Modification of Zinc Anodes by In Situ ZnO Coating for High-Performance Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries have been regarded as promising candidates for advanced energy storage devices due to their high capacity and safety. However, they usually suffer from dendrite growth and side reactions, which severely destabilize the electrode/electrolyte interface and undermine the electrochemical performance. Herein, we report ZnO nanorod-decorated Zn anodes using a facile in situ hydrothermal method. The reactions and evolution at the anode–electrolyte interface are systematically investigated. Various characterization techniques suggest that ZnO transforms into a Zn-ion conductive Zn4SO4(OH)6·4H2O (ZHS·4H2O) interphase, which enables uniform Zn deposition and suppresses dendrite growth. In addition, this passivated interphase can prevent the electrolyte from direct contact with the Zn anode and inhibit side reactions, effectively improving the coulombic efficiency (CE) and the utilization of anodes. Therefore, the Zn-ZnO anodes in the symmetric cells display a low voltage hysteresis (46 mV) and long-term cycling stability at 5 mA cm–2, a lower Zn deposition barrier, and a high Zn plating/stripping CE of 99.7%. Importantly, the Zn-ZnO//MnO2 full cells show a fairly high specific capacity of 580 mAh g–1 and superior cycling stability with 154% capacity retention after 100 cycles at 50 mA g–1 and 105% capacity retention after 800 cycles at 500 mA g–1.