Solid state batteries are something of a holy grail for electric vehicles, and it appears they’re closer than many people realize.

According to Automotive News, Toyota was planning to introduce a concept with solid state batteries at the Summer Olympics in Tokyo.

While the games were postponed by the coronavirus pandemic, development of the batteries continued and now they have been installed in multiple concepts. However, there’s no word on when they will debut as the Summer Olympics have been pushed back to 2021.

Also Read: Toyota Is Bringing A Solid State Battery-Powered Electric Vehicle To The 2020 Olympics

Little is known about the concepts, but solid state batteries promise a number of benefits over traditional lithium-ion batteries. Key among them are higher energy densities which would allow for smaller and lighter battery packs. They’re also slated to be safer and offer faster recharging times.

Toyota’s Keiji Kaita hinted at their capabilities as he told the publication their prototype solid state battery can be fully recharged in less than 15 minutes. There’s no word on the battery’s capacity, but he noted they require “significantly less” time to recharge than an equivalent lithium-ion battery.

Unfortunately, there are still a number of issues that need to be worked out. Safety and durability issues are reportedly preventing engineers from reaching high energy densities. The company also appears to be fine tuning the chemistry to minimize battery degradation.

On top of this, there’s the issue of mass production. The batteries have to be made in an “ultra-dry, nonaqueous environment” and the current method of doing this involves transparent booths where workers assemble the batteries using sealed rubber gloves. In essence, it’s a bit like building a battery is a sand blasting cabinet. This is obviously less than ideal and Kaita described it as “slow, awkward and ill-suited to mass production.”

Despite the problems, Kaita said the batteries should go into limited production by 2025. They will initially cost more than lithium-ion batteries and he suggested production volumes will likely remain low for several years.

On the bright side, Toyota appears to be committed to building some amazing batteries as one of their goals is for solid state batteries to “keep more than 90 percent of their original performance in the long run; perhaps 30 years.”