Manganese dioxide nanosheets decorated on MXene (Ti3C2Tx) with enhanced performance for asymmetric supercapacitors

The incorporation of nanosized pseudocapacitive materials and structure design are general strategies to enhance the electrochemical performance of MXene-based materials. Herein, the decoration of manganese dioxide (MnO2) nanosheets on MXene (Ti3C2Tx) surfaces was prepared by a facile liquid phase coprecipitation method. Ti3C2Tx is initially modified by polydopamine (PDA) coating to ensure the homogeneous distribution of MnO2 nanosheets and tight and close connections between MnO2 and the Ti3C2Tx backbone. Due to the obtained three-dimensional (3D) nanostructure, facilitating electron transport within the electrode and promoting electrolyte ion accessibility, the δ-MnO2@Ti3C2Tx-0.06 electrode yields superior electrochemical performances, such as a rather large areal capacity of 1233.1 mF cm−2 and high specific capacitance of 337.6 F g−1 at 2 mV s−1, as well as high cyclic stability for 10000 cycles. Furthermore, δ-MnO2@Ti3C2Tx-0.06 composites are employed as positive electrodes, and activated carbon (AC) materials act as negative electrodes with an aqueous electrolyte of 1 M Na2SO4 to assemble asymmetric supercapacitors. The prototype device is reversible at cell voltages from 0 to 1.8 V, and manifests a maximum energy density of 31.4 Wh kg−1 and a maximum power density of 2700 W kg−1. These encouraging results show enormous possibilities for energy storage applications.