Highly Active NiCoMnS ₄ Decorated NiMnO ₃ Nanosheet as High‐Performance Electrode for Supercapacitor

The rational design of multicomponent composites is an effective strategy for enhancing supercapacitor performance. This study successfully synthesized a heterostructured nanoflower‐like NiMnO ₃ @NiCoMnS ₄ (NMO@NCMS) composite on nickel foam via a hydrothermal method and subsequent thermal treatment. This unique interconnected nanosheet architecture offers a high specific surface area, facilitates rapid electron/ion transport, and mitigates volume expansion, thereby significantly improving electrochemical performance and stability. The resulting NMO@NCMS electrode achieved an outstanding specific capacitance of 1994.36 F g ⁻¹ at 1 A g ⁻¹ and maintained 1492.73 F g ⁻¹ at 10 A g ⁻¹ . It also exhibited remarkable cycling stability with 90.18% capacitance retention and 99.35% Coulombic efficiency after 20 000 cycles. Furthermore, an asymmetric supercapacitor was assembled using NMO@NCMS as the cathode and activated carbon as the anode. This device operated within a 1.7 V voltage window, delivering specific capacitance of 171.11 F g ⁻¹ at 1 A g ⁻¹ . It achieved high energy density of 68.68 Wh kg ⁻¹ at power density of 850 W kg ⁻¹ , alongside exceptional long‐term stability (87.73% capacity retention after 50 000 cycles at 20 A g ⁻¹ ). These superior properties underscore the great potential of the NMO@NCMS composite for high‐performance supercapacitor applications.