MXenes, a family of two-dimensional (2D) transition-metal carbide and nitride materials, are supposed to be promising pseudocapacitive materials because of their high electronic conductivity and hydrophilic surfaces. MXenes, prepared by removing the “A” elements of their corresponding MAX phases by hydrofluoric acid (HF) or LiF–HCl etching, possess abundant terminal groups like −F, −OH, and −O groups. It has been proven that the MXenes with fewer −F terminal groups and more −O groups showed a higher pseudocapacitor performance. In organic reactions, −OH and −X (X = halogen) groups could turn to ether groups in strong nucleophilic reagent. Inspired by that, herein, we report an n-butyllithium-treated method to turn the −F and −OH terminal groups to −O groups on the Ti3C2T x MXenes. Two types of Ti3C2T x MXenes prepared by either HF or LiF–HCl etching were systematically investigated, and a comparison with the traditional KOH/NaOH/LiOH-treated method was also carried out. It is found that most of the −F terminal groups on the Ti3C2T x MXenes can be successfully removed by n-butyllithium, and abundant −O terminal groups were formed. The n-butyllithium-treated Ti3C2T x MXenes show promising applications in high-performance pseudocapacitors. A record high capacitance of 523 F g–1 at 2 mV s–1 was obtained for the n-butyllithium-treated Ti3C2T x MXenes, and 96% capacity can remain even after 10 000 cycles.

We developed a new strategy to controllably oxidize Ti3C2Tx by readily adjusting the loading of ammonium persulfate, in order to turn the –F terminal groups to –O terminal groups on the Ti3C2Tx MXene, contributing to high performance.

MXene derivatives with different morphology and applications in energy convention and storage.