JP2012119465A - Electrode for electric double layer capacitor and electric double layer capacitor using thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric double layer capacitor with higher volume energy density and reduced internal resistance as well as easily shortened manufacturing process by using a block like aluminium porous sintered body for an electrode as a collector for the electric double layer capacitor.SOLUTION: The electrode for electric double layer capacitor comprises: a collector of an aluminium porous sintered body having a metal framework of a three-dimensional mesh structure, having holes between the metal frameworks, and being not less than 5 mm and not more than 100 mm in thickness; and a polarizable electrode material and a binder in the holes of the collector. The electrode is included in the electric double layer capacitor.

Description

  The present invention relates to an electrode of an electric double layer capacitor and an electric double layer capacitor using the same. By using a thick porous aluminum having a three-dimensional network structure as a current collector and impregnating a polarizable active material mixture slurry inside, drying and press-consolidating electrodes, the withstand voltage can be reduced. An electric double layer capacitor having a high volume capacity density is provided. In particular, it is suitable as an auxiliary power source for a solar cell power generation system.

  In recent years, with the growing interest in environmental issues, particularly global warming issues, the spread of renewable energy power generation systems, such as solar cell power generation systems, has expanded. However, in a power generation system that converts natural energy into electric power such as a solar cell, the power generation and output depend on natural phenomena such as the weather, so the demand and supply of power often do not match. One way to eliminate this mismatch is to use a storage medium as an auxiliary power source, charge the auxiliary power source with an excessive amount of power generation, and replenish the shortage amount from the auxiliary power source to balance the power supply and demand. . The auxiliary power source incorporated in such a system is used severely in which fluctuations in charging and discharging are severe. Therefore, lead-acid batteries and nickel-metal hydride batteries that are excellent in durability against load fluctuations are usually used as auxiliary power supplies. However, lead-acid batteries have problems such as being heavy and containing harmful metals, and nickel-metal hydride batteries have problems such as low discharge voltage due to the memory effect of the electrodes when the charging depth is shallow.

  On the other hand, an electric double layer capacitor is lighter than a lead storage battery and does not contain harmful metals. Moreover, since it has characteristics such as excellent durability because it does not involve a chemical change of the active material in the charge / discharge reaction, it is promising as an auxiliary power source to replace lead-acid batteries and nickel metal hydride batteries.

  An electric double layer capacitor is a capacitor that stores electric charge by an electric double layer formed on the surface of an electrode in an electrolytic solution, and is charged and discharged by adsorption and desorption of electrolyte ions on the surface of the active material. Since it does not involve a chemical reaction as in a secondary battery, it is extremely durable, and when used at a predetermined voltage or lower, it hardly deteriorates even if the charge / discharge cycle is repeated 10,000 times or more. As the active material, activated carbon having a large specific surface area is usually used. Conventionally, an electrode of an electric double layer capacitor is made into a slurry by mixing a polarizable electrode active material mixture containing graphite as a conductive agent and polytetrafluoroethylene resin as a binder in addition to activated carbon with a solvent. After being applied to both sides of an aluminum foil to a thickness of 0.05 to 0.15 mm, it is manufactured by drying and compacting. At this time, the aluminum foil acts as a current collector.

  The form of the electric double layer capacitor is a coin type in which one separator is sandwiched between two circular electrodes, and the electrodes are long ribbons, and the two electrodes are passed through one separator. There are a cylindrical type manufactured by winding and a box type manufactured by stacking a plurality of electrodes via a plurality of separators (Patent Document 1).

  The coin-type electric double layer capacitor is described as a single cell and has a small electrode area, so that the charge / discharge capacity is small and is not suitable for an auxiliary power source such as a solar battery.

  When describing the cylindrical electric double layer capacity, it is manufactured by winding a set of members composed of two electrodes and a separator, which is excellent in mass productivity. However, in order to increase the capacitance, it is necessary to lengthen the electrode, and since the distance from the tab to the end of the electrode is increased, there is a problem that the internal resistance of the electrode increases. In addition, in order to secure a sufficient charge / discharge capacity as an auxiliary power source, there is a method in which a plurality of electric double layer capacitors are connected and used as an assembled battery. There is a drawback that space is created and the volumetric energy density is reduced.

  When describing the box-shaped electric double layer capacitor, since it is a rectangular parallelepiped, dead space does not occur when a plurality of electric double layer capacitors are assembled. Further, since the distance from the tab to the end of the electrode is short, the internal resistance is small. Therefore, it can be said to be a form suitable for an auxiliary power source such as a solar battery. However, a box-type electric double layer capacitor has a large number of manufacturing steps and high cost because a tab is attached to each of a plurality of electrodes, and then the electrodes are laminated and the plurality of tabs are welded. There is a drawback of becoming.

  On the other hand, an electric double layer capacitor using a sheet-like porous aluminum having a spongy three-dimensional structure (three-dimensional network structure) instead of an aluminum foil as an electrode and having an electrode having a thickness of 0.2 to 2 mm Is disclosed (Patent Document 2). The electrode is manufactured by using porous aluminum having a thickness of 0.3 to 5 mm as a current collector, injecting a slurry of a polarizable active material mixture into the current collector, drying, pressing, and compacting. Is done. The electrode that uses aluminum foil as a current collector has a thickness of 0.1 to 0.3 mm, whereas the electrode that uses sheet-like porous aluminum can be as thick as 0.2 to 2 mm, so the same charge and discharge It is possible to reduce the number of electrodes required for assembling a capacitive electric double layer capacitor, and to reduce the number of tab welds. Therefore, the manufacturing process of the electric double layer capacitor can be shortened.

Furthermore, as described in Patent Document 2, it is known that when a sheet-like porous aluminum having a three-dimensional network structure is used as a current collector, the withstand voltage of the electric double layer capacitor is improved. That is, the energy density E of the capacitor is proportional to the square of the printing voltage V and the double layer capacitance C.
E = ^CV 2/2
For example, if the normal charging voltage per cell can be increased from 2.4V to 2.8V,
^{_{E 2.8V / E 2.4V = {(}} 2.8 2/2) · C} / {(2.4 2/2) · C} = 1.361
The energy density can be increased by 36.1%.

  Therefore, if a box-type electric double layer capacitor can be assembled using a thick porous aluminum as a current collector, the normal charging voltage can be set higher because the porous aluminum is used as a current collector. An electric double layer capacitor having a high volumetric energy density and a box shape, which has a small dead space when formed into an assembled battery, can be assembled with a small number of electrodes, and can be manufactured with a short number of steps.

JP-A-4-154106 Japanese Patent No. 3591055

  However, when an electrode of an electric double layer capacitor is manufactured by using porous aluminum as a current collector and impregnated with a slurry of a polarizable active material mixture, the porous aluminum becomes thicker. There is a problem that it becomes difficult to uniformly hold the polarizable active material mixture in the inside of the glass. In particular, when the thickness exceeds 5 mm, depending on the pore diameter, a part with little polarizable active material mixture is formed near the center, or a part without the polarizable active material mixture is formed. The desired volume capacity density cannot be obtained. On the other hand, if the pore diameter of the porous aluminum is increased, the slurry of the polarizable active material mixture is easily impregnated. However, if the pore diameter is too large, the polarizable active material mixture may fall off or the aforementioned porous aluminum There is a problem that the effect of improving the withstand voltage due to is difficult to express.

Accordingly, the inventors of the present invention are to manufacture an electrode of an electric double layer capacitor having a thick thickness and excellent voltage resistance, in which a polarizable active material mixture is uniformly held inside the porous aluminum current collector. As a result of repeated trial and error,
Porous aluminum with a three-dimensional network structure made of a sintered body of aluminum powder has irregularities in the skeleton and excellent adhesion to the polarizable active material mixture. I found it suitable. Porous aluminum made of a sintered body of aluminum powder is a method separately devised by the present inventors, that is, a small amount of titanium powder is blended in aluminum powder and molded into a foam using a known slurry foaming method or the like. It can be manufactured by a method of heating and baking at a predetermined temperature in an argon atmosphere.

  Further, it was found that blending titanium powder has the effect of improving the strength of porous aluminum and reducing the internal resistance of the electrode. The sintered body obtained by firing the mixed powder of aluminum powder and titanium powder has a microstructure in which titanium and the compound of aluminum and titanium are dispersed and distributed in the aluminum sintered body, but no titanium is present. The thickness of the oxide film on the surface of the sintered body is thinner at the site where titanium is present. This is considered to contribute to the decrease in internal resistance.

  Next, the skeleton density in the vicinity of the surface of the porous aluminum having a large pore diameter is increased in advance, and the porous aluminum is impregnated with the slurry of the polarizable active material mixture, dried, and press-consolidated. It was found that the polarizable active material mixture can be uniformly held inside. The porous aluminum can increase the skeleton density in the vicinity of the surface by roll rolling or the like at a predetermined rolling reduction.

  Further, when porous aluminum having a three-dimensional network structure made of a sintered body of aluminum powder is used for the current collector, the average diameter of the pore diameter before consolidation is the number of holes crossed by a 1 cm long line segment. When 8 or more porous aluminum was used, it turned out that the effect of withstand voltage improvement expresses.

The present invention has been made on the basis of such knowledge, and an electric double layer capacitor having a high withstand voltage and a large volumetric capacity density using porous aluminum having a thick three-dimensional network structure as a current collector The problem for manufacturing the electrode is solved by the following configuration.
(1) A metal skeleton having a three-dimensional network structure and pores between the metal skeletons, a current collector of an aluminum porous sintered body having a thickness of more than 5 mm and not more than 100 mm, and pores of the current collector An electrode for an electric double layer capacitor comprising a polarizable electrode material and a binder therein.
(2) The electrode for an electric double layer capacitor according to the above (1), wherein an Al—Ti compound is dispersed in a metal skeleton.
(3) The electrode for an electric double layer capacitor according to (1) or (2) above, wherein the aluminum porous sintered body is a prismatic type or a cylindrical type.
(4) A step of rolling or pressing a block-shaped aluminum porous sintered body to increase the surface skeleton density, and the polarizable electrode material-containing slurry obtained by kneading the polarizable electrode material together with a solvent into the aluminum porous sintered body The manufacturing method of the electrode for electric double layer capacitors which includes the process of impregnating a body, the process of drying, and the process of compaction in this order.
(5) An electric double layer capacitor comprising the current collector for an electric double layer capacitor according to any one of (1) to (3) above.
(6) A solar cell power generation system including the current collector for an electric double layer capacitor according to (5) above and a solar cell.

  According to the present invention (1), an electric double layer capacitor having a high capacity, a high volume energy density and a low internal resistance can be produced in a simple and short process. Moreover, according to this invention (5), the electrical double layer capacitor suitable as an auxiliary power supply of a solar cell power generation system can be provided.

It is a schematic diagram of a current collector provided with a cylindrical aluminum porous sintered body having an electrolyte solution circulation hole. It is an example of the schematic diagram of the electric double layer capacitor which uses a prism-shaped electrode. It is an example of the schematic diagram of the electric double layer capacitor which uses a prism-shaped electrode. It is an example of the schematic diagram of the electric double layer capacitor which uses a cylindrical electrode. It is a schematic diagram of the exterior body used with the test cell. It is a figure explaining the lamination | stacking method of the positive electrode and negative electrode of the comparative example 1. FIG. It is a figure explaining the welding part of the positive electrode current collection tab of the comparative example 1, and a negative electrode current collection tab.

  Hereinafter, the present invention will be specifically described based on embodiments. Unless otherwise indicated,% is% based on mass unless otherwise specified.

[Electrode for electric double layer capacitor]
The electrode for an electric double layer capacitor of the present invention (hereinafter referred to as “electrode”) has a metal skeleton having a three-dimensional network structure and voids between the metal skeletons, and has a thickness of more than 5 mm and not more than 100 mm (hereinafter, “ And a polarizable electrode material and a binder in the pores of the current collector. Here, from the viewpoint of increasing the volume energy density, the thickness is greater than 5 mm, preferably 10 mm or more, and more preferably 20 mm or more. Further, from the viewpoint of maintaining good output characteristics and maintaining low internal resistance, the thickness is 100 mm or less. Here, the thickness is a length in a direction perpendicular to the surface in contact with the separator.

  For example, the thickness of a conventional box-type electrode used for a box-type electric double layer capacitor is usually about 0.2 mm. Here, if the thickness of the electrode of the present invention is, for example, 20 mm, the thickness of the conventional box electrode is 100 times, and if the volume density of the polarizable electrode material is the same, the electrode of the present invention is This corresponds to 100 conventional box electrodes. Further, when 100 conventional box-shaped electrodes are stacked, gaps or shifts occur between the electrodes, and depending on the stacking method, an appropriate number of separators are required, so that the volume energy density is reduced. Furthermore, laminating 100 electrodes has a problem that the number of processes is large and handling is difficult. The electrodes of the present invention can overcome these problems. The electric double layer capacitor is charged / discharged by the electric double layer in the vicinity of the electrode, so that high-rate charging / discharging is possible even if the electrode is thick.

  The aluminum porous sintered body has a metal skeleton having a three-dimensional network structure and has pores between the metal skeletons. More specifically, the porous aluminum sintered body forms pores by a metal skeleton having a three-dimensional network structure. Also, the metal skeleton itself has a high porosity.

  In order to obtain the desired aluminum porous sintered body strength, pore diameter, and porosity, the metal skeleton of the aluminum porous sintered body has a metal skeleton diameter (the thickness of the thinnest part of each metal bone forming the metal skeleton). Is preferably 5 to 100 μm. Further, this metal skeleton preferably has skeleton vacancies having a pore diameter of 0.1 to 3 μm. Here, the metal skeleton diameter and the pore diameter of the skeleton vacancies are measured by scanning electron micrographs of the skeleton surface and the skeleton cross section.

  In addition, the vacancies between the metal skeletons (hereinafter referred to as interframe vacancies) are communicated from the viewpoint of easily including a polarizable electrode material, a binder, and the like, and ensuring good conductivity with the electrolytic solution. It is preferable.

  From the viewpoint of filling a desired amount of polarizable electrode material, the pore diameter of the inter-framework holes is preferably 20 to 500 μm. After consolidation by rolling or pressing, the pore diameter of the interstitial pores is preferably an elliptical shape with a long longitudinal direction of the aluminum porous sintered body, and the pore diameter in the longitudinal direction is preferably 300 to 1100 μm. The pore diameter in the thickness direction is preferably 50 to 300 μm. Here, the pore diameter is measured by scanning electron micrographs of the surface and cross section of the sample.

  The total porosity of the aluminum porous sintered body is preferably 70 to 99%, more preferably 80 to 97%, from the viewpoint of filling a desired amount of polarizable electrode material. In addition, the porosity after consolidation is preferably 55 to 92%, and more preferably 70 to 90%. Here, the porosity is calculated from the dimensions, mass, and density of the porous aluminum sintered body.

  In addition, it is preferable that the aluminum porous sintered body has a pore diameter before consolidation, and an average number of pores crossed by a 1 cm-long line segment is 8 or more, since an effect of improving withstand voltage is exhibited. Here, the average number of holes is measured from a scanning electron microscope (SEM) photograph.

  Here, the aluminum porous sintered body is preferable when the Al—Ti compound is dispersed in the metal skeleton. The Al—Ti compound having a metal skeleton is derived from titanium contained in a sintering aid used when producing an aluminum porous sintered body. Titanium not only makes it possible to produce an aluminum porous sintered body by pressureless sintering, but also makes the aluminum porous sintered body high strength, especially high tensile, by forming an Al-Ti compound. Make it strong.

  The aluminum porous sintered body preferably contains 0.1 to 20 parts by mass of titanium with respect to 100 parts by mass of aluminum and titanium in total. If titanium is less than 0.1 part by mass, a good aluminum porous sintered body cannot be obtained. If it exceeds 20 parts by mass, sintering aid powder containing titanium in the aluminum mixed raw material powder at the time of sintering. They come to have contacts, making it impossible to control the reaction heat between aluminum and titanium, and making it impossible to obtain a desired porous sintered body. Here, the quantitative analysis of aluminum and titanium is performed by the ICP method.

  The block-shaped aluminum porous sintered body is preferably a prismatic type or a cylindrical type from the viewpoint that a non-aqueous electrolyte secondary battery can be easily manufactured. Here, before compaction, in the case of a prismatic type, the short side is preferably 5 to 200 mm, more preferably 15 to 100 mm. The long side is preferably 5 to 200 mm, and more preferably 15 to 100 mm. The short side and the long side may have the same length, that is, a rectangular parallelepiped. In the case of a cylindrical type, the diameter is preferably 5 to 200 mm, and more preferably 15 to 100 mm. Further, from the viewpoints of energy density improvement and output characteristics, it is preferable to compact the rolling reduction within a range of 5 to 35% by rolling or the like, and it is more preferable to increase the density to 8 to 25%. In addition, about thickness before rolling etc., it is preferable in it being 5-100 mm, and it is more preferable in it being 7-70 mm. The thickness after rolling or the like is as described above.

  Examples of the polarizable electrode material contained in the pores of the porous aluminum sintered body include those used as polarizable electrode materials for electric double layer type capacitors, which can be polarized in an electrolyte. If there is, it will not be specifically limited. Conventionally, it is sufficient if it is generally used, and specifically, activated carbon having nano-sized pores is preferable. The polarizable electrode material is preferably a powder having an average particle diameter of 2 to 20 μm from the viewpoint of increasing the capacity of the electric double layer capacitor. Here, the average particle diameter is measured by a laser diffraction method.

  Examples of the binder contained together with the polarizable electrode material in the pores of the aluminum porous sintered body include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), SBR, and polyimide. It is not limited.

  When 100 to 800 parts by mass of the polarizable electrode material is contained with respect to 100 parts by mass of the aluminum porous sintered body, it is preferable from the viewpoint of improving the energy density of the electric double layer capacitor, and more preferably 250 to 750 parts by mass.

  When the binder is contained in an amount of 2 to 80 parts by mass with respect to 100 parts by mass of the aluminum porous sintered body, it is preferable from the viewpoint of appropriately holding the polarizable electrode material in the pores of the aluminum porous sintered body, More preferably, 60 parts by mass is included.

  In the present invention, the polarizable electrode material and the binder are contained in the pores of the aluminum porous sintered body, but also between the aluminum porous sintered body that is a current collector and the separator, Polarized electrode materials and binders can be included. In the present invention, the polarizable electrode material and the binder contained in the pores of the porous aluminum sintered body are 90 parts per 100 parts by mass of the polarizable electrode material and the binder in the electric double layer capacitor. It is preferable that it is ˜99.5 parts by mass from the viewpoint of improving the high energy density of the electric double layer capacitor and increasing the output.

  Moreover, it is preferable from the viewpoint of high output that the pores of the aluminum porous sintered body further include a conductive additive. Examples of the conductive assistant include, but are not limited to, carbon black, acetylene black, ketjen black, natural graphite, and artificial graphite.

  Including 1 to 100 parts by mass of a conductive additive with respect to 100 parts by mass of the aluminum porous sintered body is preferable from the viewpoint of increasing the capacity of the electric double layer capacitor, and more preferably 7 to 70 parts by mass.

  Examples of the electrolytic solution when using the electrode of the present invention include an aqueous electrolytic solution and a non-aqueous electrolytic solution. From the viewpoint of widening the potential window of the electrolytic solution and not dissolving the aluminum porous sintered body, Aqueous systems are preferred. A preferred example of the non-aqueous electrolyte is shown below, but any non-aqueous electrolyte may be used as long as it is used in a normal electric double layer capacitor, and is not particularly limited.

The supporting electrolyte of the nonaqueous electrolytic solution, for example, the general _formula; R 4 ^{N +,} and the general _formula; R ^{4 N} + (R is an alkyl group) and a quaternary onium cation represented by, BF ₄ ^- boric such fluoride anions, and PF ₆ ^- salt of phosphorus fluoride anion, such as can be used.

  Organic solvents such as propylene carbonate, propylene carbonate derivatives, ethylene carbonate, ethylene carbonate derivatives, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate can be used as the solvent for the nonaqueous electrolytic solution.

The block-shaped aluminum porous sintered body can be provided with electrolyte solution flow holes. In FIG. 1, the schematic diagram of a collector provided with the cylindrical aluminum porous sintered compact 100 which has the electrolyte solution through-hole 200 is shown. Electrolyte flow hole 200 can contribute to good output characteristics by securing an electrolyte flow path and suppressing an increase in internal resistance of the electric double layer capacitor. For this reason, as shown in FIG. 1, it is preferable that the electrolyte circulation holes 200 are formed at regular intervals, and the electrolyte circulation holes 200 are preferably penetrated in the thickness direction. The diameter of the electrolyte circulation hole 200 is preferably 0.5 to 2 mm, the electrolyte circulation hole 200 is preferably formed at an interval of 1 to 7 mm, and the electrolyte circulation hole 200 is 3 per cm ^2. It is preferable that ~ 90 are formed.

[Electric double layer capacitor]
2, 3 and 4 are schematic views of the electric double layer capacitor of the present invention. FIGS. 2 and 3 are examples using prismatic electrodes, and FIG. 4 is an example using cylindrical electrodes. As can be seen from FIGS. 2 to 4, the volume of the separators 3 and 13 occupying the electric double layer capacitor can be significantly reduced by using the electrodes 1 and 11 using the block-like porous aluminum sintered body. In particular, in FIG. 2, the volume occupied by the separators 3 and 13 is remarkably reduced. In FIGS. 3 and 4, the tabs 2 and 12 can be easily attached in the same direction. Therefore, it can be appropriately selected depending on the convenience of electrical connection to the electric double layer capacitor. When actually used, the electric double layer capacitor is sealed and accommodated in an outer can such as a can or a pack in an electrically connected state. For cans and packs, materials known to those skilled in the art such as appropriately insulated aluminum and stainless steel are used. The separators 3 and 13 that protrude from the electrodes 1 and 11 may be folded to either side when stored in an outer package such as a can or a pack.

  Since the distance between the tabs 2 and 12 and the ends of the electrodes 1 and 11 (the other end farthest from the tab) is the same as that of the conventional box electrode, the tabs 2 and 12 have a small internal resistance even at one place. . In the case of the conventional aluminum expo, a tab must be attached after applying and drying a polarizable electrode material or the like. In the electrode of the present invention, the tabs 2 and 12 can be formed in advance. For example, when the electrode is immersed in a slurry containing a polarizable electrode material, it can be carried with a tab, which is preferable. The tab can be joined by welding or the like, and can be joined simultaneously with the sintering of the aluminum porous sintered body.

  The electric double layer capacitor of the present invention is suitable as an auxiliary power source for a solar cell power generation system. Here, when a plurality of electric double layer capacitors are connected and used, it is preferable to use a prismatic electrode from the viewpoint of reducing a dead space between the electric double layer capacitors. When used as a solar cell power generation system, one or a plurality of electric double layer capacitors and a solar cell can be stacked and used. Further, when used as an auxiliary power source of a solar battery power generation system, it is preferable to include a predetermined control circuit, and this control circuit may be known to those skilled in the art.

[Method for producing current collector for electric double layer capacitor]
A method for producing a block-shaped aluminum porous sintered body will be described below, which is a preferable material, which is an aluminum porous sintered body in which an Al—Ti compound is dispersed in a metal skeleton.

1) Preparation of raw material Al powder-containing slurry Al powder +1 to 10% by mass Ti powder: 100 parts by mass Water-soluble methylcellulose derivative: 5 to 10 parts by mass Water: 100 parts by mass Surfactant: 0.1 to 1 part by mass Mix and use a B-type viscometer to achieve 50,000-80,000 cPs at 100 rpm.

  Here, the average particle diameter of the Al powder is preferably 2 to 200 μm, more preferably 2 to 100 μm, and still more preferably 7 μm to 40 μm. Here, the average particle diameter is measured by a laser diffraction method.

  As the Ti powder, metal Ti or titanium hydride can be used, and titanium hydride is preferable from the viewpoint of sinterability. The average particle diameter of titanium hydride is preferably 0.1 (μm) ≦ r ≦ 30 (μm), more preferably 4 (μm) ≦ r ≦ 20 (μm). This is because if the average particle size of titanium hydride is smaller than 0.1 μm, spontaneous ignition may occur, and if it exceeds 30 μm, desired strength cannot be obtained in the sintered body. The blending amount of titanium hydride is preferably 1 (mass%) ≦ W ≦ 10 (mass%). When the content is less than 1% by mass, sintering becomes insufficient. On the other hand, when the blending ratio W of the sintering aid powder exceeds 10% by mass, the sintered body becomes brittle and a desired porous sintered body is obtained. Because it will not be possible.

2) Molding / Sintering Prepare the viscous plastic material prepared above.
→ Stir with a whisk to make cream.
→ Pour the creamy viscous composition into the mold.
→ Place the mold in a container that can be decompressed.
→ Cool the whole decompression vessel to 1-5 ° C. This step is precooling in order to quickly freeze.
→ Depressurize to increase bubble size. The pore diameter in the viscous plastic material can be controlled by the pressure at this time.
→ Freeze the whole decompression container with decompression.
→ Freeze-dry.
→ Take out the compact.
→ The binder is removed in the atmosphere at 360 to 420 ° C. for 1 to 10 minutes.
→ Sintering is performed in Ar at 660 to 665 ° C. for 1 to 30 minutes.

  The mold used above is produced in consideration of the shrinkage rate during sintering. Moreover, it is preferable to perform pressure reduction at 0.05-0.5 atmosphere.

[Method of manufacturing electrode for electric double layer capacitor]
A method for producing an electrode for an electric double layer capacitor includes a step of rolling or pressing a block-shaped aluminum porous sintered body to increase the surface skeleton density, and a polarizable electrode material containing a polarizable electrode material kneaded with a solvent A step of impregnating the slurry into the aluminum porous sintered body, a step of drying, and a step of compacting are included in this order.

  First, a block-shaped aluminum porous sintered body is rolled or pressed to increase the skeleton density near the surface, and the porosity of the portion is decreased. At this time, from the viewpoint that the polarizable electrode material-containing slurry can be uniformly held inside the porous aluminum, it is preferable that the skeleton density is high up to about 5% from the surface in the thickness direction, and the porosity in the vicinity of the surface is 70 to 80% is preferable.

The polarizable electrode material-containing slurry is prepared with the following content.
Activated carbon powder (polarizable electrode material): 80-90 parts by mass Ketjen black (conductive material): 5-10 parts by mass Water-soluble cellulose derivative (thickener): 0.1-2 parts by mass of polytetrafluoroethylene resin dispersion Liquid (binder + solvent): 5-15 parts by mass The above mixture is kneaded and a B-type viscometer is used so that the rotational speed is 100 rpm and 5,000 to 20,000 cps.

  Next, the pores of the aluminum porous sintered body are impregnated with the polarizable electrode material-containing slurry and dried. Examples of the impregnation method include a method of dipping an aluminum porous sintered body into a slurry of a polarizable electrode material, a method of pouring the slurry from the upper part of the aluminum porous sintered body, and a method of passing between two rolls. Or by rubbing with a spatula and surplus polar electrode material slurry adhering to the surface is pushed into the interior to more effectively fill the pores of the porous aluminum sintered body with the polarizable electrode material. it can. Drying may be left in the air, or a dryer or the like may be used. After drying, measure the mass ratio between the porous aluminum sintered body and the polarizable electrode material and the binder. If the polar ratio of the polarizable electrode material and the binder is low, repeat the dipping and drying again. The desired amount can be obtained. On the other hand, when the mass ratio of the polarizable electrode material and the binder is high, the viscosity of the slurry can be lowered, and dipping and drying can be performed again to obtain a desired amount.

  Next, the aluminum porous sintered body containing the polarizable electrode material and the binder is consolidated to obtain an electrode. Consolidation is performed by roll rolling or pressing. The aluminum porous sintered body can be rolled to a desired thickness by roll rolling, etc., the porosity of the electrode body can be reduced, and the electrode density can be increased, thereby making the electric double layer capacitor have a high volume energy. Densify. Here, rolling is preferable from the viewpoint of productivity, and a mechanical press using a die is preferable from the viewpoint of uniform densification.

  The electrode for an electric double layer capacitor of the present invention can produce an electric double layer capacitor having a high volume energy density and a low internal resistance in a simple and short process.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

[Preparation of block-shaped aluminum porous sintered body]
According to the above-described embodiment, a block-shaped aluminum porous sintered body was manufactured. First, an aluminum powder having an average particle diameter of 24 μm (containing impurities: Fe: 0.15 mass%, Si: 0.05 mass% and Ni: 0.01 mass%), and hydrogen having an average particle diameter of 9.1 μm The titanium halide powder was mixed in a total of 500 g so that the mass ratio of the aluminum powder and the titanium hydride powder was 95: 5 to prepare an aluminum mixed raw material powder.

  The binder solution was adjusted with water-soluble methylcellulose derivative: 25 g, water: 500 g, and surfactant: 1 g.

  The aluminum mixed raw material powder and the binder solution were mixed to prepare a raw material Al powder-containing slurry.

Next, this raw material Al powder-containing slurry was stirred with a whisk to form a cream, and the raw material Al powder-containing slurry made into a cream was made into polytetrafluoroethylene having a length: 120 mm, a width: 60, and a height: 100 mm. The resin mold was poured into a height of 10 mm. Then, it put into the stainless steel pressure reduction container equipped with the pressure gauge and the exhaust port with a cock, and cooled to 1-5 degreeC with the said pressure reduction container. After cooling, the pressure was reduced to about 0.1 atm to increase the bubble size to a diameter of about 0.5 to 2 mm. Then, with the pressure reduced, the whole decompression vessel was put in a freezer set to −20 ° C. and frozen, and then the frozen molded body was taken out from the pressure reduction vessel, transferred to a vacuum dryer, decompressed and freeze-dried. Next, the freeze-dried molded product was taken out, heated in the atmosphere at 390 ° C. for 5 minutes to remove the binder, and then heated in Ar at 660 ° C. for 10 minutes and fired. The obtained porous aluminum sintered body had a length: 105 mm, a width: 53, and a thickness: 88 mm. As a result of observing the porous aluminum sintered body by X-ray diffraction, Al and an Al ₃ Ti compound were confirmed.

  The obtained aluminum porous sintered body was rolled three times with a roll mill at a reduction rate of 2% to increase the surface skeleton density.

[Manufacture of electrodes for electric double layer capacitors]
Example 1

  Coconut shell activated carbon powder as a polarizable electrode material, ketjen black as a conductive material, a water-soluble methylcellulose derivative as an image material, and a polytetrafluoroethylene resin dispersion as a binder at a mass ratio of 80: 9: 2: 9, a total of 200 g was mixed to prepare a polarizable electrode material-containing slurry.

  Next, the produced positive electrode current collector was immersed in this polarizable electrode material-containing slurry for 10 minutes, taken out and dried, and then mechanically pressed to produce an electrode having a thickness of 20 mm. Here, after the aluminum porous sintered body is immersed in the polarizable electrode material slurry, dried, and before mechanical press, the polarizable electrode material-containing slurry adhering to the surface of the aluminum porous sintered body is wiped off, and almost the entire amount is obtained. The polarizable electrode material and the binder were included in the pores of the aluminum porous sintered body to form an electrode. Two electrodes were produced.

[Production of test cell]
An electric double layer capacitor test cell was fabricated. An aluminum tab was welded to one central portion of the end faces of the two electrodes.

  Further, as a separator, a separator 12 of a porous cellulose sheet (thickness: 20 μm) was cut into a length: 110 mm and a width: 62 mm. As shown in FIG. 2, these were placed in the order of tab 2, electrode, separator 3, electrode 1, and tab 2.

  As shown in FIG. 5, an aluminum laminate film exterior body 4 in which 4A on one side was welded and cut to a size that can accommodate the above-described placement body was prepared.

In an inert atmosphere, the laminate is inserted from one opening of the outer package 14 and the tab 2 is welded by one welding portion 4B, and then from the other opening 4B at a concentration of 1 mol / L. After injecting a propylene carbonate solution containing etraethylammonium tetrafluoroborate ((C ₂ H ₅ ) ₄ N ⁺ BF ₄ ⁻ ), the remaining opening 4B of the outer package 4 is welded and sealed, and the operation is performed. The test cell of Example 1 was made.

(Comparative Example 1)
After applying the slurry containing polarizable electrode material prepared in Example 1 to an aluminum foil having a thickness of 20 μm, drying and rolling, 20 sheets of length: 105 mm and width: 88 mm were cut. A positive electrode and a negative electrode were obtained. At this time, the thickness of the electrode was 0.2 mm.

  After welding a positive electrode current collector tab / a negative electrode current collector tab made of aluminum to the positive electrode / negative electrode, as shown in FIG. 6, 10 sets of positive electrode, separator, negative electrode, and separator were laminated in this order. The same separator as used in Example 1 was cut into a length of 110 mm and a width of 62 mm.

Next, as shown in FIG. 7, ten positive electrode current collecting tabs 51a, ten negative electrode current collecting tabs 51b are welded at a positive electrode current collecting tab welding portion 51b and a negative electrode current collecting tab welding portion 51b, Integrated. In FIG. 6 and FIG. 7, three sets of cells are described for convenience. Ten sets of integrated cells were inserted into the outer package in the same manner as in Example 1, and then etraethylammonium tetrafluorofluoride ((C ₂ H ₅ ) ₄ N ⁺ BF ₄ ⁻ ) at a concentration of 1 mol / L. A propylene carbonate solution containing was injected and welded to prepare a test cell of Comparative Example 1.

[Test cell performance test]
(Discharge capacity test)
The test cell was charged to an atmospheric temperature of 60 ° C., charged current density: 100 mA / g to 2.5 V, discharged to 0 V at a discharge current density of 100 mA / g, and the discharge capacity at this time was measured. . The current density was based on the mass of the coconut shell activated carbon powder. The above charge / discharge was repeated 1000 cycles, and the discharge capacity was measured. In addition, the rest for 1 minute was provided after discharge after discharge. Further, [“discharge capacity after 1000 cycles” / “initial discharge capacity”] was defined as a capacity maintenance rate (unit: “%”). A similar test was performed at a charging voltage of 3V. Table 1 shows these results.

  As can be seen from Table 1, in Example 1, the charge voltage was 2.5 V, the initial discharge capacity was high, and the capacity retention rate after 1000 cycles was remarkably high at 98.9%. The initial discharge capacity was high even at a charge voltage of 3.0 V, and the capacity retention rate after 1000 cycles was remarkably high at 97.4%. On the other hand, in Comparative Example 1, the capacity retention rate after 1000 cycles was as low as 97.8% even at 2.5V, and the capacity retention rate after 1000 cycles was considerably low at 52.6% at 3.0V.

  As described above, according to the electrode for an electric double layer capacitor of the present invention, an electric double layer capacitor having a high capacity, a high volume energy density, and a low internal resistance can be produced in a simple and short process. The manufactured electric double layer capacitor is particularly suitable as an energy storage medium or an assist power source for a solar cell power generation system.

DESCRIPTION OF SYMBOLS 1 Square columnar aluminum porous sintered body 2 Tab 3 Separator 4 Exterior body 4A Welding part 4B Opening and welding part 11 Cylindrical aluminum porous sintered body 12 Tab 13 Separator 51 Positive electrode 51a Positive electrode current collection tab 51a Positive electrode collection Welded portion of electric tab 52 Negative electrode 52a Negative electrode current collecting tab 52b Welded portion of negative electrode current collecting tab 53 Separator 100 Columnar aluminum porous sintered body 200 Electrolyte flow hole

Claims (6)

  A current collector of an aluminum porous sintered body having a thickness of more than 5 mm and not more than 100 mm having pores between the metal skeleton having a three-dimensional network structure and the metal skeleton, and being divided into the pores of the current collector An electrode for an electric double layer capacitor, comprising a polar electrode material and a binder.   The electrode for an electric double layer capacitor according to claim 1, wherein an Al-Ti compound is dispersed in the metal skeleton.   The electrode for an electric double layer capacitor according to claim 1 or 2, wherein the aluminum porous sintered body is a prismatic type or a cylindrical type.   A step of rolling or pressing a block-shaped aluminum porous sintered body to increase the surface skeleton density, and a polarizable electrode material-containing slurry obtained by kneading a polarizable electrode material together with a solvent into the aluminum porous sintered body A method for producing an electrode for an electric double layer capacitor, comprising an impregnation step, a drying step, and a consolidation step in this order.   The electrical double layer capacitor containing the electrical power collector for electrical double layer capacitors of any one of Claims 1-3. A solar cell power generation system comprising the current collector for an electric double layer capacitor according to claim 5 and a solar cell.