Pictures: Seven Ingredients for Better Electric Car Batteries

Manganese: Abundant and Stable

Photograph by Nir Elias, Reuters

A worker piles coal onto a cart at a silicon-manganese alloy factory in Longsheng, in southern China's Guangxi Zhuang Autonomous Region.

Coal and manganese typically work hand-in-hand today as essential materials in steelmaking. But manganese also plays an important role in the bid for cleaner energy: It's a key ingredient in the batteries selected to power the Nissan Leaf, Chevy Volt, and Fisker Karma.

Manganese was used by ancient people in the Atacama Desert in South America to mummify skeletons. Thanks to its durability, it also has been found to have desirable properties for energy storage. Lithium-manganese oxide batteries are more stable than those made of lithium-cobalt oxide, which are widely used in consumer electronics, but can lead to thermal runaway problems if overheated. Manganese, said Persson, is "the one we try to put in all the batteries if we can."

It's also relatively cheap and abundant, although resources are not shared evenly around the world. South Africa has 75 percent of the world's known manganese resources; China and Australia follow as top producers.

Manganese has one important drawback: a troubling tendency to dissolve in the electrolyte. "It migrates over to the anode and attacks the anode," said Persson. This hinders battery longevity—an important consideration for cars that are meant to last 15 years or more on the road. "We've been trying to solve this problem for a long time," Persson says.

Envia Systems, a start-up company in Newark, California, has attracted investment from General Motors' venture capital arm and grants from the U.S. government with its plan for a lower cost, higher energy density battery featuring a manganese-rich cathode and an anode made of silicon-carbon nanocomposites.

Arun Majumdar, then-director of the U.S. Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E), cited Envia in testimony on Capitol Hill earlier this year on why battery research was critical. The record-setting energy density Envia achieved in its design (400 watt-hours per kilogram) could mean the difference between paying $40 for fuel to drive a gas car from Washington, D.C. to New Jersey, or paying $6 for electricity to make the same trip in an EV,  he said.  The problem is that such a battery pack, as of now, would cost $30,000. "ARPA-E's goal is to reduce the cost of batteries so that electric cars can have comparable range and cost as gasoline-based cars so that they can be sold without subsidies, and reduce our dependence on imported petroleum," he said.

(Related: "Pictures: Death-Cult Mummies Inspired by Desert Conditions?")

Published September 14, 2012

Lithium: Lightweight, High Capacity

Photograph by Bobby Haas, National Geographic

A plow carves pinstripes across snow-white fields of lithium near the edge of northern Chile's huge salt flat, Salar de Atacama. Lithium is the element that has delivered portable rechargeable electronics to the world, and has paved the way for today's electric cars.

"I think we're going to be stuck with lithium for a while," says Persson. "It's still the one technology that's feasible today." In just the past several years, the nickel-metal hydride battery chemistry used for hybrids including the Toyota Prius has given way to lithium-ion chemistries that offer twice the energy density for the same weight and bulk.

But there are practical limitations to lithium-ion batteries, including the time they take to recharge. They still add too much weight and bulk to vehicles. And there are political reasons to look beyond lithium. "You can't dig it out of the ground everywhere," said Persson. "You need these mines that have the salts." Much of the world's lithium resources are controlled by Bolivia, China, and Chile—the latter is by far the world's top producer.

(Related "Pictures: China's Rare-Earth Minerals Monopoly" and "While Rare-Earth Trade Dispute Heats Up, Scientists Seek Alternatives")

Another concern is safety. "Drop a tiny piece of lithium in water, and it goes psshhhh," Persson said, describing a common grade school lab experiment, in which the lithium metal gives its electrons to the water and forms lithium hydroxide and bubbling hydrogen. But what's cool in science class requires careful management in a car.

(Related: "Afghanistan's Lithium Wealth Could Remain Elusive")

"It's always going to be slightly dangerous putting it in water. But it's still the best element," Persson said. "Because of it's high reactivity, it also comes with a high voltage."

Battery innovation does not always go as planned. Nanophosphate lithium-ion battery maker A123 Systems, backed by $249 million in U.S. government grants, won contracts to supply batteries for the plug-in hybrid Fisker Karma and the upcoming electric Chevy Spark from General Motors. But amid slower-than-expected EV sales, defects that forced A123 to replace batteries in Fisker models earlier this year, and nearly $83 million in losses for the second quarter, A123 turned to Chinese auto supplier Wanxiang Group for emergency investment. Eventually, Wanxiang is expected to own up to 80 percent of A123 with a total $465 million investment.

(Related: "A123 Deal Ignites Debate Over China, Energy")

(Related:  "Replacing Oil Addiction With Metals Dependence?")

Published September 14, 2012

Copper: Metal for a Super Charge

Photograph by George Steinmetz, National Geographic

The rock waste of a century-old open-pit copper mine in Chile fans out into a wedge covering 3 square miles (8 square kilometers) and plunging nearly 2,000 feet (600 meters) deep.

This mine in Chuquicamata, Atacama, dates back to 1911, testimony to copper's long history as a crucial metal. Copper cathodes actually were deployed in the original battery back in 1800. While that practice fell out of fashion long ago, copper could acquire a shining role in the future of batteries if early-stage work with the metal in nanowire form pans out.

Typically copper is used as a current collector in batteries, not as an electrode material. Like manganese, it tends to dissolve in the electrolyte, Persson said. And it's relatively expensive.

Yet Prieto Battery, a start-up spun out of Colorado State University, has prototyped a lithium-ion battery that swaps out the conventional graphite in the anode for nanowires constructed from copper and antimonide. These are 50,000 times thinner than a human hair, and Prieto claims they can store twice as many lithium ions as state-of-the-art graphite anode materials. With further development, the technology could pave the way for electric cars that can get a full charge in minutes, rather than hours.

Published September 14, 2012

Sodium: A Flavor for Power

Photograph by George Steinmetz, Corbis

Tourists snap photos as they tread on salt accretions in the Dead Sea Works salt evaporation ponds, near beach resorts in Ein, Israel.

The ponds deposit about 8 inches (20 centimeters) of edible salt, or sodium chloride, per year. Huge evaporation pans located to the south are used to extract potash, magnesium, and bromides from the salt.

"Going from lithium to magnesium, you're losing voltage, but you're doubling the capacity. It's also dirt cheap and the sixth most abundant element in the earth's crust," said Persson, whose company Pellion Technologies is developing a battery featuring a magnesium metal anode. Of course, magnesium ore needs to be processed in order to perform well in a battery, Persson said, "but at least on the element level it is not expensive."

Plentiful, low-cost sodium offers an alluring alternative—or possibly companion—to lithium. "There are a lot of commonalities between lithium and sodium, so it's a drop-in replacement," said Persson. Researchers with Tokyo Science University have developed a rechargeable battery using oxides of sodium, iron, and manganese for the positive electrode, and sodium metal for the negative electrode. The device is said to hold a charge on par with lithium-ion batteries, while relying on much more widely available materials.

Meanwhile, General Electric has demonstrated a battery system for heavy buses and delivery trucks that pairs sodium and lithium technology together—"essentially combining the pickup that today's passenger EVs have with the power storage that big industrial batteries offer," according to a statement from the company. Lithium batteries "provide a lot of power for acceleration, but are not optimized to store energy for driving range," GE says. Capable of storing large amounts of energy but falling short on power, sodium batteries are a logical complement.

Safety, however, remains a weak spot for sodium batteries. "Sodium has a very, very low melting point," Persson said. "You tend to form these pockets of sodium metal deposited all over the cell." And, like lithium metal, sodium metal is very reactive. "As soon as you have any kind of alkali metal around in the battery, that is a very reactive component. As soon as you heat anything up, then that little part is going to spark."

Published September 14, 2012

Silicon: A Crystal-Clear Advantage

Photograph by Peter Ginter, Corbis

A bird's-eye view of this Chilean silicon mine resembles a litmus strip cast across a cocoa-colored landscape. Theoretically, silicon can store ten times more energy than the graphite commonly used in lithium-ion batteries today.

"Silicon anodes, that's a great idea," said Persson. The element is abundant, making up more than one-quarter of the Earth's crust. And years of experience with extremely pure silicon in the semiconductor industry has produced "a lot of understanding about how to make it cheap."

But engineering challenges remain, largely because silicon swells during charging. "It's like blowing up a balloon," Persson explains. "If you paint a layer on that balloon, blow it up, and then deflate it, the layer will fall off. So you have to reform it. Every time that layer reforms, you're losing active materials. Every cycle, you're losing active material and losing capacity."

Published September 14, 2012

Oxygen: A Breath of the Future

Photograph courtesy University of Dayton Research Institute  

In the search for plentiful, cheap, safe, and light-weight battery ingredients, what could be more enticing than the idea of harnessing the very air we breathe?

The cell pictured here, developed in 2009 by the University of Dayton Research Institute's electrochemical power group, was billed as the first solid-state, rechargeable lithium-oxygen battery, designed to address the fire and explosion risks of other lithium rechargeable batteries.

The Dayton researchers employed a solid glass-ceramic material for the electrolyte, rather than liquid electrolytes, which can leak, cause corrosion, and produce volatile reactions. Rather than storing all the necessary chemicals inside the battery, "one of the chemicals—oxygen—is left out," Dayton engineer Binod Kumar explained in an announcement about his lithium-oxygen prototypes. Oxygen is extracted from the surrounding air and used in the cathode.

"Oxygen is obviously tremendously abundant and cheap—very cheap," Persson said. "The problem is you really only want the oxygen. You can't tolerate any moisture, so you have to separate oxygen from the hydrogen and everything else in the air."

At this point, lithium-oxygen technology is very much a moon shoot. If it works, it could enable batteries with 10 times the capacity of today's lithium-ion batteries, cars that can travel up to 500 miles (800 kilometers), and cell phones that can handle a week of calls on a single charge.

But despite recent advances (including a recent Scottish study demonstrating a lithium-oxygen battery with a gold electrode that could sustain charge-discharge cycles without degrading) a heap of problems remain to be solved. "It's not a drop-in replacement for the current lithium batteries," Persson said. "It needs air ducts and filters and all kinds of plumbing, basically, to make it work. It needs a lot of device engineering around it." What's more, the chemistry involves "unbelievably reactive agents," including lithium peroxide, which results from oxygen mixing with lithium ions. She said, "Finding things that stand up to those—it's not easy."

Published September 14, 2012

Next: Photos: Rare Look Inside Carmakers' Drive for 55 MPG

Photograph by Jeffrey Sauger, National Geographic

Published September 14, 2012