Lead/methanesulfonic acid redox flow battery

Redox-flow batteries are considered as a promising solution for massive electrical storage. In particular, the soluble lead-methanesulfonic acid technology is interesting due to the simple design of the cells and the potentially low associated costs. However some hurdles remain for its development, namely a low energy efficiency as well as a very limited lifetime, both of which being associated with the positive PbO₂-electrode. The first goal of this Ph.D. thesis is to provide a better understanding of the electrochemical mechanisms taking place at the positive electrode. The kinetic behaviour of the parasitic oxygen evolution during charging is assessed. Some mechanisms involved in the dissolution of PbO₂ are proposed and additives are tested for improving its cyclability. The complex potential responses of the electrode during galvanostatic cycling are also interpreted. The second purpose is to suggest a new reactor comprising a high specific surface area positive electrode. The honeycomb structure is especially studied. A reactor that includes a honeycomb-shaped positive electrode is proposed: its main characteristics are simulated using an electrochemical model and prototypes are fabricated and experimentally tested in cycling. (author)