JP2013246945A - Method for manufacturing electrode using porous metal collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode using a porous metal collector capable of filling electrode mixtures containing active material into an empty hole of a collector made of a porous metal with high density.SOLUTION: In the method or manufacturing an electrode having an electrode mixture containing active material, an electrode using a porous metal collector is manufactured by mounting a porous metal collector having an empty hole filled with electrode mixtures on a filter for causing a solvent of slurry with the electrode mixtures scattered to permeate, injecting the slurry to a high pressure side while pressure of a side with porous metal mounted through the filter is higher than that of the opposite side, accumulating a residue of the slurry in the empty hole made of the porous metal by filtering the slurry with the filer while permeating the slurry into the porous metal, drying the porous metal with the residue accumulated in the empty hole to scatter and evaporate the solvent and filling the electrode mixtures into the empty hole.

Description

  The present invention relates to a method for producing an electrode using a porous metal current collector, which can be filled with an electrode mixture containing an active material in pores of the porous metal at a high packing density.

  A metal foil such as an aluminum foil or a copper foil is generally used as an electrode current collector (support) that carries the positive electrode material or the negative electrode material. A porous aluminum current collector has been proposed as an electrode current collector for the purpose of increasing the capacity instead of such a metal foil.

Patent Document 1 describes a high energy density electrode in which porous aluminum having a characteristic metal skeleton cross-sectional shape is filled with an active material. This porous aluminum forms a metal film that forms a low-melting eutectic alloy with aluminum on the skeleton of foamed resin, and after depositing aluminum powder on it, the foamed resin is burned off and the metals are sintered together To obtain.
Patent Document 2 describes a high energy density current collector in which titanium is used as a sintering aid and porous aluminum produced by a slurry foaming method is filled with an active material.

  However, the conventional electrode using the porous aluminum current collector has a problem that the amount of the active material filled in the pores of the porous aluminum is not sufficient, and a desired electrode capacity cannot be obtained.

JP-A-8-170126 JP 2010-236082 A

  An object of the present invention is to provide a method for producing an electrode using a porous metal current collector that can be filled with an electrode mixture containing an active material at high density in the pores of the current collector made of the porous metal. That is.

  In order to fill the electrode mixture in the pores of the porous metal, a method of pushing the slurry containing the electrode mixture into the porous metal with a spatula or the like is usually employed. In such a system, the composition of the slurry existing in the pores is the same as before the pushing, and finally, only a small amount of the electrode mixture component remaining together with the solvent in the pores can be filled in the pores. In addition, a dipping method is also employed in which the electrode mixture component is diffused into the pores of the porous metal by dipping the porous metal in the slurry. However, even in this method, only a small amount of the electrode mixture component diffused with the solvent in the pores can be filled in the pores.

  As a result of intensive studies to solve the above-mentioned problems, the inventors have placed a porous metal on a filter that allows the solvent in the slurry in which the electrode mixture is dispersed to pass through the porous metal, and the slurry is passed through the filter. It was found that a large amount of the electrode mixture component blocked by permeation of the slurry solvent through the filter can be retained in the pores by adopting a method of filtering the slurry. Thereby, the electrode mixture containing the active material can be filled into the pores of the porous metal with high density, and an electrode having a high electrode capacity can be obtained.

  That is, the present invention provides a method for producing an electrode containing an electrode mixture containing an active material according to claim 1, wherein the electrode mixture is on a filter that allows the solvent in the slurry in which the electrode mixture is dispersed to pass therethrough. Place the porous metal current collector with pores to be filled, and inject the slurry into the high pressure side with the pressure on the side where the porous metal is placed through the filter higher than the opposite side Then, the slurry filtrate is filtered through a filter while penetrating the slurry inside the porous metal, thereby depositing the filtrate of the slurry in the pores of the porous metal, and the porous metal in which the filtrate is deposited in the pores. A method for producing an electrode using a porous metal current collector is characterized in that the pores are filled with the electrode mixture by drying and scattering and evaporating the solvent.

  In the second aspect of the present invention, in the first aspect, the filter has a pore size smaller than the particle size of the active material.

  According to a third aspect of the present invention, in the first or second aspect, the slurry is filtered with a filter until the surface of the porous metal is covered with the filtrate of the slurry, and the surface of the porous metal is covered before drying. Excess filtrate was removed. Furthermore, in the present invention, the present invention is the fourth aspect, wherein the slurry is filtered by a filter until the surface of the porous metal is covered with the filtrate of the slurry, and the surface of the porous metal is covered after drying. It was assumed that the excess electrode mixture was removed.

  According to a fourth aspect of the present invention, the method according to any one of the first to fourth aspects of the present invention further comprises a step of pressing a porous metal in which pores are filled with the electrode composite material after the electrode composite material filling step. It was supposed to be prepared.

  By the electrode manufacturing method using the porous metal current collector according to the present invention, an electrode in which the electrode mixture containing the active material is filled in the pores of the porous metal current collector with high density is obtained. High energy density lithium ion secondary batteries and capacitors can be manufactured.

It is a scanning electron micrograph which shows the cross section of the porous aluminum electrical power collector used for this invention. It is a schematic diagram explaining the manufacturing method of the electrode using the porous metal electrical power collector which concerns on this invention.

  In the method for producing an electrode using a porous metal current collector that contains an electrode mixture containing an active material according to the present invention, the electrode composite is placed on a filter that allows the solvent in the slurry in which the electrode mixture is dispersed to pass through. A porous metal having pores filled with a material is placed. Then, the pressure on the side where the porous metal is placed through the filter is higher than that on the opposite side, and the slurry in which the electrode mixture is dispersed in the solvent is injected into the high pressure side, and this slurry penetrates into the porous metal. And filter through a filter. Thereby, a large amount of the slurry filtrate can be deposited in the pores of the porous metal. Thus, the porous metal in which the filtrate is deposited in the pores is dried, and the solvent is scattered and evaporated to fill the pores with the electrode mixture. Moreover, it is preferable to filter the slurry with a filter until the surface of the porous metal is covered with the filtrate of the slurry, and to remove excess filtrate or the electrode mixture covering the surface of the porous metal. Thereby, the electrode mixture can be filled with high density in the entire pores of the porous metal. In addition, it is preferable to adjust the filling density of the electrode mixture by further pressing the porous metal in which the electrode mixture is filled in the pores.

1. Porous metal 1-1. Structure and Shape As shown in FIG. 1, the porous metal used in the present invention is a porous sintered body having a metal wall 2 formed by sintering metal powder as a skeleton. A number of pores 1 are formed in the porous metal, and the pores 1 are defined by metal walls 2. A small hole 3 is opened in the metal wall 2, and the holes 1 communicate with each other through the small hole 3. The electrode mixture containing the active material filled in the holes 1 is held so as to be enclosed by the metal wall 2 surrounding the holes 1.

  The shape of the porous metal can be an arbitrary shape such as a sheet shape or a cylindrical shape depending on the electrode shape. The thickness is preferably about 200 μm to 1 mm, and the pore diameter is preferably about 10 to 1000 μm. Here, the hole diameter means the maximum inner diameter of the hole. The small holes 3 formed in the metal wall 2 have various shapes such as a circle, an ellipse, and a rectangle.

1-2. Porosity The porosity of a porous metal is defined by the porosity. The porosity of the porous metal used in the present invention is preferably 80 to 95%. If it is less than 80%, the pores 1 may not be filled with a large amount of the electrode mixture component. On the other hand, if it exceeds 95%, the strength of the porous metal itself may be insufficient and the function as a current collector may not be achieved.

The porosity p (%) of the porous metal is calculated by the following formula (1).
p = [{hv− (hw / d)} / hv] × 100 (1)
Here, hv: the total volume of the porous metal (cm ³ )
hw: Mass of porous metal (g)
d: Density (g / cm ³ ) of the metal material.

2. Electrode mixture The electrode mixture to be used is supported in a state filled in the pores of the porous metal. The electrode mixture may contain a conductive additive and a binder in addition to the active material.

2-1. Active material The active material used is suitable for the battery in which the electrode is used. When the electrode according to the present invention is used, for example, as a positive electrode for a nonaqueous electrolyte secondary battery, the positive electrode active material may be a lithium metal oxide such as lithium cobaltate, lithium manganate, lithium nickelate, or lithium iron phosphate. Etc. can be used. When used for a negative electrode for non-aqueous electrolyte secondary batteries, the negative electrode active material includes natural graphite, artificial graphite, mesocarbon microbeads (MCMB), carbon materials such as hard carbon and soft carbon; Al, Si, Sn, etc. Metal materials and alloy materials that can be combined with lithium; oxide materials such as lithium titanate (Li ₄ Ti ₅ O ₁₂ ) can be used.

2-2. Conductive aid By adding a conductive aid to the electrode mixture, the conductivity of the electrode mixture is improved. As the conductive aid used, carbon powder, metal powder, and the like are used, and among these, carbon powder is preferably used. Examples of the carbon powder include acetylene black, ketjen black, furnace black, and carbon nanotube. Among these, it is preferable to use acetylene black that has a relatively long length as an aggregate and can improve conductivity even when the addition amount is small.

2-3. Binder By adding a binder to the electrode mixture, the binding of components via the binder, that is, the bonding between the active materials, the conductive assistants, and the active material and the conductive assistant is strengthened. This makes it difficult for the active material to fall off the current collector. It does not specifically limit as a binder to be used, A well-known or commercially available thing can be used. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and the like.

  When a conductive additive and a binder are added to the electrode mixture, the ratio of the active material to the total electrode mixture (active material + conductive additive + binder) is 85 to 95% by mass. preferable. If this ratio is less than 85% by mass, the active material may be insufficient and high electrode capacity may not be achieved. On the other hand, if this ratio exceeds 95% by mass, the conductivity of the entire electrode is reduced, and sufficient coupling between components and between components cannot be obtained, and this also makes it impossible to achieve high electrode capacity.

2-4. Packing density of electrode mixture The packing density of an electrode mixture containing an active material is defined as the mass of the electrode mixture filled per unit volume of pores in the porous metal. Specifically, it calculates | requires as follows. First, from the total volume of the electrode, the volume of the metal material obtained by dividing the mass of the porous metal by the density of the metal material constituting the porous metal is subtracted to obtain the void volume (cm ³ ) in the electrode. Next, the mass (g) of the electrode mixture is obtained by subtracting the mass of the porous metal before filling the electrode mixture from the total mass of the porous metal after filling. Finally, the mass (g) of the electrode mixture is divided by the pore volume (cm ³ ), and the amount of electrode mixture (g / cm ³ ) filled in the pores per unit volume is obtained to determine the packing density and To do.

Such a filling density is preferably more than 50% of the composite density. Here, the composite material density refers to the density of the composite material layer obtained by applying the composite material slurry to the aluminum foil in the manner of providing the composite material layer and drying it. The composite density is the value obtained by subtracting the mass (g) of the aluminum foil from the total mass (g) of the aluminum foil coated with the composite slurry, and the aluminum foil from the total volume (cm ³ ) of the aluminum foil coated with the composite slurry. Divided by the value obtained by subtracting the volume (cm ³ ). When the packing density is 50% or less of the composite material density, the amount of active material contained in the electrode is small and sufficient electrode capacity cannot be obtained. On the other hand, the upper limit of the packing density is not particularly limited. However, when the packing density after the press treatment exceeds 250% of the composite material density, it becomes difficult for the electrolyte solution to penetrate into the electrode, and the charged component such as lithium ion does not reach In some cases, diffusion is hindered and battery characteristics are deteriorated.

3. Manufacturing method of electrode 3-1. Method for producing porous metal After pressure-molding a mixed powder of metal powder and support powder at a predetermined pressure, the pressure-molded body in an inert atmosphere at a temperature not less than 0.5 times the melting point of the metal powder, And it sinters by the heat processing in the range which does not exceed 1.05 times the melting | fusing point of metal powder, and a porous metal is manufactured by removing a support powder after that.

(A) Metal powder The metal powder used in the present invention includes pure aluminum powder, aluminum alloy powder or an aluminum powder which is a mixture thereof; and metal powder such as titanium powder, copper powder, nickel powder and SUS powder, and alloy powder. And mixed powders thereof are used. From the viewpoints of lightness and corrosion resistance, it is preferable to use aluminum powder.

  When aluminum powder is used, it is preferable to use pure aluminum powder if the alloy components cause corrosion resistance deterioration under the usage environment. Pure aluminum is aluminum having a purity of 99.0 mass% or more. On the other hand, when it is desired to obtain higher strength, it is preferable to use aluminum alloy powder or a mixture of this and pure aluminum powder. As the aluminum alloy, 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, and 7000 series aluminum alloys are used.

  When aluminum powder is used, a mixture obtained by adding additive element powder to pure aluminum powder may be used. As such an additive element, a plurality of elements consisting of a single element selected from magnesium, silicon, titanium, iron, nickel, copper, zinc and the like or any combination of two or more are preferably used. Such a mixture forms an alloy of aluminum and an additive element by heat treatment. Depending on the type of additive element, an intermetallic compound of aluminum and the additive element is further formed. Various effects can be obtained by including such an aluminum alloy or an intermetallic compound. For example, in an aluminum alloy of aluminum and an additive element such as silicon or copper, the melting point of the aluminum powder is lowered and the temperature required for the heat treatment can be lowered, so that the energy required for production can be reduced and the strength by alloying can be reduced. Will improve. Further, when an intermetallic compound of aluminum and an additive element such as nickel is formed, heat is generated and sintering is promoted, and a structure in which the intermetallic compound is dispersed is formed, so that high strength can be achieved.

  The additive element powder may be added to the aluminum alloy powder, or the additive element powder may be added to a mixture of the aluminum alloy powder and the pure aluminum powder. In these cases, new alloy systems and intermetallic compounds are formed. Furthermore, an additive element alloy powder obtained by alloying a plurality of additive element powders may be used as the additive element powder. The addition amount of the additive element powder or additive element alloy powder to the aluminum alloy powder or pure aluminum powder is appropriately determined based on the chemical formula amount of the alloy or intermetallic compound to be formed.

  The particle size of the metal powder is preferably 1 to 50 μm. In order to uniformly cover the surface of the support powder with the metal powder in the production of the porous metal current collector, the metal powder preferably has a smaller particle size, more preferably 1 to 10 μm. The particle size of the metal powder is defined by the median diameter measured by the laser diffraction scattering method (microtrack method). Even when aluminum powder is used as the metal powder, the particle diameters of pure aluminum powder, aluminum alloy powder, additive element powder and additive element alloy powder are preferably 1 to 50 μm, and more preferably 1 to 10 μm, as described above.

(B) Support powder In the present invention, the support powder is preferably a water-soluble salt, and sodium chloride or potassium chloride is preferably used because of its availability. Since the space formed by removing the supporting powder becomes pores of the porous metal, the particle size of the supporting powder is reflected in the pore diameter. Therefore, the particle size of the support powder used in the present invention is preferably 10 to 1000 μm. The particle size of the support powder is defined by the opening of the sieve. Therefore, a porous metal having a uniform pore diameter can be obtained by aligning the particle diameter of the support powder by classification.

(C) Metal plate In this invention, you may use the mixed powder of a metal powder and support powder in the state compounded with the metal plate. The metal plate is a non-porous plate or foil, and a net-like body such as a perforated wire mesh, expanded metal, or punching metal. The metal plate serves as a support, and the strength of the porous metal current collector is improved and the conductivity is further improved. As the metal plate, a material that does not evaporate or decompose during heat treatment, specifically, a metal such as aluminum, titanium, iron, nickel, copper, or an alloy thereof can be suitably used.

The composite of the mixed powder and the metal plate refers to an integrated state in which, for example, when a metal mesh is used for the metal plate, the entire net is covered with the mixed powder while filling the mixed powder in the mesh. When, for example, a catalyst or an active material is filled in a porous metal provided with bonded metal powder walls on both sides of the metal plate, if the metal plate is a perforated network, the filling is from one side of the region divided by the metal plate. However, since the other region can be filled, the metal plate is preferably a net-like body. Here, the perforated means a mesh part of a metal mesh, a punch part of a punching metal, a mesh part of an expanded metal, and a gap part between fibers of metal fibers.
The pore diameter of the perforated body of the network may be larger or smaller than the diameter of the pores obtained by removing the supporting powder from the joined mixed powder.
The aperture ratio of the perforated holes in the network is preferably large so as not to impair the porosity of the porous metal current collector.

(D) Mixing method The mixing ratio of the metal powder and the support powder is preferably such that Val / (Val + Vs), which is the volume ratio of the metal powder, is 5 to 20%, more preferably 5 with the respective volumes being Val and Vs. -10%. Here, the volumes Val and Vs are values obtained from the respective mass and specific gravity. When the volume ratio of the metal powder exceeds 20%, the support powder content is too small and the support powders exist independently without contacting each other, and the support powder cannot be removed sufficiently. . Support powder that cannot be removed causes corrosion of the porous metal. On the other hand, when the volume ratio of the metal powder is less than 5%, the metal wall constituting the porous metal becomes too thin, the strength of the porous metal becomes insufficient, and handling and shape maintenance become difficult.
Also, in order to achieve a state where the support powder is sufficiently covered with the metal powder, the particle size (dal) of the metal powder is sufficiently smaller than the particle size (ds) of the support powder, for example, dal / ds. Is preferably 0.1 or less.

  In addition, as a mixing means for mixing the metal powder with the support powder, a vibration agitator, a container rotation mixer, or the like is used, but there is no particular limitation as long as a sufficient mixed state can be obtained.

(E) Pressure molding method The pressure during pressure molding is preferably 200 MPa or more. By forming by applying sufficient pressure, the metal powders rub against each other, and the strong oxide film on the surface of the metal powder that inhibits the sintering of the metal powders is destroyed. This oxide film confines molten metal, prevents contact with each other, and is inferior in wettability with molten metal, and has the effect of rejecting liquid metal. Therefore, when the pressure of pressure molding is less than 200 MPa, the destruction of the oxide film on the surface of the metal powder is insufficient, and the metal melted during heating oozes out of the molded body to form a ball-shaped metal lump. There is a case. When an electrode is produced in the presence of a metal lump, this ball-shaped metal lump breaks through the separator, causing a short circuit. It is preferable that the molding pressure is as large as the apparatus and mold used allow the porous metal wall to be formed to be strong. However, if it exceeds 400 MPa, the effect tends to be saturated. For the purpose of enhancing the releasability of the pressure-molded body, it is preferable to use a lubricant such as a fatty acid such as stearic acid, a metal soap such as zinc stearate, various waxes, synthetic resins, and olefinic synthetic hydrocarbons.

(F) Compounding method When the mixed powder is pressure-molded, the mixed powder filled in the molding die and the metal plate may be compounded. As a composite form, a metal plate may be sandwiched between mixed powders, or a mixed powder may be sandwiched between metal plates. Further, the composite of the mixed powder and the metal plate can be repeated to make multiple stages. At the time of compounding, mixed powders having different particle sizes and mixing ratios of metal powder and support powder, and a plurality of different types of metal plates can be combined.

(G) Heat treatment method The heat treatment is performed in the vicinity of the melting point of the metal powder to be used, at a temperature of at least 0.5 times the melting point and not exceeding 1.05 times the melting point of the metal powder. Even when the mixed powder is combined with a metal plate, heat treatment is performed at a temperature near the melting point of the metal powder, at least 0.5 times the melting point. Here, the melting point of the metal powder is a temperature at which a liquid phase is generated in the case of a single substance, and a temperature at which a liquid phase of a single component having the highest proportion is generated in the case of an alloy. Similarly, the melting point of the metal plate is a temperature at which a liquid phase is generated. In particular, when aluminum powder is used as the metal powder, heat treatment is performed at a temperature equal to or higher than its melting point. Even when the mixed powder of the aluminum powder and the supporting powder is combined with the metal plate, heat treatment is performed at a temperature equal to or higher than the melting point of the aluminum powder. Since a strong oxide film exists on the surface of the aluminum powder, the liquid phase oozes out of the aluminum powder or this and the metal plate by heating to a temperature at which the liquid phase is generated above the melting point of the aluminum powder. By contacting each other, the aluminum powders, and the aluminum powder and the metal plate are firmly bonded metallically.

  When the heat treatment temperature is less than 0.5 times the melting point of the metal powder, the sintering between the metal powders and between the metal powder and the metal plate becomes insufficient. In the case of aluminum powder, a liquid phase is not generated from the aluminum powder unless its melting point is exceeded, so that the bonding between the aluminum powder and the aluminum powder and the metal plate becomes insufficient. By heating the metal powder to a melting point of 0.5 times or more of the melting point of the metal powder, the metal powder covering the surface of the support powder located on the outermost surface of the sintered body is removed, and a sintered body having a surface with a large aperture ratio is obtained. It is formed. A large aperture ratio of the sintered body is advantageous for filling the active material when applied to the current collector.

  When the heating temperature exceeds 1.05 times the melting point of the metal powder, the viscosity of the molten metal decreases, and the molten metal oozes out to the outside of the pressure-formed body, forming a convex metal lump. Is done. When an electrode is produced in the presence of a metal block, this convex portion breaks the separator and causes a short circuit, which is a harmful effect. The heat holding time in the heat treatment is preferably about 1 to 60 minutes. Further, a load may be applied to the pressure-formed body during the heat treatment to compress the pressure-formed body, or heating and cooling may be repeated a plurality of times.

The inert atmosphere in which the heat treatment is performed is an atmosphere that suppresses metal oxidation, and an atmosphere of vacuum; nitrogen, argon, hydrogen, decomposed ammonia, and a mixed gas thereof is preferably used, and a vacuum atmosphere is preferable. The vacuum atmosphere is preferably 2 × 10 ⁻² Pa or less, more preferably 1 × 10 ⁻² Pa or less. When it exceeds 2 × 10 ⁻² Pa, removal of moisture adsorbed on the surface of the metal powder becomes insufficient, and oxidation of the metal surface proceeds during heat treatment. As described above, the oxide film on the metal surface is inferior in wettability with the liquid metal, and as a result, the molten metal exudes and a ball-like lump is formed. In the case of an inert gas atmosphere such as nitrogen, it is preferable that the oxygen concentration is 200 ppm or less and the dew point is −35 ° C. or less.

(H) Support powder removal method The support powder in the sintered body is preferably removed by eluting the support powder into water. The supporting powder can be easily eluted by a method such as immersing the sintered body in a sufficient amount of water bath or flowing water bath. When a water-soluble salt is used as the support powder, the water for eluting it is preferably free from impurities such as ion exchange water or distilled water, but tap water is not particularly problematic. The immersion time is usually appropriately selected within the range of several hours to 24 hours. Elution can be promoted by applying vibration by ultrasonic waves or the like during the immersion.

3-2. Method for filling electrode mixture (a) Preparation of filling slurry The electrode mixture is filled into the pores of the porous metal produced as described above. The electrode mixture preferably contains an active material, and further contains a conductive additive and a binder. The concentration of the active material, the conductive additive, and the binder in the slurry is not limited. For example, the concentration may be selected so that the viscosity of the slurry becomes a viscosity suitable for filtration. Further, a thickener may be added to adjust the viscosity, and a dispersant may be added to obtain a good dispersion state. The solvent for the slurry is not particularly limited, and for example, N-methyl-2-pyrrolidone, water and the like are preferably used. When using polyvinylidene fluoride as a binder, it is preferable to use N-methyl-2-pyrrolidone as a solvent. When using polytetrafluoroethylene, polyvinyl alcohol, carboxymethyl cellulose (CMC), etc. as a binder, Preferably, water is used as a solvent.

(B) Slurry filtration Slurry in which an active material, conductive auxiliary agent and / or binder as necessary, and electrode mixture components such as thickener and / or dispersant as necessary are dispersed or dissolved in a solvent. Is filtered by a filter through a porous metal. In the present invention, it is important to mainly deposit the active material in the electrode mixture component into pores of the porous metal by using a filter as a filtered material. The active material in the slurry is subjected to cake filtration by the deposited filtrate, but in order to filter the active material in a larger amount, the pore size of the filter is preferably smaller than the particle size of the active material. Of the electrode mixture components other than the active material, those having a particle size smaller than that of the active material, such as a conductive additive, are more easily transmitted through the filter than the active material. Further, among the electrode mixture components other than the active material, those that dissolve in a solvent such as a binder pass through the filter together with the solvent.

  The filtration process will be described. As shown in FIG. 2, the filter 4 is set in the funnel 9, and the porous metal 5 is placed thereon. The pressure on the side on which the porous metal 5 is placed is set higher than that on the opposite side through the filter 4. Such a pressure difference may depressurize the side opposite to the side on which the porous metal 5 is placed, or pressurize the side on which the porous metal 5 is placed instead. When reducing the pressure, it is preferable to reduce the pressure by 0.01 to 0.1 MPa from atmospheric pressure. On the other hand, when pressurizing, it is preferable to pressurize 0.01 to 0.5 MPa.

  In this way, the slurry 8 in which the electrode mixture 10 is dispersed in the solvent 6 is injected into the high pressure side of the funnel 9 in which the filter 4 and the porous metal 5 are set. The slurry 8 is filtered by the filter 4 while penetrating into the porous metal 5 due to the pressure difference. The slurry solvent 6 permeates the filter, and the slurry filtrate 7 is gradually deposited in the pores so as to fill the pores (indicated by 1 in FIG. 1) of the porous metal 5. After the filtrate 7 is deposited in the pores of the porous metal 5, excess filtrate 7 that cannot be deposited in the pores is deposited so as to cover the surface of the porous metal 5. In the present invention, it is preferable to continue filtering the slurry 8 until such a state is reached. This is because the filtrate 7 is deposited in all the holes to increase the packing density of the electrode mixture. Here, the filtered product 7 is a paste-like material in which the solvent in the slurry 8 is reduced and hardly has fluidity.

  The excess filtrate 7 deposited so as to cover the surface of the porous metal 5 is peeled off from the surface of the porous metal 5 using a spatula or the like. Such removal may be performed immediately after filtration or after drying described later.

(C) Scattering / evaporation of solvent The porous metal on which the slurry is deposited as described above is dried by scattering / evaporating the solvent. The drying conditions are as long as the solvent can be sufficiently scattered / evaporated. It is not particularly limited. As specific drying conditions, it is preferable to hold at 50 to 200 ° C. for 1 to 60 minutes.

3-3. Press treatment The packing density of the electrode mixture containing the active material is adjusted by subjecting the porous metal current collector thus produced to press treatment using a roll press or a flat plate press. Is preferred. As a pressing method, it is desirable to use a flat plate press. The pressure of the press treatment may be appropriately selected so that the filling density exceeds 50% of the composite density as described above, preferably 60% or more, and more preferably 80 to 250%.

4). Battery The electrode according to the present invention is, for example, a positive electrode and a negative electrode for a non-aqueous electrolyte secondary battery as described above, and these electrodes are combined using a separator disposed between the positive and negative electrodes and a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery is obtained. As the separator, generally used polymer films such as polyethylene (PE) and polypropylene (PP) are used. As the non-aqueous electrolyte, lithium hexafluorophosphate (LiPF ₆ ) or lithium perchlorate (LiClO ₄ ) dissolved in an organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC) is used. it can.

  The present invention will be specifically described below with reference to invention examples and comparative examples. The present invention is not limited to the following examples.

1. Invention Example 1
(Preparation of porous aluminum)
First, porous aluminum was produced as follows as a porous metal current collector used in the present invention.
The following pure aluminum powder (A1) was used as the aluminum powder, and the following sodium chloride powder (B1) was used as the support powder. These powders were mixed at a volume ratio of A1: B1 = 1: 9 to prepare a mixed powder.

A1: Pure aluminum powder (aluminum purity 99.9 mass%), median diameter 3 μm (melting point: 660 ° C.)
B1: Particle size 400 μm (median sieve opening) (melting point: 800 ° C.)

The mixed powder was filled in a mold having a hole with a diameter of 13 mm, and pressure-molded at a pressure of 400 MPa. The filling amount of the mixed powder was set to a mass at which the thickness of the pressure molded body was 1 mm. This press-molded body was heat-treated at a temperature of 670 ° C. for 5 minutes in an atmosphere having a maximum ultimate pressure of 1 × 10 ⁻² Pa or less to produce a sintered body. Next, the obtained sintered body was immersed in flowing water (tap water) at 20 ° C. for 6 hours to elute the supporting powder. Further, the sintered body was dried at 105 ° C. for 1 hour. In this way, a porous aluminum sample (φ13 mm × thickness 1 mm) having a porosity of 90% was produced.

(Filling electrode mixture)
Lithium iron phosphate (LiFePO ₄ , particle size 3 μm) 89.5 parts by weight as a positive electrode active material, acetylene black (particle size 48 nm) 5.0 parts by weight as a conductive assistant, PVDF (mesh opening 355 μm below sieve) ) Using 5.5 parts by weight, these were dispersed in 200 parts by mass of NMP as a solvent to prepare slurry 1 of electrode mixture.

The porous aluminum sample was placed on a filter paper having a pore diameter of 1 μm, and the side opposite to the porous aluminum sample was decompressed with a rotary pump through the filter paper. Slurry 1 was supplied to the porous aluminum sample side, which is on the high pressure side, through the filter paper, and the slurry 1 was filtered through the filter paper while allowing the slurry 1 to penetrate into the porous aluminum sample. The filtration of slurry 1 was continued until the surface of the porous aluminum sample was completely covered with the filtrate of slurry 1. Thereafter, excess filtrate on the surface of the porous aluminum sample was removed by removing with a spatula. Furthermore, this porous aluminum sample was dried at 120 ° C. for 1 hour. The packing density of the electrode mixture was 0.92 g / cm ³ . Since the density of the mixture layer obtained by applying slurry 1 on aluminum foil and drying was 1.50 g / cm ³ , the packing density was 61% of this mixture density. The case where the filling density exceeds 50% of the composite material density is accepted, and the case where it is 50% or less is rejected.

  The mass ratio of the porous aluminum sample to the entire electrode was obtained by dividing the mass of the porous aluminum sample before filling with the electrode mixture by the mass after filling and drying the electrode mixture. This mass proportion was 22%.

2. Invention Example 2
In Invention Example 1, instead of depressurizing the opposite side of the porous aluminum sample through the filter paper, the porous aluminum sample side was pressurized (0.2 MPa), and after filtration, excess filtrate on the surface of the porous aluminum sample Instead of removing, the excess electrode mixture on the surface of the porous aluminum sample was removed by drying and peeling off with a spatula. Except for these, the electrode mixture was filled in a porous aluminum sample in the same manner as in Invention Example 1. The filling density of the electrode mixture was 0.95 g / cm ³ , which was 63% of the mixture density. Moreover, the mass ratio of porous aluminum was 22%.

3. Invention Example 3
Except for using a filter paper having a pore diameter of 6 μm, slurry 1 is supplied to the porous aluminum sample side, which is the high pressure side, through the filter paper in the same manner as in Invention Example 1, and the filter paper is used to penetrate the slurry 1 into the porous aluminum sample. Slurry 1 was filtered. The filtration of slurry 1 was continued until the surface of the porous aluminum sample was completely covered with the filtrate of slurry 1. Thereafter, excess filtrate on the surface of the porous aluminum sample was removed by removing with a spatula. Compared with Invention Example 1, the amount of active material passing through the filter was large, and it took a long time until the surface of the porous aluminum sample was completely covered with the filtrate of the slurry 1. Furthermore, this porous aluminum sample was dried at 120 ° C. for 1 hour. The filling density of the electrode mixture was 0.90 g / cm ³ , which was 60% of the mixture density. Moreover, the mass ratio of porous aluminum was 23%.

4). Comparative Example 1
(Preparation of porous aluminum)
The same porous aluminum sample as in Invention Example 1 was used.
(Filling electrode mixture)
Lithium iron phosphate (LiFePO ₄ , particle size 3 μm) 89.5 parts by weight as a positive electrode active material, acetylene black (particle size 48 nm) 5.0 parts by weight as a conductive assistant, PVDF (mesh opening 355 μm below sieve) ) Using 5.5 parts by weight, these were dispersed in 150 parts by mass of NMP as a solvent to prepare slurry 2 of an electrode mixture. The amount of solvent in the slurry was reduced as compared with Invention Examples 1 and 2. The reason is that when the slurry viscosity is about the same as that of Invention Examples 1 and 2, the slurry filled in the pores of the porous aluminum sample does not stay in the pores and easily leaks to the outside. is there.

Using the above immersion method, the porous aluminum sample was immersed in the slurry 2, and the pressure was reduced by a rotary pump for 5 minutes. Next, after returning to atmospheric pressure, excess deposits adhered to the surface of the porous aluminum sample were removed by removing with a spatula. Thereafter, the porous aluminum sample was dried at 120 ° C. for 1 hour. The packing density of the electrode mixture was 0.49 g / cm ³ . Since the density of the mixture layer obtained by applying slurry 2 on aluminum foil and drying was 1.49 g / cm ³ , the packing density was 33% of this mixture density. The mass proportion of porous aluminum was 36%.

5. Comparative Example 2
(Filling electrode mixture)
Lithium iron phosphate (LiFePO ₄ , particle size 3 μm) 89.5 parts by weight as a positive electrode active material, acetylene black (particle size 48 nm) 5.0 parts by weight as a conductive assistant, PVDF (mesh opening 355 μm below sieve) ) Using 5.5 parts by weight, these were dispersed in 125 parts by weight of NMP to prepare slurry 3 of an electrode mixture. In Comparative Example 1, the slurry 3 was used in place of the slurry 2, and instead of removing excess deposits on the surface of the porous aluminum sample after immersion, the excess electrode mixture on the surface of the porous aluminum sample was dried and then spatulated. And then removed. Except these, it carried out similarly to the comparative example 1, and filled the electrode compound material in the porous aluminum sample. The filling density of the electrode mixture was 0.73 g / cm ³ . Since the density of the mixture layer obtained by applying slurry 3 on aluminum foil and drying was 1.47 g / cm ³ , the packing density was 50% of this mixture density. The mass proportion of porous aluminum was 26%.

  In each of Invention Examples 1 to 3, the filling density of the electrode mixture exceeds 50% of the mixture density, the mass ratio of the porous aluminum sample is small, and the electrode mixture is dense in the pores of the porous aluminum sample. Could be filled. On the other hand, in Comparative Examples 1 and 2, since the slurry was not filtered by the filter, the filling density of the electrode mixture was 50% or less of the mixture density, and the mass ratio of the porous aluminum sample was large. The electrode mixture could not be filled with high density into the pores of the sample.

  By the electrode manufacturing method according to the present invention, an electrode capable of being filled with an electrode mixture containing an active material at high density in the pores of a current collector made of a porous metal is obtained.

1 .... Hole 2 .... Metal wall 3 .... Small hole 4 .... Filter 5 .... Porous metal 6 .... Solvent 7 ... Filtrate 8 .... Slurry 9 .... Fun funnel 10 .... Electrode composite

Claims (5)

  A method for producing an electrode containing an electrode mixture containing an active material, the porous metal having pores filled with the electrode mixture on a filter that allows the solvent in the slurry in which the electrode mixture is dispersed to permeate In the state where the pressure on the side where the porous metal is placed through the filter is higher than the opposite side, the slurry is injected into the high pressure side, and the slurry is placed inside the porous metal. The slurry filtrate is deposited in the pores of the porous metal by filtering through a filter while infiltrating into the pores, the porous metal deposited in the pores is dried, and the solvent is scattered and evaporated. A method for producing an electrode using a porous metal current collector, wherein the pores are filled with an electrode mixture.   The method for producing an electrode using the porous metal current collector according to claim 1, wherein the pore size of the filter is smaller than the particle size of the active material.   The slurry is filtered through a filter until the surface of the porous metal is covered with the filtrate of the slurry, and the excess filtrate covering the surface of the porous metal before drying is removed. The manufacturing method of the electrode using the porous metal electrical power collector of description.   The slurry is filtered through a filter until the surface of the porous metal is covered with the filtrate of the slurry, and the excess electrode mixture covering the surface of the porous metal is removed after the porous metal is dried. The manufacturing method of the electrode using the porous metal electrical power collector of description.   The electrode using the porous metal current collector according to any one of claims 1 to 4, wherein after the filling of the electrode mixture, the porous metal filled with the electrode mixture is pressed. Manufacturing method.

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