Electrochemical characterization of a polar β-phase poly (vinylidene fluoride) gel electrolyte in sodium ion cell

A polar β-phase poly (vinylidene fluoride) (PVDF) membrane is developed through the electrospinning method. PVDF gel electrolyte for sodium ion batteries was obtained by saturating the bare porous membrane in a liquid electrolyte, 1 M NaClO₄ in EC: DEC (1:1 vol%). The physical and electrochemical characteristics of the polar β-phase PVDF membrane are explored by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Atomic force microscope (AFM), sodium ion conductivity, linear sweep voltammetry (LSV) and sodium ion transference number. The ionic conductivity of a polar β-phase PVDF gel electrolyte exhibited 9.2 × 10⁻⁴ S cm⁻¹, higher than the commercially used Celgard® 2400 membrane 0.36 × 10⁻⁴ S cm⁻¹ at ambient temperature. The electrochemical expolarations of the sodium ion half-cell (Na_2/3Fe_1/2Mn_1/2O₂) as a cathode and sodium metal as a counter electrode) conducted from PVDF gel electrolyte are analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV of the battery showed a pseudo capacitive nature. The equivalent circuit model of the sodium ion cell brought out the effect of dipole moments in the polymer chains on the battery performance.