Solid/Quasi-Solid Phase Conversion of Sulfur in Lithium-Sulfur Battery

The lithium-sulfur (Li-S) battery is considered as one of the most promising options because the redox couple has almost the highest theoretical specific energy (2600 Wh kg(-1)) among all solid anode-cathode candidates for rechargeable batteries. The solid-liquid-solid mechanism has become a dominating phase transformation process since it was first reported, although this cathode mode suffers from a tough shuttle phenomenon due to the dissolution of the soluble intermediate polysulfides generated during the charging-discharging process, which causes rapid loss of energy-bearing material and shortened lifespan. For decades, tremendous efforts have been made to restrict the shuttle effect. Changing sulfur conversion to solid-solid mode or quasi-solid mode, which successfully exceed the limit of the dissolution of the intermediates, and may address the root of the problem. In this review, the main focus is on the fundamental chemistry of the solid-solid and quasi-solid phase transformation of the sulfur cathode. First, the strategies of sulfur immobilization in solid-liquid-solid multi-phase conversions as well as the pivotal influence factors for the electrochemical conversion process are briefly introduced. Then, the different routes are summarized to realize the solid-solid and quasi-solid redox mechanisms. Finally, a perspectives on building high-energy-density Li-S batteries are provided.

Automated summary

The lithium-sulfur (Li-S) battery is a promising option with high theoretical specific energy. Efforts have been made to overcome the shuttle effect by changing the sulfur conversion mode to solid-solid or quasi-solid. This review focuses on the fundamental chemistry of the solid-solid and quasi-solid phase transformation of the sulfur cathode.