Solid-state batteries: Factorial leverages Japanese electrolyte expertise
Battery developer Factorial Energy has formed 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 sulfphide-based electrolytes.
In agreement: Alex Yu, co-founder and CTO of Factorial Energy (left), and Dr. Kiyotaka Yasuda of Mitsui Kinzoku.
Image: Factorial Energy
At the heart of the new cooperation is Factorial Energy’s all-solid-state battery platform, named Solstice. Mitsui Kinzoku will now contribute its expertise in electrolytes to the industrialisation of this technology. In an accompanying statement, the US developer describes its new Japanese partner as “one of the few companies in the world holding foundational solid-state electrolyte technology”.
For background: Factorial is a US specialist in solid-state battery cells, backed by Mercedes-Benz, Stellantis, and Hyundai-Kia. The company is pursuing multiple development strands. For example, Factorial already delivered B-sample cells of its FEST brand solid-state batteries – with a charge capacity of over 106 Ah – to Mercedes-Benz in June 2024.
At the same time, the company – once again with Mercedes – is working on cells under the Solstice brand name. These currently hold A-sample status but are expected to stand out due to even higher energy density and a dry cathode coating process. The cells feature an NMC cathode and a lithium-metal anode. In September 2024, Factorial promised an energy density of up to 450 Wh/kg for its Solstice product (though without specifying whether this refers to cell or pack level). Additionally, the company announced the next development step a year and a half ago, when this cell type achieved a charge capacity of 40 Ah.
To industrialise the Solstice platform, the Americans are now also incorporating Japanese expertise. Mitsui Kinzoku is known as a manufacturer of sulphide-based solid electrolytes and is also a “global leader in ultra-thin copper foil, with an estimated 90% share of the semiconductor market for that foil,” Factorial emphasises. This materials science expertise also forms the basis for a sulphide solid electrolyte introduced by Mitsui Kinzoku as early as 2016, whose mass production is being advanced in a dedicated facility in Saitama, Japan.
“I am very pleased that we have been able to enter into this joint development agreement 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 still remain. That is precisely why we believe it is necessary to go beyond the extension of existing technologies and take on the challenge of creating new value.”
Within the new cooperation, Factorial will continue to lead cell design, process development, supply chain qualification, line integration, and manufacturing validation. Factorial CEO Siyu Huang commented: “Battery innovation can’t be done by one single company. It’s driven by the entire supply chain and, increasingly, by an entire industry coalition. Mitsui Kinzoku’s foundational electrolyte technology brings critical materials expertise to our work to move Solstice toward commercial deployment. We’re not just building a battery. We’re building the connective thread that helps the whole industry move forward together.”
Factorial is indeed currently seeking more partners. Just a few weeks ago, the Americans also announced a strategic cooperation with major battery manufacturer SK On to accelerate the market ramp-up of its other development strand – the FEST technology – which is currently being tested in practice, among others, with Stellantis brand Dodge. Factorial has also recently secured strategic investments from IQT and Posco Future M. Additionally, the company states that Factorial received “its first commercial orders for passenger vehicles in January and for aerospace in July In June”, and also celebrated its listing on the Nasdaq -under the FAC ticker symbol.