JP2011151143A - Manufacturing method of electrode for storage device and storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode for storage device wherein the surface of a collector is physically roughened, a surface area of the collector is expanded and an oxide layer of the surface is removed while suppressing changing into spongy state of a surface layer of the collector, collector fracture in a manufacturing process is prevented, an adhesion strength between the collector and an intermediate layer is enlarged, and electric resistance reduction is accelerated, and to provide a storage device provided with the electrode for storage device. <P>SOLUTION: In the manufacturing method of the electrode for storage device, a polishing roll 32 is so arranged as to press against a fixed roll 31 by a predetermined pressure, and the fixed roll 31 is rotary-driven, and the polishing roll 32 is rotary-driven in the reverse direction, and a metal foil 30 as the collector is made to pass between the fixed roll 31 and the polishing roll 32. At this time, since the polishing roll 32 rotates in the reverse direction of a reel-out direction of the metal foil 30 by the fixed roll 31, an uneven surface 32a is pressed against the surface of the metal foil 30 by the predetermined pressure and frictionally moved, and the surface of the metal foil 30 is ground, and a roughened surface 30a is formed on the surface of the metal foil 30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing an electrode for an electricity storage device, and more particularly to a method for producing an electrode for an electricity storage device having an increased adhesion strength between an intermediate layer and a current collector, and an electricity storage device provided with an electrode produced by the production method.

In recent years, interest in power storage has been increasing in various fields such as power sources for portable devices, main and auxiliary power sources for electric vehicles and hybrid vehicles, regenerative energy storage, instantaneous voltage drop compensation devices, etc. Power storage devices are attracting attention.
Storage devices include secondary batteries and capacitors (capacitors), which are properly used according to their use. Regarding secondary batteries, development of lithium ion secondary batteries that are lightweight and have a high capacity is underway. In addition, research on electric double layer capacitors has been actively conducted in recent years. The electric double layer capacitor is an electric storage device that physically adsorbs and desorbs ions in the electrolyte solution on the electrode surface, and has no advantages in that it has a high output and a long life because it does not involve a chemical reaction.

  The electrodes used in these electricity storage devices are composed of an active material, a conductive auxiliary agent such as carbon black for complementing the electrical conductivity of the active material, a binder for molding as an electrode, and other additives. It consists of an electrode layer and a current collector for obtaining a current. Furthermore, in order to reduce the interface resistance between the electrode layer and the current collector, an intermediate layer made of carbon or the like may be formed. And the low adhesiveness between an electrode layer and a collector or an intermediate | middle layer and a collector has been a problem.

  In view of such a situation, conventionally, an etching foil whose surface is roughened by chemical etching or electric field etching is used as a current collector, and between the current collector and the electrode layer or between the current collector and the intermediate layer. There has been proposed a capacitor electrode with improved adhesion between them (see, for example, Patent Document 1).

JP 2005-191423 A

  In the conventional capacitor electrode described in Patent Document 1, since the etching foil having an etching process applied to the surface is used as a current collector, the surface area of the current collector is increased, and the current collector, the electrode layer, Although the adhesion between the current collector and the current collector and the intermediate layer can be improved, the surface layer of the current collector becomes spongy, the strength of the current collector decreases, and there is a problem that it breaks in the manufacturing process. It was.

  In addition, an oxide layer is usually formed on the surface of a metal foil such as an aluminum foil, and corrosion is prevented by the dense oxide layer, but the contact resistance is reduced by the oxide layer on the surface. There was a tendency to become larger. In order to reduce the contact resistance, an intermediate layer is formed. However, if the oxide layer is thick, there is a problem that the resistance reduction effect is reduced. In particular, when the surface of the metal foil is chemically etched, there is also a problem that the formation rate of the oxide layer after the processing is increased.

  The present invention has been made to solve such a problem. The surface of the current collector is physically roughened, and the surface layer of the current collector is suppressed from being spongy, and the current collector is collected. Increases the surface area of the current collector and removes the oxide layer on the surface, eliminates the current collector breakage during the manufacturing process, increases the adhesion strength between the current collector and the intermediate layer, and lowers the electrical resistance. An object of the present invention is to provide a method for producing an electrode for an electricity storage device that can be promoted, and an electricity storage device provided with the electrode for the electricity storage device.

  A method of manufacturing an electrode for an electricity storage device according to the present invention includes a current collector made of a metal foil, an intermediate layer containing conductive particles formed on the current collector, and an electrode formed on the intermediate layer And a roughening method for physically roughening the surface of the current collector prior to the step of forming the intermediate layer on the current collector. It has a process.

  According to this invention, the surface of the current collector is physically roughened. Therefore, compared to the case of chemically roughening, since the spongy state of the surface layer of the current collector is suppressed, there is little decrease in strength of the current collector, and it is possible to prevent the current collector from being broken in the manufacturing process. it can. In addition, since the surface area of the current collector is increased and the oxide layer on the surface of the current collector is removed, the contact resistance between the current collector and the intermediate layer is reduced, and the resistance is reduced. The adhesion strength between the electric body and the intermediate layer is increased.

It is sectional drawing which shows typically the structure of the electrical double layer capacitor which concerns on this invention. It is a perspective view explaining the 1st roughening method in the manufacturing method of the electrode for electrical storage devices concerning this invention. It is a perspective view explaining the 2nd roughening method in the manufacturing method of the electrode for electrical storage devices concerning this invention. It is a perspective view explaining the 3rd roughening method in the manufacturing method of the electrode for electrical storage devices concerning this invention. It is a schematic diagram explaining the manufacturing method of the electrode for electrical storage devices which concerns on this invention. It is a figure which shows the result of having measured the resistance of the electrode for electric double layer capacitors concerning this invention. It is a figure which shows the result of having measured the adhesive strength of the electrode for electric double layer capacitors concerning this invention. It is a figure which shows the result of having measured the resistance and contact | adhesion intensity | strength of the electrode for electric double layer capacitors concerning this invention, changing the magnitude | size of the surface unevenness | corrugation of a polishing roll. It is a figure which shows the result of having measured the resistance and contact | adhesion intensity | strength of the electrode for electrical double layer capacitors concerning this invention, changing the speed ratio of a polishing roll and a collector.

  FIG. 1 is a sectional view schematically showing the structure of an electric double layer capacitor according to the present invention.

  In FIG. 1, an electric double layer capacitor 1 as an electricity storage device is impregnated with an organic electrolyte in a state where a positive electrode body 2 and a negative electrode body 3 face each other with a separator 4 interposed therebetween, and is accommodated in an outer container (not shown). Configured. The positive electrode body 2 is configured by laminating a positive electrode layer 11 and a positive electrode current collector 12 via a positive electrode intermediate layer 13, and the negative electrode body 3 includes a negative electrode layer 21 and a negative electrode current collector 22 that are connected to a negative electrode intermediate layer 23. It is comprised by laminating | stacking. The positive electrode current collector 12 and the negative electrode current collector 22 are usually provided with tabs (not shown) as electrode connection terminals.

  The positive electrode current collector 12 and the negative electrode current collector 22 are made of a metal foil such as aluminum, nickel, titanium, and stainless steel. From the viewpoints of conductivity, voltage resistance, and productivity, it is preferable to use an aluminum foil. . If the thickness of the positive electrode current collector 12 and the negative electrode current collector 22 is less than 5 μm, the strength of the positive electrode current collector 12 and the negative electrode current collector 22 may be insufficient. If the thickness exceeds 100 μm, the energy density of the electrode is increased. May decrease. Therefore, the thickness of the positive electrode current collector 12 and the negative electrode current collector 22 is preferably 5 μm or more and 100 μm or less.

  The surface of the metal foil is usually a smooth (plain) glossy surface or matte surface, but the surface is roughened in order to improve adhesion with the intermediate layer and reduce resistance. It is preferable to increase the surface area and remove the oxide layer present on the surface. Here, a metal foil whose surface is physically roughened is used for the positive electrode current collector 12 and the negative electrode current collector 22. Then, a polishing roll is pressed against the surface of the metal foil, or a polishing roll is pressed against the surface of the metal foil and rubbed to physically roughen the surface of the metal foil. Thereby, irregularities are engraved on the surface of the metal foil, or the surface of the metal foil is partially scraped off to increase the roughness of the surface and remove the oxide layer on the surface. In addition, since the oxide layer on the surface of the metal foil is physically removed, the growth rate of the oxide layer after treatment is slower than when the oxide layer is chemically removed.

  Here, the polishing roll is a roll having an uneven surface made of a material harder than the positive electrode current collector 12 and the negative electrode current collector 22, or a structure in which an abrasive sheet is attached to or wound around a roll core material. Say. When the size of the irregularities formed on the surface of the polishing roll is less than 1 μm, the surface roughening effect of the positive electrode current collector 12 and the negative electrode current collector 22 is small, and the adhesion to the intermediate layer cannot be improved. . On the other hand, when the size of the unevenness is larger than 50 μm, the adhesion with the intermediate layer is not improved, and the strength of the positive electrode current collector 12 and the negative electrode current collector 22 is reduced, leading to breakage in the manufacturing process. Therefore, the size of the unevenness formed on the surface of the polishing roll is preferably 1 μm or more and 50 μm or less.

  Specifically, the polishing roll is an outer peripheral surface of a cylindrical body made of a material harder than the positive electrode current collector 12 and the negative electrode current collector 22, for example, a steel material such as carbon steel, special steel, tool steel, and stainless steel. Are formed with fine irregularities. Although the method of forming fine unevenness | corrugation in the outer peripheral surface of a steel-made cylindrical body is not specifically limited, For example, an etching and laser processing can be used. The polishing roll thus produced may be subjected to quenching treatment or surface treatment such as hard chrome plating.

  The polishing roll is an outer periphery of a cylindrical roll core made of a material harder than the positive electrode current collector 12 and the negative electrode current collector 22, for example, a steel material such as carbon steel, special steel, tool steel, and stainless steel. A ceramic particle such as alumina, silicon nitride, or silicon carbide may be directly fixed to the surface. Further, the polishing roll is an outer periphery of a roll core made in a columnar shape by a material harder than the positive electrode current collector 12 and the negative electrode current collector 22, for example, a steel material such as carbon steel, special steel, tool steel, and stainless steel. A surface of which a polishing sheet having abrasive grains such as alumina or silicon carbide is attached or wound may be used.

Next, the physical roughening method will be specifically described with reference to the drawings.
First, in the first roughening method shown in FIG. 2, the polishing roll 32 is arranged so as to press against the fixed roll 31 with a predetermined pressure, the fixed roll 31 is driven to rotate, and the polishing roll 32 is moved. The metal foil 30 used for the positive electrode current collector 12 and the negative electrode current collector 22 is rotated between the fixed roll 31 and the polishing roll 32 by being rotated in the reverse direction.

  Although the material of the fixed roll 31 is not specifically limited, For example, a rubber roll is used. Use of a rubber roll is preferable because slipping between the metal foil 30 and the fixed roll 31 can be suppressed. The polishing roll 32 has a large-diameter portion having an axial length corresponding to the width of the roughened surface 30a of the metal foil 30, and small-diameter portions on both sides in the axial direction of the large-diameter portion, using a steel material. An uneven surface 32a is formed by forming an uneven surface on the outer peripheral surface of the large-diameter portion by etching. Then, when the metal foil 30 passes between the fixed roll 31 and the polishing roll 32, the radius of the large diameter portion is several mm larger than the radius of the small diameter portion so that the non-roughened surface 30b is not plastically deformed. is doing.

  In this first roughening method, the metal foil 30 is pressed and sandwiched between the fixed roll 31 and the polishing roll 32, and the polishing roll 32 rotates in the opposite direction to the fixed roll 31, that is, the fixed roll 31. The metal foil 30 is rotated in the direction opposite to the feeding direction of the metal foil 30. Therefore, the uneven surface 32 a is pressed against the surface of the metal foil 30 with a predetermined pressure and rubbed, the surface of the metal foil 30 is shaved, and the roughened surface 30 a is formed on the surface of the metal foil 30. .

  Next, in the second roughening method shown in FIG. 3, a polishing roll 33 configured by adhering a polishing sheet 35 to the outer peripheral surface of a columnar roll core material 34 manufactured using a steel material is used. ing. The polishing sheet 35 is made by fixing abrasive grains such as alumina and silicon carbide on the sheet surface, and can be used up to # 240 to # 4000 with a count representing surface roughness. This second roughening method is the same as the first roughening method, except that the polishing roll 33 is used instead of the polishing roll 32. Also in the second roughening method, the polishing sheet 35 is pressed against the surface of the metal foil 30 with a predetermined pressure and rubbed, and the surface of the metal foil 30 is shaved to roughen the roughened surface 30a. Is formed on the surface of the metal foil 30.

  Next, in the third roughening method shown in FIG. 4, a polishing composed of a cylindrical roll core material 34 made using a steel material and a polishing sheet 35 wound around the roll core material 34. A roll is used. The abrasive sheet 35 is disposed by pressing the abrasive grain fixing surface against the metal foil 30 by the roll core material 34, and when the fixed roll 31 is driven, the roll core material 34 is rotationally driven in the reverse direction and fixed. The metal foil 30 is wound up at a constant speed in the direction opposite to the feeding direction of the metal foil 30 by the roll 31. Also in this third roughening method, the polishing sheet 35 is pressed against the surface of the metal foil 30 with a predetermined pressure and rubbed, and the surface of the metal foil 30 is shaved to roughen the roughened surface 30a. Is formed on the surface of the metal foil 30. The polishing sheet 35 may be made endless with a predetermined length and circulated. And you may make it replace | exchange after a fixed period.

  Here, since the polishing rolls 32 and 33 and the roll core material 34 are rotationally driven in the direction opposite to the fixed roll 31, the metal foil 30 can be roughened efficiently. Further, providing a speed difference between the polishing rolls 32 and 33 and the roll core material 34 and the fixed roll 31 leads to efficient and fine roughening. The speeds of the polishing rolls 32 and 33 and the roll core material 34 (polishing sheet 35) may be faster or slower than the speed of the metal foil 30, but the speed ratio between them is 5 times to 1/5 times. It is preferable to do.

  The polishing rolls 32 and 33 and the roll core 34 are driven to rotate in the direction opposite to the fixed roll 31, but may be driven to rotate in the same direction as the fixed roll 31, or the polishing rolls 32 and 33 and roll The core member 34 may be configured to be rotatable, and may be rotated in the same direction by the rotational driving force of the fixed roll 31. When the polishing rolls 32 and 33 and the roll core 34 rotate in the feeding direction of the metal foil 30 at the same speed as the metal foil 30, the uneven surface 32a and the polishing sheet 35 are pressed against the metal foil 30, and the unevenness is made of metal. Stamped on the foil 30.

  In addition, when the polishing rolls 32 and 33 and the roll core material 34 are rotationally driven in the same direction as the fixed roll 31, the metal foil 30 and the polishing rolls 32 and 33 and the roll core material 34 do not need to be at the same speed. The speed may be different. In this case, as in the case of being driven to rotate in the opposite direction to the fixed roll 31, the uneven surface 32a and the polishing sheet 35 are pressed against the surface of the metal foil 30 and rubbed, and the surface of the metal foil 30 is scraped. The surface roughness increases, the oxide layer is scraped off, the adhesion with the intermediate layer is improved, and the resistance is reduced.

  For the positive electrode intermediate layer 13 and the negative electrode intermediate layer 23, a slurry for forming an intermediate layer made of conductive particles and a binder is applied on the positive electrode current collector 12 and the negative electrode current collector 22, respectively, and the coating film is dried. Produced. The thickness of the positive electrode intermediate layer 13 and the negative electrode intermediate layer 23 is desirably 0.1 μm or more and 10 μm or less. The slurry for forming the intermediate layer is mainly mixed and dispersed in a solvent that dissolves the conductive particles, the binder, the binder, and the like, and may contain other additives such as a dispersant.

  Although it does not specifically limit as electroconductive particle used for the slurry for intermediate | middle layer formation, What is necessary is just fine particles which show electroconductivity, and materials, such as a metal particle and a carbon particle, are mentioned. For example, examples of the metal particles include aluminum fine particles and nickel fine particles, and examples of the carbon particles include carbon black acetylene black, ketjen black, furnace black, thermal black, and channel black. Further, graphite-based artificial graphite, natural graphite, graphitized carbon black, and the like can be used as the carbon particles. Moreover, electroconductive metal oxide fine powders, such as a titanium oxide and a tin oxide, can also be used as electroconductive particle. In the case of carbon black-based carbon particles, the average primary particle size is preferably 20 nm to 100 nm. In the case of metal particles or graphite-based carbon particles, the average particle size is preferably 0.1 μm to 10 μm. These particles may be used alone, or two or more kinds of particles may be mixed and used. The conductive particles are preferably contained in the intermediate layer in the range of 50% by mass to 95% by mass, and more preferably in the range of 70% by mass to 90% by mass.

  The binder used in the slurry for forming the intermediate layer is generally used in electrodes for lithium secondary batteries, electrodes for electric double layer capacitors, etc., and is chemically and electrochemically used inside the electric double layer capacitor. Any material can be used as long as it has a binding property to an active material powder such as activated carbon or a current collector. For example, the fluororesin used for the binder may be a vinylidene fluoride homopolymer (polyvinylidene fluoride), a vinylidene fluoride copolymer (eg, vinylidene fluoride-hexafluoropropylene copolymer, fluoride Vinylidene-pentafluoropropylene-based copolymer, vinylidene fluoride-chlorotrifluoroethylene-based copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based copolymer, etc.), and other fluorine resins , Ethylene-tetrafluoroethylene copolymer, propylene-tetrafluoroethylene copolymer and the like. In addition, polyvinyl alcohol, vinyl acetate, rubbers (such as styrene-butadiene copolymer latex (SBR) and acrylonitrile-butadiene copolymer latex), cellulose derivatives (sodium salt or ammonium salt of carboxymethyl cellulose (CMC), hydroxy, etc. Ethyl cellulose (HEC), hydroxymethyl cellulose (HMC) and the like), polyamide resin, polyimide resin and its precursor (polyamic acid and the like), polyacrylonitrile (PAN), polyacrylic acid and the like. These resins may be obtained by modifying a part of the resin. These resins may be used alone or in combination of two or more. The binder is preferably contained in the intermediate layer in the range of more than 0.1% by mass and not more than 50% by mass as the solid content, more preferably in the range of more than 0.5% by mass and not more than 30% by mass. More preferably.

  The solvent used in the intermediate layer forming slurry is not particularly limited as long as the binder used in the intermediate layer forming slurry can be dissolved or dispersed. Further, an aqueous solvent or an organic solvent can be used.

  The positive electrode layer 11 and the negative electrode layer 21 are formed by applying a slurry for forming an electrode layer made of an active material, a conductive additive, a binder and the like onto the positive electrode intermediate layer 13 and the negative electrode intermediate layer 23, respectively, and drying the coating film. Produced. The thicknesses of the positive electrode layer 11 and the negative electrode layer 21 are not particularly limited, but are usually 5 μm or more and 500 μm or less. As the electrode layer forming slurry, those generally used in electric double layer capacitor electrodes and the like can be used, preferably in a solvent that dissolves an active material, a conductive additive, a binder, a binder, and the like. And may be mixed with other thickeners and additives.

  As a conductive support agent used for the slurry for electrode layer formation, the same thing as the electroconductive particle illustrated by the intermediate | middle layer can be used. The above-described conductive assistants may be used alone or in combination of two or more kinds of conductive assistants. If the average primary particle size of the conductive auxiliary agent exceeds 10 μm, the contact surface between the conductive auxiliary agent and the active material is decreased, and the conductivity may be lowered. Therefore, the average primary particle size of the conductive auxiliary agent is 10 μm or less. It is desirable that Moreover, it is preferable to contain a conductive support agent in the range of 1 mass% or more and 20 mass% or less in an electrode layer, and it is still more preferable to contain in the range of 3 mass% or more and 12 mass% or less.

  As the binder used for the electrode layer forming slurry, the same binder as exemplified in the intermediate layer can be used. The binder is preferably contained in the electrode layer in a range of 0.5% by mass or more and 20% by mass or less as a solid content, and may be contained in a range of 1% by mass or more and 10% by mass or less. Further preferred.

The active material used for the electrode layer forming slurry is not particularly limited as long as it is a material that can store electricity in the electric double layer or a material that works like a double layer capacitor in a pseudo manner. Typical active materials include coconut shells, synthetic resins (phenol, vinyl chloride, etc.), pitch, petroleum coke, tar and other carbonized materials such as water vapor, potassium hydroxide and other alkalis, carbon dioxide, concentrated sulfuric acid, etc. Examples include activated carbon. Among these activated carbons, those having a specific surface area of 100 m ² / g or more are preferred, and those having a specific surface area of 800 m ² / g or more and 3,000 m ² / g or less are more preferred. The shape of the active material is not particularly limited, and examples thereof include particles and fibers.

  As active materials other than activated carbon, carbon obtained by firing graphite such as artificial graphite and natural graphite, polymer compounds such as phenolic resin, cellulose, polyacrylonitrile, carbon obtained by firing coke, mesophase pitch, and mesophase carbon Various carbon-based materials such as can be used. Further, as an active material other than activated carbon, non-porous carbon such as graphite-like microcrystalline carbon described in JP-A Nos. 11-317333 and 2002-25867 can be used.

  The average particle diameter of the particulate active material is preferably 0.5 μm or more and 15 μm or less. When the average particle diameter of the particulate active material is outside the above range, the adhesion between the electrode layer and the intermediate layer may be lowered. The active material is preferably contained in the electrode layer in the range of 50% by mass to 95% by mass, and more preferably in the range of 70% by mass to 90% by mass.

  Various apparatuses can be used as an apparatus for mixing and dispersing the above-mentioned raw materials in a wet manner to produce a slurry for forming an intermediate layer and an electrode layer. For example, a ball mill, a planetary ball mill, a bead mill, a planetary can be used. Examples include a mixer, a kneader, a pressure kneader, a homogenizer, an ultrasonic homogenizer, a roll mill, a fluid facing collision disperser, a stirring defoaming device, and a thin-film swirl type high-speed mixer.

  The apparatus for forming the coating film by applying the slurry for forming the intermediate layer and the electrode layer on the current collector or the intermediate layer is not particularly limited, and examples thereof include a roll coater, a reverse roll coater, and a die coater. , Slot die coater, bar coater, dip roll coater, bar coater, lip coater, gravure coater, comma coater, two roll reverse coater, three roll reverse coater, micro bar coater, kiss coater and the like.

  The drying conditions of the formed coating film are not particularly limited as long as the solvent contained in the coating film can be appropriately evaporated. Drying may be performed at a constant temperature, or may be performed in two or more stages from a low temperature to a high temperature. After the coating film is dried, it is preferable to perform a heat treatment at 100 ° C. or more and 250 ° C. or less in order to evaporate the solvent contained in the coating film almost completely. Examples of the heat treatment include air drying and reduced pressure (vacuum) drying.

Next, a method for manufacturing an electrode for an electricity storage device will be described with reference to FIG.
The metal foil 30 is unwound from the winding drum 40 and enters a roughening process. In the roughening step, the metal foil 30 passes between the fixed roll 31 and the polishing roll 32, and one surface thereof is roughened. Next, the roughened metal foil 30 enters the intermediate layer coating process. In the intermediate layer coating step, when the metal foil 30 is wound around the first coating roll 41 and moved, the intermediate layer forming slurry is applied to the roughened surface of the metal foil 30. Next, the metal foil 30 coated with the intermediate layer forming slurry is passed through the first drying furnace 42 to dry the coating film, and then enters the electrode layer coating step. In the electrode layer coating step, when the metal foil 30 with the intermediate layer formed is wound around the second coating roll 43 and moved, the electrode layer forming slurry is applied onto the intermediate layer of the metal foil 30. Next, the metal foil 30 coated with the electrode layer forming slurry is passed through the second drying furnace 44 to dry the coating film. Thereby, the electrode for electrical storage devices formed by laminating the intermediate layer and the electrode layer on one surface of the metal foil 30 is manufactured. The electricity storage device electrode thus manufactured is used for the positive electrode body 2 and the negative electrode body 3 of the electric double layer capacitor 1.

  The power storage device electrodes (the positive electrode body 2 and the negative electrode body 3) thus manufactured are subjected to a rolling process for the purpose of increasing the thickness accuracy and increasing the density of the electrode layers (the positive electrode layer 11 and the negative electrode layer 21). It is preferable. The rolling process may be a batch process using a flat plate press or a continuous calendar process using a calendar roll. The rolling temperature may be room temperature or may be processed by raising the temperature to the melting point or lower of the binder.

  In the method for manufacturing an electrode for an electricity storage device according to the present invention, the intermediate layer is coated and the electrode layer is coated after the roughening step. Then, after the roughening treatment, the intermediate layer is applied without taking time, so that the intermediate layer is formed in a state where the oxide layer is not formed thick on the surface of the metal foil 30 (current collector), and the resistance is further increased. The effect of reducing is increased. The period from the physical roughening step to the intermediate layer coating step is preferably within one week if possible.

  Moreover, if this physical roughening step, the step of forming the intermediate layer, and the step of forming the electrode layer can be performed continuously, a dedicated device may be used for each step, One integrated device may be used. And it is also possible to apply | coat an intermediate | middle layer and an electrode layer simultaneously by devising a coating part, ie, using a die coater, an extrusion-type coater, etc. By simultaneously applying the intermediate layer and the electrode layer, productivity can be further improved.

Moreover, although the drying process is described as being performed both after the formation of the intermediate layer and after the formation of the electrode layer, it may be performed only after the formation of the electrode layer.
Further, after the physical roughening step, a step of removing the current collector fine dust generated in the roughening step with a dust removing device may be added. The dust removal method is not particularly limited, and examples thereof include a suction method, a push-pull method, an electrostatic roller collection method, a brush cleaning method, and a wet cleaning method.

  The positive electrode body 2 and the negative electrode body 3 manufactured as described above are impregnated with an organic electrolytic solution in a state of being opposed to each other with the separator 4 interposed therebetween, and are accommodated in an outer container (not shown), so that the electricity shown in FIG. A double layer capacitor 1 is obtained.

  Examples of the separator 4 include polyolefin-based porous films such as polyethylene and polypropylene, cellulose-based porous films, inorganic ceramic powder-containing porous films, polyimide / polyamide-based porous films, and nonwoven fabrics. A solid electrolyte membrane, a gel electrolyte-containing separator, or the like can also be used as the separator 4.

  As the organic electrolytic solution, a known one used in electric double layer capacitors can be used, and specifically, an organic electrolytic solution composed of an organic solvent and an electrolyte can be mentioned. Examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, 3-methyl sulfolane, γ-butyrolactone, and acetonitrile. These organic solvents may be used alone or in combination of two or more. Examples of the electrolyte include tetraethylammonium tetrafluoroborate, triethylmonomethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, spiro quaternary ammonium salt, room temperature molten salt (ionic liquid), solid electrolyte, gel electrolyte, and the like.

  The outer container is not particularly limited, and those having a known structure and material can be used. Specific examples include those made of a metal can or an aluminum laminate sheet.

According to the present invention, since the metal foil 30 whose surface is physically roughened is used for the positive electrode current collector 12 and the negative electrode current collector 22, the surface areas of the positive electrode current collector 12 and the negative electrode current collector 22 are reduced. The oxide layer present on the surface increases and is removed, and the growth rate of the oxide layer after the treatment becomes slow. Therefore, the adhesion strength between the positive electrode current collector 12 and the negative electrode current collector 22 and the positive electrode intermediate layer 13 and the negative electrode intermediate layer 23 is increased and the resistance is reduced, so that the capacitance is high and An electrode for an electric double layer capacitor having a low resistance is obtained.
Moreover, the electric double layer capacitor provided with the electrode for the electric double layer capacitor according to the present invention has a high electrostatic capacity, a low electric resistance, and an excellent cycle life characteristic.

Further, according to the present invention, the surface of the metal foil 30 is physically roughened using a polishing roll, so that a rough surface having a large surface area and from which an oxide film has been removed can be produced inexpensively and efficiently. It can be formed on the surface of the metal foil 30.
Further, since the roughening step and the intermediate layer coating step are continuously performed, the intermediate layer is applied before the oxide film is formed thick on the roughened surface 30a of the metal foil 30, and the adhesion strength is increased. The resistance can be increased and the resistance can be reduced.

  Further, when electrolytic polishing or chemical polishing is performed on the metal foil 30, the degree of dissolution is caused due to the metal component, surface state, crystal structure, etc. of the metal foil 30, and the surface of the metal foil 30 is roughened. The Thus, when chemically roughening, since the surface of the metal foil 30 is partially dissolved, the surface layer after the roughening of the metal foil 30 is more spongy than before the roughening. Become. However, when the surface is physically roughened, since the abrasive grains are roughened by being pressed against the surface of the metal foil 30 and rubbed, the thickness of the portion of the metal foil 30 where the abrasive grains do not hit is ensured. The Thus, when the same unevenness | corrugation is formed in the surface of the metal foil 30 of the same board thickness, the physical roughening method is the sponge of the metal foil 30 compared with the chemical roughening method. Since the state is suppressed, the strength reduction of the metal foil 30 is suppressed, and the breakage of the metal foil 30 in the manufacturing process is suppressed.

  In the above description, the cell structure of the electric double layer capacitor includes the positive electrode intermediate layer and the positive electrode layer formed on one side of the positive electrode current collector, and the negative electrode intermediate layer and the negative electrode formed on one side of the negative electrode current collector. The cell structure of the electric double layer capacitor has a positive electrode body in which an intermediate layer and an electrode layer are formed on both sides of a current collector, and a negative electrode body. Alternatively, a stacked structure in which layers are alternately stacked, or a bipolar structure may be used. The cell structure of the electric double layer capacitor may be a structure in which a sheet-like electrode in which an intermediate layer and an electrode layer are formed on both sides of a current collector is wound or folded together with a separator.

In the above description, the electrode for the electricity storage device is applied to the electrode for the electric double layer capacitor. However, the electrode for the electricity storage device is not limited to the electrode for the electric double layer capacitor, for example, a lithium ion capacitor. It can be applied to an electrode for a battery or an electrode for a lithium ion battery.
In the case of a lithium ion capacitor electrode and a lithium ion battery electrode, an aluminum foil having a thickness of 5 to 30 μm is used for the positive electrode current collector, and a thickness of 5 μm is used for the negative electrode current collector. Copper foil formed to ˜20 μm is used.

In the case of an electrode for a lithium ion capacitor, activated carbon particles are used as the active material for the positive electrode layer, and carbon particles such as graphite that occlude lithium are used as the active material for the negative electrode layer. It is desirable that the diameter of the particles be several μm to several tens of μm.
On the other hand, in the case of an electrode for a lithium ion battery, the active material of the positive electrode layer uses an oxide lithium compound such as cobalt, nickel, manganese, or olivine type lithium iron phosphate. In this case, carbon particles such as graphite that occlude lithium are used, and the diameter of each electrode active material particle is preferably several μm to several tens μm.

The lithium ion capacitor is obtained by doping a positive electrode for an electric double layer capacitor and a negative electrode for a lithium ion battery with lithium ions, and can obtain an upper limit voltage higher than that of the electric double layer capacitor.
In addition, since a lithium ion battery uses an active material containing lithium for a positive electrode and can stably store lithium filled in a negative electrode, the battery has a high energy density.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Example 1]
Using a 30 μm thick aluminum foil as a current collector, this is driven while being fixed with a rubber roll (fixed roll), and a polishing roll applied with a constant load with an air cylinder is pressed against the surface of the aluminum foil. Rotated the polishing roll in the opposite direction, and roughened at a speed ratio (| polishing roll speed | / | aluminum foil speed |) 2. The polishing roll was prepared by attaching a polishing sheet of count # 800 (average grain size of abrasive grains: 20 μm) to the surface of the iron roll core material.

  Carboxymethylcellulose ammonium (CMC) powder (DN-400 manufactured by Daicel Chemical Industries, Ltd.) as a thickener was dissolved in an aqueous solvent to a concentration of 3% by mass to prepare an aqueous CMC solution. Using a planetary mixer, acetylene black (ACB) powder (DENKA BLACK, manufactured by Denki Kagaku Kogyo Co., Ltd., average primary particle size 0.035 μm) as conductive carbon is mixed with an aqueous CMC solution, and as a binder. A styrene butadiene-rubber (SBR) aqueous dispersion (BM-400B manufactured by Nippon Zeon Co., Ltd.) was added and further diluted with an aqueous solvent to prepare a slurry for forming an intermediate layer.

  Using a desktop coater, this intermediate layer forming slurry was applied to one side of the above-mentioned roughened aluminum foil. The thickness of the coating film was adjusted with a Baker type applicator. After coating, the mixture was blown and dried at 80 ° C. for 1 hour with a blow dryer, and then vacuum dried at 200 ° C. for 24 hours with a vacuum dryer. The thickness of the intermediate layer formed on the aluminum foil was about 2 μm.

CMC powder was dissolved in an aqueous solvent to a concentration of 3% by mass to prepare a CMC aqueous solution. Using a planetary mixer, ACB powder as a conductive additive and CMC aqueous solution are mixed, and further a water solvent and water vapor activated activated carbon (average particle size 5 μm, specific surface area about 2,000 m ² / g) as an active material. The mixture was mixed and kneaded for 30 minutes. Thereafter, an SBR aqueous dispersion as a binder was added and diluted with an aqueous solvent to prepare an electrode layer forming slurry.

  This electrode layer forming slurry was applied to the upper surface of the intermediate layer formed on one side of the aluminum foil using a desktop coater. The thickness of the coating film was adjusted with a Baker type applicator. After coating, the resultant was blown and dried at 80 ° C. for 1 hour with a blow dryer, and then vacuum dried at 200 ° C. for 24 hours with a vacuum dryer to prepare an electrode sheet. The thickness of the electrode layer in the electrode sheet was about 90 μm.

  This electrode sheet was calendered at 150 ° C. with a hot roll press, and the thickness of the electrode layer was about 80 μm. An electrode piece of 20 mm × 20 mm and 20 mm × 100 mm was cut out from the electrode sheet after the calendar treatment, and a 90 ° peel test was performed to measure electrode resistance and evaluate adhesion.

  The electrode resistance was measured using a milliohm meter in a state where a 20 mm × 20 mm electrode piece was sandwiched between two gold-plated copper plates and a pressure of about 2.7 MPa was applied. In the 90 ° peel test, an electrode piece of 20 mm × 100 mm was fixed to a fixed base, and a test tape was applied thereto, and the adhesion strength between the current collector and the intermediate layer was evaluated while pulling the tape 90 °. .

[Example 2]
An electrode piece was prepared in the same manner as in Example 1 except that an intermediate layer and an electrode layer were formed one month after the roughening treatment was performed on the aluminum foil as the current collector, and the same evaluation was performed.

[Example 3]
An electrode piece was produced in the same manner as in Example 1 except that a roll having a mirror-finished surface and a surface having no irregularities was used as a polishing roll, and the same evaluation was performed.

[Example 4]
An electrode piece was prepared in the same manner as in Example 1 except that a roll having 1 μm irregularities imprinted on the surface was used as a polishing roll, and the same evaluation was performed.

[Example 5]
An electrode piece was produced in the same manner as in Example 1 except that a roll having 50 μm irregularities imprinted on the surface was used as a polishing roll, and the same evaluation was performed.

[Example 6]
An electrode piece was prepared in the same manner as in Example 1 except that a roll having 100 μm irregularities stamped on its surface was used as a polishing roll, and the same evaluation was performed.

[Example 7]
An electrode piece was prepared in the same manner as in Example 1 except that a polishing roll prepared by attaching a # 800 polishing sheet to the surface of an iron roll core was used and a roughening treatment was performed at a speed ratio of 5. The same evaluation was performed.

[Example 8]
An electrode piece was prepared in the same manner as in Example 1 except that a polishing roll prepared by attaching a polishing sheet of count # 800 to the surface of an iron roll core was used and a roughening treatment was performed at a speed ratio of 10. The same evaluation was performed.

[Example 9]
An electrode piece was obtained in the same manner as in Example 1 except that a polishing roll produced by attaching a count # 800 polishing sheet to the surface of an iron roll core was used and a roughening treatment was performed at a speed ratio of 1/2. The same evaluation was performed.

[Example 10]
An electrode piece was prepared in the same manner as in Example 1 except that a polishing roll prepared by attaching a count # 800 polishing sheet to the surface of an iron roll core was used and the surface was roughened at a speed ratio of 1/5. The same evaluation was performed.

[Example 11]
An electrode piece was prepared in the same manner as in Example 1 except that a polishing roll prepared by attaching a count # 800 polishing sheet to the surface of an iron roll core was used and the surface was roughened at a speed ratio of 1/10. The same evaluation was performed.

[Comparative Example 1]
An electrode piece was produced in the same manner as in Example 1 except that an aluminum foil that was not subjected to roughening treatment was used for the current collector, and the same evaluation was performed.

[Comparative Example 2]
An electrode piece was produced in the same manner as in Example 1 except that the intermediate layer was not formed, and the same evaluation was performed.

[Comparative Example 3]
An electrode piece was produced in the same manner as in Example 1 except that an aluminum foil that was not subjected to roughening treatment was used for the current collector and an intermediate layer was not formed, and the same evaluation was performed.

The measurement results of the electrode resistance in Examples 1 and 2 and Comparative Examples 1 to 3 are shown in FIG.
6 that the electrodes of Examples 1 and 2 and Comparative Example 1 have a lower resistance than the electrodes of Comparative Examples 2 and 3. This resistance reduction effect is assumed to be due to the intermediate layer interposed between the current collector and the electrode layer. It can also be seen that the resistances of the electrodes of Examples 1 and 2 are lower than those of the electrode of Comparative Example 1. This resistance reduction effect is presumed to be due to the removal of the oxide film on the current collector surface by the roughening treatment. Further, the resistance of the electrode of Example 1 was lower than that of the electrode of Example 2. This was because the period from the roughening treatment to application of the intermediate layer was as long as one month, and the roughened surface of the current collector This is presumably due to the formation of an oxide film.

Moreover, the result of having measured the adhesion strength of the electrode in Examples 1, 2 and Comparative Examples 1-3 is shown in FIG.
From FIG. 7, it can be seen that the adhesion strength of the electrodes of Examples 1 and 2 is higher than that of Comparative Examples 1 and 3. This adhesion improving effect is presumed to be due to an increase in the surface area of the current collector due to the roughening treatment.

Moreover, the result of having measured the electrode resistance in Example 1, 3-6 and the contact | adhesion intensity | strength of an electrode is shown in FIG.
From FIG. 8, the adhesion strength decreases rapidly when the surface roughness of the polishing roll is smaller than 1 μm, gradually increases when it exceeds 1 μm, takes a maximum value at 20 μm, and gradually decreases when it exceeds 20 μm. It can be seen that when the thickness exceeds 50 μm, it is significantly reduced. Further, from FIG. 8, the electrode resistance increases rapidly when the size of the surface irregularities of the polishing roll becomes smaller than 1 μm, gradually decreases when exceeding 1 μm, takes a minimum value at 20 μm, and gradually increases when exceeding 20 μm. It turns out that it becomes high when it exceeds 50 μm.

  Thus, from the viewpoint of reducing the electrode resistance and increasing the adhesion strength of the electrode, the size of the unevenness of the polishing roll is preferably 1 μm or more and 50 μm or less. This is because, when the size of the surface irregularities of the polishing roll is smaller than 1 μm, the effect of roughening the current collector is reduced, the increase in the surface area of the current collector is suppressed, and the size of the surface irregularities of the polishing roll is 50 μm. When it becomes larger, the area where the projections (abrasive grains) of the polishing roll hit the surface of the current collector is reduced, the effect of roughening the current collector is reduced, and the increase in the surface area of the current collector is suppressed. It is inferred.

Moreover, the result of having measured the electrode resistance in Example 1, 7-11 and the contact | adhesion intensity | strength of an electrode is shown in FIG.
From FIG. 9, the adhesion strength decreases rapidly when the speed ratio is less than 1/5, gradually increases when it exceeds 1/5, takes a maximum value at about 1, and gradually decreases when it exceeds 1. It turns out that it will become rapidly small when 5 is exceeded. Further, from FIG. 9, the electrode resistance increases rapidly when the speed ratio is less than 1/5, gradually decreases when it exceeds 1/5, takes a minimum value at about 1, and gradually increases when it exceeds 1. It can be seen that when it exceeds 5, the value increases rapidly.

  Thus, it is preferable that the speed ratio is 1/5 or more and 5 or less from the viewpoint of reducing the electrode resistance and increasing the adhesion strength of the electrode. This is because when the speed ratio is less than 1/5, the current collector moves at an excessive speed in a state where the abrasive grains are pressed against the surface. Moves at an excessive speed while pressed against the surface of the current collector, so that a large flash is formed at the edge of the concave portion of the surface of the current collector formed by scraping with the abrasive grains, and the intermediate layer or electrode This is presumably due to the fact that the layer could not be uniformly applied to the current collector surface.

  Further, ten 200 mm × 20 mm test pieces were cut out from the roughened aluminum foil prepared in Example 1, and a tensile strength test was performed in the long side direction. An intensity of cm was shown. On the other hand, 10 200 mm × 20 mm test pieces were similarly cut out from a commercially available 30 μm-thick etched aluminum foil, and a tensile strength test was conducted in the long side direction. As a result, 7 out of 10 pieces were about 4.5 kg. Although the strength of / cm was shown, three pieces broke at 2 kg / cm or less. From this, it was confirmed that the strength of the roughened aluminum foil according to Example 1 was high.

  DESCRIPTION OF SYMBOLS 1 Electric double layer capacitor (electric storage device), 2 Positive electrode body (electrode for electrical storage devices), 3 Negative electrode body (electrode for electrical storage devices), 11 Positive electrode layer, 12 Positive electrode collector, 13 Positive electrode intermediate layer, 21 Negative electrode layer, 22 Negative electrode current collector, 23 negative electrode intermediate layer, 30 metal foil (current collector), 32, 33 polishing roll, 34 roll core material, 35 polishing sheet.

Claims (6)

A method for producing an electrode for an electricity storage device, comprising: a current collector made of metal foil; an intermediate layer containing conductive particles formed on the current collector; and an electrode layer formed on the intermediate layer Because
Prior to the step of forming the intermediate layer on the current collector, a method for producing an electrode for an electricity storage device, comprising a roughening step of physically roughening a surface of the current collector.   The method for producing an electrode for an electricity storage device according to claim 1, wherein, in the roughening step, a polishing roll is pressed against the surface of the current collector to roughen the surface of the current collector.   2. The electrode for an electricity storage device according to claim 1, wherein, in the roughening step, a polishing roll is pressed against the surface of the current collector and rubbed to roughen the surface of the current collector. Manufacturing method.   The method for producing an electrode for an electricity storage device according to claim 2 or 3, wherein the surface roughness of the polishing roll is 1 µm or more and 50 µm or less.   The production of the electrode for an electricity storage device according to any one of claims 1 to 4, wherein the roughening step and the step of forming an intermediate layer on the current collector are continuously performed. Method.   The electrical storage device using the electrical storage device electrode manufactured by the manufacturing method of the electrical storage device electrode of any one of the said Claim 1 thru | or 5.

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