Dispersed Cu2S/Ni3S2 nanoparticles encased in carbon layers as high-performance anodes for sodium-ion batteries

Owing to high theoretical capacity, nickel sulfides are competitive anode materials for sodium-ion batteries (SIBs). Nevertheless, their developments are greatly obstructed by low conductivity, as well as poor cycle stability resulted from structural pulverization and collapse. Herein, dispersed Ni3S2 nanoparticles (20-30 nm) are encased in carbon shells (NiSx@C) through a simple hydrothermal reaction and carbon coating process. The dispersed nanoparticles provide short ion transport channels and a large number of active sites for sodium storage, and carbon coating can enhance the conductivity and structural stability of materials. Meanwhile a small amount of copper is added to further increase the capacity of materials based on synergistic effect and increase of defects. The Cu2S/NiSx@C composite electrode exhibits an outstanding pseudocapacitive behavior in reaction kinetics. Evaluated as an anode for SIBs, such electrode performs a high rate capability of 343.8 mAh g(-1)- at 5 A g(-1) and excellent cycling performance of 485.3 mAh g(-1) at 0.1 A g(-1) after 100 cycles and 350.4 mAh g(-1) at 0.5 A g(-1) after 500 cycles. This work shows that nickel sulfides are promising materials for sodium-ion storage through structural design and modification, and would be of great significance to promote the development of advanced SIBs.

Automated summary

This work presents a strategy to enhance the conductivity and stability of nickel sulfides for sodium-ion storage by preparing dispersed Ni3S2 nanoparticles encased in carbon shells. The Cu2S/NiSx@C composite electrode shows outstanding performance in pseudocapacitive behavior, exhibiting high rate capability and excellent cycling performance for SIBs. This study signifies the promising application of nickel sulfides in advanced sodium-ion batteries through structural design and modification.