Classifications

• • 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
  • C08J9/36—After-treatment
  • C08J9/40—Impregnation
  • C08J9/42—Impregnation with macromolecular compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/411—Organic material
  • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/411—Organic material
  • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
  • H01M50/417—Polyolefins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/411—Organic material
  • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
  • H01M50/42—Acrylic resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/411—Organic material
  • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
  • H01M50/426—Fluorocarbon polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/431—Inorganic material
  • H01M50/434—Ceramics
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/443—Particulate material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
  • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
• • 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
  • H01M50/463—Separators, membranes or diaphragms characterised by their shape
• • 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to a porous film, a secondary battery separator, and a secondary battery.
• Secondary batteries such as lithium-ion batteries are used in automotive applications such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, as well as portable applications such as smartphones, tablets, mobile phones, laptops, digital cameras, digital video cameras, and handheld game consoles. It is widely used in digital devices, electric tools, electric motorcycles, electric assist bicycles, etc.
• Lithium ion batteries generally have a secondary battery separator and an electrolyte interposed between a positive electrode in which a positive electrode active material is laminated on a positive electrode current collector and a negative electrode in which a negative electrode active material is laminated on a negative electrode current collector. have a configuration.
• Polyolefin-based porous substrates are used as separators for secondary batteries.
• the characteristics required for secondary battery separators are the ability to contain electrolyte in the porous structure and enable ion movement, and the ability to close the porous structure by melting when the lithium ion battery overheats. and a shutdown characteristic that stops the discharge by stopping ion migration.
• the battery form is being replaced from the wound type to the laminated type.
• the laminated type in the manufacturing process of a secondary battery using an electrode laminate in which a positive electrode, a separator, and a negative electrode are laminated, when the electrode laminate is transported, the laminate structure may be maintained, or the electrode laminate may be rolled into a cylinder. When inserting into a mold, square, etc.
• a battery is required to have adhesiveness (dry adhesiveness) between the separator and the electrode before being impregnated with the electrolytic solution in order to prevent the shape from being deformed after being inserted into the outer packaging material. Therefore, in the above process, the electrode laminate may be subjected to hot pressing. On the other hand, it is necessary to prevent impregnation of the electrolyte into the electrode laminate after hot pressing, that is, deterioration of electrolyte pourability. Lithium-ion batteries are also required to have good battery characteristics such as adhesion (wet adhesion) to electrodes impregnated with electrolyte, high output, and long life.
• Patent Document 1 In response to the above requirement for dry adhesion, in Patent Document 1, an adhesive layer formed on a heat-resistant layer is laminated to develop dry adhesion with the electrode.
• Patent Document 2 the dry adhesion to the electrode is enhanced by satisfying a specific relationship between the particle size of the particulate polymer and the particle size of the inorganic particles. Further, it is known that the impregnability of the electrolytic solution is improved by roughening the outermost surface of the separator (Patent Document 3). In addition, by exhibiting both dry adhesiveness and wet adhesiveness, improvement of yield during battery production and during initial charge/discharge is being studied (Patent Document 4).
• the hot press process in the manufacturing process of secondary batteries requires both the dry adhesion of the electrodes and the separator and the pourability of the electrolyte. Furthermore, due to the increase in size of batteries, there is a demand for larger electrode laminates and higher capacities, and it is necessary to improve not only dry adhesion to electrodes but also wet adhesion and electrolyte pourability. In addition, due to the increase in demand for laminated type batteries, productivity improvement is also required, and it is also necessary to shorten the heat press time for improving adhesiveness. In order to achieve both adhesion to the electrode and electrolyte pourability, it has been studied to appropriately adjust the amount of organic resin particles responsible for adhesion to the electrode. is decreased, and the battery resistance is increased, resulting in deterioration of rate characteristics and battery life. On the other hand, when the amount of organic resin is reduced, there is also a problem that the adhesiveness to the electrode is lowered.
• the object of the present invention is to provide a porous film having excellent adhesion (dry adhesion, wet adhesion) with electrodes, electrolytic solution pourability, thermal dimensional stability, and low resistance. do.
• the present inventors focused on the adhesiveness with the electrode by high pressure heat press for shortening the heat press time, and as a result of extensive studies, the arithmetic mean height of the porous substrate was set to a certain height. It has been found that organic resin particles are unevenly distributed on the surface layer and layer-separated from the inorganic particles, resulting in excellent dry adhesion to the electrode and electrolyte pourability. Furthermore, they have found that by appropriately selecting the composition of the organic resin particles, in addition to the properties described above, the wet adhesion is also excellent.
• the porous film of the present invention has the following configuration.
• the arithmetic mean height (Sa) in 2200 ⁇ m square of the surface on the side in contact with the porous layer is 0.01 ⁇ m or more and less than 0.09 ⁇ m, and the volume of the inorganic particles when the volume of all constituent components of the porous layer is 100% by volume
• porous substrate according to any one of (1) to (4), wherein the surface in contact with the porous layer has an arithmetic mean roughness (Ra) of 10 nm or more and less than 80 nm in a 12 nm square. porous film.
• the porous substrate has a protruding peak height (Spk) of 0.01 ⁇ m or more and less than 0.12 ⁇ m in a 2200 ⁇ m square on the surface on the side in contact with the porous layer.
• Spk protruding peak height
• the porous film according to any one of (1) to (7), wherein the porous substrate is a polyolefin microporous film (9)
• the inorganic particles are an inorganic hydroxide, an inorganic oxide and an inorganic sulfuric acid
• the porous film according to any one of (1) to (8) which is a particle composed of at least one selected from the group consisting of compounds.
• the organic resin particles are fluorine-containing (meth)acrylate monomers, unsaturated carboxylic acid monomers, (meth)acrylate monomers, styrene-based monomers, olefin-based monomers, and diene-based monomers.
• the ratio of the (meth)acrylate monomer having a hydroxyl group is greater than 0% by mass and 7.0% by mass when the total constituent monomer components of the organic resin particles are 100% by mass.
• the glass transition of the polymer when at least one of the monomers that are the raw materials of the polymer is polymerized only with that monomer.
• the monomer having a glass transition temperature of ⁇ 100° C. or more and 0° C. or less when polymerized only by the monomer accounts for 100% by mass of the total constituent monomer components of the organic resin particles.
• the porous film according to (16) which is greater than 0% by mass and 10.0% by mass or less.
• a secondary battery separator comprising the porous film according to any one of (1) to (21).
• a porous film having a porous substrate and a porous layer containing inorganic particles and organic resin particles on at least one surface of the porous substrate,
• the porous substrate is made of a polyolefin microporous membrane whose surface in contact with the porous layer has an arithmetic mean height (Sa) of 0.01 ⁇ m or more and less than 0.09 ⁇ m in a 2200 ⁇ m square
• the inorganic particles are particles composed of at least one selected from the group consisting of inorganic hydroxides, inorganic oxides and inorganic sulfates
• the organic resin particles contain a fluorine-containing (meth)acrylate monomer, an unsaturated carboxylic acid monomer, a (meth)acrylic acid ester monomer, a styrene monomer, an olefin monomer, and a diene monomer.
• the volume content ratio ⁇ of the inorganic particles is 30% by volume or more and 80% by volume or less,
• the battery separator wherein the relationship between the volume content ⁇ of the inorganic particles and the occupation ratio ⁇ of the inorganic particles in the surface portion of the porous layer satisfies ⁇ >0 and ⁇ / ⁇ 1.
• the present invention it is possible to provide a porous film having excellent adhesion (dry adhesion, wet adhesion) with electrodes, electrolytic solution pourability, thermal dimensional stability, and low resistance. In particular, when subjected to high-pressure heat pressing, excellent dry adhesion can be exhibited. Further, by using the porous film as a battery separator, it is possible to improve the yield in the battery manufacturing process and provide a secondary battery having excellent battery life and rate characteristics.
• the porous film of the present invention is a porous film having a porous substrate and a porous layer containing inorganic particles and organic resin particles on at least one surface of the porous substrate, wherein the porous
• the base material has an arithmetic mean height (Sa) of 0.01 ⁇ m or more and less than 0.09 ⁇ m in a 2200 ⁇ m square of the surface on the side in contact with the porous layer, and the volume of all constituent components of the porous layer is 100% by volume.
• Sa arithmetic mean height
• porous film of the present invention will be described in detail below.
• the porous film of the present invention has an arithmetic mean height (Sa) of 0.01 ⁇ m or more and less than 0.09 ⁇ m in a 2200 ⁇ m square on the surface of the porous substrate on the side in contact with the porous layer.
• Sa arithmetic mean height
• the adhesion to the electrode can be further improved.
• the upper limit of the arithmetic mean height (Sa) to less than 0.09 ⁇ m, the electrode laminate in which the electrode and the porous film are adhered is easily impregnated with the electrolyte, and the electrolyte injection is improved. , the rate characteristics and battery life are improved when used as a battery separator.
• the porous film of the present invention has an arithmetic mean height (Sa) of 0.01 ⁇ m or more and less than 0.09 ⁇ m in a 2200 ⁇ m square on the surface of the porous substrate on the side in contact with the porous layer. It was found that both the performance and electrolyte injection performance can be compatible.
• the arithmetic mean height (Sa) within the above range, the arithmetic mean height of the surface of the porous layer is also reduced, and during the dry adhesion step (heat press) with the electrode, the active material present in the electrode is affected.
• the conformability to irregularities can be adjusted, and both dry adhesion to the electrode and electrolyte pourability can be achieved.
• the dry adhesion to the electrode can be improved without increasing the amount of the organic resin particles, and the cost can be reduced. Therefore, a battery using the porous film of the present invention as a battery separator can achieve both rate characteristics and battery life.
• the arithmetic mean height (Sa) in 2200 ⁇ m square of the porous substrate surface on the side in contact with the porous layer is determined by the type of resin of the porous substrate, the type of plasticizer, the presence or absence of cooling after sheet formation, and the stretching method. , the stretching ratio, the stretching temperature, and the dry re-stretching after stretching can be adjusted to achieve a predetermined range.
• the porous layer in the present invention contains inorganic particles and organic resin particles.
• the porous layer has a volume content rate ⁇ (% by volume) of inorganic particles when the volume of all constituent components of the porous layer is 100% by volume, and an occupation rate ⁇ ( area %) satisfies ⁇ / ⁇ 1.
• ⁇ / ⁇ is less than 1, it means that the occupancy rate of the inorganic particles in the surface portion of the porous layer is lower than the content rate of the inorganic particles in the entire porous layer. It shows that it is unevenly distributed on the surface of the Since the organic resin particles are unevenly distributed on the surface portion of the porous layer, a large amount of organic resin particles are present on the surface portion, thereby exhibiting sufficient adhesiveness to the electrode.
• volume content ⁇ of the inorganic particles and the occupation ratio ⁇ of the inorganic particles described above are obtained by the method described in the Examples section.
• the porous film of the present invention uses a porous substrate having an arithmetic mean height (Sa) of 0.01 ⁇ m or more and less than 0.09 ⁇ m at 2200 ⁇ m on the surface of the porous substrate on the side in contact with the porous layer. And, when the total constituent components of the porous layer are 100% by volume, the porous layer has a volume content rate ⁇ (% by volume) of the inorganic particles and an occupation rate ⁇ of the inorganic particles at the surface of the porous layer ( area %) satisfies ⁇ / ⁇ 1, high dry adhesion and wet adhesion to the electrode, and electrolyte pourability can be obtained especially when high-pressure heat pressing is performed.
• Sa arithmetic mean height
• ⁇ / ⁇ is more preferably 0.5 or less, still more preferably 0.3 or less.
• the lower limit of ⁇ / ⁇ is not particularly limited, it is preferably 0.01 or more.
• the lower limit of ⁇ / ⁇ is not particularly limited, it is preferably 0.01 or more.
• a porous layer in which ⁇ / ⁇ is within the above range it may be formed through a two-step coating process using two types of coating liquids, or one step using one type of coating liquid. It is more preferable to form in the coating step of . If it can be formed by a one-stage coating process, the cost can be reduced by reducing the number of times of coating. For a one-stage coating process, for example, the surface free energy of the organic resin particles, the viscosity of the coating liquid, the solid content concentration, and the drying temperature can be adjusted appropriately to set ⁇ / ⁇ within a predetermined range. It becomes possible. Details will be described later.
• the volume content ⁇ of the inorganic particles is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less, when the volume of all constituent components of the porous layer is 100% by volume. and more preferably 50% by volume or more and 60% by volume or less.
• the volume content ⁇ of the inorganic particles is preferably 30% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 70% by volume or less, when the volume of all constituent components of the porous layer is 100% by volume. and more preferably 50% by volume or more and 60% by volume or less.
• the occupancy ⁇ of the inorganic particles on the surface of the porous layer is preferably greater than 0%. More preferably, it is 1% or more, and still more preferably 5% or more.
• the cost can be reduced by reducing the number of times of coating by a one-step coating process or by reducing the cost of coating materials by reducing raw materials.
• the upper limit is not particularly limited, it is preferably less than 50%. More preferably less than 30%, still more preferably less than 20%.
• the surface portion of the porous layer is a surface layer having a depth that affects the adhesiveness between the outer surface of the porous layer and the electrode, and is shown in the image obtained using SEM-EDX, which will be described later. .
• porous layer In the porous film of the present invention, a porous layer containing inorganic particles and organic resin particles is formed on at least one surface of a porous substrate which will be described later in detail.
• the lower limit of the film thickness of the porous layer is preferably 2 ⁇ m or more, more preferably 3 ⁇ m or more, and still more preferably 4 ⁇ m or more.
• the upper limit of the film thickness of the porous layer is preferably 8 ⁇ m or less, preferably 7 ⁇ m or less, and more preferably 6 ⁇ m or less.
• the film thickness of the porous layer as used herein refers to the total thickness of the porous layers provided on the porous substrate.
• the surface free energy of the porous layer is preferably 10 mN/m or more and 80 mN/m or less, more preferably 15 mN/m or more and 70 mN/m or less, and still more preferably 20 mN/m or more and 60 mN/m or less.
• 10 mN/m or more the coating stability of the porous layer is improved.
• 80 mN/m or less uneven surface distribution due to layer separation of the organic resin particles is likely to occur, and ⁇ / ⁇ can be easily controlled.
• the porous layer preferably has a glass transition temperature of 20°C or more and less than 80°C.
• the lower limit is more preferably 30°C or higher, still more preferably 40°C or higher.
• the upper limit is more preferably 70° C. or lower, still more preferably 60° C. or lower.
• Organic resin particles improve adhesion to electrodes.
• the resin constituting the organic resin particles is preferably a resin having adhesiveness to the electrode, and by unevenly distributing the organic resin particles on the surface layer of the porous film, the ion permeability is improved and the rate characteristics are improved.
• ⁇ / ⁇ can be lowered by lowering the surface free energy of the organic resin particles.
• organic resin particles examples include fluorine-containing (meth)acrylate monomers, unsaturated carboxylic acid monomers, (meth)acrylic acid ester monomers, styrene monomers, olefin monomers, and diene monomers. It is preferable to have a polymer polymerized by using at least one monomer selected from the group consisting of monomers, acrylamide-based monomers, and vinylidene fluoride monomers.
• the organic resin particles are a mixture of a polymer polymerized only with a fluorine-containing (meth)acrylate monomer and other polymers, or a polymer polymerized using a fluorine-containing (meth)acrylate monomer.
• (meth)acrylate means both “acrylate” and “methacrylate”.
• Polymers polymerized using fluorine-containing (meth)acrylate monomers contain repeating units obtained by polymerizing fluorine-containing (meth)acrylates.
• Fluorine-containing (meth)acrylate monomers include 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluoropropyl (meth)acrylate, 2-(perfluorobutyl ) ethyl (meth) acrylate, 3-(perfluorobutyl)-2-hydroxypropyl (meth) acrylate, 2-(perfluorohexyl) ethyl (meth) acrylate, 3-perfluorohexyl-2-hydroxypropyl (meth) acrylates, 3-(perfluoro-3-methylbutyl)-2-hydroxypropyl (meth)acrylate, 1H,1H,3H-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,7H-dodecafluoroheptyl (meth)acrylate, 1
• the proportion of the fluorine-containing (meth)acrylate monomer used in the organic resin particles is preferably greater than 20% by mass, more preferably 22%, based on 100% by mass of all constituent monomer components of the organic resin particles. % by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. Also, it is preferably 80% by mass or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, still more preferably 40% by mass or less, and most preferably 35% by mass or less. Within the above range, the organic resin particles are likely to be unevenly distributed on the surface layer, and sufficient adhesiveness to the electrode can be obtained.
• the fluorine-containing (meth)acrylate monomer is used in the organic resin particles, and the proportion of the fluorine-containing (meth)acrylate monomer used in the organic resin particles are measured using a known method.
• a known method can do. For example, first, the porous layer is removed from the porous film using an organic solvent such as water and alcohol, and then the organic solvent such as water and alcohol is sufficiently dried to obtain the constituents contained in the porous layer. An organic solvent capable of dissolving the organic resin component is added to the resulting component to dissolve only the organic resin component. Subsequently, the organic solvent is dried from the solution in which the organic resin component is dissolved, and only the organic resin component is extracted.
• nuclear magnetic resonance spectroscopy 1 H-NMR, 19 F-NMR, 13 C-NMR
• infrared absorption spectroscopy IR
• X-ray photoelectron spectroscopy XPS
• fluorescence It can be calculated from the intensity of the signal derived from the fluorine-containing (meth)acrylate monomer by X-ray analysis (EDX), elemental analysis, pyrolysis gas chromatograph mass spectrometer (pyrolysis GC/MS), etc. can.
• the number of fluorine atoms contained in one molecule of the fluorine-containing (meth)acrylate monomer is preferably 3 or more and 13 or less.
• the number of fluorine atoms is more preferably 3 or more and 11 or less, still more preferably 3 or more and 9 or less.
• the number of fluorine atoms in the fluorine-containing (meth)acrylate can be measured using a known method. For example, first, the porous layer is removed from the porous film using an organic solvent such as water and alcohol, and then the organic solvent such as water and alcohol is sufficiently dried to obtain the constituents contained in the porous layer. An organic solvent capable of dissolving the organic resin component is added to the resulting constituent components to dissolve only the organic resin component and separate it from the inorganic particles. Subsequently, the organic solvent is dried from the solution in which the organic resin component is dissolved, and only the organic resin component is extracted.
• an organic solvent such as water and alcohol
• nuclear magnetic resonance spectroscopy 1 H-NMR, 19 F-NMR, 13 C-NMR
• infrared absorption spectroscopy IR
• XPS X-ray photoelectron spectroscopy
• fluorescence It can be calculated from the intensity of the signal derived from the fluorine-containing (meth)acrylate monomer by X-ray analysis (EDX), elemental analysis, pyrolysis gas chromatograph mass spectrometer (pyrolysis GC/MS), etc. can.
• pyrolysis GC/MS is particularly useful.
• unsaturated carboxylic acid monomers examples include acrylic acid, methacrylic acid, and crotonic acid.
• One type of unsaturated carboxylic acid monomer may be used alone, or two or more types may be used in combination at an arbitrary ratio.
• (Meth)acrylate monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, and octyl acrylate.
• a (meth)acrylate monomer having a hydroxyl group it is preferable to use a (meth)acrylate monomer having a hydroxyl group.
• a (meth)acrylate monomer having a hydroxyl group By using a (meth)acrylate monomer having a hydroxyl group, the glass transition temperature of the organic resin particles can be adjusted and the dry adhesion to the electrode can be improved.
• the (meth)acrylate monomers having a hydroxyl group may be used singly or in combination of two or more at any ratio. Hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (4-HBA), and 2-hydroxypropyl acrylate (2-HPA) are particularly preferred.
• Styrenic monomers include styrene, ⁇ -methylstyrene, paramethylstyrene, t-butylstyrene, chlorostyrene, chloromethylstyrene, hydroxymethylstyrene and the like.
• olefinic monomers include ethylene and propylene.
• diene-based monomers include butadiene and isoprene.
• acrylamide-based monomers examples include acrylamide.
• one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.
• the vinylidene fluoride monomer may be a homopolymer using a vinylidene fluoride monomer alone or a copolymer with other monomers.
• Monomers copolymerizable with vinylidene fluoride include, for example, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichloroethylene, vinyl fluoride, (meth)acrylic acid, methyl (meth)acrylate, (meth)acrylic acid (Meth)acrylic acid esters such as ethyl, vinyl acetate, vinyl chloride, acrylonitrile and the like. These may be used individually by 1 type, and may be used in combination of 2 or more types by arbitrary ratios.
• the organic resin particles are a mixture containing a polymer polymerized using a fluorine-containing (meth)acrylate monomer and a polymer polymerized using a (meth)acrylate monomer having a hydroxyl group, or It preferably contains a copolymer polymerized using a monomer mixture containing a fluorine-containing (meth)acrylate monomer and a hydroxyl group-containing (meth)acrylate monomer.
• the content of the polymer or copolymer polymerized using a (meth)acrylate monomer having a hydroxyl group contained in the organic resin particles is 0 when the total constituent components of the organic resin particles are 100% by mass. More than mass % and 7.0 mass % or less are preferable. It is more preferably 0.5% by mass or more and 5.0% by mass or less, and still more preferably 1.0% by mass or more and 3.0% by mass or less. When this content is greater than 0% by mass, the polymerization stability of the organic resin particles is improved. In addition, by making it 7.0% by mass or less, sufficient dry adhesion with the electrode can be obtained, and by suppressing swelling in the electrolytic solution, sufficient wet adhesion with the electrode can be obtained. , the distance between the electrodes becomes constant, and the decrease in capacity during initial charge/discharge can be suppressed, so that the yield during initial charge/discharge is improved.
• the content of the polymer or copolymer polymerized using the (meth)acrylate monomer having a hydroxyl group contained in the organic resin particles can be measured using a known method. For example, first, the porous layer is detached from the porous film using an organic solvent such as water and alcohol, and then the organic solvent such as water and alcohol is sufficiently dried to obtain the constituents contained in the porous layer. An organic solvent capable of dissolving the organic resin component is added to the resulting component to dissolve only the organic resin component. Subsequently, the organic solvent is dried from the solution in which the organic resin component is dissolved, and only the organic resin component is extracted.
• an organic solvent such as water and alcohol
• a monomer having two or more reactive groups per molecule is used. It is preferred to carry out the polymerization using a monomer.
• a monomer having two or more reactive groups per molecule it has excellent electrolyte resistance with suppressed swelling in the electrolyte, dry adhesion with the electrode, and electrode in the electrolyte. It is possible to obtain polymer particles having excellent wet adhesiveness with.
• the monomer having two or more reactive groups per molecule for example, it is preferable to use a (meth)acrylate monomer having two or more reactive groups per molecule, and alkylene glycol di(meth) ) acrylates and urethane di(meth)acrylates are more preferred.
• the polymer contained in the organic resin particles has a glass transition temperature of ⁇ It is preferable that a monomer having a temperature of 100° C. or higher and 0° C. or lower is used and polymerized.
• the glass transition temperature range is more preferably -70°C or higher and -10°C or lower, more preferably -50°C or higher -20°C.
• the glass transition temperature is the midpoint glass transition temperature measured by differential scanning calorimetry (DSC) according to JIS K7121:2012.
• the midpoint glass transition temperature is defined as the temperature at the point where a straight line equidistant in the vertical axis direction from the extended straight line of each base line intersects with the curve of the stepwise change portion of the glass transition.
• the ratio of the monomer having a glass transition temperature of ⁇ 100° C. or more and 0° C. or less when polymerized only with the monomer alone is 100% by mass of the total constituent components of the organic resin particles, It is preferably greater than 0 mass % and 10.0 mass % or less. This ratio is more preferably 1% by mass or more and 7.0% by mass or less, and still more preferably 3.0% by mass or more and 5.0% by mass or less.
• the amount is greater than 0% by mass, the organic resin particles are softened and the adhesiveness is improved.
• the amount is less than 10.0% by mass, the softening of the organic resin particles is less likely to occur, and the swelling of the organic resin particles in the electrolytic solution can be suppressed.
• the porous layer of the porous film of the present invention may contain organic resin particles that impart different functions in addition to organic resin particles that have adhesiveness to electrodes. That is, the porous layer can contain at least two types of organic resin particles.
• an emulsion binder is used to adhere the organic resin particles to each other or to adhere the organic resin particles and the inorganic particles to each other, or to provide a binder function to adhere the organic resin particles to the porous substrate. You can use it as Adhesion is improved by the binder function, and adhesion to the electrode can be further improved.
• As the organic resin particles a resin that is electrochemically stable within the battery usage range is preferable.
• the organic resin particles include, in addition to those having a particle shape, those partially formed into a film and fused with the surrounding particles and binder.
• the shape is not particularly limited, and may be spherical, polygonal, flat, fibrous, or the like.
• the average particle size of the organic resin particles is preferably 100 nm or more. It is more preferably 120 nm or more, still more preferably 150 nm or more, and most preferably 170 nm or more. Also, it is preferably 500 nm or less, more preferably 400 nm or less, still more preferably 300 nm or less, and most preferably 250 nm or less.
• the average particle size is preferably 100 nm or more. It is more preferably 120 nm or more, still more preferably 150 nm or more, and most preferably 170 nm or more. Also, it is preferably 500 nm or less, more preferably 400 nm or less, still more preferably 300 nm or less, and most preferably 250 nm or less.
• the average particle size of organic resin particles can be measured using the following method.
• An image (image 1) obtained by imaging the surface of the porous layer at a magnification of 30,000 times using a field emission scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.), and only inorganic particles are contained in the same field of view.
• An EDX image (image 2) of the element is obtained.
• the image size is 4.0 ⁇ m ⁇ 3.0 ⁇ m, the number of pixels is 1,280 pixels ⁇ 1,024 pixels, and the size of one pixel is 3.1 nm ⁇ 2.9 nm.
• Particles that do not contain the element that only the inorganic particles in Image 2 have are defined as organic resin particles.
• the organic resin particles are defined as those containing elemental fluorine by elemental analysis.
• the particle diameters of all the organic resin particles found in Image 1 were measured, and the arithmetic average value was taken as the average particle diameter.
• 50 organic resin particles are not observed in image 1, a plurality of images are taken, and the total number of particles of all the organic resin particles contained in the plurality of images reaches 50. I took a picture and found it.
• the organic resin particles were measured, and the arithmetic average value was taken as the average particle size.
• the porous layer of the porous film of the present invention contains inorganic particles.
• the porous layer contains inorganic particles, it is possible to impart thermal dimensional stability and suppress short circuits due to foreign matter.
• inorganic particles include inorganic oxide particles such as aluminum oxide, boehmite, silica, titanium oxide, zirconium oxide, iron oxide, and magnesium oxide; inorganic nitride particles such as aluminum nitride and silicon nitride; calcium fluoride; Poorly soluble ionic crystal particles such as barium fluoride and barium sulfate may be used.
• the inorganic particles are preferably particles composed of at least one selected from the group consisting of inorganic hydroxides, inorganic oxides and inorganic sulfates. Among them, aluminum oxide which is effective in increasing strength, and organic resins.
• boehmite and barium sulfate which are effective in reducing wear of parts during the process of dispersing particles and inorganic particles.
• one type of these inorganic particles may be used, or two or more types may be mixed and used.
• the shape of the inorganic particles used may be spherical, plate-like, needle-like, rod-like, elliptical, etc. Any shape may be used. Among them, a spherical shape is preferable from the viewpoint of surface modification properties, dispersibility, and coatability.
• Binder The porous layer of the porous film of the present invention is composed of: It may contain a binder.
• a binder a resin that is electrochemically stable within the battery usage range is preferred.
• binders include organic solvent-soluble binders, water-soluble binders, emulsion binders, and the like, and may be used alone or in combination.
• the preferred viscosity of the binder itself is preferably 10000 mPa ⁇ s or less when the concentration is 15% by mass. It is more preferably 8000 mPa ⁇ s or less, still more preferably 5000 mPa ⁇ s or less. When the concentration is 15% by mass and the viscosity is 10,000 mPa s or less, the viscosity increase of the coating material can be suppressed, and the organic resin particles are unevenly distributed on the surface, thereby improving dry adhesion and wet adhesion with the electrode. .
• the dispersant includes water and organic solvents such as alcohol solvents such as ethanol and ketone solvents such as acetone.
• organic solvents such as alcohol solvents such as ethanol and ketone solvents such as acetone.
• the particle size of the emulsion binder is 30-1000 nm, preferably 50-500 nm, more preferably 70-400 nm, still more preferably 80-300 nm.
• Resins that can be used as binders include, for example, polyamide, polyamideimide, polyimide, polyetherimide, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polysulfone, polyketone, polyetherketone, Resins such as polycarbonate, polyacetal, polyvinyl alcohol, polyethylene glycol, cellulose ether, acrylic resin, polyethylene, polypropylene, polystyrene, and urethane can be used. Among these, it is particularly preferable to use an acrylic resin because stronger adhesion can be obtained by interacting with the organic resin particles.
• polyvinylidene fluoride resin vinylidene fluoride-hexafluoropropylene copolymer
• the adhesiveness with the electrode in the electrolytic solution is further improved.
• these resins may be used singly or in combination of two or more if necessary.
• the vinylidene fluoride content of the polyvinylidene fluoride-based resin is preferably 80% by mass or more and less than 100% by mass of the components constituting the resin. More preferably, it is 85% by mass or more and 99% by mass or less. More preferably, it is 90% by mass or more and 98% by mass or less. If the vinylidene fluoride content is less than 80% by mass, sufficient mechanical strength cannot be obtained, and although the adhesiveness to the electrode is exhibited, the strength is weak and the adhesiveness may be easily peeled off. Moreover, when the vinylidene fluoride content is 100% by mass, the electrolytic solution resistance is lowered, and sufficient adhesiveness may not be obtained.
• the content in the porous layer is preferably 0.5% by mass or more with respect to the total amount of the organic resin particles and the inorganic particles. It is more preferably 1% by mass or more, still more preferably 1.5% by mass or more. Moreover, 10 mass % or less is preferable. More preferably 8% by mass or less, still more preferably 6% by mass or less.
• the content in the porous layer is preferably 1% by mass or more with respect to the total amount of the organic resin particles and the inorganic particles. It is more preferably 5% by mass or more, still more preferably 7.5% by mass or more, and most preferably 10% by mass or more. Also, it is preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less. Sufficient adhesion between the porous layer and the porous substrate can be obtained by setting the content of the emulsion binder to 1% by mass or more. Moreover, by making it 30% by mass or less, an increase in air permeability can be suppressed, and battery characteristics are improved.
• the content of 7.5% by mass or more and 20% by mass or less not only promotes the adhesion of the organic resin particles and the inorganic particles and the adhesion of these particles to the substrate, but also interacts with the organic resin particles, and the electrodes. dry adhesion and wet adhesion are also improved.
• Porous Layer A method for forming the porous layer will be described below.
• the porous layer may be formed through a two-step coating process using two types of coating liquids, or may be formed through a one-step coating process using one type of coating liquid.
• the two-step coating process involves preparing a coating liquid consisting of inorganic particles and a solvent, applying this onto a porous substrate, drying the solvent in the water-based dispersion coating liquid, and then applying organic resin particles and
• a coating liquid containing a solvent is prepared, the coating liquid is applied onto the inorganic particle coating layer, and the solvent in the coating liquid is dried to form a porous layer, thereby obtaining a porous film.
• Spray coating may be used as the coating method.
• a coating solution comprising organic resin particles, inorganic particles and a solvent is prepared, the coating solution is applied onto a porous substrate, and the solvent of the coating solution is dried to form a porous layer. , a method of obtaining a porous film.
• the coating method is not particularly limited, but the latter can reduce costs by reducing the number of coatings. Therefore, the method for forming the porous layer by the latter method will be described below.
• a coating liquid is prepared by dispersing organic resin particles at a predetermined concentration.
• the aqueous dispersion coating liquid is prepared by dispersing, suspending, or emulsifying organic resin particles in a solvent.
• the solvent for the coating liquid is not necessarily limited, but is not particularly limited as long as it can disperse, suspend or emulsify the organic resin particles in a solid state. Examples include organic solvents such as methanol, ethanol, 2-propanol, acetone, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, N-methylpyrrolidone, dimethylacetamide, dimethylformamide and dimethylformamide. From the viewpoints of low environmental load, safety, and economy, water-based emulsions in which an organic resin is emulsified in water or a mixture of water and alcohol are preferred. When water is used, a solvent other than water may be added.
• the solid content concentration of the coating liquid is preferably 5% or more and 40% or less. By setting it to the predetermined range, both coating stability and uneven surface distribution during coating and drying can be achieved. Moreover, the solution viscosity of the coating liquid is preferably 5 mPa ⁇ s or more and 50 mPa ⁇ s or less. By setting it to the predetermined range, both the dispersibility of the coating liquid and the surface uneven distribution during coating and drying can be achieved. By adjusting the solid content concentration of the coating liquid to be low and the viscosity to be low within the above preferable range, the organic resin particles can be adjusted so as to be unevenly distributed in the outer layer.
• film-forming aids may be added to the coating liquid as necessary.
• Examples of methods for dispersing the coating liquid include ball mills, bead mills, sand mills, roll mills, homogenizers, ultrasonic homogenizers, high-pressure homogenizers, ultrasonic devices, and paint shakers.
• a dispersing method (bead mill, sand mill) in which a high pressure is applied to the inorganic particles and the organic resin particles during dispersing, the dispersibility is improved and the surface uneven distribution of the organic resin particles is more likely to occur.
• a plurality of these mixing and dispersing machines may be combined for stepwise dispersion.
• Coating methods include, for example, dip coating, gravure coating, slit die coating, knife coating, comma coating, kiss coating, roll coating, bar coating, spray coating, dip coating, spin coating, screen printing, inkjet printing, and pad printing. , other types of printing, etc. are available.
• the coating method is not limited to these, and the coating method may be selected according to preferable conditions such as the organic resin, binder, dispersant, leveling agent, solvent to be used, and base material.
• the solvent of the coating liquid is dried to form a porous layer.
• the drying temperature is preferably 40°C or higher and 100°C or lower.
• the porous layer is uniformly dried, and the arithmetic mean height (Sa) in 2200 ⁇ m square of the porous film surface on the side in contact with the porous layer is the height of the porous substrate surface on the side in contact with the porous layer. It becomes susceptible to the arithmetic mean height (Sa) in 2200 ⁇ m square, and the adhesiveness with the electrode is improved. If the temperature is less than 40°C, the solvent in the coating liquid will not dry.
• the drying temperature is higher than 100° C., the amount of heat during drying increases and the shape of the particles cannot be maintained, resulting in film formation. Therefore, it is possible to achieve both good adhesiveness with the electrode and cost reduction by improving the coating and drying speeds by setting the content to a predetermined range.
• the porous substrate has a structure in which micropores are formed therein and these micropores are connected from one surface to the other surface.
• porous substrates include microporous membranes, non-woven fabrics, and porous membrane sheets made of fibrous materials.
• the porous base material is preferably a polyolefin microporous membrane because of ease of adjustment of the arithmetic mean roughness (Ra) in 2200 ⁇ m square and the height of protruding peaks (Spk) in 2200 ⁇ m square. That is, it is preferably a porous membrane made of polyolefin. Resins constituting the polyolefin microporous membrane include polyethylene, polypropylene, ethylene-propylene copolymers, and mixtures thereof.
• the polyolefin microporous membrane may be a single membrane or a laminated membrane having a plurality of layers. Examples thereof include a single membrane containing 90% by mass or more of polyethylene and a laminated membrane made of polyethylene and polypropylene.
• the lower limit of the arithmetic average roughness (Ra) of 12 nm square on the surface of the porous substrate on the side in contact with the porous layer is preferably 10 nm or more and less than 80 nm.
• the average roughness is also improved, and since fine unevenness exists in a local area of 12 nm square, it becomes easier to follow the unevenness of the active material in the electrode, so dry adhesion and wet adhesion to the electrode can be further improved.
• the upper limit of the arithmetic mean roughness (Ra) is preferably 60 nm or less, more preferably 40 nm or less.
• the height (Spk) of protruding peaks in a 2200 ⁇ m square of the porous substrate on the surface of the porous substrate on the side in contact with the porous layer is preferably 0.01 ⁇ m or more and less than 0.12 ⁇ m, and the lower limit is 0.03 ⁇ m. 0.05 ⁇ m or more is more preferable.
• the upper limit of the protruding peak height (Spk) is more preferably less than 0.12 ⁇ m, and still more preferably 0.10 ⁇ m or less.
• the transportability of the porous base material when forming the porous layer is improved, so that a uniform layer can be formed.
• the uneven distribution of the organic resin particles on the surface layer tends to occur, and the dry adhesion and wet adhesion to the electrode are improved.
• the height (Spk) of the protruding peak portion is set to less than 0.12 ⁇ m, electrolyte pourability is improved, and favorable rate characteristics and battery life are obtained.
• the thickness of the porous substrate is preferably 3 ⁇ m or more and 15 ⁇ m or less, more preferably 5 ⁇ m or more as the lower limit, and more preferably 12 ⁇ m or less as the upper limit.
• the method for manufacturing the porous base material will be explained.
• the method for producing the porous substrate is not particularly limited, but the method for producing the polyolefin microporous membrane will be described below.
• a plasticizer is added to the polyolefin resin composition described above in a twin-screw extruder, and melt-kneaded to prepare a resin solution.
• the polyolefin resin composition is composed of a polyolefin resin, and may be a single composition or a mixture of two or more polyolefin resins.
• Polyolefin resins include, but are not limited to, polyethylene, polypropylene, and the like.
• As the polyethylene resin ultra-high molecular weight polyethylene, high density polyethylene, and medium density polyethylene low density may be used as a single composition, or a mixture of different molecular weights may be used. It is preferable to use a mixture of two or more polyethylenes selected from the group consisting of ultra - high molecular weight polyethylene, high-density polyethylene, medium-density polyethylene and low-density polyethylene.
• a mixture of A) and polyethylene (B) having an Mw of 1 ⁇ 10 4 or more and less than 9 ⁇ 10 4 is preferable, and it is more preferable to contain an ultra-high molecular weight polyethylene having an Mw of 1 ⁇ 10 6 or more.
• the ratio of ultra high molecular weight polyethylene (A) and polyethylene (B) is 50% by mass, with the total of ultra high molecular weight polyethylene (A) and polyethylene (B) being 100% by mass. It is preferable that it is less than.
• the plasticizer enables stretching at a relatively high magnification
• the plasticizer is preferably liquid at room temperature.
• Specific examples include aliphatic hydrocarbons such as nonane, decane, decalin, paraxylene, undecane, dodecane, and liquid paraffin.
• the content of the polyolefin resin composition is preferably 50% by weight or more and 90% by weight or less.
• the gel-like sheet is stretched.
• the gel-like sheet is preferably stretched at a predetermined magnification by a tenter method, a roll method, an inflation method, or a combination thereof.
• the stretched area ratio is preferably 4 times or more and 100 times or less, more preferably 12 times or more and 64 times or less, and particularly preferably 25 times or more and 49 times or less.
• the higher the draw ratio the smaller the arithmetic mean height (Sa) and protruding peak height (Spk) in 2200 ⁇ m square of the porous substrate, and the arithmetic mean roughness (Ra) in 12 nm square.
• the plasticizer is removed using a washing solvent, and the polyolefin microporous membrane can be obtained by drying.
• stretching also called dry re-stretching
• the second stretching can be performed by a tenter method or the like while heating the polyolefin microporous membrane in the same manner as the stretching described above.
• the re-stretching ratio is preferably 1.01 to 2.0 times in the case of uniaxial stretching, and preferably 1.01 to 2.0 times in the case of biaxial stretching.
• the porous film of the present invention preferably has an arithmetic mean height (Sa) of 0.005 ⁇ m or more and less than 0.085 ⁇ m in a 2200 ⁇ m square on the surface on which the porous layer is provided. More preferably, it is 0.060 ⁇ m or less.
• the arithmetic mean height (Sa) in a 2200 ⁇ m square of the surface on which the porous layer is provided is the arithmetic mean height (Sa) in a 2200 ⁇ m square on the surface of the porous substrate on which the porous layer is provided ( Sa) tends to be greatly affected, and the arithmetic mean height (Sa) in a 2200 ⁇ m square of the surface of the porous substrate on the side in contact with the porous layer is appropriately selected within the above preferable range. can be within
• the porous film of the present invention can be suitably used as a separator for secondary batteries such as lithium ion batteries.
• a lithium-ion battery has a configuration in which a secondary battery separator and an electrolyte are interposed between a positive electrode in which a positive electrode active material is laminated on a positive electrode current collector and a negative electrode in which a negative electrode active material is laminated on a negative electrode current collector.
• the positive electrode is obtained by laminating a positive electrode material composed of an active material, a binder resin , and a conductive aid on a current collector.
• Lithium-containing transition metal oxides having a layered structure, spinel-type manganese oxides such as LiMn 2 O 4 , and iron-based compounds such as LiFePO 4 can be used.
• a resin having high oxidation resistance may be used as the binder resin. Specific examples include fluorine resins, acrylic resins, styrene-butadiene resins, and the like. Carbon materials such as carbon black and graphite are used as conductive aids.
• a metal foil is suitable, and an aluminum foil is often used in particular.
• the negative electrode is obtained by laminating a negative electrode material composed of an active material and a binder resin on a current collector, and the active material includes carbon materials such as artificial graphite, natural graphite, hard carbon and soft carbon, tin and silicon. , metal materials such as metallic lithium, and lithium titanate (Li 4 Ti 5 O 12 ).
• a fluorine resin, an acrylic resin, a styrene-butadiene resin, or the like is used as the binder resin.
• metal foil is suitable, and copper foil is often used in particular.
• the electrolytic solution serves as a field for transferring ions between the positive electrode and the negative electrode in the secondary battery, and is made by dissolving the electrolyte in an organic solvent.
• electrolytes include LiPF 6 , LiBF 4 , and LiClO 4 , and LiPF 6 is preferably used from the viewpoint of solubility in organic solvents and ionic conductivity.
• organic solvent include ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, etc. Two or more of these organic solvents may be used in combination.
• an active material and a conductive agent are dispersed in a solution of a binder resin to prepare a coating liquid for an electrode.
• a positive electrode and a negative electrode are obtained by drying.
• the film thickness of the coating film after drying is preferably 50 ⁇ m or more and 500 ⁇ m or less.
• a secondary battery separator is placed between the obtained positive electrode and negative electrode so as to be in contact with the active material layer of each electrode, enclosed in an outer packaging material such as an aluminum laminate film, and after injecting an electrolytic solution, the negative electrode lead and the Install a safety valve and seal the exterior material.
• the secondary battery thus obtained has high adhesion between the electrode and the secondary battery separator, has excellent rate characteristics and battery life, and can be manufactured at low cost.
• volume content rate ⁇ of inorganic particles in the porous layer (volume content rate ⁇ ) A 10 cm ⁇ 10 cm sample cut out from the porous film was used to extract the porous layer using 40 g of water, and the water was sufficiently dried to obtain the constituent components of the porous layer.
• an organic solvent such as alcohol may be used when water cannot be used to sufficiently desorb.
• the constituent components were burned at a high temperature to melt and decompose the organic resin component, and after separating the organic resin component and the inorganic component, the mass of only the inorganic particles was measured. .
• the content of the inorganic particles in the porous layer was calculated in % by mass from the formula (mass of inorganic particles/mass of total amount of constituent components) ⁇ 100.
• the content of the organic resin component in the porous layer was calculated in mass % by the formula ((mass of the total amount of the constituent components ⁇ mass of the inorganic particles)/(mass of the total amount of the constituent ingredients)) ⁇ 100.
• the specific gravity of each component was measured with a hydrometer.
• the volume content of the inorganic particles in the porous layer was calculated in volume % from the mass content (% by mass) of the inorganic particles and the organic resin component obtained above and the density of the inorganic particles and the organic resin component. The above measurements were performed on five samples, and the measured values were averaged.
• the threshold level of the threshold is set to 130 nm as a detection method
• the area ratio (%) which is a parameter representing the area of the portion corresponding to the inorganic element of the inorganic particle with respect to the area of the image as a percentage, is the occupancy rate of the inorganic particle. ⁇ . The above measurements were performed on five samples, and the measured values were averaged.
• Arithmetic mean roughness (Ra) of 12 nm square on the surface of the porous substrate on the side in contact with the porous layer 50 g of water was used to remove the porous layer from a sample cut out from the porous film to a size of 12 cm ⁇ 12 cm, and the water was sufficiently dried to obtain the target porous substrate.
• an organic solvent such as alcohol is used, and after the desorption, it is sufficiently dried.
• the porous substrate is fixed to the sample stage with carbon tape, the cantilever is SI-DF40, the measurement area is 12 ⁇ m square, and the amplitude attenuation rate is ⁇ 0.
• Arithmetic mean roughness (Ra) was measured in DFM mode with a scanning frequency of 0.5 Hz.
• Ra Arithmetic mean roughness
• the interface was defined as a place where the inorganic particles were no longer observed in the region where the inorganic particles were present.
• the above measurements were performed on five samples, and the measured values were arithmetically averaged.
• Thermal shrinkage rate (%) [(length between midpoints before heat treatment - length between midpoints after heat treatment) / (length between midpoints before heat treatment)] x 100
• Dry Adhesion with Electrode Active material is Li(Ni 5/10 Mn 2/10 Co 3/10 )O 2
• binder is vinylidene fluoride resin
• conductive aid is acetylene black and graphite positive electrode 20 mm ⁇ 50 mm. and a porous film of 25 mm ⁇ 55 mm are placed so that the active material and the porous layer are in contact, and hot press is performed for 10 seconds at a pressure of 6 MPa in a heating environment of 75 ° C. to bond the electrode and the porous film. .
• the adhesive strength between the porous film and the negative electrode in which the active material is graphite, the binder is vinylidene fluoride resin, and the conductive agent is carbon black is measured. It was determined as adhesive strength.
• ⁇ Excellent adhesion strength The electrode and the porous film were separated with a stronger force.
• Adhesive strength is "excellent”: The electrode and the porous film were separated with a strong force.
• Good adhesion strength The electrode and the porous film were separated with a slightly strong force.
• ⁇ Adhesion strength is “Fair”: The electrode and the porous film were peeled off with a weak force.
• - “Poor” adhesive strength The electrode and the porous film were separated with very weak force.
• a negative electrode (width 20 mm ⁇ length 70 mm) containing graphite as an active material, vinylidene fluoride resin as a binder, and carbon black as a conductive aid was used as an electrode.
• a porous film (width 25 mm ⁇ length 80 mm) was placed so that the ends of the electrode and the porous film overlapped in the length direction, and the active material and the porous layer were in contact, and the condition a (70 C. for 6 seconds at a pressure of 5 MPa) to adhere the electrode and the porous film to prepare a test piece.
• the test piece is placed in a bag-shaped aluminum laminate film with three pieces closed, and after the electrolytic solution injection process (1 g of electrolytic solution is impregnated from the porous film side of the test piece), the aluminum is sealed using a vacuum sealer. The remaining one side of the laminate film was enclosed.
• the aluminum laminate film after enclosing this test piece was stored in a 60° C. environment for 17 hours under static conditions. The test piece was taken out from the aluminum laminate film, and the electrolytic solution on the surface of the test piece was wiped.
• Electrolyte Pouring Properties Five negative electrodes each containing graphite as an active material, vinylidene fluoride resin as a binder, and carbon black as a conductive aid are cut out to a size of 8 cm ⁇ 8 cm. Also, 6 porous films are cut into 8.5 cm ⁇ 8.5 cm. After that, the negative electrode and the porous film were alternately placed so that the active material layer and the porous layer were in contact with each other, and hot pressing was performed at 75° C./6 MPa/10 seconds to form a laminate in which the negative electrode and the porous film were adhered. made.
• the degree of impregnation of the electrolyte into the porous film was evaluated in the following five stages. ⁇ Excellent electrolyte pourability: 90% or more of the porous film was impregnated with the electrolyte. - “Excellent” electrolyte pourability: 75% or more and less than 90% of the porous film was impregnated with the electrolyte. - Electrolyte pourability is “good”: 60% or more and less than 75% of the porous film was impregnated with the electrolyte. ⁇ Electrolyte pourability is “good”: 45% or more and less than 60% of the porous film was impregnated with the electrolyte. - Electrolyte pourability is "improper”: Less than 45% of the porous film was impregnated with the electrolyte.
• the positive electrode sheet contains 96 parts by mass of Li(Ni 5/10 Mn 2/10 Co 3/10 )O 2 as a positive electrode active material, and 1.0 parts by mass of acetylene black and graphite as positive electrode conductive aids.
• Each positive electrode slurry was prepared by dispersing 2 parts by mass of polyvinylidene fluoride as a positive electrode binder in N-methyl-2-pyrrolidone using a planetary mixer. (Coating basis weight: 10.0 mg/cm 2 ).
• This positive electrode sheet was cut into a size of 40 mm ⁇ 40 mm. At this time, a current-collecting tab bonding portion without an active material layer was cut out to a size of 5 mm ⁇ 5 mm outside the active material surface.
• An aluminum tab having a width of 5 mm and a thickness of 0.1 mm was ultrasonically welded to the tab bonding portion.
• the negative electrode sheet 98 parts by mass of natural graphite as a negative electrode active material, 1 part by mass of carboxymethyl cellulose as a thickener, and 1 part by mass of a styrene-butadiene copolymer as a negative electrode binder are dispersed in water using a planetary mixer. The resulting negative electrode slurry was coated on a copper foil, dried, and rolled to prepare a negative electrode slurry (coating basis weight: 6.6 mg/cm 2 ). This negative electrode sheet was cut into a size of 45 mm ⁇ 45 mm.
• a current-collecting tab bonding portion without an active material layer was cut out to a size of 5 mm ⁇ 5 mm outside the active material surface.
• a copper tab having the same size as the positive electrode tab was ultrasonically welded to the tab bonding portion.
• the porous film was cut into a size of 55 mm ⁇ 55 mm, and the positive electrode and the negative electrode were superimposed on both sides of the porous film so that the active material layer separated the porous film, and the positive electrode coated portion was entirely opposed to the negative electrode coated portion. Arranged to obtain an electrode group.
• hot pressing was performed for 10 seconds at a pressure of 6 MPa in a heating environment of 75° C. to bond the positive electrode, the porous film, and the negative electrode.
• the above positive electrode, porous film, and negative electrode were sandwiched between a sheet of aluminum laminate film of 90 mm ⁇ 200 mm.
• 1.5 g of the electrolytic solution was poured into a bag-shaped aluminum laminate film, and the short sides of the aluminum laminate film were heat-sealed while being impregnated under reduced pressure to obtain a laminate type battery.
• Discharge load characteristics were tested according to the following procedures and evaluated by the discharge capacity retention rate. Using the laminate type battery, the discharge capacity when discharged at 0.5 C at 25 ° C. and the discharge capacity when discharged at 10 C at 25 ° C. are measured, (discharge capacity at 7 C) / ( The discharge capacity retention rate (%) was calculated by the formula of (discharge capacity at 0.5 C) ⁇ 100.
• the charging conditions were constant current charging at 0.5C and 4.3V, and the discharging conditions were constant current discharge at 2.7V.
• Five laminate-type batteries were produced, and the average of the measurement results of the three batteries after removing the maximum and minimum discharge capacity retention rates was taken as the capacity retention rate.
• a discharge capacity retention rate of less than 40% was rated as "bad”, 45% or more and less than 50% as "good”, 50% or more and less than 55% as "excellent", and 55% or more as "excellent”.
• Charging and discharging were set as one cycle, charging conditions were constant current charging at 2C and 4.3V, and discharging conditions were constant current discharging at 2C and 2.7V, and charging and discharging were repeated 300 times at 25°C.
• the discharge capacity retention rate (%) was calculated by the formula of (discharge capacity at 300th cycle)/(discharge capacity at 1st cycle) ⁇ 100. Five laminate-type batteries were produced, and the average of the measurement results of the three batteries after removing the maximum and minimum discharge capacity retention rates was taken as the capacity retention rate. Life characteristics are "bad” when the discharge capacity retention rate is less than 50%, life characteristics are “good” when 50% or more and less than 60%, life characteristics are “excellent” when 60% or more and less than 70%, and life characteristics are 70% or more. said "excellent”.
• Example 1 Dispersion A 120 parts of ion-exchanged water and 1 part of Adekaria Sorb SR-1025 (an emulsifier manufactured by Adeka Corporation) were charged into a reactor, and stirring was started. To this, 0.4 parts of 2,2′-azobis(2-(2-imidazolin-2-yl)propane) (manufactured by Wako Pure Chemical Industries, Ltd.) was added under a nitrogen atmosphere, and 2,2,2- Trifluoroethyl methacrylate (3FM) 24 parts, cyclohexyl acrylate (CHA) 56 parts, hydroxyethyl methacrylate (HEMA) 12 parts, alkylene glycol dimethacrylate (AGDMA) 9 parts, Adekaria Sorb SR-1025 (emulsifier, manufactured by Adeka Co., Ltd.) 8 and 115 parts of ion-exchanged water are continuously added dropwise at 70° C. over 1.5 hours. A dispersion A containing coalescence
• Dispersion Z Using alumina particles (aluminum oxide) having an average particle size of 0.5 ⁇ m as inorganic particles, adding water in the same amount as the inorganic particles as a solvent, and carboxymethyl cellulose as a dispersant at 1% by mass relative to the inorganic particles, followed by bead milling. to prepare a dispersion liquid Z.
• alumina particles aluminum oxide having an average particle size of 0.5 ⁇ m as inorganic particles
• Coating liquid Dispersion liquid A and dispersion liquid Z are dispersed in water so that the volume content ⁇ of the inorganic particles contained in the porous layer is 50% by volume and the solid content concentration is 22% by mass, and mixed with a stirrer. did.
• the resulting coating liquid had a viscosity of 13 mPa ⁇ s.
• the obtained coating liquid was applied to a polyolefin microporous film (arithmetic mean height (Sa) 0.06 ⁇ m, protruding peak height (Spk) 0.06 ⁇ m, arithmetic average roughness (Ra) 40 nm, thickness 9 ⁇ m), dried for 1 minute in a hot air oven (drying set temperature 45 ° C.), and volatilizing the contained solvent to form a porous layer, A porous film was obtained.
• Table 1 shows the arithmetic mean height (Sa) of the porous substrate surface on the side in contact with the porous layer used in Examples 1 to 30, the type of inorganic particles, the volume content ⁇ , the type of organic resin particles, Coating conditions are shown.
• Table 2 shows the ⁇ / ⁇ of the porous films obtained in Examples 1 to 30, the occupation ratio ⁇ of the inorganic particles in the porous surface layer portion, and the arithmetic mean height of the surface of the porous film on the side having the porous layer.
• (Sa) surface free energy, glass transition temperature (°C) of the porous film, and thickness of the porous layer.
• Table 3 shows the thermal dimensional stability, peel strength, dry adhesion to electrodes, electrolyte pourability, rate characteristics, and life characteristics of the porous films obtained in Examples 1 to 30 and the batteries using them. shows the measurement results of
• Example 2 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.04 ⁇ m.
• Example 3 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.08 ⁇ m.
• Example 4 A porous film of the present invention was obtained in the same manner as in Example 1, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.01 ⁇ m.
• Example 5 A porous film was obtained in the same manner as in Example 1, except that the volume content ⁇ of the inorganic particles contained in the porous layer was changed to 30% by volume.
• Example 6 A porous film was obtained in the same manner as in Example 1, except that the volume content ⁇ of the inorganic particles contained in the porous layer was changed to 80% by volume.
• Example 7 A porous film was obtained in the same manner as in Example 1, except that the solid content concentration of the coating liquid was changed to 10% by mass and the viscosity was changed to 10 mPa ⁇ s.
• Example 8 A porous film was obtained in the same manner as in Example 1, except that the solid content concentration of the coating liquid was changed to 40% by mass and the viscosity was changed to 40 mPa ⁇ s.
• Example 9 Dispersion liquid A and dispersion liquid Z were prepared in the same manner as in Example 1.
• Dispersion B A dispersion liquid B was prepared comprising a polymer (polymer B) (particle size: 140 nm) composed of methyl acrylate as an acrylate monomer. After that, the dispersion liquid A, the dispersion liquid Z, and the dispersion liquid B were mixed in the porous layer so that the volume content ⁇ of the inorganic particles contained in the porous layer was 50% by volume, the content of the organic resin particles (polymer A) was 35% by volume, and the organic resin The particles (polymer B) were dispersed in water so that the content of the particles (polymer B) was 15% by volume and the solid concentration was 22% by mass, and mixed with a stirrer.
• the resulting coating liquid had a viscosity of 13 mPa ⁇ s. Except that the organic resin particles are a mixture of two kinds of particles containing 90% by mass of a polymer A composed of a fluorine-containing methacrylate monomer and 10% by mass of a polymer B (average particle diameter 130 nm) composed of an acrylic acid ester monomer. obtained a porous film in the same manner as in Example 1.
• Example 10 2,2,2-trifluoroethyl methacrylate (3FM) was replaced with 1H,1H,5H-octafluoropentyl acrylate (8FA), prepared in the same manner as dispersion A of Example 1 to contain polymer C Dispersion C was prepared. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• Example 11 24 parts of 2,2,2-trifluoroethyl methacrylate (3FM), 56 parts of cyclohexyl acrylate (CHA), 12 parts of hydroxyethyl methacrylate (HEMA) as monomers for constituting the polymer D forming the organic resin particles and 9 parts of alkylene glycol dimethacrylate (AGDMA) were replaced with 100 parts of ethyl methacrylate as the methacrylic acid ester monomer. Dispersion D was prepared. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• 3FM 2,2,2-trifluoroethyl methacrylate
• CHA cyclohexyl acrylate
• HEMA hydroxyethyl methacrylate
• ALDMA alkylene glycol dimethacrylate
• Example 12 A porous film was obtained in the same manner as in Example 11, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.08 ⁇ m.
• Example 13 A porous film was obtained in the same manner as in Example 11, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.01 ⁇ m.
• Example 14 24 parts of 2,2,2-trifluoroethyl methacrylate (3FM), 56 parts of cyclohexyl acrylate (CHA), 12 parts of hydroxyethyl methacrylate (HEMA) as monomers for constituting the polymer E forming the organic resin particles and 9 parts of alkylene glycol dimethacrylate (AGDMA) were replaced with 100 parts of a vinylidene fluoride monomer. manufactured. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• 3FM 2,2,2-trifluoroethyl methacrylate
• CHA cyclohexyl acrylate
• HEMA hydroxyethyl methacrylate
• ALDMA alkylene glycol dimethacrylate
• Example 15 A porous film was obtained in the same manner as in Example 1, except that the average particle size of the organic resin particles was 75 nm.
• Example 16 A porous film was obtained in the same manner as in Example 1, except that the average particle size of the organic resin particles was 100 nm.
• Example 17 A porous film was obtained in the same manner as in Example 1, except that the average particle size of the organic resin particles was 500 nm.
• Example 18 A porous film was obtained in the same manner as in Example 1, except that the average particle size of the organic resin particles was 700 nm.
• Example 19 A porous film was obtained in the same manner as in Example 1, except that the inorganic particles were barium sulfate particles.
• Example 20 A porous film was obtained in the same manner as in Example 1, except that boehmite particles were used as the inorganic particles.
• Example 21 A porous film was obtained in the same manner as in Example 1, except that the film thickness of the porous layer was 5 ⁇ m.
• Example 22 A porous film was obtained in the same manner as in Example 1, except that the film thickness of the porous layer was 8 ⁇ m.
• Example 23 Polymer F was obtained by adjusting the amounts of CHA, HEMA, and AGDMA so that the glass transition temperature was 20° C. under the conditions for producing dispersion liquid A of Example 1, with 20 parts of 3FM. A porous film was obtained in the same manner.
• Example 24 Polymer G was obtained by adjusting the amounts of CHA, HEMA, and AGDMA so that the glass transition temperature was 20° C. under the conditions for producing Dispersion A of Example 1, with the exception that 80 parts of 3FM was used. A porous film was obtained in the same manner.
• Example 25 A porous film was obtained in the same manner as in Example 1, except that the drying temperature of the coating liquid was set to 75°C.
• Example 26 A porous film was obtained in the same manner as in Example 1, except that the drying temperature of the coating liquid was set to 100°C.
• Example 27 Using the same polyolefin microporous membrane as in Example 1 as the porous substrate, the dispersion liquid Z was coated on both sides of the polyolefin microporous membrane using a #9 wire bar, and dried in a hot air oven (drying set temperature 50 ° C.). The first porous layer was formed by drying in the chamber for 1 minute and volatilizing the contained solvent. After that, dispersion liquid A was dispersed in water so as to have a solid content concentration of 6% by mass, and mixed with a stirrer. The resulting coating liquid had a viscosity of 7 mPa ⁇ s.
• the coating liquid is coated on both sides of the first coating layer using a #1.5 wire bar and dried in a hot air oven (drying temperature set at 50°C) for 1 minute to volatilize the contained solvent.
• a porous film was obtained in the same manner as in Example 6, except that the second porous layer was formed by heating.
• the occupation ratio ⁇ of the inorganic particles in the surface portion of the porous layer was 20%.
• Example 28 A porous film was obtained in the same manner as in Example 27, except that polymer D was used.
• Example 29 Polymer H obtained by selecting a methacrylic acid ester monomer (butyl methacrylate) suitable for constituting the polymer forming the organic resin particles so that the glass transition temperature of the porous layer is 20° C. A porous film was obtained in the same manner as in Example 28, except that it was used.
• Example 30 Acrylic acid ester monomers containing fluorine-containing acrylate monomers (50 parts of methyl acrylate, 50 parts of methyl acrylate, A porous film was obtained in the same manner as in Example 1, except that Copolymer I obtained by selecting 50 parts of butyl acrylate was used.
• Polymers in the table represent the following.
• Polymer A A polymer polymerized using a fluorine-containing methacrylate monomer (ratio of fluorine-containing methacrylate monomer to total monomers used: 30% by mass)
• Polymer B A polymer polymerized using an acrylate monomer
• Polymer C A polymer polymerized using a fluorine-containing acrylate monomer
• Polymer D A methacrylic acid ester monomer
• Polymer E polymer polymerized using a vinylidene fluoride monomer
• Polymer F polymer polymerized using a fluorine-containing methacrylate monomer (total monomers used Proportion of fluorine-containing methacrylate monomer accounted for: 20% by mass)
• Polymer G a polymer polymerized using a fluorine-containing methacrylate monomer (ratio of fluorine-containing methacrylate monomer to total monomers used: 80% by mass)
• Polymer H polymer polymerized using me
• Example 31 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean roughness (Ra) of the polyolefin microporous membrane was changed to 5 nm.
• Example 32 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean roughness (Ra) of the polyolefin microporous membrane was changed to 10 nm.
• Example 33 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean roughness (Ra) of the polyolefin microporous membrane was changed to 50 nm.
• Example 34 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean roughness (Ra) of the polyolefin microporous membrane was changed to 70 nm.
• Example 35 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean roughness (Ra) of the polyolefin microporous membrane was changed to 100 nm.
• Example 36 A porous film was obtained in the same manner as in Example 1, except that the height (Spk) of the protrusion peaks of the polyolefin microporous membrane was changed to 0.01 ⁇ m.
• Example 37 A porous film was obtained in the same manner as in Example 1, except that the height (Spk) of the protrusion peaks of the polyolefin microporous membrane was changed to 0.04 ⁇ m.
• Example 38 A porous film was obtained in the same manner as in Example 1, except that the height (Spk) of the protrusion peaks of the polyolefin microporous membrane was changed to 0.09 ⁇ m.
• Example 39 A porous film was obtained in the same manner as in Example 1, except that the height (Spk) of the protrusion peaks of the polyolefin microporous membrane was changed to 0.15 ⁇ m.
• Tables 4 and 5 show the measurement results of peel strength, dry adhesion to electrodes, rate characteristics, and life characteristics of the film and the battery using it.
• Example 40 Dispersion J containing polymer J was prepared in the same manner as dispersion A of Example 1, except that the composition of the organic resin particles was changed as shown in Table 6. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• Example 41 Dispersion K containing polymer K was prepared in the same manner as dispersion A of Example 1, except that the composition of the organic resin particles was changed as shown in Table 6. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• Example 42 Dispersion L containing polymer L was prepared in the same manner as dispersion A of Example 1, except that the composition of the organic resin particles was changed as shown in Table 6. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• Example 43 Dispersion M containing polymer M was prepared in the same manner as Dispersion A of Example 1, except that the composition of the organic resin particles was changed as shown in Table 6. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• Example 44 Dispersion N containing polymer N was prepared in the same manner as dispersion A of Example 1, except that the composition of the organic resin particles was changed as shown in Table 6. Thereafter, in the same manner as in Example 1, a porous film was obtained.
• Example 45 Dispersion liquid O containing polymer O was produced in the same manner as dispersion liquid A of Example 1, except that the composition of the organic resin particles was changed as shown in Table 6. Then, in the same manner as in Example 1, a porous film was obtained.
• Example 46 A porous film of the present invention was obtained in the same manner as in Example 42, except that the volume content ⁇ of the inorganic particles contained in the porous layer was changed to 30% by volume.
• Example 47 A porous film of the present invention was obtained in the same manner as in Example 42, except that the volume content ⁇ of the inorganic particles contained in the porous layer was changed to 80% by volume.
• Example 48 A porous film of the present invention was obtained in the same manner as in Example 42, except that the porous substrate was changed to a polyolefin microporous membrane having an arithmetic mean height (Sa) of 0.08 ⁇ m.
• Example 49 A porous film of the present invention was obtained in the same manner as in Example 1, except that the porous substrate was changed to a polyolefin microporous membrane having an arithmetic mean height (Sa) of 0.01 ⁇ m.
• Table 6 shows the arithmetic mean height (Sa) of the porous substrate used in Examples 40 to 49, the type of monomer used for polymerization of the polymer constituting the organic resin particles, and each monomer
• the glass transition temperature (° C.) of the polymer polymerized using only the monomer, the proportion (%) of each monomer used, and the glass transition temperature of the polymer polymerized only with the monomer are ⁇ 100. ° C. to 0 °C.
• Table 7 shows the types of inorganic particles used in Examples 40 to 49, the volume content ⁇ , the resulting porous film ⁇ / ⁇ , the inorganic particle occupation ratio ⁇ in the porous surface layer, the porous Arithmetic mean height (Sa) of the surface of the porous film on the layered side (Sa), surface free energy, glass transition temperature (°C), thermal dimensional stability, peel strength, dry adhesion with electrode, wet with electrode It shows adhesion, rate characteristics and life characteristics of batteries using the porous film.
• Example 1 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.09 ⁇ m.
• Example 2 A porous film was obtained in the same manner as in Example 1, except that the solid content concentration of the coating liquid was changed to 50% by mass and the viscosity was changed to 80 mPa ⁇ s.
• Example 3 A porous film was obtained in the same manner as in Example 1, except that the drying temperature of the coating liquid was set to 110°C.
• Example 4 A porous film was obtained in the same manner as in Example 1, except that the composition shown in Table 8 was used without using the organic resin particles A.
• Example 5 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.15 ⁇ m.
• Example 6 A porous film was obtained in the same manner as in Example 1, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.008 ⁇ m.
• Example 7 A porous film was obtained in the same manner as in Example 42, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.008 ⁇ m.
• Example 8 A porous film was obtained in the same manner as in Example 42, except that the arithmetic mean height (Sa) of the polyolefin microporous membrane was changed to 0.15 ⁇ m.
• Table 8 shows the arithmetic mean height (Sa) of the porous substrate used in Comparative Examples 1 to 8, the type of monomer used for polymerization of the polymer constituting the organic resin particles, and each monomer
• the glass transition temperature (° C.) of the polymer polymerized using only the monomer, the proportion (%) of each monomer used, and the glass transition temperature of the polymer polymerized only with the monomer are ⁇ 100. ° C. to 0 °C.
• Table 9 shows the types of inorganic particles used in Comparative Examples 1 to 8, the volume content ⁇ , the obtained porous film ⁇ / ⁇ , the occupation ratio ⁇ of the inorganic particles in the porous surface layer, the porous
• the arithmetic mean height (Sa), surface free energy, glass transition temperature (° C.) and film thickness of the porous film on the layered side of the porous film are shown.
• Table 10 shows the thermal dimensional stability, peel strength, dry adhesion to electrodes, wet adhesion to electrodes, rate characteristics, and life of the porous films obtained in Comparative Examples 1 to 8 and batteries using them. The measurement results of the characteristics are shown.
• Examples 1 to 49 all have a porous substrate and a porous layer containing inorganic particles and organic resin particles on at least one surface of the porous substrate.
• the porous substrate has an arithmetic mean height (Sa) of 0.01 ⁇ m or more and less than 0.09 ⁇ m in a 2200 ⁇ m square on the surface of the porous substrate on the side in contact with the porous layer,
• Sa arithmetic mean height
• the volume of all constituent components of the layer is 100% by volume
• the volume content ⁇ (% by volume) of the inorganic particles and the occupation ratio ⁇ (% by mass) of the inorganic particles at the surface of the porous layer are ⁇ / ⁇ 1.
• It is a porous film has excellent dry adhesion to electrodes, and has good rate characteristics and battery life.
• Examples 40 to 44 and 46 to 49 have excellent wet adhesion to the electrode by appropriately selecting the composition of the organic resin particles.
• Comparative Example 4 does not contain organic resin particles, uneven distribution of the organic resin particles on the surface does not occur.
• the arithmetic mean height (Sa) of the surface of the porous substrate on the side in contact with the porous layer is less than 0.01 ⁇ m, so the adhesiveness to the electrode is poor.

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