JP6956003B2 - Separator for electrochemical elements - Google Patents

Description

The present invention relates to a separator for an electrochemical element. More specifically, the present invention relates to a separator used for an electrochemical element such as a battery, a capacitor, a capacitor, a sensor, a fuel cell, and an electrolyzer.

In recent years, the importance of electrochemical elements such as batteries has been rapidly increasing in many industries from small portable devices to large-scale applications such as automobiles, and they are mainly superior in terms of capacity, energy density and secondary batteries. Various new battery systems with properties have been developed and improved.

Various developments and improvements have also been made to separators used in electrochemical elements, for example, anions containing polymers and compounds containing at least one element selected from Groups 1 to 17 of the Periodic Table. A separator composed of a conductive material is disclosed (see, for example, Patent Document 1). Further, it is an anion conductive film containing a conjugated diene polymer and / or a (meth) acrylic polymer and the above compound, and the cross section thereof is the total area of the compound particles and anion conduction other than the compound. A separator composed of an anionic conductive film having a ratio of 70/30 to 30/70 to the total area of the sex film forming material components is disclosed (see, for example, Patent Document 2).

Further, as a separator for a non-aqueous secondary battery, one provided with a porous layer containing an inorganic filler is disclosed (see, for example, Patent Documents 3 to 6).

International Publication No. 2014/1196665 Japanese Unexamined Patent Publication No. 2017-27931 Japanese Unexamined Patent Publication No. 2012-134024 Japanese Unexamined Patent Publication No. 2016-9579 Japanese Unexamined Patent Publication No. 2010-559942 Japanese Unexamined Patent Publication No. 2011-108444

The separators described in Patent Documents 1 and 2 have excellent anionic conductivity and can suppress morphological changes of electrode active materials such as shape change and dendrite of electrode active materials. On the other hand, separators for electrochemical elements such as batteries, capacitors, capacitors, sensors, fuel cells, and electrolyzers (also simply referred to as electrolyzers in the present specification) still have cracks in the film forming process. When isolated as a sheet, there is a problem that defects such as dents occur and the moldability is impaired.

The present invention has been made in view of the above situation, and provides a method for isolating a sheet as a sheet with good moldability while sufficiently preventing the occurrence of cracks in the film forming process for obtaining a separator for an electrochemical device. The purpose is.

The present inventors have studied various methods for isolating the sheet as a sheet with good formability while sufficiently preventing the occurrence of cracks in the film forming process for obtaining a separator for an electrochemical element, and have made specific water as a material for the separator. Focusing on the use of magnesium oxide, a separator containing magnesium hydroxide having a specific surface area of 5 m ² / g or more and 15 m ² / g or less and an organic polymer was prepared. The present inventors have found that this separator can be isolated as a sheet with good moldability while sufficiently preventing the occurrence of cracks in the film forming process. The reason is considered to be as follows. That is, particles having a large specific surface area are prone to agglomeration, and the particles and organic polymers are unevenly distributed due to the retention of pores inside the agglomerated particles, which causes cracks in the film forming process and makes it difficult to isolate the sheet. Tends to be. Even if a sufficient amount of dispersant is added so that the primary particles can be dispersed, the particle size of the primary particles is small due to the large specific surface area, and a large number of particles tend to gather in a certain place. Therefore, the shrinkage during film formation was large, and defects were likely to occur in the film. By using magnesium hydroxide having a specific surface area in a predetermined range as the particles, the magnesium hydroxide particles are in a good dispersed state in which they are less likely to aggregate in the film forming process, and the separator has good moldability. The present inventors have come up with the idea that the above problems can be solved brilliantly in this way, and have arrived at the present invention.

That is, the present invention is a separator used for an electrochemical element composed of an aqueous electrolytic solution, wherein the separator has a specific surface area of 5 m ² / g or more and 15 m ² / g or less, and magnesium hydroxide. , A separator for an electrochemical element, which is characterized by containing an organic polymer.

The separator for an electrochemical element of the present invention can be isolated as a sheet with good moldability while sufficiently preventing cracks in the film forming process for obtaining a separator for an electrochemical element.

The present invention will be described in detail below.
A combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

<Separator for electrochemical elements>
The separator for an electrochemical element of the present invention ^{contains magnesium hydroxide having a specific surface area of 5 m 2} / g or more and 15 m ² / g or less, and an organic polymer. In the present specification, the separator for an electrochemical device of the present invention may be simply referred to as a separator. Also, the polymer may be a homopolymer or a copolymer, except as clearly limited.

(Magnesium hydroxide)
The magnesium hydroxide has a specific surface area of 5 m ² / g or more and 15 m ² / g or less.
The specific surface area is ^{preferably 5.5 m 2} / g or more, more preferably 6 m ² / g or more, and further preferably 6.5 m ² / g or more.
The specific surface area is ^{preferably 13 m 2} / g or less, ^{more preferably 11.5 m 2} / g or less, ^{further preferably 10 m 2} / g or less, and 8.5 m ² / g or less. It is particularly preferable to have.
The above-mentioned specific surface area is a specific surface area measured by a BET method using liquid nitrogen, and more specifically, it is measured and calculated according to the method described in Examples.

As a method for preparing particles having a specific surface area in the above range, for example, an aqueous solution of a magnesium salt (magnesium chloride, magnesium nitrate, etc.) or an aqueous dispersion of magnesium oxide obtained by a conventionally known method may be used. A method of obtaining particles having a desired specific surface area by performing a hydrothermal reaction under alkaline conditions as a raw material and optimizing the hydrothermal reaction conditions when producing magnesium hydroxide particles, or preparing magnesium hydroxide particles. In addition to a method of adjusting to a desired specific surface area by crushing with a ball mill or the like, a method of sorting by sieving or the like can be mentioned.

The magnesium hydroxide is in the form of particles, and examples of the shape thereof include a plate-like shape such as a scale-like shape and a flaky shape, a fine powder-like shape, a powder-like shape, a granular shape, a granular shape, a polyhedron shape, a rod shape, and a curved surface-containing shape. Such magnesium hydroxide particles (primary particles) may be single crystals or polycrystals, and any of them exhibits the effects of the present invention.
The magnesium hydroxide preferably has an average particle size (hereinafter, also referred to as a measured particle size) of 10 μm or less when measured by the following measuring method. The measured particle size is more preferably 8 μm or less, still more preferably 6 μm or less. The measurement particle size is preferably 0.01 μm or more, more preferably 0.1 μm or more, further preferably 0.2 μm or more, and particularly preferably 0.3 μm or more. ..

<Measuring method of average particle size (measured particle size) of magnesium hydroxide particles>
Laser diffraction / scattering type particle diameter of magnesium hydroxide particle dispersion liquid in which magnesium hydroxide particles (powder) and 0.2% by mass sodium hexametaphosphate aqueous solution are mixed and dispersed using an ultrasonic cleaner. Measurement is performed with a distribution measuring device (trade name: LA-950, manufactured by Horiba Seisakusho Co., Ltd.), and the median diameter in the obtained volume-based particle size distribution is defined as the measured particle size of magnesium hydroxide particles.

The magnesium hydroxide preferably has an average particle size (hereinafter, also referred to as a calculated particle size) of 5 μm or less when calculated by the following calculation method. The calculated particle size is more preferably 2 μm or less, further preferably 1 μm or less, and particularly preferably 0.5 μm or less. The calculated particle size is preferably 0.01 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, and particularly preferably 0.2 μm or more. ..

<Calculation method of magnesium hydroxide particles Calculation method of particle size>
From the measured specific surface area of magnesium hydroxide particles (m ² / g) and the density of magnesium hydroxide (true specific gravity; 2.36 g / cm ³ is used), water when the particles are assumed to be spherical according to the following formula. Calculation of magnesium oxide particles The particle size (μm) is calculated.
(Calculated particle size) = 6 / [(Density) x (Specific surface area)]

The particles having a measurement particle size in the preferable range as described above are made from, for example, an aqueous solution of a magnesium salt (magnesium chloride, magnesium nitrate, etc.) or an aqueous dispersion of magnesium oxide obtained by a conventionally known method. , A method of obtaining particles with a desired particle size by performing a hydrothermal reaction under alkaline conditions and optimizing the conditions of the hydrothermal reaction when producing magnesium hydroxide particles, or using a ball mill for the prepared magnesium hydroxide particles. It can be produced by a method of crushing the crushed particles with or the like, dispersing the obtained crushed particles in a dispersion medium to obtain a desired particle size, and then drying the crushed particles, or a method of selecting the particle size by sieving the crushed particles. It is possible.

The magnesium hydroxide preferably has a particle size ratio (measured particle size / calculated particle size) of 1 or more and 20 or less.

The mass ratio of magnesium hydroxide is preferably 30% by mass or more in 100% by mass of the separator for an electrochemical element of the present invention from the viewpoint of improving the strength and ionic conductivity of the separator. The mass ratio is more preferably 40% by mass or more, still more preferably 45% by mass or more. The mass ratio is preferably 95% by mass or less. The mass ratio is more preferably 90% by mass or less, still more preferably 85% by mass or less.

The mass ratio of magnesium hydroxide is preferably 60% by mass or more in 100% by mass of the portion excluding the porous base material described later from the separator for an electrochemical element of the present invention. The mass ratio is more preferably 65% by mass or more, still more preferably 70% by mass or more. The mass ratio is preferably 99% by mass or less. The mass ratio is more preferably 98% by mass or less, further preferably 97% by mass or less, and particularly preferably 95% by mass or less.
The above-mentioned "portion in which the porous base material is removed from the separator for an electrochemical element of the present invention" may be rephrased as a portion in which the polymer constituting the porous base material is removed from the separator for an electrochemical element of the present invention. .. When the separator for an electrochemical element of the present invention does not have a porous base material (polymer constituting the porous base material), the above-mentioned "part of the separator for an electrochemical element of the present invention excluding the porous base material". Is the separator for an electrochemical element of the present invention.

(Organic polymer)
As the organic polymer, various ones can be used and may be either thermoplastic or thermosetting. For example, a conjugated diene polymer, a (meth) acrylic polymer, a fluoroethylene polymer, or a polysulfone. Examples thereof include based polymers, aliphatic polyamides, aromatic polyamides, polyether ketones, polyolefin polymers, polyvinyl alcohol polymers, styrene polymers, polyester polymers, etc. Among them, conjugated diene polymers and (meth) acrylic polymers. , Fluorine-containing ethylene-based polymer, polysulfone-based polymer, aromatic polyamide, polyether ketone, polyolefin-based polymer, and polyvinyl alcohol-based polymer, preferably at least one selected from the group. Further, the organic polymer may function as a binder polymer, or may be a polymer constituting a porous base material described later. Binder polymers include, for example, conjugated diene-based polymers, (meth) acrylic-based polymers, fluoroethylene-based polymers, polysulfone-based polymers, aromatic polyamides, polyether ketones, and polyolefin-based polymers (more preferably, for example, carboxy-modified. It is preferably at least one selected from the group consisting of (polyolefin-based polymers). The polymer constituting the porous substrate is selected from the group consisting of, for example, a polyolefin polymer, a polyvinyl alcohol polymer, a fluoroethylene polymer, an aliphatic polyamide, an aromatic polyamide, a styrene polymer, and a polyester polymer. It is preferable that the amount is at least one. In addition, these organic polymers (particularly, polymers constituting a porous base material such as polyolefin-based polymers and polyvinyl alcohol-based polymers) may be fibrous. The fibrous organic polymer is preferably used to form a porous substrate, as will be described later. Further, the organic polymer may be further crosslinked with a known cross-linking agent compound.

The conjugated diene polymer has a monomer unit derived from a conjugated diene monomer.
The conjugated diene-based monomer is preferably an aliphatic conjugated diene-based monomer. Examples of the aliphatic conjugated diene-based monomer include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene and the like, and 1,3-butadiene is preferable. The conjugated diene-based monomer may be used alone or in combination of two or more.

As the conjugated diene-based polymer, one or more monomer units derived from the conjugated diene-based monomer can be used, and the uniformity of the composition according to the present invention and the mechanical strength of the obtained separator can be determined. From the viewpoint of increasing the value and preferably adjusting the elongation and stress, it is preferable to further have, for example, a monomer unit derived from an aromatic vinyl monomer.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, and o-methoxystyrene. , M-methoxystyrene, p-methoxystyrene, o-ethoxystyrene, m-ethoxystyrene, p-ethoxystyrene, o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, o-chlorostyrene, m-chlorostyrene , P-chlorostyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-acetoxystyrene, m-acetoxystyrene, p-acetoxystyrene, o-tert-butoxystyrene, m-tert-butoxystyrene, Examples thereof include p-tert-butoxystyrene, o-tert-butylstyrene, m-tert-butylstyrene, p-tert-butylstyrene and vinyltoluene. Among these, styrene and α-methylstyrene are preferable in that the heat resistance and mechanical strength of the separator can be increased, and the elongation rate and stress can be preferably adjusted. These aromatic vinyl monomers may be used alone or in combination of two or more.

In the conjugated diene polymer, the mass ratio of the monomer unit derived from the aliphatic conjugated diene monomer and the monomer unit derived from the aromatic vinyl monomer is preferably 1/9 or more and 9/1 or less, for example, 2 It is more preferably 8/8 or more and 8/2 or less, and further preferably 3/7 or more and 7/3 or less.

The conjugated diene-based polymer has a carboxy-modified having a carboxy group and / or a carboxylate group which is a salt thereof, from the viewpoint of increasing the binding force between magnesium hydroxide and the organic polymer and improving the strength of the separator. It is preferably a conjugated diene-based polymer, and more preferably, for example, one further having a monomer unit derived from an unsaturated monomer having a carboxyl group and / or a carboxylate group which is a salt thereof. Examples of the unsaturated monomer having a carboxylate group which is a carboxy group and / or a salt thereof include an unsaturated monocarboxylic acid (salt) such as (meth) acrylic acid (salt); maleic acid (salt) and fumaric acid (salt). ), Unsaturated dicarboxylic acid (salt) such as itaconic acid (salt), etc., and these may be used alone or in combination of two or more.

The conjugated diene polymer has a mass ratio of 0.2% by mass of a monomer unit derived from an unsaturated monomer having a carboxy group and / or a carboxylate group which is a salt thereof from the viewpoint of improving the strength of the separator. The above is preferable, 0.3% by mass or more is more preferable, and 0.5% by mass or more is further preferable. Further, from the viewpoint of making the ionic conductivity of the separator more excellent, the mass ratio is preferably 10% by mass or less, more preferably 8% by mass or less, and more preferably 5% by mass or less. More preferred.

Examples of the conjugated diene polymer include styrene-butadiene polymer, carboxy-modified styrene-butadiene polymer, polybutadiene polymer, carboxy-modified polybutadiene polymer, polyisoprene polymer, carboxy-modified polyisoprene polymer, and acrylonitrile-butadiene polymer. One or more of carboxy-modified acrylonitrile-butadiene-based polymers and the like can be preferably used. Among these, a styrene-butadiene polymer and a carboxy-modified styrene-butadiene polymer are preferable, and a carboxy-modified styrene-butadiene polymer is particularly preferable.

The conjugated diene-based polymer is other than a monomer unit derived from an aliphatic conjugated diene-based monomer, a monomer unit derived from an aromatic vinyl monomer, and a monomer unit derived from an unsaturated monomer having a carboxy group and / or a carboxylate group which is a salt thereof. , Other unsaturated monomer-derived monomer units may be used.

Examples of other unsaturated monomers include sulfonic acid group-containing vinyl monomers such as acrylamide methylpropane sulfonic acid and styrene sulfonate; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and the like. N-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, (meth) acrylic (Meta) acrylic acid ester monomers such as octyl acid, 2-ethylhexyl (meth) acrylic acid, nonyl (meth) acrylic acid, decyl (meth) acrylic acid; 2-hydroxyethyl (meth) acrylic acid, (meth) acrylic acid Hydroxyl group-containing vinyl monomer such as 4-hydroxybutyl; nitrile group-containing vinyl monomer such as (meth) acryliconitrile; (meth) acrylamide, N-methylol (meth) acrylamide, N-ethylol (meth) acrylamide, dimethyl (meth) acrylamide, (Meta) acrylamide-based monomers such as diethyl (meth) acrylamide; bifunctional vinyl monomers such as divinylbenzene, ethylene glycol dimethacrylate, isopropylene glycol diacrylate, tetramethylene glycol dimethacrylate; 3-methacryloxypropylmethyldimethoxysilane, 3 Examples thereof include alkossisilane group-containing vinyl monomers such as methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane.

The mass ratio of the monomer unit derived from other unsaturated monomers in 100% by mass of the conjugated diene polymer is preferably 30% by mass or less, more preferably 5% by mass or less, and 0.1% by mass. The following is more preferable.

The (meth) acrylic polymer may have a monomer unit derived from a monomer having a (meth) acryloyl group, but a typical one mainly contains a monomer unit derived from a (meth) acrylic acid ester monomer. Examples thereof include (meth) acrylic acid ester-based polymers.

When the monomer unit derived from the (meth) acrylic acid ester monomer is mainly used, the content of the monomer unit derived from the (meth) acrylic acid ester monomer is 50% by mass or more in 100% by mass of the (meth) acrylic acid ester polymer. Say something. The content is preferably 70% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass.
The (meth) acrylic acid ester monomer is specifically as described above as one of the other unsaturated monomers in the carboxy-modified conjugated diene polymer.

The (meth) acrylic polymer is a monomer unit derived from an unsaturated monomer having a carboxy group and / or a carboxylate group which is a salt thereof, in addition to the monomer unit derived from the (meth) acrylic acid ester monomer, and other unsaturated monomers. It may have a monomer unit derived from a monomer. The (meth) acrylic polymer has a carboxy group and / or a carboxylate group which is a salt thereof, from the viewpoint of increasing the binding force between the magnesium hydroxide and the organic polymer and making the strength of the separator more excellent. It is preferably a (meth) acrylic polymer having a monomer unit derived from an unsaturated monomer.

As the other unsaturated monomer, the same as the above-mentioned unsaturated monomer in the carboxy-modified conjugated diene polymer can be mentioned (however, the (meth) acrylic acid ester monomer is excluded).

The fluorine-containing ethylene-based polymer has a structure in which a hydrogen atom of polyethylene is replaced with a fluorine atom, and examples thereof include polyvinylidene fluoride and polytetrafluoroethylene.

The polysulfone-based polymer refers to a polymer having a sulfonyl group as a repeating unit, and examples thereof include polysulfone (PSU), polyethersulfone (PESU), and polyphenylsulfone (PSSU).
The aromatic polyamide refers to a polymer composed of an aromatic dicarboxylic acid component and an aromatic diamine component, or an aromatic aminocarboxylic acid component, and examples thereof include polyphenylene terephthalamide and polyphenylene isophthalamide.
The polyetherketone is a polymer having an ether bond and a ketone bond, and examples thereof include polyetherketoneketone and polyetheretherketone.

The polyolefin-based polymer may have a monomer unit derived from an unsaturated hydrocarbon.
The unsaturated hydrocarbons include, for example, ethylene, propylene, 1-butene, 1-hexene, 1-pentene, isoprene, diisobutylene, 1-heptene, 1-octene, 1-nonene, 1-undecene, 1-dodecene, 1 -Tridecene, 1-tetradecene, 1-pentadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, propylene trimmers and tetramers, terminal olefins such as styrene, vinyltoluene, divinylbenzene; 2-butene, Examples thereof include intramolecular olefins such as 2-octene, 2-methyl-1-hexene, and 2,3-dimethyl-2-butene, and these may be used alone or in combination of two or more.

The polyolefin-based polymer is a carboxy-modified polyolefin having a carboxy group and / or a carboxylate group which is a salt thereof, from the viewpoint of increasing the binding force between magnesium hydroxide and the organic polymer and improving the strength of the separator. It is preferably a based polymer. Examples of the carboxy-modified polyolefin-based polymer include those having a monomer unit derived from an unsaturated monomer having a carboxy group and / or a carboxylate group which is a salt thereof, and a polyolefin which is graft-modified with an organic peroxide or the like. Therefore, a polymer containing a monomer unit derived from an unsaturated monomer having a carboxyl group and / or a carboxylate group which is a salt thereof is introduced into the side chain of the polyolefin. The preferred type and preferred mass ratio of the unsaturated monomer having a carboxylate group which is a carboxy group and / or a salt thereof are the same as those described above in the above-mentioned carboxy-modified conjugated diene-based polymer. The viewpoint that the carboxy-modified polyolefin-based polymer has an aggregate structure by allowing metal ions such as sodium ion and zinc ion to act (ionomer) to improve the flexibility of the separator. Therefore, it is preferable.

The polyolefin-based polymer has a monomer unit derived from an unsaturated hydrocarbon, a monomer unit derived from an unsaturated monomer having a carboxylate group which is a carboxy group and / or a salt thereof, and a monomer unit derived from another unsaturated monomer. You may be doing it.

Examples of other unsaturated monomers include those similar to those described above in the above-mentioned conjugated diene-based polymer.
The mass ratio of the monomer unit derived from other unsaturated monomers in 100% by mass of the polyolefin-based polymer is preferably 30% by mass or less, more preferably 5% by mass or less, still more preferably 0.1% by mass or less. ..

The polyvinyl alcohol-based polymer is a polymer obtained by saponifying polyvinyl acetate, and a polymer having a saponification degree of 100 mol% is represented by the general formula [CH ₂ CH (OH)] _n . The average degree of polymerization n of the polyvinyl alcohol-based polymer is not particularly limited, but is preferably 300 to 5000, for example.
The average degree of polymerization n can be calculated by the method described in JIS K6726.
The average saponification degree is preferably 50 to 100 mol%, more preferably 80 to 100 mol%, and further preferably 90 to 100 mol%.
The average saponification degree can be measured by the method described in JIS K6726.
The polyvinyl alcohol-based polymer is a carboxy-modified polyvinyl alcohol having a monomer unit derived from an unsaturated monomer having a carboxy group and / or a carboxylate group which is a salt thereof, and a polyethylene oxide-modified by adding polyethylene oxide to a hydroxyl group after saponification. It may be polyvinyl alcohol or vinylon that is further acetalized after saponification.

By selecting the type of organic polymer contained in the separator for an electrochemical device of the present invention, the elongation rate and stress can be appropriately adjusted. For example, the separator for an electrochemical element of the present invention may contain at least one selected from the group consisting of a conjugated diene polymer, a polysulfone polymer, a polyolefin polymer, a fluorine-containing ethylene polymer, and a polyvinyl alcohol polymer. Especially preferable.

The organic polymer can be produced by copolymerizing a monomer component forming a structural unit contained in the polymer in the presence of a radical generator, and graft-modifying the monomer component if necessary.
The method for polymerizing the monomer component is not particularly limited, and examples thereof include an aqueous solution polymerization method, an emulsion polymerization method, a reverse phase suspension polymerization method, a suspension polymerization method, a solution polymerization method, and a bulk polymerization method.

The separator for an electrochemical device of the present invention preferably further has a porous substrate. The porous base material is constructed by using the polymer constituting the above-mentioned porous base material, and among them, polyolefin-based polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and cyclic polyolefin-based polymer. Polyvinyl alcohol-based polymers such as vinylon; aliphatic polyamides; aromatic polyamides; styrene-based polymers; non-woven fabrics, woven fabrics, microporous films and the like made of resin materials such as polyester-based polymers are preferable. Of these, polyolefin-based polymers and polyvinyl alcohol-based polymers are more preferable. The porous substrate may be hydrophilized by a conventionally known method. The porous base material is preferably, for example, a polyvinyl alcohol-based resin or a hydrophilized material. In these porous substrates, the introduction of hydroxyl groups and carboxy groups on the surface improves the bonding force with the composition according to the present invention, and the strength of the separator becomes more excellent.
When the separator for an electrochemical element of the present invention has a porous base material, it may be a laminate in which a film obtained from the composition according to the present invention described above and a porous base material are laminated, and the present invention may be used. The film obtained from the composition according to the present invention obtained by impregnating the porous base material with the composition according to the above invention and the porous base material may be integrated. In the above laminated body, a part of the composition according to the present invention is impregnated with a part of the porous base material, and the film obtained from the composition according to the present invention and the porous base material are partially formed. The composition according to the present invention may fill some or all of the pores in the porous substrate.

The mass ratio of the organic polymer is preferably 5% by mass or more in 100% by mass of the separator for an electrochemical element of the present invention from the viewpoint of suitably adjusting the ionic conductivity of the separator and the elongation rate and stress of the separator. It is more preferably 10% by mass or more, and further preferably 15% by mass or more. The mass ratio is preferably 70% by mass or less, more preferably 60% by mass or less, and further preferably 55% by mass or less.

When the separator for an electrochemical element of the present invention contains the binder polymer, the mass ratio of the binder polymer is 1% by mass or more in 100% by mass of the portion of the separator for an electrochemical element of the present invention excluding the porous substrate. It is preferably 2% by mass or more, more preferably 3% by mass or more, and particularly preferably 5% by mass or more. The mass ratio is preferably 40% by mass or less, more preferably 35% by mass or less, and further preferably 30% by mass or less.
The above-mentioned "portion in which the porous base material is removed from the separator for an electrochemical element of the present invention" may be rephrased as a portion in which the polymer constituting the porous base material is removed from the separator for an electrochemical element of the present invention. .. When the separator for an electrochemical element of the present invention does not have a porous base material (polymer constituting the porous base material), the above-mentioned "part of the separator for an electrochemical element of the present invention excluding the porous base material". Is the separator for an electrochemical element of the present invention.

(Other ingredients)
The separator for an electrochemical element of the present invention may contain a water-soluble polymer used as a dispersant for magnesium hydroxide or the like.
Examples of the water-soluble polymer include celluloses such as carboxymethyl cellulose; poly (meth) acrylic acid (salt) such as sodium polyacrylate; and unsaturated carboxylic acids such as (meth) acrylic acid (salt) and maleic acid (salt). Examples thereof include polymers with unsaturated sulfonic acids (salts) such as acid (salt) and vinyl sulfonic acid (salt), and one or more of these can be used.

When the separator for an electrochemical element of the present invention contains a water-soluble polymer, the content ratio of the water-soluble polymer is for the electrochemical element of the present invention from the viewpoint of sufficiently dispersing magnesium hydroxide and exerting its action and effect. It is preferably 0.1% by mass or more in 100% by mass of the separator. Further, the content ratio is preferably 3% by mass or less from the viewpoint of further suppressing the water-soluble polymer from absorbing an electrolytic solution such as water to plasticize the separator.

The separator for an electrochemical element of the present invention may further contain other inorganic components such as conductive carbon and conductive ceramics.
The content ratio of other inorganic components in the separator for an electrochemical device of the present invention is preferably 30% by mass or less in 100% by mass of the separator from the viewpoint of the strength of the separator. It is more preferably 10% by mass or less, further preferably 1% by mass or less, and particularly preferably 0.1% by mass or less.

The separator for an electrochemical device of the present invention preferably has an average film thickness of 10 μm to 1 mm. If it is 10 μm or more, it is possible to sufficiently prevent the occurrence of damage during film formation. Further, if it is 1 mm or less, it is advantageous in terms of cost, and the ability of ion permeation is sufficiently excellent. The average film thickness is more preferably 15 μm or more, further preferably 20 μm or more, and particularly preferably 25 μm or more. The average film thickness is more preferably 800 μm or less, further preferably 500 μm or less, and particularly preferably 200 μm or less.
The average film thickness can be measured according to the method described in Examples.

The separator for an electrochemical device of the present invention preferably has a porosity of 1 to 90%. As a result, the separator for an electrochemical device of the present invention more sufficiently satisfies the basic performance required for the separator, and can be suitably used as a separator. The porosity is more preferably 3% or more, further preferably 6% or more, and particularly preferably 10% or more. The porosity is more preferably 80% or less, further preferably 70% or less, and particularly preferably 60% or less.
The porosity is calculated according to the method described in Examples.

The separator for an electrochemical element of the present invention is intended to be used as a separator used for an electrochemical element such as a battery, a capacitor, a capacitor, a sensor, a fuel cell, and an electrolytic device, which is composed of an aqueous electrolytic solution. ..
Since the separator for an electrochemical element of the present invention contains magnesium hydroxide particles having a highly hydrophilic surface, not only the surface of the separator but also the inside of the separator forms a state having particularly good affinity with an aqueous electrolytic solution. ing. In such a state, the permeation of the electrolytic solution into the separator becomes faster, and more stable electrochemical characteristics are obtained in the electrochemical element (particularly the battery) composed of the aqueous electrolytic solution having high thermal safety. Is considered to be obtained.

(Method for Manufacturing Separator for Electrochemical Device of the Present Invention)
The separator for an electrochemical element of the present invention is prepared by preparing a composition (also simply referred to as a composition according to the present invention in the present specification) used for forming a film to obtain a separator for an electrochemical element, and this composition. The product can be produced by forming a film by a method described later.
First, the raw materials of the composition according to the present invention (magnesium hydroxide having a specific specific surface area according to the present invention, an organic polymer, and other components) are mixed. For mixing, a mixer, blender, kneader, sand mill, bead mill, ready mill, roll mill, ball mill and the like can be used. At the time of mixing, water, an organic solvent such as methanol, ethanol, propanol, isopropanol, butanol, hexanol, tetrahydrofuran, N-methylpyrrolidone, or a mixed solvent of water and an organic solvent may be added as a medium.
After mixing, filtration, defoaming and the like can be performed as necessary to obtain the composition according to the present invention.
The magnesium hydroxide dispersion may be produced before mixing. For example, magnesium hydroxide and, if necessary, a dispersant of magnesium hydroxide and the like are mixed. By producing the magnesium hydroxide dispersion before mixing, it is possible to suppress the destabilization of the organic polymer during preparation. The above-mentioned equipment and medium can be used for mixing.

The method for producing a film from the composition according to the present invention is not particularly limited, and the composition according to the present invention is coated on a release base material such as a mirror-finished metal roll or a polyethylene terephthalate (PET) film. A method of drying and peeling the obtained coating film to obtain a film (casting method), a method of rolling with a roll to form a film, a method of rolling with a flat plate press or the like to form a film, or injection molding. A method of forming into a film such as a method or an extrusion molding method, or a method of coating and drying on an electrode sheet to form a film integrated with the electrode sheet can be used. These molding methods may be used alone or in combination of two or more methods.

The production method preferably includes a step of drying the film during and / or after the step of forming the composition according to the present invention into a film.
The drying step after the film formation may be performed by heating the film, if necessary. The heating temperature and heating time of the film may be appropriately set.

When the separator for an electrochemical element of the present invention further has a porous base material, for example, a film obtained from the composition according to the present invention and a porous base material may be laminated by a conventionally known method, or the present invention may be used. After coating the composition according to the present invention on a peeling base material, the porous base material is contacted and impregnated, the film is solidified, and then the peeling base material is peeled off to form a separator for an electrochemical element of the present invention. Can be manufactured.

<Electrochemical element>
The present invention is also an electrochemical element composed of the separator for an electrochemical element of the present invention and an aqueous electrolyte solution.
Examples of the electrochemical element of the present invention include a battery; a capacitor such as an electrolytic capacitor; a capacitor such as an electric double layer capacitor and a lithium ion capacitor; a sensor such as a humidity sensor and a gas sensor; a fuel cell such as an alkaline fuel cell; an alkaline type. Examples thereof include an electrolytic device such as a water electrolytic device.

The aqueous electrolyte is not particularly limited as long as it uses water as the main component of the electrolytic solution raw material, which is usually used as the aqueous electrolyte of the electrochemical element, and may contain an organic solvent together with water. Using water as the main component of the electrolytic solution raw material means that the mass ratio of water is 50% by mass or more in 100% by mass of the aqueous electrolytic solution. The mass ratio is preferably 80% by mass or more. Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxymethane, diethoxymethane, dimethoxyethane, tetrahydrofuran, methyl tetrahydrofuran, diethoxyethane, dimethylsulfoxide, sulfolane, acetonitrile, benzo. Examples thereof include nitriles, ionic liquids, fluorine-containing carbonates, fluorine-containing ethers, polyethylene glycols, fluorine-containing polyethylene glycols, and the like, and any one or more of these can be used.

Above all, the electrochemical element of the present invention is preferably an electrochemical element composed of an electrolytic solution using only water as an electrolytic solution raw material. An electrolytic solution using only water as an electrolytic solution raw material has higher thermal safety, and more stable electrochemical characteristics can be obtained by using the separator for an electrochemical element of the present invention.

The aqueous electrolytic solution is preferably, for example, an alkaline electrolytic solution. Examples of the alkaline electrolytic solution include potassium hydroxide aqueous solution, sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, zinc sulfate aqueous solution, zinc nitrate aqueous solution, zinc phosphate aqueous solution, zinc acetate aqueous solution and the like, and these may be used alone. It can also be used as an aqueous solution in which two or more of these solutes are mixed.

(battery)
The case where the electrochemical element of the present invention is a battery will be described in detail below.
Batteries are usually configured to further include a positive electrode. As the active material of the positive electrode, a compound usually used as a positive electrode active material of a primary battery or a secondary battery can be used, and is not particularly limited. For example, oxygen (when oxygen is the positive electrode active material, the positive electrode is oxygen). Perovskite type compounds, cobalt-containing compounds, iron-containing compounds, copper-containing compounds, manganese-containing compounds, vanadium-containing compounds, nickel-containing compounds, iridium-containing compounds, platinum-containing compounds; palladium-containing compounds; gold Containing compound; Silver-containing compound; Air electrode composed of carbon-containing compound, etc.); Nickel-containing compound such as nickel oxyhydroxide, nickel hydroxide, cobalt-containing nickel hydroxide; Manganese-containing compound such as manganese dioxide; Oxidation Silver; lithium-containing compounds such as lithium cobaltate; iron-containing compounds; zinc species such as metallic zinc and zinc oxide.
Further, it is also one of the preferred embodiments of the present invention that the positive electrode active material is oxygen, such as an air battery.

The battery is usually configured to further include a negative electrode. As the negative electrode active material, those usually used as the negative electrode active material of the battery, such as carbon, lithium, sodium, magnesium, zinc, nickel, tin, cadmium, hydrogen storage alloy, and silicon-containing material, can be used. For example, the present invention can be suitably applied to a battery using an active material such as zinc, lithium, nickel, magnesium, cadmium, etc., which may generate dendrites due to an electrode reaction, as the negative electrode active material. .. Above all, it is preferable that the negative electrode active material contains a zinc compound.

Electrodes such as positive electrodes and negative electrodes constituting the battery can be manufactured by forming an active material layer on a current collector.
The current collectors that make up the electrodes include (electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punching copper, copper alloys such as brass, brass foil, brass mesh (expanded metal), foamed brass, and punching brass. , Nickel foil, corrosion resistant nickel, nickel mesh (expanded metal), punching nickel, metallic zinc, corrosion resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punching) steel plate, conductive non-woven fabric; Ni, Zn, (Electrolytic) copper foil with Sn, Pb, Hg, Bi, In, Tl, brass, etc. added, copper mesh (expanded metal), foamed copper, punched copper, copper alloy such as brass, brass foil, brass mesh (expanded metal) ), Foamed brass, punching brass, nickel foil, corrosion resistant nickel, nickel mesh (expanded metal), punching nickel, metallic zinc, corrosion resistant metallic zinc, zinc foil, zinc mesh (expanded metal), (punching) steel plate, non-woven fabric; Ni, (Electrolytic) copper foil copper mesh (expanded metal) plated with Zn, Sn, Pb, Hg, Bi, In, Tl, brass, etc., foamed copper, punched copper, copper alloys such as brass, brass foil, brass mesh ( Expanded metal), foamed brass, punching brass, nickel foil, corrosion-resistant nickel, nickel mesh (expanded metal), punching nickel, metallic zinc, corrosion-resistant metal zinc, zinc foil, zinc mesh (expanded metal), (punching) steel plate, non-woven fabric; Silver: Examples of materials used as current collectors and containers for alkaline (storage) batteries and air zinc batteries.

The form of the battery is usually a secondary battery (storage battery) that can be charged and discharged. The battery of the present invention uses a mechanical discharge (mechanical replacement of a zinc negative electrode) in addition to a general secondary battery; a battery using a third pole (as a positive electrode, an electrode suitable for charging). It may be in any form such as (one in which electrodes suitable for discharge are used respectively).

(Fuel cell or electrolyzer)
The case where the electrochemical element of the present invention is a fuel cell or an electrolytic device will be described in detail below.
The separator for an electrochemical element of the present invention is suitably used as a member of an alkaline fuel cell and an alkaline water electrolyzer. Examples of the alkaline fuel cell and the alkaline water electrolyzer include an anode, a cathode, and a separator for an electrochemical element of the present invention arranged between the anode and the cathode. More specifically, the alkaline fuel cell and the alkaline water electrolyzer have an anode chamber in which the anode is present and a cathode chamber in which the cathode is present, which are separated by the separator for the electrochemical element of the present invention.
Examples of the anode and the cathode include known electrodes including a conductive substrate containing nickel, a nickel alloy, or the like.

[Fuel cell power generation method]
The method of power generation using the alkaline fuel cell including the separator for an electrochemical element of the present invention is not particularly limited, and a known method can be used. For example, an alkaline fuel cell containing the above-mentioned separator for an electrochemical element of the present invention is filled with an electrolytic solution, and an oxidizing agent (for example, oxygen) and a fuel (for example, hydrogen) are supplied to each of the anode and cathode in the electrolytic solution. By doing so, power can be generated.

[Electrolysis method of water electrolyzer]
The method of electrolyzing water using the alkaline water electrolyzer including the separator for an electrochemical element of the present invention is not particularly limited, and a known method can be used. For example, it can be carried out by filling the alkaline water electrolyzer including the above-mentioned separator for an electrochemical element of the present invention with an electrolytic solution and applying an electric current in the electrolytic solution.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "part" means "part by weight" and "%" means "mass%".

<Specific surface area of magnesium hydroxide particles>
The specific surface area of the magnesium hydroxide particles was measured using a BET specific surface area meter (trade name: Macsorb HM model-1210, manufactured by Mountech). Specifically, magnesium hydroxide particles (powder) were charged into the cell as a measurement sample, and degassing treatment was performed at 200 ° C. while flowing nitrogen gas in the cell. After the degassing treatment, the cell was immersed in liquid nitrogen while nitrogen gas was flowing through the cell, and nitrogen was adsorbed on the measurement sample at a temperature of -196 ° C. Next, the specific surface area by the BET method was measured by keeping the cell at room temperature and measuring the amount of nitrogen desorbed. The measurement was performed three times per sample, and the average value was taken as the specific surface area (m ² / g) of the magnesium hydroxide particles.

<Measured particle size of magnesium hydroxide particles>
The average particle size (measurement particle size) of the magnesium hydroxide particles was measured by the above-mentioned measuring method.

<Calculated particle size calculated from the specific surface area of magnesium hydroxide particles>
The average particle size (calculated particle size) of the magnesium hydroxide particles was calculated by the above-mentioned calculation method.

<Film thickness>
The thickness of the obtained separator was measured using a digital micrometer (manufactured by Mitutoyo Co., Ltd.). Arbitrary 10 points were measured, and the average value was taken as the film thickness.

<Film formation>
Regarding the film-forming property, in the coating film formed on the polyethylene terephthalate film or the coating film integrated with the non-woven fabric, a region of 80 mm × 80 mm was selected, and the surface condition in that region was visually observed to determine the presence or absence of cracks. Based on the amount of cracks generated and the size of the cracks generated, evaluation was performed according to the following criteria.
5: No cracks 4: 1 fine crack is generated 3: 2 to 5 fine cracks are generated 2: 6 to 10 fine cracks are partially generated, or 1 to 2 large cracks are generated 1 : Cracks occur on almost the entire surface

<Sheet isolation>
For sheet isolation, select a region of 60 mm x 60 mm in the coating film formed on the polyethylene terephthalate (PET) film or the coating film integrated with the non-woven film, and select the coating film (for the coating film integrated with the non-woven film, each non-woven film). ) Was peeled off from the PET film, the size of the obtained coating film, the presence or absence of defects such as dents, and the state of the peeling interface were visually observed and evaluated according to the following criteria.
A separator of 5:50 mm × 50 mm or more was obtained without defects. A separator of 4:50 mm × 50 mm or more was obtained, but some peeling defects were observed. A separator of 3:50 mm × 50 mm or more was obtained, but the peeled surface was obtained. A dent defect was observed on the entire surface 2: Cracks occurred during peeling, and only a sheet with a size of 10 mm × 10 mm to 50 mm × 50 mm was obtained 1: Cracks occurred during peeling, and the size was 10 mm × 10 mm or more. Table 1 shows the specific surface area, measured particle size, calculated particle size, and particle size ratio (measured particle size / calculated particle size) of magnesium hydroxide particles A to G (particles A to G). Is shown.

[Example 1]
Weigh 100 parts by mass of magnesium hydroxide particles A having the specific surface area shown in Table 1, 3 parts by mass of polyacrylate aqueous solution (nonvolatile content 40%), and 42 parts by mass of ion-exchanged water, and disperse them for 1 hour using a sand mill. After that, filtration was performed to obtain an aqueous dispersion of magnesium hydroxide particles.
Weigh 50 parts by mass of the obtained magnesium hydroxide particle aqueous dispersion and 21 parts by mass of a carboxy-modified styrene-butadiene polymer aqueous dispersion (nonvolatile content: 48%), mix them, and then perform filtration and vacuum defoaming. A film-forming composition was obtained.
The obtained film-forming composition was coated on a polyethylene terephthalate (PET) film with a comma coater and dried, and the obtained coating film was peeled from the PET film to obtain a separator.
The film thickness of the obtained separator was 85 μm, the film-forming property was evaluated as 5, and the sheet isolation property was evaluated as 5.

[Example 2]
In Example 1, a separator was obtained in the same manner as in Example 1 except that the magnesium hydroxide particles A were changed to magnesium hydroxide particles B having the specific surface area shown in Table 1.
The film thickness of the obtained separator was 87 μm, the film-forming property was evaluated as 5, and the sheet isolation property was evaluated as 4.

[Example 3]
In Example 1, a separator was obtained in the same manner as in Example 1 except that the magnesium hydroxide particles A were changed to magnesium hydroxide particles C having the specific surface area shown in Table 1.
The film thickness of the obtained separator was 72 μm, the film-forming property was evaluated as 5, and the sheet isolation property was evaluated as 5.

[Example 4]
In Example 1, a separator was obtained in the same manner as in Example 1 except that the magnesium hydroxide particles A were changed to the magnesium hydroxide particles D having the specific surface area shown in Table 1.
The film thickness of the obtained separator was 92 μm, the film-forming property was evaluated as 4, and the sheet isolation property was evaluated as 4.

[Example 5]
In Example 1, a separator was obtained in the same manner as in Example 1 except that the magnesium hydroxide particles A were changed to the magnesium hydroxide particles E having the specific surface area shown in Table 1.
The film thickness of the obtained separator was 89 μm, the film-forming property was evaluated as 3, and the sheet isolation property was evaluated as 4.

[Comparative Example 1]
In Example 1, a separator was obtained in the same manner as in Example 1 except that the magnesium hydroxide particles A were changed to magnesium hydroxide particles F having the specific surface area shown in Table 1.
The film thickness of the obtained separator was 95 μm, the film-forming property was evaluated as 2, and the sheet isolation property was evaluated as 1.

[Comparative Example 2]
In Example 1, a separator was obtained in the same manner as in Example 1 except that the magnesium hydroxide particles A were changed to the magnesium hydroxide particles G having the specific surface area shown in Table 1.
The film thickness of the obtained separator was 84 μm, the film-forming property was evaluated as 3, and the sheet isolation property was evaluated as 2.

From the comparison of Examples 1 to 5 and Comparative Examples 1 and 2, the separator using magnesium hydroxide particles prepared to have a ^{specific surface area of 5 m 2} / g or more and 15 m ^{2 / g or less has good film forming property.} It was possible to obtain a separator capable of sheet isolation with a sufficient area (good sheet isolation).

[Example 6]
Weigh 100 parts by mass of magnesium hydroxide particles B having the specific surface area shown in Table 1, 3 parts by mass of polyacrylate aqueous solution (nonvolatile content 40%), and 42 parts by mass of ion-exchanged water, and disperse them for 1 hour using a sand mill. After that, filtration was performed to obtain an aqueous dispersion of magnesium hydroxide particles.
Weigh 50 parts by mass of the obtained magnesium hydroxide particle aqueous dispersion and 21 parts by mass of a carboxy-modified styrene-butadiene polymer aqueous dispersion (nonvolatile content: 48%), mix them, and then perform filtration and vacuum defoaming. A film-forming composition was obtained.
The obtained film-forming composition is coated on a polyethylene terephthalate (PET) film with a non-woven fabric so that the weighing value of the film-forming composition at the time of drying is 9.0 mg / cm ^2. A non-woven fabric made of polyvinyl alcohol-based fiber (weighing value: 2.4 mg / cm ² , thickness: 88 μm) is brought into contact with the non-woven fabric, dried, and the coating film is peeled off from the PET film together with the non-woven fabric to coat the non-woven fabric. A separator with an integrated membrane was obtained.
The film thickness of the obtained separator was 105 μm, the film-forming property was evaluated as 5, and the sheet isolation property was evaluated as 5.

[Example 7]
In Example 6, the non-woven fabric made of polyvinyl alcohol fibers was changed to a non-woven fabric made of polyolefin fibers (weighing value: 4.0 mg / cm ² , thickness: 90 μm), and the same as in Example 6 with the non-woven fabric. A separator having an integrated coating film was obtained.
The film thickness of the obtained separator was 98 μm, the film-forming property was evaluated as 5, and the sheet isolation property was evaluated as 4.

[Example 8]
In Example 6, 21 parts by mass of the carboxy-modified styrene-butadiene polymer aqueous dispersion was changed to 5 parts by mass of the polyolefin ionomer aqueous dispersion (nonvolatile content 27%), except that the non-woven fabric was used in the same manner as in Example 6. A separator having an integrated coating film was obtained.
The film thickness of the obtained separator was 103 μm, the film-forming property was evaluated as 5, and the sheet isolation property was evaluated as 4.

[Example 9]
Magnesium hydroxide particles A and N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) having the specific surface area shown in Table 1 are mixed so as to have a mass ratio of 1: 1 and placed in a pot mill containing zirconia media balls. Then, the dispersion treatment was carried out at room temperature for 6 hours to obtain a magnesium hydroxide particle dispersion.
200 parts by mass of the obtained magnesium hydroxide particle dispersion, polysulfone resin (trade name: Ultrazone S3010, manufactured by BASF) at a concentration of 30% by mass at 80 to 100 ° C. N-methyl-2-pyrrolidone (Wako Pure Chemical Industries, Ltd.) Weigh 110 parts by mass of the polysulfone resin solution obtained by heat-dissolving it in (Yaku Kogyo Co., Ltd.), and use a rotation / revolution mixer (trade name: Awatori Rentaro ARE-500, manufactured by Shinky Co., Ltd.) at room temperature. After mixing for about 10 minutes at a rotation speed of 1000 ^{min -1} , filtration was performed to obtain a film-forming composition.
A film-forming composition is applied onto a polyethylene terephthalate (PET) film with an applicator so that the weighing value is 18.0 mg / cm ² , and a non-woven fabric made of polyolefin fibers (weighed value 6.0 mg / cm) is applied thereto. ^{2. The} non-woven fabric was completely impregnated with the film-forming composition by contacting the non-woven fabric (thickness: 160 μm). Then, the non-woven fabric impregnated with the film-forming composition is allowed to be bathed in water at room temperature for 10 minutes to solidify the coating film, and then the coating film is peeled off from the PET film together with the non-woven fabric in water to form magnesium hydroxide particles. , A water-containing film made of a polysulfone resin and a non-woven fabric was obtained. The obtained membrane was dried at 80 ° C. for 30 minutes in a dryer to obtain a separator.
The film thickness of the obtained separator was 240 μm, the film-forming property was evaluated as 5, and the sheet isolation property was evaluated as 5.

As shown in Examples 6 and 7, even in combination with the non-woven fabric, the film-forming property is good by using magnesium hydroxide particles prepared to ^{have a specific surface area of 5 m 2} / g or more and 15 m ^{2 / g or less.} Therefore, it was possible to obtain a separator capable of isolating a sheet having a sufficient area (good sheet isolation property). Furthermore, in Examples 8 and 9, it was confirmed that these effects were retained even when different organic polymers were used.

Claims (3)

A separator used in an electrochemical device that contains an aqueous electrolyte solution.
The separator is a separator for an electrochemical device, which comprises magnesium hydroxide having a specific surface area of 5 m ² / g or more and 15 m ² / g or less, and an organic polymer. The separator for an electrochemical device according to claim 1, wherein the separator further has a porous base material. An electrochemical device comprising the separator for an electrochemical device according to claim 1 or 2 and an aqueous electrolytic solution.