This company claims a battery breakthrough. Now they need to prove it.

When a company claims to have created what’s essentially the holy grail of batteries, there are bound to be some questions.

Interest has been swirling since Donut Lab, a Finnish company, announced last month that it had a new solid-state battery technology, one that was ready for large-scale production. The company said its batteries can charge super-fast and have a high energy density that would translate to ultra-long-range EVs. What’s more, it claimed the cells can operate safely in the extreme heat and cold, contain “green and abundant materials,” and would cost less than lithium-ion batteries do today.

It sounded amazing—this sort of technology could transform the EV industry. But many quickly wondered if it was all too good to be true. Now, Donut Lab is releasing a series of videos that it says will prove its technology has the secret sauce. Let’s dig into why this company is making news, why many experts are skeptical, and what it all means for the battery industry right now.

Solid-state batteries could deliver the next generation of EVs. In place of a liquid electrolyte (the material that ions move through inside a battery), the cells use a solid material, so they can be more compact. That means a significantly longer range, which could get more people excited to drive EVs.

The problem is, getting these batteries to work and making them at the large scale required for the EV industry hasn’t been a simple task. Some of the world’s most powerful automakers and battery companies have been trying for years to get the technology off the ground. (Toyota at one point said it would have solid-state batteries in cars by 2020. Now it’s shooting for 2027 or 2028.)

While it’s been a long time coming, it does feel as if solid-state batteries are closer than ever. Much of the progress so far has been on semi-solid-state batteries, which use materials like gels for electrolytes. But some companies, including several in China, are getting closer to true solid state. The world’s largest battery company, CATL, plans to manufacture small quantities in 2027. Another major Chinese automaker, Changan, plans to start testing installation of all-solid-state batteries in vehicles this year, with mass production expected to begin next year.

Still, Donut Lab surprised the battery industry when, in a video released in early January ahead of the Consumer Electronics Show in Las Vegas, the company claimed it would put the world’s first all-solid-state battery into production vehicles.

One of the splashiest claims in the announcement was that cells would have an energy density of 400 watt-hours per kilogram (the top commercial lithium-ion batteries today sit at about 250 to 300 Wh/kg). It was also claimed that the cells could charge in as little as five minutes, last 100,000 cycles, and retain 99% of capacity at high and low temperatures—while costing less than lithium-ion cells and being made from “100% green and abundant materials with global availability.”

Many experts were immediately skeptical. “In the solid-state field, the technical barriers are very high,” said Shirley Meng, a professor of molecular engineering at the University of Chicago, when I spoke with her last month. She’d recently attended CES and visited Donut Lab’s booth. “They had zero demo, so I don’t believe it,” she says. “Call me conservative, but I would rather be careful than be sorry later.”

“It’s one of those things where nobody knows—they’ve never heard of it,” said Eric Wachsman, a professor at the University of Maryland and cofounder of the solid-state battery company Ion Storage Systems, in a January interview. “They came out of nowhere.”

Donut Lab has shared very little about what, exactly, this technology might be. It’s not uncommon for battery companies (or any startup, for that matter) to be quiet about technical details before they can get patents filed to protect their technology. But the combination of claims didn’t seem to line up with any known chemistries, leaving experts speculating and, in many cases, doubting Donut Lab’s claims.

“All the parameters are contradictory,” said Yang Hongxin, chairman and CEO of the Chinese battery giant Svolt Energy, in remarks to news outlets in January. For example, there’s often a trade-off between high energy density, which requires thicker electrodes that can store more energy, and fast charging, which requires ions to move quickly through cells. High-performance batteries are also expected to be costly, but Donut Lab claims its technology will be cheaper than lithium-ion technology. 

In a new video released last week, Donut Lab cofounder and CEO Marko Lehtimäki announced the company would be releasing a video series, called “I Donut Believe,” that would provide evidence for their claims. As a header on the accompanying website reads: “Fair enough. Here you go.”

When the website went up last week, it included a countdown timer to Monday February 23, when the company released results from its first third-party testing: a fast charging test. The test showed that a single cell could charge from 0% to 80% capacity in about four and a half minutes—incredibly quick and quite impressive results. (One potential caveat to note is that the cells heated up quite a bit, so thermal management could be important in designing vehicles that use these batteries.)

Even as we see the first technical test results, I’m still left with a lot of questions. How many cycles could this battery do at this charging speed? Can this same cell meet the company’s other performance claims? (I’ve reached out to Donut Lab several times over the past month, both to the company’s press email and to leadership on LinkedIn, but I haven’t gotten a response yet.)

The company has certainly drummed up a lot of interest and attention with its rollout, and the theatrics aren’t over yet. There’s another countdown timer on Donut Lab’s site, which ends on Monday, March 2.

I’m the first one to get excited about a new battery technology. But there’s a sentiment I’ve seen pop up a lot recently online, and one I can’t get out of my head as I continue to follow this story: “Extraordinary claims require extraordinary proof.”

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