VANADIUM ELECTROLYTE PREPARATION USING ASYMMETRIC VANADIUM REDUCTION CELLS AND USE OF AN ASYMMETRIC VANADIUM REDUTION CELL FOR REBALANCING THE STATE OF CHARGE OF THE ELECTROLYTES OF AN OPERATING VANADIUM REDOX BATTERY

摘要

A method of producing an acid vanadium electrolyte solution containing V+3 and V+4 in a desired concentration ratio from solid vanadium pentoxide fed in to the electrolyte solution, comprising the steps of electrochemically reducing at least partly of the dissolved vanadium in the acid electrolyte solution by circulating the electrolyte solution through a plurality of electrolytic cells in cascade to at least a V+3 state of the oxidation or lower; reacting the reduced vanadium content in electrolyte solution outlet from the last of said electrolytic cells with a stoichiometrically calculated quantity of vanadium pentoxide for obtaining an electrolyte solution containing vanadium in a V+4 state of oxidation & optionally separating the solution from any residual undissolved particle of vanadium pentoxide & thereafter. adding acid and water to maintain molarity of the solution; continously recycling the electrolyte solution through the cascade of electrolytic cells while bleeding a stream of yielded electrolyte solution containing V+3 and V+4 in the desired concentrations at the exit of one of the cells of said cascade; each cell having a cathode surrounding an anode with respective surface morphologies, geometry and mutual disposition such to establish on the anode surface a current density from 5 to 20 times greater than the current density on the cathode surface facing the anode for promoting oxygen evolution at the anode (Fig.1).