Effect of gelling on the electrode kinetics of the Pb/PbSO₄ and hydrogen-electrode reactions in maintenance-free lead/acid batteries

Abstract

The electrode kinetics of the Pb/PbSO₄ and the hydrogen-evolution reactions on porous lead electrodes in sulfuric acid has been studied using a quantitative analysis of galvanostatic transients in the linear polarization domain. Significant changes are observed in the kinetics with the addition of thixotropic agents (e.g., sodium silicate) that are often employed in the manufacture of maintenance-free lead/acid batteries. The effects of these thixotropic agents on the charge-transfer and ohmic components of the Pb/PbSO₄ reaction and charge-transfer components of hydrogen-electrode reaction are analysed with the help of a 'pore-plugging' model. This study allows a non-destructive determination of the electrode kinetic parameters and the internal resistance contribution from pore-plugging. This is useful when designing maintenance-free lead/acid batteries.