Phosphoric Acid Activation of Titanium-Supported Lead Dioxide Electrodes for Bipolar Battery Applications

Abstract

Titanium foil coated with doped tin dioxide is an attractive option for the positive current collector interface of bipolar lead batteries due its corrosion resistance and mechanical performance. The phosphoric acid and two of its derivatives, one inorganic (calcium hydrogen phosphate) and one organic (poly-vinylphosphonic acid), have been studied as additives with potential for improvement of the capacity retention of such positive electrodes. The results show that the jar-formation process of the electrodes in the sulfuric acid electrolyte containing phosphoric acid successfully overcomes the capacity retention problem at all studied cases. This leads also to considerable improvement of the lead dioxide utilization. The cycling ageing of the electrodes combined with periodic impedance spectroscopy measurements, indicate progressive capacity loss corresponding to the typical processes of degradation of the lead dioxide structure. Rather small changes in the electrode resistance prove the corrosion and the passivation resistance of the current collectors. It is concluded that the combined doping with phosphoric acid species in the electrolyte and in the positive paste offers a potential for further improvements of the electrodes cyclability.