Enhancing the capacitive energy storage ability of Ti3C2Tx MXene and PVA-derived carbon composite aerogels through structural disorder

MXene materials exhibit substantial energy storage capabilities owing to their high specific surface areas, tunable interlayer spacings, and excellent electrical conductivities. However, these layers are prone to re-stacking, negatively affecting the energy storage capacity of the material. Herein, through a process involving liquid nitrogen-assisted freeze-drying and subsequent annealing, Ti3C2Tx nanosheets were combined with polyvinyl alcohol (PVA) polymer chains via hydrogen bonding to produce MXene and PVA-derived carbon composite aerogels (MPAs) with microstructures ranging from ordered to disordered arrangements. The incorporation of PVA inhibited nanosheet stacking, and PVA carbonization enhanced the electrical conductivity of the aerogel. The carbonized aerogel (MPA2.0) exhibited a larger specific capacitance along with a more disordered and denser microstructure, thereby accounting for the increased capacitance due to enhanced ion storage in the more structurally disordered carbon nanopores. The optimized MPA aerogel demonstrated a high power density, along with an excellent specific capacitance (MPA2.0 = 348.14 F g- 1, 2 mV s-1 scan rate), and a cycling stability of 92.52 % after 10,000 charge/discharge cycles. Furthermore, the MPA2.0-based supercapacitor obtained an impressive energy density (37.8 Wh kg-1) and an exceptionally high power density (1800 W kg-1) at a current density of 1 A g- 1. By adjusting the PVA loading, the shrinkage and stress-strain characteristics of the microstructure during freeze-drying and carbonization were altered, and the microstructural orientation of the resulting aerogels was controlled. The increased disorder in the aerogel enhanced its capacitor energy storage ability, providing a new approach for the design of multi-component high-performance hybrid supercapacitor electrodes.