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To improve the electrochemical performance of supercapacitors, pseudocapacitive electrode materials must be synthesized with high surface activity, high electrical conductivity, and ultralong cycle life, which presents a significant challenge. In this study, we reported on the synthesis of sulfur-vacancy-enriched sheet-like Ni 3 S 2 @ZnS composites based on 3D network porous nickel foam (NF) using a two-step electrodeposition protocol. The Ni 3 S 2 @ZnS/NF exhibited a specific capacitance of 1141.9 C g−1 (241.0 mC cm−2) at a current density of 19 A g−1 (5 mA cm−2). The Ni 3 S 2 @ZnS/NF positive electrode was used to fabricate an all-solid asymmetric supercapacitor, which demonstrated an ultrahigh energy density of 12.0 μWh cm−2 at a power density of 7.2 mW cm−2, as well as an ultrahigh capacitance retention rate of 86.7% after 50,000 cycles. Experimental and theoretical results indicated that the introduction of sulfur vacancies could improve the surface activity of the electrode, as well as its hydroxide diffusion and adsorption ability by adjusting the surrounding local electron concentration of cations around them. This accelerated the interfacial redox reaction and resulted in remarkable electrochemical performance for the Ni 3 S 2 @ZnS/NF electrode. This research provides a pathway for the controlled synthesis of 2D nanosheets with vacancy-rich structures and their potential electrochemical applications. • The sulfur-vacancy-enriched sheet-like Ni 3 S 2 @ZnS composite has been conceived. • Abundant sulfur vacancies make the material have high capacitive properties. • The theoretical studies further deepen structure-activity relationship of sulfur vacancies. • An ultrahigh capacitance retention supercapacitor is fabricated. [ABSTRACT FROM AUTHOR]