PIM‐1 as a Multifunctional Framework to Enable High‐Performance Solid‐State Lithium–Sulfur Batteries

Poly(ethylene oxide) (PEO) is a promising solid electrolyte material for solid‐state lithium–sulfur (Li–S) batteries, but low intrinsic ionic conductivity, poor mechanical properties, and failure to hinder the polysulfide shuttle effect limits its application. Herein, a polymer of intrinsic microporosity (PIM) is synthesized and applied as an organic framework to comprehensively enhance the performance of PEO by forming a composite electrolyte (PEO‐PIM). The unique structure of PIM‐1 not only enhances the mechanical strength and hardness over the PEO electrolyte by an order of magnitude, increasing stability toward the metallic lithium anode but also increases its ionic conductivity by lowering the degree of crystallinity. Furthermore, the PIM‐1 is shown to effectively trap lithium polysulfide species to mitigate against the detrimental polysulfide shuttle effect, as electrophilic 1,4‐dicyanooxanthrene functional groups possess higher binding energy to polysulfides. Benefiting from these properties, the use of PEO‐PIM composite electrolyte has achieved greatly improved rate performance, long‐cycling stability, and excellent safety features for solid‐state Li‐S batteries. This methodology offers a new direction for the optimization of solid polymer electrolytes. The unique molecular structure of polymer of intrinsic microporosity (PIM‐1) not only enhances the mechanical properties of poly(ethylene oxide) (PEO) electrolyte but also increases its ionic conductivity by lowering crystallinity. Moreover, polysulfide shuttling is also retarded due to the higher binding energy between polysulfides and electrophilic functional groups. Thus, the PEO‐PIM composite electrolyte enables high‐performance solid‐state lithium–sulfur batteries.