JP5338533B2 - ELECTRIC DOUBLE LAYER CAPACITOR ELECTRODE AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode that achieves high reliability, high output, and high energy density of an electric double-layer capacitor. <P>SOLUTION: An electrode for an electric double-layer capacitor contains an aluminum porous sintered body, while a polarizable electrode material, an electrically-conductive auxiliary agent, and a binder are contained in voids of the aluminum porous sintered body. The aluminum porous sintered body has a metal skeleton of a three-dimensional network structure; there are voids between the metal skeletons; an Al-Ti compound is dispersed in the metal skeleton; and unevenness formed by a level difference between grain boundaries of the aluminum porous sintered body exists on the surface of the metal skeleton. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention particularly relates to an electrode using an aluminum porous sintered body suitable for a lithium ion secondary battery or a lithium ion polymer secondary battery, and a method for producing the same.

  In recent years, non-aqueous electrolyte secondary batteries such as electric double layer capacitors, lithium ion batteries, and lithium ion polymer batteries have come to be used in electric vehicles, hybrid vehicles, etc. Electrode current collectors in batteries are required to support high reliability, high output, and high energy density. Currently, an aluminum foil is generally used as an electrode current collector of these batteries, but an aluminum porous body having open pores having a three-dimensional network structure is becoming known as an electrode current collector ( Patent Documents 1 and 2).

  As a method for producing such an aluminum porous body, for example, after thickening molten aluminum with a thickener, titanium hydride is added as a foaming agent, and hydrogen gas generated by a thermal decomposition reaction of titanium hydride is used. There is known a foam melting method in which molten aluminum is solidified while being foamed (Patent Document 3). However, the foamed aluminum obtained by this method had large closed pores of several mm.

  In addition, as a second method, there is a method of obtaining foamed aluminum having a sponge skeleton by press-fitting aluminum into a mold having sponge urethane as a core and filling aluminum into a cavity formed by burning out urethane. According to this method, a foamed aluminum having a pore diameter of 40 PPI or less, that is, a pore diameter of 40 cells or less per inch (pore diameter: about 600 μm or more) is obtained.

Further, as a third method, there is a method in which aluminum is foamed by decomposition of TiH ₂ powder by heating and rolling a mixed powder of AlSi alloy powder and TiH ₂ powder between aluminum plate materials. The foamed aluminum to be obtained has a large pore diameter of several mm (Patent Document 4).

  Furthermore, as a fourth method, there is a method in which a metal having a eutectic temperature with aluminum lower than the melting point of aluminum is mixed with aluminum and heated and fired at a temperature higher than the eutectic temperature and lower than the melting point of aluminum. (Patent Document 5) The foamed aluminum obtained by the same method has a porosity as small as about 40% even if the pore diameter can be reduced. For this reason, the amount of the polarizable electrode material penetrating into the pores of the foamed aluminum as the current collector is small, and the desired high output and high energy density cannot be achieved.

  Therefore, among the above-described methods, the second method can be adopted as a method for producing foamed aluminum having minute open pores that can achieve the objectives of high reliability, high output, and high energy density. .

  However, even in this second method, in order to further reduce the pore diameter of the open pores, it is necessary to use fine sponge urethane, and the flow of aluminum becomes worse, making it impossible to press-fit or casting. Since the pressure becomes too high, it is difficult to produce foamed aluminum having a pore diameter smaller than 40 PPI.

  On the other hand, a foaming slurry containing metal powder and a foaming agent is used as a method for producing a high-porosity foam metal having small pore sizes and sized open pores in which a large number of minute open pores are evenly arranged. There is a slurry foaming method in which the material is foamed, dried and then sintered (Patent Document 6). According to this method, if a raw material powder that can be sintered is available, it is a high-porosity foam metal having dimensionally open pores having an arbitrary pore size ranging from about 10 PPI to about 500 PPI, that is, a pore size ranging from 2.5 mm to 50 μm. Can be easily manufactured. The slurry foaming method means a method in which a foamed metal is obtained by foaming by adding a foaming agent to a slurry containing metal powder, or by foaming by gas injection or stirring, drying, and sintering. .

  However, conventionally, in the slurry foaming method, it was difficult to produce foamed aluminum because non-pressure sintering of aluminum could not be performed due to the presence of an oxide film on the surface of the aluminum powder. Even if foamed aluminum can be manufactured, pure aluminum is soft, so the foamed aluminum breaks when rolling to increase the energy density after filling the pores with a polarizable electrode material. I am worried about it.

Japanese Patent No. 3591055 Japanese Patent No. 3689948 Japanese Patent Application Laid-Open No. 08-209265 Special table 2003-520292 gazette Japanese Examined Patent Publication No. 61-48566 Japanese Patent No. 3535282

  The present inventors have found that by using a sintering aid containing titanium, a high-strength aluminum porous sintered body can be produced by non-pressure sintering. The present invention makes it possible to achieve high reliability, high output, and high energy density of an electric double layer capacitor by using the porous aluminum sintered body as a current collector for an electrode for an electric double layer capacitor. It is an object to provide an electrode.

The present invention relates to an electric double layer capacitor electrode and a method of manufacturing the same, which have solved the above problems with the following configuration.
(1) An aluminum porous sintered body, and an electrode for an electric double layer capacitor comprising a polarizable electrode material, a conductive additive and a binder in the pores of the aluminum porous sintered body, wherein the aluminum porous The sintered compact has a metal skeleton with a three-dimensional network structure, has pores between the metal skeletons, an Al-Ti compound is dispersed in the metal skeleton, and on the surface of the metal skeleton. Is an electrode for an electric double layer capacitor, characterized in that there are irregularities formed by a grain boundary step of the aluminum porous sintered body.
(2) The electrode for an electric double layer capacitor according to (1) above, wherein the average crystal grain size of the aluminum porous sintered body is 10 to 100 μm.
(3) The electric double layer capacitor according to (1) or (2), wherein the aluminum porous sintered body contains 0.1 to 20 parts by mass of titanium with respect to 100 parts by mass of aluminum and titanium in total. electrode.
(4) The electrode for an electric double layer capacitor according to any one of (1) to (3) above, comprising 100 to 800 parts by mass of a polarizable electrode material with respect to 100 parts by mass of aluminum porous sintered.
(5) The electrode for an electric double layer capacitor according to any one of the above (1) to (4), comprising 1 to 100 parts by mass of a conductive additive with respect to 100 parts by mass of aluminum porous sintered.
(6) A metal skeleton having a three-dimensional network structure, vacancies between the metal skeletons, an Al—Ti compound dispersed in the metal skeleton, and aluminum on the surface of the metal skeleton After filling the pores of the aluminum porous sintered body having irregularities formed by the grain boundary steps of the porous sintered body with a slurry containing a polarizable electrode material, a conductive additive and a binder, and drying, A method for producing an electrode for an electric double layer capacitor, comprising rolling.
(7) The method for producing an electrode for an electric double layer capacitor according to (6), wherein the porous aluminum sintered body contains 0.1 to 20 parts by mass of titanium with respect to 100 parts by mass of aluminum and titanium in total. .
(8) The electricity described in (6) or (7) above, wherein the total porosity of the aluminum porous sintered body is 70 to 99% by forming 20 or more holes per 1 cm of linear length. A method of manufacturing an electrode for a double layer capacitor.
(9) An electric double layer capacitor including the electrode for an electric double layer capacitor according to any one of (1) to (5).

  According to the present invention (1), since there are irregularities formed by grain boundary steps on the surface of the metal skeleton of the aluminum porous sintered body, the metal skeleton, the polarizable electrode material, the conductive auxiliary agent, and the bonding A highly reliable electric double layer capacitor electrode having excellent adhesion to the agent and excellent in holding the polarizable electrode material even when bent can be obtained. Furthermore, since the aluminum porous sintered body by the dispersion of the Al—Ti compound is high in strength, by adding a polarizable electrode material to the pores of the aluminum porous sintered body and rolling it, It is possible to provide an electrode for an electric double layer type capacitor having a high energy density at a power density.

  According to the present invention (6), a highly reliable electric double layer capacitor electrode can be easily obtained, and furthermore, by using an aluminum porous sintered body in which a high-strength Al—Ti compound is dispersed. It becomes possible to roll, and it is possible to easily manufacture an electrode for an electric double layer capacitor having a high output density and a high energy density.

It is a scanning electron micrograph of the aluminum porous sintered compact of an Example. 2 is a partially enlarged scanning electron micrograph of FIG. 3 is a partially enlarged scanning electron micrograph of FIG. It is an image figure of the section of the electrode for electric double layer type capacitors of the present invention. It is an example of the secondary electron image of an aluminum porous sintered compact. It is an example of Ti mapping of EPMA of an aluminum porous sintered body. It is sectional drawing of the coin cell produced by the Example and the prior art example.

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

[Electric double layer capacitor electrode]
An electrode for an electric double layer capacitor of the present invention includes an aluminum porous sintered body, and an electric double layer capacitor including a polarizable electrode material, a conductive additive and a binder in the pores of the aluminum porous sintered body The porous aluminum sintered body has a metal skeleton having a three-dimensional network structure, has pores between the metal skeletons, and an Al-Ti compound is dispersed in the metal skeleton. And the surface of the said metal frame | skeleton has the unevenness | corrugation formed by the grain boundary level | step difference of an aluminum porous sintered compact, It is characterized by the above-mentioned.

  The porous aluminum sintered body of the present invention has a metal skeleton having a three-dimensional network structure, has pores between the metal skeletons, an Al-Ti compound is dispersed in the metal skeleton, and the metal skeleton. There are irregularities formed by the grain boundary steps of the porous aluminum sintered body.

  FIG. 1 is a scanning electron micrograph of the porous aluminum sintered body before rolling produced in the example, FIG. 2 is a partially enlarged scanning electron micrograph of FIG. 1, FIG. A partially enlarged scanning electron micrograph is shown. As apparent from FIGS. 1, 2, and 3, the porous aluminum sintered body forms pores by a metal skeleton having a three-dimensional network structure. In addition, the surface of the metal skeleton has irregularities formed by grain boundary steps of the aluminum porous sintered body, and the metal skeleton itself has a high porosity.

  The metal skeleton is preferably formed of aluminum crystal grains having an average crystal grain size of 10 to 100 μm, and more preferably 15 to 60 μm. Due to the presence of irregularities formed by the grain boundary steps due to the crystal grains, the anchor effect works, and the adhesion with the polarizable electrode material, the conductive additive and the binder is excellent, and the polarizable electrode even when bent A highly reliable electric double layer capacitor electrode with excellent material retention can be obtained, but the number and size of the irregularities are affected by the aluminum crystal grain size. Becomes smaller and a sufficient anchoring effect is not exhibited. On the other hand, when the crystal grain size of the aluminum crystal grains of the metal skeleton is larger than 100 μm, the retainability of the polarizable electrode material is lowered and the strength of the aluminum porous sintered body is lowered. Here, the crystal grain size is measured by a line intercept method from an optical micrograph or a scanning electron micrograph. The aluminum crystal grains more preferably have a crystal grain size of 70% or more in the range of 15 to 60 μm.

  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. The 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 rolling, the pore diameter of the interstitial pores becomes an elliptical shape having a long longitudinal direction of the aluminum porous sintered body. The pore diameter in the longitudinal direction is preferably 30 to 600 μm, and the voids in the thickness direction are preferred. The pore diameter is preferably 10 to 200 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 rolling is preferably 10 to 60%, and more preferably 15 to 40%. Here, the porosity is calculated from the dimensions, mass, and density of the porous aluminum sintered body.

  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 atmospheric pressure sintering, but also forms an Al-Ti compound to make the aluminum porous sintered body high strength, especially high tensile strength. To.

  It is preferable that an aluminum porous body contains 0.1-20 mass parts of titanium with respect to a total of 100 mass parts of aluminum and titanium. 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 thickness of the aluminum porous sintered body is preferably 0.05 to 5 mm and more preferably 0.1 to 3 mm before rolling, from the viewpoint of improving the energy density of the electric double layer capacitor. The thickness of the aluminum porous sintered body is preferably 0.03 to 3 mm after rolling, and more preferably 0.8 to 2.5 mm.

  The width of the aluminum porous sintered body is generally determined from the shape of the electric double layer capacitor, but after preparing the aluminum porous sintered body with a width corresponding to a plurality of widths, the polarizable electrode material is used. After containing and rolling, it can also be made into one width by a slit or the like.

  Since the aluminum porous sintered body is usually produced in a roll shape, the length of the aluminum porous sintered body is usually produced by a length corresponding to many pieces, contains a polarizable electrode material, and is rolled. After that, the length is reduced to one by cutting or the like.

  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 size of 2 to 20 μm from the viewpoint of increasing the output of the electric double layer capacitor. Here, the average particle diameter is measured by a laser diffraction method.

  Examples of the conductive additive contained in the pores of the porous aluminum sintered body include carbon black, acetylene black, ketjen black, natural graphite, and artificial graphite, but are not limited thereto. Not.

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

  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. Here, the quantitative analysis of the polarizable electrode material is performed by the ICP method.

  When 1 to 100 parts by mass of a conductive additive is contained with respect to 100 parts by mass of the aluminum porous sintered body, it is preferable from the viewpoint of increasing the output of the electric double layer capacitor and preventing loss of polarizable electrode material.

  When the binder is included in an amount of 2 to 80 parts by mass with respect to 100 parts by mass of the aluminum porous sintered body, the polarizable electrode material is appropriately retained in the pores of the aluminum porous sintered body, It is preferable from the viewpoint of preventing omission.

  FIG. 4 shows an image view of a cross section of the electric double layer capacitor electrode of the present invention. It is considered that the polarizable electrode material, the conductive additive and the binder layer 2 cover the metal skeleton with the pores 3 of the aluminum porous sintered body 1 and reduce the pore volume.

  In the present invention, the pores of the aluminum porous sintered body contain a polarizable electrode material, a conductive additive, and a binder, but the aluminum porous sintered body that is a current collector and the separator There may also be included polarizable electrode materials, conductive aids and binders. In the present invention, the polarizable electrode material contained in the pores of the aluminum porous sintered body with respect to the total of 100 parts by mass of the polarizable electrode material, the conductive additive and the binder in the electric double layer capacitor, It is preferable that the conductive assistant and the binder are 60 to 95 parts by mass from the viewpoint of improving the reliability and energy density of the electric double layer capacitor and increasing the output.

  Examples of the electrolyte when using the electric double layer capacitor electrode of the present invention include an aqueous electrolyte and a non-aqueous electrolyte. From the viewpoint of withstanding voltage of the electrolyte and not dissolving the aluminum porous sintered body, the non-aqueous electrolyte is used. Is preferred. The non-aqueous electrolyte may be either a liquid electrolyte (electrolytic solution) or a polymer gel electrolyte. The nonaqueous electrolyte is not particularly limited as long as it is used in a normal secondary battery, although a preferred example is shown below.

As an electrolytic solution, LiBOB (lithium bis oxide _{borate), LiPF 6, LiBF 4,} LiClO 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _{as, (C} 2 _{H 5} ) ₄ NBF ₄ , (C ₂ H ₅ ) ₃ CH ₃ NBF ₄ , (C ₂ H ₅ ) ₄ NPF ₆ , (C ₂ H ₅ ) ₃ CH ₃ NPF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, including at least one electrolyte salt selected from organic acid anion salts such as Li (C ₂ F ₅ SO ₂ ) ₂ N, such as propylene carbonate (PC) and ethylene carbonate (EC) Cyclic carbonates;
Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate; ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; γ- Lactones such as butyrolactone; nitriles such as acetonitrile; esters such as methyl propionate; amides such as dimethylformamide; methyl acetate, methyl formate; at least one selected from at least one selected from sulfolane, The thing using organic solvents (plasticizer), such as a protic solvent, can be used.

  The polymer gel electrolyte is not particularly limited, but the same electrolyte solution is held in the skeleton of the electrolyte polymer having an ionic conductivity or the electrolyte polymer having no ionic conductivity. And the like.

  The electrolyte solution contained in the polymer gel electrolyte is the same as described above. Examples of the electrolyte polymer having ion conductivity include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. A polyalkylene oxide polymer exhibits excellent mechanical strength by dissolving the above-described electrolyte salt well and forming a crosslinked structure.

  Examples of the electrolyte polymer having no ionic conductivity include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, polyvinyl chloride (PVC), polyacrylonitrile (PAN), Monomers that form gelling polymers such as polymethyl methacrylate (PMMA) can be used. However, it is not necessarily limited to these. Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity, and therefore can be used as an electrolyte polymer having the above ionic conductivity. It was exemplified as a polymer for electrolyte that does not have ionic conductivity.

  The ratio (mass ratio) between the electrolyte polymer (host polymer) and the electrolyte solution in the polymer gel electrolyte may be determined according to the purpose of use, but is in the range of 2:98 to 90:10. Thereby, it can seal effectively also about the oozing-out of the electrolyte from the outer peripheral part of an electrode polarizable electrode material layer by providing an insulating layer and an insulation process part.

[Method for producing electrode for electric double layer capacitor]
The method for producing an electrode for an electric double layer capacitor according to the present invention comprises a metal skeleton having a three-dimensional network structure, pores between the metal skeletons, and an Al—Ti compound dispersed in the metal skeleton. In addition, a polarizable electrode material, a conductive additive, and a bond are formed in the pores of the aluminum porous sintered body in which irregularities formed by grain boundary steps of the aluminum porous sintered body exist on the surface of the metal skeleton. The slurry containing the agent is filled, dried and then rolled.

  The aluminum porous sintered body can be manufactured as follows.

  First, aluminum mixed raw material powder is prepared by mixing titanium powder and / or titanium hydride with aluminum powder to obtain an aluminum mixed raw material powder (aluminum mixed raw material powder preparation step). The aluminum mixed raw material powder is mixed with a water-soluble resin binder, water, and a plasticizer to prepare a viscous composition (viscous composition preparation step). This viscous composition is dried in a state where air bubbles are mixed to form a pre-sintered molded body (pre-sintering process), and the pre-sintered molded body is Tm-10 (° C.) ≦ heat-fired in a non-oxidizing atmosphere. It is heated and fired at a temperature (T) ≦ 685 (° C.) (sintering step). Here, Tm (° C.) is a temperature at which the aluminum mixed raw material powder starts to melt.

  In this aluminum mixed raw material powder preparation step, aluminum powder having an average particle size of 2 to 200 μm is used. Here, when the average particle size is reduced, the aluminum powder is used in order that the viscous composition is so viscous that it can be formed into a desired shape, and that the pre-sintered compact has handling strength. A large amount of water-soluble resin binder must be added. However, if a large amount of the water-soluble resin binder is added, the amount of carbon remaining in the aluminum increases when the pre-sintered molded body is heated and fired, and the sintering reaction is hindered. On the other hand, when the particle diameter of the aluminum powder is too large, the strength of the aluminum porous sintered body is lowered. Therefore, as the aluminum powder, those having an average particle diameter in the range of 2 to 200 μm, more preferably in the range of 2 to 100 μm, and still more preferably in the range of 7 to 40 μm are used as described above. Here, the average particle diameter is measured by a laser diffraction method.

This aluminum powder is mixed with a sintering aid containing titanium, specifically, titanium and / or titanium hydride. Thereby, titanium is mixed with aluminum powder, and when the pre-sintered compact is heated and fired at Tm-10 (° C.) ≦ heating and firing temperature T ≦ 685 (° C.), a lump of droplets is generated. No pressureless sintering of aluminum is possible. Further, titanium hydride (TiH ₂ ) has a titanium content of 47.88 (molecular weight of titanium) / (47.88 + 1 (molecular weight of hydrogen) × 2) and is 95% by mass or more, and is 470 to 530 ° C. In order to dehydrogenate, it is thermally decomposed into titanium during the above-mentioned heating and firing. Therefore, even when titanium hydride is mixed, pressureless sintering of aluminum is possible without generating droplets. As the sintering aid, a sintering aid powder other than titanium or titanium hydride may be used, or a sintering aid powder containing titanium may be used.

  The sintering aid containing titanium preferably contains 0.1 to 20 parts by mass of titanium with respect to a total of 100 parts by mass of aluminum and titanium.

  Here, when the average particle diameter of titanium and / or titanium hydride is r (μm) and the blending ratio of titanium and / or titanium hydride is W (mass%), 1 (μm) ≦ r ≦ 30 ( μm), 0.1 (mass%) ≦ W ≦ 20 (mass%), and preferably 0.1 ≦ W / r ≦ 2. That is, in the case of titanium hydride powder having an average particle size of 4 μm, since 0.1 ≦ W / 4 ≦ 2, the compounding ratio W is preferably 0.4 to 8% by mass. In the case of titanium powder having an average particle diameter of 20 μm, the blending ratio: W is 2 to 40% by mass from the condition of 0.1 ≦ W / 20 ≦ 2, but the blending ratio: W is 0. .1 (mass%) ≦ W ≦ 20 (mass%) is added, and 2 to 20 mass% is preferable.

  The average particle size of titanium hydride is preferably 0.1 (μm) ≦ r ≦ 30 (μm), more preferably 4 (μm) ≦ r ≦ 20 (μm). If the average particle size of titanium hydride is smaller than 0.1 μm, there is a risk of spontaneous ignition, and if it exceeds 30 μm, the Al—Ti compound is formed from the titanium particles coated with the Al—Ti compound produced by sintering. This is because the phases are easily separated and desired strength cannot be obtained in the sintered body.

  Further, 0.1 (mass%) ≦ W ≦ 20 (mass%) is preferable because when the mixing ratio W of the sintering aid powder exceeds 20 mass%, the sintering aid powder in the aluminum mixed raw material powder. This is because they have contact points, making it impossible to control the reaction heat between aluminum and titanium, and making it impossible to obtain a desired porous sintered body.

  However, when tested under various conditions, the reaction heat between aluminum and titanium is large depending on the particle size of the sintering aid powder even within the range of 0.1 (mass%) ≦ W ≦ 20 (mass%). In some cases, the temperature of the aluminum melted by the reaction heat rises further, the viscosity decreases, and droplets may be generated.

  Therefore, from the results of observing specimens prepared under various conditions with an electron microscope, within a range in which the calorific value can be controlled by the blending amount of titanium and the particle diameter, the thickness of the titanium particles is almost constant from the exposed surface side. Only the surface layer was found to react with aluminum. Thus, it was experimentally found that it is desirable that 1 (μm) ≦ r ≦ 30 (μm) and 0.1 ≦ W / r ≦ 2 in order to prevent the generation of droplets.

  Next, in the viscous composition preparation step, at least one selected from the group consisting of polyvinyl alcohol, methylcellulose and ethylcellulose as a water-soluble resin binder is added to the aluminum mixed raw material powder as a plasticizer, and polyethylene glycol, glycerin and phthalate as plasticizers. At least one selected from the group consisting of di-n-butyl acid is added, and distilled water and alkylbetaine as a surfactant are added.

  Thus, when polyvinyl alcohol, methylcellulose, or ethylcellulose is used as the water-soluble binder, the amount added is relatively small. Therefore, the addition amount of the water-soluble resin binder is 0.5 to 7 parts by mass with respect to 100 parts by mass of the aluminum mixed raw material powder. When the amount is more than 7 parts by mass with respect to 100 parts by mass of the aluminum mixed raw material powder, the sintering reaction is hindered by an increase in the amount of carbon remaining in the pre-sintered molded body before heating and firing, and 0.5 parts by mass It is because the handling intensity | strength of the molded object before sintering is not ensured that it is less than.

  Moreover, 0.02-3 mass parts of alkylbetaines are added with respect to 100 mass parts of mass of aluminum mixed raw material powder. When the amount is 0.02 parts by mass or more with respect to 100 parts by mass of the aluminum mixed raw material powder, bubbles are effectively generated when the water-insoluble hydrocarbon organic solvent described later is mixed, and 3 parts by mass or less. In this case, inhibition of the sintering reaction due to an increase in the amount of carbon remaining in the green body before sintering is prevented.

  And after kneading these, it is made to foam by mixing the water-insoluble hydrocarbon type organic solvent of C5-C8, and the viscous composition with which the bubble was mixed is adjusted. As the water-insoluble hydrocarbon organic solvent having 5 to 8 carbon atoms, at least one selected from the group consisting of pentane, hexane, heptane and octane can be used.

  In the next pre-sintering step, doctor blade method, slurry extrusion method, screen printing method, etc., so that the viscosity composition has a thickness of 0.05 mm to 5 mm on the stripping surface of the strip-shaped polyethylene sheet After the coating, the ambient temperature and humidity are controlled for a certain period of time, the air bubbles are sized, and then dried at a temperature of 70 ° C. with an air dryer.

  And the viscous composition after drying is peeled off from a polyethylene sheet, it cuts out in a desired shape, and the molded object before sintering is obtained.

  In the next sintering step, the above-mentioned pre-sintered compact is placed on an alumina setter coated with a powder such as zirconia and heated at 520 ° C. for 1 hour in an argon atmosphere with a dew point of −20 ° C. or lower. Pre-baking is performed. This removes the binder that volatilizes and / or decomposes the binder solution of the water-soluble resin binder component, plasticizer component, distilled water and alkylbetaine of the green body before sintering, and also hydrogenates as a sintering aid powder. When titanium is used, dehydrogenation is performed.

  Thereafter, the pre-sintered compact after preliminary firing is fired at Tm-10 (° C.) ≦ heat firing temperature (T) ≦ 685 (° C.) to obtain an aluminum porous sintered body.

  Here, the pre-sintered compact is considered to start the reaction between aluminum and titanium when heated to Tm (° C.): 660 ° C., which is the melting temperature of aluminum. The melting point is lowered by the eutectic alloy elements such as Fe and Si contained, and in fact, the reaction between aluminum and titanium is started by heating at Tm-10 (° C.), and an aluminum porous sintered body is formed. Is done. Specifically, while the melting point of aluminum is 660 ° C., the melting start temperature is around 650 ° C. for atomized powder having a purity of about 98% to 99.7% distributed as pure aluminum powder. On the other hand, if the heating and baking temperature is maintained at a temperature higher than 685 ° C., a liquid lump of aluminum is generated in the sintered body.

  In addition, in order to suppress the growth of the oxide film of the aluminum particle surface and the titanium particle surface, it is necessary to perform the heat baking in the sintering process in a non-oxidizing atmosphere. However, if the heating temperature is 400 ° C. or less and maintained for about 30 minutes, the oxide film on the aluminum particle surface and the titanium particle surface does not grow so much even when heated in air. After debinding by heating and holding at 300 ° C. to 400 ° C. for about 10 minutes in air, it may be fired at a predetermined temperature in an argon atmosphere.

  Here, the non-oxidizing atmosphere means an atmosphere that includes an inert atmosphere or a reducing atmosphere and does not oxidize the aluminum mixed raw material powder. In addition, the above-described heating and firing temperature is not the temperature of the aluminum mixed raw material powder, that is, the reaction temperature of the aluminum mixed raw material powder or the like, but means the holding temperature around the aluminum mixed raw material powder. .

  The aluminum porous sintered body thus obtained has a metal skeleton with a three-dimensional network structure, has pores between the metal skeletons, and the Al-Ti compound is almost uniformly formed on the metal sintered body. Are dispersed. FIG. 5 shows a secondary electron image of the porous aluminum sintered body, and FIG. 6 shows an example of Ti mapping of EPMA. As is apparent from FIG. 6, Al—Ti compounds are dispersed almost uniformly (5 to 100 in the range of 200 μm square).

  The aluminum porous sintered body has an electric double layer of 70 to 90% when the total porosity of the aluminum porous sintered body is 70 to 90% by forming 20 or more holes per 1 cm of linear length. It is preferable from the viewpoint of improving the reliability and energy density of the electrode for type capacitor or increasing the output, and is suitably used as a current collector for electric double layer type capacitor.

  In addition, the aluminum porous sintered body is composed of 2 pores derived from bubbles at the time of slurry foaming in the above viscous composition preparation step and pores formed in the metal skeleton itself derived from being a sintered body. Has different types of holes. Here, the realization of high reliability by holding the polarizable electrode material, which is a remarkable effect of the present invention, is that the voids between the skeletons of the aluminum porous sintered body and the vacancies in the skeletons formed in the metal skeleton itself. This is probably due to the synergistic effect of the pores.

  A slurry containing a polarizable electrode material, a conductive additive and a binder can be obtained, for example, as follows. First, the binder is dissolved or uniformly dispersed in an organic solvent. This mixed solution, polarizable electrode material powder, and conductive additive are mixed to form a slurry. Alternatively, after the polarizable electrode material, the conductive additive and the binder are uniformly mixed, an organic solvent is added to form a slurry, or the conductive additive is dispersed in the organic solvent, and then the polarizable electrode material and the binder are mixed. There is a method of adding, but is not particularly limited. At this time, the apparatus to be used may be those normally used by those skilled in the art, such as a planetary mixer, a ball mill, and a Henschel mixer. Here, the organic solvent has a viscosity that allows the slurry to be easily immersed in the aluminum porous sintered body in the step of immersing the next aluminum porous sintered body in the slurry, for example, 10 to 60 Pa · s. It is preferable to add.

  Examples of the organic solvent for dissolving or dispersing the binder include tetrahydrofuran (hereinafter referred to as THF), methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, N-methylpyrrolidone, acetone, acetonitrile, dimethyl carbonate, ethyl acetate, butyl acetate, and the like. Although it can be used, in order to selectively remove this organic solvent by drying, a volatile organic solvent having a boiling point of 100 ° C. or lower such as THF or acetone, or N-methylpyrrolidone having a high ability to dissolve a binder is preferable.

  Next, the pores of the aluminum porous sintered body are filled with a slurry of polarizable electrode material and dried. Examples of the filling 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 a polarizable electrode material, a conductive additive and a binder is rolled to obtain an electrode for an electric double layer capacitor. Since the aluminum porous sintered body of the present invention has an Al-Ti compound dispersed in a metal skeleton and has high strength, particularly tensile strength, the aluminum porous sintered body can be rolled to a desired thickness. It is possible to decrease the porosity of the electrode body and increase the electrode density. Here, the electrode thickness is preferably 0.03 to 3 mm. Here, the density of the aluminum porous sintered body can be increased by pressing or the like, but rolling is preferable from the viewpoint of productivity.

  The electrode for an electric double layer capacitor of the present invention is very effectively used for an electric double layer capacitor with high reliability, high energy density and high output.

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

[Production of porous aluminum sintered body]
According to the above-described embodiment, an 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 at a total of 500 g so that the mass ratio of the aluminum powder and the titanium hydride powder was 99: 1 to prepare an aluminum mixed raw material powder.

  Binder solution: 100 parts by mass of binder solution: 0.1 parts by mass of methyl cellulose, 2.9 parts by mass of ethyl cellulose, 3 parts by mass of glycerin, 3 parts by mass of polyethylene glycol, 0.5 parts by mass of alkyl betaine It was prepared in a total of 500 g at a ratio of part and remaining water.

  Aluminum mixed raw material powder: 50 parts by mass, binder solution: 49 parts by mass, and hexane: 1 part by mass were mixed in a total of 500 g to prepare a viscous composition.

  Next, this viscous composition is stretched and applied onto a polyethylene sheet coated with a release agent by the doctor blade method, and the temperature and humidity are controlled to be maintained for a certain period of time. It dried at the temperature of 70 degreeC with the air dryer. The coating thickness of the viscous composition at this time was 0.35 mm, the temperature was 35 ° C., the humidity was 90 minutes, and the holding time was 20 minutes. Subsequent drying was performed at 70 ° C. for 50 minutes. And the viscous composition after drying was peeled off from the polyethylene sheet, and it cut out to the circular shape of diameter 100mm, and obtained the molded object before sintering.

  This pre-sintered compact was placed on an alumina setter with zirconia powder spread, pre-fired (debindered) in an argon air flow atmosphere, then heat-fired and a foamed aluminum porous sintered body 1 was obtained. Debinding was performed at 520 ° C. for 30 minutes. Heating and baking were performed at 663 ° C. for 30 minutes in an argon atmosphere to obtain an aluminum porous sintered body 1. The thickness of the obtained aluminum porous sintered body 1 was 1.2 mm.

The shrinkage rate and porosity of the obtained aluminum porous sintered body 1 were calculated. The shrinkage rate was calculated from the change in thickness of the aluminum porous sintered body 1 before and after heating and firing, and the porosity was calculated from the dimensions, weight, and density. In addition, the number of three-dimensional vacancies was measured from the stereomicrograph, and the number of vacancies in the skeleton per 100 μm length of the metal skeleton was measured from the scanning electron microscope (SEM) photograph. The presence or absence of solidification was confirmed, and further, the presence or absence of an Al—Ti compound was confirmed on the skeleton surface of the aluminum porous sintered body 1 by surface analysis using an electron beam microanalyzer (EPMA). Here, the number of vacancies in the skeleton per 100 μm length of the metal skeleton was prepared with five scanning electron micrographs of 300 times magnification, each of which was taken from different fields so that the metal skeleton was shown in the center of the photograph. Draw a diagonal line, draw a line segment equivalent to 100 μm in length on the metal skeleton part on the diagonal line from the intersection to the four corners, count the number of vacancies in the skeleton in the metal skeleton of the line segment, and calculate by averaging For the number of interstitial pores, prepare 5 stereomicrographs with a magnification of 10 times for each different field of view, and draw a diagonal line in the same way to create a line segment corresponding to a length of 5 mm on the diagonal line from the intersection to the four corners. It was calculated by drawing four on each photograph, counting the number of metal skeletons crossed by the line segment, and multiplying by 25.4 / 5 on average. These results are shown in Table 1. (Here, the unit of the number of interstitial holes: “PPI” is the number of holes per inch (25.4 mm)). Moreover, the SEM photograph of the obtained aluminum porous sintered compact 1 is shown in FIG. 1, and the one part enlarged photograph is shown in FIG. 2 and FIG. 3, respectively. As is apparent from FIGS. 1 to 3, the surface of the metal skeleton of the aluminum porous sintered body 1 has irregularities formed by grain boundary steps of the aluminum porous sintered body. The average crystal grain size of the body crystal grains was 39 μm. Here, the average crystal grain size of the porous sintered aluminum crystal grains, a measurement sample was filled resin, polished to a mirror surface, Keller reagent (48% hydrofluoric acid: 0.5 cm ^3, concentrated hydrochloric acid: 1. 5 cm ³ , concentrated nitric acid; 2.5 cm ³ , distilled water; 95 cm ³ ) etched by immersion for 30 seconds, photographed with an optical microscope at a magnification of 100 times, line intercept method (ASTM, E-112, Linear Intercept) (Procedure).

  Next, the aluminum porous sintered body 1 was rolled and rolled at a reduction ratio of 20%, and the presence or absence of cracks was confirmed with sight (20% reduction test), and then cut into a 20 mm × 50 mm rectangular shape. The electrical resistivity between the opposite corners was measured. Next, the rectangular aluminum porous sintered body 1 was wound around the outer periphery of a cylindrical body having a diameter of 5 mm, and the presence or absence of cracks was confirmed implicitly. Table 1 shows these results.

  The aluminum porous sintered body 1 was used except that a titanium hydride powder having an average particle size of 21 μm was used and the mass ratio of the aluminum powder to the titanium hydride powder was 85:15. A sintered material 2 was prepared and subjected to each test. Table 1 shows these results. In addition, the thickness of the obtained aluminum porous sintered body 2 was 1.3 mm.

  As can be seen from Table 1, the obtained aluminum porous sintered bodies 1 and 2 have 3 to 4 pores per 100 μm of the skeleton length of the porous metal sintered body and between the metal skeletons. 52 holes per inch, that is, 20 or more holes per cm. And the droplet-shaped lump did not arise in an aluminum porous sintered compact, the electrical resistivity was low, and there was no crack by a winding test. Therefore, it is suitable for an electrode current collector of an electric double layer capacitor that requires high energy density and high output.

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

  The electrode is obtained by mixing coconut shell activated carbon powder as a polarizable electrode material, ketjen black (KB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder at a mass ratio of 80:10:10, and a total of 200 g. A polarizable electrode material slurry 1 was prepared by mixing 162 g of N-methyl-2-pyrrolidone as a solvent with this electrode agent.

  Next, the produced aluminum porous sintered body 1 is immersed in this polarizable electrode material slurry 1 for 10 minutes, taken out and dried, and then rolled and rolled into an electric double layer of Example 1 having a thickness of 0.5 mm. Type capacitor electrodes were fabricated. Here, after the porous aluminum sintered body 1 is immersed in the polarizable electrode material slurry 1 and dried, before the rolling, the polarizable electrode material slurry 1 adhered to the surface of the porous aluminum sintered body 1 is wiped off. Almost all of the polarizable electrode material, the conductive aid and the binder were contained in the pores of the aluminum porous sintered body 1.

(Conventional example 1)
As the foamed aluminum of Conventional Example 1, 30 PPI foamed aluminum produced by press-fitting aluminum into a mold having sponge urethane as a core, which is the second method of the prior art, was used.

  The electric double layer type of Conventional Example 1 having a thickness of 0.5 mm is rolled after the foamed aluminum of Conventional Example 1 is immersed in the polarizable electrode material slurry 1 produced in Example 1 for 10 minutes, taken out and dried. An electrode of a capacitor ion battery was produced.

(Examples 2 to 10)
Polarizable electrode material slurries 2 and 3 having the compositions shown in Table 2 were produced in the same manner as polarizable electrode material slurry 1. Next, the electrodes of the electric double layer type capacitor batteries of Examples 2 to 10 were produced in the combinations shown in Table 3.

[Performance test of electrode for electric double layer type capacitor]
(Polarized electrode material packing density)
About each electrode of Examples 1-6 and the prior art examples 1 and 2, From the mass change of the aluminum porous sintered compact when producing an electrode, content of the polarizable electrode material with respect to 100 mass parts of aluminum porous sintered bodies The (part by mass) and the polarizable electrode material filling density were calculated. Here, the ratio of the polarizable electrode material, the conductive additive and the binder was calculated on the assumption that the polarizable electrode material slurry was still produced. Similarly, the content (parts by mass) of the conductive additive with respect to 100 parts by mass of the aluminum porous sintered body was calculated. Table 4 shows these results.

(Electrode winding test)
Next, cylindrical bodies having diameters of 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, and 5 mm were prepared, and the electrodes of Examples 1 to 10 and Conventional Example 1 were wound. Whether or not the polarizable electrode material was peeled was visually observed, and the minimum diameter in which no peeling was observed is shown in Table 4.

(Energy density)
In order to measure the energy density, a coin cell of an electric double layer type capacitor was produced. FIG. 7 shows a cross-sectional view of the used coin cell.

The electrode was punched at 15 mmφ to obtain a positive electrode 10 and a negative electrode 11. As the non-aqueous electrolyte, 1.5M (C ₂ H ₅ ) ₃ CH ₃ NBF ₄ / PC was used.

  First, the negative electrode 11 was fitted into the stainless steel battery lid 12 and pressed.

  Next, the positive electrode 10 was placed in a stainless steel outer can 13, and a separator 14 made of a polypropylene microporous film (thickness: 20 μm) was placed thereon. After pouring a nonaqueous electrolyte into this, the said battery cover 12 was mounted, it sealed by filling with the sealant 15 which consists of a mixture of a styrene butadiene rubber and a pitch, and the coin cell was produced. The coin cell has a diameter of 20 mm and a height of 3.2 mm.

  The cell was charged at a charge rate of 0.2C and a charge voltage of 0 to 2.5V. From the discharge capacity result, the energy density of the electrode was calculated. Table 5 shows these results. Here, the amount of the polarizable electrode material of the positive electrode was calculated from the packing density of the polarizable electrode material and the electrode area, and used for calculating the energy density.

(Output characteristics)
Using the cell, charging was performed at a charging rate of 20C and a charging voltage of 0 to 2.5V. Next, (charge capacity at 20 C) / (charge capacity at 0.2 C) was calculated, and output characteristics were evaluated. Table 5 shows these results.

  As can be seen from Table 4, in the electrodes of Examples 1 to 10, with respect to 100 parts by mass of the aluminum porous sintered body, 260 to 720 parts by mass of the polarizable electrode material and 14 to 160 parts by mass of the conductive auxiliary agent , And could be contained at high density. Moreover, it turned out that the electrode of Examples 1-10 is highly reliable from the result of an electrode winding test, and a polarizable electrode material does not fall easily. On the other hand, Conventional Example 1 can contain only 200 parts by mass of the polarizable electrode material with respect to 100 parts by mass of the aluminum porous sintered body, and the polarizability is less than 5 mmφ in the electrode winding test. The electrode material dropped out.

Moreover, as can be seen from Table 5, the electrodes of Examples 1 to 10 have a high energy density of 47.6 mWh / cm ³ or more with 0.2 C discharge, and in Example 6 using the electrode slurry 2 in particular, Each was high energy density of 87.9 mWh / cm ³ . In addition, it was found that the electrodes of Examples 1 to 10 retained 0.97 or more of the capacity at the time of 0.2 C discharge even at 20 C discharge, and were extremely high output. On the other hand, Conventional Example 1 has a low energy density of 41.5 Wh / cm ^3, and 20C discharge can only hold 0.95 of the capacity at 0.2C discharge, and the output characteristics are not good.

  As described above, the electric double layer capacitor having high reliability, high output density, and high energy density can be manufactured by the electric double layer capacitor electrode of the present invention.

DESCRIPTION OF SYMBOLS 1 Aluminum porous sintered body 2 Polarization electrode material, conductive support agent, and binder layer 3 Pore 10 Positive electrode 11 Negative electrode 12 Battery cover 13 Exterior can 14 Separator 15 Sealant

Claims (9)

A porous sintered aluminum, the polarizable electrode material in the pores of the porous sintered aluminum, an electrode for an electric double layer capacitor including a conductive aid and a binder, wherein the aluminum porous sintered The body is obtained by non-pressure sintering of aluminum particles having an average particle size of 7 to 40 μm and titanium hydride of 0.1 to 30 μm, and the aluminum porous sintered body has a three-dimensional network structure. A metal skeleton, vacancies between the metal skeletons, skeleton vacancies formed in the metal skeleton itself, an Al-Ti compound dispersed in the metal skeleton, and An electrode for an electric double layer capacitor, characterized in that unevenness formed by grain boundary steps of an aluminum porous sintered body exists on the surface of the metal skeleton.   2. The electrode for an electric double layer capacitor according to claim 1, wherein an average crystal grain size of crystal grains of the aluminum porous sintered body is 10 to 100 [mu] m.   The electrode for electric double layer capacitors according to claim 1 or 2, wherein the aluminum porous sintered body contains 0.1 to 20 parts by mass of titanium with respect to 100 parts by mass of aluminum and titanium in total.   The electrode for an electric double layer capacitor according to any one of claims 1 to 3, comprising 100 to 800 parts by mass of a polarizable electrode material with respect to 100 parts by mass of the aluminum porous sintered body.   The electrode for an electric double layer capacitor according to any one of claims 1 to 4, comprising 1 to 100 parts by mass of a conductive additive with respect to 100 parts by mass of the aluminum porous sintered body. Obtained by non-pressure sintering of aluminum particles having an average particle size of 7 to 40 μm and titanium hydride of 0.1 to 30 μm, and having a three-dimensional network structure metal skeleton, between the metal skeletons The metal skeleton itself has vacancies in the skeleton, and an Al-Ti compound is dispersed in the metal skeleton. Fill the pores of the porous aluminum sintered body with unevenness formed by the grain boundary steps of the compact with a slurry containing a polarizable electrode material, a conductive additive and a binder, dry, and then roll A method for producing an electrode for an electric double layer type capacitor, characterized in that   The method for producing an electrode for an electric double layer capacitor according to claim 6, wherein the aluminum porous sintered body contains 0.1 to 20 parts by mass of titanium with respect to 100 parts by mass of aluminum and titanium in total.   The electrode for an electric double layer capacitor according to claim 6 or 7, wherein the total porosity of the aluminum porous sintered body is 70 to 99% by forming 20 or more pores per linear length of 1 cm. Manufacturing method.   The electric double layer type capacitor containing the electrode for electric double layer type capacitors of any one of Claims 1-5.