Toward a Unified Mechanistic Understanding of Polymer Electrolytes for Advanced Solid‐State Batteries

Polymer electrolytes (PEs) are widely regarded as a promising platform for solid-state batteries (SSBs), offering the potential to simultaneously achieve high energy density with improved safety. However, in current literature, PEs spanning liquid-percolated gels, liquid-assisted quasi-solids, and truly polymer-governed solids are often indiscriminately grouped as solid polymer electrolytes (SPEs), obscuring their distinct ion transport mechanisms, interfacial behaviors, and practical performance constraints, and leading to misleading performance comparisons and unrealistic expectations regarding solid-state operation. Herein, we establish a mechanistic framework that categorizes PEs into gel polymer electrolytes (GPEs), quasi-solid polymer electrolytes (QSPEs), and all-solid polymer electrolytes (ASPEs) based on their dominant ion-solvation environment and transport pathways. By systema…