A porous poly (vinylidene fluoride-co-hexafluoropropylene) based separator-cum-gel polymer electrolyte for sodium-ion battery

We report the preparation of amorphous poly (vinylidene fluoride-co-hexafluoropropylene) [P(VdF-co-HFP)] based electrospun fibrous membrane by a simple electrospinning technique for sodium-ion battery applications. The physicochemical characteristics of as-prepared fibrous polymer membranes were characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The separator-cum gel polymer electrolyte (SGPE) was activated by soaking the freshly prepared electrospun fibrous membranes in a liquid electrolyte solution containing 1 M NaClO4, EC/DEC (1:1 by volume) in an argon-filled glove box. The highly porous electrospun P(VdF-co-HFP) based polymer exhibited a high ionic conductivity of 1.13 x 10(-3)S cm(-1) at ambient temperature in contrast to the commercial Celgard membrane. The electrochemical stability window of the SGPE was above 4.8 V versus Na+/Na. Further, the electrochemical investigations of the sodium half-cell (NaNi0.5Mn0.5O2 as a cathode and unadulterated sodium as an anode) assembled from SGPE are illustrated. It showed 97% retention columbic efficiency from initial to even after 50 cycles at 0.1 C rate, however, the capacity loss is inherent for the cathode material.