Porosity meets robustness: design of ultralight MXene/PVA composite foams for high-performance flexible supercapacitors

Abstract

The conventional electrodes of flexible supercapacitors often suffer from poor mechanical properties or low specific capacitance, which significantly impedes their application in flexible electronics. Herein, MXene/PVA composite foams with porous structures were controllably fabricated. Compared with many reported MXene/polymer electrodes that enhance mechanical robustness, such MXene/PVA foams are designed to simultaneously achieve high strength and superior electrochemical performance for flexible supercapacitors. On one hand, the hydrogen bonding formed between MXene sheets and PVA molecules effectively improves the mechanical performance of the composite foams. On the other hand, the construction of continuous ion transport channels in MXene/PVA foams efficiently restrains restacking of MXene sheets and promotes rapid ion transport during electrochemical reactions, thus improving the electrochemical performance. Therefore, flexible supercapacitors based on MXene/PVA foams deliver a high specific gravimetric capacitance of 240.77 F g⁻¹ and areal capacitance of 66.21 mF cm⁻², superior rate capability, and long-term cycle stability (12 000 cycles at 2.0 A g⁻¹ with 100% capacitance retention). More importantly, the device exhibits robust electrochemical stability under diverse mechanical deformations, including bending at multiple states and 1200 cycle bending endurance testing, with negligible degradation in capacitance and Coulombic efficiency.