Method for manufacturing electrode plates

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 electrode plates. [Background technology]

[0002] Energy storage devices such as lithium-ion secondary batteries include an electrode body in which a positive electrode plate and a negative electrode plate face each other via a separator. Hereinafter, these positive and negative electrode plates will be collectively referred to as "electrode plates." These electrode plates include, for example, an electrode core, which is a foil-shaped metal member, and an electrode active material layer containing electrode active material applied to the surface of the electrode core. In the manufacture of an electrode plate with such a configuration, first, an electrode active material layer is applied to the surface of a large electrode core. This produces a strip-shaped electrode plate material. At the short end of this electrode plate material, a core exposure region is formed where the electrode core is exposed and no electrode active material layer is applied. An electrode tab is formed by cutting out the region including this core exposure region with a laser or the like to create an uneven surface. An example of the technology for forming this electrode tab is disclosed in Japanese Patent Publication No. 2022-82036, Japanese Patent Publication No. 2021-146358, and others. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-82036 [Patent Document 2] Japanese Patent Publication No. 2021-146358 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, with conventional technology, variations sometimes occurred in the cutting quality of the edges of the electrode plates after manufacturing (i.e., the state of the laser-cut marks). When variations in the cutting quality of the electrode plate edges occur, there is a risk that the cut portion, which remains connected to a part of the electrode plate edge, may be forcibly peeled off. This may cause the electrode plate to break after manufacturing. In addition, there is a risk that foreign matter that remains after cutting may adhere to the edges of the electrode plate after manufacturing. If this foreign matter peels off after the energy storage device is constructed, it may cause an internal short circuit. The technology disclosed herein was developed to solve these problems. [Means for solving the problem]

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

[0006] The electrode plate manufacturing method disclosed herein comprises 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 it is being transported in a first direction along the longitudinal direction, thereby producing an electrode plate having a plurality of electrode tabs at its short-side end. In this manufacturing method, the tab cutting step is controlled such that the laser's travel speed on the electrode plate material remains constant relative to the irradiation position of the laser on the transported electrode plate material.

[0007] The inventors investigated the causes of variations in cutting quality at the edges of electrode plates after manufacturing and obtained the following findings. First, in the manufacturing of electrode plates, the electrode plate material is transported along the longitudinal direction while the laser irradiation position in the short direction of the electrode plate material is moved. This allows for the formation of an uneven electrode tab at the short-side end of the manufactured electrode plate. At this time, since the electrode plate material is transported along the longitudinal direction, if the laser irradiation position is moved slowly in the short direction, the longitudinal and width directions are combined, and the electrode plate material is cut at a large angle. On the other hand, in the manufacturing of electrode plates, it is necessary to form an electrode tab (uneven shape) that conforms to the specifications of the battery. For this reason, in a typical tab cutting process, the laser travel speed in the short direction is set to high. However, when the laser is moved at high speed in this way, there is a large difference in the relative speed of the laser to the transport speed of the electrode plate material between when cutting along the short direction and when cutting along the longitudinal direction. As a result, the laser path will have regions that are heated for a long time by a laser with a slow relative speed and regions that are heated for a short time by a laser with a fast relative speed. This may cause variations in the cutting quality at the edges of the electrode plates after manufacturing. In contrast, the manufacturing method disclosed herein controls the laser's travel speed on the electrode plate material so that the relative speed of the laser irradiation position to the electrode plate material during transport remains constant. This suppresses variations in the cutting quality at the edges of the electrode plates after manufacturing. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic plan view showing an example of an electrode plate after manufacturing. [Figure 2] Figure 2 is a flowchart showing a method for manufacturing an electrode plate according to one embodiment. [Figure 3] Figure 3 is a plan view illustrating a method for manufacturing an electrode plate according to one embodiment. [Figure 4] Figure 4 is a schematic plan view showing the laser path in region A in Figure 3. [Figure 5] Figure 5 is a schematic plan view showing another example of an electrode plate after manufacturing. [Modes for carrying out the invention]

[0009] Embodiments of the technology disclosed herein will be described below with reference to the drawings. Matters other than those specifically mentioned herein but necessary for carrying out the technology disclosed herein (e.g., the general configuration and manufacturing process of energy storage devices) can be understood as design matters for those skilled in the art based on prior art. The technology disclosed herein can be carried out based on the content disclosed herein and common technical knowledge in the art. In this specification, the notation "A to B" indicating a range encompasses not only the meaning of A or greater and B or less, but also the meanings of "preferably greater than A" and "preferably less than B".

[0010] In this specification, the term "energy storage device" encompasses a concept that includes devices in which a charge-discharge reaction occurs through the movement of a charge carrier between a pair of electrode plates (positive electrode plate and negative electrode plate). In other words, the energy storage devices in the technology disclosed herein include not only secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, but also capacitors such as lithium-ion capacitors and electric double-layer capacitors.

[0011] 1. Description of the products to be manufactured The following describes the general outline of the electrode plate to be manufactured, followed by a description of the manufacturing method of the electrode plate according to this embodiment. Figure 1 is a schematic plan view showing an example of an electrode plate after manufacturing. The manufacturing method according to this embodiment targets the negative electrode plate 20 of an energy storage device.

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

[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 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 in Figure 1). The first edge 21a extends in the longitudinal direction L of the negative electrode plate 20. The second edge 21b extends outward from the first edge 21a in the short direction S (upper in Figure 1). The third edge 21c extends in the longitudinal direction L from the tip of the second edge 21b. The fourth edge 21d extends inward from the tip of the third edge 21c in the short direction S (lower in Figure 1). As shown in Figure 1, the first edge 21a in this embodiment is the same as the edge 20b1 of the electrode plate body 20b. Furthermore, in this embodiment, the negative electrode tab 22t is the region surrounded by the second edge 21b, the third edge 21c, and the fourth edge 21d. As will be described in detail later, the technology disclosed herein makes it possible to suppress variations in the cutting quality of each of the first edge 21a to the fourth edge 21d.

[0014] For each member constituting the negative electrode plate 20, materials that can be used in conventional general power storage devices can be used without particular limitation. For example, for the negative electrode core 22, a metal material having predetermined conductivity can be preferably used. Such a negative electrode core 22 is preferably made of, for example, copper or a copper alloy. Further, the thickness of the negative electrode core 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. As the negative electrode active material, a material that can reversibly occlude and release charge carriers in relation to the positive electrode active material is used. Examples of such negative electrode active materials include carbon materials, silicon-based materials, etc. As the carbon material, for example, graphite, hard carbon, soft carbon, amorphous carbon, etc. can be used. Also, amorphous carbon-coated graphite in which the surface of graphite is coated with amorphous carbon can also be used. On the other hand, examples of silicon-based materials include silicon, silicon oxide (silica), etc. Also, the silicon-based material may contain other metal elements (for example, alkaline earth metals) and their oxides. Further, the negative electrode active material layer 24 may contain additives other than the negative electrode active material. Examples of such additives include binders, thickeners, etc. Specific examples of the binder include rubber-based binders such as styrene-butadiene rubber (SBR). Also, specific examples of the thickener include carboxymethyl cellulose (CMC), etc. Note that when the total solid content of the negative electrode active material layer 24 is 100% by mass, the content of the negative electrode active material is generally 30% by mass or more, and typically 50% by mass or more. Note that the negative electrode active material may occupy 80% by mass or more, or 90% by mass or more of the negative electrode active material layer 24. Further, 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. Method for manufacturing an electrode plate Next, a method for manufacturing the negative electrode plate 20 with the above structure will be described. FIG. 2 is a flowchart showing a method for manufacturing an electrode plate according to the present embodiment. Further, FIG. 3 is a plan view for explaining the method for manufacturing an electrode plate according to the present embodiment. As shown in FIG. 2, the manufacturing method according to the present embodiment includes a preparation step S10 and a tab cutting step S20. Hereinafter, each step will be described.

[0017] (1) Preparation step S10 In this step, a strip-shaped electrode plate material before tab cutting is prepared. The "electrode plate material" in this specification refers to an electrode plate before an electrode tab is formed. As shown in FIG. 3, when manufacturing the 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 negative electrode core 22 that is a strip-shaped metal foil. The area of the negative electrode core 22 of this negative electrode plate material 20A is wider than the area of the negative electrode plate 20 (see FIG. 2) after manufacturing. And, a negative electrode active material layer 24 is provided on the surface of the negative electrode core 22. Note that the negative electrode active material layer 24 is provided at the central portion of the negative electrode core 22 in the short side direction S. And, 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 provided is referred to as "negative electrode active material application region A1". On the other hand, at both ends in the short side direction S of the negative electrode plate material 20A (regions outside the short side direction S from 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, such a region where the negative electrode core 22 is exposed is referred to as "negative electrode core exposure region A2". The means for preparing the negative electrode plate material 20A with the above structure is not particularly limited, and various conventionally known methods can be adopted without particular limitation. For example, the negative electrode plate material 20A can be produced by applying a raw material paste containing a negative electrode active material or the like to the surface of the negative electrode core 22 and then drying it. Also, the preparation step S10 is not particularly limited as long as the negative electrode plate material 20A can be prepared. For example, a separately produced 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 can also adopt a structure in which a negative electrode core exposure region is formed only at one end in the short side direction.

[0018] (2) Tab cutting process S20 In this process, the electrode plate material (negative electrode plate material 20A) is transported in a first direction L1 along the longitudinal direction L, and a laser is irradiated onto the transported electrode plate material (negative electrode plate material 20A). Here, in the tab cutting process S20 in this embodiment, the laser irradiation position is moved as shown in LN1 to LN4 in Figure 4 while transporting the negative electrode plate material 20A so that the laser path shown in LN1 to LN4 in Figure 3 is formed. Specifically, Figure 4 is a schematic plan view showing the laser path in region A in Figure 3. Figure 4 shows the movement pattern of the laser in absolute position in the tab cutting process S20. In the configuration shown in Figure 4, the movement pattern of the laser in absolute position moves in a figure-eight shape, as shown by the dotted lines LN1 to LN4. As will be explained in more detail later, the absolute position of the laser in this embodiment moves in the opposite direction (second direction L2) to the transport direction (first direction L1), moves outward in the short-side direction (S1 direction) while moving in the transport direction (first direction L1), or moves inward in the short-side direction (S2 direction) while moving in the transport direction (first direction L1). As a result of the combination of this laser path and the transport of the negative electrode plate material 20A toward the first direction L1, the negative electrode plate material 20A is cut as shown in LN1 to LN4 in Figure 3. Note that the movement pattern of the absolute position of the laser shown in Figure 4 can be programmed in advance.

[0019] In this embodiment, the tab cutting process S20 comprises a first step, a second step, a third step, and a fourth step. Each step will be described in more detail below.

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

[0021] In the first step, the laser irradiation position P1 only needs to move 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 direction of laser movement in the longitudinal direction L is not particularly limited. For example, if the laser is moved in the second direction L2, the relative speed at which laser cutting is performed (processing speed) becomes significantly faster as a result of combining it with the transport of the negative electrode plate material 20A moving in the first direction L1. 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. Also, if the laser movement speed is to be slower than the transport speed of the negative electrode plate material 20A, the laser may be made to follow 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 of the first to fourth steps more uniform, it is preferable that the laser in the first step moves in the second direction L2, which is opposite to the transport direction.

[0022] (b) Second step As shown by the dotted line LN2 in Figure 4, in the second step, after the first step described above, the laser irradiation position P2 is moved to the outside S1 in the short-side direction S while moving in the first direction L1. As a result, as shown by the dotted line LN2 in Figure 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, and the negative electrode plate material 20A is cut diagonally. In contrast, in the second step of 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, so that the laser travel speed does not become unnecessarily fast, and the negative electrode plate material 20A can be cut toward the outside S1 in the short-side direction S. As a result, a second edge portion 21b extending outward S1 in the short direction S can be formed.

[0023] (c) Third step As shown by the dotted line LN3 in Figure 4, in the third step, after the second step described above, the laser irradiation position P3 in the short direction S is fixed, and then the laser irradiation position P3 is moved relatively toward the second direction L2. When this laser movement and the transport of the negative electrode plate material 20A toward the first direction L1 are combined, the negative electrode core exposure 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 Figure 3. As a result, the third edge portion 21c of the negative electrode plate 20 (see Figure 1) is formed. Note that, as with the first step described above, the actual direction of laser movement 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 Figure 4, in the fourth step, after the third step described above, the laser irradiation position P4 is moved in the first direction L1 while moving inward S2 in the short direction S. In other words, in the fourth step, the laser is moved inward S2 in the short direction S while following the first direction L1 (transport direction). As a result, the relative movement in the longitudinal direction L is canceled out, so that the laser travel speed does not become unnecessarily fast, and the negative electrode plate material 20A can be laser cut along the inward S2 in the short direction S. As a result, a fourth edge portion 21d extending inward S2 in the short direction S can be formed.

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

[0026] In this embodiment, the tab cutting process S20 controls the laser's travel speed on the negative electrode plate material 20A so that the relative speed of the laser irradiation position to the negative electrode plate material 20A during transport remains constant. This suppresses variations in the cutting quality of the edges of the manufactured electrode plate. Specifically, in a typical tab cutting process, it is necessary to move the laser at high speed along the shorter direction in order to form electrode tabs with the desired uneven shape. However, if the laser's travel speed along the shorter direction is increased, a difference in the relative speed of the laser with respect to the transport speed of the electrode plate material occurs between the cutting in the longer direction, where the laser is not moved at high speed, and the cutting in the shorter direction. As a result, variations in the cutting quality of the edges of the manufactured electrode plate may occur. In contrast, as described above, the tab cutting process S20 in this embodiment includes a process (such as the second and fourth steps) in which the laser follows the transport direction (first direction L1) of the negative electrode plate material 20A. By following the laser in the transport direction in this manner, it is possible to form electrode tabs with the desired uneven shape even if the laser travel speed along the shorter direction is reduced. This allows the relative speed throughout the tab cutting process to be kept constant, thereby suppressing variations in cutting quality after laser cutting.

[0027] In this specification, "constant relative speed" means that when the average value of the relative speed throughout the entire tab-cutting process S20 is taken as 100%, the relative speed at any irradiation position is within the range of 90% to 110%. According to the inventors' experiments, it has been confirmed that variations in cutting quality after laser cutting can be sufficiently suppressed if the fluctuation in relative speed is within ±10%. In terms of more reliably preventing variations in cutting quality, the above relative speed fluctuation range 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 value of relative speed refers to the average value of the laser relative speed in each of the first to fourth processes.

[0028] As described above, the tab cutting step S20 in the present embodiment is composed of four steps, namely the first step to the fourth step. In this case, it is preferable that the laser traveling speed A in the first step, the laser traveling speed B in the second step, the laser traveling speed C in the third step, and the laser traveling speed D in the fourth step are set to satisfy the following formulas (1) and (2). Thereby, the relative speed in each of the first step to the fourth step can be made constant. A = C < B (1) A = C < D (2)

[0029] In addition, the laser traveling speeds A to D in each step are related to the conveyance speed V of the electrode plate material W , the ratio α of the total laser traveling distance to the total length of the negative electrode plate material 20A, the inclination angle θ2 of the second edge portion 21b with respect to the longitudinal direction (see FIG. 5), and the inclination angle θ4 of the fourth edge portion 21b with respect to the longitudinal direction (see FIG. 5). Specifically, it is preferable that the laser traveling speeds A to D are controlled to satisfy the following formulas (3) to (5). As shown in FIG. 5, in the second step and the fourth step, it is necessary to relatively move the laser obliquely with respect to the first step and the third step. Therefore, by increasing the traveling speed B of the second step and the traveling speed D of the fourth step based on trigonometric functions as in the following formulas, the relative speed of the laser in the first step to the fourth step can be easily made 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 transport speed of the negative electrode plate material 20A is set to 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 Figure 3, the laser path is longer than the transport path of the negative electrode plate material 20A because it includes irregularities. In contrast, as described above, if the relative speed of the laser is faster than the transport speed of the negative electrode plate material 20A, the total length of the negative electrode plate material 20A and the total distance traveled by the laser can be easily matched. As a result, a negative electrode plate 20 having multiple negative electrode tabs 22t can be manufactured stably.

[0031] The specific transport 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 transport speed increases, damage to the negative electrode tab due to peeling of the curved portion becomes more likely. However, the technology disclosed herein can suppress the formation of a curved portion on the negative electrode tab 22t, thus enabling stable high-speed transport. On the other hand, if the transport speed of the negative electrode plate material 20A becomes too fast, it becomes difficult to move the laser in accordance with the transport speed. From this viewpoint, the transport 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] Furthermore, 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, "laser processing speed" refers to the average value of the relative movement speed of the pulsed laser with respect to the electrode plate material during transport. As described above, moving the pulsed laser in accordance with the transport direction of the electrode plate material reduces the laser processing speed. Conversely, moving the pulsed laser in the direction opposite to the transport direction of the electrode plate material increases the laser processing speed. A faster laser processing speed prevents the concentration of laser heat at specific locations, thus more effectively suppressing variations in cutting quality. For this reason, from the viewpoint of more effectively suppressing the formation of curved surfaces, a laser processing speed of 34 m / min or more is preferred, and 36 m / min or more is particularly preferred.

[0033] In addition, conventionally known lasers can be used without any particular limitations in the tab cutting process S20. That is, 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 concentrate a large amount of energy over a short time (high peak output), so they can quickly cut the electrode plate material and contribute to improving manufacturing efficiency. When using a pulsed laser, it is preferable to set the laser irradiation conditions as follows.

[0034] For example, the pulse width of the pulsed 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 cutting failures due to insufficient energy. On the other hand, if the pulse width of the pulsed laser is too long, excessive energy is applied around the laser irradiation position, increasing the likelihood of curved surfaces being formed after cutting. From this viewpoint, the pulse width of the pulsed 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 suppresses 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 prevents cutting defects due to insufficient energy.

[0036] Furthermore, the overlap rate 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. When the overlap rate is small, the area of ​​the laser that is irradiated repeatedly at the same position on the electrode plate material becomes small, making it difficult to form a curved portion on the negative electrode tab 22t after cutting. The overlap rate 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 suppress the occurrence of cutting defects. In this specification, "lapping rate" is a value that indicates the degree to which two adjacent spots overlap during pulsed laser irradiation. 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 from the negative electrode plate material 20A.

[0037] (Other processes) As described above, the tab cutting process S20 in this embodiment forms a plurality of negative electrode tabs 22t by repeating the first to fourth steps (dotted lines LN1 to LN4 in Figures 3 and 4). Subsequently, in the manufacturing method according to this embodiment, as shown by the dashed line C1 in Figure 3, the central part of the negative electrode plate material 20A in the short direction S is cut along the long direction L. This makes it possible to produce a negative electrode plate 20 (see Figure 2) in which negative electrode tabs 22t are formed only on one side of the edge portion 20b1 of the electrode plate body portion 20b. In addition, in this embodiment, as shown by the dashed line C2, the negative electrode plate material 20A is cut along the short direction S with predetermined intervals in the long direction L. This makes it possible to manufacture a negative electrode plate 20 of a desired length. Note that laser cutting is not required for cutting the negative electrode plate material 20A along the dashed lines C1 and C2; cutting blades, molds, cutters, etc., may be used. Furthermore, when using laser cutting for cutting along the dashed lines C1 and C2, it is preferable to use a laser, similar to the tab cutting process S20 described above. This more effectively suppresses the peeling and detachment of fragments of the negative electrode active material layer 24. Moreover, these cuts along the dashed lines C1 and C2 may be performed as appropriate depending on the shape of the negative electrode plate after manufacturing, and are not limited to the technology disclosed herein.

[0038] <Other Embodiments> The above describes one embodiment of the technology disclosed herein. The above embodiment is merely an example of how the technology disclosed herein may be applied and is not intended to limit the scope of 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 negative electrode plates, but may also be a positive electrode plate. According to the manufacturing method disclosed herein, even when a positive electrode plate is manufactured, it is possible to suppress variations in the cutting quality of the edges of the manufactured electrode plate (positive electrode plate).

[0040] Furthermore, as shown in Figures 1 and 3, in the manufacturing method according to the above embodiment, the laser irradiation position in the tab cutting step S20 is controlled so that a negative electrode tab 22t is formed in which the second edge 21b and the fourth edge 21d extend substantially perpendicular to the longitudinal direction L (i.e., along the short 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 Figure 5. Specifically, in the second step, the inclination angle θ2 of the second edge 21b after manufacturing can be adjusted by controlling the speed of the laser that follows the first direction and the laser movement angle θ1. Specifically, increasing the movement angle θ1 in Figure 4 and decreasing the laser's tracking speed in the first direction tends to increase the inclination angle θ2 of the second edge 21b in Figure 5 (the inclination of the second edge 21b becomes gentler). Similarly, in the fourth step, the inclination angle θ4 of the fourth edge 21d can be adjusted by controlling the speed of the laser that tracks the first direction and the laser's movement angle θ3.

[0041] Furthermore, multiple electrode tabs 22t are formed on the negative electrode plate 20 after manufacturing. These multiple electrode tabs 22t may each have a different shape. In this case, the first to fourth steps described above may be considered as one cycle, and the movement pattern of the absolute position of the laser may be changed with each cycle. For example, by making the amount of movement along the short direction S in the second and fourth steps different with each cycle, multiple types of electrode tabs with different protrusion amounts from the first edge 21a can be formed. Also, by making the movement angles θ1, θ3 and the laser tracking speed different with each cycle in the second and fourth steps, multiple types of electrode tabs with different inclination angles θ2 of the second edge 21b and 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 illustrative. That is, the technology disclosed herein includes various modifications and changes to the specific examples described above. [Explanation of Symbols]

[0043] 20: Negative electrode plate 20A: Negative electrode plate material 20b: Electrode body section 20b1: Enbu 22: Negative electrode core 22t : Negative pole tab 24: Negative active material layer A1: Negative active material application area A2: Area where the negative electrode core is exposed

Claims

1. Preparation steps for preparing strip-shaped electrode plate material before tab cutting, A tab-cutting step is performed in which, while conveying the electrode plate material in a first direction along the longitudinal direction, a laser is irradiated onto the electrode plate material during conveyance to produce an electrode plate having a plurality of electrode tabs at its short-side end. Equipped with, In the tab cutting process, the laser's travel speed on the electrode plate material is controlled so that the relative speed of the laser's irradiation position to the electrode plate material during transport remains constant. When the average value of the relative speed throughout the entire tab-cutting process is taken as 100%, the laser's travel speed is controlled so that the relative speed at any irradiation position is within the range of 90% to 110%. The electrode plate after the tab cutting process is The first edge portion extending in the longitudinal direction of the electrode plate, A second edge extending outward in the short direction from the first edge, A third edge extending longitudinally from the tip of the second edge, A fourth edge extending inward in the short direction from the tip of the third edge and Equipped with, The aforementioned tab cutting process is A first step involves fixing the laser irradiation position in the aforementioned short-side direction, and then relatively moving the laser irradiation position toward a second direction which is opposite to the first direction. A second step is performed after the first step, in which the irradiation position of the laser is moved outward in the short-side direction while moving in the first direction, A third step is performed in which, after fixing the laser irradiation position in the short direction, the laser irradiation position is moved relatively toward the second direction, A fourth step is performed in which the irradiation position of the laser is moved inward in the short-side direction while moving it in the first direction, It is equipped with, The laser travel speed A in the first step, the laser travel speed B in the second step, the laser travel speed C in the third step, and the laser travel speed D in the fourth step satisfy the following equations (1) and (2), When the transport speed of the electrode plate material is VW, the ratio of the total laser travel distance to the total length of the electrode plate material is α, the inclination angle of the second edge of the electrode plate with respect to the longitudinal direction is θ2, and the inclination angle of the fourth edge of the electrode plate with respect to the longitudinal direction is θ4, A method for manufacturing an electrode plate, wherein the aforementioned travel speed A and travel speed C satisfy the following equation (3), the aforementioned travel speed B satisfies the following equation (4), and the aforementioned travel speed D satisfies the following equation (5). A = C < B (1) A = C < D (2) 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)

2. A preparation step of preparing a strip-shaped electrode plate material before tab cutting, A tab-cutting step is performed in which, while conveying the electrode plate material in a first direction along the longitudinal direction, a laser is irradiated onto the electrode plate material during conveyance to produce an electrode plate having a plurality of electrode tabs at its short-side end. Equipped with, In the tab cutting process, the laser's travel speed on the electrode plate material is controlled so that the relative speed of the laser's irradiation position to the electrode plate material during transport remains constant. When the average value of the relative speed throughout the entire tab-cutting process is taken as 100%, the laser's travel speed is controlled so that the relative speed at any irradiation position is within the range of 90% to 110%. The electrode plate after the tab cutting process is The first edge portion extending in the longitudinal direction of the electrode plate, A second edge extending outward in the short direction from the first edge, A third edge extending longitudinally from the tip of the second edge, A fourth edge extending inward in the short direction from the tip of the third edge and Equipped with, The aforementioned tab cutting process is A first step involves fixing the laser irradiation position in the aforementioned short-side direction, and then relatively moving the laser irradiation position toward a second direction which is opposite to the first direction. A second step is performed after the first step, in which the irradiation position of the laser is moved outward in the short-side direction while moving in the first direction, A third step is performed in which, after fixing the laser irradiation position in the short direction, the laser irradiation position is moved relatively toward the second direction, A fourth step is performed in which the irradiation position of the laser is moved inward in the short-side direction while moving it in the first direction, It is equipped with, A method for manufacturing an electrode plate, wherein, when the transport speed of the electrode plate material is set to 100%, the average value of the relative speed is 120% to 130%.

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