Dielectric relaxation, Li-ion transport, electrochemical, and structural behaviour of PEO/PVDF/LiClO4/TiO2/PC-based plasticized nanocomposite solid polymer electrolyte films

Poly(ethylene oxide) (PEO)/poly(vinylidene fluoride) (PVDF) (75/25 wt/wt%) host polymer blend matrix, lithium perchlorate (LiClO4) ionic dopant (25 wt%), titanium dioxide (TiO2) inorganic nanofiller (10 wt%), and propylene carbonate (PC) plasticizer (10-30 wt%) based different compositions electrolyte films were prepared. The morphological study reveals that the spherulite and fibril-like microstructures of the 75PEO/25PVDF-25 wt % LiClO4 primary electrolyte film turned highly complex having cracks, pores, and some crumpled fluffier structures when TiO2 and PC were added. X-ray diffractograms of these films confirm their semicrystalline structures having alpha-, beta-, and gamma-phase crystals of PVDF, and also the characteristic crystallites of PEO and TiO2 nanoparticles. Complex dielectric permittivity, dielectric loss tangent, ac electrical conductivity, impedance, and electric modulus spectra over the frequency range 20 Hz-1 MHz at 27 degrees C were reported and analyzed for confirmation of various polarization processes and relaxations in these heterogeneous electrolyte materials. It is found that the dc ionic conductivity of these materials is principally ruled by the ions coupled chain segmental dynamics which promotes the cations hopping mechanism. The results confirm that the electrolyte films containing 10 wt% TiO2 along with PC >= 20 wt% have dc ionic conductivity more than two times higher as compared to that of the primary electrolyte film. All these electrolyte films have considerable electrochemical performance and nearly unity value of total ion transference number. The fascinating ionic conduction and electrochemical properties confirm these flexible-type electrolytes as appealing materials for advances in all-solid-state lithium ion conducting devices.