Electrochemical energy storage technology has emerged as a crucial research focus in the development of advanced energy storage systems, owing to its high energy conversion efficiency, flexible modular design, and environmental benignity. In recent years, the growing demand for large-scale energy storage in renewable energy integration and smart grids has further accelerated research in this field. Compared with conventional lithium-ion batteries, which are constrained by high production costs, limited lithium resources, and potential safety risks associated with flammable organic electrolytes, aqueous zinc-ion capacitors (ZICs) have attracted considerable attention as promising alternatives for large-scale energy storage applications. This advantage mainly stems from the intrinsic merits of zinc metal anodes, including high theoretical capacity, low redox potential, natural abundance, low cost, and excellent safety when operated in aqueous electrolytes. Despite these advantages, the practical application of zinc ion batteries (ZIBs) is still severely restricted by the intrinsic challenges associated with zinc metal anodes. During repeated zinc plating/stripping processes, non-uniform Zn deposition tends to occur, leading to the formation of zinc dendrites. Meanwhile, unavoidable side reactions such as hydrogen evolution, corrosion, and by-product formation further deteriorate the anode surface and electrolyte environment. These issues collectively result in rapid capacity decay, poor cycling stability, and low Coulombic efficiency, ultimately impacting the long-term reliability and commercial viability of aqueous zinc-ion batteries. In order to solve the above problems, this study proposed a zinc electrode (APS@Zn) strategy to construct a compact three-dimensional ZnO layer by ammonium persulfate (APS) treatment. The method is simple and controllable, and the dense ZnO layer formed can not only effectively regulate the nucleation behavior of Zn²⁺, inhibit dendrite growth and side reactions, but also significantly improve ion transport kinetics and cycle reversibility, and realize uniform electroplating and stripping of zinc. Therefore, APS@Zn electrode shows better electrochemical performance than bare zinc electrode. The assembled symmetrical battery can be stably cycled for 4500 h under the conditions of 5 mA•cm⁻² and 1 mAh•cm⁻², and can still run stably for 1800 h even under the high current density of 20 mA•cm⁻² and 0.5 mAh•cm⁻². The zinc ion capacitor paired with active carbon anode can be stably cycled for more than 40000 cycles under the condition of 2 A•g⁻¹. It can be seen that the three-dimensional porous compact ZnO layer formed by APS treatment not only effectively improves the stability and reversibility of the electrode, but also makes the battery show higher and more stable specific capacity.

Key words: zinc-ion capacitors, zinc anode modification, ZnO, 3D structure, solid electrolyte interphase (SEI)