A Defective Disc-Like Cu_1.96S Anode Material with the Efficient Cu Vacancies for High-Performance Sodium-Ion Storage

Due to their significant capacity and reliable reversibility, transition metal sulphides (TMSs) have received attention as potential anode materials for sodium-ion batteries (SIBs). Nonetheless, a prevalent challenge with TMSs lies in their significant volume expansion and sluggish kinetics, impeding their capacity for rapid and enduring Na⁺ storage. Herein, a Cu_1.96S@NC nanodisc material enriched with copper vacancies is synthesised via a hydrothermal and annealing procedure. Density functional theory (DFT) calculations reveal that the incorporation of copper vacancies significantly boosts electrical conductivity by reducing the energy barrier for ion diffusion, thereby promoting efficient electron/ion transport. Moreover, the presence of copper vacancies creates ample active sites for the integration of sodium ions, streamlines charge transfer, boosts electronic conductivity, and, ultimately, significantly enhances the overall performance of SIBs. This novel anode material, Cu_1.96S@NC, demonstrates a reversible capacity of 339 mAh g^-1 after 2000 cycles at a rate of 5 A g^-1. In addition, it maintains a noteworthy reversible capacity of 314 mAh g^-1 with an exceptional capacity retention of 96% even after 2000 cycles at 20 A g^-1. The results demonstrate that creating cationic vacancies is a highly effective strategy for engineering anode materials with high capacity and rapid reactivity.