In Situ Ice Template Approach to Fabricate 3D Flexible MXene Film-Based Electrode for High Performance Supercapacitors

MXenes with metallic conductivity, high pseudo-capacitance and 2D structure, are promising flexible electrode materials for supercapacitors, but suffer from the restacking issue, which hinders ion accessibility and causes sluggish ion kinetics. Herein, a simple in situ ice template strategy is proposed to fabricate free-standing, flexible 3D porous Ti 3 C 2 T x /carbon nanotubes (CNTs) film (3D-PMCF) by freeze-drying Ti 3 C 2 T x -based hydro-films without any postprocessing. During the freeze-drying process, small ice grains are in situ transformed from the residual water molecules in the Ti 3 C 2 T x interlayer and then act as a self-sacrifice template to construct a 3D porous network. CNTs introduced in the hydro-film increase the amount of interlayer water and the resultant porosity. The 3D structure of Ti 3 C 2 T x significantly increases the exposed surface active sites and accelerates the ion transport, meanwhile maintaining good flexibility. Consequently, the flexible 3D-PMCF film delivers a capacitance of 375 F g −1 at 5 mV s −1 and retains 251.2 F g −1 at 1000 mV s −1 with excellent cycling stability, much superior to the conventional densely stacked Ti 3 C 2 T x film. Being assembled into a symmetric supercapacitor, an energy density of 9.2 Wh kg −1 is realized. This work demonstrates a simple and efficient route for constructing high-performance and flexible 3D MXene film electrodes for supercapacitors.