JP6249546B2 - Electric double layer capacitor - Google Patents

Description

  The present invention relates to an electric double layer capacitor using activated carbon obtained by carbonizing and activating a fiber material as a polarizable electrode.

  When the conductor is in contact with the electrolytic solution, an electric double layer composed of a positively charged layer and a negatively charged layer is formed at the interface between the electrolytic solution and the conductor. An electric double layer capacitor stores electric energy by utilizing this phenomenon.

  This electric double layer capacitor is capable of rapid charging and has an excellent characteristic that it hardly deteriorates even after repeated charging and discharging as compared with a conventional secondary battery. There is a drawback that the energy capacity stored is smaller than that of the secondary battery.

  On the other hand, in recent years, an electric double layer capacitor has been developed, which uses an activated carbon with a large surface area as a polarizable electrode and increases the contact area between the electrode and the electrolyte, thereby increasing the capacitance. It has become.

  To describe a specific configuration, while interposing an electrolyte between a pair of collector electrodes, a space between the collector electrodes is separated by a separator that is an insulator that allows passage of ions, and a polarizable electrode made of activated carbon is Provided on the separator-side surface of each collector electrode.

  And as an improvement of this, an electric double layer capacitor shown in Patent Document 1 in which activated carbon obtained by carbonizing and activating a fiber material is used as a polarizable electrode and the capacitance is increased is known. ing.

JP 2002-299185 A

  However, in the electric double layer capacitor of the above-mentioned document, when the stored energy capacity is further increased, the surface area of the active body is increased by increasing the size, or a set of a pair of collector electrode, polarizable electrode and separator is used. It is necessary to prepare a plurality of sets, which increases the cost.

  An object of the present invention is to provide an electric double layer capacitor capable of realizing further increase in capacity at a low cost by using activated carbon obtained by carbonizing and activating a fiber material as a polarizable electrode.

In order to solve the above-mentioned problems, the present invention firstly is an insulator that interposes an electrolyte between a pair of collector electrodes 6 and 6 and allows the passage of ions between the collector electrodes 6 and 6. Separate by some separator 7, a polarizable electrode 8 is activated carbon obtained by activating carbonized fiber material, an electric double layer capacitor provided on the surface of the separator 7 side of the collector electrode 6, the electrolyte liquid is an electrolyte of an aqueous, the polarizable electrode 8 is Ri Do from cotton activated carbon obtained from the cotton-like fiber material, the electrolytic solution is impregnated in the polarizable electrode 8, the polarizable electrode 8 In pressing the collector electrode 6, the polarizable electrode 8 is filled in a compressed state in the space between the separator 7 and the collector electrode 6.

Second, the container 9 is formed with a container 12 that can be flexibly changed. The separator 7, the pair of collector electrodes 6, 6, and the pair of polarizable electrodes 8, 8 are provided in the container 9. The polarizable electrodes 8 and 8 are filled in a compressed state by storing and discharging the air in the storage portion 9 in this state .

Third, each collecting electrode 6, constituted by the electrodes a conductive container having an opening, a polarizable electrode 8, and filled and compressed in the housing portion 9 formed in the electrode container 6, a pair of electrodes The insides of the containers 6, 6 are partitioned by a separator 7, and the openings of the electrode containers 6, 6 are connected to each other.

Fourth, the flange portion 17 is formed in the opening of each electrode container 6, and the flange portions 17, 17 of the pair of electrode containers 6, 6 are fastened and fixed while being insulated from each other. To do.

Fifth, the surface layer portion of the collector electrode 6 is characterized in that irregularities having a size corresponding to the pores of the polarizable electrode 8 are formed .

Sixth , the electrolytic solution is any one of an aqueous potassium hydroxide solution, an aqueous sodium hydroxide solution, or an aqueous potassium carbonate solution.

  According to the above configuration, the electrolyte solution is applied to a polarizable electrode formed by stacking a plurality of sheet-like activated carbons obtained from a sheet-like fiber material, or a polarizable electrode made of cotton-like activated carbon obtained from a cotton-like fiber material. By impregnating, it is possible to increase the surface area of the activated carbon without separately requiring a collector electrode or a separator, and at a lower cost, the capacitance can be further increased. Since the polarizable electrode is pressed against the collector electrode, the internal resistance is also reduced.

Moreover, according to what the fiber substance is cotton, since cotton is cheap, cost further reduces.

  Moreover, according to what cotton is a nonwoven fabric or a woven fabric, an electrostatic capacitance increases further.

  Furthermore, according to what forms the sheet-like activated carbon superposed | stacked by carrying out the carbonization process and activation process in the state which piled up the sheet-like fiber substance in advance, a sheet-like activated carbon is superposed | stacked. This eliminates the need for work, reduces manufacturing costs, and prevents damage when the sheet-like active material is touched.

  Each collecting electrode is constituted by a conductive electrode container having an opening, the polarizable electrode is filled in the electrode container, and the inside of the pair of electrode containers is partitioned by a separator, According to what connected the opening part side, it is not necessary to prepare the member which accommodates various members separately, and cost is further reduced.

It is a side view of a capacitor unit formed by unitizing a plurality of electric double layer capacitors to which the present invention is applied. It is a top view of a capacitor unit formed by unitizing a plurality of electric double layer capacitors to which the present invention is applied. FIG. 3 is a front view of the electric double layer capacitor shown in FIGS. 1 and 2. FIG. 3 is a side view of the electric double layer capacitor shown in FIGS. 1 and 2. FIG. 3 is a cross-sectional plan view of the electric double layer capacitor shown in FIGS. 1 and 2. It is a top view which shows the modification of the capacitor unit shown in FIG.1 and FIG.2. It is a sectional side view which shows the structure of another embodiment of an electrical double layer capacitor. It is an exploded side sectional view showing the composition of another embodiment of an electric double layer capacitor. It is a top view of the collector electrode shown in FIG.7 and FIG.8. (A) is a measurement circuit of an electric double layer capacitor, and (B) is a characteristic graph of charge and discharge of the electric double layer capacitor.

  As a result of intensive studies, the inventors of the present application focused on the fact that the activated carbon obtained by carbonizing and activating the fiber material is excellent in impregnation, and separated the flocculent activated carbon or a plurality of superimposed activated carbons. It is found that the capacitance of the electric double layer capacitor is increased by using the polar electrode and containing the electrolyte in the polarizable electrode.

  Hereinafter, embodiments of the present invention will be described.

  1 and 2 are a side view and a plan view of a capacitor unit obtained by unitizing a plurality of electric double layer capacitors to which the present invention is applied. The capacitor unit includes a plurality of electric double layer capacitors 1 formed in a thick plate shape, and a pair of holding members sandwiched from both ends in the overlapping direction in a state where the plurality of electric double layer capacitors 1 are stacked in the thickness direction. Plates 2 and 2 and a plurality of connecting bolts 3 for connecting the pair of sandwiching plates 2 and 2 to each other are provided.

  The connecting bolts 3 are respectively disposed at the four corners of the sandwiching plates 2 and 2 so as to avoid the electric double layer capacitor 1 between the sandwiching plates 2 and 2. Each connecting bolt 3 is inserted from one holding plate 2 into the other holding plate 2, and a connecting nut 4 is screwed and tightened to the tip of the connecting bolt 3 protruding from the other holding plate 2. Thus, the electric double layer capacitor 1 between the sandwiching plates 2 and 2 is fastened and fixed in a state in which the electric double layer capacitor 1 is tightly compressed.

  As will be described later, adjacent ones of the plurality of electric double layer capacitors 1 are connected in series, and electricity is charged and discharged through the electric double layer capacitors 1 on both ends. Hereinafter, the configuration of the electric double layer capacitor 1 will be described in detail.

  3 to 5 are a front view, a side view, and a plan sectional view of the electric double layer capacitor shown in FIGS. 1 and 2. The electric double layer capacitor 1 includes a pair of plate-like collector electrodes 6, 6 that face each other in parallel, a rectangular sheet-like separator 7 that partitions the space between the two collector electrodes 6, 6, and each collector electrode 6. Contains a polarizable electrode 8 inserted between the separator 7 and the separator 7, an electrolyte solution impregnated in each polarizable electrode 8 so as to be interposed between the pair of collector electrodes 6 and 6, and various members And a plate-like connection terminal 11 attached to each collector electrode 6, 6.

  The collector electrode 6 is formed in a rectangular plate shape whose vertical direction is the longitudinal direction, and at least the surface (inner surface) on the side in contact with the polarizable electrode 8 needs to be constituted by a conductor. It consists of The metal used as the conductor is, for example, nickel, cobalt, iron, silver, gold, or platinum, and may be a combination thereof. In this example, iron is a collector electrode in consideration of cost. It is used as a conductor for 6. In addition, you may comprise the collector electrode 6 by coating the surface of a resin sheet with a conductor layer, and specifically, a metal film is plated on the surface of a resin sheet.

  Further, on the surface layer portion of the inner surface of the collector electrode 6, irregularities (not shown) corresponding to the infinite number of pore sizes formed in the activated carbon used as the polarizable electrode 8 (close to the pore size) are formed. Specifically, a plurality of fine holes of about 0.1 mm to several mm may be formed on the surface of the collector electrode 6.

  When the collector electrode 6 is configured by coating the surface of the fibrous resin sheet with a conductor for the collector electrode 6, the surface of the collector electrode 6 is naturally formed with irregularities of the above size. In addition, if a metal wire made of a metal for the collector electrode 6 or a metal wire plated with the metal for the collector electrode 6 is knitted to form a mesh sheet, and this mesh sheet is used as the plate-like collector electrode 6, the collector electrode The aforementioned irregularities are also formed on the surface of 6. By forming these fine holes and irregularities, the electrical resistance between the contact surfaces of the collector electrode 6 and the polarizable electrode 8 can be reduced.

  The electrolytic solution is an aqueous electrolytic solution, specifically, a potassium hydroxide aqueous solution having a concentration of 10 to 40% by weight, a sodium hydroxide aqueous solution having a concentration of 10 to 30% by weight, or a potassium carbonate aqueous solution. Etc. are used. By the way, the electrolytic solution that becomes a strong alkali can be easily neutralized with hydrochloric acid or the like, so that it can be safely discarded after use, and the environmental load is small.

  The polarizable electrode 8 is constituted by superposing a plurality of sheet-like activated carbons or made of cotton-like activated carbon having a certain thickness. This sheet-like or cotton-like (sheet-like activated carbon in the illustrated example) activated carbon 8 is obtained by gas-activating or alkali-activating fibrous carbon produced by carbonizing a sheet-like or cotton-like fiber substance. It is the fibrous activated carbon obtained.

  As the fiber material, for example, cellulose fiber, polyacrylonitrile (PAN) fiber, pitch-based carbon fiber made from coal tar or petroleum pitch, carbon fiber made of rayon, phenol, or the like can be used. Of these, in particular, it is preferable in terms of cost to use woven or non-woven cotton or cotton-like cotton as cellulose fibers.

  Thus, since the fibrous activated carbon 8 obtained by carbonizing and activating a fiber substance is excellent in impregnation property, it is possible to contain a large amount of electrolytic solution. Incidentally, this fibrous activated carbon can be used for the polarizable electrode 8 as it is, or it can be cut into a predetermined size and used for the polarizable electrode 8. Hereinafter, the manufacturing method of the polarizable electrode 8 will be described in detail separately for the case of gas activation and the case of alkali activation.

  First, the manufacturing method by gas activation treatment will be described in detail. In a carbonization furnace in which a fiber material is installed, the temperature is raised to 300 to 800 ° C. (more preferably, 400 to 800 ° C.) and kept in that state for 25 minutes to 8 hours. After that, fibrous carbon is obtained by lowering the temperature to room temperature. Subsequently, the temperature was raised to 450 to 950 ° C. while injecting water vapor, carbon dioxide gas or a mixed gas thereof into an inert gas atmosphere such as nitrogen gas or argon gas into the tubular furnace in which the fibrous coal was installed. Then, gas activation for holding this state for 25 minutes to 8 hours is performed to obtain fibrous activated carbon 8.

  On the other hand, in detail about the manufacturing method by alkali activation treatment, in a carbonization furnace in which a fiber material is installed, the temperature is raised to 400 ° C. to 1200 ° C., held in that state for 5 minutes to 20 hours, and then cooled to room temperature. Obtain fibrous carbon. Incidentally, when carbonization is performed at a temperature of 950 ° C. or higher, the activation rate described later is slowed down, and the processing takes time.

  Subsequently, an alkali activation treatment of the fibrous carbon is performed using an inert gas composed of nitrogen gas, argon gas, a mixture thereof, or the like and a potassium hydroxide aqueous solution, a sodium hydroxide aqueous solution, or a potassium carbonate aqueous solution. Specifically, the aqueous solution is prepared about 0.5 to 4 times the weight of the charcoal, and this is added to the fibrous charcoal and sufficiently adsorbed. Thereafter, an alkali activation treatment is performed by performing a heat treatment in an inert gas atmosphere to obtain fibrous activated carbon 8.

  In this heat treatment, in order to prevent the aqueous solution adsorbed on the fibrous charcoal from rapidly evaporating, the temperature is raised from room temperature to 150 ° C. at 2 ° C. per minute. And from 150 degreeC to predetermined activation temperature, it heats up at 5 degreeC per minute. The activation temperature at this time shall be about 500-1000 degreeC. The heat treatment is performed for about 10 minutes to 6 hours.

  In addition, since the alkali activation treatment is performed using the same or the same material as that used for the electrolytic solution in this way, the fibrous activated carbon 8 obtained by the activation treatment can be immersed in the electrolytic solution as it is, It is possible to reduce or eliminate the neutralization treatment by acid washing, repeated washing treatment with ion-exchanged water, and drying treatment.

  The separator 7 is an alkali-resistant insulating sheet that prevents contact between one polarizable electrode 8 and collector electrode 6 and the other polarizable electrode 8 and collector electrode 6 (particularly contact between collector electrodes 9 and 9). Yes, the flow of ions between the collector electrodes 9 and 9 and the flow of ions between the polarizable electrodes 8 and 8 are not hindered. Specifically, an alkali-resistant filter paper that hardly shrinks when impregnated with a liquid, or a separator 7 made of cellulose fiber or polyvinyl alcohol fiber is used.

  The connection terminal 11 is a rectangular plate-like member separately provided on the outer surface side of the pair of collector electrodes 6, 6, and is connected to the collector electrode 6 in a state where its longitudinal direction is directed toward the collector electrode 6. is set up. Specifically, the connection terminal 11 is composed of a conductor (more specifically, metal), and in the illustrated example, is composed of iron which is the same metal as the collector electrode 6.

  The lower half of each connection terminal 11 is in close contact with the upper part of the outer surface of the collector electrode 6, while the upper half of the connection terminal 11 extends upward from the upper end of the collector electrode 6. The electric double layer capacitor 1 shown in the figure is charged and discharged through the connection terminal 11. In addition, one connection terminal 11 is disposed closer to one side in the width direction of the collector electrode 6, and the other connection terminal 11 is disposed closer to the other side in the width direction of the collector electrode 6.

  The accommodating portion 9 is formed inside an alkali-resistant (specifically, polyethylene) accommodating bag (accommodating body) 12 that can be flexibly deformed. The storage bag 12 is formed into a flat cylindrical shape, and the interior of the storage bag 12, that is, the storage portion 9 is impregnated with the separator 7, the pair of collector electrodes 6 and 6, and the electrolyte. All of the pair of polarizable electrodes 8 and 8 and a part of the pair of connection terminals 11 and 11 are inserted and accommodated in a state in which the thickness direction coincides with the accommodation bag 12. The upper end portion or the lower end portion is sealed by thermocompression between the opposing surfaces.

  In addition, the accommodation bag 12 is formed with a slit-shaped insertion port 12 a that protrudes the connection terminal 11 upward from the inside to the connection terminal 11. Through this insertion port 12 a, the upper part of the connection terminal 11 that is in contact with the collector electrode 6 with the lower side in close contact is exposed to the outside of the housing bag 12.

  The space between the insertion opening 12a and the connection terminal 11 is sealed by a sealing means. Specifically, the inner side fixing such as a double-sided tape or an adhesive that fixes and seals the collector electrode 9 side surface (inner surface) of the connection terminal 11 and the surface (outer surface) opposite to the storage portion 9 of the storage bag 12. The outer surface of the means 13, the surface of the connecting terminal 11 opposite to the collector electrode 6 (outer surface), and the surface (inner surface) of the housing bag 12 on the housing portion 9 side are fixed and sealed. The adhering means described above includes the adhering means 14 and the highly water-repellent sealing seal 16 adhering to the outer surface of the connecting terminal 11 and the outer surface of the containing bag 12 so as to cover the boundary between the outer surface of the connecting terminal 11 and the outer surface of the containing bag 12. Is configured.

  The housing portion 9 becomes a sealed space by the sealing on the insertion port 12a side by the close contact means and the sealing by thermocompression of the opposing surfaces on the opening end side described above. Thus, since the accommodating part 9 becomes sealed space, while being able to prevent the electrolyte solution contained in the polarizable electrode 8 from flowing out from the accommodating part 9, it also prevents external air from flowing into the accommodating part 9 it can.

  Further, air is exhausted from the housing portion 9 by a vacuum pump or the like, and the inside of the housing portion 9 is set to a low pressure state, unlike a vacuum state or a vacuum. Thereby, since the oxidation of the part (specifically inner surface of the collector electrode 6) which contacts the electrolyte solution of the collector electrode 6 is suppressed more, rust can be prevented efficiently.

  Further, by pressing between the pair of collector electrodes 1 and 1, a little amount of the electrolyte impregnated in the polarizable electrode 8 and the separator 7 flows out and collects on the bottom side, but a part of the storage bag 12 is cut off, etc. The electrolytic solution is discharged to the outside by opening it, and then the space is discharged by a vacuum pump or the like through this opening portion, and the housing portion 9 is brought into a low-pressure state or a vacuum state, and then the opening portion. May be sealed by thermocompression bonding or the like.

  In this way, by setting the inside of the storage bag 12 to a low pressure or a vacuum, each collector electrode 6 is pressed inside by the inner surface of the storage bag 12, and a pair of polarizable electrodes disposed between the collector electrodes 6 and 6. As a result, the collector electrode 6, the polarizable electrode 8, and the separator 7 are pressed against each other and are in close contact with each other. Internal resistance is reduced.

  In addition, you may prevent the oxidation of the collector electrode 6 by making an accommodating part into inert gas atmosphere. Specifically, by introducing the electric double layer capacitor 1 in which the upper end, the lower end side or other portions are opened into a room under an inert gas atmosphere, the containing bag 12 is filled with the inert gas. In this chamber, the opening of the electric double layer capacitor 1 is sealed. Incidentally, by forming an inert gas atmosphere in a glove box (not shown) and performing the above-described operation with the glove inside the glove box, an efficient assembling operation can be performed.

  Further, as described above, in the capacitor unit shown in FIGS. 1 and 2, the plurality of electric double layer capacitors 1 arranged in the thickness direction are sandwiched by the sandwiching plates 2 at both ends so that the adjacent ones are crimped to each other. Therefore, the polarizable electrode 8 and the separator 7 are compressed in the thickness direction, and the adhesion between the polarizable electrode 8 and the collector electrode 6 is further enhanced.

  Further, in the capacitor unit, the adjacent electric double layer capacitors 1 and 1 are formed in a symmetrical shape with respect to each other's close contact surface so that the connection terminals 11 and 11 are in close contact with each other. A plurality of electric double layer capacitors 11 arranged in the thickness direction are electrically connected in series, and the connection terminals 11A and 11B on the side close to the sandwiching plate 2 in the electric double layer capacitors 11 and 11 on both ends are connected to the capacitor. It becomes the charging / discharging terminal of the unit.

  Incidentally, the connection terminals 11 and 11 that are in close contact with each other are pressed toward the electric double layer capacitor, and the adjacent electric double layer capacitors 1 and 1 are in contact with each other or in close contact with each other. The contact resistance between the connection terminals 11 and 11 is also suppressed to a minimum.

  According to the capacitor unit configured as described above, even when iron that is easily oxidized in the air is used as the collector electrode 6, the inside of the housing portion 9 can be sealed to prevent oxidation. Can be manufactured at low cost.

  In addition, since the collector electrode 6 and the polarizable electrode 8 are in close contact with each other, the internal resistance is reduced and the energy efficiency is improved. Incidentally, even in the case where the inside of the accommodating portion 9 is filled with an inert gas to prevent oxidation, the electric double layer capacitor 1 is compressed in the thickness direction by the pair of sandwiching plates 2 and 2 and the plurality of connecting bolts 3. The adhesion between the collector electrode 6 and the polarizable electrode 8 is maintained.

  Furthermore, since the fibrous activated carbon with good impregnation of the electrolytic solution is used for the polarizable electrode 8, it is not necessary to immerse the entire collecting electrode 6 and polarizable electrode 8 in the electrolytic solution, the configuration is simplified, and the cost is reduced. Is also reduced.

  In addition, although the example using a water-system electrolyte solution was mentioned above as an electrolyte solution, you may use an organic electrolyte solution. In this case, the method for activating the polarizable electrode is the same as in the above-described example, but since the electrolytic solution and the aqueous solution used for the activation treatment are different, it is necessary to perform cleaning and drying more carefully.

  Further, although the polarizable electrode 8 is pressed and brought into close contact with the collector electrode 6, both may be brought into close contact with a conductive adhesive. Specifically, the above-described collector electrode 6 is adhered by a conductive adhesive which is a conductive adhesive obtained by mixing the above-mentioned activated carbon powder, iron powder or nickel powder.

  Specifically, polarizability is applied to an adhesive (trade name: GP Clear, manufactured by Konishi Co., Ltd.) obtained by dissolving styrene butadiene rubber (43%) in an organic solvent (57%) such as dichlorohexane, acetone, or a mixture thereof. An adhesive is produced by kneading the pulverized activated carbon used in the electrode 8 so that the weight ratio is 1: 9, and this is used as the conductive adhesive. And after apply | coating this electrically conductive adhesive to the collector electrode 6, a sheet-like activated carbon is crimped | bonded to the collector electrode 6 side, and it is made to dry over about 2 hours at the temperature of about 100 degreeC, and the organic in an electrically conductive adhesive is carried out. The collector electrode 6 and the polarizable electrode 8 are integrated by volatilizing the solvent.

  Moreover, although the sheet-like activated carbon 8 may be formed for each sheet, a plurality of sheets are overlapped by performing carbonization treatment and activation treatment in a state where a plurality of sheet-like fiber materials are overlapped in advance. The activated carbon 8 may be integrally formed.

  FIG. 6 is a plan view showing a modification of the capacitor unit shown in FIGS. 1 and 2. In the illustrated example, the plurality of electric double layer capacitors 1 constituting the capacitor unit are juxtaposed in the thickness direction so as to have the same posture in plan view.

  As a result, in the adjacent electric double layer capacitors 1, 1, the connection terminals 11, 11 on the opposing surfaces are arranged so as to wrap adjacently in the width direction in a side view. Incidentally, a plurality of electric double layer capacitors arranged in series are electrically connected in series by providing a wiring for electrically connecting the connection terminals 11 and 11 adjacent in the width direction.

  Next, another embodiment of the electric double layer capacitor will be described with reference to FIGS.

  7 and 8 are a side sectional view and an exploded side sectional view showing the configuration of another embodiment of the electric double layer capacitor, and FIG. 9 is a plan view of the collector electrode shown in FIGS. 7 and 8. Each collector electrode 6 is composed of a cylindrical (more specifically, cylindrical) electrode container having one end opened and the other end closed. A circular ring-shaped flange portion 17 is integrally formed on the open end side of the conductive electrode container 6, and the accommodating portion 9 described above is formed on the inner peripheral side of the electrode container 6.

  In this accommodating portion 9, a polarizable electrode 8 made of cotton-like activated carbon or a polarizable electrode 8 formed by stacking a plurality of sheet-like activated carbon (in the example shown, a polarizable electrode 8 made of cotton-like activated carbon) However, it is compressed and filled in a state where the electrolyte solution is fully impregnated. In this way, the flange portions 17 and 17 are fastened and fixed to each other so that the open ends of the pair of electrode containers 6 and 6 in which the polarizable electrode 8 is accommodated face each other. At this time, the accommodating portions 9 and 9 are separated from each other by one or two sheet-like separators 7 interposed between the electrode containers 6 and 6.

  Further, in the example shown in the figure, the fixing member for fastening and fixing the flange portions 17 and 17 is a fastening bolt 18 and a fastening nut 19, and the flange portion 17 and the separator 7 are connected to the periphery of the flange portion 17. Mounting holes 17a and 7a are formed at predetermined intervals along the direction, and a fastening nut 17 is threadedly engaged with a distal end portion of a fastening bolt 18 inserted through the mounting holes 17a and 7a. , 17 are fastened and fixed together.

  Furthermore, an insulating means for insulating the fastening bolt 18 or the fastening nut 19 and the collector electrode 6 is provided so that the fastening bolt 18 or the fastening nut 19 does not connect the collector electrodes 6 and 6 to each other. It has been. Specifically, an insulating ring 21 through which the shaft portion of the fastening bolt 18 is inserted is interposed between the bolt head of the fastening bolt 18 and the flange portion 17 and between the fastening nut 19 and the flange portion 17. In addition, an insulating sleeve 22 is externally mounted on the shaft portion of the fastening bolt 18, and the insulating ring 21 and the insulating sleeve 22 constitute the above-described insulating means. In addition, you may comprise an insulation means by comprising fixing member itself with an insulator.

  According to the electric double layer capacitor 1 configured as described above, the accommodating portion 9 is formed by the collector electrode 6, so that there is no need to separately provide the polarizable electrode 8 and the accommodating body 12 for accommodating the electrolytic solution, The number of parts is reduced and the manufacturing cost is reduced. Further, since the collector electrode 6 is exposed to the outside, the connection terminal 11 is not necessary, and the cost is further reduced.

  Next, a method for measuring the capacitance and internal resistance of the electric double layer capacitor 1 will be described with reference to FIG.

  FIG. 10A is a measurement circuit of an electric double layer capacitor, and FIG. 10B is a characteristic graph of charge / discharge of the electric double layer capacitor. The measurement circuit 31 shown in the figure has two switches SW1 and SW2, and these two switches SW1 and SW2 are not turned on at the same time, either one is ON and the other is OFF, or both. Both are operated OFF.

When the switch SW1 is ON and the switch SW2 is OFF, the electric double layer capacitor 1 to be measured and the charging current detection resistor _Rc are connected in series and directly connected to the power source E, and the charging current detection resistor R _A voltage V _c applied to _c and a capacitor voltage V which is a voltage applied to the electric double layer capacitor 1 are measured by a voltmeter. The charging current I _c flowing through the charging current detecting resistor R _c are determined from the following equation.

On the other hand, when the switch SW1 is OFF and the switch SW2 is ON, the electric double layer capacitor 1 to be measured and the discharge resistor _RD are directly connected to form an RC circuit, and the capacitor voltage V directly becomes the discharge resistor _RD . becomes such a state, the voltage V _D applied to the discharge resistor R _D, the capacitor voltage V is measured with a voltmeter. The charging current I _D flowing through the discharge resistor R _D is obtained from the following equation.

  In addition, as the operation of the measurement circuit 31, first, a charging process is performed in which the switch SW1 is turned on and the switch SW2 is turned off. Through a self-discharging process for disconnection, a discharging process for turning off the switch SW1 and turning on the switch SW2 is performed.

In the charging step, the charging current I _c becomes zero or close to it decreases, the same maximum value and the power source E a capacitor voltage V is increased becomes (maximum voltage V _max), a constant value in the value At that time, charging of the electric double layer capacitor 1 is completed.

In the self-discharge process after the charging process, the capacitor voltage V decreases by the decrease voltage ΔV _SD from the maximum voltage V _max by self-discharge of the electric double layer capacitor 1. This shifts after self-discharge process in the following discharging process, but the capacitor voltage V of this transition immediately before an initial voltage V _0.

In the discharging process, at the initial stage, the capacitor voltage V is reduced by a drop voltage ΔV _D at a stroke, and thereafter, the capacitor voltage V is gradually discharged. The capacitor voltage V after t seconds from the start of discharge is expressed by the following formula, where C is the capacitance of the electric double layer capacitor to be measured.

  The time constant τ is expressed by the following formula.

  Thus, the capacitor voltage when t = τ is obtained by the following equation.

That is, the time for the capacitor voltage V to decrease from the initial voltage V ₀ to 1 / e times becomes the time constant τ, and once this time constant τ is obtained, the discharge resistance _RD is also known. It becomes possible to measure the capacitance C of the multilayer capacitor.

Further, by measuring the initial current I ₀ which is the discharge current _ID flowing at the moment when the discharge process is started, the internal resistance r of the electric double layer capacitor 1 can be calculated from the initial current I ₀ . Incidentally, the calculation formula at that time is based on the following formula.

  As described above, the capacitance C and the internal resistance r of the electric double layer capacitor 1 can be measured with the simple measurement circuit 31.

  Then, the experimental result which measured the electrostatic capacitance C and the internal resistance r of the electric double layer capacitor 1 comprised as mentioned above is demonstrated.

<Experiment 1>
As the fiber material, toweling cotton is used, the temperature at the time of carbonization is set to 450 ° C., the activation temperature is set to 750 to 850 ° C., the activation treatment is performed by alkali activation using potassium hydroxide, and then the acidity is set. A fibrous sheet-like activated carbon is produced by drying what is washed with an aqueous solution of the above, and this is cut into a square shape having a side length of 5 cm. The electric double layer capacitor 1 was manufactured using iron and an aqueous solution of potassium hydroxide having a potassium hydroxide concentration of 30% by weight as the electrolyte.

  This electric double layer capacitor 1 is shown in FIGS. 3 to 5 and was tested in a state in which the collector electrodes 6 and 6 were compressed in a direction approaching each other with an instrument or the like.

  Incidentally, as the electric double layer capacitor 1, each polarizable electrode 8 is constituted by using one sheet-like activated carbon, and each polarizable electrode 8 is constituted by laminating two sheet-like activated carbons. Four types were used, one in which each polarizable electrode 8 was constituted by laminating three sheet-like activated carbons, and one in which each polarizable electrode 8 was constituted by laminating five sheet-like activated carbons.

  Each type of electric double layer capacitor 1 is measured 25 times a total of 5 times a day for 5 days by the method shown in FIG. 10, and the average value of the measured values is calculated for each electric double layer capacitor. The electrostatic capacity C and the internal resistance r were 1. The measurement results are shown below.

  According to the result of the said table | surface, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. It was also observed that the internal resistance r did not increase with the increase in the number of sheet-like activated carbon.

<Experiment 2>
As the fiber material, woven cotton was used, and the other conditions were the same as in Experiment 1. As the electric double layer capacitor 1, each polarizable electrode 8 is configured by using one sheet-like activated carbon, each polarizable electrode 8 is configured by stacking two sheet-like activated carbons, The polarizable electrode 8 is constructed by laminating three sheet-like activated carbons, each polarizable electrode 8 is constructed by laminating five sheet-like activated carbons, and each polarizable electrode 8 is made of sheet-like activated carbon. Six types were used, each of which was formed by laminating 10 sheets, and each of the polarizable electrodes 8 being formed by laminating 15 sheets of sheet-like activated carbon. The measurement results are shown below.

  According to the result of the said table | surface, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. It was also observed that the internal resistance r did not increase with the increase in the number of sheet-like activated carbon.

<Experiment 3>
The experiment was performed under the same conditions as in Experiment 2, except that a fibrous sheet-like activated carbon cut into a square shape with a side length of 2.5 cm was used as the polarizable electrode 8. Incidentally, as the electric double layer capacitor 1, each polarizable electrode 8 is constituted by using one sheet-like activated carbon, and each polarizable electrode 8 is constituted by laminating two sheet-like activated carbons. Four types were used, one in which each polarizable electrode 8 was constituted by laminating three sheet-like activated carbons, and one in which each polarizable electrode 8 was constituted by laminating five sheet-like activated carbons. The measurement results are shown below.

  According to the result of the said table | surface, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. It was also observed that the internal resistance r did not increase with the increase in the number of sheet-like activated carbon.

<Experiment 4>
The experiment was performed under the same conditions as in Experiment 2 except that a fibrous sheet-like activated carbon cut into a square shape with a side length of 7.5 cm was used as the polarizable electrode 8. Incidentally, as the electric double layer capacitor 1, each polarizable electrode 8 is constituted by using one sheet-like activated carbon, and each polarizable electrode 8 is constituted by laminating two sheet-like activated carbons. Four types were used, one in which each polarizable electrode 8 was constituted by laminating three sheet-like activated carbons, and one in which each polarizable electrode 8 was constituted by laminating five sheet-like activated carbons. The measurement results are shown below.

  According to the result of the said table | surface, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. It was also observed that the internal resistance r did not increase with the increase in the number of sheet-like activated carbon.

<Experiment 5>
The experiment was performed under the same conditions as in Experiment 2 except that a fibrous sheet-like activated carbon cut into a rectangular shape having a length of 10 cm and a width of 17 cm was used as the polarizable electrode 8. Incidentally, as the electric double layer capacitor 1, each polarizable electrode 8 is constituted by using one sheet-like activated carbon, and each polarizable electrode 8 is constituted by laminating two sheet-like activated carbons. The polarizable electrodes 8 are formed by stacking three sheet-like activated carbons, and the polarizable electrodes 8 are formed by stacking five sheet-like activated carbons. The measurement results are shown below.

  According to the result of the said table | surface, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. It was also observed that the internal resistance r did not increase with the increase in the number of sheet-like activated carbon.

  Furthermore, from the results of Experiments 2 to 5, it became clear that not only the number of sheet-like activated carbon layers but also the area of the sheet-like activated carbon is proportional to or substantially proportional to the capacitance C. From these, it is considered that the electrostatic capacity C of the sheet-like activated carbon is proportional to the volume of the activated carbon. From this experimental result, the following experiment 6 was conducted on the possibility that activated carbon was manufactured from cotton dust that could be increased in volume at low cost and could be used for the polarizable electrode 8.

<Experiment 6>
As the fiber material, cotton dust is used, and potassium carbonate is used for alkali activation. Otherwise, carbonization and activation treatment are performed in the same manner as in Experiment 1 and cut into a square shape with a side length of 5 cm. The thick plate-shaped polarizable electrode 8 was used, and the other experimental conditions were the same as in Experiment 1. Incidentally, as the electric double layer capacitor 1, one in which each polarizable electrode 8 is configured by using one sheet-like activated carbon was used. The measurement results are shown below.

According to the result of the said table | surface, even if cotton-like activated carbon was used, the electrostatic capacitance C per volume comparable as the woven cotton was obtained. It was also observed that the internal resistance r was small. In this experiment, potassium carbonate aqueous solution was used for alkali activation, and potassium hydroxide was used for the electrolyte. However, since these two substances did not cause a chemical reaction, substances having different properties may be used. , as the electric double layer capacitor 1, it was confirmed that there is no problem.

<Experiment 7>
For the alkali activation, potassium carbonate was used, and as the electrolytic solution, an aqueous potassium carbonate solution having a concentration of 50% by weight was used, and the other conditions were the same as in Experiment 2. Incidentally, as the electric double layer capacitor 1, each polarizable electrode 8 is constituted by using one sheet-like activated carbon, and each polarizable electrode 8 is constituted by laminating two sheet-like activated carbons. Four types were used, one in which each polarizable electrode 8 was constituted by laminating three sheet-like activated carbons, and one in which each polarizable electrode 8 was constituted by laminating five sheet-like activated carbons. The measurement results are shown below.

According to the result of the said table | surface, even if it used potassium carbonate for electrolyte solution, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. It was also observed that the internal resistance r did not increase with the increase in the number of sheet-like activated carbon. However, it has also been clarified that when potassium carbonate is used as the electrolyte, the capacitance per volume is smaller than when potassium hydroxide is used.

<Experiment 8>
The experiment was carried out under the same conditions as in Experiment 2 while using potassium carbonate for alkali activation. Incidentally, as the electric double layer capacitor 1, each polarizable electrode 8 is constituted by using one sheet-like activated carbon, and each polarizable electrode 8 is constituted by laminating two sheet-like activated carbons. The polarizable electrodes 8 are formed by stacking five sheets of activated carbon, and the polarizable electrodes 8 are stacked of 10 sheets of activated carbon. The measurement results are shown below.

  According to the result of the said table | surface, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. In addition, when compared with the results of Experiment 2, when potassium hydroxide is used as the electrolyte, the woven fabric cotton activated with potassium carbonate has the same capacitance as that activated with potassium hydroxide. Became clear.

<Experiment 9>
The activation treatment was performed by alkali activation using potassium carbonate, and the other conditions were the same as in Experiment 1 and the experiment was performed. Incidentally, as the electric double layer capacitor 1, each polarizable electrode 8 is constituted by using one sheet-like activated carbon, and each polarizable electrode 8 is constituted by laminating three sheet-like activated carbons. The polarizable electrodes 8 are used in the form of a laminate of five sheet-like activated carbons. The measurement results are shown below.

  According to the result of the said table | surface, the state which the electrostatic capacitance C increased proportionally by increasing the number of sheet-like activated carbon was observed. It was also observed that the internal resistance r did not increase with the increase in the number of sheet-like activated carbon. It was revealed that cotton towels activated with potassium carbonate have the same capacitance as that activated with potassium hydroxide.

6 Current collector 7 Separator 8 Polarized electrode (activated carbon)
12 Containment bag (container)
17 Flange

Claims (6)

While interposing an electrolyte between the pair of collector electrodes (6, 6), the space between the collector electrodes (6, 6) is separated by a separator (7) which is an insulator that allows passage of ions,
An electric double layer capacitor in which a polarizable electrode (8), which is activated carbon obtained by carbonizing and activating a fiber material, is provided on the separator (7) side surface of each collector electrode (6),
The electrolytic solution is an aqueous electrolytic solution,
The polarizable electrode (8) is made of cotton-like activated carbon obtained from cotton-like fiber material,
The polarizable electrode (8) is impregnated with the electrolytic solution,
In pressing the polarizable electrode (8) against the collector electrode (6), the polarizable electrode (8) is packed in a compressed state in the space between the separator (7) and the collector electrode (6). Double layer capacitor. A housing (12) having a housing (9) formed therein and changeable flexibly;
The separator (7), the pair of collector electrodes (6, 6), and the pair of polarizable electrodes (8, 8) are housed in the housing portion (9), and the air in the housing portion (9) in this state is discharged. it allows electric double layer capacitor according to claim 1, wherein the polarizable electrodes (8,8) is filled in a compressed state to. Each collecting electrode (6) is constituted by a conductive electrode container having an opening,
The polarizable electrode (8) is compressed and filled into the accommodating part (9) formed in the electrode container (6),
The electric double layer capacitor according to claim 1, wherein the insides of the pair of electrode containers (6, 6) are partitioned by a separator (7) and the openings of the electrode containers (6, 6) are connected to each other. Forming a flange (17) in the opening of each electrode container (6);
The electric double layer capacitor according to claim 3, wherein the flange portions (17, 17) of the pair of electrode containers (6, 6) are fastened and fixed in a state of being insulated from each other. The surface layer portion of the collector electrode (6), electric double layer capacitor according to any one of claims 1 to 4 to form irregularities of a size corresponding to the pores of the polarizable electrode (8). The electrolyte, aqueous potassium hydroxide, the electric double layer capacitor according to any one of claims 1 to 5 is either aqueous sodium carbonate or aqueous potassium hydroxide solution.

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