Electrode plate manufacturing method and electrode plate manufacturing equipment

Abstract

To provide a manufacturing method capable of manufacturing a pole plate with small curvature and waviness.SOLUTION: A disclosed manufacturing method includes: a step (i) of forming a strip of sheet 100 including a mixture layer containing an active material; and a step (ii) of winding the sheet 100 on a wind roll after correcting a curvature of the sheet 100 by passing the sheet 100 over a straightening roll 300 while applying a tension to the sheet 100. In the step (i), the sheet 100 is formed so that there is a non-coating area 100b where the mixture layer is not formed at both ends of the sheet 100 in the width direction. The straightening roll 300 includes a sheet passing portion 310 through which the sheet passes. The roll diameter of the sheet passing section 310 gradually increases from the central part of the roll facing the center in the width direction of the mixture layer towards the outer portion of the roll facing the non-coating area 100b.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electrode plate, an apparatus for manufacturing an electrode plate, and a battery. [Background technology]

[0002] Various batteries, such as nonaqueous electrolyte secondary batteries, have been used for some time. A typical battery plate includes a current collector and a mixture layer formed on the current collector. Such a plate can be formed by applying a slurry to the current collector and then rolling it. Plates formed by such methods may become wavy or curved. Therefore, methods for straightening curved plates have been proposed.

[0003] Patent Document 1 (JP 2003-100286 A) discloses "a method for manufacturing a strip electrode from a strip material in which an active material is continuously coated in the longitudinal direction on a portion of the width direction of a long metal foil, and an uncoated portion extending in the longitudinal direction is left on the remaining portion in the width direction, wherein both sides of the strip material are compressed with a pair of compression rolls, the strip material compressed by the compression rolls is wound up with a take-up roll while being tensioned, and a straightening roll is pressed against the strip material between the compression rolls and the take-up roll to give a concentrated elongation to the uncoated portion, thereby manufacturing a strip electrode."

[0004] Patent Document 2 (JP 2015-090805 A) describes an electrode manufacturing device for a battery, which includes a press unit that compresses an electrode sheet having a coated region where an electrode layer is coated along the longitudinal direction of the surface of a strip-shaped substrate and an uncoated region where the electrode layer is not coated, and a curvature correction roller that has a small diameter portion and a large diameter portion along the width direction of the electrode sheet, the small diameter portion facing the coated region of the electrode sheet and the large diameter portion facing the uncoated region of the electrode sheet, and a curvature correction section that corrects the curvature of the uncoated area of ​​the electrode sheet by bringing the uncoated area of ​​the sheet into contact with the large diameter section and applying tension to the uncoated area of ​​the electrode sheet, wherein the width of the small diameter section along the width direction of the electrode sheet is set smaller than the width of the coated area along the width direction of the electrode sheet so that the boundary between the coated area and the uncoated area of ​​the electrode sheet is located closer to the large diameter section than the boundary between the large diameter section and the small diameter section of the curvature correction roller.

[0005] Patent Document 3 (JP 2014-035876 A) describes a method for manufacturing an electrode, comprising the steps of: "compression-molding an active material-containing layer of a strip-shaped electrode plate, the active material-containing layer of the strip-shaped electrode plate including a strip-shaped current collector; a current collector exposed portion formed on at least one long side of the strip-shaped current collector, with no active material-containing layer on either side; and an active material-containing layer formed on at least a portion of the strip-shaped current collector other than the current collector exposed portion; and placing the strip-shaped electrode plate on a roller having a step protruding from a circumferential surface and a recess adjacent to the step such that the current collector exposed portion is located on the step and the active material-containing layer is located in the recess; and applying tension in the long side direction of the strip-shaped electrode plate, wherein the step of the step satisfies the following formula: 750 <H Here, H is the size (%) of the step when the thickness of the active material-containing layer of the electrode per one surface of the strip-shaped current collector is taken as 100%. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-100286 [Patent Document 2] Japanese Patent Application Publication No. 2015-090805 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-035876 Summary of the Invention [Problem to be solved by the invention]

[0007] However, it has been difficult to sufficiently reduce the curvature and waviness of electrode plates using conventional methods. In light of this situation, one of the objects of the present disclosure is to provide a manufacturing method and manufacturing apparatus for electrode plates with minimal curvature and waviness. [Means for solving the problem]

[0008] One aspect of the present disclosure relates to a method for manufacturing an electrode plate, the method including: (i) applying a slurry containing an active material to a strip-shaped current collector including a strip-shaped metal foil along the longitudinal direction of the current collector, and then rolling the coated current collector to form a strip-shaped sheet including a mixture layer containing the active material; and (ii) passing the sheet over a straightening roll while applying tension to the sheet to straighten the sheet, and then winding the sheet onto a take-up roll, the sheet being formed in the step (i) so that uncoated regions where the mixture layer is not formed are present at both ends of the sheet in the width direction, the straightening roll including a sheet passing section through which the sheet passes, the roll diameter of the sheet passing section gradually increasing from a central portion of the roll facing the center of the mixture layer in the width direction to an outer portion of the roll facing the uncoated regions.

[0009] One aspect of the present disclosure relates to an electrode plate manufacturing apparatus, the manufacturing apparatus including: a conveying mechanism for conveying a strip-shaped sheet including a strip-shaped current collector and a strip-shaped mixture layer formed on the current collector; and a straightening roll; the conveying mechanism includes a take-up roll for winding the sheet that has passed over the straightening roll, each of which defines a non-coated region where the mixture layer is not formed at both ends of the sheet in the width direction; the conveying mechanism conveys the sheet such that the sheet passes over the straightening roll while being tensioned; the straightening roll includes a sheet passing section through which the sheet passes; and the roll diameter of the sheet passing section gradually increases from a central portion of the roll facing the center of the mixture layer in the width direction toward an outer portion of the roll facing the non-coated region.

[0010] One aspect of the present disclosure relates to a battery including two electrode plates, at least one of which includes a current collector including a metal foil and a mixture layer including an active material disposed on the current collector, one of two widthwise ends of the at least one electrode plate being an uncoated region where the mixture layer is not formed, the current collector in the uncoated region having no wavy irregularities, or if present, a pitch between adjacent protrusions or adjacent recesses of 15 mm or more, where L (mm) is the length of a straight line connecting two corners on the uncoated region side, and Y (mm) is the amount of curvature of the outer edge of the uncoated region side relative to the straight line at the center of the straight line, and the following formula (1) is satisfied: -8×10 -6 ×L 2 ≦Y≦8×10 -6 ×L 2 (1) is satisfied. [Effects of the Invention]

[0011] According to the present disclosure, electrode plates with minimal curvature and waviness can be manufactured, and batteries with excellent performance can be manufactured with high yield. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram illustrating one step of the manufacturing method according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 1 is a schematic diagram showing the configuration of a manufacturing apparatus according to a first embodiment. [Figure 4] FIG. 2 is a cross-sectional view illustrating the shape of an example of a straightening roll. [Figure 5] FIG. 10 is a cross-sectional view illustrating the shape of another example of a straightening roll. [Figure 6] FIG. 3 is a cross-sectional view schematically showing the configuration of a battery according to a second embodiment. [Figure 7A] FIG. 10 is a schematic diagram for explaining the amount of bending. [Figure 7B] FIG. 10 is another schematic diagram for explaining the amount of bending. [Figure 7C] FIG. 10 is another schematic diagram for explaining the amount of bending. [Figure 8] FIG. 10 is a schematic diagram for explaining a method for determining the pitch of the waviness. [Figure 9] FIG. 10 is a schematic diagram for explaining a method for determining the thickness of the electrode plate. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes embodiments of the present disclosure using examples, but the embodiments of the present disclosure are not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the invention of the present disclosure can be implemented. 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." In the following description, when a lower limit and an upper limit are exemplified for numerical values ​​of specific physical properties or conditions, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit.

[0014] (Electrode plate manufacturing method) A manufacturing method according to an embodiment of the present disclosure is a method for manufacturing an electrode plate. This manufacturing method can manufacture an electrode plate for a battery. This manufacturing method may be hereinafter referred to as "manufacturing method (M)."

[0015] The production method (M) includes steps (i) and (ii) in this order, each of which will be described below.

[0016] (Step (i)) Step (i) is a step of applying a slurry containing an active material in a strip shape to a strip-shaped current collector including a strip-shaped metal foil along the longitudinal direction of the current collector, and then rolling the applied slurry to form a strip-shaped sheet including a mixture layer containing the active material. The current collector may be a strip-shaped metal foil, or may be a current collector having a layer (e.g., a conductive layer) formed on a strip-shaped metal foil. In either case, the planar shape of the strip-shaped current collector is the same as the planar shape of the strip-shaped metal foil.

[0017] In step (i), the sheet is formed so that both ends in the width direction of the sheet have uncoated regions where no mixture layer is formed. Specifically, when the slurry is applied to the current collector, the slurry is not applied to both ends in the width direction of the current collector.

[0018] There are no particular limitations on the metal foil, and any metal foil that can be used as a current collector for an electrode plate may be used. For example, known metal foils used as current collectors may be used. Examples of materials for the metal foil include pure aluminum, or aluminum (or aluminum alloy) that is primarily composed of aluminum and contains trace elements such as iron, silicon, and manganese. The thickness of the metal foil may be in the range of 5 μm to 50 μm (e.g., 10 μm to 20 μm or 12 μm to 16 μm). There are no particular limitations on the width of the sheet (the width of the metal foil), and it is selected depending on the battery to be used. The width of the sheet (the width of the metal foil) may be in the range of 15 mm to 60 mm (e.g., 20 mm to 50 mm or 25 mm to 45 mm).

[0019] The coating method and rolling method included in step (i) are not particularly limited as long as they can form a mixture layer. For example, known coating methods and known rolling methods used to form mixture layers may be used. There is no limitation on the thickness of the mixture layer to be formed. The mixture layer is formed on one or both sides of the current collector, but is usually formed on both sides.

[0020] Rolling is performed for reasons such as increasing the density of the mixture layer. Rolling causes the sheet to become wavy or curved. Here, waviness refers to the displacement of the sheet in a direction perpendicular to the main surface of the sheet. Curvature refers to the deviation of the side that constitutes the outer edge of the sheet from the straight line connecting the two corners.

[0021] (Step (ii)) In step (ii), the sheet is passed over a straightening roll while tension is applied to the sheet to straighten the curvature of the sheet, and then the sheet is wound up on a take-up roll. Step (ii) may be referred to hereinafter as the "straightening step." The straightening roll includes a sheet passing section through which the sheet passes. The roll diameter of the sheet passing section gradually increases from the central part of the roll facing the center of the mix layer in the width direction toward the outer part of the roll facing the non-coated region.

[0022] Here, "the roll diameter in the sheet passage section gradually increases from the central part of the roll facing the center in the width direction of the mixture layer toward the outer part of the roll facing the non-coated region" means that the roll diameter in the sheet passage section does not decrease from the central part of the roll toward the outer part of the roll. Examples of a form in which the roll diameter gradually increases include a form in which the roll diameter always increases from the central part of the roll toward the outer part of the roll. Furthermore, examples of a form in which the roll diameter gradually increases include a form in which the sheet passage section is composed of a region where the roll diameter does not change and a region where the roll diameter increases from the central part of the roll toward the outer part of the roll.

[0023] Step (ii) produces electrode plates with minimal curvature and waviness. Conventional electrode plate straightening methods involve intensive stretching of the uncoated regions of the electrode plate. However, the sheet obtained by the rolling process has a gradient in the amount of stretch across the width of the coated region (the region where the composite layer is formed). Conventional electrode plate straightening methods do not take this gradient into account, resulting in significant waviness in the uncoated region when adjusting the amount of curvature of the electrode plate. Manufacturing method (M) uses a straightening roll with a shape that corresponds to the gradient in the amount of stretch across the coated region. Therefore, electrode plates with minimal curvature and waviness can be produced. Manufacturing method (M) makes it possible to produce the electrode plate (P) described below.

[0024] In this specification, small waviness or low waviness means that there is no waviness or the pitch of the waviness is large.

[0025] The roll diameter in the sheet passing section may increase stepwise and / or in a reverse tapered manner from the central portion of the roll toward the outer portion of the roll. For example, the roll diameter in the sheet passing section may increase stepwise or in a reverse tapered manner from the central portion of the roll toward the outer portion of the roll, or may increase stepwise in part and in a reverse tapered manner in the remaining part. In a cross section perpendicular to the central axis of the straightening roll, the outer edge of the sheet passing section is a circle.

[0026] The roll diameter in the sheet passing section is preferably smallest at the central section of the roll and largest at the outer section of the roll. Furthermore, it is preferable that the roll diameter increases in at least two or more (e.g., three or more) steps from the central section of the roll to the outer section of the roll, or increases in an inverse tapered manner. When the roll diameter increases in two steps from the central section of the roll to the outer section of the roll, this means that the roll diameter increases in two steps from the central section of the roll to the outer section of the roll in the section facing the mixture layer in the sheet passing section. Hereinafter, the section facing the mixture layer in the sheet passing section may be referred to as the "mixture layer passing section."

[0027] The form in which the roll diameter increases in an inverse tapered manner from the central portion of the roll toward the outer portion of the roll includes both a form in which the roll diameter increases in an inverse tapered manner throughout the entire mixture layer passage section, and a form in which the roll diameter increases in an inverse tapered manner only in a portion of the mixture layer passage section.

[0028] The roll diameter may increase in two, three, four, five, or six steps from the center of the roll toward the outer edge of the roll, or may increase in more steps. There is no particular upper limit to the number of steps, and the number may be 10 or more. When the roll diameter at the mixture layer passing portion changes in a stepwise manner, it is particularly preferable that the roll diameter increase in three or more steps from the center of the roll toward the outer edge of the roll. This configuration results in an electrode plate with particularly little curvature and waviness.

[0029] It is preferable that the roll diameter increases approximately uniformly from the center of the roll toward the outer edge of the roll. For example, when the roll diameter increases in an inverse tapered manner, the gradient of the increase in the roll diameter may vary, but is preferably constant or approximately constant. Furthermore, when the roll diameter increases in a stepped manner, it is preferable that the distance from the center of the sheet passage section to the first step (step) and the distance between two adjacent steps are constant or approximately constant, and that the height of each step is constant or approximately constant. Here, "approximately constant" preferably means that the deviation from the average value is within ±50% (for example, within ±30% or ±10%).

[0030] The length of the sheet passage section through which the mixture layer passes is 2 RL (mm). The roll diameter at a position that is a distance Q (e.g., 0.5 RL) from the center portion of the roll is preferably larger than the roll diameter at the center portion of the roll. The roll diameter at the distance Q being larger than the roll diameter at the center portion of the roll means, for example, that there is a step where the roll diameter increases in the range from the center portion of the roll to the distance Q, or that there is a portion where the roll diameter increases in an inverse tapered manner. In other words, within the distance Q from the center portion of the roll, the roll diameter begins to increase toward the outer portions of the roll. The distance Q may be 0.5 RL or less (e.g., 0.4 RL or 0.3 RL). This configuration can particularly effectively accommodate the inclination in the width direction of the amount of elongation of the electrode plate in the mixture layer.

[0031] The difference (Dmax-Dmin) between the maximum roll diameter Dmax and the minimum roll diameter Dmin in the sheet passing section may be in the range of 0.8 to 1.2 mm, which can particularly suppress curvature and waviness of the electrode plate.

[0032] The sheet passage section preferably has a symmetrical shape with respect to the center of the sheet passage section in the axial direction. Typically, the gradient of the amount of elongation in the width direction of the coated section is roughly symmetrical with respect to the center of the width direction of the coated section. Therefore, by making the sheet passage section symmetrical, it is possible to particularly appropriately deal with the gradient of the amount of elongation of the electrode plate in the width direction of the coated area.

[0033] In step (ii), the sheet that has passed through the correction roll may be slit along the center of the width of the mixture layer and then wound up on a take-up roll. Alternatively, the sheet that has been subjected to step (ii) may be slit along the center of the width of the mixture layer. The slit strip-shaped sheet may be cut to a predetermined length and used as an electrode plate.

[0034] The tension applied to the sheet when passing through the straightening rolls may be in the range of 1.3 to 1.6 N / mm per unit length in the width direction of the sheet.

[0035] The tension applied when the sheet is wound around the winding roll may be in the range of 0.3 to 0.7 N / mm per unit length in the width direction of the sheet, which can prevent the electrode plate from curving after winding.

[0036] As will be explained later with respect to the manufacturing apparatus (D), in the step (ii), the unwinding tension and the winding tension can be set to different values ​​by using a nip roll or the like.

[0037] In step (i), the mixture layer may be formed so that the average thickness of the widthwise end portions of the mixture layer is smaller than the average thickness of the widthwise central portion of the mixture layer. A sheet formed in this manner has a large gradient in the amount of elongation of the mixture layer in the width direction, making it particularly difficult to properly straighten it with a conventional straightening roll. Since the manufacturing method (M) uses the above-described straightening roll, even a sheet formed as described above can be properly straightened. Of course, in step (i), the sheet may be formed so that the shape of the mixture layer has a shape other than the above. A method for determining the magnitude relationship between the average thickness of the widthwise end portions of the mixture layer and the average thickness of the widthwise central portion of the mixture layer will be described later.

[0038] The metal foil constituting the current collector may be a foil made of aluminum or an aluminum alloy, and the active material may be a composite oxide containing lithium. Such an electrode plate can be used as a positive electrode of a battery (e.g., a positive electrode of a non-aqueous electrolyte secondary battery). Of course, the electrode plate produced by the production method (M) may be an electrode plate other than a positive electrode of a non-aqueous electrolyte secondary battery.

[0039] (Electrode plate manufacturing equipment) A manufacturing apparatus according to an embodiment of the present disclosure is an apparatus for manufacturing electrode plates. This manufacturing apparatus can manufacture electrode plates for batteries. This manufacturing apparatus may be referred to hereinafter as a "manufacturing apparatus (D)." The manufacturing apparatus (D) can easily implement the manufacturing method (M). Note that the matters described for the manufacturing method (M) can be applied to the manufacturing apparatus (D), and therefore redundant explanations will be omitted. Furthermore, the matters described for the manufacturing apparatus (D) may also be applied to the manufacturing method (M).

[0040] The manufacturing apparatus (D) includes a conveying mechanism that conveys a strip-shaped sheet including a strip-shaped current collector and a strip-shaped mixture layer formed on the current collector, and a straightening roll. The conveying mechanism includes a take-up roll for winding up the sheet that has passed through the straightening roll. Each of the widthwise ends of the sheet is a non-coated area where the mixture layer is not formed. The conveying mechanism conveys the sheet so that the sheet passes over the straightening roll while tension is applied to the sheet. The straightening roll includes a sheet passing section through which the sheet passes. The roll diameter of the sheet passing section gradually increases from the central part of the roll facing the widthwise center of the mixture layer to the outer part of the roll facing the non-coated area.

[0041] The sheet may be, for example, the sheet manufactured in step (i) of manufacturing method (M). The metal foil and the mixture layer have been described above, so a duplicated description will be omitted. Similarly, the correction roll described in manufacturing method (M) can be used, so a duplicated description will be omitted.

[0042] As explained for the manufacturing method (M), the manufacturing apparatus (D) may satisfy at least one of the following conditions (1) to (7): Note that the effects obtained by satisfying the following conditions are as explained for the manufacturing method (M). (1) The roll diameter in the sheet passage section increases in a stepped and / or inversely tapered manner from the center of the roll toward the outer periphery of the roll. (2) When the length of the mixture layer passing section of the sheet passing section through which the mixture layer passes is 2RL, the roll diameter at a position 0.5RL away from the center of the roll is larger than the roll diameter at the center of the roll. (3) The difference (Dmax-Dmin) between the maximum roll diameter Dmax in the sheet passing section and the minimum roll diameter Dmin in the sheet passing section is in the range of 0.8 to 1.2 mm. (4) The sheet passage portion has a symmetrical shape with respect to the center of the sheet passage portion in the axial direction. (5) A slitting mechanism for slitting the sheet along the center of the mix layer in the width direction is further included between the correction roll and the take-up roll. (6) The tension applied to the sheet when passing through the straightening roll is in the range of 1.3 to 1.6 N / mm per unit length in the width direction of the sheet. (7) The tension applied when the sheet is wound by the winding roll is in the range of 0.3 to 0.7 N / mm per unit length in the width direction of the sheet.

[0043] The manufacturing apparatus (D) may include a mechanism for making the unwinding tension when the sheet is unwound from the unwinding roll and the winding tension when the sheet is wound around the winding roll different. An example of such a mechanism is a nip roll. The nip roll is disposed, for example, between the straightening roll and the winding roll, and presses the sheet flowing therebetween with a predetermined range of force. This allows the unwinding tension and the winding tension to be different.

[0044] The slitting mechanism is not particularly limited, and any known slitting mechanism can be used. Two sheets are obtained by slitting the sheet along the center of the mix layer in the width direction. Each of the two sheets can be cut to a predetermined length to form an electrode plate.

[0045] (battery) A battery according to an embodiment of the present disclosure includes two electrode plates. At least one of the two electrode plates includes a current collector including a metal foil and a mixture layer including an active material disposed on the current collector. Hereinafter, the at least one electrode plate may be referred to as the "electrode plate (P)." One of the two widthwise ends of the electrode plate (P) is an uncoated region where no mixture layer is formed. The current collector in the uncoated region does not have wavy projections or depressions, or if wavy projections or depressions are present, the pitch between adjacent projections or depressions is 15 mm or more. When the length of the line connecting the two corners on the uncoated region side is L (mm) and the amount of curvature of the outer edge of the uncoated region side (the outer edge of the current collector) relative to the line at the center of the line is Y (mm), the following formula (1) is satisfied: -8×10 -6 ×L 2 ≦Y≦8×10 -6 ×L 2 (1)

[0046] The method for measuring the pitch (pitch length) will be described later. The electrode plate (P) can be manufactured by the above-mentioned manufacturing method (M), and may also be manufactured using the above-mentioned manufacturing apparatus (D). Therefore, the matters explained in the manufacturing method (M) and the manufacturing apparatus (D) can be applied to the electrode plate (P), and therefore, overlapping explanations may be omitted. Furthermore, the matters explained about the electrode plate (P) can also be applied to the manufacturing method (M) and the manufacturing method (D).

[0047] The difference (T1-T2) between the average thickness T1 of the electrode plate at the center of the mix layer in the width direction and the average thickness T2 of the electrode plate at the end of the mix layer on the uncoated region side may be 5 μm or less. A method for measuring the difference (T1-T2) will be described later.

[0048] As described above, in one example of the electrode plate (P), the metal foil is a foil made of aluminum or an aluminum alloy, the active material is a composite oxide containing lithium, and the electrode plate (P) is used as a positive electrode (positive electrode plate), for example, as a positive electrode of a non-aqueous electrolyte secondary battery. As described above, the electrode plate (P) may be an electrode plate other than a positive electrode of a non-aqueous electrolyte secondary battery, and may be used as a negative electrode (negative electrode plate). In that case, the current collector, active material, etc. are selected depending on the type of electrode plate used.

[0049] There are no particular limitations on the structure of the battery, except that it contains electrode plates (P). A battery typically includes a positive electrode, a negative electrode, a separator, an electrolyte, and an exterior body that houses them. These components can be selected depending on the type of battery. The positive electrode, the negative electrode, and the separator constitute an electrode plate assembly. In the electrode plate assembly, the separator is disposed between the positive electrode and the negative electrode.

[0050] The type of battery is not particularly limited as long as it can use the electrode plate (P), and it may be a secondary battery (a nonaqueous electrolyte secondary battery or a nickel-metal hydride secondary battery). The electrode plate assembly may be a wound electrode plate assembly obtained by winding a positive electrode, a negative electrode, and a separator, or a stacked electrode plate assembly obtained by stacking a positive electrode, a negative electrode, and a separator. The shape of the battery may be cylindrical, rectangular, or other shapes. Examples of cylindrical batteries include pin-shaped batteries. When measuring the curvature and waviness pitch of electrode plates included in a battery, first disassemble the battery and remove the electrode plates. Next, the electrode plates are flattened, and when measuring the curvature, the electrode plates are sandwiched and fixed between a metal plate and a glass plate, which have reference lines and scales. When measuring the waviness pitch, the electrode plates are sandwiched and fixed between two glass plates. Then, the curvature and waviness pitch can be measured using the method described in the examples.

[0051] An example of the configuration when the battery is a non-aqueous electrolyte secondary battery (lithium ion secondary battery) will be described below.

[0052] (positive electrode) The positive electrode mixture layer may be formed, for example, by the following method. First, a material containing a positive electrode active material and other optional components (such as a binder, a thickener, and a conductive material) is dispersed in a dispersion medium to prepare a positive electrode slurry. Next, the positive electrode slurry is applied to the surface of a positive electrode current collector and then dried to form a coating film. Thereafter, the current collector and the coating film are rolled together to form a positive electrode sheet including the positive electrode mixture layer.

[0053] (Negative electrode) The negative electrode includes a negative electrode active material. The negative electrode typically includes a negative electrode current collector and a layered negative electrode mixture layer disposed on the negative electrode current collector. The negative electrode mixture layer can be formed by applying a negative electrode slurry, in which the components of the negative electrode mixture layer are dispersed in a dispersion medium, to the surface of the negative electrode current collector and drying the slurry. The dried coating may be rolled as necessary.

[0054] The negative electrode mixture layer contains a negative electrode active material and other optional components (such as a binder, a thickener, and a conductive material). A known negative electrode mixture layer used in the negative electrodes of non-aqueous electrolyte secondary batteries can be used for the negative electrode mixture layer. A material capable of electrochemically absorbing and desorbing lithium ions can be used as the negative electrode active material. Examples of such materials include carbonaceous materials and Si-containing materials.

[0055] (non-aqueous electrolyte) A non-aqueous electrolyte (non-aqueous electrolyte solution) contains a solvent and a solute dissolved in the solvent. Examples of the solute include lithium salts. Examples of the solvent include propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC).

[0056] (separator) The separator may be a microporous membrane, a woven fabric, a nonwoven fabric, etc. Examples of the separator material include polyolefin and other resins.

[0057] Below, examples of the manufacturing method (M), manufacturing apparatus (D), and electrode plate (P) will be specifically described with reference to the drawings. The above-mentioned explanations can be applied to the manufacturing method, manufacturing apparatus, and electrode plate described below, and modifications may be made based on the above-mentioned explanations. Furthermore, the matters described below may be applied to the above-mentioned embodiments. Furthermore, in the examples described below, components that are not essential to the manufacturing method, manufacturing method, and electrode plate according to the present disclosure may be omitted.

[0058] (Embodiment 1) In embodiment 1, examples of manufacturing method (M) and manufacturing method (D) are described. In the manufacturing method of embodiment 1, first, as shown in FIG. 1, a sheet 100 is formed, including a current collector 101 and a mixture layer 102 formed on the current collector 101. Specifically, a slurry containing an active material is applied in a strip shape along the longitudinal direction of the current collector 101, including a strip-shaped metal foil, and then rolled. This results in a strip-shaped sheet 100 including a mixture layer 102 containing an active material. The obtained sheet 100 may be wound around a roll, or may be subjected to a straightening process before being wound around a roll. FIG. 2 shows a cross-sectional view of the sheet 100 taken along line II-II in FIG. 1.

[0059] In the first embodiment, an example in which a mixture layer 102 is formed on both sides of a current collector 101 will be described. As shown in FIGS. 1 and 2, in step (i), the sheet 100 is formed so that an uncoated region 100b where the mixture layer 102 is not formed is present at each end of the width direction WD (a direction perpendicular to the longitudinal direction LD of the sheet 100). The sheet 100 can be divided into a coated region 100a where the mixture layer 102 is formed and an uncoated region 100b. Typically, the two uncoated regions 100b are formed so that they have substantially the same width. When the two uncoated regions 100b have the same width, the center of the width direction of a sheet passage section 310 (described below) and the center of the width direction of a mixture layer passage section 310x (described below) will be the same.

[0060] As a result of investigation, the inventors of the present application have newly discovered that the amount of elongation of the sheet 100 during the rolling process varies depending on the position in the width direction WD of the sheet 100, as shown in FIG. 1. Furthermore, they have discovered that conventional straightening rolls cannot accommodate the differences in the amount of elongation of the sheet 100, resulting in insufficient straightening. In this embodiment, a straightening roll that accommodates the differences in the amount of elongation of the sheet 100 is used. As a result, the curvature and waviness of the sheet 100 after straightening can be significantly reduced compared to conventional methods.

[0061] The example mix layer 102 shown in FIG. 2 is formed so that the average thickness Td of the mix layer 102 at the ends in the width direction WD is smaller than the average thickness Tc of the mix layer 102 at the center 102c in the width direction WD. The thickness of the mix layer 102 shown in FIG. 2 is approximately constant near the center in the width direction WD and becomes thinner toward the ends. This shape can be achieved by controlling the conditions for coating the slurry. For example, in die coating, the shape shown in FIG. 2 can be achieved by controlling the ratio between the opening width Ws when the slurry is discharged from the opening of the inner deckle (coating shim) toward the current collector surface and the width Wp of the coated area when the discharged slurry is spread to the coated area. The higher the spreading ratio, i.e., the smaller the Ws / Wp ratio, the more likely it is that the shape shown in FIG. 2 will be obtained. When forming the mixture layer 102 having the shape shown in FIG. 2, the value of the Ws / Wp ratio is preferably 0.94 or less, for example, in the range of 0.86 to 0.92 (particularly, in the range of 0.88 to 0.90).

[0062] The magnitude relationship between the average thickness Tc and the average thickness Td can be determined by the following procedure. First, the center 102c of 20 arbitrary locations is selected and the thickness of the sheet 100 at that location is measured. Next, the thicknesses of the 20 measured locations are arithmetically averaged, and the obtained average value is defined as the average thickness Tc. Next, 20 predetermined positions 102d on the edge are arbitrarily selected and the thickness of the sheet 100 at each position 102d is measured. Position 102d is a position 1 mm from the edge of the non-coated region 100b side of the mixture layer 102 toward the center 102c. Next, the thicknesses of the 20 measured locations are arithmetically averaged, and the obtained average value is defined as the average thickness Td. If the value of (Tc - Td) is positive, the average thickness Td of the edge is smaller than the average thickness Tc of the center.

[0063] Next, as shown in Fig. 3, step (ii) is performed using a manufacturing apparatus 200. Specifically, the sheet 100 wound around an unwinding roll 211 is sent out toward the straightening roll 300, and the sheet 100 is passed over the straightening roll 300 while tension is applied to the sheet 100, thereby straightening the curvature of the sheet 100, and then the straightened sheet is taken up around a take-up roll 212 (straightening step).

[0064] The manufacturing apparatus 200 includes a conveying mechanism 210, nip rolls 230, a slitter 240, and a straightening roll 300. The conveying mechanism 210 includes an unwinding roll 211 and a take-up roll 212. The conveying mechanism 210 further includes a roll 213, a roll 214, an edge detection sensor 215, a drive mechanism (e.g., a motor) for unwinding by the unwinding roll 211, a drive mechanism (e.g., a motor) for winding by the take-up roll 212, and a measuring device for monitoring the unwinding tension and the take-up tension. The rolls 213, 214, and the edge detection sensor 215 function as a meandering control mechanism (EPC). The components other than the straightening roll 300 are not particularly limited, and known components may be used. The manufacturing apparatus 200 may further include a meandering control mechanism arranged upstream of the straightening roll 300.

[0065] The sheet 100 passes over the straightening roll 300 while in contact with the straightening roll 300, with tension applied to the sheet 100 in its longitudinal direction. As a result, the sheet 100 is pressed against the straightening roll 300 and is stretched according to the shape of the straightening roll 300, resulting in a straightened sheet 100x. Specifically, the larger the roll diameter, the greater the stretching of the sheet 100. As will be described later, the roll diameter of the portion of the straightening roll 300 through which the mixture layer passes gradually increases from the center toward the outer portion. Therefore, it is possible to increase the stretching of the sheet closer to the non-coated region 100b.

[0066] There is no particular limitation on the central angle α of the part of the straightening roll 300 that contacts the sheet 100, but if the central angle α is too small, it becomes difficult to obtain the straightening effect. The central angle α may be in the range of 90° to 180° (for example, in the range of 150° to 170°).

[0067] The straightened sheet 100x is slit along the center of the width direction WD of the mixture layer 102 by a slitter 240 and divided into two pieces. The slit sheet 100y is taken up by a take-up roll 212. The sheet 100y thus obtained is cut to a predetermined length to obtain an electrode plate. The manufacturing method and manufacturing apparatus of the first embodiment use a straightening roll 300. Therefore, as described above, an electrode plate with little curvature and waviness can be obtained.

[0068] In the first embodiment, an example is shown in which the manufacturing apparatus 200 includes the slitter 240 and the straightened sheet 100 is slit, but the manufacturing apparatus 200 does not have to include the slitter 240. When the sheet 100 is slit, the winding roll 212 may include two winding rolls for winding up the two sheets after slitting.

[0069] Furthermore, the manufacturing apparatus 200 may include two or more (e.g., two) straightening rolls, and the straightening process may be performed two or more times using two or more (e.g., two) straightening rolls. By doing so, the tension applied to the sheet when it passes through the straightening rolls can be reduced, making it possible to achieve both suppression of waviness in the non-coated region and straightening of the electrode plate curvature at a high level.

[0070] The manufacturing apparatus 200 may also include a coating device that coats the current collector with a slurry and dries it, and a rolling device that rolls the coating film formed by the coating device. These devices form the sheet 100, which can then be subjected to the straightening process without being wound onto a roll. In this case, the current collector is unwound from the unwinding roll. There are no particular limitations on the coating device and rolling device, and known devices may be used.

[0071] The correction roll 300 includes a sheet passing section 310 through which the sheet 100 passes. The roll diameter of the sheet passing section 310 increases in a stepped and / or reverse tapered manner from a central portion facing the center 102c of the mix layer 102 in the width direction WD toward an outer portion facing the non-coated region 100b.

[0072] A cross-sectional view of an example of the straightening roll 300 is shown in Fig. 4. The cross-sectional view in Fig. 4 is a cross-sectional view taken along the central axis 300ca of the straightening roll 300. Fig. 4 also shows the position where the sheet 100 passes over the straightening roll 300. In the cross-sectional view of the straightening roll, hatching is omitted to make the drawing easier to see.

[0073] 4 includes a sheet passing section 310 through which the sheet 100 passes. The sheet passing section 310 has a symmetrical shape with respect to a roll center section 300cc of the sheet passing section 310 on a central axis 300ca. The sheet passing section 310 includes a mix layer passing section 310x facing the coating region 100a (mixture layer 102) and two roll outer sections 310y facing the two non-coating regions 100b.

[0074] The roll diameter of the sheet passing portion 310 increases in a three-step staircase shape from the roll central portion 300cc facing the center 102c of the coating layer 102 toward the two outer portions 310y.

[0075] The sheet passing portion 310 includes a first portion (roll central portion 311) having the minimum roll diameter Dmin, two second portions 312 having a roll diameter D2, two third portions 313 having a roll diameter D3, and two fourth portions (roll outer portions 314) having the maximum roll diameter Dmax. The roll diameters satisfy the relationship Dmin < D2 < D3 < Dmax. The two roll outer portions 314 are located at both ends of the sheet passing portion 310. The two third portions 313 are arranged between the two fourth portions. The two second portions 312 are arranged between the two third portions 313. The central portion 311 is arranged between the two second portions 312. The boundary between the third portion 313 and the roll outer portion 314 preferably faces the coating region 100a (coating layer 102). Note that the correction roll 300 includes a portion where the roll outer portion 314 extends outward so as to be wider than the width of the sheet 100.

[0076] The roll central portion 300cc (the center of the coating layer passing portion 310x) has the minimum roll diameter Dmin. Here, let the length from the roll central portion 300cc to the roll outer portion 314 be the length RL (mm). That is, the length of the coating layer passing portion 310x along the central axis 300ca is 2RL (mm). The roll diameter of the sheet passing portion 310 is preferably larger than Dmin at a position where the distance from the roll central portion 300cc is within a predetermined range. The predetermined range may be within the range described above.

[0077] When the roll diameter increases in an inverse taper shape in a part of the coating layer passing portion 310x, the length along the central axis 300ca of the portion where the roll diameter increases in an inverse taper shape may be within the range of 0.4RL to 2RL in the coating layer passing portion 310x.

[0078] A cross-sectional view of another example of the straightening roll 300 is shown in Fig. 5. The cross-sectional view in Fig. 5 is a cross-sectional view taken along the central axis 300ca of the straightening roll 300. Fig. 5 also shows the position where the sheet 100 passes over the straightening roll 300.

[0079] The roll diameter of the sheet passing section 310 increases in an inverse tapered manner from a central portion 300 cc of the roll facing the center of the mixture layer 102 toward two outer portions 310y of the roll. The outer portions 310y have a constant roll diameter.

[0080] As shown in Figures 4 and 5, the straightening roll 300 does not include a portion where the roll diameter decreases from the roll center portion 300cc toward the roll outer portion 314. Compared to the inverse tapered shape shown in Figure 5, the stepped shape shown in Figure 4 has the advantage that a high straightening effect can be easily obtained even with low tension and waviness can be suppressed. In particular, it is preferable that the mix layer passing portion 310x includes a stepped shape, since it can easily accommodate the gradient of the elongation amount of the mix layer 102 portion.

[0081] (Embodiment 2) An example of the battery according to this embodiment will be described in Embodiment 2. In Embodiment 2, an example in which the battery is a non-aqueous electrolyte secondary battery will be described.

[0082] A cross-sectional view of a battery according to Embodiment 2 is shown in Fig. 6. Fig. 6 is a schematic longitudinal cross-sectional view of a pin-shaped cylindrical secondary battery 1 according to Embodiment 2. The secondary battery 1 includes a cylindrical battery case 20 with an opening and a bottom, a wound electrode plate assembly 10 and a non-aqueous electrolyte (not shown) housed in the battery case 20, and a sealing member 40 that seals the opening of the battery case 20. The electrode plate assembly 10 is formed by winding the positive electrode 11, the negative electrode 12, and the separator 13 such that the separator 13 is disposed between the positive electrode 11 and the negative electrode 12.

[0083] The closing member 40 is hat-shaped and includes a ring-shaped brim 40a and cylindrical terminal portions 40b and 40c. A ring-shaped insulating gasket 30 is disposed around the periphery of the closing member 40 so as to cover the brim 40a. The periphery of the closing member 40 is crimped to the open edge of the battery case 20, with the gasket 30 sandwiched between them.

[0084] A first insulating ring 50A is disposed between the upper end surface (top surface) of the electrode plate pack 10 and the bottom surface of the sealing member 40. A donut-shaped second insulating ring 50B made of an electrically insulating material is disposed so as to cover the outer surface of the bent open end of the battery case 20 and the surface of the gasket 30 around it.

[0085] The polarities of the battery case 20 and the sealing member 40 can be determined arbitrarily. That is, the battery case 20 may be either a positive electrode terminal or a negative electrode terminal. In the example shown in Fig. 5, the battery case 20 is connected to the negative electrode 12 and used as an external negative electrode terminal, and the sealing member 40 is connected to the positive electrode 11 and used as an external positive electrode terminal.

[0086] The positive electrode 11 and the sealing member 40 are electrically connected via a positive electrode current collector lead 60. The sealing member 40 functions as a positive electrode terminal. One end of the negative electrode current collector lead 70 is connected to the inner wall of the battery case 20 at a welding point 70a. The negative electrode 12 and the battery case 20 are electrically connected via the negative electrode current collector lead 70. The battery case 20 functions as an external negative electrode terminal.

[0087] The positive electrode 11 is the electrode plate (P) described above. FIGS. 7A to 7C show top views of the positive electrode 11 when laid out flat. Note that in these figures, the curvature is emphasized for ease of understanding. As shown in FIG. 7A, the positive electrode 11 includes a current collector 101 and a mixture layer 102. The mixture layer 102 is formed on both sides of the current collector 101. One of the two ends of the positive electrode 11 in the width direction WD is an uncoated region 100b where the mixture layer 102 is not formed. The positive electrode 11 can be divided into a coated region 100a where the mixture layer 102 is formed, and an uncoated region 100b.

[0088] An example of a method for measuring the curvature Y will be described with reference to FIG. 7A. The method described below is an example of a simple method for measuring the curvature Y. First, the positive electrode 11 is sandwiched and fixed between a metal plate and a glass plate. A virtual reference line BL is drawn on the metal plate, and a scale is provided on the reference line. As shown in FIG. 7A, the outer edge 101p of the current collector 101 of the positive electrode 11 is positioned below and near the reference line BL. The outer edge 101p is the outer edge between the two corners 101a and 101b on the non-coated region 100b side of the current collector 101. At this time, the outer edge 101p is positioned as parallel as possible to the reference line BL. Specifically, the electrode plate is positioned so that the difference in distance between the corners 101a and 101b and the reference line BL is 0.5 mm or less to prevent tilting.

[0089] Next, position A is identified where a perpendicular line can be drawn from reference line BL and pass through the upper left corner of current collector 101. Similarly, position C is identified where a perpendicular line can be drawn from reference line BL and pass through the upper left corner of current collector 101. Then, position B is identified, which is centered between positions A and C. Here, the lengths Xa (mm), Xb (mm), and Xc (mm) of the perpendicular lines extended from positions A, B, and C to the outer edge 101p are measured from a glass plate using a factory microscope. At this time, the above-mentioned curvature amount Y (mm) can be calculated using the formula Y = Xb - (Xa + Xc) / 2.

[0090] As shown in Fig. 7A, when the outer edge 101p has an inwardly concave shape, the curvature amount Y is a positive value. Fig. 7A shows the width direction WD of the positive electrode 11 (electrode plate (P)). The width direction WD of the electrode plate (P) is the direction connecting one side (outer edge 101p) on the non-coated region 100b side and the opposite side.

[0091] 7B shows an example in which the outer edge 101p is not curved. In this case, the amount of curvature Y=Xb−(Xa+Xc) / 2=0.

[0092] 7C shows an example in which the outer edge 101p has a shape that is convex toward the inside. In this case, the value of the amount of curvature Y=Xb-(Xa+Xc) / 2 is a negative value.

[0093] By producing the positive electrode 11 by the production method (M), the amount of curvature Y of the current collector 101 can be reduced, and the above formula (1) can be satisfied.

[0094] A method for measuring the pitch (pitch length) of the waviness of the positive electrode 11 (electrode plate (P)) will be described. When measuring the pitch of the waviness of the positive electrode 11, the positive electrode 11 is first sandwiched and fixed between two flat glass plates. The state at that time is shown in FIG. 8. FIG. 8 is a diagram of the outer edge 101p of the current collector 101 sandwiched between the two glass plates, viewed from the non-coated region 100b side.

[0095] Consider the case where wavy projections and recesses are present on the outer edge 101p of the current collector 101. As shown in FIG. 8, when two projections CP (or two recesses) are present on the outer edge 101p, the distance PL (mm) between the two projections CP (or two recesses) is the pitch. When there are no wavy projections or recesses on the outer edge 101p, or when there is only one wavy projection or recess, the pitch is L (mm) or greater. For example, when the length L is 30 mm and there is only one wavy projection or recess on the outer edge 101p, the pitch is 30 mm or greater.

[0096] The method for measuring the average thickness T1 of the electrode plate at the center of the mix layer 102 of the positive electrode 11 (electrode plate (P)) in the width direction WD and the average thickness T2 of the electrode plate at the end of the mix layer on the uncoated region 100b side will be described with reference to FIG. 9 . The average thickness T1 is determined by the following procedure. First, 20 locations are arbitrarily selected in the center 102e of the mix layer 102 in the width direction WD, and the thickness of the positive electrode 11 (electrode plate (P)) at the 20 locations is measured. The arithmetic mean of the thicknesses measured at the 20 locations is then defined as the average thickness T1. The average thickness T2 is determined by the following procedure. First, 20 positions 102f are arbitrarily selected, and the thickness of the positive electrode 11 (electrode plate (P)) at the 20 locations is measured. The positions 102f are located 1 mm from the end of the mix layer 102 on the uncoated region 100b side toward the center 102e. The arithmetic mean of the thicknesses measured at the 20 locations is then taken as the average thickness T2. [Example]

[0097] The present embodiment will be specifically described below based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0098] In this example, electrode plates were corrected under multiple conditions, and the corrected electrode plates were evaluated. A positive electrode for a secondary battery was used as the electrode plate. Aluminum foil with a width of 30.6 mm and a thickness of 13 μm was used as the current collector. A slurry was applied to both sides of this current collector and dried to form a coating film. Next, the coating film was rolled to form a strip-shaped positive electrode sheet including the current collector and a mixture layer, and the sheet was wound around a roll (the unwinding roll in the correction process). At this time, the mixture layer was formed so that both ends of the current collector in the width direction were uncoated regions where no mixture layer was formed. The width of each uncoated region was 2.4 mm. The width of the mixture layer was 25.8 mm.

[0099] In this example, multiple positive electrode sheets (sheets 100) were produced by varying the conditions for applying the slurry. For the positive electrode sheets before the correction process, the average thickness Tc of the electrode plate at the center in the width direction of the mixture layer and the average thickness Td of the mixture layer at the end in the width direction were measured using the method described above. Then, the difference (Tc - Td) was calculated.

[0100] The curvature of the positive electrode sheet was corrected using an apparatus similar to that shown in Fig. 3. The correcting rolls used were correcting rolls A1 to A5, in which the roll diameter increases stepwise, correcting rolls B1 and B2, in which the roll diameter increases in an inverse tapered manner, and correcting rolls C1 to C3, which were modified from the correcting roll shown in Fig. 4 so that only the outermost step portion was provided.

[0101] The straightening roll A3 has a shape shown in FIG. 4. Referring to FIG. 4, the minimum diameter Dmin of the straightening roll A3 was 99.2 mm. The distance SL1 from the roll center portion 300 cc to the second portion 312 (first step) was 4.1 mm. The step SH1 between the second portion 312 and the roll center portion 311 was 0.13 mm. The length SL2 of the second portion 312 in the width direction was 3.9 mm. The step SH2 between the second portion 312 and the third portion 313 was 0.13 mm. Similarly, the length SL3 of the third portion 313 in the width direction was 3.9 mm. The step SH3 between the third portion 313 and the roll outer portion 314 was 0.14 mm. The difference (Dmax - Dmin) between the maximum roll diameter Dmax and the roll diameter Dmin was 0.80 mm.

[0102] The change in the roll diameter of the correction roll 300 is very small compared to the width of the sheet 100. Therefore, it can be considered that the width of the mixture layer 102 does not change substantially on the correction roll 300. That is, it can be considered that the length of the mixture layer passing portion 310x is substantially the same as the width of the mixture layer 102. In other words, it can be considered that the length 2RL of the mixture layer passing portion 310x is the same as the width of the mixture layer 102.

[0103] As described above, the width of the mix layer is 25.8 mm. Therefore, for the straightening rolls A1 to A5, the above-mentioned length 2RL (see FIG. 4) can be considered to be 25.8 mm (RL = 12.9 mm). Also, SL1 is 4.1 mm. For the straightening roll A3, the distance from the roll center portion 300 cc to the second portion 312 in FIG. 4 is 0.32RL (RL × 4.1 / 12.9). For the straightening rolls B1 and B2, the distance from the roll center portion 300 cc to the portion where the diameter increases can be considered to be a value close to zero. That is, for all of the straightening rolls A1 to A5 and the straightening rolls B1 and B2, the roll diameter gradually increases toward the outer portion of the roll within a distance of 0.5RL (more specifically, a range of 0.4RL) from the roll center portion 300 cc.

[0104] The straightening rolls A2, A4, and A5 are rolls whose roll diameter difference (Dmax - Dmin) is the value shown in Table 1. The SL1, SL2, and SL3 of the straightening rolls A2, A4, and A5 were the same as those of the straightening roll A3, and the SH1, SH2, and SH3 of the straightening rolls A2, A4, and A5 were set to be approximately equal. The straightening roll A1 had an asymmetric shape.

[0105] The straightening roll B2 has the shape shown in Figure 5. The minimum roll diameter Dmin was 99.2 mm, and the maximum roll diameter Dmax was Dmin + 0.80 mm. The straightening roll B1 had a roll diameter of one outer portion Dmin + 0.60 mm, and a roll diameter of the other outer portion Dmin + 0.80 mm. In other words, the straightening roll B1 had an asymmetric shape.

[0106] The positive electrode sheet was straightened and slit by varying the type of straightening roll, the unwinding tension described above, the winding tension described above, and the shape of the composite layer (the (Tc-Td) value described above). Two positive electrode sheets were obtained by straightening and slitting. The resulting positive electrode sheet was cut to a predetermined length to obtain multiple positive electrodes (500 mm long, 15.3 mm wide). The resulting positive electrode sheet can be cut shorter and used as the positive electrode for a smaller secondary battery (e.g., a pin-type secondary battery). The amount of curvature Y and the pitch of the wavy shape of the resulting positive electrode were evaluated using the method described above. The amount of curvature Y was measured by measuring the amount of curvature Y0 immediately after the positive electrode was fabricated and the amount of curvature Y1 after storage for 60 days while wound on a winding roll. The change in the amount of curvature = Y1-Y0 (the difference between Y1 and Y0) was then calculated. Some of the experimental conditions and the evaluation results are shown in Table 1.

[0107] The amount of bending Y in this example is the value when the length L in formula (1) is 500 mm. In this case, the right side of formula (1) is 8×10 -6 ×500 2 =2.0. Therefore, in this embodiment, equation (1) is expressed as follows: -2.0≦Y≦2.0

[0108] [Table 1]

[0109] An electrode plate with a positive value of (Tc - Td) has a shape similar to that shown in Fig. 2. On the other hand, an electrode plate with a negative value of (Tc - Td) has an average thickness Td of the electrode plate at the end portion in the width direction of the mixture layer that is greater than the average thickness Tc of the electrode plate at the center portion in the width direction of the mixture layer.

[0110] Experimental Examples 1 to 14 are examples using the manufacturing method (M) and manufacturing apparatus (D). As shown in Table 1, experimental examples 1 to 14 produced electrode plates with a small amount of curvature and a long waviness pitch. Furthermore, as can be seen from a comparison between experimental examples 7 and 9 to 11, the amount of change in the amount of curvature could be reduced by setting the winding tension in the range of 0.3 to 0.7 N / mm. [Industrial Applicability]

[0111] The present disclosure can be used in a method for manufacturing an electrode plate, an apparatus for manufacturing an electrode plate, and a battery. [Explanation of symbols]

[0112] 1: Secondary battery 11: Positive electrode 100: Sheet 100a: Coating area 100b: Uncoated area 101: Current collector 102: Mixture layer 200: Manufacturing equipment 210:Transport mechanism 211: Unwinding roll 212: Winding roll 230: Nip roll 240: Slitter 300: Straightening roll 300ca: Central axis 300cc, 311: Center of the roll 310: Sheet passage area 310x: Mixture layer passage section 310y, 314: Roll outer part

Claims

1. A method for manufacturing an electrode plate, a step (i) of applying a slurry containing an active material in a strip shape onto a strip-shaped current collector including a strip-shaped metal foil along the longitudinal direction of the current collector, and then rolling the applied slurry to form a strip-shaped sheet including a mixture layer containing the active material; and (ii) a step of passing the sheet over a straightening roll while tension is applied to the sheet to straighten the curvature of the sheet, and then winding the sheet onto a winding roll, In the step (i), the sheet is formed so that uncoated regions where the mixture layer is not formed are present at both ends of the sheet in the width direction, The straightening roll includes a sheet passing portion through which the sheet passes, the roll diameter of the sheet passing section gradually increases from a central portion of the roll facing the center in the width direction of the mixture layer toward an outer portion of the roll facing the non-coated region, a sheet passing section having a length of 2RL through which the composite layer passes, and a roll diameter at a position 0.5RL away from the roll center portion, the roll diameter being larger than the roll diameter at the roll center portion.

2. The method for manufacturing an electrode plate according to claim 1 , wherein the roll diameter in the sheet passage section increases in a stepped and / or inversely tapered manner from the central portion of the roll toward the outer portion of the roll.

3. the roll diameter in the sheet passing section is smallest at a central portion of the roll and largest at an outer portion of the roll, 3. The method for manufacturing an electrode plate according to claim 1, wherein the roll diameter increases in a stepwise manner in at least two steps or in a reverse tapered manner from the central portion of the roll toward the outer portion of the roll.

4. The method for manufacturing an electrode plate according to any one of claims 1 to 3, wherein the difference (Dmax - Dmin) between the maximum roll diameter Dmax in the sheet passing portion and the minimum roll diameter Dmin in the sheet passing portion is in the range of 0.8 to 1.2 mm.

5. The method for manufacturing an electrode plate according to any one of claims 1 to 4, wherein the sheet passage portion has a shape symmetrical with respect to a center in the axial direction of the sheet passage portion.

6. 6. The electrode plate manufacturing method according to any one of claims 1 to 5, wherein in the step (ii), the sheet that has passed through the correction roll is slit along the center portion in the width direction of the mixture layer, and then wound up by the winding roll.

7. The tension applied to the sheet when passing through the correction roll is in the range of 1.3 to 1.6 N / mm per unit length in the width direction of the sheet. The method for manufacturing an electrode plate according to any one of claims 1 to 6.

8. The method for manufacturing an electrode plate according to any one of claims 1 to 7, wherein the winding tension when winding the sheet by the winding roll is in the range of 0.3 to 0.7 N / mm per unit length in the width direction of the sheet.

9. In the step (i), the mixture layer is formed so that the average thickness of the end portions in the width direction of the mixture layer is smaller than the average thickness of the central portion in the width direction of the mixture layer. The method for manufacturing an electrode plate according to any one of claims 1 to 8.

10. the metal foil is a foil made of aluminum or an aluminum alloy, the active material is a composite oxide containing lithium, The method for manufacturing an electrode plate according to any one of claims 1 to 9, wherein the electrode plate is a positive electrode.

11. An apparatus for manufacturing electrode plates, a conveying mechanism that conveys a strip-shaped sheet including a strip-shaped current collector and a strip-shaped mixture layer formed on the current collector; a straightening roll; the conveying mechanism includes a take-up roll for taking up the sheet that has passed through the straightening roll, each of both ends in the width direction of the sheet is an uncoated region where the mixture layer is not formed; the conveying mechanism conveys the sheet so that the sheet passes over the straightening roll while tension is applied to the sheet; The straightening roll includes a sheet passing portion through which the sheet passes, the roll diameter of the sheet passing section gradually increases from a central portion of the roll facing the center in the width direction of the mixture layer toward an outer portion of the roll facing the non-coated region, When the length of the composite layer passing section of the sheet passing section through which the composite layer passes is 2RL, the roll diameter at a position 0.5RL away from the central portion of the roll is larger than the roll diameter at the central portion of the roll.

12. 12. The electrode plate manufacturing apparatus according to claim 11, wherein the roll diameter in the sheet passage section increases in a stepped and / or inversely tapered manner from the central portion of the roll toward the outer portion of the roll.

13. the roll diameter in the sheet passing section is smallest at a central portion of the roll and largest at an outer portion of the roll, 13. The electrode plate manufacturing apparatus according to claim 11, wherein the roll diameter increases in a stepwise manner with at least two steps or in a reverse tapered manner from the central portion of the roll toward the outer portion of the roll.

14. The electrode plate manufacturing apparatus according to any one of claims 11 to 13, wherein the difference (Dmax - Dmin) between the maximum roll diameter Dmax in the sheet passing section and the minimum roll diameter Dmin in the sheet passing section is in the range of 0.8 to 1.2 mm.

15. The electrode plate manufacturing apparatus according to any one of claims 11 to 14, wherein the sheet passing section has a shape symmetrical with respect to the center of the sheet passing section in the axial direction.

16. 16. The electrode plate manufacturing apparatus according to any one of claims 11 to 15, further comprising a slitting mechanism for slitting the sheet along the center portion in the width direction of the mixture layer between the correction roll and the winding roll.

17. The tension applied to the sheet when passing through the correction roll is in the range of 1.3 to 1.6 N / mm per unit length in the width direction of the sheet. The electrode plate manufacturing apparatus according to any one of claims 11 to 16.

18. The electrode plate manufacturing apparatus according to any one of claims 11 to 17, wherein the winding tension when winding the sheet by the winding roll is in the range of 0.3 to 0.7 N / mm per unit length in the width direction of the sheet.

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