Hydrogen Evolution and Zinc Nodular Growth in the Zinc Chloride Battery

The problem of hydrogen evolution in the zinc chloride battery is investigated experimentally with special respect to the magnitude of the phenomenon under various and supporting electrolyte concentrations, p H, current density, and electrolyte purity. Metallic impurities of low hydrogen overvoltage can be responsible for accelerated hydrogen evolution during charge and discharge. In addition, the morphology and porosity of the zinc deposit and the presence of dendrites affect the magnitude of hydrogen evolution. Low hydrogen evolution rates are observed on rough and dendritic deposits and vice versa. Two methods of decreasing hydrogen evolution are presented: ( i ) pretreatment of the electrolyte with zinc particles, and ( ii ) potentiostatic deposition of metallic impurities in flow‐through porous‐graphite electrode above the zinc deposition potential.