Flux XII Fundraising Boosts Next-Gen Grid Energy Storage
Flux XII, Inc., a next-generation energy storage company pioneering advanced materials for aqueous flow batteries, has announced the successful close of a $3.95 million seed funding round. This new investment represents a major step forward in the company’s mission to transform grid-scale energy storage through safer, more cost-effective, and sustainable battery technologies.
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 seed financing builds upon earlier support from Activate Fellowship, Third Derivative, Gigascale Capital, The Collaborative Fund, Safar Partners, and LiquidMetal Ventures. This wide-ranging investor backing reflects strong confidence in Flux XII’s unique materials-integration approach to grid-scale energy storage — a method that aims to deliver performance, affordability, and safety advantages over conventional lithium-ion technologies.
Scaling a Disruptive Energy Storage Platform
With this fresh round of funding, Flux XII has already scaled up electrolyte and membrane production using industrial manufacturing processes. The company has begun testing multiple kilowatt-scale prototypes to validate the performance and durability of its systems. In 2026, Flux XII plans to complete validation of its minimum viable product (MVP) module under controlled testing conditions. This milestone will be followed by the design of a fully integrated, containerized Battery Energy Storage System (BESS) — a turnkey unit designed to provide grid operators and developers with a scalable, high-efficiency energy storage solution.
Looking ahead, Flux XII is building a multi-stakeholder consortium of utilities, project developers, universities, and research organizations to support pilot system deployments in 2027. This collaboration is expected to accelerate real-world testing, optimize performance for diverse grid applications, and position Flux XII as a leading provider in the long-duration energy storage market.
A Vision for the Future of the Grid
Dr. Patrick Sullivan, co-founder and CEO of Flux XII, emphasized the company’s commitment to solving one of the most pressing challenges in the energy transition: large-scale, affordable, and sustainable energy storage.
“Grid power developers need more capacity, and it needs to be cheaper, safer, and cleaner than gas or lithium-ion batteries,” said Dr. Sullivan. “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.”
Dr. Sullivan, who has been researching energy markets and battery technologies since 2018, believes the next wave of growth in renewables will depend on the availability of low-cost, long-duration energy storage. He sees Flux XII’s technology as a vital enabler of grid modernization — allowing greater integration of renewable sources, improved reliability, and reduced dependence on fossil fuels.
Why It Matters
The transition to a low-carbon grid requires scalable, safe, and cost-efficient storage systems capable of balancing variable renewable generation. Lithium-ion batteries, while dominant today, face key limitations related to safety, supply chain constraints, and lifecycle costs. This has created an urgent demand for alternative storage chemistries that can deliver comparable or better performance with greater sustainability and lower total cost of ownership.
Flux XII’s aqueous flow battery technology directly addresses these needs.
- Technology Platform: Flux XII develops high-performance, tunable flow battery materials from abundant and low-cost chemical feedstocks. These materials are engineered to provide high energy density and efficiency while maintaining exceptional chemical and thermal stability. The result is a storage system that reduces both cost and physical footprint without compromising reliability.
- Proven Scalability: One of Flux XII’s distinguishing features is its manufacturability. The company’s electrolyte and membrane materials can be produced through simple, existing industrial processes. This enables rapid scale-up and integration into commercial system hardware, allowing deployment at megawatt-scale using standard supply chains.
- Market Unlock: By focusing on material and system-level cost reductions, Flux XII aims to reduce the capital expenditure (CapEx) of flow battery systems by up to 50% at 100-megawatt scales. Achieving this benchmark would dramatically expand access to cost-effective energy storage — supporting new load growth from data centers, electric vehicles, domestic manufacturing, and grid electrification.
Investor Confidence and Industry Impact
Investors see Flux XII as a critical player in advancing the economics of renewable energy. Josh Agenbroad of the Grantham Foundation highlighted the company’s potential to reshape the energy storage landscape:
“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.”
The Grantham Foundation’s investment reflects a broader trend among climate-focused funds prioritizing technologies that can accelerate decarbonization while strengthening grid resilience. With energy storage demand projected to surge as renewable capacity expands worldwide, innovations like Flux XII’s are essential for achieving global net-zero goals.
Positioning for the Energy Transition
Flux XII’s long-term strategy extends beyond the laboratory. By integrating materials innovation with practical engineering, the company is positioning itself as a system-level solution provider for utilities and developers seeking sustainable storage infrastructure. Its modular approach enables flexible configurations for applications ranging from renewable energy integration and peak shaving to grid balancing and microgrid support.
As the energy landscape continues to evolve, the combination of abundant raw materials, scalable manufacturing, and superior safety gives Flux XII a competitive edge in the fast-growing market for long-duration energy storage (LDES). The company’s upcoming demonstration projects in 2026 and 2027 will serve as key validation milestones, paving the way for commercial deployment and partnership expansion.
In a sector characterized by rapid innovation and rising investment, Flux XII’s breakthrough in aqueous flow battery chemistry represents more than just technological progress — it signals a path toward a cleaner, more resilient, and affordable energy future.
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