Investigation of flexible electrochemical storage with Li+/PVdF-HFP/PEO blend

Abstract

ABSTRACT Design and development of lithium ion batteries with flexible solid polymer electrolyte along with high ionic conductivity is crucial and challenging so as to protect from electrical short circuits within electrochemical devices. The present research work describes the fabrication of lithium based solid polymer electrolytes (LSPEs) using polymer blends of poly (vinylidene fluoride- hexafluoropropylene) (PVdF-HFP), poly (ethylene oxide) (PEO) with selective weight ratios of lithium trifluoromethanesulfonate (LiCF3SO3) salt by using solution-cast approach. The scanning electron microscopy (SEM) exposed morphology of LSPE membranes depicts crosslinking of polymer network with salt elevates strong dissociation behavior of LiCF3SO3. The amorphous behavior of LSPEs explored using X-ray diffraction (XRD) crystallographs clearly accommodates reduction of average crystallite size from 10─6 m to 10─9 m. The complexation studies, bond length and force constants calculations, interaction of ions, ionic pairs and aggregates of LiCF3SO3 in LSPE films were briefly analyzed using Fourier transform infrared spectroscopy (FTIR). IR modes correspond to [δs (SO3)], [υas (SO3)], [υas (CF3)], and amorphous phase of PVdF-HFP results in complexation, whereas IR modes correspond to [δas (SO3)], [δs (CF3)], [δas (CF3)], [υs (SO3)], C=O and β-phase of PVdF-HFP attributes ionic pairs and aggregation phenomena. The [υs (SO3)] mode contribution toward ionic conductivity was detailed. The ionic conductivity (σionic) values were estimated using Electrochemical impedance spectroscopy (EIS). The σionic values were enhanced from 10─7 S/cm to 10─4 S/cm as salt concentration increases. Charge accumulation, ionic strength, and transference number analysis of LSPE membranes were investigated using Chronoamperometry and Cyclic Voltammetry. Further, we have fabricated flexible electrochemical storage device (FESD) which are accentuating carriers of smart electronics technology (SET) in terms of foldable and stretchable electronic devices. We have explored discharge characteristics of our FESD with an average discharge current of 3 mA for 25 hours and denoted using 0.04C rating.