JP2015170393A - Separator for power storage device and manufacturing method therefor, and power storage device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for power storage device using an epoxy resin composition, as a separator capable of contributing to enhancement of the performance of a power storage device.SOLUTION: A method of manufacturing a separator for power storage device including an epoxy resin porous membrane includes a porosification step for porosifying so as to obtain an epoxy resin porous membrane by removing porogen from an epoxy resin sheet, containing a hardened epoxy resin composition and porogen, by using a solvent, and a processing step for bringing a process liquid into contact with the epoxy resin porous membrane or epoxy resin sheet. The processing step includes a processing step (b1) using a solution, containing an inorganic and/or a polyvalent organic acid, as the process liquid, and a processing step (b2) using a solution, containing a carboxylic acid anhydride, as the process liquid, following to the processing step (b1).

Description

  The present invention relates to an electricity storage device separator, a method for producing the same, and an electricity storage device using the separator.

  Storage devices such as lithium ion secondary batteries, lithium ion capacitors, electric double layer capacitors, and electrolytic capacitors are used in various fields. Various membranes have been used and studied as separators used in these electricity storage devices. For example, a polyolefin porous membrane is used as a separator for nonaqueous electrolyte electricity storage devices (for example, Patent Document 1). In addition, as a separator for an aqueous electrolyte power storage device, a fiber sheet made of inorganic fibers (for example, Patent Document 2) and a porous film using a polyolefin resin (for example, Patent Document 3) are used. Electrolytic paper is generally used as a separator for electrolytic capacitors, but the use of a cellulose film has also been studied (Patent Document 4).

JP 2001-192487 A JP 2005-327935 A JP-A-2005-109244 International Publication No. 2013/069146

  Power storage devices are required to improve performance, and these separators are also required to contribute to improving the performance of power storage devices.

  Therefore, an object of the present invention is to provide a separator for an electricity storage device using an epoxy resin composition that can contribute to the improvement of the performance of the electricity storage device.

That is, the present invention
A method for producing a separator for an electricity storage device provided with an epoxy resin porous membrane,
In order to obtain an epoxy resin porous film, a porosification step of removing the porogen from the epoxy resin sheet containing a cured product of the epoxy resin composition and the porogen and removing the porogen to make it porous,
A treatment step of bringing a treatment liquid into contact with the epoxy resin porous membrane or the epoxy resin sheet;
Comprising
The processing step includes
(A) a step of using a solution containing an inorganic acid and / or a polyvalent organic acid and a carboxylic acid anhydride as a treatment liquid;
(B) A treatment step (b1) using a solution containing an inorganic acid and / or a polyvalent organic acid as a treatment solution, and a treatment step using a solution containing a carboxylic acid anhydride as the treatment solution after the treatment step (b1). (B2) comprising,
(C) A treatment step (c1) using a solution containing a carboxylic acid anhydride as a treatment solution, and a treatment step using a solution containing an inorganic acid and / or a polyvalent organic acid as the treatment solution after the treatment step (c1). A step comprising (c2),
Any one of
The polyvalent organic acid has a plurality of carboxyl groups,
A method for producing a separator for an electricity storage device is provided.

Furthermore, the present invention provides
An electrical storage device separator obtained by the method for manufacturing an electrical storage device separator of the present invention is provided.

From another aspect, the present invention provides:
Two types of electrodes;
The separator of the present invention disposed between the electrodes;
An electricity storage device comprising:

  ADVANTAGE OF THE INVENTION According to this invention, the separator for electrical storage devices using the epoxy resin composition which can contribute to the improvement of the performance of an electrical storage device, and its manufacturing method are obtained. In addition, an electricity storage device utilizing the excellent characteristics of the separator can be obtained.

1 is a schematic cross-sectional view of a nonaqueous electrolyte electricity storage device according to an embodiment of the present invention. The figure which shows an example of the change of the infrared absorption spectrum of the epoxy resin porous film which implemented the process by carboxylic acid anhydride (acetic anhydride) after the process by an inorganic acid (sulfuric acid)

  The following is a description illustrating embodiments of the present invention, and is not intended to limit the present invention to the following embodiments. Moreover, below, normal temperature means the temperature range of 5 to 35 degreeC.

  Examples of the electricity storage device include non-aqueous electrolyte electricity storage devices such as lithium ion secondary batteries and lithium ion capacitors, water based electrolyte electricity storage devices such as electric double layer capacitors, and electrolytic capacitors such as aluminum electrolytic capacitors. Hereinafter, a nonaqueous electrolyte electricity storage device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the nonaqueous electrolyte electricity storage device 100 according to this embodiment includes two types of electrodes, that is, a cathode 2, an anode 3, a separator 4, and a case 5. The separator 4 is disposed between the cathode 2 and the anode 3. The cathode 2, the anode 3 and the separator 4 are integrally wound to constitute an electrode group 10 as a power generation element. The electrode group 10 is accommodated in a case 5 having a bottom. The electricity storage device 100 is typically a lithium ion secondary battery.

  In the present embodiment, the case 5 has a cylindrical shape. That is, the electricity storage device 100 has a cylindrical shape. However, the shape of the electricity storage device 100 is not particularly limited. The electricity storage device 100 may have, for example, a flat square shape. Moreover, the electrode group 10 does not require a winding structure. A plate-like electrode group may be formed by simply laminating the cathode 2, the separator 4 and the anode 3. The case 5 is made of a metal such as stainless steel or aluminum. Furthermore, the electrode group 10 may be put in a case made of a flexible material. The flexible material is composed of, for example, an aluminum foil and a resin film bonded to both surfaces of the aluminum foil.

  The power storage device 100 further includes a cathode lead 2a, an anode lead 3a, a lid body 6, a packing 9, and two insulating plates 8. The lid 6 is fixed to the opening of the case 5 via the packing 9. The two insulating plates 8 are respectively disposed on the upper and lower portions of the electrode group 10. The cathode lead 2 a has one end electrically connected to the cathode 2 and the other end electrically connected to the lid body 6. The anode lead 3 a has one end electrically connected to the anode 3 and the other end electrically connected to the bottom of the case 5. The electricity storage device 100 is filled with a nonaqueous electrolyte (typically a nonaqueous electrolyte) having ion conductivity. The nonaqueous electrolyte is impregnated in the electrode group 10. As a result, ions (typically lithium ions) can move between the cathode 2 and the anode 3 through the separator 4.

  The cathode 2 can be composed of, for example, a cathode active material that can occlude and release lithium ions, a binder, and a current collector. For example, the cathode 2 can be produced by mixing a cathode active material with a solution containing a binder to prepare a mixture, and applying and drying the mixture on a cathode current collector.

As a cathode active material, the well-known material used as a cathode active material of a lithium ion secondary battery can be used, for example. Specifically, lithium-containing transition metal oxides, lithium-containing transition metal phosphates, chalcogen compounds, and the like can be used as the cathode active material. Examples of the lithium-containing transition metal oxide include LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , and compounds in which a part of these transition metals is substituted with another metal. Examples of the lithium-containing transition metal phosphorous oxide include compounds in which a part of the transition metal (Fe) of LiFePO ₄ and LiFePO ₄ is substituted with another metal. Examples of the chalcogen compound include titanium disulfide and molybdenum disulfide.

  As the binder, a known resin can be used. For example, fluorine resins such as polyvinylidene fluoride (PVDF), hexafluoropropylene, polytetrafluoroethylene, hydrocarbon resins such as styrene butadiene rubber and ethylene propylene terpolymer, and mixtures thereof can be used as the binder. A conductive powder such as carbon black may be contained in the cathode 2 as a conductive aid.

  As the cathode current collector, a metal material excellent in oxidation resistance, for example, aluminum processed into a foil shape or a mesh shape is preferably used.

  The anode 3 can be composed of, for example, an anode active material that can occlude and release lithium ions, a binder, and a current collector. The anode 3 can also be produced by the same method as the cathode 2. The same binder as that used for the cathode 2 can be used for the anode 3.

As the anode active material, for example, a known material used as an anode active material of a lithium ion secondary battery can be used. Specifically, a carbon-based active material, an alloy-based active material capable of forming an alloy with lithium, a lithium-titanium composite oxide (for example, Li ₄ Ti ₅ O ₁₂ ), or the like can be used as the anode active material. Examples of the carbon-based active material include calcined bodies such as coke, pitch, phenol resin, polyimide, and cellulose, artificial graphite, and natural graphite. Examples of the alloy active material include aluminum, tin, tin compounds, silicon, and silicon compounds.

  As the anode current collector, for example, a metal material excellent in reduction stability, for example, copper or copper alloy processed into a foil shape or a mesh shape is preferably used. When a high potential anode active material such as lithium titanium composite oxide is used, aluminum processed into a foil shape or mesh shape can also be used as the anode current collector.

The non-aqueous electrolyte typically includes a non-aqueous solvent and an electrolyte. Specifically, for example, an electrolytic solution in which a lithium salt (electrolyte) is dissolved in a nonaqueous solvent can be suitably used. A gel electrolyte containing a non-aqueous electrolyte, a solid electrolyte obtained by dissolving and decomposing a lithium salt in a polymer such as polyethylene oxide, and the like can also be used as the non-aqueous electrolyte. Examples of the lithium salt include lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium trifluorosulfonate (LiCF ₃ SO ₃ ), and the like. It is done. Examples of the non-aqueous solvent include propylene carbonate (PC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane (DME), γ-butyrolactone (γ-BL), and mixtures thereof. It is done.

  Next, the separator 4 will be described in detail.

  In the present embodiment, the separator 4 includes an epoxy resin porous film having a three-dimensional network skeleton and pores. Adjacent holes may be in communication with each other so that ions can move between the front and back surfaces of the separator 4, that is, ions can move between the cathode 2 and the anode 3.

  The porous epoxy resin membrane provided in the separator 4 is subjected to a treatment using an inorganic acid and / or a polyvalent organic acid as a treatment agent and a treatment using a carboxylic acid anhydride as a treatment agent. These treatments are carried out by bringing a solution containing the treatment agent (hereinafter sometimes referred to as “treatment liquid”) into contact with the porous epoxy resin membrane or the epoxy resin sheet before being made porous. The polyvalent organic acid means an organic acid having two or more acidic groups, but has a plurality of carboxyl groups in the present embodiment.

  Separator using a porous epoxy resin membrane that has been treated with an inorganic acid and / or a polyvalent organic acid as a treatment agent and a treatment with a carboxylic acid anhydride as a treatment agent improves the characteristics of the nonaqueous electrolyte electricity storage device. Contribute to. The reason is considered as follows.

  In a treatment using an inorganic acid as a treating agent (hereinafter sometimes referred to as “inorganic acid treatment”), when the inorganic acid and the epoxy resin composition come into contact with each other, the amino group contained in the epoxy resin composition has a positive charge. Tinged. At this time, an amino group having a positive charge is present around the anion contained in the inorganic acid due to electrical attraction. Since there are a plurality of amino groups around the relatively large anion of the inorganic acid, the polymer chain contained in the porous epoxy resin membrane has a structure that is cross-linked through the anion.

  By treatment with a polyvalent organic acid as a treating agent (hereinafter sometimes referred to as “polyvalent organic acid treatment”), the electric groups that interact with the functional groups can cause the amino groups contained in the epoxy resin to interact with each other. It is considered that the carboxyl group of the polyvalent organic acid is attracted around. Since the polyvalent organic acid has a plurality of carboxyl groups, the epoxy resin porous membrane of this embodiment is considered to have a cross-linked structure in which amino groups are linked to each other through the polyvalent organic acid.

  That is, when at least one treatment selected from the group consisting of an inorganic acid treatment and a polyvalent organic acid treatment is performed, the porous epoxy resin membrane has a crosslinked structure.

  In the nonaqueous electrolyte electricity storage device, the anode and the cathode repeat expansion and contraction due to charging and discharging. Therefore, the separator placed between the electrodes repeatedly receives pressure and friction from the electrodes, and the holes are likely to be closed or reduced. However, the epoxy resin porous membrane having a crosslinked structure via an anion of inorganic acid or a polyvalent organic acid has improved shape stability like the epoxy resin porous membrane having an increased crosslinking density. The resistance to the received load is improved. As a result, it becomes difficult for the separator to close or shrink. Therefore, the separator using the epoxy resin porous membrane that has been subjected to the inorganic acid treatment and / or the polyvalent organic acid treatment contributes to the improvement of the characteristics of the nonaqueous electrolyte electricity storage device.

  On the other hand, when a carboxylic acid anhydride as a treatment agent is brought into contact with an epoxy resin porous film or an epoxy resin sheet before being made porous, an epoxy resin constituting a hydroxyl group contained in the epoxy resin porous film or an epoxy resin sheet The hydroxyl group contained in the cured product of the composition reacts with the carboxylic acid anhydride to form a carboxylic acid ester bond (hereinafter, this treatment may be referred to as “esterification treatment”). Even if the esterification treatment is performed on the epoxy resin sheet before being made porous, the produced carboxylate bond remains in the film obtained after the porosity (epoxy resin porous film).

  The amount of hydroxyl groups contained in the epoxy resin porous membrane is reduced by the esterification treatment. The hydroxyl group that reacts with the carboxylic acid anhydride is contained in the porous epoxy resin membrane in a state where it can participate in the reaction. Hereinafter, a functional group such as a hydroxyl group that can participate in the reaction may be referred to as an “active hydroxyl group” or the like. In this sense, for example, a hydroxyl group that is buried in the resin and cannot contact the reactive species is inactive.

  When an amine-based curing agent is used, when the curing reaction proceeds sufficiently, the curing agent is incorporated into the molecular chain of the epoxy resin as a tertiary amine. However, if the curing reaction does not proceed sufficiently, the amine curing agent typically remains in the epoxy resin porous membrane as a secondary amine. Similar to the active hydroxyl group, this secondary amine can also form an active reaction site in the porous epoxy resin membrane. However, when the treatment with carboxylic acid anhydride is carried out as described above, the secondary amine (—NH—) reacts with the carboxylic acid anhydride to form a tertiary amine (—NM—; where M is − C (= O) R) and a carboxylic acid amide bond is formed. The carboxylic acid amide bond is represented by the general formula: N—C (═O) —R. The treatment with carboxylic acid anhydride is basically for reducing the amount of active hydroxyl groups, but the epoxy resin is insufficient in curing reaction of epoxy resin and has a large amount of secondary amine. The membrane can be used to reduce the amount of secondary amine (active secondary amine) that can participate in the reaction.

  Therefore, the epoxy resin porous membrane subjected to the esterification treatment reduces the amount of active functional groups such as active hydroxyl groups, and reduces the active reaction points in the epoxy resin porous membrane. Accordingly, the epoxy resin porous membrane that has undergone esterification has chemical stability and long-term stability in the electrolytic solution, and is therefore suitable as a separator for non-aqueous electrolyte electricity storage devices.

  Even if all of the curing agent is changed to a tertiary amine, the hydroxyl group generated by the ring opening of the epoxy group can remain in the porous epoxy resin membrane. Therefore, the treatment with carboxylic acid anhydride usually generates at least a carboxylic acid ester bond, and the epoxy resin porous membrane in which the active secondary amine remains generates a carboxylic acid amide bond together with the carboxylic acid ester bond. It becomes.

  As the inorganic acid, preferably, at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hexafluorophosphoric acid and tetrafluoroboric acid can be used.

  As the polyvalent organic acid, an organic acid having two or more carboxyl groups is used. For example, oxalic acid having 2 carboxyl groups, malonic acid, succinic acid, glutaric acid, fumaric acid, maleic acid, phthalic acid, citric acid having 3 carboxyl groups, isocitric acid, trimellitic acid, 1 having 4 carboxyl groups , 2,3,4-butanetetracarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid, and polyvalent organic acids such as 1,2,4,5-benzenetetracarboxylic acid. From the viewpoint of the stability of the crosslinked structure in which an amino group is linked via a polyvalent organic acid, it is preferable to use an organic acid having 3 or more carboxyl groups, and more preferable to use an organic acid having 3 to 4 carboxyl groups. preferable. From the viewpoint of availability and ease of handling, it is preferable to use at least one selected from the group consisting of citric acid and isocitric acid.

  As the carboxylic acid anhydride, preferably at least one selected from the group consisting of acetic anhydride, phthalic anhydride, maleic anhydride, succinic anhydride, and propionic anhydride can be used, more preferably acetic anhydride. .

  The epoxy resin porous membrane after the treatment step includes an inorganic acid and / or a polyvalent organic acid and a structure derived from a carboxylic anhydride. The amount of inorganic acid and / or polyvalent organic acid contained in the epoxy resin porous membrane that has undergone the treatment step is, for example, 1 to 30% by weight with respect to the weight of the epoxy resin porous membrane, and 3 to 20% by weight. Preferably there is. The amount of carboxylic anhydride added is, for example, 0.1 to 15% by weight, preferably 0.5 to 10% by weight, based on the weight of the epoxy resin porous membrane. These concentrations can be determined using, for example, an IR spectrum as described later.

  For example, the separator 4 has a thickness in the range of 5 to 50 μm. If the separator 4 is too thick, it becomes difficult to move ions between the cathode 2 and the anode 3. Although it is not impossible to manufacture the separator 4 having a thickness of less than 5 μm, in order to ensure the reliability of the power storage device 100, a thickness of 5 μm or more, particularly 10 μm or more is preferable.

  The separator 4 may have a porosity in the range of 20 to 80%, for example. Moreover, you may have an average hole diameter of the range of 0.02-1 micrometer, especially 0.2-0.4 micrometer. When the porosity and average pore diameter are adjusted to such ranges, the separator 4 can sufficiently exhibit the required functions.

  The average pore diameter can be obtained by observing the cross section of the separator 4 with a scanning electron microscope, in addition to the mercury intrusion method. Specifically, image processing is performed for each of the pores existing in a range from a surface width of 60 μm to a predetermined depth from the surface (for example, 1/5 to 1/100 of the thickness of the separator 4). Thus, the pore diameter can be obtained, and the average value thereof can be obtained as the average pore diameter. Image processing can be performed using, for example, free software “Image J” or “Photoshop” manufactured by Adobe.

The separator 4 may have an air permeability (Gurley value) in the range of, for example, 1 to 1000 seconds / 100 cm ³ , particularly 10 to 1000 seconds / 100 cm ³ . Since the separator 4 has air permeability in such a range, ions can easily move between the cathode 2 and the anode 3. The air permeability can be measured according to a method defined in Japanese Industrial Standard (JIS) P8117.

  The epoxy resin porous membrane can be produced, for example, by any of the following methods (A), (B), and (C). The methods (A) and (B) are common in that the curing step is performed after the epoxy resin composition is formed into a sheet. The method (C) is characterized in that an epoxy resin block-shaped cured body is produced and the cured body is formed into a sheet shape.

Method (A)
An epoxy resin composition containing an epoxy resin, a curing agent and a porogen is applied onto a substrate so that a sheet-like molded body of the epoxy resin composition is obtained. Thereafter, the sheet-like molded body of the epoxy resin composition is heated to three-dimensionally crosslink the epoxy resin. At that time, a co-continuous structure is formed by phase separation of the crosslinked epoxy resin and the porogen. Thereafter, the porogen is removed from the obtained epoxy resin sheet by washing and dried to obtain an epoxy resin porous film having pores communicating with the three-dimensional network skeleton. The kind of board | substrate is not specifically limited, A plastic substrate, a glass substrate, a metal plate, etc. can be used as a board | substrate.

Method (B)
An epoxy resin composition containing an epoxy resin, a curing agent and a porogen is applied on the substrate. Thereafter, another substrate is placed on the applied epoxy resin composition to produce a sandwich structure. Note that spacers (for example, double-sided tape) may be provided at the four corners of the substrate in order to ensure a certain distance between the substrates. Next, the sandwich structure is heated to cross-link the epoxy resin three-dimensionally. At that time, a co-continuous structure is formed by phase separation of the crosslinked epoxy resin and the porogen. Thereafter, the obtained epoxy resin sheet is taken out, and the porogen is removed by washing, followed by drying, whereby an epoxy resin porous film having pores communicating with the three-dimensional network skeleton is obtained. The kind of board | substrate is not restrict | limited in particular, A plastic substrate, a glass substrate, a metal plate etc. can be used as a board | substrate. In particular, a glass substrate can be suitably used.

Method (C)
An epoxy resin composition containing an epoxy resin, a curing agent and a porogen is filled into a container having a predetermined shape. Thereafter, a cured product of the cylindrical or columnar epoxy resin composition is produced by three-dimensionally crosslinking the epoxy resin. At that time, a co-continuous structure is formed by phase separation of the crosslinked epoxy resin and the porogen. Then, while rotating the hardening body of an epoxy resin composition centering on a cylinder axis | shaft or a cylinder axis | shaft, the surface layer part of a hardening body is cut to predetermined thickness, and a long-shaped epoxy resin sheet is produced. Then, the porogen contained in the epoxy resin sheet is removed by washing and dried to obtain an epoxy resin porous film having pores communicating with the three-dimensional network skeleton.

  Hereinafter, the method for producing the porous epoxy resin membrane will be described in more detail while taking the method (C) as an example. In addition, the process of preparing an epoxy resin composition, the process of hardening an epoxy resin, the process of removing a porogen, etc. are common to each method. Moreover, the material which can be used is common to each method.

According to the method (C), the epoxy resin porous membrane can be manufactured through the following main steps.
(I) An epoxy resin composition is prepared.
(Ii) A cured product of the epoxy resin composition is formed into a sheet.
(Iii) The porogen is removed from the epoxy resin sheet.

  First, an epoxy resin composition containing an epoxy resin, a curing agent, and a porogen (pore forming agent) is prepared. Specifically, an epoxy resin and a curing agent are dissolved in a porogen to prepare a uniform solution.

  As the epoxy resin, any of an aromatic epoxy resin and a non-aromatic epoxy resin can be used. Examples of the aromatic epoxy resin include a polyphenyl-based epoxy resin, an epoxy resin containing a fluorene ring, an epoxy resin containing triglycidyl isocyanurate, an epoxy resin containing a heteroaromatic ring (for example, a triazine ring), and the like. Polyphenyl-based epoxy resins include bisphenol A type epoxy resins, brominated bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD type epoxy resins, stilbene type epoxy resins, biphenyl type epoxy resins, and bisphenol A novolak type epoxy resins. , Cresol novolac type epoxy resin, diaminodiphenylmethane type epoxy resin, tetrakis (hydroxyphenyl) ethane base epoxy resin and the like. Non-aromatic epoxy resins include aliphatic glycidyl ether type epoxy resins, aliphatic glycidyl ester type epoxy resins, alicyclic glycidyl ether type epoxy resins, alicyclic glycidyl amine type epoxy resins, and alicyclic glycidyl ester type epoxy resins. Etc. These may be used alone or in combination of two or more.

  Among these, bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, aromatic glycidylamine type epoxy resin, epoxy resin containing fluorene ring, triglycidyl isocyanurate Preferred is at least one selected from the group consisting of an epoxy resin, an alicyclic glycidyl ether type epoxy resin, an alicyclic glycidyl amine type epoxy resin, and an alicyclic glycidyl ester type epoxy resin. What has an equivalent can be used conveniently. When these epoxy resins are used, a uniform three-dimensional network skeleton and uniform pores can be formed, and excellent chemical resistance and high strength can be imparted to the epoxy resin porous membrane.

  As an epoxy resin used as a separator for nonaqueous electrolyte electricity storage devices, in particular, from the group consisting of bisphenol A type epoxy resin, aromatic glycidylamine type epoxy resin, alicyclic glycidylamine type epoxy resin and alicyclic glycidyl ether type epoxy resin At least one selected is preferred.

  In one embodiment of the present invention, the epoxy resin composition includes a glycidylamine type epoxy resin, such as a glycidylamine type epoxy resin and a bisphenol A type epoxy resin, a brominated bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol. AD type epoxy resin, epoxy resin containing fluorene ring, epoxy resin containing triglycidyl isocyanurate, alicyclic glycidyl ether type epoxy resin, and at least one epoxy resin selected from the group consisting of alicyclic glycidyl ester type epoxy resins Including. The separator obtained from this epoxy resin composition contributes to the improvement of the characteristics of the nonaqueous electrolyte electricity storage device.

  The glycidyl amine type epoxy resin is an epoxy resin having a structure in which the hydrogen atom of the amino group of the amine compound is substituted with a glycidyl group, and the glycidyl amine type epoxy resin has two or more diglycidyl from the viewpoint of particularly high crosslinkability. It preferably has an amino group. Specific examples of such glycidylamine type epoxy resins include 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (commercially available from Mitsubishi Gas Chemical Company under the trade name “TETRAD®-C”). N, N, N ′, N′-tetraglycidyl-m-xylenediamine (commercially available from Mitsubishi Gas Chemical Co., Ltd. under the trade name “TETRAD (registered trademark) -X”) And an epoxy resin having a diglycidylamino group. When using glycidylamine type epoxy resin, uniform 3D network skeleton and uniform pores can be formed, crosslink density after curing is improved, and epoxy resin porous membrane has high strength, heat resistance and chemical resistance Can be granted. A glycidylamine type epoxy resin may be used independently and may use 2 or more types together.

  As the curing agent, either an aromatic curing agent or a non-aromatic curing agent can be used. Aromatic curing agents include aromatic amines (eg, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzyldimethylamine, dimethylaminomethylbenzene), aromatic acid anhydrides (eg, phthalic anhydride, trimellitic anhydride) , Pyromellitic anhydride), phenol resins, phenol novolac resins, amines containing heteroaromatic rings (for example, amines containing triazine rings), and the like. Non-aromatic curing agents include aliphatic amines (for example, ethylenediamine, 1,4-butylenediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octane. Diamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, bis (hexamethylene) triamine, 1,3,6-trisaminomethylhexane, polymethylenediamine, trimethylhexamethylenediamine, polyetherdiamine), Alicyclic amines (eg, isophoronediamine, menthanediamine, N-aminoethylpiperazine, 3,9-bis (3-aminopropyl) 2,4,8,10-tetraoxaspiro (5,5) undecane adduct, Bis (4-amino-3-methyl Kurohekishiru) methane, bis (4-aminocyclohexyl) methane, these modified products), aliphatic polyamide amines containing a polyamine and a dimer acid. These may be used alone or in combination of two or more.

  Among these, a curing agent having two or more primary amines in the molecule can be preferably used. Specifically, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, polymethylenediamine, bis (4-amino-3-methylcyclohexyl) methane, bis (4-aminocyclohexyl) methane, 1,4-butylenediamine, 1 Preferably, at least one selected from the group consisting of 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine Can be used. When these curing agents are used, a uniform three-dimensional network skeleton and uniform pores can be formed, and high strength and appropriate elasticity can be imparted to the epoxy resin porous membrane. 1,6-hexanediamine (1,6-diaminohexane) is preferred because of the high crosslink density of the resulting epoxy resin porous membrane, higher chemical stability, and ease of availability and handling.

  As a combination of an epoxy resin and a curing agent, a combination of an aromatic epoxy resin and an aliphatic amine curing agent, a combination of an aromatic epoxy resin and an alicyclic amine curing agent, or an alicyclic epoxy resin and an aromatic amine A combination with a curing agent is preferred. By these combinations, excellent heat resistance can be imparted to the epoxy resin porous membrane.

  The porogen can be a solvent that can dissolve the epoxy resin and the curing agent. Porogens are also used as solvents that can cause reaction-induced phase separation after the epoxy resin and curing agent are polymerized. Specifically, cellosolves such as methyl cellosolve and ethyl cellosolve, esters such as ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate, glycols such as polyethylene glycol and polypropylene glycol, polyoxyethylene monomethyl ether and polyoxyethylene Ethers such as dimethyl ether can be used as the porogen. These may be used alone or in combination of two or more.

  Among these, at least one selected from the group consisting of methyl cellosolve, ethyl cellosolve, polyethylene glycol having a molecular weight of 600 or less, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, polypropylene glycol, polyoxyethylene monomethyl ether, and polyoxyethylene dimethyl ether. Can be preferably used. In particular, at least one selected from the group consisting of polyethylene glycol having a molecular weight of 200 or less, polypropylene glycol having a molecular weight of 500 or less, polyoxyethylene monomethyl ether, and propylene glycol monomethyl ether acetate can be preferably used. When these porogens are used, a uniform three-dimensional network skeleton and uniform pores can be formed. These may be used alone or in combination of two or more.

  Moreover, even if it is insoluble or hardly soluble at room temperature with each epoxy resin or curing agent, a solvent in which a reaction product of the epoxy resin and the curing agent is soluble can be used as a porogen. Examples of such porogen include brominated bisphenol A type epoxy resin (“Epicoat 5058” manufactured by Japan Epoxy Resin Co., Ltd.).

  The porosity, average pore size, and pore size distribution of the epoxy resin porous membrane vary depending on the type of raw material, the mixing ratio of the raw material, and the reaction conditions (for example, heating temperature and heating time during reaction-induced phase separation). Therefore, it is preferable to select optimum conditions in order to obtain the target porosity, average pore diameter, and pore diameter distribution. In addition, by controlling the molecular weight, molecular weight distribution, solution viscosity, crosslinking reaction rate, etc. of the crosslinked epoxy resin during phase separation, the co-continuous structure of the crosslinked epoxy resin and porogen is fixed in a specific state and stable. A porous structure can be obtained.

  As for the compounding ratio of the curing agent to the epoxy resin, for example, the curing agent equivalent is 0.6 to 1.5, preferably 0.7 to 1.4, more preferably 0. It is 7-1.2, Most preferably, it is 0.8-1.1. Appropriate curing agent equivalent contributes to improvement of properties such as heat resistance, chemical durability and mechanical properties of the porous epoxy resin membrane.

  In addition to the curing agent, a curing accelerator may be added to the solution in order to obtain the desired porous structure. Examples of the curing accelerator include tertiary amines such as triethylamine and tributylamine, and imidazoles such as 2-phenol-4-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenol-4,5-dihydroxyimidazole. It is done.

  In general, 40 to 80% by weight of the porogen can be used, based on the total weight of the epoxy resin, the curing agent and the porogen. By using an appropriate amount of porogen, an epoxy resin porous membrane having a desired porosity, average pore diameter and air permeability can be formed.

  One method for adjusting the average pore diameter of the porous epoxy resin membrane to a desired range is a method of using a mixture of two or more epoxy resins having different epoxy equivalents. In this case, the difference in epoxy equivalent is preferably 100 or more, and there are cases where an epoxy resin that is liquid at normal temperature and an epoxy resin that is solid at normal temperature are mixed and used.

  Next, the hardening body of an epoxy resin composition is produced from the solution containing an epoxy resin, a hardening | curing agent, and a porogen. Specifically, the solution is filled in a container and heated as necessary. A cured body having a predetermined shape is obtained by three-dimensionally crosslinking the epoxy resin. In that case, a co-continuous structure is formed by phase-separation of a crosslinked epoxy resin and a porogen.

  The shape of the cured body is not particularly limited. If a columnar or cylindrical container is used, a cured body having a cylindrical or columnar shape can be obtained. If the cured body has a cylindrical or columnar shape, it is easy to perform the cutting process.

  The dimension of a hardening body is not specifically limited. When the cured body has a cylindrical or columnar shape, the diameter of the cured body is, for example, 20 cm or more, and preferably 30 to 150 cm, from the viewpoint of manufacturing efficiency of the epoxy resin porous membrane. The length (axial direction) of the cured body can also be appropriately set in consideration of the dimensions of the epoxy resin porous film to be obtained. The length of the cured body is, for example, 20 to 200 cm, and is preferably 20 to 150 cm, and more preferably 20 to 120 cm from the viewpoint of ease of handling.

  Next, the cured body is formed into a sheet. The cured body having a cylindrical or columnar shape can be formed into a sheet shape by the following method. Specifically, the hardened body is attached to the shaft, and the surface layer portion on the side surface of the hardened body is cut at a predetermined thickness using a cutting blade (slicer) so that an epoxy resin sheet having a long shape is obtained. (Slice). Specifically, the surface layer portion of the cured body is cut while rotating the cured body relative to the cutting blade around the cylindrical axis O (or the columnar axis) of the cured body. According to this method, an epoxy resin sheet can be efficiently produced.

  The line speed when cutting the cured body is, for example, in the range of 2 to 70 m / min. The thickness of the epoxy resin sheet is determined according to the target thickness (5 to 50 μm) of the epoxy resin porous membrane. Since the thickness is slightly reduced when the porogen is removed and dried, the epoxy resin sheet is usually slightly thicker than the target thickness of the porous epoxy resin membrane. Although the length of an epoxy resin sheet is not specifically limited, From a viewpoint of the manufacturing efficiency of an epoxy resin sheet, it is 100 m or more, for example, Preferably it is 1000 m or more.

  Further, the porogen is extracted from the epoxy resin sheet and removed (porosification step). Specifically, it is preferable to remove the porogen from the epoxy resin sheet by immersing the epoxy resin sheet in a solvent. Thereby, an epoxy resin porous membrane is obtained. The solvent is preferably a halogen-free solvent that does not have a large environmental load.

  As the halogen-free solvent for removing the porogen from the epoxy resin sheet, at least one selected from the group consisting of water, DMF (N, N-dimethylformamide), DMSO (dimethyl sulfoxide) and THF (tetrahydrofuran) is used. Can be used depending on the type. Also, supercritical fluids such as water and carbon dioxide can be used as a solvent for removing porogen. In order to positively remove the porogen from the epoxy resin sheet, ultrasonic cleaning may be performed, or the solvent may be heated and used.

  A cleaning apparatus for removing the porogen is not particularly limited, and a known cleaning apparatus can be used. When removing the porogen by immersing the epoxy resin sheet in a solvent, a multi-stage cleaning apparatus having a plurality of cleaning tanks can be suitably used. The number of cleaning stages is more preferably 3 or more. Moreover, you may perform multistage washing | cleaning substantially by utilizing a counterflow. Furthermore, the temperature of the solvent may be changed or the type of the solvent may be changed in the cleaning of each stage.

  After removing the porogen, the porous epoxy resin membrane is dried. The drying conditions are not particularly limited, and the temperature is usually about 40 to 120 ° C, preferably about 50 to 100 ° C, and the drying time is about 10 seconds to 5 minutes. For the drying treatment, a drying apparatus employing a known sheet drying method such as a tenter method, a floating method, a roll method, or a belt method can be used. A plurality of drying methods may be combined. However, when the epoxy resin porous membrane is subsequently treated with a treating agent, this drying step may be omitted.

In the step of treating the porous epoxy resin membrane using the treating agent (hereinafter referred to as “treating step”), an inorganic acid and / or a polyvalent organic acid and a carboxylic acid anhydride are used as the treating agent. That is, the processing step is any one of the following (a) to (d).
(A) a step of using a solution containing an inorganic acid and / or a polyvalent organic acid and a carboxylic acid anhydride as a treatment liquid;
(B) A treatment step (b1) using a solution containing an inorganic acid and / or a polyvalent organic acid as a treatment solution, and a treatment step (using a solution containing a carboxylic acid anhydride as a treatment solution after the treatment step (b1)). b2) and
(C) A treatment step (c1) using a solution containing a carboxylic acid anhydride as a treatment solution, and a treatment step (using a solution containing an inorganic acid and / or a polyvalent organic acid as a treatment solution after the treatment step (c1)) ( c2) and
(D) A step of preparing a solution containing an inorganic acid and / or a polyvalent organic acid and a solution containing a carboxylic acid anhydride and simultaneously using the solution as a treating agent.

  The treatment process is preferably any one of (a) to (c) from the viewpoint of production efficiency. From the viewpoint of good interaction between the inorganic acid and / or polyvalent organic acid and the epoxy resin, and from the viewpoint of good reaction efficiency between the carboxylic acid anhydride and the epoxy resin, the above step (b) is more preferable. .

  Hereinafter, the processing step will be described in more detail while taking the step (b) as an example. In addition, the material which can be used, the method of performing a process, etc. are common in (a)-(d).

  In the step (b), the epoxy resin porous membrane or the epoxy resin sheet before being made porous is brought into contact with the treatment liquid containing the treatment agent. Specifically, (a) the epoxy resin porous membrane or the epoxy resin is brought into contact with the treatment liquid. It can be carried out by immersing the sheet, or (b) applying or spraying the treatment liquid on the porous epoxy resin membrane or the epoxy resin sheet. The solvent contained in the treatment liquid is preferably water, methanol or a mixed solvent thereof, but is not limited thereto, and depending on the type of the treatment agent, toluene, ethyl acetate, N, N-dimethylformamide ( DMF), polar solvents such as acetonitrile, ethanol, isopropanol, or a mixed solvent thereof may be used. Further, when the treatment agent is liquid at the treatment temperature, the liquid can be used as the treatment liquid as it is. That is, as the processing liquid, a liquid processing agent or a solution containing the processing agent can be used.

  The step (b) may be performed before or after the porosification step for removing the porogen. Step (b) can also be carried out as a merge step with the porous step. That is, the relationship between the step (b) and the porous step is as shown in the following 1) to 5).

1) The treatment steps (b1) and (b2) can be performed before the porosification step. In this case, the epoxy resin sheet containing the cured epoxy resin composition and porogen before being made porous is the target of treatment.
2) The treatment steps (b1) and (b2) can be performed after the porosification step. In this case, the epoxy resin porous membrane is the target of processing.
3) The treatment step (b1) can be carried out before the porous step, and the treatment step (b2) can be carried out after the porous step.
4) The treatment step (b1) can be carried out as a merge step with the porous step. In this case, in the combined step of the treatment step (b1) and the porous step, a treatment solution containing the treatment agent and a solvent for removing the porogen is used. The treatment step (b2) can be performed after the porosification step.
5) The treatment step (b1) can be carried out before the porosification step, and the treatment step (b2) can be carried out as a merge step with the porosification step. In this case, in the combined step of the treatment step (b2) and the porosity step, a treatment liquid containing the treatment agent and a solvent for removing the porogen is used.

The processing step (b1)
It may be a step of using a solution containing an inorganic acid or a polyvalent organic acid as a treatment liquid,
It may be a treatment step using a solution containing an inorganic acid and a polyvalent organic acid as a treatment liquid,
It may be a step comprising a treatment step using a solution containing an inorganic acid as a treatment liquid, and a treatment step using a solution containing a polyvalent organic acid as a treatment liquid after the treatment step,
It may be a step comprising a treatment step using a solution containing a polyvalent organic acid as a treatment liquid, and a treatment step using a solution containing an inorganic acid as a treatment liquid after the treatment step,
A treatment step may be used in which a solution containing an inorganic acid and a solution containing a polyvalent organic acid are respectively prepared and used simultaneously as a treatment agent.

  The reaction in the processing step can be controlled by the processing time of the processing step (b1) and the processing step (b2), the concentration of the processing agent, the processing temperature, and the like.

  The treatment liquid may contain 0.1 mmol to 5.0 mol / L of inorganic acid, and preferably contains 0.001 to 2.0 mol / L. If the concentration of the inorganic acid is greater than 5.0 mol / L, it will be difficult to remove the inorganic acid remaining in the porous epoxy resin membrane after the inorganic acid treatment, and the time required for cleaning the porous epoxy resin membrane will be difficult. May be long.

  The treatment liquid may contain 0.1 mmol / L to 5 mol / L of a polyvalent organic acid, preferably 1 mmol / L to 1 mol / L. If the concentration of the polyvalent organic acid becomes too high, excess polyvalent organic acid is present in the epoxy resin porous membrane after the polyvalent organic acid treatment, and the time required for cleaning the epoxy resin porous membrane may be increased. is there.

  The treatment liquid may be used without diluting the carboxylic acid anhydride, may be used diluted with a solvent, for example, may be used diluted to 0.1 mmol / L to 11 mol / L, You may dilute and use to 1 mol / L-11 mol / L. As the solvent, for example, an aprotic solvent such as acetone, acetonitrile or toluene, or a protic solvent can be used. As the protic solvent, it is preferable to use a solvent that does not cause hydrolysis of the carboxylic acid anhydride. For example, a dehydrating solvent such as concentrated sulfuric acid can be used. When the carboxylic acid anhydride is liquid, it is more preferable to use it without dilution.

  As a specific example of the step (b), FIG. 2 shows an example of a change in the IR spectrum of the epoxy resin. In this example, the treatment step (b2) using acetic anhydride was performed after the treatment step (b1) using sulfuric acid, and the spectrum was obtained from a sample prepared by the same production method as in the examples described later. It is what was done.

The IR spectrum of the epoxy resin porous membrane after the treatment step (b1) has an absorption peak in the range of 3000 to 3700 cm ⁻¹ . Thereafter, by carrying out the process step (b2), the smaller the absorption peak of 3000～3700Cm ^-1, absorption peaks occurs in the vicinity of 1740 cm ^-1.

  From such a change in the IR spectrum of FIG. 2, it is considered as follows.

In the treatment step (b1), when sulfuric acid and the epoxy resin come into contact with each other, amino groups contained in the epoxy resin are attracted around the anion of sulfuric acid by an electric attractive force. Since sulfuric acid is bonded to an amino group by electrical attraction, the sulfuric acid is retained in the three-dimensional network skeleton of the epoxy resin, and an absorption peak derived from sulfuric acid is generated at 1000 to 1200 cm ⁻¹ in the IR spectrum.

Thereafter, in the treatment step (b2), acetic anhydride and the epoxy resin are contacted. When the treatment step (b2) is performed, the intensity of 1000 to 1200 cm ⁻¹ of the absorption peak derived from sulfuric acid decreases. On the other hand, an absorption peak (derived from absorption by C═O bond of acetic anhydride) occurs at 1740 cm ⁻¹ in the IR spectrum, and the intensity of an absorption peak from 3000 to 3700 cm ⁻¹ (derived from absorption by OH bond) decreases. That is, the alcoholic hydroxyl group (C—OH) and acetic anhydride (CH ₃ COO) ₂ O present in the porous epoxy resin membrane react to form a carboxylic acid ester bond.

  When the treatment step (b2) is performed, the hydroxyl group contained in the epoxy resin is converted to acetyl (ester) by acetic anhydride, and the corresponding part becomes bulky. As a result, it is considered that the amino group attracted to the sulfate anion by electrical attraction becomes difficult to come close to the sulfate anion, and the coordination between the sulfate anion and the amino group is eliminated.

  The epoxy resin porous film after the treatment process has improved shape stability, and has improved resistance to a load received from the electrode. As a result, it becomes difficult for the separator to close or shrink. Moreover, since there are few active reaction points, it becomes an epoxy resin porous membrane which has long-term stability. Therefore, the separator using the epoxy resin porous membrane subjected to these treatments contributes to the improvement of the characteristics of the nonaqueous electrolyte electricity storage device.

  The content of inorganic acid, polyvalent organic acid, and addition amount of carboxylic acid anhydride in the epoxy resin porous membrane can be determined, for example, by analyzing the porous membrane. Specifically, it can be determined from the absorbance ratio of the IR spectrum.

For example, it is possible to quantify the content of inorganic acid (for example, sulfuric acid) and the addition amount of polyvalent organic acid (for example, citric acid) and carboxylic acid anhydride (for example, acetic anhydride) from the absorbance ratio of IR spectrum. The content of sulfuric acid can be determined from the ratio of the absorption intensity in the vicinity of 1090 cm ^{−1 to the} absorption intensity in the vicinity of 1605 cm ⁻¹ . The citric acid content can be determined from the ratio of the absorption intensity at 1716 cm ⁻¹ (carboxyl group) to the absorption intensity at 830 cm ⁻¹ (phenyl group). Additional amount of acetic anhydride can be determined from the ratio of the absorption intensity at around 1740 cm ^-1 for absorption intensity at around 1605 cm ^-1. Specifically, a method described later can be used.

  The treatment by applying or spraying the treatment liquid does not need to consider the evaporation of the treatment liquid, so it is not necessary to adjust the concentration of the treatment liquid, it is easy to estimate the required amount of the treatment liquid, and the temperature of the discharge port is adjusted This is suitable for mass production because the temperature of the treatment liquid can be easily controlled.

  The treatment using the treatment liquid can also be carried out by (v) bringing the vapor of the treatment liquid into contact with the porous epoxy resin membrane. For example, the wound epoxy resin porous membrane, that is, the wound body of the epoxy resin porous membrane, can be processed by leaving it in contact with the atmosphere containing the treatment liquid vapor. It is. This treatment can be carried out, for example, by supplying the vapor of the treatment liquid to a container or treatment chamber in which the wound body of the epoxy resin porous membrane is placed inside.

  The treatment liquid only needs to be brought into contact with the porous epoxy resin membrane or the epoxy resin sheet at normal temperature, but may be heated to a temperature exceeding normal temperature as necessary. The heating temperature in this case depends on the type of solvent used, but is, for example, in the range of over 120 ° C., particularly in the range of over 100 ° C. over normal temperature. In addition, the treatment time may be a time for the treatment agent to sufficiently spread on the surface of the epoxy resin porous membrane or the like, but in the case of dipping or coating, for example, at room temperature for 10 seconds to 30 minutes, in a temperature range exceeding room temperature. 1 second to 5 minutes is appropriate.

  After the contact with the treatment liquid, the epoxy resin porous membrane may be heated as necessary.

  In order to remove the excess treatment agent present in the membrane, the epoxy resin porous membrane may be washed, and in this case, a drying treatment is further performed. Water is suitable as a solvent for washing, but methanol, ethanol, isopropanol, N, N-dimethylformamide (DMF), acetonitrile, a mixed solvent thereof, a mixed solvent of these with water, or the like may be used. Good. Regarding the apparatus and temperature for washing and drying, the apparatus and temperature described above for the washing and drying of the porogen can be applied. In addition, since the inorganic acid or polyvalent organic acid held in the three-dimensional network skeleton is bonded to the amino group by electric attraction, it is difficult to remove by washing with water as described above.

  According to the above 1), the treating agent can be removed together with the porogen in the porous step of removing the porogen. For this reason, it is not necessary to perform additional cleaning for removing the treatment agent. Moreover, according to said 4) and 5), a part of processing process by a processing agent can be combined and implemented with a porosity forming process.

Even when any of the above 1) to 5) is adopted, in the present embodiment, as a step for obtaining an epoxy resin sheet before the porous step and the treatment step,
Preparing an epoxy resin composition comprising an epoxy resin, a curing agent and a porogen;
As described above, the step of molding the cured product of the epoxy resin composition into a sheet or curing the sheet-shaped product of the epoxy resin composition is performed so that the epoxy resin sheet is obtained.

  In addition, the separator 4 may be comprised only by the epoxy resin porous membrane, and may be comprised by the laminated body of an epoxy resin porous membrane and another porous material. Examples of other porous materials include polyolefin porous films such as polyethylene porous films and polypropylene porous films, cellulose porous films, and fluororesin porous films. Other porous materials may be provided only on one side of the epoxy resin porous membrane, or may be provided on both sides.

  Similarly, the separator 4 may be configured by a laminate of an epoxy resin porous film and a reinforcing material. Examples of the reinforcing material include woven fabric and non-woven fabric. The reinforcing material may be provided only on one side of the epoxy resin porous membrane, or may be provided on both sides.

  As another embodiment, a separator for an electricity storage device provided with the porous epoxy resin membrane of the present invention is used as a separator for an aqueous electrolyte electricity storage device. Moreover, the water-system electrolyte electrical storage device provided with this separator for water-system electrolyte electrical storage devices can be formed. Specifically, a water-based electrolyte electricity storage device including the positive electrode, the negative electrode, the separator of the present embodiment disposed between the positive electrode and the negative electrode, and a water-based electrolytic solution impregnated in the separator can be formed. A specific example of the water-based electrolyte electricity storage device is an electric double layer capacitor, for example.

  As yet another embodiment, an electricity storage device separator provided with the porous epoxy resin membrane of the present invention is used as an electrolytic capacitor separator. Moreover, an electrolytic capacitor provided with this electrolytic capacitor separator can be formed. Specifically, it is an electrolytic capacitor comprising an anode, a cathode, a separator according to this embodiment disposed between the anode and the cathode, and an electrolytic solution impregnated in the separator. The electrolytic capacitor is, for example, an aluminum electrolytic capacitor.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples. In the following, RO water means pure water obtained by processing using a reverse osmosis membrane. The evaluation method of characteristics was as follows.

[Characteristic evaluation of lithium ion secondary battery]
89 parts by weight of lithium cobalt oxide (manufactured by Nippon Chemical Industry Co., Ltd., Cellseed C-10), 10 parts by weight of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., Denka Black), 5 parts by weight of polyvinylidene fluoride (Kureha Corporation) Made of PVDF, product number KF polymer L # 1120), and N-methyl-2-pyrrolidone was added so that the solid content concentration was 15 wt% to obtain a cathode slurry. This slurry was applied to a thickness of 200 μm on an aluminum foil (current collector) having a thickness of 20 μm. The coating film was vacuum dried at 80 ° C. for 1 hour and 120 ° C. for 2 hours, and then pressed by a roll press. As a result, a cathode having a cathode active material layer having a thickness of 100 μm was obtained.

  80 parts by weight of mesocarbon microbeads (manufactured by Osaka Gas Chemical Co., Ltd., MCMB6-28), 10 parts by weight of acetylene black (manufactured by Denki Kagaku Co., Ltd., Denka Black), 10 parts by weight of PVDF (manufactured by Kureha Corporation, KF polymer L # 1120) was mixed, and N-methyl-2-pyrrolidone was added so that the solid content concentration was 15% by weight to obtain an anode slurry. This slurry was applied to a thickness of 200 μm on a copper foil (current collector) having a thickness of 20 μm. The coating film was vacuum dried at 80 ° C. for 1 hour and 120 ° C. for 2 hours, and then pressed by a roll press. As a result, an anode having an anode active material layer having a thickness of 100 μm was obtained.

Next, an electrode group was assembled using a cathode, an anode, and a separator. Specifically, a cathode, an epoxy resin porous membrane (separator), and an anode were laminated to obtain an electrode group. After the electrode group was put in an aluminum laminate package, an electrolytic solution was injected into the package. As the electrolytic solution, a solution containing LiPF ₆ at a concentration of 1.0 mol / L in a solvent containing ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 3 and containing 2% by weight of vinylene carbonate was used. Finally, the package was sealed to obtain a lithium ion secondary battery.

  Using each lithium ion secondary battery obtained as described above, the 3C / 0.5C discharge capacity retention rate was measured as follows.

[3C / 0.5C discharge capacity maintenance ratio]
Each battery was held in a constant temperature bath at a temperature of 25 ° C. First, the battery was charged with a constant current corresponding to 0.5 CmA until the voltage reached 4.2V. After the voltage reached 4.2 V, charging was performed until the current value attenuated to 5% corresponding to 0.5 CmA at a constant voltage of 4.2 V (0.5 C charging). Next, discharging was performed at a current value corresponding to 0.5 CmA until the voltage reached 2.75 V (0.5 C discharging). 0.5C charge and 0.5C discharge were repeated 3 times, and the discharge capacity at the time of the third 0.5C discharge was defined as 0.5C discharge capacity. Thereafter, 0.5C charge and 3C discharge (discharge until the voltage reached 2.75V at a current value corresponding to 3CmA) were performed, and the discharge capacity at the time of 3C discharge was set as the 3C discharge capacity. The ratio of the 3C discharge capacity to the 0.5C discharge capacity was defined as the 3C / 0.5C discharge capacity retention rate.

[150 cycle test]
The battery that had been subjected to the 3C discharge was held in a constant temperature bath at 25 ° C. After the voltage reached 4.2 V, charging was performed until the current value attenuated to 5% corresponding to 0.5 CmA at a constant voltage of 4.2 V (0.5 C charging). Next, discharging was performed at a current value corresponding to 0.5 CmA until the voltage reached 2.75 V (0.5 C discharging).
After that, the battery is charged with a constant current corresponding to 1 CmA until the voltage reaches 4.2 V, and after the voltage reaches 4.2 V, the battery is charged with a constant voltage of 4.2 V until the current value is attenuated to 5% corresponding to 1 CmA. Thereafter, a charge / discharge cycle in which discharge was performed until the voltage reached 2.75 V at a current value corresponding to 1 CmA was defined as one cycle, and 150 cycles were repeated.

[3C / 0.5C discharge capacity maintenance ratio after 150 cycle test]
A 3C / 0.5C discharge capacity retention rate was measured for the battery after the 150 cycle test.

[Decrease rate of discharge capacity maintenance rate by cycle test]
The reduction rate of the discharge capacity maintenance rate by the cycle test was calculated | required using the following formula | equation.
(Decrease rate of discharge capacity maintenance rate by cycle test) (%) =
100 × ((3C / 0.5C discharge capacity maintenance rate) − (3C / 0.5C discharge capacity maintenance rate after 150 cycles)) / (3C / 0.5C discharge capacity maintenance rate)

[Addition amount of acetic anhydride]
The IR spectrum (infrared absorption spectrum) was measured using a transmission type FT-IR apparatus (Nicolet iS5, manufactured by Thermo Fisher Scientific). The epoxy resin porous membrane was measured as it was as a measurement sample. From the resulting chart was determined the ratio of the absorption intensity at 1607 cm ^-1 for absorption intensity at 1738 cm ^-1. Based advance in the prepared calibration curve (the addition weight ratio of acetic anhydride for the ratio of the absorption intensity at 1607 cm ^-1 for absorption intensity at 1738 cm ^-1), was determined an additional amount of acetic anhydride contained in the epoxy resin porous membrane.

[Sulfuric acid content]
The IR spectrum (infrared absorption spectrum) was measured using a transmission type FT-IR apparatus (Nicolet iS5, manufactured by Thermo Fisher Scientific). The epoxy resin porous membrane was measured as it was as a measurement sample. From the resulting chart was determined the ratio of the absorption intensity at 1087cm ^-1 for the absorption intensity at 1738 cm ^-1. Based on the previously prepared calibration curve (the addition weight ratio of sulfuric acid with respect to the ratio of the absorption intensity at 1087cm ^-1 for the absorption intensity at 1738 cm ^-1), it was determined the content of sulfuric acid contained in the epoxy resin porous membrane.

(Comparative Example 1)
In a 3 L cylindrical plastic container, jER (registered trademark) 828 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 184 to 194 g / eq.) 100 parts by weight, TETRAD (registered trademark) -C (glycidylamine) Type epoxy resin, Mitsubishi Gas Chemical Co., Ltd., epoxy equivalent 95-110 g / eq.) 25 parts by weight is dissolved in polypropylene glycol (ADEKA Co., Ltd., Adeka Polyether P-400) 211.9 parts by weight, epoxy resin / A polypropylene glycol solution was prepared. Thereafter, 22.3 parts by weight of 1,6-hexanediamine (1,6-diaminohexane) was added to the polycontainer to prepare an epoxy resin / amine / polypropylene glycol solution. After that, using a planetary agitator (trade name “Awatori Nertaro (registered trademark)” manufactured by Shinky Co., Ltd.), vacuum defoaming was performed at about 0.7 kPa, and at the same time, revolution 800 rpm under the condition of self / revolution ratio 3/4. The procedure of stirring at a ratio of 10 minutes was repeated twice.

  Then, it was naturally cooled for several days, the epoxy resin block was taken out from the plastic container, and continuously sliced with a thickness of 20 μm using a cutting lathe device to obtain an epoxy resin sheet.

  This epoxy resin sheet was ultrasonically cleaned in a mixed solution of RO water / DMF = 1/1 (v / v) for 10 minutes, then ultrasonically cleaned using RO water for 10 minutes, and then immersed in RO water for 12 hours. To remove the polypropylene glycol. Then, it was made to dry for 2 hours in 80 degreeC atmosphere, and the epoxy resin porous membrane was obtained. The resulting epoxy resin porous membrane had a thickness of 21 μm, an average pore diameter of 280 nm, a porosity of 56%, and a Gurley value of 25 sec / dl.

(Comparative Example 2)
The epoxy resin sheet obtained in Comparative Example 1 was immersed in a methanol solution containing 40 mmol / L sulfuric acid for 2 minutes. Then, after immersing in a methanol / RO water = 1/1 (v / v) mixed solution for 10 minutes and then immersing in RO water for 10 minutes, it is dried in an oven at 80 ° C. for 2 hours to carry out an inorganic acid (sulfuric acid) treatment. The performed epoxy resin porous membrane was obtained. The obtained epoxy resin porous film had a film thickness of 23 μm, an average pore diameter of 275 nm, a porosity of 56%, and a Gurley value of 25 sec / dl.

(Comparative Example 3)
The epoxy resin sheet obtained in Comparative Example 1 was immersed in acetic anhydride for 10 minutes. Then, it is immersed in ethanol / RO water = 1/1 (v / v) mixed solution for 10 minutes, then immersed in RO water for 10 minutes, then dried in an oven at 80 ° C. for 2 hours, and esterified (acetic anhydride treatment). An epoxy resin porous membrane was obtained. The resulting epoxy resin porous membrane had a thickness of 22 μm, an average pore diameter of 275 nm, a porosity of 56%, and a Gurley value of 24 sec / dl.

Example 1
The epoxy resin sheet obtained in Comparative Example 2 was immersed in acetic anhydride for 10 minutes. Then, after immersing in ethanol / RO water = 1/1 (v / v) mixed solution for 10 minutes, then immersed in RO water for 10 minutes, dried in an oven at 80 ° C. for 2 hours, treated with inorganic acid (sulfuric acid) and An epoxy resin porous membrane subjected to esterification treatment (acetic anhydride treatment) was obtained. The amount of sulfuric acid added in the obtained porous epoxy resin membrane was 10% by weight, and the amount of acetic anhydride added was 1% by weight. The resulting epoxy resin porous membrane had a thickness of 22 μm, an average pore diameter of 275 nm, a porosity of 56%, and a Gurley value of 24 sec / dl.

(Reference example)
A polypropylene porous membrane CG2400 made by Celgard was used.

  The results are summarized in Table 1.

  In the porous film obtained in Example 1, the 3C / 0.5C discharge capacity retention rate was improved, and the decrease rate of the discharge capacity retention rate after the cycle test was low.

  The separator provided by the present invention can be used for an electricity storage device separator, a separation filtration membrane, a sound-permeable membrane, and the like. For example, it can be suitably used for nonaqueous electrolyte electricity storage devices such as lithium ion secondary batteries, aqueous electrolyte electricity storage devices such as electric double layer capacitors, and electrolytic capacitors such as aluminum electrolytic capacitors.

2 Cathode 3 Anode 4 Separator 100 Non-aqueous electrolyte battery

Claims (7)

A method for producing a separator for an electricity storage device provided with an epoxy resin porous membrane,
In order to obtain an epoxy resin porous film, a porosification step of removing the porogen from the epoxy resin sheet containing a cured product of the epoxy resin composition and the porogen and removing the porogen to make it porous,
A treatment step of bringing a treatment liquid into contact with the epoxy resin porous membrane or the epoxy resin sheet;
Comprising
The processing step includes
(A) a step of using a solution containing an inorganic acid and / or a polyvalent organic acid and a carboxylic acid anhydride as a treatment liquid;
(B) A treatment step (b1) using a solution containing an inorganic acid and / or a polyvalent organic acid as a treatment solution, and a treatment step using a solution containing a carboxylic acid anhydride as the treatment solution after the treatment step (b1). (B2) comprising,
(C) A treatment step (c1) using a solution containing a carboxylic acid anhydride as a treatment solution, and a treatment step using a solution containing an inorganic acid and / or a polyvalent organic acid as the treatment solution after the treatment step (c1). A step comprising (c2),
Any one of
The polyvalent organic acid has a plurality of carboxyl groups,
A method for producing a separator for an electricity storage device. The thickness of the epoxy resin porous membrane is in the range of 5 to 50 μm.
The manufacturing method of the separator for electrical storage devices of Claim 1. The processing step is
(B) The treatment step (b1) using a solution containing an inorganic acid and / or a polyvalent organic acid as a treatment liquid, and the solution containing a carboxylic acid anhydride as the treatment liquid after the treatment step (b1). A process comprising a processing step (b2),
The manufacturing method of the separator for electrical storage devices of Claim 1 or 2. The inorganic acid is at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hexafluorophosphoric acid and tetrafluoroboric acid;
The manufacturing method of the separator for electrical storage devices of any one of Claims 1-3. The polyvalent organic acid has 3 or more carboxyl groups,
The manufacturing method of the separator for electrical storage devices of any one of Claims 1-4.   The separator for electrical storage devices obtained by the manufacturing method of the separator for electrical storage devices of any one of Claims 1-5. Two types of electrodes;
The separator according to claim 6 disposed between the electrodes;
An electricity storage device comprising:

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