Three-dimensional ordered and porous Ti3C2Tx@Chitosan film enabled by self-assembly strategy for high-rate pseudocapacitive energy storage

MXenes with outstanding electric conductivity and surface chemistry are promising materials for future energy storage. However, processing MXenes into free-standing films can lead to restacking and aggregation of the 2D nanosheets, which limits the ionic kinetics within materials. Current solutions are difficult for films to satisfy both rate performance and flexibility. Herein, we propose a novel chitosan-induced self-assembly strategy to construct MXene into flexible Ti3C2Tx@Chitosan films with 3D ordered and porous structure. The interconnected 3D network provides fast transport channels for electrons and electrolyte ions. Therefore, the film exhibits excellent rate capability and low mass-loading dependence. The Ti3C2Tx@Chitosan film with a high mass loading of 4 mg−2 delivers a capacitance of 245.2F g−1 at 2 V s−1, which demonstrates 57.1% capacitance retention with 400-fold scan rate increase. The crosslinked chitosan is interconnected and interwoven with MXene nanosheets, resulting in enhanced mechanical strength and flexibility for Ti3C2Tx@Chitosan. Furthermore, by applying Ti3C2Tx@Chitosan film to assemble flexible symmetrical supercapacitors, an ultra-high power density of 143.2 μWh cm−2 can be attained. This work develops a simple route for assembling 2D MXene into 3D high-flexible porous films as state-of-the-art electrodes for high-rate pseudocapacitive energy storage.