Routes to Electrochemically Stable Sulfur Cathodes for Practical Li–S Batteries

Abstract Lithium–sulfur (Li–S) batteries have been investigated intensively as a post‐Li‐ion technology in the past decade; however, their realizable energy density and cycling performance are still far from satisfaction for commercial development. Although many extremely high‐capacity and cycle‐stable S cathodes and Li anodes are reported in literature, their use for practical Li–S batteries remains challenging due to the huge gap between the laboratory research and industrial applications. The laboratory research is usually conducted by use of a thin‐film electrode with a low sulfur loading and high electrolyte/sulfur (E/S) ratios, while the practical batteries require a thick/high sulfur loading cathode and a low E/S ratio to achieve a desired energy density. To make this clear, the inherent problems of dissolution/deposition mechanism of conventional sulfur cathodes are analyzed from the viewpoint of polarization theory of porous electrode after a brief overview of the recent research progress on sulfur cathodes of Li–S batteries, and the possible strategies for building an electrochemically stable sulfur cathode are discussed for practically viable Li–S batteries from the authors’ own understandings.