8 Companies Promised Solid-State Batteries by 2025. Zero Delivered. Now They’re Promising 2027.

Zero production vehicles on any road anywhere in the world run on a solid-state battery. After more than $10 billion in cumulative investment across Toyota, Samsung, CATL, QuantumScape, and a half-dozen others, after a full decade of press releases promising imminent breakthroughs and investor presentations filled with hockey-stick production curves, the count of shipping solid-state-powered cars, trucks, motorcycles, or scooters remains stubbornly, embarrassingly at zero.

What follows is not another article about the science. It tracks only the promises, specifically the dates: what each company publicly committed to deliver, when they committed to deliver it, and what actually happened when the calendar caught up. Compiled into a scorecard, these commitments reveal a slippage pattern so consistent it functions as a predictive model for when the current batch of 2027 promises will actually materialize.

Promise-to-Delivery Scorecard

Eight companies made public, date-specific commitments to deliver solid-state battery production at commercial scale, and every single one of those commitments has either been missed, downscoped, or not yet reached its deadline.

Company	Original Promise	Current Status (April 2026)	Slippage
Toyota	SSB demo at 2020 Olympics (announced 2019)	Pilot production FY2027, 10,000 cars by 2030. Idemitsu Kosan electrolyte plant under construction.	7+ years
QuantumScape	Cells for VW by 2024 (2020 SPAC filing)	Eagle Line pilot opened Feb 2026. QSE-5 sampling. No production timeline. Stock: $6.86, market cap ~$4.2B. Pre-revenue after 14 years.	2+ years, ongoing
Samsung SDI	Production by 2027 (stated ~2023, eepower.com)	Still targeting 2027. Sulfide chemistry. No pilot line announced.	TBD
CATL	Mass production 2025-2026 (earlier investor presentations)	Chairman Robin Zeng rates industry at "4 out of 9" maturity. Limited production 2027, mass production ~2030.	4-5 years
Chery	Mass production 2027 (Battery Night, March 2026)	Downscoped to "validation vehicles" in Q4 2026. 400 Wh/kg sulfide cell claimed, 600 Wh/kg version targeting 2027.	Downscoped
Greater Bay Technology	GWh production "in 2026" (April 14, 2026 press release)	A-sample cells off production line. Composite electrolyte, 260-500 Wh/kg. GWh scale unproven.	New claim, untested
Donut Lab	Q1 2026 Verge motorcycle delivery (CES 2026)	Q1 2026 passed. 5 independent VTT test reports released. None verify the two core claims: 400 Wh/kg energy density or 100,000-cycle life.	Already missed
ProLogium	Commercial deployment (CES 2026 claims)	600,000+ cells shipped from Taiwan. France gigafactory breaking ground, 12 GWh by 2032. All-inorganic ceramic separator, 860 Wh/L volumetric.	Long runway

Arithmetic Nobody Bothered With

Take the five companies with measurable slippage: Toyota at 7 years, QuantumScape at 2-plus years and still counting, CATL at 4.5 years, Chery downscoped within months of its announcement, and Donut Lab which missed its deadline immediately upon arrival. Exclude Samsung SDI and Greater Bay whose deadlines have not yet arrived, along with ProLogium whose 2032 target is too distant to evaluate.

Average slippage across those five: 4.1 years, with Toyota as an outlier at 7. Even stripping Toyota out, the remaining four average 2.9 years of delay or immediate failure, which means the optimistic scenario is still nearly three years of broken promises.

Now apply that 4.1-year average to the current cluster of 2027 promises from Samsung SDI, CATL's limited production target, and Chery's validation vehicles. Implied actual delivery: 2031.

Remarkably, that number aligns almost exactly with the most conservative public estimate in the entire industry, from the person with the best factory-floor visibility in the battery business. CATL chairman Robin Zeng, whose company controls roughly 37% of the global EV battery market, told investors the industry sits at "4 out of 9" on a maturity scale and that mass production will arrive "around 2030." Zeng has no incentive to undersell the timeline because CATL is investing billions in the technology, and his conservatism reflects what he sees on his own production lines rather than what the marketing department hopes to announce at the next trade show.

Pilot Lines and the Manufacturing Chasm

QuantumScape opened its Eagle Line in San Jose in February 2026, Greater Bay Technology pulled A-sample cells off a production line in April, and ProLogium has shipped over 600,000 cells from its Taiwan facility, achievements that are real and physical and also entirely meaningless at production scale.

A pilot line produces hundreds to thousands of cells per month while a production factory produces millions, and bridging that gap is not an incremental scaling exercise but an entirely different engineering discipline requiring different equipment, different quality control systems, different supply chains, and defect rates measured in parts per million rather than percentage points.

IEEE Spectrum warned in January 2024 that solid-state batteries face "production hell" comparable to what Tesla experienced ramping Model 3 production, and it detailed the specific challenges for each chemistry: sulfide electrolytes react violently with moisture and require dry rooms far more stringent than lithium-ion factories need, oxide electrolytes demand sintering temperatures above 1,000°C that are difficult to maintain uniformly across large-format cells, and polymer electrolytes work only above 60°C requiring active thermal management inside the vehicle itself.

Samsung SDI bets on sulfide, ProLogium uses ceramic oxide, and Greater Bay claims a composite approach, but none of the three has demonstrated that its chosen chemistry can be manufactured at automotive scale.

What Donut Lab Revealed About Independent Verification

Donut Lab deserves close attention because its story illustrates what happens when hype collides with independent testing, and the results are not pretty.

At CES 2026, Donut Lab announced a solid-state battery for the Verge TS Ultra motorcycle, claiming 400 Wh/kg energy density and a 100,000-cycle lifespan that would make it the longest-lived battery cell ever produced. Q1 2026 came and went with no motorcycles delivered. Then Electrek obtained five independent test reports from VTT Technical Research Centre of Finland, and not one of those reports verified either of the two headline claims.

Company-reported performance numbers populate nearly every press release in the solid-state space, but they are marketing claims rather than independently verified data, and when independent testing does arrive the numbers tend to shrink. Of the eight companies on this scorecard, only Donut Lab and ProLogium have submitted cells to independent labs. Investors and journalists treating the other six companies' self-reported figures as established fact are making an assumption that VTT's Donut Lab results directly contradict.

Strongest Counterargument

A pattern this consistent invites a simple conclusion, but the counterargument deserves to be stated at full strength: this cycle genuinely is different because physical infrastructure is being built, not just slides being presented.

Toyota and Idemitsu Kosan are constructing a pilot electrolyte plant targeting completion by end of 2027, with capacity for several hundred tons of sulfide electrolyte annually, and that construction permit represents a capital commitment that previous hype cycles never reached. QuantumScape spent real money on a real building filled with real equipment. ProLogium is breaking ground on a gigafactory in Dunkirk, France. Greater Bay has A-sample cells you can hold in your hand, photograph, and test.

Previous hype cycles consisted almost entirely of PowerPoint slides and press releases, while this one includes concrete poured, steel erected, and functioning prototype cells shipped to automaker partners for evaluation. Whether those manufacturing problems separating a lab cell from a factory cell can actually be solved on the timelines these companies are now promising is a separate question, and one that the 4.1-year average slippage pattern answers more reliably than any corporate roadmap.

What This Scorecard Cannot Tell You

Several important caveats limit what the slippage pattern can predict.

Internal targets may have been more conservative than public announcements, meaning companies that quietly delayed milestones before going public will show less slippage than they actually experienced. Aggregating all solid-state chemistries into a single scorecard overstates the coherence of the field because a sulfide breakthrough would not necessarily help an oxide company, and a polymer discovery would do nothing for either of them.

Chinese companies operate under subsidy structures and government industrial policy pressure that American or Japanese firms do not face, and Chery's aggressive timeline may reflect political incentives rather than engineering confidence. Energy density claims are almost always measured at the cell level, not the pack level, and a cell delivering 400 Wh/kg becomes roughly 250-300 Wh/kg after thermal management, structural housing, and battery management electronics are added, a distinction most press releases quietly omit.

QuantumScape has maintained a $4.2 billion market capitalization while being pre-revenue for 14 years. That entire valuation is constructed from future promises, the exact asset class this scorecard measures and finds systematically unreliable.

What You Can Do

If you are considering an EV purchase: Do not wait for solid-state. Current lithium-ion technology, both lithium iron phosphate and nickel manganese cobalt formulations, delivers 300 to 500 miles of range today, and while the performance gap that solid-state promises to close is real it is irrelevant for the vast majority of actual daily driving patterns, so buy the car that exists rather than the battery that does not.

If you are an investor: Apply what might be called "Zeng's Rule" after CATL's chairman: when the company controlling 37% of the global battery market says mass production arrives around 2030, and a startup with zero revenue says 2027, bet on the conservative number and discount any solid-state startup's stated production date by 3 to 5 years. Track factory construction permits, equipment purchase orders, and independent test results rather than press releases, and remember that a pilot line opening is to mass production what a garage prototype is to an assembly line.

If you evaluate energy technology professionally: Demand independent test data from VTT, Argonne National Laboratory, or any of several university labs offering third-party cell testing, because a company that refuses independent verification of its headline claims is communicating something important through that refusal.

If you cover this industry: Write "the company claims 400 Wh/kg" rather than "the battery achieves 400 Wh/kg," because VTT's Donut Lab results proved the gap between those two phrasings is not a semantic distinction but an empirical one with measurable consequences for investor decisions and public understanding.

Bottom Line

Solid-state batteries will almost certainly arrive, and the underlying science is genuinely sound and worth pursuing: solid electrolytes eliminate flammable liquid solvents, enable lithium metal anodes, and promise energy densities that lithium-ion chemistry physically cannot match. But the timelines attached to every public commitment so far have proven systematically unreliable. Eight companies promised delivery by 2025, zero delivered, and those same companies now promise 2027 while the scorecard's 4.1-year average slippage points squarely at 2031, a date that CATL's chairman, the person with the deepest factory-floor visibility in the entire battery industry, independently confirms, so plan accordingly.

Sources: Reuters, Toyota solid-state battery announcement (2019); QuantumScape SPAC filing, SEC (2020); KrAsia/36Kr, "Despite Renewed Hype" (Nov 2025); Electrek, Donut Lab investigation (March 2026); CnEVPost, Chery Battery Night (March 2026); IEEE Spectrum, "Solid-State Batteries Could Face Production Hell" (Jan 2024); ProLogium Technology; eepower.com, Samsung SDI solid-state overview; Idemitsu Kosan, electrolyte plant announcement; Greater Bay Technology press release (April 2026).