Flow Batteries and Long-Duration Energy Storage

Invinity Energy Systems, Sumitomo Electric, Form Energy, and Eos Energy Enterprises are among the active companies. Invinity develops utility-scale vanadium redox batteries, while Form Energy is developing iron-air storage. Google is also associated with a West Virginia solar-plus-storage project using zinc-based long-duration batteries. These examples span battery developers, manufacturers, and project partners.

Quino Energy, VRB Energy Inc., and XL Batteries are identified as startups working on flow batteries; Form Energy and Noon Energy are also active in long-duration storage. Quino develops aqueous organic redox-flow batteries, while XL Batteries commissioned an organic flow-battery pilot with Stolthaven Terminals. These examples indicate different chemistry and deployment strategies, rather than a definitive ranking.

Chinese Academy of Sciences CAS, Xi'an Jiaotong University, and Dalian University of Technology are among the active research organizations. Their recent work includes zinc-slurry batteries, vanadium-battery membranes, and electrolyte formulations. Recent publications also name Fudan University in zinc-slurry research. These organizations span materials development, battery chemistry, and system performance research.

Recorded grant funding totals $157,487,994 across 148 grants since 2020. The topic data also lists 27 funding rounds, but the individual round entries include unrelated or unclear items, so they do not provide a dependable total for flow-battery and long-duration storage investment. Grant funding is the clearer figure for comparing the recorded public support.

Sumitomo Electric leads the listed patent holders with 18 patents, followed by VRB Energy Inc. with 15 and Reinz Dichtungs GmbH with 12. Robert Bosch GmbH has 8 listed patents, as do Ionomr Innovations Inc., Energy Storage NL, ESS 2 Tech, LLC, and LIVA Power Management Systems GmbH. These figures identify leading holders in the supplied patent-holder list.

Patent activity is down in the reported comparison: 369 patents fall within the 24-month window, and the reported patent growth is -39.6%. Publication activity moved in the opposite direction, with 1,305 publications in the last year and growth of 4.9%. The contrast suggests research output remains active even as patenting has softened.

Recent developments include Fudan University and Chinese Academy of Sciences research on flowing zinc slurry in August 2026, and a Chinese Academy of Sciences CAS study of rigid microporous membranes in September 2026. The membrane work targets proton selectivity and oxidation stability in vanadium batteries. A September 2026 publication also used an extended Kalman filter to monitor vanadium-battery charge and health.

Emerging terms include reaction kinetics, Nafion membranes, ion exchange, and ion-exchange membranes. Recent methods include rigid microporous membrane blends for vanadium batteries, VCN-modified graphite-felt electrodes, and surrogate-assisted evolutionary search for organic-battery flow fields. The work reflects a focus on improving selectivity, electrode activity, and electrolyte transport while managing degradation.

The listed applications include grid-scale electricity shifting, renewable energy integration, microgrids and remote power, data centers, and mining and industrial sites. Grid shifting has 1,347 associated documents, while renewable integration has 913. These uses value extended discharge and flexible system design, especially where variable generation or sustained electricity demand makes short-duration storage less suitable.