On September 10th, Mercedes-Benz and Factorial announced a partnership to develop solid-state batteries with an energy density figure of 450 Wh/kg, increasing vehicle range by a claimed 80%. 

Mercedes, Hyundai and Stellantis have all invested in Factorial, a US-based company aiming to bring solid-state cells to market at commercial scale. Recently, Factorial has been developing semi- solid-state cells for use in Mercedes EV models from 2026. Semi- solid-state is considered a transition technology on the route to full solid-state. However, they suffer similar limitations with performance and safety as traditional lithium-ion as they still use a liquid electrolyte. 

Although semi- solid-state cells will be commercialised sooner, they are not considered a long-term solution to the problem. Many OEMs and cell producers remain focused on developing solid-state cells to try and stay ahead of the competition and to differentiate in the upper section of the industry. This is a strategy that has been attempted by many in the West to keep pace with developments in China and to become world leaders when the technology reaches technological maturity. 

If successful, Mercedes and Factorial’s latest project would provide a leap forward in proposed energy density and safety credentials. Current state of the art NCM811 cells can exhibit energy densities of up to ~300 Wh/kg, and although improvements will be made at the anode and cathode, they are approaching the limitations of cell design for traditional cell architecture. 

The outlook of the development of solid-state cells is not entirely smooth however. Many challenges are still present, from component manufacturing to cycling stability. The production of the often-brittle solid electrolyte is a hurdle not yet overcome at scale, whilst materials with inherently lower ionic conductivities limit the performance and output of cells currently. Production cost also remains a high, which is a characteristic of many nascent technologies. This will limit market penetration initially, and unless costs are reduced, solid-state cells will be reserved only for the most premium EVs that command the top performance characteristics.