Effect of phosphoric acid on the performance of low antimony grid of Pb‐acid cell under constant current charging and discharging

Effect of phosphoric acid on the performance of Pb-1.7%Sb grid of lead-acid cell is studied in 5 M H(2)SO(4) by cyclic galvanostatic polarization and impedance spectroscopy. An increase in capacitance to a maximum is recorded during the initial stages of the electro-reduction of PbO(2) into Pb(II) compounds and attributed to concurrent compositional and dimensional changes. These changes include removal of O(2) bubbles, insertion of large amounts of H(2)SO(4) and H(2)O. Efficiency of PbO(2) formation decreases, while its rate of self-discharge increases with increasing the charging current and in the presence of H(3)PO(4). The charge capacity increases with increasing the discharging current due to the decrease in the self-discharge. The charge capacity is lower in the presence of H(3)PO(4). On increasing the cycle number, the corrodibility of the grid increases, because more layers of the surface Pb are involved in the self-discharge. H(3)PO(4) significantly retards the effect of cycle number.