Evaluation of Precipitation Inhibitors for Supersaturated Vanadyl Electrolytes for the Vanadium Redox Battery

As part of a project aimed at increasing the energy density of the vanadium redox battery for mobile applications, a number of additives was evaluated as precipitation inhibitors to enhance the stability of supersaturated vanadyl electrolytes in . While the saturation solubility of vanadyl sulfate in is less than at , supersaturated vanadyl sulfate solutions could readily be prepared. A blank solution of vanadyl sulfate in began to precipitate after 22 days at , reaching an equilibrium concentration of after 80 days. In the presence of or sodium hexametaphosphate, however, there was no sign of precipitation after 80 days at .