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00:00This is what the inside of a lithium-ion battery looks like.
00:03It's not exactly high-tech, just two meters of foil coated in black paste,
00:09all packed into this tiny 45-gram cylinder.
00:12But these are some of the best batteries we have.
00:15They power everything from laptops and electric vehicles to orbiting satellites.
00:20Yet when a battery fails, all that energy can get released in the wrong way.
00:25Oh my god.
00:27The latest incident involving lithium-ion batteries.
00:30So how did something so rudimentary looking end up in almost every electronic device on the planet?
00:37And why don't we have anything better?
00:39In the early 1980s, most rechargeable batteries were stuck at just 40 to 60 watt-hours per kilogram,
00:46meaning you would need a kilogram of battery to power a 40-watt light bulb for just an hour.
00:52As a result, when the first commercial mobile phone launched in 1983,
00:55it was pretty unimpressive.
00:58It took 10 hours to charge for just 30 minutes of talk time.
01:02Laptops, cameras, even medical devices all suffered from the same bulky batteries.
01:07Everyone from electronics giants to oil companies were trying to make a better battery,
01:11because they knew that even just doubling the energy density
01:14could unlock a new era of portable electronics and power the digital revolution.
01:18But what no one realized is that someone had already found the solution.
01:25In 1972, a 32-year-old British chemist named Stanley Whittingham
01:29was studying how different materials store energy at Exxon's research lab in New Jersey.
01:34Yes, that Exxon, the multinational oil giant, then the largest oil company in the world.
01:41They were researching batteries.
01:44The next year, war broke out between Egypt, Syria, and Israel.
01:49When the U.S. backed Israel, Arab oil producers cut off oil exports in retaliation.
01:54And on December 22nd, the price of crude oil more than doubled from $5.12 a barrel to $11.65.
02:01In response, President Nixon created policies to try to keep oil prices down.
02:06But they backfired, and the shortage only got worse.
02:10Americans were left queuing for hours at gas stations
02:13as the government introduced a rationing program.
02:16It got so bad that they even dropped the national speed limit to 55 miles per hour
02:20just to cut consumption.
02:21At Exxon, executives were worried that supplies would run out entirely.
02:28So they started looking seriously at alternatives, like electricity.
02:32This wasn't a new idea.
02:34In fact, in 1900, when cars were first taking off,
02:37the top-selling car was electric, ahead of steam and gas-powered cars.
02:42But the problem with these electric cars was their batteries.
02:45They weighed 360 kilograms, around 40% of the car's weight.
02:49But they could only take you around 60 kilometers.
02:53And the energy density wasn't just low, it also degraded over time.
02:57Every time you recharged, it got worse.
02:59After fewer than 500 charges, your range would have dropped to about 40 kilometers.
03:05So by 1924, gas-powered cars outnumbered electric 10,000 to 1.
03:10But now that the oil supplies were running out,
03:13it seemed to Exxon that there was no other solution than to bring back the electric car.
03:18And to do that, they needed a battery with a much higher energy density.
03:21So suddenly, Whittingham's side project became a top priority.
03:26Exxon poured in resources, giving him free reign to, in his words,
03:30do pretty much what I wanted as long as it did not involve petroleum.
03:33The very first battery dates back to a curious incident in the 1780s,
03:39when Italian scientist Luigi Galveni was dissecting a frog to study its anatomy.
03:45He anchored one side of the frog on a brass hook and went to cut it open with a steel scalpel.
03:50But when he touched the scalpel to the frog's leg,
03:52he noticed it suddenly twitched, as if it had come back to life.
03:57Galveni believed he'd discovered a sort of animal electricity,
04:00a living force produced by the tissue itself.
04:03But Galveni's rival, Alessandro Volta, disagreed.
04:07He thought it came from the metals themselves.
04:10And you can see this with lots of different materials.
04:13Veritasium producer Gregor set up a version of this experiment,
04:16minus the frog, to test it out.
04:19I have zinc, magnesium, and iron here.
04:22I can take any of these metals, stick them into one side of a lemon,
04:26and stick some copper on the other side.
04:29If I hook these up to a voltmeter, I should be getting a voltage.
04:33And we got around 0.8 volts.
04:36Now the reason this happens is because some elements want to get rid of their electrons more than others.
04:40So if you pair one that really doesn't want its electrons with one that really wants some,
04:46well then the electrons are going to be traveling across.
04:48Let's look at the zinc.
04:51What's happening here is that zinc is losing its electrons.
04:54The zinc ions enter the juice and the electrons are forced to go through the circuit to get to the other side.
05:00There, hydrogen ions in the lemon juice want those electrons,
05:03so they receive them and turn into hydrogen gas.
05:06You've got one side that gives up electrons, that's the anode,
05:10and you've got one that receives them, that's the cathode.
05:13But why do you need the lemon at all?
05:15If there's no flow of the positive ions through to the other side,
05:19the electrons stop moving almost immediately.
05:22This happens because all of the electrons now get bunched up in the copper,
05:26making it extremely negatively charged,
05:28and that is just going to push away any more electrons from coming over to the other side.
05:32That's because electrons can't travel through lemon juice.
05:36Liquids like this don't have free electrons the way metals do,
05:38so electrons stay in the wire.
05:41They'll only leave the circuit at the copper side if there's something in the juice,
05:44like hydrogen ions ready to take them,
05:47and if the reaction releases enough energy to make that transfer happen.
05:51But positive ions in the juice can move.
05:53They travel across to balance the charge, allowing the current to keep flowing.
05:58A solution that carries charge this way, by moving ions, is called an electrolyte.
06:03But we could also do this with the other metals to get a similar reaction,
06:07and we can actually quantify how much each of these metals wants or doesn't want electrons.
06:13With zinc, we already got around 0.9 volts,
06:16but if you tried with iron, for example, you get something lower.
06:190.5 or 0.6 volts.
06:21Now, magnesium is tricky, and it would be a bit higher,
06:24but it oxidizes so quickly that even if I scrape some of the oxide from the surface,
06:28I'm still getting only around 0.7 volts.
06:34The idea is that the larger the voltage on the voltmeter,
06:37the more energy each electron has to give as it passes through the circuit.
06:41But there's also a limit to this.
06:44See, this beaker is full of lemon juice from the lemons we used earlier,
06:48and they're hooked up using spoons and these wires to a variable power source.
06:52Now, look what happens when I up the voltage.
06:56You'll actually start to see bubbles forming on both spoons,
07:00and that's water in the lemon juice actually being broken down into oxygen and hydrogen gas.
07:06This already starts happening at 1.23 volts,
07:09and that sets a limit on how much voltage you can push through this electrolyte.
07:15Up until the early 1970s,
07:17just about every commercial battery used a water-based electrolyte,
07:21and as a result, none of these battery cells could push much beyond the 1.23 volt limit.
07:26Now, the total energy a battery can store depends on how much energy each charge has to give
07:32times how much charge can move.
07:35That is, the battery's voltage times its capacity.
07:38So if you can't increase the voltage,
07:40your only option is to make more battery, more cells or bigger cells.
07:44But that won't increase the energy density.
07:48And this is exactly the problem Whittingham was trying to solve.
07:52He was searching for materials that could store large amounts of energy
07:55in a compact space with light weight.
07:58That led him to a class of compounds called transition metal dichalcogenides.
08:02He zeroed in on one in particular, titanium disulfide.
08:06Titanium in this compound has effectively lost four electrons,
08:10two to each sulfur atom,
08:12meaning it sits at a plus four oxidation state.
08:15That leaves it very electron hungry,
08:18exactly what you want in a battery cathode.
08:20But titanium disulfide has a second key advantage.
08:23This material is made of stacked layers held together by weak Van der Waals forces.
08:28This creates natural gaps between sheets of titanium and sulfur atoms
08:31just wide enough to let certain ions slip between the layers,
08:35a process known as intercalation.
08:38Better still, the structure can expand and contract repeatedly without breaking down.
08:43Now Whittingham just had to decide which ions to use.
08:46He initially looked at potassium,
08:50but it was just too reactive and far too dangerous to work with.
08:54Oh yeah!
08:57He turned to this,
08:58a soft silvery metal called lithium.
09:02What makes lithium unique
09:04is not the fact that it has one electron in its outer shell that it wants to get rid of.
09:09No, that it shares with the other elements in its group.
09:12What sets it apart is how much energy you can get out of lithium when it reacts in a battery.
09:18See, when it loses that outer electron,
09:21it forms a tiny, incredibly stable positive ion.
09:24And so that reaction paired with the right cathode releases more energy per electron than any other metal.
09:31That's why it produces the highest voltage of any metal used in batteries.
09:36And because it's so small with just three protons,
09:39lithium is also the least dense metal at just 0.53 grams per cubic centimeter.
09:44This combination of low density and the tendency to give away its electron
09:48made lithium perfect for Whittingham's vision of this high energy density battery.
09:53But while lithium was easier to work with than potassium,
09:57easier still didn't mean easy.
09:59I mean, they only let me hold it in this glove box.
10:02And matter of fact, here's what happens to lithium if you put it in a glass of water.
10:11Safe to say you don't want this happening inside your battery.
10:14So Whittingham had to switch out the water-based electrolyte for something else.
10:19And that change unlocked the possibility of higher voltages.
10:24He turned to a solution of lithium salt in an organic solvent.
10:28And it worked.
10:30But it came with serious risks.
10:33The solvent was volatile.
10:35The lithium salt was chemically unstable.
10:37Together, they formed a mixture that could explode or release toxic fumes if mishandled.
10:42Everything had to be done with extreme caution.
10:44A stray spark or a trace of moisture could destroy the experiment or start a fire.
10:49But if you could get around the danger, this new electrolyte was a huge perk.
10:54It let lithium ions shuttle between electrodes without breaking down the solvent or the cell,
10:59at least not until much higher voltages.
11:02Whittingham had unlocked lithium's potential.
11:05And in the process, he'd broken through the 1.23 volt ceiling.
11:09His new chemistry delivered nearly double, a huge 2.4 volts per cell.
11:14He now had a working prototype.
11:16A metallic lithium anode on one side, a titanium disulfide cathode on the other.
11:21His new liquid electrolyte in between.
11:23There was also a thin porous separator that kept the electrodes apart,
11:27so they couldn't touch and short circuit.
11:29Here's how it works.
11:30When you close the circuit, lithium atoms at the anode give up their electrons.
11:35Those electrons travel through the external circuit toward the cathode,
11:38generating a current that powers whatever's connected.
11:41At the same time, the lithium ions are released into the electrolyte,
11:45and then they pass through the porous separator and migrate toward the cathode.
11:49The electrons arriving through the circuit are taken up by the titanium atoms
11:52and the titanium disulfide.
11:54The positive lithium ions slide between the layers to balance out the negative charge of
11:59the electrons, and they become locked in place.
12:02And this process is reversible.
12:04When you apply a voltage to recharge,
12:06the extra electrons are stripped from the titanium and pulled back to the anode.
12:10The lithium ions are forced out of the titanium disulfide layers into the electrolyte,
12:14and they too migrate to the anode, where metallic lithium reforms.
12:19What Whittingham had created here was a rechargeable battery,
12:23one that worked reliably, cycle after cycle, with incredible consistency.
12:27I don't normally think about batteries this way, but what they really are is tiny little contained
12:34chemical reactions.
12:35And in a chemical reaction, if you could get a 60% yield, that would be considered good.
12:41But in a battery, especially one that you want to recharge a thousand times,
12:45you need that reaction to be, say, 99.9% efficient.
12:49Because if it's not, the capacity of that battery rapidly deteriorates.
12:54If you have, say, a 95% yield, then you'd lose a significant fraction of lithium ions every cycle.
13:00After just 50 cycles, you'd only have 8% of your original capacity left.
13:05So it's pretty incredible that every single lithium ion has to leave one electrode,
13:10pass through the electrolyte, and slot neatly into the layered crystal structure of titanium disulfide.
13:15And then when you recharge it, they have to leave again,
13:18cleanly, without incident, without getting stuck, make their way all the way back to the anode.
13:22Amazingly, despite just being an early prototype,
13:25Whittingham's battery came close to that 99%.
13:29In the winter of 1973, Exxon's managers summoned Whittingham to the company's New York office.
13:37Whittingham later said,
13:38I went in there and explained it.
13:40Five minutes, ten minutes at the most.
13:42And within a week, they said yes, they wanted to invest in this.
13:45They got to work at the Exxon Laboratory, but it wasn't all smooth sailing.
13:52Firefighters had to be called out repeatedly.
13:54They were called so often, they threatened to start charging the lab for the special chemicals needed to extinguish the burning lithium.
14:00The problem was the anode.
14:02Whittingham's design used pure lithium, which worked brilliantly until it did it.
14:07We've made a special cell.
14:09We made a transparent battery.
14:11That's so cool.
14:12But they're very, very small.
14:13So we have a microscope lens just to allow us to see it.
14:17What you're seeing here is a piece of copper, which we're gradually plating with lithium.
14:23So this is analogous to the first generation lithium metal batteries, which use lithium metal as the anode.
14:30On this side, we have a piece of lithium.
14:33As we charge the battery, we're stripping the lithium from that electrode and we're plating it.
14:37And actually what's happening right now is the ideal reaction where it's very slow.
14:42We're getting a dense plate.
14:44The challenge then becomes if we go too fast.
14:47Oh, that is huge.
14:51Everything's fine until all of a sudden it's not fine.
14:55So we want the lithium to plate evenly across everywhere, but instead it forms in that one location.
15:01And that is what is a lithium dendrite.
15:04That lithium dendrite can grow.
15:06The length scales of this is on the order of, you know, millimeters.
15:11So that would have easily short-circuited the battery.
15:13And that dendrite can just keep growing and eventually it's going to poke through the separator and reach to the other side.
15:21Now the electrons are going to have a shortcut.
15:23So instead of going through the circuit, they race straight from the anode to the cathode using the dendrite.
15:29And that sudden surge of electrons cause intense heating and that can trigger a chain reaction inside the battery, leading to a fire or even an explosion.
15:39For all its promise, Whittingham's battery was just too dangerous.
15:44And then the oil crisis ended.
15:47Prices dropped and Exxon's urgency evaporated.
15:50The company shut down its lithium battery program.
15:53Whittingham published his design in 1976 and Exxon licensed the patent to a few manufacturers.
15:59But with no funding and no momentum, the first lithium battery revolution died before it had a chance to take off.
16:05Fortunately, a copy of Whittingham's paper made it across the Atlantic to Oxford University in England, where it caught the attention of John B. Goodenough, an American physicist leading a solid-state chemistry group.
16:18As he read the paper, one thing stood out.
16:21The cell voltage was being held back.
16:23The material Whittingham chose for the cathode, titanium disulfide, capped the cell at just 2.4 volts.
16:30But Goodenough believed that with a better cathode material, he could do better.
16:34He had previously worked with compounds called transition metal oxides.
16:39They were more stable than sulfides, and some, he knew, were extremely hungry for electrons, perfect for a cathode.
16:46He tried one of these compounds in his battery, and the voltage immediately spiked from 2.4 volts to 4 volts.
16:52This jump was incredible.
16:54But what was even more surprising was the fact that this compound already had lithium in it.
17:00The material was lithium cobalt oxide.
17:02Lithium cobalt oxide is arranged so that the cobalt and oxygen atoms form tightly bonded layers, with lithium ions nestled in between.
17:12This means that your supply of lithium ions doesn't just have to come from the dangerous lithium metal on the anode side.
17:18It's already there, pre-built into the cathode.
17:21So theoretically, you don't even need lithium metal at all.
17:24You could assemble the cell in a discharged state, with all your lithium ions in the cathode.
17:30Then when you connect it to a charger, these ions will get expelled from the cathode crystal lattice and into the electrolyte.
17:35At the same time, nearby cobalt atoms will give up an electron to balance out the charge,
17:40and those electrons then go through the wire to the anode to meet with the ions.
17:44If Goodenough could find an anode that would replace lithium metal,
17:48the battery would become safe enough to leave the lab and actually power real-world devices.
17:53Goodenough was so excited about the potential of his design that he reached out to battery companies across the US, the UK, and Europe.
18:01But incredibly, no one was interested.
18:04So he asked Oxford to file a patent, but they refused.
18:09So he took it to a government lab near Oxford, the Atomic Energy Research Establishment.
18:14And finally, they agreed to fund the patent, but only if Goodenough signed away his financial rights.
18:21Seeing no other option, he agreed, and the lab patented the invention in 1981.
18:27Now, this should have been a goldmine, but the lab didn't realize what they had.
18:33And so for the second time, the lithium battery revolution was boxed up and shelved.
18:38This should have been a turning point for battery science, but bureaucracy and inertia stalled progress.
18:44Every field has its bottlenecks.
18:46For batteries, it was slow-moving institutions.
18:49For developers today, it's slow-moving code reviews.
18:53And I can relate.
18:54When we make these videos, especially the ones with simulations or complex animations,
18:58it's rarely the ideas that slow us down.
19:00It is the reviews.
19:02Developers face the same thing.
19:03They're writing code faster than ever, thanks to tools like Copilot and Cursor.
19:08But code reviews?
19:09Well, they're still manual and still slow.
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20:01And now, back to Goodenough's design, a breakthrough with nowhere to go yet.
20:07While Goodenough's battery design was gathering dust 10,000 kilometers away in Japan,
20:11a 34-year-old chemist named Akira Yoshino was trying to find a safer battery anode,
20:17one that didn't require lithium metal.
20:20Yoshino was actually looking at plastic.
20:22Now, normally, plastic is an insulator, but the kind Yoshino was looking at is different.
20:28It's called polyacetylene, and its carbon atoms are arranged in a repeating chain of single and double bonds,
20:34a structure that gives it unusual electronic properties.
20:38If you tweak polyacetylene by adding or removing electrons,
20:42electrons can actually move along this carbon chain.
20:45So the plastic conducts electricity like a metal.
20:48And that got Yoshino thinking.
20:50What if polyacetylene could work as a battery anode?
20:53During charging, it could absorb lithium ions and electrons,
20:57and then, during discharge, it would give up those electrons to the circuit,
21:01just like lithium metal does.
21:02If it worked, it could eliminate the most dangerous part of the battery,
21:06the metallic lithium.
21:08But for months, Yoshino struggled.
21:10Obviously, since he removed lithium metal from the anode,
21:13he had to get lithium ions from somewhere else.
21:15And he couldn't figure it out.
21:17And then, just as he was losing hope,
21:19on the last workday of 1982, while cleaning out his office,
21:23he stumbled upon a 1980 paper by John B. Goodenough.
21:26It described a cathode made of lithium cobalt oxide,
21:29a cathode that already contained lithium.
21:33This was the missing piece.
21:35He sketched out the reaction between lithium cobalt oxide and his lithium-free anode,
21:40and then built a test cell using the two materials.
21:43It worked, safely and reliably.
21:46But Yoshino wasn't satisfied.
21:48The material he used for the anode, the polyacetylene,
21:51had an extremely low density.
21:53I mean, it couldn't pack in enough lithium.
21:56So the energy density of the battery was terrible.
21:59Yoshino needed something more lightweight, compact, conductive,
22:03and crucially, something that could reversibly accept and release lithium ions
22:07within its structure without breaking down.
22:09He tested material after material, and every single one failed,
22:13until a breakthrough came from within his own company.
22:17Another team had developed a new form of carbon with a unique crystalline structure.
22:21They called it vapor-grown carbon fiber.
22:24He got his hands on a sample, tried it in the lab, and it worked.
22:29To prove it, he placed a test cell containing metallic lithium into a safety rig,
22:34one that's designed to test explosives.
22:36Then he dropped a heavy iron rod onto it.
22:39It exploded violently.
22:42Then he ran the same test again, but this time with his new design,
22:45using carbon as the anode.
22:47He charged the cell, placed it in the rig, and dropped the rod.
22:51But nothing happened.
22:53The contrast was undeniable.
22:57Later, Yoshino would say,
22:59that was the moment when the lithium-ion battery was born.
23:03But his employer, Asahi Chemical,
23:05well, they weren't a battery company,
23:07and they didn't know how to make batteries.
23:11So, in 1986,
23:12Asahi executive Izeo Kurabayashi flew to Boston on a top-secret mission,
23:17carrying three jars containing cathode, anode, and electrolyte materials.
23:22He handed them to a tiny firm called Battery Engineering,
23:25working out of a converted truck garage,
23:27and he asked them to turn the materials into cylindrical cells,
23:31like the kind you might buy for a flashlight.
23:33The team did just that, completely unaware of what they were handling.
23:38It wasn't until 2020 that employees learned the truth,
23:41that they had helped assemble the world's first pre-production lithium-ion batteries.
23:46Two weeks later,
23:48Kurabayashi returned to Japan with 200 finished, perfectly functioning cells.
23:53Even then, Asahi's leadership hesitated.
23:56Kurabayashi refused to give up.
23:58On the 21st of January, 1987, he visited Sony,
24:01and he took one of the prototype cells and rolled it across the conference table to the Sony execs.
24:06And at last,
24:08they saw its potential.
24:10They reworked the design,
24:12swapping out Yoshino's carbon material for graphite
24:14that could better intercalate lithium-ions between its layers.
24:17And in 1991,
24:19Sony launched the first commercial lithium-ion battery inside this,
24:23the Sony Handycam.
24:25Their battery was compact, rechargeable, powerful,
24:28and crucially, free of unstable lithium metal.
24:32It was Sony who first coined the name lithium-ion.
24:35And it stuck.
24:38But this wasn't just about one camcorder.
24:41Competing companies like Panasonic and Sanyo raced to catch up.
24:44Lithium-ion batteries started appearing in phones,
24:48CD players,
24:48laptops.
24:49Manufacturers actually began to advertise the use of lithium-ion batteries
24:53as a key selling point to their products.
24:55I'm showing my age here.
24:56I joined the industry when lithium-ion cells were first introduced.
25:00And there was a Sony camcorder that was introduced.
25:03And then there was Dell Computer.
25:04And I still remember the ads when Dell Computer introduced their lithium-ion battery.
25:08And they had eight hours of runtime.
25:10So they had an advertisement in a magazine.
25:12It was eight pages long.
25:13Each one was an hour longer.
25:15So it was a big deal.
25:17But what's crazy is that even after all this,
25:19these batteries should never have worked.
25:21See, when you charge the battery for the first time,
25:24lithium-ions move from the cathode to the graphite anode.
25:27And here, they react with the electrolyte to form
25:30this weird, complex patchwork of compounds
25:33that build up on the anode's surface.
25:36These parasitic side reactions should keep going on indefinitely,
25:39using up all the lithium and destroying the cell.
25:42But they don't.
25:44Instead, they form a thin protective layer known as the solid electrolyte interface, or SEI.
25:50It's a kind of chemical shield protecting both the graphite anode and the electrolyte from further reactions.
25:56But crucially, lithium-ions can still slip through it.
25:59When the SEI originally forms, during the first charging cycle,
26:04around 5% of the lithium in the cell actually gets stuck in this layer,
26:08decreasing the battery's capacity.
26:10But this little trade-off is what makes the battery stable enough to be used for years,
26:14or even decades.
26:16Which is why today, lithium-ion batteries are virtually everywhere.
26:19From 1991 to 2023, the price per kilowatt hour dropped by 99%,
26:26from nearly $9,000 to just $100.
26:29At the same time, energy density and cycle life,
26:32how many times a battery can be charged and discharged before it wears out,
26:36improved dramatically, crossing a critical threshold.
26:39Lithium-ion batteries had become powerful enough,
26:41and finally cheap enough for something bigger.
26:44The return of the electric car.
26:46Today, lithium-ion powers a $100 billion industry.
26:53In 2019, Whittingham, Goodenough, and Yoshino
26:55finally received the Nobel Prize in Chemistry
26:57for an invention that, in the committee's words,
27:00revolutionized our way of life.
27:02This made Goodenough the oldest Nobel laureate in history,
27:06receiving the award at the age of 97.
27:10But lithium-ion isn't perfect.
27:13Scary moments aboard a jet blue plane,
27:15a fire erupting after a passenger's backpack suddenly exploded.
27:19Every week, inside an airplane, there is at least one event
27:22of a battery, of a phone, of an iPad, or a toy, or something
27:27that has got into fire.
27:28What? Every week?
27:29Yeah, yeah, yeah, every week.
27:30It's just the latest incident aboard a plane involving lithium-ion batteries.
27:35So far this year, 60 onboard battery incidents through early October.
27:39Every flight in the U.S. has a bag, a specialized bag,
27:44with very thick, non-flammable materials,
27:47where you put the phone inside, and you close it.
27:50And you still have a hazard, and you have to deal with these gases.
27:53But now you have put the fire ignition away from anything else,
27:57and if it bursts into fireworks, then at least it's in a container.
28:02And then you tell the captain, we need to land immediately.
28:05So what is actually happening when a battery fails like that?
28:09This is a classic lithium-ion battery,
28:12and today we're going to do something I always wanted to do.
28:14We're going to tear one down.
28:15I guess, safe to say, don't do this at home.
28:19But what would happen if you were to do this outside of the glove box?
28:22If you charged up the cell, and then you tried to tear it up,
28:26then you could accidentally short it, and then it could burn,
28:30and it could even explode or fire.
28:32If you discharged it and you opened it up,
28:35you'd release all the different gases and really toxic chemicals,
28:39and if you inhale those, then you'd probably end up in hospital.
28:43So at this point, we have what we call the jelly roll.
28:47So it's a roll of a cathode, separates an anode,
28:50stuck together a bit of tape.
28:52So Liren's just going to scalpel off the tape,
28:54and then we should be able to unroll it into a nice sheet.
28:58So these little patches are the electrolyte?
29:00Yeah.
29:00So as time goes by, we'll start evaporating out.
29:03That is so cool.
29:05It's so obvious when you see it,
29:07but I don't think anyone intuitively thinks
29:09that it's a rolled up sheet of anode and cathode inside.
29:13But these layers inside the battery,
29:15they're not going to stay perfect forever.
29:17Here's an electrode from a new cell
29:19compared to one from an old one.
29:21You can see that the lithium is building up in all the wrong places,
29:25and if this sort of degradation gets out of hand,
29:28well, we're about to push a cell past its breaking point.
29:32How do we blow up a battery?
29:33So today we've got a prismatic battery.
29:36It's a small battery from sort of a power tool
29:39or a phone or something similar.
29:41We're going to wrap it in some micron wire.
29:43So we pass current through this wire,
29:46something like 200 watts we pass through this wire.
29:49Yeah, it's a significant battery.
29:51We want it to go, and we want it to go pretty spectacularly.
29:53Good luck, Harry.
29:59What we're simulating here is a catastrophic battery failure,
30:03the kind that could happen if a cell is damaged or overheated
30:06or even just badly manufactured.
30:08It starts around 80 degrees Celsius
30:10when the protective SEI layer on the anode starts to break down.
30:14It's going to try to reform,
30:16but these reactions are going to release more heat,
30:19and if that heat can escape,
30:20the temperature is going to keep rising.
30:23How close is it to exploding now?
30:26What do you think?
30:27It's just burst very soon.
30:29At roughly 130 degrees Celsius,
30:31the polymer separator is going to melt,
30:33and now the anode and cathode can come into direct contact,
30:37and a massive internal short follows.
30:40The cathode itself starts to decompose,
30:43and because transition metal oxides release oxygen
30:45from their crystal structure,
30:47they're going to fuel the combustion,
30:48and now the fire is just feeding itself.
30:52Oh.
30:52Yes.
30:54Oh.
30:54Oh my God.
30:57That's really violent.
30:59This is insane.
31:00From one small battery like that?
31:02And it's only 50% of the state of charge.
31:05What we call ignition happens inside the battery,
31:08not outside the battery,
31:08and it requires a fuel
31:11or a substance that will undergo a reaction.
31:14It requires an oxidizer,
31:16or the equivalent of the oxidizer,
31:17and it requires heat.
31:18The battery contains these three inside,
31:21so it has its own equivalent to an oxidizer,
31:24its own equivalent to a fuel,
31:25and its own source of heat.
31:27Yeah.
31:27All of it in one device.
31:30So it's not actually lithium that burns.
31:32A modern lithium-ion battery,
31:35like this one here,
31:36contains very little lithium, ironically.
31:38It's actually everything else inside here
31:40that's dangerous.
31:41It must be really hard putting out a battery fire
31:45if it really has everything it needs.
31:47Yeah, exactly.
31:48So you can still put the blanket
31:49and stop the oxygen from arriving,
31:52but the fire will not go to zero.
31:54It will be smaller,
31:56but it will still be there.
31:57And then with water,
31:58yeah, water has the ability to take heat away.
32:00So it is possible to take the heat away
32:02from the battery with water.
32:03The best thing is to put an immersive battery
32:05into a bath of water.
32:07Yeah.
32:08It's brutal.
32:09You can do it with one battery,
32:11with 10 batteries,
32:12with 10, 15 batteries,
32:13but when you have very large packs of batteries
32:16with thousands of batteries,
32:17you cannot physically put that under water.
32:20Yeah, one thing that is popping up recently
32:22as a threat to cities is electric car fires.
32:26Well, we know a lot of water works.
32:28Yeah, well, if there's a water source nearby,
32:30I guess, yeah.
32:31Yeah, I mean, this is what they do
32:32in some countries around the world.
32:34They have a truck,
32:35a specialist truck full of water
32:37and you just take the car
32:38that has been involved in electric fire
32:40and they dump it into the...
32:41No way.
32:42Yeah, they do.
32:43And actually it works.
32:45So how dangerous is it really?
32:48It's very rare.
32:49Every million batteries,
32:50there is a fire.
32:51Okay.
32:51So that's very safe.
32:52That in the standards of engineering,
32:54that's like,
32:54oh, you have a good system,
32:55one out of a million,
32:56that's a fire.
32:57But batteries are everywhere.
32:59We don't even think about it.
33:01So within our lifetimes,
33:03we are going to reach a point
33:04where we would have been exposed
33:06to more than a million batteries.
33:08So we would be,
33:08all of us,
33:09experiencing a fire of a battery.
33:11With billions of batteries in circulation,
33:13even rare failures become inevitable.
33:17Meanwhile, demand is skyrocketing.
33:20By 2030,
33:21we're projected to need
33:22over 17 million tons
33:23of battery-grade materials.
33:25And making lithium-ion batteries
33:27comes at a cost.
33:29Lithium only makes up
33:29around 20 parts per million
33:31of Earth's crust.
33:32It's expensive
33:33and water-intensive to extract.
33:35And 70% of cobalt,
33:37another key ingredient
33:38in many lithium-ion designs,
33:40comes from
33:40the Democratic Republic of Congo,
33:42much of it mined
33:43under hazardous,
33:43often exploitative conditions.
33:46We need more batteries,
33:47and we need them fast.
33:48We can't just rely
33:49on lithium alone.
33:51So it's not like
33:51lithium is as good
33:52as we're going to get.
33:53Then we're going to get
33:54much better batteries
33:55in the future.
33:56If our priorities
33:57are about saving the planet
33:59from runaway climate change,
34:01we need to have
34:02massive-scale energy storage system
34:04and electrify
34:05almost everything else
34:06that we do.
34:07The hunt is still on.
34:09For safer batteries,
34:10for cheaper ones,
34:11ones that last longer,
34:13charge faster,
34:13and ones that store
34:14far more energy.
34:16The lithium-ion battery
34:17changed the world,
34:19but the future of energy storage
34:20won't be about
34:21just conquering one element.
34:23It'll be about
34:23mastering many.
34:29depending on your
34:31what verd weitere concerning
34:32what they allow
34:33technologygangen
34:34to waste from
34:37across the continent.
34:39And take a look at
34:41the biosăăă
34:42where they want
34:42that satellite
34:43itself.
34:44They're also
34:44depending on
34:45the Niss Đ”Ń
34:45as to the
34:46denk aus.
34:47And we're
34:48trying to
34:49keep the
34:50catering
34:51and
34:52catering
34:54to
34:54Imp 1990
34:54cy
34:56away
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