R&D engineer at the Laboratory for Electrochemical Storage, CEA Liten
Titanium foil coated with doped tin dioxide is very attractive option for positive current collector interface of bipolar lead batteries due its outstanding corrosion resistance and excellent mechanical performance. Despite these advantages, lead dioxide electrodes prepared by pasting and formation exhibit rather poor capacity retention during cycling with moderate depth of discharge. The phosphoric acid and two of its derivatives, one inorganic (calcium hydrogen phosphate) and one organic (poly-vinylphosphonic acid), have been studied as additives for improvement of the capacity retention of such positive electrodes. The experiments have been carried out on small-scale working electrodes with construction resembling the end-plate electrode of a bipolar battery. The electrochemical cells employed oversized conventional negative plate and externally compressed AGM separators. The results showed that the jar-formation process in the sulfuric acid electrolyte containing phosphoric acid successfully overcomes the capacity retention problem at all studied cases. It leads also to considerable improvement of the lead dioxide utilization. The cycling ageing of the electrodes combined with periodic impedance spectroscopy measurements, indicated progressive capacity loss corresponding to the typical processes of degradation of the lead dioxide structure and rather small changes in the electrode resistance, thus proving the corrosion 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.
Dr. Angel KIRCHEV has been R&D engineer at the Laboratory for Electrochemical Storage of CEA-LITEN since 2005. His work is focused on the study and optimization of energy storage systems operating with aqueous and aprotic electrolytes – alkaline, lead-acid, redox-flow and lithium-ion batteries. He holds a PhD in Electrochemistry from the Bulgarian Academy of Sciences and a Habilitation degree from the University of Grenoble.