Research on the microstructure transformation and mechanical properties of lead alloy layer covering copper electrodes of high-capacity lead-acid batteries upon heat treatment

Abstract

The lead alloy layer on the copper electrodes of high-capacity lead-acid batteries is manufactured by gravity casting. In the cast state, the lead alloy layer exhibits a dendritic, unbalanced crystal structure, a high hardness of 27.9 HV, high residual internal stress, and a high resistance of 0.312 ÷ 0.420 mΩ, making it prone to microcracks and unfavourable for the battery. Through heat treatment, including quenching at 220 °C for 60 minutes followed by aging at 110 °C for 7 hours, the cast microstructure transforms into a more balanced, polygonal, axial crystal structure. The hardened phase forms, achieving an optimal hardness of 16.2 HV, and the average resistance is reduced to 0.06 mΩ, making it suitable for the manufacture of high-capacity lead-acid batteries.