Abstract: MnNiS_x@Ti₃C_2x as the positive electrode of supercapacitor was successfully prepared by hydrothermal method with the assistance of amino-functionalized ionic liquids. The micromorphological structures of MnNiS_x@Ti₃C_2x were analyzed using X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, transmission electron microscope, and energy dispersive spectrometer to reveal the synergistic effect between MnNiS_x and Ti₃C_2x MXene. MnNiS_x grew into a three-dimensional coral-like structure on the surface and between layers of Ti₃C_2x nanosheets. This structure alleviated the collapse and stacking of Ti₃C_2x, increased the specific surface area of Ti₃C_2x, and promoted the charges transfer on the surface of Ti₃C_2x. The electrochemical performances of MnNiS_x@Ti₃C_2x positive electrode, such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy, were investigated. The synergistic effect between MnNiS_x and Ti₃C_2x MXene improved the specific capacitance and the capacitance retention of the MnNiS_x@Ti₃C_2x electrode. An asymmetric solid-state supercapacitor (ASC) assembled using MnNiS_x@Ti₃C_2x as cathode material had the power density of 816.34 W·kg^-1, and the energy density of 35.11 Wh·kg^-1. The capacitance retention of ASC reached 98% after 5000 cycles at a current density of 5 A·g^-1.

Key words: Supercapacitor, Transition metal sulfide, MXene, Structure characterization, Electrochemical performance

摘要： MnNiS_x@Ti₃C_2x as the positive electrode of supercapacitor was successfully prepared by hydrothermal method with the assistance of amino-functionalized ionic liquids. The micromorphological structures of MnNiS_x@Ti₃C_2x were analyzed using X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, transmission electron microscope, and energy dispersive spectrometer to reveal the synergistic effect between MnNiS_x and Ti₃C_2x MXene. MnNiS_x grew into a three-dimensional coral-like structure on the surface and between layers of Ti₃C_2x nanosheets. This structure alleviated the collapse and stacking of Ti₃C_2x, increased the specific surface area of Ti₃C_2x, and promoted the charges transfer on the surface of Ti₃C_2x. The electrochemical performances of MnNiS_x@Ti₃C_2x positive electrode, such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy, were investigated. The synergistic effect between MnNiS_x and Ti₃C_2x MXene improved the specific capacitance and the capacitance retention of the MnNiS_x@Ti₃C_2x electrode. An asymmetric solid-state supercapacitor (ASC) assembled using MnNiS_x@Ti₃C_2x as cathode material had the power density of 816.34 W·kg^-1, and the energy density of 35.11 Wh·kg^-1. The capacitance retention of ASC reached 98% after 5000 cycles at a current density of 5 A·g^-1.

关键词: Supercapacitor, Transition metal sulfide, MXene, Structure characterization, Electrochemical performance