Efficient Sodium Storage in Cu 1.96 S@NC Anode Achieved by Robust S─C Bonds and Current Collector Self-Induced Forming Cu 2 S Quantum Dots.

Transition metal sulfides are investigation hotspots of anode material for sodium-ion batteries (SIBs) due to their structural diversity and high storage capacity. However, they are still plagued by inevitable volume expansion during sodiation/desodiation and an unclear energy storage mechanism. Herein, a one-step sulfidation-carbonization strategy is proposed for in situ confined growth of Cu 1.96 S nanoparticles in nitrogen-doped carbon (Cu 1.96 S@NC) using octahedral metal-organic framework (Cu-BTC) as a precursor and investigate the driving effect of Cu current collector on its sodium storage. The generation of S─C bonds in Cu 1.96 S@NC avoids the volume change and structural collapse of Cu 1.96 S nanoparticles during the cycling process and improves the adsorption and transport capacity of the material for Na + . More exciting, the Cu species in the Cu current collector are self-induced forming Cu 2 S quantum dots to enter the original anode material during the initial few charging and discharging cycles, which unique small-size effect and abundant edge-active sites enhance the energy storage capacity of Cu 1.96 S. Thus, the Cu 1.96 S@NC exhibits a superior first discharge capacity of 608.56 mAh g -1 at 0.2 A g -1 with an initial Coulomb efficiency (ICE) of 75.4%, as well as provides excellent rate performance and long cycle durability up to 2000 cycles.