Is Tesla Working on a Cheap, 300-Mile "Metal Air" Battery?

A couple of recent reports have noted that Tesla has filed patents on the use of metal air battery technology. Could this be the route the company intends to take to produce affordable cars with a range similar to gas-powered cars (see “How Tesla Is Driving Electric Car Innovation”)?

Metal air batteries have very high theoretical energy capacities in part because unlike other batteries, they don’t store all the necessary reactants on board. They get some of the material needed to generate electricity from the air. Indeed, Toyota has decided to focus research efforts on these batteries for just this reason, and Tesla gets its batteries from Panasonic, a company with a close relationship to Toyota.

But metal air batteries, especially the lithium air batteries that have some of the best theoretical energy storage, have lifetime and cost issues, and solving these issues can detract from their ability to store energy. If Tesla’s predictions that it can make a $35,000 car with a 200-mile-plus range rest on the use of metal air, I’d be a little worried.

But in my visit to Tesla’s labs earlier this year Tesla CTO JB Straubel–whose name appears on the metal air patents–told me he thinks regular-old lithium ion batteries, the type the company uses now, still have a lot of room for improvement. I wouldn’t be surprised if the next couple of generations of batteries continue to use lithium ion technology as metal air technology is improved. If Tesla does eventually use metal air, it will likely be in conjunction with lithium ion batteries to lessen the strain on the metal air technology.

If there is a breakthrough in metal air, it looks like Tesla will be ready to use the technology.