The Critical Role of Functionalised Filler in Li‐Polymer Composite Electrolyte: Ionic Conductivity and Dielectric Relaxation Behavior Study

ABSTRACT Herein, an alternative structural design approach for a polymer composite electrolyte based on a PVDF host and a PVP‐functionalised LATP ceramic filler has been proposed. The results demonstrate that the PVP‐coated surface filler interacts with the PVDF host, enhancing the polar properties of the polymer matrix and promoting Li‐salt dissociation. Similarly, residual DMF solvent contributes to the dissociation of LiTFSI, forming a complex with a locally high concentration of Li + and ionic liquid properties. Furthermore, the PCE containing 10 wt% PVP‐LATP filler exhibits maximum ionic conductivity (1.8 × 10 −4 S cm −1 at 30°C). However, increasing the filler loading decreases the ionic conductivity due to the inhomogeneous dispersion of the filler particles. The maximum ionic conductivity correlates with the minimum relaxation time ( τ tanδ ) at 30°C. This supports the idea that the functionalised filler enhances the flexibility of the polymer chain's segmental mobility, thereby facilitating ion hopping in the host matrix. Finally, the ac frequency‐dependent conductivity analysis of the PCE membranes shows that the conduction mechanism follows the correlated barrier hopping (CBH) model.