Patent ID: 6743876
Filing Date: 2004-06-01
Classification: C08F,H01M,Y02E

Abstract:
An improved electrochemical cell having a positive electrode, an absorber-separator and a negative electrode wherein at least either one of the electrodes comprises a vinylidene fluoride polymer having an electrolyte material combined therewith and/or said absorber-separator comprises a vinylidene fluoride polymer having an electrolyte material combined therewith wherein the improvement comprises the vinylidene fluoride polymer consisting essentially of a copolymer of vinylidene fluoride and hexafluoropropylene containing a maximum of about 24 weight percent hexafluoropropylene, having a uniform distribution of hexafluoropropylene residues between chains; wherein the copolymer containing up to 8 weight percent nominal hexafluoropropylene content has weight percent extractables within plus or minus 1.5% of the percent by weight extractables calculated by an equation selected from the group consisting of:Wt. % Extractables=1.7(HFP mole %)âˆ’3.2, and Wt. % Extractables=âˆ’1.2+1.5(HFP mole %)âˆ’8Ã—10âˆ’6(Mn) when HFP mole % is calculated by Method A where Mn is number-average molecular weight; and wherein the copolymer containing 8 weight percent or greater nominal hexafluoropropylene content has a DSC melting point equal to or less than that defined by the equation:DSC melting point Â°C.=166.7âˆ’2.9(HFP wt %) when the HFP wt % is determined by Method B.