Effect of nano-clay on ionic conductivity and electrochemical properties of poly(vinylidene fluoride) based nanocomposite porous polymer membranes and their application as polymer electrolyte in lithium ion batteries

Hybrid organic-inorganic polymer gel electrolytes (PGEs) based on polymer-clay nanocomposite microporous membrane containing 1 M lithium hexafluorophosphate (LiPF₆) in ethylene carbonate/diethyl carbonate (EC/DEC) are fabricated and their electrochemical characteristics in lithium ion batteries are studied. Poly(vinylidene fluoride) (PVdF)-clay nanocomposite membrane containing different clay loading are prepared by phase inversion method. Aqueous suspension of montmorrillonite (MMT) clay in dimethyl acetamide (DMAc) is used as the nano-clay. The morphology of the clay dispersion with sonication time is studied by environmental scanning electron microscope (E-SEM). The intercalation/exfoliation of polymer-clay nanocomposite is characterized by X-ray diffraction (XRD). Differential scanning calorimetry (DSC) and thermal gravimetric analysis are used for the evaluation of thermal properties. DSC analysis shows that crystallinity of nanocomposite decreases with increasing nano-clay content. The effect of clay on the membrane morphology, ionic conductivity and electrochemical properties of the PGEs in lithium ion rechargeable batteries are studied and results are compared. Incorporation of 2 wt.% nano-clay in PGE enhances its ionic conductivity from 0.78 to 3.08 mS cm^-1 at room temperature. Li-ion half cell comprising of Li/PVdF-clay_{(2 wt.%)}-PGE/LiMn₂O₄ delivers high charge-discharge capacity (∼120 mAh g^-1) and shows stable cycle performance.