Vanadium redox flow battery

A rechargeable battery that stores energy in liquid vanadium electrolytes with different oxidation states. Its electrolyte tanks separate energy capacity from the power rating set by its cell stack.

Vanadium redox couples: Reversible oxidation–reduction reactions involving vanadium ions in different oxidation states. The battery stores charge by shifting vanadium between V²⁺, V³⁺, V⁴⁺, and V⁵⁺ states.
Oxidation state: A formal measure of an atom’s electron accounting in a compound or ion. The battery’s stored charge is encoded in vanadium’s changing oxidation states.
Grid energy storage: Storage systems that help balance electricity supply and demand across an electrical grid. Long-duration vanadium systems can shift renewable generation and support grid operations.
Lithium-ion battery: A rechargeable battery that stores and releases energy through lithium-ion movement between electrodes. Lithium-ion cells generally offer higher energy density, while vanadium systems separate tanks from stack power.
Vanadium crossover: The unwanted transport of vanadium species across a membrane between battery half-cells. Crossover can cause capacity imbalance and reduce performance over time.
Ion-exchange membrane: A membrane that selectively transports ions while limiting the passage of other species. It carries charge-balancing ions between electrolytes while keeping the vanadium solutions largely apart.
Vanadium: A chemical element with atomic number 23 and several accessible oxidation states. Its multiple water-soluble redox states enable both battery half-reactions.
Renewable energy storage: Technologies that store energy from variable renewable sources for later use. The battery can store surplus wind or solar electricity and return it when generation falls.
Zinc-bromine battery: A rechargeable flow battery that uses zinc and bromine electrochemistry to store energy. It is a competing flow chemistry with different materials, operating constraints, and system design.
Electrolyte imbalance: A mismatch in the amount or state of charge of electrolyte in a battery’s two half-cells. Unequal vanadium transfer or side reactions can shift the two electrolyte inventories out of balance.

Linked from 5 pages