Chemical-Combined Ball-Milling Synthesis of Fluorine-Free Porous MXene for High-Performance Lithium Ion Batteries

MXenes exhibit great promise for energy storage. Fluorine-based reagents have always been the mainstream of MXenes preparation. However, the high toxicity of fluorine-containing reagents is the bottleneck restricting the development and application of MXene. Furthermore, layered MXenes are easily stacked, reflecting unsatisfactory performance of lithium ion batteries. Considering the shortcomings of the fluorine-containing reagent etching MAX, it has aroused great research interest in exploring the morphology and fluorine-free synthetic method. Here, Ti3C2 with a unique hierarchical porous structure (P-Ti3C2) was first prepared by a fluorine-free chemical-combined ball-milling method. The as-produced P-Ti3C2 shows a significantly increased specific surface area, which is 8 times higher than that of HF-Ti3C2 obtained from traditional HF treatment. Benefitting from the porous structures as well as fluorine-free terminal groups, P-Ti3C2 exhibits excellent electrochemical performances, for example, high reversible capacity of 310 mAh g–1 at a current density of 100 mA g–1, better than that of HF-Ti3C2. Especially, after cycling 3000 cycles at a high current density of 1 A g–1, a reversible capacity of 97 mA h g –1 could be steadily maintained. Therefore, this simple strategy could be extended as a universal approach for preparing various fluorine-free and porous MXenes with potential performance.