Abstract: Carbon-constraint NiS₂ nanomaterials (NiS₂@C) with core-shell structure were successfully synthesized by a combination method of arc evaporation and solid-state vulcanization. Characterization results of X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy show that there existed rich defects in the carbon shell. The thickness of the carbon shell was 4 nm, and the diameter of the NiS₂ core was 28 nm. The electrochemical performance of NiS₂@C electrode was measured as the cathode materials for Na-S batteries. The Coulombic efficiency of NiS₂@C electrode remained above 90% after four cycles at a current density of 100 mA·g^-1, and the reversible specific capacity of 106.8 mAh·g^-1 remained after 500 cycles, which showed high cyclic stability. The electrochemical impedance analysis reveals that the electrode reactions were accelerated and the dynamic equilibrium of ion migration at the interface was maintained due to its good electronic conductivity and excellent structural stability by the constraint of the external carbon layer.

DOI: 10.11901/1005.3093.2019.431