JP2006245149A - Wet electrolytic capacitor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet electrolytic capacitor which has an increased adhesive strength between a metal foil and a metal porous material which constitute an anode. <P>SOLUTION: A porous anode 28 consists of a niobium foil 33 and a niobium porous material 35. The niobium porous material 35 is formed in the central part of the niobium foil 33. Especially, a through-hole 34 is formed nearly at the center of the niobium foil 33. The end of the niobium foil 33 is formed as a terminal 25 of the anode. The niobium porous material 35 is integrally formed on both surfaces of the niobium foil 33 through the through-hole 34. On the surface of the porous anode 28 except for the terminal 25 of the anode, an anode oxide film is formed. Niobium as a valve metal has its film (for example, an oxide film) exhibiting a valve action (rectification action). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wet electrolytic capacitor and a method for manufacturing the same, and more particularly to a wet electrolytic capacitor suitable for use in cases where it is necessary to reduce the size and thickness of a portable electronic device such as a mobile phone. It relates to the manufacturing method.

  In recent years, portable electronic devices such as cellular phones have been designed to reduce current and voltage during operation, but depending on their functions, a very large current may be required instantaneously. When a voltage fluctuation (IR drop or the like) occurs in a power source such as a battery, the electronic circuit may not operate normally or the battery life may be shortened. For example, if the battery voltage falls below the lower limit of the operating voltage of the CPU (central processing unit) even for a moment, the CPU becomes frozen and the electronic device becomes inoperable. For this reason, as a measure for avoiding the freeze state, an electric double layer capacitor having a lower impedance than that of the battery is connected in parallel to the battery. As a result, when a large current is instantaneously required, electric power is supplied to the electronic device from an electric double layer capacitor capable of rapid charging and discharging, and a sudden drop in battery voltage is avoided. Furthermore, with the miniaturization and thinning of electronic devices, proposals for miniaturization and thinning have also been made for electric double layer capacitors such as the electric double layer capacitor described in Patent Document 1. .

  However, as electric double layer capacitors become smaller and thinner, the resistance of electrodes, terminals, leads, etc. increases, and as a result, the equivalent series resistance (hereinafter referred to as “ESR”) increases. However, it is difficult to supply a large current as an original function. For this reason, in order to achieve miniaturization, thinning, and low ESR at the same time, instead of this electric double layer capacitor, for example, a wet electrolytic capacitor is used in addition to the solid electrolytic capacitor described in Patent Document 2. Has been proposed.

Conventionally, this type of wet electrolytic capacitor has been shown, for example, in FIG.
As shown in FIG. 6, the wet electrolytic capacitor 1 includes a cell 2, a cathode plate 4 that sandwiches the cell 2 while being in pressure contact with a current collector 3 constituting the cell 2, an anode terminal portion 5, and a cathode Laminate exterior materials 7 and 7 are provided for sealing other than the terminal portions with the terminal portions 6 exposed.

FIG. 7 is an exploded perspective view showing the configuration of the main part of the cell 2 in FIG.
As shown in FIG. 7, the cell 2 includes a porous anode body 8, current collectors 3 and 3 disposed opposite to the porous anode body 8, and the current collectors 3 and 3, for example, Separators 11, 11 separating the activated carbon layers 9, 9 formed by the screen printing method, the porous anode body 8 and the current collectors 3, 3 on which the activated carbon layers 9, 9 are formed, the porous anode body 8, It has a gasket 12 for hermetically sealing the activated carbon layers 9 and 9 and the separators 11 and 11 formed on the electric body 3 in a state in which sulfuric acid as an electrolytic solution is sealed.

FIG. 8 is a diagram showing a configuration of a main part of the porous anode body 8 in FIG. 7, in which FIG. 8 (a) is a plan view, and FIG. 8 (b) is a CC line in FIG. It is sectional drawing.
The porous anode body 8 is composed of a niobium foil 13 and a niobium porous body 15 as shown in FIG. The niobium foil 13 is formed in a planar shape, and the niobium porous body 15 is formed at the center of the niobium foil 13. Moreover, the niobium porous body 15 is formed on both surfaces of the niobium foil 13 as shown in FIG. An anodic oxide film (not shown) is formed on the surface of the porous anode body 8 excluding the anode terminal portion 5.

  In the manufacturing process of the wet electrolytic capacitor 1, the niobium porous body 15 is formed by vacuum sintering after a niobium paste containing niobium powder is printed on the niobium foil 13. And the porous anode body 8 is produced by performing an anodizing process. Thereafter, activated carbon layers 9 and 9 printed and formed on the current collectors 3 and 3 are arranged opposite to each other on both sides of the porous anode body 8 with the separators 11 and 11 therebetween. An electrolyte solution (sulfuric acid) is sealed between the current collectors 3 and 3 and the porous anode body 8, and the activated carbon layers 9 and 9 and the separators 11 and 11 are hermetically sealed by the gaskets 12 and 12. Is produced. Next, the cell 2 is sandwiched from the outside so as to be in pressure contact with the current collectors 3 and 3 by the cathode plate 4, and the portions other than the anode terminal portion 5 and the cathode terminal portion 6 are sealed and sheathed by the laminate sheathing materials 7 and 7. Thus, the wet electrolytic capacitor 1 is manufactured.

  In addition, in the electric double layer capacitor described in Patent Document 1, a plurality of unit capacitor cells in which a current collector and a polarizable electrode are oppositely bonded are sandwiched with a porous separator sealed with an exterior package interposed therebetween. Yes. A pressure terminal plate having a uniform inclined surface is provided as the element structure, and the capacitor elements of the element structure are pressed against each other.

Moreover, in the solid electrolytic capacitor described in Patent Document 2, a low-melting valve action metal foil and an electrode layer are provided on the valve action metal foil, and the electrode layer has a melting point higher than that of the valve action metal foil. High valve action metal or alloy powders are used. Thereby, even if the valve-acting metal foil and the powder of the valve-acting metal are sintered at a lower temperature than before, adhesion between the valve-acting metal foil and the electrode layer is ensured.
JP 2001-244155 A (Abstract, FIG. 1) JP 2003-272958 A (Abstract, FIG. 1)

However, the conventional wet electrolytic capacitor has the following problems.
That is, when the niobium porous body 15 is formed on the niobium foil 13 by vacuum sintering, the niobium foil 13 and the niobium porous body 15 are shrunk, but there is a difference in the shrinkage ratio between them. When the adhesion strength between the niobium porous body 15 and the niobium foil 13 is weak, the niobium porous body 15 may be peeled off from the niobium foil 13, resulting in a defective product.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a wet electrolytic capacitor in which adhesion strength between a metal foil constituting an anode and a metal porous body is improved and peeling is prevented.

  In order to solve the above-described problems, the first invention is provided with an anode and a cathode disposed opposite to each other, and sandwiched between the anode and the cathode, and impregnated with an electrolyte solution, thereby allowing ion permeability. A wet electrolytic capacitor that stores a charge between the anode and the cathode when a predetermined voltage is applied between the anode and the cathode, the anode having at least one penetration The metal foil in which the hole was formed, and the metal porous body integrally formed by penetrating the through-hole on both surfaces of the metal foil are provided.

  In the first invention, the metal foil and the metal porous body of the anode are preferably formed of a valve metal, and a dielectric film is formed on the surface of the anode.

  Moreover, it is preferable that the said separator consists of an insulating porous body, and the said cathode consists of an electroconductive porous body.

  A second invention relates to a method of manufacturing a wet electrolytic capacitor in which an anode and a cathode are arranged opposite to each other through a separator having ion permeability by being impregnated with an electrolyte solution, and at least one through hole is formed. The anode is produced by integrally forming a metal porous body by sintering the metal powder through the through-holes on both surfaces of the formed metal foil.

  In the second aspect of the invention, after applying the metal paste containing the metal powder through the through-holes on both surfaces of the metal foil, the metal paste is sintered and the metal is applied to the surface of the metal foil. It is preferable to form a porous body.

  Further, a valve metal is used as the metal foil and the metal powder, the metal paste is sintered to form the metal porous body on the surface of the metal foil, and then the surface of the anode is subjected to anodization. It is preferable to form a dielectric film.

  Furthermore, it is preferable to use an insulating porous body as the separator and a conductive porous body as the cathode.

  According to the configuration of the present invention, the anode includes a metal foil in which at least one through-hole is formed, and a metal porous body integrally formed through the through-hole on both surfaces of the metal foil. Therefore, it is possible to provide a wet electrolytic capacitor in which adhesion between the metal foil and the metal porous body is maintained, and defective peeling of the metal porous body is reduced. Further, the anode is manufactured by integrally forming a metal porous body by sintering the metal powder through both sides of the metal foil in which at least one through hole is formed and sintering the metal powder. Therefore, even if there is a difference in sintering shrinkage between the metal foil and the metal porous body, the adhesion between the metal foil and the metal porous body is maintained, and the metal foil and the metal powder are sufficiently sintered. As a result, defects in peeling of the metal porous body can be reduced.

  The metal porous body is integrally sintered on both sides of the metal foil through at least one through-hole formed in advance, and the adhesion between the metal foil and the metal porous body is maintained, and the peeling failure of the metal porous body is reduced. A wet electrolytic capacitor is provided.

FIG. 1 is a view for explaining the structure and assembling method of main parts of a wet electrolytic capacitor according to an embodiment of the present invention.
As shown in the figure, the wet electrolytic capacitor 21 of this example includes a cell 22, a cathode plate 24 sandwiching the cell 22 in a state of being in pressure contact with the current collector 23 constituting the cell 22, an anode terminal portion 25, and With the cathode terminal part 26 exposed, laminate exterior film materials 27 and 27 are provided for sealing other than these terminal parts.

2 is a cross-sectional view taken along the line AA of the wet electrolytic capacitor 21 in FIG. 1, and FIG. 3 is an exploded perspective view showing the configuration of the main part of the cell 22 in FIG.
In this wet electrolytic capacitor 21, as shown in FIG. 2 or FIG. 3, the cell 22 includes a porous anode body 28, separators 31 and 31, activated carbon layers 29 and 29, current collectors 23 and 23, It consists of gaskets 32 and 32. That is, separators 31 and 31 are provided on both sides of the porous anode body 28, and activated carbon layers 29 and 29 printed on the current collectors 23 and 23 are disposed opposite to each other on the outside of the separators 31 and 31. Yes. The porous anode body 28 includes a niobium foil 33, a through-hole 34 provided substantially at the center of the niobium foil 33, and a niobium porous body integrally formed on both surfaces of the niobium foil 33 through the through-hole 34. 35.

The activated carbon layers 29 and 29 are made of activated carbon having an average particle diameter of, for example, 20 μm or less and a specific surface area of approximately 1200 m ² / g, and are formed on the current collectors 23 and 23 to have a thickness of 20 ± 5 μm by, for example, screen printing. ing. As the activated carbon, for example, phenol resin activated carbon is used. The current collectors 23 and 23 are made of, for example, a conductive rubber sheet in which carbon powder is dispersed. The porous anode 28, the activated carbon layers 29 and 29, and the separators 31 and 31 are hermetically sealed by current collectors 23 and 23 and gaskets 32 and 32. The separators 31 and 31 are made of an insulating porous body, and have ion permeability when impregnated with an electrolyte solution (sulfuric acid). The gaskets 32 and 32 are made of a heat-sealable resin having insulating properties and acid resistance.

4A and 4B are diagrams showing a configuration of a main part of the porous anode body 28 in FIG. 3, in which FIG. 4A is a plan view, and FIG. 4B is an AA line in FIG. It is sectional drawing.
The porous anode body 28 is composed of a niobium foil 33 and a niobium porous body 35 as shown in FIG. The niobium foil 33 is formed, for example, in a planar shape having a thickness of 0.1 mm, and the niobium porous body 35 is formed at the center of the niobium foil 33. In particular, in this embodiment, a through hole 34 having a diameter of, for example, 0.3 mm is provided in the approximate center of the niobium foil 33. Further, the end portion of the niobium foil 33 is formed as the anode terminal portion 25. Further, as shown in FIG. 4B, the niobium porous body 35 is integrally formed by penetrating through holes 34 on both surfaces of the niobium foil 33. An anodic oxide film (not shown) is formed on the surface of the porous anode body 28 excluding the anode terminal portion 25. In general, niobium as a valve metal has a film (for example, an oxide film) that exhibits a valve action (rectifying action). When there is an oxygen supply source, the valve metal is oxidized to form an oxide film on the surface. Since the oxide film is an insulator or a semiconductor and has ionic conductivity, an ionic current corresponding to the potential gradient generated in the oxide film flows. For this reason, a current corresponding to the same potential gradient flows as a current for generating an oxide film.

FIG. 5 is a diagram showing a configuration of a main part of a porous anode body 28A provided in place of the porous anode body 28 in FIG. 3, in which FIG. 5 (a) is a plan view and FIG. It is BB sectional drawing of the same figure (a). In this figure, elements common to those in FIG. 4 are given common reference numerals.
In this porous anode body 28A, as shown in FIG. 5A, a niobium foil 33A and a niobium porous body 35A are provided in place of the niobium foil 33 and the niobium porous body 35 in FIG. . In the niobium foil 33A, for example, two through holes 36 and 36 having a diameter of 0.3 mm are provided. The through holes 36 and 36 are formed in two places which divide the long side direction of the niobium foil 33A into three equal parts and become the central part in the short side direction. Further, as shown in FIG. 5B, the niobium porous body 35A is integrally formed by penetrating through holes 36, 36 on both surfaces of the niobium foil 33A. The other configuration is the same as that of FIG.

  In this wet electrolytic capacitor 21, when a predetermined voltage is applied between the anode terminal portion 25 and the cathode terminal portion 26, charges are accumulated between the porous anode body 28 or 28 </ b> A and the activated carbon layers 29 and 29. The

Next, the processing content of the manufacturing method of the wet electrolytic capacitor of this example will be described.
This wet electrolytic capacitor is assembled by placing the porous anode body 28 or 28A and the activated carbon layers 29 and 29 opposite to each other through separators 31 and 31 having ion permeability when impregnated with an electrolyte solution. In setting example 1 in which the number of through-holes in the niobium foil is set to 1, the porous anode body 28 passes through the through-holes 34 on both surfaces of the niobium foil 33 in which the through-holes 34 are formed, and the niobium powder is sintered. The niobium porous body 35 is processed and formed integrally. Further, in setting example 2 in which the number of through-holes in the niobium foil is set to 2, the porous anode body 28A passes through the through-holes 36 and 36 on both surfaces of the niobium foil 33A in which the through-holes 36 and 36 are formed. Thus, the niobium powder is sintered and the niobium porous body 35A is integrally formed.

That is, in setting example 1, as shown in FIG. 4, a niobium foil 33 having a thickness of approximately 0.1 mm in which a through hole 34 having a diameter of 0.3 mm is formed is prepared, and the niobium foil 33 is filled so as to fill the through hole 34. Niobium paste is applied and formed on both sides using a 0.25 ± 0.05 mm printing mask. This niobium paste includes a niobium powder having a specific surface area of 7 m ² / g as a valve action metal powder, 2-2 butoxyethoxyethanol (BC) as a dispersing agent, an acrylic resin binder as a binder, and a plasticizer. And butyl phthalyl glycolate (BPBG) as a weight ratio of 70%, 18%, 6%, and 6%, respectively.

  Next, a niobium foil 33 having a niobium paste applied and formed on both sides through the through hole 34 is introduced into a vacuum vessel, and the holding time is 30 minutes at a sintering temperature of 1000 ° C. in a vacuum of about 50 μTorr. The niobium paste is sintered. Thereby, the niobium porous body 35 is integrally formed on both surfaces of the niobium foil 33 through the through holes 34. Next, the niobium foil 33 on which the niobium porous body 35 is formed is subjected to anodization by applying a voltage of 4.6 V in phosphoric acid of 0.6 vol% for 12 hours, and the anode terminal portion 25 is removed. An anodized film as a dielectric film is formed on the surfaces of the niobium foil 33 and the niobium porous body 35. In this way, the porous anode body 28 is produced.

  Next, as shown in FIG. 2 or FIG. 3, separators 31, 31 are provided on both sides of the porous anode body 28, and printed on the current collectors 23, 23 outside the separators 31, 31. Activated carbon layers 29 and 29 are arranged to face each other. Next, the porous anode body 28, the activated carbon layers 29 and 29, and the separators 31 and 31 are hermetically sealed in a state where the electrolyte solution (sulfuric acid) is sealed with the current collectors 23 and 23 and the gaskets 32 and 32, A cell 22 is produced.

  Next, as shown in FIG. 1, the cell 22 is sandwiched from the outside so as to be in pressure contact with the current collectors 23, 23 by the cathode plate 24, and the laminate exterior material other than the anode terminal portion 25 and the cathode terminal portion 26 is further provided. The wet electrolytic capacitor 11 is completed by sealing and enclosing with 27 and 27.

  Further, in setting example 2, as shown in FIG. 5, niobium foil 33A in which through holes 36 and 26 are formed is prepared, and porous anode body 28A is produced in the same manner as in setting example 1, and wet electrolytic capacitor 11 is prepared. Manufacturing.

Here, in setting example 1 and setting example 2, for example, an electrolyte solution corresponding to a rated voltage of 4 V is prepared, and 100 wet electrolytic capacitors 21 are manufactured in accordance with a standard of floor surface dimensions of 38.5 mm × 26.5 mm. To do. The wet electrolytic capacitors 21 thus manufactured were disassembled and the products from which the niobium porous bodies 35 and 35A were peeled were counted. 6 were manufactured according to the same standard as the wet electrolytic capacitor 21, and the products from which the niobium porous body 15 was peeled were counted as a comparative example. Table 1 shows the counting results.

  As shown in Table 1, in setting example 1, there are four electrode separation failure products, and the product yield is 96%. In setting example 2, the number of defective electrode separation is zero, and the product yield is 100%. On the other hand, in the comparative example, there are 42 defective electrode peeling products, and the product yield is 58%. As described above, according to the configuration of these setting examples, the niobium paste containing niobium powder applied to both surfaces of the niobium foils 33 and 33A through the at least one through-holes 34, 36, and 36 formed in advance is integrally sintered. . For this reason, adhesion between the niobium foils 33 and 33A and the sintered body of niobium paste (niobium porous bodies 35 and 35A) is maintained, and sufficient sintering of the niobium foil and the niobium powder is obtained. It was confirmed that the separation failure of the niobium porous body 35, 35A was reduced.

  In addition, the product yield of setting example 1 is 96% and the product yield of setting example 2 is 100%. In both setting examples, the yield is significantly improved from 58% of the yield of the conventional product. In this case, it was confirmed that the niobium porous body 35, 35A was bonded to only a part of the contact surface with the niobium foil 33, 33A. This phenomenon is called partial peeling and is shown in parentheses in Table 1. It was confirmed that the number of partial peelings was 23 in setting example 1 and 2 in setting example 2, and was smaller in setting example 2.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiment, and even if there is a design change without departing from the gist of the present invention, Included in the invention.
For example, the electrolyte solution is not limited to sulfuric acid, and an appropriate organic electrode solution may be used. In addition to niobium, the valve metal may be aluminum or tantalum. Moreover, there is no restriction | limiting in the shape of the through-hole (34, 36, 36) formed in metal foil (niobium foil 33, 33A), a magnitude | size, and quantity, For example, you may use a mesh-shaped metal foil. Further, the sintering temperature of the niobium paste is not limited to 1000 ° C., and for example, it may be set higher than this and the holding time may be shorter than 30 minutes.

  In addition, the activated carbon is not limited to the phenol resin-based activated carbon, and for example, ashigara activated carbon or petroleum coke-based activated carbon may be used. Moreover, as an activation method of activated carbon, a steam activation treatment method may be used, or a molten KOH activation treatment method may be employed. Further, as the current collectors 23, 23, a metal plate such as aluminum, copper, or nickel may be used. Further, instead of activated carbon, other conductive porous bodies having acid resistance may be used. For example, carbon materials such as carbon nanotubes and fullerenes, porous ITO (Indium Tin Oxide) conductive plastics, porous ceramics such as titanium nitride and titanium carbide, and unformed niobium porous bodies can be used.

  The present invention can be applied to all wet electrolytic capacitors in which an anode is composed of a metal foil and a metal porous body formed on both surfaces of the metal foil.

It is a figure explaining the structure and assembly method of the principal part of the wet electrolytic capacitor which is an Example of this invention. It is the sectional view on the AA line of the wet electrolytic capacitor 21 in FIG. It is a disassembled perspective view which shows the structure of the principal part of the cell 22 in FIG. It is a figure which shows the structure of the principal part of the porous anode body 28 in FIG. FIG. 4 is a diagram showing a configuration of a main part of a porous anode body 28A provided in place of the porous anode body 28 in FIG. It is a figure explaining the structure and assembly method of the principal part of the conventional wet electrolytic capacitor. It is a disassembled perspective view of the cell 2 in FIG. It is a figure which shows the structure of the principal part of the porous anode body 8 in FIG.

Explanation of symbols

21 Wet electrolytic capacitor 22 cells (part of wet electrolytic capacitor)
23 Current collector (part of wet electrolytic capacitor)
24 Cathode plate (part of wet electrolytic capacitor)
25 Anode terminal (part of wet electrolytic capacitor)
26 Cathode terminal (part of wet electrolytic capacitor)
27 Laminate exterior material (part of wet electrolytic capacitor)
28,28A Porous anode body (anode)
29 Activated carbon layer (cathode)
31 Separator (part of wet electrolytic capacitor)
32 Gasket (part of wet electrolytic capacitor)
33,33A Niobium foil (metal foil)
34, 36 Through-hole 35, 35A Niobium porous body (metal porous body)

Claims (7)

An anode and a cathode disposed opposite to each other;
A separator provided between the anode and the cathode and having ion permeability by being impregnated with an electrolyte solution;
A wet electrolytic capacitor that accumulates electric charge between the anode and the cathode when a predetermined voltage is applied between the anode and the cathode;
The anode is
A metal foil in which at least one through hole is formed;
A wet electrolytic capacitor comprising a metal porous body integrally formed on both surfaces of the metal foil through the through hole. The metal foil and metal porous body of the anode are formed of a valve metal,
The wet electrolytic capacitor according to claim 1, wherein a dielectric film is formed on a surface of the anode. The separator is made of an insulating porous body,
The wet electrolytic capacitor according to claim 1, wherein the cathode is made of a conductive porous body. A method of manufacturing a wet electrolytic capacitor in which an anode and a cathode are arranged to face each other through a separator having ion permeability by being impregnated with an electrolyte solution,
The anode is manufactured by integrally forming a metal porous body by sintering the metal powder through the through-holes on both surfaces of the metal foil in which at least one through-hole is formed. Manufacturing method.   After applying the metal paste containing the metal powder through the through holes on both sides of the metal foil, the metal paste is sintered to form the metal porous body on the surface of the metal foil. The method for producing a wet electrolytic capacitor according to claim 4. Using valve metal as the metal foil and the metal powder,
6. The dielectric film is formed on the surface of the anode by anodizing after forming the metal porous body on the surface of the metal foil by sintering the metal paste. A method of manufacturing a wet electrolytic capacitor. Using an insulating porous body as the separator,
7. The method of manufacturing a wet electrolytic capacitor according to claim 4, wherein a conductive porous body is used as the cathode.

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