Benzyl benzoate as an inhibitor of the sulfation of negative electrodes in lead-acid batteries

Abstract

Abstract The lead sulfate crystals formed on the surface of the negative electrodes of lead-acid batteries during discharge gradually grow in size as a result of recrystallization processes. The big PbSO4 crystals have low solubility and are involved but very slightly in the charge process, thus causing progressive sulfation of the negative electrodes on cycling. In order to reduce or suppress this sulfation, the processes of PbSO4 recrystallization should be inhibited. It has been established that, besides lignosulfonates, some organic substances, too, may be used as additives to the negative active material to effectively inhibit the growth of lead sulfate crystals during battery discharge. The research results discussed in the present paper indicate that the aromatic ester compound of carboxylic acid, Benzyl benzoate (C6H5CH2O2CC6H5), has such inhibiting properties. Lead-acid test cells with negative plates containing Benzyl benzoate (BB) have improved cycle life performance, the beneficial effect of the BB additive to NAM being most pronounced at a loading level of 0.3%. Cells with BB added to the electrolyte have also been tested. In this case, the additive exhibits its inhibiting effect on the processes of PbSO4 crystal growth most strongly when added to the electrolyte at concentration levels of 0.3% or 0.5%.