JP4876478B2 - Method for producing sheet for electrochemical element electrode - Google Patents

Description

  The present invention may be referred to simply as an “electrochemical element electrode” (herein simply referred to as “electrode”) used in an electrochemical element such as a lithium ion secondary battery or an electric double layer capacitor, particularly suitable for an electric double layer capacitor. ) Sheet manufacturing method and manufacturing apparatus.

  Electrochemical elements such as lithium ion secondary batteries and electric double layer capacitors that are small and light, have high energy density, and can be repeatedly charged and discharged are rapidly expanding their demands by utilizing their characteristics. Lithium ion secondary batteries are used in mobile phones, notebook personal computers, and other fields because of their relatively high energy density, and electric double layer capacitors can be rapidly charged and discharged. It is used as a power source. Furthermore, the electric double layer capacitor is expected to be applied as a large power source for electric vehicles. Also, with the aim of achieving both high energy density and charge / discharge speed, a hybrid capacitor that uses a Faraday reaction electrode for one of the positive electrode and the negative electrode and a non-Faraday reaction electrode for the other has been developed. In addition, redox capacitors that utilize the oxidation-reduction reaction (pseudo electric double layer capacitance) on the surface of metal oxides or conductive polymers are also attracting attention due to their large capacity. With the expansion and development of applications, these electrochemical elements are required to further improve characteristics such as low resistance, high capacity, and improved mechanical characteristics. Under such circumstances, in order to improve the performance of the electrochemical device, various improvements have been made on the method of forming the electrochemical device electrode.

The electrochemical element electrode can be obtained, for example, by forming an electrode material containing an electrode active material or the like into a sheet shape and pressing the sheet (active material layer) onto a current collector.
In order to obtain this sheet-like molded product, Patent Document 1 discloses that a raw material composed of carbon fine powder, a conductive auxiliary material and a binder is mixed and kneaded to obtain a kneaded product, and then this kneaded product has a predetermined thickness by a roll press. A method for producing a sheet-like molded article is described. Specifically, as shown in FIG. 1, a kneaded product 3 is stored in a space formed by a pair of rolls 5 and a partition plate 4, and the kneaded product is press-molded by the pair of rolls to form a sheet-like molded body. 2 is used.

Patent Document 2 describes a method in which a mixture of graphite particles and copper particles is formed into a sheet-like molded body having a predetermined thickness by a roll press together with a copper foil serving as a current collector. Specifically, as shown in FIG. 2, a mixture of graphite particles and copper particles is stored in two spaces formed by a pair of rolls, a partition plate, and a current collector, and the mixture is collected by the pair of rolls. A manufacturing apparatus that obtains an electrode sheet in which an active material layer is formed on a current collector by pressing with the current collector is used.
Further, in Patent Document 3, as shown in FIG. 3, an electrode material is stored in a space formed by a pair of heating rolls and a partition plate, and an electrode material sheet is obtained by the pair of heating rolls. And the electrode core material are supplied to a pair of pressure rolls existing on the downstream side of the heating roll, and the electrode material sheet and the electrode core material are pressure bonded with the pressure roll.
However, the electrode sheet obtained by these production methods has a non-uniform film thickness and a large variation in electrode density. In particular, the variation in the width direction (TD direction) is large, and improvement is required.

JP 2001-230158 A JP 2003-317707 A JP 2002-237298 A

  An object of the present invention is to provide a method for producing a sheet for an electrochemical element electrode having a uniform film thickness in both the length direction (MD direction) and the TD direction and a small variation in electrode density.

  The inventor has noticed that unevenness occurs in the supply amount of the electrode material stored in the space formed by the pair of rolls and the partition plate to the rolls. Therefore, the present inventor provided a quantitative feeder above the pair of rolls, and by supplying the electrode material to the roll with this quantitative feeder, an electrochemical element electrode sheet having a uniform film thickness and small variations in electrode density was obtained. It was found that it can be obtained. Further, it has been found that by preheating the electrode material to a specific temperature, the supply of the electrode material can be made uniform, and an electrochemical element electrode sheet having a uniform film thickness can be obtained. The present invention has been completed based on these findings.

Thus, according to the present invention, (1) an electrode material is supplied to a pair of press rolls or belts arranged substantially horizontally by a quantitative feeder, and the electrode material is formed into a sheet-like molded body by the press rolls or belts. The manufacturing method of the sheet | seat for electrochemical element electrodes including the process to perform is provided.
According to the present invention, (2) an electrode material at 40 to 160 ° C. is supplied to a pair of press rolls or belts arranged substantially horizontally by a feeder, and the electrode material is formed into a sheet shape by the press rolls or belts. There is provided a method for producing an electrochemical element electrode sheet, comprising a step of forming a body.

As a preferred embodiment of the production method of the present invention, (3) the sheet-shaped current collector is further supplied to a press roll or belt, and the electrode material is formed into a sheet-shaped molded body with the press roll or belt. A method for producing the sheet for an electrochemical element electrode, comprising a step of pressure bonding to a sheet-like current collector,
(4) The method for producing an electrochemical element electrode sheet, wherein the sheet-shaped current collector has pores,
(5) Furthermore, the manufacturing method of the said sheet | seat for electrochemical element electrodes including the process which prevents the said electrode material supplied on the said roll or belt surface from rolling, and / or

(6) The quantitative feeder consists of a powder storage tank, a spreading roll and a discharge body,
The spray roll is disposed below the powder storage tank,
The discharge body is disposed below the peripheral surface of the spreading roll,
The powder storage tank has a structure capable of storing an electrode material and supplying it to the spray roll,
The electrode material supplied from the powder storage tank is attached to the spray roll,
Rotate the spreading roll to carry the electrode material downward,
The electrochemical element having a mechanism in which a voltage is applied to the discharge body to discharge, the electrode material adhering to the spray roll by this discharge is released from the spray roll, and the electrode material is sprayed. A method for producing an electrode sheet is provided.

Further, according to the present invention, (7) an electrochemical element electrode sheet comprising a pair of pressing rolls or belts disposed substantially horizontally and a quantitative feeder disposed above the pressing rolls or belts. A manufacturing apparatus is provided.
As a preferred aspect of the production apparatus of the present invention, (8) the electrochemical device electrode sheet production apparatus further comprising means for preventing the electrode material from rolling on the surface of the press roll or belt, and / or (9) determination. The feeder is composed of a powder storage tank, a spray roll, and a discharge body, the spray roll is disposed below the powder storage tank, the discharge body is disposed near a peripheral surface of the spray roll, The powder storage tank has a structure capable of storing an electrode material and supplying the electrode material to the spray roll. The electrode material supplied from the powder storage tank is attached to the spray roll, and the electrode roll is rotated to rotate the electrode material. Carrying down, discharging the electrode by applying a voltage to the discharge body, releasing the electrode material adhering to the spreading roll by this discharge from the spreading roll, and a mechanism for spreading the electrode material Is intended to apparatus for producing the sheet for an electrochemical device electrode, it is provided.

  According to the method for producing an electrochemical element electrode sheet of the present invention, an electrochemical element electrode sheet having a uniform film thickness in both the MD and TD directions and a small variation in electrode density can be obtained. As a result, an electrode having a small electric resistance and a large capacity can be efficiently manufactured in a large amount, and the manufacturing cost of the secondary battery or the electric double layer capacitor can be greatly reduced.

  In the method for producing an electrochemical element electrode sheet of the present invention, an electrode material is supplied to a pair of press rolls or belts arranged substantially horizontally by a quantitative feeder, and the electrode material is formed into a sheet form with the press rolls or belts. It includes forming into a molded body.

The electrode material used in the present invention is used for obtaining an electrochemical element electrode. Specifically, the electrode material contains at least an electrode active material and a binder, and further includes a conductive material and a soluble resin as necessary. Etc.
The electrode active material is appropriately selected depending on the type of electrochemical element. As an electrode active material for a positive electrode of a lithium ion secondary battery, lithium-containing composite metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO ₄ ; TiS ₂ , TiS ₃ , non Transition metal sulfides such as crystalline MoS ₃ ; transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ O · P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ ; Illustrated. Furthermore, conductive polymers such as polyacetylene and poly-p-phenylene are listed.

  Examples of the electrode active material for the negative electrode of the lithium ion secondary battery include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), and pitch-based carbon fibers; high conductivity such as polyacene Examples include molecules. These electrode active materials can be used individually or in combination of 2 or more types according to the kind of electrochemical element. When the electrode active materials are used in combination, two or more types of electrode active materials having different average particle sizes or particle size distributions may be used in combination.

The electrode active material used for the electrode of the lithium ion secondary battery is preferably sized into spherical particles. When the shape of the particles is spherical, a higher density electrode can be formed during electrode molding. A mixture of fine particles having a weight average particle diameter of about 1 μm and relatively large particles having a weight average particle diameter of 3 to 8 μm, or particles having a broad particle size distribution of 0.5 to 8 μm is preferable. Particles having a particle size of 50 μm or more are preferably used after being removed by sieving or the like. The tap density defined by ASTM D4164 of the electrode active material is not particularly limited, but those having a positive electrode of 2 g / cm ³ or more and those of a negative electrode of 0.6 g / cm ³ or more are preferably used.

As an electrode active material for an electric double layer capacitor, an allotrope of carbon is usually used. The electrode active material for an electric double layer capacitor is preferably one that can form an interface with a larger area even with the same weight, that is, one having a large specific surface area. Specifically, the specific surface area of ^{30 m} 2 / g or more, preferably preferably 500~5,000m ² / g, more preferably 1,000~3,000m ² / g. Specific examples of the allotrope of carbon include activated carbon, polyacene, carbon whisker, and graphite, and these powders or fibers can be used. A preferable electrode active material for the electric double layer capacitor is activated carbon, and specific examples include phenol-based, rayon-based, acrylic-based, pitch-based, and coconut shell-based activated carbon. These allotropes of carbon can be used singly or in combination of two or more as an electrode active material for electric double layer capacitors. When carbon allotropes are used in combination, two or more types of carbon allotropes having different average particle diameters or particle size distributions may be used in combination.

In addition, nonporous carbon having microcrystalline carbon similar to graphite and having an increased interlayer distance of the microcrystalline carbon can be used as the electrode active material. Such non-porous carbon is obtained by dry-distilling graphitized charcoal with microcrystals of a multilayer graphite structure at 700 to 850 ° C., then heat-treating with caustic at 800 to 900 ° C., and if necessary with heated steam. It is obtained by removing the residual alkali component.
When a powder having a weight average particle diameter of 0.1 to 100 μm, preferably 1 to 50 μm, more preferably 5 to 20 μm is used as an electrode active material for an electric double layer capacitor, the electrode for the electric double layer capacitor can be made thin. It is preferable because it is easy and the capacitance can be increased.

The conductive material is made of an allotrope of particulate carbon that has conductivity and does not have pores capable of forming an electric double layer, and improves the conductivity of the electrochemical element electrode. The weight average particle diameter of the conductive material is preferably smaller than the weight average particle diameter of the electrode active material, and is usually in the range of 0.001 to 10 μm, preferably 0.05 to 5 μm, more preferably 0.01 to 1 μm. is there. When the particle size of the conductive material is within this range, high conductivity can be obtained with a smaller amount of use. Specific examples of the conductive material include conductive carbon black such as furnace black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennaut Shap); graphite such as natural graphite and artificial graphite. . Among these, conductive carbon black is preferable, and acetylene black and furnace black are more preferable. These conductive materials can be used alone or in combination of two or more.
The amount of the conductive material is usually 0.1 to 50 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. When an electrode having an amount of the conductive material within this range is used, the capacity of the electrochemical element can be increased and the internal resistance can be decreased.

  The binder is a compound that can bind an electrode active material or a conductive material. Suitable binders have a property of being dispersed in a solvent, and examples thereof include polymer compounds such as fluorine polymers, diene polymers, acrylate polymers, polyimides, polyamides, polyurethanes, and the like. Includes a fluorine-based polymer, a diene-based polymer, and an acrylate-based polymer. These binders can be used alone or in combination of two or more.

  The fluorine-based polymer is a polymer containing a monomer unit containing a fluorine atom. The ratio of the monomer unit containing fluorine in the fluoropolymer is usually 50% by weight or more. Specific examples of the fluorine-based polymer include fluorine resins such as polytetrafluoroethylene and polyvinylidene fluoride, and polytetrafluoroethylene is preferable.

  The diene polymer is a homopolymer of a conjugated diene or a copolymer obtained by polymerizing a monomer mixture containing a conjugated diene, or a hydrogenated product thereof. The proportion of the conjugated diene in the monomer mixture is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. Specific examples of the diene polymer include conjugated diene homopolymers such as polybutadiene and polyisoprene; aromatic vinyl / conjugated diene copolymers such as carboxy-modified styrene / butadiene copolymer (SBR); Examples include vinyl cyanide / conjugated diene copolymers such as acrylonitrile / butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, and the like.

  The acrylate polymer is a copolymer obtained by polymerizing a homopolymer of acrylic acid ester and / or methacrylic acid ester or a monomer mixture containing them. The ratio of acrylic acid ester and / or methacrylic acid ester in the monomer mixture is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. Specific examples of the acrylate polymer include 2-ethylhexyl acrylate / methacrylic acid / acrylonitrile / ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate / methacrylic acid / methacrylonitrile / diethylene glycol dimethacrylate copolymer, acrylic Crosslinking of 2-ethylhexyl acid / styrene / methacrylic acid / ethylene glycol dimethacrylate copolymer, butyl acrylate / acrylonitrile / diethylene glycol dimethacrylate copolymer, and butyl acrylate / acrylic acid / trimethylolpropane trimethacrylate copolymer Type acrylate polymer; ethylene / methyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / ethyl acrylate copolymer, and Copolymer of ethylene and (meth) acrylic acid ester such as ethylene / ethyl methacrylate copolymer; Graft obtained by grafting a radical polymerizable monomer to the above copolymer of ethylene and (meth) acrylic acid ester Polymer; and the like. In addition, as a radically polymerizable monomer used for the said graft polymer, methyl methacrylate, acrylonitrile, methacrylic acid etc. are mentioned, for example. In addition, a copolymer of ethylene and (meth) acrylic acid such as an ethylene / acrylic acid copolymer or an ethylene / methacrylic acid copolymer can be used as a binder.

  Among these, from the viewpoint that an active material layer excellent in binding property and surface smoothness with a current collector can be obtained, and an electrode for an electrochemical element having high capacitance and low internal resistance can be produced. Diene polymers and cross-linked acrylate polymers are preferred, and cross-linked acrylate polymers are particularly preferred.

  The binder is not particularly limited depending on its shape, but has good binding properties, and can be prevented from being deteriorated due to a decrease in the capacitance of the created electrode or repeated charge / discharge, so that it is particulate. Is preferred. Examples of the particulate binder include those in which particles of a dispersion-type binder such as latex are dispersed in water, and powders obtained by drying such a dispersion.

  Further, the binder may be particles having a core-shell structure obtained by polymerizing a mixture of two or more kinds of monomers stepwise. A binder having a core-shell structure is obtained by first polymerizing a monomer that gives the first-stage polymer to obtain seed particles, and in the presence of the seed particles, a single quantity that gives the second-stage polymer. It is preferable to manufacture by polymerizing the body.

  The ratio between the core and the shell of the binder having the core-shell structure is not particularly limited, but the core part: shell part is usually 50:50 to 99: 1, preferably 60:40 to 99: 1 by mass ratio. Preferably it is 70: 30-99: 1. The polymer which comprises a core part and a shell part can be selected from said polymer. It is preferable that one of the core part and the shell part has a glass transition temperature of less than 0 ° C and the other has a glass transition temperature of 0 ° C or higher. Moreover, the difference of the glass transition temperature of a core part and a shell part is 20 degreeC or more normally, Preferably it is 50 degreeC or more.

  The particulate binder is not particularly limited depending on its number average particle diameter, but is usually 0.0001 to 100 μm, preferably 0.001 to 10 μm, more preferably 0.01 to 1 μm. It is what has. When the number average particle diameter of the binder is within this range, an excellent binding force can be imparted to the active material layer even when a small amount of the binder is used. Here, the number average particle diameter is a number average particle diameter calculated as an arithmetic average value obtained by measuring the diameter of 100 binder particles randomly selected in a transmission electron micrograph. The shape of the particles can be either spherical or irregular.

  The amount of the binder used is usually 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, and more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the electrode active material. is there.

  In addition, the electrode material preferably contains a resin that is soluble in a solvent (hereinafter referred to as “dissolvable resin”). The soluble resin is preferably used by being dissolved in a slurry solvent in the production of composite particles described later, and further has an action of uniformly dispersing the electrode active material, the conductive material, and the like in the solvent. The soluble resin is preferably a resin that dissolves in water, and specifically includes cellulosic polymers such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and ammonium salts or alkali metal salts thereof; poly (meta ) Poly (meth) acrylates such as sodium acrylate; polyvinyl alcohol, modified polyvinyl alcohol, polyethylene oxide; polyvinyl pyrrolidone, polycarboxylic acid, oxidized starch, phosphate starch, casein, various modified starches, chitin, chitosan derivatives, etc. Can be mentioned. These soluble resins can be used alone or in combination of two or more. Among these, a cellulose polymer is preferable, and carboxymethyl cellulose or an ammonium salt or an alkali metal salt thereof is particularly preferable.

  The use amount of the soluble resin is not particularly limited, but is usually 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and more preferably 0.8 to 100 parts by weight of the electrode active material. It is in the range of 8 to 2 parts by weight. By using the dissolution type resin, sedimentation and aggregation of solid content in the slurry can be suppressed. Moreover, since the clogging of the atomizer at the time of spray drying can be prevented, spray drying can be performed stably and continuously.

  The electrode material may further contain other additives as necessary. Examples of other additives include a surfactant. Examples of the surfactant include amphoteric surfactants such as anionic, cationic, nonionic, and nonionic anions. Among them, anionic or nonionic surfactants that are easily thermally decomposed are preferable. The amount of the surfactant is not particularly limited, but is 0 to 50 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the electrode active material. It is a range.

The electrode material suitably used in the present invention is in the form of particles containing the above components in a composite (hereinafter sometimes referred to as composite particles). The composite particles usually include at least an electrode active material, a conductive material, and a binder, and the electrode active material and the conductive material are bound by a binder.
The weight average particle size of the composite particles used in the present invention is usually in the range of 0.1 to 1000 μm, preferably 5 to 500 μm, more preferably 10 to 100 μm.

The composite particles suitable for the present invention have a particle size displacement rate of usually 5 to 70%, preferably 20 to 50% when compressed to a maximum load of 9.8 mN at a load speed of 0.9 mN / sec by a micro compression tester. is there. The particle size displacement rate is a ratio (= ΔD / D ₀ × 100) of the amount of particle size reduction (ΔD = D ₀ −D ₁ ) due to compression to the particle size D ₀ before compression of the composite particles. Incidentally, D ₁ is a value that varies according to the load amount of the particle diameter when being under a load.

  In addition, the composite particles suitably used in the present invention preferably have a change in particle size displacement rate per unit second when compressed to a maximum load of 9.8 mN at a load speed of 0.9 mN / sec using a micro compression tester. It is 25% or less, more preferably 10% or less, and particularly preferably 7% or less. The change amount of the particle size displacement rate per unit second is the change amount per unit second of the particle size change rate when the load increases at a load speed of 0.9 mN / sec. The particle size displacement rate when compressed to a maximum load of 9.8 mN measured by a micro-compression tester is a numerical value necessary to show the shape maintenance force of the composite particles. If the particle size displacement rate is too small, the composite particles are hardly deformed even by pressurization, so that the contact area between the particles is small and the conductivity is not increased. On the other hand, when the particle size displacement rate is too large, the composite particles are crushed, the network formed by the conductive material and the electrode active material formed in the composite particles is broken, and the conductivity is lowered. Further, the change amount of the particle size displacement rate per unit second is an index for determining the presence or absence of crushing. When crushing occurs, the particle size decreases rapidly, so the amount of change in particle size displacement rate per unit second exceeds 25%. By crushing, the network formed by the conductive material and the electrode active material formed in the composite particles is broken, and the conductivity is lowered. Since the composite particle having a particle size displacement rate of 5 to 70% when compressed to a maximum load of 9.8 mN has appropriate softness, the contact area between the particles is large. And since it does not crush, the network of an electroconductive material and an electrode active material is maintained.

  The composite particles used in the present invention are not particularly limited by the production method. For example, (1) a step of obtaining a slurry containing a conductive material, a dispersion-type binder, a soluble resin, and other additives, electrode activity Fluidizing the substance, spraying the slurry thereon, fluidized bed granulation, rolling granulation of the particles obtained in the fluidized granulation, and heat treatment as necessary (2) A step of obtaining a slurry containing an electrode active material, a conductive material, a dispersion-type binder and a soluble resin, a step of spray-drying the slurry, spray granulating, and a heat treatment as necessary The thing etc. which have a process are mentioned.

The quantitative feeder used for this invention will not be specifically limited if it is a feeder which can supply an electrode material quantitatively. Here, quantitative supply means that the electrode material is continuously supplied using such a feeder, the supply amount is measured a plurality of times at regular intervals, and the average value m of the measured values and the standard deviation σ _{m are} obtained. The CV value (= σ _m / m × 100) obtained is 4 or less.
The quantitative feeder used in the present invention preferably has a CV value of 2 or less. Specific examples of the quantitative feeder include a gravity feeder such as a table feeder and a rotary feeder, and a mechanical force feeder such as a screw feeder and a belt feeder. Of these, the rotary feeder is preferred.

  The rotary feeder particularly preferably used in the present invention includes a powder storage tank, a spray roll, and a discharge body. The powder storage tank has a structure capable of storing an electrode material and supplying it to the spray roll. The electrode material supplied from the powder storage tank is attached to the spraying roll disposed below, the spraying roll is rotated and carried below the electrode material, and the discharge disposed below the peripheral surface of the spraying roll. A voltage is applied to the body to cause discharge, and the electrode material adhering to the spreading roll by this discharge is released from the spreading roll and has a mechanism for spreading the electrode material.

  FIG. 4 is a diagram illustrating an example of a rotary feeder. As shown in FIG. 4, the rotary feeder 50 includes a powder storage tank 57 configured to store the particulate electrode material 3 and to spray the stored electrode material 3 from below. More specifically, the powder storage tank 57 is formed with an accommodation space extending in the roll axis direction inside. Furthermore, a rectangular opening that is long in the roll axis direction is provided at the bottom of the storage tank 57, and the spray roll 52 is disposed substantially horizontally so as to close the opening and to expose the lower half of the roll to the outside. Yes. A blade opening is provided at the lower outer edge of the powder storage tank 57 so that the tip opening width is narrowed in a V shape and is in contact with the circumferential surfaces on both sides of the spreading roll 52. The blade fills the gap between the spreading roll 52 and the lower opening of the storage space of the powder storage tank 57, so that the electrode material 3 does not fall.

  The spreading roll 52 has a cylindrical shape, and fine irregularities (not shown) are provided on the outer peripheral surface. When the spreading roll 52 rotates, the electrode material 3 that has entered the fine irregularities is a blade. The layer thickness is set to a predetermined value, and is carried to the lower part of the spreading roll as the spreading roll 52 rotates. The supply amount of the electrode material 3 can be arbitrarily adjusted by the rotation speed of the spreading roll, and the supply amount is constant at a constant rotation speed.

  Below the spreading roll 52, the discharge body 51 extends in the axial direction and is arranged close to the peripheral surface of the spreading roll 52. And the discharge body 51 comprises the well-known discharge spray apparatus (refer Unexamined-Japanese-Patent No. 9-1039, Unexamined-Japanese-Patent No. 2004-58018) with the spreading roll 52, and is connected to the high voltage alternating current power supply which is not shown in figure. The electrode material 3 carried to the lower part by the spreading roll 52 is separated from the spreading roll 52 by electric discharge, and the electrode material 3 is sprayed and supplied to the peripheral surface of the press roll 5 or belt rotating below the spreading roll 52. To do. Since the electrode material is uniformly sprayed on the peripheral surface of the press roll 5 and pressed in the sprayed state, the non-uniform density of the electrode material is very small.

  Further, in the rotary feeder shown in FIG. 4, partition rolls 55 and 56 are provided in order to prevent the electrode material separated from the spray roll 52 from being sprayed to places other than the press roll 5. Discharge bodies 53 and 54 are installed in the vicinity of the partition roll, and the discharge of the discharge bodies 53 and 54 allows the electrode material adhering to the partition roll to be detached and sprayed on the press roll 5. The rotation direction of the partition roll is not limited to the direction shown in FIG. 4, and the rotation direction and rotation speed can be adjusted as appropriate according to the type of electrode material.

In the production method of the present invention, the electrode material is supplied to a pair of press rolls or belts arranged substantially horizontally by the quantitative feeder, and the electrode material is formed into a sheet-like molded body with the press rolls or belts. .
FIG. 5 shows that the electrode material is supplied to the pair of pressing rolls 5 by the quantitative feeder 50, and the supplied electrode material is pressed by the pressing roll to obtain a sheet-like molded body. The pair of press rolls shown in FIG. 5 can be replaced with a pair of press belts.

  Moreover, in the other manufacturing method of this invention, the said electrode material heated at 40-160 degreeC is supplied to a pair of press roll or belt arranged substantially horizontally, and this press roll or belt uses this electrode material. Is formed into a sheet-like molded body. The temperature of the supplied electrode material is preferably 70 to 140 ° C. When an electrode material in this temperature range is used, there is no slippage of the electrode material on the surface of the press roll or belt, and the electrode material is continuously and uniformly supplied to the press roll or belt. In addition, an electrochemical element electrode sheet with small variations in electrode density can be obtained.

  The temperature at the time of molding is usually 0 to 200 ° C., preferably higher than the melting point or glass transition temperature of the binder, and more preferably 20 ° C. higher than the melting point or glass transition temperature. The forming speed in the case of using a roll is usually 0.1 to 20 m / min, preferably 1 to 10 m / min. Moreover, the press linear pressure between the rolls for a press is 0.2-30 kN / cm normally, Preferably it is 0.5-10 kN / cm. The forming speed in the case of using a belt is usually 1 to 15 m / min, preferably 5 to 10 m / min. The pressure between the pressing belts is usually 5 to 50 MPa, preferably 10 to 30 MPa.

In the production method of the present invention, the sheet-shaped current collector is further supplied to a pair of press rolls, and the electrode material is formed into a sheet-shaped molded body with the press rolls and is crimped to the sheet-shaped current collector. It is preferable to contain.
In FIG. 5, the sheet-like current collector 1 is supplied to the press roll 5, and the electrode material 3 is press-molded by the press roll 5 on both surfaces of the current collector 1. As the material of the sheet-like current collector used in the present invention, for example, metal, carbon, conductive polymer and the like can be used, and metal is preferably used. As the current collector metal, aluminum, platinum, nickel, tantalum, titanium, stainless steel, and other alloys are usually used. Among these, it is preferable to use aluminum or an aluminum alloy in terms of conductivity and voltage resistance. In addition, when high voltage resistance is required, high-purity aluminum disclosed in JP 2001-176757 A can be suitably used. The current collector is in the form of a film or a sheet, and the thickness thereof is appropriately selected according to the purpose of use, but is usually 1 to 200 μm, preferably 5 to 100 μm, more preferably 10 to 50 μm.

  The sheet-like current collector may have pores. That is, examples of the shape of the holes include a quadrangle, a rhombus, a turtle shell shape, a hexagon, a round shape, a star shape, and a cross shape. Specific examples of the sheet-like current collector having pores include expanded metal obtained by expanding a flat plate into a rhombus or turtle shell-shaped net, punching metal obtained by perforating a flat plate, or a metal wire or a metal band plain weave or Examples thereof include a wire net obtained by twilling or fitting a crimp metal wire. When a sheet-like current collector having pores is used, the capacity per volume of the obtained electrode can be increased. When the sheet-like current collector has holes, the ratio of the holes is preferably 10 to 79 area%, more preferably 20 to 60 area%.

In a preferable manufacturing method of the present invention, after the electrode material 3 is supplied to the press roll 5 or the belt, the electrode material is fixed by means for preventing the electrode material from rolling on the surface of the press roll or belt. .
As means for preventing the electrode material from rolling on the surface of the press roll or belt, means for increasing the temperature of the surface of the press roll or belt and thermally fusing the electrode material, corona discharge on the surface of the press roll or belt, etc. Immediately after the electrode material is spread and charged, the electrode sheet is charged and adhered, for example, inserted from the gap between the partition roll 56 and the spread roll 52 in FIG. (It is preferable to use a sheet-like current collector as the cover sheet.) And a means for suppressing the electrode material.

  In order to eliminate the variation in the thickness of the molded body, increase the density, and increase the capacity, further pressurization may be performed as necessary. The post-pressing method is generally a press process using a roll. In the roll press process, two cylindrical rolls are arranged in parallel at a narrow interval in the vertical direction, and each is rotated in the opposite direction. The temperature of the roll may be adjusted by heating or cooling.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not restrict | limited to the following Example. Parts and% are based on weight unless otherwise specified.

Example 1
100 parts of an electrode active material (activated carbon with a specific surface area of 2000 m ² / g and a weight average particle size of 5 μm), 5 parts of a conductive material (acetylene black “Denka Black Powder” manufactured by Denki Kagaku Kogyo Co., Ltd.), a dispersion-type binder (40% aqueous dispersion of cross-linked acrylate polymer having a number average particle size of 0.15 μm and a glass transition temperature of −40 ° C .: “AD211”; manufactured by Nippon Zeon Co., Ltd.) 7.5 parts, soluble resin (carboxy 93.3 parts of a 1.5% aqueous solution of methylcellulose “DN-800H” (manufactured by Daicel Chemical Industries, Ltd.) and 231.8 parts of ion-exchanged water K. The mixture was stirred and mixed with a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a slurry having a solid content of 25%. Next, the slurry was spray-dried with hot air at 150 ° C. using a spray dryer (with a pin type atomizer manufactured by Okawara Chemical Industries Co., Ltd.) to obtain spherical composite particles having a weight average particle size of 50 μm. The weight average particle diameter of the composite particles was measured using a powder measuring apparatus (Powder Tester PT-R: manufactured by Hosokawa Micron Corporation).

The composite particles were compressed at a maximum load of 9.8 mN and a load speed of 0.9 mN / sec using a micro compression tester (manufactured by Shimadzu Corporation: MCT-W). The change rate of the particle size displacement rate and the change rate of the particle size displacement rate per second were 22% and 8%, respectively. The obtained composite particles are rolled using a quantitative feeder (Nikka Spray KV, manufactured by Nikka Co., Ltd.) as shown in FIG. 4 at a feed rate of 70 g / min. It was supplied to a press roll (roll temperature 120 ° C., press linear pressure 4 kN / cm) manufactured by Hirano Giken Kogyo Co., Ltd. The surface of the pressing roll is charged by corona discharge, and the composite particles supplied from the quantitative feeder are attached so as not to roll on the pressing roll, and are pressure-molded at a molding speed of 6.0 m / min, and an average thickness of 390 μm. A sheet-like molded body having an average density of 0.57 g / cm ³ was obtained. The thickness variation in the MD direction was σ _n-1 = 2.83, and the thickness variation in the TD direction was σ _n-1 = 2.57.

Example 2
The sheet press is the same as in Example 1 except that the roll press used in Example 1 is replaced with a belt press (double belt press: press pressure 1.5 MPa, pressure zone length 1 m, temperature 120 ° C.). A molded body was obtained. This sheet-like molded body has an average density of 0.545 g / cm ³ , an average thickness of 390 μm, MD direction thickness variation σ _n-1 of 4.62, and TD direction thickness variation σ _n-1 of 4.33. Met.

Example 3
When press-molding the composite particles in Example 1, an aluminum foil having a thickness of 20 μm (having a surface treated with a conductive adhesive) is simultaneously inserted into a roll like the sheet-like current collector 1 of FIG. The sheet-like molded body integrated with the current collector was obtained by pressure molding in the same manner as in Example 1. The average density of the sheet-like molded body was 0.535 g / cm ³ , the average thickness was 415 μm, the MD direction thickness variation σ _n-1 was 4.78, and the TD direction thickness variation σ _n-1 was 3.69. there were.

Example 4
In Example 1, instead of corona discharge, a conductive film having a thickness of 50 μm (KZ-45 manufactured by Kinugawa Rubber Industrial Co., Ltd.) was inserted as shown in the cover sheet 11 of FIG. A sheet-like molded body integrated with the current collector was obtained by pressure molding in the same manner as in Example 1 except that it was changed to 140 g / min. The average density of this sheet-like molded body is 0.520 g / cm ³ , the average thickness is 445 μm, the MD direction thickness variation σ _n-1 is 4.48, and the TD direction thickness variation σ _n-1 is 3.38. there were.

Example 5
In Example 4, integrated with the current collector in the same manner as in Example 4 except that the conductive film having a thickness of 50 μm was replaced with an aluminum foil having a thickness of 20 μm (the surface was treated with a conductive adhesive). A sheet-like molded body was obtained. The average density of the sheet-like molded body is 0.530 g / cm ³ , the average thickness is 415 μm, the MD direction thickness variation σ _n-1 is 4.28, and the TD direction thickness variation σ _n-1 is 4.18. there were.

Example 6
Acetylene black was blended with low density polyethylene and calendered to obtain a film, and the surface was treated with a conductive adhesive to obtain a conductive thin film having a thickness of 30 μm.
The conductive thin film is inserted as shown in the cover sheet 11 of FIG. 4, and an aluminum foil having a thickness of 20 μm is simultaneously inserted into a roll like the sheet-like current collector of FIG. The pressure was molded in the same manner as in Example 1 except that the pressure was changed to 140 g / min to obtain a sheet-like molded body integrated with the current collector. The average density of this sheet-like molded body was 0.510 g / cm ³ , the average thickness was 484 μm, the MD direction thickness variation σ _n-1 was 6.48, and the TD direction thickness variation σ _n-1 was 5.38. there were.

Example 7
In Example 1, a sheet-like molded product was obtained in the same manner as in Example 1 except that the powder storage tank of the quantitative feeder (Nikka Spray K-V) was heated and maintained at 100 ° C. . A sheet-like molded body having an average thickness of 403 μm and an average density of 0.58 g / cm ³ was obtained. The thickness variation in the MD direction was σ _n-1 = 1.41, and the thickness variation in the TD direction was σ _n-1 = 1.24.

Example 8
In Example 3, instead of an aluminum foil having a thickness of 20 μm, a current collector was formed by pressure molding in the same manner as in Example 3 except that an expanded metal having a thickness of 50 μm and a void ratio of 37 area% was used. An integrated sheet-like molded body was obtained. The average density of the sheet-like molded body was 0.57 g / cm ³ , the average thickness was 480 μm, the MD direction thickness variation σ _n-1 was 4.32, and the TD direction thickness variation σ _n-1 was 3.97. there were.

Comparative Example 1
A sheet-like molded body was obtained in the same manner as in Example 1 except that the quantitative feeder used in Example 1 was not used and a roll press machine having an apparatus configuration as shown in FIG. 1 was used. Unevenness occurred in the supply amount of the composite particles, and distribution occurred in the temperature of the roll surface. The obtained sheet-like molded product had an average density of 0.513 g / cm ³ , an average thickness of 430 μm, an MD direction thickness variation σ _n-1 of 38.12, and a TD direction thickness variation σ _n-1 of 41. .24.

Comparative Example 2
A sheet-like molded body was obtained in the same manner as in Example 1 except that the quantitative feeder used in Example 1 was not used and a roll press machine having an apparatus configuration as shown in FIG. 3 was used. The sheets supplied from the two pairs of rolls have uneven thickness, and the sheet-like molded body obtained by press-bonding them has an average density of 0.505 g / cm ³ , an average thickness of 750 μm, and a MD direction thickness variation σ _n-1. Was 47.22 and TD direction thickness variation σ _n-1 was 58.91.

(Measurement method of electrode density)
The sheet-like molded body was cut into a size of 40 mm × 60 mm, its weight and volume were measured, and the electrode density excluding the current collector portion was calculated.
(Measurement method of electrode thickness and variation)
The electrode thickness was measured using a contact type web thickness meter RC-101 manufactured by Meisho Co., Ltd., and the electrode thickness at 20 points was measured at intervals of 0.5 mm to obtain an average value and variation.

  From the above Examples and Comparative Examples, it can be seen that the sheet-like molded bodies of Examples 1 to 5 manufactured according to the manufacturing method of the present invention have a small thickness variation in both the MD direction and the TD direction and have a high density. In particular, the thickness variation in the TD direction is improved. On the other hand, it can be seen that the sheet-like molded bodies of Comparative Examples 1 and 2 manufactured according to the conventional method have a large thickness variation particularly in the TD direction and a low density.

  By using the method for producing an electrochemical element electrode sheet of the present invention, an electrochemical element electrode sheet having a uniform film thickness and small variations in electrode density can be easily obtained. This electrochemical element electrode sheet is used as a backup power source for memories such as personal computers and portable terminals, a power source for instantaneous power failure such as personal computers, application to electric vehicles or hybrid vehicles, solar power generation energy storage system combined with solar cells, batteries Can be suitably used for various applications such as a load leveling power source combined with the above.

The figure which shows an example of the manufacturing apparatus of the conventional electrode sheet. The figure which shows another example of the manufacturing apparatus of the conventional electrode sheet. The figure which shows another example of the manufacturing apparatus of the conventional electrode sheet. The enlarged view of the part (quantitative feeder) enclosed with the dotted line of FIG. The figure which shows an example of the manufacturing apparatus of the sheet | seat for electrochemical element electrodes of this invention.

Explanation of symbols

1: Sheet-shaped current collector 2: Active material layer 3: Electrode material 4: Partition plate 11: Cover sheet 50: Fixed feeder 51, 53, 54: Discharge body 52: Dispersion roll 55, 56: Partition roll

Claims (9)

An electrode material composed of composite particles is obtained by spraying and granulating a slurry containing an electrode active material, a conductive material, a dispersion-type binder, and a soluble resin ,
The electrode material is supplied to a pair of press rolls or belts arranged substantially horizontally by a quantitative feeder,
The manufacturing method of the sheet | seat for electrochemical element electrodes including the process of shape | molding electrode material into a sheet-like molded object with this roll for a press or a belt. An electrode material composed of composite particles is obtained by spraying and granulating a slurry containing an electrode active material, a conductive material, a dispersion-type binder, and a soluble resin ,
Supply the electrode material at 40 to 160 ° C. to a pair of press rolls or belts arranged substantially horizontally by a feeder,
The manufacturing method of the sheet | seat for electrochemical element electrodes including the process of shape | molding electrode material into a sheet-like molded object with this roll for a press or a belt.   Furthermore, the sheet-shaped current collector is supplied to the pressing roll or belt, and the step of forming the electrode material into the sheet-shaped molded body with the pressing roll or belt and press-bonding to the sheet-shaped current collector is further included. The manufacturing method of the sheet | seat for electrochemical element electrodes of 1 or 2.   The method for producing a sheet for an electrochemical element electrode according to any one of claims 1 to 3, wherein the sheet-like current collector has pores.   Furthermore, the manufacturing method of the sheet | seat for electrochemical element electrodes in any one of Claims 1-4 including the process of preventing the said electrode material supplied on the surface of the said roll for a roll or a belt. The feeder is a powder reservoir, a metering feeder ing from spraying the roll and the discharge member,
The spray roll is disposed below the powder storage tank,
The discharge body is disposed below the peripheral surface of the spreading roll,
The powder storage tank has a structure capable of storing an electrode material and supplying it to the spray roll,
The electrode material supplied from the powder storage tank is attached to the spray roll,
Rotate the spreading roll to carry the electrode material downward,
The discharge member voltage applying to be discharged into the electrode material adhering to said distributing roll by the discharge released from the spraying roll, and has a mechanism for spraying the electrode material, according to claim 1 to 5, The manufacturing method of the sheet | seat for electrochemical element electrodes as described in any one of these . A means for granulating an electrode material composed of composite particles by spraying a slurry containing an electrode active material, a conductive material, a dispersion-type binder, and a soluble resin, and a pair of presses arranged substantially horizontally An apparatus for producing an electrochemical element electrode sheet comprising a roll or a belt and a quantitative feeder disposed above the press roll or belt.   The apparatus for producing an electrochemical element electrode sheet according to claim 7, further comprising means for preventing the electrode material from rolling on the surface of the press roll or the belt. The quantitative feeder consists of a powder storage tank, a spray roll and a discharge body,
The spray roll is disposed below the powder storage tank,
The discharge body is disposed below the peripheral surface of the spreading roll,
The powder storage tank has a structure capable of storing an electrode material and supplying it to the spray roll,
The electrode material supplied from the powder storage tank is attached to the spray roll,
Rotate the spreading roll to carry the electrode material downward,
9. The device according to claim 7, wherein a voltage is applied to the discharge body to cause discharge, and the electrode material adhering to the spreading roll by this discharge is released from the spreading roll to disperse the electrode material. The manufacturing apparatus of the sheet | seat for electrochemical element electrodes of description.

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