Porous Two-Dimensional Transition Metal Carbide (MXene) Flakes for High-Performance Li-Ion Storage

Herein we develop a chemical etching method to produce porous two-dimensional (2D) Ti₃C₂T_x MXenes at room temperature in aqueous solutions. The as-produced porous Ti₃C₂T_x (p-Ti₃C₂T_x) have larger specific surface areas and more open structures than their pristine counterparts, and can be fabricated into flexible films with, or without, the addition of carbon nanotubes (CNTs). The as-fabricated p-Ti₃C₂T_x/CNT films showed significantly improved lithium ion storage capabilities compared to pristine Ti₃C₂T_x based films, with a very high capacity of ≈1250 mAh g⁻¹ at 0.1 C, excellent cycling stability, and good rate performance (330 mAh g⁻¹ at 10 C). Using the same chemical etching method, we also made porous Nb₂CT_x and V₂CT_x MXenes. Therefore, this study provides a simple, yet effective, procedure to introduce pores into MXenes and possibly other 2D sheets that in turn, can enhance their electrochemical properties.