JP2000306783A - Electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lengthen service life of an electric double layer capacitor provided with a positive pole which is constituted by forming a positive pole active material layer containing a positive pole active material on a current collector body. SOLUTION: A positive pole 210 and a negative pole 220 are so placed that a side end surface 214a of a positive pole active material layer 214 faces a surface 224a of the negative pole 220 over the entire perimeter. In this constitution, deterioration at a side end part 214b of the positive pole active material layer 214 is suppressed, and deterioration of charge/discharge property is suppressed more than in conventional electric double layer capacitors, even if charge and discharge are repeated many times, so that service life is lengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor which can be used as a battery for an electric vehicle or the like, and more particularly to a positive electrode having a positive electrode active material layer containing a positive electrode active material formed on a positive electrode current collector. The present invention relates to an electric double layer capacitor provided.

[0002]

2. Description of the Related Art An electric double layer capacitor is composed of a pair of electrodes and an electrolytic solution interposed between the electrodes. In many electric double layer capacitors, one electrode is specialized for a positive electrode and the other electrode is specialized for a negative electrode. In such an electric double layer capacitor, in general, a positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on a current collector is used in order to enhance the current collection performance of the positive electrode. Most of the positive electrode active material layers are formed by binding powdered electrode active materials to each other and to a current collector with a binder.

[0003] Further, as the negative electrode, a negative electrode in which a negative electrode active material layer containing a negative electrode active material is formed on a current collector is used in order to enhance the current collection performance of the negative electrode. The negative electrode active material layer is also formed by the same method as the positive electrode. on the other hand,
As the electrode structure of the positive electrode and the negative electrode, for example, FIGS.
As shown in the figure, the positive electrode plates 1 each having a sheet-like shape
An electrode body (hereinafter, referred to as a laminated electrode body) in which 0 and negative electrode plates 20 are alternately stacked, and a positive electrode plate and a negative electrode plate each having a band shape (not shown) are stacked on each other. There is a wound electrode body (hereinafter, a wound electrode body) and the like. In FIG. 8, the positive electrode plate 10
As a negative electrode plate 20, a current collector 12 having a positive electrode active material layer 14 including a positive electrode active material formed thereon is shown.
The thing which formed the negative electrode active material layer 24 containing the negative electrode active material on the current collector 22 was shown. In this electrode body, a separator 30 is provided between the positive electrode plate 10 and the negative electrode plate 20.

In a conventional electric double layer capacitor,
As shown in FIG. 8, the positive electrode active material layer 14 of the positive electrode 10 and the negative electrode (negative electrode active material layer 24) are disposed so as to have the same area when viewed macroscopically. That is, the positive electrode 10 and the negative electrode 20 are arranged such that the side end surface 14a of the positive electrode active material layer 14 and the surface 24a of the negative electrode active material layer 24 do not face each other.

[0005]

In the above-mentioned conventional electric double layer capacitor, the charge / discharge characteristics are deteriorated when the charge / discharge operation is repeated many times, and the life is extended. However, the life is not sufficiently long. I could not say. The present invention has been made in view of the above circumstances, and has as its object to provide an electric double layer capacitor that can have a longer life than the conventional electric double layer capacitor.

[0006]

According to a first aspect of the present invention, there is provided an electric double layer capacitor, comprising: a positive electrode having a positive electrode active material layer including a positive electrode active material formed on a current collector; And the negative electrode, wherein the positive electrode and the negative electrode are disposed such that side end surfaces of the positive electrode active material layer face the surface of the negative electrode over the entire circumference. .

[0007] The electric double layer capacitor according to claim 2 of the present invention for solving the above-mentioned problems is the electric double layer capacitor according to claim 1, wherein the negative electrode is located on the side end face of the positive electrode active material layer. And a side protruding portion, and the side end face faces the surface of the protruding portion.
The electric double-layer capacitor according to claim 3 of the present invention for solving the above-mentioned problem is the electric double-layer capacitor according to claim 2, wherein the projecting length of the projecting portion is a side end face of the positive electrode active material layer. And the distance between the side end face of the positive electrode active material layer and the surface of the negative electrode is equal to or longer than the total length.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies focusing on the positive electrode in order to find out why the charge / discharge characteristics of the electric double layer capacitor are repeatedly reduced and its life is shortened. went. As a result of the research, the present inventors found that in the above-described conventional electric double-layer capacitor (for example, in the electric double-layer capacitor shown in FIG. 8), the side end 14b of the positive electrode active material layer 14 The binding of the positive electrode active material layer 14 may be such that the binding is released (the positive electrode active material particles are released from the positive electrode active material layer 14) or the side end 14b of the positive electrode active material layer 14 is separated from the current collector. It has been found that deterioration at the side end 14b is observed.

The present inventors consider that such deterioration of the positive electrode active material layer is one of the factors that deteriorates the charge / discharge characteristics of the electric double layer capacitor when the charge / discharge is repeated many times.
Further studies have been conducted on a method for preventing the deterioration of the positive electrode active material layer at the side edges. As a result of the research, the present inventors arranged the positive electrode and the negative electrode such that the side end surfaces of the positive electrode active material layer face the surface of the negative electrode over the entire circumference. It has finally been found that the deterioration at the side end (the part including the side end surface) is suppressed and the life of the electric double layer capacitor is prolonged.

The present invention has been made based on the above findings. In the electric double layer capacitor according to the present invention, the fact that the side end surface of the positive electrode active material layer faces the surface of the negative electrode over the entire circumference means that the positive electrode active material layer has a positional relationship that allows mutual recognition. Here, if a separator is interposed between the side end surface of the positive electrode active material layer and the surface of the negative electrode, it means that the separator has a positional relationship such that they can be seen through each other through the separator. In addition, “over the entire circumference” means, for example, in the case of a stacked type in which square electrode plates as shown in FIG. 2 are stacked, the four sides of the square (however, the electrode lead (tab) portion connected to the positive electrode terminal) In the case of a wound type, it means all of the upper and lower sides of the belt-shaped positive electrode forming the upper and lower surfaces of the cylindrical wound body.

On the other hand, the surface of the negative electrode facing the side end surface of the positive electrode active material layer is a surface capable of causing an electric field to act on the side end surface of the positive electrode active material layer and causing polarization. . The side end of the positive electrode active material layer refers to a part of the positive electrode active material layer including at least the side end surface of the positive electrode active material layer.

As an example of the electric double layer capacitor of the present invention, there is a laminated electrode body shown in FIG.
The electrode body illustrated in FIG. 1 is a stacked electrode body in which a positive electrode 110 and a negative electrode 120 are alternately stacked with a separator 130 interposed between the positive electrode 110 and the negative electrode 120. The positive electrode 110 is formed by forming a positive electrode active material layer 114 including a positive electrode active material on a current collector 112. The negative electrode 120 is a collector 1
A negative electrode active material layer 124 including a negative electrode active material is formed on 22. In this electrode body, by using the positive electrode 110 in which the positive electrode active material layer 114 has a tapered side end surface 114 a with respect to the current collector 112, the side end surface 114 a of the positive electrode active material layer 114 is entirely covered with the surface of the negative electrode. (The surface 124a of the negative electrode active material layer 124).

By arranging the positive electrode and the negative electrode in this way, it is possible to suppress the deterioration at the side end of the positive electrode active material layer as described above. Although the reason is not clear, the interaction between the side end face of the positive electrode active material layer and the surface of the negative electrode causes an electric field to act on the side end face of the positive electrode active material layer. It is considered that the deterioration at the side end of the positive electrode active material layer was suppressed.

Therefore, according to the electric double layer capacitor of the present invention, even if charge / discharge is repeated many times, the deterioration of the charge / discharge characteristics is suppressed as compared with the conventional electric double layer capacitor, and the life is extended. The electric double layer capacitor of the present invention can be constituted by using the following respective positive electrode, negative electrode and electrolytic solution.

As for the positive electrode, the material of the current collector is not particularly limited, but it is preferable to use a metal material having excellent conductivity such as aluminum. Also,
The shape is not particularly limited, but is preferably plate-like, and particularly preferably has a certain thickness. When the current collector has a plate shape, the plate thickness is not particularly limited, and is appropriately selected so as to obtain a desired current collection performance.

The type of the positive electrode active material is not particularly limited, and a known positive electrode active material can be used. However, it is necessary to use an electrode active material that does not cause a chemical reaction with the electrolytic solution, and in particular, does not cause an electrochemical reaction with the electrolytic solution even when polarization occurs during charging. Therefore, it is necessary to select an appropriate one according to the electrolyte used. Further, it is preferable to use a positive electrode active material having a large specific surface area. Activated carbon etc. is mentioned as an electrode active material satisfying such requirements.

As a material constituting the positive electrode active material layer, it is preferable to use a binder or a conductive agent in addition to the positive electrode active material. The type of the binder is not particularly limited, but cellulose, Teflon (registered trademark), or the like can be used. For example, methyl cellulose can be used. Further, the kind of the conductive material is not particularly limited, but for example, carbon black can be used.

The method for forming the positive electrode active material layer is not particularly limited either, and it can be formed by a known forming method. For example, the positive electrode active material layer can be formed as follows. First, a powdery positive electrode active material, a conductive material, and a binder are prepared, added to an appropriate dispersion medium, mixed well, and dispersed to prepare a paste-like positive electrode mixture. This positive electrode mixture is uniformly applied on the surface of the sheet-shaped current collector by a predetermined application method to form a mixture application layer. The mixture coating layer is dried to remove the dispersion medium to form a positive electrode active material layer. If necessary, it is press-formed by an appropriate press-forming method to adjust the shape and density.

The material of the negative electrode is not particularly limited by the composition of the material, but it is preferable to use a material in which a negative electrode active material layer containing a negative electrode active material is formed on a current collector. In this case, the type of the negative electrode active material is not particularly limited, and a known negative electrode active material can be used. It is necessary to use a negative electrode active material that does not cause a chemical reaction with the electrolytic solution, and particularly does not cause an electrochemical reaction with the electrolytic solution even when polarization occurs during charging. Therefore, it is necessary to select an appropriate one according to the electrolyte used. Also,
As the negative electrode active material, a material having a large specific surface area is preferably used, and the same active material as the positive electrode such as activated carbon can be used.

As a material constituting the negative electrode active material layer, it is preferable to use a binder or a conductive agent in addition to the negative electrode active material. The types of the binder and the conductive agent are not particularly limited, and the same materials as those for the positive electrode can be used. In addition, the method for forming the negative electrode active material layer is not particularly limited, and the negative electrode active material layer can be formed by a known formation method, and the negative electrode active material layer can be formed by a method similar to that for the positive electrode.

Furthermore, the arrangement of the positive electrode and the negative electrode is not particularly limited, and can be applied to any known arrangement. For example, as described above, for example, a laminated It can be applied to a round electrode body. Further, in addition to the electrode bodies, a positive electrode plate and a negative electrode plate each having a sheet-like shape are configured to face each other, and a cylindrical positive electrode and a negative electrode having different diameters are alternately concentric with each other. The present invention can also be applied to arrangements such as those provided.

In the above arrangement of the electrodes, a separator is generally provided between the positive electrode and the negative electrode. In the present invention, such a separator is preferably provided. As the separator, a known separator can be used. For example, a separator made of polyethylene or the like can be used. For the electrolyte interposed between the electrodes,
There is no particular limitation, and a known electrolytic solution can be used. In the present invention, an aqueous solution of an electrolyte may be used, or a non-aqueous electrolyte in which a supporting salt is dissolved in an organic solvent may be used. When using the latter non-aqueous electrolyte, the solvent,
It is preferable to use a carbonate-based organic solvent such as propylene carbonate. In addition, (C ₂
H ₅₎ It is preferable to use an onium salt such as ₄ NBF _4.

According to the present invention, it is preferable that the negative electrode has a protruding portion protruding from the side end surface of the positive electrode active material layer, and the side end surface faces the surface of the protruding portion. The projecting portion may extend in a direction in which the negative electrode extends, or may extend in a direction at an angle to the extending direction. Further, the protruding portion may extend in a plane with respect to the extending direction, or may extend in a curved surface.

By disposing the positive electrode and the negative electrode in this way, the side end surface of the positive electrode active material layer and the surface of the protruding portion of the negative electrode can be easily faced. Therefore, deterioration at the side end of the positive electrode active material layer can be more easily suppressed than in the electric double layer capacitor having the above configuration. As a result, even if charge / discharge is repeated many times, the deterioration of the charge / discharge characteristics is further suppressed as compared with the electric double layer capacitor having the above configuration, and the life thereof is further extended.

For example, in an electric double layer capacitor provided with a laminated electrode body, as shown in FIGS. 2 and 3,
The negative electrode 220 has a protruding portion 2 that protrudes in the extending direction of the negative electrode 220 with respect to the side end surface 214 a of the positive electrode active material layer 214.
20a can be provided. In this electrode body, the side end surface 214a of the positive electrode active material layer 214 and the surface of the negative electrode 220 (the surface 224 of the negative electrode active material layer 224 at the protrusion 220a)
a) can be easily faced. This configuration will be described in detail in an embodiment described later.

In the present invention, the protrusion length of the protrusion is defined by a layer thickness at a side end face of the positive electrode active material layer and a distance between a side end face of the positive electrode active material layer and the surface of the negative electrode. It is preferably longer than the sum of the lengths. For example, in an electric double layer capacitor having a stacked electrode body, as shown in FIG. 3, the projection length of the projection of the negative electrode is set to L, and the layer thickness at the side end surface of the positive electrode active material layer is set to L. D, the distance between the side end surface of the positive electrode active material layer and the surface of the negative electrode (separator 2
When 30 is expressed as W, it is preferable to provide the negative electrode projection so as to satisfy the relational expression 1 of L / (D + W) ≧ 1. Note that D is a given value if the thickness of the positive electrode active material layer is constant.
It becomes the thickness of the positive electrode active material layer. By disposing the positive electrode and the negative electrode in this manner, deterioration at the side end of the positive electrode active material layer can be further suppressed as compared with the electric double layer capacitor having the above configuration. As a result, even if charge / discharge is repeated many times, the deterioration of the charge / discharge characteristics is further suppressed as compared with the electric double layer capacitor having the above configuration, and the life thereof is further extended.

The above relational expression 1 has been found from empirical knowledge. However, if L is too large, it is difficult for the electric field to act on the tip of the protruding portion of the negative electrode from the positive electrode. As a result, polarization is less likely to occur at the tip of the protrusion,
The discharge capacity decreases. Therefore, it is preferable to appropriately set the length of L so that an electric field can easily act on all of the protrusions of the negative electrode from the positive electrode.

As described above, when the negative electrode is provided with a protruding portion that protrudes from the side end surface of the positive electrode active material layer with respect to the extension direction, macroscopically, the surface area of the positive electrode active material layer is reduced. The surface area is smaller than the surface area of the negative electrode active material layer located on the side facing the positive electrode active material layer. Therefore, each surface of the positive electrode active material layer and the negative electrode active material layer should be microscopically viewed, and the specific surface area of each layer should be appropriately selected so that optimal polarizability can be obtained between the electrodes. Is desirable.

As another example of the electrode structure in which the negative electrode is provided with the protrusion as described above, as shown in FIG.
A positive electrode 310 in which a positive electrode active material layer 314 has a tapered side end surface 314 a with respect to a current collector 312 is used.
In addition, a protrusion 320a protruding from the side end surface 314a of the positive electrode active material layer 314 in the extending direction of the negative electrode can be provided. In addition, 330 is a separator.

As shown in FIG. 5, in the other part of the electrode body where the tab connected to the positive electrode terminal is provided on the positive electrode, the protrusion 420a of the negative electrode 420 is connected to the side end surface 414a of the positive electrode active material layer 414. You may provide so that it may cover. For example, in an electric double layer capacitor having a laminated electrode body, such a protruding portion 420a is formed by laminating a positive electrode 410 and a negative electrode 420 with a separator 430 interposed therebetween as shown in FIG. After that, the protruding portion 420a of the negative electrode and the protruding portion 430a of the separator 430 can be formed by bending in the direction of the arrow. In addition,
The negative electrode 420 includes a current collector 422 and a negative electrode active material layer 424.

On the other hand, in the electric double layer capacitor of the present invention having the above structure, the surface of the negative electrode facing the positive electrode active material layer and the extension in which the side end surface of the positive electrode active material layer extends toward the surface of the negative electrode facing the positive electrode active material layer. It is preferable that the surfaces make an angle within a predetermined angle with each other. In the electric double layer capacitor shown in FIG. 1, θ ₁ corresponds to the angle, and in the electric double layer capacitor shown in FIG. 4, θ ₂ corresponds to the angle.

The predetermined angle is not particularly limited, but is preferably an upper limit angle at which the side end surface of the positive electrode active material layer and the surface of the negative electrode facing each other can act on each other with an electric field. By disposing the positive electrode and the negative electrode in this manner, deterioration at the side end of the positive electrode active material layer can be further suppressed as compared with the electric double layer capacitor having the above configuration.

In particular, when the predetermined angle is within 90 °, it becomes easy to cause an electric field to act between the side end face of the positive electrode active material layer and the surface of the negative electrode. Therefore,
The upper limit angle is preferably 90 °.

[0034]

The present invention will be described below in detail with reference to examples. As shown in FIG. 2, the electric double layer capacitor of this embodiment has a rectangular positive electrode 210 and a negative electrode 220 each having a separator 230 between the positive electrode 210 and the negative electrode 220.
Is an electric double layer capacitor provided with a laminated electrode body alternately laminated with interposing.

The positive electrode 210 is formed by forming a positive electrode active material layer 214 containing a positive electrode active material on a current collector 212. The positive electrode active material layer 214 is a layer having a constant thickness of 0.05 mm. The separator has a constant thickness of 0.05 mm. The negative electrode 220 is formed by forming a negative electrode active material layer 224 including a negative electrode active material on a current collector 222.

In each of the electric double layer capacitors of Examples 1 to 4, the negative electrode 220 is connected to the positive electrode active material layer 214.
The protruding portions 220a protruding in the extending direction of the negative electrode 220 with respect to the side end surface 214a are provided with different protruding lengths. Here, as shown in FIG.
0a is represented by L, and the positive electrode active material layer 21
4 is denoted by D, and the side end surface 21 of the positive electrode active material layer 214
Table 1 shows the value of L / (D + W) for each electric double layer capacitor of Examples 1 to 4, where W represents the distance (thickness of the separator 230) between 4a and the surface 224a of the negative electrode active material layer 224. .

The positive electrode 21 of these electric double layer capacitors
As the 0 and the negative electrode 220, those formed as follows were used. As the separator 230, a porous film made of polyethylene was used. Further, as an electrolytic solution (not shown), a nonaqueous electrolytic solution prepared by dissolving a supporting salt in an organic solvent was used as described after the method for forming the positive electrode 10 and the negative electrode 220. [Method of Forming Positive Electrode 210] Activated carbon (A
C), carbon black (CB) as a conductive material, and methylcellulose (MC) as a binder in a predetermined weight ratio (AC: CB: MC = 24: 3: 3), and are dispersion media. The mixture was mixed well with N-methyl-pyrrolidone (NMP) to prepare a positive electrode mixture. This positive electrode mixture is placed on both sides of a sheet-like current collector 212 (aluminum foil),
The mixture was applied uniformly with a predetermined thickness by a predetermined coating method to form a mixture coating layer. After drying this mixture applied layer by a predetermined drying method, it was press-molded to a predetermined thickness by a predetermined press molding method to obtain a predetermined density. Thus, the positive electrode 21
A predetermined number of 0s were formed. [Method of Forming Negative Electrode 220] A predetermined number of negative electrodes 220 were formed in the same manner as for the positive electrode 210. In each of the electric double layer capacitors of the above embodiments, the negative electrode 220 was provided with electrodes provided at both ends in the electrode laminating direction. With respect to the negative electrodes 220 provided at both ends, only one surface of the current collector 222 on the positive electrode 210 side is provided.
What formed 24 was used. [Method for Preparing Electrolyte Solution] Tetraethylammonium tetrafluoroboron ((C ₂ H ₅ ) ₄ NBF ₄ ) as a supporting salt
Was dissolved at a predetermined concentration in a mixed organic solvent obtained by mixing propylene carbonate (PC) and dimethoxyethane (DME) at a predetermined volume ratio in an organic solvent to prepare an electrolytic solution. COMPARATIVE EXAMPLE 1 As a comparative example of the electric double layer capacitor of the above embodiment, as shown in FIGS.
0, except that the positive electrode active material layer 14 and the negative electrode active material layer 24 are disposed so as to have the same area when viewed macroscopically. An electric double layer capacitor provided with the same electrolytic solution as in the example was produced. That is, the positive electrode 10 and the negative electrode 20 were arranged so that L / (D + W) = 0 without providing the negative electrode 220 with the protrusion 220a as in the above-described embodiment. [Test Method] A charge / discharge test was performed for each of the electric double layer capacitors of Examples 1 to 4 and Comparative Example 1 under the following conditions.

At an ambient temperature of 70 ° C., charging / discharging at a constant power of 0.1 W / F was performed for 100,000 cycles in a voltage range of 1.5 V to 25 V. After the charge / discharge test, the binding of the positive electrode active material is lost (positive electrode active material particles are released from the positive electrode active material layer 214) on the side end surface of the positive electrode active material layer of each electric double layer capacitor, It was examined whether or not deterioration at the side end of the positive electrode active material layer was observed such that the side end itself of the material layer 214 was separated from the current collector 212. As a result, the investigation results as shown in Table 1 were obtained.

[0039]

[Table 1] According to the investigation results in Table 1, in the electric double layer capacitors of Example 1 and Example 2, although the deterioration at the side end 214b of the positive electrode active material layer 214 was slightly observed, compared with Comparative Example 1, the deterioration was observed. The degree of deterioration was found to be low. On the other hand, in the electric double layer capacitors of the third and fourth embodiments, the side end 214 of the positive electrode active material layer 214
No deterioration was observed in b.

As described above, from the results of each charge / discharge test for the electric double layer capacitors of Examples 1 to 4, the negative electrode 2
20, a protruding portion 220a protruding from the side end surface 214a of the positive electrode active material layer 214 in the direction in which the negative electrode 220 extends.
The positive electrode active material layer 214 is disposed such that the side end surface 214a of the positive electrode active material layer 214 faces the surface of the negative electrode 220 (the surface 224a of the negative electrode active material layer 224 at the protrusion 220a) over the entire circumference. Side end face 2
14a, the side end 214b of the positive electrode active material layer 214
It is clear that the deterioration at the time can be suppressed.

In particular, in the electric double layer capacitors of the third and fourth embodiments, the relational expression of L / (D + W) ≧ 1 is satisfied. That is, the protrusion 220a of the negative electrode 20
Is determined by determining the layer thickness at the side end surface 214a of the positive electrode active material layer 214 and the distance between the side end surface 214a of the positive electrode active material layer 214 and the surface of the negative electrode 220 (the surface 224a of the negative electrode active material layer 224). It is apparent that by setting the length to be equal to or longer than the sum, deterioration at the side end 214b of the positive electrode active material layer 214 can be prevented.

However, if the protrusion length of the protrusion 220a of the negative electrode 20 becomes 1 mm or more, the protrusion 220a
It becomes difficult for the electric field to act from the positive electrode 210 to the front end of “a”.
Therefore, the protrusion length L of the protrusion 220a of the negative electrode 20 is represented by L
It is desirable to select appropriately so as to satisfy the formula of / (D + W) ≦ 10.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a part of a side end of an electrode body of an example of an electric double layer capacitor of the present invention.

FIG. 2 is a cross-sectional view schematically showing a part of a side end of an electrode body of an example of the electric double layer capacitor of the present invention (the electric double layer capacitor of the embodiment).

3 is a perspective view schematically showing the electric double layer capacitor shown in FIG. 2 as viewed through the arrangement of a positive electrode plate and a negative electrode plate from the front of an electrode body.

FIG. 4 is a cross-sectional view schematically showing a part of a side end of an electrode body of an example of the electric double layer capacitor of the present invention.

FIG. 5 is a cross-sectional view schematically showing a part of a side end of an electrode body of an example of the electric double layer capacitor of the present invention.

6 is a cross-sectional view of a part of a side end of the electrode body schematically showing a process of forming the electrode body in forming the electric double layer capacitor shown in FIG.

FIG. 7 is a perspective view showing an example of a conventional electric double-layer capacitor (electric double-layer capacitor of Comparative Example 1) showing a state of an electrode body.

8 is a cross-sectional view schematically showing a part of a side end of an electrode body of the conventional electric double layer capacitor shown in FIG.

[Explanation of symbols]

210: positive electrode plate 212: current collector 214: positive electrode active material layer 214a: side end surface 214b:
Side end 220: negative electrode plate 220a: projecting portion 222: current collector 224: negative electrode active material layer 224a: surface 230: separator

Claims (3)

[Claims] 1. An electric double-layer capacitor including a positive electrode in which a positive electrode active material layer including a positive electrode active material is formed on a current collector, and a negative electrode, wherein the positive electrode and the negative electrode are connected to the positive electrode active material. An electric double layer capacitor, wherein a side end face of a material layer is disposed so as to face a surface of a negative electrode over the entire circumference. 2. The electric double layer according to claim 1, wherein the negative electrode has a protrusion protruding from the side end face of the positive electrode active material layer, and the side end face faces the surface of the protrusion. Capacitors. 3. The projecting length of the projecting portion is a length obtained by adding a layer thickness at a side end surface of the positive electrode active material layer and a distance between a side end surface of the positive electrode active material layer and the surface of the negative electrode. The electric double-layer capacitor according to claim 2, which is more than the above.