Mercedes-Benz road and race engineers and Factorial Energy cell engineers working on a solid-state battery test program have brought their first car powered by a lithium-metal solid-state battery to the road. After intensive bench testing, the prototype solid-state battery was integrated into an EQS at the end of 2024 to prepare for the road tests that started in February 2025.

“Developing an automotive-scale solid-state battery underlines our commitment to innovation and sustainability,” said Markus Schäfer, Member of the Board of Management of Mercedes Benz Group AG. Chief Technology Officer, Development & Procurement. “We’re therefore excited to announce that we’ve started road testing with a prototype vehicle equipped with this advanced technology. We will gain crucial insights into possible series integration of this cutting-edge battery technology.”

Mercedes AMG HPP (High Performance Powertrains) and the Mercedes‑Benz Center of Competence for Battery Systems designed and developed the battery system. The all-electric Mercedes Benz car was slightly modified to fit the solid-state battery and was equipped with all accessories to operate it.

Mercedes AMG HPP, based in Brixworth, Northamptonshire, UK, is a subsidiary of the Mercedes-Benz Group specializing not only in industry-leading Formula One technology but also in rapidly transferring the know-how into high-performance automotive projects. It has a team of over 1000 people responsible for designing, manufacturing, testing, and racing F1 power for Mercedes-AMG F1 and customer teams. Its Advanced Technologies Team transfers F1 technologies and know-how into high-performance automotive projects and products such as the Mercedes‑AMG ONE and Mercedes-Benz Vision EQXX.

With roots stretching back to 1984 and the foundation of Ilmor Engineering, the team has been responsible for the design and development of every F1 engine to wear the Mercedes‑Benz badge since 1995. Renamed Mercedes-Ilmor Ltd in 2002, it became a wholly owned subsidiary of Mercedes‑Benz Group AG in 2005 (at that time Daimler AG), operating under the name of Mercedes‑Benz High Performance Engines, later switching to Mercedes AMG HPP.

Solid-state batteries, which use a solid electrolyte instead of a liquid one and allow new anode types like lithium metal, have enhanced cell safety and reduced weight to enable next-level energy densities, explained Mercedes-Benz. The solid-state technology has the potential to increase gravimetric energy density for vehicle batteries, by up to 450 W·h/kg at the cell level, for better driving range.

“Being the first to successfully integrate lithium metal solid-state batteries into a production vehicle platform marks a historic achievement in electric mobility,” said Siyu Huang, CEO and Co-Founder of Factorial Energy. “This breakthrough demonstrates that solid-state battery technology has moved beyond the laboratory and into real-world application, setting a new benchmark for the entire automotive industry. Our collaboration with Mercedes-Benz proves that the future of electric vehicles is not just a vision, but a reality we’re delivering today.”

The Mercedes‑Benz solid-state battery features an innovative floating cell carrier, for which a patent has already been granted. When the battery charges, the materials expand, and when it discharges, it contracts. To support the cells during these volume changes, the Mercedes‑Benz solid-state battery is equipped with pneumatic actuators that interact with the cell volume change during charging and discharging, improving battery performance and life.

“This latest model is currently undergoing extensive road and condition testing, and the results are proving that our shared commitment to longer-range, safer, and more efficient electric vehicles is making real progress,” wrote Alex Yu, Founder and CTO at Factorial Energy, on LinkedIn. He cited a 25%+ longer driving range compared to conventional lithium-ion batteries and 1000 km (620 mi) prototype range is now in road testing for the lighter and safer “quasi solid-state design.” Further weight and energy efficiency is achieved through passive battery cooling.

For comparison, with a battery capacity of 118 kW·h, the current EQS 450+ has a combined consumption of 19.9-16.3 kW·h/100 km and offers an WLTP range of over 800 km (497 mi). Over the next few months, Mercedes-Benz will further test in the lab and on the road the solid-state battery and its overall performance in the electric vehicle.

Mercedes-Benz started collaborating with Boston-headquartered Factorial in 2021 to develop a new generation of battery technology. In June 2024, Futurride reported that Factorial had delivered lithium-metal solid-state battery cells with the company’s FEST (Factorial Electrolyte System Technology) solid-state platforms to Mercedes‑Benz, which marked the first claimed lithium-metal solid-state battery B sample shipment to a global OEM.

In September 2024, Factorial revealed its Solstice all-solid-state battery for next-generation EVs developed with Mercedes-Benz. Set to achieve a breakthrough energy density of up to 450 W·h/kg, it incorporates a novel dry cathode design for more efficient and sustainable production. The new cell complements Factorial’s FEST for automotive and other electric mobility applications while expanding the company’s total addressable market to include consumer electronics. It expects the technology to be introduced by OEMs before the end of the decade.

Solstice’s sulfide-based all-solid-state electrolyte system addresses safety concerns associated with more flammable and volatile liquid electrolyte designs, targeting an EUCAR safety rating of 2 and maintaining stability at operating temperatures over 90°C (194°F). This also has the potential to reduce the cooling system requirements within the battery pack to lower overall vehicle cost.

Solstice eliminates the need for hazardous solvents and energy-intensive steps commonly used in traditional cathode production through a new dry coating process. The technology bypasses the formation process, the most energy-consuming stage of lithium-ion battery manufacturing. Combining these innovations reduces operating costs, energy consumption, and environmental impact, paving the way for a more sustainable future for battery production.