Method for manufacturing electrode plate and method for manufacturing secondary battery

Abstract

According to the present disclosure, there is provided a manufacturing method of an electrode plate capable of preventing a foreign object having electric conductivity from being peeled off from the electrode plate after manufacturing, and contributing to improvement in safety of a secondary battery, a manufacturing method of a secondary battery, an electrode plate, and a secondary battery. The manufacturing method of the electrode plate disclosed herein includes: a precursor preparation step of preparing an electrode precursor including an active material setting region in which an electrode active material layer is provided on a surface of an electrode core, and a core exposed region in which the electrode active material layer is not provided and the electrode core is exposed; an active material setting region cutting step of cutting the active material setting region using a pulse laser; and a core exposed region cutting step of cutting the core exposed region using the pulse laser. The frequency of the pulse laser in the core exposed region cutting step is higher than the frequency of the pulse laser in the active material setting region cutting step, and the overlapping rate of the pulse laser in the core exposed region cutting step is 90% or more.

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 have an electrode body with a positive electrode plate and a negative electrode plate facing each other across a separator. Hereinafter, these positive and negative electrode plates will be collectively referred to as "electrode plates." This electrode plate, for example, has an electrode core as a foil-shaped metal component and an electrode active material layer disposed on the surface of the electrode core, containing electrode active material. In manufacturing this type of electrode plate, firstly, an electrode active material layer is disposed on 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 area where the electrode active material layer is provided (active material setting area). Therefore, when cutting the electrode plate from the electrode precursor, the outer periphery of the active material setting area is usually removed using a laser. In addition, in a typical electrode plate, in order to ensure the connection position with conductive components such as electrode terminals, it is necessary to provide a portion of the electrode core (metal foil) exposed. Therefore, in the cutting of the electrode plate, the following process is also performed: a portion of the electrode core exposed by the substrate without the electrode active material layer is partially cut out (core exposed area) to form an electrode tab. As described above, in the manufacturing of the electrode plate, the process of cutting off the active material setting area and the process of cutting off the core exposed area are performed (for example, see Patent Document 1).

[0004] Existing technical documents

[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

[0008] However, the electrode plates manufactured using the above methods are characterized by the tendency for fragments of the electrode active material layer and fine metal sheets (sputterings) to detach and peel off. Furthermore, when these conductive foreign objects detach or peel off inside the secondary battery, they may cause internal short circuits. Summary of the Invention

[0009] The problem that the invention aims to solve

[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 objects from falling off or peeling off from the manufactured electrode plate and contribute to the improvement of the safety of secondary batteries.

[0011] Methods for solving problems

[0012] In order to solve the above-mentioned problems, the inventors conducted various studies and discovered the causes of the detachment and peeling of the electrode active material layer fragments and the detachment 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, during the manufacture of the electrode plate, the outer periphery of the active material placement area is removed using a laser. Sometimes, due to the heat of the laser, the electrode core melts and mixes with a portion of the electrode active material layer. Furthermore, the adhesion of the electrode active material layer mixed with this molten metal is significantly reduced, making it easily detached and peeled off even with slight impact. The inventors believe that, in order to suppress the reduction in adhesion of the electrode active material layer caused by the incorporation of this molten metal, a pulsed laser can be used to cut the active material placement area. This pulsed laser can repeatedly irradiate at very short time intervals, concentrating a large amount of energy on the cut portion, thus enabling rapid cutting of the electrode core with a small amount of molten metal.

[0014] Next, the reasons for the detachment and peeling of 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 fine metal sheets that are easily detached and peeled off due to slight impacts. The inventors believe that, in order to suppress the scattering of this sputtered material, a continuous wave laser (CW laser) can be used to cut the core exposed area. This CW laser continuously irradiates the electrode core with a low-energy laser, melting and cutting it, thereby suppressing the scattering of sputtered material and forming the electrode tabs.

[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 placement area, and CW lasers are needed to prevent the shedding or peeling of sputtered material from the core exposure area. However, the method of cutting the active material placement area and the core exposure area separately by switching the laser used results in a significant reduction in manufacturing efficiency, making it difficult to adopt in actual manufacturing environments. Furthermore, when cutting the active material placement area and the core exposure area separately, it is required to connect the cut lines formed in each area without offset, which may also lead to frequent cutting defects. Considering this, the inventors have researched a method that can prevent the generation of the two types of conductive foreign matter and can continuously cut the active material placement area and the core exposure area.

[0016] The electrode plate manufacturing method disclosed herein is based on the above-described understanding, and manufactures an electrode plate having an electrode core as a metal foil and an electrode active material layer disposed on the surface of the electrode core and containing electrode active material. Furthermore, the electrode plate manufacturing method includes: a precursor preparation step, in which an electrode precursor is prepared, the electrode precursor having an active material placement region on the surface of the electrode core where the electrode active material layer is disposed and a core exposure region where no electrode active material layer is disposed and the electrode core is exposed; an active material placement region cutting step, in which the active material placement 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 frequency of the pulsed laser in the core exposure region cutting step is higher than the frequency of the pulsed laser in the active material placement region cutting step, and the overlap rate of the pulsed lasers in the core exposure region cutting step is 90% or more.

[0017] In the manufacturing method of the electrode plate with the above-described structure, a pulsed laser is used when cutting the active material setting area. This suppresses the incorporation of molten metal from the electrode core 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 this disclosed manufacturing method, to prevent a significant decrease in manufacturing efficiency and the occurrence of poor cutting, a pulsed laser is also used in cutting the core exposed area, continuously cutting both the active material setting area and the core exposed area. However, in this disclosed manufacturing method, the state of the pulsed laser used to cut the core exposed area is close to that of a CW laser. Specifically, in this disclosed manufacturing method, the frequency of the pulsed laser in the core exposed area cutting process is higher than the frequency of the pulsed laser in the active material setting area cutting process. Therefore, even with the use of a pulsed laser, the impact during laser cutting can be reduced. Furthermore, in this disclosed manufacturing method, the overlap rate of the pulsed lasers in the core exposed area cutting process is 90% or more. This increases the amount of molten metal in the electrode core to the same level as a CW laser, enabling the electrode core to be melted and cut. As described above, the manufacturing method disclosed herein reduces the impact during laser cutting and increases the amount of molten material during melting, thus suppressing the scattering of sputtered material. As described above, the electrode plate manufacturing method disclosed herein prevents conductive foreign matter from detaching or peeling off from the manufactured electrode plate, thereby contributing to improved safety of the secondary battery.

[0018] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the frequency of the pulsed laser in the active material setting area cutting process is 100kHz to 2000kHz. This more effectively prevents the shedding or peeling of fragments from the electrode active material layer.

[0019] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the frequency of the pulsed laser in the core exposed area cutting process is 450 kHz to 4000 kHz. This allows for more effective prevention of sputtering material detachment and peeling.

[0020] Furthermore, in a preferred embodiment of the electrode plate manufacturing method disclosed herein, the overlap rate of the pulsed laser in the active material setting area cutting process is smaller than the overlap rate of the pulsed laser in the core exposed 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.

[0021] As another aspect of the technology disclosed herein, a method for manufacturing a secondary battery is provided. Specifically, in the method for manufacturing a secondary battery having a pair of electrode bodies with electrode plates facing each other separated by a separator, the method for manufacturing electrode plates with the above-described structure is characterized in that at least one of the pair of electrode plates is manufactured. According to this manufacturing method, 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, thus obtaining a secondary battery with excellent safety.

[0022] Furthermore, according to the electrode plate manufacturing method disclosed herein, an electrode plate with the following structure can be manufactured. Specifically, the manufactured electrode plate includes an electrode core as a foil-shaped metal member and an electrode active material layer disposed on the surface of the electrode core and containing electrode active material. The electrode plate also includes: an electrode plate main body portion on which the electrode active material layer is disposed on the surface of the electrode core; and an electrode tab, which is a region where the electrode active material layer is not disposed and the electrode core is exposed, the electrode tab protruding outward from a portion of the outer periphery of the electrode plate main body portion. Furthermore, the electrode plate disclosed herein forms a first thick-walled portion on the outer periphery of the electrode tab, which is thicker than the central portion of the electrode tab, and the aspect ratio of the first thick-walled portion in cross-section along the thickness direction of the electrode tab is 0.85 or more. Moreover, a second thick-walled portion, thicker than the electrode core in the central portion of the electrode plate main body portion, is formed at at least one end of the electrode core on the outer periphery of the electrode plate main body portion, and a coating layer containing electrode active material is attached to the surface of the second thick-walled portion.

[0023] The electrode plate with the above-described structure has a first thick-walled portion formed at the outer periphery of the electrode tab. This first thick-walled portion is the mark left after laser cutting. Furthermore, in the manufacturing method of the electrode plate with the above-described structure, when cutting the electrode tab (cutting the exposed core area), the pulsed laser conditions are made close to those of a CW laser. When performing molten cutting using such a pulsed laser, the amount of melting in the electrode core becomes the same as that of a CW laser, thus the cross-sectional shape of the cutting mark (first thick-walled portion) can be approximately circular (length-to-width ratio of 0.85 or higher). On the other hand, in the manufacturing method of the electrode plate with the above-described structure, when cutting the electrode plate body (cutting the active material placement area), a high-energy pulsed laser is used to suppress the decrease in adhesion of the electrode active material layer caused by the incorporation of molten metal. Therefore, a coating layer containing the electrode active material can be attached to the laser cutting mark (second thick-walled portion) formed at the outer periphery of the electrode plate body. This coating layer, unlike the electrode active material layer mixed with molten metal, is not easily peeled off or detached from the electrode core.

[0024] Furthermore, in a preferred embodiment of the electrode plate disclosed herein, the second thick-walled portion has a claw shape, which includes a cap protruding to one or both sides in the thickness direction and a recess formed between the cap 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 a high-energy pulsed laser is used, the amount of metal melted during cutting becomes very small, thus sometimes forming a claw-shaped cutting mark (second thick-walled portion) as described above. This claw-shaped second thick-walled portion exhibits an excellent anchoring effect, thus more effectively preventing the electrode active material layer from detaching or peeling off.

[0025] 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. This allows the second thick-walled portion to be appropriately coated with the coating layer of the electrode active material, thus appropriately preventing other components (e.g., the separator of a secondary battery) from being damaged by the second thick-walled portion.

[0026] 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. This electrode plate structure facilitates the bending of the electrode tabs, thus contributing to improved manufacturing efficiency of the secondary battery. Such a first thick-walled portion can be formed when the electrode tabs are cut using a pulsed laser with conditions approximating a CW laser, as described above.

[0027] 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, the first region and the second region being 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 an overlap rate of 90% or more. 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 is sparse.

[0028] Furthermore, according to the method for manufacturing a secondary battery disclosed herein, a secondary battery with the following structure can be manufactured. Specifically, in the disclosed technology, a secondary battery having a pair of electrode plates facing each other with a separator between them is characterized in that at least one of the pair of electrode plates uses an electrode plate with the above-described structure. This suppresses the leaching of conductive foreign matter (fragments of the electrode active material layer, sputtered matter) from the electrode plates, thus contributing to improved safety of the secondary battery. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating a method for manufacturing an electrode plate according to one embodiment.

[0030] 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.

[0031] Figure 3 This is a top view illustrating a method for manufacturing an electrode plate according to one embodiment.

[0032] Figure 4 This is a graph illustrating the overlap rate of pulsed lasers.

[0033] Figure 5 yes Figure 2 VV-direction sectional view in the middle.

[0034] Figure 6 yes Figure 2 Sectional view from VI to VI.

[0035] Figure 7 This is a perspective view schematically illustrating one embodiment of a secondary battery.

[0036] Figure 8 It is along Figure 7 A schematic longitudinal section view of lines VIII-VIII in the diagram.

[0037] Figure 9 It is along Figure 7 A schematic longitudinal section view of the IX-IX line.

[0038] Figure 10 It is along Figure 7 A schematic cross-sectional view of the XX line.

[0039] Figure 11 It is a schematic perspective view of the electrode body installed on the sealing plate.

[0040] Figure 12 It is a perspective view schematically showing an electrode body with a positive second collector and a negative second collector installed.

[0041] Figure 13 This is a perspective view illustrating the electrode body of a secondary battery according to one embodiment.

[0042] Figure 14 This is a front view of the electrode body of a secondary battery according to one embodiment.

[0043] Figure 15 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate in Example 1.

[0044] 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 Example 1.

[0045] Figure 17 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate in Example 3.

[0046] Figure 18 This is a cross-sectional SEM image (1000x magnification) of the side edge of the main body of the negative electrode plate in Example 3.

[0047] Figure 19 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab of the negative electrode plate in Example 6.

[0048] Figure 20 This is a cross-sectional SEM image (370x magnification) of the side edge of the main body of the negative electrode plate in Example 6.

[0049] Explanation of reference numerals in the attached figures

[0050] 10 Positive Plate

[0051] 12 Positive electrode core

[0052] 12t positive electrode tab

[0053] 14 Positive electrode active material layer

[0054] 16 protective layers

[0055] 20 Negative electrode plate

[0056] 20A Negative Electrode Precursor

[0057] 20b Electrode plate main body

[0058] 22 Negative electrode core

[0059] 22t negative electrode tab

[0060] 23 First Thick-walled Section

[0061] 24 Negative electrode active material layer

[0062] 25 Second thick-walled section

[0063] 25b coating layer

[0064] 30 Diaphragm

[0065] 38. Winding fixing tape

[0066] 40. Winded electrode body

[0067] 42 Positive electrode tabs

[0068] 44 Negative electrode tabs

[0069] 50 Battery casing

[0070] 60 Positive extremes

[0071] 65 Negative extremes

[0072] 70 Positive current collector

[0073] 75 Negative electrode current collector

[0074] 100 rechargeable batteries

[0075] A1 Negative Electrode Active Material Setting Area

[0076] A2 Exposed area of ​​negative electrode core

[0077] A3 Repeated Irradiation Area

[0078] A4 Single Irradiation Area

[0079] S1 Precursor Preparation Process

[0080] S2 Active substance setting area cutting process

[0081] S3 Core Exposed Area Cutting Process Detailed Implementation

[0082] The following description, with reference to the accompanying drawings, illustrates embodiments of the technology disclosed herein. It should be noted that matters necessary for implementing the technology disclosed herein, other than those specifically mentioned in this specification (e.g., the general structure and manufacturing process of a battery), can be understood by those skilled in the art based on prior art in this field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the art. It should be noted that in this specification, the expression "A~B" indicating a range includes the meaning of A and below B, and includes the meanings of "preferably larger than A" and "preferably smaller than B".

[0083] It should be noted that, in this specification, "secondary battery" refers to an energy storage device that generates a charging and discharging reaction by the movement of 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. The following describes an embodiment using a lithium-ion secondary battery as an example.

[0084] <Method for manufacturing electrode plates>

[0085] The method for manufacturing the electrode plate disclosed herein is a method for manufacturing an electrode plate having an electrode core as a metal foil and an electrode active material layer disposed on the surface of the electrode core and containing electrode active material. Hereinafter, as an embodiment of the method for manufacturing the 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 in the diagram. It should be noted that... 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".

[0086] like Figure 1 As shown, the electrode plate manufacturing method of this embodiment includes a precursor preparation step S1, an active material placement 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.

[0087] (Overview of the negative electrode plate)

[0088] like Figure 2 As shown, the negative electrode plate 20 is a long 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 disposed on the surface of the negative electrode core 22. Furthermore, from the viewpoint of battery performance, the negative electrode active material layer 24 is preferably disposed on 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 disposed. On the other hand, the negative electrode tab 22t is the region where the negative electrode active material layer 24 is not disposed and the negative electrode core 22 is exposed. 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 2The negative electrode plate 20 shown has a plurality of negative electrode tabs 22t. These plurality of negative electrode tabs 22t are arranged at predetermined intervals along the long side direction L of the negative electrode plate 20.

[0089] The components constituting the negative electrode plate 20 can be made of materials 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.

[0090] The negative electrode active material layer 24 is a layer containing a negative electrode active material. As the negative electrode active material, a material capable of reversibly absorbing and releasing charge carriers in relation to the positive electrode active material is 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). Silicon-based materials may also contain other metallic elements (e.g., alkaline earth metals) and their oxides. Furthermore, the negative electrode active material layer 24 may also contain additives other than the negative electrode active material. Examples of such additives include adhesives and thickeners. Specific examples of adhesives include rubber-based adhesives such as styrene-butadiene rubber (SBR). Specific examples of thickeners include carboxymethyl cellulose (CMC). It should be noted that 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. It should also be noted that the negative electrode active material can account for 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.

[0091] like Figure 1 As shown, the negative electrode plate 20 with the above structure is manufactured by performing a precursor preparation process S1, an active material setting area cutting process S2, and a core exposed area cutting process S3. Each process will be described below.

[0092] (Preparation step S1)

[0093] In this process, an electrode precursor is prepared as the precursor to the electrode plate. Figure 3The 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 2 The negative electrode core 22 has a large area. Furthermore, a negative electrode active material layer 24 is provided on the surface of the negative electrode core 22. The negative electrode active material layer 24 extends along the long side direction L and is located at the center of the negative electrode core 22 in the short side direction S. In this specification, the area where the negative electrode active material layer 24 is provided is referred to as the "negative electrode active material provision 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) do not have a negative electrode active material layer 24 provided, 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 method for preparing the negative electrode precursor 20A with the above structure is 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 as long as the negative electrode precursor 20A can be prepared. For example, a separately manufactured negative electrode precursor 20A can also be purchased for preparation. Furthermore, 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 structured such that the negative electrode core is exposed only on one side edge.

[0094] (Active substance setting area cutting process S2)

[0095] In this process, a pulsed laser is used to cut the negative electrode active material setting region A1 of the negative electrode precursor 20A. Specifically, in the active material setting region cutting process S2, as follows... Figure 3 The dashed line L in N1 As shown, a pulsed laser scans the negative electrode active material setting region A1 along the side edge A1a of the negative electrode active material setting region A1. This allows the side edge A1a of the negative electrode active material setting region A1, where the thickness of the negative electrode active material layer 24 is uneven, to be removed, thus creating a negative electrode plate 20 with a uniform thickness of the negative electrode active material layer 24. Here, when the dashed line L is as described... N1When the negative electrode active material setting 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 mix 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 slight impact. Therefore, in the active material setting area cutting process S2 of this embodiment, to prevent the reduction in adhesiveness caused by the mixing of molten metal, a pulsed laser is used when cutting the negative electrode active material setting area A1, and the frequency of the pulsed laser in the active material setting area cutting process S2 is lower than the frequency of the pulsed laser in the core exposed area cutting process S3 described later. Such a low-frequency pulsed laser can concentrate a large amount of energy (high peak output) in a shorter time interval, thus enabling rapid cutting of the negative electrode core 22 with a small amount of molten material. Therefore, the reduced adhesion of the negative electrode active material layer 24 caused by the mixing of molten metal can be suppressed, thus preventing the fragments of the negative electrode active material layer 24 from falling off or peeling off.

[0096] Furthermore, the specific frequency of the pulsed laser in the active material setting region cutting process S2 is preferably 2000 kHz or less, more preferably 1500 kHz or less, and even more preferably 1000 kHz or less. This further increases the peak output when cutting the negative electrode active material setting region A1, thus preventing the molten negative electrode core 22 from mixing into the negative electrode active material layer 24, and making it easier to cut the negative electrode precursor 20A. On the other hand, the lower limit of the frequency of the pulsed laser in the active material setting region cutting process S2 is preferably 100 kHz or more, more preferably 150 kHz or more, and even more preferably 200 kHz or more. By increasing the frequency of the pulsed laser in this way, the peak output decreases, thus preventing a portion of the irradiated negative electrode active material layer 24 from being blown away.

[0097] It should be noted that the conditions of the pulsed laser in the active material setting area cutting process S2 are not particularly limited, and are preferably 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, as the average output of the pulsed laser increases, it tends to make it easier to cut the negative electrode precursor 20A. On the other hand, as the average output of the pulsed laser decreases, the impact during laser irradiation decreases, thus preventing a portion of the negative electrode active material layer 24 from being blown away by the laser impact. In addition, the spot diameter of the pulsed laser in the active material setting area cutting process S2 is preferably 10μm to 60μm, more preferably 20μm to 50μm, and even more preferably 25μm to 40μm. Therefore, the negative electrode plate 20 can be easily cut from the negative electrode precursor 20A.

[0098] Furthermore, the overlap rate of the pulsed laser in the active material setting area cutting process S2 is preferably smaller than that in the core exposure area cutting process S3 described later. As the overlap rate of the pulsed laser decreases, there is a tendency to easily cut the negative electrode core 22 when the molten amount is low. On the other hand, as the overlap rate increases, the state of the pulsed laser approaches that of a CW laser, thus there is a tendency to easily suppress the generation of sputtering material described later. Therefore, in the active material setting area cutting process S2, where the incorporation of molten negative electrode core 22 is a problem, it is preferable to use a pulsed laser with a small overlap rate. Specifically, the overlap rate of the pulsed laser in the active material setting area cutting process S2 is preferably 40% to 95%, more preferably 50% to 90%, and even more preferably 70% to 90%.

[0099] Next, the scanning speed of the pulsed laser in the active material setting 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 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 setting 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, as the pulse width of the pulsed laser decreases, there is a tendency for the peak output to increase, thus making it easier to reduce the amount of molten negative electrode core 22 during laser cutting. On the other hand, as the pulse width increases, the impact applied to the negative electrode active material layer 24 decreases, thus preventing a portion of the negative electrode active material layer 24 from being blown away during laser irradiation.

[0100] (Core exposed area cutting process S3)

[0101] 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 scans along the short side direction S of the negative electrode precursor 20A, moving from the negative electrode active material setting region A1 toward the negative electrode core exposed region A2. Then, the pulsed laser scans a certain distance along the long side direction L of the negative electrode precursor 20A, and then again scans along the short side direction S, moving toward the negative electrode active material setting region A1. This cuts a portion of the negative electrode core exposed region A2 into a convex shape to form a negative electrode tab 22t (see reference). Figure 2 Furthermore, in this embodiment, the active material setting area cutting process S2 is performed repeatedly at regular intervals. Figure 3 The dashed line L in N1 ) and core exposed area cutting process S3 ( Figure 3 The dashed line L in N2 Thus, the side edge A1a of the negative electrode active material setting area A1 can be removed, and multiple negative electrode tabs 22t can be cut out.

[0102] In the electrode plate manufacturing method of this embodiment, during the core exposure area cutting process S3, the state of the pulsed laser irradiating the negative electrode core exposure area A2 is made close to that of a CW laser. Firstly, in this embodiment, the pulsed laser in the core exposure area cutting process S3 (refer to...) Figure 3 The dashed line L in N2 The frequency of the pulsed laser in the active material setting area cutting process S2 (refer to) is higher than that of the pulsed laser in the active material setting area cutting process S2 (refer to) Figure 3 The dashed line L in N1 The frequency of the pulsed laser is high. As mentioned above, as the frequency of the pulsed laser increases, the peak output tends to decrease. As a result, the impact when the laser cuts the exposed area A2 (negative electrode core 22) of the negative electrode core is reduced, thus reducing the likelihood of sputtering. Furthermore, the specific frequency of the pulsed laser in the core exposed area cutting process S3 is preferably 450 kHz or higher, more preferably 1000 kHz or higher, and particularly preferably 2000 kHz or higher. This allows for more appropriate prevention of sputtering. On the other hand, from the viewpoint of ensuring a certain peak output and ensuring the cutting efficiency of the exposed area A2 of the negative electrode core, the frequency of the pulsed laser in the core exposed area cutting process S3 is preferably 4000 kHz or lower, more preferably 3500 kHz or lower, and particularly preferably 3000 kHz or lower.

[0103] Next, in the electrode plate manufacturing method of this embodiment, in order to make the state of the pulsed laser in the core exposed area cutting process S3 close to that of a CW laser, the overlap rate of the pulsed laser is controlled to be 90% or more. Specifically, as the overlap rate of the pulsed laser increases, the laser irradiation approaches continuous irradiation, thus making it easier to produce a cut with a large amount of melting, similar to a CW laser, and suppressing sputtering. Furthermore, from the viewpoint of more appropriately suppressing sputtering, the overlap rate of the pulsed laser in the core exposed area cutting process S3 is preferably 90.5% or more, more preferably 91% or more, further preferably 91.5% or more, and particularly preferably 92% or more. On the other hand, the upper limit of the overlap rate of the pulsed laser in the core exposed area cutting process S3 is not particularly limited, and can be 99% or less. However, as the overlap rate decreases, the scanning speed of the pulsed laser tends to increase, thus tending to improve manufacturing efficiency. From this perspective, the overlap rate of the pulsed laser in the core exposed area cutting process S3 is preferably 98.5% or less, more preferably 98% or less, even more preferably 97.5% or less, and particularly preferably 97% or less.

[0104] In addition, such as Figure 4As shown, in laser cutting using a pulsed laser, multiple points R1 and R2 are irradiated while being shifted little by little towards a predetermined scanning direction D. This results in a repeated irradiation area A3 where adjacent points R1 and R2 are irradiated in an overlapping manner, and a single irradiation area A4 where a single point R1 and R2 is irradiated. The "overlap rate" in this specification refers to the degree to which adjacent points R1 and R2 overlap during the irradiation of the pulsed laser. This overlap rate Y can be calculated based on the following equation (1) when the point diameter is set to W1 and the irradiation interval between adjacent points is set to W2. Furthermore, both the point diameter W1 and the irradiation interval W2 are lengths along the scanning direction D of the pulsed laser. That is, during irradiation... Figure 4 In the case of elliptical points R1 and R2 as shown, the point diameter W1 refers to the diameter of points R1 and R2 along the scanning direction D. Furthermore, when irradiating elliptical points, each point may be tilted relative to the scanning direction D. Even in this case, the length along the scanning direction D is used as the point diameter W1 of each point, and the irradiation interval W2 is measured. Moreover, the specific point diameter W1 of the pulsed laser in the core exposure 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.

[0105] Overlap rate Y (%) = (W1-W2) / W1×100 (1)

[0106] Furthermore, the pulsed laser in the core exposed area cutting process S3 only needs to meet the aforementioned frequency and overlap rate; other conditions are not particularly limited. For example, other conditions of the pulsed laser in the core exposed area cutting process S3 are preferably appropriately adjusted 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 of the pulsed laser in the core exposed area cutting process S3 is preferably 10 ns or more, more preferably 30 ns or more, and even more preferably 120 ns or more. As the pulse width of the pulsed laser increases, the heat-affected time applied to the metal component is longer, and the molten portion expands, thus there is a tendency for sputtering to be less likely to occur. On the other hand, the upper limit of the pulse width of the pulsed laser in the core exposed area cutting process S3 can be 300 ns or less, or 240 ns or less. As the pulse width of the pulsed laser decreases, there is a tendency for the negative electrode core exposed area A2 to be cut more easily.

[0107] 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. As the average output of the pulsed laser increases, cutting the negative electrode core exposure area A2 tends to become easier. 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.

[0108] 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. As the scanning speed decreases, there is a tendency to reduce the likelihood of poor cutting of 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 improved manufacturing efficiency due to shorter 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 setting area cutting process S2 and the core exposure area cutting process S3.

[0109] (Other processes)

[0110] As described above, in the manufacturing method of this embodiment, the active material setting area cutting process S2 is performed repeatedly at certain intervals. Figure 3 The dashed line L in N1 ) and core exposed area cutting process S3 ( 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 2 As 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 along the long side direction L. This allows the negative electrode plate 20 to be manufactured to the desired length. 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 other tool can be used. Furthermore, along the double-dotted line L... N3L N4 When laser cutting is used in the cutting process, it is preferable to use the cutting process S2 (dashed line L) that cuts the area where the active material is located. N1 The same pulsed laser conditions were applied. This allows for more effective suppression of the peeling and shedding of fragments from the negative electrode active material layer 24. Furthermore, along these double-dotted lines L... N3 L N4 The cutting can be carried out appropriately according to the shape of the manufactured negative electrode plate, and is not limited to the technology disclosed herein.

[0111] As described above, in the electrode plate manufacturing method of this embodiment, when cutting off the negative electrode active material placement area A1 (refer to the dashed line L)... N1 A pulsed laser is used. This suppresses the incorporation of molten metal into the negative electrode active material layer 24, preventing a decrease in the adhesion of the negative electrode active material layer 24 and thus preventing fragments of the negative electrode active material layer 24 from detaching or peeling off from the manufactured negative electrode plate 20. Furthermore, in the manufacturing method of this embodiment, a pulsed laser is also used when cutting the exposed negative electrode core area A2, continuously cutting the negative electrode active material placement area A1 and the exposed negative electrode core area A2. This prevents a significant decrease in manufacturing efficiency and the occurrence of poor cutting due to switching laser types. Moreover, in this embodiment, the frequency of the pulsed laser used to cut the exposed negative electrode core area A2 is higher than that used to cut the negative electrode active material placement area A1, and the overlap rate of the pulsed lasers in the core exposed area cutting process S3 is controlled to be 90% or higher. This reduces the impact during laser cutting and increases the amount of molten electrode core during laser cutting to the same level as with a CW laser, thus suppressing the scattering of sputtering material when cutting the exposed negative electrode core area A2. As described above, according to this embodiment, conductive foreign matter can be prevented from falling off or peeling off from the manufactured negative electrode plate 20, thus contributing to the improvement of the safety of the secondary battery.

[0112] <Negative electrode plate>

[0113] Next, as an example of an electrode plate manufactured using the electrode plate manufacturing method disclosed herein, a negative electrode plate for a lithium-ion secondary battery will be described.

[0114] (Overview of the negative electrode plate)

[0115] 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 a region where the negative electrode active material layer 24 is disposed on the surface of the negative electrode core 22, namely the electrode plate body portion 20b, and a region where the negative electrode active material layer 24 is not disposed and the negative electrode core 22 is exposed, namely the negative electrode tab 22t. These have already been described, so repeated descriptions are omitted.

[0116] (First thick-walled section)

[0117] And, as Figure 5 As shown, in this embodiment, the negative electrode plate 20 has a first thick-walled 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-walled portion 23 is the trace of laser cutting in the core exposed area cutting process S3. 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 exposed area A2 (refer to...) is cut... Figure 3 The state of the pulsed laser at that time is similar to that of the CW laser. In the outer periphery 22t1 of the negative electrode tab 22t cut with such a pulsed laser, similar to the case of cutting with a CW laser, a first thick-walled portion 23, which is close to a circular cross-section, can be formed, leaving a mark of melting and cutting the metal foil. Furthermore, "close to a circular cross-section" here means... Figure 5 The aspect ratio of the first thick-walled portion 23 in the cross-section along the thickness direction T of the negative electrode tab 22t, as shown, is close to 1 (e.g., 0.8 or more, typically 0.85 or more). 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 the following... Figure 15 A 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. Furthermore, 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 taken as the aspect ratio. In addition, 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 a circle or ellipse; it may also have a notch or deformation in a portion. Even for a first thick-walled portion with such a notch or deformation, the aspect ratio can be calculated using the steps described above.

[0118] Furthermore, when the cross-sectional shape of the first thick-walled portion 23 is close to a circle, in other components (e.g.) Figure 13When the diaphragm 30 (shown) comes into contact with the outer peripheral edge 22t1 of the negative electrode tab 22t, it can prevent damage to the other components. 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 can 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 can be 1.1 or more, or 1.2 or more, or 1.4 or more, or 1.5 or more. On the other hand, the upper limit of t1 / t2 can be 7 or less, or 6 or less, or 5 or less, or 3 or less.

[0119] Furthermore, in the electrode plate manufacturing method of this embodiment, as described above, the exposed area A2 of the negative electrode core is cut off (refer to...). Figure 3 The overlap rate of the pulsed laser is controlled to be above 90%. When the exposed area A2 of the negative electrode core is melted and cut using such a high overlap rate pulsed laser, the molten electrode core deforms into a roughly spherical shape due to surface tension, thus alternately forming areas where molten metal is concentrated and areas where molten metal is sparse. 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 can be alternately formed.

[0120] Furthermore, when using a pulsed laser to cut the exposed area A2 of the negative electrode core, since the negative electrode tab 22t and the exposed area A2 of the negative electrode core can be separated at the moment of laser irradiation, it is not necessary to peel 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 mark formed by the CW laser (see reference) 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. 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 the improvement of the manufacturing efficiency of the secondary battery.

[0121] (Second thick-walled section)

[0122] On the other hand, such as Figure 6As 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 trace left by irradiating the negative electrode active material placement area A1 of the negative electrode precursor 20A with a pulsed laser during the active material placement area cutting process S2. This 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 this 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. Alternatively, 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 with the negative electrode active material layer mixed with molten metal, the coating layer 25b has excellent adhesion to the surface of the negative electrode core 22 (second thick-walled portion 25), thus effectively preventing the peeling and shedding of conductive foreign matter. Furthermore, the aforementioned second thick-walled portion 25 and coating layer 25b are formed on the outer periphery of the electrode body portion 20b (see reference). 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 a pulsed laser, a second thick-walled portion 25 and a covering layer 25b are formed in the region between the negative electrode tabs 22t.

[0123] Furthermore, the second thick-walled portion 25 has a hook-like shape, which includes a cap 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 25a1 and the negative electrode core 22. Unlike the first thick-walled portion 23 described above, the second thick-walled portion 25 is formed by a high-output pulsed laser, resulting in less melting of the negative electrode core 22, sometimes forming 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. This provides an excellent anchoring effect, thus further securing the coating layer 25b and more effectively preventing the shedding or peeling of fragments of the negative electrode active material layer 24. In addition, when such a hook-shaped second thick-walled portion 25 is formed, it may become a cause of damage to other components (such as the separator of 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, and it can be 20 μm or less, 17.5 μm or less, or 15 μm or less.

[0124] Furthermore, the thickness of the cap 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. Also, the "thickness of the cap" mentioned above refers to the thickness of one side of the cap 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 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 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 25a1 can be 1 μm to 30 μm, 5 μm to 25 μm, or 10 μm to 20 μm. Moreover, the height of the entrance (the dimension in the thickness direction T) of 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 (the 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. This allows an appropriate amount of the coating layer 25b to be maintained inside the recess 25a2, resulting in a more suitable anchoring effect. Furthermore, the angle at which the cap portion 25a1 rises from the surface of the negative electrode core 22 is preferably greater than 0° and less than 90°.

[0125] 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, the second thick-walled portion 25 has a cutting mark formed by a high-energy pulsed laser, therefore, unlike the first thick-walled portion 23, its cross-sectional shape is unlikely to be approximately circular. 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.

[0126] Secondary batteries

[0127] 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 line 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 7 A 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.

[0128] like Figures 7-10As 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. Although not shown in the diagram, 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 electrolyte 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 electrolytes include fluorinated lithium salts such as LiPF6.

[0129] (Battery casing)

[0130] 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 can be the same as conventionally used materials, without particular limitation. The battery housing 50 is preferably made of metal, and more preferably of materials such as aluminum, aluminum alloy, iron, or iron alloy. The battery housing 50 includes an outer casing 52 and a sealing plate 54.

[0131] The outer casing 52 is a flat, bottomed, square container with an opening 52h on its upper surface. For example... Figure 7 As shown, the outer casing 52 includes: a bottom wall 52a that is generally rectangular in plan view, a pair of long side walls 52b extending from the long side of the bottom wall 52a in the vertical direction Z, and a pair of short side walls 52c extending from the short side of the bottom wall 52a in the vertical direction Z. On the other hand, the sealing plate 54 is a plate-shaped member that is generally rectangular in plan view and closes 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 (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 to break (open) at a preset pressure when a large amount of gas is generated inside the battery casing 50, thereby discharging the gas inside the battery casing 50.

[0132] (Electrode terminals)

[0133] Additionally, one side of the sealing plate 54 in the long side direction Y of the secondary battery 100 ( Figure 7 , Figure 8A positive terminal 60 is installed at the end of the battery casing 50 (on the left side). This positive terminal 60 is connected to the 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. These 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.). It should be noted that the external conductive members are preferably made of a metal with excellent conductivity (aluminum, aluminum alloy, copper, copper alloy, etc.).

[0134] (Electrode current collector)

[0135] 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 , 11 As shown, the positive electrode current collector 70 includes a plate-shaped conductive member extending along the inner side of the sealing plate 54, namely the first positive electrode current collector 71, and a plurality of plate-shaped conductive members extending along the vertical direction Z, namely the second positive electrode current collectors 72. Furthermore, the lower end 60c of the positive terminal 60 extends toward the interior of the battery casing 50 through the terminal insertion hole 58 of the sealing plate 54 and connects 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 such that the second positive electrode current collector 72 faces one side 40a 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.

[0136] On the other hand, the negative terminal 65 is connected to each of the 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 plate-shaped conductive member extending along the inner surface of the sealing plate 54, namely a first negative current collector 76, and plate-shaped conductive members extending along the vertical direction Z, namely a plurality of second negative current collectors 77. Furthermore, the lower end 65c of the negative terminal 65 extends into the interior of 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 such that the second current collector 77 of the negative electrode faces the other side 40b of the wound electrode body 40 (see reference). Figure 10 Therefore, the upper end of the negative electrode second collector 77 is electrically connected to the negative electrode first collector 76.

[0137] (Insulating components)

[0138] Furthermore, in the secondary battery 100 of this embodiment, various insulating members are installed to prevent the winding electrode body 40 from conducting with 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 7 This prevents the positive electrode external conductive component 62 and the negative electrode external conductive component 67 from conducting with the sealing plate 54. Additionally, washers 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, preventing direct contact between the winding electrode body 40 and the sealing plate 54. Furthermore, the wound electrode body 40 is held by an electrode body retainer 98 made of an insulating resin sheet (see reference). Figure 9The electrode body 40 is contained within the battery casing 50 in a covered state. This prevents direct contact between the wound electrode body 40 and the outer casing 52. Furthermore, the materials of the various insulating components are not particularly limited as long as they have the predetermined insulating properties. As an example, synthetic resin materials such as polyolefin resins (e.g., polypropylene (PP), polyethylene (PE)) and fluorine resins (e.g., perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE)) can be used.

[0139] (Wound electrode body)

[0140] Next, the electrode body used in the secondary battery 100 of this embodiment will be described. In this embodiment, the electrode body used is... Figure 13 The wound electrode body 40 shown serves as the electrode body. The wound electrode body 40 is wound with a pair of electrode plates (positive electrode plate 10, negative electrode plate 20) facing each other across a separator 30. In manufacturing this wound electrode body 40, first, a laminated body is formed, consisting of a strip-shaped separator 30 sandwiched between two layers of strip-shaped positive electrode plates 10 and strip-shaped negative electrode plates 20. Then, after winding this laminated body along its long side, a winding fixing strip 38 (see reference) is applied. Figure 14 The electrode is attached to the terminal portion 30a of the diaphragm 30 disposed on the outermost periphery. This allows the winding electrode body 40 to be manufactured. Furthermore, in this embodiment, the negative electrode plate 20 with the above-described structure is used in the manufacture of this winding electrode body 40. The winding electrode body 40 of this embodiment will be described below.

[0141] First, the separator 30 is a sheet-like component that prevents 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 separator 30, a resin sheet with multiple fine pores allowing charge carriers to pass through can be described. This resin sheet preferably comprises a resin layer made of a 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.

[0142] The positive electrode plate 10 includes a positive electrode core 12 as a foil-shaped metal component, a positive electrode active material layer 14 disposed on the surface of the positive electrode core 12, and a protective layer 16 disposed on the surface of the positive electrode core 12 adjacent to the side edge portion 10a of the positive electrode plate 10. Furthermore, on the side edge portion 10a of the positive electrode plate 10, a plurality of outer surfaces facing the short side direction S are disposed at predetermined intervals along the long side direction L of the positive electrode plate 10. Figure 13The positive electrode tab 12t protrudes from the left side of the image. This positive electrode tab 12t is the area where the positive electrode active material layer 14 and the protective layer 16 are not provided, and the positive electrode core 12 is exposed. It should be noted that, from the viewpoint of battery performance, the positive electrode active material layer 14 and the protective layer 16 are preferably provided on both sides of the positive electrode core 12. Alternatively, the protective layer 16 may be provided such that a portion of it covers the side edge of the positive electrode active material layer 14. It should be noted that the materials of the various components constituting the positive electrode plate 10 (positive electrode core 12, positive electrode active material layer 14, and protective layer 16) can be any conventionally known materials that can be used in general secondary batteries (such as lithium-ion secondary batteries) without particular restriction, and are not limited to the technologies disclosed herein; therefore, detailed descriptions are omitted.

[0143] 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. This negative electrode plate 20 has a negative electrode active material placement region A1 (see reference 20A) from the negative electrode precursor 20A. Figure 3 A pulsed laser is used when cutting out the main body 20b of the electrode plate. Therefore, the negative electrode plate 20 of this embodiment suppresses the decrease in adhesion of the negative electrode active material layer 24 caused by the incorporation of molten metal. As a result, after constructing the secondary battery 100, it is possible to prevent fragments of the negative electrode active material layer 24 from detaching or peeling off and causing internal short circuits. Furthermore, the negative electrode plate 20 exposes the negative electrode core from the negative electrode precursor 20A in region A2 (see reference 2000). Figure 3 When 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 causing an internal short circuit. In other words, the secondary battery 100 of this embodiment has high safety because it prevents various conductive foreign objects from detaching or peeling off from the negative electrode plate 20.

[0144] <Other Implementation Methods>

[0145] The above describes one embodiment of the technology disclosed herein. Furthermore, the above embodiment illustrates an example of applying the technology disclosed herein and is not intended to limit the scope of the technology disclosed herein.

[0146] For example, having Figure 5The negative electrode plate 20 with a first thick-walled portion 23 having an aspect ratio of 0.85 or more shown is an example of an electrode plate manufactured using the electrode plate manufacturing method disclosed herein, and is not intended to limit the technology disclosed herein. Specifically, the electrode plate manufacturing method disclosed herein suppresses sputtering by making the state of the pulsed laser in the core exposed area cutting process close to that of a CW laser, thereby preventing conductive foreign matter from falling off or peeling off from the manufactured electrode plate. However, the shape of the laser cutting mark (first thick-walled portion) may vary depending on the material and thickness of the electrode core to be cut, so even if the sputtering is appropriately suppressed by applying the electrode plate manufacturing method disclosed herein, the aspect ratio of the first thick-walled portion may be less than 0.85. That is, the electrode plate manufacturing method disclosed herein is a method of reducing the amount of sputtering generated by making the state of the pulsed laser in the core exposed area cutting process close to that of a CW laser, and is not limited to the method of manufacturing a negative electrode plate having a first thick-walled portion having an aspect ratio of 0.85 or more.

[0147] Furthermore, in the above embodiments, 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 a positive electrode plate is used as 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). It should be noted that, compared with the positive electrode plate, the negative electrode plate manufactured in the above embodiments 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 is particularly suitable for the manufacture of negative electrode plates.

[0148] 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 face each other with a separator in between. As another example of the electrode body structure, a stacked electrode body formed by sequentially stacking multiple positive and negative electrode plates while clamping a separator can be cited. When manufacturing the negative electrode plate for such a stacked electrode body, it can be implemented for each negative electrode tab 22t. Figure 3 double-dotted line L N4 The cutting is done along the short side direction S as shown. Although detailed explanations are omitted, the fabrication of the positive electrode plate is the same. Furthermore, multiple positive and negative electrode plates are stacked while a separator is sandwiched, with the positive electrode tabs stacked in the same position and the negative electrode tabs of the negative electrode plate stacked in the same position. In this way, a stacked electrode body can be fabricated.

[0149] Furthermore, in the above embodiment, a high-capacity secondary battery 100 with three wound electrode bodies 40 housed inside the battery casing 50 is described. However, the number of electrode bodies housed in one 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 (such as nickel-metal hydride batteries), there is also a process of using a laser to cut off the active material placement area of ​​the electrode precursor and the core exposure area, so the technology disclosed herein can be applied without particular limitation.

[0150] 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 the separator sandwiched between the positive and negative electrode plates. In this all-solid-state battery, the separator and electrolyte are integrated and contained within the electrode body, thus preventing electrolyte leakage. In the manufacturing process of such an all-solid-state battery, there is also a process of using a laser to cut the active material placement area of ​​the electrode precursor and the core exposure area, therefore the technology disclosed herein can be applied without particular limitation.

[0151] [Experimental Example]

[0152] The following describes experimental examples related to the present invention. It should be noted that the content of the experimental examples described below is not intended to limit the present invention.

[0153] 1. Sample preparation

[0154] (Example 1)

[0155] In Example 1, pulsed lasers under different conditions were used in the negative electrode active material placement area of ​​the negative electrode precursor and the core exposure area to manufacture a negative electrode for a lithium-ion secondary battery. First, a negative electrode precursor with a negative electrode active material layer of 80 μm thickness was prepared, on both sides of an 8 μm thick negative electrode core (copper foil). The negative electrode active material layer of this negative electrode precursor contained negative electrode active material, a thickener, and a binder in a ratio of 98.3:0.7:1.0. It should be noted that 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 a negative electrode plate.

[0156] Specifically, in the cutting of the negative electrode active material setting area in Example 1, a pulsed laser with a pulse width of 240 ns, an overlap rate of 92%, and a frequency of 400 kHz was used. On the other hand, in the cutting of the core exposed area, a pulsed laser with a pulse width of 240 ns, an overlap rate of 90%, and a frequency of 450 kHz was used. In addition, the spot diameter of the pulsed laser was uniformly 30 μm.

[0157] (Example 2~Example 5)

[0158] In Examples 2 through 5, the negative electrode for a lithium-ion secondary battery was manufactured under the same conditions as in Example 1, except that the overlap rate and frequency of the pulsed lasers used in cutting the exposed area of ​​the core were different. Furthermore, the overlap rate and frequency of the pulsed lasers in each example are shown in Table 1, which will be described later.

[0159] (Example 6)

[0160] In Example 6, a CW laser under the same conditions was used in both the negative electrode active material setting area and the core exposure area. First, the negative electrode precursor prepared in Example 6 was the same as that prepared in Examples 1-5. Then, in Example 6, a CW laser with an output of 1000W and a scanning speed of 6000mm / sec was used to cut off both the negative electrode active material setting area and the core exposure area. It should be noted that the spot diameter of the CW laser used in Example 6 was 20μm.

[0161] 2. Evaluation Test

[0162] In this experiment, the laser-cut portions of the negative plates manufactured in each example were first observed using a scanning electron microscope (SEM). It should be noted that in this experiment, SEM observations were performed on two portions of the negative plate: the side edge of the negative electrode tab and the side edge of the plate body. Figure 15 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab in 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 in Example 3. Figure 18 This is a cross-sectional SEM image (1000x magnification) of the main body of the electrode plate in Example 3. Figure 19 This is a cross-sectional SEM image (1000x magnification) of the negative electrode tab in Example 6. Figure 20 This is a cross-sectional SEM image (370x) of the electrode body of Example 6.

[0163] Next, based on the aforementioned cross-sectional SEM images, the following aspects were evaluated for the fabricated negative electrode plate. First, based on the cross-sectional SEM images of the negative electrode tabs in each example, the aspect ratio of the laser cutting mark (first thick-walled portion) was measured. Next, the condition near the outer periphery of the negative electrode tab was confirmed, with cases where no sputtering material was attached being evaluated as "○", and cases where one or more sputtering materials were attached being evaluated as "×". Then, the condition of the side edge of the electrode plate body was confirmed, with cases where no layer of negative electrode active material mixed with molten metal was formed being evaluated as "○", and cases where a layer of negative electrode active material mixed with molten metal was formed being evaluated as "×".

[0164] 3. Evaluation Results

[0165] The results of the above evaluation tests are shown in Table 1 below.

[0166] [Table 1]

[0167]

[0168] (1) Cutting results of the exposed area of ​​the core

[0169] First, the condition near the outer periphery of the negative electrode tab in each example (i.e., near the area where the core is exposed after laser cutting) was compared. In Example 1, no metal sheet (sputtered material) was observed adhering near the outer periphery of the negative electrode tab (see reference). Figure 15 Furthermore, a first thick-walled portion with a thickness greater than that of the central portion of the negative electrode tab is formed at the outer periphery of the negative electrode tab. It is presumed that this first thick-walled portion is formed by solidifying molten negative electrode core. Moreover, the aspect ratio of the first thick-walled portion of the negative electrode tab formed in Example 1 is 0.95. Although the illustration is omitted, this result is also observed in Examples 2 and 6, suppressing the adhesion of sputtered material to the negative electrode tab and forming a first thick-walled portion with a large aspect ratio. On the other hand, in Example 3, it was confirmed that a large amount of sputtered material adhered near the outer periphery of the negative electrode tab (see [reference]). Figure 17 Furthermore, the aspect ratio of the first thick-walled portion of the negative electrode tab formed in Example 3 decreased to 0.82. Although the illustrations are omitted, Examples 4 and 5 also showed the same result, with a large amount of sputtered material adhering to the negative electrode tab, and the aspect ratio of the first thick-walled portion decreased. Based on these results, it can be seen that when the frequency of the pulsed laser that cuts the difference in the exposed area of ​​the core is increased and the overlap ratio is made greater than 90%, the state of the pulsed laser can be made similar to that of a CW laser, thus suppressing the generation of sputtered material.

[0170] Furthermore, in Example 6, the center of the first thick-walled portion, which has a roughly circular cross-section, is offset downwards from the center of the negative electrode core in the thickness direction. It is speculated that this is because, in Example 6 using a CW laser, immediately after laser irradiation, the negative electrode tab is not completely separated from the exposed area of ​​the core, requiring peeling of the negative electrode tab from the exposed area. The laser cutting mark (first thick-walled portion) is pulled during this peeling process.

[0171] (2) Cutting results of the active substance layer setting area

[0172] Next, the conditions near the side edge of the electrode body in each example (i.e., near the area where the active material layer is disposed after being cut by the laser) were compared and studied. First, as... Figure 20 As shown, in Example 6, where the active material layer area is cut using a CW laser, a negative electrode active material layer mixed with molten metal is attached to the side edge of the cut electrode body. Furthermore, it is known that the negative electrode active material attached to the side edge of the electrode body can easily detach and peel off due to small impacts. On the other hand, in Examples 1 and 3, the mixing of molten metal into the negative electrode active material layer was not confirmed (see...). Figure 16 and Figure 18 Furthermore, in Examples 1 and 3, a second thick-walled portion with a thickness greater than that of the negative electrode core at the end of the negative electrode core at the side edge of the negative electrode plate body is formed. Additionally, a coating layer containing the negative electrode active material is attached to the surface of this second thick-walled portion. Although figures are omitted, this result is the same in Examples 2, 4, and 5. From the above, it can be seen that by using a pulsed laser when cutting the active material layer area, it is possible to prevent the mixing of molten metal into the negative electrode active material layer.

[0173] The present invention has been described in detail above, but the above description is merely illustrative. That is, the technology disclosed herein includes technologies obtained by various modifications and alterations to the specific examples described above.

Claims

1. A method for manufacturing an electrode plate, wherein the method manufactures an electrode plate comprising an electrode core as a metal foil and an electrode active material layer disposed on the surface of the electrode core and containing an electrode active material, characterized in that, have: The precursor preparation process includes preparing an electrode precursor, which has an active material setting area on the surface of the electrode core where the electrode active material layer is provided and a core exposure area where the electrode active material layer is not provided and the electrode core is exposed. The active substance setting area cutting process involves using a pulsed laser to cut the active substance setting area. as well as The core exposed area cutting process involves using a pulsed laser to cut the core exposed area. The frequency of the pulsed laser in the process of cutting off the core exposed area is greater than the frequency of the pulsed laser in the process of cutting off the active material setting area, and... The overlap rate of the pulsed laser in the process of cutting off the exposed area of ​​the core is above 90%. The electrode core is made of copper or a copper alloy, and the electrode active material contains carbon materials.

2. The method for manufacturing the electrode plate according to claim 1, characterized in that, The frequency of the pulsed laser in the active material setting area cutting process is 100kHz~2000kHz.

3. The method for manufacturing the electrode plate according to claim 1 or 2, characterized in that, The frequency of the pulsed laser in the core exposed area cutting process is 450KHz~4000KHz.

4. The method for manufacturing the electrode plate according to claim 1 or 2, characterized in that, The overlap rate of the pulsed laser in the active material setting area cutting process is smaller than the overlap rate of the pulsed laser in the core exposed area cutting process.

5. A method for manufacturing a secondary battery, the secondary battery comprising a pair of electrode bodies with electrode plates facing each other separated by a separator, the method for manufacturing the secondary battery being characterized in that... At least one of the pair of electrode plates is manufactured using the manufacturing method of the electrode plate according to any one of claims 1 to 4.

Images