Molten Salts Etching Route Driven Universal Construction of MXene/Transition Metal Sulfides Heterostructures with Interfacial Electronic Coupling for Superior Sodium Storage

Abstract

The MXene-based heterostructures have recently attracted great interest as anode materials for sodium-ion batteries (SIBs). Nonetheless, the complicated and harsh preparation process impedes their further commercialization. Herein, a novel, safe, low-destructive, and universal strategy for rationally fabricating Ti₃C₂T_x MXene/transition metal sulfides (MS_y) heterostructures is presented via Lewis acidic molten salts etching and subsequent in situ sulfurization treatment. Benefiting from the interfacial electronic coupling between highly conductive Ti₃C₂T_x MXene (T_x = O and Cl) and MS_y (M = Fe, Co and Ni), the heterostructures possess remarkably improved electronic conductivity, promoted Na⁺ migration kinetics, and robust architectures. As a proof-of-concept demonstration, the Ti₃C₂T_x/FeS₂ heterostructure demonstrates outstanding rate performance (456.6 mAh g⁻¹ at 10 A g⁻¹) and long-term cyclic stability (474.9 mAh g⁻¹ after 600 cycles at 5 A g⁻¹) when serving as SIB anodes. Impressively, a sodium-ion full battery with Ti₃C₂T_x/FeS₂ anode delivers an excellent reversible capacity of 431.6 mAh g⁻¹ after 1000 cycles at 3 A g⁻¹. Moreover, the dual sodium storage behavior of Ti₃C₂T_x/FeS₂ heterostructure and underlying mechanism toward exceptional electrochemical performance are revealed by comprehensive characterizations and theoretical calculations. Based on the full utilization of molten salt etching products, the present work offers new insight into the fabrication of MXene-based heterostructures.