Interfacial engineering of montmorillonite clay in an electrospun PVdF-co-HFP nanocomposite separator for high-performance sodium ion batteries

Abstract

Due to the natural abundance of sodium, affordability, and potential for sustainable grid-scale energy storage, sodium-ion batteries (SIBs) are being intensively researched as a potentially viable, more sustainable alternative to lithium-ion batteries (LIBs). The development of high-performance separators that deliver excellent ionic conductivity, mechanical robustness, and thermal stability is a crucial challenge for advancing SIB technology. In this work, a novel electrospun nanocomposite separator for SIB applications was developed using poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-co-HFP) mixed with montmorillonite (MMT). The homogeneous dispersion of MMT within the PVdF-co-HFP matrix was confirmed by field-emission scanning electron microscopy (FESEM), resulting in a continuous fibrous network with increased tensile strength (19 MPa). Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were used to investigate the interaction between the PVdF-co-HFP polymer and the MMT filler. Superior ionic conductivity (1.85 mS cm⁻¹) and decreased interfacial resistance were shown by electrochemical impedance spectroscopy (EIS), while galvanostatic charge–discharge (GCD) studies showed enhanced electrochemical stability and a specific discharge capacity of 167 mAh g⁻¹ at 0.1C. The material's structural integrity at high temperatures was demonstrated by improved thermomechanical stability observed in mechanical and thermal testing. These results demonstrate that MMT's synergistic integration with the PVdF-co-HFP framework significantly enhances the nanocomposite's physicochemical and electrochemical properties, making it a strong contender for future SIBs.