Synergistic catalysis of MoS2-Ni3S2 heterojunctions to accelerate polysulfide conversion for high-performance Li-S battery

Abstract

The sluggish conversion kinetics of polysulfides and its unprevented dissolution will lead to loss of active sulfur and act as the biggest obstacle for the widespread use of lithium-sulfur (Li-S) batteries. However, it is a great challenge to simultaneously response to the above-mentioned multiple requirements by the adoption of single catalyst. Herein, by incorporating the merits of strong adsorption and high electron conductivity of Ni3S2 with good catalytic of MoS2, a self-supported heterojunction MoS2-Ni3S2 catalyst has been developed with uniform rod-like morphology, which can provide larger specific surface area, better compensation of electrons, more effective catalysis, and faster solid phase transformation compare to its single component catalyst. Theoretical calculations and mechanism analyses suggest that the heterojunctions exhibit a synergistic process of “adsorption-diffusion-conversion” for polysulfides (LiPSs) and effectively facilitate the liquid-solid phase conversion(Li2S6→Li2S2/Li2S). Integrating the merits of Ni3S2 and MoS2, MoS2-Ni3S2 heterojunctions catalytic cathode deliver a good cycling stability with 70 % capacity retention after 150 cycles at 0.2 C with a high sulfur loading of 5.0 mg cm−2. Therefore, this work proposed a feasible catalyst design of bi-metal sulfides heterostructure which can simultaneously meet multiple kinetics requirements of Li-S system.