Batteries are everywhere — they’re in our phones, our computers, our cars, our toys. But how do they work? To find out, we talk to a scientist who’s making really big batteries to store renewable energy, another who’s working on really small ones to power our phones, and we play in a park with a dog. All that, plus the mystery sound!

Want to hear more about electricity? Listen to the rest of our Electricity series:

Part 1: Shocking! The science of static

Part 2: High voltage! How electric power reaches your outlet

Part 3: Charged up! The science of batteries

Part 4: The nerve! Electricity in our bodies

Audio Transcript

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[DING] KATHY: Oh. My pie is ready.

GRIFF JENKINS: Hey, Brains On! Two of the world's most rad celebrity chefs here-- me, Griff Jenkins.


Yeah-- ha-ha!

KATHY: And Kathy from Cooking with Kathy.


GRIFF JENKINS: You might be asking yourself, why are there so many chefs on a science podcast?

KATHY: Well, Brains On! is no ordinary show. We find science everywhere-- in baking bread--


Oh, look. My bread is ready.

GRIFF JENKINS: Or in elevator's.


KATHY: Or slime.


GRIFF JENKINS: Or molecular bonds.


KATHY: Actually, that one's kind of already science.

GRIFF JENKINS: Yeah. I probably should have--

KATHY: Maybe another example?

GRIFF JENKINS: Right. Oh, we find science in farts.




Check it-- ha-ha.


KATHY: Oh, excuse me. My bean and broccoli casserole is ready.


GRIFF JENKINS: Jeez, how much are you cooking right now?

KATHY: Just a few things to snack on. Anyway, no matter what you're curious about, we can help you find the science behind it.

GRIFF JENKINS: Understanding science not only helps you go far in life, it's also totally righteous.



Oh, the cupcakes! So because learning about the world is important to you--


Oh, right, the pizza. Where was I? Oh, yeah, because learning is important, please support--


Can you take out the chicken, Griff? Please support Brains On! with a gift--


--of amount to keep the show going.



Excuse me. I think something's burning. Can you take over?

GRIFF JENKINS: No problemo. To support the show, just go to You can get a rad color-changing water bottle or Brains On! headphones. And don't forget, donating to Brains On! is tax deductible, bruh. Saving on tax day is boss.


So once again, that's Thanks!


KATHY: Chris, bring the fire extinguisher.

ANNOUNCER 1: You're listening to Brains On! where we're serious about being curious.

ANNOUNCER 2: Brains On! is supported in part by a grant from the National Science Foundation.

MOLLY BLOOM: Welcome to the third installment of our Brains On! electricity series.

And the third event in the electric game.


ANNOUNCER 3: Today, two thinkers, two experimenters, take it to the mat-- the gym mat. They will hurtle themselves down the floor and over the vaulting horse, powered only by the steam of their ideas. Will they stick the landing? Will they impress the judges? First with an attempt is Luigi Galvani.


LUIGI GALVANI: You guys, this cool thing happened when I was dissecting a frog. His leg jerked, even though he was dead.


It made me think we have electricity flowing through our tissue. Huh-- animal electricity.


ANNOUNCER 3: Very interesting and very unexpected. Next up, Alessandro Volta.


ALESSANDRO VOLTA: Yeah, that leg jerked.


But it was because of the metal in your knife, no animal tissue necessary. [GRUNTS] I can create current just using metal.


ANNOUNCER 3: What? Amazing! And he sticks the landing. What will the judges say? Who is right? Stay tuned.


(SINGING) E-L-E-C-T-R-I-C-I-T-Y, electricity, my, oh, my. It's an exchange of charge from electrons, you'll see. And it's a form of energy. Woo! Electricity, electricity, electricity, electricity, electricity, electricity, electricity, electricity, electricity, electricity, electricity.


MOLLY BLOOM: You're listening to Brains On! from American Public Media. I'm Molly Bloom, and my co-host for this electricity series is Habte Martone. Hi, Habte.

HABTE MARTONE: I'm electrified to be here on my favorite, favorite, favorite podcast. Do you get it-- electrified?

MOLLY BLOOM: (LAUGHING) I know. That's good. So far in our series, we've talked static electricity and current electricity. And today is all about batteries.

HABTE MARTONE: As you just heard, the story of batteries starts with two scientists, Luigi Galvani and Alessandro Volta.

MOLLY BLOOM: Luigi Galvani was a professor of anatomy in Bologna.

LUIGI GALVANI: That's me. I'm Luigi.

HABTE MARTONE: And, as you do in anatomy, he spent a good amount of time dissecting frogs.

MOLLY BLOOM: That means he was looking at the insides of frogs that were no longer alive.

LUIGI GALVANI: What? You want me to do it when the frog is still alive?

HABTE MARTONE: And like lots of scientists of his time, he was very interested in electricity.

LUIGI GALVANI: Have you seen my electrostatic generator? And how about my sweet Leyden jar here? And check this out. If I touch this frog's nerve with a scissors during a lightning storm, the frog's leg twitches. It's like it's alive! It's alive!


But it's not. It's most certainly dead.

MOLLY BLOOM: He did many experiments with electricity and frogs and eventually published his findings, announcing a new force called--

MOLLY AND LUIGI: Animal electricity.

HABTE MARTONE: So you might be saying to yourself, sure, hearing about frog dissections and electricity is awesome. But what does that have to do with batteries?

ALESSANDRO VOLTA: That's where I come in.

MOLLY BLOOM: That's Alessandro Volta.

ALESSANDRO VOLTA: Alessandro Giuseppe Antonio Anastasio Volta.

HABTE MARTONE: He was also an Italian scientist.

MOLLY BLOOM: An Italian scientist who did not agree with Galvani's idea.

ALESSANDRO VOLTA: I do not agree.

HABTE MARTONE: So he set out to prove that this current had nothing to do with the animal and everything to do with the metals involved.

ALESSANDRO VOLTA: I call it metallic electricity.

MOLLY BLOOM: He experimented with different metals and was able to generate a weak current.

ALESSANDRO VOLTA: There weren't any instruments to help detect it, so I used my tongue.

HABTE MARTONE: That doesn't sound safe.

ALESSANDRO VOLTA: Oh, and let me tell you about this experiment. I got four people together. The first put his finger on the second's tongue. The second put their finger on the third's eyeball. And the third and fourth held either side of a skinned, gutted frog.

Then the first held a piece of zinc, and the last held a piece of silver. When the two metals touched, the second person had a weird acid taste on their tongue. The third had a flash in their eye. And the frog twitched pretty violently. Nifty, huh? And all thanks to the metals.


HABTE MARTONE: Then Volta moved on to making piles of metals.

ALESSANDRO VOLTA: OK, get this. I made stacks of alternating zinc and silver disks-- zinc, silver, zinc, silver. You get the picture.

MOLLY BLOOM: And between each disk was a piece of cloth or paper or leather soaked in salt water or vinegar.

HABTE MARTONE: That moisture was inspired by the moisture on our tongues, in our eyeballs, or in a frog.

ALESSANDRO VOLTA: I noticed some moisture was needed. Sure, call it frog juice, whatever, but it worked. My piles generated a steady current.

HABTE MARTONE: These became known as voltaic piles. The discovery rocked the scientific world, and Galvani's ideas were quietly pushed aside for a time.

MOLLY BLOOM: And you know the term volt?

HABTE MARTONE: yep-- Named after Alessandro Volta.

ALESSANDRO VOLTA: Alessandro Giuseppe Antonio Anastasio Volta.

MOLLY BLOOM: But the disagreement between Volta and Galvani was not ferocious. In fact, Volta name the phenomenon of electricity produced by chemical action galvanism after Galvani. And he once wrote that Galvani's work contains--

MOLLY AND ALESSANDRO: --one of the most beautiful and surprising--

ALESSANDRO VOLTA: --discoveries and the seed for many others.

HABTE MARTONE: And it turned out that Galvani was right, too. There is electricity in our bodies.

MOLLY BLOOM: But we'll have to wait until the next episode to hear more about that.

ANNOUNCER: Stay tuned.

(SINGING) Ba-ba ba-ba ba-ba ba-ba-ba ba ba Brains On!

HABTE MARTONE: So, with the voltaic pile, Volta invented batteries. But how exactly do they work?

MOLLY BLOOM: Here to explain is Brains On! producer Sanden Totten.

SANDEN TOTTEN: Batteries are great. You pop a couple in, say, your flashlight, and, bam, you have portable light in your pocket with a portable energy source. So long, wires. But lots of you want to know how these things actually work.

AURORA: My name is Aurora from Houston, Texas.

ANGELINE: My name is Angeline. I'm from California.

SOFIA: My name is Sofia from Scotch Plains, New Jersey.

AURORA: How do you batteries have that much energy inside when they are so little?

ANGELINE: How do batteries make things work?

SOFIA: What is inside a battery?

SANDEN TOTTEN: OK. I want you to picture your typical AA battery. One end has a plus sign, the other a minus sign-- positive and negative. Now, those aren't just there to show you how to put the battery in your flashlight. Let's zoom in and see what's inside.

(SINGING) Zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom.

At each end of the battery is something called an electrode. The electrodes contain metals. The one on the positive side is called the cathode, and the one on the negative side is called the anode. When the battery gets charged, the metal atoms from the cathode become positive.


At the same time, the charging makes the anode become negative.


So the positive metal atoms from the cathode, they move to the negatively charged anode because opposites attract. Positive likes to find negative. And since those cathode atoms have a positive charge, they also attract negatively charged electrons-- you know, to balance themselves out.

So now you have these pairs, these positively charged atoms with their newfound electrons, hanging out, all of them in the negatively charged anode. And it stays like this until you turn on your device.


That makes them want to go back to their home, the cathode. But the problem is, in a battery, there's an electrolyte, or a paste or liquid, in between them and their home. Now, the positive atom can just go right through that electrolyte, no problem. But the electron can't.

So the electron is forced to take the long way back to the cathode-- through a circuit outside the battery. And as the electron passes through that circuit on its way back to the cathode, it creates electricity. And that powers the device. Now, I know this is kind of hard to picture, so let's imagine it like this.


In this scenario, you are the atom. Your normal resting state is at home. It's like the positively charged cathode. Now, let's say you get all charged up by eating a bowl of sugary cereal.




Now you're in a positive mood, and you want to go out and play. So you head out to the playground on the other side of the lake. The playground is the anode. So there's you, swinging on the swings, sliding on the slide, enjoying life. And since you're so positive, you attract a dog--


--one who's all alone, feeling negative. Remember, opposites attract.


This dog is like that stray electron that joins the positive cathode atom. And the two of you quickly become a pair.


So you're playing. You're having a good time. But when it's time for you to go home to that nice, cozy cathode, the most direct route for you is to swim right through that lake. You're a great swimmer. No problem.


That poor stray dog you just met, he can't swim at all.


He's forced to go around the lake in order to get your house. On the way back, he does some work. He chases a few squirrels out of Mrs. Goldstein's garden.


He eats some garbage on the sidewalk. It was just kind of cluttering things up. Now it's clean. Awesome. And he provides a boost to everyone who sees him.


SANDEN TOTTEN: Because who doesn't love seeing a dog? They're the best. OK, so the two of you meet back at home. You snuggle into bed. Now, imagine the same thing happening over and over again with lots of kids, lots of dogs, over and over, really fast, and you've kind of got the idea of how a battery works.

Speaking of the battery, once all of those positively charged atoms of metal and their partner electrons have made it back to the cathode, your battery's all out of energy, just like you and your new dog at the end of the day and kind of like me right now. So I'm gonna take off. Bye, guys.

KIDS: Brains On!

MOLLY BLOOM: OK, Habte, are your ears all charged up and ready to go?

HABTE MARTONE: Yep. It's time for the mystery sound.


CHILD: (WHISPERING) Mystery sound.

MOLLY BLOOM: Here it is.



OK, what is your guess?

HABTE MARTONE: A mix of an electric saw and a drill.

MOLLY BLOOM: Excellent guess. We are going to be back with the answer later in the show.


HABTE MARTONE: Hey, everyone. The next Brains On! debate is coming soon, and we need your opinions.

MOLLY BLOOM: And we know you have them.

HABTE MARTONE: Which is cooler--

MOLLY BLOOM: --dolphins or octopuses?

HABTE MARTONE: Dun, dun, dun! We know they're both really cool, but you have to pick just one.

MOLLY BLOOM: Record your thoughts and send them to And make sure you tell us why you think dolphins or octopuses are more awesome.

HABTE MARTONE: You could also send questions, mystery sounds, and drawings to that same email address--


HABTE MARTONE: Can't wait to hear your dolphin and octopus thoughts.


You're listening to Brains On! from American Public Media. I'm Habte Martone.

MOLLY BLOOM: And I'm Molly Bloom.

HABTE MARTONE: Even though batteries have been around for hundreds of years, there are new things happening with them all the time.

MOLLY BLOOM: In our last episode, we heard how storing electricity generated by renewable sources like wind and solar is a problem. This is where batteries come in.

HABTE MARTONE: To find out how scientists are working to store clean sources of energy, we have Melanie Sanford here.

MOLLY BLOOM: She's a chemistry professor from the University of Michigan.



HABTE MARTONE: Why isn't everything powered with solar panels?

MELANIE SANFORD: So the reason that everything isn't powered with solar panels is mainly because the sun doesn't shine all the time. It can't actually take an energy and then power things when the sun isn't shining, unless you connect it to some kind of energy storage device, or a battery.

HABTE MARTONE: How do people build batteries?

MELANIE SANFORD: So, well, the kind of batteries that I study are made up of molecules. The scientists that work in my lab can make, sort of in the same way that you put things together with LEGOs-- and so what the scientists in my lab do is take the different elements from the periodic table and snap them together, kind of like LEGOs, to build molecules that have the properties that they can store energy in a battery.

HABTE MARTONE: Cool. What type of molecules can store energy?

MELANIE SANFORD: Well, actually, lots of molecules can store energy. So you know that electricity is electrons flowing through wires, right? And so basically, what you're doing with the molecules that we're working with is actually taking those electrons from the wire and actually directly injecting them into the molecule.

And then when we want to get them back later, we actually pull those electrons out of the molecule to release the energy into the circuit. So we're designing molecules that are specifically designed that they can take those electrons, that electricity, and actually directly store it, store those electrons in them.


MELANIE SANFORD: Yeah. So it's pretty sweet. It's pretty cool. But you can imagine that when you inject an electron into a molecule, things can go horribly wrong. And so if you don't design your molecule right, the molecule can basically explode. And then you can't store any more energy in it because it's gone. So that's bad.

HABTE MARTONE: Kaboom, it exploded.

MELANIE SANFORD: Yeah. I mean, it doesn't explode literally. But the molecule basically-- it's like if you took your LEGO and you smashed it. All the bonds break, and the atoms are kind of blown apart. And so you can't store any more energy.

HABTE MARTONE: Why are there different types and sizes of batteries?

MELANIE SANFORD: So that's a great question. So the reason that there are different types and sizes of batteries is because people need batteries for different things. Let's say you have a cell phone.

You would want a battery for a cell phone that would be really light. And you would want it to be able to store a relatively small amount of energy because it just has to power a phone, which is a pretty small device.

In contrast, if you wanted a battery that would power your whole house, it wouldn't matter if it was light because you don't have to carry that battery around all the time. That would just be sitting in one place. But you'd want it to be able to store a lot of energy because your house uses way more energy than your phone.

And so the kind of battery that you might want for a phone or a car that would be light and wouldn't store that much energy would be really different. You could use it and make it out of really different materials or molecules than the kind of battery that would power your house, for example.

HABTE MARTONE: Why do batteries fill up?

MELANIE SANFORD: The reason that batteries fill up is because-- so remember, I was telling you that we are storing energy in these molecules that can accept an electron. And so you can only store as much energy as you have molecules.

So the great thing about being able to store is that-- so if you have a solar panel on your house during the day, you can power your house with a solar panel. At night, you have to use electricity from the electrical grid.

In principle, if you have a battery, you could store all the excess energy from the sun that's generated during the day, use it to power your house at night, and then you never have to use the electrical grid at all. So it makes you completely independent, potentially, from the electrical grid. Because it sort of levels out, or it allows you to capture the energy that's in excess during the day and then use it at night.

MOLLY BLOOM: So this idea. Seems like so like, yes, of course, you would store it in a battery. So why hasn't it been able to happen yet?

MELANIE SANFORD: Well, so the challenge is we don't have batteries that are really good for this. Most of the battery research that we've done has been focused on batteries for a computer or batteries for a cell phone or batteries for a car That's been the major emphasis in battery research over the last 30 years.

And those kind of devices, they need different things than you would need for storing this huge amount of solar energy. The amount of energy that needs to be stored is way, way more. And because of that, you need to have lots and lots and lots of these batteries. And so you need the batteries to be really cheap.

And they, second, have to be really, really stable. And you need to be able to charge them and then get the energy back and charge them and get the energy back many, many, many, many thousands of times, whereas with a cell phone, after a couple years, that battery dies, and you just throw that out and get a new cell phone.

MOLLY BLOOM: So how close do you think we are to being able to have that kind of battery?

MELANIE SANFORD: So there are some-- there are a number of batteries that are sort of being piloted for this kind of application. And the challenge there is that, although there are these small installations of these batteries, the materials that are currently used, basically, the molecules that are currently used to store those electrons, they're made of an element called vanadium.

And there's not enough vanadium on the planet. And so we need to do research to make the molecules better, cheaper, more stable, storing more energy, so that you could actually do this on the scale that you would need to put batteries like this everywhere.

HABTE MARTONE: Thanks, Melanie. Bye.

MELANIE SANFORD: Great. Thanks a lot. Yeah, it was really fun.


MOLLY BLOOM: OK, Habte, so you ready to go back to the mystery sound again?


MOLLY BLOOM: All right. Let's hear it.



Any new thoughts?

HABTE MARTONE: My thought is that it's definitely either a drill or a mechanical saw.

MOLLY BLOOM: Excellent guess. Well, here is the answer.

ANDY: That was the sound of a cordless circular saw. It's powered by a rechargeable 18-volt battery. I use a circular saw for woodworking, cutting straight lines on things like plywood or cutting pieces of 2 by 4's down.

It's really nice to have a tool that's battery powered because, in case of a saw that if you had a cord on it, you'd only be able to go three, four feet. But if you have a battery on it, you can take it wherever you need to cut something.

MOLLY BLOOM: So Habte, that's amazing. You got that mystery sound totally right. How did you know?

HABTE MARTONE: It sounded like a mix of a drill and a saw, so I thought of mechanical saw.

MOLLY BLOOM: So smart. So actually, that person revealing the mystery sound was my husband, Andy. So thanks, Andy. Do you have any batteries in your life that are rechargeable batteries?


MOLLY BLOOM: Well, that circular saw and your phone is rechargeable thanks to lithium-ion batteries.

EMILY ALLEN: And lithium-ion batteries are really, really cool.

MOLLY BLOOM: Here to tell us why they're so cool is reporter Emily Allen.

EMILY ALLEN: Do you know what a lithium-ion battery is? You should. After all, you're using one, aren't you? If you're listening to us on your phone, your iPad, or your computer, all of those are powered by lithium-ion batteries. There are many types of batteries. The battery in your car--


--is different than the battery in your toy. The battery in your computer is different than the battery in your smoke alarm.


But let's focus on the coolest battery of all-- lithium-ion batteries. These batteries are special because they're light, and they can be really small. So you can carry them around. But most importantly, you're also able to recharge lithium batteries, so things like your phone will last a lot longer than just a couple of hours. Here's how it works.


A lithium ion is a lithium atom that's missing an electron. That missing electron gives it a positive charge. An atom with a charge is called an ion. Hence the name lithium-ion battery. Energy comes from taking the extra electron off the atom. So lithium is good at producing energy because it's really good at losing electrons.

Once you've taken all the electrons off the ions, you have no more power, so time to recharge. When you're charging the lithium-ion battery in your phone, the process is being reversed. Electrons are reattaching to atoms so the atoms can become ions and lose electrons all over again. But Dr. Prashant Jain thinks lithium-ion batteries can be way better.

PRASHANT JAIN: I'm an associate professor of chemistry and also at the Materials Research Lab at the University of Illinois.

EMILY ALLEN: Remember the parts of the battery we talked about earlier? There's the anode, the cathode, and an electrolyte. In lithium-ion batteries, the electrolyte is a liquid. Liquids are great because they let ions flow through them easily.

But eventually, the liquid dries up, and the battery just doesn't work anymore. That's usually after a couple of years of charging and recharging your phone, so you have to just get a new battery. But wouldn't it be cool if they just lasted longer?

PRASHANT JAIN: We are designing special solids that, even though they have the mechanical strength and the structural properties of a solid, yet they selectively allow liquids to travel through them as if the lithium was in a liquid. So they are special. They combine the best of both worlds-- the strength of a solid and the ability to allow lithium to go through them as if they were liquids.

EMILY ALLEN: Prashant says these are called superionic solids.

PRASHANT JAIN: If you were to look at them, you'd think that they were like any other solid powder that you've seen. But down at the atomic level, they are different. It's a solid that has a split personality. Half of the solid is mechanically strong and stable and doesn't move around-- the anions. And the other half, the cations, can move around as if they are liquid.

EMILY ALLEN: Prashant says researchers still have a long way to go when it comes to replacing liquid electrolytes with solids. For one, superionic solids only work when they're really hot, like 150 degrees Celsius hot.

But they're working hard because replacing this liquid electrolyte might mean our phones and our computers can last a lot longer and be safer. And if we make lithium-ion batteries safer, one day, they might even power electric cars, which are better for the environment.

PRASHANT JAIN: Imagine that, instead of having vehicles that run on gasoline, we all had electrical vehicles that performed as well as our gasoline vehicle.

EMILY ALLEN: So that little lithium-ion battery in your phone, it might just be powering bigger things like cars in the near future, and saving the planet, too.


HABTE MARTONE: Batteries let us take electricity with us.

MOLLY BLOOM: They do this by converting chemical energy to electrical energy.

HABTE MARTONE: A battery is basically made of an anode, cathode, and electrolyte.

MOLLY BLOOM: Electrons flow from the anode to the cathode. But the electrolyte forces them to take the long way--

HABTE MARTONE: --and providing us with electricity on the way.

MOLLY BLOOM: That's it for this episode of Brains On!

HABTE MARTONE: Brains On! is produced by Marc Sanchez, Shannon Totten, and Molly Bloom.

MOLLY BLOOM: We had production help this week from Jon Lambert, Lauren Dee, and Emily Allen, and engineering help from Cameron Wiley, Johnny Vince Evans, Ryan Roberts, and Mike Wood. Many thanks to [INAUDIBLE], Emily Ryan, Susan Odom, Becky Burnett, James Delbourgo, Eric Wrangham, and Curtis Gilbert.

HABTE MARTONE: You can keep up with us on Instagram and Twitter.

MOLLY BLOOM: We're at brains_on.

HABTE MARTONE: And we're on Facebook, too.

MOLLY BLOOM: And if you like the show, please consider leaving a review in Apple Podcasts.

HABTE MARTONE: It helps people find out about the show and sends 10,000 volts of joy through our hearts.

MOLLY BLOOM: And the show wouldn't be possible without the questions, drawings, and mystery sounds that you sent us.

HABTE MARTONE: We thank all the kids that shared their ideas by adding them to the Brain's Honor Roll.

MOLLY BLOOM: Here's the latest group.



(SINGING) Brains Honor Roll. Bye-bye.

We'll be back next week to talk about bioelectricity, the electricity that comes from our bodies.

HABTE MARTONE: You're electric.

MOLLY BLOOM: It's super cool.

HABTE MARTONE: Until then, thanks for listening.

(SINGING) E-L-E-C-T-R-I-C-I-T-Y-- electricity, my, oh, my. It's an exchange of a charge from electrons. You'll see. And it's a form of energy. Woo!

Static is a charge with potential. Current is a charge when it's in the flow. Batteries can take a charge on the go. Bioelectric bodies are charged animals. Woo. Zap.

E-L-E-C-T-R-I-C-I-T-Y-- electricity, my, oh, my. E-L-E-C-T-R-I-C-I-T-Y. Electricity, electricity, electricity, electricity.

And atoms and electrons will leap and will fly, sharing negative charges, hello and goodbye. Hello, goodbye, hello, goodbye. Hello, goodbye, hello, goodbye. Hello, goodbye, hello, goodbye. Hello, goodbye, hello, goodbye.

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