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May 24, 2026
May 24, 2026
The article reports that ESS Tech Inc., known for its iron flow battery business, has signed a letter of intent for a strategic partnership with Alsym Energy that would add 8.5GWh of US-made sodium-ion battery cells and modules to ESS’s portfolio. Energy-Storage.news says the deal marks an important shift for ESS because it expands the company beyond long-duration storage into the short- and medium-duration BESS market. That is notable because ESS has recently been trying to sharpen its focus around its Energy Base platform, a 12–14-hour long-duration system aimed at data centres and other heavy-load customers, while also improving its financial position after reporting a 2025 net loss of $63.4 million, which was still an improvement on the previous year.
The article frames the partnership as a chemistry-combination strategy rather than a simple supply deal. ESS says Alsym’s sodium-ion batteries are better suited to applications that need high power, fast cycling, and rapid response, while its existing iron-flow systems remain better aligned with 8–24 hour storage where deep daily cycling, long asset life, and zero capacity degradation matter most. The piece also notes that Alsym launched its Na-Series battery in October 2025 as a non-flammable, non-toxic, and cost-effective option for data centres and renewable projects, and argues that such chemistries could help projects get approved in places where lithium-ion systems face siting and safety concerns. Overall, the story presents the ESS–Alsym tie-up as an effort to build a broader non-lithium storage platform for utilities, independent power producers, data centres, and commercial customers seeking more flexible American-made storage options.
