Methods for manufacturing electrode plates, methods for manufacturing secondary batteries, electrode plates and secondary batteries

Abstract

This disclosure relates to a method for manufacturing an electrode plate, a method for manufacturing a secondary battery, an electrode plate, and a secondary battery, which can prevent conductive foreign matter from detaching or peeling off from the manufactured electrode plate and contribute to the improvement of the safety of the secondary battery. The electrode plate manufacturing method disclosed herein is characterized by comprising: a precursor preparation step, preparing an electrode precursor having an active material-assigned region and a core-exposed region, the active material-assigned region being a region on the surface of an electrode core to which an electrode active material layer is applied, and the core-exposed region being a region where the electrode core is exposed without an electrode active material layer applied; an active material-assigned region cutting step, cutting the active material-assigned region using a pulsed laser; and a core-exposed region cutting step, cutting the core-exposed region using a pulsed laser. Furthermore, when the pulse width of the pulsed laser in the core-exposed region cutting step is set to X and the overlap rate is set to Y, the condition shown by Y≥-3logX+106 is satisfied.

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 batteries, typically include electrode bodies with positive and negative electrodes facing each other separated by a spacer. Hereinafter, these positive and negative electrodes will be collectively referred to as "electrode plates." Each electrode plate, for example, includes an electrode core as a foil-shaped metal component and an electrode active material layer applied to the surface of the electrode core, containing electrode active material. In manufacturing this type of electrode plate, firstly, an electrode active material layer is applied to the surface of a large electrode core. This forms a precursor for the electrode plate (hereinafter referred to as the "electrode precursor"). Then, an electrode plate of the desired size is cut from the electrode precursor using a laser or the like. An example of a technique related to the cutting of this electrode plate is disclosed in Patent Documents 1 and 2.

[0003] Furthermore, in the electrode precursor of the above structure, the thickness of the electrode active material layer tends to become uneven at the outer periphery of the region where the electrode active material layer is applied (active material application area). Therefore, when cutting the electrode plate from the electrode precursor, the outer periphery of the active material application area is typically removed using a laser. Additionally, in a typical electrode plate, to ensure the connection position with conductive components such as electrode terminals, a portion of the electrode core (metal foil) needs to be exposed. Therefore, in the cutting of the electrode plate, a process is also performed whereby a portion of the area where the electrode core is exposed by the substrate (core exposed area) without the electrode active material layer applied is cut out to form an electrode tab. As described above, in the manufacturing of the electrode plate, the processes of cutting the active material application area and cutting the core exposed area are performed (see, for example, Patent Document 1).

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-34009

[0007] Patent Document 2: Japanese Patent Application Publication No. 2016-33912 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, the electrode plates manufactured using the above methods are characterized by the easy detachment and peeling of fragments and fine metal sheets (sputterings) from the electrode active material layer. Furthermore, if these conductive foreign objects detach or peel off inside the secondary battery, they may become a cause of internal short circuits.

[0010] The present invention was made in view of the above-mentioned problems, and its object is to provide a technology that can prevent conductive foreign matter from falling off or peeling off from the manufactured electrode plate and contribute to the improvement of the safety of secondary batteries.

[0011] Solution for solving the problem

[0012] As a result of various studies conducted to solve the above-mentioned problems, the inventors discovered the causes of the shedding and peeling of fragments of the electrode active material layer and the shedding and peeling of sputtered material.

[0013] First, the reasons for the detachment and peeling of the electrode active material layer will be explained. As described above, in the manufacture of the electrode plate, the outer periphery of the active material delivery area is removed using a laser. At this time, the electrode core sometimes melts due to the heat of the laser and mixes with a portion of the electrode active material layer. Furthermore, since the adhesion of the electrode active material layer mixed with this molten metal is significantly reduced, it is easily detached and peeled off by even minor impacts. To suppress the reduction in adhesion of the electrode active material layer caused by the incorporation of this molten metal, the inventors conceived of using a pulsed laser to cut the active material delivery area. This pulsed laser can repeatedly irradiate the area with very short time intervals, allowing for concentrated application of large amounts of energy to the cut portion. Therefore, the electrode core can be quickly cut off with a small amount of molten metal remaining.

[0014] Next, the reasons for the detachment and peeling of the fine metal sheets (sputtered material) will be explained. As mentioned above, in the manufacture of the electrode plate, a portion of the core exposed area needs to be cut out in order to form the electrode tabs. However, when a high-energy laser is irradiated onto the exposed portion of the metal component, such as the core exposed area, sputtered material may scatter from the irradiated area. Furthermore, when this sputtered material adheres to the electrode plate, it becomes a fine metal sheet that is easily detached and peeled off by even minor impacts. To suppress the scattering of this sputtered material, the inventors conceived of using a continuous wave laser (CW laser) to cut the core exposed area. For this CW laser, a low-energy laser is continuously irradiated to melt and cut the electrode core. Thus, the electrode tabs can be formed while suppressing the scattering of sputtered material.

[0015] As described above, according to the inventors' research, to prevent the shedding or peeling of fragments from the electrode active material layer, pulsed lasers are needed to cut the active material-bearing region, and CW lasers are needed to prevent the shedding or peeling of sputtered material from the core-exposed region. However, the method of cutting the active material-bearing region and the core-exposed region separately by switching the laser used results in a significant reduction in manufacturing efficiency, making it difficult to implement in actual manufacturing environments. Furthermore, when cutting the active material-bearing region and the core-exposed region separately, it is required that the cut lines formed in each region be connected without offset, which may also lead to frequent cutting defects. Considering this, the inventors have researched a method that can continuously cut the active material-bearing region and the core-exposed region while preventing the generation of the aforementioned two types of conductive foreign matter.

[0016] The electrode plate manufacturing method disclosed herein is based on the above-mentioned insights. It manufactures an electrode plate having an electrode core and an electrode active material layer, wherein the electrode core is a metal foil, and the electrode active material layer is applied to the surface of the electrode core and contains electrode active material. Furthermore, the electrode plate manufacturing method includes: a precursor preparation step, in which an electrode precursor having an active material application region and a core exposure region is prepared, wherein the active material application region is a region on the surface of the electrode core to which the electrode active material layer is applied, and the core exposure region is a region where the electrode core is exposed without an electrode active material layer; an active material application region cutting step, in which the active material application region is cut using a pulsed laser; and a core exposure region cutting step, in which the core exposure region is cut using a pulsed laser. Furthermore, in the electrode plate manufacturing method disclosed herein, the following condition is satisfied when the pulse width (ns) of the pulsed laser in the core exposure region cutting step is set to X and the overlap rate (%) is set to Y:

[0017] Y≥-3logX+106 (1).

[0018] In the manufacturing method of the electrode plate with the above-described structure, a pulsed laser is used when cutting the active material delivery area. This prevents molten metal from the electrode core from mixing into the electrode active material layer, thus preventing fragments of the electrode active material layer from detaching or peeling off from the manufactured electrode plate. On the other hand, in the manufacturing method disclosed herein, to prevent a significant decrease in manufacturing efficiency and the occurrence of poor cutting, a pulsed laser is also used when cutting the core exposure area, continuously cutting both the active material delivery area and the core exposure area. However, in the manufacturing method disclosed herein, the state of the pulsed laser used to cut the core exposure area is close to that of a CW laser. Specifically, according to experiments conducted by the inventors, a pulsed laser satisfying the above formula (1) can increase the melting amount of the electrode core to the same level as a CW laser. This allows for melting and cutting of the electrode core, suppressing the scattering of sputtered material. As described above, according to the manufacturing method of the electrode plate disclosed herein, since conductive foreign matter can be prevented from detaching or peeling off from the manufactured electrode plate, it contributes to improving the safety of the secondary battery.

[0019] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the frequency of the pulsed laser in the active material imparting area cutting process is lower than the frequency of the pulsed laser in the core exposure area cutting process. This allows for more effective prevention of the detachment and peeling of fragments and sputtered material from the electrode active material layer.

[0020] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the frequency of the pulsed laser in the active material imparting area cutting process is 100 kHz to 2000 kHz. This allows for more appropriate prevention of the shedding or peeling of fragments from the electrode active material layer.

[0021] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the pulse width X of the pulsed laser in the core exposed area cutting process is 30 ns to 240 ns. This allows for more appropriate prevention of sputtering material detachment and peeling.

[0022] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the overlap rate of the pulsed laser in the active material imparting area cutting process is smaller than the overlap rate of the pulsed laser in the core exposure area cutting process. This allows for more appropriate prevention of the detachment and peeling of fragments and sputtered material from the electrode active material layer.

[0023] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the overlap rate of the pulsed laser in the core exposed area cutting process is 90% to 99%. This allows for more appropriate prevention of sputtering material detachment and peeling.

[0024] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the electrode plate is a negative electrode plate comprising a negative electrode core made of copper or a copper alloy and a negative electrode active material layer containing carbon material as the electrode active material. This structure of negative electrode plate is particularly prone to a decrease in the adhesion of the electrode active material layer due to the incorporation of molten metal. However, according to the electrode plate manufacturing method disclosed herein, the decrease in the adhesion of the electrode active material layer can be appropriately suppressed during the manufacturing of this structure of negative electrode plate.

[0025] As another aspect of the technology disclosed herein, a method for manufacturing a secondary battery is provided. Specifically, the technology disclosed herein provides a method for manufacturing a secondary battery comprising an electrode body having a pair of electrode plates facing each other with a spacer between them, characterized in that at least one of the pair of electrode plates is manufactured using the electrode plate manufacturing method described above. According to this manufacturing method, since conductive foreign matter (fragments of the electrode active material layer, sputterings) can be suppressed from detaching and peeling off from the electrode plates inside the secondary battery, a secondary battery with excellent safety can be obtained.

[0026] Additionally, as another aspect of the technology disclosed herein, an electrode plate is provided. This electrode plate includes: 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 the electrode active material. Furthermore, the electrode plate includes: an electrode plate main body portion, on which the electrode active material layer is applied to the surface of the electrode core; and electrode tabs, which are areas of the electrode core exposed where no electrode active material layer is applied, protruding outward from a portion of the outer periphery of the electrode plate main body portion. Moreover, the electrode plate disclosed herein has a first thick-walled portion formed at the outer periphery of the electrode tabs, which is thicker than the central portion of the electrode tabs, and the aspect ratio of the first thick-walled portion in cross-section along the thickness direction of the electrode tabs is 0.85 or more. Furthermore, a second thick-walled portion, thicker than the electrode core portion at the central portion of the electrode plate main body portion, is formed at at least one end of the electrode core at the outer periphery of the electrode plate main body portion, and a coating layer containing the electrode active material is attached to the surface of the second thick-walled portion.

[0027] The electrode plate disclosed herein is manufactured using the method described above. Specifically, the electrode plate has a first thick-walled portion formed on the outer periphery of the electrode tab. This first thick-walled portion is a laser-cut mark. Furthermore, in the method for manufacturing the electrode plate with the above structure, when cutting out the electrode tab (cutting out the core exposed area), the pulsed laser conditions are made close to those of a CW laser. When performing molten cutting using such a pulsed laser, since the amount of melting of the electrode core becomes the same as that of a CW laser, the cross-sectional shape of the cutting mark (first thick-walled portion) becomes approximately circular (with an aspect ratio of 0.85 or higher). On the other hand, in the method for manufacturing the electrode plate with the above structure, when cutting out the electrode plate body (cutting out the active material delivery area), a high-energy pulsed laser is used to suppress the decrease in adhesion of the electrode active material layer caused by the mixing of molten metal. Therefore, a coating layer containing the electrode active material is attached to the laser-cut mark (second thick-walled portion) formed on the outer periphery of the electrode plate body. This coating layer differs from the electrode active material layer mixed with molten metal, making it difficult to peel off or detach from the electrode core.

[0028] Furthermore, in a preferred embodiment of the electrode plate disclosed herein, the second thick-walled portion has a claw shape, the claw shape having a cap-shaped portion protruding to both sides or one side in the thickness direction and a recess formed between the cap-shaped portion and the electrode core. As described above, the second thick-walled portion is a laser cutting mark formed by a high-energy pulsed laser. When using a high-energy pulsed laser, since the amount of metal melted during cutting becomes very small, a claw-shaped cutting mark (second thick-walled portion) as described above is sometimes formed. Since this claw-shaped second thick-walled portion can provide excellent anchoring effect, it is possible to more effectively prevent the electrode active material layer from detaching or peeling off.

[0029] Furthermore, in a preferred embodiment of the electrode plate disclosed herein, the thickness of the coating layer attached to the surface of the second thick-walled portion is 1 μm to 20 μm. Therefore, since the second thick-walled portion can be appropriately coated with the coating layer of the electrode active material, damage to other components (e.g., spacers in a secondary battery) can be appropriately prevented using the second thick-walled portion.

[0030] Furthermore, in a preferred embodiment of the electrode plate disclosed herein, the center point of the first thick-walled portion is disposed between a pair of extended lines extending from each surface of the central portion of the electrode tab. For this electrode plate structure, the bending process of the electrode tab is easy, thus contributing to improved manufacturing efficiency of the secondary battery. Such a first thick-walled portion can be formed when the electrode tab is cut using a pulsed laser satisfying the above formula (1).

[0031] Furthermore, in a preferred embodiment of the electrode plate disclosed herein, the first thick-walled portion has a first region with a relatively thick thickness and a second region with a relatively thin thickness, and the first and second regions are alternately formed along the outer periphery of the electrode tab. In the manufacturing method of the electrode plate with the above structure, the electrode core (negative electrode tab) is melted and cut using a pulsed laser with a high overlap rate satisfying formula (1). In this case, the molten electrode core deforms into a roughly spherical shape due to surface tension, thus alternately forming a first region as a location where molten metal accumulates and a second region as a location where molten metal becomes sparse.

[0032] As another aspect of the technology disclosed herein, a secondary battery is provided. Specifically, the technology disclosed herein provides a secondary battery having a pair of electrode plates facing each other with a spacer between them, characterized in that at least one of the pair of electrode plates uses an electrode plate with the above-described structure. Thus, since conductive foreign matter (fragments of the electrode active material layer, sputterings) can be suppressed from leaching from the electrode plates, the safety of the secondary battery can be improved. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating a method for manufacturing an electrode plate according to one embodiment.

[0034] Figure 2 This is a schematic top view of a negative electrode plate manufactured in a method for manufacturing an electrode plate according to one embodiment.

[0035] Figure 3 This is a top view illustrating a method for manufacturing an electrode plate according to one embodiment.

[0036] Figure 4 This is a graph illustrating the overlap rate of pulsed lasers.

[0037] Figure 5 yes Figure 2 VV-direction sectional view.

[0038] Figure 6 yes Figure 2 Sectional view from VI to VI.

[0039] Figure 7 This is a perspective view schematically showing one embodiment of a secondary battery.

[0040] Figure 8 It is along Figure 7 A schematic longitudinal section view of lines VIII-VIII in the diagram.

[0041] Figure 9 It is along Figure 7 A schematic longitudinal section view of the IX-IX line.

[0042] Figure 10 It is along Figure 7 A schematic cross-sectional view of the XX line.

[0043] Figure 11 It is a schematic perspective view of the electrode body installed on the sealing plate.

[0044] Figure 12 It is a perspective view schematically showing an electrode body with a positive second collector and a negative second collector installed.

[0045] Figure 13 This is a perspective view illustrating the electrode body of a secondary battery according to one embodiment.

[0046] Figure 14 This is a front view of the electrode body of a secondary battery according to one embodiment.

[0047] Figure 15 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate in the embodiment.

[0048] Figure 16 This is a cross-sectional SEM image (1000x magnification) of the side edge of the main body of the negative electrode plate in the embodiment.

[0049] Figure 17 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate in Comparative Example 1.

[0050] Figure 18 This is a cross-sectional SEM image (1000x magnification) of the side edge of the negative electrode body of Comparative Example 1.

[0051] 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.

[0052] Figure 20 This is a cross-sectional SEM image (370x magnification) of the side edge of the negative electrode body of Comparative Example 2.

[0053] Figure 21 This is a graph showing the relationship between the overlap rate and pulse width for each sample measured in the second experiment.

[0054] Explanation of reference numerals in the attached figures

[0055] 10 Positive electrode plate

[0056] 12 Positive electrode core

[0057] 12t positive electrode tab

[0058] 14 Positive electrode active material layer

[0059] 16 protective layers

[0060] 20 Negative electrode plate

[0061] 20A Negative Electrode Precursor

[0062] 20b Electrode plate main body

[0063] 22 Negative electrode core

[0064] 22t negative electrode tab

[0065] 23 First Thick-walled Section

[0066] 24 Negative electrode active material layer

[0067] 25 Second thick-walled section

[0068] 25b coating layer

[0069] 30 spacers

[0070] 38. Winding fixing tape

[0071] 40. Winded electrode body

[0072] 42 Positive electrode tabs

[0073] 44 Negative electrode tabs

[0074] 50 Battery casing

[0075] 60 Positive extremes

[0076] 65 Negative extremes

[0077] 70 Positive current collector

[0078] 75 Negative electrode current collector

[0079] 100 rechargeable batteries

[0080] A1 Anode Active Material Conferring Region

[0081] A2 Exposed area of ​​negative electrode core

[0082] A3 Overlapping Irradiation Area

[0083] A4 Single Irradiation Area

[0084] S1 Precursor Preparation Process

[0085] S2 Active substance delivery area cutting process

[0086] S3 Core Exposed Area Cutting Process. Detailed Implementation

[0087] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the accompanying drawings. Furthermore, matters necessary for implementing the technology disclosed herein (e.g., the general structure and manufacturing process of a battery) other than those specifically mentioned in this specification can be understood as design matters for those skilled in the art based on prior art. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the field. Furthermore, the expression "A to B" indicating a range in this specification includes the meaning of A or more and B or less, and includes the meanings of "preferably larger than A" and "preferably smaller than B".

[0088] Furthermore, in this specification, "secondary battery" generally refers to an energy storage device that generates a charging and discharging reaction by moving charge carriers between a pair of electrodes (positive and negative electrodes) via an electrolyte. This secondary battery includes not only so-called storage batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, but also capacitors such as electric double-layer capacitors. Hereinafter, an embodiment is described using a lithium-ion secondary battery as the object.

[0089] <Method for manufacturing electrode plates>

[0090] The method for manufacturing an electrode plate disclosed herein is a method for manufacturing an electrode plate having an electrode core and an electrode active material layer, wherein the electrode core is a metal foil, and the electrode active material layer is applied to the surface of the electrode core and contains electrode active material. Hereinafter, as an embodiment of the method for manufacturing an electrode plate disclosed herein, a method for manufacturing an electrode plate (negative electrode plate) on the negative electrode side of a secondary battery will be described. Figure 1 This is a flowchart illustrating a method for manufacturing the electrode plate according to this embodiment. Figure 2 This is a schematic top view of the negative electrode plate manufactured in the electrode plate manufacturing method of this embodiment. Figure 3 This is a top view illustrating the manufacturing method of the electrode plate according to this embodiment. Additionally, Figure 4 This is a graph illustrating the overlap rate of pulsed lasers. Figure 5 yes Figure 2 The VV-direction sectional view in the image. Additionally... Figure 6 yes Figure 2 The VI-VI sectional view. Furthermore... Figure 2 , 3 In the figures 5 and 6, reference numeral L indicates the "long side direction" of the negative electrode plate 20 (or negative electrode precursor 20A), reference numeral S indicates the "short side direction", and reference numeral T indicates the "thickness direction".

[0091] like Figure 1As shown, the electrode plate manufacturing method of this embodiment includes a precursor preparation step S1, an active material delivery area cutting step S2, and a core exposed area cutting step S3. Thus, a electrode plate is manufactured... Figure 2 The negative electrode plate 20 shown is an example of a structure. Following an overview of the negative electrode plate 20, which is the subject of this description, the following will discuss... Figure 1 Each process shown is explained.

[0092] (Overview of the negative electrode plate)

[0093] like Figure 2 As shown, the negative electrode plate 20 is a strip-shaped component. The negative electrode plate 20 includes a negative electrode core 22 as a foil-shaped metal component and a negative electrode active material layer 24 applied to the surface of the negative electrode core 22. Furthermore, 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. Moreover, the negative electrode plate 20 has two regions when viewed from above: an electrode plate body portion 20b and a negative electrode tab 22t. The electrode plate body portion 20b is the region on the surface of the negative electrode core 22 where 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 core 22 is exposed without the negative electrode active material layer 24 applied. Additionally, the negative electrode tab 22t extends outward from a portion of the outer periphery 20b1 of the electrode plate body portion 20b (in... Figure 2 The middle section protrudes above the shorter side (S). Additionally, Figure 2 The negative electrode plate 20 shown has a plurality of negative electrode tabs 22t. The plurality of negative electrode tabs 22t are arranged at predetermined intervals along the long side direction L of the negative electrode plate 20.

[0094] The components constituting the negative electrode plate 20 can be made of materials that are commonly used in conventional secondary batteries without particular limitations. For example, the negative electrode core 22 can preferably be made of a metallic material with a predetermined conductivity. The negative electrode core 22 is preferably made of copper or a copper alloy, for example. In addition, 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.

[0095] The negative electrode active material layer 24 is a layer containing the negative electrode active material. For the negative electrode active material, a material capable of reversibly absorbing and releasing charge carriers in relation to the positive electrode active material can be used. Examples of such negative electrode active materials include carbon materials and silicon-based materials. Examples of carbon materials include graphite, hard carbon, soft carbon, and amorphous carbon. Alternatively, graphite with amorphous carbon coating can be used. On the other hand, examples of silicon-based materials include silicon and silicon oxide (silicon dioxide). Furthermore, silicon-based materials may also contain other metallic elements (e.g., alkaline earth metals) or their oxides. Additionally, 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 carboxymethyl cellulose (CMC). Furthermore, when the solid content of the negative electrode active material layer 24 is set to 100% by mass, the content of the negative electrode active material is approximately 30% by mass or more, typically 50% by mass or more. Additionally, the negative electrode active material can occupy either 80% or more by mass of the negative electrode active material layer 24, or 90% or more by mass. Furthermore, 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.

[0096] like Figure 1 As shown, the negative electrode plate 20 with the above structure is manufactured by performing the precursor preparation step S1, the active material delivery area cutting step S2, and the core exposed area cutting step S3. Each step will be described below.

[0097] (Preparation step S1)

[0098] In this process, an electrode precursor is prepared as the precursor to the electrode plate. Figure 3 The electrode precursor shown is the precursor to the negative electrode plate (negative electrode precursor 20A). This negative electrode precursor 20A has a negative electrode core 22 formed as a strip-shaped metal foil. The area of ​​the negative electrode core 22 of the negative electrode precursor 20A is larger than that of the manufactured negative electrode plate 20 (see reference). Figure 2The negative electrode core 22 has a large area. Furthermore, a negative electrode active material layer 24 is applied to the surface of the negative electrode core 22. Additionally, the negative electrode active material layer 24 is applied to the central portion of the negative electrode core 22 in the short-side direction S, extending along the long-side direction L. In this specification, the area where the negative electrode active material layer 24 is applied is referred to as the "negative electrode active material application area A1". On the other hand, the two side edges of the negative electrode precursor 20A (the areas outside the negative electrode active material layer 24 in the short-side direction S) are not coated with the negative electrode active material layer 24, and the negative electrode core 22 is exposed. In this specification, the area where the negative electrode core 22 is exposed is referred to as the "negative electrode core exposure area A2". The means of preparing the negative electrode precursor 20A with the above structure are not particularly limited, and various conventionally known methods can be used without particular restriction. For example, the negative electrode precursor 20A can be manufactured by applying a raw material paste containing a negative electrode active material, etc., to the surface of the negative electrode core 22 and then allowing it to dry. Furthermore, this process is not particularly limited to simply having the negative electrode precursor 20A available. For example, a separately manufactured negative electrode precursor 20A can also be purchased and prepared. Moreover, the negative electrode precursor is not limited to... Figure 2 The structure shown is as follows. For example, the negative electrode precursor can also be constructed such that the negative electrode core is exposed only on one side edge.

[0099] (Active substance imparting area cutting process S2)

[0100] In this process, a pulsed laser is used to cut the negative electrode active material delivery region A1 of the negative electrode precursor 20A. Specifically, in the active material delivery region cutting process S2, as follows... Figure 3 The dashed line L in N1 As shown, a pulsed laser is scanned along the side edge A1a of the negative electrode active material delivery region A1. This removes the side edge A1a of the negative electrode active material delivery region A1, where the thickness of the negative electrode active material layer 24 is uneven, thus enabling the fabrication of a negative electrode plate 20 with a uniform thickness of the negative electrode active material layer 24. Here, as shown by the dashed line L above… N1When the negative electrode active material delivery area A1 is cut using a laser as shown, a portion of the negative electrode core 22, which melts due to the heat of the laser, may become mixed into the negative electrode active material layer 24. Furthermore, when the molten metal solidifies within the negative electrode active material layer 24, the adhesiveness of the negative electrode active material layer 24 is significantly lost, and fragments of the negative electrode active material layer 24 may easily detach or peel off due to minor impacts. In the active material delivery area cutting process S2 of this embodiment, a pulsed laser is used when cutting the negative electrode active material delivery area A1 to prevent a decrease in adhesiveness caused by the mixing of molten metal. Since the pulsed laser can concentrate and apply a large amount of energy (high peak output) at short time intervals, the negative electrode core 22 can be cut quickly with a small amount of molten metal. Therefore, since the decrease in adhesiveness of the negative electrode active material layer 24 caused by the mixing of molten metal can be suppressed, the detachment or peeling of fragments of the negative electrode active material layer 24 can be prevented.

[0101] Furthermore, the conditions of the pulsed laser in the active material imparting area cutting process S2 are not particularly limited, but preferably, they are appropriately adjusted 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 process is preferably 70W to 1000W, more preferably 100W to 900W, and even more preferably 150W to 800W. This prevents the negative electrode active material layer 24 from detaching or peeling off, and makes it easier to cut the negative electrode precursor 20A. Specifically, there is a tendency that as the average output of the pulsed laser increases, the cutting of the negative electrode precursor 20A becomes easier. On the other hand, since the impact during laser irradiation is reduced as the average output of the pulsed laser decreases, it is possible to prevent a portion of the negative electrode active material layer 24 from being blown away by the laser impact.

[0102] Furthermore, the repetition frequency of the pulsed laser in the active material imparting area cutting process S2 is preferably 100 kHz to 2000 kHz, more preferably 150 kHz to 1500 kHz, and even more preferably 200 kHz to 1000 kHz. This prevents the molten negative electrode core 22 from mixing into the negative electrode active material layer 24 and allows for easy cutting of the negative electrode precursor 20A. Specifically, when the pulsed laser frequency is lower, the peak output is higher, thus making it easier to cut the negative electrode core 22. On the other hand, when the pulsed laser frequency is higher, the peak output is lower, thus preventing a portion of the irradiated negative electrode active material layer 24 from being blown away. Additionally, the spot diameter of the pulsed laser in the active material imparting area cutting process S2 is preferably 10 μm to 60 μm, more preferably 20 μm to 50 μm, and even more preferably 25 μm to 40 μm. This allows for easy cutting of the negative electrode plate 20 from the negative electrode precursor 20A.

[0103] Furthermore, it is preferable that the overlap rate of the pulsed laser in the active material imparting region cutting step S2 is smaller than the overlap rate of the pulsed laser in the core exposure region cutting step S3 described later. There is a tendency that as the overlap rate of the pulsed laser decreases, it is easier to cut the negative electrode core 22 with a small amount of molten material. On the other hand, since the state of the pulsed laser approaches that of a CW laser as the overlap rate increases, there is a tendency to easily suppress the generation of sputtering material described later. Therefore, in the active material imparting region cutting step S2, where the incorporation of the molten negative electrode core 22 is a problem, it is preferable to use a pulsed laser with a smaller overlap rate. Specifically, the overlap rate of the pulsed laser in the active material imparting region cutting step S2 is preferably 40% to 95%, more preferably 50% to 90%, and even more preferably 70% to 90%.

[0104] Next, the scanning speed of the pulsed laser in the active material imparting area cutting process S2 is preferably 5000 mm / sec or less, more preferably 3000 mm / sec or less. By slowing down the scanning speed in this way, poor cutting of the negative electrode core 22 can be suppressed. On the other hand, the lower limit of the pulsed laser scanning speed is not particularly limited, and can also be 20 mm / sec or more. Furthermore, from the viewpoint of improving manufacturing efficiency due to the shortening of the cutting time, the lower limit of the pulsed laser scanning speed is preferably 200 mm / sec or more, more preferably 500 mm / sec or more. In addition, the pulse width of the pulsed laser in the active material imparting area cutting process S2 is preferably 30 ns to 240 ns, more preferably 60 ns to 120 ns. As a result, it is possible to more appropriately prevent the molten negative electrode core 22 from mixing into the negative electrode active material layer 24. Specifically, since there is a tendency for the peak output to increase as the pulse width of the pulsed laser decreases, it is easier to reduce the amount of molten negative electrode core 22 during laser cutting. On the other hand, since the impact applied to the negative electrode active material layer 24 decreases as the pulse width increases, it is possible to prevent a portion of the negative electrode active material layer 24 from being blown away during laser irradiation.

[0105] (Core exposed area cutting process S3)

[0106] In this process, the exposed area A2 of the negative electrode core of the negative electrode precursor 20A is cut using a pulsed laser. Specifically, in the core exposed area cutting process S3, firstly, as... Figure 3 The dashed line L in N2 As shown, a pulsed laser is scanned along the short side direction S of the negative electrode precursor 20A, from the negative electrode active material receiving region A1 toward the negative electrode core exposed region A2. Then, after scanning a certain distance along the long side direction L of the negative electrode precursor 20A, the pulsed laser is scanned again along the short side direction S, toward the negative electrode active material receiving region A1. As a result, a portion of the negative electrode core exposed region A2 is cut into a convex shape to form a negative electrode tab 22t (see reference). Figure 2 Furthermore, in this embodiment, the active substance delivery area cutting process S2 is performed repeatedly at regular intervals. Figure 3 The dashed line L in N1 S3 (and core exposed area cutting process) Figure 3 (The dashed line LN2 in the figure). Thus, the side edge A1a of the region A1 to which the negative electrode active material is imparted can be removed, and multiple negative electrode tabs 22t can be cut out.

[0107] In the electrode plate manufacturing method of this embodiment, the pulsed laser irradiating the exposed area A2 of the negative electrode core in the core exposed area cutting process S3 is controlled to satisfy the following formula (1). In the following formula (1), "X" is the pulse width (ns) of the pulsed laser, and "Y" is the overlap rate (%) of the pulsed laser.

[0108] Y≥-3logX+106 (1)

[0109] In the manufacturing method of this embodiment, a pulsed laser satisfying the above formula (1) is used to cut off the exposed area A2 of the negative electrode core. Therefore, although a pulsed laser is used, since the exposed area A2 of the negative electrode core can be melted and cut off like a CW laser, sputtering can be suppressed. Specifically, as the overlap ratio of the pulsed laser increases, the laser irradiation approaches continuous irradiation, thus making it difficult to generate sputtering. On the other hand, the degree of sputtering generated when a pulsed laser is irradiated onto a metal component is affected not only by the overlap ratio but also by the pulse width. Specifically, as the pulse width of the pulsed laser increases, the heat-affected time applied to the metal component increases, and the molten portion expands, thus making it difficult to generate sputtering. In other words, when using a pulsed laser to cut off the exposed area A2 of the negative electrode core, the overlap ratio can be increased and the pulse width lengthened. Therefore, the state of the pulsed laser can be made close to that of a CW laser, thus suppressing sputtering. Equation (1) above represents the irradiation conditions of the pulsed laser that the inventors discovered, based on repeated experiments conducted according to this insight, are capable of sufficiently suppressing sputtering (relationship between overlap rate and pulse width) (see [reference]). Figure 21 ).

[0110] In addition, such as Figure 4 As shown, in laser cutting using a pulsed laser, multiple light spots R1 and R2 are gradually offset towards a predetermined scanning direction D while being irradiated. This results in an overlapping irradiation area A3 where adjacent light spots R1 and R2 are irradiated in an overlapping manner, and a single irradiation area A4 where a single light spot R1 or R2 is irradiated. The "overlap rate" in this specification refers to the degree to which adjacent light spots R1 and R2 overlap during the irradiation of the pulsed laser. This overlap rate Y can be calculated based on the following equation (2) when the light spot diameter is set to W1 and the irradiation interval between adjacent light spots is set to W2. Furthermore, the light spot diameter W1 and the irradiation interval W2 are both lengths along the scanning direction D of the pulsed laser. That is, during irradiation... Figure 4In the case of elliptical light spots R1 and R2 as shown, the light spot diameter W1 is the diameter of light spots R1 and R2 along the scanning direction D. Alternatively, when irradiating elliptical light spots, each light spot can be tilted relative to the scanning direction D. In this case, the length along the scanning direction D is also measured as the light spot diameter W1 of each light spot and the irradiation interval W2. Furthermore, the specific light spot diameter W1 of the pulsed laser in the core exposed area 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.

[0111] Overlap rate Y(%) = (W1-W2) / W1×100 (2)

[0112] As described above, in the manufacturing method of this embodiment, various conditions are adjusted to satisfy the condition that the overlap ratio Y of the pulsed laser in the core exposed area cutting process S3 is -3logX+106 or more. This suppresses the scattering of sputtering material when cutting the negative electrode core exposed area A2. Furthermore, when the aforementioned overlap ratio Y increases, sputtering material scattering can be suppressed more appropriately. From this viewpoint, it is more preferable that the pulsed laser in the core exposed area cutting process S3 is controlled to have an overlap ratio Y of -3logX+107 or more. On the other hand, the upper limit of the overlap ratio Y of the pulsed laser in the core exposed area cutting process S3 is not particularly limited, and can be 99% or less. However, since the scanning speed of the pulsed laser tends to increase as the overlap ratio Y decreases, there is a tendency to improve manufacturing efficiency. From this viewpoint, it is preferable that the pulsed laser in the core exposed area cutting process S3 is controlled to have an overlap ratio Y of -3logX+109 or less (more preferably -3logX+108 or less).

[0113] Furthermore, the pulsed laser in the core exposed area cutting process S3 only needs to satisfy the above formula (1), and other conditions are not particularly limited. For example, it is preferable to appropriately adjust other conditions of the pulsed laser in the core exposed area cutting process S3 according to the structure of the negative electrode core exposed area A2 (typically, the thickness and material of the negative electrode core 22). For example, the pulse width X constituting the above formula (1) can be 10ns to 300ns, 30ns to 240ns, or 120ns to 240ns. As in formula (1) and Figure 21 As shown, in the core exposed area cutting process S3, the overlap rate Y is required to increase as the pulse width X decreases.

[0114] Furthermore, the average output of the pulsed laser in the core exposure area cutting process S3 can be 70W–2000W, 100W–1800W, or 200W–1500W. There is a tendency that as the average output of the pulsed laser increases, the negative electrode core exposure area A2 is easier to cut. On the other hand, as the average output of the pulsed laser decreases, the impact during laser irradiation decreases, thus reducing the likelihood of sputtering.

[0115] Furthermore, the repetition frequency of the pulsed laser in the core exposure area cutting process S3 can be 400kHz to 4000kHz, 1000kHz to 3500kHz, or 2000kHz to 3000kHz. Since the peak output increases as the pulsed laser frequency decreases, there is a tendency for the negative electrode core 22 to be easily cut. On the other hand, there is a tendency that as the pulsed laser frequency increases, it becomes difficult to generate sputtering.

[0116] Next, the scanning speed of the pulsed laser in the core exposure area cutting process S3 is preferably 5000 mm / sec or less, more preferably 3000 mm / sec or less. There is a tendency that as the scanning speed is slowed down, it becomes less likely to produce cutting defects in the negative electrode core 22. On the other hand, the lower limit of the pulsed laser scanning speed is not particularly limited, and can be 20 mm / sec or more. Furthermore, from the viewpoint of improving manufacturing efficiency due to the reduction in cutting time, the lower limit of the pulsed laser scanning speed is preferably 200 mm / sec or more, more preferably 500 mm / sec or more. Moreover, the pulsed laser scanning speed can be at the same level in both the active material imparting area cutting process S2 and the core exposure area cutting process S3.

[0117] (Other processes)

[0118] As described above, in the manufacturing method of this embodiment, the active material delivery region cutting process S2 is performed repeatedly at regular intervals. Figure 3 The dashed line L in N1 S3 (and core exposed area cutting process) Figure 3 The dashed line L in N2 This process removes the side edge A1a of the negative electrode active material layer 24, where the thickness of the negative electrode active material layer 24 is prone to becoming uneven, and forms multiple negative electrode tabs 22t. Furthermore, in the manufacturing method of this embodiment, as... Figure 3 double-dotted line L N3 As shown, the central portion of the negative electrode precursor 20A along the short side direction S is cut off along the long side direction L. Thus, as... Figure 2As shown, a negative electrode plate 20 can be manufactured in which the negative electrode tab 22t is formed only on one side of the outer peripheral edge 20b1 of the electrode plate body 20b. Furthermore, in this embodiment, as shown by the double-dotted line L... N4 As shown, the negative electrode precursor 20A is cut along the short side direction S at predetermined intervals in the length direction L. This allows the negative electrode plate 20 of the desired length to be manufactured. Furthermore, along the double-dotted line L... N3 L N4 In the cutting of the negative electrode precursor 20A, laser cutting can be used without laser cutting, or a cutting blade, mold, or cutter can be used. Furthermore, along the double-dotted line L... N3 L N4 In the cutting process, when laser cutting is used, it is preferable to use a cutting process S2 (dashed line L) with the area to which the active material is applied. N1 The same pulsed laser conditions are applied. This allows for more effective suppression of the peeling and shedding of fragments from the negative electrode active material layer 24. Furthermore, by appropriately implementing the double-dotted line L along the shape of the manufactured negative electrode plate... N3 L N4 The cutting is sufficient; the technology disclosed here is not limited.

[0119] As described above, in the electrode plate manufacturing method of this embodiment, when the negative electrode active material delivery region A1 is cut (refer to the dashed line L) N1 A pulsed laser is used. This prevents the molten metal from mixing into the negative electrode active material layer 24, thus reducing the adhesion of the negative electrode active material layer 24 and preventing fragments of the negative electrode active material layer 24 from detaching or peeling off from the manufactured negative electrode plate 20. On the other hand, in the manufacturing method of this embodiment, a pulsed laser is also used when cutting the exposed area A2 of the negative electrode core to continuously cut the negative electrode active material imparting area A1 and the exposed area A2 of the negative electrode core. This prevents a significant decrease in manufacturing efficiency and the occurrence of poor cutting due to switching laser types. Furthermore, in this embodiment, the pulsed laser used to cut the exposed area A2 of the negative electrode core is controlled to meet the conditions specified in formula (1) above. This increases the amount of molten electrode core when cutting the exposed area A2 of the negative electrode core using a pulsed laser to the same level as a CW laser, thus suppressing the scattering of sputtered material. As a result, it prevents fine metal sheets from detaching or peeling off from the manufactured negative electrode plate 20. As described above, according to this embodiment, since conductive foreign matter can be prevented from falling off or peeling off from the manufactured negative electrode plate 20, it can help improve the safety of the secondary battery.

[0120] <Negative plate>

[0121] Next, the detailed structure of the electrode plate (negative electrode plate 20) manufactured using the electrode plate manufacturing method of this embodiment will be described.

[0122] (Overview of the negative electrode plate)

[0123] First, such as Figure 2 As shown, the negative electrode plate 20 of this embodiment includes a negative electrode core 22 and a negative electrode active material layer 24. Furthermore, the negative electrode plate 20 includes an electrode body portion 20b and a negative electrode tab 22t. The electrode body portion 20b is the area on the surface of the negative electrode core 22 to which the negative electrode active material layer 24 is applied, and the negative electrode tab 22t is the area where the negative electrode core 22 is exposed without the negative electrode active material layer 24 applied. Since these have already been described, repeated descriptions are omitted.

[0124] (First thick-walled section)

[0125] And, as Figure 5 As shown, in this embodiment, the negative electrode plate 20 has a first thick wall 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 thick wall portion 23 is the trace of laser cutting in the core exposure area cutting process S3 described above. Specifically, in the electrode plate manufacturing method of this embodiment, as described above, in order to suppress the scattering of sputtered material, the negative electrode core exposure area A2 (refer to...) is... Figure 3 The pulsed laser used for cutting is similar to that used in CW laser cutting. Similar to the case of cutting with a CW laser, a first thick-walled portion 23, resembling a circular cross-section, is formed on the outer periphery 22t1 of the negative electrode tab 22t cut by such a pulsed laser, creating a mark obtained by melting and cutting the metal foil. Furthermore, "circular cross-section" here refers to the shape along... Figure 5 The aspect ratio of the first thick-walled portion 23 at the cross-section along the thickness direction T of the negative electrode tab 22t, as shown, is 0.85 or higher. This aspect ratio of the first thick-walled portion 23 is based on a cross-sectional photograph of the electrode tab obtained using a scanning electron microscope (SEM) (see reference). Figure 15 The aspect ratio of the first thick-walled portion 23 is calculated as follows. First, obtain... Figure 15A cross-sectional photograph of the negative electrode tab as shown is presented. Next, in this cross-sectional photograph, the first thick-walled portion is surrounded by a quadrilateral having two sides along the surface of the negative electrode core. Then, the short and long sides of the rectangle surrounding the first thick-walled portion are measured, and the value obtained by dividing the short side by the long side (short side / long side) is set as the aspect ratio. Furthermore, the "aspect ratio" in this specification is the average of the aspect ratios of the first thick-walled portion confirmed in multiple fields of view (typically more than one field of view). Furthermore, the cross-sectional shape of the first thick-walled portion is not limited to circular or elliptical; it may have defects or deformations in a portion. Even with such defects or deformations in the first thick-walled portion, the aspect ratio can be calculated using the above steps.

[0126] Furthermore, when the cross-sectional shape of the first thick-walled portion 23 is made close to a circle, other components (e.g.) Figure 13 When the spacer 30 shown contacts the outer peripheral edge 22t1 of the negative electrode tab 22t, it can prevent damage to the other component. Therefore, the aspect ratio of the first thick-walled portion 23 is preferably 0.88 or more, more preferably 0.90 or more. On the other hand, the upper limit of the aspect ratio of the first thick-walled portion 23 is not particularly limited, and may be 1.00 or less. In addition, the first thick-walled 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 (t1 / t2) of the thickness t1 of the first thick-walled portion 23 to the thickness t2 of the central portion 22t2 may be 1.1 or more, 1.2 or more, 1.4 or more, or 1.5 or more. On the other hand, the upper limit of the above-mentioned t1 / t2 may be 7 or less, 6 or less, 5 or less, or 3 or less.

[0127] Furthermore, in the electrode plate manufacturing method of this embodiment, as described above, the exposed area A2 of the negative electrode core (refer to...) is cut off. Figure 3 The conditions for pulsed laser pulses at the time of application are controlled to satisfy the above formula (1). When the exposed area A2 of the negative electrode core is melted and cut using such a pulsed laser with a high overlap rate, the molten electrode core will deform into a roughly spherical shape due to surface tension. Therefore, areas with concentrated molten metal and areas with sparse molten metal will alternately form. Therefore, in the negative electrode tab 22t1 of the negative electrode plate 20 in this embodiment, a first region with a relatively thick thickness and a second region with a relatively thin thickness may alternately form.

[0128] Furthermore, when using a pulsed laser to cut the exposed area A2 of the negative electrode core, since the negative electrode tab 22t can be separated from the exposed area A2 of the negative electrode core at the moment of laser irradiation, it is unnecessary to perform the process of peeling the negative electrode tab 22t from the exposed area A2 of the negative electrode core as is required when using a CW laser. As a result, in the manufactured negative electrode plate 20, the cutting marks formed by the CW laser (see reference) are removed. Figure 19 Unlike other batteries, the center point C of the first thick-walled portion 23 can be easily positioned between a pair of extended lines E1 and E2 extending from each surface (upper and lower surfaces) of the central portion 22t2 of the negative electrode tab 22t. In this way, when the center point C of the first thick-walled portion 23 is positioned near the center in the thickness direction of the negative electrode tab 22t, the bending process of the negative electrode tab 22t becomes easier, thus contributing to improved manufacturing efficiency of the secondary battery.

[0129] (Second thickest wall section)

[0130] On the other hand, such as Figure 6 As shown, in this embodiment, a second thick-walled portion 25, thicker than the negative electrode core 22 in the central portion 20b2 of the electrode body 20b, is formed at the end of the negative electrode core 22. This second thick-walled portion 25 is a mark obtained by irradiating the negative electrode active material delivery region A1 of the negative electrode precursor 20A with a pulsed laser during the active material delivery region cutting process S2. The second thick-walled portion 25 is formed by cutting the negative electrode core 22 using a high-energy pulsed laser. Furthermore, a coating layer 25b is attached to the surface of the second thick-walled portion 25. This coating layer 25b is the negative electrode active material layer 24 after being irradiated with a pulsed laser, and contains the negative electrode active material. Additionally, the negative electrode active material layer 24 may also contain a sintered product of the negative electrode active material, etc. Furthermore, as... Figure 6 As shown, the thickness of the coating layer 25b is thinner than the thickness of the negative electrode active material layer 24. Compared to the negative electrode active material layer containing molten metal, the coating layer 25b exhibits excellent adhesion to the surface of the negative electrode core 22 (second thick-walled portion 25), thus effectively preventing the peeling or detachment of conductive foreign matter. Furthermore, the second thick-walled portion 25 and the coating layer 25b are formed only on the outer periphery of the electrode body portion 20b (see reference 25b). Figure 2 At least one side is sufficient. Specifically, in this embodiment, since the outer peripheral edge 20b1 of the electrode body 20b located between the negative electrode tabs 22t is cut off by the pulsed laser, a second thick-walled portion 25 and a covering layer 25b are formed in the region between the negative electrode tabs 22t.

[0131] Furthermore, the second thick-walled portion 25 has a hook-like shape, which includes a cap-shaped portion 25a1 protruding from one or both sides in the thickness direction T of the negative electrode core 22 and a recess 25a2 formed between the cap-shaped portion 25a1 and the negative electrode core 22. Unlike the first thick-walled portion 23 described above, since the second thick-walled portion 25 is formed by outputting a larger pulsed laser, the amount of melting in the negative electrode core 22 is less, sometimes resulting in a hook-like shape as described above. The coating layer 25b enters the interior of the recess 25a2 of the hook-shaped second thick-walled portion 25. As a result, due to the excellent anchoring effect, the coating layer 25b is further firmly held, thus more effectively preventing the detachment and peeling of fragments of the negative electrode active material layer 24. In addition, the formation of such a hook-shaped second thick-walled portion 25 may become a cause of damage to other components (such as spacers in a secondary battery). However, in this embodiment, since the second thick-walled portion 25 is covered by the covering layer 25b, it is possible to appropriately prevent other components from being damaged by the claw-shaped second thick-walled portion 25. Furthermore, from the viewpoint of more appropriately preventing damage to other components caused by the second thick-walled portion 25, the thickness of the covering layer 25b attached to the surface of the second thick-walled 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 covering layer 25b is not particularly limited; it can be 20 μm or less, 17.5 μm or less, or 15 μm or less.

[0132] Furthermore, the thickness of the cap-shaped portion 25a1 of the second thick-walled 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 suitable anchoring effect. Additionally, the "thickness of the cap-shaped portion" refers to the thickness of one side of the cap-shaped portion 25a1 with the core surface as a reference. Furthermore, from the viewpoint of more reliably preventing damage to other components, the upper limit of the thickness of the cap-shaped 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-shaped portion 25a1 (the dimension in the short side direction S of the negative electrode plate) is not particularly limited. For example, the width of the cap-shaped portion 25a1 can be 1 μm to 30 μm, 5 μm to 25 μm, or 10 μm to 20 μm. Furthermore, the height (dimension in the thickness direction T) of the entrance to the recess 25a2 of the second thick-walled portion 25 is preferably 1 μm to 10 μm, more preferably 2.5 μm to 7.5 μm. On the other hand, the depth (dimension in the short side direction S of the negative electrode plate) of the recess 25a2 of the second thick-walled portion 25 is preferably 0.1 to 10 μm, more preferably 2.5 μm to 7.5 μm. As a result, an appropriate amount of coating layer 25b can be maintained inside the recess 25a2, and a more suitable anchoring effect can be achieved. In addition, the angle at which the cap-shaped portion 25a1 rises from the surface of the negative electrode core 22 is preferably greater than 0° and less than 90°.

[0133] Furthermore, the aspect ratio of the second thick-walled portion 25 can be smaller than that of the first thick-walled portion 23. As described above, since the second thick-walled portion 25 has a cutting mark formed by a high-energy pulsed laser, its cross-sectional shape is difficult to be approximately circular, unlike the first thick-walled portion 23. Specifically, the upper limit of the aspect ratio of the second thick-walled portion 25 can be 0.85 or less (typically 0.82 or less, for example, 0.80 or less). On the other hand, the lower limit of the aspect ratio of the second thick-walled portion 25 can be 0.40 or more (typically 0.45 or more, for example, 0.50 or more). Moreover, the aspect ratio of the second thick-walled portion can be measured using the same steps as the aspect ratio of the first thick-walled portion described above.

[0134] Secondary batteries

[0135] Next, a secondary battery made using the negative electrode plate 20 of this embodiment will be described. Figure 7 This is a schematic perspective view of the secondary battery according to this embodiment. Figure 8 It is along Figure 7 A schematic longitudinal section view of lines VIII-VIII in the diagram. Figure 9 It is along Figure 7 A schematic longitudinal section view of the IX-IX line. Figure 10 It is along Figure 7A schematic cross-sectional view of the XX line. Figure 11 It is a schematic perspective view of the electrode body installed on the sealing plate. Figure 12 It is a perspective view schematically showing an electrode body with a positive second collector and a negative second collector installed. Figure 13 This is a perspective view illustrating the electrode body of the secondary battery according to this embodiment. Figure 14 This is a front view of the electrode body of the secondary battery according to this embodiment. Furthermore, Figures 7-14 In the accompanying drawings, reference numeral X indicates the "thickness direction," reference numeral Y indicates the "width direction," and reference numeral Z indicates the "vertical direction." Furthermore, in the thickness direction X, F indicates "front," and Rr indicates "rear." In the width direction Y, L indicates "left," and R indicates "right." And in the vertical direction Z, U indicates "up," and D indicates "down." However, these directions are determined for ease of explanation and are not intended to limit the arrangement of the secondary battery 100.

[0136] like Figures 7-10 As shown, the secondary battery 100 includes a wound electrode body 40, a battery casing 50, a positive terminal 60, a negative terminal 65, a positive current collector 70, and a negative current collector 75. Furthermore, although not shown in the figure, a non-aqueous electrolyte is contained inside the battery casing 50 of the secondary battery 100, in addition to the wound electrode body 40. This non-aqueous electrolyte is prepared by dissolving a supporting salt in a non-aqueous solvent. Examples of non-aqueous solvents include carbonate solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorinated lithium salts such as LiPF6.

[0137] (Battery casing)

[0138] The battery housing 50 is a frame that houses the wound electrode body 40. Here, the battery housing 50 has a flat, bottomed cuboid shape (square). The material of the battery housing 50 is the same as conventionally used materials and is not particularly limited. The battery housing 50 is preferably made of metal, for example, more preferably aluminum, aluminum alloy, iron, iron alloy, etc. The battery housing 50 includes an outer casing 52 and a sealing plate 54.

[0139] The outer casing 52 is a flat, bottomed, square container with an opening 52h on its upper surface. For example... Figure 7As shown, the outer casing 52 has a generally rectangular bottom wall 52a, a pair of long side walls 52b, and a pair of short side walls 52c in plan view. The pair of long side walls 52b extend vertically along the long side of the bottom wall 52a, and the pair of short side walls 52c extend vertically along the short side of the bottom wall 52a. On the other hand, the sealing plate 54 is a generally rectangular plate-shaped member in plan view that blocks the opening 52h of the outer casing 52. Furthermore, the outer periphery of the sealing plate 54 is joined (e.g., welded) to the outer periphery of the opening 52h of the outer casing 52. Thus, a battery casing 50 with its interior airtightly sealed is produced. Additionally, the sealing plate 54 is provided with an injection hole 55 and a gas vent valve 57. The injection hole 55 is provided for injecting a non-aqueous electrolyte into the interior of the battery casing 50 after the outer casing 52 and the sealing plate 54 are joined. Furthermore, the injection hole 55 is sealed by the sealing member 56 after the non-aqueous electrolyte is injected. In addition, the gas discharge valve 57 is a thin-walled part designed such that when a large amount of gas is generated inside the battery housing 50, it breaks (opens) under a preset pressure to discharge the gas inside the battery housing 50.

[0140] (Electrode terminals)

[0141] Additionally, one side of the sealing plate 54 in the long side direction Y of the secondary battery 100 ( Figure 7 , Figure 8 A positive terminal 60 is installed at the end of the battery casing 50 (on the left side). This positive terminal 60 is connected to a plate-shaped positive electrode external conductive member 62 on the outside of the battery casing 50. On the other hand, the other side of the sealing plate 54 in the long side direction Y of the secondary battery 100 (… Figure 7 , Figure 8 A negative terminal 65 is installed at the right end of the battery. A plate-shaped external conductive member 67 is also installed on the negative terminal 65. The external conductive members (positive external conductive member 62 and negative external conductive member 67) are connected to other secondary batteries and external devices via external connecting members (busbars, etc.). Furthermore, it is preferable that the external conductive members are made of a metal with excellent conductivity (aluminum, aluminum alloy, copper, copper alloy, etc.).

[0142] (Electrode current collector)

[0143] In the secondary battery 100, a plurality of (three in the figure) wound electrode bodies 40 are housed inside the battery casing 50. The positive terminal 60 is connected to each of the plurality of wound electrode bodies 40 via a positive current collector 70 housed within the battery casing 50. Specifically, a positive current collector 70 connecting the positive terminal 60 to the wound electrode bodies 40 is housed inside the battery casing 50. Figure 8 , 11As shown, the positive electrode current collector 70 includes a first positive electrode current collector 71 and a plurality of second positive electrode current collectors 72. The first positive electrode current collector 71 is a plate-shaped conductive member extending along the inner side of the sealing plate 54, and the plurality of second positive electrode current collectors 72 are plate-shaped conductive members extending along the vertical direction Z. Furthermore, the lower end 60c of the positive terminal 60 extends through the terminal insertion hole 58 of the sealing plate 54 toward the interior of the battery casing 50 and is connected to the first positive electrode current collector 71 (see reference). Figure 8 ).like Figure 11 , 12 As shown, the second positive current collector 72 is connected to the positive electrode tabs 42 of each of the plurality of wound electrode bodies 40. Furthermore, as... Figure 10 As shown, the positive electrode tab assembly 42 of the wound electrode body 40 is bent so that the second positive electrode current collector 72 faces the side surface 40a of one side of the wound electrode body 40. Thus, the upper end of the second positive electrode current collector 72 is electrically connected to the first positive electrode current collector 71.

[0144] On the other hand, the negative terminal 65 is connected to a plurality of wound electrode bodies 40 via a negative current collector 75 housed within the battery casing 50. The connection structure on the negative side is substantially the same as the connection structure on the positive side described above. Specifically, the negative current collector 75 includes a first negative current collector 76 and a plurality of second negative current collectors 77. The first negative current collector 76 is a plate-shaped conductive member extending along the inner side of the sealing plate 54, and the plurality of second negative current collectors 77 are plate-shaped conductive members extending along the vertical direction Z. Furthermore, the lower end 65c of the negative terminal 65 extends into the battery casing 50 through a terminal insertion hole 59 and is connected to the first negative current collector 76 (see reference). Figure 8 The negative electrode second current collector 77 is connected to the negative electrode tabs 44 of each of the plurality of wound electrode bodies 40 (see reference). Figure 11 , 12 Furthermore, the negative electrode tab assembly 44 is bent so that the second negative electrode current collector 77 is opposite to the other side 40b of the wound electrode body 40 (see reference). Figure 10 Thus, the upper end of the negative electrode second collector 77 is electrically connected to the negative electrode first collector 76.

[0145] (Insulating components)

[0146] Furthermore, in the secondary battery 100 of this embodiment, various insulating members are installed to prevent the winding electrode body 40 from conducting through the battery casing 50. Specifically, an external insulating member 92 (see reference 67) is sandwiched between the positive electrode external conductive member 62 (negative electrode external conductive member 67) and the outer side of the sealing plate 54. Figure 7This prevents the positive electrode external conductive member 62 and the negative electrode external conductive member 67 from conducting with the sealing plate 54. Additionally, gaskets 90 are installed in the terminal insertion holes 58 and 59 of the sealing plate 54 (see reference). Figure 8 This prevents the positive terminal 60 (or negative terminal 65) inserted into the terminal insertion holes 58 and 59 from conducting with the sealing plate 54. Furthermore, an internal insulating member 94 is disposed between the positive first current collector 71 (or negative first current collector 76) and the inner surface of the sealing plate 54. This internal insulating member 94 has a plate-shaped base 94a sandwiched between the positive first current collector 71 (or negative first current collector 76) and the inner surface of the sealing plate 54. This prevents the positive first current collector 71, the negative first current collector 76, and the sealing plate 54 from conducting with each other. Moreover, the internal insulating member 94 has a protrusion 94b protruding from the inner surface of the sealing plate 54 toward the winding electrode body 40. This restricts the movement of the winding electrode body 40 in the vertical Z direction and prevents direct contact between the winding electrode body 40 and the sealing plate 54. Furthermore, the wound electrode body 40 is mounted on an electrode body support 98 made of an insulating resin sheet (see reference). Figure 9 The electrode body 40 is housed inside the battery casing 50 while covered. This prevents direct contact between the wound electrode body 40 and the outer casing 52. Furthermore, the materials of the aforementioned insulating components are not particularly limited as long as they have the predetermined insulating properties. For example, synthetic resin materials such as polyolefin resins (e.g., polypropylene (PP), polyethylene (PE)) and fluorinated resins (e.g., perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE)) can be used.

[0147] (Wound electrode body)

[0148] Next, the electrode body used in the secondary battery 100 of this embodiment will be described. In this embodiment, Figure 13 The wound electrode body 40 shown is used as the electrode body. The wound electrode body 40 is wound in a state where a pair of electrode plates (positive electrode plate 10, negative electrode plate 20) are facing each other with a spacer 30 in between. When manufacturing this wound electrode body 40, firstly, a laminate is formed by stacking the long strip-shaped positive electrode plate 10 and the long strip-shaped negative electrode plate 20 with the long strip-shaped spacer 30 sandwiched between them. Then, after winding the laminate along the long side direction, a winding fixing tape 38 (see reference) is attached to the end portion 30a of the spacer 30 located on the outermost periphery. Figure 14 Therefore, the wound electrode body 40 can be manufactured. Furthermore, in this embodiment, the negative electrode plate 20 with the above-described structure is used in the manufacture of the wound electrode body 40. Hereinafter, the wound electrode body 40 of this embodiment will be described.

[0149] First, the spacer 30 is a sheet-like component that functions to prevent contact between the positive electrode plate 10 and the negative electrode plate 20 while allowing charge carriers to pass through. As an example of this spacer 30, a resin sheet with multiple fine pores through which charge carriers can pass can be cited. Preferably, the resin sheet comprises a resin layer made of polyolefin resin (e.g., polyethylene (PE), polypropylene (PP)). Alternatively, a heat-resistant layer comprising inorganic fillers such as alumina, boehmite, aluminum hydroxide, and titanium dioxide may be formed on the surface of the resin sheet.

[0150] The positive electrode plate 10 includes: a positive electrode core 12, which is a foil-shaped metal component; a positive electrode active material layer 14, which is applied to the surface of the positive electrode core 12; and a protective layer 16, which is applied to the surface of the positive electrode core 12 in a manner adjacent to the side edge 10a of the positive electrode plate 10. Furthermore, on the side edge 10a of the positive electrode plate 10, the outer side (in the short-side direction S)... Figure 13 On the left side of the positive electrode plate 10, a plurality of positive electrode tabs 12t protruding from the positive electrode plate 10 are provided at predetermined intervals along the long side L. These positive electrode tabs 12t are the areas where the positive electrode core 12 is exposed without the positive electrode active material layer 14 and the protective layer 16 being applied. Furthermore, from the viewpoint of battery performance, it is preferable that the positive electrode active material layer 14 and the protective layer 16 are applied to both sides of the positive electrode core 12. Alternatively, the protective layer 16 may be applied such that a portion of it covers the side edge of the positive electrode active material layer 14. Furthermore, the materials constituting each component of the positive electrode plate 10 (positive electrode core 12, positive electrode active material layer 14, and protective layer 16) can be conventionally known materials that are commonly used in general secondary batteries (e.g., lithium-ion secondary batteries) without particular limitation. Since the technology disclosed herein is not intended to be limited, detailed descriptions are omitted.

[0151] On the other hand, the structure of the negative electrode plate 20 used in the secondary battery 100 of this embodiment is as described above. For this negative electrode plate 20, in the region A1 (refer to) where the electrode plate body 20b is supplied with the negative electrode active material from the negative electrode precursor 20A... Figure 3 A pulsed laser is used during the cutting process. Therefore, the negative electrode plate 20 of this embodiment can suppress the decrease in adhesion of the negative electrode active material layer 24 caused by the incorporation of molten metal. 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 and peeling off, thus preventing them from causing internal short circuits. Moreover, the negative electrode plate 20 has a negative electrode core exposed region A2 (see reference 20) from the negative electrode precursor 20A. Figure 3When cutting out the negative electrode tab 22t, a pulsed laser, similar to a CW laser, is used. Therefore, the negative electrode plate 20 of this embodiment suppresses the adhesion of fine metal sheets (sputtered material). As a result, after constructing the secondary battery 100, it is possible to prevent sputtered material from detaching or peeling off and becoming a cause of internal short circuits. That is, in the secondary battery 100 of this embodiment, since it is possible to prevent various conductive foreign objects from detaching or peeling off from the negative electrode plate 20, it has high safety.

[0152] <Other Implementation Methods>

[0153] The above describes one embodiment of the technology disclosed herein. Furthermore, the above embodiment illustrates an example of applying the technology disclosed herein and does not limit the scope of the technology disclosed herein.

[0154] For example, in the above embodiment, the electrode plate manufacturing method disclosed herein is used to manufacture a negative electrode plate. However, the electrode plate manufacturing method disclosed herein is not limited to manufacturing a negative electrode plate, and can also manufacture a positive electrode plate. Even when the positive electrode plate is the manufacturing target, conductive foreign matter (fragments of the positive electrode active material layer, sputterings) can be prevented from detaching or peeling off from the manufactured electrode plate (positive electrode plate). Furthermore, compared with the positive electrode plate manufactured by the above embodiment, the negative electrode plate tends to have reduced adhesion of the electrode active material layer due to the incorporation of molten metal. In contrast, the electrode plate manufacturing method disclosed herein can appropriately suppress the incorporation of molten metal. Therefore, the electrode plate manufacturing method disclosed herein can be particularly suitable for manufacturing negative electrode plates.

[0155] Furthermore, in the above 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 are positioned opposite each other with a spacer between them. As another example of the electrode body construction, a stacked electrode body can be listed, in which multiple positive and negative electrode plates are stacked sequentially while the spacer is clamped between them. To manufacture the negative electrode plate for such a stacked electrode body, it can be implemented with each negative electrode tab being 22t. Figure 3 The cut is made along the short side direction S, as shown by the double-dotted line LN4. Although detailed explanations are omitted, the fabrication of the positive electrode plate is similar. Then, multiple positive and negative electrode plates are stacked while clamping spacers, with positive electrode tabs stacked in the same positions and negative electrode tabs stacked in the same positions. In this way, a stacked electrode body can be fabricated.

[0156] Furthermore, in the above embodiment, a high-capacity secondary battery 100 with three wound electrode bodies 40 housed inside the battery casing 50 is considered. However, the number of electrode bodies housed in a battery casing is not particularly limited; it can be two or more, or it can be one. Moreover, the secondary battery 100 in the above embodiment is a lithium-ion secondary battery with lithium ions as the charge carrier. However, the secondary battery disclosed herein is not limited to lithium-ion secondary batteries. In the manufacturing process of other secondary batteries (e.g., nickel-metal hydride batteries), since there is a process of cutting the active material delivery area of ​​the electrode precursor and the core exposure area using a laser, the technology disclosed herein can also be applied without particular limitation.

[0157] Furthermore, the secondary battery 100 of 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. As another example of the structure of a secondary battery, an all-solid-state battery can be cited. In this all-solid-state battery, a solid electrolyte layer formed into a sheet shape is used as a spacer sandwiched between the positive and negative electrode plates. In this all-solid-state battery, since the spacer and the electrolyte are integrated and contained within the electrode body, leakage of the electrolyte can be prevented. In the manufacturing process of such an all-solid-state battery, since there is a process of cutting the active material delivery area of ​​the electrode precursor and the core exposure area using a laser, the technology disclosed herein can also be applied without particular limitations.

[0158] [Experimental Example]

[0159] The following describes test examples related to the present invention. Furthermore, the content of the test examples described below is not intended to limit the present invention.

[0160] <First Experiment>

[0161] (1) Sample preparation

[0162] (Example 1)

[0163] In Example 1, a negative electrode for a lithium-ion secondary battery was manufactured using pulsed lasers with different conditions in the negative electrode active material depositing region of the negative electrode precursor and the core exposure region. First, a negative electrode precursor was prepared, on which a negative electrode active material layer of 80 μm thickness was deposited on both sides of an 8 μm thick negative electrode core (copper foil). In the negative electrode active material layer of this negative electrode precursor, negative electrode active material, thickener, and binder were contained in a ratio of 98.3:0.7:1.0. Furthermore, graphite was used as the negative electrode active material, carboxymethyl cellulose (CMC) as the thickener, and styrene-butadiene rubber (SBR) as the binder. Next, the negative electrode precursor was cut into a predetermined shape to cut out the negative electrode plate. Specifically, when cutting the negative electrode active material depositing 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. Furthermore, the frequency of the pulsed laser cutting off the region where the negative electrode active material is imparted is 300 kHz, and the frequency of the pulsed laser cutting off the region where the core is exposed is 450 kHz. Additionally, the spot diameter of the pulsed laser is set to 30 μm in both the region where the negative electrode active material is imparted and the region where the core is exposed.

[0164] (Comparative Example 1)

[0165] In Comparative Example 1, a negative electrode for a lithium-ion secondary battery was manufactured using a pulsed laser under the same conditions in both the negative electrode active material delivery 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 that prepared in Example 1. Furthermore, in Comparative Example 1, both the negative electrode active material delivery region and the core exposure region were cut off using a pulsed laser with a pulse width of 240 ns and an overlap rate of 89%. In addition, the frequency of the pulsed laser used in Comparative Example 1 was 400 kHz, and the spot diameter was 30 μm.

[0166] (Comparative Example 2)

[0167] 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 delivery region of the negative electrode precursor and the core exposure region. First, the negative electrode precursor prepared in Comparative Example 2 was the same as that prepared in Examples 1 and 1. Furthermore, in Comparative Example 2, a CW laser with an output of 1000W and a scanning speed of 6000mm / sec was used. Additionally, the spot diameter of the CW laser used in Comparative Example 2 was 20μm.

[0168] (2) Evaluation test

[0169] In this experiment, firstly, the laser-cut portions of the negative plates manufactured in each example were observed using a scanning electron microscope (SEM). Furthermore, in this experiment, SEM observations were performed on the side edges of the negative electrode tabs and the side edges of the plate body for each example of the negative plate. Figure 15 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of Example 1. Figure 16 This is a cross-sectional SEM image (1000x magnification) of the electrode body of Example 1. Figure 17 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of Comparative Example 1. Figure 18 This is a cross-sectional SEM image (1000x magnification) of the electrode body of Comparative Example 1. Figure 19 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of Comparative Example 2. Furthermore, Figure 20 This is a cross-sectional SEM image (370x magnification) of the electrode body of Comparative Example 2. Based on the above... Figures 15-20 The SEM images shown confirm the following aspects.

[0170] First, the condition of the area near the outer periphery of the negative electrode tab in each case (i.e., the area near the core exposed by the laser cut) was compared and studied. For example... Figure 15 As shown, in Example 1, no metal sheet (sputtered material) was observed adhering near the outer periphery of the negative electrode tab. Furthermore, a first thick-walled portion with a thickness greater than the central portion of the negative electrode tab was formed at the outer periphery. It is presumed that this first thick-walled portion was formed by the solidification of the molten negative electrode core. Moreover, the aspect ratio of the first thick-walled portion of the negative electrode tab in Example 1 is 0.95. On the other hand, as... Figure 17 As shown, in Comparative Example 1, it was confirmed that a large amount of sputtered material adhered near the outer periphery of the negative electrode tab. Furthermore, the aspect ratio of the first thick-walled portion of the negative electrode tab formed in Comparative Example 1 was 0.82. And, as... Figure 19 As shown, in Comparative Example 2, no sputtering was found to adhere near the outer periphery of the negative electrode tab. Furthermore, the aspect ratio of the first thick-walled portion of the negative electrode tab formed in Comparative Example 2 was 0.96. From the above, it can be seen that in Example 1, which used a pulsed laser to approximate CW laser conditions, and Comparative Example 2, which used a CW laser, sputtering during the cutting of the exposed core area was suppressed, and a first thick-walled portion with a generally circular cross-sectional shape was formed at the outer periphery of the negative electrode tab. Additionally, in Comparative Example 2, the center of the first thick-walled portion with a generally circular cross-section deviated downwards from the center of the negative electrode core in the thickness direction. This is presumably because, in Comparative Example 2 using a CW laser, immediately after laser irradiation, the negative electrode tab was not completely cut away from the exposed core area, requiring peeling of the negative electrode tab from the exposed core area, and the laser cutting mark (first thick-walled portion) was pulled by the peeling of the negative electrode tab.

[0171] Next, the state near the side edge of the electrode body in each example (i.e., near the region where the active material layer is laser-cut) is compared and studied. First, as... Figure 16 As shown, in Embodiment 1, a second thick-walled portion with a thickness greater than that of the negative electrode core in the central portion of the negative electrode body is formed at the end of the negative electrode core in the side edge portion of the negative electrode plate body. Furthermore, a coating layer containing a negative electrode active material is attached to the surface of this second thick-walled portion. Additionally, as... Figure 18 As shown, in Comparative Example 1, a second thick-walled portion is also formed at the end of the negative electrode core at the side edge of the negative electrode plate body, and a coating layer containing a negative electrode active material is attached to the surface of this second thick-walled portion. On the other hand, as Figure 20 As shown, in Comparative Example 2, no thick-walled portion was formed at the end of the negative electrode core. Furthermore, a negative electrode active material mixed with molten metal was attached to the side edge of the electrode body in Comparative Example 2. It was also observed that the negative electrode active material attached to the side edge of the electrode body was easily detached or peeled off due to minor impacts.

[0172] The above test results show that in order to prevent conductive foreign matter (fragments and sputterings of the negative electrode active material layer) from detaching or peeling off from the manufactured negative electrode plate, different pulsed laser conditions can be used in the negative electrode active material imparting area and the core exposed area when the negative electrode plate is cut out from the negative electrode precursor.

[0173] <Second Experiment>

[0174] In this experiment, as in Example 1 of the first experiment, eight experimental examples were prepared using pulsed lasers with different conditions in the negative electrode active material delivery area and the core exposed area. Furthermore, the negative electrode plates fabricated in each experimental example were observed, and the conditions for pulsed lasers that could suppress sputtering during laser cutting in the core exposed area were investigated. The specific conditions are described below.

[0175] (1) Sample preparation

[0176] (Experiments 1-8)

[0177] As described above, in this experiment, eight experimental examples (Experimental Examples 1 to 8) were prepared using pulsed lasers under different conditions in the negative electrode active material delivery region and the core exposure region of the negative electrode precursor. Furthermore, the negative electrode precursor prepared in this experiment was the same as the negative electrode precursor prepared in the first experiment described above. Also, in this experiment, the pulse width and overlap rate of the pulsed laser used to cut off the core exposure region differed in each experimental example. The pulsed laser conditions for each experimental example are shown in Table 1, which will be described later.

[0178] (2) Evaluation test

[0179] Similar to the first experiment, cross-sectional SEM was performed on the manufactured negative electrode plate to compare the condition near the outer periphery of the negative electrode tab. Figure 21 The results are shown in Table 1. Furthermore, Figure 21 In Table 1, “○” indicates that no sputtering was observed in the above SEM observations and the aspect ratio of the first thick-walled portion is 0.85 or higher. On the other hand, “×” indicates that more than one sputtering was observed and the aspect ratio of the first thick-walled portion is less than 0.85.

[0180] Table 1

[0181]

[0182] As shown in Table 1 and Figure 21 As shown, in test examples 1, 3, 5, and 7, sputtering was suppressed, and a first thick-walled portion with a roughly circular cross-section was formed at the end of the cut negative electrode core. Furthermore, as... Figure 21 As shown, it can be seen that the following tendency exists: as the overlap ratio of the pulsed laser increases, the generation of sputtering material is more easily suppressed. On the other hand, based on the results of this experiment, it was also confirmed that the following tendency exists: as the pulse width of the pulsed laser increases, the generation of sputtering material is more easily suppressed. Furthermore, it can be seen that there is a threshold condition for the pulsed laser that can suppress the generation of sputtering material between test examples 1, 3, 5, and 7 where the generation of sputtering material is suppressed and test examples 2, 4, 6, and 8 where the generation of sputtering material is not suppressed. Based on the results of this experiment, it can be understood that the threshold for suppressing the sputtering material is as follows (1):

[0183] Y≥-3logX+106 (1).

[0184] The present invention has been described in detail above, but the above description is merely illustrative. That is, the technology disclosed herein includes structures obtained by various modifications and alterations to the above-described specific examples.

Claims

1. A method of manufacturing an electrode plate, which is a method of manufacturing an electrode plate provided with an electrode core that is a metal foil and an electrode active material layer imparted to a surface of the electrode core and containing an electrode active material, characterized by comprising: a precursor preparation step in which an electrode precursor provided with an active material imparting region that is a region of the surface of the electrode core to which the electrode active material layer is imparted and a core exposing region that is a region in which the electrode core is exposed without the electrode active material layer being imparted; an active material imparting region cutting step in which the active material imparting region is cut using a pulsed laser; and a core exposing region cutting step in which the core exposing region is cut using a pulsed laser, wherein a pulse width ns of the pulsed laser in the core exposing region cutting step is set to X, and an overlap ratio % is set to Y, and the following (1) is satisfied: Y ≥ -3 log X + 106 (1), the electrode plate being a negative electrode plate provided with 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.

2. The method of manufacturing an electrode plate according to claim 1, characterized in that a frequency of the pulsed laser in the active material imparting region cutting step is lower than a frequency of the pulsed laser in the core exposing region cutting step.

3. The method of manufacturing an electrode plate according to claim 1 or 2, characterized in that the frequency of the pulsed laser in the active material imparting region cutting step is 100 kHz to 2000 kHz.

4. The method of manufacturing an electrode plate according to claim 1 or 2, characterized in that a pulse width X of the pulsed laser in the core exposing region cutting step is 30 ns to 240 ns.

5. The method of manufacturing an electrode plate according to claim 1 or 2, characterized in that an overlap ratio of the pulsed laser in the active material imparting region cutting step is lower than an overlap ratio of the pulsed laser in the core exposing region cutting step.

6. The method of manufacturing an electrode plate according to claim 1 or 2, characterized in that the overlap ratio Y of the pulsed laser in the core exposing region cutting step is 90% to 99%.

7. A method of manufacturing a secondary battery provided with an electrode body in which a pair of electrode plates face each other with a separator interposed therebetween, characterized by manufacturing at least one of the pair of electrode plates using the method of manufacturing an electrode plate according to any one of claims 1 to 6.

8. An electrode plate provided with an electrode core that is a foil-like metal member and an electrode active material layer imparted to a surface of the electrode core and containing an electrode active material, characterized by comprising: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A tab main portion to which the electrode active material layer is not applied and from which the electrode core is exposed, protruding from a part of an outer peripheral edge portion of the tab main portion toward the outside, A first thick wall portion having a thickness larger than that of a central portion of the electrode tab is formed in an outer peripheral edge portion of the electrode tab, and an aspect ratio of the first thick wall portion in a cross section in a thickness direction of the electrode tab is 0.85 or more, A second thick wall portion having a thickness larger than that of the electrode core of a central portion of the tab main portion is formed in an end portion of the electrode core of at least one side of the outer peripheral edge portion of the tab main portion, and a coating layer containing the electrode active material is attached to a surface of the second thick wall portion, The electrode plate is a negative electrode plate provided with a negative electrode core made of copper or copper alloy and a negative electrode active material layer containing carbon material as the electrode active material.

9. The electrode plate according to claim 8, wherein The second thick wall portion has a hook shape provided with a cap-shaped portion protruding to both sides or one side in the thickness direction and a recess formed between the cap-shaped portion and the electrode core.

10. The electrode plate according to claim 8 or 9, wherein The thickness of the coating layer attached to the surface of the second thick wall portion is 1 μm to 20 μm.

11. The electrode plate according to claim 8 or 9, wherein A center point of the first thick wall portion is disposed between a pair of extension lines extending from each surface of the central portion of the electrode tab.

12. The electrode plate according to claim 8 or 9, wherein The first thick wall portion has a first region having a relatively thick thickness and a second region having a relatively thin thickness, and the first region and the second region are alternately formed along the outer peripheral edge portion of the electrode tab.

13. A secondary battery provided with a pair of electrode plates facing each other with a separator, characterized in that At least one of the pair of electrode plates is the electrode plate according to any one of claims 8 to 12. ​ ​

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