Annealing modification of MXene films with mechanically strong structures and high electrochemical performance for supercapacitor applications

Two-dimensional transition metal carbides and nitrides (MXene) have shown outstanding performances in electrochemical energy storage, but their investigations of both mechanical and electrochemical performance for structural power systems are lack of being discussed. In this work, modified MXene films with mechanically strong structures and high electrochemical performance are obtained via directly annealing strategies. Due to the beneficial chemical composition on the surface and the structural variation under appropriate annealing treatment conditions, the modified Ti3C2Tx MXene electrode can deliver an ultrahigh volumetric capacitance of 1590 F cm−3 with a gravimetric value of 442 F g−1 at 0.5 A g−1, a good rate capability of 1030 F cm−3 at 20 A g−1, a cycling stability with a retention of 95.4% after 5000 cycles in the acid electrolyte and a high tensile strength of 32 MPa, demonstrating its great potential as a multifunctional electrode for structural energy and power systems. The influences of different electrolytes on the intercalation-induced electrochemical process of modified MXene films were also probed. Furthermore, the assembled symmetric supercapacitor with the modified Ti3C2Tx MXene film demonstrates a favorable volumetric energy density of 15.2 Wh L−1 and a power density of 204.8 W L−1.