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    Flow batteries

    Also known as redox flow battery, vanadium redox flow battery, VRFB

    A flow battery stores energy in two liquid electrolytes that are pumped through a cell stack, so its energy capacity (tank size) and power (stack size) can be scaled separately.[1][2] Vanadium designs dominate, and in May 2025 China connected the first gigawatt-hour-scale flow battery, a 200 MW / 1 GWh plant in Xinjiang.[3][4]

    Editor reviewedUpdated Batteries and energy storageEnergy and climateScience
    Key facts

    How it works

    In a flow battery, the chemicals that store energy are dissolved in two liquid electrolytes. Pumps circulate them through separate porous electrodes divided by a thin membrane.[1] Because the energy sits in tanks, capacity and power can be sized separately. Making the tanks bigger adds capacity, and making the reactor bigger adds power.[2] That makes the design suited to storage lasting many hours, and commercial vanadium systems are offered with 2 to 18 hours of discharge.[5]

    Vanadium and its trade-offs

    The most widely used design uses vanadium in different oxidation states on both sides of the cell.[3] Vanadium is found around the world, but only in dilute amounts, and it is hard to extract. Production is concentrated in Russia, China and South Africa, and prices are high and volatile.[6] Supporters stress durability and safety. Vanadium flow maker Invinity says its batteries deliver more than 20,000 deep cycles without the degradation seen in lithium batteries, and that they are non-flammable.[7]

    Landmark project

    On 28 May 2025 Rongke Power connected a 200 MW / 1 GWh vanadium flow battery station in Jimsar County, Xinjiang, to the grid. It was described as the first flow battery at gigawatt-hour scale.[4]

    The business picture

    Flow batteries compete with lithium-ion systems, which keep getting cheaper. Stationary lithium-ion packs averaged 70 dollars per kilowatt-hour in 2025, 45% less than a year earlier.[8] Some flow companies have struggled. ESS Tech began in 2011 as an iron flow battery maker, but now expects most near-term revenue from sodium-ion and other storage products. Its mid-2026 filing disclosed substantial doubt about its ability to continue as a going concern.[9][10] For multi-day storage, flow batteries also face iron-air rivals, which aim at durations of up to 100 hours.[11]

    Questions readers ask

    How is a flow battery different from a lithium-ion battery?

    Its energy is stored in liquid electrolytes held in tanks and pumped through the cell, so making the tanks bigger adds capacity and making the reactor bigger adds power.[1][2]

    Why vanadium?

    The most widely used design uses vanadium in different oxidation states on both sides. Vanadium is hard to extract, however, and its prices are high and volatile.[3][6]

    What is the biggest flow battery?

    Rongke Power's 200 MW / 1 GWh vanadium flow station in Xinjiang, connected to the grid in May 2025, described as the first at gigawatt-hour scale.[4]

    Sources

    Each numbered claim is a statement we checked against the sources listed with it. Status shows how well established it is.

    1. [1]

      In a flow battery, pumps circulate two liquid electrolytes through separate porous electrodes divided by a thin membrane. confirmedas of 2023-04-07

    2. [2]

      Flow battery energy capacity is raised by enlarging the electrolyte tanks and power by enlarging the reactor, so the two can be sized separately. confirmedas of 2023-04-07

    3. [3]

      The most widely used flow battery design uses vanadium in different oxidation states on its two sides. confirmedas of 2023-04-07

    4. [4]

      Rongke Power's 200 MW / 1 GWh vanadium flow battery station in Jimsar County, Xinjiang, was connected to the grid on 28 May 2025, billed as the first gigawatt-hour-scale flow battery. confirmedas of 2025-05-29

    5. [5]

      Invinity offers vanadium flow battery configurations with discharge durations of 2 to 18 hours. confirmedas of 2026-10-10

    6. [6]

      Vanadium is widespread but dilute and hard to extract, production is concentrated in Russia, China and South Africa, and its prices are high and volatile. confirmedas of 2023-04-07

    7. [7]

      Vanadium flow battery maker Invinity says its batteries deliver more than 20,000 deep discharge cycles without the degradation seen in lithium batteries, and are non-flammable. reportedas of 2026-10-10

    8. [8]

      Battery pack prices for stationary storage fell to 70 US dollars per kilowatt-hour in 2025, 45% lower than in 2024. confirmedas of 2025-12-09

    9. [9]

      ESS Tech, which began in 2011 as an iron flow battery maker, expects near-term revenue mainly from its Bridge sodium-ion and Energy Base storage products. confirmedas of 2026-06-30

    10. [10]

      Iron flow battery maker ESS Tech disclosed in its mid-2026 quarterly filing that there was substantial doubt about its ability to continue as a going concern for 12 months. confirmedas of 2026-06-30

    11. [11]

      Form Energy says its iron-air system can store and discharge energy for up to 100 hours. confirmedas of 2026-10-10

    Revision history (1)
    1. Page created.

    Created Oct 10, 2026. Last reviewed by an editor on Oct 10, 2026. Next scheduled review: Jan 10, 2027.

    Cite this page

    "Flow batteries." ContentLora, updated Oct 10, 2026. https://contentlora.com/wiki/flow-batteries

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