Electrode manufacturing method

Abstract

The main purpose of the present disclosure is to provide a method for manufacturing an electrode capable of extending an uncoated portion while suppressing fracture. In the present disclosure, the above-mentioned problem is solved by providing a method for manufacturing an electrode, the method for manufacturing an electrode having a preparation step, a coating portion pressing step, and an uncoated portion pressing step before or after the coating portion pressing step, the preparation step is to prepare a precursor sheet, the precursor sheet having a metal foil and a coating portion and an uncoated portion arranged on the metal foil, the coating portion pressing step presses the coating portion in the thickness direction, the uncoated portion pressing step presses the uncoated portion in the thickness direction, the coating portion contains an electrode material containing at least an active substance, the uncoated portion does not contain an electrode material and is arranged at the end of the coating portion, and in the uncoated portion pressing step, a pair of elastic rollers having a shaft and an elastic body covering the shaft are used to perform rolling while pressing the uncoated portion in the thickness direction.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an electrode. Background Art

[0002] As a method for producing an electrode, a method of rolling a sheet obtained by coating an electrode mixture on a long metal foil is known.

[0003] For example, Patent Document 1 discloses a method for pressing a battery electrode having a coated portion coated with an electrode active material and an uncoated portion not coated with an electrode active material. Patent Document 2 discloses a method for rolling the electrode material by using a pressing roller to extend only the uncoated portion of the electrode material to which tension is applied between guide rollers. Patent Document 3 discloses a rolling method using a roller press, which is equipped with a wrinkle prevention device for suppressing wrinkles caused by rolling operations on the coated and uncoated portions of the electrode plate.

[0004] Prior art literature

[0005] Patent Document 1: Japanese Patent No. 5760366

[0006] Patent Document 2: Japanese Patent Application Publication No. 2014-220113

[0007] Patent Document 3: Japanese Patent Application Publication No. 2019-102172 Summary of the invention

[0008] As described above, when a sheet having a coated portion and an uncoated portion is pressed, the coated portion and the uncoated portion are sometimes pressed separately to adjust the elongation difference so as to avoid wrinkles. In this case, the uncoated portion located at the end of the sheet may break.

[0009] The present disclosure has been made in view of the above-mentioned situation, and a main object thereof is to provide a method for manufacturing an electrode capable of extending an uncoated portion while suppressing breakage.

[0010] In order to solve the above-mentioned problems, in the present disclosure, a method for manufacturing an electrode is provided, which comprises a preparation step, a coating part pressing step and an uncoated part pressing step before or after the coating part pressing step. The preparation step prepares a precursor sheet, the precursor sheet has a metal foil and a coating part and an uncoated part arranged on the metal foil. The coating part pressing step presses the coating part along the thickness direction. The uncoated part pressing step presses the uncoated part along the thickness direction. The coating part contains an electrode material containing at least an active substance. The uncoated part does not contain the electrode material and is arranged at the end of the coating part. In the uncoated part pressing step, a pair of elastic rollers having a shaft and an elastic body covering the shaft are used to roll the uncoated part while pressing it along the thickness direction.

[0011] According to the present disclosure, since the uncoated portion is rolled using a predetermined elastic roller, the uncoated portion can be extended while suppressing breakage.

[0012] In the above disclosure, the compressive Young's modulus of the above elastic body may be 11.1 MPa or more and 86.1 MPa or less.

[0013] In the above disclosure, the compressive Young's modulus of the above-mentioned elastic body may be 20 MPa or more.

[0014] In the above disclosure, when the thickness of the elastic body is denoted as T1 and the thickness of the electrode mixture in the coating portion is denoted as T2, T1 / T2 may be 4 or more.

[0015] In the above disclosure, the uncoated portion pressing step may be performed while applying a tension of 100N or less.

[0016] In the present disclosure, there is an effect that the uncoated portion can be extended while suppressing breakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flowchart showing an example of a method for producing an electrode in the present disclosure.

[0018] Figure 2 It is a diagram for explaining the mechanism in the present invention.

[0019] Figure 3 It is a diagram for explaining the mechanism in the present disclosure.

[0020] Figure 4 This is a schematic plan view showing an example of a precursor sheet in the present disclosure.

[0021] Figure 5 This is a diagram for explaining the uncoated portion pressing step in the present disclosure.

[0022] Figure 6 This is a diagram for explaining the elongation measurement method in Examples and Comparative Examples.

[0023] Figure 7 This is a diagram for explaining the ultimate elongation at break in Examples and Comparative Examples.

[0024] Figure 8 This is a graph showing the relationship between the compressive Young's modulus and the ultimate elongation at break in Examples.

[0025] Fig. 9 This is a diagram for explaining a reference example.

[0026] Description of Reference Numerals

[0027] 1…metal foil

[0028] 2…Coating part

[0029] 3…Uncoated part

[0030] 10…precursor piece

[0031] 21…Axis

[0032] 22…Elastomer

[0033] 20…Elastic roller DETAILED DESCRIPTION

[0034] Hereinafter, the manufacturing method of the electrode in the present disclosure is described in detail. Here, in this specification, when expressing the manner of configuring other components on a certain component, when it is simply expressed as "on", unless otherwise specified, it includes two situations: configuring other components directly above the certain component in a manner of contacting the certain component, and configuring other components above the certain component through other components.

[0035] Figure 1 : is a flowchart showing an example of a method for manufacturing an electrode in the present disclosure. Figure 1 In the process, first, a precursor sheet is prepared, wherein the precursor sheet has a metal foil and a coated portion and an uncoated portion disposed on the metal foil (preparation step). The coated portion contains an electrode material that contains at least an active substance. In addition, the uncoated portion does not contain an electrode material and is disposed at the end of the coated portion. Next, the coated portion is pressed in the thickness direction (coated portion pressing step). Then, the uncoated portion is pressed in the thickness direction (uncoated portion pressing step). Furthermore, Figure 1 In the uncoated portion pressing step, the uncoated portion pressing step is performed after the coated portion pressing step, but may be performed before the coated portion pressing step. In addition, in the uncoated portion pressing step, a pair of elastic rollers having a shaft and an elastic body covering the shaft are used to perform rolling while pressing the uncoated portion in the thickness direction.

[0036] According to the present disclosure, since the uncoated portion is rolled using a predetermined elastic roller, the uncoated portion can be extended while suppressing breakage.

[0037] In Patent Document 2, the uncoated portion is stretched by pressing a stepped roller on one side of the uncoated portion, and only tension for stretching is applied to the uncoated portion. In this method, although the uncoated portion can be stretched, there is a fear that it may break (see Figure 2 (b)). In addition, in Patent Document 3, the uncoated portion of the electrode mixture is extended by a rolling mechanism. As shown in Comparative Example 2 described later, the uncoated portion cannot be effectively extended in the method of applying only a pressing pressure (compression force).

[0038] On the other hand, in the manufacturing method of the electrode disclosed in the present invention, the uncoated portion is rolled using a predetermined elastic roller, so that the compression force and the deformation force caused by the deformation of the elastic body can be applied to the same part of the uncoated portion. As a result, the generation of voids can be suppressed, and the uncoated portion can be extended while suppressing the breakage.

[0039] The mechanism of the present disclosure is explained using the drawings. Figure 2 (a) is a schematic diagram showing a general metal foil. Figure 2 As shown in (a), metal foil generally contains a hard structure that is harder than the material of the metal foil as an inclusion. By including the hard structure, for example, the strength of the metal foil can be increased. When a tension (force in the left and right directions of the paper) is applied to stretch the metal foil, the hard structure does not deform, but the surrounding metal foil that is softer than the hard structure deforms. As a result, Figure 2 As shown in (b), a gap is formed around the hard tissue. Moreover, a plurality of gaps are connected to each other, thereby causing a break. On the other hand, in the manufacturing method of the electrode disclosed in the present invention, as Figure 2 As shown in (c), the metal foil can be locally subjected to a compressive force and an elastic deformation force. As a result, it is believed that the generation of voids around the hard tissue can be suppressed. In addition, it is believed that even if voids are generated, the expansion of the voids due to the compressive force can be suppressed. Here, the elastic deformation force is in the same direction as the tension ( Figure 2 On the other hand, the deformation force is considered to be applied to the part where the elastic body and the metal foil (uncoated part) are in contact as described later, so that, for example, the force can be applied more locally compared to the tension applied by the tension applying device.

[0040] Next, the mechanism of the present disclosure will be described using a schematic diagram of an elastic roller in the present disclosure. Figure 3As shown, the uncoated portion 3 (metal foil 1) contacts the elastic body 22 in a pair of elastic rollers 20 (A, B) during rolling. By pressing the pair of elastic rollers 20 (A, B) from the thickness direction of the front sheet, a compressive force (force from the up and down direction of the paper surface) can be applied to the uncoated portion. In addition, the elastic body 22 of the elastic rollers 20 (A, B) has elasticity, so the elastic body 22 is deformed by the compressive force, and a deformation force (force to the left and right direction of the paper surface) is applied to the uncoated portion 3 in contact with the elastic body 22. In this way, by using the elastic roller of the present disclosure, a compressive force and a deformation force of the elastic body can be applied to the same part of the uncoated portion at the same time. As a result, the uncoated portion can be extended while suppressing the breakage of the uncoated portion. Furthermore, according to the manufacturing method of the electrode in the present disclosure, the deformation force of the elastic body can be used to provide a force for extending the uncoated portion. Therefore, the uncoated portion can be extended even without separately providing a tension applying device, and the manufacturing equipment can be miniaturized.

[0041] 1. Preparation process

[0042] The preparation step in the present disclosure is a step of preparing a precursor sheet having a metal foil and a coated portion and an uncoated portion disposed on the metal foil.

[0043] The precursor sheet prepared in the preparation step has a metal foil, a coated portion, and an uncoated portion.

[0044] The material of the metal foil may be a metal used as a material of a battery current collector. Details are described in "4. Electrode". The thickness of the metal foil is, for example, 1 μm or more, or 10 μm or more. On the other hand, the thickness of the metal foil is, for example, 100 μm or less.

[0045] The coating portion of the precursor sheet contains an electrode material including at least an active material. The coating portion is disposed on a metal foil. The coating portion is subjected to a coating portion pressing step described below to become an electrode layer.

[0046] The electrode material contains at least an active material. In addition, the electrode material may contain at least one of a solid electrolyte, a conductive material, and a binder as required. The active material, the conductive material, and the binder are described in "4. Electrode".

[0047] The coating portion may be arranged only on the first surface of the metal foil in the thickness direction, or may be arranged on both the first surface and the second surface on the opposite side to the first surface.

[0048] The coating section is preferably arranged in the longitudinal direction (conveying direction) of the metal foil.

[0049] The thickness of the coating portion is not particularly limited and can be appropriately adjusted according to the desired electrode size. The thickness of the coating portion is, for example, 0.2 mm or more, 0.3 mm or more, or 0.5 mm or more. On the other hand, the thickness of the coating portion is, for example, 1.5 mm or less, 1.0 mm or less, or 0.6 mm or less.

[0050] The width of the coating portion (the length in the direction perpendicular to the length direction of the metal foil) is not particularly limited and can be appropriately adjusted according to the desired electrode size. The ratio of the width of the coating portion to the width of the metal foil is, for example, 30% or more, 50% or more, or 70% or more. In addition, the above ratio is, for example, 90% or less, or 80% or less.

[0051] The uncoated portion does not contain the electrode material and is disposed at the end of the coated portion. The uncoated portion may be disposed only at one end of the coated portion or at both ends of the coated portion. In addition, the uncoated portion may be disposed only at one end in a direction perpendicular to the length direction of the metal foil or at both ends of the metal foil.

[0052] The uncoated portion is disposed on the metal foil. In addition, the uncoated portion is usually disposed on the same surface as the surface of the metal foil on which the coated portion is disposed. The uncoated portion is, for example, a portion where the metal foil is exposed.

[0053] The width of the uncoated portion (the length in the direction perpendicular to the length direction of the metal foil) is not particularly limited and can be appropriately adjusted according to the desired electrode size. The ratio of the width of the uncoated portion to the width of the metal foil is, for example, 3% or more, or 5% or more. In addition, the above ratio is, for example, 20% or less, or 10% or less.

[0054] The ratio of the width of the uncoated portion to the width of the coated portion may be, for example, 20% or more, or 30% or more. On the other hand, the ratio may be, for example, 50% or less.

[0055] The precursor sheet can be prepared, for example, by coating an electrode material containing a dispersion medium on a metal foil and drying it. As the dispersion medium, for example, organic solvents such as butyl butyrate, dibutyl ether, and heptane can be cited. The coating method of the electrode material is not particularly limited, and a general coating method can be cited. In addition, the drying temperature is not particularly limited as long as it is a temperature at which the dispersion medium evaporates.

[0056] The precursor sheet prepared in the preparation step may be, for example, Figure 4The precursor sheet 10 shown in the top view has one row of coated portions 2 and two rows of uncoated portions 3 arranged at both ends of the coated portions 2 in a striped shape. In addition, although not shown in the figure, the precursor sheet may also be a sheet having N rows (N is an integer greater than 2) of coated portions and uncoated portions arranged at both ends of each of the N rows of coated portions in the top view. In this case, the number of rows of the uncoated portions is N+1 rows.

[0057] 2. Coating part pressing process

[0058] The coated portion pressing step is a step of pressing the coated portion in the thickness direction. The coated portion pressing step may be performed before or after the uncoated portion pressing step described below.

[0059] The method and conditions of the coating portion pressing step are not particularly limited as long as the coating portion can be pressed to extend. As a pressing method, for example, a roller pressing method of rolling the coating portion can be cited. For example, the coating portion can be pressed by passing the precursor sheet between a pair of pressing rollers and pressing the pressing rollers onto both sides of the precursor sheet in the thickness direction.

[0060] The compressive force in the coating part pressing step is not particularly limited, but is preferably greater than the compressive force in the uncoated part pressing step described later. Because wrinkles are sometimes formed in the coating part of the precursor sheet due to being wetted by the electrode material (slurry) containing the dispersion medium, a large stretching force is required to stretch the wrinkles.

[0061] 3. Uncoated part pressing process

[0062] The uncoated portion pressing step is a step of pressing the uncoated portion in the thickness direction before or after the coated portion pressing step. In the uncoated portion pressing step, a pair of elastic rollers having a shaft and an elastic body covering the shaft are used to perform rolling while pressing the uncoated portion in the thickness direction.

[0063] By pressing the uncoated portion, the uncoated portion can be stretched to adjust the difference in elongation between the uncoated portion and the coated portion. This can suppress the generation of wrinkles in the electrode. The conditions of the coated portion pressing step are appropriately adjusted with respect to the elongation of the uncoated portion.

[0064] Here, the uncoated portion pressing step will be described using the drawings. Figure 5 (a) is a schematic side view of the uncoated portion pressing step as viewed from the width direction of the metal foil. Figure 5 (b) Observe from the thickness direction of the precursor sheet (up and down direction of the paper) Figure 5 (a) Schematic top view. Figure 5 (c) Observe from the conveying direction of the precursor sheet (left and right direction of the paper) Figure 5 (a) is a schematic front view.

[0065] like Figure 5 As shown in (a) and (c), in the uncoated portion pressing step, the uncoated portion 3 (metal foil 1) is rolled by passing the precursor sheet between a predetermined pair of elastic rollers 20A and 20B and pressing the elastic rollers 20A and 20B to both sides of the precursor sheet in the thickness direction.

[0066] The elastic roller 20 is generally in the shape of a roller in which an elastic body 22 is arranged around a shaft body 21. Figure 5 As shown in (c), the elastic roller is a so-called stepped roller, which can compress only the uncoated portion. If it is a roller shape, the shaft of the elastic roller is combined with the elastic body, so compared with the sheet shape, it is possible to suppress the deformation of the elastic body in the conveying direction of the front body sheet, and the compression force can be increased. In addition, the deformation direction of the elastic body is stable, which can further suppress the generation of wrinkles.

[0067] The material of the shaft is not particularly limited, but is preferably a material having a compression Young's modulus greater than that of an elastic body. Examples of the material of the shaft include metals.

[0068] The elastic body is not particularly limited as long as it is a member having elasticity, and examples thereof include resins such as rubber and polyurethane.

[0069] The elastomer preferably has a predetermined compression Young's modulus. The compression Young's modulus is, for example, more than 10 MPa, may be more than 11.1 MPa, may be more than 15 MPa, or may be more than 20 MPa. On the other hand, the compression Young's modulus is, for example, less than 90 MPa, may be less than 86.1 MPa, may be less than 60 MPa, may be less than 40 MPa, or may be less than 35 MPa. If the compression Young's modulus is too low, the deformation of the elastomer is too large, and excessive deformation force is applied to the uncoated portion. As a result, it may not be possible to fully suppress fracture. On the other hand, if the compression Young's modulus is too high, the elastomer is difficult to deform, and it may not be possible to apply sufficient deformation force to the uncoated portion.

[0070] like Figure 5 As shown in (b), the width W1 of the elastic body may be larger than the width W2 of the uncoated portion. W1 / W2 may be, for example, 1.1 or more, 1.2 or more, or 1.3 or more.

[0071] like Figure 5 (a) and Figure 5As shown in (c), when the thickness of the elastic body is T1 and the thickness of the coating portion is T2, T1 / T2 is, for example, 4 or more, 5 or more, 10 or more, or 15 or more. On the other hand, T1 / T2 is, for example, 40 or less, 33.3 or less, 30 or less, 25 or less, or 20 or less. Typically, the thickness (T1) of the elastic body is obtained as a value obtained by subtracting the radius of the shaft from the radius of the elastic roller.

[0072] In the present disclosure, the compressive force in the pressing process of the uncoated portion is not particularly limited, and is preferably appropriately adjusted based on the material of the elastomer used, the material of the metal foil, and the necessary elongation. The compressive load is, for example, greater than 2kgf / cm, may be greater than 2.1kgf / cm, may be greater than 5kgf / cm, or may be greater than 10kgf / cm. On the other hand, the linear pressure is, for example, less than 40kgf / cm, may be less than 36kgf / cm, may be less than 30kgf / cm, or may be less than 20kgf / cm. Furthermore, the method for obtaining the compressive force (linear pressure) is described in the embodiments.

[0073] By applying a deformation force caused by the elastic roller to the uncoated portion, the uncoated portion can be extended. Therefore, in the uncoated portion pressing process of the present disclosure, the tension can be reduced compared to a case where an elastic roller is not used (for example, a case where a metal roller is used). The tension applied in the uncoated portion pressing process is, for example, 100N or less, 70N or less, or 50N or less. On the other hand, the tension is, for example, 30N or more. The tension can be applied, for example, by a tension applying device.

[0074] The uncoated part pressing step is performed before or after the coated part pressing step. That is, the uncoated part pressing step may be (i) performed before the coated part pressing step and not performed after the coated part pressing step, (ii) not performed before the coated part pressing step and performed after the coated part pressing step, or (iii) performed before the coated part pressing step and performed after the coated part pressing step.

[0075] 4. Electrodes

[0076] In the electrode manufactured by the method disclosed in the present invention, an electrode layer is formed on at least one surface of the metal foil. Furthermore, the electrode layer is a layer obtained by pressing the above-mentioned coating portion. The electrode manufactured by the method disclosed in the present invention can be a positive electrode or a negative electrode.

[0077] Typically, the metal foil functions as a current collector foil (current collector). That is, the metal foil can be a positive electrode current collector or a negative electrode current collector. When the metal foil is a positive electrode current collector, examples of the material of the metal foil include Al, SUS, and Ni. When the metal foil is a negative electrode current collector, examples of the material of the metal foil include Cu, SUS, and Ni.

[0078] The electrode layer contains at least an active material. When the electrode layer is a positive electrode layer, the active material is a positive electrode active material. As the positive electrode active material, typically an oxide active material can be cited. As the oxide active material, for example, LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layered active materials, LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4 and other spinel active materials, LiFePO4, LiMnPO4, LiNiPO4, LiCuPO4 and other olivine active materials.

[0079] In the case where the electrode layer is a negative electrode layer, the active material is a negative electrode active material. Examples of negative electrode active materials include carbon active materials, oxide active materials, and metal active materials. Examples of carbon active materials include intermediate carbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of oxide active materials include Nb2O5, Li4Ti5O 12 and SiO. Examples of the metal active material include In, Al, Si, and Sn.

[0080] In addition, the electrode layer may contain at least one of a solid electrolyte, a conductive material, and a binder as necessary.

[0081] As the solid electrolyte, for example, an inorganic solid electrolyte can be cited. As the inorganic solid electrolyte, for example, a sulfide solid electrolyte, an oxide solid electrolyte, a nitride solid electrolyte and a halide solid electrolyte can be cited. In addition, the inorganic solid electrolyte preferably has, for example, Li ion conductivity.

[0082] As the conductive material, for example, carbon materials, metal particles, and conductive polymers can be cited. As the carbon material, for example, granular carbon materials such as acetylene black (AB) and Ketjen black (KB); fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs) and carbon nanofibers (CNFs) can be cited. In addition, as the binder, for example, fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), rubber-based binders such as butadiene rubber, and acrylic binders can be cited.

[0083] As the use of the electrode in the present disclosure, for example, a Li-ion battery can be cited. In addition, the battery in the present disclosure can be an all-solid battery in which the electrolyte layer contains an inorganic solid electrolyte. In addition, the use of the battery in the present disclosure is not particularly limited, and for example, power sources for vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), electric vehicles (BEV), gasoline vehicles, and diesel vehicles can be cited. It is particularly preferably used as a driving power source for hybrid electric vehicles or electric vehicles. In addition, the battery in the present disclosure can be used as a power source for mobile bodies other than vehicles (such as railways, ships, and airplanes), and can also be used as a power source for electrical products such as information processing devices.

[0084] The present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are illustrative, and all schemes having substantially the same technical concept as that described in the claims of the present disclosure and having the same functions and effects are included in the technical scope of the present disclosure.

[0085] [Example]

[0086] [Example 1]

[0087] On one side of an aluminum foil (1N30) having a thickness of 12 μm, an electrode mixture containing a dispersion medium was applied to a thickness of 500 μm and dried. Figure 4 The precursor sheet 10 shown has a coated portion 2 and an uncoated portion 3 .

[0088] In addition, an elastic roller (stepped roller) having an elastomer arranged on the surface of a shaft (diameter 50 mm) was prepared. The thickness of the elastomer was 10 mm. The compressive Young's modulus of the elastomer used was measured as follows. First, the elastomer was adjusted to a size of 10 mm × 10 mm × 10 mm. For the elastomer, an automatic plotter was used to operate the compression deformation rate (deformation rate) to be 0% → 25% → 0% (first cycle), 0% → 25% (second cycle), and the relationship between the deformation rate and stress was measured. The compressive Young's modulus was calculated according to the following formula using the stress (σ10) when the deformation rate was 10% in the second cycle. The results are shown in Table 1.

[0089] Compression Young's modulus = σ10 / 0.1

[0090] Using the prepared precursor sheet and elastic roller, the maximum elongation of the uncoated portion was calculated as follows.

[0091] First, if Figure 6 As shown in (a), two lines were drawn at arbitrary positions in the longitudinal direction of the uncoated portion 3 (metal foil 1) of the precursor sheet 10, and the length (L0) between the lines before pressing was measured. Figure 5As shown in FIG. 1 , a pair of elastic rollers are used to perform rolling while pressing the uncoated portion in the thickness direction. Figure 6 (b) and Figure 6 As shown in (c), the uncoated portion was cut from the pressed precursor sheet, and the length (L1) between the lines after pressing was measured. The elongation (%) was calculated according to the following formula. The pressing of the uncoated portion was performed under a tension of 50N applied to the precursor sheet.

[0092] Elongation = (L1-L0) / L0×100

[0093] The load pressing the elastic roller was increased, and the maximum elongation at which no break occurred was obtained as the breaking limit elongation.

[0094] In addition, the load (linear pressure) at the time of breaking was calculated according to the following formula.

[0095] Line pressure = load (P) / (elastic body width (W1) × 2)

[0096] [Examples 2 to 7]

[0097] For Examples 2 to 4 and 6, a precursor sheet and an elastic roller were prepared in the same manner as in Example 1 except that an elastic body having a compression Young's modulus of the value shown in Table 1 was used. For Examples 5 and 7, a precursor sheet and an elastic roller were prepared in the same manner as in Example 1 except that an elastic body having a compression Young's modulus of the value shown in Table 1 was used and the thickness of the elastic body was changed to 1 mm. Using the prepared precursor sheet and elastic roller, the ultimate elongation at break and the load at break were calculated in the same manner as in Example 1. The results are shown in Table 1.

[0098] [Comparative Example 1]

[0099] A precursor sheet was prepared in the same manner as in Example 1. The ultimate elongation at break when only tension was applied was determined for the uncoated portion of the precursor sheet as follows.

[0100] The uncoated portion (aluminum foil) was punched out from the precursor sheet and subjected to a tensile test using an autograph. The ultimate elongation ε of the aluminum foil at break was calculated using the following formula: max .

[0101] Ultimate elongation at break ε max = (elongation at break εA) - (rebound at 1.0% strain εB)

[0102] Furthermore, if Figure 7 (a) and Figure 7 As shown in (b), εA is the strain (%) at fracture, and εB is the springback amount (%) from 1.0% strain.

[0103] [Comparative Example 2]

[0104] The elongation at break and the load at break were calculated in the same manner as in Example 1 except that a metal roll was used instead of the elastic roll.

[0105] Table 1

[0106]

[0107] Table 2

[0108]

[0109] As shown in Tables 1 and 2, Examples 1 to 7 have higher elongation at break than Comparative Example 1. This shows that when the elastic roller is used to simultaneously apply a deformation force and a compressive force to the uncoated portion, the uncoated portion is less likely to break than when only a tensile force is applied. Figure 8 It was confirmed that the larger the compression Young's modulus of the elastic roller, the larger the ultimate elongation at break, and the higher the effect of suppressing the breakage of the uncoated portion. On the other hand, from Comparative Example 2, when a metal roller with a large compression Young's modulus was used, the uncoated portion broke with almost no elongation. It is believed that this is because the metal roller hardly deformed and could not apply sufficient deformation force to the uncoated portion. In addition, from Examples 4 and 5, even if the thickness of the elastic body was changed, the ultimate elongation at break did not change.

[0110] [Reference Examples 1 to 11]

[0111] An elastic roller having an elastic body thickness adjusted to the value shown in Table 3 was prepared. In addition, a precursor sheet having an application portion thickness adjusted to the value shown in Table 3 was prepared. Using the elastic roller and the precursor sheet, Fig. 9 As shown, the elastic roller was stranded in the coating part and roller pressing was performed. After pressing, it was confirmed whether the electrode sheet had any breakage (stranded breakage). The results are shown in Table 3. Furthermore, the roller press was performed by applying a compressive force of 2% of the extension amount of the uncoated part. In addition, an elastic body with a compression Young's modulus of 19.6 MPa was used as the elastic roller.

[0112] Table 3

[0113]

[0114] In the pressing of the uncoated portion, a predetermined compressive force is applied to the elastic roller, and a load is applied to the elastic body in order to extend the uncoated portion by the deformation force of the elastic body. In this state, when the elastic roller is grounded in the coated portion, a greater load is applied to the elastic body in the grounded portion, and the deformation force of the elastic body increases. As a result, grounding fracture occurs. On the other hand, when the thickness of the elastomer is sufficiently large relative to the thickness of the coated portion, the influence of the load applied when the coated portion is grounded can be reduced, and the influence of the deformation force on the elastic body can be reduced. As a result, grounding fracture can be prevented.

[0115] As shown in Table 3, when the thickness of the elastic body is less than 4 times the thickness of the coating portion, stranding fracture occurs. The results of the reference example indicate that when considering the situation where the elastic roller strands in the coating portion due to meandering, the thickness of the elastic body is preferably 4 times or more the thickness of the coating portion.

Claims

1. A method for manufacturing an electrode, comprising a preparation step, a coating portion pressing step, and an uncoated portion pressing step before or after the coating portion pressing step, The preparation step is to prepare a precursor sheet having a metal foil and a coated portion and an uncoated portion arranged on the metal foil. The coating portion pressing step presses the coating portion in a thickness direction. The uncoated portion pressing step presses the uncoated portion along the thickness direction, The coating portion contains an electrode material including at least an active material, The uncoated portion does not contain the electrode material and is disposed at an end portion of the coated portion. In the uncoated portion pressing step, the uncoated portion is rolled using a pair of elastic rollers arranged along the thickness direction so that the uncoated portion is extended without being broken. Each of the pair of elastic rollers includes a shaft body and an elastic body covering the shaft body. pressing the uncoated portion with the elastic body of the pair of elastic rollers during rolling, The compression Young's modulus of the elastic body is 11.1 MPa or more and 86.1 MPa or less, The thickness of the elastic body is 1 mm, 2 mm, 5 mm or 10 mm, The elongation of the uncoated portion by rolling is 1.5%, 1.8%, 2.1%, 3.8% or 15.8%, and The uncoated portion pressing step is performed while applying a tension of 30 N or more and 100 N or less. The compressive Young's modulus of the elastic body is measured by the following measuring method: The determination method is: For an elastic body of 10 mm × 10 mm × 10 mm size, an automatic plotter was used to operate the compression deformation rate from 0% → 25% → 0% in the first cycle and from 0% → 25% in the second cycle. The relationship between the deformation rate and the stress was measured. The compressive Young's modulus was calculated according to the following formula using the stress σ10 when the deformation rate was 10% in the second cycle: Compression Young's modulus = σ10 / 0.

1. 2 . The method for producing an electrode according to claim 1 , wherein the compressive Young's modulus of the elastic body is 20 MPa or more. 3 . The method for manufacturing an electrode according to claim 1 , wherein, when the thickness of the elastic body is T1 and the thickness of the coating portion is T2 , T1 / T2 is greater than or equal to 4 and less than or equal to 33.3.

Images