JP6382051B2 - Storage device separator - Google Patents

Description

The present invention relates to an electrical storage device separator. Specifically, for example, a battery such as a primary battery, a secondary battery, or a fuel cell;
The present invention relates to a separator suitably used for an electrical energy storage device or the like.

In power storage devices such as lithium ion secondary batteries and electric double layer capacitors, a separator made of a microporous film is provided between the positive and negative electrodes. As a function of the separator, for example, in order to prevent direct contact between the positive and negative electrodes, permeate ions, etc., from the viewpoint of safety,
"Fuse characteristics" that immediately stop the battery reaction when the storage device is abnormally heated,
"Short characteristics" that maintain the original shape even at high temperatures and prevent dangerous situations where the cathode and anode materials react directly
Etc. are required.

As a material constituting such a separator, for example, non-woven fabric, paper, polyethylene terephthalate, polyolefin and the like are known.
In recent years, there has been a demand for improving the adhesion between an electrode and a separator from the viewpoint of uniform charge / discharge current and suppression of lithium dendrite growth in an electricity storage device. If the close contact between the separator and the electrode is improved, the charge / discharge current is expected to be uniform and the growth of lithium dendrite is expected to be suppressed. As a result, the charge / discharge cycle life of the electricity storage device may be improved. It will be expected.
Under such circumstances, attempts have been made to apply an adhesive polymer to a microporous membrane made of polyolefin for the purpose of improving the adhesion of the separator (see, for example, Patent Documents 1 and 2).

JP 2007-59271 A JP 2011-54502 A Special table 2009-518809 JP 2012-38597 A International Publication No. 2014/017651 Japanese Patent No. 5348444 JP 2003-171495 A

According to the techniques of Patent Documents 1 and 2 described above, certain effects are certainly recognized for improving the cycle characteristics of the electricity storage device. However, these techniques are not satisfactory in terms of lithium ion permeability, and also cause a problem that “stickiness” occurs on the surface of the separator and handling properties are lowered.
In this regard, Patent Document 3 discloses a technique in which two or more kinds of resin binders are mixed and used in order to achieve both adhesion to the electrode and suppression of stickiness on the separator surface;
Patent Document 4 discloses a technique for controlling the migration of two or more types of resin binders;
Patent Document 5 discloses a technique in which two types of resin binders are applied in layers;
Patent Document 6 discloses a technique using a fluorinated acrylic copolymer as a resin binder;
Patent Document 7 discloses a technique of using polyvinylidene fluoride (PVDF) as a resin binder.
Each is disclosed.

However, the attempts in the above Patent Documents 3 to 5 have all been successful as attempts to improve industrially meaningful forms, such as some of which have not achieved the target and some have lost productivity. Not. For example, according to the technique of Patent Document 6, the water repellency and oxidation resistance of the formed porous layer are still insufficient;
According to the technique of Patent Document 7, there is a problem that the melting point of the resin binder is excessively high and the adhesion between the resin binder and the porous film is insufficient.
The present invention has been made in order to overcome the above-described present situation. Therefore, the object of the present invention is excellent in adhesion with the electrode, adhesion strength with the porous substrate layer, and binding strength of the inorganic filler, and does not cause stickiness, handling property, water repellency, and oxidation resistance. It is another object to provide an excellent electricity storage separator. Another object of the present invention is to provide an electricity storage device separator exhibiting excellent cycle characteristics capable of maintaining a high capacity for a long time when it is provided in an electricity storage device with excellent productivity.

The inventors of the present invention have made extensive studies to achieve the above object. As a result, when producing a separator having a porous layer made of an inorganic filler and a resin binder on the porous substrate layer, the resin binder is a fluorine having different water contact angle and melting point or glass transition temperature. By mixing and using a crystalline resin binder and an amorphous resin binder, the migration of each resin binder is controlled to a desired mode by the difference in water contact angle between the resin binders, and the surface softening temperature of the formed porous layer is set. It has been found that the range can be controlled within the optimum range, and therefore the above-mentioned problem can be solved.
That is, the present invention is as follows.

[1] A porous substrate layer (A);
A separator having a porous layer (B) containing an inorganic filler (b-2), a fluorine-based crystalline resin binder (b-1-1), and an amorphous resin binder (b-1-2), ,
The surface softening temperature of the porous layer (B) is 30 to 60 ° C.,
A separator for an electricity storage device, characterized in that the water contact angle on the surface of the porous layer (B) is 75 degrees or more, and the average of all layer regions of the water contact angle of the porous layer (B) is 60 to 80 degrees.

[2] The water contact angle difference between the fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) is 10 degrees or more, according to [1]. Separator.
[3] The water contact angle of the fluorocrystalline resin binder (b-1-1) is 80 degrees or more, and the water contact angle of the amorphous resin binder (b-1-2) is 70 degrees or less. The separator according to [1] or [2].

[4] The separator according to any one of [1] to [4], wherein a melting temperature of the fluorine-based crystalline resin binder (b-1-1) is 100 ° C. or higher.
[5] The fluorine-based crystalline resin binder (b-1-1) is a monomer polymer or copolymer containing at least one selected from the group consisting of vinylidene fluoride and ethylene fluoride. The separator according to any one of [1] to [4].

[6] The separator for an electricity storage device according to any one of [1] to [5], wherein the separator has an air permeability of 10 to 500 seconds / 100 cc.
[7] an electrode;
[1] to [6] A laminate comprising the separator for an electricity storage device according to any one of [1] to [6].
[8] An electricity storage device comprising the laminate according to [7].

ADVANTAGE OF THE INVENTION According to this invention, while being excellent in all the adhesiveness between electrodes, roll peelability, water repellency, and oxidation resistance, the separator for electrical storage devices which is excellent also in productivity is provided.
The electricity storage device comprising the electricity storage device separator of the present invention exhibits a high battery capacity and a long life.
The separator of the present invention can be suitably used as a separator for power storage devices such as lithium ion secondary batteries, capacitors and capacitors.

The separator of the present invention has a porous substrate layer (A) and a porous layer (B).
<Porous substrate layer (A)>
The porous substrate layer (A) in the present invention will be described.
As the porous substrate layer (A), those having a small electron conductivity, an ionic conductivity, a high resistance to an organic solvent, and a fine pore diameter are preferable.
Examples of such porous substrate layer (A) include a porous film containing a polyolefin resin; polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, polyaramid, polycycloolefin, nylon, polytetra Examples thereof include a porous film containing a resin such as fluoroethylene, a polyolefin fiber woven (woven fabric), a polyolefin fiber nonwoven fabric, paper, and an aggregate of insulating substance particles. Among these, when a separator is obtained through a coating process, it is excellent in the coating property of the coating liquid, the separator film thickness is reduced, and the active material ratio in an electricity storage device such as a battery is increased to increase the volume per volume. From the viewpoint of increasing the capacity, a porous substrate layer (A) film containing a polyolefin resin (hereinafter also referred to as “polyolefin resin porous substrate layer (A) film”) is preferable.

  The porous substrate layer (A) is a polyolefin resin composition in which the polyolefin resin occupies 50% by mass or more and 100% by mass or less of the resin component constituting the porous film from the viewpoint of improving shutdown performance when used as a battery separator. It is preferable that the porous film is formed by the above. The proportion of the polyolefin resin in the polyolefin resin composition is more preferably 60% by mass or more and 100% by mass or less, and further preferably 70% by mass or more and 100% by mass or less.

The polyolefin resin contained in the polyolefin resin composition is not particularly limited. For example, ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene are used as monomers. Examples thereof include a homopolymer, a copolymer, or a multistage polymer. Moreover, these polyolefin resins may be used independently or may be used in mixture of 2 or more types.
Among these, polyethylene, polypropylene, copolymers thereof, and mixtures thereof are preferable as the polyolefin resin from the viewpoint of shutdown characteristics when used as a battery separator.
Specific examples of polyethylene include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, etc.
Specific examples of polypropylene include isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene, etc.
Specific examples of the copolymer include an ethylene-propylene random copolymer and ethylene propylene rubber.

Among these, polyethylene, particularly high-density polyethylene, is preferably used as the polyolefin resin from the viewpoint of satisfying required performance of a low melting point and high strength when used as a battery separator. In the present invention, high density polyethylene means polyethylene having a density of 0.942 to 0.970 g / cm ³ . In the present invention, the density of polyethylene refers to a value measured according to the D) density gradient tube method described in JIS K7112 (1999).

  Moreover, it is preferable to use the mixture of polyethylene and a polypropylene as polyolefin resin from a viewpoint of improving the heat resistance of a porous base material layer (A). In this case, the ratio of polypropylene to the total polyolefin resin in the polyolefin resin composition is preferably 1 to 35% by mass, more preferably 3 to 20% by mass from the viewpoint of achieving both heat resistance and a good shutdown function. %, More preferably 4 to 10% by mass.

  Arbitrary additives can be contained in the polyolefin resin composition. Examples of additives include polymers other than polyolefin resins; inorganic materials; antioxidants such as phenols, phosphorus and sulfur; metal soaps such as calcium stearate and zinc stearate; ultraviolet absorbers; light stabilizers An antistatic agent, an antifogging agent, a coloring pigment, and the like. The total addition amount of these additives is preferably 20 parts by mass or less with respect to 100 parts by mass of the polyolefin resin from the viewpoint of improving the shutdown performance, more preferably 10 parts by mass or less, and still more preferably 5 parts by mass. Or less.

Since the porous base material layer (A) has a porous structure in which a large number of very small holes are gathered to form a dense communication hole, it has excellent ion conductivity and at the same time withstand voltage characteristics, Moreover, it has a feature of high strength.
The porous substrate layer (A) may be a single layer film made of the above-described material or a laminated film.

  The film thickness of the porous substrate layer (A) is preferably from 0.1 μm to 100 μm, more preferably from 1 μm to 50 μm, and even more preferably from 3 μm to 25 μm. From the viewpoint of mechanical strength, 0.1 μm or more is preferable, and from the viewpoint of increasing the capacity of the battery, 100 μm or less is preferable. The film thickness of the porous substrate layer (A) can be adjusted by controlling the die lip interval, the draw ratio in the drawing step, and the like.

The average pore diameter of the porous substrate layer (A) is preferably 0.03 μm or more and 0.70 μm or less, more preferably 0.04 μm or more and 0.20 μm or less, still more preferably 0.05 μm or more and 0.10 μm or less, particularly preferably. It is 0.06 μm or more and 0.09 μm or less. From the viewpoint of high ion conductivity and withstand voltage, 0.03 to 0.70 μm is preferable. The average pore diameter of the porous substrate layer (A) can be measured by a measurement method described later.
The average pore diameter should be adjusted by controlling the composition ratio, the extrusion sheet cooling rate, the stretching temperature, the stretching ratio, the heat setting temperature, the stretching ratio at the time of heat setting, the relaxation rate at the time of heat setting, or a combination thereof. Can do.

The porosity of the porous substrate layer (A) is preferably 25% to 95%, more preferably 30% to 65%, and still more preferably 35% to 55%. 25% or more is preferable from the viewpoint of improving ion conductivity, and 95% or less is preferable from the viewpoint of withstand voltage characteristics. The porosity of the porous substrate layer (A) can be measured by the method described later.
When the porosity of the porous substrate layer (A) is a polyolefin resin porous substrate film, the mixing ratio of the polyolefin resin composition and the plasticizer, the stretching temperature, the stretching ratio, the heat setting temperature, and the heat setting temperature are as follows. It can be adjusted by controlling the draw ratio and the relaxation rate during heat setting, or by combining them.

  When the porous substrate layer (A) is a polyolefin resin porous substrate film, the viscosity average molecular weight of the polyolefin resin porous substrate film is preferably 30,000 or more and 12,000,000 or less, more preferably It is 50,000 or more and less than 2,000,000, more preferably 100,000 or more and less than 1,000,000. A viscosity average molecular weight of 30,000 or more is preferred because the melt tension during melt molding increases, moldability is improved, and the strength tends to increase due to entanglement between polymers. On the other hand, a viscosity average molecular weight of 12,000,000 or less is preferable because uniform melt kneading is facilitated and the formability of the sheet, particularly thickness stability, tends to be excellent. Furthermore, when it is used as a battery separator, a viscosity average molecular weight of less than 1,000,000 is preferable because it tends to close a hole when the temperature rises and a good shutdown function tends to be obtained. The viscosity average molecular weight of the polyolefin resin porous substrate membrane can be measured by the method described later.

There is no restriction | limiting in particular as a method of manufacturing a polyolefin resin porous substrate film as a porous substrate layer (A), A well-known manufacturing method is employable. For example;
(1) A method in which a polyolefin resin composition and a pore-forming material are melt-kneaded and formed into a sheet, and then stretched as necessary, and then the pore-forming material is extracted to make it porous.
(2) A method in which a polyolefin resin composition is melt-kneaded and extruded at a high draw ratio and then made porous by peeling off the polyolefin crystal interface by heat treatment and stretching,
(3) A method in which a polyolefin resin composition and an inorganic filler are melt-kneaded and formed on a sheet, and thereafter the interface is made porous by peeling off the interface between the polyolefin resin composition and the inorganic filler,
(4) A method of making the polyolefin resin composition porous by immersing it in a poor solvent for polyolefin to coagulate the polyolefin and simultaneously removing the solvent.

  Hereinafter, as an example of a method for producing a polyolefin resin porous substrate film, a method for extracting a pore-forming material after melt-kneading a polyolefin resin composition and a pore-forming material to form a sheet will be described.

  First, the polyolefin resin composition and the hole forming material are melt-kneaded. As the melt-kneading method, for example, the polyolefin resin and, if necessary, other additives are put into a resin kneading apparatus such as an extruder, kneader, lab plast mill, kneading roll, Banbury mixer, etc., while the resin component is heated and melted. A method of introducing and kneading the pore-forming material at an arbitrary ratio is mentioned.

  Examples of the pore forming material include a plasticizer, an inorganic material, or a combination thereof.

  Although it does not specifically limit as a plasticizer, It is preferable to use the non-volatile solvent which can form a uniform solution above melting | fusing point of polyolefin. Specific examples of such a non-volatile solvent include, for example, hydrocarbons such as liquid paraffin and paraffin wax; esters such as dioctyl phthalate and dibutyl phthalate; higher alcohols such as oleyl alcohol and stearyl alcohol. . Note that these plasticizers may be recovered and reused after extraction by an operation such as distillation. Further, preferably, before being put into the resin kneading apparatus, the polyolefin resin, other additives and plasticizer are previously kneaded in advance at a predetermined ratio using a Henschel mixer or the like. More preferably, in pre-kneading, only a part of the plasticizer is added, and the remaining plasticizer is appropriately heated in a resin kneader and kneaded while side-feeding. By using such a kneading method, the dispersibility of the plasticizer is increased, and when the sheet-shaped molded body of the melt-kneaded product of the resin composition and the plasticizer is stretched in a later step, a high magnification is obtained without breaking the film. Tend to stretch.

  Among the plasticizers, liquid paraffin is highly compatible with polyolefin resins such as polyethylene and polypropylene, and even when the melt-kneaded product is stretched, the interface between the resin and the plasticizer does not easily peel, and uniform stretching is possible. Is preferable because it tends to be easily implemented.

  The ratio of the polyolefin resin composition and the plasticizer is not particularly limited as long as they can be uniformly melt-kneaded and formed into a sheet shape. For example, the mass fraction of the plasticizer in the composition comprising the polyolefin resin composition and the plasticizer is preferably 20 to 90 mass%, more preferably 30 to 80 mass%. When the mass fraction of the plasticizer is 90% by mass or less, the melt tension at the time of melt molding tends to be sufficient for improving moldability. On the other hand, when the mass fraction of the plasticizer is 20% by mass or more, even when the mixture of the polyolefin resin composition and the plasticizer is stretched at a high magnification, the polyolefin molecular chain is not broken, and the pore structure is uniform and fine. Are easily formed, and the strength is also easily increased.

  The inorganic material is not particularly limited. For example, oxide ceramics such as alumina, silica (silicon oxide), titania, zirconia, magnesia, ceria, yttria, zinc oxide, iron oxide; silicon nitride, titanium nitride, nitriding Nitride ceramics such as boron; silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amicite, bentonite Ceramics such as asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; glass fibers. These may be used alone or in combination of two or more. Among these, silica, alumina, and titania are preferable from the viewpoint of electrochemical stability, and silica is particularly preferable from the viewpoint of easy extraction.

  The ratio between the polyolefin resin composition and the inorganic material is preferably 5% by mass or more, more preferably 10% by mass or more with respect to the total mass from the viewpoint of obtaining good separability. From the viewpoint of ensuring strength, the content is preferably 99% by mass or less, and more preferably 95% by mass or less.

  Next, the melt-kneaded product is formed into a sheet shape. As a method for producing a sheet-like molded product, for example, a melt-kneaded product is extruded into a sheet shape via a T-die or the like, and brought into contact with a heat conductor to cool to a temperature sufficiently lower than the crystallization temperature of the resin component. And then solidify. Examples of the heat conductor used for cooling and solidifying include metals, water, air, and plasticizers. Among these, it is preferable to use a metal roll because of its high heat conduction efficiency. In addition, when the extruded kneaded product is brought into contact with a metal roll, sandwiching it between the rolls further increases the efficiency of heat conduction, and the sheet is oriented to increase the film strength and improve the surface smoothness of the sheet. This is more preferable. The die lip interval when the melt-kneaded product is extruded from the T die into a sheet is preferably 200 μm or more and 3,000 μm or less, and more preferably 500 μm or more and 2,500 μm or less. When the die lip interval is 200 μm or more, the mess and the like are reduced, and there is little influence on the film quality such as streaks and defects, and the risk of film breakage and the like in the subsequent stretching process can be reduced. On the other hand, when the die lip interval is 3,000 μm or less, the cooling rate is fast and cooling unevenness can be prevented, and the thickness stability of the sheet can be maintained.

  Moreover, you may roll a sheet-like molded object. Rolling can be performed, for example, by a pressing method using a double belt press or the like. By performing rolling, the orientation of the surface layer portion can be particularly increased. The rolling surface magnification is preferably more than 1 and 3 or less, more preferably more than 1 and 2 or less. When the rolling ratio exceeds 1, the plane orientation increases and the film strength of the finally obtained porous base material layer (A) tends to increase. On the other hand, when the rolling ratio is 3 times or less, the orientation difference between the surface layer portion and the center is small, and a uniform porous structure tends to be formed in the thickness direction of the film.

  Next, the pore-forming material is removed from the sheet-like molded body to obtain a porous substrate layer (A). As a method for removing the hole forming material, for example, a method of extracting the hole forming material by immersing the sheet-shaped molded body in an extraction solvent and sufficiently drying it may be mentioned. The method for extracting the hole forming material may be either a batch type or a continuous type. In order to suppress the shrinkage of the porous base material layer (A), it is preferable to restrain the end of the sheet-like molded body during a series of steps of immersion and drying. Moreover, it is preferable to make the pore formation material residual amount in a porous base material layer (A) less than 1 mass% with respect to the mass of the whole porous base material layer (A).

  As the extraction solvent used when extracting the pore-forming material, when the porous substrate layer (A) is a polyolefin resin, it is a poor solvent for the polyolefin resin and a good solvent for the pore-forming material, It is preferable to use one having a boiling point lower than the melting point of the polyolefin resin. Examples of such an extraction solvent include hydrocarbons such as n-hexane and cyclohexane; halogenated hydrocarbons such as methylene chloride and 1,1,1-trichloroethane; non-chlorine such as hydrofluoroether and hydrofluorocarbon. Halogenated solvents; alcohols such as ethanol and isopropanol; ethers such as diethyl ether and tetrahydrofuran; ketones such as acetone and methyl ethyl ketone. These extraction solvents may be recovered and reused by an operation such as distillation. Moreover, when using an inorganic material as a pore formation material, aqueous solution, such as sodium hydroxide and potassium hydroxide, can be used as an extraction solvent.

Moreover, it is preferable to extend | stretch the said sheet-like molded object or a porous base material layer (A). The stretching may be performed before extracting the hole forming material from the sheet-like molded body. Moreover, you may carry out with respect to the porous base material layer (A) which extracted the hole formation material from the said sheet-like molded object. Furthermore, it may be performed before and after extracting the hole forming material from the sheet-like molded body.
As the stretching treatment, either uniaxial stretching or biaxial stretching can be suitably used, but biaxial stretching is preferable from the viewpoint of improving the strength and the like of the obtained porous base material layer (A). When the sheet-like molded body is stretched at a high magnification in the biaxial direction, the molecules are oriented in the plane direction, and the finally obtained porous base material layer (A) is difficult to tear and has a high puncture strength. Examples of the stretching method include simultaneous biaxial stretching, sequential biaxial stretching, multistage stretching, and multiple stretching. Simultaneous biaxial stretching is preferable from the viewpoints of improvement of puncture strength, uniformity of stretching, and shutdown property. Further, sequential biaxial stretching is preferred from the viewpoint of easy control of plane orientation.

  Here, simultaneous biaxial stretching refers to a stretching method in which stretching of MD (machine direction of continuous porous membrane forming) and stretching of TD (crossing the porous film MD at an angle of 90 °) are performed simultaneously, The draw ratio in each direction may be different. Sequential biaxial stretching refers to a stretching method in which MD and TD are stretched independently. When MD or TD is stretched, the other direction is fixed in an unconstrained state or a constant length. State.

  The draw ratio is preferably in the range of 20 times to 100 times in terms of surface magnification, and more preferably in the range of 25 times to 70 times. The draw ratio in each axial direction is preferably in the range of 4 to 10 times in MD, 4 to 10 times in TD, 5 to 8 times in MD, and 5 to 8 times in TD. More preferably, it is the range. When the total area magnification is 20 times or more, there is a tendency that sufficient strength can be imparted to the obtained porous base material layer (A). On the other hand, when the total area magnification is 100 times or less, film breakage in the stretching step is caused. It tends to prevent and achieve high productivity.

  In order to suppress the shrinkage of the porous substrate layer (A), a heat treatment can be performed for the purpose of heat setting after the stretching step or after the porous substrate layer (A) is molded. Further, the porous substrate layer (A) may be subjected to a post-treatment such as a hydrophilic treatment with a surfactant or the like, or a cross-linking treatment with ionizing radiation.

  The porous base material layer (A) is preferably subjected to heat treatment for the purpose of heat setting from the viewpoint of suppressing shrinkage. As a heat treatment method, a stretching operation performed at a predetermined temperature atmosphere and a predetermined stretching rate for the purpose of adjusting physical properties and / or a relaxation performed at a predetermined temperature atmosphere and a predetermined relaxation rate for the purpose of reducing stretching stress. Operation is mentioned. The relaxation operation may be performed after the stretching operation. These heat treatments can be performed using a tenter or a roll stretching machine.

The stretching operation may be performed by stretching the film MD and / or TD by 1.1 times or more, more preferably 1.2 times or more, so that the porous base material layer (A) having higher strength and high porosity can be obtained. It is preferable from a viewpoint obtained.
The relaxation operation is an operation for reducing the film to MD and / or TD. The relaxation rate is a value obtained by dividing the dimension of the film after the relaxation operation by the dimension of the film before the relaxation operation. When both MD and TD are relaxed, it is a value obtained by multiplying the MD relaxation rate and the TD relaxation rate. The relaxation rate is preferably 1.0 or less, more preferably 0.97 or less, and still more preferably 0.95 or less. The relaxation rate is preferably 0.5 or more from the viewpoint of film quality. The relaxation operation may be performed in both the MD and TD directions, but only one of the MD and TD may be performed.
The stretching and relaxation operations after this plasticizer extraction are preferably performed at TD. The temperature in the stretching and relaxation operation is preferably lower than the melting point of the polyolefin resin (hereinafter also referred to as “Tm”), and more preferably in the range of 1 ° C. to 25 ° C. lower than Tm. When the temperature in the stretching and relaxation operation is in the above range, it is preferable from the viewpoint of the balance between the reduction in thermal shrinkage and the porosity.

<Porous layer (B)>
The porous layer (B) containing the resin binder (b-1) and the inorganic filler (b-2) will be described.
Although it does not specifically limit as an inorganic filler (b-2) used for the said porous layer (B), Heat resistance and electrical insulation are high, and it is electrochemically stable in the use range of a lithium ion secondary battery. Some are preferred.
Examples of the inorganic filler (b-2) include an aluminum compound, a magnesium compound, and other compounds.

Examples of the aluminum compound include aluminum oxide, aluminum silicate, aluminum hydroxide, aluminum hydroxide oxide, sodium aluminate, aluminum sulfate, aluminum phosphate, and hydrotalcite.
Examples of the magnesium compound include magnesium sulfate and magnesium hydroxide.
Other compounds include oxide ceramics, nitride ceramics, clay minerals, silicon carbide, calcium carbonate, barium titanate, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, silica sand, glass fiber, etc. Is mentioned. Examples of the oxide ceramics include silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide, iron oxide and the like. Examples of nitride ceramics include silicon nitride, titanium nitride, boron nitride and the like. Examples of the clay mineral include talc, montmorillonite, sericite, mica, amicite, bentonite and the like.
These may be used alone or in combination.

  Among these, aluminum oxide, aluminum hydroxide oxide, and aluminum silicate are preferable from the viewpoints of electrochemical stability and heat resistance. A specific example of aluminum oxide is alumina. Specific examples of the aluminum hydroxide oxide include boehmite. Specific examples of aluminum silicate include kaolinite, dickite, nacrite, halloysite, and pyrophyllite.

  As the aluminum oxide, alumina is more preferable from the viewpoint of electrochemical stability. By adopting particles mainly composed of alumina as the inorganic filler (b-2) constituting the porous layer (B), a very lightweight porous layer can be realized while maintaining high permeability. Even with a thinner porous layer thickness, the thermal contraction of the separator at a high temperature is suppressed, and excellent heat resistance tends to be exhibited. Alumina has many crystal forms such as α-alumina, β-alumina, γ-alumina, and θ-alumina, and any of them can be suitably used. Of these, α-alumina is most preferable because it is thermally and chemically stable.

  As the aluminum hydroxide oxide, boehmite is more preferable from the viewpoint of preventing an internal short circuit due to generation of lithium dendrite. By adopting particles mainly composed of boehmite as the inorganic filler (b-2) constituting the porous layer (B), a very lightweight porous layer can be realized while maintaining high permeability. Even with a thinner porous layer thickness, thermal contraction of the porous film at a high temperature is suppressed, and excellent heat resistance tends to be exhibited. Synthetic boehmite that can reduce ionic impurities that adversely affect the characteristics of the electrochemical device is more preferred.

  Among the aluminum silicates, kaolinite (hereinafter, also referred to as kaolin) mainly composed of kaolin mineral is preferable from the viewpoint of lightness and air permeability. Kaolin includes wet kaolin and calcined kaolin obtained by calcining this. However, calcined kaolin releases crystallization water and removes impurities during the calcining process, so that it has electrochemical stability. Is particularly preferable. As the inorganic filler (b-2) constituting the porous layer (B), the use of particles containing calcined kaolin as the main component realizes a very lightweight porous layer (B) while maintaining high permeability. In addition, even when the thickness of the porous layer (B) is thinner, thermal shrinkage of the porous substrate layer (A) at a high temperature is suppressed, and excellent heat resistance tends to be exhibited.

  The average particle diameter of the inorganic filler (b-2) is preferably 0.1 μm or more and 10.0 μm or less, more preferably 0.2 μm or more and 5.0 μm or less, and 0.4 μm or more and 3. It is more preferably 0 μm or less, and most preferably 0.6 μm or more and 1.5 μm or less. It is preferable to adjust the average particle diameter of the inorganic filler (b-2) to the above range from the viewpoint of suppressing the air permeability and heat shrinkage at high temperature.

  As a particle size distribution of the inorganic filler (b-2), the minimum particle size is preferably 0.02 μm or more, more preferably 0.05 μm or more, and further preferably 0.1 μm or more. The maximum particle size is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 7 μm or less. The ratio of the maximum particle size / average particle size is preferably 50 or less, more preferably 30 or less, and still more preferably 20 or less. Adjusting the particle size distribution of the inorganic filler (b-2) to the above range is preferable from the viewpoint of suppressing thermal shrinkage at high temperatures. Moreover, you may have a several particle size peak between the maximum particle size and the minimum particle size. In addition, as a method of adjusting the particle size distribution of the inorganic filler (b-2), for example, the inorganic filler (b-2) is pulverized using a ball mill, a bead mill, a jet mill or the like, and adjusted to a desired particle size distribution. And a method of blending after adjusting an inorganic filler (b-2) having a plurality of particle size distributions.

  Examples of the shape of the inorganic filler (b-2) include a plate shape, a scale shape, a polyhedron, a needle shape, a columnar shape, a spherical shape, a spindle shape, a lump shape, and the like. You may use in combination of multiple types. Among these, a plate shape, a scale shape, and a polyhedron are preferable from the viewpoint of improving permeability.

  The ratio of the inorganic filler (b-2) in the porous layer (B) is the permeability and heat resistance of the separator, and the inorganic filler (b-2) is bound in the porous layer (B). It can determine suitably from viewpoints, such as the required amount of the resin binder (b-1) to make. The proportion of the inorganic filler (b-2) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, from the viewpoint of the permeability and heat resistance of the separator. Especially preferably, it is 93 mass% or more, Most preferably, it is 96 mass% or more. Moreover, from the viewpoint of the required amount of the resin binder (b-1) for binding the inorganic filler (b-2) in the porous layer (B), the ratio of the inorganic filler (b-2) is 100 masses. % Is preferable, more preferably 99.5% by mass or less, still more preferably 99% by mass or less, and particularly preferably 98% by mass or less.

A resin binder (b-1) is resin which plays the role which bind | concludes the inorganic filler (b-2) mentioned above. Moreover, it is preferable that it is resin which plays the role which bind | concludes an inorganic filler (b-2) and a porous base material layer (A) mutually.
As the type of the resin binder (b-1), a resin binder (b-1) that is insoluble in an electrolyte solution of a lithium ion secondary battery when used as a separator and is electrochemically stable within the use range of the lithium ion secondary battery. It is preferable to use it.

Specific examples of the resin binder (b-1) include the following 1) to 6).
1) Polyolefin: For example, polyethylene, polypropylene, ethylene propylene rubber, and modified products thereof;
2) Conjugated diene polymer: for example, styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride;
3) Acrylic polymer: For example, methacrylic acid ester-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer;
4) Polyvinyl alcohol resin: for example, polyvinyl alcohol, polyvinyl acetate;
5) Fluorine-containing resin: For example, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer Coalescence;
6) A resin having a melting point and / or glass transition temperature of 180 ° C. or higher or a polymer having no melting point but a decomposition temperature of 200 ° C. or higher: for example, polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyetherimide, polyamideimide , Polyamide, polyester. In particular, from the viewpoint of durability, wholly aromatic polyamides, particularly polymetaphenylene isophthalamide, are preferred.
Among these, 2) conjugated diene polymers are preferable from the viewpoint of compatibility with electrodes, and 3) acrylic polymers and 5) fluorine-containing resins are preferable from the viewpoint of voltage resistance.

The 2) conjugated diene polymer is a polymer containing a conjugated diene compound as a monomer unit.
Examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and substituted linear chains. Examples thereof include conjugated pentadienes, substituted and side chain conjugated hexadienes, and these may be used alone or in combination of two or more. Among these, 1,3-butadiene is particularly preferable.

The 3) acrylic polymer is a polymer containing a (meth) acrylic compound as a monomer unit. The (meth) acrylic compound indicates at least one selected from the group consisting of (meth) acrylic acid and (meth) acrylic acid ester.
Examples of (meth) acrylic acid used in the above 3) acrylic polymer include acrylic acid and methacrylic acid.
As the (meth) acrylic acid ester used in the above 3) acrylic polymer, for example,
Examples of (meth) acrylic acid alkyl esters include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl amethacrylate, phenyl acrylate, phenyl methacrylate, cyclohexyl acrylate, and cyclohexyl. Methacrylate etc .;
Examples of the epoxy group-containing (meth) acrylic acid ester include glycidyl acrylate and glycidyl methacrylate. These may be used alone or in combination of two or more.

  The above 2) conjugated diene polymer and 3) acrylic polymer may be obtained by copolymerizing other monomers copolymerizable therewith. Examples of other copolymerizable monomers used include unsaturated carboxylic acid alkyl esters, aromatic vinyl monomers, vinyl cyanide monomers, and unsaturated monomers containing a hydroxyalkyl group. , Unsaturated carboxylic acid amide monomer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid and the like. These may be used alone or in combination of two or more. Good. Among the above, an unsaturated carboxylic acid alkyl ester monomer is particularly preferable. Examples of unsaturated carboxylic acid alkyl ester monomers include dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, and the like. It may be used alone or in combination of two or more.

  The 2) conjugated diene polymer may be obtained by copolymerizing the (meth) acrylic compound as another monomer.

The resin binder (b-1) contained in the porous layer (B) in the separator of this embodiment is
A fluorine-based crystalline resin binder (b-1-1);
An amorphous resin binder (b-1-2),
Is included.

  By using such a plurality of types of resin binders (b-1), the coating liquid containing these resin binders (b-1) and inorganic fillers (b-2) can be converted into a porous substrate layer (A When the porous layer (B) is formed by immobilizing and solidifying by coating and drying, migration of the resin binder (b-1) occurs. Therefore, in the formed porous layer (B), the function of the resin binder (b-1) can be made different between the porous substrate layer (A) side and the porous layer (B) surface side, which is preferable. .

Here, migration refers to evaporation / porosity of a solvent (for example, water) in the step of forming the porous layer (B) by applying, immobilizing and drying the coating liquid onto the porous substrate layer (A). This is a phenomenon in which the resin binder (b-1) in the coating film moves to the outer surface side in the porous layer (B) by drying the layer (B).

  In the present embodiment, due to the migration, the fluorine-based crystalline resin binder (b-1-1) having a large water contact angle easily repels water, and thus easily migrates toward the outer surface of the coating film. The amorphous resin binder (b-1-2) having a small water contact angle is difficult to migrate because it is difficult to repel water. Therefore, in a preferred aspect of the present embodiment, the characteristics of the fluorine-based crystalline resin binder (b-1-1) appear deeply in the region near the outer surface of the porous layer (B), and conversely, the porous substrate layer (A ), The characteristics of the amorphous resinous binder (b-1-2) appear deeply.

  The fluorine-based crystalline resin binder (b-1-1) preferably has a melting temperature measured by a differential scanning calorimeter (DSC) of 100 ° C. or higher, more preferably 120 to 330 ° C. More preferably, the temperature is from 150 ° C to 250 ° C. This melting temperature means the peak top temperature of the melting endothermic peak in DSC. When there are a plurality of melting endothermic peaks, the peak top of the peak indicating the maximum endothermic amount is the melting temperature.

  One of the amorphous resin binders (b-1-2) has a glass transition temperature (Tg) measured by DSC of preferably less than 30 ° C, more preferably 5 ° C or less, still more preferably. It is −10 ° C. or lower. When the glass transition temperature of the resin binder (b-1-2) is less than 30 ° C., the binding property with the inorganic filler (b-2), the adhesive strength with the porous base material layer (A), and the electrode It is preferable from the viewpoint of adhesion.

  It is preferable that the fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) do not have complete compatibility. When these two types of resin binders do not exhibit complete compatibility, binders having different properties are present separately, and exhibit respective characteristics. Therefore, the adhesiveness with the electrode, the stickiness on the outermost surface of the separator, and the handling property can be compatible at a high level. Here, when two types of resins have complete compatibility, the binders having different properties behave as if they are one type of polymer. As a result, depending on the water contact angle and the glass transition temperature as a whole of the mixture shown after the compatibilization, it shows an averaged performance in the adhesion to the electrode and the stickiness and handling of the outermost surface of the separator. It is not preferable because it will remain in the range.

The fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) are preferably different also in water contact angle. The water contact angle difference between the fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) is preferably 10 degrees or more, and 10 to 40 degrees. Is more preferable.
Here, when it is set as a power-discharging device, the outer surface of a porous layer (B) is directly in contact with electrolyte solution, and is exposed to the oxidation reduction environment accompanying exchange of electroconductive ion. Accordingly, since the region needs to have a high degree of oxidation resistance, it is necessary to exhibit high water repellency. Therefore, a higher water contact angle is preferable. On the other hand, in the region in the vicinity of the interface with the porous base material layer (A) in the porous layer (B), from the request that the adhesion with the porous base material layer (A) should be increased to improve the powder fall-off prevention performance, A lower water contact angle is preferred.

And as mentioned above,
In the region near the outer surface of the porous layer (B), the characteristics of the fluorine-based crystalline resin binder (b-1-1) appear deeply,
In the region near the interface with the porous base material layer (A), the characteristics of the amorphous resin binder (b-1-2) appear deeply.

Therefore, more specifically,
The water contact angle of the fluorine-based crystalline resin binder (b-1-1) is 80 degrees or more, and the water contact angle of the amorphous resin binder (b-1-2) is 70 degrees or less. Is preferred. The water contact angle of the fluorine-based crystalline resin binder (b-1-1) is 75 to 115 degrees;
The water contact angle of the amorphous resin binder (b-1-2) is 30 to 75 degrees.
Each is more preferable.
Here, the water contact angles of the fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) are water contacts when the respective resin binders are individually formed into a film. Say the corner. The measured film thickness at this time is preferably 0.1 to 5 mm, for example, about 1 mm, in view of ensuring measurement accuracy and film formation.

Specific examples of the fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) as described above include the following examples as preferred embodiments. be able to.
Fluorine-based crystalline resin binder (b-1-1): 5) fluorinated resin Amorphous resin binder (b-1-2): 2) conjugated diene polymer and 3) acrylic polymer One or more selected from the group consisting of

The fluorine-based crystalline resin binder (b-1-1) is preferably a polymer or copolymer of a fluorine atom-containing monomer. Examples of the fluorine atom-containing monomer include vinylidene fluoride, vinyl fluoride, tetrafluorinated ethylene, polyfluorinated synthetic ethylene, hexafluorinated polypyrene, hexafluorinated isobutylene, perfluorinated acrylic acid, perfluorinated methacrylic acid, acrylic Examples thereof include fluorinated alkyl esters of acid or methacrylic acid, and particularly preferably one or more selected from the group consisting of vinylidene fluoride and tetrafluoroethylene.
When the fluorine-based crystalline resin binder (b-1-1) is a copolymer of fluorine atom-containing monomers, examples of the copolymerization monomer include methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, Butyl methacrylate, butyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, phenyl methacrylate, phenyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, acrylic acid, methacrylic acid, cyclohexyl vinyl ether, hydroxyethyl vinyl ether , Butadiene, isoprene, chloroprene, and the like.
The copolymer ratio of the fluorine atom-containing monomer of the fluorine-based crystalline resin binder (b-1-1) is preferably 30% by mass or more, more preferably 50% by mass or more, and further preferably 80% by mass. It is above, Especially preferably, it is 100 mass%.

The amorphous resin binder (b-1-2) is preferably a copolymer comprising a functional group-containing monomer, a functional group-free and non-crosslinkable monomer, and a crosslinkable monomer.
Specific examples of these are:
Examples of functional group-containing monomers include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, phthalic acid, fumaric acid, and maleic acid;
Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, methyl glycidyl acrylate, methyl glycidyl methacrylate;
Amide group-containing monomers such as acrylamide and methacrylamide,

Functional group-free and non-crosslinkable monomers include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate Benzyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl acrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, phenol Such as methacrylate (meth) acrylic acid ester monomer;
Vinyl cyanide monomers such as acrylonitrile and methacrylonitrile;
Aromatic vinyl monomers such as styrene and methylstyrene;
Unsaturated carboxylic acid alkyl ester monomers such as dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate;
Vinyl monomers having hydrolyzable silyl groups such as vinyl silane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, etc. , Respectively. As these functional group-containing monomers and functional group-free and non-crosslinkable monomers, it is preferable to use one or more selected from the above examples.
Examples of the crosslinkable monomer include monomers having two or more radical polymerizable double bonds.

Specific examples of monomers having two or more radical polymerizable double bonds include
As monomers having two radical polymerizable double bonds, for example, divinylbenzene, polyoxyethylene diacrylate, polyoxyethylene dimethacrylate, polyoxypropylene diacrylate, polyoxypropylene dimethacrylate, neopentyl glycol diacrylate, neo Pentyl glycol dimethacrylate, butanediol diacrylate, butanediol dimethacrylate, 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3 -Butadiene and the like;
Examples of the monomer having three radical polymerizable double bonds include trimethylolpropane triacrylate and trimethylolpropane trimethacrylate;
As monomers having four radical polymerizable double bonds, for example, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, etc.
It is preferable to use one or more selected from these.

About the amorphous resin binder (b-1-2)
The use ratio of the functional group-containing monomer to the total monomer is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and further preferably 3 to 7% by mass;
The use ratio of the functional group-free and non-crosslinkable monomer with respect to all monomers is preferably 75 to 99.4% by mass, more preferably 85 to 98.7% by mass, and still more preferably 90 to 96.5% by mass Yes; and the use ratio of the crosslinkable monomer with respect to all monomers is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, and still more preferably 0.5 to 3% by mass.

The proportion of the resin binder (b-1) in the porous layer (B) is preferably 1 to 30% by mass, more preferably 1.5 to 20% by mass, and still more preferably 2 to 2% by mass. 10% by mass.
The ratio {(b-1-1) / (b-1)} of the fluorine-based crystalline resin binder (b-1-1) in the resin binder (b-1) is 5 to 95% by mass. Is more preferable, and it is more preferable that it is 15-75 mass%, More preferably, it is 25-50 mass%.

  The position of the fluorine-based crystalline resin binder (b-1-1) in the porous layer (B) is a fluorine-based crystalline resin binder (b-1-1) present in a thickness range of 0 to 50% from the outer surface. ) As a proportion of the total amount of the fluorocrystalline resin binder (b-1-1), preferably 60% by mass or more, more preferably 65% by mass or more, still more preferably 70% by mass or more, most preferably 75% by mass or more. The presence of 60% by mass or more of the fluorine-based crystalline resin binder (b-1-1) in a thickness range of 0 to 50% from the outer surface is preferable from the viewpoint of the stickiness and handling properties of the outermost surface of the separator.

  The presence position of the amorphous resin binder (b-1-2) in the porous layer (B) is an amorphous resin binder (b-1-2) existing in a thickness range of 50% to 100% from the outer surface. Is preferably 55% by mass or more and less than 100% by mass, more preferably 65% by mass or more and less than 98% by mass, and still more preferably 70% by mass with respect to the total amount of the amorphous resin binder (b-1-2). % To 95% by mass, most preferably 75% to 90% by mass. That the amorphous resin binder (b-1-2) present in the thickness range of 50% to 100% from the surface is 55% by mass or more and less than 100%, the adhesion between the electrode and the porous substrate layer It is preferable from the viewpoint of adhesiveness.

  The layer thickness of the porous layer (B) is preferably 1 μm or more, more preferably 1.0 μm or more, further preferably 1.2 μm or more, and particularly preferably 1.5 μm from the viewpoint of improving heat resistance and insulation. Above, especially preferably 1.8 μm or more, most preferably 2.0 μm or more. Further, from the viewpoint of increasing the capacity of the battery and improving the permeability, it is preferably 50 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less, and particularly preferably 7 μm or less.

  The filling rate of the inorganic filler (b-2) in the porous layer (B) is preferably 95% by volume or less, more preferably 80% by volume or less, and 70% by volume or less from the viewpoint of lightness and high permeability. More preferred is 60% by volume or less. In light of heat shrinkage suppression and dendrite suppression, the lower limit is preferably 20% by volume or more, more preferably 30% by volume or more, and still more preferably 40% by volume or more. The filling rate of the inorganic filler (b-2) can be calculated from the layer thickness of the porous layer (B) and the mass and specific gravity of the inorganic filler (b-2).

  The surface softening temperature of the porous layer (B) is 30 to 60 ° C, preferably 30 to 50 ° C, more preferably 30 to 45 ° C, and further preferably 35 to 45 ° C. When the surface softening temperature is 30 ° C. or higher, the separator can be unwrinkled without wrinkles when the separator is unrolled when it is attempted to unwind the separator when it is crimped to the electrode. Preferably, the glass transition of a polyolefin resin in which the porous substrate layer (A) constituting the separator is generally used when the electrode and the separator are pressure-bonded using a high-temperature press when the temperature is 60 ° C. or lower. Although the temperature is not high, it is preferable in that wrinkles are not generated in the laminate obtained after pressure bonding.

  The porous layer (B) may be formed only on one side of the porous base material layer (A) or on both sides.

  As a method for forming the porous layer (B), for example, a coating containing a predetermined amount of the inorganic filler (b-2) and the resin binder (b-1) on at least one surface of the porous substrate layer (A). A method of forming a porous layer (B) by applying a liquid can be mentioned.

  The form of the resin binder (b-1) in the coating liquid may be an aqueous solution dissolved or dispersed in water or an organic medium solution dissolved or dispersed in a general organic medium. Resin latex is preferred. “Resin latex” refers to a resin dispersed in a medium. When the resin latex is used as the resin binder (b-1), the porous layer (B) containing the inorganic filler (b-2) and the resin binder (b-1) is at least one surface of the porous substrate layer (A). When laminated, the ion permeability is not easily lowered and high output characteristics are easily obtained. In addition, even when the temperature rises rapidly during abnormal heat generation, smooth shutdown characteristics are exhibited, and high safety is easily obtained.

  The average particle size of the resin binder (b-1) latex is preferably 50 to 1,000 nm, more preferably 60 to 500 nm, still more preferably 80 to 250 nm. When the average particle diameter is 50 nm or more, when the porous layer (B) containing the inorganic filler (b-2) and the resin binder (b-1) is laminated on at least one surface of the porous substrate layer (A) film When the separator is used as a separator, the heat shrinkage tends to be good and the safety tends to be excellent. When the average particle diameter is 1,000 nm or less, the ion permeability is unlikely to decrease and high output characteristics are easily obtained. In addition, even when the temperature rises rapidly during abnormal heat generation, smooth shutdown characteristics are exhibited, and high safety is easily obtained. The average particle diameter can be controlled by adjusting the polymerization time, the polymerization temperature, the raw material composition ratio, the raw material charging order, the pH, the stirring speed and the like when producing the resin latex binder.

  As a medium for the coating liquid, those capable of uniformly or stably dispersing or dissolving the inorganic filler (b-2) and the resin binder (b-1) are preferable. For example, N-methylpyrrolidone, N, N -Dimethylformamide, N, N-dimethylacetamide, water, ethanol, toluene, hot xylene, methylene chloride, hexane and the like.

  Various additives such as surfactants, thickeners, wetting agents, antifoaming agents, pH adjusters including acids and alkalis are added to the coating solution in order to stabilize dispersion and improve coating properties. An agent may be added. The total amount of these additives is 100 parts by mass of the inorganic filler (b-2) as the active ingredient (the mass of the additive component dissolved when the additive is dissolved in the solvent). 20 mass parts or less are preferable, More preferably, it is 10 mass parts or less, More preferably, it is 5 mass parts or less.

  About the method of disperse | distributing or melt | dissolving an inorganic filler (b-2) and the resin binder (b-1) in the medium of a coating liquid, it is a method which can implement | achieve the dispersion characteristic of a coating liquid required for a coating process. If there is no particular limitation. Examples thereof include a ball mill, a bead mill, a planetary ball mill, a vibrating ball mill, a sand mill, a colloid mill, an attritor, a roll mill, a high-speed impeller dispersion, a disperser, a homogenizer, a high-speed impact mill, ultrasonic dispersion, and mechanical stirring using a stirring blade.

  The method for coating the coating liquid on the porous substrate layer (A) is not particularly limited as long as it can realize the required layer thickness and coating area. For example, a gravure coater method, a small diameter gravure coater method , Reverse roll coater method, transfer roll coater method, kiss coater method, dip coater method, knife coater method, air doctor coater method, blade coater method, rod coater method, squeeze coater method, cast coater method, die coater method, screen printing method And spray coating method.

  Furthermore, when the surface treatment is applied to the surface of the porous base material layer (A) prior to the application of the coating liquid, the coating liquid can be easily applied, and the porous layer (B) after coating and the porous base material Since adhesiveness with the surface of a layer (A) improves, it is preferable. The surface treatment method is not particularly limited as long as it does not significantly impair the porous structure of the porous substrate layer (A). For example, corona discharge treatment method, plasma discharge treatment method, mechanical surface roughening method, solvent Examples thereof include a treatment method, an acid treatment method, and an ultraviolet oxidation method.

  The method for removing the medium from the coating film after coating is not particularly limited as long as it does not adversely affect the porous substrate layer (A). For example, while fixing the porous substrate layer (A), the method Examples include a method of drying at a temperature below the melting point, a method of drying under reduced pressure at a low temperature, and extraction drying. Further, a part of the solvent may be left as long as the battery characteristics are not significantly affected. From the viewpoint of controlling the shrinkage stress in the MD direction of the laminate in which the porous base material layer (A) and the porous layer (B) are laminated, it is preferable to appropriately adjust the drying temperature, the winding tension, and the like.

  The temperature for removing the medium from the coating film is preferably 20 to 100 ° C., more preferably 30 to 80 ° C., particularly from the viewpoint of appropriately controlling the migration of the resin binder (b-1). It is preferable to set it as 40-70 degreeC. The removal time is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 20 minutes, still more preferably 40 seconds to 10 minutes, and particularly preferably 1 to 3 minutes.

  The inorganic filler (b-2) in the porous layer (B) is preferably present uniformly in the porous layer (B). As an index thereof, {amount of inorganic filler in the thickness range of 0 to 50% from the outer surface (b-2U)} of the porous layer (B) / {inorganic present in the thickness range exceeding 50% to 100% The ratio of the amount of filler (b-2D)} is preferably 0.8 to 1.2, more preferably 0.85 to 1.15, and 0.9 to 1.1. Further preferred. When the ratio is 0.8 to 1.2, the pore size distribution in the porous layer (B) becomes uniform, and the reproducibility of the cycle characteristics of the battery is improved.

The location of the inorganic filler (b-2) in the porous layer (B) can be known by using a technique combining a cross-sectional photograph of the porous layer (B) and element mapping. As the cross-sectional photograph, for example, an SEM (scanning electron microscope) image;
As the element mapping method, for example, EDX (energy dispersive X-ray spectroscopy) can be employed. In these analyses, it is possible to know the location of the inorganic filler (b-2) by mapping in the cross-sectional direction while focusing on the metal element constituting the main component of the inorganic filler (b-2). . When the inorganic filler (b-2) is boehmite or kaolin, for example, the position of the inorganic filler (b-2) can be known by mapping in the cross-sectional direction of the Al (aluminum) element constituting the main component.

The porous layer (B) formed as described above is
Both a fluorine-based crystalline resin binder (b-1-1) having a water contact angle of preferably 80 degrees or more and an amorphous resin binder (b-1-2) having a water contact angle of preferably 70 degrees or less. contains. And by migration of the resin binder (b-1) when forming the porous layer (B),
On the outer surface side of the porous layer (B) (on the side opposite to the contact surface with the porous base material layer (A)), there are many fluorine-based crystalline resin binders (b-1-1),
A large amount of amorphous resin binder (b-1-1) will be present on the contact surface side of the porous layer (B) with the porous substrate layer (A). Therefore, the water contact angle of the resin binder (b-1) on the outer surface of the porous layer (B) is larger than the average value of all layers in the water contact angle of the porous layer (B).

In the present embodiment, the water contact angle on the surface of the porous layer (B) is 75 degrees or more, preferably 75 to 100 degrees, and more preferably 75 to 90 degrees.
On the other hand, the average of all layers of the water contact angle of the porous layer (B) is 60 to 80 degrees, preferably 62 to 78 degrees, and more preferably 65 to 75 degrees.

The “water contact angle on the surface of the porous layer (B)” refers to the value of the water contact angle actually measured on the outer surface of the formed porous layer (B).
In addition, “all layer region average value of water contact angle of porous layer (B)” refers to the formed porous layer (B) by scraping all the regions in the thickness direction and mixing them well, followed by hot pressing. It is the value measured about the film | membrane surface obtained by forming into a film. When the film is formed by such a method, there is no room for migration of the resin binder (b-1), so that the average water contact angle of the resin binder (b-1) in the region can be known.

Next, the separator of the present invention will be described.
The separator having the porous substrate layer (A) and the porous layer (B) containing the inorganic filler (b-2) and the resin binder (b-1) is excellent in heat resistance and has a shutdown function. Therefore, it is suitable for a battery separator that separates the positive electrode and the negative electrode in the battery.
In particular, since the separator is difficult to short-circuit even at high temperatures, it can be safely used as a separator for a high electromotive force battery.
The separator in this embodiment has high oxidation resistance.
The oxidation resistance of the separator can be judged by the degree of blackening of the separator. The blackening is caused by polyeneization caused by radical oxidation reaction of the binder polymer accompanying the reduction reaction at the positive electrode. And when blackening arises, the strength deterioration of a porous base material layer (A) will be caused. Since the separator in the present embodiment uses the fluorine-based crystalline resin binder (b-1-1) having high oxidation resistance as a part of the resin binder (b-1), the oxidation resistance is extremely high. Blackening of the separator is extremely suppressed.

  The separator has an air permeability of preferably 10 seconds / 100 cc to 650 seconds / 100 cc, more preferably 20 seconds / 100 cc to 500 seconds / 100 cc, and even more preferably 30 seconds / 100 cc to 450 seconds / 100 cc. Hereinafter, it is particularly preferably 50 seconds / 100 cc or more and 400 seconds / 100 cc or less. When the air permeability is 10 seconds / 100 cc or more, self-discharge tends to decrease when used as a battery separator, and when it is 650 seconds / 100 cc or less, good charge / discharge characteristics tend to be obtained.

  The final film thickness of the separator is preferably 2 μm to 200 μm, more preferably 5 μm to 100 μm, and still more preferably 7 μm to 30 μm. When the film thickness is 2 μm or more, the mechanical strength tends to be sufficient, and when the film thickness is 200 μm or less, the occupied volume of the separator is reduced, which tends to be advantageous in terms of increasing the battery capacity.

  Hereinafter, the electricity storage device will be described. The electricity storage device includes the separator, and other configurations may be the same as those conventionally known. The power storage device is not particularly limited, and examples thereof include a battery such as a nonaqueous electrolyte battery, a capacitor, and a capacitor. Among these, a non-aqueous electrolyte battery is preferable, a non-aqueous electrolyte secondary battery is more preferable, and a lithium ion secondary battery is still more preferable from the viewpoint of more effectively obtaining the benefits of the operational effects of the present invention. Hereinafter, a suitable aspect in the case where the electricity storage device is a non-aqueous electrolyte battery will be described.

There is no limitation in a positive electrode, a negative electrode, and a non-aqueous electrolyte, A well-known thing can be used.
Examples of the positive electrode material include lithium-containing composite oxides such as LiCoO ₂ , LiNiO ₂ , spinel type LiMnO ₄ , and olivine type LiFePO ₄ , and examples of the negative electrode material include graphite, non-graphitizable carbonaceous, and easy graphite. Carbonaceous materials such as carbonaceous carbonaceous and composite carbon bodies; silicon, tin, metallic lithium, various alloy materials, and the like.

As the non-aqueous electrolyte, an electrolyte in which an electrolyte is dissolved in an organic solvent can be used. Examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples thereof include lithium salts such as LiClO ₄ , LiBF ₄ , and LiPF ₆ .

  Although the said electrical storage device is not specifically limited, For example, it manufactures as follows. That is, the separator is manufactured as a vertically long separator having a width of 10 to 2,000 mm (preferably 80 to 1,000 mm) and a length of 200 to 4000 m (preferably 1000 to 4000 m). Next, the separator is slit to a width of 10 to 500 mm as necessary. The obtained separator is stacked together with the positive electrode and the negative electrode in the order of positive electrode-separator-negative electrode-separator or negative electrode-separator-positive electrode-separator to obtain a laminate. Next, the laminate is wound into a cylindrical or flat spiral shape to obtain a wound body. And an electrical storage device is obtained by passing the process of accommodating the said winding body in an exterior body, and also inject | pouring electrolyte solution.

The electricity storage device is formed by forming a separator, a positive electrode, and a negative electrode in a flat plate shape, and then laminating in order of positive electrode-separator-negative electrode-separator-positive electrode or negative electrode-separator-positive electrode-separator-negative electrode. After that, it can be manufactured through a process such as housing in an exterior body and injecting an electrolytic solution therein.
In addition, a battery can or a bag-like film can be used as the exterior body.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to an Example. The measurement methods and evaluation methods for various physical properties in the following production examples, examples, and comparative examples are as follows. Unless otherwise stated, various measurements and evaluations were performed under conditions of room temperature 23 ° C., 1 atm, and relative humidity 50%.

<Measurement method>
(1) Porosity of porous substrate layer (A) (% by volume)
A sample of 10 cm × 10 cm square was cut from the porous substrate layer (A), its volume (cm ³ ) and mass (g) were measured, and the film density was 0.95 (g / cm ³ ), and the following formula was used. Calculated.
Porosity (%) = (volume−mass / membrane density) / volume × 100

(2) Air permeability of the separator (sec / 100cc)
In accordance with JIS P-8117, the air resistance measured by a Gurley type densometer G-B2 (trademark) manufactured by Toyo Seiki Seisakusho was used as the air permeability.

(3) Puncture strength (g) of porous substrate layer (A)
Using a handy compression tester KES-G5 (trademark) manufactured by Kato Tech, the porous base material layer (A) was fixed with a sample holder having an opening diameter of 11.3 mm. Under an atmosphere of 25 ° C., a puncture test was performed on the central portion of the fixed porous substrate layer (A) at a puncture speed of 2 mm / sec using a needle having a radius of curvature of 0.5 mm at the tip. The maximum puncture load at this time was defined as the puncture strength (g).

(4) The average pore diameter (μm), curvature, and number of holes of the porous substrate layer (A) When the mean free path of the fluid is larger than the capillary pore diameter, the fluid inside the capillary is small in the Knudsen flow. Is known to follow the flow of Poiseuille. Therefore, it is assumed that the air flow in the air permeability measurement of the porous base material layer (A) follows the Knudsen flow, and the water flow in the water permeability measurement of the porous base material layer (A) follows the Poiseuille flow. .
The average pore diameter d (μm) and the curvature τa (dimensionless) are the air permeation rate constant R _gas (m ³ / (m ² · sec · Pa)) and the water permeation rate constant R _liq (m ³ / ( m ² · sec · Pa)), air molecular velocity ν (m / sec), water viscosity η (Pa · sec), standard pressure Ps (= 101,325 Pa) porosity ε (%), and film thickness L From (μm), the following formula was used.
d = 2ν × (R _liq / R _gas ) × (16η / 3Ps) × 10 ⁶
τa = (d × (ε / 100) × ν / (3L × Ps × P _gas )) ^1/2

Here, R _gas and R _liq are respectively obtained using the following mathematical expressions.
R _gas = 0.0001 / (air permeability × (6.424 × 10 ⁻⁴ ) × (0.01276 × 101,325))
R _liq = water permeability / 100
The air permeability and the water permeability are obtained as follows.
[Air permeability]
The air permeability referred to here can be obtained as the air resistance by measuring the porous substrate layer (A) according to the description of “(2) Air permeability of separator”.
[Water permeability]
A polyolefin microporous membrane previously immersed in ethanol was set in a stainless steel liquid-permeable cell having a diameter of 41 mm, and the ethanol in the membrane was washed with water. Thereafter, water was permeated at a differential pressure of about 50,000 Pa, and the water permeation amount per unit time, unit pressure, unit area was calculated from the water permeation amount (cm ³ ) when 120 seconds had elapsed, and this was regarded as the water permeability. .
In addition, the molecular velocity ν of air is a gas constant R (= 8.314), an absolute temperature T (K), a circumference π, and an average molecular weight M of air (= 2.896 × 10 ⁻² kg / mol). From the above, it is obtained using the following mathematical formula.
ν = {(8R × T) / (π × M)} ^1/2
The number of holes B (pieces / μm ² ) can be obtained from the following formula.
B = 4 × (ε / 100) / (π × d ² × τa)

(5) Thickness (film thickness, μm)
(5) -1 Thickness (μm) of porous substrate layer (A) and separator for electricity storage device
A 10 cm x 10 cm square sample was cut out from each of the porous base material layer (A) and the electricity storage device separator, and the film thicknesses at 9 locations (3 points x 3 points) selected in a lattice shape were measured using a microthickness meter (Toyo Measurement was performed at a room temperature of 23 ± 2 ° C. using a Seiki Seisakusho Co., Ltd., type KBM. The average value of the measured values at nine locations was taken as the thickness (μm) of the porous substrate layer (A) or the separator for the electricity storage device.
(5) -2 Thickness (μm) of porous layer (B)
The thickness of the porous layer (B) was measured by observing the cross section of the separator using a scanning electron microscope (SEM) “Model S-4800, manufactured by HITACHI”. A sample separator was cut to about 1.5 mm × 2.0 mm and stained with ruthenium. The stained sample and ethanol were placed in a gelatin capsule and frozen with liquid nitrogen, and then the sample was cleaved with a hammer. The sample was subjected to osmium vapor deposition and observed at an acceleration voltage of 1.0 kV and 30,000 times, and the thickness of the porous layer was calculated. At this time, in the SEM image, the outermost surface area where the porous structure of the cross section of the polyolefin microporous film was not visible was defined as the area of the porous layer (B).

(6) Glass transition temperature (Tg) of resin binder (b-1)
An appropriate amount of the resin binder (b-1) -containing latex was taken in an aluminum dish and dried in a hot air dryer at 130 ° C. for 30 minutes to obtain a dry film. About 17 mg of the obtained dried film was packed in an aluminum container for measurement, and a DSC curve and a DSSC (DSC differential) curve in a nitrogen atmosphere were obtained using a DSC measuring apparatus (manufactured by Shimadzu Corporation, DSC 6220). The measurement conditions were as follows.
(First stage temperature rise program)
Start at 70 ° C and heat up at a rate of 15 ° C per minute. Maintained for 5 minutes after reaching 110 ° C.
(Second stage temperature drop program)
The temperature drops from 110 ° C at a rate of 40 ° C per minute. Maintain for 5 minutes after reaching -70 ° C.
(Third-stage temperature rising program)
The temperature was raised from -70 ° C to 300 ° C at a rate of 15 ° C per minute. DSC and DDSC data are acquired at the third stage of temperature rise. The peak top temperature of the DDSC curve was taken as the glass transition temperature.

(7) Surface softening temperature of porous layer (B) Both the surface of the separator and black lasha paper are combined and calendered using a calender at a roll temperature of 20 ° C. and a calender roll linear pressure of 10 kgf / cm. It was pulled apart to confirm the presence / absence of transfer to the separator of black lasha paper. When transfer was not confirmed, the calender roll temperature was raised by 5 ° C. and the same test was performed. Thereafter, the same test was repeated while increasing the roll temperature in increments of 5 ° C., and the temperature when the transfer of the black rush paper to the separator was seen was defined as the surface softening temperature of the porous layer (B).

(8) Water contact angle (8) -1 Surface of porous layer (B) and water contact angle of resin binder (b-1) The water contact angle of the surface of porous layer (B) is that of the obtained porous layer (B). A drop of deionized water was placed on the surface and allowed to stand at 23 ° C. for 1 minute, and then measured using a CA-X150 contact angle meter manufactured by Kyowa Interface Science, Japan.
The water contact angle of the resin binder (b-1) is the same as the porous layer (for the film obtained by coating and drying latex containing the resin binder (b-1) on the glass surface with an applicator having a clearance of 1 mm. Measurement was performed using the same apparatus and method as in B).
(8) -2 The average contact of all layers in the water contact angle of the porous layer (B) The porous layer (B) was scraped off from the separator using a manipulator. After thoroughly mixing the obtained powder sample, the melting point of the first resin binder (b-1-1) (melting point on the high temperature side detected by the same method as in (6)) + 30 kg at a temperature of 100 kgf / The film was formed into a film having a thickness of about 100 μm by hot pressing at a pressure of cm ² . About this film, the water contact angle was measured by the method similar to said (8) -1, and the obtained value was made into the all-layer area | region average of the water contact angle of a porous layer (B).

(9) Ratio of fluorine-based crystalline resin binder (b-1-1) and amorphous resin binder (b-1-2) The surface of the porous layer (B) obtained in (8) above and a resin binder ( Fluorine-based crystallinity in a thickness range of 0 to 50% from the outer surface of the porous layer (B), using the water contact angle of b-1) and the average value of all layers of the water contact angle of the porous layer (B) The existing ratio of the resin binder (b-1-1) and the existing ratio of the amorphous resin binder (b-1-1) in the thickness range of 50 to 100% from the outer surface of the porous layer (B) are as follows. It was calculated by calculation.
Assumption 1: The water contact angle of the mixture of the two resin binders (b-1) matches the arithmetic average of the water contact angles of the two resin binders (b-1).
Assumption 2: The inorganic filler (b-2) and other additives do not affect the water contact angle.
Assumption 3: The abundance ratios of the fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) change linearly in the thickness direction of the porous layer (B).

(10) Adhesiveness between separator and electrode The adhesiveness between the separator and the electrode (negative electrode) was evaluated by the following procedure.
(Preparation of negative electrode)
Artificial graphite 96.9% by mass as the negative electrode active material, 1.4% by mass of ammonium salt of carboxymethylcellulose (solid content conversion) as the binder, and styrene-butadiene copolymer latex (particle size 80 nm, glass transition temperature −40 ° C.) 7% by mass (in terms of solid content) was dispersed in purified water to prepare a slurry. This slurry was applied to one side of a 12 μm thick copper foil serving as a negative electrode current collector with a die coater, dried at 120 ° C. for 3 minutes, and then compression molded with a roll press to obtain a negative electrode. At this time, the active material coating amount of the negative electrode was set to 106 g / m ² , and the active material bulk density was set to 1.35 g / cm ³ .

(Adhesion test)
The negative electrode obtained by the above method was cut into a width of 20 mm and a length of 40 mm. On this negative electrode, an electrolyte solution (manufactured by Toyama Pharmaceutical Co., Ltd.) in which ethylene carbonate and diethyl carbonate were mixed at a ratio (volume ratio) of 2: 3 was poured to the extent that the negative electrode was immersed, and a separator was laminated to obtain a laminate. It was. This laminate was placed in an aluminum zip and pressed at 80 ° C. and 10 MPa for 2 minutes.
Thereafter, the laminate was taken out, the separator was peeled off from the electrode, observed visually, and evaluated according to the following criteria.

(Evaluation criteria)
○ (good): When the negative electrode active material adheres to 30% or more of the separator area Δ (possible): When the negative electrode active material adheres to 10% or more and less than 30% of the separator area × (defect): 10 of the separator area When the negative electrode active material adheres to less than

(11) Stickiness and coating layer peel strength A positive electrode current collector (Ashiji processed paper Co., Ltd. aluminum foil 20 μm) cut to 30 mm × 150 mm as an adherend was overlaid with a separator to obtain a laminate. . The obtained laminate was sandwiched between two Teflon (registered trademark) sheets (Nichias Co., Ltd., Naflon PTFE (polytetrafluoroethylene) sheet TOMBO-No. 9000), and the press conditions were varied as follows. By performing pressing, two types of test samples with different pressing conditions were obtained.
Condition 1) Pressurization at a temperature of 25 ° C. and a pressure of 5 MPa for 3 minutes Condition 2) Pressurization at a temperature of 80 ° C. and a pressure of 10 MPa for 3 minutes

The peel strength of each test sample obtained was measured at a tensile speed of 200 mm / min according to JIS K6854-2. As a measuring device, an autograph AG-IS type (trademark) manufactured by Shimadzu Corporation was used.
Based on the obtained results, the peel strength of the separator was evaluated according to the following evaluation criteria.

[Sticky]
Regarding the sample after pressing under condition 1)
○ (good): When peel strength is 6 gf / cm or less Δ (possible): When peel strength exceeds 6 gf / cm and is 8 gf / cm or less × (poor): Peel strength is 8 gf / cm The super-obtained case was used as an index of stickiness and handling properties.

[Coating layer peel strength]
Regarding the sample after pressing in condition 2)
○ (Good): When the peel strength is 15 gf / cm or more Δ (Yes): When the peel strength is 10 gf / cm or more and less than 15 gf / cm × (Poor): The peel strength is less than 10 gf / cm It was used as an index of adhesion to the electrode, adhesive strength with the porous substrate layer (A), and binding strength of the inorganic filler (b-2).

(11) Battery cycle characteristics and separator oxidation resistance (11-1) Preparation of sample for evaluation [Preparation of electrode]
A negative electrode was prepared in the same manner as “(Preparation of negative electrode)” in “(9) Adhesiveness between separator and electrode”.
The positive electrode was produced as follows.
(Preparation of positive electrode)
92.2% by mass of lithium cobalt composite oxide (LiCoO ₂ ) as the positive electrode active material, 2.3% by mass of flake graphite and acetylene black as the conductive material, and 3.2% by mass of polyvinylidene fluoride as the binder (Solid content conversion) was dispersed in N-methylpyrrolidone (NMP) to prepare a slurry. This slurry was applied to one side of a 20 μm thick aluminum foil serving as a positive electrode current collector with a die coater, dried at 130 ° C. for 3 minutes, and then compression molded with a roll press to obtain a positive electrode. At this time, the active material coating amount of the positive electrode was 250 g / m ² and the active material bulk density was 3.00 g / cm ³ .

The positive electrode was cut to a width of about 57 mm, and the negative electrode was cut to a width of about 58 mm to form a strip, thereby preparing an evaluation electrode.
[Adjustment of non-aqueous electrolyte]
The non-aqueous electrolyte was prepared by dissolving LiPF ₆ as a solute at a concentration of 1.0 mol / L in a mixed solvent composed of ethylene carbonate / diethyl carbonate = 2/3 (volume ratio).
[Preparation of separator]
The separator for evaluation was produced by cut | disconnecting each separator obtained by the Example and the comparative example into 60 mm, and making it strip | belt shape.

(11-2) Evaluation of battery cycle characteristics [Assembly of battery]
The electrode and separator obtained in (11-1) are stacked in the order of negative electrode, separator, positive electrode and separator, wound at a winding speed of 250 gf, winding speed of 45 mm / second, and spirally wound a plurality of times. An electrode laminate was prepared. Here, the separator was laminated | stacked by making the surface in which the porous layer was formed into the negative electrode side. The electrode laminate is housed in a stainless steel container having an outer diameter of 18 mm and a height of 65 mm. An aluminum tab derived from the positive electrode current collector is used as the container lid terminal portion, and a nickel tab derived from the negative electrode current collector is used as the container. Welded to the wall. Then, it dried for 12 hours at 80 degreeC under vacuum. In the argon box, the non-aqueous electrolyte was poured into the assembled battery container and sealed to prepare an evaluation battery.

[Preprocessing]
The battery assembled as described above was charged with a constant current up to a voltage of 4.2 V at a current value of 1/3 C, then charged with a constant voltage of 4.2 V for 8 hours, and then 3.0 V with a current of 1/3 C. Discharge was performed to the end voltage. Next, after constant current charging to a voltage of 4.2 V with a current value of 1 C, 4.2 V constant voltage charging was performed for 3 hours, and then discharging was performed to a final voltage of 3.0 V with a current of 1 C. Finally, after constant current charging to 4.2 V with a current value of 1 C, 4.2 V constant voltage charging was performed for 3 hours, and the pretreatment was completed.
1C represents a current value for discharging the reference capacity of the battery in one hour.

[Cycle test]
About the battery which performed the said pretreatment, after discharging to discharge end voltage 3V with discharge current 1A on the conditions of temperature 25 degreeC, it charged to charge end voltage 4.2V with charge current 1A. Charging / discharging was repeated with this as one cycle, the capacity retention after 200 cycles with respect to the initial capacity was examined, and the cycle characteristics were evaluated according to the following criteria.
(Evaluation criteria)
○ (good): When the capacity retention is 95% or more and 100% or less △ (possible): When the capacity retention is 90% or more and less than 95% × (defect): When the capacity retention is less than 90% If there is

[Oxidation resistance of separator]
About the battery which performed the pre-processing similar to the above, after carrying out the constant current charge to the voltage of 4.2V by the electric current of 1C, the constant voltage charge of 4.2V was performed for 100 hours under 70 degreeC environmental temperature. The separator was taken out from the battery, subjected to ultrasonic cleaning in dimethoxyethane, ethanol, and hydrochloric acid having a concentration of 1 N for 15 minutes each and then dried in air. And about the separator after drying, the area ratio of the black change of the positive electrode contact surface side surface was investigated, and the degree of oxidation resistance was evaluated with the following references | standards.
When the area ratio changed to black is less than 10%: ○ (oxidation resistance “good”)
When the blackened area ratio is 10% or more: ○ (oxidation resistance “bad”)

<Production of resin binder (b-1)>
(Production Example 1a) Production of acrylic polymer latex In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer, 70.4 parts by mass of ion-exchanged water, “AQUALON KH1025” (trade name, No. 1) Ichi Kogyo Seiyaku Co., Ltd., 25% by weight aqueous solution) 0.085 parts by mass (in terms of solid content) and “Adekaria Soap SR1025” (trade name, manufactured by ADEKA Corporation, 25% by mass aqueous solution) 0.085 parts by mass ( Solid content conversion), and the temperature inside the reaction vessel was raised to 80 ° C., while maintaining the temperature at 80 ° C., 0.15 part by mass of ammonium persulfate (2% by mass aqueous solution) (in terms of solid content) Added.
5 minutes after adding the ammonium persulfate aqueous solution, 85 parts by weight of methyl methacrylate, 5.4 parts by weight of n-butyl acrylate, 2 parts by weight of 2-ethylhexyl acrylate, 0.1 part by weight of methacrylic acid, 0.1 parts of acrylic acid Part by mass, 2 parts by mass of 2-hydroxyethyl methacrylate, 5 parts by mass of acrylamide, 0.4 parts by mass of glycidyl methacrylate, 0.7 parts by mass of trimethylolpropane triacrylate (A-TMPT, manufactured by Shin-Nakamura Chemical Co., Ltd.) , "AQUALON KH1025" (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 25% by weight aqueous solution) 0.75 parts by mass (solid content conversion), "ADEKA rear soap SR1025" (trade name, manufactured by ADEKA Corporation, 25 mass) % Aqueous solution) 0.75 parts by mass (in terms of solid content), 0.05 parts by mass of sodium p-styrenesulfonate, persulfuric acid A mixture of 0.15 parts by weight of ammonia (2% by weight aqueous solution) (in terms of solid content), 0.3 parts by weight of γ-methacryloxypropyltrimethoxysilane, and 52 parts by weight of ion-exchanged water was mixed for 5 minutes using a homomixer. Thus, an emulsion was prepared. The obtained emulsion was dropped from the dropping tank into the reaction vessel over 150 minutes.
After completion of the dropwise addition of the emulsion, the reaction container was maintained at an internal temperature of 80 ° C. for 90 minutes and then cooled to room temperature to obtain an emulsion. A latex containing an acrylic polymer (1a) having a concentration of 40% by mass was obtained by adding ammonium hydroxide aqueous solution (25% by mass aqueous solution) to the obtained emulsion and adjusting the pH to 9.0.
As a result of observation with a transmission electron microscope (TEM), it was found that the acrylic polymer (1a) was spherical and monodispersed with a particle diameter of 161 nm. The obtained acrylic polymer (1a) had a water contact angle of 57 degrees and a glass transition temperature of 90 ° C.

(Production Example 1b) Production of Acrylic Polymer Latex Acrylic polymer having a solid content concentration of 40% by mass by operating in the same manner as in Production Example 1a, except that the amounts used of the following components were changed as described below. A latex containing polymer (1b) was obtained.
[Initial preparation]
Aqualon KH1025 (25% by mass aqueous solution): 0.45 parts by mass (solid content conversion)
ADEKA rear soap SR1025 (25 mass% aqueous solution): 0.45 mass part (solid content conversion)
Ammonium persulfate (2% by mass aqueous solution): 0.15 parts by mass (in terms of solid content)
[Monomer in emulsion]
Methyl methacrylate: 30.5 parts by mass n-butyl acrylate: 60.8 parts by mass 2-ethylhexyl acrylate: 2 parts by mass Methacrylic acid: 1 part by mass Acrylic acid: 1.5 parts by mass 2-hydroxyethyl methacrylate: 2 parts by mass Acrylamide: 0.2 parts by mass Glycidyl methacrylate: 2 parts by mass Trimethylolpropane triacrylate: 0.7 parts by mass As a result of observation with a transmission electron microscope (TEM), the acrylic polymer (1b) has a particle size of It was 121 nm spherical and monodisperse. Moreover, the water contact angle of the obtained acrylic polymer (1b) was 58 degrees, and the glass transition temperature was −20 ° C.

(Production Example 1c) Production of Polyvinylidene Fluoride Latex A low molecular weight polyvinylidene fluoride (PVDF) latex (1c) was produced as follows with reference to the description of Examples in Japanese Patent No. 3824331.
In a 7.5 liter stainless steel horizontal reactor equipped with a paddle stirrer, 4,375 g of demineralized water and 4 g of hydrocarbon wax melting at 50 ° C. to 60 ° C. were introduced. The reactor was sealed, degassed with a nitrogen stream and discharged. Thereafter, 1,000 g of demineralized and deaerated water containing 2.99 g of ammonium perfluorooctanoate was added. The reactor was then heated to 120 ° C. and brought to a pressure of 650 psig with gaseous vinylidene fluoride (VDF). Furthermore, 8.0 ml of methyl-tert-butyl-ether was added as a chain transfer agent. Then, 19.1 ml of di-tert-butyl-peroxide was introduced therein to start the reaction. After an introduction period of about 15 minutes, the system pressure began to drop, confirming the start of the reaction. Thereafter, VDF was continuously supplied, the pressure was maintained at 650 psig and the temperature at 120 ° C. After 3 hours, the monomer feed was stopped. Up to this point, a total of 1,898 g of VDF has been supplied.
By waiting for the reactor pressure to decrease to 150 psig, then cooling the reactor and discharging unreacted VDF. A latex containing 25% by mass of polyvinylidene fluoride (1c) was obtained.
The polyvinylidene fluoride (1c) obtained had a water contact angle of 82 degrees and a melting point of 170 ° C.

(Production Example 1d) Method for Producing Fluorinated Acrylic Polymer Latex With reference to the example of Japanese Patent No. 5348444, fluorinated acrylic polymer latex (1d) was produced as follows.
The inside of an autoclave having an internal volume of about 6 L equipped with an electromagnetic stirrer was sufficiently purged with nitrogen, then 2.5 L of deoxygenated pure water and 25 g of ammonium perfluorodecanoate as an emulsifier were charged and stirred at 350 rpm at 60 ° C. The temperature was raised to. Next, a mixed gas composed of 70% by mass of vinylidene fluoride (VDF) as a monomer and 30% by mass of propylene hexafluoride (HFP) was introduced until the internal pressure reached 20 kg / cm ² .
Thereafter, 10.0 g of a 1,3-dichloro-1,1,2,2,3-pentafluoropropane (HCFC-225cb) solution containing 50% by mass of diisopropyl peroxydicarbonate as a polymerization initiator was added with nitrogen gas. The polymerization was started by press-fitting.
During the polymerization, a mixed gas consisting of 60.2% by mass of VDF and 39.8% by mass of HFP was successively injected so that the internal pressure was maintained at 20 kg / cm ² . Further, since the polymerization rate decreased as the polymerization progressed, the same amount of the same polymerization initiator solution as described above was injected using nitrogen gas after 3 hours, and the reaction was continued for 3 hours.
Thereafter, 5 parts by mass of glycidyl methacrylate was added to the reaction solution, and the reaction was continued for another 3 hours. Then, the reaction solution was cooled, and simultaneously stirring was stopped. After the unreacted monomer was released, the reaction was stopped. A latex containing 40% by mass of polymer particles was obtained.

Next, in a separable flask with a volume of 7 L, 2 parts by mass of 3,5,5-trimethylhexanoyl peroxyside (trade name “Perroyl 355”, manufactured by NOF Corporation, water solubility: 0.01%), lauryl sulfate Sodium 0.1 mass part and water 20 mass part were prepared, and it stirred and emulsified. The latex produced above was added in an amount corresponding to 50 parts by mass in terms of polymer particles and stirred for 16 hours.
Next, after sufficiently replacing the inside of the separable flask with nitrogen, 20 parts by mass of methyl methacrylate, 25 parts by mass of 2-ethylhexyl acrylate, and 5 parts by mass of methacrylic acid were added, and stirred slowly at 40 ° C. for 3 hours. These monomer components were absorbed into the polymer particles. Thereafter, the temperature of the reaction system was raised to 75 ° C. and reacted for 3 hours, and further reacted at 85 ° C. for 2 hours. Thereafter, after cooling, the reaction was stopped, and the pH was adjusted to 7 with a 2.5N aqueous sodium hydroxide solution to obtain a latex containing 40% by mass of particles of the fluorinated acrylic polymer (1d). The obtained fluorinated acrylic polymer (1d) had a water contact angle of 68 ° and a glass transition temperature of −5 ° C. Met.

Example 1
47.5 parts by mass of homopolymer polyethylene having a volume average molecular weight of 700,000, 47.5 parts by mass of homopolymer polyethylene having a volume average molecular weight of 250,000, and 5 parts by mass of polypyrene pyrene having a volume average molecular weight of 400,000 Dry blended using a tumbler blender. 1 part by mass of pentaerythrityl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) furopionone] as an antioxidant is added to 99 parts by mass of the polymer mixture obtained. Then, a polymer equal mixture was obtained by dry blending again using a tumbler blender.
The obtained polymer equal mixture was purged with nitrogen and then fed to a twin screw extruder by a feeder under a nitrogen atmosphere. Further, liquid paraffin (kinematic viscosity at 37.78 ° C .: 7.59 × 10 ⁻⁵ m ² / s) was injected into the extruder cylinder by a plunger pump. The feeder and pump were adjusted so that the ratio of the amount of liquid paraffin in the total mixture extruded by melt kneading was 67% by mass (the concentration of the mixture such as polymer was 33% by mass). The melt kneading conditions were as follows: a preset temperature of 200 ° C., a screw rotation speed of 100 rpm, and a discharge rate of 12 kg / h.

The obtained melt-kneaded product was extruded and cast via a T-die on a cooling roll controlled at a surface temperature of 25 ° C. to obtain a gel sheet having a thickness of 1,600 μm. Next, this gel sheet was guided to a simultaneous biaxial tenter stretching machine, and biaxial stretching was performed. The set stretching conditions were an MD magnification of 7.0 times, a TD magnification of 6.1 times, and a preset temperature of 121 ° C. The stretched gel sheet was introduced into a methyl ethyl ketone bath and sufficiently immersed in methyl ethyl ketone to extract and remove the liquid paraffin, and then the methyl ethyl ketone was removed by drying. Next, the processed sheet was guided to a TD tenter and heat-set. The heat setting temperature was 120 ° C., the TD maximum magnification was 2.0 times, and the relaxation rate was 0.90.
As a result of these series of treatments, the film thickness is 17 μm, the porosity is 60%, the air permeability is 84 seconds / 100 cc, the average pore diameter d = 0.57 μm, the curvature τa = 1.45, the number of holes B = 165 / μm ^2. A polyolefin resin porous membrane (A1) having a pin puncture strength of 5,679 f in terms of 25 μm was obtained.

[Preparation of coating solution]
Next, as the inorganic filler (b-2), fired kaolin (wet kaolin mainly composed of kaolinite (Al ₂ Si ₂ O ₅ (OH) ₄ ) subjected to high-temperature firing treatment, average particle size 1.8 μm 92.5 parts by mass;
As resin binder (b-1),
2 parts by mass of the polyvinylidene fluoride (1c) latex obtained in Production Example 1c in terms of solid content, and 5 parts by mass of the acrylic polymer (1b) latex obtained in Production Example 1b in terms of solid content,
A coating liquid is prepared by uniformly dispersing 0.5 parts by mass (in terms of solid content) of ammonium polycarboxylate aqueous solution (San Nopco, SN Dispersant 5468, 40% by mass aqueous solution) in 180 parts by mass of water. did.

[Formation of porous layer (B) (manufacture of separator)]
On one side of the polyolefin microporous membrane (A1) obtained in [Manufacture of porous substrate layer (A) membrane], the coating solution obtained in [Preparation of coating solution] was applied with a microgravure coater. . The obtained coating film was dried at 60 ° C. to remove water, and a porous layer (B) having a thickness of 7 μm was formed on one side of the porous substrate layer (A) to obtain a separator.
The obtained separator was evaluated by the above method. The obtained results are shown in Table 1.

Example 2 and Comparative Examples 1-5
In Example 1, except that the resin binder (b-1) shown in Table 1 was used in the amount shown in Table 1 as the solid content converted value, the coating was performed in the same manner as in Example 1. A working solution was prepared to produce a separator.
In addition, about the comparative example 1, two types of amorphous binders (b-1-2) were used together.
The obtained separator was evaluated by the above method. The obtained results are shown in Table 1.
“100 <” and “<20” in the surface softening temperature column of Table 1 indicate that the surface softening temperature was higher than 100 ° C. or lower than 20 ° C., respectively.

The separator of the present invention is excellent in adhesion to the electrode, stickiness, water repellency, oxidation resistance, and productivity.
The electricity storage device including the separator of the present invention can maintain a high capacity for a long period.
Therefore, the separator of the present invention can be suitably used as a separator for an electricity storage device such as a battery such as a non-aqueous electrolyte secondary battery; a capacitor; a capacitor.

Claims (9)

A porous substrate layer (A);
A separator having a porous layer (B) containing an inorganic filler (b-2), a fluorine-based crystalline resin binder (b-1-1), and an amorphous resin binder (b-1-2), ,
The surface softening temperature of the porous layer (B) is 30 to 60 ° C.,
The water contact angle on the surface of the porous layer (B) is 75 degrees or more ,
All layer region average 60 to 80 degrees der water contact angle of the multi-porous layer (B) is, and
A separator for an electricity storage device , wherein a water contact angle on the surface of the porous layer (B) is larger than an average of all layer regions of a water contact angle of the porous layer (B) .   The separator according to claim 1, wherein an average of all layers of the water contact angle of the porous layer (B) is 60 to 72 degrees. The separator according to claim 1 or 2 , wherein a water contact angle difference between the fluorine-based crystalline resin binder (b-1-1) and the amorphous resin binder (b-1-2) is 10 degrees or more. . The water contact angle of the fluorine-based crystalline resin binder (b-1-1) is 80 degrees or more, and the water contact angle of the amorphous resin binder (b-1-2) is 70 degrees or less. Item 4. The separator according to any one of Items 1 to 3 . The separator as described in any one of Claims 1-4 whose melting temperature of the said fluorine-type crystalline resin binder (b-1-1) is 100 degreeC or more. The fluorine-based crystalline resin binder (b-1-1) is a polymer or copolymer of a monomer containing at least one selected from the group consisting of vinylidene fluoride and ethylene fluoride. The separator according to any one of 5 . The electrical storage device separator according to any one of claims 1 to 6 , wherein the separator has an air permeability of 10 to 500 seconds / 100 cc. Electrodes,
A laminate comprising the electricity storage device separator according to any one of claims 1 to 7 laminated. An electrical storage device comprising the laminate according to claim 8 .