Catalytic Effects in the Cathode of Li-S Batteries: Accelerating polysulfides redox conversion

Lithium-sulfur batteries (LSBs) are regarded as one of the most promising next-generation energy storage systems because of low cost, high energy density and high specific capacity. However, some inherent problems impede their commercial process, especially, the shuttle effect and the sluggish sulfur redox result in low Coulombic efficiency, self-discharge phenomenon, capacity fade and low sulfur utilization. Numerous efforts have been devoted on physical blocking and chemical adsorption for inhibiting of lithium polysulfides (LiPSs), which are not efficient enough for high sulfur-loading and ultra-long cycling life. In recent years, the concept of catalysis is proposed in LSBs, which can not only alleviate the shuttle effect, but also accelerate the redox kinetics and prolong the lifespan. Herein, we will highlight the catalytic effects in the cathode of LSBs comprehensively. Firstly, we introduce the electrochemistry mechanism of LSBs. Then, the main problems of LSBs are summarized in detail. Furthermore, we introduce the catalytic effects of electrode materials, and then divide the materials as metal-free and metal-based catalytic materials to give an insight in the rational design and catalytic effect of these materials. Finally, the challenge and future perspective of LSBs are discussed.