JP2019096917A - Lamination parallel connector of coin-type electric double-layer capacitor - Google Patents

Abstract

To provide a lamination parallel connector of a coin-type electric double-layer capacitor, parallely connected by laminating a plurality of unit cells, without using an insulation member.SOLUTION: A lamination parallel connector comprises: a plurality of unit cells in which a coin-type electric double-layer capacitor having an inner can in which a conducive protective film is formed to all bottom surfaces of an inner side contacted to an electrolyte and an outer can is a unit cell; a first connection terminal connecting the plurality of unit cells; and a second connection terminal connecting the plurality of unit cells. The plurality of unit cells is arranged so as to be laminated and direct the inner can to a lower direction. The first connection terminal is connected to a side surface part of the outer can of the odd-numbered unit cell from the lower order, and connects between the odd-numbered unit cell from the lower order with the unit cell located above. The second connection terminal is connected to the side surface part of the outer can of the even-numbered unit cell from the lower order, and connects between the bottom part of the inner can of the lower unit cell, the even-numbered unit cell, and the unit cell located above.SELECTED DRAWING: Figure 2

Description

The present invention relates to a stacked parallel connection of coin type electric double layer capacitors in which coin type electric double layer capacitors are connected in parallel .

The electric double layer capacitor is a compact, high capacity, long cycle life storage device, and used as a backup power supply for memories and watch functions in various portable devices such as mobile phones and digital cameras, as well as for power supplies and motors for solar watches. It is used as a power source of
The storage portion of the electric double layer capacitor has a structure in which two electrodes and the electrodes are insulated by a separator and filled with an electrolytic solution. When a voltage difference is externally applied between the two electrodes, cations and anions in the electrolyte move to the vicinity of the respective electrodes and are stored.

On the other hand, batteries have long been widely used as electrochemical cells having the same configuration as electric double layer capacitors. Like the electric double layer capacitor, the structure of the reaction part in the battery is a structure in which two electrodes and the electrodes are insulated by a separator and filled with an electrolytic solution.
As described above, since the structures of the battery and the capacitor are the same, in the case of a small cell, the same coin container is used in both cases.

In the case of a battery, two electrodes are made of different materials, and a material with a high voltage is a positive electrode, a material with a low voltage is a negative electrode, and the voltage difference between the two electrodes is the battery voltage. Thus, the battery has the polarity of the positive electrode and the negative electrode.
For this reason, in order to prevent the insertion mistake (connection mistake) of the positive electrode side and the negative electrode side at the time of use, the direction of polarity is defined by IEC60086-3 (standard by international electrical standard meeting) etc. in a coin type battery.

On the other hand, in the case of the electric double layer capacitor, the two electrodes are made of the same material, the charge storage portion itself has no polarity, and the positive and negative polarities are determined by the voltage difference supplied from the outside.
However, the same polarity as that of the coin-type battery is provided for the following reasons.
(A) It is necessary to use a metal with high corrosion resistance because the metal on the high voltage side is more likely to be corroded than the metal on the low voltage side when a voltage is applied from the outside and charged, but a metal with high corrosion resistance is expensive is there. For this reason, it is possible to reduce the cost by configuring one of the metals with high corrosion resistance to be the high voltage side and the other with the metal having low corrosion resistance to be the low voltage side (providing polarity).
(B) Since the outer shape is the same as that of the coin-type battery, the insertion error can be prevented by providing the polarity.

  As described above, although the charge storage portion of the electric double layer capacitor does not have polarity, it is set as the positive electrode side using an expensive metal with high corrosion resistance, and is set as the negative electrode side using an inexpensive material with low corrosion resistance. (For example, patent document 1).

Then, since the polarity is provided by distinguishing the metal to be used, as shown in FIG. 6, when a large number of single cells 100 of the electric double layer capacitor are stacked and connected in parallel, the insulating member 110 such as resin is interposed between the cells. Needs to be arranged, and the thickness has become thick.
In addition, the insulating member 110 between the cells may be displaced or pulled out due to vibration or shock, which may cause a short circuit between the positive electrode side and the negative electrode side. I had to do it.
Furthermore, if the polarity is charged incorrectly, a high voltage is applied to the metal with low corrosion resistance, which may cause the metal to corrode and deteriorate quickly.

Japanese Patent Application Laid-Open No. 62-94908

An object of the present invention is to provide a stacked parallel connection of coin-type electric double layer capacitors in which a plurality of single cells of electric double layer capacitors are stacked and connected in parallel without using an insulating member.

(1) In the invention according to claim 1, a plurality of coin-type electric double layer capacitors provided with an inner can and an outer can having a conductive protective film formed on the entire inner bottom surface in contact with the electrolytic solution are single cells , A first connection terminal for connecting a plurality of single cells, and a second connection terminal for connecting a plurality of single cells, wherein the plurality of single cells face the inner can downward. The first connection terminal is connected to the side portion of the outer can of the odd-numbered single cell from the bottom, and between the odd-numbered single cell and the single cell above it from the bottom And the second connection terminal is connected to the side portion of the even-numbered single cell outer can from the bottom, and the bottom of the lowermost single cell inner can and the even-numbered single cell And a single cell on one side thereof, wherein a stacked parallel contact of a coin-type electric double layer capacitor is characterized. To provide the body.
(2) In the invention according to claim 2, a plurality of coin-type electric double layer capacitors provided with an inner can and an outer can having a conductive protective film formed on the entire inner bottom surface in contact with the electrolytic solution are single cells , A first connection terminal for connecting a plurality of single cells, and a second connection terminal for connecting a plurality of single cells, wherein the plurality of single cells face the inner can downward. The first connection terminals are connected to the outer cans of the odd-numbered unit cells from the bottom, and the second connection terminals are connected to the bottom of the inner can of the bottom unit cell Further, the present invention provides a stacked parallel connection of coin-type electric double layer capacitors, characterized in that it is connected to the side part of the outer can of even-numbered single cells from the bottom.
(3) In the invention according to claim 3, the protective film is made of a material mainly made of any of carbon, aluminum, conductive DLC, and conductive polymer. The parallel connection body of the electrical double layer capacitor as described in is provided.
(4) In the invention according to claim 4, the electric double layer according to any one of claims 1 to 3, wherein the protective film is formed up to the inner side surface of the side surface portion. Provide a parallel connection of capacitors.

  According to the present invention, by using a coin type electric double layer capacitor provided with an inner can and an outer can having a conductive protective film formed on the entire inner bottom surface in contact with the electrolytic solution, the positive electrode and the negative electrode can be distinguished. Since connection is possible, it is possible to provide a stacked parallel connection of coin-type electric double layer capacitors in which a plurality of single cells are stacked and connected in parallel without using an insulating member.

It is a cross-sectional block diagram of an electric double layer capacitor. It is explanatory drawing which shows the state which piled up the electrical double layer capacitor and connected in parallel. It is a cross-sectional block diagram of the electric double layer capacitor in 2nd Embodiment. It is a cross-sectional block diagram of the electric double layer capacitor in 3rd Embodiment. It is explanatory drawing showing the evaluation result of an electric double layer capacitor. It is explanatory drawing which shows the state which piled up the conventional electric double layer capacitor, and connected in parallel.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the multilayer parallel connected body of coin-type electric double layer capacitors of the present invention will be described in detail below with reference to FIGS. 1 to 5.
(1) Outline of Embodiment In this embodiment, the polarity is eliminated by forming two current collecting portions in contact with the electrolytic solution with a metal material which is the same material, or forming a protective film. Here, the same material refers to the whole of the same metal such as SUS metal, and all the components are not limited to the same metal.
In the electric double layer capacitor of this embodiment, since there is no polarity (any side can be used as the positive electrode side or the negative electrode side), a can having a shape corresponding to the negative electrode can (case) of the battery is called an inner can The can of the shape corresponding to the positive electrode can is called an outer can.
In the electric double layer capacitor of the present embodiment, both of the surface of the inner can and the surface of the outer can which the electrolytic solution to be enclosed comes in contact with are required to the required charging voltage (for example, 2.5 V, 3.3 V, etc.) It has a configuration that can withstand, that is, has corrosion resistance to charging voltage.
Specifically, one of the following two methods is adopted.
(A) As a material for forming the inner can and the outer can, a metal having good drawability and sufficient hardness is used. For example, SPCD (for drawing) and SPCE (for deep drawing) defined in JIS G 3141 (cold-rolled steel plate and steel strip), or ferritic stainless steel (SUS4XX), austenitic stainless steel (SUS3XX), austenitic ferrite 2 Use duplex stainless steel (SUS329JXL) or the like. In this case, a metal having high corrosion resistance to the required charging voltage is selected. In particular, stainless steel is superior in corrosion resistance to SPCD and SPCE. Among stainless steels, corrosion resistance is superior in the order of ferrite, austenite and austenite-ferrite duplex stainless steel.
(B) When using a metal that is cheaper than the metal of (a) but has lower corrosion resistance, or even if the metal of (a) has a possibility of corrosion due to a higher required charging voltage, A protective film having conductivity between the metal used and the electrode, that is, the current collection portion (inner surface) in contact with the electrolyte is formed of the same material for both the inner and outer cans. The material of the protective film includes carbon, aluminum, conductive DLC, conductive polymer and the like.

In the present embodiment, in the case of (b), corrosion resistance is ensured by the protective film, so materials different from those of the outer can and the inner can are made of SUS329J4L and SUS304. It is also possible to form the same protective film.
The inner can and the outer can may be made of a metal having sufficient hardness, and the surfaces of the inner and outer cans in contact with the electrolyte may be formed with a protective film made of the same material having excellent withstand voltage.

(2) Details of Embodiment FIG. 1 is a cross-sectional view of a coin-type electric double layer capacitor 1 to which this embodiment is applied.
The electric double layer capacitor 1 includes an inner can 10 and an outer can 20 which form a coin (button) outer shape.
The inner can 10 and the outer can 20 form an accommodating portion on the inner side, and the first electrode 11, the second electrode 21, the separator 30, the electrolytic solution 31 and the like are enclosed in the accommodating portion through the gasket 32. There is.

The inner can 10 is provided with a circular bottom portion 10a and side portions 10b connected along the outer periphery of the bottom portion 10a and is formed with a recess having a circular opening, and is a disk-shaped metal container as a whole.
The inner can 10 functions as a lid of the electric double layer capacitor 1.
The open end side of the side surface portion 10 b of the inner can 10 is fitted in a recess (groove) formed in a thick portion of the annular (donut-shaped) gasket 32.
The gasket 32 is made of, for example, a resin, and is disposed between the outer can 20 and the inner can 10 over the entire circumference of the opening of the outer can 20. The gasket 32 hermetically seals the inside electrolyte and the like, and insulates the outer can 20 and the inner can 10 from each other.

The outer can 20 is a disc-shaped metal container as a whole, with a circular bottom portion 20a and side portions 20b connected along the outer periphery of the bottom portion 20a to form a recess having a circular opening. The outer can 20 functions as an outer case of the electric double layer capacitor 1.
The diameter of the opening of the side surface portion 20b is larger than the outer diameter of the gasket 32, and in a state where the gasket 32 fitted into the inner can 10 contacts the bottom portion 20a of the outer can 20 It is made to seal by closing.
In addition, the material which forms the inner can 10 and the outer can 20 in this embodiment is mentioned later.

A circular first electrode 11 is connected to the inner bottom surface of the bottom portion 10a of the inner can 10 by a conductive adhesive 12, and a circular second electrode 21 is conductively bonded to the inner bottom surface of the bottom portion 20a of the outer can 20. It is connected by the agent 22. In the present embodiment, the first electrode 11 and the second electrode 21 are adhered to the bottom 10 a of the inner can 10 and the bottom 20 a of the outer can 20.
A separator 30 made of an insulating material is disposed between the first electrode 11 and the second electrode 21. That is, the surface of the first electrode 11 not adhered to the inner can 10 and the surface of the second electrode 21 not adhered to the outer can 20 are disposed opposite to each other with the separator 30 interposed therebetween. ing.
An electrolytic solution 31 is filled in the electric double layer capacitor 1 sealed by the inner can 10 and the outer can 20.

Although various known materials can be used for the first electrode 11, the second electrode 21, the separator 30, and the electrolytic solution 31, the following materials are used as an example in the present embodiment.
That is, for both the first electrode 11 and the second electrode 21, a mixture of activated carbon, carbon black and PTFE is used.
As the separator 30, a polyolefin microporous membrane is used.
Further, as the electrolyte solution 31, a mixture of a non-aqueous solvent and an electrolyte is used.

Next, metal materials forming the inner can 10 and the outer can 20 will be described.
In the present embodiment, the same metal is used for both the inner can 10 and the outer can 20.

For example, the inner can 10 and the outer can 20 are made of the same steel type, such as SUS329J4L, which is austenite-ferrite duplex stainless steel, and SUS316L or SUS304, which is austenitic stainless steel.
These are all stainless steel metals and correspond to the same metal. That is, in the present embodiment, not only metals of the same component but also metals of the same series are referred to as the same metal.

Thus, in the electric double layer capacitor 1 of the present embodiment, since it is possible to connect without distinction between the positive electrode and the negative electrode, a large number of single cells of the electric double layer capacitor can be stacked without using the insulating member. Parallel connection (hereinafter referred to as stacked parallel connection) can be performed.
FIG. 2 is an explanatory view showing a state in which three nonpolar electric double layer capacitors 1a, 1b and 1c are stacked and connected in parallel according to the present embodiment.
As shown in FIG. 2 (a), one terminal 51 is connected to the side surface portion 20b of the outer can 20 of the odd-numbered electric double layer capacitor 1 from the bottom and the odd-numbered electric double layer capacitor 1 and It is connected between the one above and the electric double layer capacitor.
On the other hand, the other terminal 52 is connected to the side portion 20b of the outer can 20 of the even-numbered electric double layer capacitor 1 from the bottom and the bottom 10a of the inner can 10 of the lowermost electric double layer capacitor 1, And between the even-numbered electric double layer capacitor 1 and the electric double layer capacitor 1 above it.

When the terminal 51 is positive (+) and the terminal 52 is negative (-) as shown in FIG. 2A, the polarities of the inner can 10 and the outer can 20 of each electric double layer capacitor 1 are respectively The electric double layer capacitor 1a is positive and negative, the electric double layer capacitor 1b is negative and positive, and the electric double layer capacitor 1c is positive and negative.
Conversely, in the case where the terminal 51 is negative (−) and the terminal 52 is positive (+), the polarities of the respective parts are reversed as shown in the parentheses of FIG. 2 (a).

As described above, in the electric double layer capacitor 1 of the present embodiment, since there is no polarity, it is not necessary to arrange the insulating material between the stacked electric double layer capacitors 1, so the thickness is equal to the thickness of the insulating material. It can be reduced. Further, both electrodes of the electric double layer capacitor 1 and the terminal can be securely fixed by performing laser welding or the like.
This effect and the modification described below are the same in the other embodiments described later.

FIG. 2 (b) shows another connection method in the case of stacked parallel connection.
Although the case where each electric double layer capacitor 1 was connected to one of the terminal 51 or the terminal 52 was described in FIG. 2 (a), in the modification shown in FIG. 2 (b), each electric double layer capacitor 1 is This is an example of the case where the connection between them is also lost.
As shown in FIG. 2 (b), one terminal 51 is connected to the outer can 20 of the odd-numbered electric double layer capacitor 1 from the bottom.
The other terminal 52 is connected to the bottom 10 a of the inner can 10 of the lowermost electric double layer capacitor 1 and to the side surface 20 b of the outer can 20 of the even-numbered electric double layer capacitor 1 from the bottom. .
In the case of this modification, the bottom 20a of the outer can 20 of the electric double layer capacitor 1 of each layer and the bottom 10a of the inner can 10 of the electric double layer capacitor 1 on one layer are in direct contact with each other. Stacked parallel connection can be easily performed.

Next, a second embodiment will be described.
In the first embodiment, the case where the materials of the inner can 10 and the outer can 20 of the electric double layer capacitor 1 are made of the same material has been described, but in this second embodiment, the inner can 10 and the outer can 20 are A protective film made of the same material is formed on both bottom surfaces to configure the electric double layer capacitor 1 without polarity.
FIG. 3 shows the cross-sectional configuration of the electric double layer capacitor 1 in the second embodiment.
As shown in FIG. 3, the protective film 13 is formed on the entire inner bottom surface of the bottom 10 a of the inner can 10 of the electric double layer capacitor 1, and the protective film 23 is formed on the entire inner bottom of the bottom 20 a of the outer can 20. ing. The protective film is made of a material having good conductivity because it electrically connects the inner can or the outer can to the electrode. Moreover, it is preferable that the protective film is not decomposed by the electrolytic solution or the charging current. In addition, a film free of electrolyte absorption and pinholes is preferred. If there is a pinhole, the electrolytic solution is in contact with the outer can and the inner can, and the can is corroded. In order to reduce the number of pinholes, it is necessary to form the protective film thick. On the other hand, when the protective film is too thick, the volume occupied in the housing portion is increased, so that the amount of the electrode that can be stored is reduced and the capacity is reduced. Therefore, the film thickness of the protective film is preferably 0.1 to 100 μm, and more preferably 2 to 60 μm.

As a material of the protective films 13 and 23, any of carbon, aluminum, conductive DLC (diamond-like carbon), and conductive polymer is used.
The protective film 13 and the protective film 23 use the same protective film of the above-mentioned protective films.
The carbon protective film is formed, for example, by applying and thermally curing a paste comprising a phenol resin, carbon and a solvent on an application surface. As carbon, graphite, carbon black or the like can be used. In addition, a plurality of these various carbon materials can be used in combination.
The aluminum protective film is formed, for example, of aluminum by vapor deposition. As aluminum, in addition to pure aluminum containing 99% or more of aluminum in composition ratio, an aluminum alloy containing a trace amount of elements such as Mg, Mn, Si, Cu, etc. can be used.
The conductive DLC protective film is an amorphous thin film having a diamond bond or a graphite bond. This thin film is formed, for example, by plasmatizing a raw material gas of a hydrocarbon such as acetylene gas or benzene gas, and forming a film by CVD, PVD or the like.
The conductive polymer protective film is a polymer compound having electrical conductivity, and for example, polythiophenes, polyacetylenes and the like can be used. In addition, it is possible to use a poly (3,4-ethylenedioxythiophene) (PEDOT) coated with an aqueous dispersion of a dopant of poly (styrenesulfonate (PSS) to improve conductivity, and dried to form a film (PEDOT / PSS) These conductive polymers can be coated with one dispersed in water or an organic solvent, cured, or dried to form a film.
In addition to these materials, it is also a preferable embodiment to appropriately add and use various additives in order to improve coating properties and conductivity.

As for the materials of the inner can 10 and the outer can 20 in the second embodiment, the corrosion resistance at the required charging voltage is secured by the protective film, so the same material or different materials may be used.
For example, the inner can 10 and the outer can 20 are formed of SUS304, and the protective films 13 and 23 made of the same material are formed on the inner bottom surfaces of the bottoms 10a and 20a, or the inner can 10 is SUS304 and the outer can 20 is SUS329J4L different steel types The protective films 13 and 23 made of the same material may be formed on the inner bottom surfaces of the bottom portions 10a and 20a.

In the second embodiment, the protective films 13 and 23 are formed on the entire inner bottom surface of the bottoms 10a and 20a. However, the size of the outer peripheral portion is in contact with the gasket 32 even partially along the entire circumference. It may be That is, the outer diameter size of the protective film should be larger than the inner diameter of the corresponding gasket 32.
However, it is preferable to form a protective film on the entire inner bottom surface in consideration of the possibility of the electrolyte solution penetrating from between the gaskets 32.

Next, a third embodiment will be described.
In the electric double layer capacitor 1 described as the second embodiment and the modification thereof, the protective films 13 and 23 are formed on the inner bottom surfaces of the bottoms 10a and 20a, but the electric double layer capacitor according to the third embodiment is described. 1 further extends the formation range of the protective film.
FIG. 4 shows a cross-sectional configuration of the electric double layer capacitor 1 in the third embodiment.
As shown in FIG. 4, in the inner can 10 of the electric double layer capacitor 1, not only the inner bottom surface of the bottom portion 10a, but also the inner side surface of the side surface portion 10b and the outside of the folded portion continuous with the inner side surface. It extends to the side to form a protective film 14.
Further, the outer can 20 is extended not only to the inner bottom surface of the bottom portion 20 a but also to the inner side surface of the side surface portion 20 b to form a protective film 24.
As in Examples (Test Example 1) to be described later, when charging is continued with a large current, corrosion occurs in the can and electrolyte to which a positive potential is applied. The corrosion is particularly intense in the vicinity of the conductive adhesives 12 and 22. The further away from the conductive adhesives 12 and 22 the weaker the corrosion is and the occurrence of the corrosion of the side portions 10b and 20b is extremely small.
Such corrosion is considered to occur by the following mechanism. That is, in the electric double layer capacitor, even if charging is continued for a long time, the charging current does not become 0, and a minute current called leak current continues to flow. The larger the leak current, the easier the corrosion. It is considered that the leak current is such that the current density in the portion near the conductive adhesive is large, and the current density is smaller as the distance from the conductive adhesive is larger. Therefore, the effect of the protective film is considered to be larger at the portion closer to the conductive adhesive connecting the can and the electrode, and smaller as it gets farther from the conductive adhesive, as compared to the electric double layer capacitor as shown in FIG. It is considered that forming a protective film on the bottom of the can as in 3 is excellent in corrosion resistance, and further forming a protective film on the entire surface of the portion where the can and the electrolytic solution may come in contact as shown in FIG.

According to the third embodiment, since the formation region of the protective film is formed to extend not only to the inner bottom surface of the bottom but also to the inner side surface of the side surface portion, the electrolytic solution from between the gasket 32 to the inner side surface It can respond, also when it penetrates.
As for the inner can 10, the protective film 14 may be formed on the inner side surface of the side surface portion 10b, and further, the protective film is extended to the outer side surface portion of the side surface portion 10b (the entire range in contact with the gasket 32). You may form.

In addition, the second embodiment including the modification may be applied to one of the bottom portion 10a and the bottom portion 20a, and the third embodiment may be applied to the other.
In addition, if the protective film is formed on a metal plate and then pressed into the shape of the outer can or the inner can, there is a risk of peeling or scratching during pressing, so the metal plate can Preferably, the protective film is formed after pressing into the shape of
As a method of forming the protective film, a method more appropriate to the formation region can be appropriately adopted. For example, unlike PVD and CVD, which can form a film uniformly without collecting on the bottom by the weight of the liquid, unlike the film forming method of applying a liquid, the whole surface as in the third embodiment (FIG. 4) can be obtained. Film formation is easy. On the other hand, in the case where the protective film is formed only on the bottom as in the second embodiment (FIG. 3), a method of applying a liquid material such as a paste or a dispersion and drying it is more simple and preferable.

Next, test results for the electric double layer capacitor 1 according to the first to third embodiments will be described.
FIG. 5 shows the test results for each embodiment and the comparative example.
The test target was an electric double layer capacitor 1 configured as follows.
The first electrode 11 and the second electrode 21 were a mixture of activated carbon-carbon black-PTFE, and both of them were the same.
Electrolyte solution 31: Nonaqueous solvent-electrolyte mixture Separator: Polyolefin microporous film Carbon protective film: A paste consisting of a phenol resin, carbon black and solvent was applied and thermally cured to form a 54 μm thick film as shown in FIG. (Test Examples 2, 3 and 7). In addition, the bottom of the inner can was formed into a film as described above, and the bottom of the outer can was formed into a film using a paste using a mixture of carbon black and graphite in a weight ratio of 8: 2 instead of carbon black ( Test Example 8).
Aluminum protective film: Aluminum was vapor-deposited to form a film having a thickness of 10 μm as shown in FIG. 4 (Test Example 4).
Conductive DLC Protective Film: A conductive DLC was deposited to a thickness of 2 μm as shown in FIG. 4 (Test Example 5). Conductive Polymer Film: A liquid in which 1% PEDOT / PSS was dispersed in water was applied and dried to form a film having a thickness of 1 μm or less as shown in FIG. 3 (Test Example 6).

The tests and evaluations are as follows.
(1) Initial capacity The initial capacity was measured at room temperature. In the positive connection, charging was performed for 30 minutes by connecting the outer can 20 to +2.5 V and the inner can 10 to 0 V. In the reverse connection, charging was performed for 30 minutes by connecting 0 V to the outer can 20 and +2.5 V to 10 to the inner can. Thereafter, discharge was performed at a constant current of 0.4 mA / cm 2, and the initial capacity C 1 was calculated from the time required for the voltage to reach 80% to 40% of the charge voltage. Furthermore, the initial capacitance of the cell (electrical double layer capacitor 1) to which the positive connection was made and the initial capacitance of the cell to which the reverse connection was made were converted to the proportion of reverse connection when the capacitance of the positive connection was 100.
(2) The cell whose initial capacity was measured by positive connection was placed in a 40 ° C. constant temperature bath, and the outer can 20 was charged for 1 week at +2.5 V (positive connection). Moreover, the cell which measured the initial stage capacity | capacitance by reverse connection was also put into a 40 degreeC thermostat, and the inner can 10 was charged for 1 week by + 2.5V (reverse connection).
(3) Capacity maintenance rate The capacity C2 after storage was calculated by the same method as the initial capacity shown in (1), and the capacity maintenance rate was set to C2 / C1.

As shown in FIG. 5, in the comparative example 1 in which the inner can 10 is formed of SUS304 and the outer can 20 is formed of SUS329J4L and the both are not provided with a protective film, the initial capacity of reverse connection is 100% of the initial capacity of positive connection. It was 65 when I When the cell subjected to this reverse connection was disassembled, the inner can surface in contact with the electrolyte was corroded, and the transparent electrolyte turned brown. The corrosion of the inner can surface was severe in the portion close to the conductive adhesive 12 of the inner can 10, and the corrosion was weaker the further away from the conductive adhesive 12, and the inner can side portion 10b was free of corrosion.
In addition, the capacity retention rate was 0% in both of the positively connected cell and the reversely connected cell.
Thus, in the electric double layer capacitor of Comparative Example 1 (prior art), the outer can 20 must always be positively connected as the positive electrode side, and connection in consideration of the polarity is required.

  Further, in Comparative Example 2 in which the inner can 10 and the outer can 20 were both formed of SUS 304 and the protective film was not provided, no difference was found in the initial capacities of the positive connection and the reverse connection. However, in either of the positive and reverse connections, the initial capacity decreased to 56% of that of Test Example 1. Similar to the cell of the reverse connection of Comparative Example 1, the cells of the cell of Comparative Example 2 of either the positive connection or the reverse connection were corroded. Furthermore, the capacity retention after charging for 1 week at 40 ° C. and +2.5 V is 0% for both positive and reverse connections, indicating that the cell is broken.

On the other hand, in Test Examples 1 to 8, there is no change in the initial capacity even when charging is performed in the reverse connection. That is, it becomes possible to connect the electric double layer capacitor without considering the polarity.
In particular, among the test examples in which the protective films 13 and 23 were formed, in the electric double layer capacitors of Test Examples 2 to 5, 7 and 8, the capacity retention ratio showed a high value of 80% or more in positive connection. The reverse connection also showed a high capacity retention rate of 75% or more. By forming the protective film of these test examples, it is possible to obtain a high performance electric double layer capacitor with high corrosion resistance.
In the electric double layer capacitor of Test Example 1, although there was no change in initial capacity, the capacity retention rate became 0% when charging was continued at 40 ° C. for one week. As a result of decomposition, the surface in contact with the electrolytic solution of the one to which +2.5 V was added was corroded, and the transparent electrolytic solution turned black. The corrosion on the surface of the can was severe in the portion close to the conductive adhesive 12, 22; the corrosion was weaker the further away from the conductive adhesive 12, 22; the side portions 10b, 20b were free of corrosion.
On the other hand, in the electric double layer capacitors of Test Examples 2 to 5, 7 and 8, as described above, the positive and negative connections show high capacity retention and no corrosion as in Test Example 1 occurs. The In addition, Test Examples 2, 3, 7 and 8 show sufficient corrosion resistance and capacity retention at reverse connection even though no protective film is formed on the side portions 10b and 20b as shown in FIG. The From this, if the surface in contact with the electrolytic solution is formed of carbon, aluminum, or conductive DLC rather than stainless steel, the corrosion resistance can be further enhanced.
On the other hand, in the electric double layer capacitor in which the conductive polymer film was formed, as shown in Test Example 6, good results were obtained even if the initial capacity test was reverse connection, but the capacity retention rate was poor. This is due to the formation of a thin film having a film thickness of 1 μm or less, and there is a possibility of improvement by increasing the film thickness.

As described above, according to the electric double layer capacitor 1 of the present embodiment, the following effects can be obtained.
(1) Since both sides (the first electrode 11 and the second electrode 21 and the inner can 10 and the outer can 20) viewed from the separator 30 are made of the same material, there is no polarity, and the polarity is not considered. It becomes possible to connect.
(2) An inexpensive metal can be used by forming a protective film on the inner bottom surface. Metals with good processability and poor corrosion resistance can also be used.
(3) When charged, the degree of corrosion is higher in the vicinity of the conductive adhesive, but corrosion occurs although it is weak even at a distant place. On the other hand, in the second embodiment and the third embodiment, since the protective film is formed including the far part, the corrosion resistance can be further improved.
(4) In addition, in the electric double layer capacitor 1 of the present embodiment, since it is possible to connect without distinction between the positive electrode and the negative electrode, even in the case of layered parallel connection, between the electric double layer capacitors 1 There is no need to provide insulation. For this reason, the height in the case of stacked parallel connection can be suppressed lower.

  In addition, this embodiment can also be configured as follows for the purpose of providing an electric double layer capacitor that can be used without distinction of polarity.
(1) Configuration 1
  An inner can, an outer can sealed with the inner can and an insulating material and forming a housing with the inner can, a first electrode disposed on the inner can within the housing, and the housing And a separator disposed between the first electrode and the second electrode to insulate the two from each other, and an electrolytic solution filled in the container. An electric double layer capacitor comprising: the inner can and the outer can have the same material formed on at least a surface in contact with the electrolytic solution.
(2) Configuration 2
  The electric double layer capacitor according to Configuration 1, wherein the inner can and the outer can are both made of the same stainless steel.
(3) Configuration 3
  A protective film having corrosion resistance to the electrolytic solution is formed on the surface of the inner can and the outer can in contact with the electrolytic solution, the electric two described in the constitution 1 or the constitution 2 Multilayer capacitor.
(4) Configuration 4
  The electric double layer capacitor according to Configuration 3, wherein the protective film is made of a material mainly made of carbon, aluminum, conductive DLC, or conductive polymer.
(5) Configuration 5
  The electric double layer according to the constitution 3 or the constitution 4, wherein the inner can and the outer can are composed of a bottom portion and a side portion, and the protective film is formed on the entire inner bottom surface of the bottom portion. Capacitor.
(6) Configuration 6
  The electric double layer capacitor according to Configuration 5, wherein the protective film is formed up to the inner side surface of the side surface portion.

  According to the electric double layer capacitor of this configuration, since the same material is formed on at least the surface in contact with the electrolytic solution, the inner can and the outer can can be used without distinction of polarity.
  In addition, since there is no distinction of polarity, the insulating members become unnecessary even when stacking and connecting a plurality of electric double layer capacitors, and the overall thickness can be suppressed.

DESCRIPTION OF SYMBOLS 10 inner can 10a bottom part 10b side part 11 1st electrode 12 electroconductive adhesive 13, 14 protective film 20 outer can 20a bottom part 20b side part 21 2nd electrode 22 electroconductive adhesive 23, 24 protective film 30 separator 31 electrolyte 32 gasket

Claims (4)

  A plurality of unit cells each of which is a coin type electric double layer capacitor including an inner can and an outer can provided with a conductive protective film formed on the entire inner bottom surface in contact with an electrolytic solution;
  A first connection terminal for connecting a plurality of single cells;
  And a second connection terminal for connecting a plurality of single cells,
  The plurality of single cells are stacked and disposed with the inner cans facing downward,
  The first connection terminal is connected to the side part of the outer can of the odd-numbered single cell from the bottom, and connects between the odd-numbered single cell and the single cell above it from the bottom,
  The second connection terminal is connected to the side portion of the even-numbered single-cell outer can from the bottom, the bottom of the lower-most single-cell inner can, and the even-numbered single cell and one of the single-cell Connect with the single cell above,
A stacked parallel connected body of coin type electric double layer capacitors characterized in that.   A plurality of unit cells each of which is a coin type electric double layer capacitor including an inner can and an outer can provided with a conductive protective film formed on the entire inner bottom surface in contact with an electrolytic solution;
  A first connection terminal for connecting a plurality of single cells;
  And a second connection terminal for connecting a plurality of single cells,
  The plurality of single cells are stacked and disposed with the inner cans facing downward,
  The first connection terminal is connected to the outer can of the odd-numbered single cell from the bottom,
  The second connection terminal is connected to the bottom of the inner can of the lowermost single cell and to the side of the even-numbered outer can of the single cell from the bottom.
A stacked parallel connected body of coin type electric double layer capacitors characterized in that. The protective film is made of a material mainly made of carbon, aluminum, conductive DLC, or conductive polymer.
A stacked parallel connected body of coin type electric double layer capacitors according to claim 1 or claim 2 .   The protective film is formed to the inner side surface of the side surface portion,
A stacked parallel connected body of coin type electric double layer capacitors according to any one of claims 1 to 3, characterized in that:

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