The technology is critical for advancing the range and safety of electric vehicles, but it's not quite ready for mass production yet.
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Toyota will debut solid-state batteries, one of the most significant technologies coming to electric vehicles, at the 2020 Tokyo Olympic Games.

Speaking with Auto Express, Toyota chief technology officer, Shigeki Terashi, said at "the Tokyo Olympics, we would like to produce a car with Toyota’s own solid-state battery and unveil it for you".

"Mass-production will be later. At the 2020 Olympics it will probably be an e-Palette with Toyota’s solid-state battery in operation. I am advocating the use of solid-state batteries in e-Palette. For mass-production model you will have to wait a little while longer," he said.

Solid-state batteries address many of the issues with the lithium-ion batteries currently commonplace in phones, computers, and (of course) cars.

Rather than using a liquid electrolyte, solid-state batteries rely on a solid polymer metal electrolyte. That means there's nothing volatile or flammable inside the battery pack, improving their safety and heat-management properties.

That opens the door for batteries packing significantly more range into a smaller package – known as energy density. The potential for ultra-fast charging without significant battery degradation is also better with solid-state batteries.

The technology is "intrinsically much more stable under a variety of both normal and abnormal operating conditions" than current lithium-ion tech according to Professor Douglas MacFarlane, energy theme leader of the Australian Centre for Electromaterials Science.

"Lithium-ion batteries contain a flammable liquid electrolyte which doesn't go well once it is heated beyond about 150 degrees or so," MacFarlane told CarAdvice.

"The battery has got a tendency to overheat itself under certain kinds of maltreatment or damage, like a collision in a car would be an issue."

"And once the battery gets too hot, the whole thing just begins to go into a 'thermal runaway' we call it, which ultimately produces a fire or even a small explosion of the battery, which is pretty serious in a big battery pack."

In contrast, a Massachusetts Institute of Technology report on solid-state batteries says you could drive a nail through them, or smash them against the wall, and they'd be unlikely to catch fire.

Toyota has previously promised a mass-produced EV will solid-state batteries will debut in 2022.