S-sphere/C/MoS2 composite for high-performance Lithium–Sulfur batteries

Abstract

With the development of energy storage systems, Lithium–Sulfur (Li–S) batteries represent an ideal choice due to extremely high theoretical specific capacity (1675 mAh/g−1) and energy density (2500 Wh/kg−1) of Sulfur cathode. However, it is a challenge to solve the electroconductibility of Sulfur, shuttle effect of polysulfide and volume expansion. Although tremendous works have been carried out to improve the capacity, the practical application of Li–S batteries is still hindered by low electroconductibility of Sulfur, poor cycle life and low rate performances. Herein, S-sphere/C/MoS2 composite was prepared by the melt diffusion method for the nano-sulfur host. In comparison with the large particles sublimate Sulfur, nano-sulfur particles can shorten the diffusion path of ions and facilitate the smooth diffusion of Li+ into the interior of Sulfur at high discharging current densities. Therefore, the formation of insulating Li2S2 and Li2S is delayed. Moreover, the Few-layered MoS2 can be used to achieve chemical adsorption with Lithium polysulfide (LiPS) and Carbon spheres has good electronic conductivity, thus the rate performance and the cyclic capability of Li–S batteries have been improved. The S-sphere/C/MoS2 composite exhibits an initial discharging capacity of 1016.3 mAh/g−1 at 0.1 C, and a high capacity of 753 mAh/g−1 at 1 C with a low fade rate of 0.211%. These indicate that the S-sphere/C/MoS2 composite has good electrochemical performance and is expected to be a candidate electrode for Li–S batteries industrialization in the future.