While it's unclear which company will win the race to put solid-state batteries in a production car, Toyota and research partner Panasonic currently have the lead in patents related to the technology, Nikkei Asia reported Thursday.

Along with Tokyo-based research firm Patent Consult, Nikkei studied patent applications for solid-state battery tech in ten countries and territories filed from 2000 through the end of March of this year.

Toyota was the clear leader with 1,331 known patents, followed by Panasonic with 445 patents. In comparison, the third-place company—Idemitsu Kosan—holds 272 patents, according to the report.

2023 Toyota bZ4X Limited AWD

2023 Toyota bZ4X Limited AWD

It's worth noting that patents are a good way to judge research and development activity, but they’re no strong indication of how far along a company actually is in bringing a particular technology to production. Many other automakers and battery suppliers are also investing in solid-state battery research, lured by claims of greater energy density.

Toyota began researching solid-state batteries in the 1990s, according to Nikkei. It partnered with Panasonic for joint development of the tech in 2019. Just prior to that, Panasonic had said solid-state cells weren't going to arrive until 2028 or later. Panasonic has of course also been a longtime business partner with Tesla.

Toyota has confirmed at a couple of points that the tech is under development and scheduled for a production model around the middle of the decade. Earlier this year it revealed the first application will be a hybrid, not an EV.

2022 Toyota Prius Nightshade

2022 Toyota Prius Nightshade

Meanwhile, Nissan is looking to solid-state batteries as a key to making affordable EVs viable across a broader range of vehicle types, including pickup trucks and SUVs. Earlier this year it announced a prototype production facility for solid-state battery cells—with plans to establish a pilot production line as soon as 2024 in Japan, and market availability in an EV in 2028.

Other automakers—including Honda, BMW, Ford, and Volkswagen—have discussed using solid-state batteries in cars. But so far the only practical use has been in a different type of vehicle. Solid-state cells are already being installed into city buses in Germany, but they require some very specific conditions—like high-temperatures—that aren't practical for passenger vehicles