SK On and Factorial Energy Partner to Advance Solid-State Battery Mass Production

South Korean battery giant SK On and U.S.-based solid-state battery developer Factorial Energy recently announced a strategic partnership to accelerate industrialization of solid-state battery technology. The two parties have signed a memorandum of understanding (MOU) to integrate Factorial's proprietary FEST solid-state battery technology into SK On's globally distributed battery manufacturing network.

Solid-state batteries are widely regarded as a critical pathway for next-generation traction batteries — offering, in theory, higher energy density, extended driving range, and faster charging speeds. However, mass production has yet to break through due to persistent bottlenecks: low ionic conductivity and brittleness of solid electrolytes, complex manufacturing processes, and high costs.

A core objective of this collaboration is to assess whether SK On's existing battery production facilities and factories possess the technical readiness and retrofit feasibility required for solid-state battery lines. Drawing on Factorial's FEST technology roadmap and SK On's expertise in cell design, materials engineering, and large-scale manufacturing, the partners will jointly conduct production-line compatibility studies and process validation.

Factorial CEO Siyu Huang emphasized: "A battery breakthrough only gains real significance when it can be manufactured at scale." He noted that SK On operates an advanced global battery manufacturing system — including facilities in the U.S. — with over 200 GWh of annual capacity, calling its manufacturing capability "critical to integrating solid-state batteries into the global production ecosystem."

Public disclosures indicate Factorial has already partnered with multiple mainstream automakers: its 77 Ah FEST cells, tested on Stellantis' STLA Large platform, achieved a real-world energy density of 375 Wh/kg (after 600 cycles), support 18-minute fast charging from 15% to 90% state of charge, and operate stably across extreme temperatures from −30°C to 45°C; prototype vehicles equipped with these cells — such as the Mercedes Benz EQS — have demonstrated single-charge ranges exceeding 1,200 km; additionally, Hyundai, Kia, Mercedes-Benz, and Stellantis have all joined Factorial's commercialization partner roster.

Notably, this is not Factorial's first move into Asia's supply chain. In December 2025, the company signed an agreement with South Korea's POSCO FUTURE M to jointly develop key materials for all-solid-state batteries. Meanwhile, as the core battery supplier to the Hyundai automotive group, Ford, and Volkswagen Group, SK On's manufacturing network — and whether it can truly accommodate the technological leap required for solid-state battery production — awaits confirmation via upcoming pilot-line validation results.