JP4369656B2 - Electric double layer capacitor separator and electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for electric double layer capacitor which can be converted to an electric double layer capacitor with low resistance, and to provide the electric double layer capacitor. <P>SOLUTION: The separator for electric double layer capacitor is formed of a nonwoven fabric including a porous fiber having holes on a surface. The other separator for electric double layer capacitor is formed of a nonwoven fabric including a powder supporting fiber supporting powder on a fiber surface of a host fiber. In the separator for electric double layer capacitor, it is desirable that thickness is not more than 30&mu;m and a percentage of voids is 50 to 80%. In the electric double layer capacitor, organic solution or sulfuric acid using the separator is set to be an electrolyte. <P>COPYRIGHT: (C)2004,JPO

Description

【００８７】
この表１から明らかなように、本発明のセパレータは抵抗値が２Ωよりも低いイオン透過性の優れるものであった。なお、本発明のセパレータは厚さが２５μｍと薄いものであったが、短絡を発生させることなく抵抗値を測定できるものであった。更に、本発明のセパレータを使用してコインセル型のキャパシタを作製する際にセパレータが破断するなどの問題が発生せず、強度的にも十分なセパレータであった。
【００８８】
【発明の効果】
本発明の電気二重層キャパシタ用セパレータは、表面積が広く、電解液の保持性に優れ、電解液の保持率が高いため、電気二重層キャパシタの抵抗を低くすることができるものである。
【００８９】
本発明の電気二重層キャパシタは抵抗の低いものであることができる。
【図面の簡単な説明】
【図１】（ａ） 本発明の繊維表面のみに孔を有する多孔繊維の一部拡大断面図
（ｂ） 本発明の繊維表面のみに孔を有する別の多孔繊維の一部拡大断面図
【符号の説明】
１０ 多孔繊維
１１ 孔
１２ 繊維表面
１３ 開孔部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric double layer capacitor separator and an electric double layer capacitor.
[0002]
[Prior art]
Electric double layer capacitors have a relatively large capacity, and have a long service life and quick charge / discharge. Therefore, in addition to conventional applications such as power supply smoothing and noise absorption, personal computer memory backup power supplies and secondary power supplies In recent years, it has been used as a secondary battery for electric vehicles.
[0003]
This electric double layer capacitor has a structure in which a pair of electrodes are immersed in an ionic solution. When a voltage is applied to the electric double layer capacitor, ions having the opposite sign to the electrode are distributed in the vicinity of the electrode to form an ion layer, while charges having the opposite sign to the ion are accumulated inside the electrode. Next, when a load is connected between the electrodes, the charges in the electrodes are discharged, and at the same time, ions distributed in the vicinity of the electrodes are separated from the vicinity of the electrodes and return to the neutralized state.
[0004]
In such an electric double layer capacitor, if a pair of electrodes come into contact with each other, it becomes difficult to form an ion layer in the vicinity of the electrodes. Therefore, a separator is usually disposed between the pair of electrodes. . This separator needs to be excellent in ion permeability in addition to having the above-described short circuit prevention property between electrodes.
[0005]
As such an electric double layer capacitor having excellent ion permeability, the applicant of the present application “the electric double layer capacitor comprising a fiber sheet including a fiber having a fibril and a fine polyester fiber having a fineness of 0.45 dtex or less” (Patent Document) 1), and “a separator for an electric double layer capacitor having a thickness of 10 to 50 μm in which an oxygen-containing functional group is introduced into a fiber sheet containing 30 mass% or more of fine polyester fibers having a fineness of 0.45 dtex or less” (Patent Document 2) ) Was proposed. The electric double layer capacitor using these separators for electric double layer capacitors has a certain degree of ion permeability and low resistance, but in the market it is further excellent in ion permeability and low resistance. Capacitors have been desired.
[0006]
[Patent Document 1]
JP 2001-244150 A (Claims)
[Patent Document 2]
JP 2002-184653 A (Claims)
[0007]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems, and it is an object of the present invention to provide an electric double layer capacitor separator and an electric double layer capacitor which can be further reduced in electric double layer capacitor.
[0008]
[Means for Solving the Problems]
One electric double layer capacitor separator of the present invention (hereinafter referred to as “first separator”) The heated solid particles were brought into contact with the surface non-porous fibers and fixed by fusing or deforming the surface non-porous fibers, and then obtained by removing the solid particles. It consists of the nonwoven fabric which the said porous fiber fuse | fused including the porous fiber which has a hole on the surface. Since the first separator includes porous fibers, the porosity is high and the electrolyte retention rate is high, so that the resistance of the electric double layer capacitor can be lowered.
[0009]
If the pores of the porous fiber are formed only on the fiber surface, the entire surface of the pore can be used, and the familiarity with the electrolytic solution is good, so that the resistance of the separator for the electric double layer capacitor can be lowered. Since the mechanical strength of the porous fiber is excellent, the mechanical strength of the first separator is also excellent.
[0010]
When the average fiber diameter of the porous fibers is 7 μm or less, the thickness of the first separator can be reduced, the opening diameter can be made uniform even when the thickness is reduced, and the porosity is increased. Therefore, the insulating property is excellent and the resistance can be further reduced.
[0011]
Since it is composed of only the porous fibers, the porosity is particularly high and the retention rate of the electrolytic solution is particularly high. Therefore, the first separator can be an electric double layer capacitor having particularly low resistance.
[0012]
The porous fiber is preferably composed of a synthetic resin.
[0013]
Another separator for an electric double layer capacitor of the present invention (hereinafter referred to as “second separator”) The heated solid particles were brought into contact with the base fiber, and fixed and supported by fusion or deformation of the base fiber surface. Fiber surface of base fiber Powder It consists of the nonwoven fabric containing the powder-carrying fiber which carried the body. Since the second separator includes powder-carrying fibers, the second separator has a large surface area and excellent electrolyte retention, and thus the resistance of the electric double layer capacitor can be reduced.
[0014]
When the average fiber diameter of the base fiber is 7 μm or less, the thickness can be reduced, the opening diameter can be made uniform even when the thickness is reduced, and the surface area of the second separator is increased. Therefore, the insulation is excellent and the resistance can be further reduced.
[0015]
When the powder is made of an inorganic oxide, it is excellent in chemical stability and does not chemically react with the constituent members of the electric double layer capacitor, so that a stable electric double layer capacitor can be obtained.
[0016]
Since the second separator has a particularly large surface area and is particularly excellent in electrolytic solution retention when it is composed only of the powder-carrying fibers, the second separator can be an electric double layer capacitor with particularly low resistance. It is.
[0017]
The base fiber is preferably made of a synthetic resin.
[0018]
The separator for an electric double layer capacitor of the present invention (the first separator and the second separator, hereinafter referred to as both the first separator and the second separator when simply expressed as “separator”) has a thickness of 30 μm or less, and It is preferable that the porosity is 50 to 80%. With such a thickness and porosity, the separator can be an electric double layer capacitor having a low resistance and a high energy density per volume.
[0019]
An electric double layer capacitor (hereinafter referred to as “capacitor”) of the present invention includes the separator for an electric double layer capacitor. Therefore, the capacitor can have a low resistance and a high energy density per volume.
[0020]
The electrolytic solution constituting the capacitor can be either an organic solution or a sulfuric acid solution.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Since the first separator of the present invention contains porous fibers, the porosity is high and the electrolyte retention rate is high, so that the resistance of the electric double layer capacitor can be lowered. In addition, since the porous fiber has a large surface area, even if the basis weight is reduced and the thickness is reduced, the electrolyte retainability is excellent, and thus the resistance of the electric double layer capacitor can be reduced.
[0022]
The 1st separator of this invention is comprised from the nonwoven fabric containing the porous fiber which has a hole on the surface. In the porous fiber of the present invention, holes may be formed only on the fiber surface, or holes may be formed in the fiber in addition to the fiber surface. When holes are formed only on the fiber surface as in the former, not only the surface of the holes can be used, but also the resistance to the porous fiber is improved because it is familiar with the electrolyte, and the mechanical strength of the porous fiber is also reduced. It is excellent because it is excellent and the mechanical strength of the first separator is also excellent.
[0023]
The former “having holes formed only on the surface of the fiber” means that only holes that are visible from the surface (for example, an image obtained by photographing the surface of the fiber with a scanning electron microscope) are formed on the surface of the porous fiber. Means that As is apparent from FIGS. 1 (a) and 1 (b), which are partial enlarged cross-sectional views of the porous fiber having pores only on the fiber surface, when the holes 11 are observed from the surface side of the porous fiber 10, The deepest part of the hole 11 in the thickness direction can be confirmed from the opening part 13 of the hole 11. From another viewpoint, the hole 11 has a shape in which the fiber surface 12 is depressed or a part of the fiber surface 12 is hollowed out.
[0024]
The porous fiber of the present invention need not have pores uniformly on the entire fiber surface. For example, although the surface wall side surface of the first separator of the porous fiber has a large number of holes, the side wall side surface of the first separator of the porous fiber may have a smaller number of holes than the surface wall side surface. . Such a porous fiber is easily formed, for example, when a non-porous fiber is used to form a nonwoven fabric and then the porous fiber is formed by the method described below.
[0025]
The porous fiber of the present invention is preferably composed of a synthetic resin. Examples of the synthetic resin include a polyolefin resin, a polyester resin, and a polyamide resin, and the porous fiber can be composed of one or more kinds of synthetic resins. In the case of being composed of two or more types of synthetic resins, there can be mentioned composite fibers in which two or more types of synthetic resins having different melting points are combined, such as copolymer polyester / polyester, copolymer polypropylene / polypropylene, polypropylene / Mention may be made of composite fibers made of a combination of resins such as polyamide, polyethylene / polypropylene, polypropylene / polyester, or polyethylene / polyester.
[0026]
Further, the porous fiber of the present invention is preferably composed of synthetic resin as a whole, but fibers whose core part does not have a melting point and has a decomposition temperature, such as rayon fiber, acetate fiber, wool fiber, etc. Alternatively, it may be a fiber made of a fiber such as carbon fiber, and a sheath part made of a synthetic resin. In the porous fiber of the present invention, the core portion may be a fiber made of an inorganic fiber such as glass fiber, ceramic fiber, or metal fiber, and the sheath portion may be a fiber made of a synthetic resin. These porous fibers can be obtained, for example, by forming a sheath portion by coating or the like and then making it porous.
[0027]
The average fiber diameter of the porous fiber of the present invention is preferably 7 μm or less. If the average fiber diameter is 7 μm or less, even if the thickness is small, the texture is uniform, the opening diameter is small, the insulation is excellent, and the first separator can be easily prevented from short-circuiting. More preferably, it is 6 μm or less. In addition, although the minimum of the average fiber diameter of a porous fiber is not specifically limited, about 1 micrometer is suitable.
[0028]
The “fiber diameter” of the present invention refers to the diameter when the cross-sectional shape of the fiber is a circle, and when it is not a circle, it refers to the diameter of a circle having the same area as the cross-sectional area of the fiber, and the “average fiber diameter” The number average value of the fiber diameters by sampling from 500 or more arbitrary positions of the fiber. In addition, in the case of a commercially available fiber, when the number average fiber diameter is clearly shown in catalogs or specifications, the value may be used as the average fiber diameter of the fiber. Moreover, when the fineness is clearly shown in the catalog or specification, a value converted from the fineness based on the specific gravity may be used as the average fiber diameter.
[0029]
The “fiber length” of the porous fiber of the present invention is preferably 20 mm or less and more preferably 10 mm or less so that the dispersibility of the porous fiber is excellent and the insulation between the electrodes is excellent. In addition, although the minimum of the fiber length of a porous fiber is not specifically limited, about 1 mm is suitable. The “fiber length” in the present invention refers to a value obtained by JIS L 1015 (chemical fiber staple test method) B method (corrected staple diagram method).
[0030]
The cross-sectional shape of the porous fiber of the present invention is not necessarily circular, and may be non-circular (for example, a polygon such as a triangle, an ellipse, an ellipse, an alphabet such as a T shape, etc.). Moreover, it is preferable that the porous fiber is not fibrillated so as to be a first separator having a sufficient porosity and a high electrolyte retention rate.
[0031]
The first separator of the present invention is composed of a nonwoven fabric containing porous fibers as described above, but the greater the content of porous fibers, the greater the surface area, the higher the porosity, and the higher the electrolyte retention and retention. Since the resistance of the capacitor can be lowered and the wettability of the first separator can be improved, the porous fiber preferably accounts for 50 mass% or more of the entire first separator, and more than 60 mass%. More preferably 70 mass% or more, still more preferably 90 mass% or more, and most preferably 100 mass% porous fiber. Examples of fibers other than porous fibers include fibers that do not have any holes.
[0032]
Such a 1st separator of this invention can be manufactured as follows, for example.
[0033]
First, a porous fiber is prepared. For example, a porous fiber in which pores are formed in the inside of the fiber in addition to the fiber surface is different from a resin constituting the porous fiber and a resin different from the resin constituting the porous fiber (dissimilar resin) in a certain solvent. (2) A method for producing by foaming the foaming agent after mixing and spinning the resin constituting the porous fiber and the foaming agent. 3) Polyolefin or a polymer in which a hydrophilic polymer is uniformly blended with polyolefin is melt-spun using a normal fiber spinning die to obtain a crystalline unstretched yarn, and then stretched as it is to make it porous or polymer It can be produced by a stretched hole method in which it is annealed in a constant length or relaxed state at a melting point or lower, preferably 120 ° C. or lower, and then stretched to make it porous.
[0034]
On the other hand, a porous fiber having pores formed only on the fiber surface can be produced as follows. First, a surface non-porous fiber is prepared. The surface non-porous fiber is a fiber having at least a thermoplastic resin on the fiber surface and no pores on the fiber surface, and a porous fiber having pores formed only on the fiber surface by means described later (hereinafter referred to as “surface porous fiber”). It becomes. The area occupied by the surface of the thermoplastic resin in the surface non-porous fiber is not particularly limited, but the larger the surface area of the surface porous fiber, the larger the surface area of the surface porous fiber. It preferably occupies 50% or more of the surface area, more preferably occupies 60% or more, further preferably occupies 70% or more, more preferably occupies 90% or more, 100 Most preferably, it is made of% thermoplastic resin.
[0035]
As this surface non-porous fiber, for example, a synthetic fiber obtained by a melt spinning method, which is a conventional fiber production method, a fiber obtained by a spunbond method, a melt blow method, a flash spinning method, or the like, which is a conventional nonwoven fabric production method, or , Obtained by dissolving and removing sea components with high-temperature, strong alkaline water from a core part made of natural or inorganic fibers and a sheath part made of thermoplastic resin, and a sea part made of polyester and an island part made of polyolefin. The polyolefin fiber which consists of the produced island part can be mentioned.
[0036]
Next, solid particles are fixed to the surface of the surface non-porous fiber as described above to form solid particle fixed fibers.
[0037]
As long as the solid particles are solid particles having a melting point or decomposition temperature higher than the melting point of the thermoplastic resin constituting the surface of the surface non-porous fiber and can be removed after fixing, the solid particles are either inorganic or organic. There can also be. As such solid particles, for example, solid particles that dissolve in a solvent (for example, water, aqueous solution, acid, alkaline aqueous solution, etc.) that does not substantially dissolve the thermoplastic resin constituting the surface of the surface non-porous fiber ( For example, there are water-soluble inorganic materials, metal salts, water-soluble resins, metals, and the like. Such solid particles can be extracted and removed using the solvent. In addition to extraction and removal, solid particles that can be removed by vibration, ultrasonic cleaning, fiber shrinkage, or the like may be used. More specifically, sodium chloride, calcium chloride, calcium carbonate, other various metal salts, water-soluble resins, metal particles, ceramics, zeolite, and other various inorganic materials can be exemplified.
[0038]
The melting point or decomposition temperature of the solid particles constitutes the surface non-porous fiber surface such that the heat of the heated solid particles melts or deforms the surface of the surface non-porous fiber and the solid particles are fixed to the fiber surface. Among the thermoplastic resins to be used, it is necessary to be higher than the melting point of the resin having the lowest melting point. In the present invention, “melting point” refers to a value obtained by a differential scanning calorimetry (DSC) method, and “decomposition temperature” refers to a value obtained by a thermogravimetric analysis (TGA) method.
[0039]
The average particle size of the solid particles is not particularly limited, but the average particle size of the solid particles is 0.01 to 5 μm so that the retention rate of the electrolytic solution can be increased and the electrolytic solution can be effectively retained. Preferably, it is 0.02 to 2 μm. The average particle diameter of the solid particles in the present invention refers to the number average particle diameter of the solid particles. The “number average particle size” is calculated from the particle size of the solid particles after measuring the particle size of any 500 or more solid particles by photographing the solid particles with a scanning electron microscope or the like. The arithmetic average value. At this time, if the solid particles are not spherical, the diameter of the circumscribed circle of each solid particle that can be confirmed in the image of the captured solid particle is regarded as the particle diameter of each particle. In the case of commercially available solid particles, when the number average particle diameter is clearly shown in catalogs or specifications, the value may be used as the average particle diameter of the solid particles.
[0040]
As a method for fixing solid particles to the surface of the surface non-porous fiber, for example, the solid particles as described above are not less than the melting point of the thermoplastic resin constituting the surface of the surface non-porous fiber and less than the melting point or decomposition temperature of the solid particles. There is a method in which solid particles heated at a temperature in the range of maintaining the shape as a solid up to the above temperature are brought into contact with the surface non-porous fiber and fixed by fusing or deformation of the surface non-porous fiber surface. Also, a method of fixing the surface non-porous fiber surface by fusing or deformation by bringing the surface non-porous fiber surface into contact with the solid particles as described above while being heated to a temperature higher than the melting point of the thermoplastic resin. But it ’s okay. The former method is more preferable because solid particles are not buried and holes can be reliably formed.
[0041]
The method for contacting the surface non-porous fibers and the solid particles is not particularly limited as long as the solid particles can be fixed to the surface non-porous fibers. For example, (1) containing heated solid particles A method of spraying an air current on the surface non-porous fiber, (2) a method of allowing the heated solid particles to spontaneously fall on the surface non-porous fiber, and (3) shaking a container charged with the heated solid particles and the surface non-porous fiber. (4) a method of immersing surface nonporous fibers in heated solid particles, or (5) a method of exposing surface nonporous fibers in a fluidized bed of heated solid particles.
[0042]
Next, the solid particles of the solid particle fixed fibers are removed to obtain surface porous fibers.
[0043]
The method for removing the solid particles of the solid particle fixed fiber is not particularly limited as long as the solid particles of the solid particle fixed fiber can be removed. For example, the thermoplastic resin constituting the surface non-porous fiber surface is substantially made. There is a method in which solid particles dissolved in a solvent that does not dissolve are removed using the solvent. For example, the solid particles can be removed using a water-soluble inorganic substance, metal salt, water-soluble resin, metal, or the like as the solid particles, and water, an aqueous solution, an acid, an alkaline aqueous solution, or the like as the solvent. In particular, a method of using a metal salt or a water-soluble resin as the solid particles and removing it with water is preferable because the production cost is low. Examples of such metal salts include sodium chloride, calcium chloride, ammonium chloride, sodium bicarbonate, potassium bicarbonate, and the like. Examples of such water-soluble resins include polyvinyl alcohol, polyethylene glycol, and polyacrylic acid.
[0044]
Other methods for removing the solid particles of the solid particle fixed fiber include, for example, a method in which the solid particle fixed fiber is vibrated to separate the solid particle, a method in which the solid particle fixed fiber is separated by ultrasonic cleaning, or a solid Examples include a method in which the solid particles are exfoliated by extending or shrinking the particle fixing fibers.
[0045]
The surface porous fiber manufactured by such a manufacturing method has a large surface area having pores only on the fiber surface while maintaining various physical properties such as fiber strength inherent to the surface nonporous fiber. Moreover, since the hole according to the shape and size of the solid particle can be formed, the hole suitable for the capacitor to be applied can be formed by appropriately selecting the solid particle.
[0046]
Next, a nonwoven fabric is formed by a conventional method using the porous fibers as described above. In addition, you may form a nonwoven fabric not only with a porous fiber but with the fiber etc. which are not equipped with the hole at all.
[0047]
More specifically, the fiber web is formed by a dry method such as a card method or an air array method, or a wet method. In addition, since the fiber web obtained by the wet method has small variations in the basis weight and thickness, a first separator having more excellent insulation can be obtained. In particular, when a plurality of layers of fiber webs formed by a wet process are laminated in a wet state, a capacitor having a large energy density per unit volume can be manufactured because the opening diameter is uniform and the insulation is good even when the basis weight is small. Since it can be set as 1 separator, it is suitable.
[0048]
Next, the fiber web may be used as it is as a non-woven fabric, but it is preferable to increase the mechanical strength of the first separator by performing an entanglement treatment and / or a heat treatment. Examples of the entanglement process include water entanglement process and entanglement process by needle punch. On the other hand, the heat treatment can increase the mechanical strength of the first separator by fusing or fixing the contact points of the fiber web constituent fibers. In addition, it is necessary to adjust heat processing temperature suitably so that the hole of a porous fiber may not be block | closed. This heat treatment temperature can be appropriately determined experimentally.
[0049]
As mentioned above, although the method to manufacture a nonwoven fabric using a porous fiber was demonstrated, the 1st separator of this invention is not limited to this method, For example, a nonwoven fabric using a nonporous fiber (for example, surface nonporous fiber) After forming the non-porous fiber, the non-woven fiber containing the porous fiber can be made porous, that is, the first separator. According to this method, even if the non-porous fiber is fused to increase the mechanical strength of the first separator, the porous fiber is formed after the fusion, so that the electrolyte solution is reduced without reducing the surface area of the porous fiber. This is preferable because a first separator that can form a capacitor with excellent retention, high electrolyte retention, and low resistance can be manufactured.
[0050]
The second separator, which is another separator of the present invention, is made of a nonwoven fabric containing powder-carrying fibers in which powder is carried on the fiber surface of the base fiber. Therefore, the inclusion of powder-carrying fibers has a wide surface area and excellent electrolyte retention, so that the ion permeability is good, the resistance is low, and the energy density per unit volume is high. Can be manufactured. Further, since the powder-carrying fiber has a large surface area, even if the basis weight is reduced and the thickness is reduced, the electrolytic solution retainability is excellent, so that the resistance of the electric double layer capacitor can be further reduced. Furthermore, since the wettability with the electrolytic solution can be improved depending on the type of powder, the resistance can be further reduced.
[0051]
The powder-carrying fiber of the present invention does not need to carry the powder uniformly over the entire surface of the base fiber. For example, although a large number of powders are supported on the surface of the second separator of the powder-carrying fiber, the surface of the side wall of the second separator of the powder-carrying fiber is more powdery than the surface of the side wall. It may be in a state with a small number. Such a powder-carrying fiber is easily formed when, for example, a powder-carrying fiber is formed by a method described later after forming a nonwoven fabric using the base fiber.
[0052]
The base fiber constituting the powder-carrying fiber of the present invention is preferably composed of a synthetic resin similar to the porous fiber.
[0053]
The average fiber diameter of the base fiber of the present invention is preferably 7 μm or less. If the average fiber diameter of the base fiber is 7 μm or less, even if the thickness is thin, the texture is uniform, the opening diameter is small, the insulation is excellent, and it is easy to make a second separator that can prevent a short circuit. More preferably, it is 6 μm or less. In addition, although the minimum of the average fiber diameter of a base fiber is not specifically limited, About 1 micrometer is suitable. The “fiber length” of the base fiber is preferably 20 mm or less and more preferably 10 mm or less so that the dispersibility of the powder-carrying fiber is excellent and the insulation between the electrodes is excellent. In addition, although the minimum of the fiber length of a base fiber is not specifically limited, about 1 mm is suitable.
[0054]
The cross-sectional shape of the base fiber of the present invention does not need to be circular, and may be non-circular (for example, a polygon such as a triangle, an ellipse, an ellipse, an alphabet such as a T shape, etc.). Moreover, it is preferable that the base fiber is not fibrillated so as to be the second separator having a high retention rate of the electrolytic solution.
[0055]
The powder-supporting fiber constituting the second separator of the present invention is a fiber in which powder is supported on the surface of the base fiber as described above, but the powder can be either inorganic or organic. Examples of such solid particles include inorganic oxides, metal salts, and thermosetting resins. More specifically, examples of the inorganic oxide include titanium oxide, alumina, diatomaceous earth, hydroxyapatite, zeolite, kaolin, and silicon oxide. Examples of the metal salt include sodium chloride, calcium chloride, and calcium carbonate. As the thermosetting resin, a phenol resin, a melamine resin, an epoxy resin, and the like can be given. In addition, an aramid resin and the like can be given. Among these, inorganic oxides are suitable because they are excellent in chemical stability and do not chemically react with capacitor components.
[0056]
The average particle size of the powder is not particularly limited, but the average particle size of the powder is 0.01 to 5 μm so that the retention of the electrolytic solution is excellent and the retention rate of the electrolytic solution can be increased. It is preferable that it is 0.02 to 2 μm. The amount of the base fiber supported by the powder is not particularly limited because it varies depending on the particle size of the powder, but it is preferably an amount that covers the entire surface of the base fiber. This amount can be appropriately determined by repeating the experiment.
[0057]
The second separator of the present invention is made of a nonwoven fabric containing powder-carrying fibers as described above. The greater the content of powder-carrying fibers, the larger the surface area and the higher the electrolyte retention, and the capacitor Therefore, it is preferable that the powder-supporting fiber occupies 50 mass% or more of the entire second separator, and occupies 60 mass% or more. More preferably, it occupies 70 mass% or more, more preferably occupies 90 mass% or more, and most preferably consists of 100 mass% powder-supporting fibers. Examples of fibers other than powder-carrying fibers include fibers that do not carry powder.
[0058]
Such a 2nd separator of this invention can be manufactured as follows, for example.
[0059]
First, a base fiber is prepared. As the base fiber, a fiber exactly the same as the surface non-porous fiber that can be used at the time of manufacturing the first separator can be used.
[0060]
Next, solid particles are supported (for example, fixed) on the surface of the base fiber to form powder-supported fibers. As a method of supporting the solid particles, for example, the solid particles as described above may be used as solids up to a temperature not lower than the melting point of the thermoplastic resin constituting the surface of the base fiber and lower than the melting point or decomposition temperature of the solid particles. There is a method in which solid particles heated at a temperature in a range that maintains the shape are brought into contact with the base fiber, and are fixed and supported by fusion or deformation of the surface of the base fiber. In addition, a method in which the base fiber is heated to a temperature equal to or higher than the melting point of the thermoplastic resin constituting the surface of the base fiber, is brought into contact with the solid particles as described above, and is fixed and supported by fusion or deformation of the base fiber. But it ’s okay. The former carrying method is more preferable because the solid particles are not buried and the surface area can be reliably increased. In the case of the former supporting method, the melting point or decomposition temperature of the solid particles is such that the surface of the base fiber is fixed so that the surface of the base fiber is melted or deformed by the heat of the heated solid particles and the solid particles are fixed to the fiber surface. It is necessary to be higher than the melting point of the resin having the lowest melting point among the thermoplastic resins constituting the resin.
[0061]
The contact method between the base fiber and the solid particles can be brought into contact in exactly the same manner as the method of fixing the solid particles to the surface non-porous fiber when the first separator is manufactured.
[0062]
The powder-carrying fiber manufactured by such a manufacturing method has a large surface area while maintaining various physical properties such as fiber strength inherent to the base fiber. In addition, by appropriately selecting solid particles, the wettability with the electrolytic solution can be improved, so that the resistance can be further reduced.
[0063]
Next, a nonwoven fabric, that is, a second separator can be produced by the same method as that for the first separator, using the powder-supporting fiber as described above, and optionally using a fiber not supporting the powder. Also in the case of manufacturing the second separator, it is preferable to form a fiber web by laminating a plurality of layers of fiber webs formed by a wet method in a wet state.
[0064]
As in the first separator manufacturing method, after forming the nonwoven fabric using the base fiber, powder is supported on the base fiber to form the powder-supporting fiber. Two separators can also be used. This method is preferable because the powder-supporting fiber powder does not fall off when forming the nonwoven fabric, and the characteristics of the powder can be used effectively.
[0065]
The above-described separators (first separator and second separator) of the present invention preferably have a thickness of 30 μm or less and a porosity of 50 to 80%. This is because such a thickness and porosity can provide a separator capable of producing an electric double layer capacitor having low resistance and high energy density per volume. If the thickness is 30 μm or less, the resistance is low, and it is easy to increase the energy density per unit volume, and therefore it is more preferably 28 μm or less. The lower limit of the thickness is not particularly limited, but it is preferably 10 μm or more so that the insulating property is excellent and the adverse effects due to the voltage drop due to the fine short circuit and the tunnel current are less likely to occur. Further, the porosity is preferably 40% or more, and more preferably 45% or more so that the amount of retained electrolyte is large, the ion permeability is excellent, and as a result, the resistance is low. On the other hand, it is preferably 70% or less, more preferably 65% or less so that the insulation and mechanical strength (particularly tensile strength) are excellent. In the present invention, “thickness” refers to a value measured with a micrometer (value at a load of 500 g), and “porosity (P)” refers to a value obtained by the following equation.
Porosity (P) = {1−W / (T × d)} × 100
Here, W is the basis weight of the separator (g / m ² ), T means the thickness (μm) of the separator, d is the density (g / cm) of the separator constituting resin (for example, fiber) ^Three ). In addition, when two or more types of constituent resins are present, the density of the constituent resins refers to the mass average of the constituent resins. For example, density d ₁ Resin A is a (mass%) and density d ₂ When resin B is present in b (mass%), the density (d) of the constituent resin is a value obtained by the following equation.
Density (d) = d ₁ × a / 100 + d ₂ × b / 100
[0066]
The capacitor of the present invention is provided with the separator (the first separator or the second separator) as described above, and may be exactly the same as the conventional capacitor except that the above-described separator is used. it can.
[0067]
For example, activated carbon, a conductive filler (such as carbon black or acetylene black) and a pair of electrode materials molded after kneading a binder are insulated by the separator of the present invention. A current collector such as an aluminum foil is in close contact with the side that does not come into contact with the separator, and the entire structure is housed in a case or an aluminum laminate pack. Although the separator holds the electrolytic solution, the electrolytic solution can be held by either an organic solvent or a sulfuric acid solution.
[0068]
Examples of the present invention will be described below, but the present invention is not limited to the following examples.
[0069]
【Example】
(Example 1)
Polyethylene terephthalate (melting point: 260 ° C., softening temperature: 253 ° C.) (fineness: 0.11 dtex, fiber length: 5 mm, average fiber diameter: 3 μm, cross-sectional shape: circular, not fibrillated) and polyethylene Prepared with unstretched fibers (fineness: 0.22 dtex, fiber length: 3 mm, average fiber diameter: 5 μm, cross-sectional shape: circular, not fibrillated) made of terephthalate (melting point: 260 ° C., softening temperature: 231 ° C.) did.
[0070]
Next, a fiber web was formed from a slurry in which 70 mass% of the ultrafine fibers and 30 mass% of unstretched fibers were dispersed, and then three sheets were laminated in a wet state to form a laminated fiber web.
[0071]
Next, the laminated fiber web is heat-treated with a drier set at a temperature of 180 ° C., so that unstretched fibers are pressure-bonded, and the basis weight is 15 g / cm. ² Thus, a pressure-bonded nonwoven fabric having a thickness of 40 μm was manufactured.
[0072]
Next, a base material for a separator (thickness: 25 μm, porosity: 57%) was produced by passing this pressure-bonded nonwoven fabric between a pair of thermal calender rolls set at a temperature of 180 ° C.
[0073]
Next, sodium chloride (melting point: 800 ° C., manufactured by Wako Pure Chemical Industries, Ltd.) was pulverized with a pulverizer to obtain sodium chloride fine particles having an average primary particle size of 0.5 μm.
[0074]
Next, 100 g of this sodium chloride fine particle was placed in a petri dish having a diameter of 15 cm, heated in a dryer set at a temperature of 300 ° C. for 30 minutes or more with the lid on, and immediately after the petri dish was taken out of the dryer, the separator substrate (10 cm square) was put in a petri dish, and the petri dish was quickly vibrated for 30 seconds as it was to fix sodium chloride fine particles to the entire separator base material, thereby manufacturing a separator base material to which the sodium chloride fine particles were fixed.
[0075]
Thereafter, the separator base material to which the sodium chloride fine particles are fixed is washed with water to remove the sodium chloride fine particles, and the first separator (thickness: 25 μm, porosity: consisting of only porous fibers having pores formed only on the surface) 58%).
[0076]
(Example 2)
A separator base material (thickness: 25 μm, porosity: 57%) was produced in exactly the same manner as in Example 1.
[0077]
Next, silicon dioxide (melting point: 1700 ° C., manufactured by Mitsubishi Materials Corporation) was pulverized with a pulverizer to obtain silicon dioxide fine particles having an average primary particle size of 0.5 μm.
[0078]
Next, 100 g of this silicon dioxide fine particle was placed in a petri dish having a diameter of 15 cm, heated in a dryer set at a temperature of 300 ° C. for 30 minutes or more with the lid on, and immediately after the petri dish was taken out of the dryer, (10 cm square) is put in a petri dish, and the petri dish is vibrated quickly for 30 seconds, and the silicon dioxide fine particles are fixedly supported on the whole base material for the separator, and the second separator is composed only of powder-carrying fibers carrying the silicon dioxide fine particles. (Thickness: 25 μm, porosity: 56%) was produced.
[0079]
(Comparative Example 1)
A fibril fiber made of para aromatic polyamide (registered trademark: Kevlar, manufactured by DuPont, carbonization temperature: 500 ° C. or higher) and a fine fiber made of polyethylene terephthalate having a fineness of 0.11 dtex and a fiber length of 3 mm (melting point: 260 ℃, softening temperature: 253 ℃, cross-sectional shape: circular).
[0080]
Next, after forming a slurry containing fibril fibers and fine fibers at a mass ratio of 1: 1, a fiber web was formed by an inclined wire type short net system.
[0081]
Next, this fiber web was dried by a hot air circulation drier set at a temperature of 120 ° C.
[0082]
Next, this dried fiber web was pressed (linear pressure: 4.7 kN / cm) with a pair of thermal calender rolls set at a temperature of 220 ° C., and the basis weight was 30 g / m. ² Separator for comparison (thickness: 36 μm, porosity: 40%).
[0083]
(Comparative Example 2)
A separator base material (thickness: 25 μm, porosity: 57%) produced in exactly the same manner as in Example 1 was used as a comparative separator.
[0084]
(Measurement of resistance value)
As an electrode, granular activated carbon, carbon black and polytetrafluoroethylene were mixed and kneaded, an aluminum foil as a collector, separators of Examples 1 and 2 and Comparative Examples 1 and 2 as a separator, and tetraethylammonium tetra as an electrolyte A solution prepared by dissolving fluoroborate in propylene carbonate (organic system) and 30% by weight sulfuric acid (aqueous system) were prepared.
[0085]
Next, after producing a coin cell type capacitor for each separator from these materials, their internal resistance was measured. These results were as shown in Table 1.
[0086]
[Table 1]

[0087]
As apparent from Table 1, the separator of the present invention was excellent in ion permeability having a resistance value lower than 2Ω. Although the separator of the present invention was as thin as 25 μm, the resistance value could be measured without causing a short circuit. Furthermore, when producing a coin cell type capacitor using the separator of the present invention, the separator was not broken and the strength was sufficient.
[0088]
【The invention's effect】
Since the separator for an electric double layer capacitor of the present invention has a large surface area, excellent electrolytic solution retention, and high electrolytic solution retention, the resistance of the electric double layer capacitor can be reduced.
[0089]
The electric double layer capacitor of the present invention can have a low resistance.
[Brief description of the drawings]
FIG. 1 (a) is a partially enlarged cross-sectional view of a porous fiber having pores only on the fiber surface of the present invention.
(B) Partially enlarged sectional view of another porous fiber having pores only on the fiber surface of the present invention
[Explanation of symbols]
10 Porous fiber
11 holes
12 Fiber surface
13 Opening

Claims (14)

The porous material comprising porous fibers having pores on the surface obtained by bringing the heated solid particles into contact with the surface non-porous fibers and fixing them by fusing or deforming the surface non-porous fibers, and then removing the solid particles. A separator for an electric double layer capacitor, comprising a nonwoven fabric in which fibers are fused.   2. The separator for an electric double layer capacitor according to claim 1, wherein the pores of the porous fiber are formed only on the fiber surface.   The separator for an electric double layer capacitor according to claim 1 or 2, wherein an average fiber diameter of the porous fibers is 7 µm or less.   The separator for an electric double layer capacitor according to any one of claims 1 to 3, wherein the separator is composed of only the porous fiber.   The separator for an electric double layer capacitor according to any one of claims 1 to 4, wherein the porous fiber is made of a synthetic resin. The heated solid particles are contacted with the matrix fibers, by fixed by fusion or deformation of the matrix fiber surface was supported, characterized in that it consists of a nonwoven fabric comprising a powder-carrying fibers carrying the powder on the fiber surface of the matrix fibers An electrical double layer capacitor separator.   The separator for an electric double layer capacitor according to claim 6, wherein an average fiber diameter of the base fiber is 7 μm or less.   The separator for an electric double layer capacitor according to claim 6 or 7, wherein the powder is made of an inorganic oxide.   The separator for an electric double layer capacitor according to any one of claims 6 to 8, wherein the separator is only composed of the powder-carrying fibers.   The separator for an electric double layer capacitor according to any one of claims 6 to 9, wherein the base fiber is made of a synthetic resin.   The separator for an electric double layer capacitor according to any one of claims 1 to 10, wherein the separator has a thickness of 30 µm or less and a porosity of 50 to 80%.   The electrical double layer capacitor provided with the separator for electrical double layer capacitors in any one of Claims 1-11.   The electric double layer capacitor according to claim 12, wherein the electrolytic solution is an organic solution.   13. The electric double layer capacitor according to claim 12, wherein the electrolytic solution is a sulfuric acid solution.

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