Method for manufacturing electrode plates, method for manufacturing secondary batteries, electrode plates and secondary batteries

Abstract

To prevent a conductive foreign material from falling and peeling from an electrode board after a production, and contribute an improvement of a safety of a secondary battery.SOLUTION: A manufacturing method of an electrode plate, disclosed here, comprises: a precursor preparation step of preparing an electrode precursor 20A comprising: an active material application region A1 to which an electrode active material layer 24 is applied to a front surface of an electrode core body 22; and a core body exposure region A2 in which the electrode core body 22 is exposed without applying the electrode active material layer 24; an active material application region cutting step of cutting the active material application region A1 with a pulse laser; and a core body exposure region cutting step of cutting the core body exposure region A2 with the pulse layer. Then, when a pulse width (ns) of the pulse layer in the core body exposure region cutting step is X, and a lap rate (%) is Y, a condition indicated by a formulation of Y≥-3logX+106 is satisfied. According to the manufacturing method of the electrode plate, since a conductive foreign material can be prevented from being fallen and peeled from the electrode plate after the manufacturing, a safety of the secondary battery can be improved.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing an electrode plate, a method for manufacturing a secondary battery, an electrode plate, and a secondary battery. [Background technology]

[0002] Secondary batteries, 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 an electrode plate precursor (hereinafter referred to as "electrode precursor"). Then, an electrode plate of the desired size is cut out from the electrode precursor using a laser or the like. An example of a technique for cutting out such an electrode plate is disclosed in Patent Documents 1 and 2.

[0003] Incidentally, in the electrode precursor with the above configuration, the thickness of the electrode active material layer tends to be uneven at the outer edge of the region to which the electrode active material layer is applied (active material application region). For this reason, when cutting an electrode plate from the electrode precursor, the outer edge of the active material application region is usually cut off with a laser. In addition, in a normal electrode plate, it is necessary to provide a portion where the electrode core (metal foil) is exposed for connection with conductive members such as electrode terminals. For this reason, when cutting out the electrode plate, a portion of the region where the electrode active material layer is not applied and the substrate for the electrode core is exposed (core exposure region) is also cut out to form an electrode tab. As described above, in the manufacture of an electrode plate, a process of cutting the active material application region and a process of cutting the core exposure region are carried out (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-34009 [Patent Document 2] Japanese Patent Publication No. 2016-33912 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, electrode plates manufactured using the above-described method had the characteristic of being prone to shedding and peeling of fragments and fine metal particles (sputter) from the electrode active material layer. If these conductive foreign materials detach or peel off inside the secondary battery, they can cause internal short circuits.

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a technology that can prevent conductive foreign matter from falling off or peeling off from electrode plates after manufacturing, thereby contributing to the improvement of the safety of secondary batteries. [Means for solving the problem]

[0007] As a result of various studies conducted to solve the above-mentioned problems, the inventors have identified the causes of detachment and peeling of the electrode active material layer and detachment and peeling of the sputtering.

[0008] First, let's explain the cause of the detachment and peeling of the electrode active material layer. As mentioned above, in the manufacture of electrode plates, the outer edge of the active material application area is cut with a laser. At this time, the heat from the laser may melt the electrode core and mix with a part of the electrode active material layer. When this molten metal is mixed into the electrode active material layer, its adhesiveness is greatly reduced, and it easily detaches and peels off with even a slight impact. The inventors of this invention considered that the reduction in adhesiveness of the electrode active material layer due to the inclusion of molten metal could be suppressed by cutting the active material application area using a pulsed laser. Such a pulsed laser can repeatedly irradiate the spot with a very short time width, concentrating a large amount of energy on the cutting area, and thus quickly cutting the electrode core with a small amount of melting.

[0009] Next, we will explain the cause of the detachment and peeling of minute metal fragments (spatter). As mentioned above, in the manufacture of electrode plates, it is necessary to cut out a portion of the core exposed area in order to form electrode tabs. However, when a high-energy laser is irradiated onto an exposed metal component such as the core exposed area, spatter may scatter from the irradiated area. When this spatter adheres to the electrode plate, it becomes minute metal fragments that easily detach and peel off with even a slight impact. The inventors of this invention considered that the core exposed area could be cut using a continuous wave laser (CW laser) to suppress this spatter scattering. This CW laser melts and cuts the electrode core by continuously irradiating it with a low-energy laser, so it is possible to form electrode tabs while suppressing spatter scattering.

[0010] As described above, the inventors' research indicates that in order to prevent the detachment and peeling of electrode active material layer fragments, it is necessary to use a pulsed laser to cut the active material application region, and in order to prevent the detachment and peeling of sputtering, it is necessary to use a CW laser to cut the core exposure region. However, switching the laser used to cut the active material application region and the core exposure region separately would significantly reduce manufacturing efficiency, making it difficult to adopt in actual manufacturing settings. Furthermore, when the active material application region and the core exposure region are cut separately, it is necessary to connect the cut lines formed in each region without misalignment, which can lead to frequent cutting defects. Considering these points, the inventors investigated a method that can continuously cut the active material application region and the core exposure region while preventing the generation of each of the two types of conductive foreign matter mentioned above.

[0011] The electrode plate manufacturing method disclosed herein is based on the above-mentioned findings and manufactures an electrode plate comprising an electrode core which is a metal foil and an electrode active material layer which is applied to the surface of the electrode core and contains an electrode active material. The electrode plate manufacturing method comprises a precursor preparation step of preparing an electrode precursor which comprises an active material application region on the surface of the electrode core which has an electrode active material layer applied and a core exposed region on which the electrode core is exposed without the electrode active material layer applied, an active material application region cutting step of cutting the active material application region with a pulsed laser, and a core exposed region cutting step of cutting the core exposed region with a pulsed laser. The electrode plate manufacturing method disclosed herein is characterized in that, when the pulse width (ns) of the pulsed laser in the core exposed region cutting step is X and the overlap rate (%) is Y, the following equation (1) is satisfied. Y≧-3logX+10⁶ (1)

[0012] In the electrode plate manufacturing method described above, a pulsed laser is used when cutting the active material application region. This suppresses the mixing of molten metal originating from the electrode core into the electrode active material layer, thereby preventing fragments of the electrode active material layer from falling off or peeling off the electrode plate after manufacturing. On the other hand, in the manufacturing method disclosed herein, in order to prevent a significant decrease in manufacturing efficiency and the occurrence of cutting defects, a pulsed laser is also used to cut the core exposure region, and the active material application region and the core exposure region are cut continuously. However, in the manufacturing method disclosed herein, the state of the pulsed laser used to cut the core exposure region is made to be close to that of a CW laser. Specifically, according to experiments conducted by the inventors, a pulsed laser that satisfies the above formula (1) increases the amount of melted electrode core to the same level as a CW laser, and since the electrode core is melted and cut, sputter scattering can be suppressed. As described above, the electrode plate manufacturing method disclosed herein can prevent conductive foreign matter from falling off or peeling off the electrode plate after manufacturing, thus contributing to the improvement of the safety of secondary batteries.

[0013] Also, in a preferred embodiment of the method for manufacturing an electrode plate disclosed herein, the frequency of the pulsed laser in the active material application region cutting step is lower than the frequency of the pulsed laser in the core body exposure region cutting step. Thereby, it is possible to more appropriately prevent the detachment and peeling of each of the fragments and sputter of the electrode active material layer.

[0014] Also, in a preferred embodiment of the method for manufacturing an electrode plate disclosed herein, the frequency of the pulsed laser in the active material application region cutting step is 100 kHz to 2000 kHz. Thereby, it is possible to more appropriately prevent the detachment and peeling of the fragments of the electrode active material layer.

[0015] Also, in a preferred embodiment of the method for manufacturing an electrode plate disclosed herein, the pulse width X of the pulsed laser in the core body exposure region cutting step is 30 ns to 240 ns. Thereby, it is possible to more preferably prevent the detachment and peeling of the sputter.

[0016] Also, in a preferred embodiment of the method for manufacturing an electrode plate disclosed herein, the lap rate of the pulsed laser in the active material application region cutting step is lower than the lap rate of the pulsed laser in the core body exposure region cutting step. Thereby, it is possible to more appropriately prevent the detachment and peeling of each of the fragments and sputter of the electrode active material layer.

[0017] Also, in a preferred embodiment of the method for manufacturing an electrode plate disclosed herein, the lap rate of the pulsed laser in the core body exposure region cutting step is 90% to 99%. Thereby, it is possible to more preferably prevent the detachment and peeling of the sputter.

[0018] Also, in a preferred embodiment of the method for manufacturing an electrode plate disclosed herein, the electrode plate is a negative electrode plate including a negative electrode core body made of copper or a copper alloy and a negative electrode active material layer containing a carbon material as an electrode active material. In a negative electrode plate having such a configuration, a decrease in the adhesiveness of the electrode active material layer due to the mixing of molten metal is particularly likely to occur. However, according to the method for manufacturing an electrode plate disclosed herein, even in the manufacture of a negative electrode plate having such a configuration, a decrease in the adhesiveness of the electrode active material layer can be appropriately suppressed.

[0019] As another aspect of the technology disclosed herein, a method for manufacturing a secondary battery is provided. Specifically, in the method for manufacturing a secondary battery according to the technology disclosed herein, in a method for manufacturing a secondary battery including an electrode body in which a pair of electrode plates face each other via a separator, at least one of the pair of electrode plates is manufactured using the method for manufacturing an electrode plate having the above-described configuration. According to such a manufacturing method, since it is possible to suppress the dropout and peeling of conductive foreign matters (fragments of the electrode active material layer, sputtering) from the electrode plate inside the secondary battery, a secondary battery excellent in safety can be obtained.

[0020] Further, as another aspect of the technology disclosed herein, an electrode plate is provided. Such an electrode plate includes an electrode core body that is a foil-shaped metal member, and an electrode active material layer containing an electrode active material provided on the surface of the electrode core body. And this electrode plate includes a plate main body portion having an electrode active material layer provided on the surface of the electrode core body, and a region where the electrode active material layer is not provided and the electrode core body is exposed, and the electrode tab that protrudes outward from a part of the outer peripheral edge portion of the plate main body portion. And in the electrode plate disclosed herein, a first thick portion having a greater thickness than the central portion of the electrode tab is formed at the outer peripheral edge portion of the electrode tab, and the aspect ratio of the first thick portion in a cross-sectional view along the thickness direction of the electrode tab is 0.85 or more. Further, a second thick portion having a greater thickness than the electrode core body at the central portion of the plate main body portion is formed at the end portion of the electrode core body on at least one side of the outer peripheral edge portion of the plate main body portion, and a coating layer containing an electrode active material adheres to the surface of the second thick portion.

[0021] The electrode plate disclosed herein is manufactured by the electrode plate manufacturing method having the above configuration. Specifically, this electrode plate has a first thickened portion formed on the outer peripheral edge of the electrode tab. This first thickened portion is the trace of laser cutting. In the electrode plate manufacturing method having the above configuration, when cutting out the electrode tab (cutting the core exposure area), the pulse laser conditions are brought close to those of a CW laser. When melt cutting is performed with such a pulse laser, the amount of melted electrode core is about the same as with a CW laser, so the cross-sectional shape of the cut mark (first thickened portion) becomes approximately circular (aspect ratio of 0.85 or more). On the other hand, in the electrode plate manufacturing method having the above configuration, when cutting out the electrode plate body (cutting the active material application area), a high-energy pulse laser is used to suppress the decrease in the tackiness of the electrode active material layer due to the mixing of molten metal. As a result, the coating layer containing the electrode active material adheres to the laser cutting mark (second thickened portion) formed on the outer peripheral edge of the electrode plate body. Unlike electrode active material layers containing molten metal, this coating layer is less likely to peel off or detach from the electrode core.

[0022] Furthermore, in a preferred embodiment of the electrode plate disclosed herein, the second thickened portion has a claw shape comprising a cap portion protruding from both or one side in the thickness direction and a recess formed between the cap portion and the electrode core. As described above, the second thickened portion is a laser cutting mark formed by a high-energy pulsed laser. When a high-energy pulsed laser is used, the amount of metal melted during cutting is very small, which can result in the formation of a claw-shaped cutting mark (second thickened portion) as described above. This claw-shaped second thickened portion exhibits an excellent anchoring effect, which further effectively prevents the detachment and peeling of the electrode active material layer.

[0023] Furthermore, in one preferred embodiment of the electrode plate disclosed herein, the thickness of the coating layer attached to the surface of the second thickened portion is 1 μm to 20 μm. This allows the second thickened portion to be properly covered with the coating layer of the electrode active material, thereby effectively preventing damage to other components (for example, the separator of a secondary battery) by the second thickened portion.

[0024] Furthermore, in one preferred embodiment of the electrode plate disclosed herein, the center point of the first thickened portion is located between a pair of extension lines extending from each surface of the central part of the electrode tab. Because the electrode tab of such an electrode plate is easy to bend, it can contribute to improving the manufacturing efficiency of secondary batteries. Such a first thickened portion can be formed when the electrode tab is cut out with a pulsed laser that satisfies formula (1) above.

[0025] Furthermore, in a preferred embodiment of the electrode plate disclosed herein, the first thickened portion has a first region that is relatively thicker and a second region that is relatively thinner, and the first and second regions are alternately formed along the outer peripheral edge of the electrode tab. In the manufacturing method of the electrode plate with the above configuration, the electrode core (negative electrode tab) is melted and cut with a pulsed laser with a high overlap ratio that satisfies formula (1). In this case, the molten electrode core deforms into a substantially spherical shape due to surface tension, so that a first region where molten metal is concentrated and a second region where molten metal is sparsely distributed are alternately formed.

[0026] Another aspect of the technology disclosed herein is a secondary battery. Specifically, the technology disclosed herein provides a secondary battery comprising an electrode body in which a pair of electrode plates face each other via a separator, characterized in that at least one of the pair of electrode plates uses an electrode plate with the above configuration. This suppresses the release of conductive foreign matter (fragments of the electrode active material layer, sputter) from the electrode plate, thereby contributing to improved safety of the secondary battery. [Brief explanation of the drawing]

[0027] [Figure 1] This is a flowchart showing a method for manufacturing an electrode plate according to one embodiment. [Figure 2] This is a schematic plan view showing a negative electrode plate manufactured in a method for manufacturing an electrode plate according to one embodiment. [Figure 3] This is a plan view illustrating a method for manufacturing an electrode plate according to one embodiment. [Figure 4] This diagram illustrates the overlap rate of pulsed lasers. [Figure 5]This is a cross-sectional view taken along the VV arrow in Figure 2. [Figure 6] This is a cross-sectional view taken along the line VI-VI in Figure 2. [Figure 7] This is a schematic perspective view showing a secondary battery according to one embodiment. [Figure 8] This is a schematic longitudinal cross-section along the line VIII-VIII in Figure 7. [Figure 9] This is a schematic longitudinal cross-section along the line IX-IX in Figure 7. [Figure 10] This is a schematic cross-sectional view along line XX in Figure 7. [Figure 11] This is a schematic perspective view showing the electrode body attached to the sealing plate. [Figure 12] This is a schematic perspective view showing an electrode body to which a positive electrode second current collector and a negative electrode second current collector are attached. [Figure 13] This is a perspective view illustrating the electrode body of a secondary battery according to one embodiment. [Figure 14] This is a front view of the electrode body of a secondary battery according to one embodiment. [Figure 15] This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate in the example. [Figure 16] This is a cross-sectional SEM image (1000x magnification) of the side edge of the electrode plate body of the negative electrode plate in the example. [Figure 17] This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate of Comparative Example 1. [Figure 18] This is a cross-sectional SEM image (1000x magnification) of the side edge of the electrode plate body of the negative electrode plate of Comparative Example 1. [Figure 19] This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate in Comparative Example 2. [Figure 20] This is a cross-sectional SEM image (370x magnification) of the side edge of the electrode plate body of the negative electrode plate of Comparative Example 2. [Figure 21] This graph shows the relationship between the overlap rate and pulse width for each sample measured in the second test. [Modes for carrying out the invention]

[0028] 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 a battery) can be understood as design matters for those skilled in the art based on the 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".

[0029] In this specification, "secondary battery" refers to any energy storage device in which a charge-discharge reaction occurs through the movement of a charge carrier between a pair of electrodes (positive electrode and negative electrode) via an electrolyte. Such secondary batteries include not only so-called rechargeable batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, but also capacitors such as electric double-layer capacitors. The following describes embodiments of lithium-ion secondary batteries among the secondary batteries mentioned above.

[0030] <Method for manufacturing electrode plates> The electrode plate manufacturing method disclosed herein is a method for manufacturing an electrode plate comprising an electrode core which is a metal foil and an electrode active material layer which is applied to the surface of the electrode core and contains an electrode active material. Hereinafter, as one embodiment of the electrode plate manufacturing method disclosed herein, a method for manufacturing the negative electrode plate (negative electrode plate) of a secondary battery will be described. Figure 1 is a flowchart of the electrode plate manufacturing method according to this embodiment. Figure 2 is a schematic plan view showing the negative electrode plate manufactured in the electrode plate manufacturing method according to this embodiment. Figure 3 is a plan view illustrating the electrode plate manufacturing method according to this embodiment. Figure 4 is a diagram illustrating the overlap rate of a pulsed laser. Figure 5 is a cross-sectional view taken along the VV arrow in Figure 2. Figure 6 is a cross-sectional view taken along the VI-VI arrow in Figure 2. In Figures 2, 3, 5, and 6, the symbol L indicates the "longitudinal direction" of the negative electrode plate 20 (or negative electrode precursor 20A), the symbol S indicates the "short direction", and the symbol T indicates the "thickness direction".

[0031] As shown in Figure 1, the method for manufacturing the electrode plate according to this embodiment comprises a precursor preparation step S1, an active material application region cutting step S2, and a core body exposure region cutting step S3. This produces a negative electrode plate 20 with the configuration shown in Figure 2. Below, an overview of the negative electrode plate 20 to be manufactured will be described, followed by a description of each step shown in Figure 1.

[0032] (Overview of the negative electrode plate) As shown in Figure 2, 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 a plan view, the negative electrode plate 20 has two regions: the electrode plate body portion 20b and the 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 where the negative electrode active material layer 24 is not applied and the negative electrode core 22 is exposed. The negative electrode tab 22t also protrudes outward (upward in the short direction S in Figure 2) from a part of the outer peripheral edge portion 20b1 of the electrode plate body portion 20b. Furthermore, the negative electrode plate 20 shown in Figure 2 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.

[0033] Each component constituting the negative electrode plate 20 can use any material that can be used in conventional secondary batteries without any particular limitations. For example, a metal material having a predetermined conductivity can preferably be used for the negative electrode core 22. Such a negative electrode core 22 is preferably made of copper or a copper alloy. 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.

[0034] The negative electrode active material layer 24 is a layer containing the negative electrode active material. The negative electrode active material is a material that can reversibly absorb and release charge carriers in relation to the positive electrode active material. Examples of such negative electrode active materials include carbon materials and silicon-based materials. As carbon materials, for example, graphite, hard carbon, soft carbon, amorphous carbon, etc. can be used. 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 and silicon oxide (silica). Furthermore, silicon-based materials may also contain other metallic elements (e.g., alkaline earth metals) or their oxides. In addition, the negative electrode active material layer 24 may 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 carboxymethylcellulose (CMC). The content of the negative electrode active material, when the total solid content of the negative electrode active material layer 24 is taken as 100% by mass, is generally 30% by mass or more, and typically 50% by mass or more. The negative electrode active material may account for 80% by mass or more, or 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.

[0035] The negative electrode plate 20 with the above configuration is manufactured by performing a precursor preparation step S1, an active material application region cutting step S2, and a core body exposure region cutting step S3, as shown in Figure 1. Each of these steps will be described below.

[0036] (Precursor preparation step S1) In this process, an electrode precursor, which is a precursor to the electrode plate, is prepared. The electrode precursor shown in Figure 3 is a precursor to the negative electrode plate (negative electrode precursor 20A). This negative electrode precursor 20A is equipped with a negative electrode core 22, which is a strip-shaped metal foil. The area of ​​the negative electrode core 22 of this negative electrode precursor 20A is larger than the area of ​​the manufactured negative electrode plate 20 (see Figure 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 part of the negative electrode core 22 in the short direction S, extending along the long direction L. In this specification, the region to which this negative electrode active material layer 24 is applied is referred to as the "negative electrode active material applied region A1". On the other hand, the negative electrode active material layer 24 is not applied to both side edges of the negative electrode precursor 20A (the region outside the negative electrode active material layer 24 in the short direction S), and the negative electrode core 22 is exposed. In this specification, the region in which the negative electrode core 22 is exposed is referred to as the "negative electrode core exposure region A2". The means for preparing the negative electrode precursor 20A with the above configuration are not particularly limited, and various conventionally known methods can be adopted without particular restriction. For example, the negative electrode precursor 20A can be produced by applying a raw material paste containing the negative electrode active material, etc., to the surface of the negative electrode core 22 and then drying it. Furthermore, this process is not particularly limited as long as the negative electrode precursor 20A can be prepared. For example, a separately manufactured negative electrode precursor 20A may be purchased and prepared. Note that the negative electrode precursor is not limited to the structure shown in Figure 2. For example, the negative electrode precursor can also employ a structure in which the negative electrode core exposure region is formed only on one side edge.

[0037] (Active material application area cutting step S2) In this process, the negative electrode active material-added region A1 of the negative electrode precursor 20A is cut with a pulsed laser. Specifically, in the active material-added region cutting process S2, the dotted line L in Figure 3 is used. N1 As shown, a pulsed laser is scanned over the negative electrode active material application region A1 so as to follow the side edge A1a of the negative electrode active material application region A1. This removes the side edge A1a of the negative electrode active material application region A1, where the thickness of the negative electrode active material layer 24 is uneven, and a negative electrode plate 20 with a uniform thickness of the negative electrode active material layer 24 can be fabricated. Here, the dotted line L N1As shown, when the negative electrode active material application region A1 is cut with a laser, there is a possibility that a portion of the negative electrode core 22, which is melted by the heat of the laser, may be mixed into the negative electrode active material layer 24. When this molten metal solidifies within the negative electrode active material layer 24, the adhesiveness of the negative electrode active material layer 24 is significantly reduced, and fragments of the negative electrode active material layer 24 may easily detach or peel off with even a slight impact. In the active material application region cutting step S2 of this embodiment, a pulsed laser is used when cutting the negative electrode active material application region A1 in order to prevent such a decrease in adhesiveness due to the mixing of molten metal. Because such a pulsed laser can concentrate a large amount of energy over a short time (high peak output), the negative electrode core 22 can be cut quickly with a small amount of melting. This suppresses the decrease in adhesiveness of the negative electrode active material layer 24 due to the mixing of molten metal, and thus prevents fragments of the negative electrode active material layer 24 from detaching or peeling off.

[0038] The conditions for the pulsed laser in the active material application region cutting step S2 are not particularly limited and are preferably adjusted as appropriate according to the structure of the negative electrode precursor 20A (typically, the thickness and material of the negative electrode active material layer 24 and the negative electrode core 22). For example, the average output of the pulsed laser in this step is preferably 70W to 1000W, more preferably 100W to 900W, and even more preferably 150W to 800W. This allows for easy cutting of the negative electrode precursor 20A while preventing the detachment and peeling of the negative electrode active material layer 24. Specifically, as the average output of the pulsed laser increases, the cutting of the negative electrode precursor 20A tends to become easier. On the other hand, as the average output of the pulsed laser decreases, the impact during laser irradiation decreases, thus preventing a portion of the negative electrode active material layer 24 from being blown away by the laser impact.

[0039] Furthermore, the repetition frequency of the pulsed laser in the active material application region cutting step S2 is preferably 100KHz to 2000KHz, more preferably 150KHz to 1500KHz, and even more preferably 200KHz to 1000KHz. This prevents the molten negative electrode core 22 from mixing with the negative electrode active material layer 24, while allowing for easy cutting of the negative electrode precursor 20A. Specifically, when the pulsed laser frequency is low, the peak output is high, making it easier to cut the negative electrode core 22. On the other hand, when the pulsed laser frequency is high, the peak output is low, preventing a portion of the negative electrode active material layer 24 irradiated by the laser from being blown away. Furthermore, the spot diameter of the pulsed laser in the active material application region cutting step S2 is preferably 10μm to 60μm, more preferably 20μm to 50μm, and even more preferably 25μm to 40μm. This allows for easy cutting of the negative electrode plate 20 from the negative electrode precursor 20A.

[0040] Furthermore, it is preferable that the overlap rate of the pulsed laser in the active material application region cutting step S2 is smaller than the overlap rate of the pulsed laser in the core body exposure region cutting step S3, which will be described later. As the overlap rate of the pulsed laser decreases, it tends to become easier to cut the negative electrode core body 22 with a small amount of melted material. On the other hand, as the overlap rate increases, the state of the pulsed laser approaches that of a CW laser, which tends to make it easier to suppress the generation of sputter, which will be described later. For this reason, in the active material application region cutting step S2, where the inclusion of molten negative electrode core body 22 is a problem, it is preferable to use a pulsed laser with a small overlap rate. The specific overlap rate of the pulsed laser in the active material application region cutting step S2 is preferably 40% to 95%, more preferably 50% to 90%, and even more preferably 70% to 90%.

[0041] Next, the scanning speed of the pulsed laser in the active material application region cutting step S2 is preferably 5000 mm / sec or less, and more preferably 3000 mm / sec or less. By slowing down the scanning speed in this way, cutting defects of the negative electrode core 22 can be suppressed. On the other hand, the lower limit of the scanning speed of the pulsed laser is not particularly limited and may be 20 mm / sec or more. However, from the viewpoint of improving manufacturing efficiency by shortening the cutting time, the lower limit of the scanning speed of the pulsed laser is preferably 200 mm / sec or more, and more preferably 500 mm / sec or more. Furthermore, the pulse width of the pulsed laser in the active material application region cutting step S2 is preferably 30 ns to 240 ns, and more preferably 60 ns to 120 ns. This makes it possible to more effectively prevent the molten negative electrode core 22 from mixing with the negative electrode active material layer 24. Specifically, as the pulse width of the pulsed laser tends to decrease, the peak output tends to increase, making it easier to reduce the amount of melted negative electrode core 22 during laser cutting. On the other hand, as the pulse width increases, the impact applied to the negative electrode active material layer 24 decreases, thus preventing a portion of the negative electrode active material layer 24 from being blown away during laser irradiation.

[0042] (Core exposed area cutting step S3) In this process, the negative electrode core exposure region A2 of the negative electrode precursor 20A is cut with a pulsed laser. Specifically, in the core exposure region cutting process S3, first, the dotted line L in Figure 3 N2 As shown, the pulsed laser is scanned along the short-side direction S of the negative electrode precursor 20A, moving from the negative electrode active material application region A1 toward the negative electrode core exposure region A2. Then, the pulsed laser is scanned for a certain distance along the long-side direction L of the negative electrode precursor 20A, and then the pulsed laser is scanned again along the short-side direction S toward the negative electrode active material application region A1. As a result, a portion of the negative electrode core exposure region A2 is cut out in a convex shape to form the negative electrode tab 22t (see Figure 2). In this embodiment, the active material application region cutting step S2 (dotted line L in Figure 3) is then performed. N1 ) and core body exposure region cutting process S3 (dotted line L in Figure 3) N2This process is repeated at regular intervals. This allows the side edge A1a of the negative electrode active material application region A1 to be cut off, and multiple negative electrode tabs 22t to be cut out.

[0043] In the electrode plate manufacturing method according to this embodiment, the pulsed laser irradiated onto the negative electrode core exposure region A2 in the core exposure region cutting step S3 is controlled to satisfy the following equation (1). In equation (1) below, "X" is the pulse width (ns) of the pulsed laser, and "Y" is the overlap rate (%) of the pulsed laser. Y≧-3logX+10⁶ (1)

[0044] In the manufacturing method according to this embodiment, the negative electrode core exposed region A2 is cut using a pulsed laser that satisfies the above formula (1). As a result, even though a pulsed laser is used, the negative electrode core exposed region A2 can be melted and cut like a CW laser, thus suppressing sputter scattering. Specifically, as the overlap rate of the pulsed laser increases, the laser irradiation approaches continuous irradiation, so sputter tends to be less likely to occur. On the other hand, the degree of sputter generation when a pulsed laser is irradiated onto a metal member is affected not only by the size of the overlap rate but also by the length of the pulse width. Specifically, as the pulse width of the pulsed laser increases, the heat-affected time applied to the metal member increases, and the molten area expands, so sputter tends to be less likely to occur. In other words, when cutting the negative electrode core exposed region A2 using a pulsed laser, it is desirable to increase the overlap rate and increase the pulse width. This makes the state of the pulsed laser closer to that of a CW laser, and sputter generation can be suppressed. Equation (1) above represents the pulse laser irradiation conditions (relationship between overlap rate and pulse width) that the inventors discovered can sufficiently suppress sputtering, based on repeated experiments conducted using the aforementioned findings (see Figure 21).

[0045] As shown in Figure 4, in laser cutting using a pulsed laser, multiple spots R1 and R2 are irradiated while slightly shifting them in a predetermined scanning direction D. This creates an overlapping irradiation area A3 where adjacent spots R1 and R2 are irradiated together, and a single irradiation area A4 where a single spot R1 or R2 is irradiated. In this specification, "lapping rate" is a value that indicates the degree to which adjacent spots R1 and R2 overlap during such pulsed laser irradiation. This overlap rate Y can be calculated based on the following equation (2), where W1 is the spot diameter and W2 is the irradiation interval between adjacent spots. Note that both the spot diameter W1 and the irradiation interval W2 are lengths in the direction along the scanning direction D of the pulsed laser. That is, when irradiating with elliptical spots R1 and R2 as shown in Figure 4, the spot diameter W1 refers to the diameter of spots R1 and R2 along the scanning direction D. Also, when irradiating with elliptical spots, each spot may be inclined with respect to the scanning direction D. Even in this case, the length along the scanning direction D is measured as the spot diameter W1 and irradiation interval W2 of each spot. The specific spot diameter W1 of the pulsed laser in the core body exposure region cutting process S3 is preferably 10 μm to 60 μm, more preferably 20 μm to 50 μm, and even more preferably 25 μm to 40 μm. Wrap rate Y(%) = (W1 - W2) / W1 × 100 (2)

[0046] As described above, in the manufacturing method according to this embodiment, various conditions are adjusted so that the overlap rate Y of the pulsed laser in the core body exposed region cutting step S3 satisfies the condition of -3logX+106 or more. This makes it possible to suppress the scattering of sputter when cutting the negative electrode core body exposed region A2. At this time, if the overlap rate Y is large, the scattering of sputter can be suppressed even more effectively. From this viewpoint, it is more preferable that the pulsed laser in the core body exposed region cutting step S3 is controlled so that the overlap rate Y is -3logX+107 or more. On the other hand, the upper limit of the overlap rate Y of the pulsed laser in the core body exposed region cutting step S3 is not particularly limited and may be 99% or less. However, as the overlap rate Y decreases, it becomes easier to increase the scanning speed of the pulsed laser, so there is a tendency for manufacturing efficiency to improve. From this viewpoint, it is preferable that the pulsed laser in the core body exposed region cutting step S3 is controlled so that the overlap rate Y is -3logX+109 or less (more preferably -3logX+108 or less).

[0047] The pulsed laser in the core exposure region cutting step S3 only needs to satisfy the above-described equation (1), and other conditions are not particularly limited. For example, other conditions of the pulsed laser in the core exposure region cutting step S3 are preferably adjusted as appropriate according to the structure of the negative electrode core exposure region A2 (typically the thickness and material of the negative electrode core 22). For example, the pulse width X constituting the above equation (1) may be 10 ns to 300 ns, 30 ns to 240 ns, or 120 ns to 240 ns. As shown in equation (1) and Figure 21, in the core exposure region cutting step S3, it is required to increase the overlap rate Y as the pulse width X decreases.

[0048] Furthermore, the average output of the pulsed laser in the core body exposure region cutting process S3 may be 70W to 2000W, 100W to 1800W, or 200W to 1500W. As the average output of the pulsed laser increases, the cutting of the negative electrode core body exposure region A2 tends to become easier. On the other hand, as the average output of the pulsed laser decreases, the impact during laser irradiation decreases, which tends to reduce the scattering of sputter.

[0049] Also, the repetition frequency of the pulsed laser in the core exposure area cutting step S3 may be 400KHz to 4000KHz, may be 1000KHz to 3500KHz, or may be 2000KHz to 3000KHz. Since the peak output increases as the frequency of the pulsed laser decreases, the cutting of the negative electrode core 22 tends to be facilitated. On the other hand, as the frequency of the pulsed laser increases, the scattering of sputter tends to be less likely to occur.

[0050] Next, the scanning speed of the pulsed laser in the core exposure area cutting step S3 is preferably 5000 mm / sec or less, and more preferably 3000 mm / sec or less. As the scanning speed is decreased, the occurrence of cutting defects in the negative electrode core 22 tends to be less likely. On the other hand, the lower limit value of the scanning speed of the pulsed laser is not particularly limited, and may be 20 mm / sec or more. From the viewpoint of improving the manufacturing efficiency by shortening the cutting time, the lower limit value of the scanning speed of the pulsed laser is preferably 200 mm / sec or more, and more preferably 500 mm / sec or more. The scanning speed of the pulsed laser may be approximately the same in the active material application area cutting step S2 and the core exposure area cutting step S3.

[0051] (Other processes) As described above, in the manufacturing method according to the present embodiment, in the active material application area cutting step S2 (dotted line L in FIG. 3 N1 ), and the core exposure area cutting step S3 (dotted line L in FIG. 3 N2 ), by repeating at a certain cycle, the side edge portion A1a of the negative electrode active material application area A1 where the thickness of the negative electrode active material layer 24 is likely to be non-uniform is cut off, and a plurality of negative electrode tabs 22t are formed. Further, in the manufacturing method according to the present embodiment, as shown by the two-dot chain line L in FIG. 3 N3 , the central portion of the negative electrode precursor 20A in the short side direction S is cut along the long side direction L. As a result, as shown in FIG. 2, a negative electrode plate 20 in which the negative electrode tab 22t is formed only on one side of the outer peripheral edge portion 20b1 of the electrode plate main body portion 20b can be manufactured. Also, in the present embodiment, the two-dot chain line L N4As shown, the negative electrode precursor 20A is cut along the short direction S with predetermined intervals in the length direction L. This allows for the production of a negative electrode plate 20 of the desired length. Note that the dashed line L N3 , L N4 For cutting the negative electrode precursor 20A along the dashed line L, laser cutting is not required; cutting blades, molds, cutters, etc., may be used. N3 , L N4 When using laser cutting in cutting along the above active material application area cutting step S2 (dotted line L N1 It is preferable to use a pulsed laser under the same conditions as above. This makes it possible to more effectively suppress the peeling and detachment of fragments of the negative electrode active material layer 24. Also, these dashed lines L N3 , L N4 Cutting along the line may be performed as appropriate depending on the shape of the negative electrode plate after manufacturing, and is not limited to the technology disclosed herein.

[0052] As described above, in the electrode plate manufacturing method according to this embodiment, when cutting the negative electrode active material application region A1 (dotted line L N1(See reference) A pulsed laser is used. This prevents molten metal from mixing with the negative electrode active material layer 24 and reducing its tackiness, thus preventing fragments of the negative electrode active material layer 24 from falling off or peeling off from the negative electrode plate 20 after fabrication. On the other hand, in the manufacturing method according to this embodiment, a pulsed laser is also used when cutting the negative electrode core exposed region A2, and the negative electrode active material application region A1 and the negative electrode core exposed region A2 are cut continuously. This prevents a significant decrease in manufacturing efficiency and the occurrence of cutting defects due to switching the type of laser. Furthermore, in this embodiment, the pulsed laser used when cutting the negative electrode core exposed region A2 is controlled to satisfy the conditions specified in the above equation (1). This makes it possible to increase the amount of melting of the electrode core when cutting the negative electrode core exposed region A2 with a pulsed laser to the same level as with a CW laser, thereby suppressing sputter scattering. As a result, it is possible to prevent fine metal fragments from falling off or peeling off from the negative electrode plate 20 after fabrication. As described above, this embodiment prevents conductive foreign matter from falling off or peeling off the negative electrode plate 20 after manufacturing, thus contributing to the improvement of the safety of secondary batteries.

[0053] <Negative electrode plate> Next, the detailed structure of the electrode plate (negative electrode plate 20) manufactured using the electrode plate manufacturing method according to this embodiment will be described.

[0054] (Overview of the negative electrode plate) First, as shown in Figure 2, the negative electrode plate 20 according to this embodiment comprises a negative electrode core 22 and a negative electrode active material layer 24. Furthermore, the negative electrode plate 20 comprises an electrode plate body portion 20b, which is a region on the surface of the negative electrode core 22 to which the negative electrode active material layer 24 is applied, and a negative electrode tab 22t, which is a region where the negative electrode active material layer 24 is not applied and the negative electrode core 22 is exposed. These have already been explained, so a redundant explanation will be omitted.

[0055] (1st thick part) As shown in Figure 5, the negative electrode plate 20 according to this embodiment has a first thickened portion 23 formed on the outer peripheral edge 22t1 of the negative electrode tab 22t, which is thicker than the central portion 22t2 of the negative electrode tab 22t. This first thickened portion 23 is the mark of the laser cutting in the core body exposure region cutting step S3. Specifically, in the electrode plate manufacturing method according to this embodiment, as described above, in order to suppress the scattering of sputter, the state of the pulsed laser when cutting the negative electrode core body exposure region A2 (see Figure 3) is approximated to a CW laser. On the outer peripheral edge 22t1 of the negative electrode tab 22t cut by such a pulsed laser, a first thickened portion 23 with a cross-section close to circular is formed, which is the mark of melting and cutting the metal foil, similar to the case when cutting with a CW laser. Here, "circular cross-section" means that the aspect ratio of the first thickened portion 23 in the cross-section along the thickness direction T of the negative electrode tab 22t, as shown in Figure 5, is 0.85 or more. The aspect ratio of the first thickened portion 23 is calculated based on a cross-sectional photograph of the electrode tab (see Figure 15) obtained using a scanning electron microscope (SEM). The specific method for calculating the aspect ratio of the first thickened portion 23 is as follows: First, a cross-sectional photograph of the negative electrode tab is obtained as shown in Figure 15. Next, in this cross-sectional photograph, the first thickened portion is enclosed by a rectangle having two sides along the surface of the negative electrode core. Then, the long and short sides of the rectangle enclosing the first thickened portion are measured, and the value obtained by dividing the long side by the short side (short side / long side) is taken as the aspect ratio. In this specification, "aspect ratio" is the average value of the aspect ratio of the first thickened portion confirmed in multiple fields of view (typically one or more fields of view). The cross-sectional shape of the first thickened portion is not limited to circular or elliptical, and may have chips or distortions in part. Even if the first thickened portion has such chips or distortions, the aspect ratio can be calculated according to the procedure described above.

[0056] Furthermore, as the cross-sectional shape of the first thickened portion 23 approaches a circular shape, it is possible to prevent damage to other members (for example, the separator 30 shown in Figure 13) when they come into contact with the outer peripheral edge 22t1 of the negative electrode tab 22t. For this reason, the aspect ratio of the first thickened portion 23 is preferably 0.88 or higher, and more preferably 0.90 or higher. On the other hand, the upper limit of the aspect ratio of the first thickened portion 23 is not particularly limited and may be 1.00 or lower. Also, the first thickened portion 23 only needs to be thicker than the central portion 22t2 of the negative electrode tab 22t, and its specific thickness is not particularly limited. For example, the ratio of the thickness t1 of the first thickened portion 23 to the thickness t2 of the central portion 22t2 (t1 / t2) may be 1.1 or higher, 1.2 or higher, 1.4 or higher, or 1.5 or higher. On the other hand, the upper limit of t1 / t2 above may be 7 or less, 6 or less, 5 or less, or 3 or less.

[0057] Furthermore, in the electrode plate manufacturing method according to this embodiment, as described above, the pulse laser conditions when cutting the negative electrode core exposure region A2 (see Figure 3) are controlled to satisfy the above equation (1). When the negative electrode core exposure region A2 is melt-cut with such a pulse laser with a high overlap ratio, the molten electrode core deforms into a substantially spherical shape due to surface tension, so that areas where molten metal is concentrated and areas where molten metal is sparse are formed alternately. For this reason, the outer peripheral edge portion 22t1 of the negative electrode tab 22t of the negative electrode plate 20 according to this embodiment may alternately form a first region with a relatively thicker thickness and a second region with a relatively thinner thickness.

[0058] Furthermore, when the negative electrode core exposed region A2 is cut using a pulsed laser, the negative electrode tab 22t and the negative electrode core exposed region A2 can be separated at the moment the laser is irradiated. Therefore, there is no need to peel the negative electrode tab 22t from the negative electrode core exposed region A2, as is the case when a CW laser is used. As a result, in the manufactured negative electrode plate 20, unlike the cut marks formed by a CW laser (see Figure 19), the center point C of the first thickened portion 23 is more likely to be located between a pair of extension lines E1 and E2 extending from each surface (top and bottom) of the central portion 22t2 of the negative electrode tab 22t. When the center point C of the first thickened portion 23 is located near the center in the thickness direction of the negative electrode tab 22t in this way, the bending process of the negative electrode tab 22t becomes easier, which can contribute to improving the manufacturing efficiency of secondary batteries.

[0059] (2nd thick part) On the other hand, as shown in Figure 6, in this embodiment, a second thickened portion 25 is formed at the end of the negative electrode core 22 at the outer peripheral edge 20b1 of the electrode plate body 20b, which is thicker than the negative electrode core 22 at the central portion 20b2 of the electrode plate body 20b. This second thickened portion 25 is the trace left by the pulse laser irradiation of the negative electrode active material application region A1 of the negative electrode precursor 20A in the active material application region cutting step S2. This second thickened portion 25 is formed by the cutting of the negative electrode core 22 by a high-energy pulse laser. Furthermore, a coating layer 25b is attached to the surface of this second thickened portion 25. This coating layer 25b is the negative electrode active material layer 24 after irradiation with the pulse laser, and contains the negative electrode active material. The negative electrode active material layer 24 may also contain sintered material such as the negative electrode active material. As shown in Figure 6, the thickness of the coating layer 25b is thinner than the thickness of the negative electrode active material layer 24. Compared to a negative electrode active material layer containing molten metal, the coating layer 25b exhibits superior adhesion to the surface of the negative electrode core 22 (second thickened portion 25), thus effectively preventing the peeling and detachment of conductive foreign matter. The second thickened portion 25 and the coating layer 25b described above only need to be formed on at least one side of the outer peripheral edge (see Figure 2) of the electrode plate body 20b. Specifically, in this embodiment, the outer peripheral edge 20b1 of the electrode plate body 20b located between the negative electrode tabs 22t is cut by a pulsed laser, and the second thickened portion 25 and the coating layer 25b are formed in the region between these negative electrode tabs 22t.

[0060] Furthermore, the second thickened portion 25 has a claw shape comprising a cap portion 25a1 protruding from both or one side of the thickness direction T of the negative electrode core body 22, and a recess 25a2 formed between the cap portion 25a1 and the negative electrode core body 22. Unlike the first thickened portion 23 described above, the second thickened portion 25 is formed by a pulsed laser with high output, resulting in less melting of the negative electrode core body 22, which can lead to the claw shape described above. The coating layer 25b is embedded inside the recess 25a2 of the claw-shaped second thickened portion 25. This provides an excellent anchoring effect, further strengthening the retention of the coating layer 25b and thus more effectively preventing the detachment and peeling of fragments of the negative electrode active material layer 24. However, the formation of such a claw-shaped second thickened portion 25 can cause damage to other components (for example, the separator of the secondary battery). However, in this embodiment, since the second thickened portion 25 is covered by the coating layer 25b, damage to other components by the claw-shaped second thickened portion 25 can be effectively prevented. From the viewpoint of more effectively preventing damage to other components by the second thickened portion 25, the thickness of the coating layer 25b attached to the surface of the second thickened portion 25 is preferably 1 μm or more, more preferably 2.5 μm or more, and even more preferably 5 μm or more. On the other hand, the upper limit of the thickness of the coating layer 25b is not particularly limited and may be 20 μm or less, 17.5 μm or less, or 15 μm or less.

[0061] Furthermore, the thickness of the cap portion 25a1 of the second thickened portion 25 is preferably 1 μm or more, more preferably 2.5 μm or more, and even more preferably 4 μm or more. This allows for a more favorable anchoring effect. The "thickness of the cap portion" refers to the thickness of one side of the cap portion 25a1 with respect to the core surface. Also, from the viewpoint of more reliably preventing damage to other components, the upper limit of the thickness of the cap portion 25a1 is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. On the other hand, the width of the cap portion 25a1 (dimension in the short direction S of the negative electrode plate) is not particularly limited. For example, the width of the cap portion 25a1 may be 1 μm to 30 μm, 5 μm to 25 μm, or 10 μm to 20 μm. Furthermore, the height of the entrance to the recess 25a2 of the second thickened portion 25 (dimension in the thickness direction T) is preferably 1 μm to 10 μm, and more preferably 2.5 μm to 7.5 μm. On the other hand, the depth of the recess 25a2 of the second thickened portion 25 (dimension in the short-side direction S of the negative electrode plate) is preferably 0.1 to 10 μm, and more preferably 2.5 μm to 7.5 μm. This allows an appropriate amount of coating layer 25b to be retained inside the recess 25a2, thereby enabling a more favorable anchoring effect. In addition, the angle at which the cap portion 25a1 rises from the surface of the negative electrode core body 22 is preferably greater than 0° and 90° or less.

[0062] Furthermore, the aspect ratio of the second thickened portion 25 may be smaller than that of the first thickened portion 23. As mentioned above, since the second thickened portion 25 is a cut mark formed by a high-energy pulsed laser, unlike the first thickened portion 23, its cross-sectional shape is unlikely to be approximately circular. Specifically, the upper limit of the aspect ratio of the second thickened portion 25 may be 0.85 or less (typically 0.82 or less, e.g., 0.80 or less). On the other hand, the lower limit of the aspect ratio of the second thickened portion 25 may be 0.40 or more (typically 0.45 or more, e.g., 0.50 or more). The aspect ratio of the second thickened portion can be measured using the same procedure as the aspect ratio of the first thickened portion described above.

[0063] <Secondary battery> Next, a secondary battery fabricated using the negative electrode plate 20 according to this embodiment will be described. Figure 7 is a schematic perspective view of the secondary battery according to this embodiment. Figure 8 is a schematic longitudinal cross-sectional view along the line VIII-VIII in Figure 7. Figure 9 is a schematic longitudinal cross-sectional view along the line IX-IX in Figure 7. Figure 10 is a schematic transverse cross-sectional view along the line XX in Figure 7. Figure 11 is a schematic perspective view of the electrode body attached to the sealing plate. Figure 12 is a schematic perspective view of the electrode body to which the positive electrode second current collector and the negative electrode second current collector are attached. Figure 13 is a perspective view illustrating the electrode body of the secondary battery according to this embodiment. Figure 14 is a front view of the electrode body of the secondary battery according to this embodiment. In Figures 7 to 14, the symbol X indicates the "thickness direction" of the secondary battery 100, the symbol Y indicates the "width direction", and the symbol Z indicates the "up and down direction". Also, in the thickness direction X, F indicates the "front" and Rr indicates the "rear". In the width direction Y, L indicates "left" and R indicates "right". In the vertical direction Z, U indicates "up" and D indicates "down". However, these directions are defined for the sake of explanation and are not intended to limit the installation configuration of the secondary battery 100.

[0064] As shown in Figures 7-10, the secondary battery 100 comprises a wound electrode body 40, a battery case 50, a positive electrode terminal 60, a negative electrode terminal 65, a positive electrode current collector 70, and a negative electrode current collector 75. Although not shown in the figures, the battery case 50 of the secondary battery 100 also contains a non-aqueous electrolyte in addition to the wound electrode body 40. This non-aqueous electrolyte is prepared by dissolving a support salt in a non-aqueous solvent. Examples of non-aqueous solvents include carbonate-based solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. An example of a support salt is a fluorine-containing lithium salt such as LiPF6.

[0065] (Battery case) The battery case 50 is a housing that accommodates the wound electrode body 40. The battery case 50 has a flattened, bottomed rectangular parallelepiped (square) shape. The material of the battery case 50 can be the same as that used conventionally, and there are no particular restrictions. The battery case 50 is preferably made of metal, and more preferably of aluminum, aluminum alloy, iron, iron alloy, etc. The battery case 50 comprises an outer casing 52 and a sealing plate 54.

[0066] The outer casing 52 is a flat, bottomed, rectangular container with an opening 52h on its top surface. As shown in Figure 7, the outer casing 52 comprises a bottom wall 52a that is approximately rectangular in plan, a pair of long side walls 52b extending vertically in the Z direction from the long side of the bottom wall 52a, and a pair of short side walls 52c extending vertically in the Z direction from the short side of the bottom wall 52a. The sealing plate 54 is a plate-like member that is approximately rectangular in plan and closes the opening 52h of the outer casing 52. The outer peripheral edge of the sealing plate 54 is joined (e.g., welded) to the outer peripheral edge of the opening 52h of the outer casing 52. This creates a battery case 50 with an airtight seal inside. The sealing plate 54 is also provided with an injection hole 55 and a gas discharge valve 57. The injection hole 55 is provided for injecting a non-aqueous electrolyte into the battery case 50 after the outer casing 52 and the sealing plate 54 have been joined together. The injection hole 55 is sealed by the sealing member 56 after the non-aqueous electrolyte is injected. The gas discharge valve 57 is a thin-walled section designed to rupture (open) at a predetermined pressure when a large amount of gas is generated inside the battery case 50, thereby discharging the gas from inside the battery case 50.

[0067] (electrode terminal) Furthermore, a positive electrode terminal 60 is attached to one end (the left side in Figures 7 and 8) of the sealing plate 54 in the long side direction Y of the secondary battery 100. This positive electrode terminal 60 is connected to a plate-shaped positive electrode external conductive member 62 on the outside of the battery case 50. On the other hand, a negative electrode terminal 65 is attached to the other end (the right side in Figures 7 and 8) of the sealing plate 54 in the long side direction Y of the secondary battery 100. A plate-shaped negative electrode external conductive member 67 is also attached to this negative electrode terminal 65. These external conductive members (positive electrode external conductive member 62 and negative electrode external conductive member 67) are connected to other secondary batteries or external devices via external connecting members (bus bars, etc.). It is preferable that the external conductive members are made of a metal with excellent conductivity (aluminum, aluminum alloy, copper, copper alloy, etc.).

[0068] (Electrode current collector) The secondary battery 100 houses multiple (three in the figure) wound electrode bodies 40 inside the battery case 50. The positive electrode terminal 60 is connected to each of the multiple wound electrode bodies 40 via a positive electrode current collector 70 housed inside the battery case 50. Specifically, the positive electrode current collector 70 that connects the positive electrode terminal 60 to the wound electrode bodies 40 is housed inside the battery case 50. As shown in Figures 8 and 11, the positive electrode current collector 70 comprises a positive electrode first current collector 71, which is a plate-shaped conductive member extending along the inner surface of the sealing plate 54, and multiple positive electrode second current collectors 72, which are plate-shaped conductive members extending along the vertical direction Z. The lower end portion 60c of the positive electrode terminal 60 extends into the inside of the battery case 50 through the terminal insertion hole 58 of the sealing plate 54 and is connected to the positive electrode first current collector 71 (see Figure 8). As shown in Figures 11 and 12, the second positive electrode current collector 72 is connected to each of the positive electrode tab groups 42 of the multiple wound electrode bodies 40. Then, as shown in Figure 10, the positive electrode tab groups 42 of the wound electrode bodies 40 are bent so that the second positive electrode current collector 72 and one side surface 40a of the wound electrode bodies 40 face each other. This electrically connects the upper end of the second positive electrode current collector 72 to the first positive electrode current collector 71.

[0069] On the other hand, the negative electrode terminal 65 is connected to each of the multiple wound electrode bodies 40 via a negative electrode current collector 75 housed in the battery case 50. This negative electrode connection structure is substantially the same as the positive electrode connection structure described above. Specifically, the negative electrode current collector 75 comprises a negative electrode first current collector 76, which is a plate-shaped conductive member extending along the inner surface of the sealing plate 54, and a plurality of negative electrode second current collectors 77, which are plate-shaped conductive members extending along the vertical direction Z. The lower end portion 65c of the negative electrode terminal 65 extends into the battery case 50 through the terminal insertion hole 59 and is connected to the negative electrode first current collector 76 (see Figure 8). The negative electrode second current collectors 77 are connected to each of the negative electrode tab groups 44 of the multiple wound electrode bodies 40 (see Figures 11 and 12). The negative electrode tab group 44 is bent so that the negative electrode second current collector 77 and the other side surface 40b of the wound electrode body 40 face each other (see Figure 10). This electrically connects the upper end of the negative electrode second current collector 77 and the negative electrode first current collector 76.

[0070] (Insulating material) Furthermore, in the secondary battery 100 according to this embodiment, various insulating members are attached to prevent electrical conductivity between the wound electrode body 40 and the battery case 50. Specifically, an external insulating member 92 is interposed between the positive electrode external conductive member 62 (negative electrode external conductive member 67) and the outer surface of the sealing plate 54 (see Figure 7). This prevents the positive electrode external conductive member 62 and the negative electrode external conductive member 67 from making electrical contact with the sealing plate 54. In addition, gaskets 90 are fitted to each of the terminal insertion holes 58 and 59 of the sealing plate 54 (see Figure 8). This prevents the positive electrode terminal 60 (or negative electrode terminal 65) inserted into the terminal insertion holes 58 and 59 from making electrical contact with the sealing plate 54. Furthermore, an internal insulating member 94 is arranged between the positive electrode first current collector 71 (or negative electrode first current collector 76) and the inner surface of the sealing plate 54. The internal insulating member 94 includes a plate-shaped base portion 94a interposed between the positive electrode first current collector 71 (or negative electrode first current collector 76) and the inner surface of the sealing plate 54. This prevents the positive electrode first current collector 71 or the negative electrode first current collector 76 from making electrical contact with the sealing plate 54. Furthermore, the internal insulating member 94 includes a protruding portion 94b that protrudes from the inner surface of the sealing plate 54 toward the wound electrode body 40. This restricts the movement of the wound electrode body 40 in the vertical direction Z, preventing the wound electrode body 40 from making direct contact with the sealing plate 54. In addition, the wound electrode body 40 is housed inside the battery case 50, covered by an electrode body holder 98 (see Figure 9) made of an insulating resin sheet. This prevents the wound electrode body 40 from making direct contact with the outer casing 52. The materials used for each of the insulating components described above are not particularly limited as long as they possess the required insulating properties. For example, synthetic resin materials such as polyolefin resins (e.g., polypropylene (PP), polyethylene (PE)) and fluororesins (e.g., perfluoroalkoxyalkanes (PFA), polytetrafluoroethylene (PTFE)) can be used.

[0071] (Wound electrode body) Next, the electrode body used in the secondary battery 100 according to this embodiment will be described. In this embodiment, a wound electrode body 40 having the configuration shown in Figure 13 is used as the electrode body. The wound electrode body 40 is wound with a pair of electrode plates (positive electrode plate 10, negative electrode plate 20) facing each other via a separator 30. When manufacturing this wound electrode body 40, first, a laminate is formed by stacking a long strip-shaped positive electrode plate 10 and a long strip-shaped negative electrode plate 20 with a long strip-shaped separator 30 interposed between them. Then, after winding this laminate along the longitudinal direction, a winding stop tape 38 (see Figure 14) is attached to the end portion 30a of the separator 30 located on the outermost periphery. This allows the wound electrode body 40 to be manufactured. In this embodiment, the negative electrode plate 20 having the above structure is used in the manufacture of this wound electrode body 40. The wound electrode body 40 in this embodiment will be described below.

[0072] First, the separator 30 is a sheet-like member that prevents contact between the positive electrode plate 10 and the negative electrode plate 20, while also allowing the charge carrier to pass through. An example of such a separator 30 is a resin sheet having multiple fine pores through which the charge carrier can pass. It is preferable that such a resin sheet includes a resin layer made of polyolefin resin (for example, polyethylene (PE), polypropylene (PP)). Furthermore, a heat-resistant layer containing inorganic fillers such as alumina, boehmite, aluminum hydroxide, and titania may be formed on the surface of the resin sheet.

[0073] The positive electrode plate 10 comprises a positive electrode core 12 which is a foil-shaped metal member, a positive electrode active material layer 14 applied to the surface of the positive electrode core 12, and a protective layer 16 applied to the surface of the positive electrode core 12 so as to be adjacent to the side edge 10a of the positive electrode plate 10. Furthermore, multiple positive electrode tabs 12t protruding outward in the short direction S (left side in Figure 13) are provided on the side edge 10a of the positive electrode plate 10 at predetermined intervals in the longitudinal direction L of the positive electrode plate 10. These positive electrode tabs 12t are areas where the positive electrode active material layer 14 and protective layer 16 are not applied, and the positive electrode core 12 is exposed. From the viewpoint of battery performance, it is preferable that the positive electrode active material layer 14 and protective layer 16 are applied to both sides of the positive electrode core 12. In addition, a portion of the protective layer 16 may be applied so as to cover the side edge of the positive electrode active material layer 14. Furthermore, the materials for each component constituting the positive electrode plate 10 (positive electrode core 12, positive electrode active material layer 14, protective layer 16) can be conventionally known materials that can be used in general secondary batteries (e.g., lithium-ion secondary batteries) without any particular limitations, and since this does not limit the technology disclosed herein, a detailed explanation is omitted.

[0074] On the other hand, the configuration of the negative electrode plate 20 used in the secondary battery 100 according to this embodiment is as described above. In this negative electrode plate 20, a pulsed laser is used when cutting out the electrode plate body portion 20b from the negative electrode active material application region A1 (see Figure 3) of the negative electrode precursor 20A. Therefore, in the negative electrode plate 20 according to this embodiment, a decrease in the tackiness of the negative electrode active material layer 24 due to the inclusion of molten metal is suppressed. As a result, after the secondary battery 100 is constructed, it is possible to prevent fragments of the negative electrode active material layer 24 from falling off or peeling off and causing an internal short circuit. Furthermore, in this negative electrode plate 20, a pulsed laser similar to a CW laser is used when cutting out the negative electrode tab 22t from the negative electrode core exposure region A2 (see Figure 3) of the negative electrode precursor 20A. Therefore, in the negative electrode plate 20 according to this embodiment, the adhesion of fine metal fragments (sputter) is suppressed. As a result, after the secondary battery 100 is constructed, it is possible to prevent sputter from falling off or peeling off and causing an internal short circuit. In other words, the secondary battery 100 according to this embodiment has high safety because it prevents various conductive foreign substances from falling off or peeling off the negative electrode plate 20.

[0075] <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.

[0076] For example, in the embodiments described herein, the object of manufacture for the electrode plate manufacturing method disclosed herein is a negative electrode plate. However, the object of manufacture for the electrode plate manufacturing method disclosed herein is not limited to a negative electrode plate, but may also be a positive electrode plate. Even when a positive electrode plate is the object of manufacture, it is possible to prevent conductive foreign matter (fragments or sputter of the positive electrode active material layer) from falling off or peeling off from the electrode plate (positive electrode plate) after manufacture. It should be noted that negative electrode plates manufactured in the embodiments described herein tend to be more susceptible to a decrease in the tackiness of the electrode active material layer due to the inclusion of molten metal compared to positive electrode plates. In contrast, the electrode plate manufacturing method disclosed herein can appropriately suppress such inclusion of molten metal. For this reason, the electrode plate manufacturing method disclosed herein is particularly suitable for the manufacture of negative electrode plates.

[0077] Furthermore, in the above-described embodiment, a wound electrode body is used as the electrode body. However, the electrode body is not limited to a wound electrode body, as long as the positive electrode plate and the negative electrode plate face each other with a separator in between. Another example of the structure of the electrode body is a laminated electrode body in which multiple positive electrode plates and negative electrode plates are sequentially stacked with a separator in between. To manufacture a negative electrode plate for this type of laminated electrode body, follow the dashed line L in Figure 3. N4 It is preferable to perform cutting along the shorter direction S, as shown, for each negative electrode tab 22t. A detailed explanation is omitted, but the process for fabricating the positive electrode plate is similar. Then, multiple positive electrode plates and multiple negative electrode plates are stacked with separators in between, so that the positive electrode tabs are stacked in the same position and the negative electrode tabs of the negative electrode plates are stacked in the same position. This allows for the fabrication of a laminated electrode body.

[0078] Furthermore, the above-described embodiment targets a high-capacity secondary battery 100 in which three wound electrode bodies 40 are housed inside a battery case 50. However, the number of electrode bodies housed in a single battery case is not particularly limited and may be two or more (multiple), or it may be just one. Moreover, the secondary battery 100 according to the above-described embodiment is a lithium-ion secondary battery in which lithium ions are the charge carriers. However, the secondary battery disclosed herein is not limited to a lithium-ion secondary battery. Since the manufacturing process of other secondary batteries (e.g., nickel-metal hydride batteries) also includes a step of cutting the active material-added region and the core-exposed region of the electrode precursor with a laser, the technology disclosed herein can be applied without particular limitation.

[0079] Furthermore, the secondary battery 100 according to the above embodiment is a non-aqueous electrolyte secondary battery that uses a non-aqueous electrolyte as the electrolyte. However, the technology disclosed herein can also be applied to batteries other than non-aqueous electrolyte secondary batteries. Another example of a secondary battery structure is an all-solid-state battery. In this all-solid-state battery, a solid electrolyte layer, formed from a solid electrolyte in a sheet shape, is used as a separator interposed between the positive electrode plate and the negative electrode plate. In this all-solid-state battery, the separator and the electrolyte are integrated and contained inside the electrode body, thus preventing leakage of the electrolyte. In the manufacturing process of this type of all-solid-state battery, there is a step of cutting the active material-added region and the core-exposed region of the electrode precursor with a laser, so the technology disclosed herein can be applied without particular limitation.

[0080] [Example Test] The following describes test examples relating to the present invention. Note that the content of the test examples described below is not intended to limit the present invention.

[0081] <First Exam> (1) Prepare the sample (Example 1) In Example 1, a negative electrode for a lithium-ion secondary battery was manufactured by using pulsed lasers with different conditions for the negative electrode active material application region and the core exposure region of the negative electrode precursor. First, a negative electrode precursor was prepared in which an 8 μm thick negative electrode core (copper foil) had an 80 μm thick negative electrode active material layer applied to both sides. The negative electrode active material layer of this negative electrode precursor contained negative electrode active material, a thickener, and a binder in a ratio of 98.3:0.7:1.0. Graphite was used as the negative electrode active material, carboxymethylcellulose (CMC) as the thickener, and styrene-butadiene rubber (SBR) as the binder. Next, the negative electrode precursor was cut into a predetermined shape to produce a negative electrode plate. Specifically, when cutting the negative electrode active material application region, a pulsed laser with a pulse width of 240 ns and an overlap rate of 89% was used. On the other hand, when cutting the core exposure region, a pulsed laser with a pulse width of 240 ns and an overlap rate of 90% was used. The pulsed laser frequency for cutting the negative electrode active material application region was 300 kHz, and the pulsed laser frequency for cutting the core exposure region was 450 kHz. The spot diameter of the pulsed laser was set to 30 μm in both the negative electrode active material application region and the core exposure region.

[0082] (Comparative Example 1) In Comparative Example 1, a negative electrode for a lithium-ion secondary battery was manufactured using a pulsed laser under the same conditions for both the negative electrode active material application region and the core exposure region of the negative electrode precursor. First, the negative electrode precursor prepared in Comparative Example 1 was the same as the negative electrode precursor prepared in Example 1. Then, in Comparative Example 1, both the negative electrode active material application region and the core exposure region were cut with a pulsed laser having a pulse width of 240 ns and an overlap rate of 89%. The pulsed laser used in Comparative Example 1 had a frequency of 400 kHz and a spot diameter of 30 μm.

[0083] (Comparative Example 2) In Comparative Example 2, a negative electrode for a lithium-ion secondary battery was manufactured using a CW laser under the same conditions in both the negative electrode active material application region and the core exposure region of the negative electrode precursor. First, the negative electrode precursor prepared in Comparative Example 2 was the same as the negative electrode precursor prepared in Example 1 and Comparative Example 1. In Comparative Example 2, a CW laser with an output of 1000 W and a scanning speed of 6000 mm / sec was used. The spot diameter of the CW laser used in Comparative Example 2 was 20 μm.

[0084] (2) Evaluation Test In this study, the laser-cut areas of the negative electrode plates manufactured in each example were first observed using a scanning electron microscope (SEM). In this study, SEM observations were performed on two locations for each negative electrode plate: the side edge of the negative electrode tab and the side edge of the electrode plate body. Figure 15 is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of Example 1. Figure 16 is a cross-sectional SEM image (1000x magnification) of the electrode plate body of Example 1. Figure 17 is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of Comparative Example 1. Figure 18 is a cross-sectional SEM image (1000x magnification) of the electrode plate body of Comparative Example 1. Figure 19 is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of Comparative Example 2. Finally, Figure 20 is a cross-sectional SEM image (370x magnification) of the electrode plate body of Comparative Example 2. The following points were confirmed from the SEM images shown in Figures 15 to 20.

[0085] First, we will compare the condition of the area near the outer edge of the negative electrode tab (i.e., the area near the laser-cut core body exposure region) in each example. As shown in Figure 15, in Example 1, no metal fragments (spatter) were observed near the outer edge of the negative electrode tab. In addition, a first thickened portion, which was thicker than the central part of the negative electrode tab, was formed on the outer edge of this negative electrode tab. This first thickened portion is presumed to be solidified molten negative electrode core body. The aspect ratio of the first thickened portion formed on the negative electrode tab of Example 1 was 0.95. On the other hand, as shown in Figure 17, in Comparative Example 2, a large amount of spatter was found to be attached near the outer edge of the negative electrode tab. In addition, the aspect ratio of the first thickened portion formed on the negative electrode tab of Comparative Example 1 was 0.82. And, as shown in Figure 19, no spatter was found near the outer edge of the negative electrode tab in Comparative Example 2. Furthermore, the first thickened portion formed on the negative electrode tab in Comparative Example 2 had an aspect ratio of 0.96. From the above, it was found that in Example 1, which used a pulsed laser with conditions approximated to a CW laser, and in Comparative Example 2, which used a CW laser, sputter generation during cutting of the core body exposed region was suppressed, and a first thickened portion with a substantially circular cross-sectional shape was formed on the outer edge of the negative electrode tab. In addition, in Comparative Example 2, the center of the first thickened portion with a substantially circular cross-section was shifted downward from the center in the thickness direction of the negative electrode core. This is presumed to be because, in Comparative Example 2, which used a CW laser, the negative electrode tab was not completely separated from the core body exposed region immediately after laser irradiation, and it was necessary to peel the negative electrode tab from the core body exposed region, and the laser cutting marks (first thickened portion) were pulled during the peeling of the negative electrode tab.

[0086] Next, we will compare and examine the condition of the area near the side edge of the electrode plate body (i.e., the area near the laser-cut active material layer) in each example. First, as shown in Figure 16, in Example 1, a second thickened portion was formed at the end of the negative electrode core at the side edge of the negative electrode plate body, which was thicker than the negative electrode core in the central part of the electrode plate body. Furthermore, a coating layer containing negative electrode active material was attached to the surface of this second thickened portion. Also, as shown in Figure 18, in Comparative Example 1, a second thickened portion was formed at the end of the negative electrode core at the side edge of the negative electrode plate body, and a coating layer containing negative electrode active material was attached to the surface of this second thickened portion. On the other hand, as shown in Figure 20, in Comparative Example 2, no thickened portion was formed at the end of the negative electrode core. Furthermore, negative electrode active material mixed with molten metal was attached to the side edge of the electrode plate body in Comparative Example 2. It was found that this negative electrode active material attached to the side edge of the electrode plate body could be easily detached and peeled off by a small impact.

[0087] From the above test results, it was found that in order to prevent conductive foreign matter (fragments and sputtering of the negative electrode active material layer) from detaching and peeling off from the negative electrode plate after manufacturing, it is sufficient to use pulse lasers with different conditions for the negative electrode active material application region and the core exposure region when cutting the negative electrode plate from the negative electrode precursor.

[0088] <Second Exam> In this study, eight different test examples were prepared, using pulsed lasers with different conditions in the negative electrode active material application region and the core exposure region, as in Example 1 of the first test. The negative electrode plates fabricated in each test example were then observed to investigate the pulsed laser conditions that could suppress sputter generation during laser cutting in the core exposure region. The specific conditions are described below.

[0089] (1) Prepare the sample (Test examples 1-8) As described above, in this study, eight test examples (Test Examples 1-8) were prepared, using pulse lasers with different conditions for the negative electrode active material application region and the core exposure region of the negative electrode precursor. The negative electrode precursor prepared in this study is the same as the negative electrode precursor prepared in the first study described above. In this study, the pulse width and overlap rate of the pulse laser used to cut the core exposure region were varied in each test example. The conditions of the pulse laser in each test example are shown in Table 1 below.

[0090] (2) Evaluation Test Similar to the first test, a cross-sectional SEM was performed on the negative electrode plate after manufacturing, and the condition near the outer edge of the negative electrode tab was compared. The results are shown in Figure 21 and Table 1. In Figure 21 and Table 1, "○" indicates that no sputter adhesion was observed in the SEM observation and the aspect ratio of the first thickened portion was 0.85 or higher. On the other hand, "×" indicates that one or more sputter particles were observed and the aspect ratio of the first thickened portion was less than 0.85.

[0091] [Table 1]

[0092] As shown in Table 1 and Figure 21, in Test Examples 1, 3, 5, and 7, sputtering was suppressed, and a first thickened portion with a roughly circular cross-section was formed at the end of the negative electrode core after cutting. Furthermore, as shown in Figure 21, it was found that sputtering tended to be suppressed more easily as the overlap rate of the pulsed laser increased. On the other hand, the results of this test also confirmed that sputtering tended to be suppressed more easily as the pulse width of the pulsed laser increased. It was found that there is a threshold for the pulsed laser conditions that can suppress sputtering between Test Examples 1, 3, 5, and 7, where sputtering was suppressed, and Test Examples 2, 4, 6, and 8, where sputtering was not suppressed. From the results of this test, it is understood that this threshold that enables sputtering suppression is given by the following equation (1). Y≧-3logX+10⁶ (1)

[0093] 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]

[0094] 10 Positive plate 12 Positive electrode core 12t positive electrode tab 14 Cathode active material layer 16 Protective layer 20 Negative electrode plates 20A negative electrode precursor 20b Plate main body 22 Negative electrode core 22t negative electrode tab 23 1st thick part 24 Negative electrode active material layer 25 2nd thick part 25b Covering layer 30 Separators 38. Retaining tape 40 Wound electrode body 42 Positive electrode tab group 44 Negative electrode tab group 50 Battery Case 60 Positive terminal 65 Negative terminal 70 Positive electrode current collector 75 Negative electrode current collector 100 Secondary battery A1 Negative electrode active material application region A2 Negative electrode core exposed area A3 Overlapping irradiation area A4 Single Irradiation Area S1 Precursor preparation process S2 Active material application area cutting process S3 Core exposed area cutting process

Claims

1. A secondary battery comprising an electrode body in which a positive electrode plate and a negative electrode plate face each other via a separator, The aforementioned negative electrode plate is A negative electrode plate comprising an electrode core which is a foil-shaped metal member, and an electrode active material layer which is applied to the surface of the electrode core and contains an electrode active material, An electrode plate body portion having the electrode active material layer applied to the surface of the electrode core, In a region where the electrode active material layer is not applied and the electrode core is exposed, an electrode tab protrudes outward from a part of the outer peripheral edge of the electrode plate body and Equipped with, A first thickened portion is formed on the outer edge of the electrode tab, which is thicker than the central portion of the electrode tab, and the aspect ratio of the first thickened portion in a cross-sectional view along the thickness direction of the electrode tab is 0.85 or greater. A second thickened portion is formed at the end of the electrode core on at least one side of the outer peripheral edge of the electrode plate body, and the thickness is greater than that of the electrode core in the central part of the electrode plate body, and a coating layer containing the electrode active material is attached to the surface of the second thickened portion. The negative electrode plate comprises a negative electrode core made of copper or a copper alloy, and a negative electrode active material layer containing a carbon material as the electrode active material. The second thickened portion has a claw shape comprising a cap portion protruding from both or one side in the thickness direction and a recess formed between the cap portion and the electrode core. The electrode tab protrudes outward from the end of the separator. The electrode tab has an end edge located at the tip in the direction of projection from the electrode plate body and located outside the end of the separator in the projection direction. The end edge is provided with the first thickened portion. The outer peripheral edge of the electrode plate body is facing the separator, in a secondary battery.

2. The secondary battery according to claim 1, wherein the thickness of the coating layer attached to the surface of the second thickened portion is 1 μm to 20 μm.

3. The secondary battery according to claim 1 or 2, wherein the center point of the first thickened portion is located between a pair of extension lines extending from each surface of the central part of the electrode tab.

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