A hafnium oxide-coated dendrite-free zinc anode for rechargeable aqueous zinc-ion batteries

In aqueous zinc-ion batteries, metallic zinc is widely used as an anode because of its non-toxicity, environmental benignity, low cost, high abundance and theoretical capacity. However, growth of zinc dendrites, corrosion of zinc anode, passivation, and occurrence of side reactions during continuous charge-discharge cycling hinder development of zinc-ion batteries. In this study, a simple strategy involving application of a HfO₂ coating was used to guide uniform deposition of Zn²⁺ to suppress formation of zinc dendrites. The HfO₂-coated zinc anode improves electrochemical performance compared with bare Zn anode. Therefore, for zinc-zinc symmetric cells, zinc anode with HfO₂ coating (48 mV) shows lower voltage hysteresis than that of bare Zn anode (63 mV) at a current density of 0.4 mA cm^-2. Moreover, cell with HfO₂ coating also shows good cycling performance in Zn-MnO₂ full cells. At a constant current density of 1.0 A g^-1, discharge capacity of bare Zn-MnO₂ full cell is only 37.9 mAh g^-1 after 500 cycles, while that of Zn@HfO₂-MnO₂ full cell is up to 78.3 mAh g^-1. This good electrochemical performance may be the result of confinement effect and reduction of side reactions. Overall, a simple and beneficial strategy for future development of rechargeable aqueous zinc-ion batteries is provided.