An interfacial covalent bonding coupled ultrafine CuS-nanocrystals/MXene heterostructure for efficient and durable magnesium storage

Abstract

Rechargeable magnesium batteries (RMBs) hold great potential for large-scale energy storage due to the dendrite-free deposition and high theoretical volumetric capacity of the magnesium anode. However, the sluggish kinetics and poor reversibility of cathodes hinder their development in terms of high capacity and long-term cycling stability. Herein, a confined in situ growth strategy is presented to construct a novel copper sulfide (CuS)/delaminated Ti₃C₂T_x MXene (d-Ti₃C₂T_x) heterostructure, where ultrafine CuS nanocrystals are tightly anchored on the d-Ti₃C₂T_x substrate through S–Ti–C interfacial covalent bonding. Density functional theory (DFT) calculations demonstrate the strong interaction not only enhances the conductivity of CuS, enabling rapid charge transfer, but also effectively maintains structural stability during the charge/discharge process. As a result, the CuS/d-Ti₃C₂T_x heterojunction exhibited high reversible specific capacity (336.5 mA h g⁻¹) and outstanding rate capability. Remarkably, an impressive long-term cycling performance with a stable capacity of 92.2 mA h g⁻¹ at 1000 mA g⁻¹ was achieved over 1000 cycles. This study demonstrates the feasibility of integrating CuS with d-Ti₃C₂T_x MXene and provides an avenue for designing high-performance cathode materials for RMBs.