In August 2025, a modified Mercedes-Benz EQS left Stuttgart and did not stop until it reached Malmö in Sweden. It covered 749 miles without a single charging break and arrived with 85 miles of range still showing.
The battery powering the EQS was not a conventional lithium-ion pack. It was a solid-state cell developed by US-based start-up Factorial Energy, co-engineered with Mercedes-AMG High Performance Powertrains in Brixworth, the same facility that builds Formula 1 power units.
That drive marked a turning point. Solid-state batteries have been described as the industry’s next big leap for years, but progress has been slow. Now, the technology is moving off laboratory benches and onto public roads. The question for EV drivers is when it actually arrives in a car they can buy.
What makes solid-state batteries different?
A conventional lithium-ion battery uses a liquid electrolyte to carry ions between the anode and the cathode. That liquid is flammable, which creates a thermal safety risk, and it places limits on how much energy you can pack into a given space and weight.
Solid-state batteries replace the liquid with a solid material, whether ceramic, sulphide, or polymer-based. The result, in theory, is a battery that is safer, more energy-dense, and longer-lasting. Factorial’s Solstice cells, announced in late 2025, achieve an energy density of 450 Wh/kg, around 80 per cent higher than current lithium-ion. The company says they can deliver over 600 miles of range with 40 per cent weight savings compared to a conventional 90 kWh pack.
The Mercedes EQS in that Stuttgart-to-Malmö run achieved 25 per cent more usable energy than the standard EQS battery, at the same weight and size. That is a meaningful gain, not a laboratory anomaly.
Who is building them right now?
Several major players are in active development. Toyota remains the most prominent. The Japanese carmaker has been working on solid-state batteries for nearly a decade and is targeting mass production between 2027 and 2028, with a sulfide-based electrolyte design promising 620 miles of range and a ten-minute charge from ten to eighty per cent. In October 2025, Toyota confirmed an agreement with Sumitomo Metal Mining to produce cathode materials, reinforcing its timeline.
Factorial Energy is working with Mercedes-Benz, Stellantis, Hyundai, and Kia. Its cells could appear in high-end production vehicles as early as 2027, with luxury and performance models likely first. The Dodge Charger Daytona is one candidate. Factorial went public in late 2025 after completing its Stuttgart-to-Malmö milestone drive, and its CEO has said commercial deployment by 2027 is realistic.
QuantumScape, backed by Volkswagen’s manufacturing arm PowerCo, reached two significant milestones in 2025. In June, it integrated its Cobra separator process into baseline production. Cobra processes ceramic separators approximately 25 times faster than its predecessor and uses a fraction of the factory space, which matters enormously for cost. In October, QuantumScape shipped its first QSE-5 B1 samples to customers. In February 2026, it inaugurated its Eagle Line, a highly automated pilot production line in San Jose designed as the template for future gigawatt-hour-scale manufacturing.
Why isn’t every new EV already using one?
Manufacturing is the problem, not the chemistry. Liquid electrolytes fill every pore in a cell and maintain reliable contact automatically. Solid electrolytes require exact pressure, precise fabrication, and defect-free layers across every square centimetre. Small inconsistencies that a liquid would simply flow around can cause a solid-state cell to fail.
The yield rate is a useful illustration. Factorial’s pilot facility currently achieves around 85 per cent yield. That is good for a start-up demonstrating new technology. A commercial manufacturer, according to Factorial’s own CEO, needs closer to 95 per cent to produce cells profitably at scale. That gap is the difference between a working prototype and a car you can order.
Material choices add further complexity. Sulphide electrolytes conduct ions efficiently but are highly sensitive to moisture and require specialist production environments. Oxide ceramics are more stable but brittle, and densifying them into usable layers is energy-intensive. Neither is a straightforward manufacturing problem.
When will it reach most drivers?
The likely answer is the early 2030s for true mass-market availability. The first solid-state vehicles, arriving around 2027 to 2028, will be premium or performance models in limited volumes. Semi-solid and hybrid designs, which use small amounts of liquid alongside a solid matrix, are likely to bridge the gap. They carry a cost premium of only five to ten per cent over conventional cells, according to industry data, which makes them commercially viable sooner.
China is setting a national solid-state battery standard targeted for release in mid-2026, which will define what qualifies as fully solid and accelerate domestic commercialisation. Chinese manufacturers including BYD, Changan, and Chery are all working to aggressive timelines.
The technology’s promise is no longer theoretical. A car drove from Germany to Sweden on a solid-state battery and arrived with range to spare. The factory lines that will produce millions of those batteries are being built now. The 2030s are when solid-state stops being a promise and starts being a key component of the specification sheet.
