JP6634364B2 - Non-aqueous electrolyte secondary battery separator, laminated separator for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery member, and non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a separator for a non-aqueous electrolyte secondary battery, a laminated separator for a non-aqueous electrolyte secondary battery, a member for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries, particularly lithium secondary batteries, are widely used as batteries used in personal computers, mobile phones, portable information terminals, electric vehicles, and the like because of their high energy density. In particular, in recent years, lithium secondary batteries have been used for electric vehicles and the like, and the production volume has increased remarkably. Under these circumstances, there is a demand for problems during battery manufacturing and improvement in yield.

  In order to improve the yield, a separator having excellent slippage is required as a separator disposed between a positive electrode and a negative electrode in a nonaqueous electrolyte secondary battery. In a wound type nonaqueous electrolyte secondary battery such as a cylindrical type or a square type, a separator and a positive electrode and a negative electrode are overlapped and wound on a pin. Thereafter, the battery is assembled through a step of removing the spiral battery element from the pin. At this time, if the slipperiness of the separator in contact with the pin is poor, the battery element cannot be pulled out of the pin. Also, if it is difficult to pull out, it will affect battery production. Therefore, in order to improve the slipperiness of the separator with respect to the pin, Patent Literature 1 discloses a technique of performing a surface treatment on the pin to reduce the friction coefficient of the pin, and Patent Literature 2 discloses a technique of reducing the static friction coefficient of the separator. Techniques for lowering are disclosed.

JP 2009-070726 A (released on April 2, 2009) Japanese Patent Application Laid-Open No. 2011-126275 (released on June 30, 2011)

  In order to improve the yield, the separator is required to have not only the above-mentioned slipperiness but also a cutting workability. If the cutting workability is poor, the separator cannot be cut neatly into a desired size, the separator is torn in an unintended direction at the time of cutting, or the frequency of replacing the cutting blade of the separator cutting device increases, and the production amount is lost. I do. However, Patent Documents 1 and 2 do not consider cutting workability.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a separator for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery which are excellent in slipperiness and cutting workability with respect to a pin. To provide a laminated separator for use, a member for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.

  The present inventor has found that the lowest ball height at which tearing occurs when a ball having a diameter of 14.3 mm and a weight of 11.9 g is dropped is correlated with slipperiness with respect to a pin and cutting workability. It was found for the first time, and the present invention was completed.

  The separator for a non-aqueous electrolyte secondary battery according to the present invention is a porous film containing polyolefin as a main component, having a thickness of 20 μm or less, a porosity of 20 to 55%, and a diameter of 14.3 mm. When a sphere weighing 11.9 g is dropped on the porous film, the minimum height of the sphere at which tearing occurs is 50 cm or more.

  Further, a laminated separator for a non-aqueous electrolyte secondary battery according to the present invention includes the above-described separator for a non-aqueous electrolyte secondary battery and a porous layer.

  Further, the laminated separator for a non-aqueous electrolyte secondary battery according to the present invention is a laminated film for a non-aqueous electrolyte secondary battery comprising a porous film containing a polyolefin as a main component, and a porous layer, The thickness of the porous film is 20 μm or less, the porosity of the porous film is 20 to 55%, and the sphere having a diameter of 14.3 mm and a weight of 11.9 g is laminated with the nonaqueous electrolyte secondary battery. When dropped on the separator, the minimum height of the sphere at which tearing occurs may be 50 cm or more.

  Further, the non-aqueous electrolyte secondary battery member according to the present invention, the positive electrode, the non-aqueous electrolyte secondary battery separator or the non-aqueous electrolyte secondary battery laminated separator, and the negative electrode in this order It is characterized by being arranged.

  Further, a non-aqueous electrolyte secondary battery according to the present invention includes the above-described separator for a non-aqueous electrolyte secondary battery or the above-described laminated separator for a non-aqueous electrolyte secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that it is excellent in the sliding property with respect to a pin, and cutting workability.

It is a figure which shows the jig used for drop test evaluation. It is a figure showing the evaluation method of cutting workability. It is a figure which shows the lower surface and side surface of the sled member for measuring pin removal resistance. It is a figure showing a measuring method of pin omission resistance.

  An embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims, and the technical means disclosed in different embodiments may be appropriately combined. The embodiments obtained are also included in the technical scope of the present invention. Unless otherwise specified in this specification, “A to B” representing a numerical range means “A or more and B or less”.

<First embodiment>
[1. Non-aqueous electrolyte secondary battery separator)
A non-aqueous electrolyte secondary battery separator according to an embodiment of the present invention (hereinafter, sometimes referred to as a separator) is a film-shaped separator disposed between a positive electrode and a negative electrode in a non-aqueous electrolyte secondary battery. It is a porous film.

  The porous film may be any porous and film-like substrate (polyolefin-based porous substrate) containing a polyolefin-based resin as a main component, and has a structure having pores connected therein. This is a film through which gas and liquid can pass from one surface to the other surface.

  The porous film melts when the battery generates heat and renders the separator nonporous, thereby giving the separator a shutdown function.

  The thickness of the porous film is 20 μm or less, preferably 4 to 20 μm, more preferably 6 to 16 μm, and still more preferably 9 to 16 μm.

  The volume-based porosity of the porous film is set to be 20 to 55% by volume so as to increase the amount of retained electrolyte and to obtain a function of reliably preventing (shut down) an excessive current from flowing at a lower temperature. And more preferably 40 to 55% by volume.

  The porous film is cut into a predetermined size when incorporated into a non-aqueous electrolyte secondary battery as a separator. If a tear or the like in an unintended direction occurs at the time of cutting, the yield decreases. In particular, cutting workability is desired for a porous film having the above film thickness and porosity.

  Therefore, the present inventors have conducted intensive studies, and as a result, have found that the minimum height and cutting workability of a sphere that is torn when a sphere having a diameter of 14.3 mm and a weight of 11.9 g is freely dropped on a porous film are obtained. Have found for the first time a correlation, and completed the present invention. Specifically, by setting the minimum height to 50 cm or more, it is possible to suppress the occurrence of tearing in an unintended direction during cutting. Note that the minimum height is preferably 150 cm or less. In order for the minimum height to exceed 150 cm after balancing MD (Machine Direction) and TD (Transverse Direction), it is necessary to increase the film thickness or decrease the porosity. However, when the film thickness is increased, there is a problem that the energy density of the battery is reduced, and when the porosity is reduced, there is a problem that the battery characteristics (particularly, rate characteristics) are deteriorated.

  The porous film is obtained by a rolling process as described later. During the rolling process, a hard and brittle skin layer is formed on the surface. Further, depending on the conditions of the rolling step, an orientation difference between MD and TD occurs. The orientation difference between MD and TD also occurs depending on the stretching conditions. Stretching only in TD increases the orientation of TD, and stretching only in MD increases the orientation of MD. The proportion of the skin layer in the porous film and the orientation balance between MD and TD are related to the tearing of the porous film. In other words, as the proportion of the brittle skin layer increases, the skin layer becomes weaker against impact and tends to tear in an unintended direction. Also, if the orientation is biased to either MD or TD, unintended tearing along the direction in which the orientation is aligned tends to occur. Therefore, the ratio of the skin layer and the orientation balance between MD and TD affect the cutting processability of the porous film.

  The inventors of the present invention have found that the ratio of the skin layer and the tearability due to the orientation balance between MD and TD are such that when a sphere having a diameter of 14.3 mm and a weight of 11.9 g is freely dropped on a porous film, the ball is broken. It was found that it was correlated with the minimum height of the sphere that occurred. That is, the higher the minimum height, the smaller the proportion of the skin layer and the smaller the orientation difference between MD and TD. Then, as shown in Examples described later, by setting the minimum height to 50 cm or more, it is possible to suppress the occurrence of tearing in an unintended direction when cutting the porous film, and to cut the porous film. The performance is improved.

  Further, if the orientation is biased to either MD or TD, the friction in the direction perpendicular to the direction in which the orientation is relatively strong increases. That is, the orientation balance between MD and TD affects the frictional force when the porous film contacts another member. The present inventors have come into contact with other members in a porous film having a minimum height of 50 cm or more, in which a sphere having a diameter of 14.3 mm and a weight of 11.9 g is torn when dropped freely. It has been found that the orientation balance between MD and TD is such that the frictional force at the time can be reduced. Therefore, when assembling a wound type non-aqueous electrolyte secondary battery, the separator and the electrode are wound around the pin so that the pin contacts the surface of the porous film having the minimum height of 50 cm or more. By doing so, the slipperiness of the separator with respect to the pin can be improved. As a result, the pin can be easily pulled out, and defects in the step of pulling out the pin can be reduced.

  The proportion of the polyolefin component in the porous film is usually 50% by volume or more, preferably 90% by volume or more, and more preferably 95% by volume or more of the entire porous film.

  Examples of the polyolefin resin constituting the porous film include a high molecular weight homopolymer or copolymer obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, or the like. Can be. Among these, high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more, mainly composed of ethylene, is preferable. In addition, the porous film does not prevent inclusion of components other than polyolefin as long as the function of the layer is not impaired.

  The method for producing a porous film containing a polyolefin-based resin as a main component is, for example, when the porous film is formed from a polyolefin resin containing ultra-high molecular weight polyethylene and a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less. From the viewpoints of cost and physical properties, it is preferable to produce by the following method.

  That is, (1) a step of kneading an ultrahigh molecular weight polyethylene, a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and a pore forming agent such as calcium carbonate or a plasticizer to obtain a polyolefin resin composition; A step of rolling the polyolefin resin composition with a rolling roll to form a sheet (rolling step); (3) a step of removing a pore-forming agent from the sheet obtained in step (2); and (4) a step (3). And e) stretching the sheet obtained in step (a) to obtain a porous film.

  In the above-mentioned rolling step, by increasing the film thickness as compared with the related art, the number of skin layers generated in the rolling step can be reduced. In addition, since the film thickness is larger than before, the rolling process is fast, the orientation of MD becomes gentle, and the orientation difference between MD and TD can be reduced. Thereby, it is possible to manufacture a porous film having a minimum height of 50 cm or more, in which a sphere having a diameter of 14.3 mm and a weight of 11.9 g is torn when dropped freely.

[2. Non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary battery according to the present invention includes the above separator. More specifically, the non-aqueous electrolyte secondary battery according to the present invention includes a non-aqueous electrolyte secondary battery member in which a positive electrode, a separator, and a negative electrode are arranged in this order. That is, the non-aqueous electrolyte secondary battery member is also included in the scope of the present invention.

  In a non-aqueous electrolyte secondary battery, a battery element in which an electrolyte is impregnated in a structure in which a negative electrode sheet and a positive electrode sheet face each other via the above-described non-aqueous electrolyte secondary battery separator is enclosed in an exterior material. It has the structure which was done. The non-aqueous electrolyte secondary battery manufactured using the non-aqueous secondary electrolyte battery separator according to the present invention described above has a low frequency of replacement of the cutting blades of the separator cutting device, and has good pin detachability. High yield.

  Hereinafter, a lithium ion secondary battery will be described as an example of the nonaqueous electrolyte secondary battery. The components of the non-aqueous electrolyte secondary battery other than the separator are not limited to the components described below.

In the nonaqueous electrolyte secondary battery according to the present invention, for example, a nonaqueous electrolyte obtained by dissolving a lithium salt in an organic solvent can be used. Examples of the lithium salt include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , and Li ₂ B ₁₀ Cl. ₁₀ , lower aliphatic carboxylic acid lithium salt, LiAlCl _{4 and the} like. The lithium salt may be used alone or in combination of two or more.

Among the lithium salts, at least one selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiC (CF ₃ SO ₂ ) ₃ More fluorine-containing lithium salts are more preferred.

  As the organic solvent constituting the non-aqueous electrolyte, specifically, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one Carbonates such as 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropylmethyl ether, 2,2,3,3-tetrafluoropropyldifluoromethyl Ethers such as ether, tetrahydrofuran and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethyla Amides such as toamide; carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone; and sulfur-containing compounds obtained by introducing a fluorine group into the organic solvent. A fluorine organic solvent; The organic solvent may be used alone or in combination of two or more.

  Among the above organic solvents, carbonates are more preferable, and a mixed solvent of a cyclic carbonate and an acyclic carbonate or a mixed solvent of a cyclic carbonate and an ether is further more preferable.

  As a mixed solvent of a cyclic carbonate and an acyclic carbonate, the operating temperature range is wide, and even when graphite material such as natural graphite or artificial graphite is used as the negative electrode active material, it is hardly decomposable. A mixed solvent containing dimethyl carbonate and dimethyl carbonate is more preferred.

  As the positive electrode, a sheet-shaped positive electrode in which a positive electrode mixture containing a positive electrode active material, a conductive material, and a binder is supported on a positive electrode current collector is usually used.

  As the positive electrode active material, for example, a material capable of doping / dedoping lithium ions can be used. Specifically, the material includes, for example, a lithium composite oxide containing at least one transition metal such as V, Mn, Fe, Co, and Ni.

Among the above lithium composite oxides, lithium composite oxides having an α-NaFeO ₂ type structure, such as lithium nickelate and lithium cobaltate, and lithium composites having a spinel type structure, such as lithium manganese spinel, because of a high average discharge potential Oxides are more preferred. The lithium composite oxide may contain various metal elements, and a composite lithium nickelate is more preferable.

  Further, the number of moles of at least one metal element selected from the group consisting of Ti, Zr, Ce, Y, V, Cr, Mn, Fe, Co, Cu, Ag, Mg, Al, Ga, In and Sn; The composite lithium nickelate containing the metal element is used such that the ratio of the at least one metal element is 0.1 to 20 mol% with respect to the sum of the number of moles of Ni in the lithium nickel oxide. Is particularly preferable because of excellent cycle characteristics when used in a high capacity. Among them, an active material containing Al or Mn and having a Ni ratio of 85% or more, more preferably 90% or more, is used in a high capacity nonaqueous electrolyte secondary battery including a positive electrode containing the active material. It is particularly preferable because it has excellent cycle characteristics.

  Examples of the conductive material include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds. As the conductive material, only one kind may be used, or two or more kinds may be used in combination, for example, a mixture of artificial graphite and carbon black.

  Examples of the binder include polyvinylidene fluoride, vinylidene fluoride copolymer, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer And a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, and thermoplastic resins such as thermoplastic polyimide, polyethylene, and polypropylene. Further, an acrylic resin or styrene-butadiene rubber may be used. The binder also has a function as a thickener.

  Examples of a method for obtaining a positive electrode mixture include a method for obtaining a positive electrode mixture by pressing a positive electrode active material, a conductive material, and a binder on a positive electrode current collector; A method of obtaining a positive electrode mixture by converting a material and a binder into a paste; and the like.

  Examples of the positive electrode current collector include conductors such as Al, Ni, and stainless steel. Al is more preferable because it can be easily processed into a thin film and is inexpensive.

  As a method for producing a sheet-shaped positive electrode, that is, a method for supporting a positive electrode mixture on a positive electrode current collector, for example, a positive electrode active material, a conductive material, and a binder serving as a positive electrode mixture are applied on the positive electrode current collector. Press molding method: After a positive electrode mixture is obtained by forming a positive electrode active material, a conductive material and a binder using an appropriate organic solvent into a paste, the positive electrode mixture is applied to a positive electrode current collector, and dried. And fixing the sheet-shaped positive electrode mixture obtained as described above to a positive electrode current collector.

  As the negative electrode, a sheet-shaped negative electrode in which a negative electrode mixture containing a negative electrode active material is supported on a negative electrode current collector is usually used. The sheet-shaped negative electrode may contain the above-mentioned conductive material and binder.

Examples of the negative electrode active material include a material capable of doping and undoping lithium ions, lithium metal and a lithium alloy. As the material, specifically, for example, carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds; Chalcogen compounds such as oxides and sulfides for doping and undoping lithium ions; aluminum (Al), lead (Pb), tin (Sn), bismuth (Bi), silicon (Si), etc., which are alloyed with alkali metals Cubic intermetallic compounds (AlSb, Mg ₂ Si, NiSi ₂ ), lithium nitrogen compounds (Li ₃ -xM _x N (M: transition metal)), etc., which allow the insertion of metals and alkali metals between lattices are used. be able to. Of the above-mentioned negative electrode active materials, the potential flatness is high, and since a large energy density is obtained when combined with the positive electrode because of a low average discharge potential, natural graphite, a graphite material such as artificial graphite is used as a main component. A carbonaceous material is more preferable, and a mixture of graphite and silicon, in which the ratio of Si to C is 5% or more, is more preferable, and a negative electrode active material having 10% or more is more preferable.

  As a method for obtaining the negative electrode mixture, for example, a method in which the negative electrode active material is pressurized on the negative electrode current collector to obtain a negative electrode mixture; And a method for obtaining the same.

  Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Particularly, in a lithium ion secondary battery, Cu is more preferable because it is difficult to form an alloy with lithium and easily processed into a thin film.

  As a method for producing a sheet-shaped negative electrode, that is, a method for supporting a negative electrode mixture on a negative electrode current collector, for example, a method in which a negative electrode active material to be a negative electrode mixture is pressure-formed on a negative electrode current collector; After the negative electrode active material is paste-formed using an organic solvent to obtain a negative electrode mixture, the negative electrode mixture is applied to a negative electrode current collector, and the sheet-shaped negative electrode mixture obtained by drying is pressed. And fixing to the negative electrode current collector. The conductive paste and the binder may be included in the paste.

  After forming the nonaqueous electrolyte secondary battery member by disposing the positive electrode, the separator, and the negative electrode in this order, the nonaqueous electrolytic solution is placed in a container serving as a housing of the nonaqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to the present invention can be manufactured by charging the liquid secondary battery member, filling the container with a non-aqueous electrolyte, and sealing the container while reducing the pressure. The shape of the nonaqueous electrolyte secondary battery is not particularly limited, and may be any shape such as a thin plate (paper) type, a disk type, a cylindrical type, a prismatic type such as a rectangular parallelepiped, and the like. The method for manufacturing the nonaqueous electrolyte secondary battery is not particularly limited, and a conventionally known manufacturing method can be employed.

<Embodiment 2>
In the first embodiment described above, the separator for a non-aqueous electrolyte secondary battery that is a porous film is used as the separator of the non-aqueous electrolyte secondary battery. However, the separator according to the present invention includes a non-aqueous electrolyte secondary battery separator that is the porous film according to Embodiment 1, and a known porous layer such as an adhesive layer, a heat-resistant layer, and a protective layer. It may be a laminated separator for a water electrolyte secondary battery (hereinafter, sometimes referred to as a laminated separator).

  Since the porous film is as described in Embodiment 1, the porous layer will be described here. The thickness of the porous film contained in the laminated separator for a non-aqueous electrolyte secondary battery, the porosity, and the minimum height of the sphere at which destruction occurs in the falling ball test are the values of the porous state before the porous layer is laminated. May be measured for a porous film, or may be measured for a porous film remaining after a porous layer is separated from a laminated separator for a non-aqueous electrolyte secondary battery.

  The porous layer is laminated on one surface of a non-aqueous electrolyte secondary battery separator that is a porous film. The porous layer is preferably laminated on the surface of the porous film facing the positive electrode when the nonaqueous electrolyte secondary battery is used, and more preferably laminated on the surface in contact with the positive electrode.

  The porous layer is preferably a resin layer containing a resin. The resin constituting the porous layer is preferably insoluble in the electrolyte of the non-aqueous electrolyte secondary battery and electrochemically stable in the range of use of the non-aqueous electrolyte secondary battery.

  Examples of the resin constituting the porous layer include polyolefins such as polyethylene, polypropylene, polybutene, and ethylene-propylene copolymer; fluorine-containing resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene; vinylidene fluoride Fluorine-containing rubbers such as hexafluoropropylene-tetrafluoroethylene copolymer and ethylene-tetrafluoroethylene copolymer; aromatic polyamides; wholly aromatic polyamides (aramid resins); styrene-butadiene copolymers and hydrogenated products thereof; Rubbers such as methacrylate copolymer, acrylonitrile-acrylate copolymer, styrene-acrylate copolymer, ethylene propylene rubber and polyvinyl acetate; polyphenylene ether, polysulfone, Resins having a melting point or glass transition temperature of 180 ° C. or higher such as ether sulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyetheramide, and polyester; polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, poly Water-soluble polymers such as acrylamide and polymethacrylic acid; and the like.

  Specific examples of the aromatic polyamide include poly (paraphenylene terephthalamide), poly (metaphenylene isophthalamide), poly (parabenzamide), poly (metabenzamide), and poly (4,4 ′). -Benzanilide terephthalamide), poly (paraphenylene-4,4'-biphenylenedicarboxylic acid amide), poly (metaphenylene-4,4'-biphenylenedicarboxylic acid amide), poly (paraphenylene-2,6-naphthalenedicarboxylic acid) Acid amide), poly (metaphenylene-2,6-naphthalenedicarboxylic amide), poly (2-chloroparaphenyleneterephthalamide), paraphenyleneterephthalamide / 2,6-dichloroparaphenyleneterephthalamide copolymer, metaphenylene Terephthalamide / 2 6-dichloro-para-phenylene terephthalamide copolymer and the like. Of these, poly (paraphenylene terephthalamide) is more preferred.

  Among the above resins, polyolefins, fluorine-containing resins, aromatic polyamides, and water-soluble polymers are more preferable. Among them, a fluorine-containing resin is particularly preferable. When a fluorine-containing resin is used, various performances such as a rate characteristic and a resistance characteristic (liquid resistance) of the non-aqueous electrolyte secondary battery due to acidic deterioration during operation of the non-aqueous electrolyte secondary battery are easily maintained. Since water can be used as the solvent for forming the porous layer, the water-soluble polymer is more preferable from the viewpoint of the process and the environmental load. Cellulose ether and sodium alginate are more preferable, and cellulose ether is particularly preferable.

  Specific examples of the cellulose ether include carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), carboxyethylcellulose, methylcellulose, ethylcellulose, cyanoethylcellulose, and oxyethylcellulose. CMC and HEC which are excellent in chemical stability are more preferable, and CMC is particularly preferable.

  More preferably, the porous layer contains a filler. Therefore, when the porous layer contains a filler, the resin has a function as a binder resin. The filler is not particularly limited, and may be an organic filler or an inorganic filler.

  As the filler made of an organic substance, specifically, for example, a homopolymer or two or more kinds of monomers such as styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate Fluorinated resins such as polytetrafluoroethylene, tetrafluoroethylene-6-fluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer and polyvinylidene fluoride; melamine resin; urea resin; polyethylene; Fillers composed of polypropylene; polyacrylic acid, polymethacrylic acid; and the like.

  As the inorganic filler, specifically, for example, calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, Examples of the filler include inorganic fillers such as boehmite, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, titanium nitride, alumina (aluminum oxide), aluminum nitride, mica, zeolite, and glass. Only one type of filler may be used, or two or more types may be used in combination.

  Of the above fillers, fillers made of inorganic substances are preferable, and silica, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, zeolite, aluminum hydroxide, and fillers made of inorganic oxides such as boehmite are more preferable. At least one filler selected from the group consisting of magnesium oxide, titanium oxide, aluminum hydroxide, boehmite and alumina is more preferred, and alumina is particularly preferred. Alumina has many crystal forms such as α-alumina, β-alumina, γ-alumina, θ-alumina, and any of them can be suitably used. Among them, α-alumina is most preferable because of particularly high thermal stability and chemical stability.

  The shape of the filler varies depending on the method of producing the organic or inorganic material as the raw material, the dispersion conditions of the filler when preparing the coating liquid for forming the porous layer, and the like, and is spherical, oval, short, and gourd. Any shape such as a shape such as a shape or an irregular shape having no specific shape may be used.

  When the porous layer contains a filler, the content of the filler is preferably from 1 to 99% by volume of the porous layer, and more preferably from 5 to 95% by volume. By setting the content of the filler to the above range, voids formed by the contact between the fillers are less likely to be closed by a resin or the like, and sufficient ion permeability can be obtained, and the per unit area can be obtained. The basis weight can be set to an appropriate value.

  In the present invention, usually, a coating liquid for forming a porous layer is prepared by dissolving the resin in a solvent and dispersing the filler.

  The solvent (dispersion medium) is not particularly limited as long as it does not adversely affect the porous film and can uniformly and stably dissolve the resin and uniformly and stably disperse the filler. Specific examples of the solvent (dispersion medium) include water; lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and t-butyl alcohol; acetone, toluene, xylene, hexane, N -Methylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide; As the solvent (dispersion medium), only one type may be used, or two or more types may be used in combination.

  The coating liquid may be formed by any method as long as conditions such as a resin solid content (resin concentration) and a filler amount necessary for obtaining a desired porous layer can be satisfied. Specific examples of the method for forming the coating liquid include a mechanical stirring method, an ultrasonic dispersion method, a high-pressure dispersion method, and a media dispersion method.

  Further, for example, the filler may be dispersed in the solvent (dispersion medium) using a conventionally known disperser such as a three-one motor, a homogenizer, a media type disperser, or a pressure type disperser. Further, a liquid obtained by dissolving or swelling the resin or an emulsion of the resin is supplied into a wet pulverizer at the time of wet pulverization to obtain a filler having a desired average particle diameter, and is applied simultaneously with the wet pulverization of the filler. A liquid can also be prepared. That is, the wet pulverization of the filler and the preparation of the coating liquid may be performed simultaneously in one step.

  In addition, the coating liquid may include additives such as a dispersant and a plasticizer, a surfactant, and a pH adjuster as components other than the resin and the filler, as long as the object of the present invention is not impaired. . The amount of the additive may be in a range that does not impair the purpose of the present invention.

  The method for applying the coating liquid to the separator, that is, the method for forming the porous layer on the surface of the separator that has been subjected to a hydrophilic treatment as necessary is not particularly limited.

  As a method for forming the porous layer, for example, a method in which a coating liquid is applied directly to the surface of a separator and then a solvent (dispersion medium) is removed; ) Is removed to form a porous layer, and then the porous layer is pressed against the separator, and then the support is peeled off; a coating liquid is applied to a suitable support, and then a porous film is applied to the coated surface. To remove the solvent (dispersion medium) after removing the support; and to remove the solvent (dispersion medium) after dipping the separator in a coating liquid and performing dip coating; and the like. Is mentioned.

  The thickness of the porous layer is determined by the thickness of the coating film in the wet state (wet) after coating, the weight ratio between the resin and the fine particles, and the solid content concentration of the coating liquid (the sum of the resin concentration and the fine particle concentration). And the like can be controlled. As the support, for example, a resin film, a metal belt, a drum, or the like can be used.

  The method of applying the coating liquid to the separator or the support is not particularly limited as long as it can achieve the required basis weight and the required coating area. As a method for applying the coating liquid, a conventionally known method can be adopted. As such a method, specifically, for example, gravure coater method, small-diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, dip coater method, knife coater method, air doctor blade coater method, blade Examples include a coater method, a rod coater method, a squeeze coater method, a cast coater method, a bar coater method, a die coater method, a screen printing method, and a spray coating method.

  The method of removing the solvent (dispersion medium) is generally a method by drying. Examples of the drying method include natural drying, blast drying, heating drying, and drying under reduced pressure. Any method may be used as long as the solvent (dispersion medium) can be sufficiently removed. An ordinary drying device can be used for the drying.

  In addition, drying may be performed after replacing the solvent (dispersion medium) contained in the coating liquid with another solvent. As a method of replacing the solvent (dispersion medium) with another solvent and then removing the solvent, for example, the solvent may be dissolved in the solvent (dispersion medium) contained in the coating liquid and not dissolved in the resin contained in the coating liquid. The solvent (hereinafter referred to as solvent X) is used to immerse the separator or the support on which the coating liquid is applied to form the coating film in the solvent X, and the solvent in the coating film on the separator or the support ( After the solvent X is replaced with the solvent X, the solvent X is evaporated. According to this method, the solvent (dispersion medium) can be efficiently removed from the coating liquid.

  When heating is performed to remove the solvent (dispersion medium) or solvent X from the coating liquid of the coating liquid formed on the separator or the support, the pores of the porous film shrink and the air permeability increases. In order to avoid a decrease in the air permeability, it is desirable to carry out at a temperature at which the air permeability of the separator does not decrease, specifically 10 to 120 ° C, more preferably 20 to 80 ° C.

  The thickness of the porous layer formed by the above-described method is preferably 0.5 to 15 μm, more preferably 2 to 10 μm.

  When the thickness of the porous layer is less than 0.5 μm, when the laminated separator is used for a non-aqueous electrolyte secondary battery, it is possible to sufficiently prevent an internal short circuit due to breakage of the non-aqueous electrolyte secondary battery. Can not. Further, the amount of the electrolyte retained in the porous layer is reduced.

  On the other hand, if the thickness of the porous layer exceeds 15 μm, when the laminated separator is used for a non-aqueous electrolyte secondary battery, the permeation resistance of lithium ions in the entire region of the separator increases. The positive electrode of the electrolyte secondary battery deteriorates, and the rate characteristics and cycle characteristics deteriorate. Further, since the distance between the positive electrode and the negative electrode increases, the size of the nonaqueous electrolyte secondary battery increases.

The basis weight per unit area of the porous layer may be appropriately determined in consideration of the strength, the film thickness, the weight, and the handleability of the laminated separator. In the case of using a laminated separator in a non-aqueous electrolyte secondary battery, it basis weight per unit area of the porous layer is generally to be from 1 to 20 g / m ² and preferably, 2 to 10 g / m ² Is more preferred.

  By setting the basis weight per unit area of the porous layer within these numerical ranges, the weight energy density and the volume energy density of the nonaqueous electrolyte secondary battery including the porous layer can be increased. If the basis weight of the porous layer exceeds the above range, the nonaqueous electrolyte secondary battery including the laminated separator becomes heavy.

  The porosity of the porous layer is preferably from 20 to 90% by volume, and more preferably from 30 to 80% by volume, so as to obtain sufficient ion permeability. Further, the pore diameter of the pores of the porous layer is preferably 1 μm or less, more preferably 0.5 μm or less. By setting the pore diameter to these sizes, the nonaqueous electrolyte secondary battery including the laminated separator including the porous layer can obtain sufficient ion permeability.

  The air permeability of the laminated separator is preferably a Gurley value of 30 to 1000 sec / 100 mL, more preferably 50 to 800 sec / 100 mL. When the laminated separator has the above air permeability, sufficient ion permeability can be obtained when the laminated separator is used as a member for a nonaqueous electrolyte secondary battery.

When the air permeability is less than the above range, it means that the laminated structure of the laminated separator is rough because the porosity of the laminated separator is high, and as a result, the strength of the separator is reduced, particularly at high temperatures. May have insufficient shape stability. On the other hand, when the air permeability exceeds the above range , when the laminated separator is used as a member for a non-aqueous electrolyte secondary battery, sufficient ion permeability cannot be obtained, and the non-aqueous electrolyte The battery characteristics of the secondary battery may be degraded.

  In the case of the present embodiment, a non-aqueous electrolyte secondary battery may be assembled in the same manner as in the first embodiment. However, the place where the separator (separator) for the non-aqueous electrolyte secondary battery in Embodiment 1 is replaced with the laminated separator for non-aqueous electrolyte secondary battery according to the present embodiment. Then, when assembling the wound type non-aqueous electrolyte secondary battery, the laminated separator for non-aqueous electrolyte secondary battery and the electrode are wound around the pin such that the surface of the porous film comes into contact with the pin. As described above, when a sphere having a diameter of 14.3 mm and a weight of 11.9 g is freely dropped, the sphere at which the minimum height of the sphere at which tearing occurs is 50 cm or more is applied when the sphere contacts another member. And the orientation balance between MD and TD is small enough to reduce the frictional force. Thereby, the slipperiness of the separator with respect to the pin can be improved, and problems in the step of pulling out the pin can be reduced.

<Embodiment 3>
In the second embodiment, the porous film constituting the laminated separator for a non-aqueous electrolyte secondary battery has a diameter of 14.3 mm and a weight of 11.9 g. The minimum height was 50 cm or more.

  However, the present invention is not limited to this. The laminated separator for a non-aqueous electrolyte secondary battery including a porous film and a porous layer, not a porous film, has a diameter of 14.3 mm and a weight of 11.9 g. The minimum height of the sphere at which tearing occurs when the sphere is dropped freely may be 50 cm or more. In other words, regarding the porous film, even if the minimum height of the sphere at which a sphere having a diameter of 14.3 mm and a weight of 11.9 g is torn when dropped freely is not 50 cm or more, the non-aqueous electrolyte secondary battery can be used. Regarding the laminated separator itself, the minimum height of the sphere at which tearing occurs when a sphere having a diameter of 14.3 mm and a weight of 11.9 g is freely dropped may be 50 cm or more.

  Also in the present embodiment, the ratio of the skin layer and the orientation balance of MD and TD in the laminated separator for a non-aqueous electrolyte secondary battery itself are improved in the cutting workability and slipperiness with respect to a pin of the laminated separator for a non-aqueous electrolyte secondary battery. It becomes a suitable state, and it is possible to improve the cutting workability and the slipperiness with respect to the pin of the laminated separator for a non-aqueous electrolyte secondary battery.

  Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

<Methods for measuring various physical properties>
Various physical properties of the porous film (separator for a non-aqueous electrolyte secondary battery) or the laminated separator for a non-aqueous electrolyte secondary battery according to the following Examples and Comparative Examples were measured by the following methods.

(1) Film thickness The film thickness D (μm) of the porous film was measured according to JIS standard (K7130-1992).

(2) Porosity The porous film was cut into a square having a side length of 10 cm, and the weight W (g) was measured. Then, using the film thickness D (μm) and the weight W (g),
Porosity (volume%) = (1- (W / specific gravity) / (10 × 10 × D / 10000)) × 100
The porosity (volume%) of the porous film was calculated according to the formula:

(3) Falling Ball Test Evaluation FIG. 1 is a diagram showing a jig used in the falling ball test evaluation. FIG. 1A is a top view of a frame 10 on which a measurement sample (a porous film or a laminated separator for a non-aqueous electrolyte secondary battery) 1 is placed. As shown, the frame 10 has a hole 11 of 47 mm × 35 mm, and has a rectangular shape of 85 mm × 65 mm. The measurement sample 1 cut into a size of 85 mm × 65 mm is placed on the frame 10. At this time, the MD of the measurement sample 1 is set to be parallel to the long side of the hole 11. Next, as shown in FIG. 1B, a SUS plate 12 having the same shape as the frame 10 is placed on the measurement sample, and the frame 10 and the SUS plate 12 are placed near the center of each side. Secure with a clamp (non-twist clamp) so that it does not slip. FIG. 1C is a side view of a state where the measurement sample 1 is fixed to a jig. As shown in FIG. 1C, the measurement sample 1 is held between the frame 10 and the SUS plate 12.

  With the measurement sample fixed to the jig as shown in FIG. 1 (c), a sphere having a diameter of 14.3 mm and a weight of 11.9 g is freely dropped from above the hole to break (break) the measurement sample. Perform a falling ball test several times to confirm the presence or absence of Each time one drop test is completed, a new measurement sample is replaced.

During the first falling ball test, the height h ₁ of the sphere to fall freely from the measurement sample is set in advance. For example, to determine the measurement sample is destroyed likely height by preliminary tests, may be the height and h _1. Then, first of falling ball test results, if the fracture in the measurement sample was confirmed, the sphere in the second falling ball test height h ₂ and (h ₁ -5 cm), breaking the measurement sample is not confirmed case, the sphere in the second falling ball test height _{h 2} and _(h 1 + 5cm). In this way, the falling ball test is repeated while changing the height of the ball. That is, as a result of the k-th ball drop test (k is an integer of 1 or more), when destruction is confirmed in the measurement sample, the height h _{k + 1} of the ball in the (k + 1) -th ball drop test is set to (h _k −5 cm). If no destruction is confirmed in the measurement sample, the height h _{k + 1} of the sphere in the (k + 1) -th ball drop test is set to (h _k +5 cm).

  Then, for each of the examples and comparative examples, the ball drop test was repeated until the number of times of the ball drop test where destruction was confirmed and the number of times of the ball drop test where destruction was not confirmed became 5 or more, and the destruction was confirmed. The lowest ball height (minimum height) in the performed falling ball test was specified.

(4) Evaluation of cutting workability FIG. 2 is a diagram showing a method of evaluating cutting workability. As shown in FIG. 2A, the length of the measurement sample (separator for non-aqueous electrolyte secondary battery (porous film) or laminated separator for non-aqueous electrolyte secondary battery) 1 cut to MD 10 cm and TD 5 cm. One side was fixed with a tape 14. Then, as shown in FIG. 2B, the cutter knife was cut by 3 cm parallel to the TD with the cutter knife standing at an angle of 80 ° with respect to the horizontal direction. At this time, the cutter knife was moved at a speed of about 8 cm / s. Thereafter, the cutting state was confirmed. Specifically, those in which a tear in an unintended direction (MD) was confirmed at the cut portion were evaluated as x, and those in which no tear was confirmed were evaluated as ○.

  In addition, the cutter knife used the part number A300 made by NT cutter, and the cutter base used the part number -44N made by KOKUYO. The blade was replaced for each test, and a part number BA-160 made by NT Cutter was used as a replacement blade.

(5) Pin pull-out test The separator (separator for a non-aqueous electrolyte secondary battery or laminated separator for a non-aqueous electrolyte secondary battery) according to each example and each comparative example was cut into a strip having a size of TD62 mm × MD30 cm and cut into a MD. With a 300 g weight attached to one end, the other end was wound five times around a stainless steel ruler (Shinwa Corporation product number 13131). At this time, winding was performed so that the TD of the separator and the longitudinal direction of the stainless steel ruler were parallel. Thereafter, the stainless steel ruler was pulled out at a speed of about 8 cm / s, and the sensitivity of detachability (extraction sensitivity) was evaluated. Specifically, the case where the sample was smoothly pulled out without any resistance was evaluated as 場合, the case where slight resistance was felt as △, and the case where there was resistance and there was a sense of difficulty in pulling out was evaluated as x. The stainless steel ruler has a bent knob formed at one end in the longitudinal direction, and is pulled out to the side where the bent knob is formed.

  Further, before and after the stainless steel ruler was pulled out, the width of the TD of the separator in five wound portions was measured with a vernier caliper, and the change (mm) was calculated. The amount of change indicates the amount of elongation in the pulling direction when the separator is spirally deformed due to the frictional force between the stainless steel ruler and the separator moving the beginning of winding of the separator in the pulling direction of the stainless steel ruler.

(6) Pin Removal Resistance FIG. 3 is a diagram showing a sled member for measuring pin removal resistance indicating the magnitude of frictional force between the separator surface and another member. FIG. 3A is a bottom view of the sled member, and FIG. 3B is a side view of the sled member. As shown in FIG. 3, the sled member 15 has two projecting ridges having a curvature of 3 mm on the lower surface thereof. The two ridges are arranged at a distance of 28 mm so as to be parallel to each other.

  The separator (separator (porous film) for non-aqueous electrolyte secondary battery or laminated separator for non-aqueous electrolyte secondary battery) according to each example and each comparative example was cut into TD6 cm and MD5 cm to prepare a measurement sample. . Then, the measurement sample is affixed to the sled member on a tape such that the TD of the measurement sample matches the direction of the ridge. At this time, the measurement sample is positioned below the two ridges. In addition, about the measurement sample of the laminated separator for non-aqueous electrolyte secondary batteries, it arrange | positioned so that a porous layer might face the sled member 15. FIG.

  Next, as shown in FIG. 4, the sled member 15 on which the measurement sample 1 is stuck on the lower surface is converted to a plate processed with a fluororesin (here, a plate 16 processed with Silverstone (registered trademark)). Put on. A weight 17 is placed on the sled member 15, and the total weight of the weight 17 and the sled member 15 is 1800 g. As shown in FIG. 4, the measurement sample 1 is disposed between the sled member 15 and the plate 16 subjected to the silverstone processing.

  The silverstone processing was performed on a plate of high-speed tool steel SKH51 by Hakusui Corporation. The thickness of the silverstone processing is 20 to 30 μm, and the surface roughness Ra (measured by handy surf) is 0.8 μm.

Then, the sled member 15 was pulled at a speed of 20 mm / min by an autograph (product number: AG-I, Shimadzu Corporation), and the tension was measured. The tension indicates a frictional force between the silverstone-processed plate 16 and the measurement sample 1. From the obtained results, using the tension F (N) at a point advanced 10 mm from the starting point,
Pin removal resistance = F x 1000 / 9.80665 / 1800
According to the formula, the pin dropout resistance was calculated.

  Supercast PE Throw No. 2 (manufactured by SUNLINE) was used as the thread to pull the sled.

<Examples and Comparative Examples of Nonaqueous Electrolyte Secondary Battery Separator>
In the following manner, separators for non-aqueous electrolyte secondary batteries as porous films according to Examples 1 to 4 and Comparative Examples 1 to 3 were produced.

(Example 1)
78% by weight of ultra high molecular weight polyethylene powder (GUR2024, manufactured by Ticona), 32% by weight of polyethylene wax having a weight average molecular weight of 1,000 (FNP-0115, manufactured by Nippon Seiro Co., Ltd.), and the total of the ultra high molecular weight polyethylene and polyethylene wax As 100 parts by weight, 0.4% by weight of an antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals), 0.1% by weight of an antioxidant (P168, manufactured by Ciba Specialty Chemicals), sodium stearate 1. 3% by weight, and further, calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) having an average pore size of 0.1 μm was added so as to be 38% by volume with respect to the total volume. The mixture was melted and kneaded with a kneader to obtain a polyolefin resin composition. This polyolefin resin composition was subjected to first rolling at R1, R2 and second rolling at R2, R3 using three rolling rolls R1, R2, R3 having a surface temperature of 150 ° C., and changing the speed ratio. The sheet was cooled stepwise while being pulled by a take-up roll (draw ratio (take-up roll speed / rolling roll speed): 1.4 times) to form a sheet having a thickness of about 64 μm. This sheet was immersed in an aqueous hydrochloric acid solution (4 mol / L hydrochloric acid, 0.5% by weight of a nonionic surfactant) to remove calcium carbonate, and then from a porous film stretched 6.2 times at 100 ° C. A separator for a non-aqueous electrolyte secondary battery according to Example 1 was obtained.

(Example 2)
71.5% by weight of ultra-high molecular weight polyethylene powder (GUR4032, manufactured by Ticona), 28.5% by weight of polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiro Co., Ltd.), this ultra-high molecular weight polyethylene and polyethylene Antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals) 0.4% by weight, antioxidant (P168, Ciba Specialty Chemicals) 0.1% by weight, stearin 1.3% by weight of sodium acid was added, and calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) having an average pore diameter of 0.1 μm was further added so as to be 37% by volume based on the total volume, and these were mixed as they were with a Henschel mixer. Thereafter, the mixture was melt-kneaded with a twin-screw kneader to obtain a polyolefin resin composition. This polyolefin resin composition was subjected to first rolling at R1, R2 and second rolling at R2, R3 using three rolling rolls R1, R2, R3 having a surface temperature of 150 ° C., and changing the speed ratio. The sheet was cooled in a stepwise manner while being pulled with a roll (draw ratio (winding roll speed / rolling roll speed) 1.4 times) to form a sheet having a film thickness of about 70 μm. This sheet was immersed in an aqueous hydrochloric acid solution (4 mol / L hydrochloric acid, 0.5% by weight of a nonionic surfactant) to remove calcium carbonate, and then from a porous film stretched 7.0 times at 100 ° C. A non-aqueous electrolyte secondary battery separator of Example 2 was obtained.

(Example 3)
70% by weight of ultra high molecular weight polyethylene powder (GUR4032, manufactured by Ticona), 30% by weight of polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiro Co., Ltd.), and the total of the ultra high molecular weight polyethylene and polyethylene wax As 100 parts by weight, 0.4% by weight of an antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals), 0.1% by weight of an antioxidant (P168, manufactured by Ciba Specialty Chemicals), sodium stearate 1. 3% by weight, and further, calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) having an average pore size of 0.1 μm was added so as to be 36% by volume with respect to the total volume. The mixture was melted and kneaded with a kneader to obtain a polyolefin resin composition. The polyolefin resin composition is rolled with a pair of rolls having a surface temperature of 150 ° C. and cooled stepwise while being pulled by rolls having different speed ratios (draw ratio (winding roll speed / rolling roll speed) 1.4 times). ), To produce a single-layer sheet having a thickness of about 41 μm. Next, similarly, a single-layer sheet having a thickness of about 44 μm was prepared. The obtained single-layer sheets are pressure-bonded with a pair of rolls having a surface temperature of 150 ° C., and gradually cooled while being pulled by rolls having different speed ratios (draw ratio (winding roll speed / rolling roll speed)). 1.4 times), and a laminated sheet having a thickness of about 67 μm was produced. This sheet was immersed in an aqueous hydrochloric acid solution (4 mol / L hydrochloric acid, 0.5% by weight of a nonionic surfactant) to remove calcium carbonate, and subsequently from a porous film stretched 6.2 times at 105 ° C. A non-aqueous electrolyte secondary battery separator of Example 3 was obtained.

(Example 4)
71.5% by weight of ultra-high molecular weight polyethylene powder (GUR4032, manufactured by Ticona), 28.5% by weight of polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiro Co., Ltd.), this ultra-high molecular weight polyethylene and polyethylene Antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals) 0.4% by weight, antioxidant (P168, Ciba Specialty Chemicals) 0.1% by weight, stearin 1.3% by weight of sodium acid was added, and calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) having an average pore diameter of 0.1 μm was further added so as to be 37% by volume based on the total volume, and these were mixed as they were with a Henschel mixer. Thereafter, the mixture was melt-kneaded with a twin-screw kneader to obtain a polyolefin resin composition. This polyolefin resin composition was subjected to first rolling at R1, R2 and second rolling at R2, R3 using three rolling rolls R1, R2, R3 having a surface temperature of 150 ° C., and changing the speed ratio. The sheet was cooled in a stepwise manner while being pulled by the rolls (draw ratio (winding roll speed / rolling roll speed) 1.4 times) to form a sheet having a thickness of about 100 μm. This sheet was immersed in an aqueous hydrochloric acid solution (hydrochloric acid 4 mol / L, nonionic surfactant 0.5% by weight) to remove calcium carbonate, and then from a porous film stretched 5.8 times at 105 ° C. A separator for a non-aqueous electrolyte secondary battery according to Example 4 was obtained.

(Comparative Example 1)
70% by weight of ultra high molecular weight polyethylene powder (GUR4032, manufactured by Ticona), 30% by weight of polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiro Co., Ltd.), and the total of the ultra high molecular weight polyethylene and polyethylene wax As 100 parts by weight, 0.4% by weight of an antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals), 0.1% by weight of an antioxidant (P168, manufactured by Ciba Specialty Chemicals), sodium stearate 1. 3% by weight, and further, calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) having an average pore size of 0.1 μm was added so as to be 36% by volume with respect to the total volume. The mixture was melted and kneaded with a kneader to obtain a polyolefin resin composition. The polyolefin resin composition is rolled with a pair of rolls having a surface temperature of 150 ° C. and cooled stepwise while being pulled by rolls having different speed ratios (draw ratio (winding roll speed / rolling roll speed) 1.4 times). ), To produce a single layer sheet having a thickness of about 29 μm. Next, a single-layer sheet having a thickness of about 34 μm was similarly prepared. The obtained single-layer sheets are pressure-bonded with a pair of rolls having a surface temperature of 150 ° C., and gradually cooled while being pulled by rolls having different speed ratios (draw ratio (winding roll speed / rolling roll speed)). (1.4 times) and a laminated sheet having a thickness of about 51 μm was produced. This sheet was immersed in an aqueous hydrochloric acid solution (4 mol / L hydrochloric acid, 0.5% by weight of a nonionic surfactant) to remove calcium carbonate, and subsequently from a porous film stretched 6.2 times at 105 ° C. Thus, a non-aqueous electrolyte secondary battery separator of Comparative Example 1 was obtained.

(Comparative Example 2)
A commercially available polyolefin porous film (polyolefin separator) was used as the separator for a non-aqueous electrolyte secondary battery of Comparative Example 2.

  Table 1 shows the property evaluation results of the separators (porous films) for non-aqueous electrolyte secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2.

  As shown in Table 1, the separators (porous films) for nonaqueous electrolyte secondary batteries of Examples 1 to 4 had a thickness of 20 µm or less and a porosity of 20 to 55%. In Examples 1 to 4, it was confirmed that the minimum height at which destruction occurred in the ball drop test was 50 cm or more. In Examples 1, 2, and 4, the porous film was formed in a single layer, and the film thickness at the time of rolling was large, so it is considered that the proportion of the skin layer was smaller than in the comparative example. In addition, by rolling with a thick film and rolling twice with three rolling rolls, the orientation of MD does not become large as compared with TD, and the orientation balance of MD and TD is excellent. Therefore, it is considered that the minimum height is 50 cm or more. In Example 3, the porous film was composed of two single-layer sheets. However, since the thickness of each single-layer sheet was large, the proportion of the skin layer was smaller than that of the comparative example, and the orientation balance was small. It is considered that the minimum height is 50 cm or more.

  In Examples 1 to 4 in which the minimum height at which destruction occurs in the ball drop test is 50 cm or more, the cutting workability and the dropout sensitivity are good (○), and the change in the width of the stainless steel ruler before and after drawing is 0. It was confirmed that it was as small as 0.04 or less. This is because, as described above, the ratio of the skin layer is smaller and the orientation balance between MD and TD is in an appropriate range as compared with Comparative Examples 1 to 3 in which the minimum height at which destruction in the ball drop test occurs is less than 50 cm. It is thought that it is.

  Further, it was confirmed that the pin pullout resistance was 0.1 or less in Examples 1 to 4, whereas the pin pullout resistance exceeded 0.1 in Comparative Examples 1 to 3. It can be seen that the value of the pin pull-out resistance correlates with the result of the pin pull-out test, and indicates the ease of pulling out the pin when assembling the wound nonaqueous electrolyte secondary battery.

  As described above, it was confirmed that by setting the minimum height at which destruction occurs in the ball drop test to 50 cm or more, excellent cutting workability was exhibited. Also, it was confirmed that the sliding property with respect to the pin when assembling the wound type nonaqueous electrolyte secondary battery was excellent.

<Examples and Comparative Examples of Laminated Separator for Nonaqueous Electrolyte Secondary Battery>
Next, laminated separators for nonaqueous electrolyte secondary batteries according to Examples 5 to 7 and Comparative Example 3 were produced as follows.

(Adjustment of coating liquid)
The production of poly (paraphenylene terephthalamide) was carried out using a 3-liter separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a powder addition port. The flask was sufficiently dried, 2200 g of N-methyl-2-pyrrolidone (NMP) was charged, 151.07 g of calcium chloride powder vacuum-dried at 200 ° C for 2 hours was added, and the temperature was raised to 100 ° C to completely dissolve. . After returning to room temperature, 68.23 g of paraphenylenediamine was added and completely dissolved. While maintaining this solution at 20 ° C. ± 2 ° C., 124.97 g of terephthalic acid dichloride was added in about 10 minutes in 10 portions. Thereafter, with stirring, the solution was aged for 1 hour while maintaining the solution at 20 ° C. ± 2 ° C. The mixture was filtered through a 1500 mesh stainless steel wire mesh. The resulting solution had a para-aramid concentration of 6%. 100 g of this para-aramid solution was weighed into a flask, and 300 g of NMP was added thereto to prepare a solution having a para-aramid concentration of 1.5% by weight, followed by stirring for 60 minutes. 6 g of alumina C (manufactured by Nippon Aerosil Co., Ltd.) and 6 g of advanced alumina AA-03 (manufactured by Sumitomo Chemical Co., Ltd.) were mixed with the above solution having a para-aramid concentration of 1.5% by weight, and the mixture was stirred for 240 minutes. The resulting solution was filtered through a 1000-mesh wire gauze, and then 0.73 g of calcium oxide was added thereto, and the mixture was stirred for 240 minutes to neutralize, and defoamed under reduced pressure to prepare a coating solution on the slurry.

(Example 5)
The porous film of Example 2 was fixed on a PET film having a thickness of 100 μm, and a slurry coating solution was applied on one surface of the porous film by a bar coater. While the porous film and the coating film on the PET film are integrated, the porous film and the coating film are immersed in water as a poor solvent to deposit a porous layer of para-aramid (heat-resistant layer), and then the solvent is dried. By removing, the laminated separator for non-aqueous electrolyte secondary batteries of Example 5 in which the porous layer was laminated on one surface of the porous film was obtained.

(Example 6)
The porous film of Example 3 was fixed on a PET film having a thickness of 100 μm, and a slurry coating solution was applied on one surface of the porous film by a bar coater. While the porous film and the coating film on the PET film are integrated, the porous film and the coating film are immersed in water as a poor solvent to deposit a porous layer of para-aramid (heat-resistant layer), and then the solvent is dried. By removing, the laminated separator for non-aqueous electrolyte secondary batteries of Example 6 in which the porous layer was laminated on one side of the porous film was obtained.

(Example 7)
The porous film of Example 4 was fixed on a PET film having a thickness of 100 μm, and a slurry coating solution was applied on one surface of the porous film by a bar coater. While the porous film and the coating film on the PET film are integrated, the porous film and the coating film are immersed in water as a poor solvent to deposit a porous layer of para-aramid (heat-resistant layer), and then the solvent is dried. By removing, the laminated separator for non-aqueous electrolyte secondary batteries of Example 7 in which the porous layer was laminated on one surface of the porous film was obtained.

(Comparative Example 3)
The porous film of Comparative Example 1 was fixed on a PET film having a thickness of 100 μm, and a slurry coating solution was applied on one side of the porous film by a bar coater. While the porous film and the coating film on the PET film are integrated, the porous film and the coating film are immersed in water as a poor solvent to deposit a porous layer of para-aramid (heat-resistant layer), and then the solvent is dried. By removing, the laminated separator for non-aqueous electrolyte secondary batteries of Comparative Example 4 in which the porous layer was laminated on one surface of the porous film was obtained.

  Table 2 shows the characteristic evaluation results of the laminated separators for non-aqueous electrolyte secondary batteries of Examples 5 to 7 and Comparative Example 3. The pin detachment resistance of the laminated separator for a nonaqueous electrolyte secondary battery of Examples 5 to 7 and Comparative Example 3 was determined by the pin detachment of the separator for a nonaqueous electrolyte secondary battery made of a porous film included in each separator. The values are substantially the same as the resistances (that is, the pin disconnection resistances of Examples 2 to 4 and Comparative Example 1 respectively), and therefore are not described in Table 2.

  As shown in Table 2, in the laminated separators for nonaqueous electrolyte secondary batteries of Examples 5 to 7, the minimum height at which destruction occurs in a ball drop test is 50 cm or more, and excellent cutting workability is exhibited. Was confirmed. Also, it was confirmed that the sliding property with respect to the pin when assembling the wound type nonaqueous electrolyte secondary battery was excellent.

Claims (5)

A porous film, which is a stretched film containing 90% by volume or more of polyethylene ,
The film thickness is 20 μm or less,
The porosity is 20-55%,
Between the frame and the plate having a rectangular hole of 47 mm × 35 mm, the porous film is arranged so that the long side of the hole is parallel to the MD, and the porous film is placed between the frame and the plate. And a ball test with a diameter of 14.3 mm and a weight of 11.9 g dropped freely onto the porous film from above the center of the hole to confirm the presence or absence of tearing of the porous film. While changing the height of the ball, the number of times of the falling ball test in which tearing was confirmed and the number of times of the falling ball test in which no tearing was confirmed were repeated until at least 5 times. A separator for a non-aqueous electrolyte secondary battery, wherein the height of the lowest sphere is 50 cm or more and 150 cm or less ,
A laminated separator for a non-aqueous electrolyte secondary battery, comprising: a porous layer containing a resin . A non-aqueous electrolyte secondary battery separator as a porous film, which is a stretched film containing 90% by volume or more of polyethylene, has a thickness of 20 μm or less, and has a porosity of 20 to 55%;
A porous layer containing a resin laminated on the non-aqueous electrolyte secondary battery separator, and a non-aqueous electrolyte secondary battery laminate separator comprising:
The laminated separator for a non-aqueous electrolyte secondary battery is disposed between a frame and a plate having a rectangular hole of 47 mm × 35 mm such that the long side of the hole is parallel to the MD, A laminated separator for a liquid secondary battery is sandwiched between the frame and the plate, and a sphere having a diameter of 14.3 mm and a weight of 11.9 g is placed on the laminated separator for a non-aqueous electrolyte secondary battery from above the center of the hole. While changing the height of the ball in the ball drop test to confirm the presence or absence of tearing of the laminated separator for non-aqueous electrolyte secondary battery when dropped freely, the number of ball drop tests where tearing was confirmed, and Non-water, characterized in that the minimum ball height in the falling ball test in which tearing was confirmed is 50 cm or more and 150 cm or less, in which the number of times of the falling ball test that was not confirmed was repeated five times or more. Laminated cell for electrolyte secondary battery Regulator. The laminated separator for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the resin is an aromatic polyamide. A non-aqueous electrolyte secondary, comprising: a positive electrode, a laminated separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, and a negative electrode arranged in this order. Battery components. Non-aqueous electrolyte secondary battery, comprising the nonaqueous electrolyte laminated separator for a secondary battery according to any one of claims 1 to 3.

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