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

Abstract

Abstract 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\xa0nm) 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\xa0A\xa0g−1 and excellent cycling performance of 485.3 mAh g−1 at 0.1\xa0A\xa0g−1 after 100 cycles and 350.4 mAh g−1 at 0.5\xa0A\xa0g−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.