Supercapacitive properties of MnNiSx@Ti3C2Tx MXene positive electrode assisted by functionalized ionic liquid

Abstract

MnNiSx@Ti3C2Tx as the positive electrode of supercapacitor was successfully prepared by hydrothermal method with the assistance of amino-functionalized ionic liquids. The micromorphological structures of MnNiSx@Ti3C2Tx 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 MnNiSx and Ti3C2Tx MXene. MnNiSx grew into a three-dimensional coral-like structure on the surface and between layers of Ti3C2Tx nanosheets. This structure alleviated the collapse and stacking of Ti3C2Tx, increased the specific surface area of Ti3C2Tx, and promoted the charges transfer on the surface of Ti3C2Tx. The electrochemical performances of MnNiSx@Ti3C2Tx positive electrode, such as cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy, were investigated. The synergistic effect between MnNiSx and Ti3C2Tx MXene improved the specific capacitance and the capacitance retention of the MnNiSx@Ti3C2Tx electrode. An asymmetric solid-state supercapacitor (ASC) assembled using MnNiSx@Ti3C2Tx 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.