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-Fe2O3–C–MoS2-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–2 and 541 F g–1). 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–2 (12.36 W h·kg–1), making this sandwich structure electrode a promising candidate for high-energy-density devices.

Currently, MXene-based supercapacitors (MSCs) have been widely studied due to their good flexibility and excellent electrochemical performance. At present, the application of supercapacitors is more and more extensive, which requires them to face various complex environments. However, MSCs applied under high-temperature conditions have not been reported. In this paper, the MXene−V 2 O 5 −polyaniline (MVP) ternary composite material is used as the electrode material, and sulfonated polybenzimidazole (SPBI) is used as the solid electrolyte to design high-temperature MSCs for the first time. The preparation of MVP is achieved by introducing V 2 O 5 into the MXene layer and loading polyaniline (PANI) on its surface, which not only greatly improves the capacitance performance of the electrode but also ensures its stability at a high temperature. The capacitance value of the MVP electrode was as high as 3180 mF cm −3 (880 F g −1 ), with excellent mechanical properties and increased flexibility at the same time. Furthermore, the assembled supercapacitor has a high energy density of 79.2 Wh L −1 (22.1 Wh kg −1 ). Moreover, its capacitance value can reach 985.3 mF cm −3 (276 F g −1 ) at 120 °C. This work provides an efficient design of an energy storage device that can be used for high-temperature applications.

Herein, composite proton exchange membranes based on block polybenzimidazole (bPBI) and a phosphotungstic acid-ionic liquid (PWA-IL) organic−inorganic filler have been prepared. The bPBI was prepared by block copolymerization of poly[2,2′-(p-phenylene)-5,5′benzimidazole] and poly(4,4′-diphenylether-5,5′-bibenzimidazole) oligomers. bPBI combined the advantages of both rigid and flexible segments. The block structure of the segmented block copolymer helped build proton transmission channels and made the transmission of protons easier. The PWA-IL was evenly distributed in the membranes. The PWA-IL has good electrochemical properties and can also form hydrogen bonds with phosphoric acid (PA), which is beneficial to proton conduction. The membranes had excellent mechanical properties (11 MPa) owing to the low acid doping level (ADL). Moreover, the membranes exhibit 0.05 S cm −1 proton conductivity at 170 °C at a low ADL and exhibit over 60% PA retention.