Safety problems with lithium-metal batteries can arise when they’re recharged. “When you charge and discharge, you have to electroplate and strip the metal over and over again,” says Dahn, who is not a contributor to the IBM project. Over time, just as in a lithium-ion battery, the lithium-metal surface becomes rough, which can lead to thermal runaway, when the battery literally burns until all the reactants inside are used up. But Narayan says that lithium-air batteries are inherently safer than previously developed lithium-metal batteries as well as today’s lithium-ion batteries because only one of the reactants is contained in the cell. “A lithium-air cell needs air from outside,” says Narayan. “You will never get a runaway reaction because air is limited.”
PolyPlus Battery has been working on lithium metal-air technology for about six years and has some dramatic evidence of the technology’s viability: floating among clownfish in an aquarium tank at the company’s headquarters, a lithium-metal battery pulls in oxygen from the salt water to power a green LED. The company has also developed a prototype battery that pulls oxygen from ambient air. But Steven Visco, founder and vice president of research at the company, says that lithium metal-air batteries are “still a young technology that’s not ready to be commercialized.”
IBM’s Narayan points to two remaining major problems with lithium metal-air technology. First, the design of the cathode needs to be optimized so that the lithium oxide that forms when oxygen is pulled inside the battery won’t block the oxygen intake channels. Second, better catalysts are needed to drive the reverse reaction that recharges the battery.
Narayan says that it won’t be clear how much money and how much time the project will take until about a year and half from now, after research has begun. He estimates that the company will devote about five years to the project. IBM will probably not make the batteries but will license the technology to manufacturers.