Explainer-How could solid-state batteries improve next-gen EVs?

Toyota Motor has said it is moving toward production of solid-state batteries for the next generation of electric vehicles (EVs), bringing a technology that promises more energy storage and faster charging closer to market.

HOW ARE SOLID-STATE BATTERIES DIFFERENT?
Solid-state batteries use thin layers of solid electrolytes that carry lithium ions between electrodes.

The lithium-ion (li-ion) batteries widely in use, by contrast, use liquid electrolytes.

Solid-state batteries have been used in small electronic devices such as pacemakers and smart watches. Mass-market production of the batteries for EVs has been slower to develop.

Toyota said it has overcome an issue with the durability of solid-state batteries that would pave the way for production, which it expects to begin in 2027-2028.

WHAT ARE THE ADVANTAGES OF SOLID-STATE BATTERIES?
They have been called "the grail" of battery development and "the kiss of death" for combustion-engine offerings because of their power and the driving range possible on a single charge.

Solid-state batteries can hold more energy than liquid lithium-ion batteries, a gain that would potentially speed the transition to EVs by addressing a consumer concern: range. A Reuters poll in March found 35 per cent of Americans surveyed wanted EVs with ranges of 500 miles or more (804 km or more), a distance few currently offer. Solid-state batteries have also been promoted as a way to reduce charging time.

Toyota said it expects its solid-state battery would have a charging time of 10 minutes or less. By comparison, the Tesla Supercharger network, the largest of its kind, offers the equivalent of 321 km of charge in 15 minutes.

There is also safety. The electrolyte in liquid lithium-ion batteries is volatile and flammable at high temperatures, meaning there is a risk of fire or chemical leaks.

WHY IS IT DIFFICULT TO MANUFACTURE SOLID STATE BATTERIES?
Automakers and technology companies have produced solid-state battery cells for EVs in prototype, but have been unable so far to scale to mass production.

It is hard to design a solid electrolyte that is stable and chemically inert and yet is still a good conductor of ions between the electrodes. They are also expensive to fabricate and prone to cracking.

That has made solid-state batteries far more expensive than liquid lithium-ion batteries.

Toyota did not disclose cost estimates for its new solid-state battery EV or the additional investment it would have to make to ramp up production.

WHO'S TRYING TO MAKE THEM?
Most major automakers - with the exception of Tesla - have disclosed development efforts or partnerships.

Toyota has been pushing solid-state battery development and has teamed with Panasonic on related projects.

Nissan Motor, the first automaker to launch a mass-market EV with the Leaf, has said it is developing solid-state batteries and is working toward mass production by 2028.

Honda is developing solid-state batteries but has not detailed a timeline for bringing them to market.

U.S. battery start-up QuantumScape, backed by Bill Gates and Volkswagen, has said it has contracts with six electric vehicle makers, including Volkswagen.

Automotive Cells Co, a venture between Mercedes-Benz, Stellantis and TotalEnergies, has an agreement to develop solid-state batteries with Taiwan-based battery maker ProLogium Technology.

Ford and BMW have invested in U.S.-based startup Solid Power, which is producing prototype batteries. Hyundai Motor, another Solid Power investor, has said it plans to mass produce solid-state batteries by 2030.

Tesla has not detailed solid-state battery development plans. The EV market leader has been focused on the rollout of more powerful 4680 cells for its Cybertruck and other vehicles.