Growth of NiMn LDH nanosheet arrays on KCu7S4 microwires for hybrid supercapacitors with enhanced electrochemical performance

Abstract

The rational design and synthesis of hierarchical three-dimensional nanostructures with diversified compositions and fascinating morphologies can provide abundant choices and enhanced probability for applications in the energy storage field. Herein, we report an effective, metal catalyst- or surfactant-free approach for the controlled growth of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures. The quasi-paralleled and interlaced nanosheet arrays of NiMn layered double hydroxides are grown on KCu₇S₄ microwires with a quasi-one-dimensional channel. The supersaturation of the system and screw dislocation-driven growth pattern of 2D materials could be key factors in determining the structure of the nanosheets arrays of NiMn LDHs. The electrochemical investigation shows that the KCu₇S₄@NiMn LDHs have a significantly enhanced specific capacitance (879 F g⁻¹ at 1 mV s⁻¹, 733.8 F g⁻¹ at 1 A g⁻¹) and rate capability (76.9% retention at 30 A g⁻¹) that far exceed those of the reported individual KCu₇S₄ electrodes. A hybrid supercapacitor based on KCu₇S₄@NiMn LDH//activated graphene electrode also presents good cycle stability (an 84.8% capacitance retention after 16 000 cycles). The outstanding supercapacitor performance forebode the enormous potential of KCu₇S₄@NiMn LDH composites in electrochemical properties.