The vanadium redox battery (VRB), also known as the vanadium flow battery (VFB) or vanadium redox flow battery (VRFB), is a type of rechargeable flow battery. It employs vanadium ions as charge carriers. The battery uses vanadium’s ability to exist in a solution in four different oxidation states to make a battery with a single electroactive element instead of two. For several reasons, including their relative bulkiness, vanadium batteries are typically used for energy storage.

Redox flow batteries differ from other conventional batteries in the way the energy storage occurs in a liquid media, and charging and discharging processes can take place within a single cell. This particular feature of redox flow batteries allows energy storage and conversion to be scaled flexibly and separately as per specific requirements. 

Similar to other electrochemical energy storage systems, redox flow batteries can also be developed in various size classes, ranging from a few hundred megawatts of power and watt-hours of storage to multi-megawatts and megawatt-hours systems for use as large grid-scale energy storage devices. 

Redox flow batteries can be effectively utilized for all types of stationary energy storage tasks, though their higher lifetimes result in the lowest Levelized cost of energy storage. Currently, there are various types of redox flow batteries that are being evaluated. However, the best-known redox flow battery is the vanadium redox battery.