Anchoring Oxidized MXene Nanosheets on Porous Carbon Nanotube Sponge for Enhancing Ion Transport and Pseudocapacitive Performance.

Two-dimensional (2D) MXene nanosheets are attractive for electrochemical energy storage applications due to their superior surface-controlled charge storage capacity. However, the slow ion transport in the closely packed electrode limits their electrochemical performances. Meanwhile, the restricted surface-controlled pseudocapacitance of MXene nanosheets requires to be enhanced. Herein, a well-controlled electrophoretic deposition strategy is developed to disperse Ti 3 C 2 T x nanosheets into a freestanding, porous carbon nanotube (CNT) sponge. The constructed Ti 3 C 2 T x @CNT hybrid sponge can provide high-speed ion-transport pathways for the charge-discharge process. Furthermore, by tuning the deposition potential, the inserted MXene nanosheets can be partially oxidized, boosting the pseudocapacitance performance. A large gravimetric capacitance of 468 F g -1 at 10 mV s -1 and a retention of 79.8% at 100 mV s -1 can be achieved in the Ti 3 C 2 T x @CNT electrode. Meanwhile, the highest areal capacitance of 661 mF cm -2 at 1 mA cm -2 was obtained in the sample with high-loading Ti 3 C 2 T x . For the assembled symmetric supercapacitor, 92.8% of the capacitance is retained after 10 000 cycles of the charge-discharge process at 10 mA cm -2 . Thus, this study develops a promising electrophoretic deposition strategy for dispersing 2D MXene nanosheets and boosting their pseudocapacitive performance, resulting in a high-capacitive electrochemical energy storage electrode.