Effect of innovative carbon additives in the positive active mass of absorbent glass mat lead acid battery

Abstract

A well-known problem of lead acid batteries (LABs) is the limited charge efficiency and cyclability, due to the heavy electrode degradation during the discharging-charging process. Specifically, grid corrosion remains a detrimental issue to solve in flooded LAB. In this regard, it was observed that the addition of carbons in the positive active mass (PAM) of LABs improves the battery performances specifically the mechanical strength and the conductivity, which is beneficial for uniform current distribution during the charge-discharge process. In this paper, three different carbon-based compounds namely carbon black, carbon nanotubes, and graphitic carbon were selected as additives based on their physicochemical and electrochemical properties such as surface area, porosity, graphitization degree, conductivity, contact angle (wettability), and overpotential versus the hydrogen evolution reaction. Positive active masses at different carbon additive loadings (0.04 ÷ 0.4 % wt_PbO) were tested in an absorbent glass mat (AGM) LAB 1+/2− prototype cell. The prepared cells were tested under a standard charge-discharge protocol and then water loss was evaluated by coupling electrochemical polarization and gas analysis in accumulation mode. Incorporating carbon additives results in a remarkable increase in grid corrosion resistance and oxygen recombination.