As EV sales increase, supplies of lithium may get tight. So some companies are incorporating cells with sodium, which provides almost as big a charge.
HALF A CENTURY ago, the battery of the future was built out of sodium. The reason has to do with why the seas are salty. Sodium is a light element that ionizes easily, giving up one of its electrons. In a battery, those ions shuttle back and forth between two oppositely charged plates, generating a current. This looked like a promising way to power a house or a car. But then another element crashed the party: lithium, sodium’s upstairs neighbor on the periodic table. In 1991, Sony commercialized the first rechargeable lithium-ion battery, which was small and portable enough to power its handheld video cameras. Lithium was lighter and easier to work with than sodium, and so a battery industry grew up around it. Companies and research labs raced to pack more energy into less space. Sodium faded into the background.
So it was surprising this summer when China’s CATL, one of the world’s largest battery makers, announced sodium would play a role in the electrified future. CATL, like its competitors, is a lithium company through and through. But starting in 2023, it will begin placing sodium cells alongside lithium ones inside the battery packs that power electric cars. Why? Well, for one thing, a CATL executive pointed out that sodium is cheaper than lithium, and performs better in cold weather. But it was also hedging against an issue that was difficult to imagine in 1991. By the end of this decade, the world will be running short on the raw materials for batteries—not just lithium, but also metals like nickel and cobalt. Now that electrification is actually happening on a big scale, it’s time to think about diversifying. A CATL spokesperson tells WIRED it started thinking about sodium 10 years ago.
CATL’s announcement “really injected new energy into the people who work on sodium,” says Shirley Meng, a battery scientist at the University of California, San Diego who works extensively with both elements. As a young professor, Meng started working with sodium in part because she was looking for a suitably weird niche to stand out in—but also because she believed it had potential. “The biggest barrier to success for sodium was that lithium was so successful,” she says.
Lithium is not exceptionally rare. But deposits are concentrated in places that are hard to mine. So companies like CATL compete to secure a slice of the supply from a limited number of mines, mostly located in Australia and the Andes. Meanwhile, reserves in North America are tied up in environmental disputes, raising concerns in the US about the security of the supply chains. Competition is even fiercer for nickel—which Elon Musk has called the “biggest concern” for the future of EV batteries, due to price and supply constraints—and for cobalt, 70 percent of which is dug up in the Democratic Republic of the Congo.