Tech + Engineering
20
Sep

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For Electric Cars, Two Battery Technologies May Be Better Than One

What’s not to like about electric cars? They’re quiet, torquey, and don’t spew emissions from a tailpipe. So why isn’t everyone driving them? Two main reasons—range and refill time. Electric cars have less of the former and take longer for the latter compared with their fossil fuel counterparts.
Tesla, though, has an idea that could close at least one of those gaps gap. Today, Teslas are powered by lithium-ion batteries, the current state-of-the-art when it comes to car batteries. But if a new patent issued to the company turns into something useful, they could be supplemented by another battery using metal-air technology. It would create, in essence, an electric-electric hybrid which could travel farther than a single battery-type car.

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A future Tesla model could be an electric-electric hybrid.
 
Metal-air batteries have several advantages over lithium-ion batteries, not least of which is their light weight. Metal-air batteries draw oxygen from the atmosphere to use as one of their reactants. A lithium-air battery, for example, would be significantly lighter than lithium-ion batteries, which have to carry all of their reactants with them at all times. (That’s like if a fossil fuel vehicle had to carry with it all the oxygen needed to combust the hydrocarbons._

So why not make the jump to metal-air batteries? Here’s Kevin Bullis, writing for Technology Review:
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.
Tesla’s patent includes makes a reference to metal-air batteries, which Bullis notes could mean the auto manufacturer has solved some of the technology’s problems. But even if they haven’t, they may have found a way around metal-air’s limitations simply by pairing those batteries with proven lithium-ion designs.

According to the patent’s abstract, the metal-air battery would act as a reserve battery, providing extended range when necessary without adding lots of weight to the car. By only using the metal-air battery infrequently—most people drive less than 100 miles per day—its longevity issues shouldn’t be much of a concern. It’s a clever solution, and one that may help alleviate so-called range anxiety.