Tailoring Oxygen-Depleted and Unitary Ti₃C₂T_x Surface Terminals by Molten Salt Electrochemical Etching Enables...

Two-dimensional Ti₃C₂T_x MXene materials, with metal-like conductivities and versatile terminals, have been considered to be promising surface modification materials for Zn-metal-based aqueous batteries (ZABs). However, the oxygen-rich and hybridized terminations caused by conventional methods limit their advantages in inhibiting zinc dendrite growth and reducing corrosion-related side reactions. Herein, -O-depleted, -Cl-terminated Ti₃C₂T_x was precisely fabricated by the molten salt electrochemical etching of Ti₃AlC₂, and controlled in situ terminal replacement from -Cl to unitary -S or -Se was achieved. The as-prepared -O-depleted and unitary-terminal Ti₃C₂T_x as Zn anode coatings provided excellent hydrophobicity and enriched zinc-ionophilic sites, facilitating Zn²⁺ horizontal transport for homogeneous deposition and effectively suppressing water-induced side reactions. The as-assembled Ti₃C₂S_x@Zn symmetric cell achieved a cycle life of up to 4200 h at a current density and areal capacity of 2 mA cm^-2 and 1 mAh cm^-2, respectively, with an impressive cumulative capacity of up to 7.25 Ah cm^-2 at 5 mA cm^-2//2 mAh cm^-2. These findings provide an effective electrochemical strategy for tailoring -O-depleted and unitary Ti₃C₂T_x surface terminals and advancing the understanding of the role of specific Ti₃C₂T_x surface chemistry in regulating the plating/stripping behaviors of metal ions.