenwen, Hu and, uh, Guillermo Rein.

00:35:06.344 --> 00:35:08.324
<v Francesco Restuccia>, and I have worked on self-heating at Imperial.

00:35:08.353 --> 00:35:13.864
<v Francesco Restuccia>Um, and, , a lot of what I'm going to say is the Zhenwen the Xuanze his work and their PhDs.

00:35:13.963 --> 00:35:18.463
<v Francesco Restuccia>, and you know, they studied a lot on what happens when you have XL.

00:35:18.614 --> 00:35:21.074
<v Francesco Restuccia>These X's are chemical reactions are always happening, right.

00:35:21.074 --> 00:35:22.514
<v Francesco Restuccia>So they increase your temperature.

00:35:22.543 --> 00:35:22.634
<v Francesco Restuccia>Okay.

00:35:23.233 --> 00:35:24.914
<v Francesco Restuccia>I care about self-ehating ignition.

00:35:24.914 --> 00:35:30.340
<v Francesco Restuccia>I've done self-heating ignition for non batteries,, for, you know, other reactive media in my PhD.

00:35:30.550 --> 00:35:35.440
<v Francesco Restuccia>And the problem is very easily post to me is, well, the behavior is the same.

00:35:35.590 --> 00:35:51.039
<v Francesco Restuccia>So what happens if in an open circuit cell, instead of abusing it, instead of adding an internal short circuit, I just considered a battery itself and the heating that it's caused, if the, if the heat cannot be dissipated, , And the heat starts building up.

00:35:51.219 --> 00:35:57.574
<v Francesco Restuccia>Then I might reach a critical temperature for which self-heating ignition can happen and thermal runaway can happen.

00:35:57.574 --> 00:35:57.784
<v Francesco Restuccia>Right?

00:35:57.934 --> 00:36:07.474
<v Francesco Restuccia>So I can reach a condition where these exothermic chemical reactions are causing enough heat to be produced, that the environment around it is not providing enough cooling.

00:36:07.804 --> 00:36:10.313
<v Francesco Restuccia>And so eventually the temperature will go up and all be.

00:36:10.983 --> 00:36:22.864
<v Francesco Restuccia>If that's a single cell, you do the calculations and Xuanze done experiment to, and I, you know, you get a ridiculous high temperature that you will not reach in our warehouse, but if you increase the size.

00:36:23.103 --> 00:36:32.407
<v Francesco Restuccia>So with self-heating theory, if you go back to seminar or if you go back to, the work in the eighties, or even some of my work in my PhD, you, you see that for most reactive media.

00:36:32.407 --> 00:36:37.777
<v Francesco Restuccia>If you increase the size, the temperature threshold for which you will reach a critical.

00:36:38.603 --> 00:36:41.344
<v Francesco Restuccia>temperature that will eventually reach the thermal runaway will decrease.

00:36:41.644 --> 00:36:44.585
<v Francesco Restuccia>And so by how much it decreases, it changes.

00:36:44.855 --> 00:36:48.994
<v Francesco Restuccia>And so what they did in their PhD was they looked at this phenomenon for battery.

00:36:49.014 --> 00:36:54.297
<v Francesco Restuccia>So, they said, okay, A stack of batteries and those batteries are all heating up.

00:36:54.567 --> 00:36:57.657
<v Francesco Restuccia>The center core battery might be heating up more, right.

00:36:57.657 --> 00:37:00.416
<v Francesco Restuccia>Cause it's not releasing that heat to the environment.

00:37:00.476 --> 00:37:03.086
<v Francesco Restuccia>So you're leasing it to batteries next to it, which are also causing heat.

00:37:03.356 --> 00:37:03.657
<v Francesco Restuccia>Right.

00:37:04.204 --> 00:37:13.143
<v Francesco Restuccia>and eventually you might reach the condition where you have temperatures that cause ignition temperatures that you can reach and warehouses,

00:37:13.400 --> 00:37:15.230
<v Wojciech Wegrzynski>the state of batteries is idle.

00:37:15.230 --> 00:37:16.250
<v Wojciech Wegrzynski>They they're not being

00:37:16.514 --> 00:37:17.715
<v Francesco Restuccia>Yeah, they're open circuits.

00:37:17.715 --> 00:37:19.155
<v Francesco Restuccia>So imagine you have a warehouse, right?

00:37:19.394 --> 00:37:31.625
<v Francesco Restuccia>So, uh, Zhenwen did this calculation, , in his PhD, which was that he took the size of a warehouse and he said, okay, imagine I'm packaging batteries,, in this warehouse and it's old batteries at what size.

00:37:32.355 --> 00:37:37.844
<v Francesco Restuccia>Will I need of number of batteries for them to ignite that room temperature in the warehouse.

00:37:38.085 --> 00:37:41.389
<v Francesco Restuccia>And he found the number to be very, very high, you know, racks and racks of them.

00:37:41.748 --> 00:37:45.949
<v Francesco Restuccia>But that's, if there is no installation, there is no packaging.

00:37:46.338 --> 00:37:49.009
<v Francesco Restuccia>And so he said, okay, now what happens if I start adding packaging?

00:37:49.009 --> 00:37:49.278
<v Francesco Restuccia>Right.

00:37:49.429 --> 00:37:55.429
<v Francesco Restuccia>So packaging causes insulation, in fact, so it lets you retain the heat and he saw that that temperature started dropping massively.

00:37:55.699 --> 00:37:58.458
<v Francesco Restuccia>Um, and one of his papers found effectively.

00:37:59.173 --> 00:38:01.454
<v Francesco Restuccia>Depending on what insulation you have between the batteries.

00:38:01.603 --> 00:38:06.193
<v Francesco Restuccia>It actually massively lowers the temperature for which self-heating ignition happens.

00:38:06.494 --> 00:38:09.463
<v Francesco Restuccia>Um, and Xuanze then did this experimentally.

00:38:09.463 --> 00:38:13.664
<v Francesco Restuccia>So he measured self-feeding ignition for a stack of batteries.

00:38:13.873 --> 00:38:19.634
<v Francesco Restuccia>Um, and he saw that as you increase the stock size, the temperature for which they reached ignition reduced.

00:38:20.193 --> 00:38:34.706
<v Wojciech Wegrzynski>and then this was , passive self-feeding that you would encounter in, when you store the batteries, uh, where there, like you said, that there was a certain charging point at which they should be stopped.

00:38:34.945 --> 00:38:37.911
<v Wojciech Wegrzynski>So did, did you guys try, like different charging points

00:38:37.936 --> 00:38:38.507
<v Francesco Restuccia>Yes.

00:38:38.567 --> 00:38:39.586
<v Francesco Restuccia>Yeah, absolutely.

00:38:39.601 --> 00:38:40.561
<v Francesco Restuccia>Very good question.

00:38:40.561 --> 00:38:43.530
<v Francesco Restuccia>So, so that was one of our first questions.

00:38:43.530 --> 00:38:43.831
<v Francesco Restuccia>Okay.

00:38:43.831 --> 00:38:46.501
<v Francesco Restuccia>We did everything at a single star charging point initially.

00:38:46.621 --> 00:38:51.911
<v Francesco Restuccia>So Xuanze his first experiments, that he did, back in China, he had state of charge of 30%.

00:38:51.911 --> 00:38:53.291
<v Francesco Restuccia>So he had the low one that you use.

00:38:54.001 --> 00:38:57.001
<v Francesco Restuccia>Transport by then he said, okay, but what happens if I increase it?

00:38:57.001 --> 00:38:57.240
<v Francesco Restuccia>Right.

00:38:57.240 --> 00:38:59.251
<v Francesco Restuccia>So what happens if I go to higher states of charge?

00:38:59.431 --> 00:39:10.900
<v Francesco Restuccia>And in fact, he found that you have more electrical energy stored inside, but he also found that your temperature threshold for, self-heating ignition, um, massively reduces.

00:39:10.990 --> 00:39:16.121
<v Francesco Restuccia>And so the more state of charge, the lower temperature, it will get lower critical.

00:39:16.121 --> 00:39:18.760
<v Francesco Restuccia>The temperature for which ignition is triggered,

00:39:19.251 --> 00:39:23.391
<v Wojciech Wegrzynski>And by by ignition, you mean the beginning of this cascading processes or something

00:39:23.800 --> 00:39:27.110
<v Francesco Restuccia>So the beginning, so basically where the process becomes unstoppable.

00:39:27.110 --> 00:39:27.351
<v Francesco Restuccia>Right.

00:39:27.916 --> 00:39:30.646
<v Francesco Restuccia>and at some point, yeah.

00:39:30.677 --> 00:39:33.586
<v Francesco Restuccia>What, what is that trigger temperature?

00:39:33.586 --> 00:39:38.746
<v Francesco Restuccia>So if I go back to something that we've looked at in fire from the 1980s is coal, right?

00:39:38.746 --> 00:39:42.916
<v Francesco Restuccia>So this was done a lot for coal fires is, you know, what is that?

00:39:43.711 --> 00:39:44.521
<v Francesco Restuccia>Temperature for storage.

00:39:44.521 --> 00:39:45.782
<v Francesco Restuccia>So Cole has the same problem, right?

00:39:45.782 --> 00:39:47.222
<v Francesco Restuccia>Call it a reactive material.

00:39:47.222 --> 00:39:48.692
<v Francesco Restuccia>It oxidizes with oxygen.

00:39:48.931 --> 00:39:52.202
<v Francesco Restuccia>So if there's oxygen in the room, your coal is going to be producing its own heat.

00:39:52.322 --> 00:39:53.702
<v Francesco Restuccia>It doesn't matter that you're not burning it.

00:39:53.882 --> 00:39:55.112
<v Francesco Restuccia>It's gotta be producing heat.

00:39:55.208 --> 00:39:56.559
<v Francesco Restuccia>and so the.

00:39:56.911 --> 00:40:02.192
<v Francesco Restuccia>Mine's that use coal or power plants that use coal always had that policy of first in, first out, right?

00:40:02.371 --> 00:40:05.791
<v Francesco Restuccia>The coal that gets into storage first is the first one that's going to be used.

00:40:05.791 --> 00:40:07.652
<v Francesco Restuccia>You don't leave it in storage for a long time.

00:40:07.891 --> 00:40:09.601
<v Francesco Restuccia>You don't start using the one that comes later.

00:40:09.842 --> 00:40:15.902
<v Francesco Restuccia>Uh, not because of, you know, aging of Cola and, you know, like whiskey the age, the better it's the opposite.

00:40:15.902 --> 00:40:19.831
<v Francesco Restuccia>It's, you know, the more aging it has, the more heat is had a chance to produce.

00:40:20.101 --> 00:40:23.798
<v Francesco Restuccia>And so for coal, they found obviously that the bigger, the storage.

00:40:24.599 --> 00:40:27.809
<v Francesco Restuccia>The lower the temperature for which you would have that trigger.

00:40:28.139 --> 00:40:42.626
<v Francesco Restuccia>And so that's what we were looking at from a battery site is can we find a similar behavior, to what we have seen in many, many fuels, over the history and fire science and which maybe the battery community was not really used to thinking about.

00:40:43.266 --> 00:40:43.985
<v Wojciech Wegrzynski>And okay.

00:40:44.016 --> 00:40:49.956
<v Wojciech Wegrzynski>And when you did this experiments, I know there is a fancy technique that you have, ruins for everyone else.

00:40:50.496 --> 00:40:52.615
<v Wojciech Wegrzynski>And that that's Accelerating Rate Callorimetry.

00:40:52.778 --> 00:40:58.389
<v Francesco Restuccia>yeah, so, so that was a, the last chapter of Xuanze's PhD thesis with Guillermo Rein at Imperial.

00:40:58.418 --> 00:41:04.442
<v Francesco Restuccia>Um, You know, the way we get kinetics that we use for a lot of our stuff is using accelerating rate calorimetry.

00:41:05.271 --> 00:41:09.021
<v Francesco Restuccia>We often investigate thermal runaway promise there.

00:41:09.021 --> 00:41:13.612
<v Francesco Restuccia>So those, you know, probably there's the bring you to runaway by assuming adiabatic conditions.

00:41:13.641 --> 00:41:16.552
<v Francesco Restuccia>So you assume that your conditions exactly.

00:41:16.581 --> 00:41:22.072
<v Francesco Restuccia>And you put into this machine, that's called accelerating rate calorimetry and out pop the kinetics effectively.

00:41:22.072 --> 00:41:28.492
<v Francesco Restuccia>That's a really simple way of putting it, but what Xuanze and Guillermo and I, and a couple of others, thoughts as well.

00:41:28.978 --> 00:41:29.998
<v Francesco Restuccia>We do heat transfer.

00:41:30.509 --> 00:41:37.365
<v Francesco Restuccia>Adiabatic seem surprising when you have a system that has its own temperature generation, right.

00:41:37.815 --> 00:41:39.585
<v Francesco Restuccia>And it's not microscopic, right.

00:41:39.615 --> 00:41:43.005
<v Francesco Restuccia>A battery is not a millimeter

00:41:43.115 --> 00:41:45.766
<v Wojciech Wegrzynski>Let us assume the batteries appointing spaced.

00:41:45.976 --> 00:41:47.025
<v Francesco Restuccia>and so exactly.

00:41:47.025 --> 00:41:54.092
<v Francesco Restuccia>So, so Xuanze did measurements, um, to figure out if you do not ignore the heat transfer.

00:41:54.842 --> 00:41:58.411
<v Francesco Restuccia>So basically what you're assuming is that you're ignoring internal heat transfer, right?

00:41:58.501 --> 00:42:01.592
<v Francesco Restuccia>When you use accelerating rate calorimetry and he said, well, what happens?

00:42:01.592 --> 00:42:03.369
<v Francesco Restuccia>Can we ignore, internal heat transfer?

00:42:03.489 --> 00:42:12.615
<v Francesco Restuccia>So within the cell and external heat transfer at the cell surface, because in a accelerator colorimetry you have a constant temperature wall.

00:42:12.902 --> 00:42:13.981
<v Francesco Restuccia>and he found that actually.

00:42:15.362 --> 00:42:17.739
<v Francesco Restuccia>For, I think he used, I'm on the paper.

00:42:17.739 --> 00:42:20.289
<v Francesco Restuccia>So I'd be, I need to be careful here with not getting things wrong.

00:42:20.498 --> 00:42:23.936
<v Francesco Restuccia>Um, so you use lithium cobalt batteries, lithium cobalt oxide.

00:42:24.115 --> 00:42:29.396
<v Francesco Restuccia>So for his lithium cobalt oxide, prismatic cell, he found that actually for.

00:42:29.759 --> 00:42:32.422
<v Francesco Restuccia>Temperatures are much lower than thermal runaway.

00:42:32.601 --> 00:42:39.202
<v Francesco Restuccia>So, you know, very low temperature then the temperature variation was between one, 1.5 degrees.

00:42:39.496 --> 00:42:42.865
<v Francesco Restuccia>so between zero and one and a half degrees, so relatively small, right?

00:42:43.076 --> 00:42:52.885
<v Francesco Restuccia>The, the heat, uh, that you are missing the negligence that you're getting from the heat transfer effects by that he found that when thermal runaway does occur.

00:42:52.885 --> 00:42:55.931
<v Francesco Restuccia>So when you reach those higher temperatures than the.

00:42:55.931 --> 00:43:02.181
<v Francesco Restuccia>Temperature that you've missed the change that you've missed by ignoring the heat transfer effect can go from 10 degrees to 130 degrees.

00:43:02.452 --> 00:43:13.641
<v Francesco Restuccia>And so he found that actually, if you ignore heat transfer, external heat transfer effects, then you are underestimating the heat of reaction of the cell by about 12% for the cell that he was using.

00:43:13.851 --> 00:43:16.161
<v Francesco Restuccia>That's a lot, you know, if the heater reaction.

00:43:16.811 --> 00:43:25.842
<v Francesco Restuccia>Underestimated by 12% means that your kinetics, the estimate that kinetics will have a bigger error and that error will grow as the number of cells grows.

00:43:25.842 --> 00:43:26.052
<v Francesco Restuccia>Right.

00:43:26.052 --> 00:43:31.481
<v Francesco Restuccia>So I said that that temperature for feeding will decrease as you increase the size.

00:43:31.692 --> 00:43:35.081
<v Francesco Restuccia>So imagine you have more and more cells, then that error will compound.

00:43:35.126 --> 00:43:35.277
<v Wojciech Wegrzynski>Yeah.

00:43:35.407 --> 00:43:39.137
<v Wojciech Wegrzynski>And did they go back to the warehouse calculations knowing that.

00:43:40.362 --> 00:43:42.617
<v Francesco Restuccia>so, so the paper, the paper came out.

00:43:42.617 --> 00:43:43.865
<v Francesco Restuccia>Last week, in fact.

00:43:43.865 --> 00:43:45.846
<v Francesco Restuccia>So it's a very new paper from his thesis.

00:43:46.268 --> 00:43:56.402
<v Francesco Restuccia>and, basically our conclusion was that, um, if you ignore heat transfer effects, then the thermal runaway parameters that you're quantifying using this technique will have.

00:43:57.197 --> 00:44:00.166
<v Francesco Restuccia>Errors that can propagate in your battery safety design.

00:44:00.467 --> 00:44:15.047
<v Francesco Restuccia>And so if you go back to the warehouse, you know, make sure that if you're using that data for your calculation, you are aware of the errors so that you can use it in your prediction, because I mean, you do way more CFD than I do, which I can, you know, that's, it's fine.

00:44:15.047 --> 00:44:19.036
<v Francesco Restuccia>As long as you know what the error is, you can account for it and you can do error propagation.

00:44:19.277 --> 00:44:24.376
<v Francesco Restuccia>But if you don't know what it is, and you don't have an error propagation, then you're going to have a lot of issues with

00:44:24.652 --> 00:44:38.431
<v Wojciech Wegrzynski>Yeah, I had a very nice talk, about, I both life the engineer with Mike Spearpoint and there was this consistent level of crudeness being mentioned that, when you do, um, very fine simulations and you have a.

00:44:39.047 --> 00:44:54.916
<v Wojciech Wegrzynski>Under pinning assumption that has a major error, no matter how fancy your technique was, this, uh, initial error will propagate to whatever you do and will increase the uncertainty of whatever you've done by a lot.

00:44:54.947 --> 00:44:55.847
<v Wojciech Wegrzynski>And if here.

00:44:56.452 --> 00:45:03.592
<v Wojciech Wegrzynski>The first thing, you would assume that the reaction rate is this, and you've missed it by 12%.

00:45:03.652 --> 00:45:10.581
<v Wojciech Wegrzynski>And that's the underpinning point of every single analysis you do for, for the next of your research.

00:45:10.608 --> 00:45:15.195
<v Wojciech Wegrzynski>that's a huge miss and not, uh, not the biggest one in the industry, but

00:45:15.576 --> 00:45:16.775
<v Francesco Restuccia>But I learned this with Guillermo.

00:45:16.775 --> 00:45:26.346
<v Francesco Restuccia>So I did my PhD with Guillermo Rein and when I started doing so I started looking at self-heating from modeling side and I realized that I couldn't find the data I wanted and literature, because I wanted the errors.

00:45:26.496 --> 00:45:29.496
<v Francesco Restuccia>I wanted to know what the uncertainty was and I couldn't find the uncertainty.

00:45:29.496 --> 00:45:31.235
<v Francesco Restuccia>I said, well, if I model need, I don't know.

00:45:31.306 --> 00:45:33.335
<v Francesco Restuccia>I don't mind how big the uncertainty is.

00:45:33.335 --> 00:45:34.115
<v Francesco Restuccia>I need to know what it is.

00:45:34.356 --> 00:45:37.675
<v Francesco Restuccia>So then I ended up doing experiments to get set data, and then.

00:45:38.286 --> 00:45:44.795
<v Francesco Restuccia>Put the errors and Guillermo and I were having discussions in my first paper, in my PhD because my aerobars are quite large.

00:45:45.036 --> 00:45:49.385
<v Francesco Restuccia>And so then when I upscaled to real life scenarios, I was having these really big error bars.

00:45:49.385 --> 00:45:55.056
<v Francesco Restuccia>And in fact, if you look even now with Xuanze, Zhenwen in our battery papers, when we upscale our error bars are quite big.

00:45:55.715 --> 00:46:03.786
<v Francesco Restuccia>I went back to Guillermo and we were looking at my figures and I was like, I'm really worried and give him, I said, but why, you know, if that's the uncertainty that we're getting, that's the important thing.

00:46:03.786 --> 00:46:06.726
<v Francesco Restuccia>And that's,  when you then use the data, you need to know what the uncertainty was.

00:46:06.905 --> 00:46:08.286
<v Francesco Restuccia>So we sent the paper for review.

00:46:08.706 --> 00:46:10.775
<v Francesco Restuccia>I got demolished by one of the reviewers.

00:46:10.985 --> 00:46:12.155
<v Francesco Restuccia>I got a little bit demoralized.

00:46:12.215 --> 00:46:13.025
<v Francesco Restuccia>We resubmitted the paper.

00:46:13.971 --> 00:46:18.951
<v Francesco Restuccia>To combustion and flame in fact, got great reviews back, no problem with the errors.

00:46:18.981 --> 00:46:21.681
<v Francesco Restuccia>Uh, in fact, he knows very good that you specified all the data.

00:46:21.860 --> 00:46:23.900
<v Francesco Restuccia>And so for me, it was actually a beginning.

00:46:23.900 --> 00:46:27.351
<v Francesco Restuccia>It was a bit worrying, but in fact, I learned, and I've kept this throughout my career.

00:46:27.351 --> 00:46:34.101
<v Francesco Restuccia>And now that I'm an academic and I have my own PhD students, I am very careful always with, um, or even with my postdoc on error.

00:46:34.101 --> 00:46:40.311
<v Francesco Restuccia>Uncertainty analysis is, you know, I don't mind if there is big, but it needs to be accurate so that if you then use it for modeling.

00:46:40.777 --> 00:46:43.567
<v Francesco Restuccia>You have as accurate as you can get data.

00:46:44.137 --> 00:46:52.193
<v Wojciech Wegrzynski>It's something that my, , my mentor professor Czernecki said, do you want to be, uh, roughly correct or precisely wrong?

00:46:52.224 --> 00:46:53.003
<v Wojciech Wegrzynski>And, uh,

00:46:53.804 --> 00:46:54.164
<v Francesco Restuccia>I like

00:46:54.233 --> 00:47:03.083
<v Wojciech Wegrzynski>roughly correct is sometimes, , that's all you can get and, to understand the limitations of, of your errors means you can.

00:47:03.893 --> 00:47:13.947
<v Wojciech Wegrzynski>I mean, The data does not need to be super high fidelity to be useful models do not have to replicate reality in a hundred percent to be useful.

00:47:14.336 --> 00:47:16.407
<v Wojciech Wegrzynski>These are tools for engineers.

00:47:16.407 --> 00:47:24.947
<v Wojciech Wegrzynski>And I think here another lesson that comes for the general fire safety engineering audience, who may not be that big fans of cathodes and anodes.

00:47:24.976 --> 00:47:33.152
<v Wojciech Wegrzynski>But, here we are talking about quiet Difficult engineering topic where so many fields of science interlap.

00:47:33.621 --> 00:47:39.472
<v Wojciech Wegrzynski>And then again, if this battery's burned down, it's us fire engineers was going to be blamed it.

00:47:39.831 --> 00:47:53.052
<v Wojciech Wegrzynski>We didn't solve this issue and metabolically going through it, understanding the limitations, understanding the impact of the small factors gives you, uh, in the end, the holistic view on.

00:47:53.632 --> 00:47:59.188
<v Wojciech Wegrzynski>On the system, in this case, on the battery cell that, gives you space to work with.

00:47:59.219 --> 00:48:13.106
<v Wojciech Wegrzynski>And it's not that we're going to magically solve the problems of, batteries if one exists, exists, but, , we need to learn how to live with them and how to manage them in a way that is acceptable.

00:48:13.106 --> 00:48:14.996
<v Wojciech Wegrzynski>And I think this is an achievable goal.

00:48:14.996 --> 00:48:15.565
<v Wojciech Wegrzynski>What do you think.

00:48:16.485 --> 00:48:17.206
<v Francesco Restuccia>Yeah, I agree.

00:48:17.206 --> 00:48:20.686
<v Francesco Restuccia>And in fact, you know, I, if I go back even to Xuanze's first experiments, right?

00:48:20.865 --> 00:48:29.686
<v Francesco Restuccia>He's one single cell in self-heating feeding requires a room temperature and the cell at low 30% state of charge.

00:48:29.686 --> 00:48:30.795
<v Francesco Restuccia>So, you know, really safe.

00:48:30.826 --> 00:48:40.695
<v Francesco Restuccia>The one for travel is single cell, super healthy, no issues requires something like 150 degrees or 160 degrees room temperature, which is never going to be achievable.

00:48:41.655 --> 00:48:53.239
<v Francesco Restuccia>If then two cells requires 154 cells acquire a hundred and thirty, forty five, you know, and then you scale and you get down figuring out that from what you can gather experimentally or numerically.

00:48:53.818 --> 00:48:54.148
<v Wojciech Wegrzynski>Um,

00:48:54.969 --> 00:48:59.079
<v Francesco Restuccia>If you can figure out what the errors that you are compounding are.

00:48:59.199 --> 00:49:06.969
<v Francesco Restuccia>For example, when we do experiments, if I am doing battery experiment and I have a pack, I I'm ignoring the material.

00:49:06.969 --> 00:49:07.929
<v Francesco Restuccia>That's inside the ball.

00:49:07.929 --> 00:49:09.548
<v Francesco Restuccia>Cause I'm ignoring the separation.

00:49:09.548 --> 00:49:10.809
<v Francesco Restuccia>I'm ignoring a lot of things.

00:49:10.809 --> 00:49:11.048
<v Francesco Restuccia>Right.

00:49:11.289 --> 00:49:13.898
<v Francesco Restuccia>But it should be good enough that we can then use it.

00:49:13.898 --> 00:49:15.699
<v Francesco Restuccia>If we try to do everything perfectly.

00:49:16.313 --> 00:49:17.333
<v Francesco Restuccia>Look at CFD.

00:49:17.454 --> 00:49:26.003
<v Francesco Restuccia>If we were to do a direct numerical simulation of Navier Stokes or a box that's bigger than a meter cube, we'd be spending 150 years waiting for the solution.

00:49:26.213 --> 00:49:26.873
<v Francesco Restuccia>And so often.

00:49:27.844 --> 00:49:29.134
<v Francesco Restuccia>You know, we do combustion, right?

00:49:29.134 --> 00:49:31.623
<v Francesco Restuccia>So in combustion we need to optimize our parameters.

00:49:31.623 --> 00:49:47.344
<v Francesco Restuccia>So if I'm looking at turbulence, um, and I care about the really precise chemistry and chemical kinetics, then I will set up my simulation one way and I will make some assumptions if I care about a really fast solution, but that gives me a temperature range for which my behavior will be in.

00:49:47.614 --> 00:49:47.884
<v Francesco Restuccia>And.

00:49:48.668 --> 00:49:59.018
<v Francesco Restuccia>Can afford to have a 50 degree error, then I will run it with much less chemistry, detailed chemistry, or we'll run it with fixed chemistry parameters and get my quick solution out.

00:49:59.048 --> 00:50:01.869
<v Francesco Restuccia>And so as an engineer, I mean, we have to wear two hats, right?

00:50:01.869 --> 00:50:08.378
<v Francesco Restuccia>So I'm a scientist, so I want things to be accurate and I want things to be precise, but as an engineer, I need it to be useful.

00:50:08.528 --> 00:50:08.798
<v Francesco Restuccia>Right.

00:50:08.798 --> 00:50:13.208
<v Francesco Restuccia>And so you need to find a balance in between the two and having to wear both hats.

00:50:14.028 --> 00:50:15.918
<v Francesco Restuccia>The fun part about research, I guess is.

00:50:16.235 --> 00:50:18.826
<v Francesco Restuccia>but yeah, we need to remember that it has to be useful at some point

00:50:18.985 --> 00:50:19.195
<v Wojciech Wegrzynski>Yeah.

00:50:19.195 --> 00:50:24.775
<v Wojciech Wegrzynski>And the third hat of managing a laboratory in health and safety, but that's not the topic for the podcasts

00:50:24.786 --> 00:50:29.195
<v Francesco Restuccia>and teaching and teaching hats and admin hats, but let's ignore those for

00:50:29.516 --> 00:50:31.226
<v Wojciech Wegrzynski>I also have a podcast hat it's great.

00:50:31.226 --> 00:50:32.065
<v Wojciech Wegrzynski>If you want to fit.

00:50:33.565 --> 00:50:34.405
<v Wojciech Wegrzynski>It's fantastic.

00:50:34.976 --> 00:50:35.425
<v Wojciech Wegrzynski>Thank you.

00:50:36.686 --> 00:50:37.315
<v Wojciech Wegrzynski>Thank you so much.

00:50:37.514 --> 00:50:42.940
<v Wojciech Wegrzynski>I think this is a difficult topic, but the more, you know, your enemy the less you are a fearful of it.

00:50:43.001 --> 00:50:50.474
<v Wojciech Wegrzynski>And, I really want, my, my audience, my people to understand what is the issue we are dealing with?

00:50:50.554 --> 00:50:53.414
<v Wojciech Wegrzynski>It's in a way, a mystical, magical technology.

00:50:53.414 --> 00:50:54.704
<v Wojciech Wegrzynski>There's the fact that you can.

00:50:54.777 --> 00:51:01.106
<v Wojciech Wegrzynski>Capture a lightning inside of a small metallic pouch, and then use it to power your electric cigarettes.

00:51:01.556 --> 00:51:08.400
<v Wojciech Wegrzynski>And someone once said, I wanted to, to charge my book, uh, but my wife was charging her cigarettes.

00:51:08.431 --> 00:51:09.391
<v Wojciech Wegrzynski>The future is stupid.

00:51:10.630 --> 00:51:13.277
<v Wojciech Wegrzynski>Uh, it's a, thing that enables us.

00:51:13.398 --> 00:51:17.304
<v Wojciech Wegrzynski>And, if you look at the world, it's is actually one of the technologies that.

00:51:18.313 --> 00:51:26.164
<v Wojciech Wegrzynski>That is necessary to change the planet, the fossil fuel to everything, to a more sustainable future and, uh, fire engineers.

00:51:26.195 --> 00:51:28.179
<v Francesco Restuccia>I like Guillermos approach to this.

00:51:28.179 --> 00:51:31.478
<v Francesco Restuccia>So I'm going to steal Guillermo to this, which he uses in other

00:51:31.523 --> 00:51:31.943
<v Wojciech Wegrzynski>you should.

00:51:31.974 --> 00:51:32.364
<v Wojciech Wegrzynski>Yes.

00:51:32.956 --> 00:51:35.766
<v Francesco Restuccia>he says, you need to think about when you think of a fire problem.

00:51:35.976 --> 00:51:36.246
<v Francesco Restuccia>It does.

00:51:36.306 --> 00:51:37.865
<v Francesco Restuccia>I mean, technology is useful, right.

00:51:37.865 --> 00:51:41.405
<v Francesco Restuccia>But you need to think about how to prevent it, how to compartmentalize it.

00:51:41.496 --> 00:51:43.356
<v Francesco Restuccia>If a fire happens, how do you compartmentalize it?

00:51:43.445 --> 00:51:45.425
<v Francesco Restuccia>How do you detect it and how do you suppress it?

00:51:45.726 --> 00:51:47.135
<v Francesco Restuccia>And all four things.

00:51:47.615 --> 00:51:50.885
<v Francesco Restuccia>Equally important because we always want to have prevention, right.

00:51:51.036 --> 00:51:55.896
<v Francesco Restuccia>We never even want to have a fire, but our job is also to figure out what happens if we do have a fire.

00:51:55.896 --> 00:51:57.155
<v Francesco Restuccia>So how do we compartmentalize it?

00:51:57.275 --> 00:51:58.115
<v Francesco Restuccia>How do we detect it?

00:51:58.115 --> 00:52:02.436
<v Francesco Restuccia>So we know it's happening and that's sort of what we were discussing earlier about voltage and temperatures.

00:52:02.719 --> 00:52:03.612
<v Francesco Restuccia>and how do you suppress it?

00:52:03.619 --> 00:52:08.239
<v Francesco Restuccia>battery fire suppression is really, really complicated because the chemistry can get really complicated.

00:52:08.449 --> 00:52:10.985
<v Francesco Restuccia>The toxicity of some of the gases can be, there's

00:52:11.346 --> 00:52:16.009
<v Wojciech Wegrzynski>I think even, even access to the cells that are reacting is, is the major

00:52:16.103 --> 00:52:16.403
<v Francesco Restuccia>Yeah.

00:52:16.673 --> 00:52:19.597
<v Francesco Restuccia>Um, and so, and so it's, it's putting all of those together.

00:52:19.628 --> 00:52:20.378
<v Francesco Restuccia>That's important.

00:52:20.378 --> 00:52:29.918
<v Francesco Restuccia>And so our technology is our future technological future is always bright and it's always improving, but from a fire site, we're never going to prevent every single fire.

00:52:30.148 --> 00:52:32.467
<v Francesco Restuccia>And so we always need to think about the other aspects as well.

00:52:32.702 --> 00:52:33.242
<v Wojciech Wegrzynski>Fantastic.

00:52:33.452 --> 00:52:36.873
<v Wojciech Wegrzynski>Thank you so much for sharing this with us.

00:52:36.873 --> 00:52:42.862
<v Wojciech Wegrzynski>And, yeah, I, I will, link to all the works that have been mentioned in the talk in the show notes.

00:52:42.862 --> 00:52:57.005
<v Wojciech Wegrzynski>And, , please send me, uh, if you have something to add to that, because I think you've mentioned that quite a lot of interesting research being done at your lab and that, at Imperial College, And, it is absolutely worth sharing.

00:52:57.036 --> 00:52:59.585
<v Wojciech Wegrzynski>I I'm sure some people would like to dig in more

00:53:00.460 --> 00:53:01.181
<v Francesco Restuccia>Absolutely.

00:53:01.181 --> 00:53:03.161
<v Francesco Restuccia>We'll be very happy to, and it's not limited to me.

00:53:03.181 --> 00:53:07.210
<v Francesco Restuccia>I'll send you the works we have done, but there's works from the U S works from Asia.

00:53:07.360 --> 00:53:09.130
<v Francesco Restuccia>You know, battery field is really growing.

00:53:09.130 --> 00:53:13.121
<v Francesco Restuccia>So I've shared our experiences, but thankfully there's a lot of researchers

00:53:13.246 --> 00:53:13.726
<v Wojciech Wegrzynski>Thank you.

00:53:13.755 --> 00:53:15.076
<v Wojciech Wegrzynski>Thank you so much for doing that.

00:53:15.106 --> 00:53:17.326
<v Wojciech Wegrzynski>And thanks for coming to the Fire Science Show.

00:53:17.326 --> 00:53:18.766
<v Wojciech Wegrzynski>I hope you've enjoyed and

00:53:18.791 --> 00:53:19.451
<v Francesco Restuccia>you so much.

00:53:19.481 --> 00:53:19.840
<v Francesco Restuccia>Yes.

00:53:19.871 --> 00:53:20.831
<v Francesco Restuccia>Thank you for having me.

00:53:20.902 --> 00:53:21.353
<v Wojciech Wegrzynski>Cheers

00:53:21.391 --> 00:53:21.684
<v Francesco Restuccia>Cheers.

00:53:22.155 --> 00:53:22.606
<v Wojciech Wegrzynski>And that's it.

00:53:22.635 --> 00:53:23.565
<v Wojciech Wegrzynski>Thank you for listening.

00:53:23.626 --> 00:53:27.856
<v Wojciech Wegrzynski>I hope this was a five-star worthy episode from my perspective.

00:53:27.885 --> 00:53:31.936
<v Wojciech Wegrzynski>It was because I finally learned what makes the batteries burn.

00:53:32.385 --> 00:53:34.905
<v Wojciech Wegrzynski>And it's an interesting lesson.

00:53:35.469 --> 00:53:35.889
<v Wojciech Wegrzynski>In the end.

00:53:35.889 --> 00:53:42.878
<v Wojciech Wegrzynski>I would like to bring your attention again to the elephant in the room that Francesco pointed that is the second life of batteries.

00:53:43.329 --> 00:53:46.028
<v Wojciech Wegrzynski>If we want a sustainable future in a circular economy.

00:53:46.329 --> 00:53:49.809
<v Wojciech Wegrzynski>There is no way we can just let them rot on the dump wastes.

00:53:50.228 --> 00:53:52.659
<v Wojciech Wegrzynski>And that will probably lead to catastrophical.

00:53:53.018 --> 00:53:54.009
<v Wojciech Wegrzynski>Fires as well.

00:53:54.009 --> 00:53:56.259
<v Wojciech Wegrzynski>So I don't think it's even the choice.

00:53:56.559 --> 00:53:58.568
<v Wojciech Wegrzynski>We need to find a way how to reuse batteries.

00:53:58.599 --> 00:54:00.789
<v Wojciech Wegrzynski>We need to find a way how to give them second life.

00:54:01.268 --> 00:54:03.188
<v Wojciech Wegrzynski>Because of how they're manufactured.

00:54:03.188 --> 00:54:09.579
<v Wojciech Wegrzynski>It's probably going to be difficult to disassemble them to first materials and then assemble again.

00:54:09.878 --> 00:54:13.929
<v Wojciech Wegrzynski>So we probably need to find a usage for used lithium-ion batteries.

00:54:14.259 --> 00:54:16.059
<v Wojciech Wegrzynski>We probably need to find a way.

00:54:16.539 --> 00:54:19.449
<v Wojciech Wegrzynski>How we can benefit from them again, once there.

00:54:19.989 --> 00:54:25.119
<v Wojciech Wegrzynski>Ended their life cycle In the primary device, they were in like car or laptop or something.

00:54:25.539 --> 00:54:27.849
<v Wojciech Wegrzynski>And I think it's going to be a huge challenge.

00:54:28.235 --> 00:54:31.775
<v Wojciech Wegrzynski>I know the focus today is on the safety of cars.

00:54:31.806 --> 00:54:32.405
<v Wojciech Wegrzynski>Buses.

00:54:32.436 --> 00:54:33.186
<v Wojciech Wegrzynski>Carparks.

00:54:33.755 --> 00:54:37.626
<v Wojciech Wegrzynski>Energy storage at buildings, mass energy storage facilities.

00:54:38.076 --> 00:54:47.166
<v Wojciech Wegrzynski>Maybe warehouses, but trust me in a decade or two, when there are billions of use cells that needs to be refurbished or used.

00:54:47.735 --> 00:54:53.766
<v Wojciech Wegrzynski>A lot of us will be dealing with the issues of how safely give battery second life.

00:54:54.155 --> 00:54:54.695
<v Wojciech Wegrzynski>And I think.

00:54:54.996 --> 00:54:56.646
<v Wojciech Wegrzynski>We should look forward to that.

00:54:56.735 --> 00:54:59.436
<v Wojciech Wegrzynski>There is no sustainable future without reuse.

00:54:59.826 --> 00:55:03.005
<v Wojciech Wegrzynski>So we need to be a significant part of that.

00:55:03.545 --> 00:55:08.132
<v Wojciech Wegrzynski>And, through the podcast, I will try to find a great guests who can talk about.

00:55:08.643 --> 00:55:12.362
<v Wojciech Wegrzynski>The second life of batteries, even though there's not that much knowledge yet.

00:55:12.813 --> 00:55:17.972
<v Wojciech Wegrzynski>But, uh, hopefully we can start working towards solutions before the problems start arising.

00:55:18.452 --> 00:55:19.262
<v Wojciech Wegrzynski>And so, yeah.

00:55:19.322 --> 00:55:20.523
<v Wojciech Wegrzynski>That would be pretty good.

00:55:20.978 --> 00:55:21.518
<v Wojciech Wegrzynski>And for now.

00:55:22.268 --> 00:55:24.878
<v Wojciech Wegrzynski>I think that's it for the today's episode.

00:55:25.148 --> 00:55:28.628
<v Wojciech Wegrzynski>Thank you very much for staying till the end and for listening to the show.

00:55:29.168 --> 00:55:33.338
<v Wojciech Wegrzynski>And if you enjoyed it, there's another episode for you waiting every Wednesday.

00:55:33.608 --> 00:55:34.838
<v Wojciech Wegrzynski>So see you there.

00:55:34.929 --> 00:55:35.318
<v Wojciech Wegrzynski>Cheers.