Role of green-synthesized SiO2 nanoparticles in modulating the electrochemical and mechanical properties of poly(vinyl alcohol)/LiClO4 solid polymer electrolytes

Poly(vinyl alcohol) (PVA)-based solid polymer electrolytes doped with lithium perchlorate (LiClO4) and reinforced with green-synthesized SiO2 nanoparticles derived from bamboo leaves were prepared by solution casting. Composites containing 0, 0.5, 1.0, and 2.5 wt. % SiO2 in a PVA/20 wt. % LiClO4 matrix were systematically characterized by FTIR, XRD, field emission scanning electron microscopy, TEM, differential scanning calorimetry, thermogravimetric analysis, AC impedance spectroscopy, and universal tensile testing. Structural analyses confirmed successful complexation, increased amorphous nature, and uniform filler dispersion at low loadings, transitioning to agglomeration at higher content. Mechanical testing showed the pristine film exhibited the highest ultimate tensile strength (≈23.5 MPa) and superior ductility. Unexpectedly, the pristine PVA/LiClO4 film exhibited the highest room-temperature ionic conductivity (2.80 × 10−4 S cm−1), which decreased progressively with SiO2 addition. Dielectric, modulus, and relaxation studies revealed that the bamboo-derived SiO2 acted as an insulating barrier, restricting segmental motion and trapping charge carriers rather than facilitating ion transport. This source-specific behavior highlights the critical influence of nanoparticle surface chemistry on electrolyte performance, establishing the unfilled PVA/LiClO4 composition as the optimal system among those investigated for potential applications in solid-state lithium batteries.