Solid-state batteries: Why Toyota’s plans could be a game-changer for EVs


Word out of Japan today is that Toyota is working on launching a new solid-state battery for electric vehicles that will put it solidly in the EV game by 2022.

Which leads to a simple question: What is a solid-state battery, and why does it matter?

Back in February, John Goodenough observed, «Cost, safety, energy density, rates of charge and discharge and cycle life are critical for battery-driven cars to be more widely adopted.» And risking a bad pun on his surname, he seemed to be implying that all of those characteristics weren’t currently good enough in autos using lithium-ion batteries.

This comment is relevant because Goodenough, professor at the Cockrell School of Engineering at the University of Texas at Austin – it so happens, he turns 95 today – is the co-inventor of the lithium-ion battery, the type of battery that is pretty much the mainstay of current electric vehicles.

And he and a research fellow at U of T were announcing they’d developed a solid-state battery, one that has improved energy density (which means a car so equipped can drive further) and can be recharged more quickly and more often (a.k.a., «long cycle life») than a lithium-ion battery.

(Did you ever notice that with time your iPhone keeps less of a charge than it did back when it was shiny and new? That’s because it has a limited cycle life. Which is one thing when you’re talking about a phone. And something else entirely when it involves a whole car.)

What’s more, there is reduced mass for a solid-state battery. And there isn’t the same safety concern that exists with li-ion batteries vis-à- vis conflagration (which is why at airplane boarding gates they say they’ll check your carryon as long as you remove all lithium-ion batteries).

Lithium-ion batteries may be far more advanced than the lead-acid batteries that are under the hood of essentially every car that wasn’t built in Fremont, Calif., but as is the case with those heavy black rectangles, li-ion batteries contain a liquid. In the lithium-ion battery, the liquid, the electrolyte, moves the lithium ions from the negative to the positive side (anode to cathode) of the battery.

In a solid-state design, there is no liquid sloshing around, which also means that there’s no liquid that would freeze at low operating temperatures.

What Toyota is using for its solid-state battery is still unknown, as is the case for the solid-state batteries that Hyundai is reportedly working on for its EVs.

In the case of Goodenough’s solid-state battery, sodium is used to form glass that serves as the electrolyte. Consider the implications of the development of solid-state batteries for powering cars and trucks versus using lithium-ion battery packs.

For one thing, it will certainly mean that those Gigafactories that are sprouting up are going to have to undergo a significant change in what they’re producing.

And for another, it will more quickly bring EVs to price parity with internal combustion engine-powered vehicles. A recent UBS study estimated that parity would occur in 2023, but that finding was based on li-ion batteries; Toyota, Hyundai, and Prof. Goodenough could provide the proverbial game-changer.