Flexible solid-state supercapacitor integrated by methanesulfonic acid/polyvinyl acetate hydrogel and Ti 3 C 2 T x

MXenes, as a rapidly developing family of materials, have achieved promising results as solid-state supercapacitor (SSS) electrode. Investigations of optimizing MXene-based SSSs concentrate on electrode recently. However, the state-of-the-art MXene-based SSSs present inferior rate performances compared to aqueous devices. Herein, we optimize the performance of MXene-based SSS by introducing a green, low temperature resistant and highly ionic conductive methanesulfonic acid/polyvinyl acetate (MSA/PVA) hydrogel as electrolyte. The assembled SSS (FT-SSS) outperforms the one fabricated by the usual liquid electrolyte casting method, showing high areal capacitance (1719 mF cm −2 ), long cycle life (92%, 80,000 cycles), low-temperature resistance (-30°C) and flexibility. More importantly, FT-SSS presents superior capacitance and rate performance that exceeds the corresponding aqueous supercapacitor (AQS). The areal capacitance increases by 127% at 1000 mV s −1 compared with AQS. Energy dispersive spectroscopy maps, X-ray diffraction and X-ray photoelectron spectroscopy analysis reveal that MSA pre-intercalate into Ti 3 C 2 T x, forming electrodes with a wrinkled and porous structure, which reduces MXene stacking effect and enhances electrolyte accessibility. -OH and H 2 O (physisorbed to -OH) content in Ti 3 C 2 T x rise, too, further improving MXene pseudocapacitive performance.