Mitigating intergranular attack and growth in lead-acid battery electrodes for extended cycle and operating life

Deterioration in the performance of lead acid batteries is primarily governed by weight loss and growth of the positive electrodes, arising from creep and intergranular corrosion/cracking. The present investigation examines the impact of increasing the frequency of grain boundaries having low-Sigma misorientations (Sigma less than or equal to 29), described by the Coincident Site Lattice (CSL) model, which are known to be resistant to these intergranular degradation phenomena. Electrode microstructures of various PbCaSn alloys processed to contain frequencies of special boundaries (in excess of 50 pct) exhibited reductions in weight loss of between 26 and 46 pct accompanied by declines in grid growth of between 41 and 72 pct. Moreover, the distribution of intergranular attack/cracking in the microstructure of these alloys can be predicted on the basis of the frequency of low-Sigma special boundaries and grain size. In general, improvements in corrosion and creep/cracking occur without compromising tensile properties such as yield strength, ultimate tensile strength (UTS), and ductility. Modifying the crystallographic structure of grain boundaries in Pb alloy battery electrodes, thus, provides an opportunity for minimizing grid thicknesses (weight) and, hence, material costs in battery production, or for maximizing energy densities (Wh/kg) and cycle life performance.