WO2010128370A1 - Membranes microporeuses et procédés de fabrication et d'utilisation de telles membranes - Google Patents

Membranes microporeuses et procédés de fabrication et d'utilisation de telles membranes Download PDF

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Publication number
WO2010128370A1
WO2010128370A1 PCT/IB2010/000938 IB2010000938W WO2010128370A1 WO 2010128370 A1 WO2010128370 A1 WO 2010128370A1 IB 2010000938 W IB2010000938 W IB 2010000938W WO 2010128370 A1 WO2010128370 A1 WO 2010128370A1
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WIPO (PCT)
Prior art keywords
membrane
layer
polyethylene
range
weight
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PCT/IB2010/000938
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English (en)
Inventor
Takeshi Ishihara
Satoshi Miyaoka
Koichi Kono
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Toray Tonen Specialty Separator Godo Kaisha
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Application filed by Toray Tonen Specialty Separator Godo Kaisha filed Critical Toray Tonen Specialty Separator Godo Kaisha
Priority to KR1020117024903A priority Critical patent/KR101690101B1/ko
Priority to JP2012507836A priority patent/JP5661101B2/ja
Priority to CN2010800179929A priority patent/CN102439760A/zh
Publication of WO2010128370A1 publication Critical patent/WO2010128370A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/494—Tensile strength
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to multi-layer microporous polymeric membranes suitable for use as battery separator film.
  • the invention also relates to a method for producing such a membrane, batteries containing such membranes as battery separator film, methods for making such batteries, and methods for using such batteries.
  • Microporous membranes can be used as battery separators in, e.g., primary and secondary lithium batteries, lithium polymer batteries, nickel-hydrogen batteries, nickel-cadmium batteries, nickel-zinc batteries, silver-zinc secondary batteries, etc.
  • the membranes' characteristics significantly affect the properties, productivity and performance of the batteries. Accordingly, it is desirable for the microporous membrane to have resistance to thermal shrinkage, particularly at elevated temperature. Resistance to thermal shrinkage (or "heat shrinkage”) can improve the battery's protection against internal short circuiting.
  • Such internal short circuiting involves a loss of dimensional stability especially near the edges of the battery separator film. Should the width of the film decrease at a temperature above the film's shutdown-temperature, the anode and cathode may come into contact. This is particularly the case in prismatic and cylindrical batteries, where even a small change in membrane width can result in anode-cathode contact at or near the battery's edges.
  • embodiments of the invention provide a multi-layer microporous membrane comprising polypropylene having an Mw > 1.0 x 10 6 , the membrane having a 130 0 C heat shrinkage ⁇ 9.5% in at least one planar direction and a normalized air permeability ⁇ 300 second/100cm 3 /20 ⁇ m.
  • Particular membranes include (a) first and third layers each comprising from 1 wt.% to 20 wt.%, based on the weight of the first layer, of polyethylene having an Mw > 1.0 x 10 6 ; and 80 wt.% to 99 wt.% of polyethylene having an Mw ⁇ 1.0 x 10 6 , based on the weight of the first layer; (b) a second layer located between the first and third layers, the second layer comprising 5 wt.% to 40 wt.% polypropylene having an Mw > 1.0 x 10 6 , greater than 0 wt.% to 10 wt.% of polyethylene having an Mw > 1.0 x 10 6 , and 60 wt.% to 95 wt.% of polyethylene having an Mw ⁇ 1.0 x 10 6 , the weight percents being based on the weight of the second layer; wherein the membrane has a total polypropylene content of greater than 0 wt.% to 10 wt.%
  • embodiments of the invention provide a method for producing a microporous membrane, comprising, (a) stretching a multi-layer layer extrudate in at least one of MD or TD, the extrudate comprising at least first and second layers, the first layer comprising a first polyolefm and at least a first diluent, and the second layer comprising a second polyolefm and at least a second diluent, the second polyolefm comprising polypropylene in an amount in the range of from 1 wt.% to 40 wt.% based on the weight of the second polyolefm, the polypropylene having an Mw > 1.0 x 10 6 and a ⁇ Hm > 110 J/g; (b) removing at least a portion of the first and second diluents from stretched extrudate to produce a dried membrane having first width along TD; (c) stretching the membrane in TD from the first width to a second width that is larger than
  • the invention provides a battery comprising an anode, a cathode, an electrolyte, and a multi-layer microporous membrane comprising polypropylene having an Mw > 1.0 x 10 6 and a ⁇ Hm > 112 J/g, the membrane having a 130 0 C heat shrinkage in at least one planar direction of 9.5% or less and a normalized air permeability ⁇ 400 second/ 100cm 3 , wherein the multi-layer microporous membrane separates at least the anode from the cathode.
  • Such battery systems may be used in a number of applications such as powering an electric vehicle or hybrid electric vehicle.
  • Fig. 1 is a cross-sectioned, perspective view showing one example of cylindrical type lithium ion secondary battery comprising an electrode assembly of the present invention.
  • Fig. 2 is a cross-sectioned view showing the battery in Fig. 1.
  • Fig. 3 is an enlarged cross-sectioned view showing a portion A in Fig. 2. DETAILED DESCRIPTION OF THE INVENTION
  • the invention relates to the discovery of microporous membranes having improved heat shrinkage properties, i.e., better dimensional stability at elevated temperature.
  • the improvement in heat shrinkage properties is observed not only at relatively low temperatures (e.g., ⁇ 110 0 C, which is within the operating temperature range of conventional lithium ion batteries), but also at relatively high temperatures (e.g., > 125°C, or > 135°C, e.g., near the shutdown temperature of conventional battery separator film for lithium ion batteries).
  • the microporous membrane comprises first and second layers.
  • the first layer comprises a first layer material
  • the second layer comprises an independently selected second layer material.
  • the first and second layer materials can be, e.g., independently selected polyolefms.
  • the membrane has a planar top layer when viewed from above on an axis approximately perpendicular to planar axes along the length and width of the membrane, and a planar bottom layer that is parallel or approximately parallel to the top layer.
  • the multi-layer microporous membrane comprises three or more layers, e.g., a membrane having first and third layers and a second layer located between the first and third layers. While the third layer can comprise an independently selected third layer material, this is not required.
  • the multi-layer microporous membrane has three or more layers, at least one layer comprises the first microporous layer material and at least one layer comprises the second microporous layer material.
  • the first and third layers are produced from (and generally comprise) substantially the same polymer or mixture of polymers (e.g., both are produced from the first layer material).
  • the multi-layer, microporous membrane comprises three layers, wherein the first and third layers (also called the "surface” or “skin” layers) comprise outer layers of the membrane and the second layer is an intermediate layer (or "core” layer) located between the first and third layers.
  • the multi-layer, microporous membrane can comprise additional layers, i.e., in addition to the two skin layers and the core layer.
  • the membrane can contain additional core layers between the first and third layers.
  • the membrane can be a coated membrane, i.e., it can have one or more additional layers on or applied to the first and third layers.
  • the second layer of the membrane has a thickness of 5% to 15% of the membrane's total thickness; and the first and third layers of the membrane have the same thickness, the thickness of the first and third layer each being in the range of 42.5% to 47.5% of the membrane's total thickness.
  • the core layer is in planar contact with one or more of the skin layers in a stacked arrangement such as AfB/ A with face-to-face stacking of the layers.
  • the membrane can be referred to as a "polyolefm membrane" when the membrane contains polyolefm. While the membrane can contain polyolefm only, this is not required, and it is within the scope of the invention for the polyolefm membrane to contain polyolefin and materials that are not polyolefin.
  • Suitable polyolefms can be produced by a variety of suitable processes, for example by polymerization in the presence of a chromium catalyst, a Ziegler-Natta catalyst, or by one or more single-site polymerization catalysts.
  • the first layer comprises polyethylene.
  • polyethylene refers to a polyolefin homopolymer or copolymer containing recurring units derived from ethylene. Such polyethylenes include but are not limited to polyethylene homopolymer and/or copolymer wherein at least 85% (by number) of the recurring units are derived from ethylene.
  • the polyethylene can be a mixture or reactor blend of individual polyethylenes, such as a mixture of two or more polyethylenes.
  • the polyethylene comprises a first polyethylene having a weight-average molecular weight ("Mw") ⁇ 1.0 x 10 6 and a second polyethylene having an Mw > 1.0 x 10 6 .
  • the third layer material comprises a first polyethylene having an Mw ⁇ 1.0 x 10 6 and a second polyethylene having an Mw > 1.0 x 10 6 .
  • the second layer material comprises polypropylene.
  • polyproylene as used herein refers to a polyolefin homopolymer or copolymer containing recurring units derived from propylene.
  • Such polypropylenes include but are not limited to polypropylene homopolymer and/or copolymer wherein at least 85% (by number) of the recurring units are derived from propylene.
  • the polypropylene can be a mixture or reactor blend of individual polypropylenes, such as a mixture of two or more polypropylenes.
  • the second layer material comprises a first polyethylene having an Mw ⁇ 1.0 x 10 6 , polypropylene having an Mw > 1.0 x 10 6 , and optionally a second polyethylene having an Mw > 1.0 x 10 6 .
  • the first polyethylene of the second and/or third layer material is the same first polyethylene as in the first layer material.
  • the second polyethylene of the second and/or third layer material is the same second polyethylene as in the first layer material.
  • neither the first nor third layer material contains polypropylene in an amount greater than 0.5 wt.%.
  • the first and/or third layer material consists essentially of polyethylene, e.g., substantially the same polyethylene or combination of polyethylenes.
  • the first layer material comprises from about 80 wt.% to about 99 wt.%, e.g., 92.5 wt.% to about 97.5 wt.%, of the first polyethylene and from about 1 wt.% to about 20 wt.%, particularly from about 1 wt.% to about 5 wt.%, of the second polyethylene; the weight percents being based on the weight of the first layer material.
  • the polyethylenes of the third layer material are selected from among substantially the same polyethylenes in approximately the same concentration ranges as the first layer material.
  • the second layer material comprises the first polyethylene, the polypropylene, for example ⁇ 40 wt.% polypropylene, and optionally the second polyethylene.
  • the second layer material can comprise from about 60 wt.% to about 95 wt.%, of the first polyethylene, from about 5 wt.% to about 40 wt.% of the polypropylene, and from about 0 wt.% to about 10 wt.% of the second polyethylene, the weight percents being based on the weight of the second layer material.
  • the second layer material comprises from about 60 wt.% to about 75 wt.% of the first polyethylene, from about 25 wt.% to about 35 wt.% of the polypropylene, and from about 0.5 wt.% to about 5 wt.% of the second polyethylene, the weight percents being based on the weight of the second layer material.
  • the microporous membrane comprises 1.5 to 5 wt.% polypropylene, 75 to 98 wt.% of the first polyethylene and greater than 0 to 5 wt.% of the second polyethylene, the weight percents being based on the weight of the second layer material.
  • the microporous membrane can contain copolymers, inorganic species (such as species containing silicon and/or aluminum atoms), and/or heat-resistant polymers such as those described in PCT Publications WO 2007/132942 and WO 2008/016174, these are not required.
  • the membrane is substantially free of such materials. Substantially free in this context means the amount of such materials in the microporous membrane is less than 1 wt.%, based on the total weight of the polymer used to produce the microporous membrane.
  • the final microporous membrane generally comprises the polymer used to produce the extrudate.
  • a small amount of diluent or other species introduced during processing can also be present, generally in amounts less than 1 wt.% based on the weight of the microporous membrane.
  • a small amount of polymer molecular weight degradation might occur during processing, but this is acceptable.
  • the Mw of the polymers in the membrane decreases by no more than, e.g., about 10%, or no more than about 1%, or no more than about 0.1% of the Mw of the polymers used to produce the membrane.
  • the first and third layer materials are produced from the first diluent and the first and second polyethylenes; and the second layer material is produced from the second diluent, the first polyethylene, the polypropylene, and optionally the second polyethylene.
  • inorganic species such as species containing silicon and/or aluminum atoms
  • heat-resistant polymers such as those described in PCT Publications WO 2007/132942 and WO 2008/016174 (both of which are incorporated by reference herein in their entirety) can be used to produce the first, second, and/or third layer materials. In an embodiment, these optional species are not used.
  • the first polyethylene has an Mw ⁇ 1.0 x 10 6 , e.g., in the range of from about 1.0 x 10 5 to about 9 x 10 5 , for example from about 4 x 10 5 to about 8 x 10 5 .
  • the first polyethylene has a molecular weight distribution ("MWD") in the range of from about 1 to about 100, for example from about 3 to about 20.
  • the first polyethylene can be one or more of a high density polyethylene ("HPDE”), a medium density polyethylene, a branched low density polyethylene, or a linear low density polyethylene.
  • the first polyethylene has an amount of terminal unsaturation > 0.2 per 10,000 carbon atoms, e.g., > 5 per 10,000 carbon atoms or > 10 per 10,000 carbon atoms.
  • the amount of terminal unsaturation can be measured in accordance with the procedures described in PCT Publication WO97/23554, for example.
  • the first polyethylene is at least one of (i) an ethylene homopolymer or (ii) a copolymer of ethylene and ⁇ 10 mol.% of a comonomer such as ⁇ -olef ⁇ n (e.g., propylene, butene-1, hexene-1, etc.).
  • a comonomer such as ⁇ -olef ⁇ n (e.g., propylene, butene-1, hexene-1, etc.).
  • ⁇ -olef ⁇ n e.g., propylene, butene-1, hexene-1, etc.
  • the comonomer is one or more of propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-l, octene-1, vinyl acetate, methyl methacrylate, or styrene, or other monomer.
  • the second polyethylene has an Mw > 1.0 x 10 6 , e.g., in the range of 1.1.0 x 10 6 to about 5 x 10 6 , for example from about 1.2 x 10 6 to about 3 x 10 6 , e.g., about 2 x 10 6 .
  • the second polyethylene has an MWD in the range of from about 2 to about 100, for example from about 3 to about 10.
  • the second polyethylene can be an ultra-high molecular weight polyethylene ("UHMWPE").
  • the first polyethylene is at least one of (i) an ethylene homopolymer or (ii) a copolymer of ethylene and ⁇ 10 mol.% of a comonomer such as ⁇ -olef ⁇ n.
  • the comonomer is one or more of propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-l, octene-1, vinyl acetate, methyl methacrylate, or styrene, or other monomer.
  • Such a polymer or copolymer can be produced by any convenient polymerization method, including Ziegler-Natta, chrome, or single-site catalyzed processes.
  • the polypropylene comprises a copolymer of propylene and ⁇ 10.0 mol.% of a comonomer (such as one or more of ⁇ -olefms), e.g., ethylene, butene-1, pentene-1, hexene-1, 4-methylpentene-l, octene-1, vinyl acetate, methyl methacrylate, and styrene, etc.; and diolefms such as butadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, etc.; and other comonomer.
  • a comonomer such as one or more of ⁇ -olefms
  • the polypropylene comprises a first polypropylene, itself comprising one or more polyprolyene homopolymer or copolymer (random or block) of propylene.
  • the first polypropylene has an Mw > 5 x 10 5 , for example from about 5.O x 10 5 to about 2.0 x 10 6 , such as from about 1.1 x 10 6 to about 1.5 x 10 6 .
  • the polypropylene has an MWD ⁇ 100, e.g., from about 1 to about 50, or 2.0 to 6.0; and/or a heat of fusion (" ⁇ Hm") > 100.0 J/g, e.g., 110.0 J/g to 120.0 J/g, such as from about 113.0 J/g to 119.0 J/g or from 114.0 J/g to about 116.0 J/g.
  • ⁇ Hm is measured using differential scanning calorimetry according to JIS K7122, as described in PCT Patent Publication No. WO2007/132942.
  • the polypropylene has one or more of the following properties: (i) the polypropylene is isotactic; (ii) an elongational viscosity of at least about 50,000 Pa sec at a temperature of 230 0 C and a strain rate of 25 sec "1 ; (iii) a melting peak (second melt) of at least about 160 0 C; and/or (iv) a Trouton's ratio of at least about 15 when measured at a temperature of about 230 0 C and a strain rate of 25 sec "1 .
  • Mw and MWD of the poly ethylenes and polypropylene are determined using a High Temperature Size Exclusion Chromatograph, or "SEC", (GPC PL 220, Polymer Laboratories), equipped with a differential refractive index detector (DRI). The measurement is made in accordance with the procedure disclosed in "Macromolecules, Vol. 34, No. 19, pp. 6812-6820 (2001)”. Three PLgel Mixed-B columns available from (available from Polymer Laboratories) are used for the Mw and MWD determination.
  • SEC High Temperature Size Exclusion Chromatograph
  • DRI differential refractive index detector
  • the GPC solvent used is filtered Aldrich reagent grade 1,2,4-Trichlorobenzene (TCB) containing approximately 1000 ppm of butylated hydroxy toluene (BHT).
  • TCB 1,2,4-Trichlorobenzene
  • BHT butylated hydroxy toluene
  • the TCB is degassed with an online degasser prior to introduction into the SEC.
  • the same solvent is used as the SEC eluent.
  • Polymer solutions are prepared by placing dry polymer in a glass container, adding the desired amount of the TCB solvent, and then heating the mixture at 16O 0 C with continuous agitation for about 2 hours. The concentration of polymer solution is 0.25 to 0.75mg/ml.
  • Sample solutions are filtered off-line before injecting to GPC with 2 ⁇ m filter using a model SP260 Sample Prep Station (available from Polymer Laboratories).
  • the separation efficiency of the column set is calibrated with a calibration curve generated using a seventeen individual polystyrene standards ranging in Mp ("Mp" being defined as the peak in Mw) from about 580 to about 10,000,000.
  • Mp being defined as the peak in Mw
  • the polystyrene standards are obtained from Polymer Laboratories (Amherst, MA).
  • a calibration curve (logMp vs. retention volume) is generated by recording the retention volume at the peak in the DRI signal for each PS standard and fitting this data set to a 2nd-order polynomial.
  • Samples are analyzed using IGOR Pro, available from Wave Metrics, Inc. Methods of producing the microporous membrane
  • the multi-layer microporous membrane of the invention is a two-layer membrane. In another embodiment, the multi-layer microporous membrane has at least three layers.
  • the method for producing the microporous membrane will mainly be described in terms of a three layer membrane having first and third layers comprising the first layer material and a second layer comprising the second layer material located between the first and third layers.
  • One method for producing the multi-layer microporous membrane of the present invention comprises layering, such as for example by lamination or coextrusion of extrudates or membranes, e.g., monolayer extrudates or monolayer microporous membranes.
  • layering such as for example by lamination or coextrusion of extrudates or membranes, e.g., monolayer extrudates or monolayer microporous membranes.
  • one or more layers comprising the first layer material can be coextruded with one or more layers comprising the second layer material, e.g., with the layers comprising the first layer material located on one or both sides of the layers (or layers) comprising the second layer material.
  • the process for producing the membrane involves cooling a multilayer extrudate having a first planar direction (e.g., the machine direction of extrusion or "MD") and an orthogonal second planar direction (e.g., the direction transverse to MD, called the transverse direction or "TD").
  • the extrudate can comprise at least first, second, and third layers, wherein the second layer is located between the first and third layers.
  • the first and third layers of the extrudate comprise the first layer material and at least a first diluent, and the second layer of the extrudate comprises the second layer material and at least a second diluent.
  • the first and third layers can be outer layers of the extrudate, also called skin layers.
  • the third layer of the extrudate could be produced from a different layer material, e.g., the third layer material, and could have a different thickness than the first layer.
  • the process also involves stretching the cooled extrudate in MD and/or TD and removing at least a portion of the first and second diluents from stretched extrudate to produce a dried membrane having a first dry length in the in the first planar direction and a first dry width in the second planar direction.
  • the process then involves stretching the dried membrane along TD and optionally MD to form the final membrane.
  • the first layer material is produced by combining the first polyethylene and optionally second polyethylene e.g., by dry mixing or melt blending.
  • the combined polymers can be combined with one or more diluents to form a mixture of polymer and diluent.
  • the polymers can be in the form of polymer resins.
  • the diluents can be, e.g., solvents for the polymers of the first layer material. When the diluents are such solvents, the diluent can be called a membrane-forming solvent and the combined polymer and diluent can be called a polymeric solution, e.g., a polyolefin solution.
  • the combined first layer material and diluent can optionally contain additives such as one or more antioxidant. In an embodiment, the amount of such additives does not exceed 1 wt.% based on the weight of the mixture of polymer and diluent.
  • the first diluent is a solvent that is liquid at room temperature. While not wishing to be bound by any theory or model, it is believed that the use of a liquid solvent to form the first polyolefin solution makes it possible to conduct stretching of the extrudate (generally a gel-like sheet) at a relatively high stretching magnification. [0039] Any species capable of forming a single phase in conjunction with the resin at the extrusion temperature may be used as a diluent of the present invention.
  • the diluent examples include aliphatic or cyclic hydrocarbon such as nonane, decane, decalin and paraffin oil, and phthalic acid ester such as dibutyl phthalate and dioctyl phthalate. Paraffin oil with kinetic viscosity of 20-200 cSt at 40 0 C can be used.
  • the choice of first diluent, mixing condition, extrusion condition, etc. can be the same as those disclosed in PCT Publication No. WO 2008/016174, for example, which is incorporated by reference herein in its entirety. [0040]
  • the amount of first diluent in the combined diluent and first layer material in the first polyolefin solution is not critical.
  • the amount of first diluent is in the range of 20 wt.% to 99 wt.%, preferably 60 wt.% to 80 wt.%, based on the combined weight of first diluent and first layer material. Higher concentrations of diluent are believed to contribute at least in part to improved heat shrink performance of some membranes described herein.
  • the second layer material and second diluent can be combined by the same methods used to combine the first layer material and first diluent.
  • the polymer comprising the second layer material can be combined by melt-blending the first polyethylene, the polypropylene, and optionally the second polyethylene.
  • the second diluent can be selected from among the same diluents as the first diluent.
  • the second diluent can be (and generally is) selected independently of the first diluent
  • the diluent can be the same as the first diluent, and can be used in the same relative concentration as the first diluent is used in the first polyolefin solution.
  • the method for preparing the second polyolefin solution differs from the method for preparing the first polyolefin solution, in that the mixing temperature is preferably in a range from the melting point (Tm2) of the polypropylene to Tm2 + 90 0 C.
  • the combined first layer material and first diluent is conducted from a first extruder to first and third dies and the combined second layer material and second diluent is conducted from a second extruder to a second die.
  • a layered extrudate in sheet form i.e., a body significantly larger in the planar directions than in the thickness direction
  • the multilayer extrudate can be exposed to a temperature in the range of 15°C to
  • Cooling rate is not particularly critical.
  • the extrudate can be cooled at a cooling rate of at least about 30°C/minute until the temperature of the extrudate (the cooled temperature) is approximately equal to the extrudate's gelation temperature (or lower).
  • Process conditions for cooling can be the same as those disclosed in
  • the cooled extrudate has a thickness ⁇ 10 mm, e.g., in the range of 0.1 mm to 10 mm, or 0.5 mm to 5 mm.
  • the second layer of the cooled extrudate has a thickness of 5% to 15% of the cooled extrudate's total thickness; and the first and third layers of the cooled extrudate have substantially the same thickness, the thickness of the first and third layer each being in the range of 42.5% to 47.5% of the cooled extrudate's total thickness.
  • the cooled extrudate is then stretched (referred to as "wet" stretching) in at least one direction (e.g., at least one planar direction, such as MD or TD) to produce a stretched extrudate.
  • the extrudate is stretched simultaneously in the transverse and machine directions to a magnification factor in the range of 4 to 6. Suitable stretching methods are described in PCT Publication No. WO 2008/016174, for example. While not required, the MD and TD magnifications can be the same. In an embodiment, the stretching magnification is equal to 5 in MD and TD.
  • the stretching is conducted at a deformation speed of ⁇ about 850%/min., ⁇ 800%/min., ⁇ 775%/min., or ⁇ 700%/min. Deformation speeds in the range of 600%/min. to about 800%/minute, or 700%/min. to 800%/min. are useful.
  • a biaxially oriented film will be stretched in both MD and TD dimensions, but as used herein the term "deformation speed" refers to the rate at least one planar dimension of the film (e.g., MD, TD, or combination thereof) is increased. For example, a film that is stretched to a magnification of 5 in MD and TD over the course of a 1 min.
  • biaxial orientation process would have a deformation speed of 500%/min. in both MD and TD, can be described as having been stretched at a deformation speed of 500%.
  • the stretching can be conducted while exposing the extrudate to a temperature in the range of from about the Ted temperature Tm.
  • Ted and Tm are defined as the crystal dispersion temperature and melting point of the polyethylene having the lowest melting point among the polyethylenes used to produce the extrudate (i.e., the first and second polyethylene).
  • the crystal dispersion temperature is determined by measuring the temperature characteristics of dynamic viscoelasticity according to ASTM D 4065.
  • the stretching temperature can be from about 90 to 125°C; preferably form about 100 to 125°C, more preferably from 105 to 125°C, even more preferably from 119 to about 125°C. It is believed that higher stretching temperatures may provide membranes having reduced shrinkage at operating conditions.
  • the stretched extrudate undergoes an optional thermal treatment before diluent removal. In the thermal treatment, the stretched extrudate is exposed to a temperature that is higher (warmer) than the temperature to which the extrudate is exposed during stretching.
  • the stretched extrudate is exposed to a temperature in the range of 120 0 C to 125 0 C for a time in the range of 1 second to 100 sees. while the wet length and wet width are held constant, e.g., by using tenter clips to hold the stretched extrudate along its perimeter.
  • the stretched extrudate is exposed to a temperature that is not higher, preferably lower (cooler) than the temperature to which the extrudate is exposed during stretching.
  • the stretched extrudate is exposed to a temperature in the range of 90 0 C to 12O 0 C, particularly about 90 0 C to 100 0 C when the stretching temperature is 119 to 120 0 C, for a time in the range of 1 second to 100 sees, while the wet length and wet width are held constant, e.g., by using tenter clips to hold the stretched extrudate along its perimeter.
  • the planar dimensions of the stretched extrudate (length in MD and width in TD) can be held constant while the stretched extrudate is exposed to the higher temperature. Since the extrudate contains polymer and diluent, its length and width are referred to as the "wet" length and "wet" width. In other words, during the thermal treatment, there is no magnification or demagnification (i.e., no dimensional change) of the stretched extrudate in MD or TD.
  • this exposure can be accomplished by heating air and then conveying the heated air into proximity with the sample.
  • the temperature of the heated air which is generally controlled at a set point equal to the desired temperature, is then conducted toward the sample through a plenum for example.
  • Other methods for exposing the sample to an elevated temperature including conventional methods such as exposing the sample to a heated surface, infra-red heating in an oven, etc. can be used with or instead heated air.
  • first and second diluents are removed (or displaced) from the stretched extrudate to form a dried membrane.
  • a displacing (or “washing") solvent can be used to remove (wash away, or displace) the first and second diluents.
  • Process conditions for removing first and second diluents can be the same as those disclosed in PCT Publication No. WO 2008/016174, for example.
  • the term "dried membrane” refers to an extrudate from which at least a portion of the diluent has been removed. It is not necessary to remove all diluent from the stretched extrudate, although it can be desirable to do so since removing diluent increases the porosity of the final membrane.
  • any remaining volatile species such as washing solvent
  • Any method capable of removing the washing solvent can be used, including conventional methods such as heat-drying, wind-drying (moving air), etc.
  • Process conditions for removing volatile species such as washing solvent can be the same as those disclosed in PCT Publications No. WO 2008/016174 and WO 2007/132942, for example. Stretching the dried membrane
  • the dried membrane is stretched (called "dry stretching") in at least TD.
  • a dried membrane that has been dry stretched is called an "oriented" membrane.
  • the dried membrane Before dry stretching, the dried membrane has an initial size in MD (a first dry length) and an initial size in TD (a first dry width).
  • first dry width refers to the size of the dried membrane in the transverse direction prior to the start of dry orientation.
  • first dry length refers to the size of the dried membrane in the machine direction prior to the start of dry orientation.
  • Tenter stretching equipment of the kind described in WO 2008/016174 can be used, for example.
  • the dried membrane can be stretched in TD from the first dry width to a second dry width that is larger than the first dry width by a magnification factor (the "TD dry stretching magnification factor”) in the range of from about 1.1 to about 1.8.
  • TD dry stretching magnification factor the "TD dry stretching magnification factor”
  • MD dry stretching magnification factor the "MD dry stretching magnification factor”
  • the amount of TD dry magnification generally does not exceed the amount of MD dry magnification.
  • the dry stretching can be simultaneous in MD and TD or sequential.
  • the dry stretching is sequential, generally MD stretching is conducted first followed by TD stretching.
  • the dry stretching is generally conducted while exposing the dried membrane to a temperature ⁇ Tm, e.g., in the range of from about Tcd-30°C to Tm.
  • a temperature ⁇ Tm e.g., in the range of from about Tcd-30°C to Tm.
  • the stretching temperature is generally conducted with the membrane exposed to a temperature in the range of from about 70 to about 135°C, for example from about 80 0 C to about 132°C, particularly from 125°C to 132°C or from 128°C to 131°C.
  • the MD dry stretching magnification factor is in the range of from about 1.1 to about 1.5, such as 1.2 to 1.4; and the TD dry stretching magnification factor is in the range of from about 1.1 to about 1.3, such as 1.15 to 1.25, with the MD stretching first, followed by stretching in the TD direction.
  • the stretching rate is preferably 3%/second or more in the stretching direction (MD or TD), and the rate can be independently selected for MD and TD stretching.
  • the stretching rate is preferably 5%/second or more, more preferably 10%/second or more, e.g., in the range of 5%/second to 25%/second.
  • the upper limit of the stretching rate is preferably 50%/second to prevent rupture of the membrane. Controlled reduction of the membrane's width
  • the dried membrane is subjected to a controlled reduction in width from the second dry width to a third width, the third dry width being in the range of from the first dry width to about 1.1 to about 1.6, particularly 1.3 to 1.5, times larger than the first dry width.
  • the width reduction generally conducted while the membrane is exposed to a temperature > Ted - 30 0 C, but less than Tm.
  • the membrane can be exposed to a temperature in the range of from about 70 0 C to about 135°C, such as from about 127°C to about 132°C, e.g., from about 128°C to about 131°C.
  • the decreasing of the membrane's width is conducted while the membrane is exposed to a temperature that is lower than Tm.
  • the third dry width is in the range of from 1.0 to about 1.6, or from 1.2 times to 1.5, times larger than the first dry width.
  • the membrane is thermally treated (heat-set) one or more times after diluent removal, e.g., after dry stretching, the controlled width reduction, or both. It is believed that heat-setting stabilizes crystals and make uniform lamellas in the membrane.
  • the heat setting is conducted while exposing the membrane to a temperature in the range Ted to Tm, e.g., a temperature e.g., in the range of from about 100 0 C to about 135°C, such as from about 127°C to about 132°C, or from about 129°C to about 131°C.
  • the heat setting is conducted for a time sufficient to form uniform lamellas in the membrane, e.g., a time in the range of 1 to 100 sees.
  • the heat setting is operated under conventional heat-set "thermal fixation" conditions.
  • thermal fixation refers to heat-setting carried out while maintaining the length and width of the membrane substantially constant, e.g., by holding the membrane's perimeter using tenter clips during the heat setting.
  • an annealing treatment can be conducted after the heat-set step.
  • the annealing is a heat treatment with no load applied to the membrane, and may be conducted by using, e.g., a heating chamber with a belt conveyer or an air- floating-type heating chamber.
  • the annealing may also be conducted continuously after the heat-setting with the tenter slackened.
  • the membrane can be exposed to a temperature in the range of
  • Tm or lower e.g., in the range from about 60 0 C to about Tm -5°C. Annealing is believed to provide the microporous membrane with improved permeability and strength.
  • Optional heated roller, hot solvent, cross linking, hydrophilizing, and coating treatments can be conducted if desired, e.g., as described in PCT Publication No. WO
  • an annealing treatment can be conducted before, during, or after the heat-setting.
  • the annealing is a heat treatment with no load applied to the membrane, and can be conducted by using, e.g., a heating chamber with a belt conveyer or an air- floating-type heating chamber.
  • the annealing can be conducted continuously, e.g., after the heat-setting with the tenter slackened.
  • the temperature to which the membrane is exposed during annealing, (the "annealing temperature”) can be, e.g., in a range from about
  • Optional heated roller, hot solvent, cross linking, hydrophilizing, and coating treatments can be conducted if desired, e.g., as described in PCT Publication No. WO
  • the membrane is a multi-layer microporous membrane.
  • the membrane's thickness is generally in the range of 3 ⁇ m or more.
  • the membrane can have a thickness in the range of from about 5 ⁇ m to about 200 ⁇ m, e.g., from about 10 ⁇ m to about 50 ⁇ m.
  • the membrane's thickness can be measured, e.g., by a contact thickness meter at 1 cm longitudinal intervals over the width of 10 cm, and then averaged to yield the membrane thickness. Thickness meters such as the Litematic available from
  • Mitsutoyo Corporation are suitable. This method is also suitable for measuring thickness variation after heat compression, as described below.
  • Non-contact thickness measurement methods are also suitable, e.g., optical thickness measurement methods.
  • the membrane has one or more of the following properties.
  • the membrane has a porosity > 25%, e.g., in the range of about 25% to about 80%, or 30% to 60%.
  • the normalized air permeability is in the range of 20.0 secs./100cm 3 /20 ⁇ m to about 400 secs./100cm 3 /20 ⁇ m, or 150 secs./100cm 3 /20 ⁇ mto 250 secs./100cm 3 /20 ⁇ m.
  • the membrane has a pin puncture strength > 130 mN/ ⁇ m, e.g., in the range of 130 mN/ ⁇ m to 250 mN/ ⁇ m.
  • Pin puncture strength is defined as the maximum load measured when a microporous membrane having a thickness of Ti is pricked with a needle of 1 mm in diameter with a spherical end surface (radius R of curvature: 0.5 mm) at a speed of 2 mm/second.
  • the membrane has an MD tensile strength > 55,000 kPa, e.g., in the range of 58,000 to 90,000 kPa, and/or a TD tensile strength > 70,000 kPa, e.g., in the range of 75,000 kPa to 110,000 kPa.
  • Tensile strength is measured in MD and TD according to ASTM D-882A. E. Tensile elongation > 100%
  • Tensile elongation is measured according to ASTM D-882A.
  • the membrane's MD and TD tensile elongation are each > 150%, e.g., in the range of 150% to 350%.
  • the membrane's MD tensile elongation is in the range of, e.g., 150% to 250% and TD tensile elongation is in the range of, e.g., 150% to 250%.
  • the membrane has a shutdown temperature ⁇ 140 0 C, e.g., in the range of about 132°C to about 138°C.
  • the microporous membrane's shutdown temperature is measured by the method disclosed in PCT publication WO2007/052663, which is incorporated by reference herein in its entirety. According to this method, the microporous membrane is exposed to an increasing temperature (5°C/minute) while measuring the membrane's air permeability.
  • the microporous membrane's shutdown temperature is defined as the temperature at which the microporous membrane's air permeability (Gurley Value) is 100,000 secs./lOO cm 3 .
  • the microporous membrane's air permeability is measured according to JIS P8117 using an air permeability meter (EGO-IT available from Asahi Seiko Co., Ltd.).
  • the membrane's rupture temperature is > 170 0 C, e.g., in the range of 171°C to 200 0 C, or 172°C to 190 0 C.
  • Rupture temperature is measured as follows. A microporous membrane of 5 cm x 5 cm is sandwiched by blocks each having a circular opening of 12 mm in diameter, and a tungsten carbide ball of 10 mm in diameter was placed on the microporous membrane in the circular opening. The membrane is then exposed to an increasing temperature at a rate of 5°C/minute.
  • the membrane's rupture temperature is defined as the temperature at which the ball first breaks through the membrane.
  • the membrane's meltdown temperature is defined as the temperature at which the ball completely penetrates the sample, i.e., the temperature at which the sample breaks.
  • the rupture temperature is in the range of from 180 0 C to 190 0 C. Since the membrane has a desirably high rupture temperature, it is suitable for use as a battery separator in high-power, high capacity lithium ion batteries such as those used for powering electric vehicles and hybrid electric vehicles. H. Meltdown temperature
  • Meltdown temperature is measured by the following procedure: A rectangular sample of 3 mm x 50 mm is cut out of the liquid-permeable microlayer membrane such that the long axis of the sample is aligned with TD and the short axis is aligned with MD. The sample is set in the thermomechanical analyzer (TMA/SS6000 available from Seiko Instruments, Inc.) at a chuck distance of 10 mm, i.e., the distance from the upper chuck to the lower chuck is 10mm. The lower chuck is fixed and a load of 19.6mN applied to the sample at the upper chuck. The chucks and sample are enclosed in a tube which can be heated.
  • TMA/SS6000 thermomechanical analyzer
  • the temperature inside the tube is elevated at a rate of 5°C/minute, and sample length change under the 19.6 mN load is measured at intervals of 0.5 second and recorded as temperature is increased.
  • the temperature is increased to 200 0 C.
  • the meltdown temperature of the sample is defined as the temperature at which the sample breaks, generally at a temperature in the range of about 145°C to about 200 0 C. In an embodiment, the meltdown temperature is > 180 0 C, e.g., in the range of from 180 0 C to 200 0 C, e.g., 185°C to about 195 0 C.
  • the membrane has a heat shrinkage at 105 0 C in at least one planar direction (e.g., MD or TD) of ⁇ 1% e.g., ⁇ 0.5%, such as in the range of from 0.1% to 0.25%.
  • the membrane's shrinkage at 105 0 C in MD and TD is measured as follows: (i) Measure the size of a test piece of microporous membrane at ambient temperature in both the MD and TD, (ii) equilibrate the test piece of the microporous membrane at a temperature of 105 0 C for 8 hours with no applied load, and then (iii) measure the size of the membrane in both the MD and TD.
  • the heat (or "thermal") shrinkage in MD and TD can be obtained by dividing the result of measurement (i) by the result of measurement (ii) and expressing the resulting quotient as a percent. J. Heat Shrinkage at 13O 0 C
  • the membrane has a TD heat shrinkage measured at 130 0 C ⁇ 8%, e.g., 1% to 7.5%.
  • a relatively low heat shrink value, e.g., ⁇ 8% can be of particular significance since 13O 0 C is generally within the operating temperature range of a lithium ion secondary battery during charging and discharging, albeit near the upper (shutdown) end of this range.
  • the measurement is slightly different from the measurement of heat shrinkage at 105 0 C, reflecting the fact that the edges of the membrane parallel to the membrane's TD are generally fixed within the battery, with a limited degree of freedom allowed for expansion or contraction (shrinkage) in TD, particularly near the center of the edges parallel to the membrane's MD. Accordingly, a square sample of microporous film measuring 50 mm along TD and 50 mm along MD is mounted in a frame, with the edges parallel to TD fixed to the frame (e.g., by tape) leaving a clear aperture of 35mm in MD and 50 mm in TD.
  • TD heat shrinkage generally causes the edges of the film parallel to MD to bow slightly inward (toward the center of the frame's aperture).
  • the shrinkage in TD (expressed as a percent) is equal to the length of the sample in TD before heating divided by the narrowest length (within the frame) of the sample in TD after heating times 100 percent.
  • the sample length measured in the temperature range of from 135°C to 145°C are recorded.
  • the maximum shrinkage in the molten state is defined as the sample length between the chucks measured at 23°C (Ll equal to 10mm) minus the minimum length measured generally in the range of about 135°C to about 145°C (equal to L2) divided by Ll, i.e., [Ll-L2]/Ll*100%.
  • the rectangular sample of 3 mm x 50 mm used is cut out of the microporous membrane such that the long axis of the sample is aligned with the transverse direction of the microporous membrane as it is produced in the process and the short axis is aligned with the machine direction.
  • MD maximum shrinkage the rectangular sample of 3 mm x 50 mm used is cut out of the microporous membrane such that the long axis of the sample is aligned with the machine direction of the microporous membrane as it is produced in the process and the short axis is aligned with the transverse direction.
  • the membrane's maximum MD heat shrinkage in the molten state is ⁇ 25% or ⁇ 20%, e.g., in the range of 1% to 25%, or 2% to 20%.
  • the membrane's maximum TD heat shrinkage in the molten state is ⁇ 11%, or ⁇ 6%, e.g., in the range of 1% to 10%, or 2% to 5.5%.
  • Fig. 1 shows an example of a cylindrical-type lithium ion secondary battery comprising two battery separators.
  • the microporous membranes of the invention are suitable for use as battery separators in this type of battery.
  • the battery has a toroidal-type electrode assembly 1 comprising a first separator 10, a second separator 11, a cathode sheet 13, and an anode sheet 12.
  • the separators' thicknesses are not to scale, and are greatly magnified for the purpose of illustration.
  • the toroidal-type electrode assembly 1 can be wound, e.g., such that the second separator 11 is arranged on an outer side of the cathode sheet 13, while the first separator 10 is arranged on the inner side of the cathode sheet.
  • the second separator 11 is arranged on inside surface of the toroidal-type electrode assembly 1, as shown in Fig. 2.
  • an anodic active material layer 12b is formed on both sides of the current collector 12a, and a cathodic active material layer 13b is formed on both sides of the current collector 13a, as shown in Fig. 3.
  • an anode lead 20 is attached to an end portion of the anode sheet 12
  • a cathode lead 21 is attached to an end portion of the cathode sheet 13.
  • the anode lead 20 is connected with battery lid 27, and the cathode lead 21 is connected with the battery can 23.
  • the separators of the invention are suitable for use in e.g., prismatic batteries such as those containing electrodes in the form of stacked plates of anode(s) 12 and a cathode (3) 13 alternately connected in parallel with the separators situated between the stacked anodes and cathodes.
  • the anode sheet 12, the cathode sheet 13, and the first and second separators 10, 11 are impregnated with the electrolytic solution to provide ion transport through the separators 10, 11.
  • the impregnation treatment is can be conducted, e.g., by immersing electrode assembly 1 in the electrolytic solution at room temperature.
  • a cylindrical type lithium ion secondary battery can be produced by inserting the toroidal-type electrode assembly 1 (see Fig. 1) into a battery can 23 having a insulation plate 22 at the bottom, injecting the electrolytic solution into the battery can 23, covering the electrode assembly 1 with a insulation plate 22, caulking a battery lid (24, 25, 26, and 27) to the battery can 23 via a gasket 28.
  • Fig. 3 (oriented so that the battery lid, i.e., the anode terminal of Fig. 1, is toward the right) illustrates the advantage of using a separator having diminished tendency to shrinkage in the transverse direction (with respect to the separator manufacturing process) as the battery temperature increases.
  • One role of the separator is to prevent contact of the anodic active material layer and the cathodic active material layer.
  • the thin edges of the separators 10 and 11 move away from the battery lid (move leftward in figure 3), thereby allowing contact between the anodic active material layer and the cathodic active material layer, resulting in a short circuit.
  • the battery is useful as a source or sink of power from one or more electrical or electronic components, Such components include passive components such as resistors, capacitors, inductors, including, e.g., transformers; electromotive devices such as electric motors and electric generators, and electronic devices such as diodes, transistors, and integrated circuits.
  • passive components such as resistors, capacitors, inductors, including, e.g., transformers; electromotive devices such as electric motors and electric generators, and electronic devices such as diodes, transistors, and integrated circuits.
  • the components can be connected to the battery in series and/or parallel electrical circuits to form a battery system.
  • the circuits can be connected to the battery directly or indirectly.
  • electricity flowing from the battery can be converted electrochemically (e.g., by a second battery or fuel cell) and/or electromechanically (e.g., by an electric motor operating an electric generator) before the electricity is dissipated or stored in a one or more of the components.
  • the battery system can be used as a power source for moving an electric vehicle or hybrid electric vehicle, for example.
  • the battery is electrically connected to an electric motor and/or an electric generator for powering an electric vehicle or hybrid electric vehicle.
  • a first polyolefm composition is prepared by dry-blending (a) 68.6 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 an MWD of 4.05, (b) 1.4 wt.% second polyethylene resin having an Mw of 1.95 x 10 6 and an MWD of 5.09, and (c) 30 wt.% polypropylene resin having an Mw of 1.1 x 10 6 , a heat of fusion of 114 J/g and an MWD of 5 , the percentages being based on the weight of the first polyolefm composition.
  • the first polyethylene resin in the composition has a Tm of 135°C and a Ted of 100 0 C. [0091] 30 wt.
  • first polyolefm composition % of the resultant first polyolefm composition is charged into a first strong-blending double-screw extruder having an inner diameter of 58 mm and L/D of 42, and 70 wt.% of liquid paraffin (50 cst at 40 0 C) is supplied to the double-screw extruder via a side feeder to produce a first polyolefm solution.
  • the weight percents are based on the weight of the first polyolefm solution.
  • Melt-blending is conducted at 210 0 C and 200 rpm.
  • a second polyolefm solution is prepared in the same manner as above by dry-blending (a) 82 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 x 10 5 and an MWD of 4.05, and (b) 18 wt.% of a second polyethylene resin having an Mw of 1.95 x 10 6 and an MWD of 5.09 the percentages being based on the weight of the second polyolefm composition.
  • the first polyethylene resin in the composition has a Tm of 135°C and a Ted Of IOO 0 C.
  • the first and second polyolefm solutions are supplied from their respective double-screw extruders to a three-layer-extruding T-die, and extruded therefrom to produce a layered extrudate (also called a laminate) of second polyolefm solution layer/first polyolefm solution layer/second polyolefm solution layer at a layer thickness ratio of 45.3/9.4/45.3.
  • the extrudate is cooled while passing through cooling rollers controlled at 20 0 C, producing an extrudate in the form of a three-layer gel-like sheet.
  • the gel-like sheet is heated to a temperature of 119.5°C for 150 sees, before being biaxially stretched (simultaneously) while exposed to a temperature of 119.5°C (the "biaxial stretching temperature") to a magnification of 5 fold in each of MD and TD at a average deformation speed of 750%/min by a tenter-stretching machine.
  • the stretched gel-like sheet is heat treated at 120.0 0 C for 18 sees.
  • the stretched three-layer gel-like sheet is fixed to an aluminum frame of 20 cm x 20 cm, immersed in a bath of methylene chloride controlled at 25°C for three minutes to remove the liquid paraffin, and dried by air flow at room temperature to produce a dried membrane.
  • the dried membrane Before dry stretching, the dried membrane has an initial dry length (MD) and an initial dry width (TD).
  • the dried membrane is dry-stretched in TD to a magnification of 1.6 fold while exposed to a temperature of 129.5°C, resulting in a second dry width.
  • the membrane's length (MD) remains approximately equal to the initial dry length during the TD dry stretching.
  • the membrane is subjected to a controlled reduction in width (TD) from the second dry width to a final magnification of 1.4 fold, the final magnification being based on the initial width of the membrane at the start of dry stretching, while exposed to a temperature of at 129.5°C (the "width reduction temperature").
  • the membrane's length (MD) remains approximately equal to the second dry length during the width reduction.
  • the membrane which remains fixed to the batch-stretching machine, is then heat-set while exposed to a temperature of 129.5°C (the "heat set temperature") for 10 minutes to produce the final multi-layer microporous membrane.
  • the dried membrane is then dry stretched.
  • a first polyolefm composition is prepared by dry-blending (a) 68.6 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 an MWD of 4.05, (b) 1.4 wt.% second polyethylene resin having an Mw of 1.95 x 10 6 and an MWD of 5.09, and (c) 30 wt.% polypropylene resin having an Mw of 1.1 x 10 6 , a heat of fusion of 114 J/g and an MWD of 5 , the percentages being based on the weight of the first polyolefm composition.
  • the first polyethylene resin in the composition has a Tm of 135°C and a Ted of 100 0 C.
  • a second polyolefm solution is prepared in the same manner as above by dry-blending (a) 98 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 an MWD of 4.05, and (b) 2 wt.% of a second polyethylene resin having an Mw of 1.95 x 10 6 and an
  • the first polyethylene resin in the composition has a Tm of 135°C and a Ted of l00°C.
  • the first and second polyolefin solutions are supplied from their respective double-screw extruders to a three-layer-extruding T-die, and extruded therefrom to produce a layered extrudate (also called a laminate) of second polyolefin solution layer/first polyolefin solution layer/second polyolefin solution layer at a layer thickness ratio of 45.5/9.0/45.5.
  • the extrudate is cooled while passing through cooling rollers controlled at 20 0 C, producing an extrudate in the form of a three-layer gel-like sheet.
  • the gel-like sheet is heated to a temperature of 119.3°C for 150 sees, before being biaxially stretched (simultaneously) while exposed to a temperature of 119.3°C (the "biaxial stretching temperature") to a magnification of 5 fold in each of MD and TD at an average deformation speed of 710%/min by a tenter-stretching machine.
  • the stretched gel-like sheet is heat treated at 95.0 0 C for 18 sees.
  • the stretched three-layer gel-like sheet is fixed to an aluminum frame of 20 cm x 20 cm, immersed in a bath of methylene chloride controlled at 25°C for three minutes to remove the liquid paraffin, and dried by air flow at room temperature to produce a dried membrane.
  • the dried membrane Before dry stretching, the dried membrane has an initial dry length (MD) and an initial dry width (TD).
  • the dried membrane is dry-stretched in TD to a magnification of 1.5 fold while exposed to a temperature of 129.0 0 C, resulting in a second dry width.
  • the membrane's length (MD) remains approximately equal to the initial dry length during the TD dry stretching.
  • the membrane is subjected to a controlled reduction in width (TD) from the second dry width to a final magnification of 1.3 fold, the final magnification being based on the initial width of the membrane at the start of dry stretching, while exposed to a temperature of at 129.0 0 C (the "width reduction temperature").
  • the membrane's length (MD) remains approximately equal to the second dry length during the width reduction.
  • the membrane which remains fixed to the batch-stretching machine, is then heat-set while exposed to a temperature of 129.0 0 C (the "heat set temperature") for 10 minutes to produce the final multi-layer microporous membrane.
  • the dried membrane is then dry stretched.
  • a first polyolefin composition is prepared by dry-blending (a) 68.6 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 an MWD of 4.05, (b) 1.4 wt.% second polyethylene resin having an Mw of 1.95 x 10 6 and an MWD of 5.09, and (c) 30 wt.% polypropylene resin having an Mw of 1.1 x 10 6 , a heat of fusion of 114 J/g and an MWD of 5 , the percentages being based on the weight of the first polyolefin composition.
  • the first polyethylene resin in the composition has a Tm of 135°C and a Ted of 100 0 C.
  • 30 wt.% of the resultant first polyolefin composition is charged into a first strong-blending double-screw extruder having an inner diameter of 58 mm and L/D of 42, and 70 wt.% of liquid paraffin (50 cst at 40 0 C) is supplied to the double-screw extruder via a side feeder to produce a first polyolefin solution.
  • the weight percents are based on the weight of the first polyolefin solution.
  • Melt-blending is conducted at 210 0 C and 200 rpm.
  • a second polyolefin solution is prepared in the same manner as above by dry-blending (a) 82 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 x 10 5 and an MWD of 4.05, and (b) 18 wt.% of a second polyethylene resin having an Mw of 1.95 x 10 6 and an MWD of 5.09 the percentages being based on the weight of the second polyolefin composition.
  • the first polyethylene resin in the composition has a Tm of 135°C and a Ted Of IOO 0 C.
  • 25 wt.% of the resultant second polyolefin composition is charged into a second strong-blending double-screw extruder having an inner diameter of 58 mm and L/D of 42, and 75 wt.% of liquid paraffin (50 cst at 40 0 C) is supplied to the double-screw extruder via a side feeder to produce the second polyolefin solution.
  • the weight percents are based on the weight of the second polyolefin solution.
  • Melt-blending is conducted at 210 0 C and 200 rpm.
  • the first and second polyolefin solutions are supplied from their respective double-screw extruders to a three-layer-extruding T-die, and extruded therefrom to produce a layered extrudate (also called a laminate) of second polyolefin solution layer/first polyolefin solution layer/second polyolefin solution layer at a layer thickness ratio of 45.8/8.4/45.8.
  • the extrudate is cooled while passing through cooling rollers controlled at 20 0 C, producing an extrudate in the form of a three-layer gel-like sheet.
  • the gel-like sheet is heated to a temperature of 117.0 0 C for 120 sees, before being biaxially stretched (simultaneously) in MD and TD while exposed to a temperature of 117.0 0 C (the "biaxial stretching temperature") to a magnification of 5 fold in each of MD and TD at a deformation speed of 940%/min by a tenter-stretching machine.
  • the stretched gel-like sheet is heat treated at 95.0 0 C for 15 sees.
  • the stretched three-layer gel-like sheet is fixed to an aluminum frame of 20 cm x 20 cm, immersed in a bath of methylene chloride controlled at 25°C for three minutes to remove the liquid paraffin, and dried by air flow at room temperature to produce a dried membrane.
  • the dried membrane Before dry stretching, the dried membrane has an initial dry length (MD) and an initial dry width (TD).
  • the dried membrane is dry-stretched in TD to a magnification of 1.6 fold while exposed to a temperature of 128.7°C, resulting in a second dry width.
  • the membrane's length (MD) remains approximately equal to the initial dry length during the TD dry stretching.
  • the membrane is subjected to a controlled reduction in width (TD) from the second dry width to a final magnification of 1.4 fold, the final magnification being based on the initial width of the membrane at the start of dry stretching, while exposed to a temperature of at 128.7°C (the "width reduction temperature").
  • the membrane's length (MD) remains approximately equal to the second dry length during the width reduction.
  • the membrane which remains fixed to the batch-stretching machine, is then heat-set while exposed to a temperature of 128.7°C (the "heat set temperature") for 10 minutes to produce the final multi-layer microporous membrane.
  • the dried membrane is then dry stretched. Comparative Example 2
  • a first polyolefm composition is prepared by dry-blending (a) 68.6 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 an MWD of 4.05, (b) 1.4 wt.% second polyethylene resin having an Mw of 1.95 x 10 6 and an MWD of 5.09, and (c) 30 wt.% polypropylene resin having an Mw of 1.1 x 10 6 , a heat of fusion of 114 J/g and an MWD of 5 , the percentages being based on the weight of the first polyolefm composition.
  • the first polyethylene resin in the composition has a Tm of 135°C and a Ted of 100 0 C.
  • first polyolefm composition 30 wt.% of the resultant first polyolefm composition is charged into a first strong-blending double-screw extruder having an inner diameter of 58 mm and L/D of 42, and 70 wt.% of liquid paraffin (50 cst at 40 0 C) is supplied to the double-screw extruder via a side feeder to produce a first polyolefm solution.
  • the weight percents are based on the weight of the first polyolefm solution.
  • Melt-blending is conducted at 210 0 C and 200 rpm.
  • a second polyolefm solution is prepared in the same manner as above by dry-blending (a) 82 wt.% of a first polyethylene resin having an Mw of 5.62 x 10 5 an MWD of 4.05, and (b) 18 wt.% of a second polyethylene resin having an Mw of 1.95 x 10 6 and an MWD of 5.09, the percentages being based on the weight of the second polyolefin composition.
  • the first polyethylene resin in the composition has a Tm of 135°C and a Tcd Of IOO 0 C.
  • the first and second polyolefin solutions are supplied from their respective double-screw extruders to a three-layer-extruding T-die, and extruded therefrom to produce a layered extrudate (also called a laminate) of second polyolefin solution layer/first polyolefin solution layer/second polyolefin solution layer at a layer thickness ratio of 45.3/9.4/45.3.
  • the extrudate is cooled while passing through cooling rollers controlled at 20 0 C, producing an extrudate in the form of a three-layer gel-like sheet.
  • the gel-like sheet is heated to a temperature of 115.5°C for 129 sees, before being biaxially stretched (simultaneously) in MD and TD while exposed to a temperature of 115.5°C (the "biaxial stretching temperature") to a magnification of 5 fold in each of MD and TD at a deformation speed of 880%/min. by a tenter-stretching machine.
  • the stretched gel-like sheet is heat treated at 95.0 0 C for 16 sees.
  • the stretched three-layer gel-like sheet is fixed to an aluminum frame of 20 cm x 20 cm, immersed in a bath of methylene chloride controlled at 25°C for three minutes to remove the liquid paraffin, and dried by air flow at room temperature to produce a dried membrane.
  • the dried membrane Before dry stretching, the dried membrane has an initial dry length (MD) and an initial dry width (TD).
  • the dried membrane is dry-stretched in TD to a magnification of 1.6 fold while exposed to a temperature of 127.3°C, resulting in a second dry width.
  • the membrane's length (MD) remains approximately equal to the initial dry length during the TD dry stretching.
  • the membrane is subjected to a controlled reduction in width (TD) from the second dry width to a final magnification of 1.3 fold, the final magnification being based on the initial width of the membrane at the start of dry stretching, while exposed to a temperature of at 127.3°C (the "width reduction temperature").
  • the membrane's length (MD) remains approximately equal to the second dry length during the width reduction.
  • the membrane which remains fixed to the batch-stretching machine, is then heat-set while exposed to a temperature of 127.3°C (the "heat set temperature") for 10 minutes to produce the final multi-layer microporous membrane.
  • the dried membrane is then dry stretched. Comparative Example 3
  • a first polyolefin composition comprising (a) 82% of a first polyethylene having an Mw of 5.6 x 10 5 and an Mw/Mn of 4.05, (b) 18% of a second polyethylene having an Mw of 1.9 x 10 6 and an Mw/Mn of 5.09, is prepared by dry-blending.
  • the polyethylene resin in the composition has a melting point of 135°C and a crystal dispersion temperature of 100 0 C.
  • a second polyolefin solution is prepared in the same manner as above except as follows.
  • a second polyolefin composition comprising (a) 63.7% of the first polyethylene having an Mw of 5.6 x 10 5 and an Mw/Mn of 4.05, and (b) 1.3% of the second polyethylene having of 1.9 x 10 6 and an Mw/Mn of 5.09, and (c) 35% of a polypropylene resin having an Mw of 1.6 x 10 6 , an Mw/Mn of 5.2 and a ⁇ Hm of 114.0 J/g, by weight of the second polyolefin composition, is prepared by dry-blending.
  • the polyethylene resin in the composition has a melting point of 135°C and a crystal dispersion temperature of 100 0 C.
  • Thirty parts by weight of the resultant second polyolefin composition is charged into a strong-blending double-screw extruder having an inner diameter of 58 mm and L/D of 42, and 70 parts by mass of liquid paraffin (50 cst at 40 0 C) is supplied to the double-screw extruder via a side feeder. Melt-blending is conducted at 210 0 C and 200 rpm to prepare a second polyolefin solution.
  • the first and second polyolefin solutions are supplied from their respective double-screw extruders to a three-layer-extruding T-die, and extruded therefrom to form an extrudate (also called a laminate) of first polyolefin solution layer/second polyolefin solution layer/first polyolefin solution layer at a layer thickness ratio of 46.45/7.1/46.45.
  • the extrudate is cooled while passing through cooling rollers controlled at 20 0 C, to form a three-layer gel-like sheet, which is simultaneously biaxially stretched at 119.3°C to a magnification of 5 fold in both machine (longitudinal) and transverse directions by a tenter-stretching machine.
  • the stretched three-layer gel-like sheet is fixed to an aluminum frame of 20 cm x 20 cm, immersed in a bath of methylene chloride controlled at 25°C to remove liquid paraffin with vibration of 100 rpm for 3 minutes, and dried by air flow at room temperature.
  • the dried membrane is re-stretched by a batch- stretching machine to a magnification of 1.5 fold in the transverse direction (TD) while exposed to a temperature of 127.3°C, and then relaxed (tenter clips re-adjusted to a narrower width) to a TD magnification of 1.3 fold at the same temperature, the magnification factors being based on the width of the membrane (TD) before dry stretching before re-stretching.
  • the re-stretched membrane which remains fixed to the batch-stretching machine, is heat-set at 127.3°C for 10 minutes to produce a three-layer microporous membrane.
  • compositions and processing conditions for the multilayer microporous membranes and comparative Examples are shown in Table 1.
  • properties of the multi-layer microporous membranes of the examples and comparative examples are shown in Table 2.
  • Comparative Examples 1 and 2 inventive Examples 1 and 2 maintain good 105 0 C heat shrinkage while providing improved heat shrink at 130 0 C and in the molten state.
  • Comparative Example 3 which has low shrinkage in the molten state and good
  • Examples 1 and 2 provide membranes that provide shrinkage performance under a range of conditions not achieved by the comparative examples while maintaining other properties such as permeability and puncture.
  • the multi-layer microporous membrane of the present invention with well-balanced properties and use of such multi-layer microporous membrane as a battery separator provides batteries having excellent safety, heat resistance, retention properties and productivity.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Laminated Bodies (AREA)
  • Cell Separators (AREA)

Abstract

La présente invention concerne des membranes polymères microporeuses appropriées pour être utilisées en tant que film de séparation de batterie. L'invention concerne également un procédé permettant de fabriquer une telle membrane, des batteries contenant de telles membranes sous forme de séparateurs de batteries, des procédés de fabrication de telles batteries et des procédés d'utilisation de telles batteries.
PCT/IB2010/000938 2009-05-04 2010-04-12 Membranes microporeuses et procédés de fabrication et d'utilisation de telles membranes WO2010128370A1 (fr)

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KR1020117024903A KR101690101B1 (ko) 2009-05-04 2010-04-12 미세다공막, 이러한 막의 제조 방법 및 사용 방법
JP2012507836A JP5661101B2 (ja) 2009-05-04 2010-04-12 微多孔膜ならびにかかる膜の製造方法および使用方法
CN2010800179929A CN102439760A (zh) 2009-05-04 2010-04-12 微孔膜以及该膜的制造方法和使用方法

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5907066B2 (ja) * 2011-02-03 2016-04-20 東レ株式会社 多孔性ポリプロピレンフィルム、蓄電デバイス用セパレータおよび蓄電デバイス
US9546253B2 (en) 2010-08-05 2017-01-17 Nitto Denko Corporation Polyolefin porous film, method for producing the same and apparatus for producing the same
WO2018089748A1 (fr) * 2016-11-11 2018-05-17 Celgard, Llc Membranes microcouches améliorées, séparateurs de batterie améliorés et procédés associés

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WO2008026780A1 (fr) * 2006-08-31 2008-03-06 Tonen Chemical Corporation Membrane microporeuse, séparateur de batterie et batterie
EP1905586A1 (fr) * 2005-07-15 2008-04-02 Tonen Chemical Corporation Membrane microporeuse multicouche constituée de polyoléfines et séparateur pour batterie
WO2009069533A1 (fr) * 2007-11-30 2009-06-04 Tonen Chemical Corporation Films microporeux, procédés de production et applications associés

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EP1905586A1 (fr) * 2005-07-15 2008-04-02 Tonen Chemical Corporation Membrane microporeuse multicouche constituée de polyoléfines et séparateur pour batterie
WO2008026780A1 (fr) * 2006-08-31 2008-03-06 Tonen Chemical Corporation Membrane microporeuse, séparateur de batterie et batterie
WO2009069533A1 (fr) * 2007-11-30 2009-06-04 Tonen Chemical Corporation Films microporeux, procédés de production et applications associés

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9546253B2 (en) 2010-08-05 2017-01-17 Nitto Denko Corporation Polyolefin porous film, method for producing the same and apparatus for producing the same
JP5907066B2 (ja) * 2011-02-03 2016-04-20 東レ株式会社 多孔性ポリプロピレンフィルム、蓄電デバイス用セパレータおよび蓄電デバイス
WO2018089748A1 (fr) * 2016-11-11 2018-05-17 Celgard, Llc Membranes microcouches améliorées, séparateurs de batterie améliorés et procédés associés
US11495865B2 (en) 2016-11-11 2022-11-08 Celgard, Llc Microlayer membranes, improved battery separators, and related methods

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