Construction of Frame-Structured Flexible Mxene Film Electrode to Achieve High Areal Capacitance Micro-Supercapacitors

Abstract

Two-dimensional MXene-based film materials as flexible electrodes have been widely studied in wearable micro-supercapacitors (MSCs). However, the existence of strong van der Waals interaction leads to serious self-stacking of MXene layers, resulting in poor ionic dynamics and loss of active sites, which makes MXene film electrode exhibits low capacitance and poor rate performance in practical studies. To solve this, a frame-structured hybrid film (labeled as CN-MX hybrid film) is constructed by introducing intercalating agents (nanometer g-C3N4 ) into MXene layers. In this unique hybrid film, the g-C3N4 nanoparticles rationally occupy the interspace between MXene layers so as to alleviate layer stacking, thus effectively expanding the electrochemically active surface and promoting proton transfer. Synergistic pseudocapacitance inducted by g-C3N4 surface groups, consequently, the CN-MX hybrid film electrode achieves an enhanced capacitive capability. In the three-electrode system, this frame-structured film electrode exhibits an ultrahigh areal capacitance of 1932.8 mF cm-2. The assembled symmetry flexible MSC device based on CN-MX hybrid film can achieve an energy density of 2.28 µWh cm-2 at 0.075 mW cm-2, as well as a superior cyclic stability with 90.4% retention after 700 cycles in alternating 90o bending and releasing states, revealing its potential in practical application.

Keywords: MXene-based film, g-C3N4, frame-structured, high areal capacitance, flexible electrode