Polyanion Electrointercalation Enables Termination-Tailored Oligolayer Ti₃C₂T_x MXene Synthesis in Alkali...

Tailoring surface chemistry and achieving non-destructive interlayer exfoliation are crucial for controlling MXene properties. Conventional synthesis strategies typically involve damaging intercalation processes and yield MXenes with mixed surface terminations, compromising their functionality. Herein, we propose an anodic etching strategy to produce facilely delaminated, termination-tailored Ti₃C₂T_x from Ti₃AlC₂ in low-temperature alkali-chloroaluminate (AlCl₃-NaCl-KCl) melts at 170 °C through the in situ electrochemical intercalation of polyanions (Al_nCl_{3 n +1} ^-, n ≥ 1). Oligolayer Ti₃C₂Cl_x (MSE-Ti₃C₂Cl_x) was readily achieved via further gently exfoliating the etching product, preserving the original surface chemistry featuring oxygen depletion and uniform chlorine termination. As functional coatings, MSE-Ti₃C₂Cl_x significantly extended the cycling lifespan of Zn anodes to 5500 h at 2 mA cm^-2 and 1 mAh cm^-2, attributed to the tailored surface chemistry and oligolayer-induced ordered alignment that enabled efficient Zn²⁺ capture and uniform deposition. The strategy's versatility was also demonstrated by tailoring terminations (e.g., -Br, -NH) via molten salt composition engineering, providing a non-destructive pathway for MXene surface engineering and interlayer delamination, thereby unlocking their full potential for advanced energy applications.