Effect of phosphoric acid on the behaviour of the lead dioxide electrode in sulphuric acid

Phosphoric acid addition to the electrolyte of lead acid batteries has been practiced for a long time. The main advantages gained by this are reduction in irreversible sulphation in the deep discharged state and extensionof cycle life. In valve regulated lead acid batteries (VRLA), it avoids the formation of insulating layer at the grid the active material interface during deep discharge cycling. The influence of phosphoric acid is very complex and is mainly confined to the positive electrode. Mechanism of the manifold action of phosphoric acid is not fully understood despite several studies. In the present investigation, the effect of H 3 PO 4 on the charge discharge reaction of the lead dioxide electrode occurring in a lead acid battery has been examined using cyclic voltammetry technique. The results have been analyzed in an attempt to have a better understanding of the mechanism of action of phosphoric acid on the positive plate of lead acid battery.