Flexible Ti 3 C 2 T x @Al electrodes with Ultrahigh Areal Capacitance: In Situ Regulation of Interlayer Conductivity and Spacing

Although Ti 3 C 2 MXene has shown great potential in energy storage field, poor conductivity and restacking between MXene flakes seriously hinders the maximization of its capacitance. Herein, a new strategy to solve the problems is developed. Gallery Al atoms in Ti 3 AlC 2 are partially removed by simple hydrothermal etching to get Ti 3 C 2 T x reserving appropriate Al interlayers (Ti 3 C 2 T x @Al). Ti 3 C 2 T x @Al keeps stable layered structure rather than isolated Ti 3 C 2 T x flakes, which avoids flake restacking. The removal of partial Al frees up space for easy electrolyte infiltration while the reserved Al as “electron bridges” ensures high interlayer conductivity. As a result, the areal capacitance reaches up to 1087 mF cm −2 at 1 mA cm −2 and over 95% capacitance is maintained after 6000 cycles. The all‐solid‐state supercapacitor (ASSS) based on Ti 3 C 2 T x @Al delivers a high capacitance of 242.3 mF cm −2 at 1 mV s −1 and exhibits stable performance at different bending states. Two ASSSs in tandem can light up a light‐emitting diode under the planar or wrapping around an arm. The established strategy provides a new avenue to improve capacitance performances of MXenes.