Electroactive poly(vinylidene fluoride) fluoride separator for sodium ion battery with high coulombic efficiency

• Optimized electrospinning process to get bead free, electroactive phase PVDF
• The EaSE has an Na ion transfer of 98.30% and an ionic conductivity of 7.38 × 10− 4 S cm− 1.
• The sodium cell with EaSE using Na0.66Fe0.5Mn0.5O2 as cathode and Na metal as anode performed with 92% coulombic efficiency

Electroactive separators are recent interest in self-charging rechargeable batteries. In this study, electrospun polyvinylidene fluoride (PVDF) is characterized as an electroactive separator for Na-ion batteries. The intrinsic β-phase with high porosity of the separator is confirmed from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and Atomic Force Microscopy (AFM) studies. The electroactive separator is immersed in 1M NaClO4-ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 by weight) solution. The physicochemical characteristics of electroactive separator electrolyte (EaSE) were investigated using sodium ion conductivity, ion transference number and contact angle measurements. Linear and cyclic voltammetry studies were also carried out for the electrolyte system to evaluate oxidation stability window. The inherent β-phases of the separator as obtained by electrospinning has an ionic conductivity of ~ 7.38 × 10− 4 S cm− 1 under ambient condition. Sodium ion cell made from EaSE with Na0·66Fe0.5Mn0·5O2 as cathode and Na metal as anode has displayed a stable cycle performance with a coulombic efficiency of 92% after 90 cycles.