JP2001052970A - Cylindrical electric double-layered capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in performance as much as possible, caused by expansion of band-like positive and negative poles due to charging, related to a cylindrical electric double-layered capacitor. SOLUTION: Related to a cylindrical electric double-layered capacitor 1, one separator 16 is inserted between band-like positive and negative poles 12 and 15 which expand by charging. An electrode winding body 3, wherein one of the band-like positive and electrode poles 12 and 15 is laminated on another separator 13, which is wound in spiral so as to be positioned on the outermost side, and a vessel 2 for housing the electrode winding body 3, are provided. The thickness of the band-like positive and negative poles 12 and 15 decreases, processing from a winding-start side to a winding-end side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical electric double layer capacitor, in particular, a separator interposed between a positive and a negative strip which expands upon charging, and another separator superimposed on one of the positive and negative strips. The present invention relates to a cylindrical electric double-layer capacitor including an electrode winding body in which the stacked product is spirally wound so that the another separator is positioned on the outermost side, and a container accommodating the electrode winding body.

[0002]

2. Description of the Related Art Heretofore, the above-mentioned band-shaped positive and negative electrodes have been formed so as to have a uniform thickness over the entirety mainly of activated carbon. Examples of the activated carbon that expands upon charging as described above include, for example, alkali activated carbon using mesophase pitch as a raw material.

[0003]

The above-mentioned alkali activated carbon has a high density and a high capacity and is extremely effective in increasing the capacitance of a cylindrical electric double layer capacitor.
As described above, since the battery expands due to charging, deformation of the belt-like positive and negative electrodes and the like may occur, and the performance of the cylindrical electric double layer capacitor may be deteriorated. This expansion progresses by a fixed amount according to the charging voltage, and hardly progresses in the constant voltage charging state. The contraction amounts of the band-shaped positive and negative electrodes are smaller than their expansion amounts.

[0004]

SUMMARY OF THE INVENTION The present invention reduces the absolute amount of expansion in the belt-shaped positive and negative electrodes as compared with the conventional example, and maintains the absolute amounts of their weights substantially equal to those of the conventional example. It is an object of the present invention to provide the cylindrical electric double-layer capacitor capable of suppressing as much as possible.

[0005] To achieve the above object, according to the present invention,
One separator is interposed between the band-shaped positive and negative electrodes that expand by charging, and another separator is superimposed on one of the band-shaped positive and negative electrodes so that the other separator is positioned on the outermost side. In a cylindrical electric double-layer capacitor including a spirally wound electrode winding body and a container for accommodating the electrode winding body, the thicknesses of the positive and negative electrodes are changed from the winding start side to the winding end side. The present invention provides a cylindrical electric double layer capacitor having a reduced size.

[0006] In the electrode wound body, the final thickness increase rate due to the expansion of the belt-like positive and negative electrodes is, for example, about 1 at the center.
0%, about 30% in the middle part, and about 50% in the outer peripheral part. The reason why the rate of increase in the thickness at the center is small is that the tightening force due to the winding is acting strongly at the center, while the rate of increase in the thickness at the outer periphery is large.
This is because the tightening force on the outer peripheral portion is weak due to the existence of the gap for fitting the electrode winding body between the electrode winding body and the container.

Therefore, when the belt-like positive and negative electrodes are configured as described above, the outer peripheral portion having the largest amount of expansion is formed to be the thinnest and the absolute amount of expansion of the entire electrode winding body is reduced as compared with the conventional example. Thereby, deformation of the belt-like positive and negative electrodes and the like can be avoided. On the other hand, the thickness of the central portion having the smallest expansion amount is formed to be the thickest so that the absolute weights of the belt-shaped positive and negative electrodes can be maintained substantially equal to those of the conventional example.

As a result, it is possible to minimize the performance deterioration such as a decrease in capacitance and an increase in internal resistance due to the expansion of the belt-like positive and negative electrodes.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a cylindrical electric double-layer capacitor 1 includes an Al container 2, an electrode winding body 3 accommodated in the container 2, and an electrolytic solution injected into the container 2. And a liquid. The container 2 comprises a bottomed cylindrical main body 4 and a terminal plate 5 for closing one end opening thereof. The terminal plate 5 is provided with positive and negative terminals 6, 7 and a safety valve 8.

The wound electrode body 3 has a positive electrode laminated band 9 and a negative electrode laminated band 10. The positive electrode laminated band 9 is formed by attaching a band-shaped polarizable electrode e to both sides of a band-shaped current collector 11 made of aluminum foil using a conductive adhesive, and PTFE (polytetrafluoroethylene) is applied to one of the band-shaped polarizable electrodes e. The first separator 13 made of ethylene is superposed. A belt-like positive electrode 12 is constituted by the pair of polarizable electrodes e.
Further, the first separator 13 is impregnated and held with the electrolytic solution.
The negative electrode laminated strip 10 has a strip-shaped polarizable electrode e adhered to both sides of a strip-shaped current collector 14 made of aluminum foil using a conductive adhesive, and a second strip made of PTFE is attached to one of the strip-shaped polarizable electrodes e. The separator 16 is overlapped. The strip-shaped negative electrode 15 is constituted by the pair of polarizable electrodes e.
In addition, the second separator 16 is impregnated and held with the electrolytic solution.

In manufacturing the electrode winding body 3, the second separator 16 of the negative electrode lamination strip 10 is superimposed on the exposed strip-shaped positive electrode 12 of the positive electrode lamination strip 9, and the superimposed product is subjected to positive electrode lamination. The band 9 is spirally wound so that the first separator 13 of the band 9 is located on the outermost side.

The strip-shaped positive electrode 12 and the strip-shaped negative electrode 15 are mainly composed of alkali activated carbon made from mesophase pitch, and therefore, the electrodes 12, 15 expand upon charging.

As the electrolytic solution, borofluorinated fourth ammonium
Compounds, such as TEMA.BF _Four[(C_TwoH_Five)_Three
CH_ThreeN ・ BF_Four(Triethyl borofluoride ammonium
), Solute] PC (propylene carbonate,
Medium) solution is used.

According to the present invention, in the cylindrical electric double layer capacitor 1 as described above, the thicknesses of the belt-like positive and negative electrodes 12, 15 are reduced from the winding start side to the winding end side. In order to reduce the thickness, specifically, a means such as a stepwise decrease or a linear decrease is employed.

In the electrode wound body 3, the final thickness increase rate due to the expansion of the strip-shaped positive and negative electrodes 12, 15 is, for example, about 10% at the central part A and at the intermediate part B as shown in FIG. About 30%, and about 50% at the outer peripheral portion C. The reason why the thickness increase rate at the central portion A is small is that the central portion A
This is because the tightening force due to the winding is acting strongly. On the other hand, the rate of increase in the thickness at the outer peripheral portion C is large because the electrode winding body 3 and the bottomed cylindrical main body 4 have the electrode winding body. This is because the tightening force on the outer peripheral portion C is weak due to the existence of the fitting gap 3.

Therefore, when the belt-shaped positive and negative electrodes 12, 15 are constructed as described above, the outer peripheral portion C having the largest expansion amount is formed to be the thinnest, and the absolute amount of expansion of the entire electrode winding body 3 is smaller than that of the conventional example. The positive and negative electrodes 12, 1
5 can be avoided. On the other hand, the absolute value of the weight of the belt-shaped positive and negative electrodes 12, 15 can be maintained substantially equal to that of the conventional example by forming the central portion A having the smallest expansion amount to have the largest thickness.

As a result, it is possible to minimize performance deterioration such as a decrease in capacitance and an increase in internal resistance due to expansion of the belt-like positive and negative electrodes 12 and 15.

Hereinafter, a specific example will be described.

The main components of the belt-shaped positive and negative electrodes 12 and 15 are:
Alkali activated carbon using mesophase pitch as a raw material, in the example, KOH activated carbon was produced by the following method.

(A) A lump of mesophase pitch is pulverized at room temperature to produce a pulverized powder having an average particle diameter of 300 μm, and then the pulverized powder is subjected to infusibilization treatment at 350 ° C. for 2 hours in an air stream. Thereafter, the pulverized powder was carbonized at 700 ° C. for 1 hour in a nitrogen stream to obtain a carbonized powder. (B) mixing carbonized powder and KOH twice as much as the carbon weight thereof, and then adding the mixture in a nitrogen atmosphere at 800 ° C., 5 ° C.
After a potassium activation treatment as an alkali activation treatment for a long time, the mixture was subjected to post-treatments such as neutralization with hydrochloric acid, washing and drying to obtain KOH-activated carbon. (C)
KOH activated carbon is crushed by a jet mill,
A fine KOH activated carbon having an average particle size of 30 μm was obtained. Less than,
This fine KOH activated carbon is simply called KOH activated carbon. [Example I] KOH-activated carbon, graphite powder (conductive filler) and PTFE (binder) were weighed in a weight ratio of 85: 12.5: 2.5, and the weighed material was kneaded. Rolling using the kneaded material, thickness 200μ
Three types of electrode sheets of m, 170 μm and 150 μm were produced. As shown in FIG.
mm, a plurality of strips 17, 18 and 19 having a length of 500 mm are cut out, and these three strips 17, 18, and 19 and a width 10
5 mm, 1500 mm long, 40 μm thick strip-shaped current collector 11
And a conductive adhesive, and a 75 μm-thick first separator 13 made of PTFE.
Was made. In this case, both strips 17 having a thickness of 200 μm are used.
Are provided on both sides of one end in the longitudinal direction of the current collector 11 and have a thickness of 15
Both band-shaped members 19 of 0 μm are provided on both surfaces on the other end side in the longitudinal direction of the current collector 11, and both band-shaped members 18 having a thickness of 170 μm are provided on both surfaces of the current collector 11 between both band-shaped members 17, 19. A strip-shaped polarizable electrode e is constituted by the strips 17, 18, and 19, and the thickness of the pair of polarizable electrodes e from one end to the other end is 2: 1.7: 1.5. A band-shaped positive electrode 12 reduced stepwise is formed.

Further, the same three strips 17 and 1 as described above are used.
The negative electrode laminated band 10 was manufactured using 8, 19, the band-shaped current collector 14, a conductive adhesive, and the second separator 16 having a thickness of 75 μm. In this case, the thickness is 200 μm
The two strips 17 of both sides at one end in the longitudinal direction of the current collector 14, the two strips 18 having a thickness of 150 μm on both sides at the other end of the collector 14 in the longitudinal direction, and the two strips of 170 μm in thickness are further provided. A body 18 is disposed on both sides of the current collector 14 between the two strips 17, 19, respectively.
9 form a strip-shaped polarizable electrode e, and 2: 1.7: 1.5 from one end to the other end of the pair of polarizable electrodes e.
The band-shaped negative electrode 15 whose thickness is reduced stepwise at the ratio of is formed.

The second separator 1 of the negative electrode laminated band 10 is applied to the exposed band-shaped polarizable electrode e of the positive electrode laminated band 9.
6 and the superimposed product is placed on the first
So that the thickness of the separator 13 is the outermost.
As shown in FIG. 2, the electrode wound body 3 is manufactured by spirally winding around the end a of the belt-shaped body 17 of 0 μm in a counterclockwise direction as shown in FIG. TEMA ・ BF
₄ was dissolved in a PC solution and the electrolyte was mixed with an inner diameter of 50 mm and a length of 1
The container 2 was placed in a bottomed cylindrical main body 4 of a 30 mm container 2, and its opening was closed using a terminal plate 5. At the time of closing, both the current collectors 11 of the positive electrode laminated band 9 and the negative electrode laminated band 10 are connected to the positive terminal 6 and the negative terminal 7 of the terminal plate 5, respectively. This cylindrical electric double layer capacitor 1 is referred to as an embodiment (1). [Example II] KOH-activated carbon, graphite powder (conductive filler), PTFE and PVDF (polyvinylidene fluoride, binder) were weighed so as to have a weight ratio of 80: 12: 2: 6. N-methyl-2-pyrrolidone (solvent) in an amount 5 times the weight of the mixture was added and mixed to obtain a paste-like electrode mixture. Using a doctor blade method, the electrode mixture was 105 mm wide, 1500 mm long,
Each of the belt-shaped current collectors 11 having a thickness of 40 μm was applied to both sides at a width of 95 mm, a length of 1500 mm, and a thickness of 220 μm, and then rolled, and as shown in FIG.
m, the thickness of the other end is 150 μm, the thickness at a bisecting position in the longitudinal direction is 175 μm, and a strip-shaped polarizable electrode e whose thickness decreases linearly from one end to the other end is formed; A belt-shaped positive electrode 12 was constituted by a pair of polarizable electrodes e. In this case, the gradient of the belt-shaped positive electrode 12 is (200-150) / 150.
0. Further, Example I was applied to one of the band-shaped polarizable electrodes e.
The same first separator 13 is overlapped to form a positive electrode laminated strip 9.
Was configured.

Next, the same electrode mixture as described above was applied by a doctor blade method to a width of 105 mm, a length of 1500 mm and a thickness of 40 mm.
95 mm width and 1500 length on both sides of the μm band current collector 14
mm and a thickness of 220 μm, and then rolled. Similarly, the thickness at one end is 200 μm, the thickness at the other end is 150 μm, and the thickness at the bisecting position in the longitudinal direction is 175 μm.
m, and a strip-shaped polarizable electrode e whose thickness decreases linearly from one end to the other end is formed, and a strip-shaped negative electrode 15 is constituted by a pair of polarizable electrodes e. In this case, the gradient of the strip-shaped negative electrode 15 is (200-150) / 150 as described above.
0. Further, the second separator 16 similar to that of Example I was superposed on one of the band-shaped negative electrodes 15 to form the negative electrode laminated band 10.

Then, the second separator 1 of the negative electrode laminated band 10 is applied to the exposed band-shaped polarizable electrode e of the positive electrode laminated band 9.
6 and the superimposed product is placed on the first
The electrode wound body 3 is manufactured by spirally winding counterclockwise as shown in FIG. 2 around the end b having the maximum thickness so that the separator 13 of FIG. This electrode wound body 3 and an electrolytic solution obtained by dissolving 1.5 mol of TEMA.BF ₄ in a PC solution are put into a bottomed cylindrical main body 4 of a container 2 having an inner diameter of 50 mm and a length of 130 mm, and the opening thereof is opened. Was closed using the terminal plate 5. At the time of the closing, the current collectors 11 and 14 of the positive electrode laminated band 9 and the negative electrode laminated band 10 are connected to the positive terminal 6 and the negative terminal 7 of the terminal plate 5, respectively. This cylindrical electric double layer capacitor 1 is referred to as an embodiment (2). Comparative Example 80: 1 KOH-activated carbon, graphite powder (conductive filler), PTFE and PVDF (binder)
The mixture was weighed so as to have a weight ratio of 2: 2: 6, and then N-methyl-2-pyrrolidone (solvent) was added to the weighed material in an amount of 5 times the weight thereof, and the mixture was mixed. Obtained. The electrode mixture was applied to a width of 1 by the doctor blade method.
05mm, 1500mm long, 40μm thick strip-shaped current collector 1
95mm wide, 1500mm long, 220μm thick on both sides
, And then rolled to form a strip-shaped polarizable electrode e having a thickness of 175 μm as shown in FIG.
No. 2 was constructed. Example I was applied to this one strip-shaped polarizable electrode e.
The same first separator 13 is overlapped to form a positive electrode laminated strip 9.
Was configured.

Next, the same electrode mixture as described above was applied by a doctor blade method to a width of 105 mm, a length of 1500 mm and a thickness of 40 mm.
95 mm width and 1500 length on both sides of the μm band current collector 14
mm and a thickness of 220 μm, and then rolling was performed to form a strip-shaped polarizable electrode e having a thickness of 175 μm over the whole, and a strip-shaped negative electrode 15 was constituted by a pair of polarizable electrodes e. A second separator 16 similar to that of Example I is overlaid on one of the strip-shaped negative electrodes 15 to form a negative electrode laminated strip 10.
Was configured.

Then, the second separator 1 of the negative electrode laminated band 10 is applied to the exposed band-shaped polarizable electrode e of the positive electrode laminated band 9.
6 and the superimposed product is placed on the first
As shown in FIG. 2, the electrode wound body 3 is manufactured by spirally winding the electrode wound body 3 so that the separator 13 is positioned on the outermost side, and this electrode wound body 3 and 1.5 mol of TEMA.BF ₄ are mixed. PC
The electrolytic solution dissolved in the solution was put into the bottomed cylindrical main body 4 of the container 2 having an inner diameter of 50 mm and a length of 130 mm, and the opening was closed using the terminal plate 5. At the time of the closing, both the current collectors 11 and 14 of the positive electrode laminated band 9 and the negative electrode laminated band 10 are connected to the terminal plate 5.
Are connected to the positive terminal 6 and the negative terminal 7, respectively. This cylindrical electric double layer capacitor 1 is a comparative example. [Performance of Electric Double Layer Capacitor] Table 1 shows Example (1),
The initial performance of (2) and the comparative example is shown.

[0027]

[Table 1]

From Table 1, the initial performance is shown in Example (1),
It can be seen that (2) is slightly better than the comparative example.

The rate of increase in the outer diameter of the wound electrode body 3 after a lapse of 30 minutes for Examples (1), (2) and Comparative Example was obtained. The results shown in Table 2 were obtained.

[0030]

[Table 2]

As shown in Table 2, in Examples (1) and (2), the absolute amount of expansion in the belt-shaped positive and negative electrodes 12 and 15 was reduced. It can be seen that the rate of increase in outer diameter is significantly small.

Next, in Examples (1), (2) and Comparative Examples, a continuous voltage application of 2.5 V for 1700 hours was performed in an atmosphere of 45 ° C. in consideration of a practical life, and their static electricity was applied. When the capacitance deterioration rate and the internal resistance rise rate were measured, the results shown in FIGS. 6 and 7 were obtained.

6 and 7, the embodiments (1) and (2) are
Since the deformation of the belt-like positive and negative electrodes 12 and 15 is avoided, and the absolute weights thereof are maintained substantially equal to those of the conventional example, the capacitance deterioration rate and the internal resistance rise rate are lower than those of the comparative example. It can be seen that both are small and have a long service life. The reason why the capacitance deterioration rate and the internal resistance rise rate change over a long period of time is not due to expansion of the band-shaped positive and negative electrodes 12 and 15 but to gas generation and the like.

[0034]

According to the present invention, there is provided a cylindrical electric double layer capacitor capable of minimizing the deterioration of the performance due to the expansion of the belt-like positive and negative electrodes due to the charging by having the above configuration. can do.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view of a main part of a cylindrical electric double layer capacitor.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is an explanatory diagram showing a relationship between a positive electrode laminated band and a negative electrode laminated band in Examples.

FIG. 4 is an explanatory diagram showing a relationship between a positive electrode laminated band and a negative electrode laminated band in another example.

FIG. 5 is an explanatory diagram showing a relationship between a positive electrode laminated band and a negative electrode laminated band in a comparative example.

FIG. 6 is a graph showing a relationship between an elapsed time and a capacitance deterioration rate.

FIG. 7 is a graph showing a relationship between an elapsed time and an internal resistance increase rate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical electric double layer capacitor 2 Container 3 Wound electrode 12 Strip-shaped positive electrode 13 First separator 15 Strip-shaped negative electrode 16 Second separator

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[Procedure amendment]

[Submission date] October 18, 2000 (2000.10.
18)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

In the manufacture of the wound electrode body 3, the second separator 16 of the negative electrode lamination strip 10 is superimposed on the exposed polarizable electrode e of the positive electrode lamination strip 9, and the superposed product is placed on the positive electrode lamination. The first strip 13 of the laminated band 9 is spirally wound so as to be located on the outermost side.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

Further, the same three strips 17 and 1 as described above are used.
The negative electrode laminated band 10 was manufactured using 8, 19, the band-shaped current collector 14, a conductive adhesive, and the second separator 16 having a thickness of 75 μm. In this case, the thickness is 200 μm
The two strips 17 of both sides at one end in the longitudinal direction of the current collector 14, the two strips 19 having a thickness of 150 μm on both sides at the other end of the current collector 14, and the two strips of 170 μm in thickness are further provided. A body 18 is disposed on both sides of the current collector 14 between the two strips 17, 19, respectively.
9 form a strip-shaped polarizable electrode e, and 2: 1.7: 1.5 from one end to the other end of the pair of polarizable electrodes e.
The band-shaped negative electrode 15 whose thickness is reduced stepwise at the ratio of is formed.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Change

[Correction contents]

The second separator 1 of the negative electrode laminated band 10 is applied to the exposed band-shaped polarizable electrode e of the positive electrode laminated band 9.
6 and the superimposed product is placed on the first
So that the thickness of the separator 13 is the outermost.
As shown in FIG. 2, the electrode wound body 3 is manufactured by spirally winding around the end a of the belt-shaped body 17 of 0 μm in a counterclockwise direction as shown in FIG. TEMA ・ BF
₄ was dissolved in a PC solution and the electrolyte was mixed with an inner diameter of 50 mm and a length of 1
The container 2 was placed in a bottomed cylindrical main body 4 of a 30 mm container 2, and its opening was closed using a terminal plate 5. At the time of the closing, the current collectors 11 and 14 of the positive electrode laminated band 9 and the negative electrode laminated band 10 are connected to the positive terminal 6 and the negative terminal 7 of the terminal plate 5, respectively.
This cylindrical electric double layer capacitor 1 is referred to as an embodiment (1). [Example II] KOH-activated carbon, graphite powder (conductive filler), PTFE and PVDF (polyvinylidene fluoride, binder) were weighed so as to have a weight ratio of 80: 12: 2: 6. N-methyl-2-pyrrolidone (solvent) in an amount 5 times the weight of the mixture was added and mixed to obtain a paste-like electrode mixture. Using a doctor blade method, the electrode mixture was 105 mm wide, 1500 mm long,
Each of the belt-shaped current collectors 11 having a thickness of 40 μm was applied to both sides at a width of 95 mm, a length of 1500 mm, and a thickness of 220 μm, and then rolled, and as shown in FIG.
m, the thickness of the other end is 150 μm, the thickness at a bisecting position in the longitudinal direction is 175 μm, and a strip-shaped polarizable electrode e whose thickness decreases linearly from one end to the other end is formed; A belt-shaped positive electrode 12 was constituted by a pair of polarizable electrodes e. In this case, the gradient of the belt-shaped positive electrode 12 is (200-150) / 150.
0. Further, Example I was applied to one of the band-shaped polarizable electrodes e.
The same first separator 13 is overlapped to form a positive electrode laminated strip 9.
Was configured.

Claims (1)

[Claims] 1. A belt-shaped positive and negative electrode (1) which expands due to charging.
One separator (16) is interposed between 2, 15),
In addition, a superposed product in which another separator (13) is superimposed on one of the strip-shaped positive and negative electrodes (12, 15) is spirally wound so that the another separator (13) is located on the outermost side. In a cylindrical electric double-layer capacitor provided with an electrode winding body (3) and a container (2) for accommodating the electrode winding body (3), the thickness of the positive and negative electrodes (12, 15) is set to A cylindrical electric double-layer capacitor characterized by being reduced from the beginning to the end of the winding.