Solid Polymer Electrolytes for All‐Solid‐State Lithium–Sulfur Batteries: Different Designs Dependent on Their Interaction with Sulfur Cathodes

Nonflammable and flexible solid polymer electrolytes (SPEs) are widely studied to improve the safety of lithium-sulfur batteries (LSBs). Studies on SPE-based LSBs primarily focus on addressing issues stemming from poor SPE properties, Li dendrites, and "shuttle effect" of polysulfides. Currently, strategies from SPE-based lithium batteries (without sulfur cathodes) and liquid electrolyte (LE)-based LSBs (without SPEs) are the most commonly employed approaches to tackle above issues. These strategies are designed without taking into account the problems caused by the coexistence of SPEs and sulfur cathodes, resulting in SPE-based LSBs exhibiting significantly inferior performance than liquid-electrolyte-based LSBs. Therefore, the strategies for SPE-based LSBs necessitate different designs. However, no reviews have focused on the aforementioned differences and analyzing their corresponding causes thus far, which is unfavorable for the development of this field. Herein, the emerging advances in SPE-based LSBs are comprehensively reviewed. In particular, for the first time, the different designs and their corresponding causes are comprehensively discussed. These causes include the high adsorption strength of SPEs with polysulfides, corrosion of polysulfides to barrier layers, deterioration of the ionic conductivity of SPEs, and defective interfaces between cathodes and SPEs. Finally, several pressing challenges and future prospects for the field are discussed.