Plastic PVDF-HFP electrolyte laminates prepared by a phase-inversion process
A method of making microporous separators and laminated plastic Li-ion batteries which avoids the use of a plasticizer extraction process is described. It is based on phase inversion of PVDF-HFP copolymers via film casting from solutions of the copolymer in a mixture of volatile solvent and non-solvent. The electrode and separator films so obtained exhibit a high electrolyte uptake and allow the fabrication of laminated plastic Li-ion batteries with good discharge rate capabilities. The unique and unexpected pore morphology obtained by the described process is illustrated by SEM microphotographs. Its effect on the mechanical stability of the microporous structure, which enables excellent bonding of the various layers via lamination under elevated temperature and pressure without destruction of the porosity, is discussed as well.