JP2019179698A - Power storage device separator and laminate including the same, wound body, lithium ion secondary battery and power storage device - Google Patents

Abstract

To provide a power storage device separator excellent in adhesiveness with an electrode and heat resistance and also excellent in ion permeability.SOLUTION: A power storage device separator includes: a base material; an inorganic filler porous layer formed on at least one face of the base material; and a thermoplastic polymer-containing layer formed on at least a part of a surface of the inorganic filler porous layer. The inorganic filler porous layer includes inorganic fillers and has a plurality of pores. The thermoplastic polymer-containing layer contains a thermoplastic polymer. The thermoplastic polymer includes a particulate polymer, the average particle size of the particulate polymer being larger than the average pore size of the inorganic filler porous layer.SELECTED DRAWING: None

Description

  The present invention relates to a separator for an electricity storage device and a laminate, a wound body, a lithium ion secondary battery, and an electricity storage device using the separator.

  In recent years, power storage devices represented by lithium ion secondary batteries have been actively developed. Usually, a power storage device is provided with a microporous membrane (separator) between positive and negative electrodes. The separator has a function of preventing direct contact between the positive and negative electrodes and allowing ions to permeate through the electrolytic solution held in the micropores.

  Conventionally, separators have characteristics that quickly stop the battery reaction when abnormally heated (fuse characteristics), maintain the shape even at high temperatures, and prevent the risk of a direct reaction between the positive and negative electrode materials Performance related to safety such as performance (short characteristics) is required.

  For the purpose of producing a battery with high safety, Patent Document 1 describes a technique for forming a separator having a porous layer containing inorganic particles and a resin binder on a polyolefin microporous film.

  In recent years, against the background of increasing the capacity of power storage devices such as batteries, a technique for reducing the volume of a wound body by hot pressing a wound body in which electrodes and separators are stacked is used. At this time, by providing the separator with adhesiveness to the electrode, the electrode and the separator are fixed after pressing, and the volume during pressing can be maintained. In addition, in the stack system in which the electrodes and separators on the single wafer are stacked one by one, the electrode and the separator are likely to be misaligned during handling of the stacked body after stacking. However, by providing the separator with adhesiveness to the electrode, the positional deviation of the stacked body conveyed at high speed is suppressed, and it becomes possible to manufacture an electricity storage device with high productivity.

  The separator having adhesiveness as described above is required to exhibit adhesiveness before the step of injecting the electrolytic solution into the wound body.

  Under such circumstances, for example, Patent Document 2 proposes a technique for supporting an aqueous dispersion of a particle-shaped acrylic copolymer on a base material as an attempt to provide adhesion to a separator. .

  Patent Document 3 discloses an aqueous dispersion of a particle-shaped acrylic copolymer on a porous layer containing inorganic particles and a resin binder for the purpose of achieving both safety and adhesion with an electrode. A technique for supporting a thermoplastic polymer layer is also disclosed.

Japanese Patent No. 5354735 JP-A-2015-128059 Japanese Patent No. 6105816

  In order to impart heat resistance and adhesion to the electrode to the porous film, it is desirable to have both a heat resistant layer containing inorganic particles and a thermoplastic polymer layer as described in Patent Document 3. However, when the inorganic filler porous layer and the thermoplastic polymer layer described in Patent Document 3 are laminated at the same time, the thermoplastic polymer is hardly supported on the inorganic filler porous layer, and is likely to fall into pores existing between the inorganic fillers. In this case, it is necessary to fill the pores existing between the inorganic fillers with a thermoplastic polymer in order to more fully develop the adhesion with the electrodes. As a result, an extra thermoplastic polymer is used, and the ion permeability of the separator tends to decrease.

  The present invention has been made in view of the above circumstances, and has a separator for an electricity storage device that is excellent in adhesion and heat resistance with an electrode and also has excellent ion permeability, and a laminate and a wound body using the separator. It aims at providing a lithium ion secondary battery and an electrical storage device.

The present inventors have found that the above problem can be solved by optimizing the combination of the inorganic particle layer disposed on the separator substrate and the thermoplastic resin layer disposed on the surface thereof, The present invention has been completed. That is, the present invention is as follows: [1] A substrate, an inorganic filler porous layer formed on at least one surface of the substrate, and at least a part of the surface of the inorganic filler porous layer A separator for an electricity storage device comprising the formed thermoplastic polymer-containing layer, wherein the inorganic filler porous layer includes an inorganic filler and has a plurality of pores, and the thermoplastic polymer-containing layer includes a heat An electricity storage device separator comprising a plastic polymer, wherein the thermoplastic polymer includes a particulate polymer, and the arithmetic average particle size of the particulate polymer is larger than the average pore size of the inorganic filler porous layer.
[2] A base material, an inorganic filler porous layer formed on at least one surface of the base material, and a thermoplastic polymer-containing layer formed on at least a part of the surface of the inorganic filler porous layer. The inorganic filler porous layer includes an inorganic filler and has a plurality of pores, the thermoplastic polymer-containing layer includes a thermoplastic polymer, and the thermoplastic polymer includes A separator for an electricity storage device comprising a particulate polymer, wherein the content of the particulate polymer contained in the inorganic filler porous layer is 20% by volume or less based on the total amount of the inorganic filler porous layer. .
[3] A base material, an inorganic filler porous layer formed on at least one surface of the base material, and a thermoplastic polymer-containing layer formed on at least a part of the surface of the inorganic filler porous layer. The inorganic filler porous layer includes an inorganic filler and has a plurality of pores, the thermoplastic polymer-containing layer includes a thermoplastic polymer, and the thermoplastic polymer includes Including a particulate polymer, the average particle diameter D50 of the inorganic filler is 0.5 μm or more and less than 1.0 μm, and the arithmetic average particle diameter of the particulate polymer is 0.20 μm or more and 1.0 μm or less. , Separator for electricity storage devices.
[4] The above-mentioned separator for an electricity storage device, wherein the particulate polymer has (meth) acrylic acid ester as a monomer unit.
[5] The above separator for an electricity storage device, wherein the glass transition point of the particulate polymer is 50 ° C. or higher.
[6] The above-mentioned separator for an electricity storage device, wherein the thermoplastic polymer-containing layer has a surface coverage with respect to the inorganic filler porous layer of 70% or less.
[7] The above-mentioned separator for an electricity storage device, wherein the thermoplastic polymer-containing layer is a layer that exists in the form of dots on the surface of the substrate.
[8] The above separator for an electricity storage device, wherein the inorganic filler porous layer has a thickness of 5.0 μm or less.
[9] The above-mentioned electricity storage device separator, wherein the electricity storage device separator has a heat shrinkage ratio at TD at 130 ° C. of 10% or less.
[10] The above-mentioned separator for an electricity storage device, wherein the inorganic filler contains an inorganic oxide.
[11] The above separator for an electricity storage device, wherein the porosity of the base material is greater than 40%.
[12] The power storage device separator, wherein the puncture strength of the power storage device separator is 300 gf / 20 μm or more.
[13] A laminate including a positive electrode, the above-described separator for an electricity storage device, and a negative electrode.
[14] A wound body obtained by winding a positive electrode, the above-described electricity storage device separator, and a negative electrode.
[15] An electricity storage device comprising the laminate or the wound body and an electrolytic solution.
[16] A lithium ion secondary battery comprising the laminate or the wound body and an electrolytic solution.

  According to the present invention, a separator for an electricity storage device that is excellent in adhesiveness and heat resistance with an electrode and also in ion permeability, a laminate, a wound body, a lithium ion secondary battery, and an electricity storage device using the separator. Can be provided.

It is explanatory drawing for demonstrating the measurement of the average hole diameter of an inorganic filler porous layer. It is explanatory drawing for demonstrating the measurement of the average hole diameter of an inorganic filler porous layer.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. However, the present invention is limited to the following embodiment. It is not a thing. The present invention can be variously modified without departing from the gist thereof. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. In the present specification, “(meth) acryl” means “acryl” and “methacryl” corresponding thereto, “(meth) acrylate” means “acrylate” and “methacrylate” corresponding thereto, “(Meth) acryloyl” means “acryloyl” and its corresponding “methacryloyl”.

<Separator for electricity storage device>
The separator for an electricity storage device of the present embodiment (hereinafter also simply referred to as “separator”) includes a base material, an inorganic filler porous layer formed on at least one surface of the base material, and a surface of the inorganic filler porous layer. And a thermoplastic polymer-containing layer formed on at least a part of. In the separator for an electricity storage device of the present embodiment, the thermoplastic polymer-containing layer containing a particulate polymer is disposed on at least one surface of the inorganic filler porous layer, whereby adhesion to the electrode active material, And excellent ion permeability. Hereinafter, preferred embodiments of each member constituting the electricity storage device separator of the present embodiment and a method for producing the electricity storage device separator will be described in detail.

[Base material]
The substrate used in the present embodiment may itself be one that has been conventionally used as a separator. As the base material, a porous film is preferable, and the porous film is more preferably a porous film having a fine pore size, having no electron conductivity and ionic conductivity, high resistance to organic solvents. As such a porous membrane, for example, a polyolefin-based (for example, polyethylene, polypropylene, polybutene and polyvinyl chloride), and a microporous membrane containing a resin such as a mixture or copolymer thereof as a main component, polyethylene terephthalate, Microporous membrane containing resin such as polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene, woven polyolefin fiber (woven fabric) ), Polyolefin fiber nonwoven fabric, paper, and aggregates of insulating substance particles. These are used singly or in combination of two or more. Among these, a polyolefin microporous membrane containing a polyolefin-based resin as a main component from the viewpoint of increasing the active material ratio in a power storage device such as a battery by increasing the thickness of the separator and increasing the capacity per volume. Is preferred. Since the polyolefin microporous film is excellent in the coating property of the coating liquid when a polymer layer is obtained through a coating process, the thickness of the separator can be further reduced. Here, “containing a polyolefin-based resin as a main component” means containing 50% by mass or more based on the total amount of the base material. The content of the polyolefin resin is preferably 75% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 98% by mass or more. 100 mass%.

  In the present embodiment, when a polyolefin microporous membrane (hereinafter also referred to as “polyolefin porous substrate”) is used as the substrate, the content of the polyolefin resin in the polyolefin microporous membrane is not particularly limited. However, from the viewpoint of shutdown performance when used as a separator for an electricity storage device, it is preferable that 50% by mass or more and 100% by mass or less of all components constituting the polyolefin microporous membrane is a polyolefin resin. The content of the polyolefin resin 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, based on all components constituting the polyolefin microporous membrane.

  Although it does not specifically limit as polyolefin resin, The polyolefin resin which can be used for normal extrusion, injection, inflation, blow molding, etc. may be sufficient. Examples of the polyolefin resin include homopolymers having monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene, and two types of these monomers. The above copolymer and multistage polymer are mentioned. These homopolymers, copolymers, and multistage polymers are used singly or in combination of two or more.

Representative examples of the polyolefin resin are not particularly limited, and examples thereof include polyethylene, polypropylene, and polybutene. More specifically, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ultrahigh molecular weight. Examples include polyethylene, isotactic polypropylene, atactic polypropylene, ethylene-propylene random copolymer, polybutene, and ethylene propylene rubber. These are used singly or in combination of two or more. As the polyolefin resin, polyethylene such as low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, and ultrahigh molecular weight polyethylene is preferable from the viewpoint of shutdown characteristics in which pores are blocked by heat melting. In particular, since it has a low melting point and high strength, high-density polyethylene is preferable, and polyethylene having a density measured according to JIS K 7112 of 0.93 g / cm ³ or more is more preferable. There is no restriction | limiting in particular in the polymerization catalyst used in the case of manufacture of these polyethylenes, For example, a Ziegler-Natta catalyst, a Philips catalyst, and a metallocene catalyst are mentioned.

  In order to improve the heat resistance of the polyolefin porous substrate, the polyolefin porous substrate preferably contains polypropylene and a polyolefin resin other than polypropylene. Here, the three-dimensional structure of polypropylene is not limited, and any of isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene may be used. Examples of polyolefin resins other than polypropylene include, for example, homopolymers having ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and the like as monomers, and single amounts thereof. Two or more types of copolymers and multi-stage polymers may be mentioned, and specific examples include those already described above.

  The content ratio of polypropylene with respect to the total amount of polyolefin in the polyolefin porous substrate is not particularly limited, but is preferably 1 to 35% by mass, more preferably 3 from the viewpoint of achieving both heat resistance and a good shutdown function. -20% by mass, more preferably 4-10% by mass. From the same viewpoint, the content ratio of the olefin resin other than polypropylene, for example, polyethylene, relative to the total amount of polyolefin in the polyolefin porous substrate is preferably 65 to 99% by mass, more preferably 80 to 97% by mass, Preferably it is 90-96 mass%. Used when producing polypropylene. The polymerization catalyst is not particularly limited, and examples thereof include a Ziegler-Natta catalyst and a metallocene catalyst.

  Examples of polyolefin resins other than polyethylene and polypropylene include polybutene and ethylene-propylene random copolymers.

The viscosity average molecular weight of the polyolefin resin constituting the polyolefin porous substrate is not particularly limited, but is preferably 30,000 or more and 12 million or less, more preferably 50,000 or more and less than 2 million, and still more preferably 100,000 or more and 100 or less. Less than 10,000. A viscosity average molecular weight of 30,000 or more is preferable because the melt tension at the time of melt molding becomes large and the moldability becomes better, and the strength tends to become higher due to entanglement between polymers. On the other hand, a viscosity average molecular weight of 12 million 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 the viscosity average molecular weight is less than 1,000,000, it is preferable because pores are likely to be blocked when the temperature rises, and a better shutdown function tends to be obtained. The viscosity average molecular weight (Mv) is calculated from the intrinsic viscosity [η] measured at a measurement temperature of 135 ° C. using decalin as a solvent based on ASTM-D4020 by the following formula.
Polyethylene: [η] = 6.77 × 10 ⁻⁴ Mv ^0.67 (Chiang formula)
Polypropylene: [η] = 1.10 × 10 ⁻⁴ Mv ^0.80

  Further, for example, instead of using a polyolefin having a viscosity average molecular weight of less than 1 million alone, a mixture of a polyolefin having a viscosity average molecular weight of 2 million and a polyolefin having a viscosity average molecular weight of 270,000, the mixture having a viscosity average molecular weight of less than 1 million May be used.

  The polyolefin porous substrate in the present embodiment can contain any additive. Such additives are not particularly limited, and include, for example, polymers other than polyolefins; inorganic particles; antioxidants such as phenols, phosphoruss, and sulfurs; metal soaps such as calcium stearate and zinc stearate; Agents; light stabilizers; antistatic agents; antifogging agents; colored pigments and the like. The total content of these additives is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass with respect to 100 parts by mass of the polyolefin resin in the polyolefin porous substrate. It is as follows.

The porosity of the polyolefin porous substrate in the present embodiment is not particularly limited, but is preferably 20% or more, more preferably 35% or more, and further preferably more than 40%. On the other hand, the porosity is preferably 90% or less, more preferably 80% or less. Setting the porosity to 20% or more is preferable from the viewpoint of securing the separator permeability more effectively and reliably. On the other hand, setting the porosity to 90% or less is preferable from the viewpoint of ensuring the puncture strength more effectively and reliably. Here, the porosity is calculated, for example, from the volume (cm ³ ), mass (g), and film density (g / cm ³ ) of the sample of the polyolefin porous substrate:
Porosity = (volume−mass / film density) / volume × 100
It can ask for. Here, for example, in the case of a polyolefin porous substrate made of polyethylene, the film density can be calculated assuming 0.95 (g / cm ³ ). The porosity can be adjusted by changing the draw ratio of the polyolefin porous substrate.

  The air permeability of the polyolefin porous substrate in the present embodiment is not particularly limited, but is preferably 10 seconds / 100 cc or more, more preferably 50 seconds / 100 cc or more, preferably 1000 seconds / 100 cc or less, more preferably 500 seconds / 100 cc or less. The air permeability is preferably 10 seconds / 100 cc or more from the viewpoint of suppressing self-discharge of the electricity storage device. On the other hand, it is preferable that the air permeability is 1000 seconds / 100 cc or less from the viewpoint of obtaining good charge / discharge characteristics. Here, the air permeability is an air resistance measured in accordance with JIS P-8117. The air permeability can be adjusted by changing the stretching temperature and / or stretching ratio of the polyolefin porous substrate.

  The average pore diameter of the polyolefin porous substrate in the present embodiment is preferably 0.15 μm or less, more preferably 0.1 μm or less, and preferably 0.01 μm or more. Setting the average pore size to 0.15 μm or less is preferable from the viewpoint of suppressing self-discharge of the electricity storage device and suppressing capacity reduction. The average pore diameter can be adjusted by changing the draw ratio when producing a polyolefin porous substrate. The average pore diameter of the substrate is measured according to the method described in the examples.

  The puncture strength of the polyolefin porous substrate in the present embodiment is not particularly limited, but is preferably 200 gf / 20 μm or more, more preferably 300 gf / 20 μm or more, further preferably 400 gf / 20 μm or more, preferably 2000 gf / It is 20 μm or less, more preferably 1000 gf / 20 μm or less. The pin puncture strength of 200 gf / 20 μm or more suppresses the fear of short-circuiting due to expansion and contraction of the electrode due to charge and discharge, and the viewpoint of suppressing the film breakage due to the active material dropped when the separator is wound together with the electrode It is also preferable from the viewpoint. On the other hand, a puncture strength of 2000 gf / 20 μm or less is preferable from the viewpoint of reducing width shrinkage due to orientation relaxation during heating. The puncture strength is measured according to the method described in Examples described later. The puncture strength can be adjusted by adjusting the draw ratio and / or the draw temperature of the polyolefin porous substrate.

  The thickness of the polyolefin porous substrate in the present embodiment is not particularly limited, but is preferably 2 μm or more, more preferably 5 μm or more, preferably 100 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. . The film thickness of 2 μm or more is preferable from the viewpoint of improving mechanical strength. On the other hand, it is preferable to set the film thickness to 100 μm or less because the occupied volume of the separator in the electricity storage device is reduced, which tends to be advantageous in terms of increasing the capacity of the electricity storage device.

[Inorganic filler porous layer]
The inorganic filler porous layer (hereinafter, also simply referred to as “filler porous layer”) includes an inorganic filler, preferably includes a resin binder, and has a plurality of holes.
(Inorganic filler)
The inorganic filler contained in the filler porous layer is not particularly limited, but has a melting point of 200 ° C. or higher, high electrical insulation, and is electrochemically stable in the usage range of an electricity storage device such as a lithium ion secondary battery. Are preferred.

  The inorganic filler is not particularly limited. For example, inorganic oxides (oxide ceramics) such as alumina, silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide, iron oxide; silicon nitride, titanium nitride, nitride Inorganic nitrides (nitride ceramics) such as boron; silicon carbide, calcium carbonate, magnesium sulfate, aluminum sulfate, aluminum hydroxide, aluminum hydroxide oxide, potassium titanate, talc, kaolinite, dickite, nacrite, halloysite, pyro Examples thereof include ceramics such as phyllite, montmorillonite, sericite, mica, amicite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; and glass fibers. These are used singly or in combination of two or more.

  Among these, inorganic oxides are preferable from the viewpoint of improving electrochemical stability and heat resistance of the separator, and aluminum oxide compounds such as alumina and aluminum hydroxide oxide; and kaolinite, dickite, nacrite, halloysite. An aluminum silicate compound having no ion exchange ability such as pyrophyllite is more preferable.

  From the same viewpoint, the aluminum oxide compound is particularly preferably aluminum hydroxide oxide (AlO (OH)). As the aluminum silicate compound having no ion exchange capacity, kaolin mainly composed of kaolin mineral is more preferable because it is inexpensive and easily available. Known kaolins include wet kaolin and calcined kaolin obtained by calcining it. In the present embodiment, calcined kaolin is particularly preferable. The calcined kaolin is particularly preferable from the viewpoint of electrochemical stability because crystal water is released during the calcining process and impurities are also removed.

  The average particle diameter D50 of the inorganic filler is preferably 0.01 μm or more, more preferably 0.2 μm or more, and further preferably 0.5 μm or more. The average particle diameter D50 is preferably 4.0 μm or less, more preferably 3.5 μm or less, and even more preferably less than 1.0 μm. Adjusting the average particle diameter D50 of the inorganic filler to the above range is preferable from the viewpoint of suppressing heat shrinkage at high temperatures even when the filler porous layer is thin (for example, 7 μm or less). Moreover, when the average particle diameter D50 of the inorganic filler is 4.0 μm or less, the heat resistance tends to be improved. On the other hand, when the average particle diameter D50 of the inorganic filler exceeds 0.01 μm, the ion permeability is good. Tend to be. Examples of a method for adjusting the particle size and distribution of the inorganic filler include a method of reducing the particle size by pulverizing the inorganic filler using an appropriate pulverizing apparatus such as a ball mill, a bead mill, or a jet mill.

  The particle size distribution of the inorganic filler preferably has one peak in the graph of frequency against particle size. If there is one peak, it becomes easy to adjust the average pore size of the inorganic filler porous layer by controlling the average particle size of the inorganic filler. In the above graph, when the trapezoidal chart has two peaks or no peak, even if the average particle size of the inorganic filler is controlled, the change in the average pore size of the inorganic filler porous layer is more generated. It becomes difficult. The average particle diameter D50 and particle size distribution of the inorganic filler are measured according to the method described in the examples.

  In the separator for an electricity storage device according to this embodiment, a particulate polymer described later (hereinafter also simply referred to as “particulate polymer”) is larger than the average pore diameter of the inorganic filler porous layer. The average pore size of the inorganic filler porous layer is a quantitative definition of the gap between the inorganic filler and the inorganic filler, the inorganic filler and the binder, or the binder and the binder in the inorganic filler porous layer. Measured according to the method.

  When measuring the average pore size of the porous inorganic filler layer, the cross section of the separator is preferably observed in a region of the separator cross section that is not involved in ion conduction. The average pore diameter of the inorganic filler porous layer may be measured, for example, on a separator that has just been manufactured and is not yet incorporated into an electricity storage device. Alternatively, after the separator is incorporated in the electricity storage device, measure the so-called “ear” portion of the separator (the region near the outer edge of the separator and not involved in ion conduction). Also good.

  The average pore size of the inorganic filler porous layer is preferably 0.01 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, and particularly preferably 0.2 μm or more. preferable. The average pore diameter is preferably 5 μm or less, more preferably 3 μm or less, still more preferably 0.7 μm or less, and particularly preferably 0.5 μm or less. When the average pore diameter of the inorganic filler porous layer is 5 μm or less, the particulate polymer existing on the inorganic filler porous layer can be further suppressed from dropping into the inorganic filler porous layer. On the other hand, when the average pore size of the inorganic filler porous layer is 0.01 μm or more, the ion permeability of the separator tends to be further improved.

  The average pore diameter of the inorganic filler porous layer is the size of the void portion formed by inorganic fillers preferably bound by a resin binder in the inorganic filler porous layer formed on at least one surface of the substrate. It is an index to represent. Since the average pore diameter of the inorganic filler porous layer is determined by the method of forming the inorganic filler porous layer, for example, the properties of the inorganic filler used, the properties of the inorganic filler porous layer slurry for forming the inorganic filler porous layer, and the inorganic filler porous It can adjust with the formation method at the time of forming a layer.

  When the average particle diameter D50 of the inorganic filler is increased, voids are increased in the inorganic filler porous layer, and therefore the average pore diameter of the inorganic filler porous layer tends to increase. As for the shape of the inorganic filler, for example, the average pore size tends to be smaller in the plate shape than in the block shape, and the average pore size tends to be smaller in the needle shape. The average pore diameter tends to increase as the structure of the inorganic filler becomes more complicated. Further, among the properties of the inorganic filler porous layer slurry for forming the inorganic filler porous layer, the viscosity of the slurry particularly affects the average pore size of the inorganic filler porous layer. When the viscosity of the slurry is high, after applying the inorganic filler porous layer slurry on the substrate, the fluidity of the inorganic filler is suppressed, so that it is difficult to arrange the inorganic fillers to be most stable. As a result, the average pore diameter of the inorganic filler porous layer tends to increase. Similarly, even if the drying conditions are increased and the drying is performed rapidly, the inorganic filler porous layer tends to have a larger average pore size because the inorganic filler does not have time for stable arrangement. In addition, when applying a coating solution containing an inorganic filler as described later, by adjusting the shear stress applied to the coating solution, or by calendering the laminate of the inorganic filler porous layer and the substrate, The average pore diameter can also be controlled.

  Examples of the shape of the inorganic filler include a plate shape, a scale shape, a needle shape, a columnar shape, a spherical shape, a polyhedral shape, and a block shape. A plurality of inorganic fillers having these shapes may be used in combination. Among these, the block shape and the plate shape are preferable from the viewpoint of more effectively and reliably achieving the effects of the present invention.

  The content ratio of the inorganic filler in the filler porous layer is 20% by mass or more and less than 100% by mass with respect to the total amount of the filler porous layer from the viewpoint of the binding property of the inorganic filler, the permeability of the separator, and the heat resistance. It is preferably 30% by mass or more and 80% by mass or less, more preferably 35% by mass or more and 70% by mass or less, and particularly preferably 40% by mass or more and 60% by mass or less.

(Resin binder)
The type of resin in the resin binder contained in the filler porous layer is not particularly limited, but is insoluble in an electrolyte solution of an electricity storage device such as a lithium ion secondary battery, and is similar to a lithium ion secondary battery. It is preferable to use an electrochemically stable resin in the usage range of the electricity storage device. In addition, in this embodiment, in addition to the resin binder (A) contained in the filler porous layer and the particulate polymer (B) contained in the thermoplastic polymer-containing layer, the resin is contained in the thermoplastic polymer-containing layer. Alternatively, a binder (C) that binds the particulate polymer (B) to the substrate or filler porous layer may be used. The resin binder (A) and the binder binder (C) are usually not in the form of particles in the separator. On the other hand, the particulate polymer (B) described later is particulate in the separator, and the particulate polymer (B) preferably contains a different type of resin from the resin binder (A) and the binder binder (C). .

  Specific examples of such a resin include, for example, polyolefins such as polyethylene and polypropylene; fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene; vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, ethylene- Fluorine-containing rubber such as tetrafluoroethylene copolymer; styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride, methacrylic acid ester -Rubbers such as acrylic ester copolymer, styrene-acrylic ester copolymer, acrylonitrile-acrylic ester copolymer, ethylene propylene rubber, polyvinyl alcohol, polyvinyl acetate; Cellulose derivatives such as roulose, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose; melting point and / or glass transition temperature of polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyamide, polyester, etc. of 180 ° C. or higher These resins are mentioned. These are used singly or in combination of two or more.

  The resin binder preferably includes a resin latex binder. When a resin latex binder is used as the resin binder, the ion permeability is less likely to be lower than when no resin latex binder is used, and an electric storage device with high output characteristics tends to be provided. Furthermore, an electricity storage device having a separator including a porous filler layer containing a resin latex binder exhibits smooth shutdown characteristics even when the temperature rises rapidly during abnormal heat generation, and tends to provide high safety.

  As the resin latex binder, from the viewpoint of improving electrochemical stability and binding properties, aliphatic conjugated diene monomers, unsaturated carboxylic acid monomers, and other monomers copolymerizable therewith A copolymer with the body is preferred. Here, examples of the aliphatic conjugated diene monomer include butadiene and isoprene, examples of the unsaturated carboxylic acid monomer include (meth) acrylic acid, and other monomers include An example is styrene. There is no particular limitation on the polymerization method of such a copolymer, but emulsion polymerization is preferred. There is no restriction | limiting in particular as a method of emulsion polymerization, A known method can be used. The method for adding the monomer and other components is not particularly limited, and any one of a batch addition method, a divided addition method, and a continuous addition method can be adopted. Either step polymerization or multistage polymerization of three or more steps can be employed.

Specific examples of the resin binder include the following 1) to 7).
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-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer;
6) Cellulose derivatives: for example, ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose; and 7) resins having a melting point and / or glass transition temperature of 180 ° C. or higher or polymers having no melting point but a decomposition temperature of 200 ° C. or higher: Polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyamide, polyester.

  From the viewpoint of further improving the safety at the time of short circuit, among these, 3) an acrylic polymer, 5) a fluororesin, and 7) a polyamide as a polymer are preferable. As the polyamide, a wholly aromatic polyamide, particularly polymetaphenylene isophthalamide is preferable from the viewpoint of durability.

  From the viewpoint of compatibility between the resin binder and the electrode, the above 2) conjugated diene polymer is preferable, and from the viewpoint of voltage endurance, the above 3) acrylic polymer and 5) a fluorine-containing resin are preferable.

  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. Conjugated pentadienes, substituted and side chain conjugated hexadienes are mentioned. These are used singly 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 said (meth) acrylic-type compound shows 1 or more types chosen from the group which consists 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.

  3) The (meth) acrylic acid ester used in the acrylic polymer is, for example, a (meth) acrylic acid alkyl ester such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2 -Ethylhexyl acrylate, 2-ethylhexyl amethacrylate; and epoxy group-containing (meth) acrylic acid esters such as glycidyl acrylate and glycidyl methacrylate. These are used singly or in combination of two or more. Among these, 2-ethylhexyl acrylate (hereinafter also referred to as “EHA”) and butyl acrylate (hereinafter also referred to as “BA”) are particularly preferable.

  The acrylic polymer is preferably a polymer containing EHA or BA as a main constituent unit from the viewpoint of safety in a collision test. The main structural unit refers to a polymer portion corresponding to a monomer occupying 40 mol% or more with respect to the total raw materials for forming a polymer.

  An acrylic polymer is an EHA-BA copolymer and / or a mixture of a polymer in which EHA is a main constituent unit and a polymer in which BA is a main constituent unit, from the viewpoint of improving safety in a collision test. Preferably, it is a mixture of a polymer in which EHA is the main constituent unit and a polymer in which BA is the main constituent unit. In the case of an EHA-BA copolymer, the mixing ratio at the time of copolymerization (mass ratio of EHA: BA) is preferably 1:99 to 99: 1, more preferably 50:50 to 95: 5, still more preferably 70. : 30 to 90:10. By using EHA, there is an effect of improving the adhesiveness between the inorganic filler and the polyolefin resin and suppressing the thermal shrinkage of the polyolefin resin. By using BA, the filler porous layer is given flexibility, and the heat shrinkage is also caused. There is an inhibitory effect. In the case of a mixture of a polymer in which EHA is the main constituent unit and a polymer in which BA is the main constituent unit, the mass mixing ratio of the two may be in the range of 1:99 to 99: 1.

  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 monomers, crotonic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid. These may be used alone or in combination of two. Among the above, unsaturated carboxylic acid alkyl esters are particularly preferred as monomers. Examples of the unsaturated carboxylic acid alkyl ester include dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate and monoethyl fumarate. These are used singly or in combination of two or more.

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

  When the resin binder is a resin latex binder, the average particle diameter (D50) is preferably 50 to 500 nm, more preferably 60 to 460 nm, still more preferably 80 to 250 nm. When the average particle diameter of the resin binder is 50 nm or more, the separator including the filler porous layer containing the binder and the inorganic filler is less likely to have low ion permeability and easily provides an electricity storage device with high output characteristics. Furthermore, even when the temperature rises rapidly during abnormal heat generation, it is easy to obtain an electricity storage device that exhibits smooth shutdown characteristics and high safety. When the average particle diameter of the resin binder is 500 nm or less, good binding properties (binding properties when the inorganic fillers are bound with the resin binder) are expressed, and the substrate and the inorganic filler porous layer in the separator The thermal contraction of the laminate is good and the safety tends to be excellent. The average particle diameter of the resin binder can be controlled by adjusting the polymerization time, polymerization temperature, raw material composition ratio, raw material charging order, pH, and the like. The average particle size of the resin binder is measured by the method described in the examples.

  The content of the resin binder in the filler porous layer is more than 0% by mass and not more than 80% by mass with respect to the total amount of the filler porous layer from the viewpoints of the binding properties of the inorganic filler, the permeability of the separator, and the heat resistance. It is preferably 1% by mass to 20% by mass, more preferably 2% by mass to 10% by mass, and particularly preferably 3% by mass to 5% by mass.

  The content of the particulate polymer described later contained in the filler porous layer is preferably less than 5% by volume of the content of the particulate polymer contained in the electricity storage device separator, more preferably less than 3% by volume, More preferably, it is less than 2% by volume. When the content of the particulate polymer is less than 5% by volume, it is preferable from the viewpoint of improving the ion permeability of the separator.

The thickness of the filler porous layer is preferably 10.0 μm or less, and more preferably 6.0 μm or less from the viewpoint of increasing the capacity of the electricity storage device and improving the permeability. Moreover, it is preferable that the thickness of a filler porous layer is 0.5 micrometer or more from a viewpoint of improving heat resistance and insulation. The layer density of the filler porous layer is preferably 0.5 g / (m ² · μm) or more and 3.0 g / (m ² · μm) or less, and is 0.7 to 2.0 (m ² · μm). More preferably. When the layer density of the filler porous layer is 0.5 g / (m ² · μm) or more, the heat shrinkage rate at a high temperature tends to be good, and is 3.0 g / (m ² · μm) or less. The air permeability tends to decrease. The density of the filler porous layer can be calculated from the thickness and mass of the filler porous layer.

[Thermoplastic polymer-containing layer]
The thermoplastic polymer-containing layer in the present embodiment contains a thermoplastic polymer, and the thermoplastic polymer contains a particulate polymer. The thermoplastic polymer-containing layer is formed on at least a part of the surface of the inorganic filler porous layer with respect to the laminate having the base material and the inorganic filler porous layer formed on at least one surface of the base material. The The thermoplastic polymer-containing layer may be disposed on the entire surface of the inorganic filler porous layer or may be partially disposed. When an inorganic filler porous layer is arrange | positioned only on the surface of the single side | surface of a base material, you may arrange | position on the surface where the inorganic filler porous layer of a base material does not exist. It is more preferable to dispose the thermoplastic polymer-containing layer only on a part of the surface of the substrate so that the obtained electricity storage device exhibits high ion permeability.

  In this embodiment, the thermoplastic polymer-containing layer is expected to be directly bonded to the electrode. For example, at least a part of at least one side of the substrate and the electrode are bonded via the thermoplastic polymer-containing layer so that the at least one thermoplastic polymer-containing layer provided in the separator for the electricity storage device is directly bonded to the electrode. Or other layers disposed on the substrate and the electrode shall be disposed so as to be bonded via the thermoplastic polymer-containing layer.

In the present embodiment, the coating amount of the thermoplastic polymer-containing layer on the base material, that is, the formation amount (arrangement amount) of the thermoplastic polymer-containing layer per area of one surface of the base material is 0.03 g / in solid content. m ² or more is preferable, and 0.05 g / m ² or more is more preferable. The coating amount is preferably 2.0 g / m ² or less, and more preferably 1.5 g / m ² or less. Setting the coating amount to 0.05 g / m ² or more improves the adhesive force between the thermoplastic polymer-containing layer and the electrode in the obtained separator, realizes more uniform charge and discharge, and device characteristics (for example, This is preferable in terms of improving the cycle characteristics of the battery. On the other hand, setting the coating amount to 2.0 g / m ² or less is preferable from the viewpoint of further suppressing the decrease in ion permeability.

  In the present embodiment, the area ratio of the surface on which the thermoplastic polymer-containing layer is present relative to the total area of the surface on which the thermoplastic polymer-containing layer is arranged, of the surface of the inorganic filler porous layer, that is, containing the thermoplastic polymer The surface coverage with respect to the inorganic filler porous layer by the layer is preferably 100% or less, more preferably 80% or less, further preferably 75% or less, and particularly preferably 70% or less. The surface coverage is preferably 5% or more, more preferably 10% or more, still more preferably 15% or more, and particularly preferably 30% or more. Setting the surface coverage to 100% or less is preferable from the viewpoint of further suppressing the blocking of the pores of the base material by the particulate polymer and further improving the permeability of the separator. On the other hand, setting the surface coverage to 5% or more is preferable from the viewpoint of further improving the adhesion to the electrode. This surface coverage is measured by observing the surface on which the thermoplastic polymer-containing layer is formed in the obtained separator with an SEM, and is specifically measured according to the method described in the examples. Further, when the thermoplastic polymer-containing layer is also disposed on the surface of the substrate, the surface coverage (the thermoplastic polymer with respect to the entire area of the surface of the substrate on which the thermoplastic polymer-containing layer is disposed) The area ratio of the surface on which the containing layer is present is preferably the same as described above.

  The surface coverage in this embodiment is applied to the surface of a base material (hereinafter simply referred to as “inorganic filler porous layer or the like”) in addition to the porous inorganic filler layer and, in some cases, in the separator manufacturing method described below, for example. It can adjust by changing the kind of the particulate polymer in the coating liquid to perform, the density | concentration of the polymer, the coating amount of a coating liquid, a coating method, and coating conditions. However, the method for adjusting the coating area is not limited thereto.

  When the thermoplastic polymer-containing layer is disposed only on a part of the surface of the inorganic filler porous layer or the like, the thermoplastic polymer-containing layer is preferably present in a sea-island shape, and as the arrangement pattern, for example, a dot shape or a stripe shape , Lattice shape, stripe shape, turtle shell shape, random shape, and the like, and combinations thereof. Among these, the dot shape is preferable from the viewpoint of more effectively and surely achieving the effects of the present invention. When the arrangement pattern is in the form of dots, the dot diameter is preferably 50 μm or more, more preferably 100 μm or more, and more preferably 200 μm or more. Further, the dot diameter is preferably 1 mm or less, and more preferably 500 μm or less. When the dot diameter is 50 μm or more, the flow of ions in the electrolytic solution is further improved and the permeability is further improved. When the dot diameter is 1 mm or less, the separator can be more uniformly bonded to the electrode, and the in-plane current density can be further uniformed. Furthermore, by providing a portion where the thermoplastic polymer is not applied in the dot-like arrangement pattern, the in-plane current density can be made more uniform.

When the thermoplastic polymer-containing layer is partially disposed, it is desirable that the surface coverage of the separator is uniform in a certain area range. Specifically, in the observation visual field range of 10 mm × 10 mm or more when the surface of the separator is observed with an SEM, the change rate of the surface coverage represented by the following formula is preferably within ± 50%.
(Change rate of surface coverage (%)) = (C1-C2) / C1 × 100
Here, C1 indicates the surface coverage in an observation field range of 10 mm × 100 mm or more, and C2 indicates the surface coverage in the other observation field range of 10 mm × 100 mm or more. For example, for a separator in which a thermoplastic polymer-containing layer is partially disposed, when the measured value of the surface coverage in an observation visual field range of 10 mm × 10 mm is 50%, any other part of the separator is observed. Even so, the surface coverage in the observation field range of 10 mm × 10 mm is preferably 25% or more and 75% or less.

  The thickness of the thermoplastic polymer-containing layer disposed on the inorganic filler porous layer or the like is preferably 0.01 μm or more per surface of the inorganic filler porous layer or the like, and is preferably 0.1 μm or more. More preferred. Further, the thickness is preferably 5.0 μm or less, more preferably 3.0 μm or less, and further preferably 2.0 μm or less per one surface of the inorganic filler porous layer or the like. Setting the thickness to 0.01 μm or more is preferable in terms of uniformly expressing the adhesive force between the electrode and the inorganic filler porous layer, and as a result, device characteristics can be improved. Moreover, it is preferable that the thickness is 5.0 μm or less from the viewpoint of suppressing a decrease in ion permeability. The thickness of the thermoplastic polymer-containing layer in the present embodiment is, for example, the type of the particulate polymer in the coating liquid applied to the inorganic filler porous layer or the like, the concentration of the polymer, the coating amount of the coating liquid, the coating method, and the coating It can be adjusted by changing the conditions. However, the adjustment method of this thickness is not limited to them. The thickness of the thermoplastic polymer-containing layer is measured by the method described in the examples.

(Particulate polymer)
In this embodiment, the thermoplastic polymer-containing layer includes a particulate polymer. In the following description, “ethylenically unsaturated monomer” means a monomer having one or more ethylenically unsaturated bonds in the molecule. By including the particulate polymer in the thermoplastic polymer-containing layer, both excellent adhesion to the electrode and ion permeability can be achieved.

  Specific examples of the particulate polymer resin species contained in the thermoplastic polymer-containing layer include conjugated diene polymers, acrylic polymers, polyvinyl alcohol resins, and fluorine-containing resins. Among these, a conjugated diene polymer is preferable from the viewpoint of compatibility with the electrode, and an acrylic polymer and a fluorine-containing resin are preferable from the viewpoint of voltage resistance. Moreover, it is preferable that a particulate polymer contains a particulate copolymer from a viewpoint which shows the effect by this invention more effectively and reliably. A particulate polymer is used individually by 1 type or in combination of 2 or more types.

  The thermoplastic polymer-containing layer is preferably 60% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, particularly preferably 98% by mass or more, based on the total amount, in the particulate form. Including polymers. Furthermore, the thermoplastic polymer-containing layer may contain a thermoplastic polymer other than the particulate polymer to such an extent that the solution of the problem of the present invention is not impaired.

  The conjugated diene polymer is a polymer having 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. Conjugated pentadienes, substituted and side chain conjugated hexadienes can be mentioned, and these may be used alone or in combination of two or more. Among these, 1,3-butadiene is particularly preferable. Further, the conjugated diene polymer may contain a (meth) acrylic compound or other monomer described later as a monomer unit. Examples of such a monomer include a styrene-butadiene copolymer and its hydride, an acrylonitrile-butadiene copolymer and its hydride, an acrylonitrile-butadiene-styrene copolymer and its hydride.

The acrylic polymer is a polymer having 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, from the viewpoint of more effectively and reliably achieving the effects of the present invention ( (Meth) acrylic acid esters are preferred. An example of such a compound is a compound represented by the following formula (P1).
^{_{CH 2 = CR Y1 -COO-R}} Y2 (P1)
Here, in formula (P1), R ^Y1 represents a hydrogen atom or a methyl group, and R ^Y2 represents a hydrogen atom or a monovalent hydrocarbon group. When R ^Y2 is a monovalent hydrocarbon group, it may have a substituent and may have a hetero atom in the chain. Examples of the monovalent hydrocarbon group include a linear alkyl group, a cycloalkyl group, and an aryl group which may be linear or branched. Examples of the substituent include a hydroxyl group and a phenyl group, and examples of the hetero atom include a halogen atom and an oxygen atom. A (meth) acrylic compound is used alone or in combination of two or more. Such (meth) acrylic compounds include (meth) acrylic acid, chain alkyl (meth) acrylate, cycloalkyl (meth) acrylate, (meth) acrylate having a hydroxyl group, and phenyl group-containing (meth) acrylate. Is mentioned.

More specifically, as the chain alkyl group which is one kind of R ^Y2 , a chain alkyl group having 1 to 3 carbon atoms such as methyl group, ethyl group, n-propyl group, and isopropyl group; n Examples thereof include chain alkyl groups having 4 or more carbon atoms, such as -butyl group, isobutyl group, t-butyl group, n-hexyl group, 2-ethylhexyl group, and lauryl group. Moreover, as an aryl group which is 1 type of R ^<Y2>, a phenyl group is mentioned, for example. Specific examples of the (meth) acrylic acid ester monomer having R ^Y2 include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, and n-hexyl. Chains such as acrylate, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate (Meth) acrylate having an alkyl group; and phenyl (meth) acrylate, and Having an aromatic ring such as benzyl (meth) acrylate (meth) acrylate.

Among these, from the viewpoint of improving the adhesion of the separator to the electrode (electrode active material), a monomer having a chain alkyl group having 4 or more carbon atoms, more specifically, R ^Y2 is a carbon atom. A (meth) acrylic acid ester monomer which is a chain alkyl group having a number of 4 or more is preferred. More specifically, at least one selected from the group consisting of butyl acrylate, butyl methacrylate, and 2-ethylhexyl acrylate is preferable. The upper limit of the number of carbon atoms in the chain alkyl group having 4 or more carbon atoms is not particularly limited, and may be 14, for example, but 7 is preferable. These (meth) acrylic acid ester monomers are used singly or in combination of two or more.

The (meth) acrylic acid ester monomer is a monomer having a cycloalkyl group as R ^Y2 instead of or in addition to the monomer having a chain alkyl group having 4 or more carbon atoms. It is also preferable to include. This also improves the adhesion of the separator to the electrode. More specifically, examples of such a monomer having a cycloalkyl group include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and adamantyl (meth) acrylate. 4-8 are preferable, as for the number of the carbon atoms which comprise the alicyclic ring of a cycloalkyl group, 6 and 7 are more preferable, and 6 is especially preferable. Further, the cycloalkyl group may or may not have a substituent. Examples of the substituent include a methyl group and a t-butyl group. Among these, at least one selected from the group consisting of cyclohexyl acrylate and cyclohexyl methacrylate is preferable in terms of good polymerization stability when preparing an acrylic polymer. These are used singly or in combination of two or more.

  Moreover, it is preferable that an acrylic polymer contains a crosslinkable monomer as a (meth) acrylic acid ester monomer instead of the above, or in addition, preferably in addition to the above. The crosslinkable monomer is not particularly limited. For example, a monomer having two or more radical polymerizable double bonds, a single monomer having a functional group that gives a self-crosslinking structure during or after polymerization. Examples include the body. These are used singly or in combination of two or more.

  Examples of the monomer having two or more radical polymerizable double bonds include divinylbenzene and polyfunctional (meth) acrylate. The polyfunctional (meth) acrylate may be at least one selected from the group consisting of a bifunctional (meth) acrylate, a trifunctional (meth) acrylate, and a tetrafunctional (meth) acrylate. Specifically, for example, polyoxyethylene diacrylate, polyoxyethylene dimethacrylate, polyoxypropylene diacrylate, polyoxypropylene dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, butanediol diacrylate, butanediol Examples include dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate. These are used singly or in combination of two or more. Especially, at least 1 sort (s) selected from the group which consists of a trimethylol propane triacrylate and a trimethylol propane trimethacrylate from a viewpoint similar to the above is preferable.

  Examples of the monomer having a functional group that gives a self-crosslinking structure during or after polymerization include, for example, a monomer having an epoxy group, a monomer having a methylol group, a monomer having an alkoxymethyl group, and hydrolysis. And monomers having a functional silyl group. As the monomer having an epoxy group, an ethylenically unsaturated monomer having an alkoxymethyl group is preferable. Specifically, examples thereof include glycidyl (meth) acrylate, 2,3-epoxycyclohexyl (meth) acrylate, 3 , 4-epoxycyclohexyl (meth) acrylate, and allyl glycidyl ether.

  Examples of the monomer having a methylol group include N-methylol acrylamide, N-methylol methacrylamide, dimethylol acrylamide, and dimethylol methacrylamide. As the monomer having an alkoxymethyl group, an ethylenically unsaturated monomer having an alkoxymethyl group is preferable. Specific examples thereof include N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, and N-butoxymethyl. Examples include acrylamide and N-butoxymethyl methacrylamide. Examples of the monomer having a hydrolyzable silyl group include vinyl silane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxy. And propyltriethoxysilane. These are used singly or in combination of two or more.

  The acrylic polymer may further have other monomers as monomer units in order to improve various qualities and physical properties. Examples of such a monomer include a monomer having a carboxyl group (excluding (meth) acrylic acid), a monomer having an amide group, a monomer having a cyano group, and a hydroxyl group. And a monomer having an aromatic vinyl monomer. Furthermore, various vinyl monomers having functional groups such as sulfonic acid groups or phosphoric acid groups, and vinyl acetate, vinyl propionate, vinyl versatic acid, vinyl pyrrolidone, methyl vinyl ketone, butadiene, ethylene, propylene, chloride Vinyl and vinylidene chloride are also used as necessary. These are used singly or in combination of two or more. The other monomer may belong to two or more of the monomers at the same time.

  Examples of the monomer having an amide group include (meth) acrylamide. The monomer having a cyano group is preferably an ethylenically unsaturated monomer having a cyano group, and specific examples thereof include (meth) acrylonitrile. As a monomer which has a hydroxyl group, 2-hydroxyethyl (meth) acrylate is mentioned, for example.

  Examples of the aromatic vinyl monomer include styrene, vinyl toluene, and α-methylstyrene. Styrene is preferred.

  The proportion of the acrylic polymer having a (meth) acrylic compound as a monomer unit is preferably 5% by mass or more and 95% by mass or less with respect to 100% by mass of the acrylic polymer. The lower limit is more preferably 15% by mass, still more preferably 20% by mass, and particularly preferably 30% by mass. When the content ratio of the monomer unit is 5% by mass or more, it is preferable in terms of binding property to a substrate and oxidation resistance. On the other hand, a more preferred upper limit is 92% by mass, a still more preferred upper limit is 80% by mass, and a particularly preferred upper limit is 60% by mass. It is preferable for the content ratio of the monomer to be 95% by mass or less because the adhesion to the substrate is improved.

  When the acrylic polymer has a chain alkyl (meth) acrylate or cycloalkyl (meth) acrylate as a monomer unit, the total content thereof is preferably 100% by mass of the acrylic polymer. 3% by mass or more and 92% by mass or less, more preferably 10% by mass or more and 90% by mass or less, still more preferably 15% by mass or more and 75% by mass or less, and particularly preferably 25% by mass or more and 55% by mass or less. It is as follows. The content of these monomers is preferably 3% by mass or more from the viewpoint of improving oxidation resistance, and the content of 92% by mass or less is preferable because the binding property to the substrate is improved.

  When the acrylic polymer has (meth) acrylic acid as a monomer unit, the content ratio is preferably 0.1% by mass or more and 5% by mass or less with respect to 100% by mass of the acrylic polymer. . When the content ratio of the monomer is 0.1% by mass or more, the separator tends to improve the cushioning property in the swollen state, and when it is 5% by mass or less, the polymerization stability tends to be good. is there.

  When the acrylic polymer has a crosslinkable monomer as a monomer unit, the content of the crosslinkable monomer in the acrylic polymer is preferably 0. 0% with respect to 100% by mass of the acrylic polymer. It is 01 mass% or more and 10 mass% or less, More preferably, it is 0.1 mass% or more and 5 mass% or less, More preferably, it is 0.1 mass% or more and 3 mass% or less. When the content ratio of the monomer is 0.01% by mass or more, the electrolytic solution resistance is further improved, and when it is 10% by mass or less, a decrease in cushioning property in the swollen state can be further suppressed.

As the acrylic polymer in the present embodiment, any one of the following aspects is preferable. The following copolymerization ratios are values based on 100% by mass of the copolymer.
(1) A copolymer having a (meth) acrylic acid ester as a monomer unit (excluding the copolymer (2) and the copolymer (3) below). Preferably, (meth) acrylic acid is 5% by mass or less (more preferably 0.1% by mass or more and 5% by mass or less) and (meth) acrylic acid ester monomer is 3% by mass or more and 92% by mass or less (more preferably). 10 mass% or more and 90 mass% or less, more preferably 15 mass% or more and 75 mass% or less, particularly preferably 25 mass% or more and 55 mass% or less), a monomer having an amide group, a monomer having a cyano group And at least one selected from the group consisting of monomers having a hydroxyl group, 15% by mass or less (more preferably 10% by mass or less) and a crosslinkable monomer 10% by mass or less (more preferably 0.01%). A copolymer of from 5% by mass to 5% by mass, and more preferably from 0.1% by mass to 3% by mass.
(2) A copolymer having an aromatic vinyl monomer and a (meth) acrylic acid ester monomer as monomer units. Preferably, the aromatic vinyl monomer is 5% by mass or more and 95% by mass or less (more preferably 10% by mass or more and 92% by mass or less, still more preferably 25% by mass or more and 80% by mass or less, and particularly preferably 40% by mass or more and 60% by mass or less. Mass% or less), (meth) acrylic acid 5 mass% or less (more preferably 0.1 mass% or more and 5 mass% or less), and (meth) acrylic acid ester monomer 5 mass% or more and 95 mass% or less ( More preferably 15% by mass or more and 85% by mass or less, further preferably 20% by mass or more and 80% by mass or less, and particularly preferably 30% by mass or more and 75% by mass or less), a monomer having an amide group, and a cyano group. 10% by mass or less (more preferably 5% by mass or less) of at least one selected from the group consisting of a monomer and a monomer having a hydroxyl group, and 10% by mass or less (cross-linkable monomer) Preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less); and (3) a monomer having a cyano group and (meth) acrylic A copolymer having an acid ester monomer as a monomer unit. Preferably, the monomer having a cyano group is 1% by mass to 95% by mass (more preferably 5% by mass to 90% by mass, and still more preferably 50% by mass to 85% by mass), and (meth) acrylic acid. 5 mass% or less (preferably 0.1 mass% or more and 5 mass% or less), and (meth) acrylic acid ester monomer 1 mass% or more and 95 mass% or less (more preferably 5 mass% or more and 85 mass% or less, And more preferably 10% by mass or more and 50% by mass or less) and at least one selected from the group consisting of a monomer having an amide group, a monomer having a cyano group, and a monomer having a hydroxyl group. % Or less (more preferably 5% by mass or less) and a crosslinkable monomer 10% by mass or less (more preferably 0.01% by mass or more and 5% by mass or less, and further preferably 0.1% by mass or more and 3% by mass or less). )When, Copolymer.

  The copolymer (2) preferably has a (meth) acrylic acid hydrocarbon ester as the (meth) acrylic acid ester monomer. In this case, the copolymerization ratio of the hydrocarbon ester of (meth) acrylic acid is preferably 0.1% by mass or more and 5% by mass or less. Moreover, when the copolymer of said (2) has a monomer which has an amide group, it is preferable that the copolymerization ratio is 0.1 to 5 mass%. Furthermore, when the copolymer (2) has a monomer having a hydroxyl group, the copolymerization ratio is preferably 0.1% by mass or more and 5% by mass or less.

  In the copolymer (3), the (meth) acrylic acid ester monomer preferably contains at least one selected from the group consisting of chain alkyl (meth) acrylates and cycloalkyl (meth) acrylates. . As the chain alkyl (meth) acrylate, a (meth) acrylic acid ester having a chain alkyl group having 6 or more carbon atoms is preferable. The copolymerization ratio of the chain alkyl (meth) acrylate in the copolymer (3) is preferably 1% by mass to 95% by mass, more preferably 3% by mass to 90% by mass, More preferably, it is 5 mass% or more and 85 mass% or less. The upper limit of the copolymerization ratio may be 60% by mass, particularly 40% by mass or 30% by mass, and particularly preferably 20% by mass. The copolymerization ratio of cyclohexylalkyl (meth) acrylate in the copolymer (3) is preferably 1% by mass or more and 95% by mass or less, more preferably 3% by mass or more and 90% by mass or less. More preferably, it is at least 85% by mass. The upper limit of the copolymerization ratio may be 60% by mass, particularly 50% by mass, and particularly preferably 40% by mass. Moreover, when the copolymer of said (3) has a monomer which has an amide group, it is preferable that the copolymerization ratio is 0.1 to 10 mass%, and is 2 to 10 mass. % Or less is more preferable. Furthermore, when the copolymer (3) has a monomer having a hydroxyl group, the copolymerization ratio is preferably 0.1% by mass or more and 10% by mass or less, and preferably 1% by mass or more. More preferably, it is 10 mass% or less.

  The acrylic polymer is obtained, for example, by a usual emulsion polymerization method. There is no restriction | limiting in particular regarding the method of emulsion polymerization, A conventionally well-known method can be used.

  For example, in a dispersion system containing the above-mentioned monomer, surfactant, radical polymerization initiator, and other additive components used as necessary in an aqueous medium as a basic composition component, each of the above monomers is included. An acrylic polymer is obtained by polymerizing the monomer composition. In the polymerization, a method of making the composition of the monomer composition to be supplied constant throughout the entire polymerization process, and changing the morphological composition of the particles of the resin dispersion produced by sequentially or continuously changing the polymerization process Various methods can be used as needed. When the acrylic polymer is obtained by emulsion polymerization, for example, it may be in the form of an aqueous dispersion (latex) containing water and a particulate acrylic polymer dispersed in the water.

  The surfactant is a compound having at least one or more hydrophilic groups and one or more lipophilic groups in one molecule. Various surfactants include non-reactive surfactants and reactive surfactants, preferably reactive surfactants, more preferably anionic reactive surfactants, and more preferably sulfonic acid. It is a reactive surfactant having a group. Since the specific example of surfactant is mentioned later, description is abbreviate | omitted here. This surfactant is preferably used in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the monomer composition. Surfactant is used individually by 1 type or in combination of 2 or more types.

  The radical polymerization initiator is one that initiates addition polymerization of monomers by radical decomposition with heat or a reducing substance, and any of inorganic initiators and organic initiators can be used. As the radical polymerization initiator, a water-soluble or oil-soluble polymerization initiator can be used. Since the specific example of a radical polymerization initiator is mentioned later, description is abbreviate | omitted here.

  The radical polymerization initiator can be used in an amount of 0.05 part by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the monomer composition. A radical polymerization initiator can be used individually by 1 type or in combination of 2 or more types.

  Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol and polyvinyl acetate. Examples of the fluorine-containing resin include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and ethylene-tetrafluoro. An ethylene copolymer is mentioned.

  Among the above thermoplastic polymers, from the viewpoint of improving the adhesion between the separator and the electrode, the high-temperature storage characteristics and the cycle characteristics of the electricity storage device, and achieving a thin film of the adhesive body between the electrode and the separator, An acrylic copolymer latex formed from an emulsion containing an emulsifier, an initiator, and water is preferred.

  In the present embodiment, the glass transition temperature (Tg) of the particulate polymer is preferably −50 ° C. or higher, more preferably −30 ° C. or higher, from the viewpoints of adhesion to the electrode and ion permeability. Preferably, it is more preferably 20 ° C or higher, and still more preferably 50 ° C or higher. Moreover, it is preferable that the glass transition temperature of a particulate polymer is 200 degrees C or less. The glass transition temperature in this embodiment is determined from a DSC curve obtained by differential scanning calorimetry (DSC). Specifically, the temperature at the intersection of a straight line obtained by extending the baseline on the low temperature side in the DSC curve to the high temperature side and the tangent at the inflection point of the stepwise change portion of the glass transition may be adopted as the glass transition temperature. it can. More specifically, it may be determined according to the method described in the examples. “Glass transition” refers to a change in calorific value associated with a change in the state of the polymer that is a test piece in DSC on the endothermic side. Such a change in heat quantity is observed as a step-like change shape in the DSC curve. The “step change” refers to a portion of the DSC curve until the curve moves away from the previous low-temperature base line to a new high-temperature base line. Note that a combination of a step change and a peak is also included in the step change. Further, the “inflection point” indicates a point at which the gradient of the DSC curve of the step-like change portion is maximized. Further, in the step-like change portion, when the upper side is the heat generation side, it can also be expressed as a point where the upward convex curve changes to the downward convex curve. “Peak” indicates a portion of the DSC curve from when the curve leaves the low-temperature side baseline until it returns to the same baseline again. “Baseline” refers to a DSC curve in a temperature region where no transition or reaction occurs in the test piece.

In this embodiment, the glass transition temperature Tg of the particulate polymer is, for example, the type of monomer used when producing the particulate polymer, and each single unit when the particulate polymer is a copolymer. It can adjust suitably by changing the compounding ratio of a monomer. That is, for each monomer used in the production of the particulate polymer, the Tg of the homopolymer generally shown (for example, described in “A WILEY-INTERSCIENCE PUBLICATION”) and the monomer The outline of the glass transition temperature can be estimated from the blending ratio. For example, a copolymer with a high proportion of monomers such as methyl methacrylate, acrylonitrile and methacrylic acid that gives a homopolymer with a Tg of about 100 ° C. has a high Tg and is about -50 ° C. A copolymer obtained by copolymerizing monomers such as n-butyl acrylate and 2-ethylhexyl acrylate at a high ratio to give a Tg homopolymer has a low Tg.
Moreover, Tg of a copolymer can be estimated also by the formula of FOX represented by following Numerical formula (1).
1 / Tg = W ₁ / Tg ₁ + W ₂ / Tg ₂ +... + W _i / Tg _i +... W _n / Tg _n (1)
Here, in the formula, Tg (K) is the Tg of the copolymer, Tg _i (K) is the Tg of the homopolymer of monomer i, and W _i is the mass fraction of each monomer. .
However, as the glass transition temperature Tg of the particulate polymer in the present embodiment, a value measured by the method using the DSC is adopted.

  From the viewpoints of wettability to the inorganic filler porous layer and the like, binding properties between the inorganic filler porous layer and the like and the thermoplastic polymer-containing layer, and adhesion to the electrode, the thermoplastic polymer-containing layer has a glass transition temperature of 20 It is preferred to include a polymer below From the viewpoint of ion permeability, the glass transition temperature of the polymer having a glass transition temperature of less than 20 ° C. is preferably −100 ° C. or higher, more preferably −50 ° C. or higher, and further preferably −40 ° C. or higher. From the viewpoint of the binding property between the thermoplastic polymer-containing layer and the thermoplastic polymer-containing layer, it is preferably less than 20 ° C, more preferably less than 15 ° C, and even more preferably less than -10 ° C.

  In this embodiment, it is preferable that the particulate polymer contained in the thermoplastic polymer-containing layer has at least two glass transition temperatures. The method for causing the particulate polymer to have at least two glass transition temperatures is not limited, but includes a method of blending two or more types of particulate polymers, and a particulate polymer having a core-shell structure. The method using is mentioned. The core-shell structure is a structure having a center part and an outer shell part covering the center part, and is a polymer having a dual structure form in which the types or compositions of the polymers constituting each part are different from each other. . In particular, the glass transition temperature of the whole particulate polymer can be controlled by combining a polymer having a high glass transition temperature and a polymer having a low glass transition temperature in a polymer blend and a core-shell structure. Moreover, a plurality of functions can be imparted to the entire particulate polymer.

  For example, when blending two or more types of particulate polymers, in particular, one or more polymers present in a region where the glass transition temperature is 20 ° C. or higher and one or more polymers present in a region where the glass transition temperature is less than 20 ° C. By blending with the polymer, it is possible to achieve both better anti-stickiness and better coatability to the substrate. The blend ratio of each polymer in the case of blending is 0.1: 99 as a ratio of the polymer existing in the region where the glass transition temperature is 20 ° C. or more and the polymer existing in the region where the glass transition temperature is less than 20 ° C. Is preferably in the range of 9.9 to 99.9: 0.1, more preferably 5:95 to 95: 5, still more preferably 50:50 to 95: 5, and particularly preferably 60: 40-90: 10.

  When using a particulate polymer having a core-shell structure, the adhesion and compatibility of the thermoplastic polymer-containing layer with other members (for example, an inorganic filler-containing layer) can be adjusted by selecting the polymer type of the outer shell portion. Can do. Further, by selecting the type of polymer in the central portion, for example, the adhesion to the electrode after hot pressing can be improved. Alternatively, the viscoelasticity of the thermoplastic polymer-containing layer can be controlled by combining a highly viscous polymer with a highly elastic polymer.

  The glass transition temperature of the outer shell portion (shell) of the thermoplastic polymer having a core-shell structure is not particularly limited, but is preferably less than 20 ° C, more preferably 15 ° C or less, and -30 ° C to 15 ° C. More preferably, it is as follows. The glass transition temperature of the central portion (core) of the thermoplastic polymer having a core-shell structure is not particularly limited, but is preferably 20 ° C or higher, more preferably 20 ° C or higher and 200 ° C or lower, and further 50 ° C or higher and 200 ° C or lower. preferable.

  The arithmetic average particle size of the particulate polymer is preferably 10 nm (0.01 μm) or more, more preferably 100 nm (0.10 μm) or more, and further preferably 200 nm (0.20 μm) or more. The arithmetic average particle size of the particulate polymer is preferably 1000 nm (1.0 μm) or less, more preferably 800 nm (0.80 μm) or less, and still more preferably 700 nm (0.70 μm) or less. . By setting the arithmetic average particle size to 10 nm or more, the size of the particulate polymer is secured so that the particulate polymer does not enter the pores in the inorganic filler porous layer, so that the ion permeability of the separator is maintained higher. it can. Therefore, in this case, it is preferable from the viewpoint of improving the adhesion between the electrode and the separator, the cycle characteristics of the electricity storage device, and the rate characteristics. In addition, it is preferable that the arithmetic average particle diameter be 1000 nm or less from the viewpoint of securing the dispersion stability when the thermoplastic polymer-containing layer containing the particulate polymer is formed from an aqueous dispersion. It is preferable from the viewpoint that the thickness of the plastic polymer-containing layer can be flexibly controlled. From these viewpoints, the arithmetic average particle diameter of the particulate polymer is 0.20 μm or more and 1.0 μm or less, and the average particle diameter D50 of the inorganic filler contained in the inorganic filler porous layer is 0.5 μm or more and 1.0. It is particularly preferred that it is less than. The arithmetic average particle diameter of the particulate polymer can be measured according to the method described in the following examples.

  The arithmetic average particle size of the particulate polymer is preferably larger than the average pore size of the inorganic filler porous layer, more preferably 1.2 times or more the average pore size of the inorganic filler porous layer, 1.5 times More preferably, it is more preferably 1.8 times or more. The arithmetic average particle size of the particulate polymer is preferably 6.0 times or less, more preferably 3.0 times or less, with respect to the average pore size of the inorganic filler porous layer. Since the arithmetic average particle size of the particulate polymer is 1.2 times or more than the average pore size of the inorganic filler porous layer, it becomes difficult for the particulate polymer to enter the pores of the inorganic filler porous layer. The permeability is further improved. On the other hand, when the arithmetic average particle size of the particulate polymer is 6.0 times or less than the average pore size of the inorganic filler porous layer, the binding force between the particulate polymer and the inorganic filler porous layer can be increased.

  The content of the particulate polymer contained in the inorganic filler porous layer is preferably 20% by volume or less, more preferably 15% by volume or less, and more preferably 10% by volume with respect to the total amount of the inorganic filler porous layer. % Or less is more preferable, and 5% by volume or less is particularly preferable. The content of the particulate polymer contained in the inorganic filler porous layer is 20% by volume or less, so that the particulate polymer that becomes a wasteful resistance in the electricity storage device is reduced, and an electricity storage device having further excellent permeability is provided. Can be provided.

  In order to balance the adhesion and blocking resistance of the separator, two or more types of particulate polymers each having different arithmetic average particle diameters can be contained in the thermoplastic polymer-containing layer. For example, a particulate polymer having an arithmetic average particle size of 10 nm or more and 300 nm or less (hereinafter referred to as “small particle size particle”) and a particulate polymer having an arithmetic average particle size of more than 100 nm and 2000 nm or less (hereinafter “ It is preferable to use a combination with “large particle size”.

  The particulate polymer described above can be produced by a known polymerization method except that the monomer described above is used. As a polymerization method, for example, an appropriate method such as solution polymerization, emulsion polymerization, bulk polymerization or the like can be employed. In particular, an emulsion polymerization method is preferred for the purpose of obtaining a particle-shaped dispersion. There is no restriction | limiting in particular regarding the method of emulsion polymerization, A conventionally well-known method can be used. For example, in a dispersion system containing the above-mentioned monomer, surfactant, radical polymerization initiator, and other additive components used as necessary in an aqueous medium as a basic composition component, each of the above monomers. A polymer is obtained by polymerizing the monomer composition. In the polymerization, the composition of the supplied monomer composition is made constant throughout the entire polymerization process, and the morphological composition change of the particles of the resin dispersion to be produced is changed by sequentially or continuously changing the polymerization process. Various methods can be used as needed, such as a giving method. When the polymer is obtained by emulsion polymerization, for example, it may be in the form of an aqueous dispersion (latex) containing water and a particulate polymer dispersed in the water.

  The surfactant is a compound having at least one or more hydrophilic groups and one or more lipophilic groups in one molecule. Examples of the surfactant include non-reactive alkyl sulfate, polyoxyethylene alkyl ether sulfate, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfosuccinate, alkyl diphenyl ether disulfonate, naphthalene sulfonate. Anionic surface activity such as formalin condensate, polyoxyethylene polycyclic phenyl ether sulfate, polyoxyethylene distyrenated phenyl ether sulfate, fatty acid salt, alkyl phosphate, polyoxyethylene alkylphenyl ether sulfate And non-reactive polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyethylene distyrenated Nonionic properties such as nyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, alkylalkanolamide, polyoxyethylene alkylphenyl ether Surfactant is mentioned. In addition to these, a so-called reactive surfactant in which an ethylenic double bond is introduced into the chemical structural formula of a surfactant having a hydrophilic group and a lipophilic group may be used.

  Examples of the anionic surfactant in the reactive surfactant include an ethylenically unsaturated monomer having a sulfonic acid group, a sulfonate group or a sulfate ester group and a salt thereof, and a sulfonic acid group, or A compound having a group (ammonium sulfonate group or alkali metal sulfonate group) which is an ammonium salt or an alkali metal salt thereof is preferable. Specifically, for example, alkylallylsulfosuccinate (for example, Eleminol (trademark) JS-20 manufactured by Sanyo Chemical Co., Ltd., Latemuru (trademark; manufactured by Kao Corporation), S-120, S-180A, S- 180), polyoxyethylene alkylpropenyl phenyl ether sulfate ester salt (for example, Aqualon (trademark; the same shall apply hereinafter) HS-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), α- [1- [ (Allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-polyoxyethylene sulfate ester salt (for example, Adeka soap (trademark; the same shall apply hereinafter) SE-10N manufactured by ADEKA Corporation), ammonium. = Α-sulfonato-ω-1- (allyloxymethyl) alkyloxypolyoxyethylene (eg, Aquaron KH-10 manufactured by Ichi Kogyo Seiyaku Co., Ltd.), styrene sulfonate (for example, Spinomer (trademark) NaSS manufactured by Tosoh Organic Chemical Co., Ltd.), α- [2-[(allyloxy)- 1- (alkyloxymethyl) ethyl] -ω-polyoxyethylene sulfate ester salt (for example, Adeka Soap SR-10 manufactured by ADEKA Corporation), polyoxyethylene polyoxybutylene (3-methyl-3- Butenyl) ether sulfate (for example, LATEMUL PD-104 manufactured by Kao Corporation) may be mentioned.

  Examples of the nonionic surfactant in the reactive surfactant include α- [1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-hydroxypolyoxyethylene (for example, Adeka Soap NE-20, NE-30, NE-40 manufactured by ADEKA Co., Ltd.), polyoxyethylene alkylpropenyl phenyl ether (for example, Aqualon RN-10, RN-20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) RN-30 and RN-50), α- [2-[(allyloxy) -1- (alkyloxymethyl) ethyl] -ω-hydroxypolyoxyethylene (for example, Adeka Soap ER manufactured by ADEKA Corporation) -10)), polyoxyethylene polyoxybutylene (3-methyl-3-butenyl) A Le (for example, Kao Corp. LATEMUL PD-420.) And the like.

  Among the above-mentioned various surfactants, reactive surfactants are preferable, anionic reactive surfactants are more preferable, and reactive surfactants having a sulfonic acid group are more preferable. The surfactant is preferably used in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the monomer composition. Surfactant is used individually by 1 type or in combination of 2 or more types.

  The radical polymerization initiator is one that initiates addition polymerization of monomers by radical decomposition with heat or a reducing substance, and any of inorganic initiators and organic initiators can be used. As the radical polymerization initiator, a water-soluble or oil-soluble polymerization initiator can be used. Examples of the water-soluble polymerization initiator include peroxodisulfates, peroxides, water-soluble azobis compounds, and peroxide-reducing agent redox systems. Examples of the peroxodisulfate include potassium peroxodisulfate (KPS), sodium peroxodisulfate (NPS), and ammonium peroxodisulfate (APS). Examples of the peroxide include hydrogen peroxide, t- Examples thereof include butyl hydroperoxide, t-butyl peroxymaleic acid, succinic acid peroxide, and benzoyl peroxide. Examples of water-soluble azobis compounds include 2,2-azobis (N-hydroxyethylisobutyramide), 2 And 2-azobis (2-amidinopropane) dichloride and 4,4-azobis (4-cyanopentanoic acid). Examples of the redox system of the peroxide-reducing agent include sodium peroxide and sodium peroxide. Sulfooxylate formaldehyde, sodium bisulfite, sodium thiosulfate Um, sodium hydroxymethanesulfinic acid, L- ascorbic acid, and its salts, cuprous salts, and include those that combine one or more reducing agents such as ferrous salts.

  The radical polymerization initiator is preferably used in an amount of 0.05 part by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the monomer composition. A radical polymerization initiator is used individually by 1 type or in combination of 2 or more types.

  In addition, the single quantity containing the ethylenically unsaturated monomer (P) which has a polyalkylene glycol group, the ethylenically unsaturated monomer (A) which has a cycloalkyl group, and another monomer (B). When the body composition is emulsion-polymerized to form a dispersion in which polymer particles are dispersed in a solvent (water), the solid content of the obtained dispersion may be 30% by mass or more and 70% by mass or less. preferable.

  The dispersion is preferably adjusted to have a pH in the range of 5 to 12 in order to maintain long-term dispersion stability. For pH adjustment, amines such as ammonia, sodium hydroxide, potassium hydroxide, and dimethylaminoethanol are preferably used, and pH is more preferably adjusted with ammonia (water) or sodium hydroxide.

  The aqueous dispersion in the present embodiment includes a polymer obtained by polymerizing the monomer composition containing the specific monomer as particles (polymer particles) dispersed in water. In addition to water and the polymer, the aqueous dispersion may contain a solvent such as methanol, ethanol, isopropyl alcohol, a dispersant, a lubricant, a thickener, a bactericide, and the like.

  In the present embodiment, since the thermoplastic polymer-containing layer can be easily formed by coating, a particulate polymer is formed by emulsion polymerization, and the resulting particulate polymer emulsion is used as an aqueous latex. It is preferable to do.

(Optional component)
The thermoplastic polymer-containing layer in the present embodiment may contain only the thermoplastic polymer, or may contain other optional components in addition to the thermoplastic polymer. Examples of the optional component include the inorganic filler described above for forming a filler porous layer. The content of the thermoplastic polymer in the thermoplastic polymer-containing layer is preferably 60% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, based on the total amount of the thermoplastic polymer-containing layer. Especially preferably, it is 98 mass% or more.

  From the viewpoint of improving the safety during the collision test, the separator of the present embodiment preferably has a thermal shrinkage ratio at TD at 130 ° C. of less than 12.0%, more preferably 0% or more and 10%. Or less, more preferably 0% or more and 5.0% or less. Here, when the thermal contraction rate at TD is less than 12.0%, occurrence of a short circuit other than a portion where an external force is applied when heat is generated by a short circuit during a collision test is more effectively suppressed. Thereby, the temperature rise of the whole battery and the smoke generation and the ignition which may be accompanied with it can be prevented more reliably. The adjustment of the thermal shrinkage rate of the separator can be performed by appropriately combining the above-described stretching operation of the substrate and heat treatment.

  The air permeability of the electricity storage device separator of the present embodiment is preferably 10 seconds / 100 cc or more and 10,000 seconds / 100 cc or less, more preferably 10 seconds / 100 cc or more and 1000 seconds / 100 cc or less, and further preferably 50 seconds. / 100cc to 500 seconds / 100cc. Thus, when the separator is applied to an electricity storage device, good high ion permeability is exhibited. This air permeability is the air resistance measured according to JIS P-8117, similar to the air permeability of the polyolefin porous substrate.

<Method for producing separator for power storage device>
[Manufacturing method of substrate]
The method for producing the substrate in the present embodiment is not particularly limited, and a known production method can be adopted. For example, when the base material is a polyolefin porous base material, the polyolefin resin composition and the plasticizer are melt-kneaded and formed into a sheet shape. A method in which a polyolefin resin composition containing a polyolefin-based resin as a main component 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, a polyolefin resin composition And an inorganic filler are melt-kneaded and formed on a sheet, and then a method of making the porous layer by peeling the interface between the polyolefin and the inorganic filler by stretching, and a poor solvent for the polyolefin after dissolving the polyolefin resin composition Porous by soaking in and coagulating polyolefin and removing solvent at the same time And a method for.

  Moreover, a well-known thing may be sufficient as the method of producing the nonwoven fabric or paper as a base material. The production method includes, for example, a chemical bond method in which a web is dipped in a binder, dried, and bonded between fibers; a heat-bondable fiber is mixed into the web, and the fibers are partially melted to bond between fibers. A needle punch method in which a needle having a stab is repeatedly stabbed into the web and mechanically entangled with the fiber;

  Hereinafter, as an example of a method for producing a polyolefin porous substrate (hereinafter, also simply referred to as “porous substrate”), a polyolefin resin composition and a plasticizer are melt-kneaded and molded into a sheet, and then the plasticizer A method of extracting the will be described. First, a polyolefin resin composition and a plasticizer are melt-kneaded. As the melt-kneading method, for example, polyolefin resin and other additives as required may be added to a resin kneading apparatus such as an extruder, kneader, lab plast mill, kneading roll, Banbury mixer, etc. A method of introducing a plasticizer at a ratio of kneading and kneading. At this time, it is preferable that the polyolefin resin, other additives, and the plasticizer are pre-kneaded in advance at a predetermined ratio using a Henschel mixer or the like before being added to the resin kneading apparatus. More preferably, only a part of the plasticizer is added in the pre-kneading, and the remaining plasticizer is kneaded while side-feeding the resin kneading apparatus.

  As the plasticizer, a non-volatile solvent capable of forming a uniform solution at a melting point or higher of the polyolefin can be used. Specific examples of such a non-volatile solvent include hydrocarbons such as liquid paraffin and paraffin wax; esters such as dioctyl phthalate and dibutyl phthalate; and higher alcohols such as oleyl alcohol and stearyl alcohol. Of these, liquid paraffin is preferred.

  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 30% by mass to 80% by mass, and more preferably 40% by mass to 70% by mass. By setting the mass fraction of the plasticizer within this range, it is preferable from the viewpoint of achieving both melt tension during melt molding and formability of a uniform and fine pore structure.

  Next, the melt-kneaded product obtained by heating and melting and kneading as described above is formed into a sheet shape. As a method for producing a sheet-like molded product, for example, the melt-kneaded product is extruded into a sheet shape via a T-die or the like, and is brought into contact with a heat conductor and cooled 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 solidification include metal, water, air, and the plasticizer itself, but a metal roll is preferable because of high heat conduction efficiency. In this case, when the molten kneaded material is sandwiched between the rolls when being brought into contact with the metal roll, the efficiency of heat conduction is further increased, the sheet is oriented and the film strength is increased, and the surface smoothness of the sheet is also improved. Therefore, it is more preferable. The die lip interval when extruding into a sheet form from the T die is preferably 400 μm or more and 3000 μm or less, and more preferably 500 μm or more and 2500 μm or less.

  It is preferable to subsequently stretch the sheet-like molded body thus obtained. As the stretching treatment, either uniaxial stretching or biaxial stretching can be suitably used. Biaxial stretching is preferred from the viewpoint of the strength and the like of the obtained microporous membrane. 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 porous substrate finally obtained is difficult to tear and has high puncture strength. Examples of the stretching method include simultaneous biaxial stretching, sequential biaxial stretching, multistage stretching, and multiple stretching. Simultaneous biaxial stretching is preferred from the viewpoints of improvement of puncture strength, uniformity of stretching, and shutdown property.

  The draw ratio is preferably in the range of 20 times to 100 times, more preferably in the range of 25 times to 50 times in terms of surface magnification. The stretching ratio in each axial direction is preferably in the range of 4 to 10 times in the MD direction, preferably in the range of 4 to 10 times in the TD direction, 5 to 8 times in the MD direction, and 5 times in the TD direction. More preferably, it is in the range of 8 times or less. By setting the draw ratio within this range, it is preferable in that a sufficient strength can be imparted, film breakage in the drawing process can be prevented, and high productivity can be obtained.

  The sheet-like molded body obtained as described above may be further rolled. Rolling can be performed, for example, by a pressing method using a double belt press or the like. By rolling, in particular, the orientation of the surface layer portion of the sheet-like molded body can be increased. The rolling surface magnification is preferably greater than 1 and 3 or less, more preferably greater than 1 and 2 or less. By setting the rolling magnification within this range, the film strength of the porous substrate finally obtained is increased, and a uniform porous structure can be formed in the thickness direction of the film, which is preferable.

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

  As the extraction solvent, it is preferable to use a solvent that is a poor solvent for the polyolefin resin and a good solvent for the plasticizer and has 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.

  In order to suppress the shrinkage of the porous substrate, a heat treatment such as heat fixation or heat relaxation may be performed after the stretching step or after the formation of the porous substrate. The porous substrate may be subjected to a post-treatment such as a hydrophilic treatment with a surfactant or the like, or a crosslinking treatment with ionizing radiation or the like.

[Method for forming porous inorganic filler layer]
An inorganic filler porous layer is formed, arranged and fixed on at least one surface (one surface) of the base material produced as described above. It does not specifically limit as a method of forming an inorganic filler porous layer on a base material, It can form by a well-known method. For example, the method of apply | coating the coating liquid containing an inorganic filler and a resin binder as needed to a base material is mentioned. The method for applying the coating solution to the substrate is not particularly limited as long as the required layer thickness and coating area can be realized. When the base material contains a resin like a polyolefin porous base material, the raw material containing the inorganic filler and the resin binder and the raw material of the base material containing the resin may be laminated and extruded by a coextrusion method. After the material and the inorganic filler porous layer (film) are produced individually, they may be bonded together.

  As the solvent of the coating solution, those capable of uniformly and stably dispersing or dissolving the inorganic filler and, if necessary, the resin binder are preferable. For example, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide , Water, ethanol, toluene, hot xylene, methylene chloride and hexane.

  Various additives such as surfactants, thickeners, wetting agents, antifoaming agents, PH preparations containing acids and alkalis are added to the coating solution in order to stabilize dispersion and improve coating properties. May be added. These additives are preferably those that can be removed when the solvent is removed, but are electrochemically stable and do not inhibit the battery reaction in the range of use of an electricity storage device such as a lithium ion secondary battery, and 200 ° C. If it is stable to an extent, it may remain in the inorganic filler porous layer.

  The method for dispersing or dissolving the inorganic filler and, if necessary, the resin binder in the medium of the coating liquid is not particularly limited as long as it is a method that can realize the dispersion characteristics of the coating liquid necessary for the coating process. Such methods include, for example, ball mill, bead mill, planetary ball mill, vibrating ball mill, sand mill, colloid mill, attritor, roll mill, high speed impeller dispersion, disperser, homogenizer, high speed impact mill, ultrasonic dispersion, stirring blade, etc. Mechanical agitation can be mentioned.

  The method for applying the coating liquid to the substrate is not particularly limited as long as the required thickness or coating area can be realized. For example, gravure coater method, small diameter gravure coater method, reverse roll coater method, transfer roll Examples include 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. .

  When applying the coating solution, the average pore size of the inorganic filler porous layer can be adjusted by adjusting the shear stress applied to the coating solution. By applying shearing, the arrangement of the inorganic filler changes, and by removing the solvent before the arrangement returns to the normal arrangement, an arrangement different from the normal arrangement can be obtained. For example, if the coating liquid has a dilatancy characteristic, the inorganic filler and the resin binder are more densely packed by shearing. Therefore, the average pore diameter of the formed inorganic filler porous layer is reduced by applying a large shear stress.

  Furthermore, if the surface treatment is applied to the surface of the substrate, particularly the polyolefin porous substrate, prior to the application of the coating solution, it becomes easier to apply the coating solution and the adhesion between the inorganic filler porous layer after coating and the substrate surface. Is preferable. The surface treatment method is not particularly limited as long as it does not significantly impair the porous structure that the substrate may have. For example, corona discharge treatment method, plasma discharge treatment method, mechanical surface roughening method, solvent treatment method , Acid treatment method, and ultraviolet oxidation method.

  In particular, the corona discharge treatment method, solvent treatment method, oxidation treatment method, or ultraviolet oxidation method changes the chemical properties of the substrate surface, affecting the average pore size of the inorganic filler porous layer after coating the coating solution. give. Although this factor is not certain, it is considered that the affinity for the solvent is changed by making the substrate surface more hydrophilic, and the solvent, the inorganic filler, and the resin binder are unevenly distributed in the coating solution. For example, when corona discharge treatment is performed on a substrate that is a porous film having a porous structure, and water is selected as the solvent of the coating solution, water collects on the surface of the porous membrane, and inorganic filler is collected at the interface between the coating solution and the atmosphere. By being driven away, the inorganic filler is arranged more densely, and as a result, the average pore diameter of the inorganic filler porous layer is considered to be small. In this case, the average pore diameter of the inorganic filler porous layer tends to decrease as the strength of the surface treatment increases.

  The method for removing the solvent from the coating film after coating is not particularly limited as long as it does not adversely affect the substrate. For example, a method of drying at a temperature below the melting point of the material constituting the substrate while fixing the substrate, a method of drying under reduced pressure at a low temperature, and immersing in a poor solvent for the resin binder to solidify the resin binder while simultaneously removing the solvent The method of extracting is mentioned. Further, a part of the solvent may be left as long as the device characteristics are not significantly affected. From the viewpoint of controlling the shrinkage stress in the MD direction of the laminate of the substrate and the inorganic filler porous layer, it is preferable to appropriately adjust the drying temperature, the winding tension, and the like.

  When removing the coating solution from the coating film by drying, the average pore size of the inorganic filler porous layer can be adjusted by changing the drying conditions. If the drying conditions are made stronger and the drying speed is increased, it is considered that the average pore size is increased as a result of fixing the inorganic filler as it is without adjusting the shape from a sufficiently dispersed state. On the other hand, when the drying conditions are more relaxed, the dispersed inorganic filler tries to take a more energetically stable structure in the process of drying the solvent, resulting in a smaller average pore size of the inorganic filler porous layer. It is considered to be. Moreover, if the viscosity of a coating liquid is low, it will become easy to take a stable structure and the average hole diameter of an inorganic filler porous layer will become smaller. Furthermore, the dispersion state of the inorganic filler is also affected by the type of the inorganic filler, the type of the solvent, the presence or absence of the added surfactant, and the type of the surfactant.

  By calendering the laminate of the inorganic filler porous layer and the substrate, the average pore size of the inorganic filler porous layer can be reduced. There is no particular limitation on the calendering method, and a method of transporting the coating liquid while applying pressure with a nip roll after drying the coating solution may be used.

[Method of arranging thermoplastic polymer-containing layer]
A thermoplastic polymer-containing layer is disposed on at least a part of the surface of the inorganic filler porous layer produced as described above. When the inorganic filler porous layer is disposed only on one side of the substrate, the thermoplastic polymer-containing layer may be disposed on at least a part of the surface of the substrate in addition to the surface of the inorganic filler porous layer. The method for disposing the thermoplastic polymer-containing layer is not particularly limited, and examples thereof include a method of applying a coating liquid containing the particulate polymer to the surface of the inorganic filler porous layer or the polyolefin porous substrate.

  As the coating solution, a dispersion in which a particulate polymer is dispersed in a solvent that does not dissolve the polymer can be preferably used. Particularly preferred is a case where a particulate polymer is synthesized by emulsion polymerization, and an emulsion obtained by the emulsion polymerization is used as it is as a coating solution.

  There is no particular limitation on the method for applying the coating solution containing the particulate polymer on the substrate as long as it can realize a desired coating pattern, coating film thickness, and coating area. For example, gravure coater method, small diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, dip coater method, knife coater method, air doctor coater method, blade coater method, rod coater method, squeeze coater method, cast Examples thereof include a coater method, a die coater method, a screen printing method, a spray coating method, and an ink jet coating method. Among these, the gravure coater method or the spray coating method is preferable from the viewpoint that the degree of freedom of the coating shape of the particulate polymer is high and a preferable area ratio can be easily obtained.

  As a medium for the coating solution, water or a mixed solvent composed of water and a water-soluble organic medium is preferable. Although it does not specifically limit as a water-soluble organic medium, For example, ethanol, methanol, etc. can be mentioned. Among these, water is more preferable. When applying the coating liquid to the base material, if the coating liquid gets into the base material, the particulate polymer containing the polymer closes the surface and the inside of the hole of the base material and the permeability is lowered. It becomes easy to do. In this regard, when water is used as the solvent or dispersion medium of the coating solution, it becomes difficult for the coating solution to enter the substrate, and the particulate polymer containing the polymer is present mainly on the outer surface of the substrate. Since it becomes easy, the fall of permeability can be controlled more effectively, and is preferred. Examples of the solvent or dispersion medium that can be used in combination with water include ethanol and methanol.

  It is preferable to perform surface treatment on the surface of the base material prior to coating, because the coating liquid can be easily applied and the adhesion between the base material and the particulate polymer is improved. Examples of the surface treatment method include a corona discharge treatment method, a plasma treatment method, a mechanical surface roughening method, a solvent treatment method, an acid treatment method, and an ultraviolet oxidation method.

  The method for removing the solvent from the coating film after coating is not particularly limited as long as it does not adversely affect the base material and the thermoplastic polymer-containing layer. For example, a method of drying the substrate at a temperature below its melting point while fixing the substrate, a method of drying under reduced pressure at a low temperature, and simultaneously solidifying the particulate polymer by dipping in a poor solvent for the particulate polymer Examples include a method of extracting a solvent.

<Power storage device>
The electricity storage device including the electricity storage device separator of the present embodiment may be the same as that conventionally used except that the electricity storage device separator is provided. Although it does not specifically limit as an electrical storage device, For example, batteries, such as a non-aqueous electrolyte secondary battery, a capacitor, and a capacitor are mentioned. Among these, from the viewpoint of more effectively obtaining the benefits of the effects of the present invention, a battery is preferable, a non-aqueous electrolyte secondary battery is more preferable, and a lithium ion secondary battery is still more preferable. Since the separator of this embodiment is provided, the electricity storage device is excellent in device characteristics such as electricity storage performance. Moreover, the lithium ion secondary battery is excellent in battery characteristics.

  It is preferable that the separator of this embodiment has a peel strength of 2 N / m or more when the separator is overlapped with an electrode and pressed under conditions of a press temperature of 90 ° C., a press pressure of 1.0 MPa, and a press time of 5 seconds. This means that the separator of this embodiment has adhesiveness to the electrode. By setting the peel strength within this range, the adhesiveness between the separator and the electrode is sufficiently ensured, and the press back when the wound body composed of the electrode and the separator is press-molded can be suppressed. In addition, it is possible to prevent peeling and positional deviation after press-molding a laminated body composed of a sheet-like electrode and a sheet-like separator. Therefore, it is possible to suppress the yield reduction in the power storage device assembly process and shorten the production process time. When pressing, it is preferable to press the cushioning material so that the pressure is evenly applied. In the measurement of peel strength, the peel strength between the electrode and the separator is measured at a tensile speed of 200 mm / min using an Autograph AG-IS type (trademark) manufactured by Shimadzu Corporation according to JIS K6854-2.

  The electrode used for measurement of the peel strength with the electrode may be either a positive electrode or a negative electrode, but in order to appropriately grasp the effect of the electricity storage device separator of this embodiment, it is appropriate to use the positive electrode. is there. In particular, when the electricity storage device is a lithium ion secondary battery, a positive electrode for a lithium ion secondary battery in which a positive electrode active material layer containing a positive electrode active material is formed on a positive electrode current collector, and the positive electrode active material layer is a separator It is appropriate that the measurement is carried out after the layers are laminated so as to face the formation surface of the thermoplastic polymer-containing layer and hot-pressed as described above. This positive electrode for a lithium ion secondary battery will be described later.

  Hereinafter, a suitable aspect in the case where the electricity storage device is a non-aqueous electrolyte secondary battery will be described.

When manufacturing a lithium ion secondary battery using the separator of this embodiment, there is no limitation in a positive electrode, a negative electrode, and a nonaqueous electrolyte, A well-known thing can be used, respectively.
As the positive electrode, a positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on a positive electrode current collector can be suitably used. Examples of the positive electrode current collector include an aluminum foil. Examples of the positive electrode active material include lithium-containing composite oxides such as LiCoO ₂ , LiNiO ₂ , spinel type LiMnO ₄ , and olivine type LiFePO ₄ . In addition to the positive electrode active material, the positive electrode active material layer may appropriately include a binder, a conductive material, and the like.

  As the negative electrode, a negative electrode in which a negative electrode active material layer containing a negative electrode active material is formed on a negative electrode current collector can be suitably used. Examples of the negative electrode current collector include copper foil. Examples of the negative electrode active material include carbon materials such as graphite, non-graphitizable carbon, graphitizable carbon, and composite carbon; silicon, tin, lithium metal, and various alloy materials.

The nonaqueous electrolytic solution is not particularly limited, but an electrolytic solution 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 of the electrolyte include lithium salts such as LiClO ₄ , LiBF ₄ , and LiPF ₆ .

<Method for manufacturing power storage device>
The method for producing the electricity storage device using the electricity storage device separator of the present embodiment is not particularly limited. For example, the following method can be illustrated. The separator of this embodiment is manufactured as a vertically long separator having a width of 10 to 500 mm (preferably 80 to 500 mm) and a length of 200 to 4000 m (preferably 1000 to 4000 m), and the separator is a positive electrode-separator-negative electrode- Laminated in the order of separator, or negative electrode-separator-positive electrode-separator, wound into a circular or flat spiral shape to obtain a wound body, and the wound body is housed in a device can (for example, a battery can); It can be manufactured by injecting an electrolytic solution. There is a laminate composed of a sheet-like separator and an electrode (for example, a positive electrode-separator-negative electrode-separator-positive electrode, or a negative electrode-separator-positive electrode-separator-negative electrode laminated in the order of a plate), or an electrode and a separator. You may manufacture by winding the thing into the device container (for example, film made from aluminum), and injecting electrolyte solution.

  At this time, it is possible to press the laminated body or the wound body. Specifically, the separator for an electricity storage device of the present embodiment, an electrode having a current collector and an active material layer formed on at least one surface of the current collector, the former thermoplastic polymer-containing layer and the active material An example of the method is that pressing is performed so that the layers face each other.

  The press temperature is preferably 20 ° C. or higher, for example, as a temperature at which adhesiveness can be effectively expressed. The press temperature is preferably lower than the melting point of the material contained in the substrate, and more preferably 120 ° C. or less, in order to suppress clogging or thermal shrinkage of holes in the separator due to hot pressing. The press pressure is preferably 20 MPa or less from the viewpoint of suppressing clogging of holes in the separator. The press time may be 1 second or less when a roll press is used, or may be a surface press for several hours, but 2 hours or less is preferable from the viewpoint of productivity. If the separator for an electricity storage device of the present embodiment is used and the manufacturing process described above is performed, it is possible to suppress press back when the wound body including the electrode and the separator is press-molded. In addition, it is possible to prevent peeling and positional deviation after press-molding a laminated body composed of a sheet-like electrode and a sheet-like separator. Therefore, it is preferable because the yield reduction in the device assembly process can be suppressed and the production process time can be shortened.

  The electricity storage device manufactured as described above, particularly the lithium ion secondary battery, has a separator having high adhesiveness and reduced ionic resistance, and therefore has excellent battery characteristics (rate characteristics) and long-term continuity. Excellent operating durability (cycle characteristics).

  The physical properties in the following examples were evaluated according to the following methods.

(1) Solid content About 1 g of the obtained thermoplastic polymer aqueous dispersion was precisely weighed on an aluminum dish, and the mass of the aqueous dispersion weighed at this time was defined as (a) g. It was dried for 1 hour with a 130 ° C. hot air dryer, and the dry mass of the dried thermoplastic polymer was (b) g. The solid content was calculated by the following formula.
Solid content = (b) / (a) × 100 [%]

(2) Average particle size (D50) and particle size distribution of inorganic filler The average particle size and particle size distribution of the inorganic filler were measured using a particle size measuring device (product name “Microtrac UPA150” manufactured by Nikkiso Co., Ltd.). As the measurement conditions, the loading index = 0.20, the measurement time was 300 seconds, and the value of 50% particle diameter (D50) in the obtained data was described as the average particle diameter.

(3) Average particle diameter of resin binder and particulate polymer (D50)
The average particle diameter (D50) of the resin binder was measured using a particle diameter measuring device (product name “Microtrac UPA150” manufactured by Nikkiso Co., Ltd.). As the measurement conditions, the loading index = 0.20, the measurement time was 300 seconds, and the value of 50% particle diameter (D50) in the obtained data was described as the average particle diameter.

(4) Average pore diameter of the inorganic filler porous layer The average pore diameter of the inorganic filler porous layer was determined by observing the separator cross section. The cross section was produced by a broad ion beam (BIB) in order to reduce the variation in the depth direction of the cross section, and the obtained cross section was observed using a scanning electron microscope. When processing with BIB, the separator was cooled to just before in order to reduce damage to the separator. Specifically, the separator was allowed to stand for 24 hours in a -40 ° C cooling device. Next, the separator cross section obtained was subjected to conduction treatment with C paste and Os coating, and then using “HITACHI S-4700” (product name, manufactured by Hitachi High-Tech Fielding Co., Ltd.), an imaging magnification of 10,000 times, acceleration voltage Photographing was performed at a setting of 1.0 kV, detector: secondary electron (information UPPER). In the observation field of view, the separator surface was oriented in parallel with the horizontal direction, and the central part of the inorganic filler porous layer in the thickness direction was reflected in the center of the field of view.

  From the obtained electronic image, the obtained observation visual field was identified for the inorganic filler particles contained in the visual field using image analysis processing software ImageJ (version 1.46). Specifically, an electronic image of a desired cross-sectional SEM was opened, and a region corresponding to the inorganic filler porous layer was selected using “Rectangular selections” in order to select an evaluation area. Specifically, the line between the interface between the base material and the inorganic filler porous layer and the part sandwiched between straight lines parallel to the interface passing through the part farthest from the base material where the inorganic filler exists were selected. Subsequently, in order to create the selected region in another file, a new electronic image of only the inorganic filler porous layer was created using “Duplicate”. Next, the inorganic filler porous layer was binarized so that the inorganic filler portion was white and the pore portion was black. Specifically, “Threshold” was selected, and processing was performed by setting the range to be inverted out of 256 gradations to “0-100”. As an example, FIG. 1 shows a schematic diagram of an inorganic filler porous layer after binarization.

  A horizontal horizontal line that divides the vertical direction of the visual field into four equal parts is drawn on the binarized image obtained here, and the inorganic filler or resin binder is closed on the line by an inorganic filler or resin binder. The length of the part where no was present was measured. All the measurement points that can be measured were measured, and only the measurement point that was 50 nm or more was regarded as the median value as the average pore diameter of the inorganic filler porous layer. For example, FIG. 2 shows an example in which a horizontal line obtained by dividing the vertical direction of the visual field into four equal parts is drawn.

(5) Content (abundance ratio) of particulate polymer contained in the inorganic filler porous layer
The cross-sectional image of the inorganic filler porous layer taken when the average pore size of the inorganic filler porous layer was determined was used to determine the abundance ratio of the particulate polymer in the inorganic filler porous layer. In the observation field of view, the cross section shows the area between the line between the interface between the base material and the porous inorganic filler layer and the straight line parallel to the interface passing through the part farthest from the base material where the inorganic filler exists. The area ratio of the particulate filler present in the inorganic filler porous layer was defined as the content (abundance ratio) of the particulate polymer. For the identification of the particulate polymer, mapping detection of carbon atoms by SEM-EDX was used. Specifically, as a pretreatment of the sample, the sample was attached to a carbon tape, and then an Os coating treatment was performed. Using this sample, a scanning electron microscope “HITACHI S-4700” (product name, manufactured by Hitachi High-Tech Fielding Co., Ltd.) and an energy dispersive X-ray analyzer “EX250” (product name, HORIBA, Ltd.) were used, and the acceleration voltage was 20 kV. Elemental mapping was performed on the SEM image at a measurement magnification of 10,000. The operating distance was 15 mm, and the number of integrations was 20 times. A grid-like line having a width of 100 μm is drawn on the obtained mapping image, and the particulate polymer has an area of a grid where the number of detection points where C is detected in one grid is 50 or more. The area. Finally, the content (presence ratio) of the particulate polymer contained in the inorganic filler porous layer was calculated by dividing the area where the particulate polymer was present by the area of the inorganic filler porous layer. In addition, according to this method, the resin binder contained in the inorganic filler porous layer is not detected.

(6) Arithmetic average particle size of particulate polymer The arithmetic average particle size of the particulate polymer was determined by using a scanning electron microscope (SEM) (model “S-4800”, manufactured by HITACHI) ) And observing at an acceleration voltage of 1.0 kV and 30000 times. The part with the largest diameter of the particulate polymer was defined as the particle diameter, and the average value of the particle diameters of 20 arbitrarily selected particulate polymers was defined as the average particle diameter.

(7) Average pore diameter of thermoplastic polymer-containing layer It is known that the fluid inside the capillary follows a Knudsen flow when the mean free path of the fluid is larger than the pore diameter of the capillary, and a Poiseuille flow when it is small. Therefore, it is assumed that the air flow in the air permeability measurement of the thermoplastic polymer-containing layer follows the Knudsen flow, and the water flow in the water permeability measurement of the microporous membrane follows the Poiseuille flow.

The average pore diameter d (μm) of the thermoplastic polymer-containing layer is such that the air permeation rate constant R _gas (m ³ / (m ² · sec · Pa)), 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 (= 101325 Pa), porosity ε (%), film thickness L (μm), It calculated | required using following Formula.
d = 2ν × (R _liq / R _gas ) × (16η / 3Ps) × 10 ⁶

Here, R _gas was calculated | required from the air permeability (sec) using the following Formula.
R _gas = 0.0001 / (air permeability × (6.424 × 10 ⁻⁴ ) × (0.01276 × 101325))

R _liq was determined from the water permeability (cm ³ / (cm ² · sec · Pa)) using the following equation.
R _liq = water permeability / 100

The water permeability was determined as follows. A thermoplastic polymer-containing layer previously immersed in ethanol was set in a stainless steel liquid-permeable cell having a diameter of 41 mm, and after the ethanol in the layer was washed with water, water was permeated at a differential pressure of about 50000 Pa, and 120 sec. The water permeability per unit time, unit pressure, and unit area was calculated from the water permeability (cm ³ ) when the time passed, and this was defined as the water permeability.

Ν is a gas constant R (= 8.314), an absolute temperature T (K), a circumference ratio π, and an average molecular weight M of air (= 2.896 × 10 ⁻² kg / mol), using the following formula. Asked.
ν = ((8R × T) / (π × M)) ^1/2

(8) Base material thickness (μm)
A sample of 10 cm × 10 cm square is cut out from the base material, nine locations (3 points × 3 points) are selected in a lattice shape, and the room temperature is 23 ± 2 using a microthickness meter (Toyo Seiki Seisakusho Co., Ltd., type KBM). The thickness was measured at ° C. The average value of the nine measured values obtained was calculated as the thickness of the substrate.

(9) Thickness of inorganic filler porous layer and thickness of thermoplastic polymer-containing layer The thickness of inorganic filler porous layer and the thickness of the thermoplastic polymer-containing layer were measured as follows. First, the separator was frozen and cut, and the cross section was confirmed by SEM (model S-4800, manufactured by HITACHI). From the obtained visual field, the thickness of the inorganic filler porous layer and the thickness of the thermoplastic polymer-containing layer were measured. Specifically, a separator sample was cut to about 1.5 mm × 2.0 mm and stained with ruthenium. The dyed sample and ethanol were placed in a gelatin capsule, frozen with liquid nitrogen, and then cleaved with a hammer. The cleaved sample was subjected to osmium vapor deposition, observed at an acceleration voltage of 1.0 kV and 30000 times, and the thickness of the inorganic filler porous layer and the thickness of the thermoplastic polymer-containing layer were calculated. In addition, the boundary line between the part where the porous structure of the cross section of the base material can be seen and the part where it cannot be seen in the SEM image, and the line farthest from the base material parallel to the inorganic filler porous layer and the thermoplastic polymer-containing layer The shortest distance was defined as the region of the thickness of the inorganic filler porous layer and the thickness of the thermoplastic polymer-containing layer, respectively. When there was a thermoplastic polymer-containing layer on the inorganic filler porous layer, the distance obtained by subtracting the thickness of the inorganic filler porous layer from the distance from the substrate to the thermoplastic polymer-containing layer was defined as the thickness of the thermoplastic polymer-containing layer.

(10) Thermal contraction rate (%) at 130 ° C. of laminate of separator and substrate and inorganic filler porous layer
A sample obtained by cutting the laminate to 100 mm in the TD direction and 100 mm in the MD direction was left in an oven at 130 ° C. for 1 hour. At this time, the sample was sandwiched between two sheets of paper so that the hot air did not directly hit the sample. After the sample was taken out of the oven and cooled, its length (mm) was measured, and the thermal contraction rate of TD was calculated by the following formula.
TD heat shrinkage rate (%) = 100-length in TD after heating (mm)

(11) Composition analysis of inorganic filler After filling an inorganic filler in a 20 mmφ aluminum ring and forming a tablet, all element qualification is performed using a fluorescent X-ray measurement apparatus (product name “ZSX-100e” (Rh tube) manufactured by Rigaku). Analysis was performed, the content of each element was calculated semi-quantitatively from the peak intensity, and the composition was determined.

(12) Measurement of glass transition temperature of thermoplastic polymer An appropriate amount of an aqueous dispersion (solid content = 38 to 42% by mass, pH = 9.0) containing a thermoplastic polymer is placed in an aluminum dish and heated at 130 ° C. And dried for 30 minutes to obtain a dry film. About 17 mg of the dried film was filled in an aluminum container for measurement, and a DSC curve and a DDSC curve in a nitrogen atmosphere were obtained with a DSC measuring apparatus (manufactured by Shimadzu Corporation, model name “DSC6220”). The measurement conditions were as follows.
First stage temperature increase program: Start at 70 ° C., increase temperature at a rate of 15 ° C. per minute. Maintained for 5 minutes after reaching 110 ° C.
Second stage temperature drop program: temperature drop from 110 ° C. at a rate of 40 ° C. per minute. Maintained for 5 minutes after reaching -50 ° C.
Third stage temperature increase program: Temperature is increased from -50 ° C to 130 ° C at a rate of 15 ° C per minute. DSC and DDSC data are acquired at the third stage of temperature rise.
The intersection of the baseline (the straight line obtained by extending the baseline in the obtained DSC curve to the high temperature side) and the tangent at the inflection point (the point where the upwardly convex curve changes to the downwardly convex curve) is defined as the glass transition temperature ( Tg).

(13) Viscosity average molecular weight Mv
Based on ASTM-D4020, the intrinsic viscosity [η] at 135 ° C. was determined in a decalin solvent. Using this [η] value, the viscosity average molecular weight Mv was calculated from the relationship of the following mathematical formula.
In the case of polyethylene: [η] = 0.00068 × Mv ^0.67
In the case of polypropylene: [η] = 1.10 × Mv ^0.80

(14) Porosity A 10 cm × 10 cm square sample was cut out from a substrate which is a polyolefin microporous film, and its volume (cm ³ ) and mass (g) were determined. Using these values, the density of the substrate was 0.95 (g / cm ³ ), and the porosity was determined from the following formula: Porosity (%) = (1−mass / volume / 0.95) × 100

(15) Air permeability (sec / 100cc)
About the base material which is a polyolefin microporous film, in accordance with JIS P-8117, the air resistance measured by a Gurley type air permeability meter G-B2 (model name) manufactured by Toyo Seiki Co., Ltd. It was. When the inorganic filler porous layer was present only on one side of the substrate, the needle was pierced from the surface where the inorganic filler porous layer was present.

(16) Puncture strength (gf)
Using a handy compression tester KES-G5 (model name) manufactured by Kato Tech, the substrate was fixed with a sample holder having a diameter of 11.3 mm at the opening. Next, a maximum puncture load is obtained by performing a puncture test in a 25 ° C atmosphere at a puncture speed of 2 mm / sec using a needle with a radius of curvature of 0.5 mm at the center of the fixed substrate. Was measured. The value obtained by converting the maximum puncture load per 20 μm thickness was defined as the puncture strength (gf / 20 μm). The same measurement method was used for the laminate of the substrate and the inorganic filler porous layer, and the laminate of the substrate, the inorganic filler porous layer, and the thermoplastic polymer. When the inorganic filler porous layer was present only on one side of the substrate, the needle was pierced from the surface where the inorganic filler porous layer was present.

(17) Rate characteristics a. Production of positive electrode 90.4% by mass of nickel, manganese, cobalt composite oxide (NMC) (Ni: Mn: Co = 1: 1: 1 (element ratio), density 4.70 g / cm ³ ) as a positive electrode active material, 1.6% by mass of graphite powder (KS6) (density 2.26 g / cm ³ , number average particle diameter 6.5 μm) and acetylene black powder (AB) (density 1.95 g / cm ³ , number average) as conductive aids The particle diameter is 48 nm) and 3.8% by mass of polyvinylidene fluoride (PVDF) (density 1.75 g / cm ³ ) as a binder is mixed at a ratio of 4.2% by mass, and these are mixed with N-methylpyrrolidone (NMP). A slurry was prepared by dispersing in the slurry. This slurry was applied to one side of a 20 μm-thick aluminum foil serving as a positive electrode current collector using a die coater, dried at 130 ° C. for 3 minutes, and then subjected to compression molding using a roll press to obtain a positive electrode. Produced. The coating amount of the positive electrode active material at this time was 109 g / m ² .

b. Graphite powder A as prepared negative active material of the negative electrode (density 2.23 g / cm ^3, number average particle diameter 12.7 [mu] m) 87.6% by weight and graphite powder B (density 2.27 g / cm ^3, number average particle diameter 6.5 μm) is 9.7% by mass, and the ammonium salt of carboxymethyl cellulose as a binder is 1.4% by mass (in terms of solid content) (solid content concentration is 1.83% by mass aqueous solution) and the diene rubber latex is 1.7% by mass ( (Solid content conversion) (solid content concentration 40 mass% aqueous solution) 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 produce a negative electrode. The coating amount of the negative electrode active material at this time was 5.2 g / m ² .

c. Preparation of non-aqueous electrolyte solution By dissolving LiPF ₆ as a solute in a mixed solvent of ethylene carbonate: ethyl methyl carbonate = 1: 2 (volume ratio) to a concentration of 1.0 mol / L, a non-aqueous electrolyte solution was prepared. Prepared.

d. Battery assembly A separator or a base material was cut into a circle of 24 mmφ, and a positive electrode and a negative electrode were cut into a circle of 16 mmφ each. The negative electrode, the separator or the substrate, and the positive electrode were stacked in this order so that the positive electrode and the active material surface of the negative electrode were opposed to each other, and were accommodated in a stainless steel container with a lid. The container and the lid were insulated, and the container was in contact with the negative electrode copper foil and the lid was in contact with the positive electrode aluminum foil. A battery was assembled by injecting 0.4 ml of the non-aqueous electrolyte into the container and sealing it.

e. Evaluation of rate characteristics d. After charging the simple battery assembled in step 3 at 25 ° C. to a battery voltage of 4.2 V at a current value of 3 mA (about 0.5 C), the current value starts to be reduced from 3 mA so as to maintain 4.2 V. The first charge after the battery was made was performed for a total of about 6 hours. Thereafter, the battery was discharged to a battery voltage of 3.0 V at a current value of 3 mA.
Next, after charging to a battery voltage of 4.2 V at a current value of 6 mA (about 1.0 C) at 25 ° C., the current value starts to be reduced from 6 mA so as to hold 4.2 V, so that a total of about 3 Charged for hours. Thereafter, the discharge capacity when discharging to a battery voltage of 3.0 V at a current value of 6 mA was defined as 1 C discharge capacity (mAh).
Next, after charging to a battery voltage of 4.2 V at a current value of 6 mA (about 1.0 C) at 25 ° C., the current value starts to be reduced from 6 mA so as to hold 4.2 V, so that a total of about 3 Charged for hours. Thereafter, the discharge capacity when discharged to a battery voltage of 3.0 V at a current value of 12 mA (about 2.0 C) was defined as 2 C discharge capacity (mAh).
Then, the ratio of the 2C discharge capacity to the 1C discharge capacity was calculated, and this value was used as the rate characteristic.
Rate characteristic (%) = (2C discharge capacity / 1C discharge capacity) × 100

Evaluation criteria for rate characteristic (%) ○ (good): rate characteristic is over 85% Δ (possible): rate characteristic is over 80% and 85% or less × (defect): rate characteristic is 80% or less

(18) Blocking resistance (handling property) of separator
A separator and a positive electrode current collector (aluminum foil manufactured by Fujishikushi Paper Co., Ltd., thickness: 20 μm) as a adherend are cut into 30 mm × 150 mm, and are stacked, and the laminate is then a Teflon (registered trademark) sheet. (Naflon (trademark) PTFE sheet TOMBO-No.9000 manufactured by NICHIAS Corporation). About each sample, the sample for a test was obtained by pressing in the lamination direction on condition of following 1) and 2).
1) 25 ° C., 5 MPa, 3 minutes 2) 40 ° C., 5 MPa, 3 minutes The peel strength between the separator and the positive electrode current collector of each of the obtained test samples was measured using an autograph AG-IS type manufactured by Shimadzu Corporation. (Trademark) was used and measured at a tensile speed of 200 mm / min according to JIS K6854-2. Based on the peel strength value, the following evaluation criteria were used.
<Evaluation criteria>
8N / m or less ... ○
Over 8N / m ... ×

(19) Surface coverage of thermoplastic polymer-containing layer The surface coverage of the thermoplastic polymer-containing layer was measured using a scanning electron microscope (SEM) (model: S-4800, manufactured by HITACHI). The separator which is a sample was vapor-deposited on osmium, and observed under conditions of an acceleration voltage of 1.0 kV and 50 times, and the surface coverage was calculated from the following formula. In addition, the area | region where the porous structure of the base-material (polyolefin microporous film) surface is not visible in a SEM image was made into the thermoplastic polymer content layer area | region.
Surface coverage of thermoplastic polymer-containing layer (%) = area of thermoplastic polymer-containing layer ÷ (area including pore portion of substrate + area of thermoplastic polymer-containing layer) × 100
The surface coverage in each sample was measured three times, and the arithmetic average value was obtained.

(20) Adhesiveness to electrode The separator for an electricity storage device obtained in each of Examples and Comparative Examples, and a positive electrode as an adherend (manufactured by Enertech, positive electrode material: LiCoO ₂ , conductive auxiliary agent: acetylene black, binder: PVDF, LiCoO ₂ / acetylene black / PVDF (mass ratio) = 95/2/3, L / W: 36 mg / cm ² on both sides, density: 3.9 g / cc, thickness of Al current collector: 15 μm, after pressing The thickness of the positive electrode of 107 μm) was cut into a rectangular shape having a width of 15 mm and a length of 60 mm, respectively, and the thermoplastic polymer-containing layer of the separator and the positive electrode active material were overlapped to obtain a laminate, The laminate was pressed under the following conditions.
Press pressure: 1 MPa
Temperature: 100 ° C
Press time: 5 seconds

About the laminated body after pressing, 90 ° at a peeling speed of 50 mm / min by a method in which an electrode is fixed, a separator is gripped and pulled using a force gauge ZP5N and MX2-500N (product name) manufactured by Imada Co., Ltd. A peel test was performed and the peel strength was measured. At this time, the average value of the peel strength in a peel test for 40 mm in length performed under the above conditions was adopted as the peel strength, and the adhesion with the electrode was evaluated according to the following criteria.
A (remarkably good): The peel strength is 15 N / m or more.
B (good): The peel strength is 5 N / m or more and less than 15 N / m.
C (defect): Peel strength is less than 5 N / m.

[Production Example 1-1] (Production of polyolefin microporous membrane B1)
Mv is 700,000, 45 parts by mass of homopolymer high density polyethylene, Mv is 300,000, 45 parts by mass of homopolymer high density polyethylene, Mv is 400,000, and Hv is polypropylene and Mv is 15 Ten parts by mass of a mixture of homopolymers of polypropylene (mass ratio = 4: 3), which was 10,000, was dry blended using a tumbler blender. 1 part by mass of tetrakis- [methylene- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane as an antioxidant was added to 99 parts by mass of the obtained polyolefin mixture, and again a tumbler blender. Was used for dry blending to obtain a mixture. The obtained mixture was supplied to the 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 operating conditions of the feeder and the pump were adjusted so that the ratio of liquid paraffin to 100 parts by mass of the total mixture to be extruded was 65 parts by mass, that is, the ratio of the resin composition was 35 parts by mass.

  Next, they are melt-kneaded while being heated to 230 ° C. in a twin-screw extruder, and the obtained melt-kneaded product is extruded through a T-die onto a cooling roll controlled at a surface temperature of 80 ° C. A sheet-like molded product was obtained by bringing into contact with a cooling roll and molding by cooling. The sheet was stretched by a simultaneous biaxial stretching machine at a magnification of 7 × 6.4 and a temperature of 112 ° C., then immersed in methylene chloride, extracted by removing liquid paraffin, dried, and then heated by a tenter stretching machine. The film was stretched twice at 130 ° C. in the transverse direction. Thereafter, the stretched sheet was relaxed by about 10% in the width direction and heat-treated to obtain a polyolefin microporous membrane B1.

  About the obtained polyolefin microporous film B1, the physical property was measured by the said method. Further, the obtained polyolefin microporous film was used as a separator as it was and evaluated by the above method. The obtained results are shown in Table 1.

[Production Example 1-2] (Production of polyolefin microporous membrane B2)
Except having changed the temperature and relaxation rate in the case of extending | stretching, it carried out similarly to manufacture example 1-1, and obtained polyolefin microporous film B2. The obtained polyolefin microporous membrane B2 was evaluated in the same manner as in Production Example 1-1. The obtained results are shown in Table 1.
[Production Example 1-3]
25 parts by mass of ultrahigh molecular weight polyethylene having a viscosity average molecular weight of 2 million, 15 parts by mass of high-density polyethylene having a viscosity average molecular weight of 700,000, 30 parts by mass of high-density polyethylene having a viscosity average molecular weight of 250,000, and a viscosity average molecular weight of 12 Ten parts by weight of copolymer polyethylene having a propylene unit content of 1 mol% was dry blended using a tumbler blender. 0.3 parts by mass of pentaerythrityl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] as an antioxidant was added to 99 parts by mass of the obtained polymer mixture. Then, again by dry blending using a tumbler blender, a polymer mixture was obtained. The obtained mixture of polymers and the like was substituted with nitrogen and then fed to the twin-screw extruder with a feeder under a nitrogen atmosphere. Liquid paraffin was injected into the extruder cylinder by a plunger pump. They were melt-kneaded, and the feeder and pump were adjusted so that the ratio of liquid paraffin in the total mixture to be extruded was 65 mass%, that is, the ratio of the resin composition was 35 mass%. The obtained melt-kneaded product was extruded and cast on a cooling roll through a T-die to obtain a sheet-like molded product. Thereafter, a polyolefin microporous membrane B3 was obtained in the same manner as in Production Example 1-1 except that the stretching temperature and the relaxation rate were changed. The obtained polyolefin microporous membrane B3 was evaluated in the same manner as in Production Example 1. The obtained results are shown in Table 1.

[Production Example 2-1]
As an inorganic filler, 47.7 parts by mass of block-like aluminum hydroxide oxide and 0.48 parts by mass of polycarboxylic acid ammonium salt are uniformly dispersed in 47.7 parts by mass of water, respectively, and subjected to bead mill treatment. Crushing was performed so that the average particle size of the filler (aluminum hydroxide oxide) was as shown in Table 2. There was one peak in the particle size distribution chart at this time. Thereafter, an aqueous solution containing 0.10 parts by mass of a thickener and 4.1 parts by mass (as a solid content) of acrylic latex (average particle size (D50): 300 μm) was corona-treated at a discharge of 1.0 kV. The surface of the polyolefin microporous membrane B1 was applied at a line speed of 30 m / min using a gravure coater. Water was removed while drying the coated film at 40 ° C. for 10 seconds and then at 70 ° C. for 10 seconds or more, and an inorganic filler porous layer having a thickness of 4 μm (layer density: 1.5 g / (m ² · μm)) was formed to obtain a multilayer porous membrane B1-1 having a total thickness of 15 μm. The obtained multilayer porous membrane was evaluated as described above. The obtained results are shown in Table 2.

[Production Examples 2-2 to 2-5]
Multilayer porous membranes B1-2 to B1-5 were obtained in the same manner as in Production Example 2-1, except that the amount of the thickener and the drying speed were changed. These multilayer porous membranes were evaluated in the same manner as in Production Example 2-1. The obtained results are shown in Table 2.

[Production Examples 2-6 to 2-7]
Multilayer porous films B1-6 to B1-7 were obtained in the same manner as in Production Example 2-1, except that the thickness of the inorganic filler porous layer containing block-like aluminum hydroxide oxide was changed. These multilayer porous membranes were evaluated in the same manner as in Production Example 2-1. The obtained results are shown in Table 2.

[Production Example 2-8]
A multilayer porous membrane B1-8 was obtained in the same manner as in Production Example 2-1, except that aluminum oxide was used as the inorganic filler. This multilayer porous membrane was evaluated in the same manner as in Production Example 2-1. The obtained results are shown in Table 2.

[Production Example 2-9]
A multilayer porous membrane B1-9 was obtained in the same manner as in Production Example 2-1, except that plate-like particles of aluminum hydroxide oxide were used. This multilayer porous membrane was evaluated in the same manner as in Production Example 2-1. The obtained results are shown in Table 2.

[Production Example 2-10]
A multilayer porous membrane B2-1 was obtained in the same manner as in Production Example 2-1, except that the polyolefin microporous membrane B2 was used. This multilayer porous membrane was evaluated in the same manner as in Production Example 2-1. The obtained results are shown in Table 2.

[Production Example 2-11]
A multilayer porous membrane B3-1 was obtained by the same method as in Production Example 2-1, except that the polyolefin microporous membrane B3 was used. This multilayer porous membrane was evaluated in the same manner as in Production Example 2-1. The obtained results are shown in Table 2.

<Synthesis of particulate polymer>
(Production Example A1) Aqueous dispersion (indicated as “raw polymer” in the table; the same applies hereinafter) A1 synthesis A reaction vessel equipped with a stirrer, reflux condenser, dropping tank, and thermometer was charged with ion-exchanged water 70. 4 parts by mass, “AQUALON KH1025” (registered trademark, 25% aqueous solution manufactured by Daiichi Kogyo Seiyaku Co., Ltd., indicated as “KH1025” in the table, the same applies hereinafter), and “Adekaria soap SR1025” ( (Registered trademark, manufactured by ADEKA Corporation, 25% aqueous solution, expressed as “SR1025” in the table, the same applies hereinafter.) 0.5 parts by mass were added, and the internal temperature of the reaction vessel was raised to 80 ° C. Thereafter, 7.5 parts by mass of ammonium persulfate (2% aqueous solution) (indicated as “APS (aq)” in the table, the same applies hereinafter) was added while maintaining the internal temperature of the container at 80 ° C.

On the other hand, methyl methacrylate (indicated as “MMA” in the table, the same shall apply hereinafter) 38.5 parts by mass, n-butyl acrylate (indicated in the table as “BA”, the same shall apply hereinafter) 19.6 parts by mass, acrylic acid 2-ethylhexyl (indicated in the table as “EHA”, the same applies hereinafter) 31.9 parts by mass, methacrylic acid (in the table, indicated as “MAA”, the same applies hereinafter) 0.1 part by mass, acrylic acid (in the table “AA” The same shall apply hereinafter.) 0.1 part by mass, 2-hydroxyethyl methacrylate (indicated as “HEMA” in the table; the same shall apply hereinafter) 2 parts by mass, acrylamide (indicated as “AM” in the table; hereinafter the same shall apply) ) 5 parts by mass, glycidyl methacrylate (indicated as “GMA” in the table, the same shall apply hereinafter) 2.8 parts by mass, “AQUALON KH1025” (registered trademark, 25% aqueous solution manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Adekaria soap SR10 5 "(registered trademark, 25% aqueous solution manufactured by ADEKA Corporation) 3 parts by mass, sodium p-styrenesulfonate (indicated as" NaSS "in the table, the same shall apply hereinafter) 0.05 part by mass, trimethylolpropane triacrylate (new) Made by Nakamura Chemical Co., Ltd., written as “A-TMPT” in the table, the same applies hereinafter.) 0.7 part by mass, γ-methacryloxypropyltrimethoxysilane (shown as “MPTMS” in the table, the same applies hereinafter) 0. A mixture of 3 parts by mass, 7.5 parts by mass of ammonium persulfate (2% aqueous solution), and 52 parts by mass of ion-exchanged water was mixed for 5 minutes with a homomixer to prepare an emulsion.
The obtained emulsion was dropped from the dropping tank into the reaction vessel. The dropping was started 5 minutes after the ammonium persulfate aqueous solution was added to the reaction vessel, and the entire amount of the emulsion was dropped over 150 minutes. The container internal temperature was maintained at 80 ° C. during the dropping of the emulsion.

  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. The obtained emulsion was adjusted to pH = 9.0 using an aqueous ammonium hydroxide solution (25% aqueous solution) to obtain an acrylic copolymer latex having a concentration of 40% by mass (raw polymer A1). The obtained raw material polymer (aqueous dispersion) A1 was evaluated by the above method. The obtained results are shown in Table 3.

(Production Examples A2 to A18) Synthesis of aqueous dispersions A2 to A18 Raw material polymer (water dispersion) A1 except that the composition of the monomer and other raw materials was changed as shown in Tables 3 to 5 respectively. In the same manner as above, copolymer latexes (raw polymer A2 to A18) were obtained. About the obtained raw material polymer (water dispersion) A2-A18, it evaluated by the said method, respectively. The obtained results are shown in Tables 3-5.

(Production Example A2-1)
An aqueous dispersion A2-1 was synthesized by taking a part of the aqueous dispersion A2 obtained in Production Example A2 and performing multistage polymerization using this as a seed polymer. Specifically, first, in a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer, 16 parts by mass of the aqueous dispersion A2 in terms of solid content, Aqualon KH1025 (registered trademark) 0.5 Part by mass and 0.5 part by mass of Adeka Soap SR1025 (registered trademark) were added, and the internal temperature of the reaction vessel was raised to 80 ° C. Thereafter, 7.5 parts by mass of ammonium persulfate (2% aqueous solution) was added while maintaining the internal temperature of the container at 80 ° C. The above is the initial preparation.

  Meanwhile, 71.5 parts by weight of methyl methacrylate, 18.9 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 part by weight of acrylic acid, 2 methacrylic acid -2 parts by weight of hydroxyethyl, 5 parts by weight of acrylamide, 0.4 parts by weight of glycidyl methacrylate, 3 parts by weight of Aqualon KH1025 (registered trademark, 25% aqueous solution), 3 parts by weight of Adekaria soap SR1025 (registered trademark, 25% aqueous solution) , 0.05 parts by weight of sodium p-styrenesulfonate, 0.4 parts by weight of trimethylolpropane triacrylate, 0.3 parts by weight of γ-methacryloxypropyltrimethoxysilane, 7.5 parts by weight of ammonium persulfate (2% aqueous solution) , And a mixture of 52 parts by mass of ion-exchanged water are mixed for 5 minutes by a homomixer, Of liquid was produced. The obtained emulsion was dropped from the dropping tank into the reaction vessel. The dropping was started 5 minutes after the ammonium persulfate aqueous solution was added to the reaction vessel, and the entire amount of the emulsion was dropped over 150 minutes. The container internal temperature was maintained at 80 ° C. during the dropping of the emulsion.

  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. The obtained emulsion was adjusted to pH = 9.0 using an aqueous ammonium hydroxide solution (25% aqueous solution) to obtain an acrylic copolymer latex having a concentration of 40% by mass (raw polymer A2-1). The obtained raw material polymer A2-1 was evaluated by the above method. The results obtained are shown in Table 6.

(Production Examples A2-2 to A18-2)
Each copolymer by multistage polymerization in the same manner as the raw material polymer (aqueous dispersion) A2-1 except that the composition of the seed polymer, monomer, and other raw materials is changed as shown in Tables 6 to 10, respectively. Latex was obtained. About the obtained raw material polymer (water dispersion), it evaluated by the said method, respectively. The obtained results are shown in Tables 6-10.

Abbreviations of raw material names in Tables 3 to 10 above have the following meanings, respectively.
<Emulsifier>
KH1025: Aqualon KH1025, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 25% aqueous solution SR1025: Adekaria soap SR1025, manufactured by ADEKA Co., Ltd., 25% aqueous solution NaSS: sodium p-styrenesulfonate <initiator>
APS: ammonium persulfate (2% aqueous solution)
<Monomer>
(Acid monomer)
MAA: methacrylic acid AA: acrylic acid ((meth) acrylic acid ester)
MMA: methyl methacrylate BA: n-butyl acrylate BMA: n-butyl methacrylate EHA: 2-ethylhexyl acrylate CHMA: cyclohexyl methacrylate (aromatic vinyl monomer)
St: Styrene (cyano group-containing monomer)
AN: Acrylonitrile (other functional group-containing monomer)
HEMA: 2-hydroxyethyl methacrylate AM: Acrylamide (crosslinkable monomer)
GMA: Glycidyl methacrylate A-TMPT: Trimethylolpropane triacrylate AcSi: γ-methacryloxypropyltrimethoxysilane

[Example 1]
An aqueous dispersion A2-2 having a solid content of 80 parts by mass and an aqueous dispersion A7 having a solid content of 20 parts by mass are uniformly dispersed in water, and a coating liquid containing a thermoplastic polymer (solid content of 30% by mass) ) Was prepared. At this time, carboxymethylcellulose was added as a thickener so that it might become 1 mass% with respect to a coating liquid, and the viscosity of the coating liquid was adjusted to 30 mPa * s. At this time, the coating liquid was apply | coated to the surface by the side of the inorganic filler porous layer of multilayer porous film B1-1 by the direct gravure coating using the gravure coater. At this time, the surface coverage of the inorganic filler porous layer by the thermoplastic polymer was 50%. Then, the coating liquid after application | coating was dried at 40 degreeC, and water was removed. Further, the coating liquid was similarly applied to the surface of the multilayer porous membrane B1-1 on the base material side, and dried again in the same manner as described above. Thus, a separator having a polymer layer formed on both sides of the multilayer porous membrane B1-1 was obtained.

[Examples 2-27, 29]
A separator was obtained in the same manner as in Example 1, except that the compositions of the multilayer porous membrane and the coating solution were changed as described in Tables 11 and 12, respectively.

[Example 28]
A separator was obtained in the same manner as in Example 1 except that the coating solution was applied to the entire surface of the multilayer porous membrane by reverse gravure coating.

[Example 30]
A separator was obtained in the same manner as in Example 1 except that PvDF-HFP latex Solef918 (Solvey) was used instead of the aqueous dispersion A2-2.

[Comparative Examples 1-3, 7]
A separator was obtained in the same manner as in Example 1 except that the compositions of the multilayer porous membrane and the coating solution were changed as shown in Table 13, respectively.

[Comparative Example 4]
Except that the coating liquid having the composition described in Table 13 was applied to the entire surface of both sides of the multilayer porous membrane by reverse gravure coating so that the thickness of the thermoplastic polymer from the surface of the inorganic filler porous layer was 1 μm. A separator was obtained in the same manner as in Example 1.

[Comparative Examples 5 to 7]
[Production Example 2-12]
Multilayer porous membranes B1-10 and B1-11 were obtained in the same manner as in Production Example 2-1, except that the number of revolutions of the bead mill was changed. A separator was obtained in the same manner as in Example 1 except that the compositions of the multilayer porous membrane and the coating solution were changed as shown in Table 13, respectively.

  Since the separator for an electricity storage device of the present invention is excellent in adhesion to an electrode and heat resistance, and is also excellent in ion permeability, it has industrial applicability in technical fields having such requirements.

Claims (16)

An electricity storage device comprising: a base material; an inorganic filler porous layer formed on at least one surface of the base material; and a thermoplastic polymer-containing layer formed on at least a part of the surface of the inorganic filler porous layer. Separator for
The inorganic filler porous layer includes an inorganic filler, and has a plurality of holes,
The thermoplastic polymer-containing layer contains a thermoplastic polymer,
The thermoplastic polymer comprises a particulate polymer;
The arithmetic average particle size of the particulate polymer is larger than the average pore size of the inorganic filler porous layer,
Electric storage device separator. An electricity storage device comprising: a base material; an inorganic filler porous layer formed on at least one surface of the base material; and a thermoplastic polymer-containing layer formed on at least a part of the surface of the inorganic filler porous layer. Separator for
The inorganic filler porous layer includes an inorganic filler, and has a plurality of holes,
The thermoplastic polymer-containing layer contains a thermoplastic polymer,
The thermoplastic polymer comprises a particulate polymer;
The content of the particulate polymer contained in the inorganic filler porous layer is 20% by volume or less with respect to the total amount of the inorganic filler porous layer.
Electric storage device separator. An electricity storage device comprising: a base material; an inorganic filler porous layer formed on at least one surface of the base material; and a thermoplastic polymer-containing layer formed on at least a part of the surface of the inorganic filler porous layer. Separator for
The inorganic filler porous layer includes an inorganic filler, and has a plurality of holes,
The thermoplastic polymer-containing layer contains a thermoplastic polymer,
The thermoplastic polymer comprises a particulate polymer;
The average particle diameter D50 of the inorganic filler is 0.5 μm or more and less than 1.0 μm,
The arithmetic average particle size of the particulate polymer is 0.20 μm or more and 1.0 μm or less,
Electric storage device separator.   The separator for electrical storage devices according to any one of claims 1 to 3, wherein the particulate polymer has (meth) acrylic acid ester as a monomer unit.   The electrical storage device separator according to any one of claims 1 to 4, wherein a glass transition point of the particulate polymer is 50 ° C or higher.   The separator for electrical storage devices of any one of Claims 1-5 whose surface coverage with respect to the said inorganic filler porous layer by the said thermoplastic polymer content layer is 70% or less.   The said thermoplastic polymer content layer is a separator for electrical storage devices of any one of Claims 1-6 which is a layer which exists in the shape of a dot on the surface of the said base material.   The electrical storage device separator according to claim 1, wherein the inorganic filler porous layer has a thickness of 5.0 μm or less. The power storage device separator according to any one of claims 1 to 8, wherein the power storage device separator has a heat shrinkage ratio at TD of 130 ° C of 10% or less.
  The electrical storage device separator according to any one of claims 1 to 9, wherein the inorganic filler contains an inorganic oxide.   The electrical storage device separator according to any one of claims 1 to 10, wherein a porosity of the substrate is greater than 40%.   The power storage device separator according to any one of claims 1 to 11, wherein a puncture strength of the power storage device separator is 300 gf / 20 µm or more.   The laminated body containing a positive electrode, the separator for electrical storage devices of any one of Claims 1-12, and a negative electrode.   A wound body obtained by winding a positive electrode, a separator for an electricity storage device according to any one of claims 1 to 12, and a negative electrode.   The electrical storage device containing the laminated body of Claim 13, or the winding body of Claim 14, and electrolyte solution.   The lithium ion secondary battery containing the laminated body of Claim 13, or the winding body of Claim 14, and electrolyte solution.