ELECTRIC DOUBLE LAYER CAPACITOR

Abstract

Provided is an electric double layer capacitor including a large capacity single cell having a large electrostatic capacity and a small capacity single cell are connected to the same exterior case in parallel, and a thickness of a separator of the large capacity single cell is made thicker than a thickness of a separator of the small capacity single cell. With this structure, a supply amount of an electrolyte solution to the large capacity single cell is markedly increased compared with the small capacity single cell, thereby being capable of preventing degradation of the large capacity single cells and the small capacity single cells and providing the electric double layer capacitor having an excellent cycle life and having a large power storage amount while keeping characteristics capable of instantaneously allowing large current to flow.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a sectional view showing a structure of an electric double layer capacitor according to a first embodiment of the present invention;

FIG. 2 is a longitudinal sectional view showing a state where the electric double layer capacitor according to the first embodiment of the present invention is received in an exterior case;

FIGS. 3A and 3B are graphs each showing charging and discharging characteristics of the electric double layer capacitor according to the first embodiment of the present invention;

FIGS. 4A to 4C are sectional views each showing a structure of an electric double layer capacitor according to a second embodiment of the present invention;

FIG. 5 is a graph showing dependency of a maximum current allowed to flow instantaneously into the electric double layer capacitor according to the second embodiment of the present invention on the number of small capacity single cells;

FIG. 6 is a sectional view showing a structure of an electric double layer capacitor according to a third embodiment of the present invention;

FIG. 7 is a schematic view showing a structure of electrodes of an electric double layer capacitor according to a fifth embodiment of the present invention;

FIG. 8 is a longitudinal sectional view showing a state where the electric double layer capacitor according to the fifth embodiment of the present invention is received in an exterior case;

FIG. 9 is a graph showing a dependency of an internal resistance on discharging time of the electric double layer capacitor according to the fifth embodiment and Comparative Examples 1 to 3 of the present invention;

FIG. 10 is a graph showing a charge and discharge efficiency depending on the discharging time of the electric double layer capacitor according to the fifth embodiment and Comparative Examples 1 to 3 of the present invention;

FIGS. 11A and 11B are schematic sectional views each showing a state of movement of electrons between a large capacity single cell and a small capacity single cell in the electric double layer capacitor according to the fifth embodiment of the present invention;

FIGS. 12A and 12B are schematic sectional views each showing a state of movement of electrons between a large capacity single cell and a small capacity single cell of parallel connecting capacitors of Comparative Example 3 of the present invention;

FIGS. 13A and 13B are equivalent circuit diagrams of the electric double layer capacitors according to Comparative Example 3 and the fifth embodiment of the present invention; and

FIG. 14 is a schematic view showing a structure of electrodes of an electric double layer capacitor according to a seventh embodiment of the present invention.

Claims

1. An electric double layer capacitor comprising a plurality of single cells including a positive electrode layer formed on a positive electrode current collector and a negative electrode layer formed on a negative electrode current collector, which are arranged so as to face each other with a porous separator provided therebetween, the plurality of the single cells being layered and disposed in an exterior case impregnated with an electrolytic solution, and being connected in parallel, wherein:the positive electrode layers are classified into a large capacity positive electrode layer and a small capacity positive electrode layer whose electrostatic capacities are different from each other;the negative electrode layers are classified into a large capacity negative electrode layer and a small capacity negative electrode layer whose electrostatic capacities are different from each other;at least one of the single cells is a combination of the large capacity positive electrode layer and the large capacity negative electrode layer;at least another one of the single cells is a combination of the small capacity positive electrode layer and the small capacity negative electrode layer;a thickness of the separator disposed between the large capacity positive electrode layer and the large capacity negative electrode layer is thicker than the thickness of the separator disposed between the small capacity positive electrode layer and the small capacity negative electrode layer.

2. An electric double layer capacitor according to claim 1, wherein: the electrostatic capacity of the large capacity positive electrode layer is two times or more of the electrostatic capacity of the small capacity positive electrode layer; andthe electrostatic capacity of the large capacity negative electrode layer is two times or more of the electrostatic capacity of the small capacity negative electrode layer.

3. An electric double layer capacitor according to claim 1, wherein: the electrostatic capacity of the large capacity negative electrode layer exceeds the electrostatic capacity of the large capacity positive electrode layer; andthe electrostatic capacity of the small capacity negative electrode layer exceeds the electrostatic capacity of the small capacity positive electrode layer.

4. An electric double layer capacitor according to claim 1, wherein a number of the single cells including the small capacity positive electrode layer and the small capacity negative electrode layers is two times or more of a number the single cells including the large capacity positive electrode layers and the large capacity negative electrode layers.

5. An electric double layer capacitor according to claim 1 wherein: the single cells including the large capacity positive electrode layers and the large capacity negative electrode layers are arranged one side with respect to a direction in which the single cells are layered; andthe single cells including the small capacity positive electrode layers and the small capacity negative electrode layers are arranged the other side with respect to the direction in which the single cells are layered.

6. An electric double layer capacitor according to claim 1 wherein: the single cells including the large capacity positive electrode layers and the large capacity negative electrode layers are arranged at a center with respect to the direction in which the single cells are layered; andthe single cells including the small capacity positive electrode layers and the small capacity negative electrode layers are arranged on an outer side with respect to the direction in which the single cells are layered.

7. An electric double layer capacitor according to claim 1 wherein: the single cells including the large capacity positive electrode layers and the large capacity negative electrode layers and the single cells including the small capacity positive electrode layers and the small capacity negative electrode layers are arranged alternately with respect to the direction in which the single cells are layered.

8. An electric double layer capacitor according to claim 1 wherein thicknesses of the electrode layers of the large capacity positive electrode layers and the large capacity negative electrode layers are thicker than the thicknesses of the electrode layers of the small capacity positive electrode layers and the small capacity negative electrode layers.

9. An electric double layer capacitor according to claim 1, wherein an electrostatic capacity of a carbon particle as a main component of the large capacity positive electrode layers and the large capacity negative electrode layers is larger than an electrostatic capacity of a carbon particle as a main component of the small capacity positive electrode layers and the small capacity negative electrode layers.

10. An electric double layer capacitor according to claim 1, wherein thicknesses of the positive electrode current collector and the negative electrode current collector, on which the small capacity positive electrode layers and the small capacity negative electrode layers are respectively formed, are thicker than thicknesses of the positive electrode current collector and the negative electrode current collector on which large capacity positive electrode layers and the large capacity negative electrode layers are respectively formed.

11. An electric double layer capacitor according claim 1, further comprising: a plurality of positive electric current collectors each including the large capacity positive electrode layer and the small capacity positive electrode layer formed on a front side and a back side thereof;a plurality of negative electric current collectors each including the large capacity negative electrode layer and the small capacity negative electrode layer formed on a front side and a back side thereof;a plurality of separators each being disposed between the large capacity positive electrode layer and the large capacity negative electrode layer, and between the small capacity positive electrode layer and the small capacity negative electrode layer, wherein:the plurality of positive electric current collectors and the plurality of negative electric current collectors are alternately arranged;the plurality of positive electric current collectors are electrically connected in parallel with each other; andthe plurality of negative electric current collectors are electrically connected in parallel with each other.

12. An electric double layer capacitor according to claim 1, wherein the large capacity electrode layers include a separator having a larger average pore diameter than that of a separator of the small capacity electrode layers.