A Compact MXene Film with Folded Structure for Advanced Supercapacitor Electrode Material

A Ti₃C₂T_x MXene film assembled by using conventional vacuum-assisted filtration has an outstanding volumetric performance due to its excellent pseudocapacitive and high density. However, the severely high energy and time consumption by vacuum-assisted filtration will limit its practical mass production as electrodes; meanwhile, the self-restacking of MXene nanosheets increases ion diffusion limitation, especially for thicker film electrodes. Herein, a simple strategy is employed to fabricate a compact and nanoporous MXene film with folded structure (CN-MX) by mechanically pressing a three-dimensional MXene aerogel, resulting in an increased packing density and electrical conductivity (8681 S m^-1) while retaining sufficiently abundant ion-accessible active sites. In addition, the formed highly interconnected nanopore channels can facilitate more rapid ionic and electronic transport. When applied as additive-free electrodes for supercapacitors, the CN-MX delivers a comparable volumetric capacitance and much improved rate capability performance compared to the MXene film fabricated by vacuum-assisted filtration. More impressively, it can still exhibit an attractive volumetric capacitance even at practical levels of mass loading (above 10 mg cm^-2). This study opens a feasible avenue forward toward commercial applications of MXene in portable and compact storage devices.