Review on polymer electrolytes for lithium-sulfurized polyacrylonitrile batteries

Lithium-sulfur (Li-S) batteries are deemed as the next generation of energy storage devices due to high theoretical specific capacity (1675 mAh g⁻¹) and energy density (2600 Wh kg⁻¹). However, the commercial application has always been constrained by lithium polysulfide (LiPSs) shuttling effects and still has a long way to go. Sulfurized polyacrylonitrile (SPAN) is a promising alternative candidate to replace traditional sulfur cathode and is conducive to eliminating LiPSs by realizing “solid-solid” direct conversion in conventional carbonate electrolytes. However, an over 25% irreversible capacity loss is exhibited inevitably in the first discharge process, the inherent structure of SPAN and the related reaction mechanism remain unclear. In this review, the structure characteristics and electrochemical behaviors of SPAN are summarized for better interpreting current knowledge and favoring the design of high performance materials. In the past few decades, many problems in traditional Li-S batteries have been solved by improving electrolytes. Polymer electrolytes (PEs) have been widely used due to structural designability, multi-functionality, exceptional chemical stability, and excellent processability. Surprisingly, the relevant researches on PEs compatible with SPAN remains limited currently. Therefore, the recent modification strategies of gel polymer electrolytes and solid polymer electrolytes in Li-SPAN batteries are introduced in terms of Li⁺ transfer and interface engineering, the design principles are concluded, the specific challenges encountered by polymer-based electrolytes are summarized and the instructive directions for future research on PEs are demonstrated, facilitating the commercialization of Li-SPAN batteries.