JP2012094493A - Slurry and method of manufacturing separator for nonaqueous electrolyte secondary battery using that slurry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide slurry exhibiting excellent storage stability which can form a separator for a nonaqueous electrolyte secondary battery, having excellent film characteristics such as shut-down performance or ion permeability, stably with good reproducibility when used in manufacture of the separator for a nonaqueous electrolyte secondary battery.SOLUTION: In the slurry containing a water soluble polymer, fine particles and a medium, and used for forming a porous film in the separator for a nonaqueous electrolyte secondary battery where a water soluble polymer porous film containing a water soluble polymer and fine particles, and a polyolefin porous film are laminated, the medium consists of a mixed solvent of water and a saturated aliphatic alcohol of 1-4C, and the concentration of the saturated aliphatic alcohol is 10-35 wt.% for the total weight of the mixed solvent.

Description

  The present invention relates to a slurry that can be used for manufacturing a separator for a non-aqueous electrolyte secondary battery and a method for manufacturing a separator for a non-aqueous electrolyte secondary battery using the slurry.

  Non-aqueous electrolyte secondary batteries, particularly lithium secondary batteries, are widely used as batteries for personal computers, mobile phones, portable information terminals and the like because of their high energy density.

Non-aqueous electrolyte secondary batteries represented by these lithium secondary batteries are high in energy density, and when an internal short circuit or external short circuit occurs due to an accident such as damage to the battery or equipment that uses the battery. Generates intense heat when a large current flows. Therefore, non-aqueous electrolyte secondary batteries are required to prevent heat generation beyond a certain level and ensure high safety.
In the case of abnormal heat generation due to an accident or the like, a general method is to provide a shutdown function to prevent further heat generation by blocking the passage of ions between the positive and negative electrodes by a separator. As a method for providing the separator with a shutdown function, a method in which a porous film made of a material that melts when abnormal heat is generated is used as the separator. That is, in the battery using the separator, the porous film melts and becomes non-porous when abnormal heat is generated, and the passage of ions can be blocked and further heat generation can be suppressed.

  As a separator having such a shutdown function, for example, a polyolefin porous film is used. A separator made of a polyolefin porous membrane suppresses further heat generation by blocking (shutdown) the passage of ions by melting and making non-porous at about 80 to 180 ° C. during abnormal heat generation of the battery. However, when the heat generation is intense, a separator made of a polyolefin porous membrane may cause a short circuit due to direct contact between the positive electrode and the negative electrode due to shrinkage or film breakage. As described above, a separator made of a polyolefin porous film has insufficient shape stability and sometimes cannot suppress abnormal heat generation due to a short circuit.

On the other hand, a method of imparting shape stability at high temperature to a separator by laminating a porous film made of a heat-resistant material on a polyolefin porous film has been studied. As such a highly heat-resistant separator, for example, a separator formed by immersing a regenerated cellulose membrane in an organic solvent to make it porous and then laminating it with a polyolefin porous membrane has been proposed (for example, see Patent Document 1). .
Such a separator has good shape stability at high temperatures, and by using the separator, a highly safe non-aqueous secondary battery can be provided. However, in such a separator, a heat-resistant porous membrane is provided on the polyolefin porous membrane, but the ion-permeable property of the heat-resistant porous membrane is often insufficient, and as a result, obtained from the separator. There was a problem that the load characteristics of the non-aqueous secondary battery became insufficient.

Therefore, the present applicant has laminated a porous film of a water-soluble polymer containing fine particles and a polyolefin porous film as a separator for a non-aqueous electrolyte secondary battery excellent in shape stability at high temperature in addition to shutdown property. We have proposed a separator for a non-aqueous electrolyte secondary battery, and reported that the use of this separator can provide a non-aqueous electrolyte secondary battery with excellent load characteristics, cycle performance, and safety. (See Patent Document 2).
The separator is formed by applying a slurry containing a water-soluble polymer, fine particles and water as a medium on the polyolefin porous film, then removing the water as a medium, and forming a porous film containing the water-soluble polymer and fine particles into a polyolefin porous film. It can be obtained by stacking on a film.
However, since the polyolefin porous membrane as the base material is not so hydrophilic, the application property of the slurry using water as a medium is not good, and as a result, membrane defects are likely to occur, and the required area is reproducibly uniform. It was difficult to form a porous film containing a water-soluble polymer and fine particles. In addition, the slurry has a drawback that fine particles tend to aggregate and cannot be stored for a long time.
On the other hand, when an amphiphilic medium such as a lower alcohol is used as the slurry medium, the coating property to the polyolefin porous film is improved, and a highly uniform film can be formed. However, the obtained separator has insufficient membrane properties such as shutdown property and ion permeability (air permeability). Further, the dispersibility of the fine particles was poor.

Japanese Patent Laid-Open No. 10-3898 JP 2004-227972 A

  Under such circumstances, the object of the present invention is excellent in storage stability, and excellent in membrane characteristics such as shutdown property and ion permeability (air permeability) when used for manufacturing a separator for a non-aqueous electrolyte secondary battery. To provide a slurry capable of stably forming a separator for a non-aqueous electrolyte secondary battery with high reproducibility, and to provide a method for producing a separator for a non-aqueous electrolyte secondary battery using the slurry. .

  As a result of intensive studies to solve the above problems, the present inventor has found that the following inventions meet the above object, and have reached the present invention.

That is, the present invention relates to the following inventions.
<1> A water-soluble polymer, fine particles, and fine particles, which are used for forming the porous film in a separator for a non-aqueous electrolyte secondary battery in which a porous film containing a water-soluble polymer and fine particles and a polyolefin porous film are laminated. A slurry containing a medium,
The medium comprises a mixed solvent of water and a saturated aliphatic alcohol having 1 to 4 carbon atoms,
A slurry in which the concentration of the saturated aliphatic alcohol is 10% by weight or more and 35% by weight or less based on the total weight of the mixed solvent.
<2> The slurry according to <1>, wherein the saturated aliphatic alcohol is methanol or ethanol.
<3> The slurry according to <1> or <2>, wherein the fine particles are made of alumina.
<4> The slurry according to any one of <1> to <3>, wherein the concentration of the water-soluble polymer with respect to the medium is 0.40 wt% or more and 1.50 wt% or less.
<5> The slurry according to any one of <1> to <4>, wherein the water-soluble polymer is at least one polymer selected from the group consisting of cellulose ether, polyvinyl alcohol, and sodium alginate.
<6> The slurry according to <5>, wherein the cellulose ether is carboxymethyl cellulose.
<7> After applying the slurry according to any one of <1> to <6> on the polyolefin porous film, the medium is removed, and a porous film containing a water-soluble polymer and fine particles is formed on the polyolefin porous film. The manufacturing method of the separator for nonaqueous electrolyte secondary batteries which carries out lamination | stacking formation.
<8> The method for producing a separator for a nonaqueous electrolyte secondary battery according to <7>, wherein the polyolefin in the polyolefin porous membrane is polyethylene.
<9> The method for producing a separator for a nonaqueous electrolyte secondary battery according to <7> or <8>, wherein the polyolefin porous membrane is subjected to a hydrophilic treatment.
<10> A separator for a nonaqueous electrolyte secondary battery produced by the method according to any one of <7> to <9>.

  By using the slurry of this invention, the separator for nonaqueous electrolyte secondary batteries excellent in membrane characteristics, such as ion permeability (air permeability) and shutdown nature, can be manufactured stably.

The present invention will be described in detail below.
The present invention relates to a water-soluble polymer porous membrane containing fine particles (hereinafter sometimes simply referred to as “porous membrane” or “A membrane”) and a polyolefin porous membrane (hereinafter simply referred to as “porous membrane” or “ And a slurry containing a water-soluble polymer, fine particles, and a medium used for forming the porous film in a separator for a non-aqueous electrolyte secondary battery.

When the medium in the slurry of the present invention is described as water (hereinafter sometimes referred to as “solvent (i)”) and a saturated aliphatic alcohol having 1 to 4 carbon atoms (hereinafter referred to as “solvent (ii)”). The concentration of the solvent (ii) is 10% by weight to 35% by weight, preferably 15% by weight to 25% by weight, based on the total weight of the mixed solvent. It is as follows.
One of the characteristics of the slurry of the present invention is that the weight ratio of the solvent (i) and the solvent (ii), which are media, and the mixed solvent is within the above range. As a result, the slurry can maintain dispersibility without agglomeration of fine particles, is excellent in applicability to the base B film, and can stably form the A film with good reproducibility.
Here, even when the concentration of the solvent (ii) in the medium exceeds 35% by weight (including the case where the solvent (ii) is 100% by weight), the coating property to the B film as the substrate is excellent, and at the visual level Although a uniform A film with few film defects is formed, the obtained separator has insufficient film characteristics such as shutdown property and ion permeability (air permeability).
If the weight ratio of the solvent (ii) in the medium is less than 10% by weight, film defects often occur in the A film, and the film characteristics become insufficient.

As water which is a solvent (i), a thing with few impurities is preferable, and a pure water and / or ion-exchange water are suitable.
Specific examples of the saturated aliphatic alcohol having 1 to 4 carbon atoms as the solvent (ii) include methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, and tert-butanol. Among these, methanol and ethanol are particularly preferable from the balance between the dispersibility of the fine particles in the slurry and the coating property. In addition, it is preferable to use what refine | purified these saturated aliphatic alcohol.
The medium may contain a solvent other than the solvent (i) and the solvent (ii), a pH adjuster, and the like as long as the effects of the present invention are not impaired.

The fine particles contained in the slurry may agglomerate in the slurry during storage or the like to produce an aggregate. If the slurry contains large fine particles (including agglomerates), coating defects will decrease, resulting in more film defects in the A film, resulting in insufficient film characteristics such as separator shutdown and ion permeability (breathability). It may become. Therefore, in the present invention, the particle size (D ₉₀ ) of the fine particles (including aggregates) contained in the slurry is preferably 6 μm or less. When the particle diameter (D ₉₀ ) of the fine particles is 6 μm or less, the slurry can be applied to the substrate (B film) with good coatability.
The particle size (D ₉₀ ) of the fine particles can be determined by a laser diffraction particle size distribution measuring device.

As the fine particles used in the present invention, inorganic or organic fine particles generally called fillers can be used. Specifically, styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, methyl acrylate, or a copolymer of two or more kinds; polytetrafluoroethylene, tetrafluoroethylene-6 Fluorine resin such as fluorinated propylene copolymer, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, etc .; melamine resin; urea resin; polyethylene; polypropylene; fine particles made of organic matter such as polymethacrylate. Also, calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide , Fine particles composed of inorganic substances such as alumina, mica, zeolite, glass and the like. These fine particle materials can be used alone or in admixture of two or more.
Among the fine particles, fine particles made of an inorganic material are preferably used from the viewpoint of stability and dispersibility in a mixed solvent containing water in the slurry of the present invention, and alumina is particularly preferable.

  The concentration of fine particles in the slurry of the present invention is 6 to 40% by weight, preferably 9 to 35% by weight. When the fine particle concentration is less than 6% by weight, it is difficult to remove the medium from the slurry. On the other hand, if it exceeds 40% by weight, fine particle aggregation tends to occur, and the coatability of the slurry may be deteriorated.

  Examples of the water-soluble polymer in the slurry of the present invention include polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, polymethacrylic acid, and the like. Cellulose ether, polyvinyl alcohol, sodium alginate are preferable, cellulose Ether is more preferred. Specific examples of the cellulose ether include carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), carboxyethyl cellulose, methyl cellulose, ethyl cellulose, cyanethyl cellulose, oxyethyl cellulose, and the like. preferable.

The concentration of the water-soluble polymer in the slurry is 0.40% by weight or more and 1.50% by weight or less, preferably 0.40% by weight or more and 1.30% by weight, based on the weight of (water-soluble polymer + medium). It is as follows.
If the concentration of the water-soluble polymer is less than 0.40% by weight, the adhesion of the coating film is poor, and the film peels off, so that the A film as a continuous film may not be formed on the B film. If it exceeds 50% by weight, the shutdown performance of the obtained separator may deteriorate. The water-soluble polymer may be used by appropriately selecting the molecular weight or the like so that the viscosity is suitable for coating.

  The slurry of the present invention may contain a surfactant, a pH adjuster, a dispersant, a plasticizer, and the like as long as the object of the present invention is not impaired, in addition to the water-soluble polymer, fine particles, and medium.

The manufacturing method of the slurry of this invention should just be a conventionally well-known method, and can manufacture it by mixing the component (water-soluble polymer, microparticles | fine-particles, and medium) of a slurry.
Mixing conditions such as mixing order and mixing temperature of the constituent components are arbitrary as long as there is no particular problem such as the generation of precipitates, and any two components or three or more components among the constituent components of the slurry are blended in advance, Thereafter, the remaining components may be mixed or all at once. Specifically, the water-soluble polymer is dissolved or swollen in the medium (if there is no problem in application, the liquid in which the water-soluble polymer swells may be used), and further, fine particles are added and mixed until uniform. Can be obtained. In other words, the water-soluble polymer may be finally dissolved in the medium.
The method for mixing the fine particles is not particularly limited, and conventionally known dispersers such as a three-one motor, a homogenizer, a media type disperser, and a pressure disperser can be used.

Next, the manufacturing method of the separator for nonaqueous electrolyte secondary batteries of this invention is demonstrated.
The separator for a non-aqueous electrolyte secondary battery of the present invention is formed by laminating a porous film (A film) containing a water-soluble polymer and fine particles and a polyolefin porous film (B film). After coating on the B film, the medium can be removed, and an A film containing a water-soluble polymer and fine particles can be laminated on the B film.
That is, when the medium is removed from the slurry applied to the B film, the slurry containing the water-soluble polymer and the fine particles becomes a porous film (A film) and is laminated on the B film.
It is assumed that when the medium is removed from the applied slurry, a gap is generated around the fine particles, and a porous film (A film) is generated. In addition, if the fine particle is not contained in the slurry containing a water-soluble polymer, it does not become a porous film (A film).

  In the separator of the present invention, the A film has heat resistance at a high temperature at which shutdown occurs, and imparts a shape stability function to the separator. Further, the B film melts and becomes non-porous in the event of abnormal overheating in the event of a battery accident, thereby providing a shutdown function to the separator. Note that the A film and the B film may be three layers or more as long as they are sequentially stacked. For example, the form etc. with which A film | membrane was formed on both surfaces of B film | membrane are mentioned.

In manufacturing the A film, when the slurry of the present invention containing a water-soluble polymer is applied on the B film, the slurry enters the pores (voids) of the B film, and the water-soluble polymer in the slurry is precipitated. Then, the A film and the B film are bonded by the so-called “anchor effect”. At this time, if the water-soluble polymer in the slurry is precipitated while excessively penetrating into the pores (voids) of the B membrane, the resulting non-aqueous electrolyte secondary battery separator has a shutdown property and permeability (ion permeation). Property) may be impaired.
In the method for producing a separator of the present invention, as a slurry used for forming the A film, a mixed solution containing water as the solvent (i) and the saturated aliphatic alcohol as the solvent (ii) in the above ratio is used as a medium. As a result, the occurrence of “streaks, repellency” and the like when the slurry is applied onto the B film can be suppressed, and the occurrence of film defects in the formed A film can be suppressed. Therefore, the uniformity of the A film is excellent, the shutdown property and the permeability (ion permeability) are excellent, and a separator for a non-aqueous electrolyte secondary battery can be obtained.

The B film as the base material in the separator of the present invention is a polyolefin porous film, and has a structure having pores connected from one surface to the other surface in the inside thereof.
When the separator of the present invention is used in a non-aqueous electrolyte secondary battery, the pores of the B film are filled with the electrolyte. That is, since the B film is always in contact with the electrolytic solution, the B film needs to be durable so as not to dissolve in the electrolytic solution.
Polyolefin has both durability against electrolyte and mechanical strength. Examples of the polyolefin include a high molecular weight homopolymer or copolymer obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and the like. Here, from the viewpoint of further improving the durability against the electrolytic solution, the polyolefin preferably contains a high molecular weight component having a molecular weight of 5 × 10 ⁵ to 15 × 10 ⁶ . High molecular weight polyethylene mainly composed of ethylene is particularly suitable.

  The porosity of the B film is preferably 20 to 80% by volume, more preferably 30 to 70% by volume. If the porosity is less than 20% by volume, the amount of electrolyte retained may be small, and if it exceeds 80% by volume, non-porous formation at a high temperature causing shutdown will be insufficient, that is, when the battery generates heat due to an accident. The current may not be cut off.

  As described above, the B film has a structure having pores connected to the inside thereof, and gas or liquid can pass from one surface to the other surface. The permeability is usually in the range of 50 to 400 seconds / 100 cc in terms of air permeability (Gurley value), and preferably in the range of 50 to 300 seconds / 100 cc.

  Moreover, the thickness of B film | membrane is 4-50 micrometers normally, Preferably it is 5-30 micrometers. If the thickness is less than 4 μm, shutdown may be insufficient. If the thickness exceeds 50 μm, the thickness of the separator for a non-aqueous electrolyte secondary battery including a water-soluble polymer porous membrane is increased, and the electric capacity of the battery May decrease. The pore size of the B film is preferably 3 μm or less, and more preferably 1 μm or less.

The production of the B film is not particularly limited. For example, as described in JP-A-7-29563, a plasticizer is added to a thermoplastic resin to form a film, and then the plasticizer is used with an appropriate solvent. As described in JP-A-7-304110, using a film made of a thermoplastic resin produced by a known method, a structurally weak amorphous part of the film is selectively stretched. And a method of forming micropores. For example, when the B film is formed from a polyolefin resin containing ultrahigh molecular weight polyethylene and a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, it should be produced by the following method from the viewpoint of production cost. Is preferred.
Specifically, (1) 100 parts by weight of ultrahigh molecular weight polyethylene, 5 to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler such as calcium carbonate are kneaded to polyolefin resin. Step (2) of obtaining a composition Step (3) of forming a sheet using the polyolefin resin composition (3) Step of removing inorganic filler from the sheet obtained in step (2) (4) In step (3) A method comprising a step of obtaining a B film by stretching the obtained sheet, or (1) 100 parts by weight of ultrahigh molecular weight polyethylene, 5 to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and inorganic filling Step of kneading 100 to 400 parts by weight of the agent to obtain a polyolefin resin composition (2) Step of molding a sheet using the polyolefin resin composition (3) From sheets obtained in extent (2), by stretching the obtained sheet in the step of removing the inorganic filler (4) Step (3), the method comprising the steps of obtaining a B layer.
In addition, about B film, the commercial item which has the characteristic of the said description can be used.

In the present invention, it is preferable to hydrophilize the B film in advance before applying the slurry onto the B film. The slurry of the present invention can be directly applied to the B film. However, by applying the hydrophilic treatment to the B film, the coating property is further improved and a more uniform porous film (A film) can be obtained. it can. This hydrophilization treatment is particularly effective when the concentration of the solvent (ii) in the medium is low.
Any method may be used for the hydrophilic treatment of the B film, and specific examples thereof include chemical treatment with an acid or alkali, corona treatment, plasma treatment, and the like.
Here, in the corona treatment, in addition to making the B film hydrophilic in a relatively short time, the modification of the polyolefin resin by corona discharge is limited only to the vicinity of the surface of the B film, and the pores of the B film are hydrophobic. There is an advantage that only the vicinity of the surface of the B film can be hydrophilized while maintaining.
Therefore, when slurry is applied, excessive penetration of the slurry containing the water-soluble polymer into the pores (voids) of the B film can be suppressed, and precipitation of the water-soluble polymer avoids impairing the shutdown performance of the B film. it can.

  The method for applying the slurry of the present invention to the B film is not particularly limited as long as it can be uniformly wet-coated, and a conventionally known method can be adopted. For example, a capillary coating method, a spin coating method, a slit die coating method, a spray coating method, a dip coating method, a roll coating method, a screen printing method, a flexographic printing method, a bar coater method, a gravure coater method, a die coater method, etc. Can do. The thickness of the formed A film can be controlled by adjusting the coating amount, the concentration of the water-soluble polymer in the slurry, and the ratio of the fine particles to the water-soluble polymer. As the support, a resin film, a metal belt, a drum, or the like can be used.

The removal of the medium from the slurry applied on the B film is generally performed by drying, but is not limited thereto.
In addition, when a slurry is apply | coated on B film | membrane, it is preferable that the drying temperature of a medium is below the temperature which does not reduce the air permeability of B film | membrane, ie, the temperature which a shutdown produces.

The thickness of the A film formed on the B film from the slurry of the present invention is usually from 0.1 μm to 10 μm, preferably from 2 μm to 6 μm. If the thickness of the A film is too thick, the load characteristics of the battery may be reduced when a non-aqueous electrolyte secondary battery is manufactured. If the film is too thin, the battery will generate heat due to an accident or the like. There is a risk that the separator may contract without being able to resist the heat shrinkage of the polyolefin porous membrane.
When the A film is formed on both surfaces of the B film, the thickness of the A film is the total thickness of both surfaces.

The A film is a porous film, and the pore diameter is preferably 3 μm or less, more preferably 1 μm or less, as the diameter of the sphere when the hole is approximated to a sphere. When the average pore diameter exceeds 3 μm, there is a possibility that problems such as short-circuiting easily occur when the carbon powder, which is the main component of the positive electrode or the negative electrode, or a small piece thereof falls off.
Further, the porosity of the A film is preferably 30 to 90% by volume, more preferably 40 to 85% by volume.

  In the separator of the present invention, the A film and the B film are laminated to constitute the separator, but other than the A film and the B film, for example, an adhesive film, a protective film, and the like do not impair the object of the present invention. It may be contained in the separator of the present invention.

The thickness of the whole separator (A film + B film) of the present invention is usually 5 to 80 μm, preferably 5 to 50 μm, particularly preferably 6 to 35 μm. If the total thickness of the separator is less than 5 μm, the membrane is easily broken, and the thickness of the separator for a non-aqueous electrolyte secondary battery including the water-soluble polymer porous membrane is increased, which may reduce the electric capacity of the battery.
Moreover, the porosity of the whole separator of this invention is 30-85 volume% normally, Preferably it is 35-80 volume%.
Further, the permeability of the separator of the present invention is usually preferably 50 to 2000 seconds / 100 cc, more preferably 50 to 1000 seconds / 100 cc in terms of air permeability (Gurley value). If the air permeability is 2000 seconds / 100 cc or more, the ion permeability of the separator and the load characteristics of the battery may be lowered. On the other hand, if it is less than 50 seconds / 100 cc, the insulating properties of the separator may be impaired.

  In the following, as a preferred use example of the separator obtained by the production method of the present invention, as an example of a non-aqueous electrolyte secondary battery such as a lithium battery, components other than the separator for the non-aqueous electrolyte secondary battery However, the method of using the separator is not limited to these.

As the nonaqueous electrolytic solution, for example, a nonaqueous electrolytic solution in which a lithium salt is dissolved in an organic solvent can be used. Examples of lithium salts include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , One or a mixture of two or more of lower aliphatic carboxylic acid lithium salts, LiAlCl _{4 and the} like can be mentioned. The lithium salt is selected from the group consisting of LiPF ₆ containing fluorine, LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiC (CF ₃ SO ₂ ) ₃ among these. It is preferable to use those containing at least one selected from the above.

  Examples of the non-aqueous electrolyte include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di (methoxycarbonyloxy) Carbonates such as ethane; ethers such as 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran Esters such as methyl formate, methyl acetate and Y-butyrolactone; nitriles such as acetonitrile and butyronitrile; amides such as N, N-dimethylformamide and N, N-dimethylacetamide Carbamates such as 3-methyl-2-oxazolidone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone, or those obtained by introducing a fluorine group into the above-mentioned substances can be used. Two or more of these are mixed and used.

  Among these, those containing carbonates are preferred, and cyclic carbonates and acyclic carbonates, or mixtures of cyclic carbonates and ethers are more preferred. As a mixture of cyclic carbonate and acyclic carbonate, ethylene carbonate and dimethyl have a wide operating temperature range and are hardly decomposable even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material. A mixture comprising carbonate and ethyl methyl carbonate is preferred.

As the positive electrode sheet, a sheet in which a mixture containing a positive electrode active material, a conductive material and a binder is carried on a current collector is usually used. Specifically, as the positive electrode active material, a material containing a material that can be doped / undoped with lithium ions, a carbonaceous material as a conductive material, and a thermoplastic resin as a binder can be used. Examples of the material that can be doped / undoped with lithium ions include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni. Among these, lithium composite oxides having an α-NaFeO ₂ type structure such as lithium nickelate and lithium cobaltate, and lithium composite oxides having a spinel type structure such as lithium manganese spinel are preferable in that the average discharge potential is high. Can be mentioned.

  The lithium composite oxide may contain various metal elements, particularly at least selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Cu, Ag, Mg, Al, Ga, In, and Sn. The metal element is included so that the at least one metal element is 0.1 to 20 mol% with respect to the sum of the number of moles of one metal element and the number of moles of Ni in lithium nickelate. It is preferable to use composite lithium nickelate because the cycle performance in use at a high capacity is improved.

  As the binder, polyvinylidene fluoride, vinylidene fluoride copolymer, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, Examples include ethylene-tetrafluoroethylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic resins such as thermoplastic polyimide, polyethylene, and polypropylene.

  Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, and carbon black. As the conductive material, each may be used alone, for example, artificial graphite and carbon black may be mixed and used.

  As the negative electrode sheet, for example, a material capable of doping and dedoping lithium ions, lithium metal, or a lithium alloy can be used. Materials that can be doped / undoped with lithium ions include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds, and lower potential than the positive electrode. And chalcogen compounds such as oxides and sulfides for doping and dedoping lithium ions. As a carbonaceous material, a carbonaceous material mainly composed of graphite materials such as natural graphite and artificial graphite, because it has a high potential flatness and a low average discharge potential, so that a large energy density can be obtained when combined with a positive electrode. Is preferred.

  As the negative electrode current collector, Cu, Ni, stainless steel, or the like can be used. In particular, in a lithium secondary battery, Cu is preferable because it is difficult to form an alloy with lithium and it can be easily processed into a thin film. The negative electrode current collector may be loaded with a mixture containing a negative electrode active material by pressure molding, or by pasting it into a paste using a solvent or the like, applying it to the current collector, pressing it, and pressing it. Is mentioned.

  The shape of the battery of the present invention is not particularly limited, and may be any of a paper type, a coin type, a cylindrical type, a rectangular shape, and the like.

  When a non-aqueous electrolyte secondary separator is produced using the slurry for a non-aqueous electrolyte secondary battery separator of the present invention, in addition to the shape stability during overheating, excellent shutdown properties and permeability (ion transmission) Can be obtained stably. Furthermore, by using this non-aqueous electrolyte secondary battery separator for a non-aqueous electrolyte secondary battery, not only safety during overheating, but also excellent shutdown performance, and even when the battery generates a lot of heat due to an accident, The separator exhibits a shutdown function, avoids contact between the positive electrode and the negative electrode due to shrinkage of the separator, and becomes a highly safe non-aqueous electrolyte secondary battery.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

In Examples and Comparative Examples, the physical properties of separators were measured by the following methods.
(1) Coating property The coating property of the slurry with respect to the B film was evaluated according to the following criteria.
A: No repelling or film roughness is observed, and the coating can be applied uniformly as a whole.
○: Some repelling is observed, but it can be applied uniformly as a whole.
X: There is repelling and / or film roughening.
(2) Thickness measurement (unit: μm)
The thickness of the separator was measured according to the JIS standard (K7130-1992).
(3) Weight per unit (unit: g / m ² )
A sample of the obtained separator was cut into a 10 cm long square and the weight W (g) was measured. The weight per unit area (g / m ² ) = W / (0.1 × 0.1) was calculated. The basis weight of the A membrane was calculated after subtracting the basis weight of the B membrane from the basis weight of the laminated porous membrane (separator).
(4) Porosity (unit: volume%)
The sample was cut into a 10 cm long square, and weight: W (g) and thickness: D (cm) were measured. The weight of the material in the sample was divided by calculation, the weight of each material: Wi (g) was divided by the true specific gravity, the volume of each material was calculated, and the porosity (volume%) was obtained from the following formula. .
Porosity (volume%)
= 100-[{(W1 / true specific gravity 1) + (W2 / true specific gravity 2) + .. + (Wn / true specific gravity n)} / (10 × 10 × D)] × 100
(5) Corona treatment Using a corona treatment machine (AGI-023) manufactured by Kasuga Electric Co., Ltd., the corona just before the coating of the A film under the condition of an output of 100 W / (m ² / min) for the B film. Processed.

(6) Air permeability (Gurley value) (Unit: sec / 100cc)
The air permeability (Gurley value) of the separator was measured with a digital timer type Gurley type densometer manufactured by Toyo Seiki Seisakusho, based on JIS P8117.
Evaluation of air permeability (Gurley value):
◎: Less than 150 sec / 100cc ○: 150 sec / 100cc or more, less than 200 sec / 100cc ×: 200 sec / 100cc or more

(7) Shutdown ultimate resistance measurement The shutdown temperature was measured with a cell for shutdown measurement (hereinafter referred to as “cell”).
A 2 × 3 cm square rectangular membrane was impregnated with an electrolytic solution, and then sandwiched between two SUS electrodes and fixed with clips to prepare a cell. As the electrolytic solution, one obtained by dissolving 1 mol / L LiBF ₄ in a mixed solvent of ethylene carbonate 50 vol%: diethyl carbonate 50 vol% was used. A terminal of an impedance analyzer was connected to both electrodes of the assembled cell, and a resistance value at 1 kHz was measured. Resistance was measured while increasing the temperature at a rate of 15 ° C./min in an oven. The maximum resistance value was defined as the ultimate resistance value. The shutdown property was evaluated according to the following criteria.
Evaluation of shutdown (SD) property:
A: Ultimate resistance value of 10 ⁵ Ω or more ○: Ultimate resistance value of 10 ⁴ Ω or more, less than 10 ⁵ Ω ×: Ultimate resistance value of less than 10 ⁴ Ω (8) Particle size distribution of fine particles:
The slurry was diluted, and the particle size distribution (D ₉₀ ) of the fine particles contained in the slurry was determined with a laser diffraction particle size distribution analyzer (SALD-2200, manufactured by Shimadzu Corporation).

The water-soluble polymer, fine particles (a) and fine particles (b), and B film used for forming the A film are as follows.
<A film>
"Water-soluble polymer"
Carboxymethyl cellulose (CMC): Serogen 4H manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
"Fine particles (a)"
Fine particles (a): AKP-G008 manufactured by Sumitomo Chemical Co., Ltd.
Average particle diameter: 0.024 μm
Specific surface area: 70 m ² / g
Particle shape: substantially spherical “fine particle (b)”
Fine particles (b1): Sumiko Random AA-03 manufactured by Sumitomo Chemical Co., Ltd.
Average particle diameter: 0.42 μm
Specific surface area: 4.8 m ² / g
Particle shape: substantially spherical / fine particle (b2): AKP-3000 manufactured by Sumitomo Chemical Co., Ltd.
Average particle diameter: 0.54 μm
Specific surface area: 4.3 m ² / g
Particle shape: Vertical type <B film>
Polyethylene porous membrane 70% by weight of ultra high molecular weight polyethylene powder (340M, manufactured by Mitsui Chemicals), 30% by weight of polyethylene wax (FNP-0115, manufactured by Nippon Seiki Co., Ltd.) having a weight average molecular weight of 1000, and this ultra high molecular weight Antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals Co., Ltd.) 0.4% by weight, antioxidant (P168, manufactured by Ciba Specialty Chemicals Co., Ltd.) with respect to 100 parts by weight of polyethylene and polyethylene wax. 1% by weight and 1.3% by weight of sodium stearate are added, and further calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) having an average particle size of 0.1 μm is added so that the total volume is 38% by volume. After mixing with a Henschel mixer, melt and knead with a twin-screw kneader. And a resin composition. The polyolefin resin composition was rolled with a pair of rolls having a surface temperature of 150 ° C. to produce a sheet. The sheet is immersed in an aqueous hydrochloric acid solution (hydrochloric acid 4 mol / L, nonionic surfactant 0.5% by weight) to remove calcium carbonate, and subsequently stretched at 105 ° C. to obtain a porous film having the following properties: B1 to B4 were obtained.

"Porous membrane B1"
Film thickness: 12.4 μm
Fabric weight: 6.2 g / m ²
Air permeability: 131 seconds / 100cc
"Porous membrane B2"
Film thickness: 16.1 μm
Fabric weight: 7.2 g / m ²
Air permeability: 114 seconds / 100cc
"Porous membrane B3"
Film thickness: 15.3 μm
Fabric weight: 7.1 g / m ²
Air permeability: 105 seconds / 100cc
"Porous membrane B4"
Film thickness: 18.1 μm
Fabric weight: 7.9 g / m ²
Air permeability: 110 seconds / 100cc

Example 1
(1) Production of slurry The slurry of Example 1 was produced by the following procedure.
First, a water-ethanol mixed solvent of water: ethanol = 0.80: 0.20 (weight ratio) was prepared as a medium. The ethanol concentration is based on the medium weight (total weight of water + ethanol).
Next, CMC was dissolved in the water-ethanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.80% by weight (vs. [water-soluble polymer + medium]).
Next, 1000 parts by weight of the fine particles (a) and 500 parts by weight of the fine particles (b1) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of Example 1 was produced by processing 3 times at 60 MPa). Table 1 shows the composition of the slurry of Example 1.
(2) Manufacture and evaluation of separator Porous membrane B1 (MD direction 100 cm, TD direction 30 cm) was fixed to the drum, and a weight of 0.6 kg was suspended on the other side so that a load was evenly applied to the B membrane. A stainless steel coating bar having a diameter of 20 mm was arranged in parallel at the top of the drum so that the clearance from the drum was 40 μm. The drum was rotated and stopped so that the end of the side fixed with the B film tape was between the drum and the coating bar. While supplying the slurry prepared above onto the B film before the coating bar, the drum was rotated at 0.5 rpm, and the slurry of Example 1 was applied to one surface of the B film. When the coating property was confirmed by visual observation, some repelling was observed, but it was confirmed that the coating was uniformly performed as a whole.
After coating, the drum was stopped and left in an atmosphere of 70 ° C. for 30 minutes to be sufficiently dried, thereby obtaining the separator of Example 1 in which the A film was laminated on one surface of the porous film B1. In the obtained separator, the A film was in close contact with the porous film B1, and peeling was not confirmed. Table 2 summarizes the properties of the separators obtained, and Table 3 summarizes the evaluation results of the separators.

Example 2
(1) Production of slurry The slurry of Example 2 was produced by the following procedure.
First, a water-ethanol mixed solvent of water: ethanol = 0.67: 0.33 (weight ratio) was prepared as a medium. The ethanol concentration is based on the medium weight (total weight of water + ethanol).
Subsequently, CMC was dissolved in the water-ethanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.60% by weight (vs. [water-soluble polymer + medium]).
Subsequently, 500 parts by weight of the fine particles (a) and 3000 parts by weight of the fine particles (b2) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of Example 2 was produced by processing 3 times at 60 MPa). Table 1 also shows the composition of the slurry of Example 2.
(2) Manufacture and Evaluation of Separator The method of Example 1 was used except that the slurry of Example 2 was used instead of the slurry of Example 1 and the porous film B2 was used instead of the porous film B1. Thus, the separator of Example 2 was obtained. In addition, when manufacturing the separator, the slurry of Example 2 was applied to one surface of the porous membrane B2, and the coating property was confirmed by visual observation. As a result, no repelling or film roughness was observed, and the entire surface was uniform. It was confirmed that the slurry could be applied. Moreover, in the obtained separator, A film | membrane was closely_contact | adhered on the porous film B2, and peeling was not confirmed.
Table 2 summarizes the properties of the separators obtained, and Table 3 summarizes the evaluation results of the separators.

Example 3
(1) Production of slurry The slurry of Example 3 was produced by the following procedure.
First, a water-ethanol mixed solvent of water: ethanol = 0.80: 0.20 (weight ratio) was prepared as a medium. The ethanol concentration is based on the medium weight (total weight of water + ethanol).
Subsequently, CMC was dissolved in the water-ethanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.60% by weight (vs. [water-soluble polymer + medium]).
Subsequently, 500 parts by weight of the fine particles (a) and 3000 parts by weight of the fine particles (b2) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of Example 3 was produced by processing 3 times at 60 MPa). Table 1 also shows the composition of the slurry of Example 3.
(2) Manufacture and evaluation of separator The method of Example 1 except that the porous membrane B3 subjected to corona treatment under the above conditions was used, and the slurry of Example 3 was used instead of the slurry of Example 1. Similarly, the separator of Example 3 was obtained. In addition, when manufacturing the separator, the slurry of Example 3 was applied to one surface of the porous membrane B3 film, and when the coating property was confirmed by visual observation, no repelling or film roughness was observed, and overall It was confirmed that the slurry could be applied uniformly. In the obtained separator, the A film was in close contact with the porous film B3, and no peeling was confirmed.
Table 2 summarizes the properties of the separators obtained, and Table 3 summarizes the evaluation results of the separators.

Example 4
(1) Production of slurry The slurry of Example 4 was produced by the following procedure.
First, a water-ethanol mixed solvent of water: ethanol = 0.90: 0.10 (weight ratio) was prepared as a medium. The ethanol concentration is based on the medium weight (total weight of water + ethanol).
Subsequently, CMC was dissolved in the water-ethanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.60% by weight (vs. [water-soluble polymer + medium]).
Subsequently, 500 parts by weight of the fine particles (a) and 3000 parts by weight of the fine particles (b2) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of Example 4 was produced by processing 3 times at 60 MPa). Table 1 also shows the composition of the slurry of Example 4.
(2) Production and Evaluation of Separator A separator of Example 4 was obtained in the same manner as in Example 3 except that the slurry of Example 4 was used instead of the slurry of Example 3. In addition, when manufacturing the separator, the slurry of Example 4 was applied to one surface of the porous film B3 and the coating property was visually confirmed. As a result, no repellency or film roughness was observed, and the entire film was uniform. It was confirmed that the slurry could be applied. In the obtained separator, the A film was in close contact with the porous film B3, and no peeling was confirmed.
Table 2 summarizes the properties of the separators obtained, and Table 3 summarizes the evaluation results of the separators.

Example 5
(1) Production of slurry The slurry of Example 5 was produced by the following procedure.
First, a water-iso-propanol mixed solvent of water: iso-propanol = 0.85: 0.15 (weight ratio) was prepared as a medium. In addition, iso-propanol is based on a medium weight (water + total weight of iso-propanol).
Next, CMC was dissolved in the water-iso-propanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.60% by weight (vs. [water-soluble polymer + medium]).
Subsequently, 500 parts by weight of the fine particles (a) and 3000 parts by weight of the fine particles (b1) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of Example 5 was produced by processing 3 times at 60 MPa). Table 1 also shows the composition of the slurry of Example 5.
(2) Production and Evaluation of Separator The separator of Example 5 was prepared in the same manner as in Example 1 except that the porous membrane B4 was used and the slurry of Example 5 was used instead of the slurry of Example 1. Got. In addition, when manufacturing the separator, the slurry of Example 5 was applied to one surface of the porous film B4, and the coating property was confirmed by visual observation. It was confirmed that the slurry could be applied. Moreover, in the obtained separator, A film | membrane was closely_contact | adhered on the porous film B4, and peeling was not confirmed.
Table 2 summarizes the properties of the separators obtained, and Table 3 summarizes the evaluation results of the separators.

Example 6
(1) Production of slurry The slurry of Example 6 was produced by the following procedure.
First, a water-n-propanol mixed solvent of water: n-propanol = 0.88: 0.12 (weight ratio) was prepared as a medium. In addition, n-propanol is based on a medium weight (total weight of water + n-propanol).
Next, CMC was dissolved in the water-n-propanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.60% by weight (vs. [water-soluble polymer + medium]).
Subsequently, 500 parts by weight of the fine particles (a) and 3000 parts by weight of the fine particles (b1) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of Example 6 was produced by processing 3 times at 60 MPa). Table 1 also shows the composition of the slurry of Example 6.
(2) Production and Evaluation of Separator A separator of Example 6 was obtained in the same manner as in Example 5 except that the slurry of Example 6 was used instead of the slurry of Example 5. In addition, when manufacturing the separator, the slurry of Example 6 was applied to one surface of the porous film B4 and the coating property was visually confirmed. As a result, no repelling or film roughness was observed, and the entire film was uniform. It was confirmed that the slurry could be applied. Moreover, in the obtained separator, A film | membrane was closely_contact | adhered on the porous film B4, and peeling was not confirmed.

Example 7
(1) Production of slurry The slurry of Example 7 was produced by the following procedure.
First, a water-tert-butanol mixed solvent of water: tert-butanol = 0.88: 0.12 (weight ratio) was prepared as a medium. In addition, n-propanol is based on a medium weight (total weight of water + tert-butanol).
Next, CMC was dissolved in the water-tert-butanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.60% by weight (vs. [water-soluble polymer + medium]).
Subsequently, 500 parts by weight of the fine particles (a) and 3000 parts by weight of the fine particles (b1) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of Example 7 was produced by processing 3 times at 60 MPa). Table 1 also shows the composition of the slurry of Example 7.
(2) Production and Evaluation of Separator A separator of Example 7 was obtained in the same manner as in Example 5 except that the slurry of Example 7 was used instead of the slurry of Example 5. In addition, when manufacturing the separator, the slurry of Example 7 was applied to one surface of the porous film B4, and the coating property was confirmed by visual observation. It was confirmed that the slurry could be applied. Moreover, in the obtained separator, A film | membrane was closely_contact | adhered on the porous film B4, and peeling was not confirmed.

Comparative Example 1
(1) Manufacture of slurry The slurry of the comparative example 1 was produced in the following procedures.
Water containing no ethanol was used as a medium, and CMC was dissolved to obtain a CMC solution having a CMC concentration of 0.60% by weight (vs. [water-soluble polymer + medium]).
Next, 1000 parts by weight of fine particles (a) and 3000 parts by weight of fine particles (b2) are added to 100 parts by weight of CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a Gorin homogenizer ( The slurry of the comparative example 1 was produced by processing 3 times at 60 MPa). Table 1 shows the composition of the slurry of Comparative Example 1.
(2) Manufacture and evaluation of separator The method of Example 1 except that the porous membrane B3 subjected to corona treatment under the above conditions was used and the slurry of Comparative Example 1 was used instead of the slurry of Example 1. Similarly, the separator of Comparative Example 1 was obtained. In addition, when manufacturing the separator, the slurry of Comparative Example 1 was applied to one surface of the porous membrane B3 and the coating property was visually confirmed. As a result, repellency and film roughness were observed, and the slurry could be applied uniformly. It wasn't.
Moreover, in the obtained separator, although a part where the A film was partially formed on the porous film B3 was confirmed, peeling was confirmed in some places.
Table 2 summarizes the properties of the separators obtained, and Table 3 summarizes the evaluation results of the separators. In addition, since the separator of Comparative Example 1 had many peelings of the A film, the air permeability and the SD property were evaluated using a portion where the A film was formed relatively uniformly.

Comparative Example 2
(1) Manufacture of slurry The slurry of the comparative example 2 was produced in the following procedures.
First, a water-ethanol mixed solvent of water: ethanol = 0.50: 0.50 (weight ratio) was prepared as a medium. The ethanol concentration is based on the medium weight (total weight of water + ethanol).
Next, CMC was dissolved in the water-ethanol mixed solvent to obtain a CMC solution having a CMC concentration of 0.80% by weight (vs. [water-soluble polymer + medium]).
Next, 1000 parts by weight of the fine particles (a) and 500 parts by weight of the fine particles (b1) are added to 100 parts by weight of the CMC solution in terms of CMC, added, mixed, and mixed under high pressure dispersion conditions using a gorin homogenizer ( The slurry of the comparative example 2 was produced by processing 3 times at 60 MPa). Table 1 shows the composition of the slurry of Comparative Example 2.
(2) Production and Evaluation of Separator A separator of Comparative Example 2 was obtained in the same manner as in Example 1 except that the slurry of Comparative Example 2 was used instead of the slurry of Example 1. In addition, when manufacturing the separator, the slurry of Comparative Example 2 was applied to one surface of the porous film B1 and the coating property was visually confirmed. As a result, no repelling or film roughness was observed, and the entire film was uniform. It was confirmed that the slurry could be applied. Moreover, in the obtained separator, the A film was in close contact with the porous film B film 1, and no peeling was confirmed. While such an A film was formed, the SD property was clearly worse compared to Examples 1-7, suggesting poor film quality compared to the separators (A film) of Examples 1-7. It was done.
Table 2 summarizes the properties of the separators obtained, and Table 3 summarizes the evaluation results of the separators.

  ADVANTAGE OF THE INVENTION According to this invention, the separator for non-aqueous secondary batteries excellent in shutdown property and ion permeability is provided. The non-aqueous electrolyte secondary battery using the separator prevents the separator from coming into direct contact with the positive electrode and the negative electrode even if the battery generates heat severely due to an accident, and has an insulating property due to rapid non-porous polyolefin membrane. Since the non-aqueous electrolyte secondary battery is highly safe by maintenance, the present invention is extremely useful industrially.

Claims (10)

Including a water-soluble polymer, fine particles, and a medium used for forming the porous film in a separator for a non-aqueous electrolyte secondary battery in which a porous film containing a water-soluble polymer and fine particles and a polyolefin porous film are laminated A slurry,
The medium comprises a mixed solvent of water and a saturated aliphatic alcohol having 1 to 4 carbon atoms,
The slurry, wherein a concentration of the saturated aliphatic alcohol is 10% by weight or more and 35% by weight or less with respect to a total weight of the mixed solvent.   The slurry according to claim 1, wherein the saturated aliphatic alcohol is methanol or ethanol.   The slurry according to claim 1 or 2, wherein the fine particles are made of alumina.   The slurry according to any one of claims 1 to 3, wherein the concentration of the water-soluble polymer with respect to the medium is 0.4 wt% or more and 1.5 wt% or less.   The slurry according to any one of claims 1 to 4, wherein the water-soluble polymer is at least one polymer selected from the group consisting of cellulose ether, polyvinyl alcohol, and sodium alginate.   The slurry according to claim 5, wherein the cellulose ether is carboxymethyl cellulose.   The slurry according to any one of claims 1 to 6 is applied on a polyolefin porous film, the medium is removed, and a porous film containing a water-soluble polymer and fine particles is laminated on the polyolefin porous film. A method for producing a separator for a non-aqueous electrolyte secondary battery.   The method for producing a separator for a nonaqueous electrolyte secondary battery according to claim 7, wherein the polyolefin in the polyolefin porous membrane is polyethylene.   The method for producing a separator for a non-aqueous electrolyte secondary battery according to claim 7 or 8, wherein the polyolefin porous membrane is subjected to a hydrophilic treatment.   A separator for a non-aqueous electrolyte secondary battery, which is manufactured by the method according to claim 7.