WO2012096220A1 - Process for production of aluminum structure, and aluminum structure - Google Patents

Abstract

The purpose of the present invention is to enable the aluminum plating of the surface of an article even when the article is a porous resin molding having a three-dimensional network structure, and to form a plating film having a uniform thickness, thereby forming an aluminum structure having high purity. A process for producing an aluminum structure, comprising a step of plating a resin porous article which has a three-dimensional network structure and of which at least the surface is rendered electrically conductive with aluminum in a bath of a molten salt, wherein the molten salt is a mixed salt of aluminum chloride and an organic salt and the plating is carried out while setting the temperature of the bath of the molten salt at a temperature falling within the range from 45 to 100˚C inclusive. It is preferred that the bath of the molten salt additionally contains 1,10-phenanthroline at a concentration of 0.25 to 7 g/l inclusive.

Description

Aluminum structure manufacturing method and aluminum structure

The present invention relates to a method of forming an aluminum structure on a resin surface by aluminum plating, and particularly to an aluminum structure that can be suitably used as a porous metal body in applications such as various filters and battery electrodes, and a method for producing the same.

Metal porous bodies having a three-dimensional network structure are used in various fields such as various filters, catalyst carriers, and battery electrodes. For example, cermet made of nickel (manufactured by Sumitomo Electric Industries, Ltd .: registered trademark) is used as an electrode material for batteries such as nickel metal hydride batteries and nickel cadmium batteries. Celmet is a metal porous body having continuous air holes, and has a feature of high porosity (90% or more) compared to other porous bodies such as a metal nonwoven fabric. This can be obtained by forming a nickel layer on the surface of the porous resin skeleton having continuous air holes such as urethane foam, then heat-treating it to decompose the foamed resin molding, and further reducing the nickel. Formation of the nickel layer is performed by depositing nickel by electroplating after applying a carbon powder or the like to the surface of the skeleton of the foamed resin molded body and conducting a conductive treatment.

Aluminum has excellent characteristics such as conductivity, corrosion resistance, and light weight. In battery applications, for example, a positive electrode of a lithium ion battery in which an active material such as lithium cobaltate is applied to the surface of an aluminum foil is used. In order to improve the capacity of the positive electrode, it can be considered that aluminum is made porous to increase the surface area, and the active material is also filled inside the aluminum. This is because the active material can be used even if the electrode is thickened, and the active material utilization rate per unit area is improved.

As a method for producing a porous aluminum body, Patent Document 1 discloses that a metal aluminum layer having a thickness of 2 to 20 μm is formed by subjecting a three-dimensional net-like plastic substrate having an internal communication space to aluminum vapor deposition by an arc ion plating method. A method is described. In Patent Document 2, a film made of a metal (such as copper) that forms a eutectic alloy below the melting point of aluminum is formed on the skeleton of a foamed resin molding having a three-dimensional network structure, and then an aluminum paste is applied. In addition, a method is described in which a metal porous body is obtained by performing heat treatment at a temperature of 550 ° C. or higher and 750 ° C. or lower in a non-oxidizing atmosphere to eliminate organic components (foamed resin) and sinter aluminum powder.

On the other hand, aluminum plating is difficult to perform electroplating in an aqueous plating bath because aluminum has a high affinity for oxygen and has a lower potential than hydrogen. For this reason, conventionally, electroplating of aluminum has been studied using a non-aqueous plating bath. For example, as a technique for plating aluminum for the purpose of preventing oxidation of the surface of a metal, Patent Document 3 uses a low melting point composition in which onium halide and aluminum halide are mixed and melted as a plating bath. An electrolytic aluminum plating method is disclosed, in which aluminum is deposited on the cathode while maintaining the amount at 2 wt% or less.

Japanese Patent No. 3413662 JP-A-8-170126 Japanese Patent No. 3202072

According to the method of Patent Document 1, an aluminum porous body having a thickness of 2 to 20 μm is obtained. However, since it is based on a gas phase method, it is difficult to produce a large area, and the thickness and porosity of the substrate are difficult. In some cases, it is difficult to form a uniform layer up to the inside. In addition, there are problems such as a slow formation rate of the aluminum layer and an increase in manufacturing cost due to expensive equipment. Furthermore, when a thick film is formed, there is a possibility that the film may crack or aluminum may fall off. According to the method of Patent Document 2, a layer that forms a eutectic alloy with aluminum is formed, and a high-purity aluminum layer cannot be formed. On the other hand, although the electroplating method of aluminum itself is known, it is only possible to plate on the metal surface, and electroplating on the surface of the resin molded body, especially the surface of the porous resin molded body having a three-dimensional network structure. The method of electroplating was not known. This is considered to be affected by problems such as dissolution of the porous resin in the plating bath.

Therefore, the present invention enables the plating of aluminum on the surface of a porous resin molded body having a three-dimensional network structure, and forms a high-purity aluminum structure by forming a thick film uniformly. It is an object of the present invention to provide a method capable of obtaining a porous aluminum body having a large area.

In order to solve the above problems, the present inventors have come up with a method of electroplating aluminum on the surface of a resin molded body having a three-dimensional network structure such as polyurethane or melamine resin. That is, the present invention is a method for producing an aluminum structure in which aluminum is plated in a molten salt bath on a resin molded body having a three-dimensional network structure with at least a surface conductive. A method for producing an aluminum structure, which is a mixed salt with an organic salt and is plated at a temperature of the molten salt bath of 45 ° C. to 100 ° C. (Claim 1).

As a method of plating aluminum on the surface of a resin molded body having a three-dimensional network structure, the present inventors are effective in plating aluminum in a molten salt bath that is a mixed salt of an organic salt and aluminum chloride. I found out. Since a mixed salt of an organic salt such as an imidazolium salt and aluminum chloride becomes liquid at room temperature, the temperature of the plating bath is generally set to a temperature near room temperature. However, when the molten salt has a high viscosity at a temperature near room temperature and has a complicated skeleton structure such as a resin molded body having a three-dimensional network structure, good plating may not be possible depending on the plating conditions. In particular, when producing a porous aluminum body having a large area, it is necessary to increase the current density. However, when the viscosity of the molten salt is low, the current density range that can be plated becomes narrow. When the temperature of the molten salt bath is 45 ° C. or higher and 100 ° C. or lower, the viscosity of the molten salt bath can be lowered, and the molten salt can be sufficiently distributed even inside the resin molded body (porous body) having a three-dimensional network structure. Can do. Therefore, uniform plating with a small difference in plating thickness between the surface portion and the inside of the porous body becomes possible. Moreover, since the plating with a uniform thickness can be formed, the strength of the aluminum layer is increased, and an aluminum structure with little breakage of the skeleton structure can be obtained even after the resin molded body is removed.

When the molten salt further contains 1,10-phenanthroline at a concentration of 0.25 g / l or more and 7 g / l or less, the smoothness of the plating surface is improved (Claim 2). By adding 1,10-phenanthroline after lowering the viscosity of the molten salt bath within a certain range and adding a synergistic effect, the surface of the skeletal surface becomes grainy (the surface has large irregularities and looks like grains in the surface observation). It is possible to obtain an aluminum structure that is strong even in a thin skeleton and is not easily broken.

The organic salt is preferably a molten salt containing nitrogen, and among them, an imidazolium salt is preferably used (Claim 3).

A mixed salt of an imidazolium salt and aluminum chloride is preferable as a molten salt bath because it melts at a relatively low temperature and has high conductivity. As the imidazolium salt, a salt containing an imidazolium cation having an alkyl group at the 1,3-position is preferably used. Particularly, a mixed salt of 1-ethyl-3-methylimidazolium chloride and aluminum chloride (AlCl ₃ -EMIC) is used. It is most preferably used because it is highly stable and hardly decomposes. In addition, since the imidazolium salt bath does not like the presence of moisture and oxygen, it is preferable to perform plating in an inert gas atmosphere such as argon or nitrogen in a sealed environment.

Urethane foam and foamed melamine can be preferably used as a porous resin body because they have high porosity, have pore connectivity and are excellent in thermal decomposability (Claim 4). Foamed urethane is preferred in terms of pore uniformity and availability, and foamed melamine is preferred in that a product having a small pore diameter can be obtained.

The method of conducting the resin porous body surface can be selected including known methods. It is possible to form a metal layer such as aluminum or nickel by electroless plating or vapor phase method, or to form a metal or carbon layer by conductive paint. The formation of an aluminum layer by vapor phase method and the electrical conductivity by carbon can be performed without mixing a metal other than aluminum into the aluminum structure after plating. Therefore, it is possible to produce a structure made of substantially only aluminum as a metal. It becomes possible.

Through the above steps, an aluminum structure having a resin molded body having a metal layer on the surface is obtained. Depending on applications such as various filters and catalyst carriers, it may be used as a composite of resin and metal as it is, or when used as a metal structure without resin due to restrictions on the usage environment, the resin may be removed. Good (claim 5).

Due to the above-described two characteristics that are difficult to break and the plating thickness is uniform inside and outside, when the finished aluminum porous body is pressed, it is possible to obtain a porous body in which the entire skeleton is hardly broken and is uniformly pressed. When an aluminum porous body is used as an electrode material for a battery or the like, the electrode is filled with an electrode active material and the density is increased by pressing, and the skeleton easily breaks during the active material filling process or pressing. It is extremely effective in applications.

According to the present invention, it is possible to plate aluminum on the surface of a porous resin molded body having a three-dimensional network structure in particular, and form an aluminum structure having a high purity and a large area with a substantially uniform thick film. And an aluminum structure can be provided.

It is a flowchart which shows the manufacturing process of the aluminum structure by this invention. It is a cross-sectional schematic diagram explaining the manufacturing process of the aluminum structure by this invention. It is a surface enlarged photograph which shows the structure of the urethane foam resin as an example of a porous resin molding. It is a figure explaining an example of the continuous electroconductivity process of the resin molding body surface with an electroconductive coating material. It is a figure explaining an example of the aluminum continuous plating process by molten salt plating. It is a cross-sectional schematic diagram which shows the structural example which applied the aluminum porous body to the molten salt battery. It is a cross-sectional schematic diagram which shows the structural example which applied the aluminum porous body to the electrical double layer capacitor. It is the surface enlarged photograph of the aluminum structure concerning an Example. It is the surface enlarged photograph of the aluminum structure concerning an Example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as an example of a process for producing a porous aluminum body as a representative example. In the drawings to be referred to below, the same reference numerals are the same or corresponding parts. In addition, this invention is not limited to this, It is shown by the claim, and it is intended that all the changes within the meaning and range equivalent to a claim are included.

(Aluminum structure manufacturing process)
FIG. 1 is a flow diagram showing a manufacturing process of an aluminum structure according to the present invention. FIG. 2 schematically shows a state in which an aluminum structure is formed using a porous resin body as a core material corresponding to the flow diagram. The flow of the entire manufacturing process will be described with reference to both drawings. First, preparation 101 of the base resin molded body is performed. FIG. 2A is an enlarged schematic view in which the surface of a porous resin body (foamed resin molded body) having a three-dimensional network structure is enlarged as an example of the base resin molded body. The pores are formed with the foamed resin molded body 1 as a skeleton. Next, the surface 102 of the resin molded body is made conductive. Through this step, a thin conductive layer 2 made of a conductive material is formed on the surface of the foamed resin molded body 1 as shown in FIG. Subsequently, aluminum plating 103 in molten salt is performed to form an aluminum plating layer 3 on the surface of the resin molded body on which the conductive layer is formed (FIG. 2C). Thus, an aluminum structure in which the aluminum plating layer 3 is formed on the surface using the resin molded body as a base material is obtained. Further, the removal 104 of the base resin molded body may be performed. An aluminum structure (porous body) in which only the metal layer remains can be obtained by disassembling and disappearing the foamed resin molded body 1 (FIG. 2D). Hereinafter, each step will be described in order.

(Preparation of porous resin)
A resin porous body having a three-dimensional network structure is prepared. Arbitrary resin can be selected as the material of the resin porous body. Examples of the material include foamed resin moldings such as polyurethane, melamine resin, polypropylene, and polyethylene. A resin porous body having an arbitrary shape can be selected as long as it has continuous pores (continuous vent holes). For example, what has a shape like a nonwoven fabric entangled with a fibrous resin can be used as the porous resin body. The porous resin body preferably has a porosity of 80% to 98% and a pore diameter of 50 μm to 500 μm. Foamed urethane and foamed melamine can be preferably used as a porous resin body because they have high porosity, have pore connectivity and are excellent in thermal decomposability. Urethane foam (urethane foam) is preferable in terms of pore uniformity and availability, and foamed melamine is preferable in that a product having a small pore diameter is obtained.

The resin porous body often has residues such as foaming agents and unreacted monomers in the foam production process, and it is preferable to perform a washing treatment for the subsequent steps. FIG. 3 shows an example of the porous resin body, which is obtained by washing urethane foam as a pretreatment. The resin molded body forms a three-dimensional network as a skeleton, thereby forming continuous pores as a whole. The urethane skeleton has a substantially triangular shape in a cross section perpendicular to the extending direction. Here, the porosity is defined by the following equation.
Porosity = (1− (weight of porous material [g] / (volume of porous material [cm ³ ] × material density))) × 100 [%]
The pore diameter is an average of the average pore diameter = 25.4 mm / cell count by enlarging the surface of the resin molded body with a micrograph and counting the number of pores per inch (25.4 mm) as the number of cells. Find the value.

(Conductivity of porous resin surface: Carbon coating)
Prepare carbon paint as conductive paint. The suspension as the conductive paint preferably contains carbon particles, a binder, a dispersant and a dispersion medium. In order to uniformly apply the conductive particles, the suspension needs to maintain a uniform suspension state. For this reason, the suspension is preferably maintained at 20 ° C. to 40 ° C. The reason is that when the temperature of the suspension is less than 20 ° C., the uniform suspension state is lost, and only the binder is concentrated on the surface of the skeleton forming the network structure of the porous resin body to form a layer. Because. In this case, the applied carbon particle layer is easy to peel off, and it is difficult to form a metal plating that is firmly adhered. On the other hand, when the temperature of the suspension exceeds 40 ° C., the amount of evaporation of the dispersant is large, and the suspension is concentrated as the coating treatment time elapses, and the amount of carbon applied tends to fluctuate. The particle size of the carbon particles is 0.01 to 5 μm, preferably 0.01 to 0.5 μm. If the particle size is large, the pores of the porous resin body may be clogged or smooth plating may be hindered. If the particle size is too small, it is difficult to ensure sufficient conductivity.

Application of the carbon particles to the resin porous body is possible by immersing the target resin porous body in the suspension, and performing squeezing and drying. FIG. 4 is a diagram schematically showing a configuration example of a processing apparatus that conducts a band-shaped resin porous body serving as a skeleton as an example of a practical manufacturing process. As shown in the figure, this apparatus includes a supply bobbin 12 for supplying a belt-shaped resin 11, a tank 15 containing a conductive paint suspension 14, a pair of squeezing rolls 17 disposed above the tank 15, A plurality of hot air nozzles 16 provided opposite to the back of the belt-like resin 11 to be wound, and a winding bobbin 18 for winding up the belt-like resin 11 after processing. Further, a deflector roll 13 for guiding the belt-shaped resin 11 is appropriately disposed. In the apparatus configured as described above, the strip-shaped resin 1 having a three-dimensional network structure is unwound from the supply bobbin 12, guided by the deflector roll 13, and immersed in the suspension in the tank 15. The strip-shaped resin 11 immersed in the suspension 14 in the tank 15 changes its direction upward and travels between the squeeze rolls 17 above the liquid level of the suspension 14. At this time, the distance between the squeezing rolls 17 is smaller than the thickness of the belt-shaped resin 11, and the belt-shaped resin 11 is compressed. Therefore, the excess suspension impregnated in the belt-shaped resin 11 is squeezed out and returned to the tank 15.

Subsequently, the strip-shaped resin 11 changes the traveling direction again. Here, the suspension dispersion medium and the like are removed by hot air jetted by the hot air nozzle 16 composed of a plurality of nozzles, and the belt-like resin 11 is wound around the winding bobbin 18 after sufficiently drying. The temperature of the hot air ejected from the hot air nozzle 16 is preferably in the range of 40 ° C to 80 ° C. When the apparatus as described above is used, the conductive treatment can be carried out automatically and continuously, and a skeleton having a network structure without clogging and having a uniform conductive layer is formed. The metal plating in the next process can be performed smoothly.

(Formation of aluminum layer: Molten salt plating)
Next, electrolytic plating is performed in a molten salt to form an aluminum plating layer on the surface of the porous resin body. A direct current is applied in a molten salt using a porous resin body having a conductive surface as a cathode and an aluminum plate having a purity of 99.99% as an anode. As the molten salt, a mixed salt (eutectic salt) of aluminum chloride and an organic salt is used. Use of an organic molten salt bath that melts at a relatively low temperature is preferable because plating can be performed without decomposing the porous resin body as a base material. As the organic salt, imidazolium salt, pyridinium salt and the like can be used. Of these, 1-ethyl-3-methylimidazolium chloride (EMIC) and butylpyridinium chloride (BPC) are preferable.

In order to lower the viscosity of the molten salt, the temperature of the molten salt bath is set to 45 ° C. or higher and 100 ° C. or lower. When the temperature is lower than 45 ° C., the viscosity cannot be lowered sufficiently. Moreover, when temperature is higher than 100 degreeC, an organic salt may decompose | disassemble. A more preferable temperature is 50 ° C. or higher and 80 ° C. or lower. Since the molten salt deteriorates when moisture or oxygen is mixed in the molten salt, the plating is preferably performed in an atmosphere of an inert gas such as nitrogen or argon and in a sealed environment.

It is preferable to add 1,10-phenanthroline to the molten salt bath to make the surface smooth. The amount of 1,10-phenanthroline added is preferably 0.25 g / l or more and 7 g / l or less. When the addition amount is less than 0.25 g / l, it is difficult to obtain the effect of smoothing the surface. The effect of smoothing the surface increases as the amount of 1,10-phenanthroline added increases, but the effect does not change much even if the amount is increased to more than 7 g / l. A more preferable range of the addition amount is 2.5 g / l or more and 5 g / l or less.

The method of reducing the viscosity by adding an organic solvent or the like to the molten salt bath requires equipment for preventing volatilization of the organic solvent and safety equipment for preventing ignition by the organic solvent. In the present invention, the temperature is kept within a certain range. Since the viscosity of the molten salt bath is reduced, plating with simple equipment becomes possible. Further, 1,10-phenanthroline does not volatilize in the range of 45 ° C. to 100 ° C., and thus has the same effect.

FIG. 5 is a diagram schematically showing the configuration of an apparatus for continuously performing metal plating on the above-described belt-shaped resin. A configuration in which the belt-like resin 22 whose surface is made conductive is sent from the left to the right in the figure. The first plating tank 21a includes a cylindrical electrode 24, an anode 25 provided on the inner wall of the container, and a plating bath 23. By passing the strip-shaped resin 22 along the cylindrical electrode 24 through the plating bath 23, a uniform current can easily flow through the entire porous resin body, and uniform plating can be obtained. The second plating tank 21b is a tank for applying a thicker and more uniform plating, and is configured to be repeatedly plated in a plurality of tanks. Plating is performed by passing the belt-like resin 22 having a conductive surface through a plating bath 28 while sequentially feeding the belt-like resin 22 by an electrode roller 26 that also serves as a feeding roller and an out-of-vessel feeding cathode. In the plurality of tanks, there are anodes 27 provided on opposite surfaces of the porous resin body via the plating bath 28, and uniform plating can be applied to both surfaces of the porous resin body.

Through the above steps, an aluminum structure (aluminum porous body) having a porous resin body as a skeleton core is obtained. Depending on applications such as various filters and catalyst carriers, the resin and metal composite may be used as they are. Further, the resin may be removed when used as a metal structure having no resin due to restrictions on the use environment. Removal of the resin can be performed by any method such as decomposition (dissolution) with an organic solvent, molten salt, or supercritical water, and thermal decomposition. Since aluminum is difficult to reduce once oxidized, unlike nickel or the like, for example, when used as an electrode material for a battery or the like, it is preferable to remove the resin by a method in which oxidation of aluminum hardly occurs. For example, a method of removing the resin by thermal decomposition in a molten salt described below is preferably used.

(Resin removal: thermal decomposition in molten salt)
Thermal decomposition in the molten salt is performed by the following method. A porous resin body having an aluminum plating layer formed on the surface is immersed in a molten salt, and heated while applying a negative potential to the aluminum layer to decompose the porous resin body. When a negative potential is applied in a state immersed in the molten salt, the porous resin body can be decomposed without oxidizing aluminum. The heating temperature can be appropriately selected according to the type of the porous resin body. However, in order not to melt aluminum, it is necessary to treat at a temperature not higher than the melting point of aluminum (660 ° C.). A preferable temperature range is 500 ° C. or more and 600 ° C. or less. The amount of negative potential to be applied is on the minus side of the reduction potential of aluminum and on the plus side of the reduction potential of cations in the molten salt.

As the molten salt used for the thermal decomposition of the resin, an alkali metal or alkaline earth metal halide salt or nitrate which can lower the electrode potential of aluminum can be used. Specifically, lithium chloride (LiCl), potassium chloride (KCl), sodium chloride (NaCl), aluminum chloride (AlCl ₃ ), lithium nitrate (LiNO ₃ ), lithium nitrite (LiNO ₂ ), potassium nitrate (KNO ₃ ), It is preferable to include one or more selected from the group consisting of potassium nitrite (KNO ₂ ), sodium nitrate (NaNO ₃ ), and sodium nitrite (NaNO ₂ ). By such a method, a porous aluminum body having a thin surface oxide layer and a small amount of oxygen can be obtained.

(Lithium ion battery)
Next, a battery electrode material and a battery using an aluminum porous body will be described. For example, when used for a positive electrode of a lithium ion battery, lithium cobaltate (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium nickelate (LiNiO ₂ ), or the like is used as an active material. The active material is used in combination with a conductive additive and a binder. Conventional positive electrode materials for lithium ion batteries have an active material coated on the surface of an aluminum foil. In order to improve the battery capacity per unit area, the coating thickness of the active material is increased. In order to effectively use the active material, the aluminum foil and the active material need to be in electrical contact with each other, so that the active material is used in combination with a conductive additive. In contrast, the porous aluminum body of the present invention has a high porosity and a large surface area per unit area. Therefore, even if the active material is thinly supported on the surface of the porous body, the active material can be used effectively, the capacity of the battery can be improved, and the mixing amount of the conductive auxiliary agent can be reduced. A lithium ion battery uses the above positive electrode material as a positive electrode, graphite as the negative electrode, and organic electrolyte as the electrolyte. Since such a lithium ion battery can improve capacity even with a small electrode area, the energy density of the battery can be made higher than that of a conventional lithium ion battery.

(Molten salt battery)
The aluminum porous body can also be used as an electrode material for a molten salt battery. When an aluminum porous body is used as a positive electrode material, a metal compound capable of intercalating cations of a molten salt serving as an electrolyte, such as sodium chromite (NaCrO ₂ ) and titanium disulfide (TiS ₂ ) as an active material Is used. The active material is used in combination with a conductive additive and a binder. As the conductive assistant, acetylene black or the like can be used. As the binder, polytetrafluoroethylene (PTFE) or the like can be used. When sodium chromite is used as the active material and acetylene black is used as the conductive additive, PTFE is preferable because both can be firmly fixed.

The aluminum porous body can also be used as a negative electrode material for a molten salt battery. When an aluminum porous body is used as a negative electrode material, sodium alone, an alloy of sodium and another metal, carbon, or the like can be used as an active material. The melting point of sodium is about 98 ° C., and the metal softens as the temperature rises. Therefore, it is preferable to alloy sodium with other metals (Si, Sn, In, etc.). Of these, an alloy of sodium and Sn is particularly preferable because it is easy to handle. Sodium or a sodium alloy can be supported on the surface of the porous aluminum body by a method such as electrolytic plating or hot dipping. In addition, after a metal (such as Si) that is alloyed with sodium is attached to the aluminum porous body by a method such as plating, a sodium alloy can be obtained by charging in a molten salt battery.

FIG. 6 is a schematic sectional view showing an example of a molten salt battery using the battery electrode material. The molten salt battery includes a positive electrode 121 carrying a positive electrode active material on the surface of an aluminum skeleton part of an aluminum porous body, a negative electrode 122 carrying a negative electrode active material on the surface of the aluminum skeleton part of an aluminum porous body, and an electrolyte. A separator 123 impregnated with molten salt is housed in a case 127. Between the upper surface of the case 127 and the negative electrode, a pressing member 126 including a pressing plate 124 and a spring 125 that presses the pressing plate is disposed. By providing the pressing member, even when there is a volume change of the positive electrode 121, the negative electrode 122, and the separator 123, the respective members can be brought into contact with each other by being pressed evenly. The current collector (aluminum porous body) of the positive electrode 121 and the current collector (aluminum porous body) of the negative electrode 122 are connected to the positive electrode terminal 128 and the negative electrode terminal 129 by lead wires 130, respectively.

As the molten salt as the electrolyte, various inorganic salts or organic salts that melt at the operating temperature can be used. As the cation of the molten salt, alkali metals such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb) and cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca) One or more selected from alkaline earth metals such as strontium (Sr) and barium (Ba) can be used.

In order to lower the melting point of the molten salt, it is preferable to use a mixture of two or more salts. For example, when potassium bis (fluorosulfonyl) amide (KFSA) and sodium bis (fluorosulfonyl) amide (NaFSA) are used in combination, the operating temperature of the battery can be made 90 ° C. or lower.

¡Use molten salt by impregnating the separator. A separator is for preventing a positive electrode and a negative electrode from contacting, and a glass nonwoven fabric, a porous resin porous body, etc. can be used for it. The above positive electrode, negative electrode, and separator impregnated with molten salt are stacked and housed in a case to be used as a battery.

(Electric double layer capacitor)
The aluminum porous body can also be used as an electrode material for an electric double layer capacitor. When an aluminum porous body is used as an electrode material for an electric double layer capacitor, activated carbon or the like is used as an electrode active material. Activated carbon is used in combination with a conductive aid and a binder. As the conductive auxiliary agent, graphite, carbon nanotube, etc. can be used. As the binder, polytetrafluoroethylene (PTFE), styrene butadiene rubber or the like can be used.

FIG. 7 is a schematic cross-sectional view showing an example of an electric double layer capacitor using the above electrode material for an electric double layer capacitor. In the organic electrolyte solution 143 partitioned by the separator 142, an electrode material in which an electrode active material is supported on a porous aluminum body is disposed as a polarizable electrode 141. The electrode material 141 is connected to the lead wire 144, and the whole is housed in the case 145. By using an aluminum porous body as a current collector, the surface area of the current collector is increased, and an electric double layer capacitor capable of high output and high capacity can be obtained even when activated carbon as an active material is thinly applied. .

(Formation of conductive layer: carbon coating)
Hereinafter, a production example of the aluminum porous body will be specifically described. A urethane foam having a thickness of 1 mm, a porosity of 95%, and a pore diameter of 300 μm was prepared as a porous resin body, and cut into 80 mm × 50 mm squares. By immersing the urethane foam in a carbon suspension and drying, a conductive layer having carbon particles attached to the entire surface was formed. The components of the suspension include graphite + carbon black 25%, and include a resin binder, a penetrating agent, and an antifoaming agent. The particle size of carbon black was 0.5 μm.

(Conductive layer formation: aluminum deposition)
The same porous resin as in the case of carbon coating was prepared, and aluminum was deposited on the surface to form an aluminum conductive layer having a thickness of 0.7 μm.

(Molten salt plating)
After setting urethane foam with a conductive layer on the surface as a work piece to a jig having a power feeding function, it was put in a glove box with an argon atmosphere and low moisture (dew point -30 ° C or less). It was immersed in a molten salt bath (33 mol% EMIC-67 mol% AlCl ₃ ) having the temperature shown in FIG. In the molten salt bath, 1,10-phenanthroline having the concentrations shown in Tables 1 and 2 was added. The jig on which the workpiece was set was connected to the cathode side of the rectifier, and an aluminum plate (purity 99.99%) was connected to the anode side of the counter electrode. The DC current having the current density shown in Table 1 is applied for 90 minutes in the case of ² A / cm ² (hereinafter referred to as “A / cm ² ”), 30 minutes in the case of 6 ASD, and 10 minutes in the case of 15 ASD. Aluminum was plated. Stirring was performed with a stirrer using a Teflon (registered trademark) rotor. Here, the current density is a value calculated by the apparent area of the urethane foam.

(Decomposition of porous resin)
Each porous resin body on which the aluminum plating layer was formed was immersed in a LiCl—KCl eutectic molten salt at a temperature of 500 ° C., and a negative potential of −1 V was applied for 5 minutes to decompose and remove polyurethane to obtain an aluminum porous body. .

The plating property inside the obtained aluminum porous body was evaluated. As the evaluation of internal plating, the plating thickness inside the porous body is thin, and the case where the urethane foam was removed after peeling into two sheets was marked as x, and the inside of the porous body was plated and the sample did not peel off. It was. In addition, as a cross-sectional evaluation, a sample cut from a cross section perpendicular to the extending direction of the surface portion and the skeleton was extracted from what was plated inside the porous body and the sample did not peel off, embedded in resin and polished Later, the cross section was observed. The cross section was observed, and the case where the thickness of the internal plating was 70% or more of the thickness of the external plating was evaluated as “◯”, the case where it was 50% or more and less than 70% was evaluated as “Δ”, Furthermore, in order to evaluate the surface smoothness of the plating (indicated as “surface” in each table), the aluminum porous body was observed with a scanning electron microscope. Those having large irregularities were marked with ×. The above results are shown in Tables 1 and 2.

As shown in Tables 1 and 2, when the plating temperature was set to room temperature, the plating ability to the inside was poor and the urethane foam was peeled off after removing the urethane foam. When the plating temperature is 60 ° C. or 80 ° C., peeling does not occur and the inside can be plated. However, in the cross-sectional evaluation and surface evaluation in which the plating state is observed in detail, there are many cases where the evaluation is x under the condition that the phenanthroline concentration is 0.25 g / l. In particular, the higher the current density, the worse the evaluation results. When the amount of phenanthroline added is small, it is necessary to lower the current density and perform plating slowly in order to improve the surface smoothness of the plating.

FIG. 8 is a photograph obtained by observing, with a scanning electron microscope, an aluminum structure produced by performing aluminum plating at a phenanthroline concentration of 0.25 g / l, a current density of 6 ASD, and a plating temperature of 60 ° C. with respect to a sample in which an aluminum conductive layer is formed. . FIG. 9 is a photograph of an aluminum structure produced by performing aluminum plating on a sample in which an aluminum conductive layer is formed at a phenanthroline concentration of 5 g / l, a current density of 6 ASD, and a plating temperature of 60 ° C., as observed with a scanning electron microscope. In FIG. 9 where the phenanthroline concentration is high, the surface of the aluminum plating is smooth, but in FIG. 8 where the phenanthroline concentration is low, it can be seen that the plating surface is uneven.

As described above, according to the present invention, it is possible to obtain a structure in which the surface of a resin molded body is plated with aluminum, and an aluminum structure from which the resin molded body is removed. The present invention can be widely applied to the case where the characteristics of aluminum are utilized in electric materials, filters for various types of filtration, catalyst carriers, and the like.

DESCRIPTION OF SYMBOLS 1 Foamed resin molding 2 Conductive layer 3 Aluminum plating layer 11 Band-shaped resin 12 Supply bobbin 13 Deflector roll 14 Suspension 15 tank 16 Hot air nozzle 17 Drawing roll 18 Winding bobbin 21a, 21b Plating tank 22 Band-shaped resin 23, 28 Plating bath 24 Cylindrical electrode 25, 27 Positive electrode 26 Electrode roller 121 Positive electrode 122 Negative electrode 123 Separator 124 Holding plate 125 Spring 126 Pressing member 127 Case 128 Positive electrode terminal 129 Negative electrode terminal 130 Lead wire 141 Polarized electrode 142 Separator 143 Organic electrolyte 144 Lead wire 145 cases

Claims (6)

1. A method for producing an aluminum structure comprising a step of plating aluminum in a molten salt bath on a resin porous body having a three-dimensional network structure at least having a conductive surface,
   The molten salt is a mixed salt of aluminum chloride and an organic salt, and is plated at a temperature of the molten salt bath of 45 ° C. or higher and 100 ° C. or lower.
2. The method for producing an aluminum structure according to claim 1, wherein the molten salt bath further contains 1,10-phenanthroline at a concentration of 0.25 g / l or more and 7 g / l or less.
3. The method for producing an aluminum structure according to claim 1 or 2, wherein the organic salt is an imidazolium salt.
4. The method for producing an aluminum structure according to any one of claims 1 to 3, wherein the resin porous body is polyurethane or melamine resin.
5. The method for producing an aluminum structure according to any one of claims 1 to 4, further comprising a step of removing the resin molded body after the step of plating.
6. An aluminum structure produced by the production method according to any one of claims 1 to 5.

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