Sandwich-like MXene/α-FeO-C-MoS-PEDOT:PSS/MXene Film Electrodes with Ultrahigh Area Capacitance for Flexible Supercapacitors.

The restacking of the MXene film limits its development to the high energy density of flexible supercapacitors. In order to promote the application of MXene films in portable electronic devices and miniaturized energy storage devices, it is necessary to increase the area capacitance of MXene films for the pursuit of high energy density. The introduction of α-FeO-C-MoS-PEDOT:PSS (FMP) into MXene significantly increases the area capacitance. Considering the large number of active sites on the surface of MXene and its excellent hydrophilicity, FMP can be well-compounded with MXene, and the accumulation and loss of FMP can be prevented. Meanwhile, it can reduce the performance degradation caused by the accumulation of MXene's own structure and greatly increase its capacitance value. It is worth mentioning that the MXene/FMP/MXene (M/FMP/M) sandwich structure on the carbon cloth is reasonably designed to show excellent performance. Therefore, the best M/FMP/M electrode could attain a breakthrough in the area capacitance (2700 mF cm and 541 F g). At the same time, the electrode maintains a fine rate capability and fabulous flexibility. In addition, the symmetrical supercapacitors also show a significant energy density of 371 μW h cm (12.36 W h·kg), making this sandwich structure electrode a promising candidate for high-energy-density devices.