Search for the Super Battery

PBS Airdate: February 1, 2017

DAVID POGUE (Host): They're in the news, in your pocket and on your mind. What's going wrong with our batteries?

NEWS ANCHOR: Turn this phone off.

DAVID POGUE: For the last few decades, batteries have powered a revolution in personal electronics, changing our lives, and now, they're headed for our cars…

Are electric cars becoming a thing?

DENISE GRAY (LG Chem Power, Inc.): Yes, they are.

DAVID POGUE: …even the grid…

DANIEL KAMMEN (University of California, Berkeley): Renewable energy means that we need storage.

DAVID POGUE: …but are we already pushing their limits?

THEODORE GRAY (Author): Anything that is able to release a lot of energy, that is a potentially dangerous thing.

DAVID POGUE: Or can they be better?

I'm not seeing any fireball.

MIKE ZIMMERMAN (Chief Executive Officer, Ionic Materials): We've got to work with people that want to introduce the true next-generation battery.

SHIRLEY MENG (University of California, San Diego): There is definitely a race: "Who will invent the next big battery technology?"

STEVE VISCO (Chief Executive Officer, PolyPlus Battery Company):The deck's stacked against all of us, but the rewards are so big.

DAVID POGUE: Can we beat the odds, as we Search for the Super Battery? Right now on NOVA.

The lowly battery, we barely notice you when you work, and we curse you when you don't. You're the "no show," the "missing ingredient," "not included." And when you die, a piece of us dies as well. Face it, battery, you have issues. But cheer up, my humble friend, things may be changing. Scientists all over the world are in a race to make you better, to make you powerful, to make you cleaner, to make you cheaper, to make you into a "Super Battery."

It won't be easy, but the stakes are huge: warmer temperatures, more severe storms, higher sea levels. What's causing all this climate change? Scientists virtually all agree, burning fossil fuels, the oil, gas and coal that have powered our civilization up to now. The challenge is to make the switch to other forms of energy, like renewables—solar and wind—and to trade our gasoline-burning vehicles for greener electric ones.

But all of these are missing the same critical component: the right energy storage, a battery. Can science transform this Clark Kent of energy into the super storage of tomorrow?

I'm David Pogue, and if that perfect future battery exists, I'm going to find it, because you never know when you might need one.

All right, castaway…deserted…nothing to survive with but my wits. Let's take inventory: luckily I have a knife; hmmm, a phone charging cable and, yes, a phone! This is going to be easy.

Hello, 911. Oh, no. No, no, no, no! It's dead!

To make this phone work, I need a portable source of electrical power. I need a battery.

Hmm, what do I remember about batteries? A battery always has a positive electrode, a negative electrode, with something called an electrolyte in between.

When there's an external connection between the two sides, the battery starts working. First, the negative side reacts with the electrolyte, and electrons are set free. As they travel through the circuit, they do useful things like produce light. When they reach the positive side, the electrons are reabsorbed.

Chemical reactions, where one material gives up electrons to another, are common. That's what happens when a fire burns or rust forms or even when you breathe.

So, building a battery isn't that hard. All you need are the right materials, like the kind of stuff you might find on a beach.

The ingredients for a battery: a negative electrode, an aluminum can; a positive electrode—in this case, I've got some charcoal in my pants; and finally, an electrolyte. I have some fresh, organic seawater.

The good news is this aluminum-can battery actually works. And if I had a device that could measure the voltage, I could show you. The bad news is I need 50 of them.

All right: 50 cans, one battery, one dead phone. This is the moment of truth.

It's charging!

Can I make a call on this thing? 9-1-1, hello? Oh, I'm so happy to hear your voice. Listen, I was on this cruise ship, and I fell overboard. I think somebody pushed me, and now I'm on this desert island. I don't know where I am. Can you…? Landmark? Look for a landmark?

Oh. Actually, never mind.

In truth, charging a smartphone from an aluminum-can battery is really difficult; my cheap low-power phone barely let me make one call. But the point is making a bad battery is easy; making a good battery, well, that's hard.

And I've asked the experts.

LEVI THOMPSON (University of Michigan): I don't know if I would call it a super battery, but to get to the next generation of battery, it would have to be higher energy density.

LYNN TRAHEY (Argonne National Laboratory): …energy density, which is how much energy you store in a given volume.

LEVI THOMPSON: What that means to the consumer is that you might be able to run that device for a longer period of time.

SHIRLEY MENG: Optimistically speaking, we should be able to double or triple the energy density in the next 10 years.

LYNN TRAHEY: Cost is another factor that is hugely important.

DENISE GRAY: Cost is very important.

STEVE VISCO: …and at the same time be safe.

LYNN TRAHEY: Safety…

VENKAT SRINIVASAN (Lawrence Berkeley National Laboratory):Safety and cost, as you can see, can play against each other, where you can make a very cheap battery, it can be very unsafe.

LYNN TRAHEY: So, those are just some of the ones that we look at all the time.

STEVE VISCO: And they're not easy things to deliver.

DAVID POGUE: So, that's a lot to ask of one battery. But finding that battery for electric vehicles may be critical to fighting climate change. Burning fossil fuels, like gasoline, emits carbon dioxide, a greenhouse gas that traps heat, causing warmer temperatures and climate instability.

Transportation accounts for about a quarter of all U.S. greenhouse gas emissions.

GEORGE CRABTREE (Joint Center for Energy Storage Research):Cars and oil are linked very, very strongly. Something like 67 percent of oil goes for gasoline, and 90-some percent of transportation fuel is gasoline.

DENISE GRAY: The whole purpose of electric vehicle is to reduce the amount of carbon footprint, to reduce the amount of emissions.

DAVID POGUE: Electric vehicles could be good for the environment, but it's going to take a lot to pry the gasoline nozzle from our hands.

The funny thing is this isn't the first time that electric batteries and gasoline have fought to win our automotive hearts. At the turn of the century, no one knew which technology, electric or gas power, would dominate the nascent car industry. In fact, quiet electric-powered cars were a common sight on the streets of New York.

To learn more, I pay a visit to one of the foremost experts, or at least one of the funniest, Jay Leno. And he's got some insider info on the car of tomorrow.

JAY LENO (Car Enthusiast): I think this is the car of the future. This is how we'll all be getting around, electric.

DAVID POGUE: This is the car of the future?

JAY LENO: Well, this is a 1909 Baker electric. There's no pollution. This was high-tech, back in the day.

DAVID POGUE: Talk about back to the future. The 1909 Baker runs on energy stored in batteries.

Wow.

JAY LENO: You have six batteries in front.

DAVID POGUE: As with today's electric cars, you could charge the batteries by plugging the car in.

I'm going to stop at exactly 10 bucks.

In those days, there were charging stations all over New York City.

JAY LENO: You want to go for a ride and see what it's like?

DAVID POGUE: Yeah! This runs? You don't take it on…

JAY LENO: Of course it runs. You seem so stunned by…

DAVID POGUE: I like this. You've got the user's manual on the seat. That's a good, good sign.

JAY LENO: But I'll show you how, sort of, maintenance-free these are. All you do is turn the key, and you are, uh…

DAVID POGUE: That's the wheel?

JAY LENO: …ready to go.

DAVID POGUE: Oh, my god. No way. Oh, my god.

Even today, it's a great ride, really quiet, just the hum of an electric motor, but back then, electric cars still lost out. Their batteries weren't dependable and many were recalled.

By the time the problems had been sorted out, a former Detroit Edison employee, Henry Ford, had unleashed the extremely affordable gasoline-powered Model T.

A few years later, one of its big drawbacks, the hand-crank starter, was replaced with an electric one. That, and the growing availability of cheap gasoline in rural areas that lacked electricity eventually sealed the deal.

Today, thanks to climate change, electric cars are getting another shot. Success probably depends once again on the battery. The best version we've managed so far is probably the one in your pocket, the battery in your phone, which uses the element lithium.

MAN #1 IN VIDEO: The hoverboard is on fire.

DAVID POGUE: And, you also may have heard, they can be dangerous.

MAN #1 IN VIDEO: I am, Mom!

REPORTER: This happened at a gas station in Kentucky, when his e-cigarette battery exploded, literally lighting his pants on fire.

REPORTER: This morning, technology giant Samsung is planning a massive recall.

DAVID POGUE: Then, of course, there's the Samsung recall of over two-and-a-half million cellphones because of lithium battery fires.

So, if it can be so dangerous, why lithium? What makes that element both the belle of the battery ball, and, at times, a fiery mess?

To learn more about lithium, I visit my friend with all the "elementary" answers, mad scientist Theo Gray, at his mad-scientist workshop, on his Illinois farm.

Nice.

In the past, Theo has shown me the power of the elements.

Oh, the humanity.

So, what's the story on lithium?

It seems like once you start digging into the battery world you hear about lithium a lot, so, what is lithium?

THEO GRAY: Yeah, so, lithium is an element that, you know, happens to have properties that make it extraordinarily well-suited for delivering a lot of electrical power in a very small, light package.

DAVID POGUE: And I'm guessing, because we're in stormtrooper outfits, that it's something dangerous.

THEO GRAY: It is able to contain and release a lot of energy, and any time you have anything which is able to release energy, that is a potentially dangerous thing.

DAVID POGUE: Theo tells me you can learn a lot about lithium just by looking at its place on the periodic table. High up means it has a low atomic weight. That means lithium doesn't weigh much.

THEO GRAY: …which is, you know a great thing if you're trying to make a battery to fly a drone or, you know, just to have something that gives you a lot of power and doesn't weigh very much.

DAVID POGUE: In fact, even though it's a metal, it floats on water.

Oh, it's silver. Pretty. Thank you.

THEO GRAY: You notice again, it weighs nothing.

DAVID POGUE: Theo also points out that lithium sits on the far left of the table, in the column called the alkali metals. Compared to other elements, they readily give up an electron, exactly what you want for the negative electrode in a battery.

The lithium in my hand is doing just that, giving up an electron to oxygen in the air, creating the blackish lithium oxide on its surface.

Theo, would we call this oxidizing?

THEO GRAY: It is oxidizing; it is, basically, rusting. It is the exact same reaction as rust forming, it's just that, you know, iron rust is kind of this reddish flaky thing, lithium rust is sort of this kind of black coating.

DAVID POGUE: When Theo whips out some lithium foil, I get an even better look at the oxidizing process, thanks to the foil's greater surface area.

You see how it's darkening?

It's tarnishing. It's like tarnish.

THEO GRAY: And that's more or less the same reaction that would happen inside the battery, except, inside the battery, it's happening in a very controlled way.

DAVID POGUE: Wow, now it's not shiny and pretty anymore.

THEO GRAY: I bet it's getting hotter, too.

DAVID POGUE: It's super hot.

The lithium foil reacts quickly in the air, but if you really want to see it in action, try water.

THEO GRAY: That was a great one.

DAVID POGUE: Light-weight, and willing to give up electrons easily, lithium is nearly a perfect metal for use as the negative electrode in a battery. But it turns out, there's a big problem if you want that lithium-metal battery to be rechargeable.

Remember the three parts to a battery? Okay, I left some things out. In a lithium-metal battery and many others, there's a separator, like a piece of plastic, to keep the electrodes apart, because if they touch… More on that later.

That separator isn't completely solid, and here's why: when a lithium-metal battery discharges, of course there's a flow of negatively charged electrons through the wires on the outside, but inside the battery there's a flow of positively charged lithium atoms, or ions, in the electrolyte. They flow from the negative lithium-metal electrode, through the permeable separator, to the positive electrode, which, kind of like an apartment building, houses the ions in its layers.

Recharging the battery sends both the electrons and the ions back the other way. And that is when using lithium metal as an electrode runs into trouble. Scientists discovered that, over time, the returning lithium ions tend to clump on the metal surface, building spiky, tree-like structures, called dendrites.

GEORGE CRABTREE: They get rougher and rougher and rougher, until they stick out, like a finger, from the surface, and continue to get longer and longer and longer.

JEFF SAKAMOTO (University of Michigan): And eventually, those dendrites can reach the other side of the battery, which is the cathode or the positively charged electrode, and then there's a short circuit, instantaneous discharge.

DAVID POGUE: Instantly, electrons flood across, releasing the battery's energy, generating heat, which in turn can cause fire and explosions.

After years of trying, no one could find a solution to the lithium-metal conundrum, so scientists invented an alternative that became part of our lives in the early '90s, in products like, the Sony Handycam®. They called it the lithium-ion battery.

The key to its success was replacing the negative lithium-metal electrode with a new "apartment building," a carbon electrode that housed lots of individual lithium ions when the battery was charged.

Everything else still worked the same. Discharging the battery sent the ions through the electrolyte, over to the positive electrode; recharging the battery sent them back. But now, at least in theory, all the welcoming spaces in the layers of the negative electrode stopped them from piling up into dangerous dendrites. That meant lithium-ion batteries were far safer than lithium-metal ones, but at a price; they stored far less energy.

REPORTER: The F.A.A. has long warned airlines of the potential dangers presented by lithium batteries.

DAVID POGUE: And safer doesn't mean completely safe.

REPORTER: Lithium-ion batteries have already been linked to numerous cargo crashes.

DAVID POGUE: All those battery fires you've been hearing about in recent years? Those are lithium-ion batteries.

To learn more about what really goes into a lithium-ion battery, I traveled to Ann Arbor, to check out the University of Michigan's battery lab, part of its Energy Institute. Senior lab manager Greg Less has offered to show me around, and even build one with me.

Turns out, lithium-ion batteries come in different shapes.

Okay, so this we've seen before, this is like a watch battery.

GREG LESS (University of Michigan Battery Lab): Right.

DAVID POGUE: This is a little bigger than the standard double A.

GREG LESS: Absolutely, that's a 18650, and you might find that in a rechargeable power tool, an older-model laptop or the Tesla Roadster.

DAVID POGUE: But I've never seen this in a power tool.

GREG LESS: Well, no, there's actually a bunch of them in there, maybe six or seven, put together in series, inside of that brick that you plug into the bottom of the tool.

DAVID POGUE: Oh, okay, and this, what, for a phone?

GREG LESS: Yep, you'd find a battery like that either in your phone or a laptop or a tablet computer device.

DAVID POGUE: And you actually made all these in this room?

GREG LESS: Yes, we sure did.

DAVID POGUE: That's cool. Walk me through it, good sir.

GREG LESS: I happily will.

DAVID POGUE: Greg gives me a whirlwind tour of the process of making an 18650. He mixes up the ingredients for the electrode material, which gets baked onto foil and sliced into smaller rolls. Then, we enter through an airlock, into a special low-humidity "dry room." Any moisture from water inside a lithium-ion battery harms the electrolyte.

Once inside, we put the rolls on this crazy machine, which winds them together with a roll of plastic separator into a "jelly roll."

Let's take a closer look.

GREG LESS: So, we have a top layer that's the separator. We'll pull that off, then we have our copper and graphite negative electrode, another layer of separator, here, and then the positive electrode layer that we made together of lithium nickel manganese cobalt oxide.

DAVID POGUE: So, every lithium-ion battery that's in one of those cylinders, including the ones that are bundled together to make laptop batteries and power drill batteries, they're all, at heart, a bunch of these ribbons?

GREG LESS: That's correct. Just a series of ribbons wrapped up together.

DAVID POGUE: Wow.

After sticking the roll in a metal can, Greg injects the last key ingredient, the liquid electrolyte.

GREG LESS: The electrolyte is the cream in the jellyroll. It's what connects everything together. The electrolyte is a liquid solution that has lithium ions dissolved in it, and when we charge or discharge the battery, the electrolyte is what allows those ions to travel back and forth between the positive and negative electrodes.

DAVID POGUE: With the final steps of welding and crimping the top onto the metal can, we were done. Somehow, I expected more, because it's batteries like the 18650 or one of the other lithium-ion styles, like these flat ones in pouches, that will determine if electric cars are a viable option to replace gas-burning ones.

So far, in the U.S., plug-in electric cars haven't had much success. In 2015, they made up less than one percent of all new car sales.

VENKAT SRINIVASAN: There are a few reasons to be skeptical of electric cars. Probably, the biggest one is cost. But costs of electric car batteries are coming down dramatically, and they'll continue to come down for the next five years. They're going to find out that more and more people can afford to buy an electric car. So that problem is getting solved as we speak.

DAVID POGUE: The other concern is called "range anxiety:" "How far can you go on a single charge?" Surveys show Americans want to be able to go hundreds of miles, even though average daily auto use is only around 40.

But there is some justification; for most of the country, roadside charging stations are few and far between. Despite lackluster sales, carmakers continue to test the waters, with lower prices and longer ranges: like the Chevy Bolt, the first moderately priced all-electric car with a range of more than 200 miles, or the new Tesla Model 3, which has similar price and range.

Anticipating a large demand, Tesla plans to produce 500,000 cars a year in the latter half of the decade. But that would require the entire current worldwide production of lithium-ion batteries.

So, they've built this: the Gigafactory, in Nevada. When completed, it will cover more land than any other building in the world, and it will produce batteries, quote, "faster than bullets from a machine gun," unquote.

I stop in at Tesla's Palo Alto Headquarters to find out where all those batteries fit in the current Tesla Model S.

ALEXIS GEORGESON (Tesla Motors): So, the battery pack actually runs the length and the width of the vehicle. So, what you're seeing right under here is our battery pack.

DAVID POGUE: Oh, oh, the batteries are already in here?

ALEXIS GEORGESON: The batteries are in here.

DAVID POGUE: Now, if I could get in there with a screwdriver and rip that open, what would the actual batteries look like? Are they just a whole bunch of little double A's?

ALEXIS GEORGESON: They're little cells, yes. So, we've got about 8,000 individual cells in there.

DAVID POGUE: Eight-thousand?

ALEXIS GEORGESON: Yes.

DAVID POGUE: And do, by any chance, do they look like this?

In fact they do.

Early on, Tesla standardized on the 18650, because of its availability. But at the Gigafactory, they'll switch to a bigger version, which they claim is the "best and cheapest in the world."

Other electric carmakers prefer the flatter pouch batteries, like those made here, for G.M., at LG Chem's plant, in Holland, Michigan.

While I was there, I stopped in to see Denise Gray. She's the President and C.E.O. of an LG Chem subsidiary that does battery research and design.

So, we've heard for years that electric cars are coming soon, but are they finally, at least almost here?

This plant makes batteries exclusively for electric cars, right? Like are electric cars becoming a thing?

DENISE GRAY: Yes, they are. Yes they are. We're still in the early stages, but we're making great progress, and I think we are accelerating down that plan of having more and more electrified powertrains on the road.

DAVID POGUE: How many Americans will buy electric cars, or how soon, remains to be seen, but with more and more electric vehicles on the road, engineers are racing to make the lithium-ion batteries they contain even better: cheaper to produce, longer lasting, and, most importantly, safer.

I travel to New Mexico to visit the Sandia National Laboratories. Scientists Leigh Anna Steele and Josh Lamb show me the Battery Abuse Testing Lab. Here, they do all the things those warning labels tell you not to do with batteries, to understand how they fail. They take me past a two-ton blast door to the testing torture chambers, where they puncture, over-charge, burn, short-circuit and drown batteries.

LEIGH ANNA STEELE (Sandia National Laboratories): The walls, ceilings and floors of this building are all made out of concrete reinforced with rebar, anywhere from 12 to 14 inches thick.

DAVID POGUE: Today, they're performing a crush test, where they'll slowly smash the middle of a battery with up to 15,000 pounds of force, the sort of thing that could happen in an electric car crash.

JOSHUA LAMB (Sandia National Laboratories): This is a hydraulic lift, here. So, it's going to, actually, start lifting up, and that impactor there is going to start crushing the battery.

DAVID POGUE: After a final check of the set-up, we are ready to go.

LEIGH ANNA STEELE: Okay, Chris, are we ready to start the test? All right, the test is going now, it sounds like, so we can hear… We heard hydraulics just turned on a little bit.

DAVID POGUE: On the hydraulic lift, the battery slowly rises into the plunger.

LEIGH ANNA STEELE: You can start seeing…the gap is starting to close in between the plunger and the battery.

DAVID POGUE: You can see the plunger is crushing the inner battery cells a surprising amount, still with no reaction, but we're getting close.

LEIGH ANNA STEELE: So, you'll start hearing some hissing. That's the battery venting when it actually starts to go into failure.

DAVID POGUE: That's why we weren't standing in that room?

LEIGH ANNA STEELE: Exactly.

JOSHUA LAMB: So, all that energy that's stored in that battery, it's just discharging all at once.

DAVID POGUE: When a lithium-ion battery cell uncontrollably overheats, it's called "thermal runaway."

Leigh Anna and Josh break it down for me.

The plunger crushed the inner cells of the battery until a negative and positive electrode made contact, a short circuit. Just like when dendrites short out a battery, electrons flooded across in a massive discharge, creating heat, which then turned some of the liquid electrolyte into gas. That burst open the battery's foil pouch, and then the vaporized electrolyte ignited. That's known as "venting with flame."

All the fire and heat set off reactions in other nearby cells, sending them into thermal runaway, as well. In the end, the fire reached a temperature of over 1,800 degrees Fahrenheit, easily hot enough to melt the aluminum used in the battery.

Leigh Anna and Josh show me some video of other tests. This is a battery that's getting overcharged, and this is a nail going into the center of a group of 18650s. The center cell fails, gradually taking down the rest of them with it.

From the videos and having seen it here myself, one thing seems obvious: if there were a way to get rid of the vaporizing flammable electrolyte, that would be a big step toward making these batteries safer.

And I'm not the only one who thinks so. Meet Mike Zimmerman. He's a Tufts University professor and materials scientist. About five years ago, he got interested in lithium-ion batteries, thinking there had to be a safer electrolyte.

Mike's background is in plastics, and I've come to take a look at what he's invented.

So, this is your battery?

MIKE ZIMMERMAN: That's the battery.

DAVID POGUE: It looks like any other lithium battery inside one of these.

MIKE ZIMMERMAN: It's the same. Same format.

DAVID POGUE: Same voltage?

MIKE ZIMMERMAN: Same voltage.

DAVID POGUE: You think this is an unusual battery?

MIKE ZIMMERMAN: It's a battery that is much safer than conventional batteries. And upon any damage, any puncture, any cutting it, it will not catch on fire.

DAVID POGUE: Did you say "any cutting it?"

MIKE ZIMMERMAN: Correct.

DAVID POGUE: Can I make a cut in this?

MIKE ZIMMERMAN: Yes.

DAVID POGUE: Really?

MIKE ZIMMERMAN: Yes.

DAVID POGUE: It's not going to jet fire into my face?

MIKE ZIMMERMAN: It will not.

DAVID POGUE: Before I do that, let's consider these examples, from YouTube, of folks poking at lithium-ion batteries. They reveal that it doesn't take much to create a dangerous short circuit, with disastrous results.

And now, is it my turn?

Big or little?

MIKE ZIMMERMAN: Whatever you want.

DAVID POGUE: I'm alive! Wow. Look at that! And guess what? The lights are still on.

This is like a Houdini thing. I mean, this is like, I'm going to make a doily. It's still on. Come on! I'm going to make you a little paper doll.

So, what's the trick? Compared to a typical lithium-ion battery, Mike's replaced the liquid electrolyte and the separator with his special plastic to create a completely solid battery. Unlike the liquid electrolyte, which easily catches fire, Mike's plastic is flame-retardant. And even though it's solid, amazingly, it allows lithium ions to pass through it at a rate equal to or better than current liquid electrolytes.

And here's the best part: the plastic physically prevents dendrites from shorting out the battery. That means that Mike can go back to a lithium-metal negative electrode, potentially doubling his battery's energy density.

Here's another demo, using an iPad with its original battery removed and, in its place, one of Mike's that's even bigger than the last one, cut to pieces, and I'm going to stick a screwdriver through it, like you saw in those YouTube videos.

Here we go. So far, I'm not seeing any fireball. Okay, you've done it. You've made a battery that doesn't explode when pierced. At the very least, I would expect to see some smoke. I would expect to feel some heat. There's nothing.

MIKE ZIMMERMAN: Yeah. It's because of the solid plastic electrolyte. It's not flammable, and it's very insulative. It doesn't get too hot and it doesn't burn.

DAVID POGUE: And it keeps working.

MIKE ZIMMERMAN: Well, that was an unintended consequence.

DAVID POGUE: Can I do it again? My mortgage is too high, and the tax rates are insane, and I dented my fender. All right, now it's not going to turn on, now. Oh, come on. Come on. That's it. A damaged battery, and yet no smoke, no flame, no sparks. Do not try this with your iPad battery.

So far, Mike's kept his company's work mostly under wraps. This, in fact, is the first television interview he's given on it. But there's still more development to go before your new smartphone makes use of it.

And if I were one of your critics, certainly there would be something I would attack you for. There's got to be something. It can't be too good to be true.

MIKE ZIMMERMAN: Right. I think that development, you know, is never done. We have to do a lot of reliability testing, and the scaling up aspect of this, it's going to be a lot of work to scale it up. So, we've got to work with people that want to do that and want to introduce a true next-generation battery.

DAVID POGUE: Whether Mike's solid-state lithium battery will come to market anytime soon is hard to know. If it does, and if it can double the energy density of the batteries in electric cars, that would be revolutionary.

But electrifying cars, as a strategy to battle climate change, comes with a big caveat. To have real impact, the source of their electricity needs to be green as well. And that means cleaning up the grid that charges them.

If you're like me, you don't even think about it. You flip on a light switch or you turn on something plugged into the wall, where does the electricity come from? When was it created? How does it arrive at your house at exactly the right time? How does the electrical grid work?

DANIEL KAMMEN: The grid has been called the most complex machine humans have ever built. It is the largest, the most extensive, has the most parts, and it also has a beautiful simplicity. It's driven by this very simple formula: energy in must equal energy out, at every moment in time.

GEORGE CRABTREE: You have to generate electricity over here, at the power station, at exactly and instantaneously the same rate that you use it over here, on all the customers.

GUENTER CONZELMANN (Argonne National Laboratory): Electricity is essentially instantaneous. So, it's a fraction of a millisecond or microsecond old, because it travels, basically, at the fraction of the speed of light across the wire. So, we have to make it instantaneously. The moment you want it, I have to make it.

DAVID POGUE: Matching the demand means constantly ramping up and down the amount of electricity generated, for example, by turning up or down gas-fired power plants, or spilling more water over dams, or even firing up an old diesel plant just to meet an hour of peak demand. It's a constant complicated dance.

Now, as we try to shift away from power plants running fossil fuels, the complicated dance that matches generation with demand has found some new partners: renewables, like wind and solar. They can range in size from a huge wind farm, generating hundreds of megawatts of power, to the small solar array on your neighbor's house. The dance just got more complicated.

GUENTER CONZELMANN: We're taking a complicated system and making it a lot more complicated. We have to be able to meet the demands, still, when the sun doesn't shine, when the clouds come through and the output falls, when the wind dies down.

DAVID POGUE: If these new renewable but intermittent sources of electricity are going to play a major role on the grid, they require a new player: energy storage.

SHIRLEY MENG: I don't think renewable penetration can go higher without a robust energy storage solution, that's for sure.

DAVID POGUE: In the U.S., there's already a little energy storage on the grid, equal to about two percent of our generating capacity. Most of it looks like this reservoir, in Bath County, Virginia. It's been called the largest battery in the world, but it's not like any battery you've seen. The system's called "pumped hydro," and it operates like a rechargeable hydro-electric dam.

During the day, when there's high demand for power, the electric company lets the water flow from an upper reservoir to a lower one, spinning turbines and generating electricity. But at night, when there's low demand, they use the excess electricity generated by other plants to pump water back up to the higher reservoir, "recharging" it.

Today, about 99 percent of all grid storage in United States is pumped hydro. It would be a relatively inexpensive way to store excess energy from renewables for later use, except for one problem. You need the right geography for the site, with changes in elevation. And even then, creating new ones can raise environmental concerns. So, the search for solutions for grid energy storage is still on.

Just outside San Francisco, in the Bay Area, one company is giving it their own spin: Amber Kinetics. They sell an energy-storage system built around massive spinning disks, called flywheels. The principle is simple: electricity powers a motor that spins up the heavy flywheel. Now, energy is stored in the flywheel's momentum. To convert that back into electricity, the flywheel engages a generator, its momentum turning the generator's shaft. As the flywheel slows, the generator creates electricity.

Needing both weight and strength, Amber Kinetics makes their flywheel out of steel.

How much do these babies weigh?

SETH SANDERS (Amber Kinetics): This is about a 5,000-pound part.

DAVID POGUE: Wow. And how fast is it going to be spinning?

SETH SANDERS: In some good number of thousands of r.p.m.

DAVID POGUE: In a finished unit, the flywheel sits inside a welded steel chamber that tightly seals shut, so it can spin in a near vacuum to reduce friction with the air. They also reduce friction using a giant magnet mounted above the flywheel, which lifts it upward, removing most of its weight, so it rests only lightly on its support bearings.

SETH SANDERS: And so, the friction in the mechanical bearing is partly determined by, "how much force is the bearing supporting?" And so we make the force extremely light.

DAVID POGUE: All of this adds up to breaking new ground. Flywheels have been used on the grid before, but mostly to store energy only for seconds or minutes.

Amber Kinetics' flywheels can store energy for up to four hours, for example, capturing the energy generated by a solar array during the day for use in the evening, a process called "time-shifting."

Seth shows me what a nearly complete flywheel unit looks like.

There's a flywheel in here that you made? But is it spinning right now?

SETH SANDERS: No, it's at rest now.

DAVID POGUE: If it were spinning, would I hear it?

SETH SANDERS: You would not be able to hear it, because the part is balanced to a very high degree, and the residual vibration is minuscule.

DAVID POGUE: As a grid storage solution, flywheels, a kind of electro-mechanical battery, have an advantage over chemical batteries. They don't wear out for decades. The same can't be said for lithium-ion batteries, but there are a lot of those getting put to work on the grid as well.

This is Tehachapi, California, near the Mojave Desert, home to some of the oldest and largest wind farms in the country. But the wind blows strongest at night, when demand for electricity is at its lowest. In 2014, Southern California Edison installed a $50-million energy storage system that uses lithium-ion batteries.

DOUG KIM (Southern California Edison): What we want to do is to be able to use this to smooth out, firm up the output of those, so it's much more predictable; for example, when the wind blows during the nighttime, capture that energy and then use it during the daytime, when the demand is high.

DAVID POGUE: Lithium-ion batteries have made inroads into grid storage, but they're still expensive. And part of the premium paid is for their light weight, which matters for electric cars and portable electronics but maybe not for the grid.

Here, in the Pittsburgh area, battery scientist Jay Whitacre has taken a different approach. He's sacrificed lithium-ion's lightweight portability to create a battery that is cheaper and safer. It's nicknamed, the saltwater battery.

Nice job.

We're going to retrace his steps, starting at square one: the periodic table: Ra, Ba, La…

All right. So these are the elements that make up our world?

JAY WHITACRE (Aquion Energy): Mmm-hmm.

DAVID POGUE: Which elements can you use to make a battery?

JAY WHITACRE: Really, almost any of them. If they have any reaction potential at all, you can make electrodes out of them, and they'll store energy. That's not that hard, but that's not really the question you want to ask, right? You want to ask, "Which of these elements can we use to really scale large, like, really big energy storage, to solve the world's problems?" Right? And to answer that question, we really get rid of most of this. Like this is gone. We slide this out. And then we start thinking about what's called "crustal abundance."

DAVID POGUE: Crustal abundance?

JAY WHITACRE: Crustal abundance.

DAVID POGUE: Crustal abundance is an estimate of the availability of an element in the earth's outer layer, its crust. The higher the percentage, the more available it is, which translates into cheaper and probably better for the environment, since it's more common.

JAY WHITACRE: So, if you can pick from crustily-abundant materials or elements, you're probably going to have the best shot at having a low-cost, environmentally safe battery.

DAVID POGUE: I'm always in favor of crustily abundant.

JAY WHITACRE: So, silicon—these will not surprise you—you have carbon, you have hydrogen, you have zinc. These are in no particular order, but you'll recognize all of them. They're very common materials. They make up everyday life, oxygen and a couple of really important ones. You've got sodium, which is, obviously, everywhere in the ocean. You've got potassium, which is a heavy biological factor, and lithium, which you might not think is crustily abundant but actually is. And these were the ones that I started looking at, in 2007, when I was trying to figure out what elements I would use, to put together in any which way, to create something that was going to be functional.

DAVID POGUE: Out of this initial collection of elements, Jay created a battery that had a sodium manganese oxide positive electrode and a carbon negative electrode. When the battery was charged, sodium ions left the positive electrode to gather at the negative carbon electrode; when discharged, they would return to the positive electrode. With each charge and discharge, they shuttled back and forth.

The electrolyte—sodium sulfate salt, dissolved in water—gave the battery its nickname, the saltwater battery.

From there, Jay began tweaking his recipe. The end result was a battery far less energy-dense than lithium-ion, but non-flammable, non-toxic and cheaper.

JAY WHITACRE: Great. So this is a barrel of our active material. This happens to be our cathode material. It's a manganese oxide base system, and it's really simple. It basically looks like dark sand or dark dirt.

DAVID POGUE: Listen, Jay, I've been to a few battery factories in my time,…

JAY WHITACRE: I'm sure you have.

DAVID POGUE: …and I've never been allowed to walk up to a barrel in a non-humidity-controlled room. What? Are you just really crude here or is this somehow…

JAY WHITACRE: No. Well, the key difference between this battery and probably all the others you've visited is that we use water as an electrolyte.

DAVID POGUE: Water changes everything in a battery. On the downside, it limits the voltage: too high and the water splits into hydrogen and oxygen gas, but it also means you don't need the expensive low-humidity dry rooms required to make lithium-ion batteries. And, of course, water is nonflammable, safer.

JAY WHITACRE: In fact, the salts that we use, the electrolyte salts are flame inhibitors.

DAVID POGUE: Is this toxic, this thing here?

JAY WHITACRE: This is not toxic at all.

DAVID POGUE: I could eat this cathode material?

JAY WHITACRE: It is biologically consumable. Yeah. I wouldn't recommend . It's going to taste a little salty to you, a little weird, but, yeah. There you go.

DAVID POGUE: Hmm. Pumpkin spice. Yeah, it's totally fine. It's not even salty.

JAY WHITACRE: No. It's just like sand.

DAVID POGUE: Yeah.

JAY WHITACRE: It is basically sand.

DAVID POGUE: It's actually a little better than sand, as a frequent sand eater.

These days, Aquion Energy is churning out batteries in a former Sony Trinitron factory outside of Pittsburgh. Here, Jay's emphasis on safe ingredients saves a lot of money in manufacturing.

The electrode material I taste-tested is pressed into cookie-like wafers, which, in turn, get assembled by these "pick-and-place" machines from the food industry, used in packaging; all without the tight humidity and dust controls found in lithium-ion battery factories.

Already, saltwater batteries are part of hundreds of solar installations around the world, ranging from utility projects to individual homes. But Jay sees himself at the beginning of a massive undertaking to bring energy storage to the grid.

JAY WHITACRE: This is not a small-scale project. To get storage to be relevant in the world, you have to make huge amounts of it, and this is just a drop in the bucket. We're just getting started.

DAVID POGUE: On that, everyone agrees. If we want energy storage to integrate renewables into the grid, we're woefully short on quantity.

In 2010, Bill Gates noted that all the batteries on Earth could store less than 10 minutes of the world's electricity production. To fill the gap, we'll need systems that can scale up easily.

Levi Thompson, at the University of Michigan, introduces me to one, a rechargeable battery unlike any other: the flow battery. He explains that a typical battery is a closed system.

LEVI THOMPSON: And this is all sealed, so, everything that you need is in there. It's like a cake. You put everything in there, you get everything you want. Every battery kind of looks like this.

DAVID POGUE: Every battery but a flow battery, says Thompson. Instead of a closed system, a flow battery has external tanks containing two chemicals. They're pumped past each other through a chamber. Because of a special thin membrane, they can't mix, but in close proximity, they do react, generating electricity.

The capacity of a flow battery depends on the size of the external tanks that hold the chemicals. Bigger tanks, bigger battery, more energy.

LEVI THOMPSON: Flow systems are, for large-scale applications, much more efficient, much more cost-effective than sealed systems. It's a much better solution to the problem.

GEORGE CRABTREE: Flow batteries will surely play a role in the grid. This is what they have always been designed for and thought of as: the grid battery.

DAVID POGUE: Some flow batteries are already in operation, like this one at Fort Devens, a U.S. Army installation, in Massachusetts. The battery helps integrate solar generation, reduces peak demand and improves power quality.

And research continues, like the work of these two members of Levi's team.

It's early days, but with more development, flow batteries might just turn out to be the answer for grid storage. This is something that's shown to work, and people are actually using it, but that's not the mindblower, so much as where it could be in 40 years.

LEVI THOMPSON: Where it could go. Absolutely.

DANIEL KAMMEN: Flow batteries are perhaps the newest exciting entrant, but I would expect, over the next decade, there's going to be a whole series of these new exciting entrants into the field.

DAVID POGUE: So in the end, we still don't know if the grid Super Battery will be one technology or a mix of pumped hydro, chemical batteries, flywheels, flow batteries and others. But if we really want to integrate renewables into the grid and trade our carbon-spewing vehicles for greener ones, and do it on the massive scale required to fight climate change, one thing's for sure: energy storage, and lots of it, will be in our future. And so will the ongoing Search for the Super Battery.