Flux to advance safe, sustainable, and cost-competitive flow battery energy storage with funding round led by Grantham Foundation.

Flux XII, Inc., a next-generation energy storage company developing advanced materials for aqueous flow batteries, announced today the raise of $3.95 million SEED funds. The round was led by The Grantham Foundation for the Protection of the Environment with participation from the Wisconsin Alumni Research Foundation (WARF), Desai Ventures, and gener8tor. The raise follows earlier backing from Activate Fellowship, Third Derivative, Gigascale Capital, The Collaborative Fund, Safar Partners, and LiquidMetal Ventures, underscoring strong confidence in Flux XII’s materials-integration approach to grid energy storage.

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Flux kilowatt prototypes

With this funding, Flux XII has already scaled up electrolyte and membrane production in industrial facilities and begun testing multiple kilowatt-scale prototypes. In 2026, the company will validate its minimal viable product (MVP) module under controlled testing and design a fully-integrated, containerized Battery Energy Storage System (BESS). Flux XII is also forming a consortium of utilities, developers, universities, and research partners to support system pilot testing in 2027.

Co-founder and CEO of Flux XII, Dr. Patrick Sullivan, has researched energy markets and battery technologies since 2018 and sees a large opportunity in this sector: “Grid power developers need more capacity, and it needs to be cheaper, safer, and cleaner than gas or lithium-ion batteries. Flux is developing a comprehensive product that builds off decades of industry advancements and addresses these key points without the tradeoffs of competing energy storage solutions.”

Why It Matters

Technology Platform: Flux XII crafts high-performance, tunable flow battery materials from abundant chemical feedstocks, dramatically reducing cost and area footprint while remaining highly efficient and stable.

Proven Scalability: Flux XII produces its electrolyte and membrane through simple industrial processes and integrates them into device and system hardware deployed by commercial suppliers at megawatt scales.

Market Unlock: Flux XII aims to reduce the CapEx of flow battery systems by 50% at 100 megawatt scales, enabling cost-effective energy storage capacity markets and supporting new load growth from data centers, EVs, onshoring manufacturing, and electrification.

“We've reviewed many new technologies, but Flux XII is a standout with the potential for greatly reducing the cost of energy storage. The chemistry is safe and rapidly scalable. This is what's needed for renewables to undercut thermal generation, even overnight or when the wind isn't blowing” – Josh Agenbroad, Grantham Foundation

About Flux XII

Flux XII is based in Madison, Wisconsin commercializing aqueous flow battery materials and modules leveraging high-performance, scalable organic chemistries. Their mission is to unlock an adaptable energy future by transforming intermittent renewable power into reliable baseload grid capacity through economical long-duration energy storage.

The company is supported by The Grantham Foundation for the Protection of the Environment, Activate Fellowship, Third Derivative, Wisconsin Alumni Research Foundation, Desai Ventures, Gener8tor, Gigascale Capital, The Collaborative Fund, Safar Partners, and LiquidMetal Ventures.

For more information, visit www.flux12.com or contact patrick.sullivan@flux12.com.

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"Flux XII is a standout with the potential for greatly reducing the cost of energy storage"