In situ fabrication of MXene/CuS hybrids with interfacial covalent bonding via Lewis acidic etching route for efficient sodium storage

Abstract

Recently, CuS has attracted intensive attention as an anode for sodium-ion batteries (SIBs) because of decent theoretical capacity based on the conversion reaction mechanism. Nevertheless, rapid capacity degradation and inferior rate performance significantly deteriorate its further application. Herein, an in situ growth strategy has been proposed to integrate CuS with highly conductive Ti₃C₂T_x MXene (T_x = –O and –Cl) through Lewis acidic molten salt etching followed by the vulcanization treatment. By virtue of the boosted Na⁺ diffusion and electronic transport kinetics, superior mechanical strain relief channel and robust interfacial covalent bonding, the as-prepared Ti₃C₂T_x/CuS anode exhibits improved cyclic performance (347.0 mA h g⁻¹ after 800 cycles at 3 A g⁻¹) and excellent rate capability (346.3 mA h g⁻¹ at 8 A g⁻¹). Furthermore, the assembled full cell by pairing the Ti₃C₂T_x/CuS anode with the Na₃V₂(PO₄)₃ cathode demonstrates excellent cyclability up to 800 cycles. More importantly, the density functional theory calculations further reveal the origin of the promoted electrochemical performance of the Ti₃C₂T_x/CuS composites. The presented strategy realizes the rational application of the Lewis acidic etching products and opens up a new door for the preparation of MXene/transition metal compounds hybrids as advanced SIB anodes.