Construction of three dimensional porous ZnO@SnO₂ microspheres composites and their effect on the stability and fast charge/discharge performance for alkaline nickel- zinc batteries

Nickel-zinc batteries are considered as the promising candidates for grid energy storage due to their high energy density and high safety. However, the low electrical conductivity of the ZnO anode, as well as issues such as side reactions and dendrite growth, leading to low conversion reaction activity, poor long-cycle life, and low high-rate capacity, which hinder their large-scale commercialization. To address these challenges, we have constructed a three-dimensional porous ZnO microsphere assembled from nanosheets and modified with SnO₂ (ZnO@SnO₂). The abundant voids between nanosheets provide multiple ion transport channels. The SnO₂ modification layer can not only increase the hydrogen evolution overpotential and enhance the corrosion resistance of the electrode, but also improve the electrical conductivity of ZnO, thereby ensuring the reversible conversion between Zn and ZnO. Benefiting from the synergistic effects of the unique porous structure and the SnO₂ protective layer, the nickel-zinc batteries using three-dimensional porous ZnO@SnO₂ microsphere composites anode maintain a discharge specific capacity of 546.6 mA·h·g⁻¹ after 700 cycles at a current density of 6 A g⁻¹, with a capacity retention rate of 94.5%, which is significantly higher than that of the pure ZnO electrode (61.7 mA·h·g⁻¹, capacity retention rate of 10.9%). Moreover, even at a high current density of 48 A g⁻¹, the discharge capacity is as high as 560.0 mA·h·g⁻¹, demonstrating excellent rate performance. It is comprehensively demonstrated that the ZnO@SnO₂ electrode has more excellent anti-corrosion performance and longer cycle life due to the synergistic effect of the porous microsphere structure and SnO₂.