JP2013165161A - Capacitors - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor ensuring the capacitor characteristics, such as the capacity, high output characteristics and durability, equivalent to or better than those when various active carbons obtained in a complex activation process having resource concerns in the art is used, by utilizing grain shells, some of which have been utilized but the majority are required to be discarded or burnt, effectively as the material of carbon.SOLUTION: The capacitor has an electrode obtained by filling an oxidation resistant metal porous body having a three-dimensional mesh structure with carbon powder containing a silica component obtained from grain shells, and a nonaqueous electrolyte containing a lithium salt or a sodium salt.

Description

  The present invention relates to a capacitor, and more particularly to a capacitor using, as an electrode, a porous metal body having a three-dimensional structure using carbon obtained from grain husks.

  As is well known, capacitors are widely used in various electric devices. Among many types of capacitors, the electric double layer capacitor has a large capacity and has attracted particular attention in recent years. Capacitors have been widely used for memory backup since ancient times, but the proportion of electric double layer capacitors has also increased dramatically in this field. Furthermore, from the viewpoint of improving fuel utilization and environmental friendliness, it is used in hybrid vehicles and electric vehicles, and future demand growth is expected.

  As a current collector for a polarizable electrode that has the greatest influence on the characteristics of the electric double layer capacitor, various types such as a metal foil mainly made of aluminum foil, punching metal, screen, and extended metal have been proposed. (For example, Patent Documents 1 and 2). Polarizing electrodes are manufactured by applying carbon powder to these. In addition, aluminum, stainless steel, etc. are mention | raise | lifted as a constituent material of a collector.

  These current collectors have a two-dimensional structure, and when a thick electrode is produced to increase the capacity density, the distance between the current collector and carbon becomes long, so that the electrical resistance increases at a distance from the current collector. Therefore, in order to solve this, recently, such as foils that have been machined to provide unevenness, foamed porous bodies obtained by incineration removal of urethane after plating on urethane foam resin, porous bodies plated on nonwoven fabric, etc. A current collector having a three-dimensional structure has been proposed (for example, Patent Document 3).

  The shape of the capacitor is the same as that of a general battery, and a button type, a cylindrical type, a square type, etc. are adopted. In the button type, a polarizable electrode having a carbon electrode layer provided on a current collector is used as a pair, and a separator is arranged between the electrodes to form a capacitor element, which is housed in a metal case together with an electrolyte. The structure which seals with the gasket which insulates is employ | adopted. The cylindrical type is a structure in which a pair of polarizable electrodes and a separator are stacked and wound to form an electric double layer capacitor element, this element is impregnated with an electrolytic solution, and stored in a cylindrical case and sealed with a sealing material. is there. The square basic structure has a structure in which polarizable electrodes are stacked in the same manner as the button type. However, a method is adopted in which the polarizable electrode group is wound and crushed into a square shape like a cylindrical type.

  It is the carbon used that influences the characteristics of the capacitor together with the current collector. Carbon is used by being activated by various means. Common carbon materials include cellulosic materials such as wood pulp, sawdust, coconut husk, cottonseed husk and rice husk, cereal starches such as straw, straw and corn, plants such as lignin and bamboo, coal and Examples thereof include minerals such as tar and petroleum pitch, and synthetic resins such as phenol resin and polyacrylonitrile.

  These materials are carbonized by heating in a non-oxidizing atmosphere. In order to improve the activity of the carbonized product, the carbonized product is activated with water vapor, a small amount of oxygen, chemicals, and the like. Examples of the chemical include zinc chloride, calcium chloride, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, phosphoric acid, and potassium sulfide. Activation with a chemical | medical agent is performed by mixing these with carbonized material and heating at the temperature of about 500-700 degreeC in non-oxidizing atmosphere gas. In general, it has been known for a long time that carbon having a high specific activity can be obtained by dramatically increasing the specific surface area compared to before treatment (for example, Patent Document 4).

  Of these carbon materials, cereal husks, especially rice husks, are by-products of milled rice that are disposed of over 2 million tons per year in Japan alone. As an effective use of rice husk, it is made into rice husk charcoal and is used in part for soil improvement materials and heat retaining materials. As a method for obtaining the rice husk charcoal, the rice husk is placed in a drum can provided with a chimney at the top, and the rice husk is ignited by heating from the bottom of the drum can with fire or combustion charcoal. In Patent Document 5, in order to improve this, a rice husk placed in a bottomed cylindrical container having an opening for supplying rice husk made of a heat-resistant and heat-retaining member is electrically ignited, and heating is stopped after ignition. However, a method has been devised that does not cause air convection in the container.

Japanese Patent Laid-Open No. 11-274012 Japanese Patent Laid-Open No. 11-150042 JP 2009-200065 A JP 2006-062954 A Japanese Patent Laid-Open No. 05-017778

  Grains such as rice and wheat are produced all over the world, including Japan, and accordingly, a huge amount of grain husks are generated when including overseas. If its effective use is established, it will be possible to utilize international resources and eliminate adverse environmental impacts. Already, husks and other cereal husks have been carbonized and used as soil improvement materials. However, if they can be used for other purposes, incineration is unnecessary and they are environmentally friendly.

  One of them is an attempt as a polarization material for capacitors. However, the grain husk contains a large amount of silicon oxide (silica component) after carbonization, which causes a problem in capacitor characteristics compared to general activated carbon.

  Therefore, although the present invention is partly used as a carbon material, most of them are effectively used for grain husks that need to be discarded and incinerated. An object of the present invention is to provide a capacitor having characteristics such as a capacitance value, high output characteristics, durability and the like equal to or higher than those when various activated carbons obtained by complicated processes are used.

  In light of the above problems, the present inventors have conducted extensive research and as a result, three-dimensional structure metal having excellent oxidation resistance for carbon obtained from cereal husks such as beans, wheat, and rice, especially rice husks. It has been found that the characteristics of a capacitor obtained by filling a porous body exhibit characteristics equal to or higher than those of conventionally used activated carbon, particularly output characteristics. The present invention has the following configuration.

(1) having an electrode obtained by filling a porous metal body having a three-dimensional structure having oxidation resistance with a carbon powder containing a silica component obtained from a grain shell,
A capacitor having a non-aqueous electrolyte containing a lithium salt or a sodium salt as the electrolyte.
(2) The capacitor according to (1) above, wherein the carbon powder contains 10% by mass to 60% by mass of a silica component.
(3) The capacitor according to (1) or (2), wherein the carbon powder is produced by heating air to rice husk while blocking air.
(4) The capacitor according to any one of (1) to (3), wherein a conductive additive is mixed in the carbon powder.
(5) The capacitor according to (4), wherein the conductive additive is contained in a mass ratio of 0.5 to 15 parts by mass with respect to 100 parts by mass of the carbon powder.
(6) The capacitor according to any one of (1) to (5), wherein a binder is mixed in the carbon powder.
(7) The metal porous body according to any one of (1) to (6), wherein the metal porous body is a metal porous body having a three-dimensional structure mainly composed of nickel and containing at least 20% by mass of chromium. Capacitor.
(8) The capacitor according to any one of (1) to (7) above, wherein the porosity of the metal porous body is 80% to 97%.
(9) nickel weight per unit area of the nickel porous body, the capacitor according to the above (7) or (8), which is a ^{150g / m 2 ~500g / m 2} .
(10) The capacitor according to any one of (7) to (9) above, wherein the amount of chromium in the metal porous body is 25 to 50% by mass with respect to the total amount of nickel and chromium.
(11) The capacitor according to any one of (1) to (10), wherein the electrode is a positive electrode.
(12) The capacitor as described in (11) above, which is a lithium ion capacitor provided with a nonaqueous electrolytic solution containing a lithium salt as the electrolytic solution.
(13) The capacitor as described in (12) above, wherein the negative electrode is formed by filling a metal porous body having a three-dimensional structure with a material capable of absorbing and desorbing or desorbing lithium as an active material.
(14) The capacitor as described in (12) or (13) above, wherein lithium is supported on the active material of the negative electrode before constituting the lithium ion capacitor.
(15) The material capable of absorbing / desorbing or desorbing / desorbing lithium is selected from the group consisting of silicon (Si), tin (Sn), germanium (Ge), oxides of these elements, and alloys of these elements and lithium. The capacitor as described in any one of (12) to (14) above, which is at least one selected.
(16) The capacitor as described in any one of (12) to (15) above, wherein the material capable of absorbing and desorbing or absorbing and desorbing lithium is silicon oxide (SiO).
(17) The capacitor as described in any one of (12) to (16) above, wherein the negative electrode potential is 0.05 V or less based on lithium.
(18) The capacitor as described in (11) above, which is a sodium ion capacitor provided with a nonaqueous electrolytic solution containing a sodium salt as an electrolytic solution.
(19) The capacitor as described in (18) above, wherein the negative electrode is an electrode formed by filling a metal porous body having a three-dimensional structure with a material capable of adsorbing / desorbing or desorbing sodium as an active material.
(20) The capacitor as described in (18) or (19) above, wherein sodium is supported on the negative electrode active material before constituting the sodium ion capacitor.
(21) The capacitor according to any one of (18) to (20) above, wherein the metal porous body of the negative electrode is a metal porous body having a three-dimensional structure mainly composed of nickel.
(22) The group in which the material capable of adsorbing / desorbing / desorbing / desorbing sodium filled in the metal porous body is made of activated carbon, graphite, hard carbon, tin, a tin compound, lithium titanate, silicon fine particles, and silicon oxide. The capacitor according to any one of (18) to (21), wherein the capacitor is one or more materials selected from the above.

  According to the present invention, the carbon material is partly used, but most of it is discarded, and the grain shells that require incineration are effectively used. It is possible to provide a capacitor having characteristics such as a capacitance value, high output characteristics, durability and the like equal to or higher than those when various activated carbons obtained by complicated processes are used.

  The carbon powder used in the present invention is obtained from cereal shells and contains a silica component, but the production method for obtaining carbon from cereal shells is not particularly limited. Basically, any method can be used as long as the grain husk is heated in an environment where air is blocked. Since the grain husk charcoal thus obtained contains a large amount of silicon oxide (silica component), it is applied to a current collector having a two-dimensional structure such as an aluminum foil to form a polarization electrode. However, it is inferior to the characteristic of the electrode using the general purpose activated carbon activated by the complicated process. Therefore, when the capacitor characteristics were evaluated by filling a porous metal body with a three-dimensional structure, it was found that, unlike general-purpose activated carbon, the characteristics were dramatically improved and the same or better characteristics were obtained.

  That is, the capacitor according to the present invention has an electrode obtained by filling a carbon powder containing a silica component obtained from a grain shell into an oxidation-resistant porous metal body having a three-dimensional structure, and an electrolytic solution. As a non-aqueous electrolyte containing a lithium salt or a sodium salt.

  The electrode used for the capacitor of the present invention can be produced as follows. First, carbon is obtained from cereal husks which are materials for polarizable electrodes. A method of obtaining carbon by heating a general grain shell in an environment where air is shut off is adopted. Carbon powder obtained by pulverizing the obtained carbon is filled into a three-dimensional porous metal body (current collector).

  In the present invention, a nonaqueous electrolytic solution containing a lithium salt or a sodium salt is used as the electrolytic solution. In this case, an organic solvent is used, the oxidation potential is much higher than that of the aqueous electrolyte system, and the lithium resistance potential is 4 V or more. For this reason, the current collector used for the electrode of the capacitor of the present invention is preferably a porous metal body having at least 20 mass% of chromium and having a three-dimensional structure mainly composed of nickel. In addition, having nickel as a main component means that the metal porous body contains more than 50% by mass of nickel. By including at least 20% by mass of chromium in the metal porous body mainly composed of nickel, a metal porous body having good oxidation resistance can be obtained.

  A porous metal body having a three-dimensional structure is more likely to be filled with a carbon material (carbon powder) when the porosity is large, and it is preferable to use a porous metal body having a three-dimensional network structure as described later. The porosity of the metal porous body is preferably about 80% to 97%, and more preferably about 90% to 96%. The average pore diameter of the metal porous body is, for example, about 20 μm to 200 μm, preferably about 30 μm to 100 μm.

In addition, the mass per unit of metal is important in order to maintain a high capacity while exhibiting high output in the capacitor, and the above-mentioned nickel of the metal porous body containing at least 20 mass% of chromium and mainly containing nickel basis weight is 150g / m ² ~500g / m ^2, preferably about may be set to 200g / m ² ~450g / m ² approximately. Thereby, it has suitable strength and can exhibit good electrolytic solution resistance when alloyed with chromium. Further, the chromium about 50g / m ² ~100g / m ² is preferred.

  As an example of a method for producing a porous metal body having such a three-dimensional structure, nickel, electrolytic nickel plating treatment, and the like after imparting conductivity to a resin porous body having a three-dimensional network structure such as a known urethane foam resin or polyolefin nonwoven fabric The chrome plating process is sequentially performed. In this case, by treating the porous body after the chromium plating by heating, chromium can be diffused and alloyed in the nickel porous body.

  In addition, after forming a nickel coating layer on the surface of the foamed resin, the resin as the base material is removed, and then heat-treated in a reducing atmosphere as necessary to reduce nickel to produce foamed nickel. Then, it can also be obtained by subjecting it to chromizing treatment or the like. The chromizing process is a process of diffusing and infiltrating chromium into the nickel film, and a known method can be adopted. For example, it is possible to employ a powder pack method in which a porous material (foamed nickel, non-woven nickel, etc.) filled with a penetrant mixed with chromium powder, halide, and alumina powder and heated in a reducing atmosphere. Alternatively, the penetrating material and the porous nickel body may be arranged separately and heated in a reducing atmosphere to form a penetrating gas to infiltrate the penetrating material into nickel on the surface of the nickel porous body.

  The chromium content in the metal porous body can be adjusted by the amount of chromium plating and the heating time of the chromizing treatment. As described above, in the present invention, the chromium content is preferably 20% by mass or more with respect to the nickel chromium alloy (total amount of nickel and chromium), more preferably 25 to 50% by mass, and 30 More preferably, it is made into 40 mass%. If the chromium content is less than 20% by mass, the oxidation resistance is insufficient and sufficient electrolyte resistance may not be exhibited. Moreover, when it exceeds 50 mass%, an electrical resistance may increase and current collection may fall.

  Since nickel chrome has an established manufacturing method, it can be manufactured at a lower cost than aluminum or stainless steel porous bodies.

  In addition to the metal porous body in which chromium is formed on the surface of such a nickel porous body, a three-dimensional network structure made of aluminum or stainless steel, such as a fibrous porous body or foam, can be used, but the pore structure is uniform. In view of the properties, the mass productivity of the production method, the ease of production, etc., the above-described metal porous body containing at least 20% by mass of chromium and having a three-dimensional structure mainly composed of nickel is most preferable.

Next, a polarizable electrode material mainly composed of cereal husk charcoal is filled into these three-dimensional porous metal bodies. As a filling method, it is optimal to employ a method in which a polarizable electrode material is made into a slurry and filled into a three-dimensional metal porous body. A slurry produced by mixing a thickener and a conductive aid, particularly carbon black (Ketjen black, acetylene black, etc.) or a binder, particularly a fluororesin, is preferred.
Although the composition ratio is not limited, it is preferable that the conductive assistant is contained in a ratio of 0.5 parts by mass to 15 parts by mass with respect to 100 parts by mass of grain husk charcoal. . In addition, since it is a current collector with a three-dimensional structure, unlike a current collector with a two-dimensional structure such as an aluminum foil, it does not require a large amount of binder, but it is still resistant to organic electrolyte and acid. It is preferable to use a fluorine-based resin having excellent chemical properties. A solution of polyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone (NMP) is more suitable. The addition amount of the binder (resin component) is preferably about 0.5 to 15 parts by mass with respect to 100 parts by mass of the carbon powder.

Hereinafter, the present invention will be described in more detail.
[Cereal shell charcoal]
Grain husk charcoal can be used after being pulverized by a known method. For example, a grain husk is put into a container, heated from the bottom of the container to ignite the grain husk, and then the heating is stopped, and the air in the container is left for about a week without convection to carbonize the grain husk. The obtained grain husk charcoal can be used. In this method, the amount of grain husks is charged in accordance with the amount of oxygen in the air in the container, thereby suppressing oxidation from reaching the ashing stage. The obtained grain husk charcoal is pulverized and adjusted so that the average particle diameter of the grain husk charcoal is 1 μm to 20 μm. In addition, since the grain husk charcoal used for the capacitor according to the present invention has not been activated, 10% to 60% by mass of silicon oxide (silica component) is contained in the powder of the grain husk charcoal (in the carbon powder). Has been.

[Current collector]
A porous metal body having a three-dimensional structure used in the capacitor of the present invention (conducting treatment, electrolytic plating and formation of a chromium layer) is sequentially applied to a porous resin body having a three-dimensional network structure such as urethane foam resin or polyolefin nonwoven fabric ( Current collector) can be manufactured.
Hereinafter, this method will be described. First, a resin porous body having a porosity of, for example, about 80% to 97%, an average pore diameter of the porous body of, for example, about 20 μm to 200 μm, and a thickness of about 300 μm to 1600 μm is prepared.

Next, as a conductive treatment for imparting conductivity to this, for example, a sputtering treatment using a conductive material such as nickel is performed. Specifically, after attaching urethane foam resin to the substrate holder, while introducing an inert gas, a DC voltage is applied between the holder and a target (a conductive material such as nickel) to create an ionized inert gas. The active gas is collided with a conductive material such as nickel, and the blown-off conductive material particles are deposited on the foamed resin surface. Basis weight of the conductive layer is not limited, for ^{example, 5mg / m 2 ~15mg / m} 2 , preferably about may be set to 7mg / m ² ~10mg / m ² approximately. Note that an electroless plating method of a conductive material may be employed instead of sputtering.

  As a material constituting the conductive layer, in addition to nickel, titanium, stainless steel, graphite powder, or the like may be applied in a required amount. In these cases, the simplest method is a method in which a mixture obtained by adding a binder (hereinafter also referred to as a binder) to fine powders of these materials is applied to a foamed resin.

  The formation of the conductive layer alone is not preferable from the viewpoints of conductivity and strength. Therefore, for example, it is preferable to improve the strength while improving the conductivity by performing electrolytic nickel plating treatment of nickel. This is done according to conventional methods. As the plating bath in this case, a known bath can be used, and examples thereof include a watt bath, a chloride bath, a sulfamic acid bath, and the like.

  A foamed urethane resin having a conductive layer formed on the surface by sputtering or electroless plating described above is immersed in a plating bath, and this is used as a cathode, for example, using a nickel plate as a counter electrode, and direct current or pulsed intermittent current is applied. Thus, a nickel coating layer is formed on the conductive layer.

The basis weight of the electrolytic nickel plating layer is not ^{limited, 150g / m 2 ~500g / m} 2 , preferably about may be set to 200g / m ² ~450g / m ² approximately. Below this range, the electrical conductivity and strength of the current collector become problems, and above this range, the amount of charge of the polarizable material decreases and the cost increases.

  After forming the electrolytic nickel plating layer, the urethane resin is removed and nickel is reduced. The removal of the resin is preferably incineration. For example, heating is performed in an oxidizing atmosphere such as air at about 600 ° C. or higher. Moreover, you may heat at about 750 degreeC or more in reducing atmosphere, such as hydrogen. Thus, after removing the resin, it is heated at about 800 to 900 ° C. in a reducing atmosphere to obtain foamed nickel.

Thereafter, the chromium powder having an average particle size of 2 to 15 [mu] m, and carboxymethylcellulose (CMC) paste with an aqueous solution having a basis weight mass, for example, is deposited so as to be ^{50g / m 2 ~100g / m 2} , 800 ℃ reducing atmosphere To form a chromium layer on the nickel layer. Both alloy layers are also included between the nickel layer and the chromium layer. In addition, a nickel chromium alloy layer and a chromium layer may be formed by chromium plating, chromizing treatment, or the like. By these methods, a porous metal current collector having a three-dimensional structure mainly containing nickel and containing at least 20% by mass of chromium can be obtained.

  The chromium content on the nickel is preferably 20% by mass or more including the nickel chromium alloy, and more preferably 25% by mass to 50% by mass. If the chromium content is low, the oxidation resistance is inferior, and if it is too high, the electrical resistance increases and the current collecting performance decreases.

[Composition and filling of polarizable electrode material]
The electrode used for the capacitor of the present invention can be obtained by filling the current collector having the three-dimensional structure with a polarizable electrode material mainly composed of cereal husk charcoal. The polarizable electrode material mainly composed of cereal husk charcoal contains a conductive additive and a binder as necessary. In this case, the grain shell charcoal content is preferably 60% by mass or more. Although the grain diameter of the grain husk charcoal to be used is not limited, it is preferably 20 μm or less. By setting this range, the internal resistance of the capacitor can be reduced and the output characteristics can be increased.
There is no restriction | limiting in particular in the kind of conductive support agent used as needed, A general purpose material can be used. For example, ketjen black is most suitable, and other examples include carbon black such as acetylene black, carbon fiber, natural graphite (flaky graphite, earthy graphite, etc.), artificial graphite, ruthenium oxide and the like. Of these, carbon fibers are also preferred. The content of these conductive assistants is not limited, but is preferably about 0.5 to 15 parts by mass with respect to 100 parts by mass of the carbon powder. If too much, the ratio of grain husk charcoal decreases and the capacitance decreases.

It is preferable to use a binder in order to improve the binding force between the porous metal body (current collector) having a three-dimensional network structure and the polarizable electrode and the binding force between the polarizable electrode powders. There is no restriction | limiting in particular in the kind, A general purpose material can be used. From the viewpoint of oxidation resistance, a fluororesin is preferred. For example, polyvinylidene fluoride and polytetrafluoroethylene are typical. Polyolefins are also relatively good. There are other polyvinyl pyrrolidone, polyvinyl chloride, styrene butadiene rubber, polyvinyl alcohol, etc., but there is a problem in oxidation resistance.
Although there is no restriction | limiting in particular also about content of a binder, Preferably it is about 0.5 mass part-15 mass parts with respect to 100 mass parts of carbon powder. Within this range, the binding property can be improved while suppressing an increase in electrical resistance and a decrease in capacitance. In order to make a slurry, it is necessary to improve the viscosity. In the case of polyvinylidene fluoride (PVdF), N-methyl-2-pyrrolidone (NMP) as a solvent plays a role, but a fluororesin (for example, PTFE disversion) For example, a known carboxymethyl cellulose aqueous solution is used.

The filling amount (content) when the current collector is filled with the grain husk charcoal slurry is not particularly limited. Basically, the thicker the current collector, the higher the capacity, and the thinner, the higher the output. Although it may be determined according to the shape of the capacitor and the like, for example, the filling amount is about 13 to 40 mg / cm ² , preferably about 16 to 32 mg / cm ² .

  As a method of filling the current collector of the present invention with cereal husk charcoal, for example, a known method such as press-fitting cereal husk charcoal paste may be used. As the press-fitting method, for example, a method of immersing a current collector in cereal husk charcoal paste and depressurizing as necessary, a method of filling cereal husk charcoal paste while pressurizing with a pump or the like from one side of the current collector, etc. Can be given.

  Grain husk charcoal paste should just contain grain husk charcoal and a solvent, and the compounding ratio is not limited. The solvent is not limited, and examples thereof include N-methyl-2-pyrrolidone (NMP) and water. In particular, when polyvinylidene fluoride (PVdF) is used as a binder, N-methyl-2-pyrrolidone (NMP) may be used as a solvent. When polytetrafluoroethylene disversion is used as a binder, water is used as a butterfly. That's fine. Moreover, you may contain additives, such as the said conductive support agent and a binder, as needed.

  After filling the grain husk charcoal paste, the electrode of the present invention may be subjected to a drying treatment as necessary to remove the solvent in the paste. Furthermore, as needed, after filling with the grain husk charcoal paste, it may be compression-molded by pressing with a roller press or the like. The thickness before and after compression is not limited, but the thickness before compression is usually 300 μm to 1500 μm, preferably 400 μm to 1200 μm, and the thickness after compression molding is usually about 100 μm to 700 μm, preferably about 150 μm to 600 μm. And it is sufficient. The electrode may be provided with a lead terminal. The lead terminal may be attached by welding or applying an adhesive.

[Lithium ion capacitor]
The capacitor according to the present invention can be a lithium ion capacitor by using an electrolytic solution containing a lithium salt. That is, the capacitor according to the present invention is a capacitor comprising at least a positive electrode, a negative electrode, and a non-aqueous electrolyte containing a lithium salt, wherein the positive electrode is an electrode containing the aforementioned carbon powder, and the negative electrode is three-dimensional. It is a lithium ion capacitor formed by filling a metal porous body having a network structure with a material capable of absorbing and desorbing or absorbing and desorbing lithium as an active material.

  As materials for the negative electrode, activated carbon is widely used for capacitors, and carbon-based materials such as graphite materials are widely used for lithium ion batteries. On the other hand, materials having lithium storage capacity far exceeding the theoretical capacity of graphite (372 mAh / g) and compounds thereof, such as silicon, tin, titanium, germanium, aluminum, indium and lithium alloy materials or silicon, tin, titanium, Oxide-based materials such as germanium, aluminum, and indium have attracted attention for quite some time, and some have been put into practical use.

In particular, silicon-based oxides have a high lithium storage capacity per mass, and are regarded as promising materials for increasing the energy density of batteries. However, since the initial efficiency is low and the volume change during lithium occlusion is larger than that of carbon-based materials, the energy density of the fabricated batteries is the same as that of lithium-based capacitors and lithium-based secondary batteries using activated carbon or graphite-based materials as negative electrodes. In comparison, there was a problem that the effect of improving the energy density was small and the charge / discharge characteristics were inferior.
In other words, these materials and their compounds cannot avoid an increase in material volume or pulverization due to repeated charge and discharge, which is the main cause of the above problems. In order to improve this, there is a proposal of a method of using a porous material with a three-dimensional structure, which is mixed with carbon materials, and excellent in electrolytic solution resistance and oxidation resistance, and the material or its compounds can be used. Became. However, there are further expectations for lithium ion capacitors in terms of high energy density, long life, and material resources.

  In particular, a lithium ion capacitor using a material or a compound having a charge / discharge capacity of 800 mAh / g or more (hereinafter also simply referred to as “capacity”) for the negative electrode has energy density, output characteristics, and charge / discharge cycle characteristics close to those of a lithium ion battery. If it can be obtained, further application expansion can be expected as a capacitor.

  As a result of further research on these points, the inventors of the present invention further performed lithium adsorption / desorption on a metal porous body having a three-dimensional network structure as a current collector for a negative electrode. A negative electrode formed by filling a material that can be occluded / desorbed and has a capacity of 800 mAh / g or more as an active material, a positive electrode comprising an electrode containing the above-mentioned carbon powder, and a non-aqueous electrolyte containing a lithium salt It was found that the ratio (N / P value) between the charge / discharge capacity of the negative electrode and the charge / discharge capacity of the positive electrode was preferably 50 to 400. If the N / P value is 50 to 400, the effect is sufficiently exhibited, and even if it is increased to over 400, the effect is small. Further, from the viewpoint of achieving both stable negative electrode voltage and energy density as a lithium ion capacitor, it is more preferable to suppress it to about 200 or less, and it is more preferable to set it to about 160 or less.

The capacitor according to the present invention can be a lithium ion capacitor using a non-aqueous electrolyte containing a lithium salt and having improved energy density, output characteristics, and charge / discharge cycle characteristics.
In the capacitor according to the present invention, the capacity ratio (N / P value) of the negative electrode and the positive electrode can be greatly increased as compared with the conventional case. Specifically, 50 to 400 can be selected as a preferable value of the N / P value. A more preferable value of the N / P value is 55 to 200, and more preferably 60 to 160. As a result, it is possible to make a capacitor that has an energy density close to that of a lithium-based secondary battery while being a capacitor, and that can have a high output and a long service life. Also, as a resource, noble metals such as cobalt and rare earths and rare metals can be used. It has the advantage that it does not need to be used.

In order to exert the features of the present invention, in the present invention, a three-dimensional metal porous body is used as a current collector for both the positive electrode and the negative electrode. That is, as a current collector for filling the carbon powder that is the active material of the positive electrode and a material such as silicon or tin that is the active material of the negative electrode or its oxide, Instead of the aluminum foil and the copper foil as the negative electrode current collector, a porous metal body having a three-dimensional structure is used as the current collector for both the positive electrode and the negative electrode.
As the metal porous body having a three-dimensional structure, those having the aforementioned three-dimensional network structure can be preferably used. That is, in terms of the fillability and porosity of the active material, a material based on urethane foam or nonwoven fabric such as foamed nickel and nonwoven fabric nickel can be preferably used. Other three-dimensional structures include a metal plate with a large number of small holes, a metal plate with irregularities and a pseudo three-dimensional structure, and a structure with a sintered body and continuous air holes. However, a three-dimensional network metal porous body obtained using urethane foam or nonwoven fabric as a base material is optimal.
In the following, an example in which a porous body having a three-dimensional network structure is used as a porous metal body including a case of a sodium ion capacitor will be described, but other three-dimensional structures may be used in the same manner. Can do.

  The active material can be filled into the three-dimensional network structure porous metal by making the active material into a slurry as described above and filling the slurry by a known method such as a press-fitting method. In addition, for example, a method of immersing the current collector in the slurry, adding a decompression step as necessary, and filling the slurry while pressurizing with a pump or the like from one side of the current collector can be employed.

First, as described above, the most preferable method is to add carbon black, a thickener, and a binder as a conductive auxiliary agent and fill the current collector as a slurry with the carbon powder as the active material for the positive electrode. There is a proposal for using a metal foil as an active material as one of the negative electrodes. In the present invention, a metal powder or a metal oxide and carbon black, a thickener, a binder, etc. A method in which the current collector is added to the current collector as a slurry is suitable.
Also for the negative electrode, carbon fibers (Ketjen black, acetylene black, etc.), carbon fiber, natural graphite, artificial graphite, etc. can be used as the conductive agent. However, ketjen black is most preferable from the viewpoint of conductivity. As for the addition amount of a conductive support agent, about 0.1-10 parts is preferable by mass ratio.

  As the binder, an NMP solution of PVdF can also be used for the negative electrode, but polytetrafluoroethylene, polyvinyl pyrrolidone, polyethylene, polypropylene, styrene butadiene rubber, polyvinyl alcohol, carboxymethyl cellulose, and the like can also be used. These are attracting attention because they can be used as emulsions or aqueous solutions. The amount of binder added is preferably about 0.5 to 10% by mass ratio, although it depends on the material. If it is less than 0.5%, the retention of the active material is inferior. If it exceeds 10%, the capacity decreases and the electrical resistance also increases.

  Both the positive electrode and the negative electrode are preferably filled with the active material slurry and then dried to remove the organic solvent. Then, after filling the slurry, it is preferable to press and compress with a roller press or the like. The thickness before and after pressing is not limited, but the thickness before compression is preferably about 250 to 1500 μm, and the thickness after pressing is preferably about 100 to 800 μm. The capacitor is preferably provided with a lead terminal. As a structure of the capacitor, a general-purpose structure such as a plate shape, a button shape, a square shape, or a cylindrical shape may be employed depending on the application.

In this way, the above-described carbon powder is used for the positive electrode, and the negative electrode is filled with a negative electrode active material mainly composed of a material having a capacity of 800 mAh / g or more or capable of absorbing and desorbing or desorbing lithium. Thus, a lithium ion capacitor is configured. Here, in this lithium ion capacitor, by constructing a lithium ion capacitor using a non-aqueous electrolyte containing a lithium salt, the calculated capacity of the negative electrode is 50 to 400 times the calculated capacity of the positive electrode, High output, long life, etc. can be achieved better.
In order to achieve such an unprecedented large N / P ratio, it is necessary to use a metal porous body having a three-dimensional network structure instead of a metal foil or a two-dimensional structure current collector as a positive electrode current collector. As described above, a nickel-chromium alloy is most suitable as the three-dimensional network metal porous body from the viewpoint of oxidation resistance and electrolytic solution resistance. As the negative electrode current collector, a nickel porous body having a three-dimensional network structure can also be used.

  Further, the positive electrode active material in the capacitor does not need to be a lithium-containing transition metal oxide as used in a lithium ion battery, and a sufficient effect is exhibited by the carbon powder. Thus, in order to increase the capacity of the lithium ion capacitor, it is preferable that the capacity of the positive electrode is large, and carbon powder is filled into a porous metal body, particularly a foamed nickel chrome porous body (current collector) in the same manner as the negative electrode. It is preferable to use it.

As the carbon powder used as the positive electrode active material, those derived from grain husks can be used as described above.
On the other hand, materials having a capacity of 800 mAh / g or more capable of absorbing / desorbing or desorbing lithium used for the negative electrode include silicon (Si), tin (Sn), germanium (Ge), oxides of these elements, and these elements. Examples include alloys with lithium.

  In addition, it is important that lithium is supported (doped) on the negative electrode active material before constituting the lithium ion capacitor. In general, adsorbing or occluding lithium ions in the negative electrode is a preferable means for sufficiently supplying lithium ions to the positive electrode by discharge, and the cell voltage can be increased. Adsorption or occlusion of lithium ions in the negative electrode is a necessary step in order to enable a high capacity using a current collector having a three-dimensional network structure in the positive electrode. As the method, there are a method in which lithium metal powder and an electrode material are mixed in advance, and an electrode is brought into contact with a lithium metal foil after the electrode is manufactured. The latter is a kind of short circuit method.

Said lithium ion capacitor can be manufactured with the following method. The basic structure of the capacitor is the same as that of the prior art, and is composed of a pair of positive and negative electrodes and a separator impregnated with an electrolyte solution disposed between the electrodes, and is accommodated in a battery case.
In addition, as a separator, well-known porous bodies, such as polyethylene, a polypropylene, a polyethylene terephthalate, polyamide, a polyimide, a cellulose, glass fiber, can be used, for example. The average pore size of the separator is not particularly limited, but a pore size of about 0.01 μm to 5 μm, a porosity of 30 to 70%, and a thickness of 10 μm to 100 μm can be employed.

[Sodium ion capacitor]
The capacitor according to the present invention can be a sodium ion capacitor by using an electrolytic solution containing a sodium salt. That is, the capacitor according to the present invention is a capacitor comprising at least a positive electrode, a negative electrode, and a non-aqueous electrolyte containing a sodium salt, wherein the positive electrode is an electrode containing the aforementioned carbon powder, and the negative electrode is three-dimensional. A metal porous body having a network structure is filled with a material capable of adsorbing / desorbing or desorbing or desorbing sodium as an active material.

The capacitor according to the present invention utilizes the advantages of being cheaper and more resource-efficient than a lithium ion capacitor by using a non-aqueous electrolyte containing a sodium salt, and further has a high energy density not found in conventional sodium ion capacitors, High output characteristics and long life can be demonstrated.
In general, lithium metal oxide is used for a positive electrode and graphite is used for a negative electrode in a general-purpose lithium ion battery, and materials or oxides such as silicon and tin are used for the negative electrode in addition to activated carbon. In addition, activated carbon is used for both electrodes in the non-aqueous capacitor, and activated carbon is used for the positive electrode and graphite is used for the negative electrode in the lithium ion capacitor. All of these use aluminum foil, copper foil or the like as a current collector.

On the other hand, the present invention pays attention to the large ionic radius of sodium ions, and the main solution is to use the metal porous body having the above-mentioned electrolyte-resistant three-dimensional network structure as the current collector of the positive electrode in particular. It is. The metal of the electrolyte-resistant metal porous body having the above three-dimensional network structure is not particularly limited. As described above, it has a three-dimensional network structure mainly containing nickel and containing at least 20% by mass of chromium. A metal porous body is preferable. For example, the metal porous body is preferably a metal porous body that is alloyed by forming a chromium layer on the surface of a nickel porous body having a three-dimensional network structure.
By using such an electrolyte-resistant metal porous body as a positive electrode current collector, the promotion of the electrochemical reaction of sodium ions having a large ionic radius is greatly improved. As a result, a sodium ion capacitor that is not inferior to a lithium ion capacitor can be obtained.

  In the capacitor of the present invention, a metal porous body having an electrolyte-resistant three-dimensional network structure is used as a positive electrode current collector. However, the metal porous body is not limited to the positive electrode, and is used for both the positive electrode and the negative electrode. You can also. In addition, you may use the nickel porous body which has a three-dimensional network structure as the collector for the electrode comprised as a negative electrode similarly to a lithium ion battery.

For example, the above-mentioned carbon powder is used as the material that can be used for filling and desorbing or sorbing and desorbing sodium in the positive electrode current collector.
In addition, the material that can be absorbed and desorbed or occluded / desorbed into the negative electrode current collector is activated carbon, graphite, hard carbon, tin, tin compounds, lithium titanate, silicon fine particles, and silicon oxide. One or more selected materials are preferred. Among these, it is particularly preferable to use hard carbon.

As the carbon powder used as the positive electrode active material, those derived from grain husks can be used as described above.
In addition to the above, the active substance (active material) used for the negative electrode is an alloy of silicon (Si), tin (Sn), etc., with these oxides or sodium, which can adsorb / desorb or occlude / desorb sodium. System materials.

  When filling the carbon powder in the metal porous body, it is preferable to add carbon black, a thickener, and a binder as a conductive aid, as described above, and fill the slurry as a slurry. The method for forming the slurry and the method for filling the metal porous body with the slurry are as described above.

  In the capacitor according to the present invention, the positive electrode is filled with the carbon powder and the negative electrode is filled with hard carbon, and the ratio of the calculated negative electrode capacity to the calculated positive electrode capacity, that is, the N / P ratio ranges from 10 to 100. It is preferable that it exists in the range of 12-80. In such a capacitor, as described above, a nickel porous body having a three-dimensional network structure can also be used as the negative electrode current collector. Moreover, what formed the chromium layer and alloyed on the surface of a nickel porous body similarly to a positive electrode can also be used.

The material capable of adsorbing / desorbing or occluding / desorbing sodium filled in the negative electrode collector is mixed with a conductive additive, a thickener, a binder, a solvent, etc. into a slurry, and filled into the current collector. Can do.
As the conductive aid, for example, ketjen black, acetylene black, carbon fiber, natural graphite, artificial graphite and the like can be used. However, ketjen black is most preferable from the viewpoint of conductivity. As for the addition amount of a conductive support agent, about 0.1-10 are preferable with respect to 85 with a mass ratio of hard carbon.

Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl pyrrolidone, polyethylene, polypropylene, styrene butadiene rubber, polyvinyl alcohol, and carboxymethyl cellulose. These are attracting attention because they can be used as emulsions or aqueous solutions.
Although the amount of the binder added depends on the material, the hard carbon is preferably about 0.5 to 15 with respect to 85 by mass ratio. If it is less than this, the retention of the active material is inferior, and if it is more than this, the capacity decreases and the electrical resistance also increases.

  As a method of filling the active substance (active material) into the negative electrode current collector (metal porous body) having a three-dimensional network structure, the active substance is made into a slurry, and this slurry is used by a known method such as a press-fitting method. do it. Other methods include, for example, immersing a current collector (metal porous body) in the slurry, adding a pressure reducing step as necessary, and filling the slurry while pressurizing it from one side of the current collector with a pump or the like. Can also be adopted.

It is preferable that the positive electrode current collector and the negative electrode current collector are filled with the active substance slurry, and then compression-molded by applying pressure using a roller press or the like. The thickness of the electrode before and after pressurization is not limited, but the thickness before compression is preferably about 250 μm to 1500 μm, and the thickness after pressurization is usually preferably about 100 μm to 800 μm.
As is well known, sodium ion capacitors are preferably provided with lead terminals and shaped like a plate, button, square, or cylinder.

Moreover, it is preferable that sodium is carried (doped) on the negative electrode active substance before constituting the sodium ion capacitor. In general, adsorption or occlusion of sodium ions in the negative electrode is a preferable means for sufficiently supplying sodium ions to the positive electrode by electric discharge, and the cell voltage can be increased. This is also an important step in order to enable a high capacity by using a current collector having a three-dimensional network structure for the positive electrode.
As the method, sodium metal powder and a negative electrode material (active substance) are mixed in advance, or the electrode is brought into contact with a sodium metal foil after production. The latter is a kind of short circuit method.

The basic structure of the capacitor according to the present invention is the same as that of the prior art, and is formed by a separator in which a positive electrode and a negative electrode are paired and an electrolyte is impregnated between the electrodes, and is accommodated in a battery case.
In addition, as a separator, well-known porous bodies, such as polyethylene, a polypropylene, a polyethylene terephthalate, polyamide, a polyimide, a cellulose, glass fiber, can be used, for example. The average pore diameter of the separator is not particularly limited, but a pore diameter of about 0.01 μm to 4 μm, a porosity of 35 to 70%, and a thickness of 10 μm to 100 μm can be employed.

  Examples of lithium ion capacitors and sodium ion capacitors will be described below as the capacitors of the present invention. However, these examples are illustrative, and the present invention is not limited by these examples. The scope of the present invention is indicated by the scope of the claims, and the scope of the claims and All changes within an equivalent meaning and scope are included.

<Example 1> Lithium ion capacitor [Preparation of negative electrode]
(Current collector)
As a current collector for a metal porous body with a three-dimensional network structure, a foamed material manufactured by chromizing treatment using a powder pack method in which foamed nickel is filled with a penetrating material containing chromium and heated in a reducing atmosphere. A nickel chrome alloy current collector was used.
The foamed nickel is conductively treated on a urethane sheet (commercially available product with an average pore diameter of 90 μm, thickness of 1.4 mm, and porosity of 96%), and then 350 g / m ² of nickel plating is applied. It was made as.

In the chromizing treatment, the foamed nickel base material is filled with a penetrating material (chromium: 90%, NH ₄ Cl: 1%, Al ₂ O ₃ : 9%) mixed with chromium powder, halide and alumina. The heating was performed at 800 ° C. in a hydrogen gas atmosphere. The resulting foamed nickel chromium base had a chromium content of 30% by mass and a thickness of 1.4 mm.
The current collector was made of foamed nickel chrome having a porosity of 96% and a pore diameter of 100 to 400 μm, the thickness of which was previously adjusted to 250, 500, 1000 and 1300 μm, and punched into a circle of 11 mm in diameter with a mold.

(Negative electrode active material)
As the negative electrode active material, silicon oxide SiO (calculated capacity density 1500 mAh / g) which is an oxide type material was used. Commercially available SiO with an average particle size of about 5 μm is 80 by mass, Ketjen black (KB) 5 as a conductive agent, polyvinylidene fluoride (PVdF) 15 as a binder, solvent N-methyl-2-pyrrolidone (NMP) While stirring 100 with a mixer, the binder was dissolved in a solvent to obtain a slurry.

(Filling current collector with negative electrode active material)
The slurry obtained above was filled by press-fitting the slurry, dried and pressurized to obtain negative electrodes A1 to A4. Twenty negative electrodes A1 to A4 were prepared.

(Lithium doping to the negative electrode)
Each of the negative electrodes A1 to A4 obtained above was contacted with a lithium foil having a diameter of 13 mm and a thickness of 100 μm and left at 50 ° C. overnight. By this operation, lithium pressure-bonded to each negative electrode is ionized and occluded by silicon oxide of each negative electrode.
The negative electrode potential after lithium doping was 0.05 V or less based on lithium.

[Production of positive electrode]
(Current collector)
As the current collector for the positive electrode, the same foamed nickel chromium porous material as that used for the negative electrode was used.
In the positive electrode, the foamed nickel chrome porous body was adjusted to a thickness of 500, 780, and 1300 μm, and punched in a circular shape with a diameter of 11 mm with a mold in the same manner as the negative electrode to obtain a current collector for the positive electrode.

(Positive electrode active material)
100 parts by mass of rice husk charcoal powder (specific surface area of 770 m ² / g, average particle size of about 8 μm) containing 49% by mass of silica component, 11 parts by mass of ketjen black as a conductive additive, and polyvinylidene fluoride powder 8 as a binder The rice husk charcoal paste was prepared by adding 55 mass parts of N-methylpyrrolidone as a mass part and a solvent, and stirring with a mixer.

(Filling current collector with positive electrode active material)
The rice husk charcoal paste was filled into the positive electrode collector so that the content of rice husk charcoal was 8 mg / cm ² . The actual filling amount was 8 mg / cm ² . Next, after drying by 100 degreeC with a dryer for 1 hour and removing a solvent, it pressurized with the roller press machine (slit: 50 micrometers) of diameter 500mm, and obtained positive electrode A1-A3. The thickness after pressing was 170 μm. Twenty positive electrodes A1 to A3 were produced respectively.

[Manufacture of capacitors]
Each of the 11 mm diameter circular positive and negative electrodes obtained above was used to form a cell with a polypropylene separator (thickness 25 μm) sandwiched between the two electrodes and housed in an R2032-sized coin cell case. Then, an electrode and a separator were impregnated using an electrolytic solution in which 1 mol / l LiPF ₆ was dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1: 1. Further, the case lid was tightened and sealed through an insulating gasket made of propylene to produce a coin-shaped lithium ion capacitor.

Tables 1 and 2 show the post-thickness thickness, post-pressurization thickness, and active material filling amount of each of the negative electrode A1 to negative electrode A4 and positive electrode A1 to positive electrode A3 produced in this manner (however, the negative electrode A5 For the negative electrode A6 and the positive electrode A4, since the metal foil is used, the thickness after the thickness adjustment is not described).
Table 1 also shows negative electrodes A5 and A6 using copper foil as a current collector for comparison. Table 2 also shows a positive electrode A4 produced using a carbon powder slurry for an aluminum foil as a comparison.
Table 3 shows the N / P values of lithium ion capacitors produced using the negative electrodes and the positive electrodes. The N / P values shown in Table 3 are average values of three capacitors having the same configuration.

N / P was determined as follows.
The capacity of SiO as the negative electrode active material is 1500 mAh / g, the capacity of the carbon powder as the positive electrode active material is 15 mAh / g, and the mass of the SiO and carbon powder contained in each electrode is multiplied by each electrode. Capacity. The value obtained by dividing the negative electrode capacity thus obtained by the positive electrode capacity was defined as the N / P ratio. The N / P ratio was adjusted by changing the amount of active material filled in the current collector.

When a discharge test was performed on a lithium ion capacitor A (N / P value: 158) in which the positive electrode A1 and the negative electrode A2 were combined, a linear discharge curve was drawn from 4V to 2V, and the lithium ion capacitor A was normal as a capacitor. Was functioning. The capacity was about 0.3 mAh / cm ² . Similarly, a good discharge curve is obtained for the lithium ion capacitor B (N / P value: 220) in which the positive electrode A2 and the negative electrode A2 are combined, and the lithium ion capacitor C (N / P value: 387) in which the positive electrode A3 and the negative electrode A1 are combined. Obtained.
On the other hand, when the discharge test of the lithium ion capacitor D (N / P value: 44) combining the positive electrode A4 and the negative electrode A5 and the lithium ion capacitor E (N / P value: 18) combining the positive electrode A4 and the negative electrode A6 was performed. The discharge curve was bent from 4 V to 2 V, and it was found that the lithium ion capacitors D and E did not function normally as capacitors.

  From the results of the above examples, the positive electrode and the negative electrode were both filled with a three-dimensional network metal porous body, the positive electrode was filled with carbon powder, and the negative electrode was filled with silicon oxide having a capacity of 800 mAh / g or more. By adopting a calculation capacity ratio, that is, an N / P value of 50 to 400, more preferably 55 to 200, particularly 60 to 160, energy density, high output density, and long life similar to those of a lithium secondary battery can be obtained. Thus, a lithium ion capacitor having excellent resource properties was obtained.

<Example 2> Sodium Ion Capacitor [Production of Porous Metal (Current Collector)]
In this example, a metal current collector having a three-dimensional network structure with a chromium layer formed on the surface of a three-dimensional network nickel porous body was used.
Specifically, a metal porous body having a three-dimensional network structure in which chromium was added to the surface of the foamed nickel porous body and heated to form a nickel chromium alloy layer was manufactured. That is, the foamed nickel-chromium alloy porous body produced by chromizing the foamed nickel was used.

The foamed nickel is subjected to a conductive treatment on a urethane sheet (commercially available product with an average pore diameter of 90 μm, a thickness of 1.4 mm, and a porosity of 96%), followed by 350 g / m ² of nickel plating. What was produced by heating was used.
And nickel was made into the nickel-chromium alloy by chromizing the foamed nickel (nickel porous body which has a three-dimensional network structure). In other words, a powder pack method is used in which a base material is filled with a penetrant mixed with chromium powder, halide, and alumina and heated in a reducing atmosphere. The penetrant (chromium: 90%, NH ₄ Cl 1%, Al ₂ O ₃ : 9%) and heated to 800 ° C. in a hydrogen gas atmosphere.
The metal porous body thus produced had a chromium content of 30% by mass and a thickness of 1.4 mm.

[Production of negative electrode]
Hard carbon (calculated capacity density 200 mAh / g) was used as an active material (active material).
Commercially available hard carbon having an average particle size of about 10 μm in mass ratio of 85, Ketjen black (KB) as the conductive agent, 3 polyvinylidene fluoride (PVdF) as the binder, N-methyl-2- While stirring pyrrolidone (NMP) 100 with a mixer, the binder was dissolved in a solvent to obtain a slurry for negative electrode.
Subsequently, the metal porous body having a thickness of about 1250 μm, a porosity of 96%, and a pore diameter of 100 to 400 μm, prepared as described above, was adjusted in advance to the thickness shown in Table 4 and punched into a circle having a diameter of 11 mm with a mold.
Then, this foamed nickel chrome porous body was used as a negative electrode current collector, and the negative electrode slurry was filled in the filling amounts shown in Table 4 below, dried and pressurized to obtain negative electrode B1, negative electrode B2, and negative electrode B3. The negative electrode was doped with sodium by electrolysis.
Moreover, the negative electrode B4 and the negative electrode B5 were produced on condition of the following Table 4 using copper foil as a comparison.

[Production of positive electrode]
As the positive electrode, the foamed nickel chrome porous body produced above (the same as used for the negative electrodes B1 and B2) was used as the positive electrode current collector. In the positive electrode, the foamed nickel chrome porous body was adjusted to a thickness of 780 μm, and was punched into a circular shape with a diameter of 11 mm with a mold in the same manner as the negative electrode to obtain a positive electrode current collector. And this was filled with carbon powder (calculated capacity density 15mAh / g).
As the carbon powder, rice husk charcoal powder (specific surface area of 770 m ² / g, average particle diameter of about 8 μm) containing 49% by mass of a silica component was used.
Also, for the active material mass ratio of 80, KB as a conductive agent, 15 PVdF as a binder, and 300 NMP as a solvent were dissolved in a solvent while stirring with a mixer to obtain a positive electrode slurry. It was.
Then, the positive electrode slurry was filled in the positive electrode current collector in the filling amount shown in Table 5 below, dried and pressurized to obtain the positive electrode B1 and the positive electrode B2.
Moreover, the positive electrode B3 and the positive electrode B4 were produced on condition of the following Table 5 using the aluminum foil as a comparison.

[Manufacture of capacitors]
A cell was formed by sandwiching a glass separator between the positive electrode B1 and the negative electrode B1 obtained above, and the cell was stored in an R2032-sized coin-shaped cell case, and 1 mol / l NaPF ₆ was dissolved. Electrodes and separators were impregnated using an electrolytic solution dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) having a volume ratio of 1: 1.
Further, the case lid was tightened and sealed through a propylene insulating gasket to produce a coin-shaped sodium ion capacitor A. Similarly, sodium ion capacitors B to F shown in Table 6 were prepared using the negative electrode B1 to the negative electrode B3 and the positive electrode B1 to the positive electrode B2.
For comparison, a sodium ion capacitor G was produced using the negative electrode B4 and the positive electrode B3, and a sodium ion capacitor H was produced using the negative electrode B5 and the positive electrode B4.
Table 6 shows the N / P value of each sodium ion capacitor.

  Moreover, when the discharge test of the sodium ion capacitor of the coin type cell using the positive electrode and the negative electrode produced as described above was carried out, the sodium ion capacitors A to F of the present invention were the copper foil (negative electrode) of the comparative example, Compared to sodium ion capacitors G and H using aluminum foil (positive electrode), the capacitance density was about 4 times.

From the results of the above examples, both the positive electrode and the negative electrode have a three-dimensional network metal porous body, in particular, a metal porous body formed by alloying by forming a chromium layer on the surface of the nickel porous body, the positive electrode is filled with carbon powder, By filling the negative electrode with hard carbon and adopting a ratio of the negative electrode calculated capacity to the calculated positive electrode capacity, that is, N / P value of 10 to 100, especially 12 to 80, energy density close to that of the sodium secondary battery, high It can be seen that a sodium ion capacitor having a high output density and a long life and excellent resource is obtained.
N / P was determined in the same manner as in the case of the lithium ion capacitor. That is, the capacity of the hard carbon as the negative electrode active material is 200 mAh / g, the capacity of the carbon powder as the positive electrode active material is 15 mAh / g, and the mass of the hard carbon and carbon powder contained in each electrode is multiplied. Was the capacity of each electrode. The value obtained by dividing the negative electrode capacity thus obtained by the positive electrode capacity was defined as the N / P ratio. The N / P ratio was adjusted by changing the amount of active material filled in the current collector.

  The lithium ion capacitor and the sodium ion capacitor into which the novel technology of the present invention is introduced can be used for portable, mobile, emergency, and other general and industrial power supplies.

Claims (22)

An electrode obtained by filling a carbon powder containing a silica component obtained from a grain shell into a porous metal body having a three-dimensional structure having oxidation resistance;
A capacitor having a non-aqueous electrolyte containing a lithium salt or a sodium salt as the electrolyte.   The capacitor according to claim 1, wherein the carbon powder contains 10% by mass to 60% by mass of a silica component.   The capacitor according to claim 1, wherein the carbon powder is manufactured by heating air to rice husk while blocking air.   The capacitor according to claim 1, wherein a conductive additive is mixed in the carbon powder.   The capacitor according to claim 4, wherein the conductive additive is contained in a mass ratio of 0.5 to 15 parts by mass with respect to 100 parts by mass of the carbon powder.   The capacitor according to claim 1, wherein a binder is mixed in the carbon powder.   The capacitor according to claim 1, wherein the metal porous body is a metal porous body having a three-dimensional structure mainly composed of nickel and containing at least 20 mass% of chromium.   The porosity of the said metal porous body is 80%-97%, The capacitor in any one of Claims 1-7 characterized by the above-mentioned. Nickel weight per unit area of the nickel porous body, capacitor according to claim 7 or 8, characterized in that a ^{150g / m 2 ~500g / m 2} .   10. The capacitor according to claim 7, wherein the amount of chromium in the metal porous body is 25 to 50 mass% with respect to the total amount of nickel and chromium.   The capacitor according to claim 1, wherein the electrode is a positive electrode.   The capacitor according to claim 11, which is a lithium ion capacitor provided with a non-aqueous electrolyte containing a lithium salt as an electrolyte.   13. The capacitor according to claim 12, wherein the negative electrode is formed by filling a metal porous body having a three-dimensional structure with a material capable of absorbing / desorbing or desorbing lithium as an active material.   14. The capacitor according to claim 12, wherein lithium is supported on the negative electrode active material before constituting the lithium ion capacitor.   The material capable of absorbing / desorbing or desorbing / desorbing lithium is at least selected from the group consisting of silicon (Si), tin (Sn), germanium (Ge), oxides of these elements, and alloys of these elements and lithium. The capacitor according to claim 12, wherein the capacitor is one type.   The capacitor according to any one of claims 12 to 15, wherein the material capable of absorbing and desorbing or desorbing or desorbing lithium is silicon oxide (SiO).   The capacitor according to claim 12, wherein the negative electrode potential is 0.05 V or less based on lithium.   The capacitor according to claim 11, wherein the capacitor is a sodium ion capacitor including a nonaqueous electrolytic solution containing a sodium salt as an electrolytic solution.   19. The capacitor according to claim 18, wherein the negative electrode is an electrode formed by filling a metal porous body having a three-dimensional structure with a material capable of adsorbing / desorbing or desorbing sodium as an active material.   20. The capacitor according to claim 18, wherein sodium is supported on the negative electrode active material before constituting the sodium ion capacitor. 21. The capacitor according to claim 18, wherein the metal porous body of the negative electrode is a metal porous body having a three-dimensional structure mainly composed of nickel. The material capable of adsorbing / desorbing / desorbing / desorbing sodium filled in the metal porous body is selected from the group consisting of activated carbon, graphite, hard carbon, tin, tin compounds, sodium titanate, silicon fine particles, and silicon oxide. The capacitor according to claim 18, wherein the capacitor is one or more materials.