Mercedes, a brand of Daimler AG, said it invested a “double-digit million dollar” amount in Factorial. Stellantis declined to specify its investment. The news comes scarcely a month after Factorial announced a separate investment and partnership deal with Hyundai and Kia, to co-develop and test battery tech in Hyundai EVs.

The first cell prototypes will likely be tested as early as next year. Looking longer-term, Mercedes aims to introduce the tech to series production within the next five years, and Stellantis wants to roll-out solid-state technology by 2026.

Many consider solid-state batteries to be the next forthcoming breakthrough in battery technology, not only for advantages in energy density but also safety. Liquid electrolyte solutions found in conventional batteries today are generally flammable, so solid-state batteries should pose less of a fire risk. Factorial says its technology, which includes a solid electrolyte material, increases range between 20% to 50%, relative to standard lithium-ion batteries.

The lure of a comparative battery advantage has proven irresistible to major automakers, who have poured billions into electrification and new startups that claim to be close to cracking the solid-state code. Factorial joins an increasingly competitive solid-state battery market, which until now has been populated chiefly by legacy battery makers like LG Chem, as well as new entrants like Quantumscape and Solid Power.

The latter two startups are also backed by major automakers. Quantumscape has received more than $300 million from Volkswagen, while Solid Power has landed backing from Ford and BMW. This latest news from Factorial – which has garnered backing from three major automakers since emerging from stealth in April – is a sign that a new horse has entered the race.