In recent years we've heard plenty about hydrogen fuel cells, bio fuels and even cars powered on wine and cheese, but what about a car battery that relies on fresh air for generating electricity?
Toyota's research department in Japan is currently investing heavily in so-called air batteries in an effort to replace the current generation of electric car batteries.
Current nickel-metal-hydrogen batteries and even the next generation of lithium-ion batteries are seen to be holding back the mass adoption of electric cars, as they can't hold enough charge for many users' needs.
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However, air batteries, which create electricity from a reaction between oxygen in the air and a zinc negative electrode, can store five times as much electricity as a similarly sized li-ion battery, although there are problems before they can be commercialised.
The most fundamental of these lies in scaling air batteries up to the size needed to power a car efficiently.
Existing air batteries have only been made large enough to power hearing aids or similar devices, which is why Toyota is working to enlarge them. Once that happens, the days of the combustion engine could finally be numbered.