Study of the interfacial stability of PVdF/HFP gel electrolytes with sub-micro- and nano-sized surface-modified silicas

The aim of the presented work was to perform a preliminary study of the physicochemical and interfacial properties of hybrid organic–inorganic gel electrolytes for Li-ion batteries based on the PVdF/HFP polymeric matrix and surface-modified silicas. Two types of silica fillers of different grain sizes (>500 nm and ∼100 nm) were used as additives. The silica particles were modified by two different functional groups, i.e. methacryloxy and vinyl ones. The gel electrolytes based on PVdF/HFP copolymer were prepared according to the so-called Bellcore two-step process. The motivation of the present work was to study more deeply those systems in terms of morphology by means of scanning electron microscopy techniques. Fillers modified with identical functional groups but differing fundamentally in the manufacturing processes were compared in terms of the impact on morphology and electrochemical performance of the resulting membranes. Interfacial properties were examined by means of impedance spectroscopy technique using Swagelok-type cells with two lithium electrodes.