Chemically resistant Cu-Zn/Zn composite anode for long cycling aqueous batteries

Abstract Rechargeable aqueous Zn metal batteries are promising candidates for renewable energy storage. However, Zn metal is chemically active and suffers from chemical corrosion in aqueous electrolyte due to its low redox potential. It is of vital importance to reveal the corrosion mechanism, and improve the chemical stability and electrochemical reversibility of Zn metal anode for its practical application. In this work, it is revealed that a Zn metal electrode readily gets oxidized during its resting in aqueous ZnSO4 electrolyte, forming zinc hydroxide sulfate and hydrogen gas, leading to the increased internal resistance and swollen problems of batteries, and eventually battery failure. To inhibit such chemical corrosion, an anti-corrosive metallic Cu is introduced to Zn metal anode to construct a uniform Cu/Zn composite with dense structure, which is electrochemically converted to Cu-Zn alloy/Zn composite during battery cycling. The as-achieved Cu-Zn/Zn electrode exhibits stable cycling for over 1500 cycles at 1 mA/cm2 and 0.5 mAh/cm2 with little change in overpotential (46 mV) after resting for 1 month, while the bare Zn electrode shows large voltage fluctuation and high overpotential (>400 mV) under the same condition, suggesting the importance of inhibiting the chemical corrosion of Zn metal anode for rechargeable aqueous batteries.