Tailored Polyphosphazene Matrices with Cross-Linking Functionality for High-Performance Solid Polymer Electrolytes with Enhanced Ionic Conductivity

 To address the key requirements for lithium secondary battery solid polymer electrolytes (SPEs), the study has developed a novel class of ion-conductive, cross-linkable polyphosphazenes. Through a facile and precise chemical modification strategy, functional groups were grafted onto the polyphosphazene backbone to achieve a balance between mechanical robusteness and rapid ionic transport. These synthesized polymers were readily processed into self-supporting, thermally stable SPE films without the need for liquid solvents. Benefiting from the highly flexible -P=N- main chain and highly conductive pendant groups, the fully solid-state films delivered a remarkable ionic conductivity of ~3.78 × 10⁻⁵ S·cm⁻¹ at room temperature (25 °C). These findings suggest that the proposed inorganic backbone-based polyphosphazene platform provides a highly viable and safe alternative for high-performance, next-generation lithium secondary batteries.