High-performance and freestanding PPy/Ti3C2Tx composite film for flexible all-solid-state supercapacitors

To utilize the flexibility and high theoretical specific capacitance of polypyrrole (PPy) and high electrical conductivity and moderate electrochemical properties of emerging two-dimensional materials, MXene, herein, a high performance, flexible, and freestanding PPy/Ti3C2Tx (a kind of MXene) composite film electrode is prepared by vacuum-assisted filtration of single- and few-layer Ti3C2Tx sheets to obtain a Ti3C2Tx film and then electrochemically deposition of PPy on the film. High-resolution scanning and transmission electron microscope (HRSTEM) observations of the focused ion beam prepared sample reveal that the electrode possesses a unique microstructure: PPy not only polymerizes on the surface of the Ti3C2Tx film, but also intercalates into the gaps within the film. An optimized sample shows an outstanding specific capacitance of 420.2 F g−1 at 1 A g−1, a remarkable cycling stability of 86% capacitance retention after 10,000 cycles, a distinguished flexibility and a good mechanical performance, owing to the special microstructure and synergistic effect of the PPy and Ti3C2Tx. A symmetric all-solid-state flexible supercapacitor fabricated by the 400PPy175/Ti3C2Tx electrode exhibits remarkable specific capacitance of 258.3 F g−1 at 0.5 A g−1, a superior energy density of 10.82 μWh·mg−1 at a power density of 0.11 mW mg−1, and an outstanding power density of 1.89 mW mg−1 at 3.99 μWh·mg−1, indicating that the PPy/Ti3C2Tx film has great potential as supercapacitor electrode.