JP2019114502A - Electrochemical element separator - Google Patents

Abstract

To provide a method for obtaining an electrochemical element separator with no such defects that promote dendrite formation, by sufficiently preventing the occurrence of cracks during film forming process.SOLUTION: An electrochemical element separator is a separator used in an electrochemical cell, which includes: magnesium hydroxide having a ratio of the integrated intensity of a peak of the (001) plane to the integrated intensity of a peak of the (110) plane of 3.3 or more, the integrated intensities being measured by X-ray diffraction; and an organic polymer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a separator for an electrochemical device. More particularly, the present invention relates to a separator used in electrochemical devices such as batteries, capacitors, capacitors, sensors, fuel cells, and electrolysis devices.

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

Various developments and improvements have also been made for separators used in electrochemical devices, and for example, anions containing a polymer and a compound containing at least one element selected from Groups 1 to 17 of the periodic table A separator comprising a conductive material is disclosed (see, for example, Patent Document 1). Further, it is an anion conductive film comprising a conjugated diene polymer and / or a (meth) acrylic polymer and the above compound, the cross section of which is the sum of the area of the compound particles and the anion conduction of other than the compound. There is disclosed a separator comprising an anion conductive membrane having a ratio of 70/30 to 30/70 with respect to the total of the area of the component of the membrane forming material (see, for example, Patent Document 2).

Furthermore, as a non-aqueous secondary battery separator, one provided with a porous layer containing an inorganic filler is disclosed (see, for example, Patent Documents 3 and 4).

By the way, the relationship between the crystallite diameter and the X-ray diffraction peak intensity ratio of magnesium hydroxide and the flame retardancy is disclosed, and it is disclosed that such magnesium hydroxide is blended in a resin and used as a flame retardant. (See, for example, Patent Document 5).

International Publication No. 2014/119665 JP 2017-27931 A JP 2012-134024 A JP 2011-108444 A JP, 2009-114016, A

The separators described in Patent Documents 1 and 2 have excellent anion conductivity and can suppress the change in shape of the electrode active material such as shape change of the electrode active material and dendrite. On the other hand, cracks still occur in the film forming process in separators for electrochemical devices such as batteries, capacitors, capacitors, sensors, fuel cells, and electrolyzers (herein also referred to simply as electrolytic devices). There is a problem in that there is room for further devising to sufficiently prevent the occurrence of a crack which is a defect acting in the direction to promote the formation of dendrite.

The present invention was made in view of the above-mentioned present situation, and in an electrochemical element separator, a method for sufficiently preventing generation of a crack in a film forming process and obtaining a separator having no defect promoting formation of dendrite. Intended to provide.

The present inventors variously study a method for sufficiently preventing the occurrence of a crack in the separator for an electrochemical element, and pay attention to using a specific magnesium hydroxide as a material of the separator, and it is measured by X-ray diffraction ( A separator including an organic polymer and magnesium hydroxide in which the ratio of the integrated intensity of the (001) plane peak to the integrated intensity of the 110) plane peak is 3.3 or more was produced. The present inventors have found that this separator can sufficiently prevent the occurrence of cracks in the film forming process. The reason is considered to be as follows. That is, the peak intensity in the X-ray diffraction represents the degree of orientation of the crystal plane, and the intensity of the crystal plane parallel to the sample mounting surface of the measurement sample plate becomes higher. The peak integrated intensity of the (001) plane perpendicular to the (110) plane is larger than the (110) plane because the (001) plane forming the plate surface of the particle is parallel to the sample mounting surface of the sample plate. Represents the state where the ratio is high. When a magnesium hydroxide particle (powder) that can easily take such a state produces a separator (hereinafter, also referred to as a sheet because the separator has a sheet shape), the plate surface of the magnesium hydroxide particles Tends to be parallel to the sheet surface. By increasing the number of magnesium hydroxide particles whose plate surface is parallel to the sheet surface, shrinkage in the thickness direction becomes preferential in the drying process during film formation, and as a result, shrinkage in the surface direction is reduced. It is possible to form a good sheet with the occurrence of being sufficiently prevented. Also, conventionally, the amount of the inorganic compound in the separator (the part excluding the porous substrate when having the porous substrate) is large, and when the porosity is high, cracks are easily generated particularly in the film forming process. However, in such a case, when the specific magnesium hydroxide described above is used as the inorganic compound particles, a higher crack preventing effect is exhibited, and the generation of cracks can be sufficiently prevented. The inventors of the present invention have arrived at the present invention in view of the fact that the above-mentioned problems can be solved in this way.

That is, the present invention is a separator for use in an electrochemical device, wherein the separator has a ratio of integrated intensity of (001) plane peak to integrated intensity of (110) plane peak measured by X-ray diffraction is 3 It is a separator for an electrochemical element characterized by containing magnesium hydroxide which is .3 or more and an organic polymer.

The separator for an electrochemical device of the present invention is one in which the occurrence of cracks in the film forming process is sufficiently prevented.

It is an image figure which shows the relationship between the (001) plane direction of a crystallite which comprises magnesium hydroxide particle, and a (110) plane direction.

The present invention will be described in detail below.
In addition, what combined two or more of each preferable form of this invention described below is also a preferable form of this invention.

<Separator for electrochemical device>
The separator for an electrochemical element of the present invention comprises magnesium hydroxide having a ratio of the integrated intensity of the (001) plane peak to the integrated intensity of the (110) plane peak measured by X-ray diffraction is 3.3 or more, And organic polymers. In the present specification, the separator for electrochemical devices of the present invention may be simply referred to as a separator. Also, the polymers may be homopolymers or copolymers, unless explicitly limited.

(Magnesium hydroxide)
In the magnesium hydroxide, the ratio of the integrated intensity of the (001) plane peak to the integrated intensity of the (110) plane peak measured by X-ray diffraction is 3.3 or more.
The ratio is preferably 4 or more, more preferably 5 or more.
The upper limit of the ratio is not particularly limited, but is usually 20 or less.

The magnesium hydroxide preferably has a crystallite diameter in the direction perpendicular to the (110) plane measured by X-ray diffraction of 10 nm or more, and more preferably 15 nm or more.
Although the upper limit of the crystallite diameter in the direction perpendicular to the (110) plane is not particularly limited, it is usually, for example, 400 nm or less.

The magnesium hydroxide preferably has a crystallite diameter in the direction perpendicular to the (001) plane of 3 nm or more, more preferably 6 nm or more, which is measured by X-ray diffraction.
The upper limit of the crystallite diameter in the direction perpendicular to the (001) plane is not particularly limited, but is usually, for example, 300 nm or less.
The integrated intensity ratio and each crystallite diameter mentioned above are measured and calculated according to the method described in the examples.

The method for obtaining magnesium hydroxide in the specific integrated intensity ratio range / crystallite size range described above is, for example, as follows.
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 is used as a raw material, and an alkaline substance (lithium hydroxide, sodium hydroxide, calcium hydroxide, ammonia water Magnesium hydroxide is prepared by performing a hydration reaction by the addition of At this time, by adding an organic acid such as formic acid, acetic acid or propionic acid, a polybasic acid such as nitric acid or sulfuric acid, or a mixture thereof, the solubility of the formed magnesium hydroxide is adjusted or the temperature of the hydrothermal reaction is By appropriately adjusting (for example, 150 ° C. to 270 ° C.) and time (for example, 30 minutes to 10 hours), particles composed of crystallites having different crystallite diameters can be prepared. The crystal growth proceeds as the addition amount of the acid increases, and the crystallite diameter increases. In addition, as the temperature of the hydrothermal reaction is higher and as the time is longer, crystal growth proceeds and the crystallite diameter increases.
Furthermore, the hydrothermal reaction temperature range is adjusted to be lower (for example, 150 ° C. to 200 ° C.), the hydrothermal reaction time is adjusted to be shorter, or the like, so that the integrated intensity ratio is adjusted. Can be prepared.

The magnesium hydroxide is in the form of particles, and examples of the shape thereof include fine powder, powder, granules, granules, scaly, polyhedrons, rods, curved surfaces, and the like. Such particles of magnesium hydroxide (primary particles) may be single crystals consisting of the above-mentioned crystallites or may be polycrystals, and the effect of the present invention can be exhibited even if any of them. Do.
The magnesium hydroxide preferably has an average particle size of 10 μm or less when measured by the following measurement method. The average particle size is more preferably 5 μm or less, still more preferably 4 μm or less. The average particle diameter is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.1 μm or more, and particularly preferably 0.2 μm or more. .

<Method of measuring average particle diameter of magnesium hydroxide particles>
Laser Diffraction / Scattering Particle Size of Magnesium Hydroxide Particle Dispersion Liquid Mixed with Magnesium Hydroxide Particles (Powder) and 0.2% by Mass of Sodium Hexametaphosphate Aqueous Solution and Dispersed Using an Ultrasonic Cleaner Measurement is performed using a distribution measurement apparatus (trade name: LA-950, manufactured by Horiba, Ltd.), and the median diameter in the obtained volume-based particle size distribution is taken as the average particle size of the magnesium hydroxide particles.

The particles having an average particle diameter in the range as described above are, for example, a method of pulverizing the particles with a ball mill or the like, dispersing the obtained coarse particles in a dispersing agent to obtain a desired particle diameter, and drying. The coarse particles can be sieved or the like to separate the particle size, and the preparation conditions can be optimized at the stage of producing the particles to obtain particles having a desired particle size.

The mass ratio of the 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 of the separator and the ion conductivity. The proportion by mass is more preferably 40% by mass or more, still more preferably 45% by mass or more. Moreover, it is preferable that this mass ratio is 95 mass% or less. The proportion by mass is more preferably 90% by mass or less, still more preferably 85% by mass or less.

Moreover, it is preferable that the mass ratio of the said magnesium hydroxide is 60 mass% or more in 100 mass% of parts which remove the porous base material mentioned later from the separator for electrochemical elements of this invention. The proportion by mass is more preferably 65% by mass or more, still more preferably 70% by mass or more. Moreover, it is preferable that this mass ratio is 99 mass% or less. The proportion by mass is more preferably 98% by mass or less, still more preferably 97% by mass or less, and particularly preferably 95% by mass or less.
The above "part from the separator for an electrochemical device of the present invention from which the porous substrate is removed" may be rephrased as a part from the separator for an electrochemical device according to the present invention from which the polymer constituting the porous substrate is removed. . Further, when the separator for an electrochemical device of the present invention does not have a porous substrate (a polymer constituting the porous substrate), the above “part of the separator for an electrochemical device of the present invention except the porous substrate "Is a separator for an electrochemical device of the present invention.

(Organic polymer)
Various organic polymers may be used as the organic polymer, and any of thermoplastic and thermosetting polymers may be used. For example, conjugated diene polymers, (meth) acrylic polymers, fluorine-containing ethylene polymers, polysulfones Based polymers, aliphatic polyamides, aromatic polyamides, polyether ketones, polyolefin polymers, polyvinyl alcohol polymers, styrene polymers, polyester polymers, etc., among which conjugated diene polymers, (meth) acrylic polymers It is preferably at least one selected from the group consisting of fluorine-containing ethylene polymers, polysulfone polymers, aromatic polyamides, polyether ketones, polyolefin polymers, and polyvinyl alcohol polymers. The organic polymer may function as a binder polymer, or may be a polymer constituting a porous substrate described later. The binder polymer includes, for example, conjugated diene polymers, (meth) acrylic polymers, fluorine-containing ethylene polymers, polysulfone polymers, aromatic polyamides, polyether ketones, and polyolefin polymers (more preferably, carboxy modified, for example) It is preferable that it is at least 1 sort (s) selected from the group which consists of polyolefin polymer. The polymer constituting the porous substrate is selected from the group consisting of, for example, polyolefin polymers, polyvinyl alcohol polymers, fluorine-containing ethylene polymers, aliphatic polyamides, aromatic polyamides, styrenic polymers, and polyester polymers. Preferably, it is at least one of In addition, these organic polymers (especially polymers which comprise a porous base material, such as a polyolefin polymer and a polyvinyl alcohol polymer) may be fibrous. The fibrous organic polymer is suitably used to constitute a porous substrate, as described later. In addition, the organic polymer may be further crosslinked by a known crosslinking 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. As an aliphatic conjugated diene type monomer, a 1, 3- butadiene, an isoprene, 2-chloro- 1, 3- butadiene, a chloroprene etc. are mentioned, for example, Especially, a 1, 3- butadiene is preferable. The conjugated diene monomers may be used alone or in combination of two or more.

As the conjugated diene-based polymer, monomer units derived from the conjugated diene-based monomer can be obtained using one or two or more kinds, but the uniformity of the composition according to the present invention or the mechanical strength of the obtained separator can be obtained. It is preferable to further have, for example, a monomer unit derived from an aromatic vinyl monomer, from the viewpoint of increasing the elongation and appropriately adjusting the elongation and stress.

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, p-tert-butoxys Ren, 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 and stress are suitably controlled. These aromatic vinyl monomers may be used alone or in combination of two or more.

The conjugated diene-based polymer preferably has a mass ratio of a monomer unit derived from an aliphatic conjugated diene-based monomer to a monomer unit derived from an aromatic vinyl monomer, for example, 1/9 or more and 9/1 or less, 2 It is more preferable that it is / 8 or more and 8/2 or less, and still more preferably 3/7 or more and 7/3 or less.

The conjugated diene-based polymer is a carboxy-modified polymer having a carboxy group and / or a carboxylate group which is a salt thereof, from the viewpoint of increasing the bonding strength between magnesium hydroxide and the organic polymer and making the separator more excellent. Conjugated diene polymers are preferable, and for example, those further having a monomer unit derived from an unsaturated monomer having a carboxy group and / or a carboxylate group which is a salt thereof are more preferable. As unsaturated monomers having a carboxyl group which is the above-mentioned carboxy group and / or a salt thereof, unsaturated monocarboxylic acids (salts) such as (meth) acrylic acid (salts); maleic acid (salts), fumaric acid (salts) And unsaturated dicarboxylic acids (salts) such as itaconic acid (salts). These may be used alone or in combination of two or more.

The mass ratio of monomer units derived from unsaturated monomers having a carboxy group and / or a carboxylate group which is a salt thereof is 0.2% by mass from the viewpoint of making the strength of the separator more excellent in the conjugated diene-based polymer It is preferable that it is the above, It is more preferable that it is 0.3 mass% or more, It is still more preferable that it is 0.5 mass% or more. Moreover, from the viewpoint of making the ion conductivity of the separator more excellent, the mass ratio is preferably 10% by mass or less, more preferably 8% by mass or less, and 5% by mass or less More preferable.

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

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

As other unsaturated monomers, for example, sulfonic acid group-containing vinyl monomers such as acrylamidomethylpropane sulfonic acid, styrene sulfonate, etc .; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (Meth) acrylic acid n-butyl, (meth) acrylic acid isobutyl, (meth) acrylic acid t-butyl, (meth) acrylic acid pentyl, (meth) acrylic acid hexyl, (meth) acrylic acid heptyl, (meth) acrylic (Meth) acrylic acid ester monomers such as octyl acid octyl, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate and decyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid Hydroxyl group-containing vinyl monomers such as 4-hydroxybutyl; (meth) ac Nitrile group-containing vinyl monomers such as ronitrile, (meth) acrylamides, N-methylol (meth) acrylamides, N-ethylol (meth) acrylamides, dimethyl (meth) acrylamides, (meth) acrylamide-based monomers such as diethyl (meth) acrylamides; Bifunctional vinyl monomers such as divinylbenzene, ethylene glycol dimethacrylate, isopropylene glycol diacrylate, tetramethylene glycol dimethacrylate; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltritriol There may be mentioned alkoxysilane group-containing vinyl monomers such as ethoxysilane.

The proportion by mass of monomer units derived from other unsaturated monomers in 100% by mass of the conjugated diene-based polymer is preferably 30% by mass or less, more preferably 5% by mass or less, and 0.1% by mass It is more preferable that it is the following.

The above (meth) acrylic polymer may be any one having a monomer unit derived from a monomer having a (meth) acryloyl group, but as a typical one, a monomer unit derived from a (meth) acrylic acid ester monomer is mainly used (Meth) acrylic acid ester-based polymers.

The content of monomer units derived from (meth) acrylic acid ester monomers is 50% by mass or more in 100% by mass of (meth) acrylic acid ester-based polymers, based on the monomer units derived from (meth) acrylic acid ester monomers as main components Say something. The content is preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 100% by mass.
Specifically, the (meth) acrylic acid ester monomer is as described above as one of other unsaturated monomers in the carboxy-modified conjugated diene-based polymer.

The above (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 a monomer unit derived from a (meth) acrylic acid ester monomer, and other unsaturated 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 bonding strength between magnesium hydroxide and the organic polymer and making the separator more excellent. It is preferable that it is a (meth) acrylic-type polymer which has a monomer unit derived from an unsaturated monomer.

In addition, as another unsaturated monomer, the thing similar to what was mentioned above as another unsaturated monomer in carboxy modified | conjugated conjugated diene type polymer can be mentioned (However, (meth) acrylic acid ester monomer is remove | excluded.).

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

The polysulfone-based polymer is a polymer having a sulfonyl group as a repeating unit, and examples thereof include polysulfone (PSU), polyethersulfone (PESU), and polyphenylsulfone (PSSU).
The above-mentioned 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, polyphenylene isophthalamide and the like.
The polyether ketone is a polymer having an ether bond and a ketone bond, and examples thereof include polyether ketone ketone and polyether ether ketone.

The said polyolefin polymer should just have a monomer unit derived from unsaturated hydrocarbon.
Examples of the unsaturated hydrocarbon include 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, trimers and tetramers of propylene, terminal olefins such as styrene, vinyl toluene, divinylbenzene, etc. 2-butene Intramolecular olefins such as 2-octene, 2-methyl-1-hexene, 2,3-dimethyl-2-butene and the like may be mentioned, and these may be used alone or in combination of two or more.

The above 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 enhancing the bonding strength between magnesium hydroxide and the organic polymer and making the separator more excellent. It is preferable that it is a system polymer. As the carboxy-modified polyolefin polymer, for example, one having a monomer unit derived from an unsaturated monomer having a carboxy group and / or a carboxylate group which is a salt thereof, and graft modifying polyolefin by using an organic peroxide or the like And polymers obtained by introducing a polymer unit containing a monomer unit derived from an unsaturated monomer having a carboxyl group and / or a carboxylate group which is a salt thereof into the side chain of the polyolefin. Preferred types and preferred mass proportions of unsaturated monomers having a carboxy group and / or a carboxylate group which is a salt thereof are the same as those described above for the carboxy-modified conjugated diene-based polymer. For example, a carboxy-modified polyolefin polymer is a polymer having an aggregate structure (ionomer) by the action of a metal ion such as sodium ion or zinc ion, from the viewpoint of making the flexibility of the separator more excellent. Is preferred.

The above-mentioned polyolefin polymer has monomer units derived from other unsaturated monomers other than unsaturated hydrocarbon-derived monomer units, carboxy groups and / or monomers derived from unsaturated monomers having a carboxylate group which is a salt thereof. It may be done.

As other unsaturated monomers, the same as those described above in the conjugated diene-based polymer can be mentioned.
The proportion by mass of monomer units derived from other unsaturated monomers is preferably 30% by mass or less, more preferably 5% by mass or less, and still more preferably 0.1% by mass or less in 100% by mass of the polyolefin-based polymer .

The polyvinyl alcohol polymer is a polymer obtainable by saponifying polyvinyl acetate, and one having a degree of saponification of 100 mol% is represented by a 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, for example, 300 to 5,000.
The average degree of polymerization n can be calculated by the method described in JIS K6726.
The average degree of saponification is preferably 50 to 100 mol%, more preferably 80 to 100 mol%, and still more preferably 90 to 100 mol%.
The average degree of saponification can be measured by the method described in JIS K6726.
The polyvinyl alcohol-based polymer is a carboxy-modified polyvinyl alcohol further 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 with polyethylene oxide added to hydroxyl groups after saponification. It may be polyvinyl alcohol or vinylon which is further acetalized after saponification.

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

The organic polymer can be produced by copolymerizing a monomer component that forms a structural unit contained in the polymer in the presence of a radical generator and graft-modifying it as necessary.
The method for polymerizing the monomer component is not particularly limited, and examples thereof include methods such as 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 comprises a porous substrate. The above-mentioned porous substrate is constituted using the polymer which constitutes the above-mentioned porous substrate, and, among them, polyolefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, cyclic polyolefin polymer etc. Polyvinyl alcohol-based polymers such as vinylon; aliphatic polyamides; aromatic polyamides; styrene-based polymers; non-woven fabrics, woven fabrics, microporous films and the like composed of resin materials such as polyester-based polymers; Among them, polyolefin polymers and polyvinyl alcohol polymers are more preferable. The porous substrate may be subjected to a hydrophilization treatment by a conventionally known method. The porous base material is preferably, for example, a polyvinyl alcohol resin or a material subjected to a hydrophilization treatment. In these porous substrates, by the introduction of a hydroxyl group or a carboxy group on the surface, the bonding strength with the composition according to the present invention is improved, and the strength of the separator becomes more excellent.
When the separator for an electrochemical element of the present invention has a porous substrate, it may be a laminate in which the film obtained from the composition according to the present invention described above and the porous substrate are laminated, the present invention The membrane obtained from the composition according to the present invention, which is obtained by impregnating the composition according to the above into the porous base material, may be integrated with the porous base material. In the above laminate, a part of the composition according to the present invention is impregnated into a part of the porous substrate, etc., and the membrane obtained from the composition according to the present invention and the porous substrate are partially formed. The composition according to the present invention may fill part 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 ion conductivity of the separator and the elongation and stress of the separator. 10 mass% or more is more preferable, and 15 mass% or more is more preferable. The mass ratio is preferably 70% by mass or less, more preferably 60% by mass or less, and still more 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 separator for an electrochemical element of the present invention excluding the porous substrate. Is more preferably 2% by mass or more, still 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 still more preferably 30% by mass or less.
The above "part from the separator for an electrochemical device of the present invention from which the porous substrate is removed" may be rephrased as a part from the separator for an electrochemical device according to the present invention from which the polymer constituting the porous substrate is removed. . Further, when the separator for an electrochemical device of the present invention does not have a porous substrate (a polymer constituting the porous substrate), the above “part of the separator for an electrochemical device of the present invention except the porous substrate "Is a separator for an electrochemical device of the present invention.

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

When the separator for an electrochemical device of the present invention contains a water-soluble polymer, the content ratio of the water-soluble polymer is that for the electrochemical device of the present invention from the viewpoint of sufficiently dispersing magnesium hydroxide and exhibiting its function and effect. It is preferable that it is 0.1 mass% or more in 100 mass% of separators. The content ratio is preferably 3% by mass or less from the viewpoint of further suppressing the plasticization of the separator by absorbing the electrolyte solution such as water by the water-soluble polymer.

The separator for an electrochemical device of the present invention may further contain other inorganic components such as conductive carbon and conductive ceramics.
It is preferable that the content rate of the other inorganic component in the separator for electrochemical elements of this invention is 30 mass% or less in 100 mass% of separators from a viewpoint of the intensity | strength of a separator. More preferably, it is 10% by mass or less, still more 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. When the thickness is 10 μm or more, the occurrence of damage at the time of film formation can be sufficiently prevented. In addition, it is advantageous from the viewpoint of cost if it is 1 mm or less, and the ability to transmit ions is also sufficiently excellent. The average film thickness is more preferably 15 μm or more, still more preferably 20 μm or more, and particularly preferably 25 μm or more. The average film thickness is more preferably 800 μm or less, still more 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 the 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 fully satisfies the basic performance required for the separator, and can be suitably used as a separator. The porosity is more preferably 3% or more, still more preferably 6% or more, and particularly preferably 10% or more. The porosity is more preferably 80% or less, still more preferably 70% or less, and particularly preferably 60% or less.
The said porosity is calculated according to the method as described in an Example.

The separator for an electrochemical device of the present invention is used for electrochemical devices such as batteries, capacitors, capacitors, sensors, fuel cells, and electrolytic devices, but is used for an electrochemical device including a water-based electrolytic solution. It is preferable that
Since the separator for an electrochemical device of the present invention contains magnesium hydroxide particles having a highly hydrophilic surface, not only the separator surface but also the inside of the separator form a state of good affinity with the aqueous electrolyte, in particular. ing. In such a state, the permeation of the electrolyte into the separator is quickened, and more stable electrochemical characteristics are obtained in the electrochemical device (particularly battery) configured to include the water-based electrolyte having high thermal safety. Is considered to be obtained.

(Method of manufacturing separator for electrochemical device of the present invention)
The separator for an electrochemical device of the present invention is prepared by preparing a composition (herein also referred to simply as the composition according to the present invention) used to form a film to obtain a separator for an electrochemical device, and this composition is used. The product can be produced by film formation by the method described later.
First, the raw materials of the composition according to the present invention (magnesium hydroxide having a specific crystallite diameter ratio 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, etc. can be used. At the time of mixing, water, an organic solvent such as methanol, ethanol, propanol, isopropanol, butanol, hexanol, tetrahydrofuran, N-methylpyrrolidone or the like, or a mixed solvent of water and an organic solvent may be added as a medium.
After mixing, filtration, degassing and the like may be performed as necessary to obtain the composition according to the present invention.
In addition, you may manufacture a magnesium hydroxide dispersion before mixing. For example, magnesium hydroxide, and, if necessary, a dispersant for magnesium hydroxide and the like are mixed. By preparing the magnesium hydroxide dispersion before mixing, it is possible to suppress the destabilization of the organic polymer during preparation. For mixing, the devices and media described above can be used.

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 peeling substrate such as a mirror-finished metal roll, polyethylene terephthalate (PET) film, A method of drying and peeling the obtained coating film to obtain a film (casting method), a method of rolling into a film by rolling with a roll, a method of rolling into a film by rolling with a flat plate press, etc. A method, a method of forming into a film shape such as an extrusion molding method, a method of coating on an electrode sheet, drying, and forming as a film integrated with the electrode sheet can be used. These molding methods may be used alone or in combination of two or more.

The above production method preferably includes the 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 carried out by heating the film, if necessary. The heating temperature and heating time of the film may be set appropriately.

When the separator for an electrochemical device of the present invention further has a porous substrate, for example, a membrane obtained from the composition according to the present invention and the porous substrate are laminated by a conventionally known method, or The composition according to the invention is coated on a release substrate, and then the porous substrate is contacted and impregnated, and after the film is solidified, the separator for the electrochemical device of the present invention is peeled off from the release substrate. Can be manufactured.

<Electrochemical device>
The present invention is also an electrochemical device comprising the separator for an electrochemical device of the present invention.
The electrochemical element of the present invention includes, for example, batteries; capacitors such as electrolytic capacitors; capacitors such as electric double layer capacitors and lithium ion capacitors; sensors such as humidity sensors and gas sensors; fuel cells such as alkaline fuel cells; An electrolytic device such as a water electrolytic device can be mentioned.

The electrochemical device of the present invention preferably further comprises an electrolytic solution, and more preferably comprises an aqueous electrolytic solution.
The water-based electrolyte is not particularly limited as long as it is generally used as a water-based electrolyte of an electrochemical element and water is used as a main component of a raw material of the electrolyte, and an organic solvent may be contained together with water. The use of water as a main component of the electrolyte material means that the proportion by mass of water is 50% by mass or more in 100% by mass of the aqueous electrolyte 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, methyltetrahydrofuran, diethoxyethane, dimethylsulfoxide, sulfolane, acetonitrile, benzo Nitriles, ionic liquids, fluorine-containing carbonates, fluorine-containing ethers, polyethylene glycols, fluorine-containing polyethylene glycols, etc. may be mentioned, and one or more of them may be used.

Among them, the electrochemical element of the present invention is preferably an electrochemical element including an electrolytic solution using only water as an electrolytic solution source. Where the electrolyte using only water as the electrolyte raw material has higher thermal safety, more stable electrochemical characteristics can be obtained by using the separator for an electrochemical device of the present invention.

The aqueous electrolyte is preferably, for example, an alkaline electrolyte. Examples of the alkaline electrolyte include aqueous potassium hydroxide solution, aqueous sodium hydroxide solution, aqueous lithium hydroxide solution, aqueous zinc sulfate solution, aqueous zinc nitrate solution, aqueous zinc phosphate solution, aqueous zinc acetate 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 device of the present invention is a battery will be described in detail below.
The battery usually further comprises a positive electrode. As an active material of a positive electrode, what is normally used can be used as a positive electrode active material of a primary battery or a secondary battery, Although it does not restrict | limit in particular, For example, when oxygen (oxygen becomes a positive electrode active material, a positive electrode is oxygen Compounds capable of reduction of water and oxidation of water, 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; Containing compound; silver containing compound; becoming an 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; Silver; lithium-containing compounds such as lithium cobaltate; iron-containing compounds; metallic zinc and zinc oxide Examples include zinc species such as lead.
In addition, 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 above-mentioned battery is usually constituted further including a negative electrode. As an active material of a negative electrode, what is normally used as a negative electrode active material of a battery, such as carbon, lithium, sodium, magnesium, zinc, nickel, tin, cadmium, a hydrogen storage alloy, a silicon containing material, can be used. For example, the present invention can be suitably applied to a battery using an active material which may generate dendrites as a negative electrode active material such as zinc, lithium, nickel, magnesium, cadmium, etc. . Among them, it is preferable that the negative electrode active material contains a zinc compound.

An electrode such as a positive electrode or a negative electrode constituting the battery can be manufactured by forming an active material layer on a current collector.
As current collectors constituting the electrode, (electrolytic) copper foil, copper mesh (expanded metal), foamed copper, punched copper, copper alloy such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass Nickel foil, corrosion resistant nickel, nickel mesh (expanded metal), punching nickel, zinc metal, zinc corrosion resistant metal, zinc foil, zinc mesh (expanded metal), (punching) steel plate, non-woven fabric imparted with conductivity; Ni, Zn, Sn, Pb, Hg, Bi, In, Tl, added brass (electrolytic) copper foil, copper mesh (expanded metal), foam 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) ), Punching nickel, metal zinc, corrosion resistant metal zinc, zinc foil, zinc mesh (expanded metal), (punching) steel plate, non-woven fabric; plated with Ni, Zn, Sn, Pb, Hg, Bi, In, Tl, brass, etc. (Electrolytic) copper foil copper mesh (expanded metal), foamed copper, punched copper, copper alloy such as brass, brass foil, brass mesh (expanded metal), foamed brass, punched brass, nickel foil, corrosion resistant nickel, nickel mesh (Expanded metal), punching nickel, zinc metal, zinc corrosion resistant metal, zinc foil, zinc mesh (expanded metal), (punching) steel plate, non-woven fabric; silver; alkaline (storage) battery or air zinc battery as current collector or container Materials used may, for example, be mentioned.

The form of the battery is usually a secondary battery (storage battery) that can be charged and discharged. In addition, the battery of the present invention utilizes mechanical charge (mechanical replacement of zinc negative electrode) in addition to general secondary batteries; battery using third electrode (electrode suitable for charge as positive electrode, It may be in any form such as one using an electrode suitable for discharge.

(Fuel cell or electrolyzer)
The case where the electrochemical device 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 or an alkaline water electrolysis apparatus. Examples of the alkaline fuel cell and the alkaline water electrolysis apparatus include an anode, a cathode, and an electrochemical element separator of the present invention disposed between the anode and the cathode. More specifically, the alkaline fuel cell and the alkaline water electrolysis apparatus have an anode chamber in which an anode is present and a cathode chamber in which a cathode is present, which are separated by the separator for an electrochemical element of the present invention.
Examples of the anode and the cathode include known electrodes including a conductive substrate containing nickel or a nickel alloy.

[Power generation method of fuel cell]
The method of power generation performed using the alkaline fuel cell including the separator for an electrochemical element of the present invention is not particularly limited, and can be performed by a known method. For example, an alkaline fuel cell including the above-mentioned separator for an electrochemical device 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 the anode and the cathode in the electrolytic solution. You can generate electricity by doing this.

[Electrolysis method of water electrolysis apparatus]
The method of electrolysis of water performed using the alkaline type water electrolysis apparatus containing the separator for electrochemical elements of this invention is not specifically limited, It can carry out by a well-known method. For example, it can carry out by filling electrolyte solution in the alkaline type water electrolysis apparatus containing the separator for electrochemical elements of this invention mentioned above, and applying an electric current in electrolyte solution.

EXAMPLES The present invention will be described in more detail by way of the following examples, but the present invention is not limited to these examples. In addition, unless there is particular notice, "part" shall mean "weight part" and "%" shall mean "mass%."

<Average particle diameter of magnesium hydroxide particles>
The average particle size of the magnesium hydroxide particles was measured by the above-described measurement method.

<Powder X-ray diffraction measurement of magnesium hydroxide particles, and calculation of ratio of integrated intensity of each crystal plane peak to integrated intensity of crystallite diameter and peak of (110) plane>
The measurement was performed on magnesium hydroxide particles (powder) using an X-ray diffractometer (trade name: SmartLab, manufactured by Rigaku Corporation) under the following conditions.
(Measurement condition)
X-ray tube Cu
X-ray output 45kV, 200mA
Scan speed 5 ° / min
Scanning range 5 to 90 °
From the peak of each crystal plane of magnesium hydroxide thus obtained, the crystallite diameter in the direction perpendicular to each crystal plane was calculated by the following method of calculating the crystallite diameter.

(Calculation of crystallite diameter)
The crystallite diameter was calculated by the Scherrer equation (the following equation).
(Crystallite diameter) = Kλ / (β cos θ)
K is a Scherrer constant, which is 0.94.
λ is the wavelength of the X-ray tube used.
β is a value obtained from β = b−B, b is a full width at half maximum of a crystal grown completely and B is a half width obtained by actual measurement.
θ is the value of θ at the diffraction angle 2θ.

(Calculation of ratio of integrated intensity of each crystal plane peak to integrated intensity of (110) plane peak)
From the peak area of each crystal plane, the ratio of the integral intensity of each crystal plane peak to the integral intensity of the (110) plane peak was determined.

<Film thickness>
The thickness of the obtained separator was measured using a Digimatic micrometer (manufactured by Mitutoyo). Ten arbitrary points were measured, and the average value was made into the film thickness.

<Void ratio>
The porosity was calculated from the following formula from the measured density value of the separator measured by the method shown below and the calculated density value calculated from the composition ratio using the density value of each composition component.
(Porosity) (%) = [1- (measured density value) / (calculated density value)] × 100
The measured density value was calculated by measuring the mass and the volume and dividing the mass by the volume for a test piece cut out from an arbitrary place of the obtained separator. The volume was calculated by measuring the length in the vertical direction and the length in the horizontal direction of the test piece using a caliper and measuring the film thickness based on the above-mentioned film thickness measurement method. Moreover, the mass of the test piece was measured using the precision balance with a four-digit decimal point about the test piece which measured the volume.

<Film forming property>
The film forming property was evaluated according to the following criteria based on the 80 mm × 80 mm area of the obtained separator, based on the presence or absence of cracks, the amount of cracks, and the size of the generated cracks.
5: No cracks 4: One fine crack is generated 3: Two to five fine cracks are generated 2: Partially, six to ten fine cracks or one or two large cracks are generated 1 : Cracks occur almost all over the surface Table 1 shows the crystallite diameter in the direction perpendicular to each crystal plane of magnesium hydroxide and the integrated intensity of the (110) plane peak calculated from powder X-ray diffraction of magnesium hydroxide particles The ratio of the integrated intensity of each crystal plane peak to.

Example 1
100 parts by mass of magnesium hydroxide particles A (average particle size: 0.5 μm, density: 2.36 g / cm ³ ) having the ratio of the integrated intensity of peaks shown in Table 1 and the crystallite diameter, polyacrylate aqueous solution ( After measuring 3 parts by mass of non-volatile content 40%, density of polymer component: 1.20 g / cm ³ and 42 parts by mass of ion-exchanged water, dispersion treatment is performed using a sand mill for 1 hour, and filtration is performed to obtain magnesium hydroxide particles. An aqueous dispersion was obtained.
Measure 50 parts by mass of the obtained aqueous solution of magnesium hydroxide particles and 21 parts by mass of carboxy-modified styrene-butadiene polymer aqueous dispersion (nonvolatile content: 48%, density of polymer component: 1.00 g / cm ³ ), After mixing, filtration and vacuum degassing were performed to obtain a film forming composition.
The obtained film forming composition is coated on a silicone-treated side of a polyethylene terephthalate (PET) film (peelable film) on one side of which is silicone-treated with a comma coater, and the obtained coating is obtained. It peeled from the peeling film and obtained the separator.
The film thickness of the obtained separator was 80 μm, the porosity was 20% (the measured density value was 1.44 g / cm ³ , the calculated density value was 1.80 g / cm ³ ), and the evaluation of the film forming property was 5.

Example 2
In Example 1, magnesium hydroxide particles B (average particle size: 3.3 μm, density: 2.36 g / cm ³⁾ having the ratio of the integrated intensity of peaks shown in Table 1 to magnesium hydroxide particles A and the crystallite diameter The separator was obtained in the same manner as in Example 1 except that 3 parts by mass of the aqueous solution of polyacrylate was changed to 6 parts by mass.
The film thickness of the obtained separator was 92 μm, the porosity was 15% (the measured density value was 1.53 g / cm ³ , the calculated density value was 1.79 g / cm ³ ), and the film forming property was evaluated as 3.

Comparative Example 1
In Example 1, magnesium hydroxide particles C (average particle size: 0.4 μm, density: 2.36 g / cm ³⁾ having the ratio of the integrated intensity of peaks shown in Table 1 to magnesium hydroxide particles A and the crystallite diameter A separator was obtained in the same manner as in Example 1 except that it was changed to).
The film thickness of the obtained separator is 90 μm, the porosity is 8.9% (measured density value is 1.63 g / cm ³ , calculated density value is 1.79 g / cm ³ ), and the film forming property is evaluated as 1. The

From the comparison of Examples 1 and 2 and Comparative Example 1, in the separator using magnesium hydroxide particles in which the ratio of the integrated intensity of the (001) plane peak to the integrated intensity of the (110) plane peak is 3.3 or more. Although the porosity was high, it was possible to obtain a separator having good film-forming properties.

Example 4
100 parts by mass of magnesium hydroxide particles A (average particle size: 0.5 μm, density: 2.36 g / cm ³ ) having the ratio of the integrated intensity of peaks shown in Table 1 and the crystallite diameter, polyacrylate aqueous solution ( After measuring 3 parts by mass of non-volatile content 40%, density of polymer component: 1.00 g / cm ³ ) and 42 parts by mass of ion-exchanged water, it is dispersed for 1 hour using a sand mill and then filtered to obtain magnesium hydroxide particles. An aqueous dispersion was obtained.
Measure 50 parts by mass of the obtained aqueous solution of magnesium hydroxide particles and 21 parts by mass of carboxy-modified styrene-butadiene polymer aqueous dispersion (nonvolatile content: 48%, density of polymer component: 1.00 g / cm ³ ), After mixing, filtration and vacuum degassing were performed to obtain a film forming composition.
The obtained film forming composition was dried on a non-woven fabric (weight: 2.4 mg / cm ² , thickness: 88 μm, true density of fiber material: 1.2 g / cm ³ ) composed of polyvinyl alcohol-based fibers. The composition for film formation was coated with a comma coater so as to have a weight value of 10.0 mg / cm ^2, and dried to obtain a separator.
The film thickness of the obtained separator was 105 μm, the porosity was 26% (measured density value: 1.22 g / cm ³ , calculated density value: 1.64 g / cm ³ ), and the evaluation of the film forming property was 5.

[Example 5]
In Example 4, the non-woven fabric made of polyvinyl alcohol fiber is dried to a non-woven fabric made of polyolefin fiber (weight value: 4.0 mg / cm ² , thickness: 90 μm, true density of fiber material: 0.9 g / cm ³ ) to 6.0 mg / cm ² weighed value of film-forming composition from 10.0 mg / cm ² when, except for changing each in the same manner as in example 4, to obtain a separator.
The film thickness of the obtained separator was 103 μm, the porosity was 26% (the measured density value was 0.95 g / cm ³ , the calculated density value was 1.28 g / cm ³ ), and the evaluation of film formability was 5.

[Example 6]
In Example 4, 21 parts by mass of a carboxy-modified styrene-butadiene polymer aqueous dispersion is dried to 5 parts by mass of a polyolefin ionomer aqueous dispersion (nonvolatile matter 27%, true density of polymer component: 0.9 g / cm ³ ) A separator was obtained in the same manner as in Example 4, except that the weight value of the film forming composition was changed from 10.0 mg / cm ² to 5.5 mg / cm ² .
The film thickness of the obtained separator was 93 μm, the porosity was 34% (the actual density value was 1.19 g / cm ³ , the calculated density value was 1.79 g / cm ³ ), and the evaluation of the film formability was 4.

[Example 7]
Magnesium hydroxide particles A (average particle size 0.5 μm) and N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) having a mass ratio 1 of the ratio of the integrated intensity of peaks shown in Table 1 and the crystallite diameter The mixture was subjected to dispersion treatment at room temperature for 6 hours in a pot mill containing zirconia media balls 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, density of polysulfone: 1.24 g / cm ³ ) at a concentration of 30% by mass at 80 to 100 ° C. 110 parts by mass of a polysulfone resin solution obtained by heat-dissolving in N-methyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) is weighed out, and a rotation and revolution mixer (trade name: Awatori Neritaro ARE-500, After mixing for about 10 minutes at a rotational speed of 1000 min ⁻¹ at room temperature using Shinky Co., Ltd.), filtration was performed to obtain a composition for film formation.
The composition for film formation is coated on a polyethylene terephthalate (PET) film so that the weight ratio of the composition for film formation after drying with an applicator is 18.0 mg / cm ² , and the film is composed of polyolefin fibers thereon. By bringing a non-woven fabric (weight value: 6.0 mg / cm ² , thickness: 160 μm, true density of fiber material: 0.9 g / cm ³ ) into contact, the non-woven fabric was completely impregnated with the film forming composition. Thereafter, the non-woven fabric impregnated with the film forming composition is subjected to a water bath at room temperature for 10 minutes to coagulate the coating film, and then the non-woven fabric is peeled off from the PET film in water to form magnesium hydroxide particles. A water-containing membrane comprising 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 porosity was 50% (the actual density value was 0.75 g / cm ³ , the calculated density value was 1.50 g / cm ³ ), and the evaluation of film formability was 5.

As shown in Examples 4 and 5, magnesium hydroxide particles in which the ratio of the integrated intensity of the (001) plane peak to the integrated intensity of the (110) plane peak is 3.3 or more even in combination with the non-woven fabric By using the above, it was possible to obtain a separator having a good film-forming property while having a high porosity. Furthermore, in Examples 6 and 7, it was confirmed that these effects were maintained even when different organic polymers were used.

Claims (3)

A separator used in an electrochemical device,
The separator contains magnesium hydroxide and an organic polymer in which the ratio of the integrated intensity of the (001) plane peak to the integrated intensity of the (110) plane peak measured by X-ray diffraction is 3.3 or more. A separator for an electrochemical device characterized by The separator for an electrochemical device according to claim 1, wherein the separator further has a porous substrate. An electrochemical device comprising the separator for an electrochemical device according to claim 1.

Images