Dual-functional SnS2–CuS heterostructure for zinc anode protection and conversion-type anode toward advanced aqueous zinc-ion batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) face critical challenges including poor cycling stability, zinc dendrite growth, and low zinc utilization. To address these issues, a multifunctional SnS₂–CuS heterostructure is proposed, serving both as a zinc anode protective layer in conventional AZIBs and a metal-free anode in rocking-chair zinc-ion batteries (RCZIBs). In AZIBs, the SnS₂–CuS heterostructure generates a synergistic effect between different phases. This effect improves interfacial charge transfer efficiency, guides the oriented deposition of Zn²⁺ along the (001) crystal plane of SnS₂, and optimizes Zn²⁺ migration kinetics. When deployed as the anode for RCZIBs, the elaborate heterostructure construction efficiently alleviates the severe volume expansion of CuS during repeated charge–discharge cycling, while interfacial charge polarization derived from heterogeneous coupling further accelerates the electrochemical reaction kinetics. To clarify the electrochemical mechanism, in situ XRD, in situ EIS, DRT analysis, and ex situ XPS are used to track phase transitions and interfacial dynamic processes. Density functional theory calculations also theoretically verify that the SnS₂–CuS heterostructure significantly enhances Zn²⁺ storage capability. Electrochemical tests show that the assembled RCZIB delivers a discharge specific capacity of 179.03 mAh g⁻¹ at 0.2 A g⁻¹, retaining 114.51 mAh g⁻¹ after 200 cycles. Moreover, it maintains 83.6% of its initial capacity after 1000 cycles at 1 A g⁻¹, demonstrating outstanding cycling stability. This study achieves the compatible application of the SnS₂–CuS heterostructure in both AZIBs and RCZIBs and highlights its considerable potential for next-generation high-performance energy storage systems.