Manufacturing method of electrode plate

Abstract

To suppress variations in cutting quality of an edge part of a manufactured electrode plate.SOLUTION: A manufacturing method of an electrode plate disclosed herein includes: a preparation step of preparing a strip-shaped electrode plate material before tab cutting; and a tab cutting step of irradiating the electrode plate material being conveyed with a laser in a first direction along a long-side direction of the electrode plate material to manufacture an electrode plate having a plurality of electrode tabs at an end part in a short-side direction. In the tab cutting step, a traveling speed of the laser on the electrode plate material is controlled so that a relative speed of an irradiation position of the laser with respect to the electrode plate material being conveyed becomes constant. As a result, since a laser irradiation time in a path of the laser in the tab cutting step becomes constant, it is possible to suppress variations in cutting quality after manufacture.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed herein relates to a method for manufacturing an electrode plate. [Background technology]

[0002] An energy storage device such as a lithium-ion secondary battery includes, for example, an electrode assembly in which a positive electrode plate and a negative electrode plate face each other via a separator. Hereinafter, these positive electrode plate and negative electrode plate will be collectively referred to as "electrode plate." This electrode plate includes, for example, an electrode core, which is a foil-shaped metal member, and an electrode active material layer containing an electrode active material applied to the surface of the electrode core. In manufacturing an electrode plate with such a configuration, first, an electrode active material layer is applied to the surface of a large electrode core. This results in a strip-shaped electrode plate material. At the short end of this electrode plate material, a core exposed region is formed in which the electrode core is exposed without the electrode active material layer applied. An electrode tab is formed by cutting out the region including this core exposed region with an uneven surface using a laser or the like. Examples of techniques related to the formation of this electrode tab are disclosed in JP 2022-82036 A, JP 2021-146358 A, and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-82036 [Patent Document 2] Japanese Patent Publication No. 2021-146358 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional technology, variations in the cutting quality of the edge of the electrode plate after manufacture (i.e., the state of the laser cutting marks) can occur. When variations in the cutting quality of the edge of the electrode plate occur, there is a risk that the cut portion that remains connected to part of the edge of the electrode plate may be forcibly peeled off. This may cause the electrode plate to break after manufacture. There is also a risk that uncut foreign matter may adhere to the edge of the electrode plate after manufacture. If this foreign matter peels off after the construction of the electricity storage device, it may cause an internal short circuit. The technology disclosed herein has been made to solve these problems. [Means for solving the problem]

[0005] To address the above-mentioned problems, there is provided a method for manufacturing an electrode plate (hereinafter also simply referred to as "manufacturing method") having the following configuration.

[0006] The method for manufacturing an electrode plate disclosed herein includes a preparation step of preparing a strip-shaped electrode plate material before tab cutting, and a tab cutting step of irradiating the electrode plate material with a laser while transporting it in a first direction along the longitudinal direction to produce an electrode plate having multiple electrode tabs at its short-side end. In the tab cutting step of this manufacturing method, the traveling speed of the laser on the electrode plate material is controlled so that the relative speed of the laser irradiation position with respect to the electrode plate material being transported is constant.

[0007] The inventors investigated the causes of variations in cutting quality at the edge of a manufactured electrode plate and discovered the following. First, in the manufacture of an electrode plate, the laser irradiation position in the lateral direction of the electrode plate material is moved while the electrode plate material is transported along the longitudinal direction. This allows for the formation of an electrode tab with an uneven shape at the lateral end of the manufactured electrode plate. Since the electrode plate material is transported in the longitudinal direction, if the laser irradiation position is moved in the lateral direction at a low speed, the longitudinal and width directions are combined, resulting in a large diagonal cut of the electrode plate material. On the other hand, in the manufacture of an electrode plate, it is necessary to form an electrode tab (with an uneven shape) in a shape that complies with battery specifications. For this reason, in a typical tab cutting process, the laser travel speed in the lateral direction is set to a high speed. However, when the laser is moved at such a high speed, a large difference occurs in the relative speed of the laser with respect to the transport speed of the electrode plate material when cutting along the lateral direction and when cutting along the longitudinal direction. As a result, there are areas in the laser path that are heated for a long time by the laser with a slow relative speed, and areas that are heated for a short time by the laser with a fast relative speed. This can cause variations in the cutting quality of the edge of the manufactured electrode plate. In response to this, the manufacturing method disclosed herein controls the traveling speed of the laser on the electrode plate material so that the relative speed of the laser irradiation position with respect to the electrode plate material being transported is constant. This can suppress variations in the cutting quality of the edge of the manufactured electrode plate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view schematically showing an example of an electrode plate after manufacture. [Figure 2] FIG. 2 is a flowchart showing a method for manufacturing an electrode plate according to one embodiment. [Figure 3] FIG. 3 is a plan view illustrating a method for manufacturing an electrode plate according to one embodiment. [Figure 4] FIG. 4 is a plan view schematically showing the path of the laser in the region A in FIG. [Figure 5] FIG. 5 is a plan view schematically showing another example of the manufactured electrode plate. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the technology disclosed herein (for example, the general configuration and manufacturing process of an electricity storage device) can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. In this specification, the expression "A to B" indicating a range means not less than A and not more than B, and also includes the meanings "preferably greater than A" and "preferably smaller than B."

[0010] In this specification, the term "electricity storage device" refers to a concept that encompasses devices in which charge and discharge reactions occur due to the movement of charge carriers between a pair of electrode plates (a positive electrode plate and a negative electrode plate). That is, the electricity storage device in the technology disclosed herein encompasses secondary batteries such as lithium ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, as well as capacitors such as lithium ion capacitors and electric double layer capacitors.

[0011] 1. Description of the object of manufacture Below, an overview of the electrode plate to be manufactured will be described, followed by a description of the method for manufacturing an electrode plate according to this embodiment. Fig. 1 is a plan view schematically showing an example of an electrode plate after manufacture. The manufacturing method according to this embodiment is intended to manufacture a negative electrode plate 20 for an electricity storage device.

[0012] As shown in FIG. 1, the negative electrode plate 20 is a long, strip-shaped member. The negative electrode plate 20 includes a negative electrode core 22, which is a foil-shaped metal member, and a negative electrode active material layer 24 provided on the surface of the negative electrode core 22. From the viewpoint of battery performance, the negative electrode active material layer 24 is preferably provided on both sides of the negative electrode core 22. In a plan view, the negative electrode plate 20 includes an electrode plate main body 20b and a negative electrode tab 22t. The electrode plate main body 20b is a region where the negative electrode active material layer 24 is provided on the surface of the negative electrode core 22. On the other hand, the negative electrode tab 22t is a region where the negative electrode active material layer 24 is not provided and where the negative electrode core 22 is exposed. The negative electrode tab 22t protrudes outward in the short-side direction S (upward in FIG. 1) from a part of an edge 20b1 of the electrode plate main body 20b in the short-side direction S. The negative electrode plate 20 also has a plurality of negative electrode tabs 22t. These plurality of negative electrode tabs 22t are provided in the longitudinal direction L of the negative electrode plate 20 at predetermined intervals.

[0013] As described above, a plurality of negative electrode tabs 22t are provided at one end of the negative electrode plate 20 in the short-side direction S. A first edge 21a, a second edge 21b, a third edge 21c, and a fourth edge 21d are formed at the end on the side where the negative electrode tabs 22t are provided (upper side in FIG. 1). The first edge 21a extends in the longitudinal direction L of the negative electrode plate 20. The second edge 21b extends from the first edge 21a outward in the short-side direction S (upper side in FIG. 1). The third edge 21c extends from the tip of the second edge 21b in the longitudinal direction L. The fourth edge 21d extends from the tip of the third edge 21c inward in the short-side direction S (lower side in FIG. 1). As shown in FIG. 1, the first edge 21a in this embodiment is the same as the edge 20b1 of the electrode plate main body 20b. Furthermore, the negative electrode tab 22t in this embodiment is an area surrounded by the second edge portion 21b, the third edge portion 21c, and the fourth edge portion 21d. As will be described in detail later, the technology disclosed herein can suppress variations in the cutting quality of each of the first edge portion 21a to the fourth edge portion 21d.

[0014] Materials that can be used in conventional general electricity storage devices can be used without particular restrictions for each member constituting the negative electrode plate 20. For example, a metal material with a predetermined conductivity can be preferably used for the negative electrode substrate 22. The negative electrode substrate 22 is preferably made of, for example, copper or a copper alloy. The thickness of the negative electrode substrate 22 is preferably 2 μm to 30 μm, more preferably 3 μm to 20 μm, and even more preferably 5 μm to 15 μm.

[0015] The negative electrode active material layer 24 is a layer containing a negative electrode active material. The negative electrode active material is a material capable of reversibly absorbing and releasing charge carriers in relation to the positive electrode active material. Examples of such negative electrode active materials include carbon materials and silicon-based materials. Examples of carbon materials that can be used include graphite, hard carbon, soft carbon, and amorphous carbon. Amorphous carbon-coated graphite, in which the surface of graphite is coated with amorphous carbon, can also be used. Examples of silicon-based materials include silicon and silicon oxide (silica). Silicon-based materials may also contain other metal elements (e.g., alkaline earth metals) or their oxides. The negative electrode active material layer 24 may also contain additives other than the negative electrode active material. Examples of such additives include binders and thickeners. Specific examples of binders include rubber-based binders such as styrene-butadiene rubber (SBR). Specific examples of thickeners include carboxymethyl cellulose (CMC). The content of the negative electrode active material is generally 30% by mass or more, and typically 50% by mass or more, when the total solid content of the negative electrode active material layer 24 is taken as 100% by mass. The negative electrode active material may account for 80% by mass or more, or may account for 90% by mass or more, of the negative electrode active material layer 24. The thickness of the negative electrode active material layer 24 is preferably 10 μm to 500 μm, more preferably 30 μm to 400 μm, and even more preferably 50 μm to 300 μm.

[0016] 2. Manufacturing method of electrode plate Next, a method for manufacturing the negative electrode plate 20 having the above configuration will be described. FIG. 2 is a flowchart showing a method for manufacturing an electrode plate according to this embodiment. FIG. 3 is a plan view illustrating the method for manufacturing an electrode plate according to this embodiment. As shown in FIG. 2, the manufacturing method according to this embodiment includes a preparation step S10 and a tab cutting step S20. Each step will be described below.

[0017] (1) Preparation process S10 In this step, a strip-shaped electrode plate material is prepared before tab cutting. In this specification, the term "electrode plate material" refers to an electrode plate before electrode tabs are formed. As shown in FIG. 3, when manufacturing a negative electrode plate 20, an electrode plate material for the negative electrode plate 20 (hereinafter referred to as "negative electrode plate material 20A") is prepared. This negative electrode plate material 20A includes a strip-shaped negative electrode core 22 that is a metal foil. The area of ​​the negative electrode core 22 of this negative electrode plate material 20A is larger than the area of ​​the manufactured negative electrode plate 20 (see FIG. 2). A negative electrode active material layer 24 is applied to the surface of the negative electrode core 22. The negative electrode active material layer 24 is applied to the central portion of the negative electrode core 22 in the short-side direction S. The negative electrode active material layer 24 extends along the long-side direction L. In this specification, the region where the negative electrode active material layer 24 is applied is referred to as the "negative electrode active material applied region A1." On the other hand, at both ends of the negative electrode plate material 20A in the short-side direction S (regions outside the short-side direction S of the negative electrode active material layer 24), the negative electrode active material layer 24 is not provided, and the negative electrode core 22 is exposed. In this specification, the region where the negative electrode core 22 is exposed is referred to as the "negative electrode core exposed region A2." The means for preparing the negative electrode plate material 20A having the above configuration is not particularly limited, and various conventionally known methods can be used without particular limitation. For example, the negative electrode plate material 20A can be prepared by applying a raw material paste containing a negative electrode active material and the like to the surface of the negative electrode core 22 and then drying it. Furthermore, the preparation step S10 is not particularly limited as long as the negative electrode plate material 20A can be prepared. For example, a separately prepared negative electrode plate material 20A may be purchased and prepared. Note that the negative electrode plate material is not limited to the structure shown in FIG. 3 . For example, the negative electrode plate material may have a structure in which a negative electrode core exposed region is formed only at one end in the short-side direction.

[0018] (2) Tab cutting process S20 In this step, the electrode plate material (negative electrode plate material 20A) is conveyed in a first direction L1 along the longitudinal direction L, and the electrode plate material (negative electrode plate material 20A) is irradiated with a laser while being conveyed. Here, in the tab cutting step S20 of this embodiment, the laser irradiation position is moved as shown by LN1 to LN4 in FIG. 4 while conveying the negative electrode plate material 20A so that laser travel paths shown by LN1 to LN4 in FIG. 3 are formed. Specifically, FIG. 4 is a plan view schematically showing the laser travel path in region A in FIG. 3. FIG. 4 shows the movement pattern of the laser at the absolute position in the tab cutting step S20. In the embodiment shown in FIG. 4, the movement pattern of the laser at the absolute position is such that the laser moves in a figure-eight pattern as shown by dotted lines LN1 to LN4. As will be described in detail later, the absolute position of the laser in this embodiment moves in the opposite direction (second direction L2) to the conveying direction (first direction L1), moves in the conveying direction (first direction L1) while moving outward in the short-side direction (direction S1), or moves in the conveying direction (first direction L1) while moving inward in the short-side direction (direction S2). As a result of combining this laser path and the conveyance of the negative electrode plate material 20A toward the first direction L1, the negative electrode plate material 20A is cut as shown by LN1 to LN4 in FIG. 3. The movement pattern of the absolute position of the laser shown in FIG. 4 can be programmed in advance.

[0019] Here, the tab cutting step S20 in this embodiment includes steps 1, 2, 3, and 4. Each step will be described in more detail below.

[0020] (a) First step As shown by the dotted line LN1 in Fig. 4, in the first step, the laser irradiation position P1 in the short-side direction S is fixed, and the laser is relatively moved in a second direction L2, which is the direction opposite to the first direction L1. When this laser movement and the transport of the negative electrode plate material 20A in the first direction L1 are combined, the negative electrode plate material 20A is laser-cut along the longitudinal direction L, as shown by the dotted line LN1 in Fig. 3. As a result, the first edge portion 21a (see Fig. 1) of the negative electrode plate 20 is formed.

[0021] In the first step, the laser irradiation position P1 may be moved in the second direction L2 relative to the negative electrode plate material 20A being transported in the first direction L1. In other words, the actual movement direction of the laser in the longitudinal direction L is not particularly limited. For example, moving the laser in the second direction L2, combined with the transport of the negative electrode plate material 20A in the first direction L1, significantly increases the relative speed (processing speed) at which laser cutting is performed. On the other hand, if the laser irradiation position in the longitudinal direction L is fixed, the processing speed and the transport speed become the same. Furthermore, if the laser movement speed is slower than the transport speed of the negative electrode plate material 20A, the laser may be moved in the transport direction (first direction L1). Even in this case, the negative electrode plate material 20A can be laser-cut along the longitudinal direction L. However, from the viewpoint of making the relative speeds in the first to fourth steps more uniform, it is preferable to move the laser in the first step in the second direction L2, which is opposite to the transport direction.

[0022] (b) Second step As shown by the dotted line LN2 in FIG. 4, in the second step, after the first step described above, the laser irradiation position P2 is moved in the first direction L1 while being moved to the outside S1 in the short-side direction S. As a result, as shown by the dotted line LN2 in FIG. 3, the negative electrode plate material 20A is laser-cut along the outside S1 in the short-side direction S. Specifically, if the laser irradiation position P is moved only in the short-side direction S while the negative electrode plate material 20A is being transported in the longitudinal direction L, the longitudinal direction L and the short-side direction S are combined, resulting in the negative electrode plate material 20A being cut obliquely. In contrast, in the second step in this embodiment, the laser is moved to the outside S1 in the short-side direction S while following the first direction L1 (transport direction). As a result, the relative movement in the longitudinal direction L is canceled out, and the negative electrode plate material 20A can be cut toward the outside S1 in the short-side direction S while preventing the laser travel speed from becoming faster than necessary. As a result, the second edge portion 21b extending to the outer side S1 in the short-side direction S can be formed.

[0023] (c) Third step As shown by the dotted line LN3 in FIG. 4, in the third step, after the second step described above, the laser irradiation position P3 in the short-side direction S is fixed, and then the laser irradiation position P3 is relatively moved toward the second direction L2. When this laser movement and the conveyance of the negative electrode plate material 20A toward the first direction L1 are combined, the negative electrode substrate exposed region A2 of the negative electrode plate material 20A is laser-cut along the longitudinal direction L, as shown by the dotted line LN3 in FIG. 3. As a result, the third edge portion 21c (see FIG. 1) of the negative electrode plate 20 is formed. As with the first step, the actual movement direction of the laser in the longitudinal direction L in the third step is not particularly limited.

[0024] (d) 4th step As shown by the dotted line LN4 in FIG. 4, in the fourth step, after the third step described above, the laser irradiation position P4 is moved in the first direction L1 while being moved toward the inner side S2 in the short-side direction S. In other words, in the fourth step, the laser is moved toward the inner side S2 in the short-side direction S while following the first direction L1 (transport direction). This cancels out the relative movement in the longitudinal direction L, so that the negative electrode plate material 20A can be laser-cut along the inner side S2 in the short-side direction S while preventing the laser travel speed from becoming faster than necessary. As a result, a fourth edge portion 21d extending toward the inner side S2 in the short-side direction S can be formed.

[0025] In the manufacturing method according to this embodiment, after the laser reaches the irradiation position P4 in Fig. 4, the above-described first step is performed again. That is, in the tab cutting step S20 according to this embodiment, the first step to the fourth step (movement of the laser along the dotted lines LN1 to LN4 in Fig. 4) are repeated. This allows a plurality of negative electrode tabs 22t to be formed at the end of the negative electrode plate material 20A in the short-side direction S.

[0026] In the tab cutting process S20 of this embodiment, the traveling speed of the laser over the negative electrode plate material 20A is controlled so that the relative speed of the laser irradiation position relative to the conveyed negative electrode plate material 20A is constant. This reduces variations in the cutting quality of the edge of the manufactured electrode plate. Specifically, in a typical tab cutting process, the laser needs to be moved at high speed along the short side to form an electrode tab with the desired uneven shape. However, if the traveling speed of the laser along the short side is increased, a difference in the relative speed of the laser to the conveying speed of the electrode plate material occurs between the longitudinal cut where the laser is not moving at high speed and the short side cut. This may result in variations in the cutting quality of the edge of the manufactured electrode plate. In contrast, the tab cutting process S20 of this embodiment includes, as described above, steps (such as the second and fourth steps) in which the laser is moved in the conveying direction (first direction L1) of the negative electrode plate material 20A. By following the laser in the conveying direction in this way, electrode tabs with the desired uneven shape can be formed even if the laser traveling speed along the short side is reduced. This allows the relative speed to be constant throughout the tab cutting process, thereby suppressing variations in cutting quality after laser cutting.

[0027] In this specification, "constant relative speed" refers to the relative speed at any irradiation position being within a range of 90% to 110% of the average relative speed throughout the entire tab cutting process S20, which is taken as 100%. Experiments conducted by the inventors have confirmed that fluctuations in relative speed within a range of ±10% can adequately suppress variations in cutting quality after laser cutting. To more reliably prevent variations in cutting quality, the fluctuation range of the relative speed is preferably 92% to 108%, more preferably 94% to 106%, even more preferably 96% to 104%, and particularly preferably 98% to 102%. In this specification, the average relative speed refers to the average relative speed of the laser in each of the first to fourth steps.

[0028] As described above, the tab cutting process S20 in this embodiment is composed of four processes, Process 1 to Process 4. In this case, it is preferable that the laser travel speed A in Process 1, the laser travel speed B in Process 2, the laser travel speed C in Process 3, and the laser travel speed D in Process 4 be set to satisfy the following formulas (1) and (2). This allows the relative speed to be constant in each of Processes 1 to 4. A=C A=C <D (2)

[0029] In addition, the laser travel speeds A to D in each process are the same as the electrode plate material transport speed V W It is preferable that the laser travel speeds A to D are set based on the ratio α of the total travel distance of the laser to the total length of the negative electrode plate material 20A, the inclination angle θ2 of the second edge portion 21b relative to the longitudinal direction (see FIG. 5), and the inclination angle θ4 of the fourth edge portion 21b relative to the longitudinal direction (see FIG. 5). Specifically, it is preferable that the laser travel speeds A to D be controlled to satisfy the following equations (3) to (5). As shown in FIG. 5, in the second and fourth steps, the laser needs to be moved relative to the first and third steps so as to be oblique. Therefore, by increasing the travel speed B in the second step and the travel speed D in the fourth step based on the trigonometric function as shown in the following equation, the relative speed of the laser in the first to fourth steps can be easily kept constant. A=C=V W ×α-V W (3) B=√(V W 2 +V W 2 ×α-2V W 2 ×α×cosθ2) (4) D=√(V W 2 +V W 2 ×α-2V W 2 ×α×cosθ4) (5)

[0030] ​Furthermore, when the conveying speed of the negative electrode plate material 20A is 100%, the average value of the relative speed of the laser is preferably 120% to 130% (more preferably 125% to 129%, for example, 127.5%). As shown in FIG. 3, the traveling path of the laser includes irregularities, and therefore is longer than the traveling path of the negative electrode plate material 20A. In contrast, as described above, if the relative speed of the laser is made faster than the conveying speed of the negative electrode plate material 20A, the total length of the negative electrode plate material 20A and the total traveling distance of the laser can be easily matched. As a result, negative electrode plates 20 having a plurality of negative electrode tabs 22t can be stably manufactured.

[0031] The specific conveying speed of the negative electrode plate material 20A is preferably 30 m / min or more, more preferably 35 m / min or more, even more preferably 40 m / min or more, and particularly preferably 45 m / min or more. This improves the production efficiency of the negative electrode plate 20. On the other hand, as the conveying speed increases, the negative electrode tab is more likely to be damaged due to peeling of the curved surface. However, the technology disclosed herein can suppress the formation of a curved surface on the negative electrode tab 22t, thereby achieving stable high-speed conveying. On the other hand, if the conveying speed of the negative electrode plate material 20A becomes too fast, it becomes difficult to move the laser in accordance with the conveying speed. From this perspective, the conveying speed of the negative electrode plate material 20A is preferably 80 m / min or less, more preferably 75 m / min or less, even more preferably 70 m / min or less, and particularly preferably 65 m / min or less.

[0032] The laser processing speed in the tab cutting process S20 may be 26 m / min or more, 28 m / min or more, 30 m / min or more, or 32 m / min or more. In this specification, the term "laser processing speed" refers to the average relative movement speed of the pulse laser relative to the electrode plate material being transported. As described above, moving the pulse laser in the direction of transport of the electrode plate material decreases the laser processing speed. Moving the pulse laser in the opposite direction to the electrode plate material transport direction increases the laser processing speed. Increasing this laser processing speed prevents laser heat from concentrating at a specific location, thereby more effectively suppressing variation in cutting quality. Therefore, from the perspective of more effectively suppressing the formation of curved surfaces, the laser processing speed is preferably 34 m / min or more, and particularly preferably 36 m / min or more.

[0033] In the tab cutting step S20, any conventionally known laser can be used without any particular restrictions. In other words, the manufacturing method disclosed herein is not limited to the type of laser. Examples of lasers that can be used in the manufacturing method disclosed herein include continuous wave lasers (CW lasers) and pulsed lasers. Among these, pulsed lasers can apply a large amount of concentrated energy in a short time span (high peak output), which allows for rapid cutting of the electrode plate material and contributes to improved manufacturing efficiency. When using this pulsed laser, it is preferable to set the laser irradiation conditions as follows:

[0034] For example, the pulse width of the pulse laser is preferably 30 ns or more, more preferably 35 ns or more, even more preferably 40 ns or more, and particularly preferably 45 ns or more. This prevents poor cutting due to insufficient energy. On the other hand, if the pulse width of the pulse laser is too long, excessive energy is applied to the area around the laser irradiation position, increasing the possibility of forming a curved surface after cutting. From this perspective, the pulse width of the pulse laser is preferably 120 ns or less, more preferably 110 ns or less, even more preferably 100 ns or less, and particularly preferably 90 ns or less.

[0035] Furthermore, the repetition frequency of the pulsed laser is preferably 2250 kHz or less, more preferably 2200 kHz or less, even more preferably 2150 kHz or less, and particularly preferably 2100 kHz or less. This can prevent the formation of curved surfaces due to excess energy. On the other hand, the repetition frequency of the pulsed laser is preferably 450 kHz or more, more preferably 500 kHz or more, even more preferably 550 kHz or more, and particularly preferably 600 kHz or more. This can prevent poor cutting due to insufficient energy.

[0036] The overlap ratio of the pulsed laser is preferably 99% or less, more preferably 98.8% or less, even more preferably 98.4% or less, and particularly preferably 98.2% or less. As the overlap ratio decreases, the area of ​​the laser irradiated overlappingly at the same position on the electrode plate material decreases, making it difficult to form a curved surface on the negative electrode tab 22t after cutting. The overlap ratio of the pulsed laser is preferably 95% or more, more preferably 96% or more, even more preferably 97% or more, and particularly preferably 97.5% or more. This can prevent cutting defects. Note that the "overlap ratio" in this specification refers to the degree to which two adjacent spots overlap when irradiated with a pulsed laser. Note that the spot diameter of the pulsed laser is preferably 10 μm to 60 μm, more preferably 20 μm to 50 μm, and even more preferably 25 μm to 40 μm. This allows the negative electrode plate 20 to be easily cut out from the negative electrode plate material 20A.

[0037] (Other processes) As described above, in the tab cutting step S20 of this embodiment, multiple negative electrode tabs 22t are formed by repeating the first to fourth steps (dotted lines LN1 to LN4 in FIGS. 3 and 4). Then, in the manufacturing method according to this embodiment, the center of the negative electrode plate material 20A in the short-side direction S is cut along the longitudinal direction L, as shown by the two-dot chain line C1 in FIG. 3 . This makes it possible to manufacture a negative electrode plate 20 (see FIG. 2 ) in which negative electrode tabs 22t are formed only on one side of the edge portion 20b1 of the electrode plate main body portion 20b. Furthermore, in this embodiment, as shown by the two-dot chain line C2, the negative electrode plate material 20A is cut along the short-side direction S at predetermined intervals in the longitudinal direction L. This makes it possible to manufacture a negative electrode plate 20 of a desired length. Note that cutting the negative electrode plate material 20A along the two-dot chain lines C1 and C2 does not necessarily require laser cutting; a cutting blade, a mold, a cutter, or the like may also be used. When laser cutting is used for cutting along the two-dot chain lines C1 and C2, it is preferable to use a laser, as in the tab cutting step S20. This more suitably prevents fragments of the negative electrode active material layer 24 from peeling off or falling off. Furthermore, cutting along these two-dot chain lines C1 and C2 may be performed as appropriate depending on the shape of the negative electrode plate after manufacture, and does not limit the technology disclosed herein.

[0038] <Other embodiments> The above describes one embodiment of the technology disclosed herein. Note that the above embodiment shows an example to which the technology disclosed herein is applied, and does not limit the technology disclosed herein.

[0039] For example, in the above-described embodiment, a negative electrode plate is manufactured as the electrode plate. However, the manufacturing target of the electrode plate manufacturing method disclosed herein is not limited to a negative electrode plate, and may be a positive electrode plate. According to the manufacturing method disclosed herein, even when a positive electrode plate is manufactured, variation in the cutting quality of the edge of the manufactured electrode plate (positive electrode plate) can be suppressed.

[0040] 1 and 3, in the manufacturing method according to the embodiment described above, the laser irradiation position in the tab cutting step S20 is controlled so as to form a negative electrode tab 22t in which the second edge 21b and the fourth edge 21d extend substantially perpendicular to the longitudinal direction L (i.e., along the short-side direction S). However, the manufacturing method disclosed herein can also form a negative electrode tab 22t in which the second edge 21b and the fourth edge 21d are inclined, as shown in FIG. 5. Specifically, in the second step, the inclination angle θ2 of the second edge 21b after manufacturing can be adjusted by controlling the laser speed in the first direction and the laser movement angle θ1. Specifically, increasing the movement angle θ1 in FIG. 4 and slowing the laser movement speed in the first direction tends to increase the inclination angle θ2 of the second edge 21b in FIG. 5 (the inclination of the second edge 21b becomes gentler). Similarly, in the fourth step, the inclination angle θ4 of the fourth edge portion 21d can be adjusted by controlling the speed of the laser that follows the first direction and the movement angle θ3 of the laser.

[0041] Furthermore, multiple electrode tabs 22t are formed on the manufactured negative electrode plate 20. These multiple electrode tabs 22t may have different shapes. In this case, the first to fourth steps are considered to be one cycle, and the movement pattern of the absolute position of the laser may be changed for each cycle. For example, by varying the movement amount along the short-side direction S in the second and fourth steps for each cycle, multiple types of electrode tabs with different protrusion amounts from the first edge 21a can be formed. Furthermore, by varying the movement angles θ1 and θ3 and the tracking speed of the laser in the second and fourth steps for each cycle, multiple types of electrode tabs with different inclination angles θ2 of the second edge 21b and inclination angles θ4 of the fourth edge 21d can be formed.

[0042] Although the present invention has been described in detail above, the above description is merely an example, and the technology disclosed herein includes various modifications and alterations of the above-described specific examples. [Explanation of symbols]

[0043] 20: Negative electrode plate 20A: Negative plate material 20b: Plate body 20b1: Border 22: negative electrode core 22t: Negative electrode tab 24: Negative electrode active material layer A1: Negative electrode active material application area A2: Negative electrode core exposed area

Claims

1. a preparation step of preparing a strip-shaped electrode plate material before tab cutting; a tab cutting process in which a laser is irradiated onto the electrode plate material while the electrode plate material is being transported in a first direction along the longitudinal direction, thereby producing an electrode plate having a plurality of electrode tabs at an end portion in a shorter direction; Equipped with A method for manufacturing an electrode plate, wherein the tab cutting process controls the traveling speed of the laser on the electrode plate material so that the relative speed of the laser irradiation position with respect to the electrode plate material during transportation is constant.

2. 2. The electrode plate manufacturing method according to claim 1, wherein the traveling speed of the laser is controlled so that the relative speed at any irradiation position is within a range of 90% to 110% when the average value of the relative speed throughout the tab cutting process is 100%.

3. The electrode plate after the tab cutting step is a first edge portion extending in a longitudinal direction of the electrode plate; a second edge portion extending outward in the short side direction from the first edge portion; a third edge portion extending in a longitudinal direction from a tip of the second edge portion; a fourth edge portion extending inward in the short-side direction from a tip of the third edge portion; The method for manufacturing an electrode plate according to claim 1 or 2, comprising:

4. The tab cutting step includes: a first step of fixing a laser irradiation position in the short-side direction and relatively moving the laser irradiation position in a second direction that is a direction opposite to the first direction; a second step of moving the laser irradiation position in the first direction and outward in the short-side direction after the first step; a third step of relatively moving the laser irradiation position in the second direction after fixing the laser irradiation position in the short-side direction after the second step; a fourth step of moving the laser irradiation position inward in the short-side direction while moving the laser irradiation position in the first direction after the third step; The method for manufacturing an electrode plate according to claim 3 , comprising:

5. 5. The method for manufacturing an electrode plate according to claim 4, wherein a traveling speed A of the laser in the first step, a traveling speed B of the laser in the second step, a traveling speed C of the laser in the third step, and a traveling speed D of the laser in the fourth step satisfy the following formulas (1) and (2). A = C < B (1) A = C < D (2)

6. The conveying speed of the electrode plate material is V Ｗ When the ratio of the total travel distance of the laser to the total length of the electrode plate material is α, the inclination angle of the second edge portion with respect to the longitudinal direction of the electrode plate is θ2, and the inclination angle of the fourth edge portion with respect to the longitudinal direction of the electrode plate is θ4, The method for manufacturing an electrode plate according to claim 5, wherein the traveling speed A and the traveling speed C satisfy the following formula (3), the traveling speed B satisfies the following formula (4), and the traveling speed D satisfies the following formula (5). A=C=V Ｗ ×α-V Ｗ (3) B=√(V Ｗ ２ +V Ｗ ２ ×α-2V Ｗ ２ ×α×cosθ2) (4) D=√(V Ｗ ２ +V Ｗ ２ ×α-2V Ｗ ２ ×α×cosθ4) (5)

7. The method for manufacturing an electrode plate according to claim 4, wherein the average value of the relative speed is 120% to 130% when the transport speed of the electrode plate material is 100%.

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