Battery separators with reduced splitting propensity
AssigneeCelgard, LLC
InventorsRobert W. Callahan, Ron W. Call, Ken J. Harleson, Ta-Hua Yu
Life of this patent
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Abstract
A split resistant microporous membrane is provided for use in preparing a battery separator. The microporous membrane has a TD tensile strength to MD tensile strength ratio of from about 0.12 to about 1.2, preferably from about 0.5 to about 1. The microporous membrane is made by a process which includes the steps of preparing a film precursor by blown film extrusion at a blow-up ratio of at least 1.5, annealing the film precursor, and stretching the resultant annealed film precursor to form the microporous membrane.
Claims20
A microporous membrane comprising a microporous membrane having at least 80% by weight of a polymer selected from the group consisting of polypropylene, polyethylene, and a copolymer thereof, and having a tear resistance in the transverse direction of at least about 50 kgf/cm2, said membrane being a single layer or a co-extruded multi-layer membrane.
A microporous membrane comprising a microporous membrane having at least about 80% of polyethylene and having tear resistance in the transverse direction of at least about 50 kgf/cm2, a ratio between the tensile strength in the transverse direction and the tensile strength in the machine direction of at least about 0.120, and a Gurley value of less than about 100 seconds, said membrane being a single layer or a co-extruded multi-layer membrane.
A microporous membrane which comprises at least 80% by weight of a polymer selected from the group consisting of polypropylene, polyethylene, and a copolymer thereof, said microporous membrane being a single layer or a co-extruded multi-layer membrane and being prepared by a process comprising:
- extruding a film precursor by a blown film method at a blow-up ratio of at least about 1.5;
- annealing said film precursor;
- and
- stretching the resultant annealed film precursor to form said microporous membrane.
A method for preparing a microporous membrane having at least 80% by weight of a polymer selected from the group consisting of polypropylene, polyethylene, and a copolymer thereof, and having a tear resistance in the transverse direction of at least about 50kgf/cm2, said membrane being a single layer or co-extruded multi-layer membrane and suitable for use as a battery separator, comprising the steps of:
- extruding a film precursor by a blown film method at a blow-up ratio of at least 1.5;
- annealing said film precursor;
- and
- stretching the resultant annealed film precursor to form said microporous membrane.
Dependencies are inferred from the claim text.