JP6396154B2 - Storage device separator - Google Patents

Description

The present invention relates to an electrical storage device separator.
The separator of the present invention is particularly preferably used as a separator in a nonaqueous electrolyte secondary battery.

In power storage devices such as lithium ion secondary batteries and electric double layer capacitors, a separator made of a microporous film is provided between the positive and negative electrodes. Examples of the function of the separator include preventing direct contact between the positive and negative electrodes and allowing ions to pass therethrough.
Polyolefin resin porous membranes are widely used as separators in power storage devices because they exhibit excellent electrical insulation and ion permeability. Particularly in recent years, lithium ion secondary batteries with high output density and high capacity density have been used as power sources for portable devices that are remarkably multifunctional and lightweight. As such a battery separator, a polyolefin resin porous film is mainly used.
However, when lithium ion secondary batteries are used in automotive applications, the use conditions such as temperature, charge / discharge current, and upper limit voltage become harsh compared to the case for portable devices, so the deterioration of electrodes and separators over time It becomes a problem.
In this regard, Patent Document 1 describes a battery separator on which a metal compound such as hydroxide, carbonate, phosphate, sulfate is supported for the purpose of preventing deterioration of electrodes and separators.

JP 2009-146611 A

According to the technique of Patent Document 1, although the oxidation deterioration of the separator is suppressed and the battery characteristics in the cycle evaluation are improved, the battery cycle characteristics at high temperature (hereinafter also referred to as “high temperature characteristics”) are insufficient. It is.
The present invention has been made in view of the above situation. Accordingly, an object of the present invention is to provide an electricity storage device separator that is excellent in battery cycle characteristics at high temperatures.

  The outline of the present invention is as follows.

[1] A separator for an electricity storage device having a porous substrate layer (A),
The outermost layer on at least one side thereof has a layer (C) containing a basic phosphate (c-1) in a part of the separator for an electricity storage device.
[2] The area of the layer (C) containing the basic phosphate (c-1) has a layer (C) containing the basic phosphate (c-1) of the separator for an electricity storage device. The separator for an electricity storage device according to [1], which is 5% or more and 90% or less with respect to the entire area.

[3] The separator for an electricity storage device according to [1] or [2], wherein the layer (C) containing the basic phosphate (c-1) is present in a dot shape.
[4] Any of [1] to [3], wherein the basic phosphate (c-1) is at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts of phosphoric acid. The separator for an electricity storage device according to one item.

[5] The electricity storage device separator comprises:
A porous layer (B) containing a resin binder (b-1) and an inorganic filler (b-2) is provided on at least one side of the porous substrate layer (A), and the basic phosphate (c-1) The separator for an electricity storage device according to any one of [1] to [4], wherein the surface on which the layer (C) containing) exists is the surface of the porous layer (B).

[6] The separator for an electricity storage device according to any one of [1] to [5];
A positive electrode;
A negative electrode,
An electricity storage device comprising an electrolyte solution.
[7] The electricity storage device according to [6], wherein the positive electrode has a potential of 4.5 V or more based on lithium and is used as a nonaqueous electrolyte secondary battery.

ADVANTAGE OF THE INVENTION According to this invention, the separator for electrical storage devices which is excellent in the battery cycle characteristic in high temperature is provided.
The separator of this invention can be used conveniently as a separator of a nonaqueous electrolyte battery, for example.

  Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

The separator in this embodiment is characterized in that at least the outermost layer on one side thereof has a layer (C) containing a basic phosphate (c-1) in a part thereof.
The separator has at least a porous substrate layer (A). A porous layer (B) containing a resin binder (b-1) and an inorganic filler (b-2) may be provided on at least one side of the porous substrate layer (A). When the separator includes a porous layer (B), the surface on which the layer (C) containing the basic phosphate (c-1) is present is preferably the surface of the porous layer (B). .

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

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

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

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

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

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

  Since the porous base material layer (A) has a porous structure in which a large number of very small holes are gathered to form a dense communication hole, it has excellent ion conductivity and at the same time withstand voltage characteristics, Moreover, it has a feature of high strength.

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

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

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

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

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

  Hereinafter, as an example of a method for producing a polyolefin resin porous membrane as the porous substrate layer (A), a method of extracting a pore-forming material after melt-kneading a polyolefin resin composition and a pore-forming material into a sheet shape Will be described.

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

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

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

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

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

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

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

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

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

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

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

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

  Here, simultaneous biaxial stretching means stretching in MD (machine direction (length method) when continuously forming the porous substrate layer (A)) and TD (MD of the porous substrate layer (A) at 90 °. In the direction crossing at an angle of 2), and the stretching ratio in each direction may be different. Sequential biaxial stretching refers to a stretching method in which MD and TD are stretched independently. When MD or TD is stretched, the other direction is fixed in an unconstrained state or a constant length. State.

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

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

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

The stretching operation is performed by stretching the MD and / or TD of the membrane by 1.1 times or more, more preferably 1.2 times or more, thereby obtaining a porous substrate layer (A) having further high strength and high porosity. From the viewpoint of
The relaxation operation is an operation for reducing the film to MD and / or TD. The relaxation rate is a value obtained by dividing the dimension of the film after the relaxation operation by the dimension of the film before the relaxation operation. When both MD and TD are relaxed, it is a value obtained by multiplying the MD relaxation rate and the TD relaxation rate. The relaxation rate is preferably 1.0 or less, more preferably 0.97 or less, and even more preferably 0.95 or less. The relaxation rate is preferably 0.5 or more from the viewpoint of film quality. The relaxation operation may be performed in both the MD and TD directions, but only one of the MD and TD may be performed.

  The stretching and relaxation operations after this plasticizer extraction are preferably performed at TD. The temperature in the stretching and relaxation operation is preferably lower than the melting point of the polyolefin resin (hereinafter also referred to as “Tm”), and more preferably in the range of 1 ° C. to 25 ° C. lower than Tm. When the temperature in the stretching and relaxation operation is in the above range, it is preferable from the viewpoint of the balance between the reduction in thermal shrinkage and the porosity.

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

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

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

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

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

  Among the aluminum silicates, kaolinite (hereinafter, also referred to as kaolin) mainly composed of kaolin mineral is preferable from the viewpoint of lightness and air permeability. Kaolin includes wet kaolin and calcined kaolin, which is calcined. However, calcined kaolin releases crystal water during the calcining process and removes impurities. Particularly preferred. As the inorganic filler (b-2) constituting the porous layer (B), by adopting particles containing calcined kaolin as a main component, a very lightweight porous layer (B) is maintained while maintaining high permeability. Moreover, even if the thickness of the porous layer (B) is thinner, thermal contraction of the separator at a high temperature is suppressed, and excellent heat resistance tends to be exhibited.

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

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

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

  The proportion of the inorganic filler (b-2) in the porous layer (B) is the permeability and heat resistance of the separator, and the resin that binds the inorganic filler (b-2) in the porous layer (B). It can be appropriately determined from the viewpoint of the required amount of the binder (b-1). The proportion of the inorganic filler (b-2) is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, from the viewpoint of the permeability and heat resistance of the separator. Particularly preferred is 95% by mass or more, and most preferred is 97% by mass or more. From the viewpoint of the required amount of the resin binder (b-1) for binding the inorganic filler (b-2) in the porous layer (B), the proportion of the inorganic filler (b-2) is 100% by mass. It is preferably less than 9, more preferably 99.5% by mass or less, and still more preferably 99% by mass or less.

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

Specific examples of the resin binder (b-1) include the following 1) to 6).
1) Polyolefin: For example, polyethylene, polypropylene, ethylene propylene rubber, and modified products thereof;
2) Conjugated diene polymer: for example, styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride;
3) Acrylic polymer: For example, methacrylic acid ester-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer;

4) Polyvinyl alcohol resin: for example, polyvinyl alcohol, polyvinyl acetate;
5) Fluorine-containing resin: For example, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene Copolymer, hexafluoropropylene-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer;
6) A resin having a melting point and / or glass transition temperature of 180 ° C. or higher or a polymer having no melting point but a decomposition temperature of 200 ° C. or higher: for example, polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyetherimide, polyamideimide , Polyamide, polyester. In particular, from the viewpoint of durability, wholly aromatic polyamides, particularly polymetaphenylene isophthalamide, are preferred.
Among these, 2) conjugated diene polymers are preferable from the viewpoint of compatibility with electrodes, and 3) acrylic polymers and 5) fluorine-containing resins are preferable from the viewpoint of voltage resistance.

The 2) conjugated diene polymer is a polymer containing a conjugated diene compound as a monomer unit.
Examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and substituted linear chains. Examples thereof include conjugated pentadienes, substituted and side chain conjugated hexadienes, and these may be used alone or in combination of two or more. Among these, 1,3-butadiene is particularly preferable.
The 3) acrylic polymer is a polymer containing a (meth) acrylic compound as a monomer unit. The (meth) acrylic compound indicates at least one selected from the group consisting of (meth) acrylic acid and (meth) acrylic acid ester.

Examples of (meth) acrylic acid used in the above 3) acrylic polymer include acrylic acid and methacrylic acid.
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, phenyl acrylate, phenyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate;
Epoxy group-containing (meth) acrylic acid esters such as glycidyl acrylate and glycidyl methacrylate may be used, and these may be used alone or in combination of two or more.

The above 2) conjugated diene polymer and 3) acrylic polymer may be obtained by copolymerizing other monomers copolymerizable therewith. Other copolymerizable monomers used include, for example, unsaturated carboxylic acid alkyl esters, aromatic vinyl monomers, vinyl cyanide monomers, unsaturated monomers containing hydroxyalkyl groups, unsaturated carboxylic acid amide monomers, Examples include crotonic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, and the like. These may be used alone or in combination of two or more. Among the above, unsaturated carboxylic acid alkyl ester monomers are particularly preferable. Examples of unsaturated carboxylic acid alkyl ester monomers include dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, and the like. Even if it uses, 2 or more types may be used together.
The 2) conjugated diene polymer may be obtained by copolymerizing the (meth) acrylic compound as another monomer.

  The glass transition temperature of resin binder (b-1) becomes like this. Preferably it is -80-30 degreeC, More preferably, it is -80-15 degreeC, More preferably, it is -80-0 degreeC. The glass transition temperature of the resin binder (b-1) being within the above range is from the viewpoint of adhesion with the porous base material layer (A) and binding strength with the inorganic filler (b-2). preferable.

As the above resin binder (b-1), only one selected from the above may be used, or two or more selected from the above may be mixed and used. .
The proportion of the resin binder (b-1) in the porous layer (B) is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass, and still more preferably 1. 5 to 10% by mass. By setting this value to 0.5% by mass or more, the adhesion with the electrode, the adhesive strength with the porous substrate layer (A), and the binding strength of the inorganic filler (b-2) are excellent. By setting it as 30 mass% or less, it will be excellent in the stickiness of a separator outermost surface, and handling property.

  The layer thickness of the porous layer (B) is preferably 1 μm or more from the viewpoint of improving heat resistance and insulation, more preferably 1.5 μm or more, and further preferably 2.0 μm or more. In addition, the thickness is preferably 50 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less, and particularly preferably 7 μm or less from the viewpoint of increasing the capacity and permeability of the battery.

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

  The surface softening temperature of the porous layer (B) is preferably 30 to 60 ° C, more preferably 30 to 50 ° C, and further preferably 35 to 45 ° C. When the surface softening temperature is 30 ° C. or higher, the separator can be unwrinkled without wrinkling when the separator is unwound when it is attempted to unwind the separator when it is crimped to the electrode after being rolled into a roll. When the temperature is 60 ° C. or lower, the polyolefin resin generally used for the porous base material layer (A) constituting the separator is a glass transition temperature when the electrode and the separator are pressure-bonded using a high-temperature press. Although it is not high, it is preferable in that wrinkles do not occur in the laminate obtained even after pressure bonding.

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

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

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

  The average particle size of the resin binder (b-1) in the resin latex is preferably 50 to 1,000 nm, more preferably 70 to 500 nm, and still more preferably 80 to 250 nm. When the average particle size is 50 nm or more, when the porous layer (B) containing the inorganic filler (b-2) and the resin binder (b-1) is laminated on at least one surface of the porous substrate layer (A), It exhibits good binding properties, and when used as a separator, it tends to have good heat shrinkage and excellent safety. When the average particle diameter is 1,000 nm or less, the ion permeability is unlikely to decrease and high output characteristics are easily obtained. In addition, even when the temperature rises rapidly during abnormal heat generation, smooth shutdown characteristics are exhibited, and high safety is easily obtained. The average particle diameter can be controlled by adjusting a polymerization time, a polymerization temperature, a raw material composition ratio, a raw material charging order, a pH, a stirring speed, and the like when producing the resin latex.

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

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

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

  The method for applying the coating liquid to the porous substrate layer (A) is not particularly limited as long as it is a method capable of realizing the required layer thickness and application area. For example, a gravure coater method, a small-diameter gravure coater method, Reverse roll coater method, transfer roll coater method, kiss coater method, dip coater method, knife coater method, air doctor coater method, blade coater method, rod coater method, squeeze coater method, cast coater method, die coater method, screen printing method, The spray coating method etc. are mentioned.

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

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

The temperature at which the medium is removed from the coating film is preferably 20 to 100 ° C, more preferably 30 to 80 ° C, and particularly preferably 40 to 70 ° C. The removal time is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 20 minutes, still more preferably 40 seconds to 10 minutes, and particularly preferably 1 to 3 minutes.
The porous layer (B) in the present embodiment is excellent in adhesiveness with the porous base material layer (A) by adopting the above-described aspect, and does not cause stickiness, and exhibits good cycle characteristics. A device can be provided and light resistance is also excellent.

<Layer (C) containing basic phosphate (c-1)>
The separator for an electricity storage device in this embodiment is
The outermost layer on at least one side thereof has a layer (C) containing a basic phosphate (c-1) in a part thereof.
When the electricity storage device separator in the present embodiment is composed only of the porous base material layer (A), the layer (C) containing the basic phosphate (c-1) is the porous base material layer (A). Formed on one or both sides;
When the electricity storage device separator is a laminate in which the porous layer (B) is formed on both sides of the porous substrate layer (A), the layer (C) containing the basic phosphate (c-1) is The outermost porous layer (B) can be formed on one or both surfaces.
When the electricity storage device separator is a laminate in which the porous layer (B) is formed on one side of the porous substrate layer (A), the layer (C) containing the basic phosphate (c-1) is And can be formed on the surface of the porous substrate layer (A) or the surface of the porous layer (B), or on both surfaces. In this case, the layer (C) containing the basic phosphate (c-1) is preferably formed only on the surface of the porous layer (B).

(Basic phosphate (c-1))
Although it does not specifically limit as basic phosphate (c-1) used in this embodiment, For example, it can be a conventionally well-known phosphate which shows basicity.
This “basic” can be determined by a conventionally known determination method. A conventionally known determination method is not particularly limited,
For example, if the basic phosphate is water-soluble, a method for measuring the base dissociation constant (pKb) of the anion contained in the basic phosphate;
For example, if the basic phosphate is water-insoluble or sparingly water-soluble, there can be mentioned a method of measuring by a temperature rising desorption method of CO ₂ which is an acidic gas. The base dissociation constant (pKb) of the anion contained in the basic phosphate is preferably 10.83 or less, more preferably 7.65 or less, and further preferably 2.00 or less. Desorption temperature of CO ₂ in the temperature elevation withdrawal method of CO ₂ is an acid gas, preferably at least 100 ° C., more preferably at least 0.99 ° C., and even more preferably 200 ° C.. When the desorption temperature of pKb or CO ₂ is within the above range, it can be determined that the phosphate is basic.
By using a phosphate having a desorption temperature of pKb or CO ₂ within the above range, a separator that provides an electricity storage device that is superior in battery characteristics and safety at high temperatures can be obtained.

The anion in the basic phosphate (c-1) is not particularly limited, and phosphate anions having various degrees of polymerization can be used. Specific examples include PO ₄ ³⁻ , P ₂ O ₇ ⁴⁻ , P ₃ O ₁₀ ⁵⁻ , P ₄ O ₁₃ ^{6− and the} like. The anion of the basic phosphate may be in any form, but is preferably an orthophosphate such as PO ₄ ³⁻ , HPO ₄ ²⁻ , or H ₂ PO ⁴⁻ . By using such an anion, a separator having higher temperature characteristics can be obtained.

As the counter cation in basic phosphate (c-1), is not particularly limited, for ^example, Li +, Na ⁺ and alkali metals ^{K +, etc.;} Mg 2+, ^{Ca 2+} alkaline earth metals such as; ^{Zn 3+} One or more selected from the group consisting of other metals such as Al ³⁺ and Ce ³⁺ are preferred.
When the basic phosphate (c-1) contains a counter cation selected from the group consisting of an alkali metal salt and an alkaline earth metal salt, a separator having more excellent high temperature characteristics can be obtained. Among these, 1 or more types of salts chosen from Li salt and Na salt are preferable, and it is preferable that Li salt is contained further. When the basic phosphate (c-1) contains one or more salts selected from sodium salts and lithium salts, a separator having more excellent high temperature characteristics can be obtained. In addition, a basic phosphate containing a single metal cation is preferable because it has a stable structure and can provide a separator with further excellent high-temperature characteristics.

  Although it does not specifically limit as a shape of basic phosphate (c-1), For example, particle shape, needle shape, plate shape, and cube shape are mentioned. Among these, a particulate shape is preferable, and an aggregated particle shape in which a large number of particles are aggregated is more preferable. The aggregated particle size of the particulate basic phosphate (c-1) is preferably 0.01 μm or more and 30 μm or less, more preferably 0.1 μm or more and 10 μm or less, and further preferably 0.2 μm or more and 5 μm or less. It is preferably 0.2 μm or more and 2 μm or less. When the basic phosphate (c-1) is in the form of particles and the aggregate particle size is in the above range, it tends to be a separator that gives an electricity storage device having lower DC insulation resistance after repeated charge and discharge. It is in. Here, “aggregated particle diameter” refers to the maximum distance between any two points on the outer periphery of one aggregated particle.

(Resin binder (c-2))
The layer (C) containing the basic phosphate (c-1) may consist of only the basic phosphate (c-1) as described above, and the basic phosphate (c-1). In addition, other components may be included.
Particularly preferably as the layer (C) containing the basic phosphate (c-1), the basic phosphate (c-1) as described above is bound by the resin binder (c-2), This is a case where a pattern coating is applied on the separator of the embodiment.

  A preferable substance as the resin binder (c-2) is a thermoplastic polymer. The thermoplastic polymer is preferable from the viewpoint of securing the binding property with the separator.

The thermoplastic polymer used in the present embodiment is not particularly limited.
Polyolefin resins such as polyethylene, polypropylene and α-polyolefin;
Fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene;
A copolymer comprising polyvinylidene fluoride, tetrafluoroethylene, etc .;
Diene polymers containing conjugated dienes such as butadiene and isoprene as monomer units;
A hydride of the diene polymer;
Acrylic polymer containing acrylic acid ester, methacrylic acid ester and the like as monomer units;
A hydride of the acrylic polymer;
Rubbers such as ethylene propylene rubber, polyvinyl alcohol, polyvinyl acetate;
A resin having a melting point or a glass transition temperature of 180 ° C. or higher, such as polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyamide, and polyester;
And mixtures thereof. As the copolymerizable monomer for the thermoplastic polymer, for example, a monomer having a functional group such as a hydroxyl group, a sulfonic acid group, a carboxyl group, an amide group, or a cyano group may be used.

  Of these thermoplastic polymers, diene polymers, acrylic polymers or rubbers are preferred because they are excellent in binding properties, strength, flexibility, solubility and the like with the basic phosphate (c-1). Particularly preferred is polyvinyl alcohol or an acrylic polymer.

  When using polyvinyl alcohol as the resin binder (c-2) in the layer (C) containing the basic phosphate (c-1), the saponification degree is preferably 85% or more and 100% or less. When the degree of saponification is 85% or more, when the obtained separator is incorporated in an electricity storage device and used, the temperature at which a short circuit (short circuit temperature) is improved and better safety performance tends to be obtained, which is preferable. The saponification degree is more preferably 90% or more and 100% or less, further preferably 95% or more and 100% or less, and particularly preferably 99% or more and 100% or less.

  The degree of polymerization of polyvinyl alcohol is preferably 200 or more and 5,000 or less, more preferably 300 or more and 4,000 or less, and still more preferably 500 or more and 3,500 or less. A polymerization degree of 200 or more is preferable because the basic phosphate (c-1) tends to be firmly bound with a small amount of polyvinyl alcohol. Moreover, since it exists in the tendency which can prevent the gelatinization at the time of preparing a coating liquid as a polymerization degree is 5,000 or less, it is preferable.

  The abundance ratio of the resin binder (c-2) in the layer (C) containing the basic phosphate (c-1) is preferably 0.1 to 99% by mass, and 1 to 70% by mass. Is more preferable, it is more preferable that it is 1.5-50 mass%, and it is especially preferable that it is 2-30 mass%. By using the resin binder (c-2) in such a range, the basic phosphate (c-1) can be bound without falling off, and the high-temperature cycle characteristics can be effectively expressed. Can do.

(Aspect of layer (C) containing basic phosphate (c-1))
As described above, in the separator according to this embodiment, at least one surface of the outermost layer has a layer (C) containing a basic phosphate (c-1) in a part thereof. The area ratio (%) of the layer (C) containing the basic phosphate (c-1) has the layer (C) containing (c-1) in the basic phosphate of the electricity storage device separator. It is preferably 90% or less, more preferably 70% or less, and still more preferably 60% or less with respect to the total area of the surface. The area ratio (%) is preferably 5% or more, more preferably 15% or more, and further preferably 30% or more. When this area ratio is 90% or less, blockage of the pores of the porous material layer (A) by the basic phosphate (c-1) can be suppressed, and ion permeability can be maintained. Moreover, when the area ratio is 5% or more, cycle characteristics at high temperatures can be further improved.

  The area ratio coating as described above has a region where the layer (C) containing the basic phosphate (c-1) is present and a layer (C) containing the basic phosphate (c-1). It is preferable that the area not to be realized is realized by an aspect of forming a sea-island shape. Although it does not specifically limit as a sea island shape, For example, a linear shape, a dot shape, a grid | lattice shape, a striped shape, a turtle shell pattern shape etc. are mentioned. Among these, a dot shape is preferable from the viewpoint of ensuring permeability and ensuring uniform adhesion with the electrode. Here, as “dot-like”, the layer (C) containing the basic phosphate (c-1) is present in an island shape on the surface of the separator and contains the basic phosphate (c-1). It is preferable that the part where the layer (C) does not exist is in a sea-island structure in which the part is sea-like. At this time, the layer (C) including the basic phosphate layer (c-1) may all exist independently in an island shape, and a plurality of islands are connected to form a continuous surface. You may do it. However, in the concept of “dot” in the present embodiment, the layer (C) containing the basic phosphate (c-1) is continuous in most parts, and most of the surface is the basic phosphate ( The case where it is covered with the layer (C) containing c-1) (when the sea of the sea-island structure is a layer (C) containing basic phosphate (c-1)) is not included .

The shape of the dot when it exists independently in an island shape is not particularly limited, and examples thereof include a circular shape, an elliptical shape, a polygonal shape, an indefinite shape, and a shape in which these are combined. Of these, a circular shape is most preferable from the viewpoint of ensuring ion permeability and ensuring uniform adhesion with the electrode.
The size of each dot is not particularly limited, but the dot average major axis is preferably 10 μm or more and 1,000 μm or less, more preferably 20 μm or more and 800 μm or less, and further preferably 50 μm or more and 500 μm or less. . It is preferable that the dot average major axis is 10 μm or more and 1,000 μm or less in terms of both adhesion to the electrode and high-temperature cycle characteristics.
The average interval between the dots is preferably 1 μm or more and 1,000 μm or less, more preferably 1 μm or more and 500 μm or less, further preferably 3 μm or more and 200 μm or less, and 5 μm or more and 100 μm or less. Is particularly preferred. The average interval between the dots is preferably 1 μm or more and 1,000 μm or less from the viewpoint of coexistence of adhesion to electrodes and high-temperature cycle characteristics.
The average major axis of the dot comprising the layer (C) containing the basic phosphate (c-1) is determined based on the basic phosphate (c-1) concentration of the liquid to be applied, the basic phosphate (c-1). ) It can be arbitrarily adjusted by changing the coating amount of the solution, the dot shape of the plate, and the coating method and coating conditions.

As the dot arrangement pattern, any periodic or non-periodic pattern can be adopted. For example, in addition to the arrangement pattern of trigonal lattice, tetragonal lattice, hexagonal lattice;
Corresponds to the vertex of each polygon in plane filling with polygons, such as plane filling with parallelograms, plane filling with parallelograms, Archimedes plane filling (8 types), Penrose tiles, Woulderberg tiles, etc. An example is a pattern in which dots are arranged at positions.
In such a dot arrangement, by appropriately adjusting the length of one side of the unit cell and the size of the dot, the layer (C) containing the basic phosphate (c-1) having a desired area ratio can be obtained. It is possible to design a pattern.
The thickness of the layer (C) containing the basic phosphate (c-1) is preferably 0.05 to 15 μm, and preferably 0.1 to 5 μm, from the viewpoint of high-temperature cycle characteristics and air permeability of the battery. it is more preferred lay, and even more preferably to a 0.1 to 3 m. When the thickness of the layer (C) containing the basic phosphate (c-1) is 0.05 μm or more, the high-temperature cycle characteristics of the battery are improved, and when the thickness is 15 μm or less, the separator has good permeability. The temperament can be maintained.

(Formation method of layer (C) containing basic phosphate (c-1))
The layer (C) containing the basic phosphate (c-1) is
On at least one side of the separator,
A coating film is formed by applying a basic phosphate (c-1), preferably a resin binder (c-2) and a solvent, each containing a predetermined amount of a composition (coating liquid) in a pattern. Can then be formed by removing the solvent from the coating.

The coating liquid may consist of only basic phosphate (c-1), resin binder (c-2), and solvent, and may further contain other components besides these. . As other components used here, for example, a dispersant (surfactant, etc.) for stabilizing the dispersion and improving the coating property;
Thickeners;
Wetting agent;
Antifoaming agent;
A pH adjuster (acid, alkali, etc.) etc. can be mentioned. These additives are preferably those that can be removed when the solvent is removed, but if they are electrochemically stable in the range of use of the lithium ion secondary battery, do not inhibit the battery reaction, and are stable up to about 200 ° C., You may remain | survive in the layer (C) containing basic phosphate (c-1).

The solvent is preferably selected from those that do not dissolve the basic phosphate (c-1) and dissolve the resin binder (c-2).
When polyvinyl alcohol is used as the resin binder (c-2), examples of the solvent include water; alcohols such as ethanol and isopropanol; ethers such as tetrahydrofuran and diethyl ether; ketones such as dimethyl ketone, diethyl ketone and methyl isobutyl ketone. Etc. can be illustrated. The amount of the solvent used is preferably such that the solid content concentration of the coating liquid is 5 to 60% by mass, more preferably 10 to 50% by mass, and 15 to 40% by mass. More preferably, the amount is as follows.

  The method for dispersing each component in the coating solution in a solvent is not particularly limited as long as it is a method capable of realizing the dispersion characteristics of the coating solution necessary for the coating process. Examples thereof include a ball mill, a bead mill, a planetary ball mill, a vibrating ball mill, a sand mill, a colloid mill, an attritor, a roll mill, a high-speed impeller dispersion, a disperser, a homogenizer, a high-speed impact mill, ultrasonic dispersion, and mechanical stirring using a stirring blade.

The method for applying the coating liquid to the separator is not particularly limited as long as the required layer thickness and coating area can be realized. 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 include a coater method, a die coater method, a screen printing method, and a spray coating method.
Prior to the application of the coating solution, a surface treatment may be applied to the surface of the porous substrate layer (A). The surface treatment is preferable because the coating liquid can be easily applied and the adhesion between the layer (C) containing the basic phosphate (c-1) and the separator surface is improved. The surface treatment method is not particularly limited as long as it does not significantly impair the porous structure of the separator. Examples thereof include a corona discharge treatment method, a mechanical surface roughening method, a solvent treatment method, an acid treatment method, and an ultraviolet oxidation method.

<Separator>
Next, the separator of this embodiment will be described.
The separator of this embodiment is suitable as a separator for an electricity storage device.
The separator having the layer (C) containing the basic phosphate (c-1) in a part of the outermost layer is excellent in heat resistance and has a shutdown function. Therefore, the separator of this embodiment is suitable for the battery separator which should express the function which isolate | separates a positive electrode and a negative electrode in a battery. Since the said separator is hard to short-circuit at high temperature, it can be safely used especially as a separator for high electromotive force batteries.

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

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

<Power storage device>
As described above, the separator of this embodiment is suitable as a separator for an electricity storage device.
The electricity storage device includes the separator according to the present embodiment. Other configurations may be the same as those conventionally known. This electricity storage device can have, for example, a positive electrode, a negative electrode, and an electrolytic solution.
Although it does not specifically limit as an electrical storage device, For example, batteries, such as a nonaqueous electrolyte battery, a capacitor | condenser, a capacitor, etc. are mentioned. Among these, a non-aqueous electrolyte battery is preferable, a non-aqueous electrolyte secondary battery is more preferable, and a lithium ion secondary battery is more preferable from the viewpoint of more effectively obtaining the benefits of the operational effects of the present embodiment. Hereinafter, a suitable aspect in the case where the electricity storage device is a non-aqueous electrolyte battery will be described.

(Nonaqueous electrolyte battery)
The non-aqueous electrolyte battery in this embodiment is
It has the separator for electrical storage devices of this embodiment, a positive electrode, a negative electrode, and a non-aqueous electrolyte. These positive electrode, negative electrode, and non-aqueous electrolyte are not particularly limited, and known ones can be used.

-Positive electrode-
For example, the positive electrode can be formed by forming a positive electrode active material layer made of a positive electrode active material, a conductive material, and a binder on a current collector.
As the positive electrode active material contained in the positive electrode active material layer, a known material that can electrochemically occlude and release lithium ions can be used. Among these, as the positive electrode active material, a material containing lithium is preferable. Examples of the positive electrode active material include a formula (1):
Li _x Mn _{2- y My} O _z (1)
(In the formula, M represents at least one element selected from the group consisting of transition metal elements, and 0 <x ≦ 1.3, 0.2 <y <0.8, 3.5 <z <4. 5)
An oxide represented by formula (2):
_{Li x M y O z (2} )
(In the formula, M represents at least one element selected from the group consisting of transition metal elements, and 0 <x ≦ 1.3, 0.8 <y <1.2, and 1.8 <z <2.2. .)
A layered oxide represented by formula (3):
_{LiMn 2 -xMa x O 4 (3} )
(In the formula, Ma represents at least one element selected from the group consisting of transition metal elements, and 0.2 ≦ x ≦ 0.7.)
A spinel oxide represented by formula (4):
Li ₂ McO ₃ (4)
(Wherein Mc represents at least one element selected from the group consisting of transition metal elements), and the formula (5):
LiMdO ₂ (5)
(Wherein Md represents at least one element selected from the group consisting of transition metal elements) and is a composite oxide with an oxide represented by formula (6):
_{zLi 2 McO 3 - (1-} z) LiMdO 2 (6)
(In the formula, Mc and Md are synonymous with those in the above formulas (4) and (5), respectively, and 0.1 ≦ z ≦ 0.9.)
Li-excess layered oxide positive electrode active material represented by formula (7):
LiMb _1-y Fe _y PO ₄ (7)
(In the formula, Mb represents at least one element selected from the group consisting of Mn and Co, and 0 ≦ y ≦ 1.0.)
An olivine-type positive electrode active material represented by formula (8):
Li ₂ MePO ₄ F (8)
(Wherein, Me represents at least one element selected from the group consisting of transition metal elements), and the like. These positive electrode active materials may be used alone or in combination of two or more.

Among these, it is preferable that the lithium transition metal oxide containing manganese is included from a viewpoint of cost. Such an oxide is not particularly limited, and examples thereof include compounds represented by formulas (1), (3), and (7).
Furthermore, the potential of the positive electrode active material is preferably 4.5 V or more on the basis of lithium. When the potential of the positive electrode active material is 4.5 V or more on the basis of lithium, even if the electrolyte is decomposed, the accompanying hydrofluoric acid can be removed by the basic compound, which is more effective.
The ratio of the positive electrode active material in the positive electrode active material layer is preferably 0.5 to 30% by mass, more preferably 1 to 25% by mass, and still more preferably 3 to 20% by mass.

As the conductive material contained in the positive electrode active material layer, a known material that can conduct electrons can be used. Such a conductive material is not particularly limited, and examples thereof include graphite, acetylene black, carbon black, ketjen black, and carbon fiber. A material selected from non-graphitic carbonaceous materials and graphite, such as activated carbon, various cokes, carbon black, and acetylene black, is preferable. These may be used alone or in combination of two or more.
0.5-30 mass% is preferable, as for the ratio of the electrically conductive material in a positive electrode active material layer, More preferably, it is 1-25 mass%, More preferably, it is 3-20 mass%.

As the binder contained in the positive electrode active material layer, a known material capable of binding at least two of the positive electrode active material, the conductive material, and the current collector can be used. Such a binder is not particularly limited, but polytetrafluoroethylene, polyvinylidene fluoride, fluorine rubber, polyethylene, nitrile rubber, polybutadiene, butyl rubber, styrene / butadiene rubber, styrene butadiene copolymer, polysulfide rubber, A material selected from nitrocellulose, cyanoethyl cellulose, chloroprene rubber, hexafluoropropylene, a tetrafluoroethylene copolymer, a vinylidene fluoride copolymer, and the like is preferable. Polyvinylidene fluoride, a vinylidene fluoride copolymer, tetrafluoroethylene A copolymer and fluororubber are more preferable. A binder may be used individually by 1 type, or may use 2 or more types together.
The ratio of the binder in the positive electrode active material layer is preferably 0.5 to 20% by mass, more preferably 0.7 to 15% by mass, and still more preferably 1.0 to 8.0% by mass. The content of the secondary battery positive electrode binder is preferably 15% by mass or less from the viewpoint of contact resistance between the active material and the conductive material and between the current collectors.
From the viewpoint of adhesion between the positive electrode active material, the conductive material, and the current collector, 0.5% by mass or more is preferable.

  The thickness of the positive electrode active material layer is preferably 1 μm or more and 200 μm or less, more preferably 30 μm or more and 100 μm or less. If it is less than 1 μm, the volume density of the current collector with respect to the whole cell increases, and the energy density per cell volume is lowered, which is not desirable. Further, if it is 200 μm or more, the electric resistance of the electrode increases and the output density of the cell decreases, which is not desirable.

Although it does not specifically limit as a collector contained in a positive electrode, For example, metal foil, such as aluminum, titanium, stainless steel;
Metal materials other than foil, such as expanded metal, punch metal, and foam metal;
Examples thereof include carbon materials such as carbon cloth and carbon paper. These may be used alone or in combination of two or more. Most preferably, aluminum foil is used.
The thickness of the current collector can be, for example, 1 to 500 μm.

-Negative electrode-
The negative electrode used in the present embodiment can be obtained, for example, by forming a negative electrode active material layer composed of a negative electrode active material and a binder on a current collector.

As the negative electrode active material contained in the negative electrode active material layer, a known material that can electrochemically occlude and release lithium ions can be used. Such a negative electrode active material is not particularly limited, and examples thereof include graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads (MCMB), carbon fibers, and the like. In addition, one of carbon-based materials capable of occluding and releasing lithium may be used alone or a mixture of two or more types;
Elements such as S, Sn, Ge, Bi, Sb, In and the like;
Compounds that can be charged and discharged at a low voltage close to lithium metal such as lithium-containing nitrides;
Lithium metal;
Examples include lithium / aluminum alloys. These may be used alone or in combination of two or more.

As the binder contained in the negative electrode active material layer, a known material capable of binding at least two of the negative electrode active material, the conductive material, and the current collector can be used. Such a binder is not particularly limited, and for example, a material selected from carboxymethyl cellulose, styrene-butadiene cross-linked rubber latex, acrylic latex, and polyvinylidene fluoride is preferable. These may be used alone or in combination of two or more.
The ratio of the binder in the negative electrode active material layer is preferably 0.5 to 15% by mass, more preferably 0.7 to 10% by mass, and still more preferably 1.0 to 8.0% by mass. The content of the binder is preferably 15% by mass or less from the viewpoint of contact resistance between the negative electrode active material and the conductive material and between the current collectors, and the negative electrode active material, the conductive material, and the current collector From the viewpoint of adhesiveness, 0.5% by mass or more is preferable.

Although it does not specifically limit as a collector contained in a negative electrode, For example, metal foil, such as copper, nickel, and stainless steel;
Metal materials other than foil, such as expanded metal, punch metal, and foam metal;
Examples thereof include carbon materials such as carbon cloth and carbon paper. These may be used alone or in combination of two or more.

-Non-aqueous electrolyte-
The nonaqueous electrolytic solution in the present embodiment contains an electrolyte or a salt thereof, and a nonaqueous solvent.
It does not specifically limit as electrolyte (salt) contained in the nonaqueous electrolyte solution used by this embodiment, A conventionally well-known thing can be used. Such an electrolyte is not particularly limited. For example, LiPF ₆ (lithium hexafluorophosphate), LiClO ₄ , LiBF ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ CkF _{2k + 1} [k is 1 to 8] _{integer], LiN (SO 2 C k F} 2k + 1) 2 [k is an integer of 1 to _{8], LiPF n (ckF 2k + 1} ) 6-n [n is an integer of 1 to 5, k is an integer of 1 to 8], _{LiPF 4 (C 2 O 4)} , LiPF 2 (C 2 O 4) 2 and the like. Among these, LiPF ₆ is preferable. By using LiPF ₆ , battery characteristics and safety tend to be superior even at high temperatures. These electrolytes may be used individually by 1 type, or may use 2 or more types together.

The non-aqueous solvent used for the non-aqueous electrolyte in the present embodiment is not particularly limited, and a conventionally known one can be used. Such a non-aqueous solvent is not particularly limited, but for example, an aprotic polar solvent is preferable. The aprotic polar solvent is not particularly limited. For example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate. Cyclic carbonates such as trifluoromethylethylene carbonate, fluoroethylene carbonate, 4,5-difluoroethylene carbonate;
Lactones such as γ-ptyrolactone and γ-valerolactone;
Cyclic sulfones such as sulfolane;
Cyclic ethers such as tetrahydrofuran and dioxane;
Chain carbonates such as ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, methyl trifluoroethyl carbonate;
Nitriles such as acetonitrile;
Chain ethers such as dimethyl ether;
Chain carboxylic acid esters such as methyl propionate;
Examples include chain ether carbonate compounds such as dimethoxyethane. These may be used alone or in combination of two or more.

  The concentration of the electrolyte (salt) in the nonaqueous electrolytic solution is preferably 0.1 to 3 mol / liter, and more preferably 0.5 to 2 mol / liter.

−Open circuit voltage−
As described above, the open circuit voltage in the fully charged state of the nonaqueous electrolyte battery of the present embodiment is preferably 4.50 V or more and 6.00 V or less, more preferably 4.55 V or more and 5.50 V or less, and 4.60 V or more. 5.00 V or less is more preferable. When the open circuit voltage is within the above range, high temperature characteristics tend to be excellent.
In a conventionally known nonaqueous electrolyte battery, the cycle capacity is significantly reduced when the open circuit voltage is 4.5 V or higher. In known batteries, for example, the decrease in cycle capacity is relatively small at 4.2 V, but when the open circuit voltage is 4.5 V, the capacity rapidly decreases with charge and discharge.
On the other hand, the battery according to this embodiment can further suppress the decrease in cycle capacity even when the open circuit voltage is 4.5 V or higher. This advantageous phenomenon is considered to be an effect of using a separator in which the layer (C) containing the basic phosphate (c-1) is partially formed in the outermost layer of the separator.
Moreover, even if the battery of this embodiment is a case where an open circuit voltage is less than 4.5V, the fall of cycle capacity can be suppressed by a higher level.

-Heat treatment-
The nonaqueous electrolyte battery according to the present embodiment is preferably used after being manufactured and then subjected to heat treatment after initial charging. By performing this heat treatment, not only the high temperature characteristics of the battery are improved, but also the life characteristics such as the cycle characteristics are improved even in the vicinity of room temperature of about 25 ° C., for example.
The ultimate voltage at the time of the initial charge performed before the heat treatment is preferably 4.4 V or higher, more preferably 4.5 V or higher, and still more preferably 4.6 V or higher. The upper limit of the ultimate voltage in the initial charge is preferably 6.0 V or less, more preferably 5.5 V or less, and further preferably 5.2 V or less. When the ultimate voltage at the first charge is within the above range, the improvement effect by the heat treatment tends to be more excellent.
The heat treatment temperature is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, and further preferably 60 ° C. or higher. Although the upper limit of heat processing temperature is not specifically limited, 85 degrees C or less is preferable. When the heat treatment temperature is within the above range, the improvement effect by the heat treatment tends to be more excellent.

(Method for manufacturing power storage device)
Although the electrical storage device of this embodiment is not specifically limited, For example, it manufactures as follows. The electricity storage device can be in the form of, for example, a wound body or a laminated body.
-When manufacturing a power storage device in the form of a wound body-
That is, the separator is produced as a vertically long separator having, for example, a width of 10 to 500 mm (preferably 80 to 500 mm) and a length of 200 to 4,000 m (preferably 1,000 to 4,000 m). Next, this separator is stacked in the order of positive electrode-separator-negative electrode-separator or negative electrode-separator-positive electrode-separator to obtain a laminate. Here, when using the separator which formed the layer (C) containing basic phosphate (c-1) only on one side, the layer (C) containing this basic phosphate (c-1) Are laminated so as to be in contact with the negative electrode.
Next, the laminate is wound in a spiral shape to obtain a wound body. As for the winding direction, the axial direction of the spiral may be either the long side direction or the short side direction of the separator, but in order to obtain a more compact battery, the axial direction of the spiral is the short side direction of the separator. It is preferable to use a flat wound body matched with the above.
And an electrical storage device is obtained by passing the process of accommodating the said winding body in an exterior body, and also inject | pouring electrolyte solution. As the outer package, a battery can or a bag-like film can be used.

-When manufacturing a laminated electricity storage device-
In addition, in the above electricity storage device, the separator, the positive electrode, and the negative electrode are each formed into a flat plate shape, and then sequentially stacked as positive electrode-separator-negative electrode-separator-positive electrode or negative electrode-separator-positive electrode-separator-negative electrode. Then, after obtaining the laminate, it can be manufactured through a process such as housing in an outer package and injecting an electrolyte there. As the outer package, a battery can or a bag-like film can be used.

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

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

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

(3) Average pore diameter (μm) of the porous substrate layer (A)
It is known that the fluid inside the capillary follows the Knudsen flow when the mean free path of the fluid is larger than the pore size of the capillary, and the Poiseuille flow when it is small. Therefore, it is assumed that the air flow in the measurement of the air permeability of the resin porous membrane follows the Knudsen flow, and the water flow in the measurement of the permeability of the porous membrane follows the Poiseuille flow.
The average pore diameter d (μm) is 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)), It calculated | required using the following numerical formula from the molecular velocity (nu) (m / sec) of air, the viscosity (eta) (Pa * sec) of water, and standard pressure Ps (= 101,325Pa).
d = 2ν × (R _liq / R _gas ) × (16η / 3Ps) × 10 ⁶

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

(4) Thickness (film thickness, μm)
(4) -1 Thickness (μm) of porous substrate layer (A) and separator
Samples of 10 cm x 10 cm square were cut out from the porous substrate layer (A) and the separator, respectively, and the film thicknesses at 9 locations (3 points x 3 points) selected in a lattice shape were measured using a microthickness meter (Toyo Seiki Seisakusho ( The measurement was carried out at room temperature 23 ± 2 ° C. using a type KBM). The average value of the measured values at 9 locations was defined as the porous substrate layer (A) and the thickness (μm) of the separator.
(4) -2 Thickness (μm) of porous layer (B) and layer (C) containing basic phosphate (c-1)
The thickness of the porous layer (B) and the layer (C) containing the basic phosphate (c-1) was measured using a scanning electron microscope (SEM) “Model S-4800, manufactured by HITACHI”. It was measured by cross-sectional observation. A sample separator was cut to about 1.5 mm × 2.0 mm and stained with ruthenium. The stained sample and ethanol were placed in a gelatin capsule and frozen with liquid nitrogen, and then the sample was cleaved with a hammer. The sample was stained with ruthenium, observed at an acceleration voltage of 1.0 kV and 30,000 times, and the thickness of the porous layer (B) and the layer (C) containing the basic phosphate (c-1) was calculated. At this time, in the SEM image, the porous layer (B) and the basic phosphate (c) due to the difference in structure (continuous structure or sea-island structure) in the region where the porous structure in the cross section of the porous substrate layer (A) is not visible. -1) and a layer (C) containing each of the layers.

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

(6) Aggregated particle size of basic phosphate (c) Observation of cross-sectional scanning electron microscope (SEM) image of multilayer porous membrane, arbitrarily selected 10 particles of basic phosphate (c-1) The average value of the maximum distances of the aggregates was defined as the aggregate particle diameter. The “maximum distance” was the maximum distance between any two points on the outer periphery of one aggregated particle. Measurement was performed in units of 0.1 μm or less, and the average value was expressed in μm units.

(7) Battery cycle characteristics (7-1) Preparation of sample for evaluation [Preparation of electrode]
(Preparation of negative electrode)
90% by mass of graphite powder (OMAC1.2H / SS, manufactured by Osaka Gas Chemical Co., Ltd.) and 10 parts by mass of graphite powder (manufactured by TIMCAL, SFG6) as the negative electrode active material, and 1.8% by mass of carboxymethyl cellulose (as solid content) as the binder ) And styrene-butadiene copolymer latex (glass transition temperature: −40 ° C., particle size: 80 nm, 40 mass% aqueous solution) 1.5 mass% (in terms of solid content) is dispersed in purified water to obtain a solid content of 45 mass%. A slurry was prepared. This slurry was coated on one side of a 18 μm thick copper foil serving as a negative electrode current collector with a die coater, dried at 120 ° C. for 3 minutes, and then compression molded with a roll press to obtain a negative electrode. At this time, the active material coating amount of the negative electrode was set to 106 g / m ² , and the active material bulk density was set to 1.35 g / cm ³ .

(Synthesis of positive electrode active material)
Synthesis of LiNi _0.5 Mn _1.5 O _{4 As} a molar ratio of transition metal elements, nickel sulfate and manganese sulfate in a ratio of 1: 3 are dissolved in water so that the total metal ion concentration becomes 2 mol / L. A nickel-manganese mixed aqueous solution was prepared. Subsequently, this nickel-manganese mixed aqueous solution was dropped into 3 L of a 2 mol / L sodium carbonate aqueous solution heated to 70 ° C. at an addition rate of 12.5 mL / min over 120 minutes. At the time of dropwise addition, air with a flow rate of 200 mL / min was blown into the aqueous solution while being bubbled under stirring. This operation produced a precipitated substance. The produced precipitated substance was collected, washed thoroughly with distilled water, and dried to obtain a nickel manganese compound. The obtained nickel manganese compound and lithium carbonate having a particle diameter of 2 μm were weighed so that the molar ratio of lithium: nickel: manganese was 1: 0.5: 1.5, and dry-mixed for 1 hour, and then an oxygen atmosphere. Then, a positive electrode active material represented by LiNi _0.5 Mn _1.5 O ₄ was obtained by firing at 1,000 ° C. for 5 hours.
(Preparation of positive electrode)
80 parts by mass of the positive electrode active material obtained as described above, 5 parts by mass of graphite powder (manufactured by TIMCAL, KS-6) and acetylene black powder (manufactured by Denki Kagaku Kogyo Co., Ltd., HS-100) ) 5 parts by mass and 10 parts by mass of polyvinylidene fluoride (as solid content) as a binder are mixed and dispersed in N-methyl-2-pyrrolidone as a dispersion solvent to prepare a slurry having a solid content of 35% by mass. did. The slurry was applied to one side of a 20 μm thick aluminum foil serving as a positive electrode current collector with a die coater, dried at 130 ° C. for 3 minutes, and then compression molded with a roll press to obtain a positive electrode. At this time, the active material coating amount of the positive electrode was 250 g / m ² and the active material bulk density was 3.00 g / cm ³ .

The positive electrode was cut to a width of about 57 mm, and the negative electrode was cut to a width of about 58 mm to form a strip, thereby preparing an evaluation electrode.
[Preparation of non-aqueous electrolyte]
The non-aqueous electrolyte was prepared by dissolving LiPF ₆ as a solute in a mixed solvent composed of ethylene carbonate / ethyl methyl carbonate = 1/2 (volume ratio) to a concentration of 1.0 mol / liter.
[Preparation of separator]
The separator for evaluation was produced by cut | disconnecting each separator obtained by the Example and the comparative example into 60 mm, and making it strip | belt shape.

(7-2) Evaluation of battery cycle characteristics [Assembly of battery]
The electrode and separator obtained in (7-1) are stacked in the order of negative electrode, separator, positive electrode and separator, wound at a winding tension of 250 gf, winding speed of 45 mm / second, and spirally wound several times, An electrode laminate was prepared. Here, the separator was laminated | stacked by making the surface in which the phosphate pattern was formed into the negative electrode side. The electrode laminate is housed in a stainless steel container having an outer diameter of 18 mm and a height of 65 mm. An aluminum tab derived from the positive electrode current collector is used as the container lid terminal portion, and a nickel tab derived from the negative electrode current collector is used as the container. Welded to the wall. Then, it dried for 12 hours at 80 degreeC under vacuum. In the argon box, the non-aqueous electrolyte was poured into the assembled battery container and sealed to prepare an evaluation battery.

[Preprocessing]
The battery assembled as described above is housed in a constant temperature bath (manufactured by Futaba Kagaku Co., Ltd., constant temperature bath PLM-73S) set at 55 ° C., and charged / discharged (asuka Electronics Co., Ltd., charged / discharged device ACD-01). Connected. Next, the battery was charged at a constant current of 0.05 C, reached 4.8 V, charged for 2 hours at a constant voltage of 4.8 V, discharged to 3.0 V at a constant current of 0.3 C, and initially Charging / discharging was performed.
1C represents a current value for discharging the reference capacity of the battery in one hour.

[Cycle test]
About the battery which performed the said pre-processing (initial charge / discharge), it accommodates in the thermostat (Futaba Kagaku company make, thermostat PLM-73S) set to 55 degreeC, and a charge / discharge device (Aska Electronics Co., Ltd. charge / discharge) Connected to device ACD-01). The battery was then charged to 4.8V with a constant current of 0.5C and discharged to 3.0V with a constant current of 0.5C. This series of charging / discharging was made into 1 cycle, and also 28 cycles charging / discharging. Subsequently, the battery was charged with a constant current of 0.1 C, reached 4.8 V, charged with a constant voltage of 4.8 V for 1 hour, and discharged to 3.0 V with a constant current of 0.1 C ( 30th cycle).
The discharge capacities after 1 cycle and 30 cycles in this test are shown in Table 1, respectively. When the discharge capacity maintenance rate of the discharge capacity at the 30th cycle relative to the discharge capacity at the 1st cycle is 80% or more, it can be evaluated that the high-temperature cycle characteristics are good without a short circuit.

[DC-IR (Insulation resistance value)]
At the time of the 30th discharge, DC-IR was calculated from the voltage value 10 seconds after the discharge according to the following formula.
DC-IR (Ω) = (4.8−voltage after 10 seconds of discharge) / discharge current value When this value is 60Ω or less, it can be evaluated that the insulation resistance between the positive and negative electrodes is good.

<Production of resin binder (b-1)>
[Synthesis Example 1] Production of acrylic polymer latex 74 parts by mass of water, Aqualon KH1025 (polyoxyethylene-1- (allyl) were added to a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer. Oxymethyl) alkyl ether sulfate ammonium salt: 25% by mass aqueous solution / Daiichi Kogyo Seiyaku Co., Ltd.) 0.125 parts by mass (in terms of solid content), and Adekaria soap SR1025 (25% by mass aqueous solution / ADEKA) 0.125 parts by mass (in terms of solid content) was added, and the temperature in the reaction vessel was kept at 75 ° C., and 0.15 parts by mass of ammonium peroxodisulfate (10 mass aqueous solution) (in terms of solid content) was added. Five minutes after the addition, 11.8 parts by mass of methyl methacrylate, 5 parts by mass of cyclohexyl methacrylate, 1 part by mass of butyl methacrylate, 33 parts by mass of butyl acrylate, 42 parts by mass of 2-ethylhexyl methacrylate, 0. 1 part by mass, 0.1 part by mass of acrylic acid, 0.8 part by mass of glycidyl methacrylate, 5 parts by mass of 2-hydroxyethyl methacrylate, and 0.2 part by mass of γ-methacryloxypropyltrimethoxysilane;
As a crosslinkable monomer, 1 part by mass of trimethylolpropane triacrylate;
As emulsifiers, Aqualon KH1025: 0.15 parts by mass (in terms of solids) and Adekaria soap SR1025 (25% by mass aqueous solution): 0.15 parts by mass (in terms of solids);
As an initiator, an emulsified mixed solution composed of 10% aqueous solution of ammonium peroxodisulfate: 0.15 parts by mass (in terms of solid content) and 65 parts by mass of water was added to the reaction vessel over 2.5 hours. Meanwhile, the reaction solution temperature was controlled to 75 ° C. After the addition of the emulsified mixture, the mixture was stirred at 75 ° C. for 1 hour, then heated from 75 ° C. to 85 ° C. over 1 hour, and further stirred at 85 ° C. for 1 hour to complete the reaction. Thereafter, the reaction solution was cooled to room temperature. From the start of the reaction to completion, the pH of the reaction solution was maintained at 4 or less.
After cooling, the reaction solution was filtered through a 200 mesh wire net to remove aggregates and the like. After filtration, the pH was adjusted to 8 with 25% by mass of ammonia water, and water was added so that the solid content was 40% by mass. After completion of the adjustment, a latex containing an acrylic polymer (1a) was obtained by performing filtration through a 325 mesh wire mesh.
As a result of observation with a transmission electron microscope (TEM), spherical particles having a particle diameter of 141 nm were monodispersed in the acrylic polymer (1a), and the glass transition temperature of the polymer was −40 ° C.

<Production of resin binder (c-2)>
[Synthesis Example 2] Production of Acrylic Polymer Latex Acrylic polymer having a solid content concentration of 40% by mass by operating in the same manner as in Synthesis Example 1 except that the use amounts of the following components were changed as described below. A latex containing polymer (1b) was obtained.
[Initial preparation]
Aqualon KH1025: 0.45 parts by mass (solid content conversion)
ADEKA rear soap SR1025: 0.45 parts by mass (solid content conversion)
Ammonium persulfate (2% by mass aqueous solution): 0.15 parts by mass (in terms of solid content)

[Monomer in emulsion]
Methyl methacrylate: 44.3 parts by mass n-butyl acrylate: 47.0 parts by mass 2-ethylhexyl acrylate: 2 parts by mass Methacrylic acid: 1 part by mass Acrylic acid: 1.5 parts by mass 2-hydroxyethyl methacrylate: 2 parts by mass Acrylamide: 0.2 parts by mass Glycidyl methacrylate: 2 parts by mass Trimethylolpropane triacrylate: 0.7 parts by mass As a result of observation with a transmission electron microscope (TEM), the acrylic polymer (1b) has a particle size of 119 nm spherical particles were monodispersed, and the glass transition temperature of the polymer was 5 ° C.

Example 1
[Production of porous substrate layer (A)]
47.5 parts by mass of a homopolymer polyethylene having a volume average molecular weight of 700,000, 47.5 parts by mass of a homopolymer polyethylene having a volume average molecular weight of 300,000 and 5 parts by mass of polypyrene pyrene having a volume average molecular weight of 400,000 Dry blended using a tumbler blender. 1 part by mass of pentaerythrityl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] is added as an antioxidant to 99 parts by mass of the obtained polymer mixture. Then, a polymer equal mixture was obtained by dry blending again using a tumbler blender.

  The obtained polymer equal mixture was purged with nitrogen and then fed to a twin screw extruder by a feeder under a nitrogen atmosphere. Further, liquid paraffin (kinematic viscosity at 37.78 ° C .: 7.59 × 10 −5 m 2 / s) was injected into the extruder cylinder by a plunger pump. The feeder and pump were adjusted so that the ratio of the amount of liquid paraffin in the total mixture extruded by melt kneading was 67% by mass (the concentration of the mixture such as polymer was 33% by mass). The melt kneading conditions were as follows: a preset temperature of 200 ° C., a screw rotation speed of 100 rpm, and a discharge rate of 12 kg / h.

  The obtained melt-kneaded product was extruded and cast via a T-die on a cooling roll controlled at a surface temperature of 25 ° C. to obtain a gel sheet having a thickness of 1,600 μm. Next, this gel sheet was guided to a simultaneous biaxial tenter stretching machine, and biaxial stretching was performed. The set stretching conditions were an MD magnification of 7.0 times, a TD magnification of 6.4 times, and a preset temperature of 112 ° C. The stretched gel sheet was introduced into a methyl ethyl ketone bath and sufficiently immersed in methyl ethyl ketone to extract and remove the liquid paraffin, and then the methyl ethyl ketone was removed by drying. Next, the processed sheet was guided to a TD tenter and heat-set. The heat setting temperature was 128 ° C., and the TD maximum magnification was 2.0 times. Thereafter, the relaxation rate is reduced to 0.90 at 131 ° C., so that the polyolefin resin porous membrane (A1) has a film thickness of 12 μm, a porosity of 40%, an air permeability of 140 seconds / 100 cc, and an average pore diameter d = 0.07 μm. Got.

[Formation of pattern consisting of layer (C) containing basic phosphate (c-1)]
70 parts by weight of Li ₃ PO ₄ as basic phosphate (c-1), and 20 mass (solids) of polyvinyl alcohol (average polymerization degree 1,700, saponification degree 99% or more) as resin binder (c-2) (Conversion) was uniformly dispersed in 250 parts by mass of water to prepare a coating solution.
Next, this coating solution was applied in a dot shape on one side of the polyolefin resin porous membrane (A1) obtained above using a dot-processed gravure coater. Subsequently, the pattern of the layer (C) containing the basic phosphate (c-1) is formed on one side of the porous substrate layer (A1) to a thickness of 2 μm by removing water by heating to 60 ° C. The separator formed was obtained.
The dot pattern adopted here is the following “pattern 1”.
[Pattern 1]
Dot shape: circular Dot arrangement pattern: triangular lattice unit cell size (length of one side of triangle in triangular lattice): 135 μm
Dot diameter: 100 μm
Area ratio: 50%
The aggregated particle size of the basic phosphate (c-1) was 3 μm.
About the separator obtained above, it evaluated by the said method. The obtained results are shown in Table 1.

Example 2
In this example, a porous layer (B) was formed on one side of a polyolefin resin porous membrane (A1) obtained in the same manner as in Example 1, and a basic phosphate (c-) was formed on the porous layer (B). What coated the layer (C) containing 1) in pattern shape was used as a separator.
[Preparation of coating liquid for forming porous layer (B)]
95.0 parts by mass of aluminum hydroxide oxide (average particle size 0.9 μm) as the inorganic filler (b-2),
As resin binder (b-1), 4 parts by mass of the acrylic polymer (1a) latex obtained in Synthesis Example 1 (in terms of solid content) and an aqueous solution of ammonium polycarboxylate (manufactured by San Nopco, SN Dispersant 5468) A coating solution having a solid content of 50% by mass was prepared by uniformly dispersing 0 part by mass (in terms of solid content) in 100 parts by mass of water.

[Formation of porous layer (B)]
After applying a corona discharge treatment (discharge amount: 50 W) to one surface of the polyolefin resin porous membrane (A1) obtained in the same manner as in [Manufacture of porous substrate layer (A)], the coating liquid is microgravure. It was coated by a coater. The obtained coating film was dried at 60 ° C. to remove water, thereby forming a porous layer (B) having a thickness of 2.0 μm on one surface of the polyolefin resin porous membrane (A1).
[Formation of pattern consisting of layer (C) containing basic phosphate (c-1)]
In [Formation of pattern consisting of layer (C) containing basic phosphate (c-1)] in Example 1 except that the dot pattern was changed to the following “Pattern 2”, the same as in Example 1, A separator in which a phosphate pattern was coated on the porous layer at a thickness of 2 μm was obtained.
[Pattern 2]
Dot shape: circular Dot arrangement pattern: triangular lattice unit cell size (length of one side of triangle in triangular lattice): 103 μm
Dot diameter: 100 μm
Area ratio: 85%
The aggregated particle size of the basic phosphate (c-1) was 3 μm.
The obtained separator was evaluated by the above method. The obtained results are shown in Table 1.

Examples 3 and 4 and Comparative Example 2
In Examples 3 and 4, the basic phosphate (c-1) shown in Table 1 was used, and “Pattern 1” was adopted as the dot pattern. A separator was obtained. The aggregated particle diameter of the basic phosphate (c-1) in these examples was 3 μm.
In Comparative Example 2, the same procedure as described above was performed except that Li ₂ CO ₃ which is a non-basic phosphate was used instead of the basic phosphate (c-1). The agglomerated particle size of Li ₂ CO ₃ was 3 μm.
Each of the obtained separators was evaluated by the above method. The obtained results are shown in Table 1.

Example 5
As the resin binder (c-2) used in the layer (C) containing the basic phosphate (c-1), the acrylic polymer (1b) obtained in Synthesis Example 2 was used, and “Pattern 1” was used as the dot pattern. A separator was obtained in the same manner as in Example 2 except that “ The aggregated particle size of the basic phosphate (c-1) was 3 μm.
The obtained separator was evaluated by the above method. The obtained results are shown in Table 1.

Example 6
A separator was obtained in the same manner as in Example 2 except that “Pattern 1” was adopted as the dot pattern and the thickness of the layer (C) containing the basic phosphate (c-1) was changed to 0.5 μm. It was. The aggregated particle size of the basic phosphate (c-1) was 3 μm.
The obtained separator was evaluated by the above method. The obtained results are shown in Table 1.

Examples 7-9
A separator was obtained in the same manner as in Example 2 except that the dot pattern of the layer (C) containing the basic phosphate (c-1) was changed to the following patterns 3 to 5, respectively. The aggregate particle diameter of the basic phosphate (c-1) was 3 μm.
[Pattern 3]
Dot shape: circular Dot arrangement pattern: triangular lattice unit cell size (length of one side of triangle in triangular lattice): 213 μm
Dot diameter: 100 μm
Area ratio: 20%
[Pattern 4]
Dot shape: circular Dot arrangement pattern: triangular lattice unit cell size (length of one side of triangle in triangular lattice): 301 μm
Dot diameter: 100 μm
Area ratio: 10%
[Pattern 5]
Dot shape: circular Dot arrangement pattern: triangular lattice unit cell size (length of one side of triangle in triangular lattice): 674 μm
Dot diameter: 100 μm
Area ratio: 2%
Each of the obtained separators was evaluated by the above method. The obtained results are shown in Table 1.

Comparative Example 1
In the formation of the pattern comprising the layer (C) containing the basic phosphate (c-1), a separator was obtained in the same manner as in Example 2 except that the dot pattern was not adopted and the entire surface was coated. In addition, the gravure roll was used for the coating of the coating liquid containing the basic phosphate (c-1) in this comparative example.
The obtained separator was evaluated by the above method. The obtained results are shown in Table 1.

Comparative Example 3
In Example 2, the separator (without (C) layer) before forming the layer (C) containing the basic phosphate (c-1) was subjected to evaluation. The obtained results are shown in Table 1.

Claims (7)

An electrical storage device separator having a porous substrate layer (A),
At least the outermost layer on one side has a layer (C) containing a basic phosphate (c-1) in a part thereof ,
The layer (C) containing the basic phosphate (c-1) is composed of the basic phosphate (c-1), or the basic phosphate (c-1) is a resin binder (c- 2) a layer having a thickness of 0.05 to 5 μm, which is bound by 2), and
The basic phosphate (c-1) a layer containing (C) is characterized that you exist in a dot shape, separator electric storage device. The area ratio of the layer (C) containing the basic phosphate (c-1) is the total area of the surface having the layer (C) containing the basic phosphate (c-1) of the electricity storage device separator The separator for an electricity storage device according to claim 1, wherein the separator is 50 % or more and 85 % or less.   In the dot shape, the layer (C) containing the basic phosphate (c-1) exists in an island shape, and the layer (C) containing the basic phosphate (c-1) does not exist. The separator for an electricity storage device according to claim 1 or 2, wherein the separator is in a sea-island structure.   The basic phosphate (c-1) according to any one of claims 1 to 3, wherein the basic phosphate (c-1) is at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts of phosphoric acid. Electric storage device separator. The electricity storage device separator,
A porous layer (B) containing a resin binder (b-1) and an inorganic filler (b-2) is provided on at least one side of the porous substrate layer (A), and the basic phosphate (c-1) 5) The separator for an electricity storage device according to any one of claims 1 to 4, wherein the surface on which the layer (C) containing) exists is the surface of the porous layer (B). The separator for an electricity storage device according to any one of claims 1 to 5,
A positive electrode;
A negative electrode,
An electricity storage device comprising an electrolyte solution. The electric storage device according to claim 6, wherein the positive electrode has a potential of 4.5 V or more based on lithium and is used as a nonaqueous electrolyte secondary battery.