JP2004153259A - Electric double-layer capacitor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor and a method of manufacturing the same which reduce the internal resistance of the electric double-layer capacitor, increase capacitance density, and keep satisfactory productivity. <P>SOLUTION: Concave-convex sections 45, 47 are formed on a worked electrode 41. A wound element 53 is formed by placing a positive electrode 51A and a negative electrode, respectively, both composed of the worked electrodes 41 containing carbon blacks between separators 12 and winding them on a wound core. Therefore, a gap D of heights of the concave-convex sections 45, 47 is formed between the separators 12 and each of the positive electrode 51A and the negative electrode 51B. As a consequence, an electrolytic solution penetrates throughout the wound element 53 even if the positive electrode 51A and the negative electrode 51B are swelled by the impregnation of the electrolytic solution or the like. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to an electric double layer capacitor and a method of manufacturing the electric double layer capacitor, and in particular, can reduce the internal resistance of the electric double layer capacitor and increase its capacitance density, and keep its productivity favorable. The present invention relates to an electric double layer capacitor and a method of manufacturing the electric double layer capacitor.

Electric double layer capacitors are excellent in terms of long-term reliability and power density due to charge / discharge cycles, and are being used for hybrid electric vehicle power supplies and emergency power supply applications. In these power supply applications, a high voltage of several hundred volts is required.
Usually, since the operating voltage of a single cell of an electric double layer capacitor is relatively low (about 2.6 V), it is used as an electric double layer module in which several tens to several hundreds of these single cells are connected in series.
As a structure of this single cell, a square cell, a cylindrical cell, etc. are common.

A perspective view (partially cut) showing the structure of the square cell is shown in FIG.
As shown in FIG. 7, the square cell 20A is formed by alternately laminating a separator 2 with a plurality of plate-like positive electrodes 1A and negative electrodes 1B to form a square element body 3, which is square-shaped. It is housed in the case 5.
Further, flat lead portions 7A and 7B extend upward from the positive electrode 1A and the negative electrode 1B, respectively, and are bundled into lead coupling portions 8A and 8B separately for the positive electrode and the negative electrode. The lead coupling portions 8A and 8B are connected and fixed to a positive terminal 9A and a negative terminal 9B that are penetrated and fixed to the square case 5.

On the other hand, FIG. 8 shows a perspective view (partially cut) showing the structure of the cylindrical cell.
As shown in FIG. 8, the cylindrical cell 20B is rolled up in a state where the separator 12 is sandwiched between a pair of long belt-like positive electrode 11A and negative electrode 11B to form a wound element body 13, which is formed in a cylindrical case. 15 is configured.
Leads 17A and 17B are connected to upper ends of the positive electrode 11A and the negative electrode 11B, and these leads 17A and 17B are connected to a positive terminal 19A and a negative terminal 19B, respectively, which are penetrated and fixed to the sealing insulating plate 16. Yes.

The single cells 20A and 20B configured in this way are connected in series, for example, to form an electric double layer module.
A perspective view showing an example of the structure of the electric double layer module is shown in FIG.
As shown in FIG. 9, the electric double layer module 25 includes a solid module structure member 21 for fixing a plurality of unit cells 20 (by the cylindrical cell 20B) and a unit cell 20 in series. And a large number of connecting bus bar members 23 for electrical connection to each other.

  In addition, as another structure of the electric double layer module 25, as shown in Patent Document 1, a feature is provided in the electrodes constituting the positive electrode 11A and the negative electrode 11B, and the cylindrical case 15 of the unit cell 20 and the module are provided. A structure in which the structural member 21 and the connection bus bar member 23 are integrated to make the electric double layer module 25 lighter and more compact is also conceivable.

By the way, in such an electric double layer capacitor for large capacity and large current charge / discharge, further reduction in internal resistance and increase in capacity per unit volume (hereinafter referred to as capacity density) are desired.
Therefore, it is conceivable to increase the surface area of the electrode and reduce the thickness of the separators 2 and 12 as much as possible.

However, in this case, there is a possibility of causing the following structural problem.
For example, the separators 2 and 12 need to have a high porosity to some extent from the viewpoint of the liquid absorbency and liquid retention of the electrolytic solution. In addition, the porosity means the ratio of the volume which a void (portion of the bubble which exists in a target object) occupies in the volume of a target object.
For this reason, if the thickness of the separators 2 and 12 is reduced while maintaining the porosity to some extent, the insulation between the positive electrode 11A and the negative electrode 11B becomes insufficient, and the positive electrode 11A and the negative electrode 11B are short-circuited microscopically. There is a risk that the self-discharge tends to occur and the manufacturing yield of the capacitor is lowered.

Moreover, if the thickness of the separators 2 and 12 is too thin (for example, 60 μm or less), it becomes difficult to increase the porosity of the separators 2 and 12, and the amount of the electrolyte in the separators 2 and 12 is reduced. There was a possibility that it would be difficult to supply the electrolyte to the positive electrode 11A and the negative electrode 11B.
In addition, since the electrolyte is not sufficiently supplied to the positive electrode 11A and the negative electrode 11B at the time of discharge, a sufficient amount of ions do not exist in the vicinity of the positive electrode 11A and the negative electrode 11B, and the voltage drop due to instantaneous large current discharge may increase. was there.

  Further, since the electrolyte is not sufficiently supplied to the positive electrode 11A and the negative electrode 11B at the time of charging, there is a possibility that the polarization of ions becomes insufficient in the positive electrode 11A and the negative electrode 11B and the voltage holding property is lowered. Furthermore, since adsorption of ions necessary for an external charging applied voltage to the positive electrode 11A and the negative electrode 11B is not performed, an electrochemical decomposition reaction other than adsorption occurs in the positive electrode 11A and the negative electrode 11B. There is a risk that the capacity increases or the capacity density decreases.

Furthermore, in order to solve this problem, if the electrolyte is sufficiently supplied to the positive electrode 11A and the negative electrode 11B, it takes time to inject the electrolyte, which may cause a problem in the productivity of the electric double layer capacitor. It was.
As a method for sufficiently supplying the electrolyte to the electrode, a method has been proposed in which a groove is formed on the electrode surface so that the electrolyte corresponding to the amount of dry-up of the electrolyte assumed at the time of use is held near the electrode. (For example, refer to Patent Document 2).
However, in this method, the limit is to hold the electrolyte solution for dry-up. For example, when the thickness of the separators 2 and 12 is reduced, an amount of the electrolyte solution sufficient for the polarization of ions is contained in the separators 2 and 12. Could not hold.
JP 2002-353078 A (FIGS. 4, 6 and 7) JP 2001-44081 A (Page 6, FIGS. 1 and 2)

  The present invention has been made in view of such a conventional problem. An electric double layer capacitor capable of reducing the internal resistance of the electric double layer capacitor, increasing its capacitance density, and maintaining good productivity. And it aims at providing the manufacturing method of this electric double layer capacitor.

  Therefore, the present invention relates to an electric double layer capacitor, and includes an electrolyte, a positive electrode and a negative electrode made of an electrode containing carbon black, which forms an electric double layer at the interface between the electrolyte, and the positive electrode and the negative electrode. An electric double layer capacitor accommodated in a case, wherein at least one of the positive electrode and the negative electrode has a protruding portion or a bent portion in a height direction with respect to the bottom surface of the case. A gap is formed between the at least one electrode and the separator by a height of the protruding portion or the bent portion.

The electrode normally expands more than the thickness before impregnation due to the impregnation of the electrolytic solution. Therefore, the electrode is not sufficiently impregnated with the electrolytic solution, and the performance of the electric double layer capacitor may not be sufficiently exhibited. It is formed continuously in the vertical direction. Therefore, a gap is formed between the separator and the electrode due to the height of the protruding portion or the bent portion, and an electrolyte impregnation path for the electrode is secured.
As a result, the internal resistance of the electric double layer capacitor can be lowered and the capacity density thereof can be increased, and the productivity can be kept good.

  The present invention also relates to an electric double layer capacitor, wherein a plurality of the positive electrodes and the negative electrodes are alternately stacked via the separator, or the long band-shaped positive electrode and the negative electrode are wound via the separator. And is housed in the bottomed cylindrical case.

  Thus, the positive electrode, the negative electrode, and the separator can be accommodated in the case to form a large capacity square or cylindrical electric double layer capacitor.

  Furthermore, the present invention relates to an electric double layer capacitor, wherein the projecting portion or the bent portion is obtained by deforming at least one of the electrodes on one side and / or both sides and in a direction perpendicular to the height direction. A plurality of them are formed at predetermined intervals.

  This makes it easier for the electrolyte to impregnate the entire electrode. More preferably, in order to supply the electrolyte solution to the front and back of the electrode, it is desirable that the protruding portions or bent portions are formed so as to protrude / bend alternately on both sides of the electrode.

  Furthermore, the present invention relates to an electric double layer capacitor, wherein the separator has a thickness of 10 μm or more and 60 μm or less, a porosity of 40% or more and 85% or less, and a maximum pore diameter according to a test method defined in JIS K3832. It is 1 μm or less.

  If the thickness of the separator is less than 10 μm, the amount of the electrolyte solution that can be held in the separator is not sufficient, so that the internal resistance may be increased, and the short circuit between the electrodes is likely to occur due to its thinness. . On the other hand, when the thickness of the separator is larger than 60 μm, there is a risk that the capacity of the electrode may be hindered. Therefore, the thickness of the separator is preferably 10 μm or more and 60 μm or less. More preferably, the thickness of the separator is 20 μm or more and 50 μm or less.

Further, when the porosity of the separator is larger than 85%, the separator itself cannot withstand the expansion of the electrodes, and there is a possibility that the electrodes are short-circuited. On the other hand, when the porosity of the separator is less than 40%, the amount of the electrolyte in the separator is reduced, and the internal resistance may be too high. Therefore, the porosity of the separator is preferably 40% or more and 85% or less.
In the electric double layer capacitor of the present invention, the electrode is expanded by impregnation with the electrolytic solution and / or at least one charging operation described later, the separator is pressed, and the electrolytic solution in the electrode is squeezed out. May rise. Therefore, more preferably, the porosity of the separator is 50% or more and less than 80%.

  Furthermore, when the maximum pore diameter specified in JIS K3832 of the separator is larger than 1 μm, the electrode may easily penetrate through the separator and short circuit may occur, or metal impurities contained in the electrode may precipitate and cause a micro short circuit. is there. Accordingly, the maximum pore diameter is preferably 1 μm or less. More preferably, the average pore diameter defined in JIS K3832 of the separator is 0.1 μm or more and 0.3 μm or less.

  Furthermore, the present invention relates to a method for producing an electric double layer capacitor, the step of forming a positive electrode and a negative electrode composed of an electrode containing carbon black, forming an electric double layer at the interface with the electrolyte, and at least of the positive electrode and the negative electrode A step of forming a projecting portion or a bent portion on one electrode, a step of forming an element by disposing a separator between the positive electrode and the negative electrode, a step of housing the element in a case, an electrolyte solution in the element The impregnation step and at least one charging operation are performed in this order, and a gap is formed between the at least one electrode and the separator by the height of the protruding portion or the bent portion.

  As a result, a gap due to the height of the projecting portion or the bent portion can be formed between the electrode and the separator, and an electrolytic solution impregnation path to the electrode can be secured. A multilayer capacitor can be manufactured.

  Furthermore, the present invention relates to a method for producing an electric double layer capacitor, wherein an electrode sheet having a carbonaceous material as a main component and having a thickness of 80 μm or more and 400 μm or less is bonded on a metal current collector through an adhesive layer. An electrode is formed, and the sum of the thickness of the electrode and the height of the protruding portion or the bent portion is 1 with respect to the thickness of the electrode, which is the sum of the thicknesses of the metal current collector, the electrode sheet, and the adhesive layer. The protruding portion or the bent portion is formed so as to be not less than 0.01 times and not more than 1.20 times, and the protruding portion or the bent portion is spaced at a distance of 20 mm or less in a direction perpendicular to the height direction of the case. It is characterized by forming.

In order to increase the capacity of the electrode, the electrode is preferably composed mainly of a carbonaceous material. Moreover, in order to ensure sufficient electrical conductivity, it is necessary to contain carbon black in the electrode sheet.
As a result, an amount of ions necessary for polarization can be secured in the electrode, and the retention of the electrolytic solution can be improved.

  Further, if the thickness of the electrode sheet is less than 80 μm, the gap between the separator and the electrode due to the protruding portion or the bent portion may be too wide with respect to the thickness of the electrode. For this reason, the distance between the electrodes is increased, which is not preferable because the resistance of the electric double layer capacitor is reduced and the capacitance density is lowered. On the other hand, if the thickness of the electrode sheet is larger than 400 μm, the gap formed between the separator and the separator may be crushed due to its expansion. Therefore, the electrolyte solution impregnation path to the electrode is interrupted, and there is a possibility that sufficient supply of the electrolyte solution to the electrode may not be possible. Therefore, the thickness of the electrode sheet is preferably 80 μm or more and 400 μm or less.

  Furthermore, if the sum of the thickness of the electrode and the height of the protruding portion or the bent portion is less than 1.01 times the thickness of the electrode, the gap between the separator and the electrode is not sufficient, There is a possibility that the impregnation property of the electrolytic solution is lowered. On the other hand, if it is larger than 1.20 times, the distance between the electrodes becomes long, so that the internal resistance becomes high and the capacity density may be lowered. Therefore, it is preferable that the sum of the thickness of the electrode and the height of the projecting portion or the bent portion is 1.01 to 1.20 times the thickness of the electrode.

In addition, if the interval between the projecting portion or the bent portion is larger than 20 mm, the gap between the separator and the electrode may be crushed during the production of the electric double layer capacitor, and a sufficient amount of electrolyte may not be supplied to the electrode. is there. Therefore, it is preferable that the protruding portions or the bent portions are formed at intervals of 20 mm or less. More preferably, this distance is 15 mm or less.
In addition, since the process itself which provides a space | interval between a protrusion part or a bending part will become difficult when the space | interval of a protrusion part or a bending part is below the thickness of an electrode, it is not realistic. Therefore, it is preferable that the protruding portions or the bent portions are provided at intervals wider than the thickness of the electrode.

  Furthermore, the present invention relates to a method for manufacturing an electric double layer capacitor, wherein the thickness of the electrode expands from 1.1 times to 1.6 times by the step of impregnating the electrolyte and the charging operation. To do.

  When the expansion of the thickness of the electrode is less than 1.1 times, an extra gap is left between the electrode and the separator even after impregnation with the electrolytic solution, which may hinder the reduction in resistance. On the other hand, if the thickness of the electrode exceeds 1.6 times, the gap between the separator and the electrode may be crushed during the production of the electric double layer capacitor, and a sufficient amount of electrolyte may not be supplied to the electrode. There is. Also, the separator cannot withstand the expansion of the electrodes, causing a short circuit between the electrodes. Therefore, it is preferable that the thickness of the electrode expands to 1.1 times or more and 1.6 times or less by the step of impregnating the electrolytic solution and at least one charging operation. More preferably, this expansion is 1.15 times or more and 1.5 times or less.

  As described above, according to the present invention, the projecting portion or the bent portion is provided in the electrode so that a gap is formed between the electrode and the separator, so that the internal resistance of the electric double layer capacitor is reduced and The capacity density can be increased and the productivity can be kept good.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each member which comprises the electric double layer capacitor concerning embodiment of this invention is demonstrated. In the following description, each member used for the cylindrical cell will be described as an example.
The electrode will be described. A cross-sectional view of the electrode is shown in FIG.
In FIG. 1, an electrode 31 has a configuration in which electrode sheets 37 </ b> A and 37 </ b> B are attached to both surfaces of a strip-shaped or strip-shaped metal current collector foil 33 with an adhesive layer 35 interposed therebetween.

The metal current collector foil 33 is not particularly limited as long as it has excellent electrochemical corrosion resistance on the positive electrode side, and foil, net, or the like of aluminum or stainless steel is used. Since the strength is sufficient and is electrochemically stable, those mainly composed of aluminum are preferable.
Moreover, the thickness of the metal current collector foil 33 is reduced within a range where the strength is acceptable, and a range of 20 to 100 μm is preferable. Moreover, chemical, electrochemical, or mechanical surface etching treatment may be performed for the purpose of improving the bonding strength with the electrode sheets 37A and 37B and reducing the bonding resistance.

  Further, the metal current collector foil 33 has an end band portion (not shown) to which the electrode sheets 37A and 37B are not attached, and this end band portion is for electrical connection with the outside. is there. Therefore, in order to increase the cell capacity, it is preferable that the end band portion is as narrow as possible, and it is preferably about 2 to 6 mm.

The electrode sheets 37A and 37B have a carbonaceous material as a main component and contain carbon black therein. The electric double layer capacitor is based on the principle that charges are accumulated in the electric double layer formed at the interface between the electrode and the electrolyte.
Therefore, in order to increase the capacity of the electric double layer capacitor, it is preferable that the specific surface area of the carbonaceous material is large, and it is preferable that the main component is a carbonaceous material having a specific surface area of 100 to 2500 m ² / g. Examples of the carbonaceous material include activated carbon, carbon black, polyacene, and carbon aerogel.

  As carbon black, those having a large oil absorption and high conductivity, such as ketjen black, are preferably used. The carbon black content in the electrode sheets 37A and 37B is preferably 5 to 30% by mass in the total amount of the carbonaceous material and the binder. If the carbon black content is less than 5% by mass, the electrolytic solution cannot be sufficiently retained, and there is a possibility that an amount of ions necessary for polarization cannot be supplied. On the other hand, if the content of carbon black exceeds 30% by mass, the electrode may be excessively expanded by impregnation with the electrolytic solution, which is not preferable.

  The adhesive layer 35 is used for attaching the electrode sheets 37 </ b> A and 37 </ b> B to the metal current collector foil 33. Therefore, sufficient adhesion and high conductivity are required. In addition, the adhesive layer 35 needs to have heat resistance enough to withstand drying when removing moisture from the electrode 31, is stable to the electrolytic solution used in the present invention, and is an electric double layer capacitor. Is required to be electrochemically stable in the voltage range used.

  Therefore, a conductive adhesive in which polyamideimide resin, polyvinylidene fluoride, polytetrafluoroethylene, polyimide resin or the like is used as a binder and graphite or carbon black is dispersed as a conductive material is preferably used. The electrode 31 of the present invention can also be produced by coating an electrode material mainly composed of a carbonaceous material on the metal current collector foil 33. However, from the viewpoint of ease of processing, the metal current collector foil 33 is provided. The above-described method of bonding the electrode sheets 37 </ b> A and 37 </ b> B through the adhesive layer 35 is more preferable.

Next, the electrolytic solution will be described.
The electrolyte used for the electric double layer capacitor includes an aqueous electrolyte and a non-aqueous electrolyte. Here, the withstand voltage of the unit cell when the aqueous electrolyte is used is about 0.8V, and the withstand voltage when the non-aqueous electrolyte is used is about 2.6V. Since the electrostatic energy of the electric double layer capacitor is proportional to the square of the withstand voltage, the electrostatic energy can be increased 10 times or more when the non-aqueous electrolyte is used than when the aqueous electrolyte is used. Therefore, in the present invention, a nonaqueous electrolytic solution is preferable from the viewpoint of energy density.

The solute contained in the non-aqueous electrolyte is preferably a quaternary onium salt in terms of electrical conductivity, solubility in a solvent, and electrochemical stability.
In particular, R ¹ R ² R ³ R ⁴ N ⁺ or R ¹ R ² R ³ R ⁴ P ⁺ (wherein R ¹ , R ² , R ³ and R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms) R ¹ R ² C ₃ H ₃ N ₂ ⁺ (wherein R ¹ and R ² are each independently alkyl having 1 to 6 carbon atoms), which is a quaternary onium cation represented by the formula: Group) or a morpholinium cation represented by R ¹ R ² C ₄ H ₈ ON ⁺ (wherein R ¹ and R ² are each independently an alkyl group having 1 to 6 carbon atoms). BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , AsF ₆ ⁻ , N (SO ₂ CF ₃ ) ₂ ⁻ , ClO ₄ ^{− and the} like. What mixed is preferable. More preferably, it is desirable that at least one of R ¹ , R ² , R ³ , and R ⁴ is a different ammonium salt or an imidazolium salt in which R ¹ and R ² are different.

Further, when the use temperature range of the electric double layer capacitor is limited to some extent or when ionic conductivity is exhibited in the use temperature range, a salt that does not contain a solvent, that is, a molten salt can be used. For example, an imidazolium salt such as (C ₂ H ₅ ) (CH ₃ ) C ₃ H ₃ N ₂ N (SO ₂ CF ₃ ) ₂ is in a molten state at room temperature and exhibits ionic conductivity. Even if configured, it functions as the electric double layer capacitor of the present invention.

  Furthermore, when dissolving a solute using an organic solvent, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, nitriles such as acetonitrile, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, Sulfolane and sulfolane derivatives are preferred. In particular, at least one selected from the group consisting of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, acetonitrile, sulfolane and methyl sulfolane is preferred.

Next, the separator will be described.
The separator 12 electrically insulates between a positive electrode 51A and a negative electrode 51B, which will be described later, while facilitating the movement of ions in the electrolyte solution with the positive electrode 51A and the negative electrode 51B that accompany charging and discharging.
Therefore, polyethylene porous film with ion permeability, polypropylene porous film, polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyester nonwoven fabric, cellulose paper, kraft paper, rayon fiber and sisal fiber mixed sheet, Manila hemp sheet, polyester fiber sheet, glass fiber Sheets are often used.

Further, since the positive electrode 51A and the negative electrode 51B normally expand by the step of impregnating the electrolytic solution and at least one charging operation, the separator 12 has a strength capable of withstanding the pressure due to the expansion and holds the electrolytic solution well. Those having stretchability so as not to break even in the stretched state are preferable.
When the thickness of the positive electrode 51A and the negative electrode 51B expands to 1.2 times or more by the step of impregnating the electrolytic solution and at least one charging operation, it has a high porosity of 70 to 85%, Ultra high molecular weight polyethylene porous film with excellent elongation, porous film of ultra high molecular weight polyethylene filled with inorganic particles, polyester nonwoven fabric made of polyethylene terephthalate fiber or polybutylene terephthalate, sheets filled with inorganic particles, etc. Is particularly preferred. In addition, when the thickness of the positive electrode 51A and the negative electrode 51B expands to 1.1 times or more and less than 1.2 times, even if it is a thin film, the maximum pore diameter defined in JIS K3832 is 1 μm or less and the cellulose has excellent denseness It is preferable to use a paper separator. In particular, it is preferable to use a cellulose paper separator obtained by making a solvent-spun rayon.

Next, the machining electrode will be described. A cross-sectional view of the machining electrode is shown in FIG. Note that the same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
In FIG. 2, the processing electrode 41 </ b> A is modified with respect to the electrode 31 so as to have a long belt-like band portion 43 similar to the conventional one and a protruding portion having a convex portion 45 a and a concave portion 45 b.
The convex portion 45a is formed to provide a predetermined gap D between the separator 12 and the belt portion 43 in a wound element body 53 to be described later, and a metal collector constituting the processing electrode 41A. The electric foil 33, the electrode sheets 37A, 37B, and the like are integrated, and the gap D is raised.

  On the other hand, the concave portion 45b is formed because the constituent members of the processing electrode 41A are integrally raised when the convex portion 45a is formed, and the cross-sectional shape of the concave portion 45b has a predetermined semi-ellipse (long diameter). Has a shape along the circumference of width B and half of its minor axis depth D).

The deformations of the convex portions 45a and the concave portions 45b (hereinafter collectively referred to as the concave-convex portions 45) are continuously spread vertically from the front side of the drawing of the processing electrode 41A to the depth direction. .
Therefore, the concavo-convex portion 45 of the processing electrode 41A can be formed, for example, by pressing the electrode 31 against the side surface of an elliptic columnar rod having a predetermined elliptical cross section.

  Furthermore, the concavo-convex portions 45 have convex portions 45a / concave portions 45b alternately upward / downward in the figure, and the convex portions 45a and the concave portions 45b are spaced apart by an interval A. . The interval A refers to the distance between two adjacent projecting portions, and corresponds to the distance in the left-right direction in the drawing from the most raised portion of the convex portion 45a to the most depressed portion of the adjacent concave portion 45b. . As a result, a gap D with the separator 12 is formed on the back and front of the processing electrode 41A, and the processing electrode 41A is easily impregnated with the electrolytic solution.

The shape of the cross section of the recess 45b is not limited to the shape along the circumference of the predetermined semi-ellipse described above, and may be a shape along a square side. Moreover, as long as it continues in the height direction with respect to the bottom surface of the case, the shape is not limited to the above-described shape perpendicular to the paper surface, and may be, for example, a hatched shape.
A sectional view (another example) of this processed electrode is shown in FIG. 2 that are the same as those in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

In FIG. 3, the cross-sectional shape of the recess 47b of the processing electrode 41B has a shape along two sides other than the base of a predetermined isosceles triangle (the base is width B and the height is D). Further, the processing electrode 41B does not include a portion corresponding to the band portion 43 of the processing electrode 41A, and is configured only by the uneven portion 47.
Therefore, it can be said that the processing electrode 41B is a modification of the electrode 31 so as to have a predetermined bending portion with respect to the electrode 31, if the expression is changed. Therefore, the processing electrode 41B can be formed, for example, by pressing the electrode 31 against a rectangular hard plate having a predetermined isosceles triangle.

As a result, the processing electrode 41B can also form an average gap D with the separator 12 with respect to the front and back.
In the following, the processing electrode 41A and the processing electrode 41B are commonly referred to as the processing electrode 41.

Next, the wound element body will be described. Cross-sectional views of the wound element body are shown in FIGS. The same elements as those in FIGS. 2, 3, and 8 are denoted by the same reference numerals, and description thereof is omitted.
Here, the sectional view of the wound element body shown in FIG. 4 corresponds to the machining electrode 41A shown in FIG. 2, and the sectional view of the wound element body shown in FIG. This corresponds to the electrode 41B.
4 and 5, the wound element body 53 is different from the wound element body 13 using the conventional long strip-like positive electrode 11 </ b> A and negative electrode 11 </ b> B by the positive electrode 51 </ b> A and the negative electrode 51 </ b> B using the processed electrode 41. It is configured. The processing electrode 41 may be used for only one of the positive electrode 51A and the negative electrode 51B, but it is preferable to use the processing electrode 41 for both the positive electrode 51A and the negative electrode 51B because the electrolytic solution can be retained well.
The wound element body 53 is formed by sandwiching a positive electrode 51A and a negative electrode 51B between separators 12 and rolling them up with a winding core (not shown).

At this time, the processing electrode 41 constituting the positive electrode 51 </ b> A and the negative electrode 51 </ b> B has a winding axis of the wound element body 53, which is a direction in which deformation of the uneven portions 45 and 47 is spread. The direction of the convex portion 45a / concave portion 45b and the convex portion 47a / concave portion 47b is “upward / downward in the drawing” so that it is the direction (height direction with respect to the bottom surface of the case). In addition, the “left and right direction in the figure” which is the direction of the distance A between the concave and convex portions 45 and 47 is the rotation direction of the winding (the direction perpendicular to the height direction with respect to the bottom surface of the case). It is arranged so that it becomes.
Accordingly, a gap D is formed between the positive electrode 51 </ b> A and the negative electrode 51 </ b> B and the separator 12 continuously in the axial direction of the wound type element body 53. As a result, an electrolyte impregnation path is ensured over the entire axial direction of the winding.

Next, a cylindrical cell will be described. A perspective view of the cylindrical cell is shown in FIG. The same elements as those in FIG. 4 and FIG.
Although not shown in FIG. 6, the cylindrical cell 60 is configured to accommodate a wound element body 53.
The wound element body 53 is accommodated so that the height direction with respect to the bottom surface of the cylindrical case 15 is the axial direction of the winding, as in the conventional case.

Further, leads 17A and 17B for electrical connection with the outside are bonded to the wound element body 53 with respect to each end band of the metal current collector foil 33 of the positive electrode 51A and the negative electrode 51B. ing.
The joining method of the end strips and the leads 17A and 17B includes mechanical pressing and conductive bonding such as a conductive adhesive, but mechanically and electrically reliable welding is preferable. As this welding method, ultrasonic welding, laser welding such as YAG, and electron beam welding are preferably used.

  The leads 17A and 17B are not particularly limited in material as long as they have high electrical conductivity and high electrochemical corrosion resistance, but aluminum and aluminum alloys are preferable. Further, the shape is not particularly limited, but it is necessary to prevent impregnation of the electrolytic solution at the end face of the wound element body 53.

  Further, a positive terminal 19A and a negative terminal 19B are connected to the leads 17A and 17B, respectively. The positive terminal 19 </ b> A and the negative terminal 19 </ b> B are fixedly penetrated to a sealing insulating plate 66 having a liquid injection hole 61, and are attached to the sealing insulating plate 66 in an airtight manner via an insulating resin.

In such a configuration, in order to reduce the resistance and the density of the electric double layer capacitor, it is conceivable to reduce the thickness of the separator 12 as much as described above. There was a risk of insufficient supply.
In order to sufficiently supply the electrolytic solution, it is effective not only to cause the electrolytic solution to exist in the separator 12 but also to impregnate a sufficient amount of electrolytic solution in the pores in the carbonaceous material of the processing electrode 41. I know that.

However, the processed electrode 41 normally expands from the initial thickness due to the impregnation with the electrolytic solution. This is because, in order to increase the capacity of the electric double layer capacitor, the processing electrode 41 according to the embodiment of the present invention increases the filling amount of the electrode sheets 37A and 37B, or the carbon black in the processing electrode 41 It becomes easy to produce by adding. In particular, when carbon black having a large amount of electrolyte solution retained per unit volume, such as ketjen black, is used, such expansion tends to occur.
At this time, due to the expansion of the processing electrode 41 itself, the electrolyte does not easily reach the inside of the wound element body 53, and it is difficult to supply the electrolyte to the processing electrode 41 itself.

Furthermore, although depending on the type of carbonaceous material used for the electrode sheets 37A and 37B, the thickness of the processed electrode 41 is usually expanded even by at least one charging operation. This is because the application of voltage to the processing electrode 41 becomes a driving force, and the adsorption of the electrolytic solution into the carbonaceous material pores of the processing electrode 41 is promoted. In particular, when an easily graphitizable alkali-activated activated carbon or the like is used as a carbonaceous material, this expansion is likely to occur.
Also in this case, the electrolytic solution is difficult to be supplied to the inside of the wound element body 53, so that the processing electrode 41 is not sufficiently impregnated, and the performance of the electric double layer capacitor may not be sufficiently exhibited.

  However, in the electric double layer capacitor of the present invention, a predetermined gap D is formed between the separator 12 and the positive electrode 51A and the negative electrode 51B, and an electrolyte impregnation path is secured in the positive electrode 51A and the negative electrode 51B. Therefore, even when the positive electrode 51 </ b> A and the negative electrode 51 </ b> B expand at the time of injecting the electrolyte and at the time of the subsequent charging operation, the electrolyte reaches the entire wound element body 53.

Therefore, during discharging, the electrolyte is sufficiently present in the vicinity of the positive electrode 51A and the negative electrode 51B, so that a voltage drop can be minimized even when an instantaneous large current discharge occurs. In addition, even during charging, the electrolyte is sufficiently supplied to the positive electrode 51A and the negative electrode 51B, so that ion polarization is sufficiently performed and voltage retention can be improved.
Furthermore, it does not take time to inject the electrolytic solution, and the productivity of the electric double layer capacitor is improved.

  In addition, the thickness of the separator 12, the porosity, or the maximum pore size, such as the thickness of the positive electrode 51A and the negative electrode 51B and the degree of expansion thereof, the spacing A and the depth D of the uneven portions 45 and 47 of the processing electrode 41 (definition is described later) As for etc., the size should be determined by paying attention to the following points.

First, the thickness of the positive electrode 51A and the negative electrode 51B is considered.
If the thickness of the positive electrode 51A and the negative electrode 51B is too thin, an excess gap may be left between the positive electrode 51A and the negative electrode 51B and the separator 12 even after the positive electrode 51A and the negative electrode 51B expand. For this reason, the distance between the positive electrode 51A and the negative electrode 51B increases, which hinders the reduction in resistance, and also leads to a decrease in capacity density.

If the positive electrode 51A and the negative electrode 51B are too thick, the gap D formed between the separator 12 and the positive electrode 51A and the negative electrode 51B may be crushed when the expansion of the positive electrode 51A and the negative electrode 51B occurs. For this reason, the electrolyte solution impregnation path to the positive electrode 51A and the negative electrode 51B is cut off in the middle of the injection, and sufficient supply of the electrolyte solution cannot be performed.
Therefore, when the positive electrode 51A and the negative electrode 51B expand, the thickness of the positive electrode 51A and the negative electrode 51B should be determined so that an appropriate gap is left between the separator 12 and in particular, the thickness of the electrode sheets 37A and 37B is 80 μm or more. The thickness is preferably 400 μm or less.

Next, the degree of expansion of the positive electrode 51A and the negative electrode 51B will be considered.
If the degree of expansion of the positive electrode 51A and the negative electrode 51B is small, the relationship between the thickness of the positive electrode 51A and the negative electrode 51B and the depth D of the concavo-convex portions 45 and 47 of the processing electrode 41 is between the positive electrode 51A and the negative electrode 51B and the separator 12. There is a risk that an extra gap will be left.

  On the other hand, when the degree of expansion of the positive electrode 51A and the negative electrode 51B is large, the gap D formed between the separator 12 and the positive electrode 51A and the negative electrode 51B may be crushed. Further, the separator 12 cannot withstand the expansion of the positive electrode 51A and the negative electrode 51B, and the positive electrode 51A and the negative electrode 51B may break through the separator 12 to cause a short circuit. Therefore, it is preferable that the thickness of the positive electrode 51A and the negative electrode 51B expands to 1.1 times or more and 1.6 times or less by the step of impregnating the electrolytic solution and at least one charging operation.

Next, the interval A and the width B of the uneven portions 45 and 47 of the processing electrode 41 are considered.
If the gap A between the concavo-convex portions 45 and 47 is too wide, the gap D is crushed when the processing electrode 41 is rolled up as the wound element body 53, and a sufficient amount of electrolyte is applied to the positive electrode 51A and the negative electrode 51B. May not be able to supply.

  In addition, it is not realistic to set the distance A between the concave and convex portions 45 and 47 to a length equal to or shorter than the thickness of the positive electrode 51A and the negative electrode 51B because processing itself becomes difficult. Therefore, when the wound element body 53 is manufactured, the interval A between the concavo-convex portions 45 and 47 may be determined so that the gap D is not crushed in an easily workable range. In particular, the interval A is preferably greater than or equal to the thickness of the positive electrode 51A and the negative electrode 51B and not greater than 20 mm.

  Furthermore, the width B of the concavo-convex portions 45 and 47 is preferably equal to or greater than twice the thickness of the positive electrode 51A and the negative electrode 51B, but there is no problem in the effect even if it exceeds this range. In addition, the uneven | corrugated | grooved part 45 may be comprised only by the convex part 45a, without providing the recessed part 45b.

Next, the depth D of the uneven portions 45 and 47 will be considered.
The depth D of the concavo-convex portions 45 and 47 can be calculated by the ratio of the apparent thickness to the original thickness of the electrode before the electrode 31 expands by electrolytic solution impregnation or charging operation. The ratio of the apparent thickness to the base thickness of the electrode is the stacked thickness of the processed electrode 41 after actually forming the uneven portions 45 and 47 with respect to the stacked thickness before forming the uneven portions 45 and 47 on the electrode 31. The ratio of

  If the ratio of the apparent thickness to the base thickness of the electrode is too small (that is, the ratio is too close to 1), the gap D formed between the positive electrode 51A and the negative electrode 51B and the separator 12 is not sufficient, so the positive electrode 51A and the negative electrode There is a possibility that the effect of improving the impregnation of the electrolytic solution into 51B cannot be obtained. If this ratio is too large, a sufficient amount of electrolyte is supplied to the positive electrode 51A and the negative electrode 51B, but the gap D with the separator 12 becomes large after the impregnation or charging operation of the electrolyte, Resistance may increase and capacity density may decrease. Therefore, this ratio is preferably 1.01 times or more and 1.20 times or less.

Next, the thickness and porosity of the separator 12 are considered.
As described above, when the thickness of the separator 12 is too thin, the amount of the electrolyte solution that can be held in the separator 12 is not sufficient, and thus the internal resistance may increase. If the separator 12 becomes too thin, a short circuit between the positive electrode 51A and the negative electrode 51B is likely to occur.
On the other hand, if the separator 12 is too thick, it is difficult to increase the capacities of the positive electrode 51A and the negative electrode 51B, which makes it difficult to improve the capacity density of the electric double layer capacitor.

On the other hand, when the porosity of the separator 12 is too high, the separator 12 cannot withstand the expansion of the positive electrode 51A and the negative electrode 51B, and a short circuit between the positive electrode 51A and the negative electrode 51B is likely to occur.
On the other hand, when the porosity of the separator 12 is too low, the amount of electrolyte impregnated in the separator 12 is reduced, so that the internal resistance is increased. Furthermore, the separator 12 is pressed by the expansion of the positive electrode 51A and the negative electrode 51B, the electrolytic solution in the separator 12 is squeezed out, and the internal resistance may increase.
Therefore, it is preferable to set the thickness and porosity of the separator 12 so as to prevent an increase in internal resistance and to prevent a short circuit between the positive electrode 51A and the negative electrode 51B. In particular, it is preferable that the separator 12 has a thickness of 10 μm to 60 μm and a porosity of 40% to 85%.

Furthermore, the maximum hole diameter of the separator 12 is considered. Here, the maximum hole diameter means the maximum hole diameter according to the test method defined in JIS K3832.
If the maximum pore diameter of the separator 12 becomes too large, the positive electrode 51A and the negative electrode 51B will easily penetrate through the separator 12, or metal impurities contained in the positive electrode 51A and the negative electrode 51B will precipitate, causing a micro short circuit. There is a fear. Therefore, the maximum pore diameter of the separator 12 is preferably 1 μm or less.

  Hereinafter, specific examples of the electric double layer capacitor of the present invention will be described.

Example 1
A method for manufacturing the electrode 31 will be specifically described.
In producing the electrode 31, 80% by mass of a steam activated activated carbon powder having a specific surface area of 1800 m ² / g made of phenol resin as a carbonaceous material, 10% by mass of carbon black as a conductive material, and 10% of polytetrafluoroethylene as a binder. A mixture consisting of mass% was prepared. Then, propylene glycol was added to the mixture as a kneading aid, and the kneaded mixture was continuously roll-rolled to produce a long sheet having a thickness of 200 μm.
Thereafter, the long sheet was continuously dried at 300 ° C. to remove the kneading aid, and further rolled and slit to produce electrode sheets 37A and 37B having a thickness of 140 μm and a width of 100 mm.

The electrode sheets 37 </ b> A and 37 </ b> B were produced by continuously joining both surfaces of the metal current collector foil 33 using a conductive adhesive as the adhesive layer 35. As the metal current collector foil 33, aluminum having a thickness of 40 μm was used, and the electrode sheets 37 </ b> A and 37 </ b> B were joined to the metal current collector foil 33 having a width of 100 mm.
And these electrode sheets 37A and 37B, metal current collector foil 33, etc. were integrated by roll-pressing together, and the elongate strip-shaped electrode 31 with a thickness of 320 micrometers was produced.

Next, a method for producing the processing electrode 41 will be specifically described.
In manufacturing the processed electrode 41, the width B of the concave portion 45b is 0.8 mm and the depth D is 0.2 mm as the concave and convex portion 45 by pressing the side surface of the elliptical columnar rod against the long strip electrode 31. The groove-shaped depressions were alternately formed on the front and back so that the distance A was about 15 mm. As a result, a machining electrode 41A as schematically shown in FIG. 2 is formed.

Next, a method for creating the wound element body 53 will be specifically described.
In the production of the wound element body 53, the positive electrode 51A and the negative electrode 51B using the processing electrode 41 are sandwiched between the separators 12, and the position in the width direction is such that the separator 12 protrudes from the positive electrode 51A and the negative electrode 51B by 4 mm on each side. Together. Then, the aligned element was scraped off with an 8 mm diameter core to produce a wound element body 53 having a diameter of 40 mm and a length of 108 m.

  Here, as the separator 12, a porous film having a thickness of 40 μm made of ultrahigh molecular weight polyethylene, a porosity of 80%, and a porous film having a maximum pore diameter of 0.8 μm according to a test method defined in JIS K3832 is slit to a width of 108 mm. Using.

Next, a method for manufacturing the cylindrical cell 60 will be described.
In manufacturing the cylindrical cell 60, the wound element body 53 was accommodated in an aluminum cylindrical case 15 having a height of 120 mm, a diameter of 41 mm, and a thickness of 0.4 mm. Then, the positive terminal 19A and the negative terminal 19B were airtightly attached to the aluminum sealing insulating plate 66 having the liquid injection hole 61 through an insulating resin. Then, after the respective leads 17A and 17B were ultrasonically welded to the positive terminal 19A and the negative terminal 19B, the sealing insulating plate 66 was fitted into the cylindrical case 15, and the cylindrical case 15 was sealed by laser welding.

Thereafter, vacuum drying was performed for 72 hours in an atmosphere at 90 ° C. with the liquid injection hole 61 of the sealing insulating plate 66 opened. After reducing the pressure inside the device to 30 Pa, an electrolytic solution in which 1.5 mol / kg (C ₂ H ₅ ) ₃ (CH ₃ ) NBF ₄ was dissolved in propylene carbonate was injected from the injection hole 61 at atmospheric pressure. And after leaving for 30 minutes, the excess electrolyte solution was removed, and the liquid injection hole 61 was loaded with a safety valve and hermetically sealed.
Thus, a cylindrical cell 60 was produced as an electric double layer capacitor.

(Example 2)
In the electrode 31 of the first embodiment, the electrode 31 is pressed against a rectangular hard plate having a predetermined isosceles triangle, thereby providing the concave and convex portions 47 alternately on the front and back sides, and bent so that the distance A is 10 mm. did. As a result, a machining electrode 41B as schematically shown in FIG. 3 is formed. Others were produced in the same manner as in Example 1.

(Example 3)
In the electrode 31 of Example 1, an alkali activated activated carbon powder having a specific surface area of 800 m ² / g made of petroleum pitch as a carbonaceous material is used, and the separator 12 is made of polyethylene terephthalate with a thickness of 50 μm, a porosity of 60%, It was produced in the same manner as in Example 1 except that it was constructed using a non-woven fabric having a maximum pore size of 0.9 μm according to the test method defined in JIS K3832.

Example 4
In the electrode 31 of Example 2, an alkali activated activated carbon powder having a specific surface area of 800 m ² / g made of petroleum pitch as a carbonaceous material is used, and the separator 12 has a thickness of 50 μm made of polyethylene terephthalate, a porosity of 60%, It was produced in the same manner as in Example 2 except that it was constructed using a nonwoven fabric having a maximum pore size of 0.9 μm according to the test method defined in JIS K3832.

(Example 5)
In Example 1, as a separator 12, a cellulose paper made by making a solvent-spun rayon (trade name: Lyocell) having a thickness of 50 μm, a porosity of 55%, and a maximum pore diameter of 0.7 μm according to a test method specified in JIS K3832. The device was manufactured in the same manner as in Example 1 except that it was configured using

(Example 6)
In the processed electrode 41 of Example 1, the concavo-convex portion 45 was produced in the same manner as in Example 1 except that the gap A was formed to be 30 mm.

(Example 7)
The separator 12 of Example 1 was formed using a nonwoven fabric having a thickness of 60 μm made of polyethylene terephthalate, a porosity of 80%, and a non-woven fabric having a maximum pore diameter of 2.5 μm according to the test method defined in JIS K3832. It produced similarly.

(Comparative Example 1)
The electrode 31 of Example 1 was prepared in the same manner as in Example 1 except that the uneven portion 45 was not formed.

(Comparative Example 2)
The electrode 31 of Example 1 was manufactured in the same manner as in Example 1 except that the conductive material was made of graphite powder instead of carbon black.

  In Examples 1 to 7 and Comparative Examples 1 and 2, the following measurements were performed.

(Measurement 1)
Before injecting the electrolytic solution, the cross-section of the wound element body 53 was observed, and the stack thickness of the stacked portions in the order of positive electrode 51A-separator 12-negative electrode 51B-separator 12 was measured.

(Measurement 2)
In addition to measurement 1, the ratio of the apparent thickness to the base thickness of the electrode was calculated.

(Measurement 3)
Next, the amount of the electrolytic solution when the cylindrical cell 60 was obtained was measured.

(Measurement 4)
Furthermore, the cylindrical cell 60 produced separately from that used for the measurement 3 was disassembled, and the initial expansion coefficient was measured.
The initial expansion coefficient refers to the ratio of the thickness of the positive electrode 51A and the negative electrode 51B after the injection of the electrolytic solution to the thickness of the positive electrode 51A and the negative electrode 51B before the injection of the electrolytic solution.

(Measurement 5)
Next, using a cylindrical cell 60 produced separately from those used in Measurement 3 and Measurement 4, after charging at a constant voltage of 2.6 V for 30 minutes, the voltage was adjusted to 30 V at a constant current of 30 A. Discharged.
At this time, the capacity of the entire cylindrical cell 60 was determined from the gradient of the discharge curve from voltage 2.6V to voltage 1.0V.

(Measurement 6)
In addition to measurement 5, the internal resistance was calculated from the voltage drop at the beginning of discharge.

(Measurement 7)
Furthermore, in addition to the measurement 6, the battery was further charged at a constant voltage of 2.6 V for 24 hours and then left in an open circuit state, and the holding voltage after 72 hours was measured.

(Measurement 8)
Thereafter, the cylindrical cell 60 after measurement 7 was disassembled, the thicknesses of the positive electrode 51A and the negative electrode 51B were measured, and the expansion coefficient was measured.
This expansion coefficient is referred to as the post-charge / discharge expansion coefficient with respect to the initial expansion coefficient of measurement 4.

  Table 1 was obtained as a result of the above measurements 1-8.

  In Table 1, from the measurement results of Example 1 and Comparative Example 1, the ratio of the apparent thickness to the base thickness of the electrode is 1.000 (the same as the case where the processed electrode 41 does not have the uneven portion 45 (conventional)). ) And the resistance of the comparative example 1 becomes 5.42 mΩ compared to the resistance of 2.21 mΩ of the first embodiment, and the resistance value increases. Also, the holding voltage is 0.221 V in Comparative Example 1 compared to the holding voltage of 2.444 V in Example 1, and it can be seen that the voltage holding characteristics are degraded. In Comparative Example 1, since the gap D is not formed between the positive electrode 51A and the negative electrode 51B and the separator 12, the impregnation property of the electrolytic solution into the positive electrode 51A and the negative electrode 51B is deteriorated, and the resistance is increased and the voltage holding property is increased. Probably caused the decline.

  In addition, from the measurement results of Example 1 and Example 2, if the distance A between the concave and convex portions 45 and 47 in the processing electrode 41 is in the range of 10 to 15 mm, the characteristics of the electric double layer capacitor are both good. I understand. Furthermore, the shape of the cross-sections of the concavo-convex portions 45 and 47 may be good, regardless of whether it is a semi-elliptical shape like the processing electrode 41A or a square shape like the processing electrode 41B. I understand.

  On the other hand, from the measurement result of Example 6, when the distance A between the concave and convex portions 45 is 30 mm, the resistance of Example 6 becomes 3.53 mΩ compared to the resistance of 2.21 mΩ of Example 1, and the resistance value is likely to increase. I understand. In Example 6, the gap A between the concavo-convex portions 45 is too wide, and the gap D between the positive electrode 51A and the negative electrode 51B and the separator 12 is crushed when the wound element body 53 is manufactured. It is considered that a sufficient amount of electrolyte solution could not be supplied to 51B, causing an increase in resistance.

  Moreover, in Example 4 which combined the shape of the uneven | corrugated | grooved part 47 of Example 2, its space | interval A, etc., and the shape of the separator 12 etc. of Example 3, it is big in a characteristic compared with the other Examples 1-3. It can be seen that there is no difference.

  On the other hand, from the measurement results of Example 7, when the thickness of the separator 12 is 60 μm, the porosity is 80%, and the maximum pore diameter is 2.5 μm, the holding voltage of Example 7 is higher than the holding voltage of 2.444 V of Example 1. It can be seen that the voltage holding characteristic is likely to be reduced to 0.507V. In Example 7, the maximum pore size of the separator 12 is too large, and the positive electrode 51A and the negative electrode 51B easily penetrate through the separator 12, and metal impurities contained in the positive electrode 51A and the negative electrode 51B are deposited to cause a short circuit. As a result, the holding voltage is considered to have decreased.

Furthermore, from the measurement results of Example 1 and Comparative Example 2, when graphite powder was used as the conductive material of the electrode sheets 37A and 37B, the resistance of Comparative Example 2 was 20.8 mΩ compared to the resistance of 2.21 mΩ of Example 1, It can be seen that the resistance value has increased. It can also be seen that the capacity holding voltage is significantly lower than that of the first embodiment.
Further, the amount of the electrolytic solution in Example 1 is 111 g, while that in Comparative Example 2 is significantly reduced to 75 g. In Comparative Example 2, by changing the material of the conductive material, the conductivity of the electrode sheets 37A and 37B itself is reduced, and the positive electrode 51A and the negative electrode 51B cannot hold the amount of electrolyte necessary for polarization, resulting in resistance. This is thought to have caused an increase and a decrease in voltage retention.

Especially, from the measurement result of Examples 1-5, the specific surface area of the carbonaceous material of electrode sheet 37A, 37B is 800-1800 m < ² > / g, the thickness of the separator 12 is 40-50 micrometers, and the porosity is 60-80%. When the maximum pore diameter is 0.8 to 0.9 μm, it can be seen that the characteristics of the electric double layer capacitor are all good. Therefore, the electric double layer capacitors of Examples 1 to 5 are particularly suitable as electric double layer capacitors for applications mainly having a large discharge capacity of 100 to 20000 F or a discharge current of 1 to 1000 A and a large current. is there.

  In addition, although the example of the electric double layer capacitor using the cylindrical cell 60 was shown as an Example of this invention, even if this Example is applied to the electric double layer capacitor using a square cell, it is the same. An effect is obtained.

Sectional drawing of the electrode which is embodiment of this invention Sectional drawing of the processing electrode which is embodiment of this invention Sectional drawing (another example) of the processing electrode which is embodiment of this invention Sectional drawing of the wound-type element body which is embodiment of this invention Sectional drawing of the wound type element body which is embodiment of this invention (another example) The perspective view of the cylindrical cell which is embodiment of this invention Perspective view showing the structure of a square cell (partially cut) Perspective view showing the structure of a cylindrical cell (partially cut) The perspective view which shows an example of the structure of a high voltage power supply module

Explanation of symbols

1A, 11A, 51A Positive electrode
1B, 11B, 51B Negative electrode
2,12 Separator
3. Square element body
13, 53 Winding element body
20A square cell
20B, 60 Cylindrical cell
31 electrodes
33 Metal current collector foil
35 Adhesive layer
37A, 37B electrode sheet
41A, 41B Processing electrode
45, 47 Concavity and convexity

Claims (7)

The case accommodated the electrolytic solution, a positive electrode and a negative electrode made of an electrode containing carbon black, which form an electric double layer at the interface between the electrolytic solution, and a separator disposed between the positive electrode and the negative electrode. An electric double layer capacitor,
At least one of the positive electrode and the negative electrode has a protruding portion or a bent portion formed continuously in the height direction with respect to the bottom surface of the case,
The electric double layer capacitor is characterized in that a gap is formed between the at least one electrode and the separator by a height of the protruding portion or the bent portion. A plurality of the positive electrodes and the negative electrodes are alternately stacked via the separator, or the long positive electrode and the negative electrode are wound through the separator and accommodated in the bottomed cylindrical case. The electric double layer capacitor according to claim 1. A plurality of the protruding portions or the bent portions are formed at predetermined intervals in a direction perpendicular to the height direction, in which the at least one electrode is deformed to one side and / or both sides. The electric double layer capacitor according to claim 1 or 2. 4. The separator according to claim 1, wherein the separator has a thickness of 10 μm or more and 60 μm or less, a porosity of 40% or more and 85% or less, and a maximum pore diameter of 1 μm or less according to a test method defined in JIS K3832. 2. The electric double layer capacitor according to item 1. Forming an electric double layer at the interface with the electrolytic solution, forming a positive electrode and a negative electrode made of an electrode containing carbon black, forming a projecting portion or a bent portion on at least one of the positive electrode and the negative electrode, A step of forming an element by disposing a separator between the positive electrode and the negative electrode, a step of accommodating the element in a case, a step of impregnating the element with an electrolytic solution, and at least one charging operation are performed in this order,
A method of manufacturing an electric double layer capacitor, wherein a gap is formed between the at least one electrode and the separator by a height of the protruding portion or the bent portion. On the metal current collector, an electrode sheet having a carbonaceous material as a main component and having a thickness of 80 μm or more and 400 μm or less is bonded through an adhesive layer to form the electrode,
The sum of the thickness of the electrode and the height of the projecting portion or the bent portion is 1.01 or more times the thickness of the electrode comprising the sum of the thicknesses of the metal current collector, the electrode sheet, and the adhesive layer. Forming the projecting portion or the bent portion to be 20 times or less,
6. The method of manufacturing an electric double layer capacitor according to claim 5, wherein the protruding portions or the bent portions are formed at intervals of 20 mm or less in a direction perpendicular to the height direction of the case. The method of manufacturing an electric double layer capacitor according to claim 6, wherein the thickness of the electrode expands to 1.1 times or more and 1.6 times or less by the step of impregnating the electrolytic solution and the charging operation.

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