Novel organic redox flow batteries using soluble quinonoid compounds as positive materials

Novel organic redox flow battery is proposed based on 4, 5- dihydroxy-1, 3-benzenedisulfonate and 2, 5 dihydroxy-benzenedisulfonate as positive materials and PbSO₄/Pb as negative electrode in aqueous H₂SO₄ solution with an ion-exchange membranes between the positive and negative electrolyte. 4, 5-dihydroxy-1, 3-benzenedisulfonate oxide and 2, 5-dihydroxybenzenedisulfonate oxide have good reversibility and relatively high potentials in acidic solutions although the two hydroquinones have different electrochemical mechanism. Hydroquinones are oxidized to quinones at positive electrode during charge and quinones are reduced to hydroquinones during discharge. Results obtained with a small laboratory cell show that high efficiencies can be achieved with an average coulombic efficiency of 99% and energy efficiency of 70% over 100 cycles. High performance obtained indicates that soluble quinones are promising positive materials of novel organic redox flow batteries.