The race for the “holy grail” of EV batteries is heating up. Mercedes-Benz is testing the world’s first production EV with a solid-state battery, promising to deliver over 621 miles of driving range.

Mercedes solid-state battery-powered EVs hit the road

Mercedes hit a big milestone, taking its solid-state EV battery tech from the lab to the real world. On Monday, the company announced it has officially put “the first car powered by a lithium-metal solid-state battery on the road” through its partnership with US-based Factorial Energy.

On-road tests in a modified EQS began earlier this month following the first lab tests at the end of 2024. The EQS is slightly modified to fit the solid-state battery and other parts.

“Being the first to successfully integrate lithium-metal solid-state batteries into a production vehicle platform marks a historic achievement in electric mobility,” Factorial’s CEO, Siyu Huang, said after the accomplishment.

The new battery pack was developed by Mercedes-Benz and Mercedes AMG High-Performance Powertrains (HPP), a leading Formula 1 supplier.

Mercedes has been working with Factorial Energy since 2021 to launch the new battery cells, promising more driving range, faster charging, and efficiency. Last summer, Factorial delivered its first solid-state battery cells based on its propriety FEST (Factorial Electrolyte System Technology).

Mercedes and Factorial took it a step further, revealing the more advanced all-solid-state Solstice battery in September.

The new batteries are being co-developed to power Mercedes’ next-gen electric models. With a sulfide-based solid electrolyte, the battery is safer and more efficient.

The holy grail of EV batteries

With a “breakthrough” energy density of 450 Wh/kg, Factorial said the new Solstice battery is expected to provide 80% more driving range than current lithium-ion batteries.

Although full specs have yet to be confirmed, Mercedes said the EQS’s 12-module battery housing was flexible enough for different configurations.

Mercedes expects the new battery to extend the driving range by about 25%. The current EQS 450+ rated with up to 511 WLTP miles range would suggest a driving range of over 620 miles.

Factorial aims to unlock over 600 miles of driving range with 40% weight savings compared to conventional Li-ion batteries. The company says Solstice is 33% smaller than a current 90 kWh battery at 580 lbs.

In December, Factorial announced a major milestone after its Solstice all-solid-state battery cells achieved 40 Ah capacity. The company is working with other major automakers, including Hyundai and Stellantis, to advance solid-state battery technology and aims to launch solid-state batteries by 2030.

According to Mercedes chief tech officer Markus Shafer, the new Solstice batteries will “set new standards in range, cost, and performance. ” Mercedes expects to be producing solid-state batteries at scale by the end of the decade.

Electrek’s Take

Mercedes is among several automakers and other companies developing solid-state batteries in hopes of unlocking more range, safety, and efficiency.

The news comes after local reports earlier this month suggested Hyundai will reveal its all-solid-state EV battery demo line in March. Japanese rival Honda unveiled its pilot line to the public in November.

Stellantis announced plans to launch a fleet of electric Dodge Chargers powered by Factorials solid-state batteries in 2026.

Hyundai, Honda, Toyota, Stellantis, and others aim to mass-produce solid-state batteries by the end of the decade.

And don’t forget that Chinese EV battery leaders BYD and CATL are also racing to launch solid-state batteries. Which company will come out on top?