Synergistic Engineering of Sulfur Vacancies and Heterointerfaces in Copper Sulfide Anodes for Aqueous Zn‐Ion Batteries with Fast Diffusion Kinetics and an Ultralong Lifespan

Abstract Aqueous Zn‐ion batteries (AZIBs) are promising candidates for implementing large‐scale energy storage, but the adverse side reactions and unsatisfactory cycle life brought by Zn‐metal anodes limit their potential in applications. Herein, an ingenious synthesized CuS 1–x @polyaniline (PANI) is proposed as an attractive conversion‐type Zn‐metal‐free anode for AZIBs, in which appropriate S‐vacancies and PANI heterointerfaces can be simultaneously constructed. This “killing three birds with one stone” strategy stabilizes the anode structure by utilizing organic–inorganic heterointerfaces and enhances Zn 2+ storage, benefiting from abundant S‐vacancies, as well as initiating fast Zn 2+ transport kinetics based on the joint effect of the two. Operando X‐ray absorption fine structure and synchrotron X‐ray diffraction further reveal the highly reversible conversion reaction of CuS 1–x @PANI via a distinct crystallization–amorphous transformation mechanism. These features endow CuS 1–x @PANI with sufficient zinc‐ion storage capacity (215 mA h g −1 at 100 mA g −1 ) and reliable current abuse tolerance (154.3 mA h g −1 at 1 A g −1 after 1000 cycles). Moreover, when matched with the optimized Zn x MnO 2 cathode, the full battery achieves a record‐high cycling performance of 10 000 cycles (80% capacity retention) at a superhigh current density of 10 A g −1 . This study provides new opportunities for developing high‐performance rocking‐chair AZIBs.