Controllable Etching of Ti₃SiC₂ to Produce Fluorine-Enriched, Hydrophobic 2D Titanium Carbide for Ultrastable Zinc Ion Batteries

MXenes are mainly produced via selectively etching MAX phases in aqueous F-containing solutions, commonly showing a highly hydrophilic character due to their plentiful -O and -OH terminations. However, the hydrophilic nature of MXenes may deteriorate their durability and stability as employed in humid and aqueous environments. Here, this work demonstrates a new etching approach to produce fluorine-enriched MXene Ti₃C₂F_x via selective etching of Si from Ti₃SiC₂ in sulfur hexafluoride (SF₆) gas. During the etching process, SF₆ enables the selective removal of Si species with the formation of volatile SiF₄ and efficiently reacts with the exposed surface of Ti₃C₂ slabs, affording Ti₃C₂F_x MXene with a fraction of -F termination up to 87 at.% and good hydrophobicity. Such hydrophobic Ti₃C₂F_x MXene is beneficial to suppress water-induced side reactions and decrease the Zn nucleation energy barrier, delivering a long cyclic lifespan of 1200 h and superior rate performance up to 6.4 mA cm⁻² in Ti₃C₂F_x/Zn symmetric cells. Coupled with nickel hexacyanoferrate (NiHCF) as a cathode, the zinc full cell with Ti₃C₂F_x/Zn anode exhibits good rate capabilities (58 mAh g⁻¹, 3.2 A g⁻¹) and long cycling stability up to 1000 cycles at 3.2 A g⁻¹.