WO2021065283A1 - Film microporeux de polyoléfine, séparateur pour batterie rechargeable à électrolyte non aqueux, et batterie rechargeable à électrolyte non aqueux - Google Patents

Film microporeux de polyoléfine, séparateur pour batterie rechargeable à électrolyte non aqueux, et batterie rechargeable à électrolyte non aqueux Download PDF

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Publication number
WO2021065283A1
WO2021065283A1 PCT/JP2020/032867 JP2020032867W WO2021065283A1 WO 2021065283 A1 WO2021065283 A1 WO 2021065283A1 JP 2020032867 W JP2020032867 W JP 2020032867W WO 2021065283 A1 WO2021065283 A1 WO 2021065283A1
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Prior art keywords
stretching
polyolefin
resin composition
peak
microporous membrane
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PCT/JP2020/032867
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English (en)
Japanese (ja)
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大友崇裕
成鎭榮
安田巨文
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東レ株式会社
東レバッテリーセパレータフィルム韓国有限会社
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Priority to JP2020553666A priority Critical patent/JPWO2021065283A1/ja
Publication of WO2021065283A1 publication Critical patent/WO2021065283A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
    • B29C67/20—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 for porous or cellular articles, e.g. of foam plastics, coarse-pored
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
    • 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
    • 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 present invention relates to a polyolefin microporous membrane, a separator for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.
  • Microporous membranes are used in various fields such as filters for filtration membranes and dialysis membranes, separators for batteries and separators for electrolytic capacitors.
  • polyolefin microporous membranes made of polyethylene as a resin material are widely used as battery separators because they are excellent in chemical resistance, insulation, mechanical strength, etc., and in particular, they are excellent in safety because they have shutdown characteristics.
  • Secondary batteries such as lithium-ion secondary batteries, are widely used as batteries used in personal computers, mobile phones, etc. because of their high energy density.
  • the secondary battery is also used as a power source for driving a motor of an electric vehicle or a hybrid vehicle.
  • the polyethylene constituting the film has a viscosity average molecular weight of 300,000 to 2 million, and the melting point peak attributable to polyethylene by differential scanning calorimetry (DSC) is 137 ° C. or less. And at least two polyolefin microporous films having a temperature of 142 ° C. or higher are disclosed.
  • Patent Document 2 discloses a method for producing a polyolefin microporous membrane as a means for easily adjusting the mechanical strength and the like of the polyolefin microporous membrane.
  • Patent Document 3 (A) a step of extruding a polyolefin composition with an extruder to form a sheet-shaped polyethylene resin composition; (B) a step of forming a sheet-shaped polyolefin resin composition formed in step (A). A step of forming a microporous film by stretching, extracting, and heat-fixing to form a microporous film; (C) A plurality of microporous films formed in step (B) are laminated and stretched to form a laminated porous film.
  • a thin, high-strength polyolefin microporous film can be obtained by a method for producing a polyolefin microporous film, which comprises a step of forming; and a step of peeling off the laminated porous film formed in step (D) (C). ing.
  • the impact resistance of polyolefin microporous membranes is required to be further improved.
  • appropriate stretching conditions are set so as to apply high stress to the polyethylene molecular chain during stretching, and the orientation of the polyolefin molecular chain is enhanced to increase the orientation of the polyolefin molecular chain.
  • Methods for improving strength are known.
  • a wound body composed of a separator and an electrode is selected by a withstand voltage test (high pot test), and the pass rate of the withstand voltage test can be improved by improving the film strength of the separator.
  • a wound body that fails the withstand voltage test cannot be used for the battery, and improving the film strength of the separator leads to an increase in the yield at the time of battery fabrication.
  • Patent Document 1 although the pore melting temperature is kept low by performing high-temperature heat treatment after stretching the sheet-shaped polyethylene resin composition, the mechanical strength and air permeation resistance are inferior due to the influence of the high-temperature heat treatment. .. Patent Documents 2 and 3 are inferior in mechanical strength, and Patent Document 3 is inferior in productivity because it is necessary to go through a process of laminating and peeling a microporous film.
  • the present invention when the battery is exposed to a high temperature while suppressing the cost by consistently producing the microporous film by the sequential stretching method without going through a plurality of steps such as a laminating step. It is an object of the present invention to provide a polyolefin microporous membrane in which pores are easily closed and excellent in strength and air permeation resistance. Another object of the present invention is to provide a separator for a non-aqueous electrolytic solution-based secondary battery using a polyolefin microporous membrane capable of imparting safety and impact resistance to the battery.
  • the present inventors set the ratio of the melting point of the polyethylene-derived peak measured by the differential scanning calorimetry of the polyolefin microporous membrane to the amount of heat absorbed by melting within a specific range, and thereby the air permeability resistance of the polyolefin microporous membrane. It has been found that the film strength is improved while suppressing the increase in the degree, and the impact resistance of the battery used as the separator is improved. That is, the present invention is as follows.
  • the melting point of the first peak detected by the first temperature rise in the differential scanning calorimetry is more than 137 ° C and 140 ° C or less, the melting point of the second peak is 145 ° C or more, and the first peak A polyolefin microporous membrane having a melting heat absorption of 0.5 or more and less than 1.0 at the second peak when the melting heat absorption is 1.0.
  • the characteristics of the polyolefin microporous membrane of the present invention will be described.
  • the melting point of the first peak exceeded 137 ° C and was 140 ° C or less, and the second peak
  • the melting point is 145 ° C. or higher and the melting heat absorption amount at the first peak is 1.0
  • the melting heat absorption amount at the second peak is 0.5 or more and less than 1.0.
  • the two peaks exceed 137 ° C. and 140 in the melting endothermic curve obtained when the polyolefin microporous membrane is first heated (also referred to as the first heating) by differential scanning calorimetry (DSC). Peaks are detected within the range of ° C. or lower and at 145 ° C. or higher, respectively.
  • the first temperature rise is carried out from 30 ° C. to 230 ° C. at a temperature rising rate of 10 ° C./min.
  • the melting point of the first peak needs to be more than 137 ° C and 140 ° C or less from the viewpoint of battery safety.
  • the melting point of the first peak By setting the melting point of the first peak in the temperature range, the pores of the polyolefin microporous membrane are easily closed when the battery is exposed to a high temperature, and the safety of the battery is improved.
  • the temperature is 137 ° C. or lower, the permeability and strength of the polyolefin microporous membrane deteriorates. If the temperature exceeds 140 ° C., the pores of the polyolefin microporous membrane are less likely to be blocked when the battery is exposed to a high temperature, and the safety of the battery is inferior.
  • the melting point of the second peak needs to be 145 ° C. or higher from the viewpoint of improving the strength of the polyolefin microporous membrane and the impact resistance of the battery. If the temperature is lower than 145 ° C., the strength of the polyolefin microporous film is lowered and the impact resistance is inferior.
  • the melting heat absorption amount of the second peak when the melting heat absorption amount of the first peak is 1.0 (hereinafter referred to as the melting heat absorption amount).
  • the ratio) is 0.5 or more and less than 1.0. If the melting heat absorption of the second peak is less than 0.5, the impact resistance deteriorates. Further, when the melting heat absorption amount of the second peak is 1.0 or more, it becomes difficult for the pores of the polyolefin microporous membrane to be melt-closed, and the safety of the battery is lowered.
  • the film thickness of the polyolefin microporous film is not particularly limited, but it is desirable that the film thickness is thin from the viewpoint of increasing the capacity of the battery. It is preferably 20 ⁇ m or less, more preferably 15 ⁇ m or less, still more preferably 12 ⁇ m or less. When the film thickness is within the above range, it is superior in transparency and film resistance, and the battery capacity can be improved by thinning the film. On the other hand, the lower limit of the film thickness is not particularly limited, but is preferably 6 ⁇ m or more, more preferably 8 ⁇ m or more from the viewpoint of battery safety. When the film thickness is within the above range, it is possible to have a practical piercing strength and a hole closing function, and it is also suitable for the demand for further increasing the capacity of the battery.
  • the upper limit of the air permeation resistance of the polyolefin microporous membrane is preferably 200 sec. From the viewpoint of battery cycle characteristics. Less than / 100 cc, more preferably 185 sec. Less than / 100 cc, more preferably 170 sec. It is / 100 cc or less.
  • the upper limit of the air permeation resistance is in the range of the previous term, the capacity decrease when the battery is used for a long period of time can be suppressed, which contributes to the improvement of the cycle characteristics of the battery.
  • the lower limit of the air permeation resistance is preferably 100 sec. From the viewpoint of battery safety.
  • the lower limit of the puncture strength of the polyolefin microporous membrane is preferably 0.45 N / ⁇ m or more, and more preferably 0.50 N / ⁇ m or more.
  • the upper limit of the puncture strength is not particularly limited, but is, for example, 1.0 N / ⁇ m.
  • the method for producing a microporous polyolefin membrane of the present embodiment preferably includes the following steps.
  • Step A Step of melt-kneading the polyolefin and the plasticizer to prepare a polyolefin resin composition
  • Step B Step of extruding the polyolefin resin composition from the base to form a sheet-shaped polyolefin resin composition
  • Step (b) The step of stretching the sheet-shaped polyolefin resin composition obtained in step 1 in the mechanical direction
  • Step d The step of stretching the polyolefin resin composition stretched in the mechanical direction in the step (c) in the width direction to obtain a polyolefin resin composition film.
  • step (E) The width of the film obtained in the step (f) step (e) of re-stretching the polyolefin resin composition film obtained in the step (d) in the width direction at a temperature lower than the stretching temperature of the step (d).
  • Step of heat-relaxing in the direction Step of extracting the plastic agent from the film obtained in step (f) and drying (h) If necessary, the microporous film obtained in step (g) is placed in the width direction.
  • a polyolefin resin composition is prepared by melt-kneading a polyolefin resin as a raw material and a plasticizer.
  • melt-kneading method for example, a method using a twin-screw extruder described in Japanese Patent No. 2132327 and Japanese Patent No. 3347835 can be used.
  • the polyolefin resin composition prepared above is fed from an extruder to a die and extruded into a sheet-like shape.
  • a sheet-shaped polyolefin resin composition is formed by cooling the extruded molded product. The cooling is preferably performed to 90 ° C., which is lower than the crystal dispersion temperature (Tcd) of the polyolefin resin, more preferably 50 ° C. or lower, and further preferably 40 ° C. or lower. Cooling can immobilize the microphases of the polyolefin that have been separated by the plasticizer.
  • Tcd crystal dispersion temperature
  • the crystallinity is maintained in an appropriate range, and a sheet-like polyolefin resin composition suitable for stretching is obtained.
  • a cooling method a method of contacting with a refrigerant such as cold air or cooling water, a method of contacting with a cooling roll, or the like can be used, but it is preferable to contact with a roll cooled with the refrigerant for cooling.
  • a method for forming the sheet-shaped polyolefin resin composition for example, the methods disclosed in Japanese Patent No. 2132327 and Japanese Patent No. 3347835 can be used.
  • the stretching in the mechanical direction is preferably divided into 2 to 4 times, more preferably 2 to 3 times, and most preferably 2 times.
  • the first stretching ratio is preferably 3 times or less, more preferably 2 times or less.
  • the draw ratio from the second time onward is preferably 8 times or less, more preferably 6 times or less.
  • the temperature at the time of stretching in the mechanical direction is preferably in the range of the crystal dispersion temperature (Tcd) of the polyolefin resin or higher and the melting point or lower of the polyolefin resin.
  • the melting point of the polyolefin resin means the melting point of the polyethylene resin in the sheet-shaped polyolefin resin composition.
  • the stretching temperature is equal to or higher than the crystal dispersion temperature (Tcd) of the polyethylene resin
  • the polyethylene resin in the sheet-shaped polyolefin resin composition can be sufficiently softened and the stretching tension can be lowered, so that the film-forming property is improved. It becomes good, suppresses film rupture during stretching, and enables stretching at a high magnification.
  • the stretching temperature is the temperature of the sheet-shaped polyolefin resin composition, and when there is a temperature difference between the front and back surfaces such as roll stretching, it means the temperature at the center in the thickness direction.
  • the lower limit of the draw ratio in the width direction is preferably 4 times or more, more preferably 5 times or more.
  • the upper limit is preferably 10 times, more preferably 9 times.
  • the temperature at the time of stretching in the width direction is from the crystal dispersion temperature of the sheet-shaped polyolefin resin composition + 20 ° C. or higher to lower than the melting point of the sheet-shaped polyolefin resin composition.
  • the stretching temperature in the width direction is equal to or lower than the melting point of the sheet-shaped polyolefin resin composition, the polyolefin resin is prevented from melting, and the molecular chains can be efficiently oriented by stretching.
  • the stretching temperature is the crystal dispersion temperature of the sheet-shaped polyolefin resin composition + 20 ° C. or higher, the polyolefin resin is sufficiently softened and the stretching stress is low, so that the film-forming property is good and the film breaks during stretching. It is difficult to do so and can be stretched at a high magnification.
  • re-stretching in the width direction is performed at a temperature lower than the stretching temperature in the width direction of step (d).
  • the re-stretching needs to be performed in a plurality of times, and the number of times of stretching is preferably 2 to 4 times, more preferably 3 times.
  • the draw ratio is preferably 1.05 times or more.
  • the upper limit is preferably 2 times, more preferably 1.5 times.
  • the re-stretching temperature is in the range of the crystal dispersion temperature of the sheet-shaped polyolefin resin composition or more and less than 100 ° C. in order to express the second peak on the high melting point side detected by the DSC described above.
  • the second peak can be expressed while maintaining the first peak on the low melting point side detected by DSC.
  • the re-stretching temperature in the width direction from the second time onward is set to 100 ° C. or higher, the structure (lamella) constituting the first peak is also stretched, so that the temperature at which the pores of the polyolefin microporous film are melted rises. Battery safety is reduced. Further, if the sheet-shaped polyolefin resin composition is re-stretched at a temperature lower than the crystal dispersion temperature, the sheet is insufficiently softened and the film is ruptured.
  • the resin constituting the polyolefin microporous film is mainly composed of polyethylene resin.
  • the proportion of the polyethylene resin is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 100%, when the entire polyolefin microporous film is 100% by mass.
  • the ratio of the polyethylene resin contained in the polyolefin microporous membrane is within the above range, practical permeability and piercing strength can be obtained.
  • the polyolefin microporous membrane may contain a resin other than the polyethylene resin.
  • a resin other than the polyethylene resin for example, a homopolymer obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and the like, a two-step polymer, a copolymer or a mixture thereof and the like can be mentioned.
  • the addition of polypropylene can improve the temperature (meltdown temperature) at which the microporous membrane can retain its shape when exposed to high temperatures.
  • a relaxation step may be provided after stretching in the width direction.
  • the relaxation temperature is preferably from the crystal dispersion temperature of the polyethylene resin constituting the polyolefin microporous film to less than 100 ° C.
  • the relaxation rate is preferably 1% to 20%, more preferably 1% to 10% from the viewpoint of the flatness of the microporous membrane. If the treatment is performed at a relaxation rate higher than 20%, slack is generated in the width direction of the microporous membrane, which interferes with the membrane-forming equipment and breaks the microporous membrane, resulting in deterioration of productivity.
  • (G) Step of extracting and drying the plasticizer The plasticizer is extracted and removed from the sheet thereafter to obtain a microporous membrane. To remove the plasticizer, wash with a washing solvent. Since the polyolefin phase is phase-separated from the plasticizer phase, when the plasticizer is removed, it is composed of fibrils that form a fine three-dimensional network structure, and is porous with pores (voids) that communicate irregularly in three dimensions. Film is obtained. Since the cleaning solvent and the method for removing the plasticizer using the cleaning solvent are known, the description thereof will be omitted. For example, the method disclosed in Japanese Patent No. 2132327 and Japanese Patent Application Laid-Open No. 2002-256099 can be used.
  • the microporous membrane from which the plasticizer has been removed is dried by a heat drying method or an air drying method.
  • the drying temperature is preferably not less than the crystal dispersion temperature (Tcd) of the polyethylene resin, and particularly preferably 5 ° C. or more lower than Tcd. Drying is preferably carried out with the microporous membrane film as 100% by mass (dry weight) until the residual cleaning solvent is 3% by mass or less, and more preferably 1% by mass or less.
  • the residual cleaning solvent is within the above range, the porosity of the polyolefin microporous membrane is maintained, and deterioration of permeability is suppressed.
  • the dried microporous membrane may be heat-fixing treatment and stretching / heat-relaxing treatment in the width direction. Crystals are stabilized by heat-fixing treatment and stretching / heat-relaxation treatment in the width direction, the lamellar layer is made uniform, and a microporous film having excellent strength and heat shrinkage can be produced.
  • the heat fixation temperature can be set within a temperature range from the crystal dispersion temperature of the polyethylene resin constituting the polyolefin microporous film to the melting point or lower, and can be carried out by a tenter method, a roll method or a rolling method.
  • the stretching / thermal relaxation temperature is set within a temperature range from the crystal dispersion temperature of the polyethylene resin constituting the polyolefin microporous film to the melting point or lower, and the stretching rate is preferably 100% to 200%, and the subsequent relaxation rate is adjusted. Is preferably 1% to 30%, more preferably 1% to 20% from the viewpoint of heat shrinkage and flatness of the microporous membrane. If the treatment is performed at a relaxation rate higher than 20%, the microporous membrane will slacken in the width direction, which will interfere with the equipment and the microporous membrane will be torn.
  • DSC Differential scanning calorimetry
  • Diamond DSC manufactured by PerkinElmer Co., Ltd.
  • a microporous polyolefin membrane was punched into a circle with a diameter of 5 mm, and several 6 mg measurement samples were placed on an open sample pan made of aluminum having a diameter of 5 mm, a clamping cover was placed on the sample, and the sample was fixed in the aluminum pan with a sample sealer. After allowing the aluminum pan to stand at 30 ° C. for 1 minute in a nitrogen atmosphere, the temperature is raised from 30 ° C. to 230 ° C.
  • the maximum value of the heat flow appearing between the above was defined as the melting point of the first peak, and the maximum value of the second peak appearing above 145 ° C. was defined as the melting point of the second peak.
  • the melting heat absorption amount of the second peak when the melting heat absorption amount of the first peak was 1.0 was defined as the melting heat absorption amount ratio.
  • the melt endothermic amounts of the first peak and the second peak when calculating the melt endothermic amount ratio were obtained by integrating the melt endothermic curves attributed to the first peak and the second peak obtained by the above fitting.
  • a digital Oken-type air permeability tester EGO1 manufactured by Asahi Seiko Co., Ltd. was used for one center point within the range of the test piece (95 mm x 95 mm) cut out from the microporous membrane, and wrinkles were formed in the measurement part.
  • the value measured according to JIS P-8117 (2009) was taken as the air permeation resistance of the sample.
  • the same measurement was performed on 10 test pieces collected from arbitrary positions, and the average value of the 10 measured values was taken as the air permeation resistance (sec / 100 ml) of the microporous membrane.
  • -Slurries were prepared by dispersing in methylpyrrolidone (NMP). This slurry was applied to one side of an aluminum foil having a thickness of 20 ⁇ m to be a positive electrode current collector with a die coater at an active material application amount of 250 g / m 2 and an active material bulk density of 3.00 g / cm 3. Then, it was dried at 130 ° C. for 3 minutes, compression-molded by a roll press machine, and then cut into a strip shape having a width of about 57 mm.
  • NMP methylpyrrolidone
  • a slurry was prepared by dispersing 96.9% by mass of artificial graphite as an active material, 1.4% by mass of an ammonium salt of carboxymethyl cellulose and 1.7% by mass of a styrene-butadiene copolymer latex as a binder in purified water.
  • This slurry is coated on one side of a copper foil having a thickness of 12 ⁇ m, which is a negative electrode current collector, with a die coater at a high packing density of an active material coating amount of 106 g / m 2 and an active material bulk density of 1.55 g / cm 3. Attached. Then, it was dried at 120 ° C. for 3 minutes, compression-molded by a roll press machine, and then cut into a strip shape having a width of about 58 mm.
  • a strip-shaped negative electrode, a separator, a strip-shaped positive electrode, and a separator were stacked in this order and wound a plurality of times in a spiral shape with a winding tension of 250 gf to prepare an electrode plate laminate.
  • This electrode plate laminate is housed in a stainless steel container having an outer diameter of 18 mm and a height of 65 mm, and an aluminum tab derived from the positive electrode current collector is attached to the container lid terminal and made of nickel derived from the negative electrode current collector. The tabs were welded to the vessel wall.
  • a withstand voltage test was performed on the 10 batteries produced before injection of the electrolyte using IMP-1090 manufactured by Nippon Technart Co., Ltd., and even one battery that had a short circuit was not allowed, and one that did not have a short circuit was excellent. I evaluated it. After that, the predominant battery before injecting the electric solution was dried under vacuum at 80 ° C. for 12 hours, the above non-aqueous electrolytic solution was injected into the container in an argon box, and the battery was sealed to prepare a cylindrical battery. did.
  • the PP ratio contained in the polyolefin microporous membrane was calculated from Equation 1.
  • the microporous membrane was cut into a size of 50 mm ⁇ 50 mm, and n microporous membranes cut out so as to have a thickness of 20 ⁇ m to 30 ⁇ m were stacked, and the film thickness and weight of the stacked microporous membranes were measured to calculate the porosity. did.
  • the absorbance Abs of the superposed microporous membranes was measured in the permeation mode.
  • Absorbance Abs used a value of 1376 cm -1 , which is a peak derived from PP, and background measurement was performed without setting any sample before measuring absorbance Abs.
  • Example 1 Mw ultra high molecular weight polyethylene of 2.5 ⁇ 10 6 (UHMwPE) 40 wt%, Mw was obtained a high-density polyethylene (HDPE) of 60 mass% were dry blended mixture is 2.8 ⁇ 10 5. 25% by mass of the obtained mixture was melt-kneaded with 75% by mass of liquid paraffin in a twin-screw extruder to prepare a polyethylene solution. This polyethylene solution was supplied to a T-die from a twin-screw extruder and extruded to obtain a molded product, which was then cooled while being taken up by a cooling roll to form a sheet-shaped polyethylene resin composition.
  • UHMwPE ultra high molecular weight polyethylene of 2.5 ⁇ 10 6
  • HDPE high-density polyethylene
  • the sheet-shaped polyethylene resin composition was stretched in two times in the machine direction using a roll stretching machine. As the first stretching, it was stretched 1.3 times at a stretching temperature of 116 ° C., and then as the second stretching, it was stretched 5.9 times at 116 ° C.
  • FIG. 1 shows the melting endothermic curve of the DSC obtained in Example 1.
  • Example 2 A microporous film having a thickness of 11.0 ⁇ m was obtained by the same method as in Example 1 except that the sheet-shaped polyethylene resin composition was stretched in the width direction and then relaxed at 80 ° C. in the width direction by 10%. .. The obtained microporous membrane was excellent in battery safety test and production stability.
  • Example 3 Mw ultra high molecular weight polyethylene of 2.5 ⁇ 10 6 (UHMwPE) 38 wt%, Mw of 2.8 ⁇ 10 5 and a high density polyethylene (HDPE) 57 wt% polypropylene having Mw of 1.6 ⁇ 10 6 A mixture was obtained by dry blending 5% by mass of (PP).
  • UHMwPE 2.5 ⁇ 10 6
  • HDPE high density polyethylene
  • Example 4 Mw ultra high molecular weight polyethylene of 2.5 ⁇ 10 6 (UHMwPE) 35 wt%, Mw of 2.8 ⁇ 10 5 and a high density polyethylene (HDPE) 48 wt% polypropylene having Mw of 1.6 ⁇ 10 6 17% by mass of (PP) was dry-blended to obtain a mixture.
  • UHMwPE 2.5 ⁇ 10 6
  • HDPE high density polyethylene
  • 35% by mass of the obtained mixture was melt-kneaded with 65% by mass of liquid paraffin using a twin-screw extruder to prepare a polyolefin solution.
  • the molded body obtained by supplying this polyolefin solution to a T-die from a twin-screw extruder and extruding it was cooled while being taken up by a cooling roll to form a sheet-shaped polyolefin resin composition.
  • the sheet-shaped polyolefin resin composition was stretched in two times in the machine direction using a roll stretching machine. As the first stretching, it was stretched 1.3 times at a stretching temperature of 116 ° C., and then as the second stretching, it was stretched 5.9 times at 117 ° C.
  • Example 1 The microporous membrane was formed in the same manner as in Example 1 except that the first width direction stretching was performed 8.2 times at 123 ° C. without performing the second and third width direction stretching. Obtained.
  • the melting point of the obtained microporous membrane was measured by DSC, only one peak was obtained, which was inferior in battery safety.
  • FIG. 2 shows the melting endothermic curve of the DSC obtained in Comparative Example 1.
  • the sheet-shaped polyethylene resin composition was stretched in three times in the machine direction using a roll stretching machine.
  • the first stretching was performed 1.3 times at a stretching temperature of 118 ° C.
  • the second stretching was performed 1.8 times at 115 ° C.
  • the third stretching was carried out 2.2 times at 114 ° C. ..
  • the first stretching is 6.8 times at a stretching temperature of 126 ° C.
  • the second stretching is 1.1 times at 100 ° C. in the width direction
  • the third stretching is 1.1 at 90 ° C. It was stretched twice.
  • the sheet-shaped polyethylene resin composition was simultaneously biaxially stretched 5 ⁇ 5 times at 117 ° C. with a tenter stretching machine.
  • the mixture was washed in a methylene chloride washing tank to remove liquid paraffin and dried.
  • the dried membrane was heat-fixed in a tenter at 126.8 ° C. while maintaining the dimensions in the width direction to obtain a polyethylene microporous membrane having a thickness of 12.0 ⁇ m.
  • Table 1 shows the physical characteristics of the obtained polyethylene microporous membrane.
  • the sheet-shaped polyethylene resin composition was simultaneously biaxially stretched 7 ⁇ 7 times at 120 ° C. using a tenter stretching machine, then heated at 140 ° C. for 10 seconds, washed in a methylene chloride washing tank, and liquid paraffin. Was removed and dried.
  • the dried membrane was stretched 1.2 times in the width direction at 115 ° C. in a tenter, then relaxed by 8.3% and heat-fixed to obtain a polyethylene microporous membrane having a thickness of 13.0 ⁇ m. ..
  • Table 1 shows the physical characteristics of the obtained polyethylene microporous membrane. Although the obtained microporous membrane had two melting point peaks by DSC, the melting heat absorption ratio was 0.10. Further, since the sheet-shaped polyethylene resin composition was stretched and then heated at 140 ° C. for 10 seconds, the air permeation resistance was significantly inferior to that of the examples.
  • the polyolefin microporous membrane of the present invention is excellent in impact resistance and production stability, it can be suitably used as a separator for a non-aqueous electrolyte type secondary battery.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Polymers & Plastics (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Cell Separators (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Abstract

La présente invention vise à fournir un film microporeux de polyoléfine qui est approprié en tant que séparateur pour une batterie rechargeable à électrolyte non aqueux et peut conférer une sécurité et une résistance au choc à la batterie, et avec lequel les coûts peuvent être maintenus bas par la production du film microporeux de façon constante par le biais d'un procédé d'étirage séquentiel sans passer par une pluralité de processus tels qu'un processus de stratification. L'invention concerne par conséquent un film microporeux de polyoléfine qui a un premier point de fusion maximal supérieur à 137 °C et pas supérieur à 140 °C détecté par calorimétrie différentielle à balayage pendant une première augmentation de température, un second point de fusion maximal d'au moins 145 °C, et une chaleur de fusion latente au niveau du second pic d'au moins 0,5 et inférieure à 1,0, la chaleur de fusion latente au niveau du premier pic étant de 1,0.
PCT/JP2020/032867 2019-09-30 2020-08-31 Film microporeux de polyoléfine, séparateur pour batterie rechargeable à électrolyte non aqueux, et batterie rechargeable à électrolyte non aqueux WO2021065283A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023054139A1 (fr) * 2021-09-29 2023-04-06 東レ株式会社 Membrane de polyoléfine microporeuse, séparateur pour batteries, et batterie secondaire

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07268118A (ja) * 1994-03-31 1995-10-17 Mitsui Petrochem Ind Ltd 高分子量ポリエチレンと高分子量ポリプロピレンの組成 物よりなる微孔性二軸延伸フィルム、その製法およびそ の用途
JP2003020357A (ja) * 2001-07-06 2003-01-24 Asahi Kasei Corp ポリオレフィン微多孔膜およびその製造方法
JP2004018838A (ja) * 2002-06-20 2004-01-22 Asahi Kasei Corp ポリオレフィン微多孔膜
WO2011118660A1 (fr) * 2010-03-23 2011-09-29 帝人株式会社 Film polyoléfinique microporeux, séparateur pour batterie secondaire non aqueuse, batterie secondaire non aqueuse, et procédé de production de film polyoléfinique microporeux
JP2011249240A (ja) * 2010-05-28 2011-12-08 Asahi Kasei E-Materials Corp 無機粒子含有ポリオレフィン微多孔膜及び非水電解液電池用セパレータ

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07268118A (ja) * 1994-03-31 1995-10-17 Mitsui Petrochem Ind Ltd 高分子量ポリエチレンと高分子量ポリプロピレンの組成 物よりなる微孔性二軸延伸フィルム、その製法およびそ の用途
JP2003020357A (ja) * 2001-07-06 2003-01-24 Asahi Kasei Corp ポリオレフィン微多孔膜およびその製造方法
JP2004018838A (ja) * 2002-06-20 2004-01-22 Asahi Kasei Corp ポリオレフィン微多孔膜
WO2011118660A1 (fr) * 2010-03-23 2011-09-29 帝人株式会社 Film polyoléfinique microporeux, séparateur pour batterie secondaire non aqueuse, batterie secondaire non aqueuse, et procédé de production de film polyoléfinique microporeux
JP2011249240A (ja) * 2010-05-28 2011-12-08 Asahi Kasei E-Materials Corp 無機粒子含有ポリオレフィン微多孔膜及び非水電解液電池用セパレータ

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023054139A1 (fr) * 2021-09-29 2023-04-06 東レ株式会社 Membrane de polyoléfine microporeuse, séparateur pour batteries, et batterie secondaire

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