Hope, challenges for solid-state batteries

TOKYO — Lithium ion batteries revolutionized electrified driving by being small, light and powerful. The trio of scientists who developed them even won the Nobel Prize in October for their work. But the advent of solid-state batteries is poised to usher in another leap forward.

Solid-state batteries differ from lithium ion batteries in using a solid material for the electrolyte, such as a ceramic or polymer, instead of a liquid or gel. The cells are less vulnerable to extreme temperatures and promise two to three times the energy density of existing lithium ion batteries.

Solid-state batteries are expected to be lighter, longer lasting, safer and eventually cheaper, too. But perfecting the technology has been tricky and commercialization is still years away.

Toyota Motor Corp. is aggressive in pursuing the technology. Last year, the carmaker vowed to have a working prototype in time for the 2020 Tokyo Summer Olympics. The Games were postponed because of COVID-19, but Toyota's development is still on schedule, said Keiji Kaita, executive vice president of Toyota's Powertrain Co. and general manager of its battery business.

Toyota is developing solid-state batteries through Prime Planet Energy and Solutions Inc., a joint venture with Panasonic. The partners are on track to put solid-state batteries into limited production in the first half of the 2020s, Kaita said. Toyota is pinning its hopes on a sulfur-based solid electrolyte pressurized into hard plates that are sealed in pouchlike cells.

But initial volume will be low and the cost will still be high compared with lithium ion cells, he said.

Also in the race are BMW, Volkswagen, Honda, Hyundai, Ford, GM and all major battery suppliers.

In March, South Korean battery supplier Samsung SDI declared a breakthrough in solid-state battery technology. Its advance was using a silver-carbon composite layer in the anode. Doing so helped the battery achieve bigger capacity, better safety and a longer life cycle, the company said.

"This promising research is expected to help drive the expansion of electric vehicles," Samsung SDI said at the time. "The prototype pouch cell that the team developed would enable an EV to travel up to 800 km [500 miles] on a single charge and features a cycle life of over 1,000 charges."

In June, Volkswagen Group said it would increase its stake in QuantumScape, an American solid-state battery hopeful. VW's goal is to create an industrial-level pilot plant, though the company did not offer a timeline.