WO2022191651A1 - Membrane microporeuse en polyoléfine - Google Patents

Membrane microporeuse en polyoléfine Download PDF

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Publication number
WO2022191651A1
WO2022191651A1 PCT/KR2022/003404 KR2022003404W WO2022191651A1 WO 2022191651 A1 WO2022191651 A1 WO 2022191651A1 KR 2022003404 W KR2022003404 W KR 2022003404W WO 2022191651 A1 WO2022191651 A1 WO 2022191651A1
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WO
WIPO (PCT)
Prior art keywords
microporous membrane
polyolefin microporous
polyolefin
pore size
coating layer
Prior art date
Application number
PCT/KR2022/003404
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English (en)
Korean (ko)
Inventor
김선영
이동원
박정환
미치조에준지
Original Assignee
도레이배터리세퍼레이터필름 한국유한회사
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Publication date
Priority claimed from KR1020210084764A external-priority patent/KR20220128244A/ko
Application filed by 도레이배터리세퍼레이터필름 한국유한회사 filed Critical 도레이배터리세퍼레이터필름 한국유한회사
Priority to KR1020237026975A priority Critical patent/KR20230136139A/ko
Publication of WO2022191651A1 publication Critical patent/WO2022191651A1/fr

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Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409Separators, membranes or diaphragms characterised by the material
    • H01M50/411Organic material
    • H01M50/414Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417Polyolefins
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409Separators, membranes or diaphragms characterised by the material
    • H01M50/446Composite material consisting of a mixture of organic and inorganic materials
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409Separators, membranes or diaphragms characterised by the material
    • H01M50/449Separators, membranes or diaphragms characterised by the material having a layered structure
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409Separators, membranes or diaphragms characterised by the material
    • H01M50/449Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a polyolefin microporous membrane, and more particularly, to a water-based coating polyolefin microporous membrane having excellent heat resistance.
  • Polyolefin-based microporous membranes used as separators for lithium ion secondary batteries are closely related to battery life, output, and safety. Therefore, suitable permeability, mechanical properties, heat resistance, etc. are required for the polyolefin microporous membrane.
  • An object of the present invention is to provide a polyolefin microporous membrane for battery separators having excellent heat resistance.
  • the present invention provides a polyolefin microporous membrane having an average pore size of 65 nm or less on at least one of both surfaces.
  • the present invention provides a coated porous film in which a water-based coating layer is formed on the above-described polyolefin microporous film.
  • the polyolefin microporous membrane for battery separator according to the present invention exhibits excellent heat resistance by adjusting the average pore size of the surface of the surface in contact with the coating layer to 65 nm or less. As a result, it is possible to improve the safety of a lithium ion secondary battery including a coating separator for a battery manufactured using the polyolefin microporous membrane according to the present invention.
  • the polyolefin microporous film of the present invention exhibits excellent heat resistance properties, it is possible to thin the coating layer, and as a result, a high-capacity secondary battery having high output characteristics can be manufactured, and also the secondary battery manufacturing cost can be reduced. have.
  • the polyolefin microporous membrane of the present invention is characterized in that the average pore size of at least one of both surfaces is 65 nm or less.
  • the average pore size of the surface of the polyolefin microporous membrane may be 30 to 65 nm, for example, 40 to 65 nm.
  • the adhesive strength is weak compared to the case where the above-mentioned range is satisfied, and the heat shrinkage reduction rate of the coated microporous membrane compared to the substrate decreases.
  • the average pore size of the surface of the polyolefin microporous membrane is less than the above-mentioned range, the amount of electrolyte impregnation may decrease and ionic resistance may increase, and as a result, the output characteristics and lifespan characteristics of the battery may be reduced.
  • the ratio (number ratio) of pores having a pore size of 100 nm or more may be 15% or less, for example, 3 to 15%, and in another example 5 to 13.5%.
  • the ratio (number ratio) of pores having a pore size of 100 nm or more satisfies the above-mentioned range, the adhesive strength of the contact surface between the polyolefin microporous membrane and the coating layer during coating further increases, so that the peel strength of the coated microporous membrane is further increased. improved and heat shrinkage is further improved, enabling thinning of the coating layer.
  • the ratio (number ratio) of pores having a pore size of 100 nm or more exceeds the above-mentioned range, the adhesive strength is weak compared to the case where the above-mentioned range is satisfied, and the reduction rate of heat shrinkage of the coated microporous membrane compared to the substrate is decreased. Problems can arise.
  • the polyolefin microporous membrane of the present invention may have a surface porosity of 10 to 25%, for example, 15 to 25%.
  • the surface porosity of the polyolefin microporous membrane satisfies the range, the adhesive strength of the contact surface between the polyolefin microporous membrane and the coating layer is further increased during coating, so that the peel strength of the coated microporous membrane is further improved and heat shrinkage is further improved.
  • the adhesive strength is weak compared to the case where the above range is satisfied, and problems such as a decrease in the rate of reduction of heat shrinkage of the coated microporous membrane compared to the substrate may occur.
  • the surface porosity of the polyolefin microporous membrane is less than the above range, the amount of electrolyte impregnation may decrease and ionic resistance may increase, and as a result, the output characteristics and lifespan characteristics of the battery may be deteriorated.
  • the thickness of the polyolefin microporous film is not particularly limited, and may be, for example, 2 to 50 um, and in another example 3 to 30 um.
  • polyolefin resin constituting the polyolefin microporous membrane of the present invention conventional polyolefin resins known in the art may be used without limitation.
  • it may include a polyethylene resin, a polypropylene resin, or a mixture thereof.
  • the content of the polyethylene resin may be, for example, 50 mass% or more, for example, 60 mass% or more, based on the total mass of the polyolefin resin.
  • the polyethylene resin may have a viscosity average molecular weight (Mv) of, for example, 2.0 ⁇ 10 5 to 4.0 ⁇ 10 6 g/mol, and in another example, 2.5 ⁇ 10 5 to 3.5 ⁇ 10 6 g/mol.
  • Mv viscosity average molecular weight
  • high-density polyethylene (HDPE), medium-density polyethylene (MDPE), or low-density polyethylene (LDPE) may be used without limitation.
  • two or more types of polyethylene having different viscosity average molecular weights (Mv) or densities may be mixed.
  • the content of the polypropylene resin may be, for example, 50 mass% or less, for example, 40 mass% or less, based on the total mass of the polyolefin resin.
  • the polypropylene resin may have a viscosity average molecular weight (Mv) of, for example, 7.0 ⁇ 10 4 to 3.2 ⁇ 10 6 g/mol, and in another example, 9.5 ⁇ 10 4 to 3.0 ⁇ 10 6 g/mol.
  • Mv viscosity average molecular weight
  • As the polypropylene atactic polypropylene (Atactic PP), syndiotactic polypropylene (Syndiotactic PP), isotactic polypropylene (isotactic PP), etc. may be used without limitation.
  • two or more polypropylenes having different viscosity average molecular weights (Mv) or densities may be mixed.
  • the polyolefin resin may further include a polyolefin that imparts a shutdown function.
  • polyolefins that impart a shutdown function include low-density polyethylene (LDPE) or polyethylene wax.
  • LDPE low-density polyethylene
  • the low-density polyethylene (LDPE) at least one selected from the group consisting of branched LDPE, linear LDPE, and ethylene/ ⁇ -olefin copolymer prepared by a single site catalyst may be used, and the amount of added sugar It may be appropriately adjusted within a range known in the art.
  • antioxidants for example, antioxidants, pore formers, etc. may be included in a range that does not impair the effects of the present invention.
  • the polyolefin microporous membrane according to the present invention may have a multilayer structure in which several layers of the microporous membrane are stacked.
  • the method for producing the polyolefin microporous membrane of the present invention is not particularly limited, and for example, (1) melt-kneading polyolefin and a plasticizer to prepare a polyolefin solution, (2) extruding the polyolefin solution and cooling it to form a sheet (3) a first stretching step of stretching the sheet-like material to form a film, (4) removing the plasticizer from the film, (5) drying the film from which the plasticizer is removed, ( 6) a second stretching step of re-stretching the dried film and (7) a heat treatment step.
  • melt-kneading polyolefin and a plasticizer to prepare a polyolefin solution
  • extruding the polyolefin solution and cooling it to form a sheet (3) a first stretching step of stretching the sheet-like material to form a film, (4) removing the plasticizer from the film, (5) drying the film from which the plasticizer is removed, ( 6) a second stretching step of re
  • a polyolefin solution is prepared by melt-kneading a polyolefin resin and a plasticizer.
  • a method of melt-kneading a composition comprising a polyolefin-based resin and a plasticizer a conventional method known in the art may be used without limitation.
  • a method of melt-kneading a polyolefin-based resin and a plasticizer at a temperature of 100 to 250° C. and using a twin-screw extruder may be used.
  • the content of the polyolefin-based resin is not particularly limited, and may be included, for example, in an amount of 20 to 50% by weight based on the total weight of the composition including the polyolefin-based resin and a plasticizer, and in another example, it may be included in an amount of 20 to 40% by weight.
  • plasticizer conventional components known in the art may be used without limitation, and for example, any organic compound forming a single phase with the polyolefin-based resin at an extrusion temperature may be used.
  • plasticizers that can be used include liquid paraffin (or paraffin oil) such as nonan, decane, decalin, liquid paraffin (LP), aliphatic or cyclic paraffin wax such as hydrocarbon; phthalic acid esters such as dibutyl phthalate and dioctyl phthalate; fatty acids having 10 to 20 carbon atoms, such as palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid; and fatty acid alcohols having 10 to 20 carbon atoms, such as palmitic alcohol, stearic alcohol, and oleic alcohol.
  • the above plasticizers may be used alone or in combination of two or more.
  • liquid paraffin is harmless to the human body and has a high boiling point and low volatile components, so it is suitable for use as a plasticizer in a wet method.
  • the content of the plasticizer is not particularly limited, and may be included, for example, in an amount of 50 to 90% by weight, for example, in an amount of 60 to 80% by weight, based on the total weight of the composition including the polyolefin-based resin and the plasticizer. .
  • polyolefin-based resin In addition to the above-described polyolefin-based resin, other resins, inorganic particles, additives, and the like conventional in the art may be included.
  • the polyolefin solution prepared in step (1) is extruded in a die having an extruder and cooled to form a sheet-like article.
  • the surface pores can be controlled by controlling the cooling rate.
  • the cooling may be performed at a rate of 40 °C/min or more, for example 100 °C/min or more, 100 to 650 °C/min in another example, and 300 to 650 °C/min in another example.
  • the cooling rate is less than the above range, the phase separation between the resin and the plasticizer and the phase separation between the polyethylene and the polypropylene in the resin proceed excessively, so that the initial micropore formation may become non-uniform, and as a result, the surface pore size and the surface pore rate are reduced to a certain range. It can be difficult to control within and to ensure a uniform pore size.
  • the cooling method is not particularly limited, and methods known in the art, for example, cooling in contact with a chill roll, cooling with cold air, or cooling by immersion in cold water may be used.
  • the sheet-like material obtained in step (2) is biaxially stretched one or more times to form a film.
  • the size of the surface and internal pores of the porous membrane is primarily controlled through stretching and heating in the first stretching process.
  • the first stretching step may be performed at a predetermined magnification by a conventional method in the art, for example, a tenter method, a roll method, an inflation method, a rolling method, or a combination of these methods.
  • a tenter method for example, a tenter method, a roll method, an inflation method, a rolling method, or a combination of these methods.
  • biaxial stretching either biaxial stretching may be performed simultaneously or sequential stretching may be performed.
  • the draw ratio is different depending on the thickness of the sheet-like material, but for example, in biaxial stretching, it is appropriate to perform at least 2 times x 2 times or more in any direction, for example, in the range of 3 to 10 times. can do.
  • the structure and pore size of the fibril may be adjusted by controlling the stretching temperature and the air volume.
  • the stretching temperature may be, for example, in the range of 100 to 130 °C, as another example, it may be in the range of 105 to 125 °C.
  • the stretching may be performed to have adequate air permeability and mechanical strength without blocking pores (pores) in the sheet.
  • the first stretching temperature exceeds the above-mentioned temperature range, the resin in the sheet is melted so that the molecular chains are not oriented by stretching and the pore size may become non-uniform.
  • the first stretching temperature is less than the above-mentioned temperature range, softening of the sheet may become insufficient, which may cause breakage by stretching, and stretching of a high magnification may not be achieved.
  • a plasticizer is extracted from the stretched film. Since the polyolefin phase is phase-separated from the plasticizer, a porous membrane in which a plurality of pore structures are formed is obtained when the plasticizer is removed.
  • a method for removing the plasticizer a conventional method known in the art may be used without limitation.
  • the washing solvent is not particularly limited as long as it is an organic solvent capable of extracting the plasticizer and can be used.
  • organic solvent capable of extracting the plasticizer
  • halogenated hydrocarbons such as methylene chloride, 1,1,1-trichloroethane, and fluorocarbons with high extraction efficiency and easy drying; hydrocarbons such as n-hexane and cyclohexane; alcohols such as ethanol and isopropanol; Ketones, such as acetone and 2-butanone, etc.
  • methylene chloride can be used as an organic solvent.
  • the polyolefin microporous membrane obtained by removing the plasticizer may be dried using a conventional drying method known in the art.
  • a heat-drying method, an air-drying method, etc. may be used.
  • the dried film is re-stretched again at least in the uniaxial direction.
  • the size of the surface pores of the porous membrane is secondarily adjusted through stretching and heating in the second stretching process, thereby preparing a final microporous membrane.
  • the second stretching process may be performed by a tenter method or the like in the same manner as the first stretching process while heating the film.
  • the stretching may be uniaxial stretching or biaxial stretching.
  • the temperature of the second stretching process may be, for example, the crystal dispersion temperature of the polyolefin resin constituting the microporous film or more, the crystal dispersion temperature + 40 ° C. or less, and as another example, the crystal dispersion temperature + 10 ° C. or more, the crystal The dispersion temperature may be in the range of up to +40 °C.
  • the crystal dispersion temperature refers to a value obtained by measuring the temperature characteristics of dynamic viscoelasticity based on ASTM D4065. When the polyolefin resin is polyethylene, the crystal dispersion temperature thereof is generally 90 to 100°C.
  • the second stretching temperature By adjusting the second stretching temperature to the above-mentioned range, it is possible to prevent a decrease in air permeability and a deviation in physical properties in the width direction of the sheet when stretching in the transverse direction (width direction: TD direction).
  • By setting the second stretching temperature within the above range it is possible to suppress the occurrence of variations in air permeation resistance in the stretched sheet width direction and to control the pore size of the membrane surface within the scope of the present invention.
  • a temperature exceeding the above range it may become difficult to control the pore size and surface porosity within the scope of the present invention due to excessive melting of the polyolefin resin, and at a temperature below the above range, the film is stretched due to insufficient softening of the film. It is easy to be damaged by , and it may be difficult to secure a uniform surface pore size because uniform elongation cannot be achieved.
  • the polyolefin resin can be sufficiently softened, and the polyolefin resin can be stretched uniformly by preventing film breakage.
  • the second stretching temperature may be in the range of 90 to 140 °C, as another example, it may be in the range of 120 to 140 °C.
  • the magnification in the uniaxial direction of the second stretching may be, for example, 1.0 to 1.8 times, and in another example, 1.2 to 1.6 times.
  • the length is 1.0 to 1.8 times in the longitudinal direction (machine direction: MD direction) or in the TD direction.
  • MD direction machine direction
  • TD direction in the case of biaxial stretching
  • it is adjusted by 1.0 to 1.8 times in the MD and TD directions, respectively.
  • the respective draw ratios in the MD direction and the TD direction may be the same or different.
  • the re-stretched film is fixed and heat-treated.
  • a conventional method known in the art may be performed without limitation, and as an example, a heat setting treatment and/or a heat relaxation treatment may be used.
  • the crystal structure of the fibrils formed by the second stretching process is stabilized to have the surface pore size and surface porosity of the present invention, and a microporous membrane having a uniform pore size distribution can be manufactured.
  • the heat setting treatment is performed within a temperature range above the crystal dispersion temperature and below the melting point of the polyolefin resin constituting the microporous film.
  • the heat setting treatment may be performed by a tenter method, a roll method, or a rolling method.
  • the thermal relaxation treatment may be performed by a tenter method, a roll method, a compression method, or may be performed using a belt conveyor or a floating roll.
  • the thermal relaxation treatment may, for example, be performed in at least one direction in a range of 20% or less of a relaxation rate, and in another example, may be performed in a range of 10% or less of a relaxation rate.
  • the polyolefin microporous membrane according to the present invention has a peel strength of 45 gf/15 mm or more of the coating layer, and the maximum heat of fusion shrinkage (%) is within 10% in the MD and TD directions.
  • the polyolefin microporous membrane according to the present invention has a low shrinkage after coating, and the shrinkage reduction before and after coating may be 65% or more, for example, 75 to 95%.
  • a coating layer may be formed on one or both surfaces of the polyolefin microporous membrane according to the present invention.
  • the coating layer may be formed on a surface having an average pore size of 65 nm or less among both surfaces of the polyolefin microporous membrane.
  • the coating solution forming the coating layer includes inorganic particles and a polymer binder.
  • the coating solution may further include a solvent if necessary.
  • Non-limiting examples of inorganic particles that can be used include, but are not limited to, Alumina, Barium Sulfate, Aluminum Hydroxide, Barium Titanium Oxide, Magnesium Oxide, Magnesium Hydroxide. ), clay, titanium oxide, glass powder, and boehmite.
  • the inorganic particles may be used alone or in combination of two or more.
  • the size of the inorganic particles is not limited, but may be in the range of 0.001 to 10 ⁇ m. When the size of the inorganic particles satisfies the above-mentioned range, a film having a uniform thickness may be formed and an appropriate porosity may be secured.
  • the inorganic particles may be used in an amount of 80 to 99% by weight based on the total weight of the solid content of the aqueous coating composition.
  • the content of the inorganic particles falls within the above-described range, the heat resistance effect according to the use of the inorganic particles may be achieved.
  • Non-limiting examples of polymeric binders that can be used include polyacrylic acid, polymethacrylic acid, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, butadiene-acrylic acid copolymer, butadiene-methacrylic acid copolymer, polyvinylsulfo.
  • the coating composition of the present invention is prepared by mixing an inorganic particle slurry dispersed in a solvent and a binder dissolved in a solvent.
  • the coating composition of the present invention may be a water-based coating composition, in which case water is used as a solvent, and an organic solvent is not used. Accordingly, there is no environmental problem caused by using the organic solvent.
  • the present invention provides a secondary battery, for example, a lithium ion secondary battery including the polyolefin microporous membrane described above.
  • the lithium ion secondary battery of the present invention may be manufactured according to a conventional method known in the art, except for using the polyolefin microporous membrane according to the present invention as a separator.
  • it can be manufactured by interposing a separator between the positive electrode and the negative electrode and introducing a non-aqueous electrolyte.
  • the lithium ion secondary battery of the present invention includes a negative electrode, a positive electrode, a separator, and an electrolyte as battery components. It conforms to the elements of phosphorus lithium ion secondary batteries.
  • the negative electrode may be manufactured using a conventional negative electrode active material for a lithium ion secondary battery known in the art, and a non-limiting example thereof is a material capable of intercalating/deintercalating lithium ions is used,
  • a material capable of intercalating/deintercalating lithium ions is used,
  • lithium metal, lithium alloy, coke, artificial graphite, natural graphite, organic high molecular compound combustor, carbon fiber, silicon type, tin type, etc. exist.
  • the non-aqueous electrolyte includes electrolyte components commonly known in the art, such as an electrolyte salt and an electrolyte solvent.
  • the electrolyte salt includes (i) a cation selected from the group consisting of Li+, Na+, K+ and (ii) PF 6 -, BF 4 -, Cl-, Br-, I-, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N(CF 3 SO 2 ) 2 -, C(CF 2 SO 2 ) 3 - may be composed of a combination of anions selected from the group consisting of, of which lithium salt is preferable.
  • Specific examples of the lithium salt include LiClO 4 , LiCF 3 SO 3 , LiPF 6 , LiBF 4 , LiAsF 6 , and LiN(CF 3 SO 2 ) 2 .
  • These electrolyte salts can be used individually or in mixture of 2 or more types.
  • the electrolyte solvent may be cyclic carbonate, linear carbonate, lactone, ether, ester, acetonitrile, lactam, or ketone.
  • Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and the like
  • examples of the linear carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC).
  • examples of the lactone include gamma butyrolactone (GBL)
  • examples of the ether include dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane and the like.
  • ester examples include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl pivalate and the like.
  • lactam includes N-methyl-2-pyrrolidone (NMP) and the like
  • the ketone includes polymethylvinyl ketone.
  • a halogen derivative of the organic solvent may also be used, but is not limited thereto.
  • the organic solvent may be glyme, diglyme, triglyme, or tetraglyme. These organic solvents can be used individually or in mixture of 2 or more types.
  • the average pore size of one surface is 57.3 nm, the ratio (number ratio) of pores having a pore size of 100 nm or more among the pores on the surface is 9%, and the surface porosity is 16.8% of a 12 ⁇ m thick polyolefin microporous membrane.
  • the water-based coating porous membrane of Example 1 was prepared.
  • the pore size of the surface of the microporous membrane was calculated by the following method.
  • the microporous membranes prepared in Examples and Comparative Examples were subjected to ion sputtering (Ion Sputter, Hitachi MC1000) at 15 mA, 180 sec. After pretreatment with the condition, using a scanning electron microscope (SEM, Hitachi SU-70), size 1,280 X 960, magnification 10K, acceleration voltage 5 kv, emission current 31 uA, Brightness 5, Contrast 1, ABC conditions were measured. Thus, an SEM image was obtained.
  • Image processing software Halcon (ver.13.0 MVtec) was used to remove noise from the 1,280 X 870 part of the SEM image (smoothed by averaging, mean_image, LowPass mask width: 3, height: 3) was subjected to binarization processing.
  • Binarization processing (dyn_threshold, input image: image from which the noise has been removed/threshold image: image processing (mean_image, LowPass mask) width: 21, height: 21 In the threshold image/offset:30/extraction region:dark) obtained in ), pixels in the image region were selected from the input image, and pixels satisfying the threshold condition for binarization were gathered and all connected values were output.
  • Each of the output values is a region corresponding to each pore in the surface SEM image.
  • the ratio of the area of the area corresponding to the pores to the total area was expressed as the surface porosity (%).
  • each of the values output above assumes that each pore is a circle in the image of the surface SEM, calculates the pore size (B) from the area (A) of the pore, and from these values, the average pore size (B ave. ) was calculated.
  • n the total number of pores
  • n the number of pores having a pore size of 100 nm or more among B a to B n
  • microporous membrane of each Example and Comparative Example was tested for physical properties by the following method, and the results are shown in Table 2 below.
  • TMA (SII Nano Technology Inc., SS6100) was used to measure the TMA maximum thermal contraction rate of the microporous membranes (width 3 mm, length 10 mm) of each Example and Comparative Example (measuring mode: stretching mode, measuring temperature: 30-200° C., temperature increase rate: 5° C./min, load: 2 gf).
  • the polyolefin microporous membrane of Examples 1-7 having an average surface pore size according to the present invention has a low shrinkage after coating and an excellent shrinkage reduction ratio according to coating.
  • the ratio (number ratio) of pores having a pore size of 100 nm or more is low, excellent heat shrinkage reduction effect after coating can be confirmed even though the thickness of the coating layer is made thin.
  • the microporous membranes of Comparative Examples 1 and 2 having a larger average pore size than the average surface pore size according to the present invention it can be seen that the reduction rate of heat shrinkage due to the coating is not large.
  • the polyolefin microporous membrane for battery separator according to the present invention exhibits excellent heat resistance by adjusting the average pore size of the surface of the surface in contact with the coating layer to 65 nm or less. As a result, it is possible to improve the safety of a lithium ion secondary battery including a coating separator for a battery manufactured using the polyolefin microporous membrane according to the present invention.
  • the polyolefin microporous film of the present invention exhibits excellent heat resistance properties, it is possible to thin the coating layer, and as a result, a high-capacity secondary battery having high output characteristics can be manufactured, and also the secondary battery manufacturing cost can be reduced. have.

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Abstract

La présente invention concerne une membrane microporeuse en polyoléfine et, plus particulièrement, une membrane microporeuse en polyoléfine ayant une excellente résistance à la chaleur. La membrane microporeuse en polyoléfine de la présente invention présente, sur au moins l'une des deux surfaces de celle-ci, une taille de pore moyenne de 30 à 65 nm.
PCT/KR2022/003404 2021-03-12 2022-03-11 Membrane microporeuse en polyoléfine WO2022191651A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008106237A (ja) * 2006-09-28 2008-05-08 Asahi Kasei Chemicals Corp ポリオレフィン製微多孔膜
JP2012502426A (ja) * 2008-09-03 2012-01-26 エルジー・ケム・リミテッド 多孔性コーティング層を備えたセパレータ及びこれを備えた電気化学素子
KR20160129543A (ko) * 2015-04-30 2016-11-09 주식회사 엘지화학 전기화학소자용 분리막
KR20160129581A (ko) * 2015-04-30 2016-11-09 주식회사 엘지화학 전기화학소자용 분리막의 제조방법 및 그로부터 제조된 전기화학소자용 분리막
KR20190112362A (ko) * 2018-03-26 2019-10-07 도레이배터리세퍼레이터필름 한국유한회사 폴리올레핀 미세 다공막

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008106237A (ja) * 2006-09-28 2008-05-08 Asahi Kasei Chemicals Corp ポリオレフィン製微多孔膜
JP2012502426A (ja) * 2008-09-03 2012-01-26 エルジー・ケム・リミテッド 多孔性コーティング層を備えたセパレータ及びこれを備えた電気化学素子
KR20160129543A (ko) * 2015-04-30 2016-11-09 주식회사 엘지화학 전기화학소자용 분리막
KR20160129581A (ko) * 2015-04-30 2016-11-09 주식회사 엘지화학 전기화학소자용 분리막의 제조방법 및 그로부터 제조된 전기화학소자용 분리막
KR20190112362A (ko) * 2018-03-26 2019-10-07 도레이배터리세퍼레이터필름 한국유한회사 폴리올레핀 미세 다공막

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