E6: Dealing with dead batteries

LHF: Hello, and welcome to Today I Learned: Climate, the climate change podcast from the Massachusetts Institute of Technology. I’m Laur Hesse Fisher.

Today’s drivers are buying a lot more electric vehicles, or EVs as they’re also known. In fact, from just 2022 to 2023, the world’s demand for the batteries that power these EVs grew by 40%.

And that’s prompted several listeners and readers to ask us: What are we going to do with all these EV batteries after they die?

As our guest today will tell you, that’s not a trivial problem.

LG: My name is Linda Gaines, and I work at Argonne National Laboratory. And I've been looking at lifecycle analysis, which is basically an analysis of what goes into the manufacture of all sorts of goods, from raw materials in the ground all the way through a finished product. Where does the product get manufactured? How does it get manufactured? And then, at the end of its life, can you reuse it? Can you repair it? Or do you have to just throw it out?

LHF: For our show, Dr. Gaines is going to bring that lens to EV batteries. What’s in them? Can we recycle all of those materials? And if not, what can we do about that?

And to get started, we should be specific about what kind of battery we’re talking about. For nearly all EVs sold today, that would be lithium-ion batteries.

LG: Lithium-ion batteries are much more energy-dense than other previous chemistries. And so you can make a much smaller, lighter battery.

LHF: Lithium-ion batteries are the reason we have phones that fit in our pockets and hold enough charge to last all day. And this technology is equally crucial for EVs.

LG: I mean there were electric vehicles previously, but they were all powered by lead acid batteries, which are very heavy. And what those vehicles ended up being was basically a battery on wheels. And there wasn't really much room for passengers or cargo or anything.

LHF: With lithium-ion batteries, we now can have roomy, zippy cars that run on electricity. Now, this is a big deal, because cars and trucks that run on gasoline produce literally billions of tons of planet-warming greenhouse gases every year. And we would eliminate almost all of that pollution if we drove EVs instead, and charged them on electricity from cleaner energy like wind, solar or nuclear.

And, fun fact, because of how energy efficient these EV batteries are, even if you were to charge your EV with electricity generated from coal, you would still produce less pollution than a traditional gasoline car.

But while EVs don’t burn gasoline, they do require new kinds of materials that gasoline-powered cars don’t. So let’s take a beat to figure out what’s inside an EV battery.

LG: In any battery, there's an anode and a cathode, and some charged particle, either an electron or a lithium ion, is going back and forth from one to the other. And in one direction it's charging the battery, and then you can connect a wire from one to the other, and electrons will go the other way, and you can get energy out.

LHF: It’s kind of like that child’s game red rover. Like, red rover, red rover, send the electrons over! When you’re driving, the electrons come running along a circuit from one side of the battery to the other, providing the power to move the car. And then when you charge it, they run back to where they started.

And there are many materials used to coax the electrons across the battery.

We’ll start with the lithium that these batteries are named for. So when we say “lithium-ion batteries,” we’re referring to the single atoms of lithium that dash across the battery, like part of the same red rover team. Lithium is a metal. It can be mined, and we also find it dissolved in water.

LG: The way that it has been extracted most until very recently is from salt lakes. In particular, there's a set of lakes in the Andes Mountains in Chile that are extremely concentrated in lithium salts. And so what happens is you pump these concentrated lithium salt solutions into big ponds and let the sun evaporate the water.

LHF: Which can cause problems when there are water shortages—as Chile is wrestling with right now. But it’s not just lithium that we’re concerned about. There’s a part of the battery called a “cathode” that is made of several metals bonded together.

LG: The cathode material in a lithium-ion battery is a chemical compound that's made of lithium and oxides of cobalt, nickel, and manganese. Historically, they've basically been dug out in either surface or underground mines, and then taken to a smelter. 

LHF: This can cause local problems. For example, cobalt, one of those cathode materials that Dr. Gaines just mentioned, mostly comes from the Democratic Republic of the Congo, where many miners live and work in terribly exploitative conditions.

So it would be ridiculous to just throw these materials away when a battery dies. But recovering them is not quite as simple yet as plucking a lump of cobalt out of an old battery pack.

That cobalt is bound up with all the other metals in the cathode. And then the battery also contains an anode, an electrolyte, and aluminum and copper. 

All these materials are arranged in super-thin sheets, and then folded or rolled up together into what is called a battery cell.

LG: But an actual battery pack has lots of cells in it. And if you think about a Tesla, Tesla has cylindrical cells, so they're kind of stuck like beer cans in a six-pack kind of thing.

LHF: If we’re talking about a Tesla Model 3, our six-pack is actually more like a three or four-thousand-pack, with all these cells cemented together. And that pack is the big rectangular slab that actually goes in the car.

And as you drive around, just like everything else, this big, complicated battery slowly, slowly starts to break down.

LG: When the battery is charged and discharged, the lithium ions can get stuck on the surface of the anode, or react with some of the molecules in the electrolyte. Basically fewer and fewer lithium ions are free to travel back and forth. And so the capacity of the battery decreases as it gets older.

LHF: And, eventually, after maybe three hundred thousand miles or so, this battery, like all batteries, will die. And when that happens, we’d really like to get the valuable materials back so that we can reuse them.

But it’s not like we’re just separating our paper from our glass here.

LG: The cathode material is a very elegant and complex crystal structure, and if you can actually retain that during the recycling process, you are getting a much higher value product out and not having to redo all of the steps that it took to make it.

LHF: Right, ideally what we want is not actually pure cobalt and nickel—we want the elegant crystal structure that’s so good at giving us our electric charge. But the closer we come to that ideal, the harder the recycling process is going to be.

So let’s say you want to do as little work as possible to recycle your battery. The method for you is called “pyrometallurgical recycling.”

LG: And in that you basically throw the battery into a big furnace. And some of this stuff burns, and some of the stuff melts. And what you get out of the bottom of the smelter is a mixed alloy of cobalt and nickel and manganese, which can then be put back into batteries after processing. 

LHF: A jumble of melted-down metals is not very close to our beautiful cathode. At least we don’t have to mine the materials from scratch! But we can do better.

The next option would be to put the battery cells through a big shredder, and get them ready for “hydrometallurgical recycling.”

LG: You basically dissolve the chopped up battery in acid. And the acid is a big soup that includes all of the different ions that were in the cathode material, and also anything that was in the electrolyte. And you can do chemical reactions on that soup to recover the different elements separately.

LHF: The cathode is still destroyed… but this time, we have pure metals to make a new cathode. That’s better, but it’s still kind of wasteful, right?

LG: Ideally, I would like to see some kind of a system where you didn't need to shred the whole thing. One small company in Switzerland in particular, has designed their own cells for recycling, and they are building a machine that grabs one electrode and another arm grabs the other one and just pulls apart this whole layered structure, so that one arm is holding anode sheets, and the other is holding strips of cathode. So there are things you can imagine, but none of them has been developed commercially at a large scale.

LHF: This is called “direct recycling,” and if we can do it, it would give us back our cathode practically intact. With a little fixing up, it would be ready to put in a brand-new battery. 

But as you can tell, direct recycling really depends on the manufacturers designing their cells to be taken apart. And so far, most battery engineers have had other innovations on their mind. 

LG: As battery technology evolves, which it's doing very quickly, that makes a big challenge for battery recyclers, because they really don't know what they're going to be having to handle ten years down the pike. And so it's hoped that we can develop some recycling technologies that are more or less generic and would work no matter what the battery design was. It's a challenge.

LHF: So there’s another issue here, and I was actually quite surprised. There aren’t yet enough batteries to recycle.

LG: Originally people thought that electric vehicle batteries would only last a few years, and probably would have to be recycled and replaced sometime during the lifetime of the car. In actual experience, these batteries are really lasting the lifetime of the car, and in fact, they may be outlasting the car. 

LHF: And when they do outlast the car, even then today’s EV batteries are mostly not going to recyclers… because they’re still good enough to find a second life.

LG: If you've got solar panels on your roof and you want to store energy to use at night, you can use an old battery as a backup. There's a big stadium in Amsterdam that's powered by old Nissan Leaf batteries. So there are lots of ways you can use these batteries if you don't demand the level of performance that people are expecting from their vehicles.

LHF: So to step back for a minute, we should also be clear about what battery recycling can and can’t do. It can leave us with less waste when batteries eventually die. But it can’t replace the need to mine more lithium and cobalt and nickel, at least not while the EV market is still growing as fast as it is.

LG: If you think about it logically, because there's been such rapid growth, even if we could get back everything that we put into circulation ten years ago, it would only be supplying a very small percentage of our demand. So we need to be thinking about where all this material is going to come from.

LHF: Can we improve mining so that it more efficiently produces the metals that we need? And how can we of course improve the conditions of these mines for local workers and communities? Or can we take the most challenging materials, like cobalt, completely out of the equation? 

A big portion of the EV market now is using a chemistry called lithium-iron-phosphate, which has no cobalt at all. And there are EV batteries that are using sodium now instead of lithium. And just while we were recording this episode, Ford announced it’s investing in cathodes that use mostly manganese, which they expect to give them a longer driving range.

So if you're asking how we'll deal with all these batteries when they die—to some extent, we just don't know yet. Partly because we're still figuring out what they'll look like when they're alive.

That’s our show. Thank you to everyone who reached out with questions about EV batteries. And if you have another question about climate change and its solutions, we’d love to hear it! Call us, leave us a voicemail at 617 253 3566, or send your question in through climate.mit.edu/ask.

TILclimate is the climate change podcast of the Massachusetts Institute of Technology. Aaron Krol is our Writer and Executive Producer. David Lishansky is our Sound Editor and Producer. Michelle Harris is our fact-checker. Madison Goldberg is our Associate Producer. Grace Sawin is our Student Production Assistant. The music is by Blue Dot Sessions. And I’m your Host and Senior Editor, Laur Hesse Fisher.