Influence of phenolic group content in lignin expanders on the performance of negative lead–acid battery plates

Negative plates for lead–acid batteries containing lignin expander UP-414 with various phenolic group contents have been investigated. The members of the family of lignins UP-414 are produced by Borregaard LignoTech, Norway and differ mainly by the amount of phenolic groups and less so by the carboxylic groups in their structure, the content of all other functional groups (methoxyl, ketonic, etc.) being the same for all UP-414 products. The influence of phenolic group content in the expander on the performance of SLI batteries has been studied. It has been established that the batteries with PbSb grids exhibit a decline in C20 capacity, CCA performance and cycle life, when the content of phenolic groups in the expander increases. The capacity, cycle life and self-discharge of batteries with PbSnCa grids do not depend on the content of phenolic groups in the lignin. It has been proved experimentally that lignin reacts with the ions of the grid alloying additives forming metal–lignin compounds, which exert an influence on the performance of the negative plates.