Facile synthesis of uniformly coated ZnO@Bi2O3 composites anode for long-cycle-life zinc–nickel battery

Zinc–nickel battery attracts much attention because of their excellent rate performance and high operating voltage. However, their applications are strongly restricted by the poor cycling performance, which is caused by the degradation of the zinc anode during battery cycling. To overcome such limitation, a facile strategy to prepare homogeneously Bi2O3 coated ZnO composites is proposed. The reaction is conducted in the liquid phase based on redox reaction of Bi3+ and I− to directly grow BiOI on commercial ZnO powders, which are then converted to ZnO@Bi2O3 by further heat treatment. Benefiting from the uniform Bi2O3 coating, the solubility of ZnO is effectively reduced. The well-connected metallic Bi network is formed, which serves as the conductive substrate for uniform zinc deposition and hence inhibits the dendrites growth. The assembled zinc–nickel battery based on ZnO@Bi2O3 composites exhibits significantly prolonged cycling life. Even under a high discharge current of 10 A (~ 138 mA cm−2), the battery can keep cycling during 400 cycles with discharge voltage higher than 1.1 V, which is extended by 3 and 1.7 times compared with that of electrodes based on pure ZnO and physical mixture of Bi2O3 and ZnO. This work provides a facile strategy for synthesizing uniformly Bi2O3 coated ZnO composites, which is helpful for large-scale synthesis of high-performance zinc anodes in practical application.