Flexible Ti3C2Tx MXene/polypyrrole composite films for high-performance all-solid asymmetric supercapacitors

Ti3C2Tx MXene has shown great potential as supercapacitor electrode due to its unique high conductivity and specific surface area, but achieving high capacitance, high energy density, good mechanical flexibility and cycling stability simultaneously is challenging. Herein, MXene/polypyrrole (M-PPy) composite films are fabricated by vacuum-assisted suction filtration of a mixture of MXene nanosheets and polypyrrole (PPy) nanofibers. MXene nanosheet layers are optimally arranged by the intercalation of PPy nanofiber to reduce MXene self-stacking while reducing PPy swelling. The optimal M-PPy3 (3 mL PPy) possesses high capacitance (563.8 F g−1, 0.5 A g−1) and excellent cycling performance (79.5%, 6000 times, 5 A g−1). Next, the flexible M-PPy3//MnO2 asymmetric supercapacitor (ASC) are assembled with MnO2 as the positive electrode and M-PPy3 as the negative electrode. The ASC exhibits 86.8% capacitance retention even after 6000 charge/discharge tests at 2 A g−1, and provides an energy density of 35.3 Wh kg−1 at 486.1 W kg−1, demonstrating remarkable energy storage capacity. Furthermore, a 1.8 V LED is successfully lit up by connecting two ASCs in series. This study provides a better electrode structure for the study of the electrochemical performances of MXene, and the M-PPy3 displays its application in flexible wearable devices.