Boosting Li⁺ Conductivity and Oxidation Stability of Solid Polymer Electrolytes Using a Sustainable Montmorillonite-Based Ion Conductor

Solid polymer electrolytes (SPEs), such as poly(ethylene oxide) (PEO), have garnered significant attention due to their compatibility with commercial lithium-ion (Li⁺) battery manufacturing, yet their application is limited by poor Li⁺ transport efficiency and low oxidation stability. We hypothesize that these challenges can be addressed by designing ion-conductors that interact with the terminal −OH groups of PEO chains. To verify this, we developed a sustainable ion-conductor (LSM) by intercalating lithium bis(trifluoromethanesulfonyl)imide and succinonitrile into the interlayer space of montmorillonite (MMT) nanosheets. The LSM ion-conductor significantly enhanced Li⁺ conductivity, Li⁺ transference number, and oxidation stability of PEO-based SPEs. Li metal batteries with PEO/LSM SPEs and LiFePO₄ cathode showed superior rate performance and cycling stability. Pouch batteries with high-voltage NCM811 cathode maintained stable operation after repeated mechanical deformation. This study provides new insights into designing advanced SPEs for Li metal batteries via a straightforward intercalation strategy using naturally abundant 2D nanomaterials.