Effect of the Current Density on the Electrodeposition Efficiency of Zinc in Aqueous Zinc-Ion Batteries

Increasing the electrodeposition efficiency of metallic zinc from quasi-neutral aqueous electrolytes is one of the major key requirements for the commercialization of rechargeable aqueous Zn-ion batteries. Several strategies have been recently reported in the literature. Unfortunately, electrochemical studies on the effect of different current densities on the zinc electrodeposition efficiency usually are not recorded in realistic experimental conditions: e. g. depth of discharges <1-10 %, use of negative electrodes with infinite reservoir of Zn2+, etc. Here, the effect of the current density on the zinc electrodeposition onto optimized bismuth-indium substrates cycled with 33 % of depth of discharge in a ZnSO4-containing aqueous solution has been investigated. It was found that low Zn plating/stripping current densities displayed higher electrodeposition efficiencies over 200 Zn electrodeposition/dissolution cycles, more homogeneous distribution of the zinc deposits and lower amounts of inactive zinc passivation products. When higher current densities were applied during the Zn plating/stripping cycles, lower electrodeposition efficiencies and a greater amount of inactive zinc hydroxides and dead zinc were observed on the electrode surface.