Mercedes‑Benz has commenced real-world testing of a prototype solid-state battery integrated into a modified EQS electric sedan. Developed in partnership with US startup Factorial Energy and Mercedes-AMG’s Formula 1 unit HPP, the vehicle aims to validate breakthrough battery performance under everyday driving conditions .
The test battery utilizes lithium-metal anodes and a solid electrolyte, offering up to 450 Wh/kg energy density at the cell level. That translates to approximately a 25 per cent gain in driving range, with the test EQS estimated to exceed 1,000 km (620 miles) per charge significantly higher than the standard EQS 450+’s range of around 800 km under WLTP testing.
Combining Mercedes’ engineering expertise and Factorial’s FEST (Factorial Electrolyte System Technology), the solid-state chemistry delivers improved safety, reduced weight, and better thermal stability compared to conventional lithium-ion cells. The integration also enables lighter overall battery pack weight and passive cooling, which further enhances efficiency.
Factorial’s semi‐solid prototype cells—tested in the EQS—mark the first time such technology has transitioned from laboratory research into a roadworthy vehicle. Mercedes began lab testing in Stuttgart in late 2024 before starting public road trials in early 2025.
Mercedes expects production versions using solid-state batteries could launch by the end of the decade, potentially even before 2030. The company is also exploring related partnerships with Taiwanese firm ProLogium and researching silicon-anode advancements to push energy density even further.
While this milestone is a major stride in EV battery innovation, industry analysts caution that scaling solid-state technology faces hurdles including high manufacturing costs and longer development timelines. Experts suggest initial adoption is likely limited to premium and niche segments before broader rollout.
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