Solid-state battery: Factorial relies on Japanese expertise for electrolytes
Battery developer Factorial Energy has entered into a strategic partnership with Japanese company Mitsui Kinzoku to accelerate the industrialization of one of its solid-state battery platforms. Mitsui Kinzoku is a manufacturer of solid, sulfide-based electrolytes.
Agreeing: Alex Yu, co-founder and CTO of Factorial Energy (left), and Dr. Kiyotaka Yasuda from Mitsui Kinzoku.
Image: Factorial Energy
The focus of this new partnership is Factorial Energies’ all-solid-state battery platform named Solistice. Mitsui Kinzoku is set to contribute its expertise in electrolytes to industrialize this technology. In a accompanying statement, the U.S. developer described its new Japanese partner as “one of the few companies in the world that possesses fundamental technologies for solid-state electrolytes.”
Here is some background: Factorial is a U.S. specialist in solid-state battery cells supported by Mercedes-Benz, Stellantis, and Hyundai-Kia. The company is working on multiple development paths. In June 2024, Factorial already delivered B-specimens of its FEST brand solid-state cells with a capacity of over 106 Ah to Mercedes-Benz.
Meanwhile, the company is working—specifically in collaboration with Mercedes—on cells under the brand name Solstice. These cells are currently at the prototype stage but are expected to stand out due to even higher energy density and a dry cathode coating process. They feature an NMC cathode and a lithium metal anode. In September 2024, Factorial promised an energy density of up to 450Wh/kg for its Solstice product (though without specifying whether this applied at the cell or pack level). Additionally, the company reported a development milestone about one and a half years ago when this cell type achieved a charging capacity of 40 Ah.
To industrialize the Solstice platform, Americans are now also drawing on Japanese expertise. Mitsui Kinzoku is regarded as a manufacturer of sulfide-based solid electrolytes and is said to be “world leader in ultra-thin copper foil, holding an estimated 90% market share in the semiconductor market for such foil,” according to Factorial. This knowledge in materials science also forms the basis for a sulfide solid electrolyte introduced by Mitsui Kinzoku in 2016, with mass production underway at a facility built specifically for this purpose in Saitama, Japan.
"I am very pleased that we were able to reach this agreement for joint development with Factorial," commented Dr. Kiyotaka Yasuda, Senior Executive Officer and Head of Business Development at Mitsui Kinzoku. "Batteries are a key technology for realizing an electrified society, but significant technical challenges remain. That is precisely why we believe it is necessary to go beyond improving existing technologies and take on the challenge of creating new values."
Under this new partnership, Factorial will continue to lead in cell design, process development, supply chain qualification, line integration, and manufacturing validation. Factorial CEO Siyu Huang commented, “Battery innovation cannot be driven by a single company. It is propelled by the entire supply chain and increasingly, by an entire industry alliance. Mitsui Kinzoku’s advanced electrolyte technology brings critical material expertise to our efforts to bring Solstice to commercial use. We are not just building a battery; we are creating the connecting thread that helps the entire industry move forward together.”
Factorial is indeed seeking more partners these days. Just a few weeks ago, the company announced a strategic partnership with major battery manufacturer SK On to accelerate the rollout of its alternative technology platform—FEST technology—in this sector. This technology is currently being tested in practice, for example, with Stellantis’ Dodge brand. Factorial has also recently received strategic investments from IQT and Posco Future M. The company states, “The first commercial orders for passenger vehicles came in January, while those for aerospace applications arrived in July.” In June, Factorial celebrated its listing on Nasdaq under the ticker symbol FAC.