JP2010231897A - Separator for power storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator having a tensile strength of a wet-paper state, the separator being wound or laminated on an electrode in a state that the separator impregnates a driving electrolyte solution. <P>SOLUTION: In the separator for a power storage device, in which two or more fabric layers with at least one layer containing a synthetic fiber are laminated, at least one layer of the fabric layers contains a thermosetting resin, and the impregnated and coated thermosetting resin is in a state of being melted and half-cured or cured, and a tensile strength in a wet-paper state is 3N/15 mm or more. The thermosetting resin is preferably composed of at least one selected from epoxy resins. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a separator for an electricity storage device, and in particular, a separator for an electricity storage device such as a lithium ion secondary battery, a polymer lithium secondary battery, an electric double layer capacitor or an aluminum electrolytic capacitor (hereinafter referred to as “separator”). )

  In recent years, electrical and electronic equipment has increased in both industrial and consumer use, and since hybrid vehicles have been put into practical use, power storage devices such as lithium ion secondary batteries and polymers mounted on them Demand for lithium secondary batteries, aluminum electrolytic capacitors, electric double layer capacitors, etc. has increased significantly. Electrical and electronic equipment has long life and high functionality, and power device separators are required to have long life and high functionality, and use in harsh environments is increasing. .

  A lithium ion secondary battery is a positive electrode in which an active material, a lithium-containing oxide, and a binder such as polyvinylidene fluoride are mixed with 1-methyl-2-pyrrolidone to form a sheet on an aluminum current collector, and lithium ions are occluded and released. A negative electrode formed by mixing a carbonaceous material and a binder such as polyvinylidene fluoride with 1-methyl-2-pyrrolidone into a sheet on a copper current collector, and a porous electrolyte membrane made of polyethylene, polypropylene, or the like, An electrode body wound or laminated in the order of an electrolyte membrane and a negative electrode is impregnated with a driving electrolyte solution and sealed with an aluminum case.

  An electric double layer capacitor is a mixture of activated carbon, conductive agent and binder, which is attached to both sides of the positive and negative current collectors made of aluminum and driven to a wound or laminated electrode body via a separator made of cellulose or the like. In this structure, the positive electrode lead and the negative electrode lead are passed through the sealing body so as not to be short-circuited by being impregnated with an electrolytic solution and packed with an aluminum case and a sealing body.

Conventionally, porous membranes such as polyethylene and polypropylene have been used as separators for the lithium ion secondary battery, and paper made of cellulose pulp and nonwoven fabric made of cellulose fibers have been used as separators for electric double layer capacitors. ing.
In general, in a conventional electricity storage device, an electrode body wound or laminated in the order of a positive electrode, a separator, and a negative electrode is hermetically sealed in a case having a liquid injection hole, and a predetermined amount of driving electrolyte is injected from the liquid injection hole. After that, the liquid injection hole portion is sealed and assembled in a reduced pressure state (see, for example, Patent Document 1).
The electrode body wound or laminated in this order of the positive electrode, the separator, and the negative electrode is hermetically sealed in a case having a liquid injection hole, and after a certain amount of driving electrolyte is injected from the liquid injection hole, the pressure is reduced. Thus, the method of sealing the liquid injection hole portion has a problem that the production efficiency of the electricity storage device is poor.

JP-A-10-64769

  The present invention provides a separator having a tensile strength in a wet paper state in which the separator can be wound or laminated with an electrode in an impregnated state with a driving electrolyte.

The separator for an electricity storage device of the present invention is an electricity storage device separator in which at least one layer is a laminate of two or more fiber layers containing synthetic fibers, and a thermosetting resin is applied to at least one of the fiber layers. The thermosetting resin contained and impregnated and coated is fused to be in a semi-cured state or a cured state, and has a tensile strength in a wet paper state of 3 N / 15 mm or more.
Moreover, it is preferable that the said thermosetting resin consists of at least 1 sort (s) chosen from the phenol resin and the epoxy resin.
The synthetic fiber is selected from polyethylene terephthalate, polybutylene terephthalate, wholly aromatic polyamide, wholly aromatic polyester, semi-aromatic polyamide, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyethylene, polypropylene, aramid, and polyarylate. It is preferable that it is at least one or more.
Moreover, it is preferable that the synthetic fiber has a fiber diameter of 5 μm or less and a fiber length of 10 mm or less.

Moreover, it is preferable that the fiber layer is formed by overlapping and making a paper-making net using an inclined wire paper machine having two or more heads.
Further, the multi-tank inclined type wet paper machine in which the fiber layer can simultaneously form a plurality of layers having a structure in which the lower part of the second flow box is located in the vicinity of the intersection of the waterline and the paper making net in the first flow box. It is preferable that the sheet is overlapped on the papermaking net.
Moreover, it is preferable that the said electrical storage device is any one of a lithium ion secondary battery, a polymer lithium secondary battery, an electric double layer capacitor, and an aluminum electrolytic capacitor.

The present invention provides a separator having a tensile strength in a wet paper state in which the separator can be wound or laminated with an electrode in an impregnated state with a driving electrolyte.
The separator of the present invention has a tensile strength in a wet paper state that can be wound or laminated with an electrode in an impregnated state with a driving electrolyte solution, and is a thin film in a high-temperature environment in the presence of an organic solvent or an ionic liquid. It is extremely excellent in durability. Therefore, the separator of the present invention is suitably used for an electricity storage device such as an electric double layer capacitor, and is excellent in preventing a short circuit between electrodes and suppressing self-discharge.

It is sectional drawing which shows the structure of the multi-tank inclination type wet paper machine concerning this invention.

In the present invention, since a thermosetting resin is impregnated and applied to a dried separator after papermaking, the bond between fibers is strengthened by semi-curing or curing the thermosetting resin by heat treatment. Strength is improved. For example, ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, halogenated hydrocarbons, esters, carbonates, nitro compounds, phosphate ester compounds, sulfolane hydrocarbons, etc. And a tensile strength in a wet paper state that can be wound or laminated with the electrode in an impregnated state with an electrolyte for driving in which an electrolyte salt is dissolved in a mixed solvent thereof is 3 N / 15 mm or more, preferably 5 N / 15 mm A separator can be provided.
In the present invention, the tensile strength in the wet paper state means that the separator is immersed in a solution of tetraethylammonium tetrafluoroborate dissolved in propylene carbonate so as to be 1 mol / L for 15 seconds, and then taken out in an environment of 25 ° C. A value obtained by allowing the separator to stand for 30 seconds and measuring the tensile strength according to JIS C2111.

  Also, since the fibers are coated with thermosetting resin, the durability against organic solvents, ionic liquids, and high-temperature conditions is high, and high-temperature and long-term use is unlikely to deteriorate even if used in a high-temperature atmosphere for a long period of time. It is possible to provide a separator having excellent durability.

The thermosetting resin is preferably at least one selected from a phenol resin and an epoxy resin.
As the phenol resin, the phenol component is one or more selected from the group consisting of pt-butylphenol, bisphenol A, cresol, pt-butylphenol type, bisphenol A type, cresol type, or those At least one selected from a co-condensation type resol type phenol resin or a cresol type phenol resin can be used.

  The epoxy resin is selected from bisphenol A glycidyl ether type epoxy compounds, bisphenol S type and bisphenol F type novolak glycidyl ether type and phenol novolac type epoxy resins, dimer acid glycidyl ester, polyoxyalkylene glycol glycidyl ether, etc. At least one of the above can be used.

The thermosetting resin is preferably contained in an amount of 5 to 200 parts by mass, particularly preferably 10 to 100 parts by mass with respect to 100 parts by mass of all fibers contained in the separator. If it is less than 5 parts by mass, the tensile strength in the wet paper state is less than 3 N / 15 mm, and if it exceeds 200 parts by mass, the pores are filled with the thermosetting resin and the separator becomes a film.
Any solvent can be used as the solvent used when impregnating and applying the thermosetting resin, but an organic solvent having a boiling point of 150 ° C. or lower is preferable as long as it is an organic solvent that dissolves the thermosetting resin.

  Synthetic fibers used in the present invention are polyethylene terephthalate, polybutylene terephthalate, wholly aromatic polyamide, wholly aromatic polyester, semi-aromatic polyamide, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyethylene, polypropylene, aramid, polyarylate Those composed of at least one resin selected from the above are preferably used, but are not necessarily limited to these, have high heat resistance, and are suitable for organic solvents and ionic liquids used in driving electrolytes. Any one that does not dissolve can be used. By laminating the fiber layer containing the synthetic fiber, durability against an organic solvent or an ionic liquid is increased, and even when the fiber layer is used in a high temperature atmosphere for a long period of time, it does not easily deteriorate.

  In the present invention, the fiber layer containing the synthetic fiber and the other fiber used in the fiber layer laminated with the fiber layer may be selected from the synthetic fibers. Any of synthetic fibers or cellulose fibers made of natural pulp can be used. These synthetic fibers, cellulose fibers, and the like are preferably beaten in order to improve the retention of the electrolytic solution and to form a uniform fiber layer.

  In the present invention, the synthetic fiber has a fiber diameter of 5 μm or less and a fiber length of preferably 10 mm or less, particularly preferably a fiber diameter of 3 μm or less and a fiber length of 3 mm or less. When the fiber diameter is 5 μm or more and the fiber length is 10 mm or more, there is a high possibility that a through-hole will be formed when the film is thinned, which is likely to cause an internal short circuit.

  In the present invention, the pore diameter of the fiber layer is preferably 0.1 μm to 15 μm, more preferably 0.1 μm to 5.0 μm, as the average pore diameter measured by the bubble point method. When the average pore diameter is smaller than 0.1 μm, the ionic conductivity is lowered and the internal resistance tends to be high. Further, since it is difficult for water to escape during the production of the separator, it is difficult to produce the separator. If it exceeds 15 μm, an internal short circuit is likely to occur when the film is thinned. In addition, the measurement of the hole diameter by the bubble point method may be performed by using a porometer manufactured by Seika Sangyo Co., Ltd.

The thickness of the separator of the present invention is preferably 50 μm or less. If the thickness of the separator exceeds 50 μm, it will be disadvantageous for thinning of the electricity storage device, and at the same time, the amount of electrode material that can be put in a certain cell volume will be reduced, the capacity will be reduced, and the resistance will be increased. It is not preferable.
The density of the separator of the present invention ^is preferably ^{0.20g / cm 3 ~0.75g / cm 3} . If it is less than 0.20 g / cm ³ , the void portion of the separator becomes excessive, and problems such as occurrence of short circuits and deterioration of self-discharge resistance are likely to occur. On the other hand, if the density is larger than 0.75 g / cm ³ , the material constituting the separator becomes excessively clogged, so that ion migration is hindered and resistance is likely to increase.

The porosity of the separator of the present invention is preferably in the range of 30% to 90% in order to achieve both prevention of short circuit and suppression of increase in resistance.
The porosity here is calculated | required by following Formula using basis weight M (g / cm < ² >), thickness T (micrometer), and density D (g / cm < ³ >).
Porosity (%) = [1- (M / T) / D] × 100

  As described above, the separator of the present invention has a laminated structure in which two or more fiber layers are laminated, and at least one layer includes a fiber layer containing the above-described heat-resistant synthetic fiber, and is thermoset. Since the thermosetting resin containing a mold resin and impregnated and applied is semi-cured or cured by heat treatment, the bond between fibers is strengthened and the tensile strength of the wet paper is improved. It can be wound or laminated with the electrode in an impregnated state, and can be suitably used for power storage devices such as lithium ion secondary batteries, lithium ion capacitors, polymer batteries, and electric double layer capacitors. In the case of assembling an electricity storage device using the separator of the present invention, any material that constitutes the electricity storage device, such as a positive electrode, a negative electrode, and an electrolytic solution, can be used as long as it is conventionally known.

Next, although the manufacturing method of the separator of this invention is demonstrated, it is not limited only to this, The separator of this invention can be manufactured also by another method.
First, one or more types of synthetic fibers cut or beaten to have a fiber diameter of 5 μm or less and a fiber length of 5 mm or less are dispersed in water. Since the fibers used in the present invention are very fine and difficult to disperse uniformly in the disaggregation step, good dispersion is possible by using a dispersing device such as a pulper or an agitator or an ultrasonic dispersing device. The water used in this dispersion step is preferably ion-exchanged water in order to reduce ionic impurities as much as possible. Next, the same synthetic fiber or different fiber as described above is dispersed in water by a dispersing device such as a pulper or agitator different from the above. The beating may be performed using a general beating machine such as a ball mill, beater, lampel mill, PFI mill, SDR (single disc refiner), DDR (double disc refiner), high pressure homogenizer, homomixer, or other refiner. it can.

  The fiber dispersion obtained above is made by applying a wet paper machine such as a long-mesh type, a short-mesh type, a circular net type, or an inclined type. Dehydrate in a continuous wire mesh dewatering part. When using an inclined wire paper machine with two heads in a wet paper machine, when two or more fiber layers are laminated together, it is difficult to create a boundary between fiber layers, and there is no pinhole. A separator is obtained. After the sheets are overlaid, a dried separator can be obtained by passing through a drying part such as a multi-cylinder type or Yankee type dryer. The separator in the dry paper state after the paper making is impregnated with a thermosetting resin solution diluted according to the target strength. As a coating method, a separator is manufactured by dipping in a coating method such as a direct roll coater, a dip coater, a spray coater, or a kiss roll coater, and drying by passing through a drying part such as a multi-cylinder type or a Yankee type dryer.

  The impregnation application of the thermosetting resin solution is more preferably spray-applied on a felt or canvas, or on a carrier with good air permeability, because paper breaks and wrinkles are likely to occur in the separator. Therefore, a spray coater is suitable as a coating method.

  In particular, as a papermaking method, a multi-tank wet type wet paper machine capable of simultaneously forming a plurality of layers having a structure in which the lower part of the second flow box is located in the vicinity of the intersection of the floodline in the first flow box and the papermaking net. A method in which the fiber layers are stacked on the papermaking net and used together is more preferable because the fibers of the fiber layers are not easily entangled and peeled between the layers. In addition, the separator obtained by the multi-tank inclined type wet paper machine is difficult to form a boundary between fiber layers, and a uniform separator without a pinhole is obtained.

  Such a multi-tank inclined type wet paper machine has a configuration as shown in FIG. As shown in FIG. 1, the papermaking net 10 travels in the direction of arrow a by a plurality of guide rollers. The inclined paper making net 10 between the guide roller 11 and the guide roller 12 is referred to as an inclined traveling unit 13. In the present invention, the lower part of the second flow box 15 is located in the vicinity A of the intersection of the floodline WL and the inclined traveling part 13 in the first flow box 14. In the vicinity A of the intersection, the dispersion 16 containing the fibers in the first flow box 14 and the dispersion 17 containing the fibers in the second flow box 15 are adjacent to each other with a partition wall 18 therebetween. There is a gap between the partition wall 18 and the inclined traveling part 13 in the vicinity A of the intersection, and the dispersion 16 that has flowed out from the first flow box 14 as the papermaking net 10 travels passes through this gap to the first position. 2 is mixed with the dispersion 17 in the flow box 15.

A polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm was placed in a pulper at a concentration of 0.05% by mass in ion-exchanged water and dispersed for 30 minutes to prepare a fiber dispersion A. Next, a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm are in a mass ratio of 1: 1. The fibers were mixed at a ratio, charged in ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion B.
The dispersion A was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, Dispersion B was made on the sheet. Thereafter, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a separator of the present invention.
The obtained separator had a thermosetting resin in a semi-cured or cured state, physical properties were a density of 0.43 g / cm ³ , a porosity of 73%, and a separator thickness of 29 μm.

The separator of the present invention was obtained in the same manner as in Example 1 except that the pt-butylphenol type resol phenol resin was changed to a bisphenol S type novolak glycidyl ether type epoxy resin.
The obtained separator had a thermosetting resin in a semi-cured state or a cured state, physical properties were a density of 0.41 g / cm ³ , a porosity of 73%, and a separator thickness of 30 μm.

In Example 1, the separator of this invention was obtained similarly except having changed the spray application quantity of pt-butylphenol type resol phenol resin into 10 mass parts.
The obtained separator had a thermosetting resin in a semi-cured or cured state, physical properties were a density of 0.42 g / cm ³ , a porosity of 72%, and a separator thickness of 31 μm.

In Example 1, the separator of this invention was obtained similarly except having changed the spray application quantity of pt-butylphenol type resol phenol resin into 60 mass parts.
In the obtained separator, the thermosetting resin was in a semi-cured state or a cured state, the physical properties were a density of 0.40 g / cm ³ , a porosity of 71%, and a thickness of the separator of 32 μm.

In Example 1, the separator of this invention was obtained similarly except having changed the spray application quantity of pt-butylphenol type resol phenol resin into 150 mass parts.
The obtained separator had a thermosetting resin in a semi-cured or cured state, physical properties were a density of 0.40 g / cm ³ , a porosity of 73%, and a separator thickness of 31 μm.

Polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm and a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm are mixed at a mass ratio of 1: 1, and ion-exchanged water. Was added to a pulper at a concentration of 0.05 mass% and dispersed for 30 minutes to prepare a fiber dispersion E. Next, solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm was charged into ion-exchanged water at a concentration of 0.05% by mass in a different pulper and dispersed for 30 minutes. Dispersion F was produced.
The dispersion E was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, Dispersion F was made on the sheet. Thereafter, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a separator of the present invention.
The resulting separator, thermosetting resin in a semi-cured state or cured state, physical properties, density 0.39 g / cm ^3, the porosity is 74%, the thickness of the separator was 20 [mu] m.

A polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm and polyphenylene sulfide fibrillated to a fiber diameter of 0.8 μm and a fiber length of 1.5 mm are mixed at a mass ratio of 1: 1, and 0 in ion-exchanged water. A fiber dispersion G was prepared by putting it into a pulper at a concentration of 0.05 mass% and dispersing it for 30 minutes. Next, solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm was charged into ion-exchanged water at a concentration of 0.05% by mass in a different pulper and dispersed for 30 minutes. Dispersion H was produced.
The dispersion G was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, a dispersion H was made on the sheet. Thereafter, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a separator of the present invention.
The obtained separator had a thermosetting resin in a semi-cured or cured state, physical properties were a density of 0.40 g / cm ³ , a porosity of 73%, and a separator thickness of 31 μm.

A fully aromatic polyester fiber fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm is charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes. Was made. Next, solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm was charged into ion-exchanged water at a concentration of 0.05% by mass in a different pulper and dispersed for 30 minutes. Dispersion J was prepared.
The dispersion I was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion J was made on the sheet. Thereafter, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a separator of the present invention.
In the obtained separator, the thermosetting resin was in a semi-cured state or a cured state, the physical properties were a density of 0.39 g / cm ³ , a porosity of 72%, and a thickness of the separator of 30 μm.

A fully aromatic polyester fiber fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm is charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes. Was made. Next, a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm are in a mass ratio of 1: 1. The mixture was mixed at a ratio, charged in deionized water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion L.
The dispersion K was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion L was made on the sheet. Thereafter, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a separator of the present invention.
The obtained separator had a thermosetting resin in a semi-cured or cured state, physical properties were a density of 0.40 g / cm ³ , a porosity of 72%, and a thickness of the separator of 30 μm.

Polyethylene terephthalate fiber having a fiber diameter of 0.5 μm and a fiber length of 5 mm was placed in a pulper at a concentration of 0.05% by mass in ion exchange water and dispersed for 30 minutes to prepare a fiber dispersion M. Next, a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm are in a mass ratio of 1: 1. The mixture was mixed at a ratio, and charged into ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion N.
The dispersion M was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion N was made on the sheet. Thereafter, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a separator of the present invention.
The obtained separator had a thermosetting resin in a semi-cured or cured state, physical properties were a density of 0.42 g / cm ³ , a porosity of 73%, and a separator thickness of 32 μm.

A polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm was placed in a pulper at a concentration of 0.05% by mass in ion-exchanged water and dispersed for 30 minutes to prepare a fiber dispersion R. Next, a wholly aromatic polyamide fibrillated to a fiber diameter of 0.6 μm and a fiber length of 1.5 mm is charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes to obtain a fiber dispersion. S was produced.
Further, the solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm is charged into ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above and dispersed for 30 minutes to disperse the fiber. A body T was prepared.
The dispersion R was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Furthermore, the dispersion S was made on the sheet. Thereafter, the dispersion T was made on the sheet. The obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then pt so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. -An ethanol solution of a butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C with a Yankee dryer to obtain a separator of the present invention.
The obtained separator had a thermosetting resin in a semi-cured state or a cured state, physical properties were a density of 0.39 g / cm ³ , a porosity of 73%, and a thickness of the separator of 37 μm.

A fiber made of polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm, a fiber made of wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm, a fiber diameter of 0.5 μm, and a fiber Fibers made of solvent-spun cellulose fibrillated to a length of 1 mm are charged into a pulper at a concentration of 0.05% by mass in ion exchange water at a mass ratio of 25:60:15, respectively, and dispersed for 30 minutes. Was made.
The dispersion U is supplied to both the first flow box 14 and the second flow box 15 in the multi-tank inclined wet paper machine shown in FIG. Shed from. Thus, after making the wet sheet | seat which laminated | stacked the fiber layer of the same fiber composition one by one and drying at 130 degreeC with a Yankee dryer, the application quantity after drying is 20 mass with respect to 100 mass parts of dry fiber. An ethanol solution of pt-butylphenol type resol phenol resin was sprayed and impregnated so as to be part, and dried at 150 ° C. with a Yankee dryer to obtain a separator of the present invention having no pinholes.
The obtained separator had a thermosetting resin in a semi-cured or cured state, physical properties were a density of 0.46 g / cm ³ , a porosity of 70%, and a thickness of the separator of 21 μm.

A fiber made of polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm was put into a pulper at a concentration of 0.05% by mass in ion-exchanged water and dispersed for 30 minutes to prepare dispersion V. A fiber made of wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm and a fiber made of solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm were each 80: Dispersion W was prepared by charging the ion exchange water at a mass ratio of 20 into the pulper at a concentration of 0.05 mass% and dispersing for 30 minutes.
The dispersion V was supplied to the first flow box 14 of the multi-tank inclined wet paper machine in FIG. 1, and the dispersion W was supplied to the second flow box 15. Next, the papermaking net 10 was run, and the dispersion was poured out from each flow box to the inclined running unit 13. Thus, after making the wet sheet | seat which laminated | stacked the fiber layer from which a fiber kind differs one by one and drying at 130 degreeC with a Yankee dryer, the coating amount after drying is 20 mass with respect to 100 mass parts of dry fiber. Sprayed with an ethanol solution of pt-butylphenol type resol phenol resin so as to be part, and dried at 150 ° C. with a Yankee dryer, so that there are no pinholes, and the separators of the present invention having different fiber types on the front and back sides Got.
The obtained separator had a thermosetting resin in a semi-cured state or a cured state, physical properties were a density of 0.47 g / cm ³ , a porosity of 69%, and a thickness of the separator of 20 μm.

(Comparative Example 1)
A polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm was put into a pulper at a concentration of 0.05% by mass in ion-exchanged water and dispersed for 30 minutes to prepare a fiber dispersion a. Next, a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm are in a mass ratio of 1: 1. The mixture was mixed at a ratio, and added to ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above and dispersed for 30 minutes to prepare a fiber dispersion b.
The dispersion a was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion b was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain a comparative separator.
Regarding the physical properties of the obtained separator for comparison, the density was 0.41 g / cm ³ , the porosity was 69%, and the thickness was 29 μm.

(Comparative Example 2)
A polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm was placed in a pulper at a concentration of 0.05% by mass in ion-exchanged water and dispersed for 30 minutes to prepare a fiber dispersion c. Next, a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm are in a mass ratio of 1: 1. The mixture was mixed at a ratio, and added to ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion d.
The dispersion c was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, a dispersion d was made on the sheet. Thereafter, the obtained wet sheet is taken out from the hand-drawing apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying becomes 1 part by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a comparative separator.
Regarding the physical properties of the obtained comparative separator, the density was 0.40 g / cm ³ , the porosity was 72%, and the thickness was 30 μm.

(Comparative Example 3)
A polyethylene terephthalate fiber having a fiber diameter of 2.5 μm and a fiber length of 6 mm was placed in a pulper at a concentration of 0.05 mass% in ion-exchanged water and dispersed for 30 minutes to prepare a fiber dispersion e. Next, a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 μm and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm are in a mass ratio of 1: 1. The mixture was mixed at a ratio, charged in ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion f.
The dispersion e was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion f was made on the sheet. After that, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying becomes 250 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a comparative separator.
The obtained separator had been turned into a film.

(Comparative Example 4)
Solvent-spun cellulose fibrillated to a fiber diameter of 0.5 μm and a fiber length of 1 mm was charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes to prepare a fiber dispersion g.
The dispersion g was made using a standard hand-making apparatus specified in JIS P8222 to obtain a wet paper sheet having a basis weight of 6 g / cm ² . Thereafter, the obtained wet sheet is taken out from the hand-making apparatus, dried at 130 ° C. with a Yankee dryer, and then dried so that the coating amount after drying is 20 parts by mass with respect to 100 parts by mass of the dry fiber. An ethanol solution of -t-butylphenol type resol phenol resin was sprayed and impregnated and dried at 150 ° C. with a Yankee dryer to obtain a comparative separator.
Regarding the physical properties of the comparative separator obtained, the density was 0.42 g / cm ³ , the porosity was 73%, and the thickness was 32 μm.

  The following evaluation was performed in the separators obtained in Examples 1 to 13 and Comparative Examples 1 to 4, and the characteristics as separators were evaluated. For each separator, the physical properties of thickness, density, and porosity are shown in Table 1.

<Assembly of electric double layer capacitor and evaluation of discharge capacity and voltage retention>
About the separator of Examples 1-13 and Comparative Examples 1, 2, and 4, the electric double layer capacitor was assembled using the electrode of a positive electrode and a negative electrode, and 100 pieces of each wound type cells were produced. In the production of the wound cell, an activated carbon electrode for electric double layer capacitor (made by Hosen Co., Ltd.) was used as the electrode. Moreover, what melt | dissolved the tetraethylammonium tetrafluoroborate (made by Kishida-Chemical Co., Ltd.) was used for the electrolyte solution in propylene carbonate so that it might become 1 mol / L.
About the produced wound cell, the initial discharge capacity, the discharge capacity after 2000 hours test, and the discharge capacity after 4000 hours test were measured with an LCR meter. Each cell was charged at 2.5 V after 2000 hours of testing, and then the electric circuit was opened and the holding voltage after 24 hours was examined. The test conditions were 80 ° C. and 2.5 V applied.
The obtained results are shown in Table 2.

  As is clear from the results in Table 2, it was confirmed that the electric double layer capacitor using the separator of the present invention maintained a sufficient discharge capacity even after the 80 ° C., 2.5 V voltage application test. On the other hand, the electric double layer capacitor using the separator of Comparative Example 4 had a very large decrease in discharge capacity and extremely poor characteristics.

<Comparison of tensile strength of separator in wet paper>
Using the separators of Examples 1 to 13 and Comparative Examples 1, 2, and 4, the tensile strength in the wet paper state was measured as follows. The separator was immersed in a solution of tetraethylammonium tetrafluoroborate (manufactured by Kishida Chemical Co., Ltd.) dissolved in propylene carbonate at 1 mol / L for 15 seconds, then taken out and left for 30 seconds in an environment at 25 ° C. The tensile strength of the latter separator was measured according to JIS C2111.
The obtained results are shown in Table 3.

As is clear from the results in Table 3, the separator of the present invention has improved tensile strength in the wet paper state and is effective for assembling an electricity storage device.
As is apparent from the results in Tables 2 and 3, the electric double layer capacitor using the separator of the present invention maintains a sufficient discharge capacity of 7.8 F or more even after a 4000 hour test at 80 ° C. and 2.5 V. In addition, a voltage of 2.26 V or higher was maintained, the tensile strength in the wet paper state was improved, and it was confirmed that the film had excellent performance. On the other hand, the electric double layer capacitor using the separator of Comparative Example 4 was significantly inferior because the discharge capacity was greatly reduced and the voltage holding performance was very poor. Moreover, the separators of Comparative Examples 1 and 2 were so low that the tensile strength in the wet paper state could not be measured.

10 Papermaking Net 11 Guide Roller 12 Guide Roller 13 Inclined Traveling Section 14 First Flow Box 15 Second Flow Box 16 Dispersion 17 Dispersion 18 Partition

Claims (7)

  A separator for an electricity storage device in which at least one layer is formed by laminating two or more fiber layers containing a synthetic fiber, and the at least one of the fiber layers contains a thermosetting resin and is impregnated and applied. A separator for an electricity storage device, wherein the curable resin is fused to be in a semi-cured state or a cured state, and a tensile strength in a wet paper state is 3 N / 15 mm or more.   The power storage device separator according to claim 1, wherein the thermosetting resin is made of at least one selected from a phenol resin and an epoxy resin.   The synthetic fiber is at least one selected from polyethylene terephthalate, polybutylene terephthalate, wholly aromatic polyamide, wholly aromatic polyester, semi-aromatic polyamide, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyethylene, polypropylene, aramid, and polyarylate. It is a seed | species or more, The separator for electrical storage devices of Claim 1 or 2 characterized by the above-mentioned.   4. The electricity storage device separator according to claim 1, wherein the synthetic fiber has a fiber diameter of 5 μm or less and a fiber length of 10 mm or less.   The separator for an electricity storage device according to any one of claims 1 to 4, wherein the fiber layer is formed by stacking on a papermaking net using an inclined wire paper machine having two or more heads. .   Using a multi-tank slanting wet paper machine capable of simultaneously forming a plurality of layers having a structure in which the lower part of the second flow box is located in the vicinity of the intersection of the floodline and the paper making net in the first flow box. The separator for an electricity storage device according to any one of claims 1 to 5, wherein the separator is made by overlapping and making a sheet on a papermaking net.   The power storage device separator according to any one of claims 1 to 6, wherein the power storage device is any one of a lithium ion secondary battery, a polymer lithium secondary battery, an electric double layer capacitor, and an aluminum electrolytic capacitor. .

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