JPS624848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in the laminated structure of double layer capacitors.

Generally, the withstand voltage of the basic cell of a double layer capacitor is determined by the decomposition voltage of the constituent electrolyte and solvent. For example, in the case of an aqueous solution system with sulfuric acid, caustic potash, etc. as the electrolyte, the withstand voltage of the basic cell is approximately
It is 1.0 volt.

Also, propylene carbonate, N/N-dimethylformamide, acetonitrile, γ (gamma)-
With high dielectric constant organic solvents such as petyrolactone, the breakdown voltage is 3 to 3, depending on the decomposition voltage of the salt ions used.
It is about 5V. If a voltage higher than the decomposition voltage of the solvent is applied to this basic cell, its function will be destroyed.

Therefore, when a high withstand voltage higher than this decomposition voltage is required as the withstand voltage of a double layer capacitor, the required number of basic cells are stacked in series, and the withstand voltage per basic cell is set to It was customary to keep the voltage below the breakdown voltage.

In this case, when a DC voltage is applied to this double layer capacitor, the voltage applied to each basic cell is
distributed in proportion to the insulation resistance of each basic cell,
The larger the variation in insulation resistance of each basic cell, the more
The variation in voltage applied to each basic cell increases.

Variations in the voltage applied to each basic cell due to such variations in insulation resistance mean that, for example, even if a voltage equivalent to the number of stacked basic cells is applied to a multilayer double-layer capacitor, some of the basic cells in the stack will be affected by the voltage applied to each basic cell. A voltage higher than the withstand voltage of the basic cell was applied, and as a result, the basic cell was often destroyed and the capacitor as a whole lost its function.

Measures to prevent this destruction include selecting the insulation resistance of the basic cells to reduce variations in voltage between basic cells, and creating enough margin to prevent destruction of the basic cell with the largest potential distribution in the multilayer double layer capacitor. It is conceivable to form a laminated double-layer capacitor with a predetermined withstand voltage by stacking a large number of basic cells, but such a measure will reduce the variation in insulation resistance to within about 10% when industrializing double-layer capacitors. Improved development of manufacturing technology such as controlling
Because variations in insulation resistance are covered by selection of insulation resistance or the number of laminated layers, there are drawbacks such as increased product costs. Due to their inferiority, they lacked marketability and industrialization was not achieved.

It is an object of the present invention to provide a double layer capacitor which eliminates the above-mentioned drawbacks regarding the structure of the double layer capacitor, equalizes the voltage applied between each elementary cell, and enables industrialization.

According to the present invention, there is obtained a double layer capacitor characterized in that resistors having equal resistance values are inserted in parallel to each stacked basic cell.

Hereinafter, the double layer capacitor according to the present invention will be explained in detail using the drawings.

As shown in FIG. 1, the basic cell 10 of the double layer capacitor includes a disc-shaped conductive separator 1 that is electronically conductive and impermeable to ions, and a paste electrode 2 made of activated carbon powder and an electrolyte solution. , a porous separator 3 that is ion-permeable and blocks electron conduction and is provided to prevent conduction between electrodes;
It consists of a non-conductive gasket 4 provided to hold the carbon electrode and isolate it from the outside world.

Next, the basic structure 20 of a double layer capacitor in which the basic cells 10 are stacked will be explained with reference to FIG. First, the electrode leads 11a and 11b of the resistor 11
, conductive separators 1 above and below the basic cell 10
7 sets were made, and these were stacked in series. This is placed in an exterior case, the top and bottom surfaces are connected as voltage application electrodes so as to be taken out from the case, and pressure is applied between the bottom of the case and the top cover to fix the case. This pressurization reduces the contact resistance between the basic cells, between the basic cells and the electrode leads, or within each basic cell, and also prevents the electrode leads of the resistor 11 from coming off, resulting in a stable structure.

Here, in order to fix and stably hold the resistor 11, it was found to be stable if it was fixed to the inner wall of the outer case.

An embodiment of the present invention will be described in detail below.

The conductive separator has a diameter of 28 mm and a thickness of approx.
A 0.3 mm conductive carbon-containing butyl rubber sheet is used as a paste electrode with a surface area of 1100 m ² /g.
(BET method), a mixture of activated carbon fine powder with a particle size of 325 mesh or less and 21% by weight sulfuric acid and thorough stirring was used. A propylene porous membrane was used as the porous separator, and the non-conductive gasket had an outer diameter of 28 mm, an inner diameter of 22 mm, a thickness of approximately 0.38 mm, and a specific resistance of 10 ^11.
A butyl rubber gasket of Ω cm was used. When a pressure of about 30 kg was applied between the conductive separators and the gasket in a basic cell, a DC capacitance of 2 to 3 F and an insulation resistance of several KΩ were obtained.

When seven of these basic cells were extracted and a laminated double layer capacitor was fabricated by inserting equal resistance 11 of approximately 100Ω (±10%) as shown in Figure 2, the capacitance increased at an applied voltage of 6V. was approximately 0.4F, and approximately 8mA was detected as a leakage current.

This is a sufficiently small value compared to the leakage current standard (CV value) of 0.03CV (μA) for conventional aluminum electrolytic capacitors. In other words, the unit of C is μF
(microfarad), the unit of V is V (volt)
The unit of the CV value, which is the product of both, is expressed in μA (microampere), so by substituting the above values C=0.4F=4×10 ⁵ μF and V=6V, we get 0.03CV=0.03×(4 ×10 ⁵ μF) × 6V=72000
μA = 72 mA, and the above leakage current value of the capacitor of the present invention is sufficiently smaller than the standard value, and because the equal resistance is inserted in parallel, the leakage current is not too large, and there is no loss of practical or industrial value. do not have.

Next, regarding this seven-layer capacitor, the potential distribution of each basic cell will be explained.

Regarding the 7-layer double-layer capacitor with the above-mentioned equal resistance sandwiched between each basic cell, each basic cell making up the double-layer capacitor is numbered from 1 to 7 from the top, and the double-layer capacitor has a DC voltage of approximately 3.5V. was applied, the voltage of each basic cell was measured, and the variation was observed. As shown by the dotted line A in FIG. 3, it was possible to equalize the potential difference between the basic cells to within 100 mV. In addition, by applying a DC voltage to the double layer capacitor and gradually increasing the voltage, the voltage of the basic cell with the maximum voltage value among the basic cells composing the double layer capacitor is determined to have a withstand voltage of 1.0V.
The withstand voltage of the double layer capacitor was measured using the voltage applied to the double layer capacitor when the voltage reached 6.0 V as the withstand voltage.

Next, we removed only the equal resistance from the seven layers of capacitors sandwiching the above equal resistance, applied a pressure of several tens of kilograms, and measured the potential distribution of each unit cell in the same way. There was a variation of more than 500mV, and the withstand voltage was only up to 4.1V. Therefore, it was found that it was necessary to stack 10 or more unit cells to achieve the same 6V withstand voltage as when equal resistance was inserted.

Next, the effects of the present invention can be specifically summarized as follows.

(b) If the insulation resistance of each basic cell is in the range of several hundred to several tens of kilohms, by inserting an equal resistance of 1/5 to 1/10 of that value, voltage equalization within 10 to 20% can be achieved. can.

(b) Therefore, it is possible to save man-hours such as selecting the insulation resistance of each basic cell, and by determining the equal resistance values, it is easy to industrialize high-voltage multilayer double-layer capacitors.

(c) By simply inserting equal resistance, the number of laminated basic cells can be greatly reduced, resulting in significant savings in material and processing costs, making it easy to manufacture and suitable for mass production.

(iv) Even in the case of high operating voltages, the reliability and stability of operation in electronic equipment can be expected because potential equalization is achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a basic cell of a conventional double layer capacitor. FIG. 2 is a schematic partial cross-sectional view of the basic structure of a laminated double layer capacitor according to the present invention. Figure 3 shows the potential distribution of each basic cell of a laminated double-layer capacitor, where the solid line B represents a capacitor simply laminated without any equal resistance in between, and the dotted line A
indicates the present invention including equal resistance. DESCRIPTION OF SYMBOLS 1... Conductive separator, 2... Paste electrode, 3... Porous separator, 4... Non-conductive gasket, 10... Basic cell, 11... Resistance, 1
1a, 11b...electrode leads.

Claims (1)

[Claims] 1. A double layer capacitor constructed by laminating a plurality of basic cells of a double layer capacitor, characterized in that a plurality of resistors having substantially equal resistance values are inserted in parallel to each of the basic cells. .