Solid-State Batteries — What’s Going On?

From smoke detectors and cell phones to EV cars, batteries power many of the things we rely on most. But despite their ubiquity, batteries are a flawed technology. Alkaline batteries have an expiration date. Lithium batteries are rechargeable, but they rely on finicky liquid or gel-based electrolytes that, if not properly maintained, can cause the battery to fail or catch fire.

Solid-state batteries (SSBs) have long been heralded as the solution to these persistent pain points, but engineering them has proven difficult, and progress has been slow. That is, until January 2026, when Finnish startup Donut Labs announced its “all-solid-state battery” was ready for the mass market.

Has Donut Labs done what other battery engineers could not? Will SSBs finally disrupt the battery industry as we know it? Is this another example of an eager tech startup over-promising and under-delivering, or something more nefarious? Let’s take a closer look.

Solid-state batteries - promises and pitfalls

As the name suggests, solid-state batteries use a solid electrolyte instead of the liquid form that can cause so many issues in lithium batteries. As Science explains, the solid electrolyte — “made of ceramic oxides, for example” — not only makes batteries safer, it also allows the batteries to use a lighter “anode of lithium metal.” “Without the dead weight of graphite, the battery can store much more energy per kilogram, which extends an EV’s driving range.”

Endgadget also notes that “Because of their higher energy density,” SSBs will not only be lighter, they can also be “smaller per watt than conventional batteries.” Safer, smaller, and a greater capacity for energy storage? If the promises of SSBs sound too good to be true, it’s because, thus far, they have been. As Science explains, “Materials that optimize one aspect of the battery’s performance—energy density, say—often degrade other properties such as charging rate.”

Leading players in China, South Korea, and Japan “have spent years juggling these trade-offs” — and, despite the necessary money and brain power at their disposal, they have been conservative about progress. For example, in 2025, Jiayan Shi, a battery technology associate at BloombergNEF, “estimated that SSBs could meet about 10% of EV and energy-storage battery demand by 2035.” That’s a long runway to meet a small fraction of the demand. Or at least it was until recently, when Donut Labs “announced it had leapfrogged these battery behemoths with the world’s first SSB ready for EV mass manufacturing.”

A charged announcement from Donut Labs

With a sleek aesthetic reminiscent of Apple and some truly astounding claims, Donut’s SSB launch was met with a mix of excitement and incredulity.

If Donut’s word is taken in good faith, the SSB they’ve created has achieved all the promised benefits without any of the ‘trade-offs’ other engineers have struggled with, including:

• Greater energy capacity: Donut claims its SSB has “400 Wh/kg of energy density” — which, according to Endgadget, is “roughly twice the energy density of the best lithium ion battery on the market.”
• “Ultra-Fast” charging: Despite its staggering energy capacity, Donut’s SSB has not sacrificed charging speed, and is, ostensibly, capable of charging “in as little as 5 minutes.”
• “Extreme” longevity: Donut’s SSB promises a lifetime of 100,000 cycles thanks to a design that’s “Built for daily fast charging and continuous use.”
•  Improved safety: Donut’s website assures visitors that their SSB is indeed devoid of “flammable liquid electrolytes,” and functions safely in extreme temperatures.
• “Clay-Like Design” and “Geopolitically-Safe Materials”: Donut’s SSB not only “adapts to the product instead of forcing the product to adapt to the battery,” it is also “100% green,” is made from “abundant materials with global availability,” and does not rely on “rare or geopolitically sensitive resources.”
• Affordability and accessibility: It’s reasonable to assume all these incredible benefits would come at a steep price point, but Donut assures customers that their SSB is “Lower cost than lithium ion,” and is “Designed for scalable production across all applications.”
• Production-ready: Unlike the dominant manufacturers in Asia, who are still a decade away from mass-market SSBs, Donut claims their battery is “available today.”

'World-shattering' implications

The significance of these claims cannot be overstated. “A battery that promised some of these features would be world-changing; one offering all of them would be world-shattering,” concludes Endgadget. “It would upend supply chains, shift the global balance of power, potentially eliminate reliance on so-called rare earth minerals and supercharge EV adoption.”

But before the global powers became too unsettled, the skeptics intervened.

The evidence for and against Donut’s SSB

The first red flag for tech experts was Donut’s sudden arrival on the scene. SSBs are not a new concept, and, as The Verge points out, “while most legitimate efforts in this field — whether academic or commercial — have some level of published research or recognizable names attached, Donut Lab seemed to have emerged out of nowhere, with no known researchers or prior presence in the field. This lack of traceability immediately raised concerns about the startup’s credibility.”

The next big concern was the lack of evidence to support Donut’s lofty claims. With, as Endgadget put it, “no hint as to what its process was based upon, and no sign it had the manufacturing capacity to deliver on its promises,” Donut’s legitimacy was soon being questioned by everyone from leading industry experts — like Yang Hongqin, CEO of Chinese battery maker Svolt, who flatly declared Donut “‘a scam’” — to Reddit readers hungry to uncover the truth.

I Donut Believe

In response to this mounting criticism, Donut’s CEO Marko Lehtimäki went on the offensive, striking back at the naysayers by publishing a second website, I Donut Believe, to highlight the “validation results and technical documentation related to the Donut Solid State Battery.” Over the course of five weeks, I Donut Believe rolled out five tests conducted independently by “the internationally renowned VTT Technical Research Centre of Finland.”

Confoundingly, Lehtimäki followed the publication of these tests with a video interview released on April 1, 2026, which began with him admitting Donut was a scam before pivoting that statement to an April Fool’s joke, and then claiming the subterfuge was a marketing tactic designed to boost engagement through “continued ambiguity.” Endgadget’s reaction to the video sums it up best: “If you're already facing credible accusations of perpetuating a scam, and your big reveal is to double down on misdirection, it's not a good look.”

The investigation heats up

Meanwhile, as Lehtimäki attempted to control the narrative, independent investigators continued digging.

At the end of April, Lauri Peltola, the chief commercial officer of Nordic Nano — a collaborator of Donut Labs — began telling journalists, including those reporting for Science, that, “‘The information that I have says that the battery is not in the state that Marko Lehtimäki announced in January.’” Nordic Nano placed Peltola on leave shortly after her statement, and issued a joint statement with Donut Labs denying that “Donut has committed any crime or misled investors.”

Then, on June 8, another bombshell dropped. A video posted by battery researcher Ziroth, and reported on by Electrek, “produced what amounts to definitive proof that Donut Lab’s ‘miracle’ solid-state battery is actually a lithium-ion cell.”

Summing up the evidence against Donut, Electrek highlights “voltage curves from VTT testing match high-nickel lithium-ion cells (NCM chemistry),” a signature “kink” in cell expansion data that’s unique to graphite anodes, proving “the cell uses lithium ions,” and energy density closer to “298 Wh/kg — what you’d expect from a good lithium-ion cell, not the 400 Wh/kg claimed.”

In addition to confirming Donut’s technical fraud, Ziroth also revealed a “web of companies behind the fraud” and a slew of troubling details about Donut’s funding, including small investment crowdfunding and intentionally inflated valuation. Electrek reports that “Finnish financial authorities and criminal authorities are reportedly investigating.”

Where does the SSB industry go from here?

Skeptical industry insiders are vindicated by the loss of Donut’s credibility, but any relief they feel will likely be tempered by concerns of a ripple effect. As Electrek puts it, the “concern now is that this damages public trust in solid-state battery technology more broadly.” The major players have the resources and expertise to make the dream of mass-market SSBs a reality, just so long as consumers don’t extend their distrust of Donut to the technology itself. Only time will tell what consequences Donut — and the SSB industry at large — will face as a result of this deception.

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