Effects of Sulfuric Acid Concentration on Volume Transfer Across Ion-Exchange Membrane in a Single-Cell Vanadium Redox Flow Battery

The vanadium redox flow battery (VRFB) is one of the technologies to be used for storing large-scale renewable energy. The objective of this research is to electrochemically synthesize the V(III) electrolytes with combinations of 2 M VOSO₄ and 2–6 M H₂SO₄, and to investigate the effects of concentration of H₂SO₄ on vanadium and water transfer across membrane. Transfer of water and vanadium across the membrane was reduced from 19.6 to 6.2 % as the concentration of H₂SO₄ in the electrolyte increased from 2 to 6 M. Change in volume transferred across the membrane decreased with each successive charge and discharge cycle, and resulted in a reduction in volume transfer from 16.7 % after the first cycle to 2.9 % after the fourth cycle. Energy storage capacity was increased by 50 % by changing the H₂SO₄ concentration from 2 to 6 M.