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

Abstract Herein we develop a chemical etching method to produce porous two‐dimensional (2D) Ti 3 C 2 T x MXenes at room temperature in aqueous solutions. The as‐produced porous Ti 3 C 2 T x (p‐Ti 3 C 2 T 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‐Ti 3 C 2 T x /CNT films showed significantly improved lithium ion storage capabilities compared to pristine Ti 3 C 2 T 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 Nb 2 CT x and V 2 CT 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.