Lithium: it’s everywhere and we know nothing about it. It powers our phones, our computers, and our cars and the control and use of lithium will, in part, define how we handle the coming petroleum crisis. That’s why Seth Fletcher’s Bottled Lightning is so fascinating.
The book explores lithium from its earliest beginnings to its use in almost everything that we use today. Fletcher, a writer for Popular Science has done his research and although the topic sounds as dull as lithium-infused brine he keeps the book well-paced and interesting throughout.
Unlike many single-topic non-fiction books (Salt,Cod,Adult Diapers), Fletcher tells us the history of a modern chemical that turned the lowly battery into a real powerhouse. Where will lithium take us next? Fletcher explores the future of lithium-air batteries in this excerpted chapter.
In the quest to rid our cars of oil and our grid of coal and gas, battery scientists have at least two essential duties. The first is to continue to grind through the periodic table in search of the incremental advances that will steadily make the technology a little better every year. The second is to chase ideas that may be decades from commercial reality, because while everyone else is arguing about state tax credits for pack assembly plants and the price of separator material, somebody has to.
Chief among these far-horizon ideas is the highest-risk, highest-reward battery technology of all: lithium-air. At the moment, lithium-air appears to be the best chance battery scientists have to beat gasoline. It is elegant in concept and, theoretically at least, extravagantly energetic.
For the sake of comparison, consider that a lead-acid battery can store something like 40 watt-hours of energy per kilogram. Today’s best lithium-ion batteries can hold about 200 watt-hours per kilogram, and lithium-ion has a theoretical maximum of 400 watt-hours per kilogram. Lithium-air has a theoretical maximum of 11,000 watt-hours per kilogram. Even after handicapping to take into account weight, efficiency, and other foreseeable technological obstacles—after assuming that, for the sake of argument, the lithium-air battery will be able to deliver only 15 or 20 percent of its theoretical energy capacity—it still approaches what gasoline, because of the poor efficiency of the internal combustion engine, can deliver. And that is why scientists have been dreaming about it for decades. “As with all things in life where there’s a big prize, it’s not an easy one to reach,” Peter Bruce said.
Lithium-air is probably the purest and earthiest battery chemistry possible, because in its simplest formulation it involves nothing but lithium, oxygen, and carbon—the lightest metal in the universe and two essential elements of all living beings. “You take the positive electrode of a lithium-ion battery and you replace it with porous carbon,” explained Bruce, who today is one of the world’s leading lithium-air researchers. “The electrolyte”—this could either be an organic solvent as in today’s lithium-ion batteries, a combination of polymers, or maybe even something based on water—“floods the pores of the carbon. Oxygen comes in from the air.” And then the lithium ions, the oxygen, and the electrons routing around through the external circuit all combine to form lithium peroxide (Li2O2), a solid. Then, as with any rechargeable battery, the whole thing happens in reverse. “When you charge up the battery, you actually decompose this solid material. It goes back to lithium ions and electrons and pumps oxygen into the atmosphere again.”
Mainly because of the signal it sends to the world—IBM is interested!—the highest-profile lithium-air project right now is probably Battery 500, a lab dedicated strictly to lithium-air research at IBM’s Almaden Research Center. “A practical electric car will need a lot more mileage than is possible with lithium-ion batteries,” said Winfried Wilcke, head of the project. “Five hundred miles is the target you really want.” That, along with a nice resonance with the Daytona 500, is why IBM decided to call its lithium-air project Battery 500—“to differentiate this from incremental improvements of lithium ion.”
IBM is taking a supercomputer-driven, fundamental-physics approach to the problem. “Electrochemistry has had a long history of a very Edisonian approach,” Wilcke said. “But for something as risky and difficult as a lithium-air project, that’s not good enough.” It’s risky and difficult because “wherever you look there are challenges,” he said. “It’s like climbing Mount Everest.”
First there’s the maddening difficulty of recharging. Getting the discharge reaction to happen once, to get the lithium to react with oxygen to form solid lithium peroxide—thanks to recent advances, that part is not a problem. What is a problem is getting that reaction to happen in reverse, to get the solid lithium peroxide to decompose into oxygen and then plate pure lithium back on the negative electrode with mirror-like smoothness. Power is another problem. The reaction between oxygen and lithium is intrinsically slow, far too sluggish to blast a car up the highway in a passing maneuver.
Hope for the power problem comes in the form of nanotechnology, which, as it does for many other lithium-based battery technologies, increases the surface area of the individual electrode particles, thereby increasing the rate at which the battery can charge and discharge. (Catalysts can also help that reaction happen more quickly.)
As with anything involving highly reactive metallic lithium, safety is a concern. (Today’s lithium-ion batteries contain no elemental lithium, which is so reactive that it doesn’t appear in nature in its pure form.) Still, Wilcke argues that we should first find out whether lithium-air batteries are even remotely feasible before worrying about safety issues. Dalhousie University professor Jeff Dahn, who experienced firsthand the hazards of batteries using lithium metal early in his career, is more cautious. “What Moli Energy found back in the late 1980s was that lithium-metal electrodes, just under normal use, led to cell failures that were at just too high an incidence rate to make it a viable business,” he said.
As chief technology officer of the Berkeley-based company PolyPlus, Steve Visco is in charge of making lithium metal safe and usable. PolyPlus was spun out of Lawrence Berkeley National Laboratory in 1990. “In many ways it operated as a kind of innovation center for batteries,” Visco said. He told me that the company did “all of the groundbreaking work in lithium-sulfur chemistry,” another promising high-energy battery candidate. As they were studying lithium-sulfur batteries, they found that they couldn’t find a way to stop the sulfur from interacting, undesirably, with the lithium. “There was only one real way we could see to stop that, and that would be to somehow encapsulate the lithium with a conductive solid electrolyte, like a thin glass layer.”
After doing some basic research, they started looking for an existing material they could use for that protective layer. They were lucky. A company in Japan called Ohara was making exactly what they needed. “I called them and had them ship us some plates, and when I talked to their representative, he said, ‘Well, I have some of these plates, but they’ve been sitting on my desk for a couple years.’ ” One of the major challenges with fabricating a material like this is making it stable enough to sit on a desktop without reacting with the moisture in the air and corroding. “And I thought, ‘Wow, if they’re that stable, that they can sit on his desk for two years without turning into a puddle, I want to look at those.’ So I said,
‘Send me the samples that have been sitting on your desk for two years.’ He did, and we immediately put lithium up against those plates after actually verifying it was conductive, and it degraded. So we said, ‘Okay, that’s why nobody’s using it— it’s not stable against lithium.’ ”
Fortuitously, PolyPlus had already developed a process for coating lithium with multiple layers of different materials that were designed to make otherwise unstable combinations of materials—combinations that normally react and corrode or melt or catch fire—stable. “Instead of lithium touching that white ceramic piece, we put something between the two that allowed lithium to move between the two but where nothing would react. We tried that and what we saw was, ‘Wow, this looks really stable.’ And then at that moment one of our electrochemists and I started talking and we said, ‘You know, if this stuff is stable in air, we might be able to build a lithium-air battery.’ ”
People had been talking about lithium-air for decades, but no one had ever figured out how to get around the fact that air contains moisture, and moisture attacks lithium. “All these discussions about lithium-air batteries, although interesting, had that basic flaw,” Visco said. “That if you were to build something, it would be a bit of a novelty. You’d never have anything practical.”
To see if they did have something practical, they decided to subject their coated lithium metal to the most direct test possible. “We put water right up against it,” Visco said. “And we said, ‘Either it’s going to get attacked and fall apart, or maybe we’ll see something.’ And it actually shocked us. What we saw was extreme, very stable electrode potential. So then we said, ‘Let’s see if we can move lithium in and out,’ and it just worked like a charm. So we said, ‘Wow, this is a big thing.’ ”
That year, 2003, PolyPlus went into stealth mode, and Visco and his colleagues spent the year writing patents. When they came out of hiding, they began talking about some of the most interesting far-horizon developments the battery world had seen in a long time. Naturally, they applied for funding from DARPA, the Pentagon’s advanced research agency, and got it. They began working on two different lines of research. First was lithium- seawater batteries, which could be used to power oceanographic research vessels or military craft. The second was lithium-air. Within the lithium-air program they began studying both primary (one-use) batteries, which today Visco says are working very well and delivering charge capacities of 800 milliamp-hours per gram, as well as the real prize, rechargeables.
PolyPlus’s lithium-air battery is based on an interesting tweak of traditional lithium-ion design. The negative electrode is made of metallic lithium, and the positive is air. Between the two is a ceramic barrier. “In our battery, things are switched around a bit,” Visco says. “It almost looks like a piece of glass, but it’s white.” But the metallic lithium anode is encased in a series of ceramic barriers that allow it to engage in the right reactions while keeping it completely isolated from moisture. “You can hold it in your hand, you can put it in a glass of water, and it’ll just sit there,” Visco said. “It’s completely stable. And as soon as you hook it up to a wire, it becomes active.”
To show exactly how stable the coated lithium electrode is, Visco’s team built a lithium- water battery in which the water “electrode” is an aquarium inhabited by clown fish. The water in which those fish live acts as the positive electrode for the battery, which is connected to a green 3- volt LED. “In a sense they’re swimming inside a lithium battery, and they’re completely unperturbed.” As always, there are hurdles to clear. Visco’s team has the same problem as all lithium-air researchers, which is recharging—getting solid lithium peroxide to break back down to its constituent parts in an orderly fashion. And they have lithium metal to deal with. The way PolyPlus encapsulates their lithium-metal electrode makes it easy to handle, but that doesn’t mean it will be easy to recharge. “No one has ever really shown [rechargeable lithium metal] to be doable yet,” Visco said. And that, in part, is why it’ll be a long time before PolyPlus’s lithium-air batteries are driving our cars. “Even if we commercialize a lithium-air battery, it’s going to take a long time before you see battery packs that are large enough and proven and tested enough that you would start thinking about transportation,” Visco said.
Today, electric cars come with too many caveats. Unless it has a backup gas engine, an electric vehicle will probably be a second car. Only when cities have charging stations in every parking meter and every parking garage will electrics truly be practical. Even then, it might take a nationwide chain of high-power, fast- charging stations or battery-swapping businesses before you can take a road trip in a purely electric car.
There are problems with waiting on the infrastructure, however. Consider fast charging, which would allow electric-car drivers to dump their batteries full of electrons in a matter of minutes, making a recharge only slightly more time- consuming than a visit to the gas station. The math isn’t promising for the prospect of a major network of electron filling stations. “Let’s say you’ve got a battery that holds 25 kilowatt-hours,” said Elton Cairns of Lawrence Berkeley National Laboratory. “If you want to charge that in fifteen minutes, then you’ve got to have a 100-kilowatt substation. If you’ve got something like the Tesla, with over 50 kilowatt-hours, and you want to charge that in fifteen minutes, you’re talking 200 kilowatts. Your house takes 1 kilowatt. If you want to have something like a gasoline fuel station that is all electrical, you’re talking about multi-megawatts of power at that station. And I just don’t see that happening.”
There are a couple of ways to react to this sort of discouraging calculus. One is defeatism. The other is research. “Infrastructure gains are the hardest there are,” IBM’s Wilcke said, “which is one reason [hydrogen] fuel cells haven’t worked.” That is exactly why Wilcke is now devoting his career to trying to find out whether the lithium-air battery can be made reality. With a breakthrough battery that can deliver a car five hundred miles on a single charge, only the most speed-addled road tripper would need fast charging or battery swapping. Everyone else will charge curbside at the hotel and then get back on the road the next morning. “I’d rather tackle a really difficult technical problem,” Wilcke said. “It’s confined to being a technical problem, and you don’t need a zillion dollars’ infrastructure.”
“Society needs higher-energy-density solutions,” Peter Bruce said. “There aren’t many options on the table. We have to explore the options that we have. Lithium-ion batteries will be with us for many years to come, and they’ll be key technologies in vehicles.” The reason Bruce and others like him have hope for the prospects of a livable, comfortable postoil civilization powered by electrons snared from the sun and generated from the wind is that, as grim as the cost estimates and think tank forecasts can sometimes be, we are just getting started. “I think the good thing about lithium-air, lithium sulfur is that at least there are some options,” Bruce said. “There is somewhere we can go.”
Excerpted from BOTTLED LIGHTNING: SUPERBATTERIES, ELECTRIC CARS, AND THE NEW LITHIUM ECONOMY by Seth Fletcher, published in May 2011 by Hill and Wang, a division of Farrar, Straus and Giroux. Copyright (c) 2011 by Seth Fletcher. All Rights Reserved. Pick it up here.