Sodium- ion conducting PEO-PEMA based composite solid polymer electrolytes: structural, dielectric and electrochemical characteristics

Abstract

In the present study, we report the synthesis of sodium-ion (Na⁺) conducting blended solid polymer electrolytes (PEO-PEMA) by the standard solution casting technique with SiO₂ filler. X-ray diffractometer (XRD) and Field emission scanning electron microscopy (FESEM) confirmed the complete salt dissociation and provided evidence of the composite formation. Furthermore, Fourier transform infrared spectroscopy (FTIR) supported the XRD analysis. Impedance spectroscopy (EIS), linear sweep Voltammetry (LSV), and i-t curve characteristics are used to investigate the electrical properties. The high conductivity value (~ 8×\({10}^{-5}\) S cm⁻¹ ) was obtainded for a 2% concentration of SiO₂ by wt. It also exhibited a high operating voltage range (4.3 V) and a high value of transference number (0.99), which makes it a potential candidate for energy storage devices. The degree of polarization and supports the high conductivity, suggesting that ion migration is mainly due to the segmental motion of the polymer chain. The shifting of loss tangent peaks toward the higher frequency window reflects the reduction of relaxation time. Loss tangent analysis confirmed this decrease in relaxation time with nanofiller addition. Furthermore, complex conductivity analysis showed a strong dependence on nanofiller content. The sigma representation (σ′′ versus σ′) validated the decrease in relaxation time, which agrees with the loss tangent analysis. Ion transport parameters (n, μ, D) were evaluated using the Bruce-Vincent (B-M) method, electrochemical impedance spectroscopy, and FTIR analysis. All the transport parameters showed good agreement with each other. Finally, an ion transport mechanism based on experimental findings was proposed to examine the possible interactions in the polymer nanocomposite matrix.