Segmental and interfacial dynamics quantitatively determine ion transport in solid polymer composite electrolytes.

Solid polymer‐ceramic composite electrolytes (PCEs) have attracted vast attention for developing solid‐state batteries. However, slow ion transport at ambient temperature impedes unlocking their potential. Improving ionic conductivity of PCEs remains a major challenge, because ion transport mechanism in complicated composites is not currently available. This article, for the first time, demonstrates that segmental motion and interfacial polarization are directly coupled, both quantitatively determine ion transport in PCEs. Adding small‐molecule additives enhances ionic conductivity in PCEs, by increasing concentration of ions participating in transport and by equally accelerating segmental motion and interfacial dynamics. Accordingly, an ionic conductivity achieves 1.3 × 10−3 S/cm at 30°C, simultaneously with high mechanical strength and toughness (solid and flexible, shear modulus G' > 1 MPa). The results may shed a light for better analysis and improved design of solid composite electrolytes, toward meeting material demands for next‐generation electrochemical energy storage. [ABSTRACT FROM AUTHOR]