Gelation and melting point depression in PVDF-based gel electrolytes

摘要: This thesis presents the designs and results of experimental investigations into gelation melting point behaviour for polymer gel electrolytes. The study used one most prominent types materials in commercial world—polyvinylidene fluoride-based (PVDF) electrolytes—focussing on effects temperature composition properties its solid While PVDF was as matrix, propylene carbonates (PC) diethyl carbonate (DEC) were solvents. Lithium tetrafluoroborate (LiBF4) lithium bisoxalatoborate (LiBOB) electrolyte salts. Gelation from molten solutions studied isothermally, using 30% PVDF/PC unsalted PVDF/PC/ LiBF4 salted gels to investigate effect salt addition behaviour. Crystallisation subsequent also investigated. Varying involved changing concentration, solvent nature concentration. measured included structure morphology, ionic conductivity. The techniques DMTA, DSC, WAXS, dielectric spectroscopy optical microscopy properties. It found that time is significantly increased at higher temperatures, reduces any given whilst extending process temperatures. occurs without crystallisation high whereas it induced by low sharp cut-off gives two distinct windows, within which via different mechanisms. The has raise about 25C 1M LiBF4, hence enhance thermal stability, attributed affecting Flory interaction parameter. Salt crystal size pore size, this nucleating molecules. incorporation up 40% DEC increases 5 10 C, accompanied a negligible reduction conductivity, shows possible route further enhancing