Polyurethane/MXene electrodes for flexible supercapacitor applications

Conventional supercapacitors have encountered application bottlenecks due to their poor flexibility. In this context, a flexible polyurethane (PU)/MXene electrode is constructed by directly depositing MXene on PU substrate that is prepared by solvent casting method. In contrast to the pure MXene film, the elongation at break of the PU film prepared with a mass fraction of 9% reaches up to 435%, 94 times higher than that of the pure MXene film. At an optimum loading amount of 1.6 mg·cm−2, PU/MXene film delivers a high mass-specific capacitance of 276 F·g−1, 1.57 times that of 175 F·g−1 for pure MXene, at a current density of 1-A·g−1 under the three-electrode system. In the two-electrode system with polyvinyl alcohol/sulfuric acid as the gel electrolyte, the PU/MXene//PU/MXene-based symmetrical supercapacitor exhibits a high mass-specific capacitance of 123.2 F·g−1 at 0.5 A·g−1, with a power density of 630.8-W·kg−1, corresponding to an energy density of 4.8 Wh·kg−1. The device still maintains 80.2% of the initial capacitance after 5000 cycles. In addition, there is no remarkable decrease in the electrochemical performance after repeated bending at different angles. This study provides a promising strategy for the facile preparation of high-performance flexible supercapacitors.