Microporous membranes, methods for making these membranes, and the use of these membranes as battery separator films
AssigneeToray Tonen Specialty Separator Godo Kaisha
InventorsTakeshi Ishihara, Satoshi Miyaoka, Koichi Kono, Patrick Brant
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Abstract
The invention relates to microporous membranes having high meltdown temperature, high air permeability, and high puncture strength. The invention also relates to the production of such membranes and the use of such membranes as battery separator film.
Claims25
A membrane comprising polymethylpentene, polypropylene, and polyethylene, the membrane being microporous and having meltdown temperature ≧180.0° C., a normalized air permeability ≦75.0 seconds/100 cm3/μm, and a pin puncture strength ≧0.90×102 mN/μm.
A process for producing a microporous membrane, comprising:
- (1) extruding a mixture of diluent and polymer, the polymer comprising an amount A1 of polymethylpentene, an amount A2 of polypropylene, and an amount A3 of polyethylene, wherein 5.0 wt. %≦A1<25.0 wt. %, 5.0 wt. %≦A2<25.0 wt. %, and A3≦90.0 wt. % with the weight percents being based on the weight of the polymer in the polymer-diluent mixture;
- (2) stretching the extrudate in at least one planar direction;
- and
- (3) removing at least a portion of the diluent from the stretched extrudate.
A battery comprising an anode, a cathode, and electrolyte, and battery separator located between the anode and the cathode, the battery separator compromising (i) ≧5.0 wt. % polymethylpentene based on the weight of the battery separator, (ii) polypropylene, and (iii) polyethylene, the membrane having meltdown temperature ≧180.0° C., a normalized air permeability ≦75.0 seconds/100 cm3/μm, and a pin puncture strength ≧0.90×102 mN/μm.
Dependencies are inferred from the claim text.