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 (MnO 2) nanosheets on MXene (Ti 3 C 2 T x) surfaces was prepared by a facile liquid phase coprecipitation method. Ti 3 C 2 T x is initially modified by polydopamine (PDA) coating to ensure the homogeneous distribution of MnO 2 nanosheets and tight and close connections between MnO 2 and the Ti 3 C 2 T x backbone. Due to the obtained three-dimensional (3D) nanostructure, facilitating electron transport within the electrode and promoting electrolyte ion accessibility, the δ-MnO 2 @Ti 3 C 2 T x -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-MnO 2 @Ti 3 C 2 T x -0.06 composites are employed as positive electrodes, and activated carbon (AC) materials act as negative electrodes with an aqueous electrolyte of 1 M Na 2 SO 4 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. A facile liquid phase coprecipitation method was used to design a manganese dioxide (MnO 2) nanosheets decorated MXene three-dimensional (3D) nanostructure with the aid of polydopamine (PDA) coating. Fast electron transport and electrolyte ions diffusion within the assembled device endows it with high electrochemical performance for practical application. [Display omitted] • PDA coating on Ti 3 C 2 T x surface can directly reduce MnO 4 − to δ-MnO 2 nanosheets and ensure their homogeneous distribution. • The obtained δ-MnO 2 @Ti 3 C 2 T x -0.06 electrode possesses a large areal capacity of 1233.1 mF cm−2 at 2 mV s−1. • The δ-MnO 2 @Ti 3 C 2 T x -0.06//AC device manifests a maximum energy density of 31.4 Wh kg−1 in the voltage range of 0−1.8 V. [ABSTRACT FROM AUTHOR]