Quasi-Solid-State Conversion Mechanism for Sulfur Cathodes

With the rapid development of electric vehicles and portable electronic products, the demand for high-energy-density battery systems is becoming more and more urgent. However, the energy density of traditional lithium-ion battery cathode materials is approaching the theoretical limit, thus it is urgent to develop the next-generation battery system with higher energy density. Sulfur cathodes possess lots of advantages, such as high energy density, natural abundance, and low cost, achieving extensive research attention. For the conventional dissolution-deposition mechanism, sulfur cathodes suffer from " shuttle effect", resulting in irreversible loss of active material, low coulomb efficiency, and poor cycle life. To alleviate the " shuttle effect", a series of strategies are usually adopted, for instance, physical confinement, chemical adsorption, and reaction accelerators, but none of them can fundamentally solve these problems. Recently, the quasi-solid-state conversion reaction of sulfur cathodes has attracted wide attention. This review discusses these approaches for constructing quasi-solid-state conversion reaction of sulfur cathodes, including the designs of microporous carbon structure, the formation of a solid electrolyte interface ( SEI) on the sulfur surface, and electrolyte engineering. The research significance is highlighted and electrochemical behaviors of the quasi-solid-state conversion reaction of sulfur cathodes are summarized. Enhancing the reactivity of sulfur cathode is an effective strategy to alleviate the intrinsic sluggish kinetics of sulfur cathodes. These strategies for quasi-solid-state conversion mechanism of sulfur cathodes are beneficial to cyclability, enabling the practical development of high-performance Li-S batteries.