Abstract: Lithium sulfur (Li-S) batteries are poised to be the next generation of high-density energy storage devices. In recent years, the concept of “electrocatalysis” has been introduced into the field of Li-S batteries, and some transition metals have been proved to catalyze the electrochemical conversion reaction of sulfur species. In this study, carbon encapsulated nickel nanoparticles (Ni@C) with a specific surface area of 146 m2/g are shown to play a definitive electrocatalytic role for the sulfur cathode. With Ni@C incorporated, the Ni@C/G-S electrode achieved a better electrochemical performance than the G-S electrode. Moreover, the reversible capacity and cycle stability were further improved through chemical modifications of the carbon shell. The influence of doping with different elements on the Li-S battery performance was also investigated in detail. Higher specific capacities of 1229 mAh/g, 927 mAh/g, and 830 mAh/g were achieved at 0.2 C, 0.5 C, and 1.0 C for the N-Ni@C-G/S electrode. Besides, the B-Ni@C-G/S electrode possessed a best cycle stability.

Key words: lithium sulfur batteries, electrocatalysis, electrochemical conversion reaction, Ni@C, chemical modifications