WO2020179294A1 - Membrane microporeuse de polyoléfine, et batterie - Google Patents

Membrane microporeuse de polyoléfine, et batterie Download PDF

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Publication number
WO2020179294A1
WO2020179294A1 PCT/JP2020/003355 JP2020003355W WO2020179294A1 WO 2020179294 A1 WO2020179294 A1 WO 2020179294A1 JP 2020003355 W JP2020003355 W JP 2020003355W WO 2020179294 A1 WO2020179294 A1 WO 2020179294A1
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WO
WIPO (PCT)
Prior art keywords
polyolefin
stretching
shutdown
microporous
film
Prior art date
Application number
PCT/JP2020/003355
Other languages
English (en)
Japanese (ja)
Inventor
遼 下川床
久万　琢也
直哉 西村
慧 金子
Original Assignee
東レ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 東レ株式会社 filed Critical 東レ株式会社
Priority to JP2020512893A priority Critical patent/JPWO2020179294A1/ja
Publication of WO2020179294A1 publication Critical patent/WO2020179294A1/fr

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Classifications

    • 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
    • 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
    • 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • 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

  • Microporous membranes are used in various fields such as filters such as filtration membranes and dialysis membranes, separators for batteries and separators for electrolytic capacitors.
  • microporous membranes made of polyolefin as a resin material are excellent in chemical resistance, insulating property, mechanical strength, etc., and have shutdown characteristics, and are therefore widely used as separators for secondary batteries in recent years.
  • Secondary batteries such as lithium-ion secondary batteries, have a high energy density and are widely used as batteries for personal computers, mobile phones, and recently drones. Secondary batteries are also expected to be used as power sources for driving motors of electric vehicles and hybrid vehicles, and as stationary storage batteries.
  • the present inventors have found that the shutdown function of the separator is largely involved not only in the structural change of the pore closure in the film surface but also in the structural change in the film thickness direction.
  • the film thickness direction means the normal direction of the surface of the polyolefin microporous film.
  • the in-plane direction means a normal direction of a plane perpendicular to the surface of the polyolefin microporous film.
  • the change in the melting point of the microporous membrane from the basic structure composed of the raw material composition is within an appropriate range, thereby in-plane.
  • the polyolefin microporous membrane of the present invention contains polyolefin as a main component.
  • the polyolefin is preferably contained in an amount of 90% by mass or more based on 100% by mass of the microporous polyolefin membrane.
  • the polyolefin include polyethylene and polypropylene.
  • the polyethylene various types of polyethylene can be used, and examples thereof include ultra-high density polyethylene, high density polyethylene, branched high density polyethylene, medium density polyethylene, branched low density polyethylene, and linear low density polyethylene.
  • Polyethylene may be an ethylene homopolymer or a copolymer of ethylene and another ⁇ -olefin.
  • the shutdown temperature of the polyolefin microporous film was evaluated with the shutdown temperature being the temperature at which the air permeability resistance obtained from the temperature-rising air permeability resistance measurement described below reached the detection limit of 1 ⁇ 10 5 seconds/100 ccAir.
  • the shutdown temperature is preferably 133°C or lower, more preferably 131°C or lower, further preferably 130°C or lower, and particularly preferably 128°C or lower.
  • the shutdown temperature is 133° C. or lower, compared to the conventional microporous membrane, the battery thermal runaway at high temperature can be suppressed and the safety is improved.
  • the lower limit of the shutdown temperature is not particularly limited, but when it is lower than 110° C., for example, there is concern about thermal stability in the case where it is arranged in the vicinity of an in-vehicle high temperature part, or the air permeation resistance rapidly deteriorates during heat fixation. I have a concern.
  • the shutdown temperature is adjusted, for example, by adjusting the stretching conditions (particularly the stretching temperature and the stretching ratio) and the raw material composition so that the change in the melting point of the microporous film from the basic structure is within an appropriate range. By doing so, the above range can be obtained. Details will be described later.
  • the 10 ⁇ m equivalent puncture strength of the polyolefin microporous film should be in the above range by containing a nucleating agent or adjusting the weight average molecular weight Mw, the raw material composition, and the stretching conditions during the production of the polyolefin microporous film.
  • the lower limit of the TD/MD tensile rupture strength ratio of the polyolefin microporous membrane is preferably 0.5 or more, more preferably 0.7 or more, still more preferably 0.9 or more.
  • the TD/MD tensile breaking strength ratio is preferably 1.5 or less, more preferably 1.3 or less, and further preferably 1.1 or less.
  • the lower limit of the porosity of the polyolefin microporous membrane is not particularly limited, but is, for example, preferably 35% or more, more preferably 38% or more, further preferably 40% or more, and particularly preferably 42% or more. Yes, remarkably preferably 43% or more.
  • the upper limit of the porosity is not particularly limited, but for example, it is preferably 70% or less, more preferably 60% or less, and further preferably 50%. When the porosity is in the above range, the amount of electrolyte retained can be increased and high ion permeability can be secured. Further, when the porosity is in the above range, the rate characteristics are improved.
  • the polyolefin microporous membrane of the present invention can contain ultra-high molecular weight polyethylene.
  • the Mw of the ultrahigh molecular weight polyethylene is preferably 1 ⁇ 10 6 or more, more preferably 1 ⁇ 10 6 or more and 8 ⁇ 10 6 or less. When the Mw of the ultra-high molecular weight polyethylene is in the above range, the moldability is good.
  • the ultra high molecular weight polyethylene may include one or more kinds. For example, two or more kinds of ultra high molecular weight polyethylene having different Mw may be mixed and used as a raw material. Further, when the ultra-high molecular weight polyethylene is contained, high mechanical strength can be obtained even when the polyolefin microporous film is thinned.
  • the ratio of polyolefin in the resin solution when forming the microporous polyolefin membrane of the present invention is calculated by the following formula. Although it depends on the composition of the raw material, the range of 20% to 50% is preferable, the range of 20% to 40% is more preferable, and the range of 25% to 35% is further preferable. If the ratio of the polyolefin and the solvent for film formation is less than 20%, there is a high possibility of molding failure of the gel sheet and film breakage during stretching, which is not preferable. When the ratio of the polyolefin and the solvent for film formation is 50% or more, the stress at the time of stretching becomes high, and the thermal stabilization of the structure by stretching proceeds more than necessary, which is not preferable.
  • the resin solution may contain components other than the above-mentioned polyolefin and solvent for film formation, and may contain, for example, a crystal nucleating agent (nucleating agent), an antioxidant, and the like.
  • the nucleating agent is not particularly limited, and known compound-based or fine particle-based crystal nucleating agents can be used.
  • the nucleating agent may be a masterbatch in which the nucleating agent is mixed and dispersed in polyolefin in advance.
  • the final area stretching ratio (surface magnification) is preferably 3 times or more, more preferably 4 times or more and 30 times or less in the case of uniaxial stretching, for example. Further, in the case of biaxial stretching, the final area stretching ratio is preferably 16 times or more, more preferably 25 times or more. The upper limit of the final area stretching ratio is preferably 81 times or less, more preferably 49 times or less. Further, the final stretching ratio is preferably 3 times or more in both the longitudinal direction (mechanical direction: MD direction) and the lateral direction (width direction: TD direction), and the stretching ratios in the MD direction and the TD direction are the same. May be different. When the draw ratio is 5 times or more, improvement in puncture strength can be expected.
  • the wet stretch ratio refers to the stretch ratio of the gel-like sheet after the wet stretch ratio based on the gel-like sheet before the wet stretch.
  • the relaxation temperature is, for example, preferably 80 ° C. or higher and 135 ° C. or lower, more preferably 90 ° C. or higher and 133 ° C. or lower, further preferably 105 ° C. or higher and 125 ° C. or lower, and particularly preferably 110 ° C. or higher and 120 ° C. It is as follows.
  • the final dry stretching ratio is, for example, 1.0 times or more and 9.0 times or less, preferably 1.2 times or more and 4.0 times or less.
  • the relaxation rate can be 0% or more and 70% or less.
  • the lower limit of the final area magnification after heat fixing of the polyolefin microporous membrane is preferably 10 times or more, more preferably 16 times or more, still more preferably 25 times or more.
  • the upper limit of the final area magnification is preferably 81 times or less, more preferably 49 times or less, and further preferably 36 times or less.
  • the final area magnification is less than 10 times, it is difficult to form the thermally stable structure required for the microporous film, the mechanical strength is lowered, and the thermally stable structure required in the film thickness direction is not formed. Not preferable.
  • the final area ratio is 81 times or more, the strain in the film thickness direction increases and the change in the film thickness direction at high temperature becomes large, which is not preferable.
  • Puncture strength (10 ⁇ m conversion) maximum load (N) ⁇ 10 ( ⁇ m) / film thickness of polyolefin microporous film T 1 ( ⁇ m) [Permeability]
  • Film thickness change rate (1 ⁇ T 2 ⁇ T 1 ) ⁇ 100.
  • Example 1 Polyolefin in resin solution shown in Table 1 is branched high density polyethylene (ethylene/1-hexene copolymer, density 0.953 g/cm 3 ) having a weight average molecular weight (Mw) of 1.8 ⁇ 10 5 as the first polyethylene.
  • a polyolefin solution was prepared by melt-kneading at a temperature of 180 ° C. while maintaining the screw rotation speed Ns at 200 rpm with a twin-screw extruder of a liquid paraffin and a strong kneading type.
  • Example 2 A polyolefin microporous membrane was obtained in the same manner as in Example 1 except that the gel-like sheet was stretched at 115°C.
  • Example 5 A polyolefin microporous membrane was obtained in the same manner as in Example 1 except that the crystal nucleating agent CN-002 (manufactured by Riken Vitamin Co.) was added in the composition shown in Table 1.
  • Example 6 Example 1 except that the stretched gel-like sheet was immersed in a methylene chloride bath to remove liquid paraffin, dried and stretched 1.5 times in the width direction at 120° C. and relaxed by 10% in the width direction. A polyolefin microporous film was obtained in the same manner as above.
  • the polyolefin solution was supplied to a T-die from a twin-screw extruder, and the extruded extrusion-molded product was cooled while being pulled by a cooling roll to form a gel-like sheet, and a polyolefin microporous membrane was prepared in the same manner as in Example 1.
  • Example 8 Polyethylene and branched high-density polyethylene having a weight average molecular weight (Mw) of 1.8 ⁇ 10 5 (ethylene/1-hexene copolymer, density 0.953 g/cm 3 ) and a weight average molecular weight (Mw) of 10 ⁇ 10 5
  • the ultra-high molecular weight polypropylene of No. 1 was melt-kneaded with liquid paraffin at the ratio of polyolefin in the resin solution shown in Table 1 with a twin-screw extruder to prepare a polyolefin solution.
  • the polyolefin solution was supplied to a T-die from a twin-screw extruder, and the extruded extrusion-molded product was cooled while being pulled by a cooling roll to form a gel-like sheet, and a polyolefin microporous membrane was prepared in the same manner as in Example 1.
  • Table 1 shows the evaluation results of the polyolefin microporous membranes obtained in Examples 2 to 8.
  • the first polyethylene is a high-density polyethylene having a weight average molecular weight (Mw) of 3.5 ⁇ 10 5 and the second polyethylene is an ultrahigh molecular weight polyethylene having a weight average molecular weight (Mw) of 2.4 ⁇ 10 6 shown in Table 2.
  • Mw weight average molecular weight
  • Table 2 weight average molecular weight
  • the polyolefin solution was supplied to a T-die from a twin-screw extruder, and the extruded molded body extruded was cooled while being taken by a cooling roll to form a gel-like sheet, and a microporous polyolefin film was prepared in the same manner as in Comparative Example 1.
  • Comparative example 4 A polyolefin microporous film was obtained in the same manner as in Comparative Example 1 except that the ratio of the polyolefin and the film-forming solvent was changed to 25%.
  • Example 5 A polyolefin microporous film was obtained in the same manner as in Example 2 except that the gel-like sheet was simultaneously biaxially stretched 9 times in both the MD direction and the TD direction by a tenter stretching machine.
  • Example 6 A polyolefin microporous membrane was obtained in the same manner as in Example 1 except that the gel-like sheet was simultaneously biaxially stretched by a tenter stretching machine at a stretching ratio of 3 times in both MD and TD.
  • the polyolefin solution was supplied from the twin-screw extruder to the T-die, and the extruded molded product was cooled while being taken up by a cooling roll to form a gel-like sheet.
  • the gel-like sheet was simultaneously biaxially stretched at 115 ° C. in both the MD direction and the TD direction by a tenter stretching machine at a magnification of 5 times.
  • the stretched gel-like sheet was immersed in a methylene chloride bath to remove liquid paraffin, dried, and heat-fixed at 120 ° C. for 10 minutes.
  • the polyolefin microporous membranes of Examples 1 to 7 have excellent air permeation resistance as a battery separator, but have a shutdown temperature of 133° C. or less and a film thickness change rate at shutdown of 33% or less, which is an excellent shutdown. It was shown to have properties.

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

Abstract

L'invention concerne une membrane microporeuse de polyoléfine ayant une polyoléfine pour principal composant, présentant une résistance à la pénétration de l'air pour １０μｍ supérieure ou égale à ５０secondes／１００ｃｃ et inférieure ou égale à ４００secondes／１００ｃｃ, et présentant un taux de variation d'épaisseur de film à l'arrêt inférieur ou égal à 33%.　Plus précisément, l'invention fournit une membrane microporeuse de polyoléfine qui se révèle excellente en termes de perméabilité et de caractéristiques d'arrêt lorsqu'elle est insérée dans une batterie en tant que séparateur.
PCT/JP2020/003355 2019-03-07 2020-01-30 Membrane microporeuse de polyoléfine, et batterie WO2020179294A1 (fr)

Priority Applications (1)

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JP2020512893A JPWO2020179294A1 (fr) 2019-03-07 2020-01-30

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JP2019-041432 2019-03-07
JP2019041432 2019-03-07

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003147109A (ja) * 2001-11-12 2003-05-21 Nitto Denko Corp 多孔質フィルム、非水電解液電池用セパレータ及び非水電解液電池
WO2007049568A1 (fr) * 2005-10-24 2007-05-03 Tonen Chemical Corporation Film microporeux a couches multiples en polyolefine, procede pour le produire et separateur de batterie
JP2011129304A (ja) * 2009-12-16 2011-06-30 Teijin Ltd 非水系二次電池用セパレータ及び非水系二次電池
JP2012136704A (ja) * 2012-02-14 2012-07-19 Asahi Kasei E-Materials Corp ポリエチレン製微多孔膜及びそれを用いた電池
JP2019157060A (ja) * 2018-03-16 2019-09-19 東レ株式会社 ポリオレフィン微多孔膜

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003147109A (ja) * 2001-11-12 2003-05-21 Nitto Denko Corp 多孔質フィルム、非水電解液電池用セパレータ及び非水電解液電池
WO2007049568A1 (fr) * 2005-10-24 2007-05-03 Tonen Chemical Corporation Film microporeux a couches multiples en polyolefine, procede pour le produire et separateur de batterie
JP2011129304A (ja) * 2009-12-16 2011-06-30 Teijin Ltd 非水系二次電池用セパレータ及び非水系二次電池
JP2012136704A (ja) * 2012-02-14 2012-07-19 Asahi Kasei E-Materials Corp ポリエチレン製微多孔膜及びそれを用いた電池
JP2019157060A (ja) * 2018-03-16 2019-09-19 東レ株式会社 ポリオレフィン微多孔膜

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