REDOX FLOW BATTERY SYSTEM WITH ELECTROCHEMICAL RECOVERY CELL

A redox flow battery system includes a redox flow battery that has a redox flow cell, and a supply/storage system external of the redox flow cell. The supply/storage system includes first and second electrolytes for circulation through the redox flow cell. At least the first electrolyte is an aqueous liquid electrolyte that has electrochemically active species with multiple, reversible oxidation states. There is a gas vent passage connected with the redox flow battery to receive water byproduct that evolves from side reaction of the first electrolyte. A bypass passage is connected with the supply/storage system to receive the aqueous electrolyte. An electrochemical recovery cell includes a first half-cell connected to the gas vent passage to receive as a reactant the water byproduct and a second half-cell connected to the bypass passage to receive as a reactant the first electrolyte.