The vanadium redox (and redox flow) battery is a type of rechargeable flow battery that employs vanadium redox couples in both half-cells, thereby eliminating the problem of cross contamination by diffusion of ions across the membrane. The present form (with sulfuric acid electrolytes) was patented by the University of New South Wales in Australia in 1986. Although the use of vanadium redox couples in flow batteries had been suggested earlier by Pissoort, by NASA researchers and by Pellegri and Spaziante in 1978, the first successful demonstration and commercial development was by Maria Skyllas-Kazacos and co-workers at the University of New South Wales in the 1980s. The vanadium redox battery exploits the ability of vanadium to exist in solution in four different oxidation states, and uses this property to make a battery that has just one electroactive element instead of two.

The main advantages of the vanadium redox battery are that it can offer almost unlimited capacity simply by using larger and larger storage tanks, it can be left completely discharged for long periods with no ill effects, it can be recharged simply by replacing the electrolyte if no power source is available to charge it, and if the electrolytes are accidentally mixed the battery suffers no permanent damage.

The main disadvantages with vanadium redox technology are a relatively poor energy-to-volume ratio, and the system complexity in comparison with standard storage batteries.