Method for producing lead member-equipped electrochemical device electrode and method for producing electrochemical device

Abstract

This method for producing a lead member-equipped electrochemical device electrode comprises: a first step for preparing a current collector foil having a roughened surface and a slurry including an activated carbon and a binder; a second step for obtaining an electrode by applying the slurry on the surface of the current collector foil and drying the same to thereby form an active layer; and a third step for connecting the electrode and the lead member. In the second step, the application of the slurry to the current collector foil is performed intermittently to form a non-application region where a surface of the current collector foil is exposed at a portion of the electrode. In the third step, the lead member is attached to the non-application region. The binder contains an elastomer, and the contained amount of the elastomer in the active layer is more than 0.25 mass% but less than 3 mass%.

Description

Method for manufacturing an electrode for an electrochemical device with a lead member and method for manufacturing an electrochemical device

[0001] The present disclosure relates to a method for manufacturing an electrode for an electrochemical device with a lead member, and a method for manufacturing an electrochemical device.

[0002] An example of an electrochemical device is the electric double layer capacitor. Compared to secondary batteries, electric double layer capacitors have a longer lifespan, can be rapidly charged, and have superior output characteristics. For these reasons, electrochemical devices such as electric double layer capacitors are widely used as backup power sources.

[0003] An electric double layer capacitor includes, for example, a wound body (capacitor element) formed by winding a pair of polarizable electrodes with a separator interposed therebetween, and an electrolyte. The electrodes are obtained, for example, by applying a slurry containing activated carbon to the surface of a current collector foil (e.g., an etched aluminum foil) with a roughened surface, followed by drying to form an active layer (see, for example, Patent Document 1).

[0004] A lead member is connected to the electrode. The electrode and lead member are connected by forming an area in part of the electrode where the surface of the current collector foil is exposed (hereinafter simply referred to as the "current collector foil exposed portion") and attaching the lead member to the current collector foil exposed portion. The current collector foil exposed portion is usually formed by heat pressing a portion of the active layer formed on the surface of the current collector foil and then rubbing it off with a brush or the like. The heat pressing is performed to make it easier to remove part of the active layer with a brush or the like.

[0005] Patent No. 5278670 specification

[0006] When the exposed portion of the current collector foil is formed by heat pressing and scraping off a portion of the active layer using a brush or the like, the active layer near the exposed portion of the current collector foil is likely to fall off from the current collector foil. This also increases the surface roughness of the exposed portion of the current collector foil, which tends to increase the resistance between the electrode and the lead member. As a result, the performance of the electrochemical device deteriorates.

[0007] In view of the above, one aspect of the present disclosure relates to a method for manufacturing an electrode for an electrochemical device with a lead member, the method including: a first step of preparing a slurry containing activated carbon and a binder, and a current collector foil having a roughened surface; a second step of applying the slurry to the surface of the current collector foil, drying the slurry, and forming an active layer to obtain an electrode; and a third step of connecting the electrode and a lead member, wherein in the second step, the slurry is intermittently applied to the current collector foil to form an uncoated region in part of the electrode where the surface of the current collector foil is exposed; and in the third step, the lead member is attached to the uncoated region, the binder containing an elastomer, and the content of the elastomer in the active layer is greater than 0.25 mass % and less than 3 mass %.

[0008] Another aspect of the present disclosure relates to a method for manufacturing an electrochemical device, comprising: step A of preparing a first electrode with a first lead member and a second electrode with a second lead member; step B of winding the first electrode and the second electrode with a separator interposed therebetween to obtain a wound body; and step C of impregnating the wound body with an electrolyte solution, wherein in step A, at least one of the first electrode with the first lead member and the second electrode with the second lead member is obtained by the above-mentioned method for manufacturing an electrode for an electrochemical device with lead members.

[0009] According to the present disclosure, it is possible to suppress the deterioration of the performance of an electrochemical device. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of its structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0010] 1 is a front view showing an example of a leaded electrode; FIG. 2 is a cross-sectional view showing an example of a leaded electrode; FIG. 3 is a partially cut-out perspective view of an electrochemical device.

[0011] Hereinafter, embodiments of the present invention will be described, but the electrochemical device according to the present invention is not limited to the following embodiments. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "numerical value A or more and numerical value B or less."

[0012] In the following description, the term "comprises" encompasses "comprises," "consists essentially of," and "consists of."

[0013] A method for manufacturing an electrode for an electrochemical device with a lead member according to one embodiment of the present disclosure includes first to third steps. In the first step, a slurry containing an electrode material and a current collector foil having a roughened surface are prepared. In the second step, the slurry is applied to the surface of the current collector foil, dried, and an active layer is formed to obtain an electrode. In the third step, the electrode and the lead member are connected. The electrode material contains, as essential components, activated carbon, which is an active material, and a binder. The active layer is a layer of the electrode material. An electrode containing activated carbon adsorbs ions during charging and desorbs ions during discharging.

[0014] In the second step, the slurry is applied intermittently to the current collector foil to form an uncoated area in which the surface of the current collector foil is exposed in part of the electrode, and in the third step, a lead member is attached to the uncoated area.

[0015] Forming the exposed portion of the current collector foil (uncoated area) by intermittent coating prevents the active layer near the exposed portion from falling off the current collector foil when the exposed portion is formed by heat pressing and scraping off part of the active layer with a brush or the like. Furthermore, an increase in surface roughness of the exposed portion of the current collector foil and the resulting increase in resistance at the connection between the electrode and the lead member are suppressed. As a result, a decrease in the performance of the electrochemical device is suppressed.

[0016] The binder contains an elastomer, and the content of the elastomer in the active layer (electrode material) is more than 0.25 mass % and less than 3 mass %. The content of the elastomer in the active layer (electrode material) means the mass ratio (percentage) of the elastomer to the entire active layer (electrode material).

[0017] When the content of the elastomer in the active layer (electrode material) is greater than 0.25% by mass, the binding strength of the active layer is increased, the adhesion between the active layer and the current collector foil is improved, and an electrochemical device with low internal resistance is obtained. In addition, the active layer is prevented from falling off, and the occurrence of micro-short circuits and a decrease in capacity in the electrochemical device are suppressed.

[0018] However, if the content of the elastomer in the active layer (electrode material) is greater than or equal to 3% by mass, the viscosity of the slurry used to form the active layer increases, which may cause tailing of the coating film when the slurry is intermittently applied to the current collector foil, thereby reducing the reliability of the formation of the exposed portion of the current collector foil.

[0019] From the viewpoint of further reducing the internal resistance of the electrochemical device, the content of the elastomer in the active layer is preferably 0.5% by mass or more and 2.5% by mass or less.

[0020] An etched metal foil (etched foil) can be used as the current collector foil with a roughened surface. Etched foil is more advantageous than plain foil in terms of improving the adhesion between the active layer and the current collector foil. By using etched foil as the current collector foil, a small amount (less than 3 mass % (or 2.5 mass % or less)) of elastomer (e.g., SBR) can effectively improve the adhesion between the active layer and the current collector foil.

[0021] Because an active layer containing activated carbon does not undergo significant expansion and contraction like the active material layer of a lithium-ion secondary battery (LIB), etched foils with appropriate thickness and strength can be used as current collector foils without compromising energy density. LIBs use active materials (e.g., graphite, Si-based active materials, etc.) that absorb and release lithium ions, which expand and contract significantly during charging and discharging. Considering the expansion and contraction of the active material layer and the thickness and strength of the current collector foil required for LIBs, etched foils are difficult to use in LIBs.

[0022] (First Step) (Slurry) The slurry is prepared by dispersing an electrode material in a dispersion medium. The electrode material contains at least activated carbon and a binder. The dispersion medium may be, for example, water. The water content in the slurry is, for example, 60% by mass or more and 80% by mass or less with respect to the total mass of the slurry.

[0023] The activated carbon (activated carbon particles) serving as the active material is not particularly limited, and known activated carbons used in electrochemical devices may be used. Activated carbon may be produced, for example, by heat-treating a raw material to carbonize it and then activating the resulting carbonized material. Examples of raw materials include wood, coconut shells, pulp waste liquor, coal or coal-based pitch obtained by its thermal decomposition, heavy oil or petroleum-based pitch obtained by its thermal decomposition, phenolic resin, petroleum coke, and coal coke. Examples of activation treatments include gas activation using a gas such as steam and chemical activation using an alkali such as potassium hydroxide. The activated carbon particles obtained by the activation treatment may be pulverized. After pulverization, classification may be performed. For example, a ball mill, a jet mill, or the like may be used for pulverization.

[0024] The content of activated carbon in the electrode material (active layer) is not particularly limited, but may be 60% by mass or more and 95% by mass or less, or 70% by mass or more and 90% by mass or less. The content of activated carbon in the electrode material (active layer) means the mass ratio (percentage) of activated carbon to the entire electrode material (active layer).

[0025] The binder contains at least an elastomer. The elastomer may contain, for example, a rubber component and at least one selected from the group consisting of styrene butadiene rubber (SBR), acrylic rubber, and acrylonitrile butadiene rubber. Among these, SBR is preferred from the viewpoint that a small amount of addition can increase the binding strength of the active layer and the adhesion strength between the active layer and the current collector foil. The binder may be composed solely of SBR.

[0026] Styrene-butadiene rubber is a copolymer containing styrene and butadiene as main monomers (for example, a copolymer of styrene and butadiene), and may be a modified version of such a copolymer.

[0027] Acrylic rubber is a polymer containing acrylic acid ester as the main monomer. Examples of acrylic rubber include copolymers of two or more monomers containing acrylic acid ester and other monomers, and also modified versions of these copolymers. Examples of other monomers include 2-chloroethyl vinyl ether and acrylonitrile. Examples of acrylic acid esters include ethyl acrylate, butyl acrylate, and methoxyethyl acrylate. Two or more types of acrylic acid esters may be mixed and used. The acrylic rubber may be fluorinated.

[0028] The binder may contain components other than the elastomer, such as a resin component such as polytetrafluoroethylene (PTFE). The proportion of the elastomer in the binder may be 75% by mass or more, 90% by mass or more, or even 100% by mass.

[0029] The electrode material may contain components other than activated carbon and a binder. Examples of the other components include a conductive agent and a thickener. Examples of the conductive agent include carbon black such as acetylene black. Examples of the thickener include carboxymethyl cellulose (CMC) (including alkali metal salts and ammonium salts of CMC).

[0030] The TI value of the slurry may be 2 or more and 4 or less, or 2.5 or more and 4 or less. When the TI value of the slurry is 2 or more, tailing of the coating film is likely to be suppressed, improving the reliability of the formation of the exposed portion of the current collecting foil. When the TI value of the slurry is 4 or less, the binding strength of the active layer is likely to be increased, and the adhesion between the active layer and the current collecting foil is likely to be improved. When the proportion of the elastomer (e.g., SBR) in the electrode material is more than 0.25 mass% and less than 3 mass% (or 0.5 mass% or more and 2.5 mass% or less), the TI of the slurry can be easily adjusted to be within the above range.

[0031] The TI value of a slurry is determined as follows: The viscosity of the slurry at 25°C is measured using a B-type viscometer or an E-type viscometer. The viscosity η1 of the slurry at a rotation speed of 1 rpm and the viscosity η2 of the slurry at a rotation speed of 10 rpm are determined. The ratio of the viscosity η1 to the viscosity η2, η1 / η2, is calculated and used as the TI value.

[0032] (Current Collector Foil) The arithmetic mean roughness Ra of the surface of the current collector foil is preferably 0.5 μm or more and 1 μm or less. The arithmetic mean roughness Ra of the surface of an etched current collector foil is, for example, 0.5 μm or more, and may be 0.6 μm or more. When the arithmetic mean surface roughness Ra of the surface of the current collector foil is 1 μm or less, the resistance of the connection between the electrode (exposed portion of the current collector foil) and the lead member is likely to be reduced. The intermittent application described above makes it easy to form an exposed current collector portion having a surface with an arithmetic mean roughness Ra within the above range. The arithmetic mean roughness Ra is an index indicating surface roughness and is determined in accordance with JIS B 0601:2013.

[0033] The thickness of the current collector foil may be 30 μm or less, or may be 20 μm or less. By reducing the thickness of the current collector foil to 20 μm or less, the amount of active material filled can be increased, resulting in higher capacity. When an elastomer (e.g., SBR) is used as a binder for a thin current collector foil of 20 μm or less, the binding strength of the active layer and the adhesion between the active layer and the current collector foil are strong, and the strength of the current collector foil is low, making it difficult to remove part of the active layer with a brush or the like. Therefore, in the above case, it is effective to form an exposed portion of the current collector foil by intermittently applying a slurry to the current collector foil.

[0034] Examples of materials for the current collector foil include aluminum, aluminum alloys, nickel, titanium, etc. Among these, aluminum or aluminum alloys are preferred from the viewpoints of low cost, adequate strength, and high conductivity.

[0035] (Second Step) In the second step, a slurry is applied to the surface of the current collector foil, the coating is dried, and compressed as necessary to form an active layer. The dispersion medium in the slurry is removed by drying, and a layer of electrode material is formed as the active layer. The thickness of the active layer (thickness per side) is, for example, 40 μm or more and 80 μm or less. The slurry may be applied to one surface of the current collector foil, or may be applied to both surfaces of the current collector foil. The slurry is applied to the current collector foil intermittently to form coated and uncoated regions. When the slurry is applied to both sides of the current collector foil, the coated and uncoated regions may be formed in the same pattern on each side of the current collector foil.

[0036] The coating method is not particularly limited as long as it is a method that allows intermittent coating, and examples thereof include die coating, comma coating, gravure coating, etc. Among these, die coating is preferred as the coating method from the viewpoints that foreign matter is not mixed in due to the sealed state and the amount of slurry to be coated can be easily controlled by using a pump.

[0037] A long current collecting foil may be supplied to a coating device, and the slurry may be intermittently coated on both sides of the current collecting foil to form a predetermined coating pattern, an active layer may be formed, and the foil may be cut at predetermined positions to produce a plurality of electrodes each having an exposed current collecting foil portion.

[0038] (Third Step) In the third step, the electrode and the lead member are connected by attaching the lead member to the uncoated area of ​​the electrode. The attachment of the lead member to the uncoated area of ​​the electrode is performed by, for example, crimping using a needle-shaped member or cold welding.

[0039] The lead member includes, for example, a flat tab portion, a lead wire, and a connection portion connecting the tab portion and the lead wire. The lead member is not particularly limited as long as it is a conductive member having a tab portion, a connection portion, and a lead wire, but can be prepared, for example, as follows: A metal rod-shaped member is prepared, and one end of the member is flattened by pressing or the like to form the tab portion. The other end is left in its rod shape to form the connection portion. The connection portion and the lead wire are connected by welding or the like.

[0040] The connection between an electrode and a lead member by crimping is performed, for example, as follows: A tab portion of the lead member is placed on one surface of the uncoated area of ​​the electrode, and an overlapping portion between the tab portion and the uncoated area is formed. A through-hole is formed by drilling a predetermined position in the overlapping portion from the tab portion side using a needle-shaped member. As the through-hole is formed, a portion of the tab portion is made to protrude from the other surface of the uncoated area of ​​the electrode, forming a protruding portion. The overlapping portion is then pressed, and the protruding portion is bent onto the other surface of the uncoated area to adhere closely, forming a petal-shaped crimping piece. The crimping process is performed, for example, at two to four predetermined positions within the uncoated area.

[0041] Here, Fig. 1 is a front view schematically showing an example of an electrode with lead members obtained by the manufacturing method of an electrode with lead members according to this embodiment. Fig. 2 is a cross-sectional view schematically showing an example of an electrode with lead members obtained by the manufacturing method of an electrode with lead members according to this embodiment. Fig. 2 shows a cross-section including a crimped portion 40. Each component in the figure is shown schematically, and the relationship between the size and thickness of each component is not limited to this.

[0042] The strip-shaped electrode 20 includes a current collector foil 21 with a roughened surface and active layers 22 supported on both sides of the current collector foil 21. The electrode 20 has a current collector foil exposed portion 23 in a portion thereof. The current collector foil exposed portion 23 is formed on each side of the electrode 20, and when the electrode 20 is viewed in the direction normal to its main surface, the current collector foil exposed portions 23 on both sides of the electrode 20 are formed so as to be substantially aligned. Meanwhile, the lead member 30 includes a flat tab portion 31, a connection portion 32, and a lead wire 33. The tab portion 31 is placed on the current collector foil exposed portion 23 on one surface of the electrode 20 and attached by crimping. In this manner, the electrode 20 and the lead member 30 are connected. The crimping portion 40 formed by crimping has a through-hole 41 and includes a crimping piece 42 formed on the current collector foil exposed portion 23 on the other surface of the electrode 20. Although two crimping portions 40 are provided, the number of crimping portions 40 is not limited to this. In this embodiment, the current collecting foil exposed portion 23 is obtained by intermittent coating (forming an uncoated region).

[0043] [Method for manufacturing an electrochemical device] A method for manufacturing an electrochemical device according to an embodiment of the present disclosure includes step A of preparing a first electrode with a first lead member and a second electrode with a second lead member, step B of winding the first electrode and the second electrode with a separator interposed therebetween to obtain a wound body, and step C of impregnating the wound body with an electrolyte. In step A, at least one of the first electrode with the first lead member and the second electrode with the second lead member is obtained by the method for manufacturing an electrode for an electrochemical device with a lead member according to an embodiment of the present disclosure. Hereinafter, the electrode with a lead member obtained by the method for manufacturing an electrode for an electrochemical device with a lead member according to an embodiment of the present disclosure is also referred to as "electrode E with a lead member."

[0044] Examples of electrochemical devices include electric double layer capacitors (EDLCs) and lithium ion capacitors (LICs). Note that "capacitor" may be read as "condenser." When the electrochemical device is an EDLC, a lead-attached electrode E may be used for at least one of a pair of lead-attached electrodes. When the electrochemical device is an LIC, a lead-attached electrode E may be used for one of the pair of lead-attached electrodes (positive electrode), and a lead-attached negative electrode used in a lithium ion secondary battery may be used for the other of the pair of lead-attached electrodes (negative electrode). The negative electrode used in a lithium ion secondary battery contains, for example, a negative electrode active material (e.g., graphite) capable of absorbing and releasing lithium ions.

[0045] The electrolyte solution includes a solvent (non-aqueous solvent) and an ionic substance. The ionic substance is dissolved in the solvent and includes a cation and an anion. The ionic substance may include, for example, a low-melting-point compound (ionic liquid) that can exist as a liquid at around room temperature. The concentration of the ionic substance in the electrolyte solution is, for example, 0.5 mol / L or more and 2.0 mol / L or less.

[0046] The solvent is preferably a high-boiling solvent, and examples thereof include lactones such as γ-butyrolactone, carbonates such as propylene carbonate, polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane, amides such as N-methylacetamide, N,N-dimethylformamide and N-methyl-2-pyrrolidone, esters such as methyl acetate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0047] Ionic substances include, for example, organic salts. Organic salts are salts in which at least one of the anion and cation contains an organic substance. Examples of organic salts in which the cation contains an organic substance include quaternary ammonium salts. Examples of organic salts in which the anion (or both ions) contains an organic substance include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolinium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate.

[0048] From the viewpoint of improving the withstand voltage characteristics, the anion preferably includes an anion of a fluorine-containing acid. Examples of the anion of a fluorine-containing acid include BF ４ － and / or PF ６ － The organic salt preferably contains, for example, a tetraalkylammonium cation and a fluorine-containing acid anion. Specifically, diethyldimethylammonium tetrafluoroborate (DEDMABF ４ ), triethylmethylammonium tetrafluoroborate (TEMABF ４ ) etc.

[0049] It is desirable to interpose a separator between the pair of electrodes. The separator has ion permeability and serves to physically separate the pair of electrodes to prevent short circuits. Examples of separators that can be used include cellulose-based nonwoven fabrics, glass fiber mats, and microporous films of polyolefins such as polyethylene.

[0050] 3 is a partially cutaway perspective view of an electrochemical device obtained by the method for manufacturing an electrochemical device according to an embodiment of the present disclosure, and shows an example of an electrochemical device obtained by the method for manufacturing an electrochemical device according to an embodiment of the present disclosure.

[0051] 3 is an electric double layer capacitor and includes a wound capacitor element 1. Capacitor element 1 is configured by winding a sheet-like first electrode 2 and a sheet-like second electrode 3 with a separator 4 interposed therebetween. First electrode 2 and second electrode 3 have a first current collector and a second current collector made of metal, respectively, and a first active layer and a second active layer carried on the surfaces thereof, and generate capacitance by adsorbing and desorbing ions.

[0052] The current collecting foil is made of, for example, etched aluminum foil. The separator 4 is made of, for example, a nonwoven fabric primarily composed of cellulose. A first lead member 5a and a second lead member 5b are connected to the first electrode 2 and the second electrode 3, respectively. The capacitor element 1 is housed in a cylindrical outer case 6 together with an electrolyte (not shown). The outer case 6 may be made of any metal, such as aluminum, stainless steel, copper, iron, or brass. The opening of the outer case 6 is sealed with a sealing member 7. The lead wires 5a and 5b are led out through the sealing member 7. The sealing member 7 is made of, for example, a rubber material, such as butyl rubber.

[0053] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples.

[0054] Example 1 A wound type electric double layer capacitor with a rated voltage of 2.7 V was fabricated as an electrochemical device. A specific method for fabricating the electrochemical device will be described below.

[0055] (Electrode Preparation) Water was added to the electrode material to prepare a slurry. The electrode material was a mixture of 88.25 parts by mass of activated carbon particles, 1.75 parts by mass of styrene butadiene rubber (SBR) as a binder, 4 parts by mass of carboxymethyl cellulose (CMC) as a thickener, and 6 parts by mass of acetylene black (AB) as a conductive agent. The content of SBR in the electrode material was 1.75% by mass relative to the total electrode material. The content of water in the slurry was 75% by mass relative to the total slurry. The TI value of the slurry determined by the above-mentioned method was 2.5.

[0056] The resulting slurry was applied to both sides of a strip-shaped current collector foil, and the coating was vacuum dried at 110°C and rolled to form an active layer (thickness 40 μm per side), to obtain an electrode (length: 500 mm, width: 59 mm). The current collector foil was an etched aluminum foil (thickness: 20 μm, arithmetic mean roughness Ra: 0.89 μm).

[0057] In the above process, the slurry was applied intermittently to the current collecting foil, forming coated and uncoated regions in the same pattern on both sides of the current collecting foil. A slot die was used as the coating device. In this way, an electrode a1 was obtained, which included a current collecting foil and active layers formed on both sides of the current collecting foil, and had an exposed current collecting foil portion (dimension in the electrode's longitudinal direction: 6 mm) formed by an uncoated region.

[0058] (Connection between electrode and lead member) A lead member including a lead wire, a connection portion, and a tab portion was prepared. The tab portion of the lead member was placed on one surface of the exposed portion of the current collecting foil of the electrode, and a crimping process was performed at the overlapping portion between the exposed portion of the current collecting foil and the tab portion. In this way, the tab portion was attached to the exposed portion of the current collecting foil, and an electrode a1 with a lead member was obtained.

[0059] (Preparation of Electrolyte) A solution of diethyldimethylammonium tetrafluoroborate (DEDMABF) in γ-butyrolactone (GBL) was prepared. ４ ) was dissolved in the electrolyte to prepare an electrolyte solution. ４ The concentration was set to 1.0 mol / L.

[0060] (Fabrication of Electrochemical Device) Two of the electrodes with lead members obtained above were prepared and wound with a cellulose nonwoven fabric separator interposed therebetween to form a capacitor element, which was then housed in a predetermined outer case together with an electrolyte solution and sealed with a sealing material to complete electrochemical device A1. Thereafter, the device was subjected to an aging treatment at 60° C. for 16 hours while applying a rated voltage.

[0061] The lead member-attached electrode a1 and the electrochemical device A1 obtained above were evaluated as follows.

[0062] [Evaluation] (Peel strength of active layer) The electrode was cut to a width of 15 mm to obtain a sample. The sample was fixed on a predetermined table using 20 mm wide double-sided tape (NW-20, manufactured by Nichiban Co., Ltd.). A 12 mm wide masking tape (No. 7239, manufactured by Nitto Denko Corporation) was attached to the sample. One end of the masking tape in the longitudinal direction was pulled with a force gauge, and the force required to peel off the active layer (peel strength) was measured. The average value for 15 seconds until the peel strength stabilized was calculated.

[0063] (Crimping resistance between electrode and lead member) A digital multimeter was used to measure the resistance (crimping resistance) between the point indicated by the arrow P1 in Fig. 1 and the point indicated by the arrow P2 in Fig. 1. The point indicated by the arrow P1 in Fig. 1 is the end of the lead wire 33 on the tab portion 31 side. The point indicated by the arrow P2 in Fig. 1 is near the end of the tab portion 31 in the current collecting foil exposed portion 23 opposite the lead wire 33.

[0064] (Capacity of Electrochemical Device) In an environment of −30° C., constant current charging was performed at a current of 1.35 A until the voltage reached 2.35 V, and then the state in which a voltage of 2.35 V was applied was maintained for 10 minutes. Thereafter, in an environment of −30° C., constant current discharging was performed at a current of 1 A until the voltage reached 0 V.

[0065] During the above discharge, the time t (sec) required for the voltage to drop from 2.0 V to 1.6 V was measured. Using the measured time t, the capacity C1 (F) of the electrochemical device was calculated using the following formula (1): Capacity C1 = Id × t / V (1) In formula (1), Id is the current value during discharge (1.0 A), and V is the value obtained by subtracting 1.6 V from 2.0 V (0.4 V).

[0066] (Direct Current Resistance (DCR) of Electrochemical Device) In an environment of −30° C., constant current charging was performed at a current of 1.35 A until the voltage reached 2.35 V, and then the state in which a voltage of 2.35 V was applied was maintained for 10 minutes. Thereafter, in an environment of −30° C., constant current discharging was performed at a current of 1.35 A until the voltage reached 0 V.

[0067] Using the discharge curve (vertical axis: discharge voltage, horizontal axis: discharge time) obtained from the above discharge, a linear approximation line was calculated for the range of 0.5 to 2 seconds after the start of discharge of the discharge curve, and the voltage VS at the intercept of the approximation line was calculated. ΔV was calculated as the value (V0-VS) obtained by subtracting the voltage VS from the voltage VO at the start of discharge (0 seconds after the start of discharge). ΔV (V) and the current value Id (1.35 A) during discharge were used to calculate the internal resistance (DCR) R1 (Ω) of the electrochemical device according to the following formula (2): Internal resistance R1=ΔV / Id (2)

[0068] (Remaining capacity of electrochemical device) The electrochemical device was charged at a constant current of 1.35 A in an environment at 25°C until the voltage reached 2.5 V, and then charged at a constant voltage of 2.5 V for 5 hours. The electrochemical device was then left in an environment at 60°C for 24 hours. After leaving it for 24 hours, the voltage of the electrochemical device was measured in an environment at 25°C. If the voltage of the electrochemical device after leaving it for 24 hours was 2.3 V or higher, it was determined that micro-short circuits were suppressed and the remaining capacity was high.

[0069] Comparative Example 1 An electrode b1 with a lead member was produced in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE) was used as the binder instead of SBR, and an electrochemical device B1 was produced and evaluated.

[0070] Comparative Example 2: Polytetrafluoroethylene (PTFE) was used as the binder instead of SBR. In the process of applying the slurry to the current collector foil, the slurry was applied to the entire surface of both sides of the current collector foil to form an active layer. A portion of the active layer was then heat-pressed at a temperature of 250 to 280°C for 3 seconds and then removed using a brush. In this way, an exposed current collector foil portion was formed at a predetermined location on the electrode. Except for the above, an electrode b2 with a lead member was fabricated in the same manner as in Example 1, and an electrochemical device B2 was fabricated and evaluated.

[0071] Comparative Example 3 In the step of applying the slurry to the current collector foil, the slurry was applied to the entire surface of both sides of the current collector foil to form an active layer. After that, a portion of the active layer was subjected to a heat press treatment, and then an attempt was made to remove it using a brush. However, because the current collector foil was thin and the binding strength of the active layer was strong, and the active layer and the active layer were closely attached to the current collector foil, it was difficult to remove the active layer, and an exposed portion of the current collector foil could not be formed.

[0072] Comparative Example 4: The thickness of the etched Al foil used for the current collector foil was 30 μm. In the slurry application process to the current collector foil, the slurry was applied to the entire surface of both sides of the current collector foil to form an active layer. A portion of the active layer was then heat-pressed and then removed using a brush. In this way, an exposed current collector foil portion was formed at a predetermined location on the electrode. Except for the above, an electrode b4 with a lead member was fabricated in the same manner as in Example 1, and an electrochemical device B4 was fabricated and evaluated.

[0073] The evaluation results are shown in Table 1. Tables 1 and 2 show the TI values ​​of the slurries determined by the method described above. In Tables 1 and 2, a circle in the coating film tailing column indicates that no coating film tailing was visually observed when the slurry was intermittently applied to the current collector foil. On the other hand, an x ​​in the coating film tailing column indicates that coating film tailing was visually observed when the slurry was intermittently applied to the current collector foil. In Tables 1 and 2, a circle in the remaining capacity column indicates that the voltage of the electrochemical device after being left standing for 24 hours was 2.3 V or more, and a high remaining capacity was obtained. On the other hand, an x ​​in the remaining capacity column indicates that the voltage of the electrochemical device after being left standing for 24 hours was less than 2.3 V, and a low remaining capacity was obtained.

[0074]

[0075] In Example 1, SBR was used as the binder, which increased the adhesive strength of the active layer in electrode a1 and resulted in high peel strength. Furthermore, intermittent application resulted in the formation of exposed collector foil portions, reducing the crimping resistance between electrode a1 and the lead member. Electrochemical device A1 achieved high capacity, low DCR, and high remaining capacity.

[0076] In Comparative Examples 1 and 2, the use of PTFE as the binder reduced the adhesive strength of the active layer in electrodes b1 and b2, and reduced the peel strength. In electrochemical devices B1 and B2, micro-short circuits occurred, and the remaining capacity decreased.

[0077] Furthermore, in Comparative Example 2, the exposed portion of the current collecting foil was formed by removing part of the active layer with a brush, which increased the surface roughness of the exposed portion of the current collecting foil and increased the crimping resistance between electrode b2 and the lead member. Electrochemical device B2 had a higher DCR than electrochemical device B1.

[0078] In Comparative Example 4, the active layer was partially removed with a brush to form an exposed portion of the current collecting foil, which increased the crimping resistance between electrode b4 and the lead member. Also, in Comparative Example 4, the thickness of the Al etched foil, which was the current collecting foil, was increased to 30 μm, which reduced the amount of filling of the active layer, thereby reducing the capacity of electrochemical device B4.

[0079] Examples 2-3 and Comparative Examples 5-7 Water was added to the electrode material to prepare a slurry. The electrode material used was a mixture of 88.25 parts by mass of activated carbon particles and a total of 11.75 parts by mass of SBR, CMC, and AB. The content of SBR in the electrode material relative to the total electrode material was the value shown in Table 2. The mass ratio of SBR to CMC to AB was 1.75:4:6.

[0080] In Examples 2 and 3 and Comparative Examples 6 and 7, electrodes with lead members a2 to a3, b6 to b7 were fabricated and electrochemical devices A2 to A3, B6 to B7 were fabricated and evaluated in the same manner as in Example 1, except that the above-mentioned slurry was used in the electrode fabrication process.

[0081] In Comparative Example 5, the content of SBR in the electrode material was 0.25% by mass, and therefore an active layer was formed in the same manner as in Example 1. However, the adhesion between the active layer and the current collecting foil was low, and an electrode could not be produced, and the peel strength of the active layer could not be measured.

[0082] The evaluation results are shown in Table 2. Table 2 also shows the evaluation results of Example 1.

[0083]

[0084] In Examples 1 to 3, in which the SBR content in the active layer (electrode material) was 0.5% by mass or more and 2.5% by mass or less, no tailing occurred during intermittent coating, and exposed current collecting foil portions were stably formed. In electrodes a2 to a3, as in the case of electrode a1, the SBR increased the adhesive strength of the active layer, resulting in high peel strength. Furthermore, because the exposed current collecting foil portions were formed by intermittent coating, the crimping resistance between electrodes a2 to a3 and the lead member was reduced. In electrochemical devices A2 to A3, as in the case of electrochemical device A1, high capacity and low DCR were obtained, and high remaining capacity was also obtained.

[0085] In Comparative Examples 6 and 7, in which the SBR content in the active layer (electrode material) was 3% by mass or more, the viscosity of the slurry increased, causing tailing of the coating film during intermittent application, and preventing stable formation of exposed current collecting foil portions. In Electrochemical Devices B6 and B7, the DCR increased.

[0086] The lead-attached electrodes obtained by the method for manufacturing an electrode for an electrochemical device with a lead member according to the present disclosure are suitable for use in electrochemical devices requiring low internal resistance. Although the present invention has been described with reference to presently preferred embodiments, such disclosure should not be construed as limiting. Various modifications and alterations will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. Accordingly, the appended claims should be construed to include all modifications and alterations that do not depart from the true spirit and scope of the present invention.

[0087] 1: capacitor element, 2: first electrode, 3: second electrode, 4: separator, 5a: first lead member, 5b: second lead member, 6: exterior case, 7: sealing member, 10: electrochemical device, 20: electrode, 21: current collecting foil, 22: active layer, 23: current collecting foil exposed portion, 30: lead member, 31: tab portion, 32: connection portion, 33: lead wire, 40: crimping portion, 41: through hole, 42: crimping piece

Claims

1. A first step of preparing a slurry containing activated carbon and a binder, and a current collector foil having a roughened surface; a second step of applying the slurry to a surface of the current collector foil, drying the slurry, and forming an active layer to obtain an electrode; and a third step of connecting the electrode and a lead member, In the second step, the slurry is intermittently applied to the current collector foil to form an uncoated region in which a surface of the current collector foil is exposed in a part of the electrode; In the third step, the lead member is attached to the uncoated area; The binder includes an elastomer, The content of the elastomer in the active layer is more than 0.25% by weight and less than 3% by weight. A method for producing an electrode for an electrochemical device with a lead member.

2. The method for producing an electrochemical device electrode with a lead member according to claim 1 , wherein the elastomer includes styrene-butadiene rubber.

3. 3 . The method for producing an electrochemical device electrode with a lead member according to claim 2 , wherein the content of the styrene-butadiene rubber in the active layer is 0.5% by mass or more and 2.5% by mass or less.

4. The method for producing an electrochemical device electrode with a lead member according to claim 2 , wherein the slurry has a TI value of 2 or more and 4 or less.

5. 5. The method for producing an electrochemical device with lead members according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the uncoated area is 0.5 μm or more and 1.0 μm or less.

6. 5. The method for producing an electrode for an electrochemical device with a lead member according to claim 1, wherein the current collector foil is an aluminum foil.

7. The method for producing an electrode for an electrochemical device with a lead member according to any one of claims 1 to 4, wherein the current collector foil has a thickness of 20 µm or less.

8. A step A of preparing a first electrode with a first lead member and a second electrode with a second lead member; A step B of winding the first electrode and the second electrode with a separator therebetween to obtain a wound body; and a step C of impregnating the wound body with an electrolyte solution, In the step A, at least one of a first electrode with a first lead member and a second electrode with a second lead member is obtained by the method for manufacturing an electrode for an electrochemical device with a lead member according to any one of claims 1 to 4.