Manufacturing method of secondary batteries and secondary batteries

Abstract

This invention relates to a method for manufacturing a secondary battery and to a secondary battery itself. It prevents the detachment and peeling of the electrode active material layer and protective layer at the laser-cut portion of the electrode plate, resulting in a secondary battery with higher safety. The manufacturing method disclosed herein includes a step of preparing a positive electrode precursor on which a positive electrode active material layer and a protective layer are formed on the surface of a positive electrode core; and a step of cutting the protective layer forming region of the positive electrode precursor using a continuously oscillating laser. This prevents the protective layer from detaching or peeling due to the impact of laser irradiation. Furthermore, the manufacturing method disclosed herein includes a step of preparing a negative electrode precursor on which a negative electrode active material layer is formed on the surface of a negative electrode core; and a step of cutting the negative electrode active material layer forming region of the negative electrode precursor using a pulsed laser. This reduces the amount of melting in the negative electrode core during the cutting of the negative electrode precursor, thus preventing the formation of a negative electrode active material layer mixed with molten metal that easily detaches or peels from the negative electrode core.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a secondary battery and to the secondary battery itself. Background Technology

[0002] Secondary batteries, such as lithium-ion batteries, include an electrode body comprising a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate of this secondary battery comprises a positive electrode core as a foil-shaped metal component and a positive electrode active material layer formed on the surface of the positive electrode core. Furthermore, a protective layer is sometimes provided on the positive electrode plate of this secondary battery to prevent internal short circuits. This protective layer is formed on the surface of the positive electrode core, for example, adjacent to the side edge of the positive electrode active material layer. On the other hand, the negative electrode plate comprises a negative electrode core as a foil-shaped metal component and a negative electrode active material layer formed on the surface of the negative electrode core. In this specification, these positive and negative electrode plates are sometimes collectively referred to as "electrode plates." Additionally, the positive and negative electrode cores are collectively referred to as "electrode cores," and the positive and negative electrode active material layers are collectively referred to as "electrode active material layers."

[0003] The electrode plate with the above-mentioned structure is manufactured by forming an electrode active material layer and a protective layer on the surface of a large electrode core to create an electrode precursor, and then cutting the electrode precursor to the desired size. For example, Patent Document 1 discloses a method for manufacturing a stacked secondary battery including the following steps: coating an electrode active material onto a metal foil larger than the electrode area to form an electrode active material layer, and then irradiating the metal foil with a laser to cut it. Patent Document 2 discloses a method for manufacturing a secondary battery including the following steps: preparing an electrode plate comprising a coated portion with an electroactive material coated on a current collector and an uncoated portion without an electroactive material coated, and irradiating the uncoated portion with a continuous wave laser beam to cut it.

[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 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, the electrode active material layer and protective layer formed on the surface of the electrode core tend to have uneven thickness at their side edges. In recent years, to meet increasing demands for battery performance, laser cutting has been performed in the areas where the electrode active material layer and protective layer are formed during the cutting of the aforementioned electrode precursor, cutting out electrode plates with the side edges of the electrode active material layer (or protective layer) removed. This allows for the production of high-quality electrode plates with uniform thickness of the electrode active material layer and protective layer.

[0010] However, if laser cutting is performed in the area where the electrode active material layer and protective layer are formed, the electrode active material layer (or protective layer) may sometimes detach or peel off at the cut portion. For example, the electrode active material layer that detaches or peels off from the electrode core acts as a conductive foreign object inside the secondary battery, and thus may become a cause of internal short circuits. On the other hand, if the protective layer detaches or peels off from the positive electrode core, the positive electrode core is exposed, and therefore, the internal short circuit prevention function based on the protective layer may not be able to function properly. Therefore, the detachment or peeling off of the protective layer may also become a cause of internal short circuits.

[0011] The present invention was made in view of the above circumstances, and its purpose is to provide a technology that can prevent the electrode active material layer and protective layer from falling off and peeling off at the laser cutting part of the electrode plate, thereby obtaining a secondary battery with higher safety.

[0012] Solution for solving the problem

[0013] To achieve the above objectives, a method for manufacturing a secondary battery with the following configuration is provided by means of the technology disclosed herein.

[0014] The manufacturing method disclosed herein is a method for manufacturing a secondary battery having an electrode body including a positive electrode plate, a negative electrode plate, and a separator. The manufacturing method includes: a step of preparing a positive electrode precursor, wherein a positive electrode active material layer containing a positive electrode active material and a protective layer with a lower conductivity than the positive electrode active material layer are formed on the surface of a positive electrode core, which is a strip-shaped metal foil; a step of cutting the region of the positive electrode precursor where the protective layer is formed using a continuous oscillating laser; a step of preparing a negative electrode precursor, wherein a negative electrode active material layer containing a negative electrode active material is formed on a negative electrode core, which is a strip-shaped metal foil; and a step of cutting the region of the negative electrode precursor where the negative electrode active material layer is formed using a pulsed laser.

[0015] The inventors conducted various studies on the causes of detachment and peeling of the electrode active material layer and protective layer at the laser-cutting location of the electrode plate. The results showed that the detachment and peeling of the negative electrode active material layer in the negative electrode plate and the detachment and peeling of the protective layer in the positive electrode plate are caused by completely different reasons. Specifically, if laser cutting is performed in the region where the negative electrode active material layer is formed in the negative electrode precursor (the negative electrode active material layer formation region), a portion of the negative electrode core, which melts due to the heat of the laser, may sometimes mix with the negative electrode active material layer. Subsequently, if the metal components from the negative electrode core solidify within the negative electrode active material layer, the adhesion of the negative electrode active material layer is damaged, and therefore, it is easily detached and peeled off from the negative electrode core due to minor impacts. On the other hand, if laser cutting is performed in the region where the protective layer is formed in the positive electrode precursor (the protective layer formation region), the protective layer may be blown away and detached due to the impact of laser irradiation.

[0016] The manufacturing method disclosed herein was carried out considering the causes of detachment and peeling of the negative electrode active material layer and the protective layer, as discovered by the inventors. Specifically, in the manufacturing method disclosed herein, a pulsed laser is used for laser cutting of the negative electrode precursor. This allows for the concentrated application of large energy over a very short time span, thus enabling cutting to be performed with a small amount of molten negative electrode core. As a result, mixing of the molten negative electrode core with the negative electrode active material layer is prevented. On the other hand, in the manufacturing method disclosed herein, a continuous wave laser (CW laser) is used for laser cutting of the positive electrode precursor. The peak output of this continuous wave laser is relatively small, thus preventing the protective layer from being blown away by the impact of laser irradiation. As described above, according to the manufacturing method disclosed herein, detachment and peeling of the negative electrode active material layer and the protective layer at the laser-cut portion of the electrode plate can be prevented, therefore, a highly safe secondary battery can be easily manufactured.

[0017] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the output of the continuously oscillating laser used to cut the positive electrode precursor is 500W to 2000W. This prevents the protective layer from peeling off and allows for easy cutting of the positive electrode precursor.

[0018] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the scanning speed of the continuously oscillating laser used to cut off the positive electrode precursor is 2000 mm / sec to 10000 mm / sec. This allows for easy cutting of the positive electrode precursor while suppressing the burning of the protective layer. It should be noted that the "scanning speed" in this specification refers to the speed at which the electrode precursor and the laser move relative to each other. That is, when only one of the electrode precursor and the laser moves, the speed at which the moving one moves is called the "scanning speed." On the other hand, when both the electrode precursor and the laser move, the sum of their respective speeds is called the "scanning speed."

[0019] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the diameter of the spot of the continuously oscillating laser used to cut the positive electrode precursor is 10 μm to 60 μm. This allows the positive electrode plate to be easily cut from the positive electrode precursor.

[0020] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the average output of the pulsed laser used to cut off the negative electrode precursor is 80W to 300W. This prevents the molten negative electrode core from mixing with the negative electrode active material layer and allows for easy cutting off of the negative electrode precursor.

[0021] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the scanning speed of the pulsed laser used to cut the negative electrode precursor is 5000 mm / sec or less. This prevents the molten negative electrode core from mixing with the negative electrode active material layer and allows for easy cutting of the negative electrode precursor.

[0022] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the pulse width of the pulsed laser used to cut off the negative electrode precursor is 30 ns to 240 ns. This prevents the molten negative electrode core from mixing with the negative electrode active material layer and allows for easy cutting off of the negative electrode precursor.

[0023] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the repetition frequency of the pulsed laser used to cut off the negative electrode precursor is 100 kHz to 2000 kHz. This prevents the molten negative electrode core from mixing with the negative electrode active material layer and allows for easy cutting off of the negative electrode precursor.

[0024] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the diameter of the pulsed laser spot used to cut the negative electrode precursor is 10 μm to 60 μm. This allows for easy cutting of the negative electrode plate from the negative electrode precursor.

[0025] In a preferred embodiment of the manufacturing method disclosed herein, the positive electrode core is made of aluminum or an aluminum alloy. In another preferred embodiment, the positive electrode active material is a lithium transition metal composite oxide. According to the manufacturing method disclosed herein, positive electrode plates having these structures can be stably fabricated.

[0026] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the negative electrode core is made of copper or a copper alloy. In another preferred embodiment, the negative electrode active material is a carbon material. According to the manufacturing method disclosed herein, negative electrode plates having these structures can be stably manufactured. Additionally, as detailed later, the negative electrode active material layer irradiated with a pulsed laser becomes a carbon-containing coating layer and firmly adheres to the surface of the negative electrode core, thus making it difficult to detach or peel off.

[0027] Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, the protective layer comprises ceramic particles and a binder. This effectively suppresses internal short circuits.

[0028] Furthermore, as another aspect of the technology disclosed herein, a secondary battery is provided. The disclosed secondary battery includes an electrode body comprising a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate of this secondary battery includes: a positive electrode core, which is a foil-shaped metal component; a positive electrode active material layer formed on the surface of the positive electrode core and containing positive electrode active material; and a protective layer formed on the surface of the positive electrode core adjacent to at least one end edge of the positive electrode core, and containing a material with a lower conductivity than the positive electrode active material layer. On the other hand, the negative electrode plate includes: a negative electrode core, which is a foil-shaped metal component; and a negative electrode active material layer formed on the surface of the negative electrode core adjacent to at least one end edge of the negative electrode core and containing negative electrode active material. Moreover, in at least one end edge of the positive electrode plate adjacent to the protective layer, a first thick-walled portion with a thickness greater than the thickness of the positive electrode core in the central region of the positive electrode plate is provided at the end of the positive electrode core. In addition, at least one of the end edges of the negative electrode plate adjacent to the negative electrode active material layer is provided with a second thick wall portion at the end of the negative electrode core, the thickness of which is greater than that of the negative electrode core in the central region of the negative electrode plate. A coating layer is attached to the surface of the second thick wall portion, the coating layer containing carbon material or a compound containing carbon element.

[0029] The secondary battery disclosed herein is manufactured using the manufacturing method described above. The positive electrode plate of this secondary battery is formed by cutting the protective layer forming region of the positive electrode precursor using a continuous oscillating laser. Therefore, a first thick-walled portion, marked by continuous oscillating laser irradiation, is formed on the side edge of the positive electrode core on the protective layer side of the positive electrode plate. The thickness of this first thick-walled portion is greater than the thickness of the positive electrode core in the central region. On the other hand, the negative electrode plate of this secondary battery is formed by cutting the negative electrode active material layer forming region of the negative electrode precursor using a pulsed laser. Therefore, a second thick-walled portion, marked by pulsed laser irradiation, is formed on the side edge of the negative electrode core on one side of the region where the negative electrode active material layer is formed. The thickness of this second thick-walled portion is greater than the thickness of the negative electrode core in the central region. Furthermore, as a result of irradiating the negative electrode active material layer forming region with a pulsed laser, a coating layer composed of carbon-based components from the negative electrode active material, etc., adheres to the second thick-walled portion. The coating layer has excellent adhesion to the surface of the negative electrode core (second thick-walled portion), thus preventing the coating layer from peeling off from the negative electrode core and becoming a conductive foreign object.

[0030] Furthermore, in a preferred embodiment of the secondary battery disclosed herein, the ratio of the thickness of the coating layer of the second thick-walled portion to the thickness of the negative electrode active material layer is 0.01 to 0.2. By adjusting the cutting conditions using a pulsed laser to form a coating layer of this thickness, the negative electrode core can be appropriately cut.

[0031] In another preferred embodiment of the secondary battery disclosed herein, the second thick-walled portion of the negative electrode core has a hook-like shape, comprising caps protruding to both sides in the thickness direction and recesses formed between the caps and the negative electrode core. The second thick-walled portion irradiated with pulsed laser marks is sometimes formed into such a hook-like shape. This hook-shaped second thick-walled portion provides excellent anchoring effect, firmly holding the negative electrode active material layer and the coating layer, and appropriately preventing their detachment or peeling. It should be noted that when such a hook-shaped second thick-walled portion is formed in the negative electrode core, the separator in contact with this second thick-walled portion may be damaged. However, in the technology disclosed herein, since the second thick-walled portion is covered by the coating layer, damage to the separator can be appropriately prevented.

[0032] Furthermore, in a preferred embodiment of the secondary battery disclosed herein, the first thick-walled portion of the positive electrode core protrudes outward from the end face of the protective layer. This restricts movement of the protective layer and more effectively prevents it from detaching.

[0033] Furthermore, in a preferred embodiment of the secondary battery disclosed herein, the thickness of the second thick-walled portion of the negative electrode core is smaller than the thickness of the first thick-walled portion of the positive electrode core. As described above, in the technology disclosed herein, to prevent the metallic components of the molten negative electrode core from mixing into the negative electrode active material layer, a pulsed laser is used to reduce the amount of molten material in the negative electrode core. The second thick-walled portion formed by this pulsed laser tends to be smaller than the first thick-walled portion formed by continuous oscillating laser.

[0034] Furthermore, in a preferred embodiment of the secondary battery disclosed herein, the boundary between the coating layer and the negative electrode active material layer is located further outward than the side edge of the positive electrode active material layer. The aforementioned coating layer has the advantage of being difficult to peel off or detach from the negative electrode core; however, it has the disadvantage of having low functionality as the negative electrode active material layer (the ability to absorb and release charge carriers). Therefore, if the coating layer and the positive electrode active material layer face each other, the distribution of charge-discharge reactions on the reaction surface of the electrode body becomes uneven, potentially leading to charge carrier deposition. From this viewpoint, the coating layer is preferably positioned in a region that does not contribute to the charge-discharge reaction (i.e., further outward than the side edge of the positive electrode active material layer).

[0035] In another preferred embodiment of the secondary battery disclosed herein, the electrode body is a wound electrode body formed by winding a strip-shaped positive electrode plate and a strip-shaped negative electrode plate with a strip-shaped separator between them. The positive electrode plate has multiple positive electrode tabs protruding outward from one side in the winding axis direction of the wound electrode body, and the negative electrode plate has multiple negative electrode tabs protruding outward from the other side in the winding axis direction of the wound electrode body. When manufacturing a wound electrode body with such electrode tabs, there is a tendency for the cutting distance when cutting the protective layer forming region and the negative electrode active material layer forming region to become longer, thus easily causing the electrode active material layer and the protective layer to detach or peel off. However, according to the technology disclosed herein, even when the cutting distance in the protective layer forming region and the negative electrode active material layer forming region becomes longer, it is possible to appropriately prevent the electrode active material layer and the protective layer from detaching or peeling off.

[0036] Furthermore, as mentioned above, the positive electrode core is preferably made of aluminum or an aluminum alloy, and the negative electrode core is preferably made of copper or a copper alloy. Additionally, the protective layer preferably comprises ceramic particles and a binder. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating a method for manufacturing a secondary battery according to one embodiment.

[0038] Figure 2 This is a schematic top view of the positive electrode plate manufactured in a secondary battery manufacturing method according to one embodiment.

[0039] Figure 3This is a top view illustrating the fabrication of the positive electrode plate in a method for manufacturing a secondary battery according to one embodiment.

[0040] Figure 4 This is a schematic top view of the negative electrode plate produced in a secondary battery manufacturing method according to one embodiment.

[0041] Figure 5 This is a top view illustrating the fabrication of the negative electrode plate in a method for manufacturing a secondary battery according to one embodiment.

[0042] Figure 6 This is a schematic diagram showing the structure of the wound electrode body manufactured in a secondary battery manufacturing method according to one embodiment.

[0043] Figure 7 It is a schematic representation Figure 6 Front view of the wound electrode body.

[0044] Figure 8 This is a perspective view schematically illustrating one embodiment of a secondary battery.

[0045] Figure 9 It is along Figure 8 A schematic longitudinal section view of the IX-IX line.

[0046] Figure 10 It is along Figure 8 A schematic longitudinal section view of the XX line.

[0047] Figure 11 It is along Figure 8 A schematic cross-sectional view of the XI-XI line.

[0048] Figure 12 It is a schematic three-dimensional view of the electrode body installed on the sealing plate.

[0049] Figure 13 It is a schematic three-dimensional view of an electrode body with a positive second collector and a negative second collector installed.

[0050] Figure 14 yes Figure 7 The XIV-XIV view in the middle.

[0051] Figure 15 This is a SEM image of the protective layer formation area of ​​sample 1.

[0052] Figure 16 This is a SEM image of the area where the protective layer of sample 2 is formed.

[0053] Figure 17 This is a SEM image of the region where the negative electrode active material layer is formed in sample 3.

[0054] Figure 18 This is a SEM image of the region where the negative electrode active material layer is formed in sample 4.

[0055] Explanation of reference numerals in the attached figures

[0056] 10 positive plates

[0057] 10A positive electrode precursor

[0058] 12 positive electrode core

[0059] 14 Positive Electrode Active Material Layer

[0060] 16 protective layers

[0061] 20 negative electrode plate

[0062] 20A Negative Electrode Precursor

[0063] 22 negative electrode core

[0064] 24 negative electrode active material layers

[0065] 30 diaphragm

[0066] 40-wound electrode body

[0067] 50 battery casing

[0068] 52 outer body

[0069] 54 sealing board

[0070] 60 positive extremes

[0071] 65 negative extremes

[0072] 70 Positive Current Collector

[0073] 75 negative electrode current collector

[0074] 100 rechargeable battery Detailed Implementation

[0075] The embodiments of the technology disclosed herein will now be described with reference to the accompanying drawings. 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 this field. It should be noted that the expression "A to B" indicating a range in this specification includes the meaning of A and below B, and includes the meanings of "preferably greater than A" and "preferably less than B".

[0076] It should be noted that, in this specification, "secondary battery" generally refers to an energy storage device that undergoes 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.

[0077] <Manufacturing Method of Secondary Batteries>

[0078] Hereinafter, one embodiment of the method for manufacturing the secondary battery disclosed herein will be described. Figure 1 This is a flowchart illustrating the manufacturing method of the secondary battery according to this embodiment. Figure 2 This is a schematic top view of the positive electrode plate manufactured in the secondary battery manufacturing method of this embodiment.

[0079] Figure 3 This is a top view illustrating the fabrication of the positive electrode plate in the manufacturing method of the secondary battery according to this embodiment. Figure 4 This is a schematic top view of the negative electrode plate manufactured in the secondary battery manufacturing method of this embodiment. Figure 5 This is a top view illustrating the fabrication of the negative electrode plate in the manufacturing method of the secondary battery according to this embodiment. Figure 6 This is a schematic diagram showing the structure of the wound electrode body manufactured in the secondary battery manufacturing method of this embodiment. Figure 7 It is a schematic representation Figure 6 The front view of the wound electrode body. It should be noted that the above... Figures 2-7 In the attached figures, reference numeral S indicates the width direction of the electrode plates (positive and / or negative plates), and reference numeral L indicates the length direction of the electrode plates.

[0080] 1. Fabrication of the positive electrode plate

[0081] like Figure 1 As shown, in the manufacturing method of this embodiment, firstly, a positive electrode preparation step S10 and a positive electrode cutting step S20 are performed. Thus, a positive electrode plate 10 for a secondary battery (see reference 10) is manufactured. Figure 2 Here, after describing the structure of the positive electrode plate 10, which is the object of manufacture, each step of the positive electrode preparation step S10 and the positive electrode cutting step S20 will be described.

[0082] (Structure of the positive electrode plate)

[0083] like Figure 2As shown, the positive electrode plate 10 manufactured by the manufacturing method of this embodiment is a long strip-shaped component. The positive electrode plate 10 includes: a positive electrode core 12 as a foil-shaped metal component; a positive electrode active material layer 14 formed on the surface of the positive electrode core 12; and a protective layer 16 formed 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 ( ) extending towards the width direction S are provided at predetermined intervals in the length direction L. Figure 2 The positive electrode tab 12t protrudes from the top of the positive electrode core 12. Specifically, the positive electrode tab 12t is formed by causing the positive electrode core 12, without the positive active material layer 14 and protective layer 16 formed, to protrude from the side edge 10a of the positive electrode plate 10 outwards in the width direction S. It should be noted that, from the viewpoint of battery performance, the positive active material layer 14 and protective layer 16 are preferably formed on both sides of the positive electrode core 12. Alternatively, the protective layer 16 may be formed such that a portion of it covers the side edge 14a of the positive active material layer 14.

[0084] The components constituting the positive electrode plate 10 can be made of conventionally known materials that are commonly used in secondary batteries (e.g., lithium-ion secondary batteries) without particular limitations. For example, the positive electrode core 12 can preferably be made of a metallic material with a specified conductivity. The positive electrode core 12 is preferably made of, for example, aluminum, aluminum alloy, etc. In addition, the thickness of the positive electrode core 12 is preferably 3μm to 30μm, more preferably 3μm to 20μm, and even more preferably 5μm to 15μm.

[0085] Furthermore, the positive electrode active material layer 14 is a layer containing the positive electrode active material. The positive electrode active material is a material capable of reversibly absorbing and releasing charge carriers. From the viewpoint of stably manufacturing a high-performance positive electrode plate 10, the positive electrode active material is preferably a lithium transition metal composite oxide. Among the aforementioned lithium transition metal composite oxides, lithium transition metal composite oxides containing at least one of the group consisting of nickel (Ni), cobalt (Co), and manganese (Mn) as transition metals are particularly preferred. Specific examples include lithium nickel cobalt manganese composite oxide (NCM), lithium nickel composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel manganese composite oxide, lithium nickel cobalt aluminum composite oxide (NCA), and lithium iron nickel manganese composite oxide. Additionally, as a preferred example of a lithium transition metal composite oxide that does not contain nickel, cobalt, and manganese, lithium iron phosphate composite oxide (LFP) is an example. It should be noted that the term "lithium nickel cobalt manganese composite oxide" in this specification refers to oxides that include oxides containing additive elements in addition to the main constituent elements (Li, Ni, Co, Mn, O). Examples of added elements include transition metal elements and typical metal elements such as Mg, Ca, Al, Ti, V, Cr, Si, Y, Zr, Nb, Mo, Hf, Ta, W, Na, Fe, Zn, and Sn. Additionally, added elements can also be half-metal elements such as B, C, Si, and P, and non-metal elements such as S, F, Cl, Br, and I. This also applies to other lithium transition metal composite oxides described as "~-system composite oxides". Furthermore, the positive electrode active material layer 14 may also contain additives other than the positive electrode active material. Examples of such additives include conductive materials, binders, and silicon-based materials. Specific examples of conductive materials include carbon materials such as acetylene black (AB). Specific examples of binders include resin binders such as polyvinylidene fluoride (PVdF). It should be noted that when the total solid content of the positive electrode active material layer 14 is set to 100% by mass, the content of the positive electrode active material is approximately 80% by mass or more, typically 90% by mass or more. It should be noted that the positive electrode active material can account for more than 95% by mass of the positive electrode active material layer 14. In addition, the thickness of the positive electrode active material layer 14 is preferably 10 μm to 500 μm, more preferably 30 μm to 400 μm, and even more preferably 50 μm to 300 μm.

[0086] On the other hand, the protective layer 16 is a layer with lower conductivity than the positive electrode active material layer 14. By forming this protective layer 16 adjacent to the side edge 10a of the positive electrode plate 10, internal short circuits caused by contact between the positive electrode core 12 and the negative electrode active material layer 24 can be prevented when the diaphragm 30 of the electrode body 40 is damaged. For example, the protective layer 16 is preferably formed as a layer containing insulating ceramic particles. Examples of such ceramic particles include inorganic oxides such as alumina (Al2O3), magnesium oxide (MgO), silicon dioxide (SiO2), and titanium dioxide (TiO2), nitrides such as aluminum nitride and silicon nitride, metal hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, and kaolin, and glass fiber. Considering insulation and heat resistance, alumina, boehmite, aluminum hydroxide, silicon dioxide, and titanium dioxide are preferred among the above materials. Additionally, the protective layer 16 may also contain an adhesive for fixing the ceramic particles to the surface of the positive electrode core 12. Examples of such adhesives include resin adhesives such as polyvinylidene fluoride (PVdF). It should be noted that the protective layer 16 is not limited to the above structure, as long as its conductivity is lower than that of the positive electrode active material layer 14. For example, the protective layer 16 may be made of an insulating resin instead of ceramic particles. Furthermore, a small amount of conductive materials such as carbon materials (acetylene black) may be added to the protective layer 16. Additionally, the thickness of the protective layer 16 is preferably thinner than that of the positive electrode active material layer 14. For example, the thickness of the protective layer 16 is preferably 1 μm to 100 μm, more preferably 5 μm to 80 μm, and even more preferably 8 μm to 50 μm.

[0087] (Positive electrode preparation process S10)

[0088] As described above, the manufacturing method of this embodiment produces the positive electrode plate 10 with the above-described structure by performing a positive electrode preparation step S10 and a positive electrode cutting step S20. Here, firstly, the positive electrode preparation step S10, which prepares the positive electrode precursor 10A as the precursor of the positive electrode plate 10, is performed. Figure 3As shown, the positive electrode precursor 10A includes a positive electrode core 12 that is a strip-shaped metal foil. The area of ​​the positive electrode core 12 of the positive electrode precursor 10A is larger than the area of ​​the positive electrode plate 10. Furthermore, a positive electrode active material layer 14 and a protective layer 16 are formed on the surface of the positive electrode core 12. Specifically, a positive electrode active material layer 14 is formed at the central portion of the positive electrode precursor 10A in the width direction S, extending along the length direction L. Moreover, a pair of protective layers 16 are formed in each region adjacent to the side edge portion 14a of the positive electrode active material layer 14, extending along the length direction L. Furthermore, the positive electrode active material layer 14 and the protective layer 16 are not formed at the two side edges of the positive electrode precursor 10A (the regions outside the protective layers 16 in the width direction S), but positive electrode exposed portions 12a are formed where the positive electrode core 12 is exposed. The method for preparing the positive electrode precursor 10A with the above structure is not particularly limited, and various conventionally known methods can be used without particular restriction. For example, by coating the surface (both sides) of the strip-shaped positive electrode core 12 with a positive electrode paste as a precursor material of the positive electrode active material layer 14 and a protective paste as a precursor material of the protective layer 16, and drying each paste, a positive electrode precursor 10A can be produced.

[0089] (Positive electrode cutting process S20)

[0090] In this process, from Figure 3 The positive electrode precursor 10A of the structure shown is cut out Figure 2 The positive electrode plate 10 is shown in the diagram. Here, in the positive electrode cutting process S20 of this embodiment, the region (protective layer forming region) where the protective layer 16 is formed on the positive electrode precursor 10A is cut using a laser. Specifically, as... Figure 3 The dashed line L in P1 As shown, a laser scans the protective layer 16 along the side edge 14a of the positive electrode active material layer 14. This removes the side edge 16a of the protective layer 16, where the thickness can easily become uneven, thus creating a positive electrode plate 10 with a uniform thickness of the protective layer 16. Furthermore, in this process, the laser scans outwards in the width direction S at regular intervals, and after cutting off a portion of the exposed positive electrode portion 12a, it scans inwards in the width direction S to cut off the protective layer formation area again (refer to the dashed line L). P1 Therefore, a portion of the exposed positive electrode portion 12a is cut into a convex shape, forming multiple positive electrode tabs 12t protruding outward in the width direction S. Furthermore, in this process, as... Figure 3 double-dotted line L P2 As shown, the central portion of the positive electrode precursor 10A in the width direction S is cut along the length direction L. This allows for the fabrication of a positive electrode plate 10 with a protective layer 16 and a positive electrode tab 12t formed only on one side edge in the width direction S. Furthermore, in this process, as... Figure 3double-dotted line L P3 As shown, the positive electrode precursor 10A is cut along the width direction S at predetermined intervals in the length direction L. This produces a strip-shaped positive electrode plate 10 of the desired length. It should be noted that along the double-dotted line L... P2 L P3 In the cutting of the positive electrode precursor 10A, laser cutting may not be used. For example, along the double-dotted line L P2 L P3 In the cutting of the positive electrode precursor 10A, a cutting knife, a mold, a cutter, etc. can also be used.

[0091] Here, in the above dashed line L P1 During the laser cutting of the protective layer forming area shown, if a large impact is applied to the protective layer 16, it may be blown away and peeled off. In this case, the positive electrode core 12 is exposed at the side edge 10a of the fabricated positive electrode plate 10, thus easily causing an internal short circuit. To prevent the protective layer 16 from peeling off, in the positive electrode cutting process S20 of this embodiment, along the dotted line L... P1 A continuous wave laser (CW laser) is used to cut the protective layer forming region. This CW laser continuously oscillates with a constant output, therefore, the peak output is relatively smaller compared to the pulsed laser described later. Therefore, it is possible to suppress large impacts on the protective layer 16, such as blowing it away, and to appropriately prevent the protective layer 16 from detaching or peeling off.

[0092] It should be noted that the conditions for the continuous oscillating laser cutting the protective layer formation area are not particularly limited, and are preferably appropriately adjusted according to the structure of the positive electrode precursor 10A (typically, the thickness and material of the protective layer 16 and the positive electrode core 12). For example, the output of the continuous oscillating laser is preferably 500W to 2000W, more preferably 700W to 1500W, and can be set to 1000W for example. This prevents the protective layer 16 from detaching or peeling off, and makes it easier to cut the positive electrode precursor 10A. Specifically, as the output of the continuous oscillating laser increases, it tends to be easier to cut the positive electrode precursor 10A. On the other hand, as the output of the continuous oscillating laser decreases, the impact applied to the protective layer 16 decreases, and therefore, it is possible to more appropriately prevent the protective layer 16 from detaching or peeling off.

[0093] Furthermore, the scanning speed of the continuous oscillating laser is preferably 2000 mm / sec to 10000 mm / sec, more preferably 4000 mm / sec to 8000 mm / sec, and for example, can be set to 6000 mm / sec. This allows for easy cutting of the positive electrode precursor 10A while suppressing burn-out of the protective layer 16. Specifically, as the scanning speed of the continuous oscillating laser increases, the heat applied to the protective layer 16 decreases, thus reducing the likelihood of burn-out of the protective layer 16 due to excessive heat. On the other hand, as the scanning speed decreases, the laser easily penetrates to the opposite side of the positive electrode precursor 10A, thus making it easier to cut the positive electrode precursor 10A. Furthermore, the spot diameter of the continuous oscillating laser is preferably 10 μm to 60 μm, more preferably 20 μm to 50 μm. This allows for easy cutting of the positive electrode plate from the positive electrode precursor.

[0094] 2. Fabrication of the negative electrode plate

[0095] Next, in the manufacturing method of this embodiment, as follows: Figure 1 As shown, the negative electrode preparation process S30 and the negative electrode cutting process S40 are performed. Thus, the negative electrode plate 20 for a secondary battery (see reference) is manufactured. Figure 4 Similar to the above description of "the fabrication of the positive electrode plate", the following will also describe each step of the negative electrode preparation step S30 and the negative electrode cutting step S40 after explaining the structure of the fabricated object (negative electrode plate 20).

[0096] (Structure of the negative electrode plate)

[0097] In the manufacturing method of this embodiment, the negative electrode plate 20 is a long strip-shaped component (see reference). Figure 4 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 formed on the surface of the negative electrode core 22. Furthermore, on the side edge 20a of the negative electrode plate 20, a plurality of outer surfaces facing the width direction S are provided at predetermined intervals in the length direction L. Figure 4 The negative electrode tab 22t protrudes from the top of the negative electrode plate 20. This negative electrode tab 22t is part of the negative electrode core 22. Specifically, the negative electrode tab 22t is formed by causing the negative electrode core 22, without the negative electrode active material layer 24 formed, to protrude from the side edge 20a of the negative electrode plate 20 outwards in the width direction S. It should be noted that, from the viewpoint of battery performance, the negative electrode active material layer 24 is preferably formed on both sides of the negative electrode core 22.

[0098] Similar to the positive electrode plate 10 described above, the components constituting the negative electrode plate 20 can use materials that are conventionally used in secondary batteries without particular restrictions. For example, the negative electrode core 22 can preferably be made of a metal material with a specified 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 3 μm to 30 μm, more preferably 2 μm to 20 μm, and even more preferably 5 μm to 15 μm.

[0099] The negative electrode active material layer 24 is a layer containing a negative electrode active material. The negative electrode active material is a material capable of reversibly adsorbing and releasing charge carriers in relation to the aforementioned positive electrode active material. 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 tackifiers. Specific examples of adhesives include rubber-based adhesives such as styrene-butadiene rubber (SBR). Specific examples of tackifiers include carboxymethyl cellulose (CMC). It should be noted that when the total 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.

[0100] It should be noted that, as will be described in detail later, in the manufacturing method of this embodiment, a portion of the negative electrode active material layer 24 irradiated by laser becomes a coating layer 24b made of carbon-based material (see reference). Figure 14The coating layer 24b adheres to the surface of the negative electrode core 22. This coating layer 24b exhibits excellent adhesion to the negative electrode core 22, thus preventing it from detaching or peeling off after the secondary battery is constructed, thus preventing conductive foreign matter from becoming free within the battery. From the viewpoint of appropriately forming this coating layer, the negative electrode active material contained in the negative electrode active material layer 24 is preferably a carbon material. However, as mentioned above, the material of the negative electrode active material is not limited to the technology disclosed herein. That is, the technology disclosed herein includes using silicon-based materials as the negative electrode active material. Even when using silicon-based materials as the negative electrode active material, if the negative electrode active material layer 24 contains carbon elements, the negative electrode active material layer 24 can be carbonized by pulsed laser treatment described later, thus forming a coating layer 24b composed of a carbon-based material.

[0101] (Negative electrode preparation process S30)

[0102] like Figure 1 As shown, the manufacturing method of this embodiment produces the negative electrode plate 20 with the above-described structure by performing a negative electrode preparation step S30 and a negative electrode cutting step S40. In the negative electrode preparation step S30, a negative electrode precursor 20A, which serves as the precursor to the negative electrode plate 20, is prepared. Figure 5 As shown, the negative electrode precursor 20A includes a negative electrode core 22, which is a strip-shaped metal foil. The area of ​​the negative electrode core 22 of the negative electrode precursor 20A is larger than the area of ​​the negative electrode plate 20. Furthermore, a negative electrode active material layer 24 is formed on the surface of the negative electrode core 22. Specifically, the negative electrode active material layer 24 is formed in the central portion of the negative electrode precursor 20A in the width direction S, extending along the length direction L. Moreover, the negative electrode active material layer 24 is not formed on the two side edges of the negative electrode precursor 20A (the region outside the negative electrode active material layer 24 in the width direction S), but negative electrode exposure portions 22a are formed where the negative electrode core 22 is exposed. 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, similar to the production of the positive electrode precursor 10A described above, a negative electrode precursor 20A can be produced by coating and drying the raw material paste, forming a negative electrode active material layer 24 on the surface of the negative electrode core 22.

[0103] (Negative electrode cutting process S40)

[0104] In this process, from Figure 5 The negative electrode precursor 20A of the structure shown is cut out Figure 4 The negative electrode plate 20 is shown in the diagram. In the negative electrode cutting process S40, the region of the negative electrode precursor 20A where the negative electrode active material layer 24 is formed (the negative electrode active material layer formation region) is cut using a laser. Specifically, as shown... Figure 5 The dashed line L in N1As shown, the laser scans along the side edge 24a of the negative electrode active material layer 24. This removes the side edge 24a of the negative electrode active material layer 24, where the thickness is prone to unevenness, thus creating a negative electrode plate 20 with a uniform thickness of the negative electrode active material layer 24. Furthermore, in this process, the laser scans outwards in the width direction S at regular intervals, and after cutting off a portion of the exposed negative electrode portion 22a, it scans inwards in the width direction S to cut off the negative electrode active material layer formation area again (refer to the dashed line L). N1 Therefore, a portion of the exposed negative electrode portion 22a is cut into a convex shape, forming a plurality of negative electrode tabs 22t protruding outward in the width direction S. Furthermore, in this embodiment, as... Figure 5 double-dotted line L N2 As shown, the central portion of the negative electrode precursor 20A in the width direction S is cut along the length direction L. Thus, as... Figure 4 As shown, a negative electrode plate 20 can be manufactured with a negative electrode tab 22t formed only on one side edge 20a in the width direction S. Furthermore, in this process, as shown by the double-dotted line L... N3 As shown, the negative electrode precursor 20A is cut along the width direction S at predetermined intervals in the length direction L. This produces a strip-shaped negative electrode plate 20 of the desired length. It should be noted that, similar to the cutting of the positive electrode precursor 10A described above, the cutting is done along the double-dotted line L... N2 L N3 In the cutting of the negative electrode precursor 20A, laser cutting can be used instead of laser cutting, or a cutting knife, mold, cutting machine, etc. can be used.

[0105] Here, as shown by the dashed line L above N1 As shown, if the region where the negative electrode active material layer is formed is cut with a laser, a portion of the negative electrode core 22, which melts due to the heat of the laser, may mix with the negative electrode active material layer 24. Furthermore, if the metal components from the negative electrode core 22 solidify within the negative electrode active material layer 24, the adhesion of the negative electrode active material layer 24 is significantly lost, and it may easily detach or peel off from the negative electrode core 22 due to minor impacts. In the negative electrode cutting process S40 of this embodiment, a pulsed laser is used in the cutting of the region where the negative electrode active material layer is formed in the negative electrode precursor 20A to prevent the detachment or peeling of the negative electrode active material layer 24. This pulsed laser can concentrate a large amount of energy (high peak output) over a short time span, thus reducing the amount of melting of the negative electrode core 22 during laser irradiation. Therefore, it is possible to suppress the mixing of a portion of the molten negative electrode core 22 into the negative electrode active material layer 24, and to appropriately prevent the detachment or peeling of the negative electrode active material layer 24.

[0106] It should be noted that the conditions for using the pulsed laser to cut the region where the negative electrode active material layer is formed are not particularly limited, but are preferably adjusted appropriately 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 is preferably 80W to 300W, more preferably 120W to 250W, and for example, it can be set to 210W. 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 be 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 impact of the laser.

[0107] Furthermore, the scanning speed of the pulsed laser is preferably 5000 mm / sec or less, more preferably 3000 mm / sec or less. By slowing down the scanning speed in this way, sufficient heat can be applied to the negative electrode precursor 20A to properly cut off the negative electrode core 22. On the other hand, the lower limit of the scanning speed of the pulsed laser is not particularly limited and can be 20 mm / sec or more. It should be noted that, from the viewpoint of improving manufacturing efficiency by shortening the cutting time, the lower limit of the scanning speed of the pulsed laser is preferably 200 mm / sec or more, more preferably 500 mm / sec or more.

[0108] Next, the pulse width of the pulsed laser is preferably 30 ns to 240 ns, more preferably 120 ns to 240 ns. This prevents the molten negative electrode core 22 from mixing with the negative electrode active material layer 24 and facilitates the cutting off of the negative electrode precursor 20A. Specifically, since there is a tendency for the peak output to increase as the pulse width of the pulsed laser decreases, it is easier to reduce the amount of melting in the laser-irradiated negative electrode core 22. 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.

[0109] Furthermore, the repetition frequency of the pulsed laser is preferably 100 kHz to 2000 kHz, more preferably 300 kHz to 1500 kHz. This prevents the molten negative electrode core 22 from mixing with the negative electrode active material layer 24 and allows for easy cutting of the negative electrode precursor 20A. Specifically, when the pulsed laser frequency is low, the peak output is high, thus making it easy to cut the negative electrode core 22. On the other hand, when the pulsed laser frequency is high, the peak output is low, thus preventing a portion of the laser-irradiated negative electrode active material layer 24 from being blown away. Additionally, the spot diameter of the pulsed laser is preferably 10 μm to 60 μm, more preferably 20 μm to 50 μm. This allows for easy cutting of the negative electrode plate 20 from the negative electrode precursor 20A.

[0110] (Electrode fabrication process S50)

[0111] Next, in the manufacturing method of this embodiment, an electrode body manufacturing step S50 is performed, which involves fabricating an electrode body 40 including a positive electrode plate 10, a negative electrode plate 20, and a separator 30. For example... Figure 6 As shown, in the electrode body manufacturing process S50, a wound electrode body 40 is formed by winding a strip-shaped positive electrode plate 10 and a strip-shaped negative electrode plate 20 together with a strip-shaped separator 30. It should be noted that 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 through which charge carriers can pass can be cited. This resin sheet preferably comprises a resin layer made of polyolefin resin (e.g., polyethylene (PE), polypropylene (PP)). Alternatively, a heat-resistant layer containing inorganic fillers such as alumina, boehmite, aluminum hydroxide, and titanium dioxide may be formed on the surface of the resin sheet.

[0112] The specific steps of this process will be explained. First, a laminated body is fabricated by stacking the separator 30, negative electrode plate 20, and positive electrode plate 10 in this order (see reference). Figure 6 At this time, from one side of the width direction S of each sheet-like component ( Figure 6 The left side edge of the positive electrode plate 10 protrudes only from the positive electrode tab 12t of the positive electrode plate 10 and from the other side ( Figure 6 The negative electrode tabs 22t of the negative electrode plate 20 protrude from the side edge of the right side of the electrode body 40, and the stacking positions of the various sheet-like components are staggered. Next, the stacked body is wound in such a way that multiple positive electrode tabs 12t are stacked at the same position on one side edge in the width direction S, and multiple negative electrode tabs 22t are stacked at the same position on the other side edge. A diaphragm 30 (see reference 40) is disposed at the outermost periphery of the wound electrode body 40 fabricated as described above. Figure 7The shape of the wound electrode body 40 is maintained by attaching a winding fixing tape 38 to the winding terminal 30a of the outermost circumference of the separator 30. Furthermore, in this wound electrode body 40, a positive electrode tab group 42, in which multiple positive electrode tabs 12t are stacked, is formed on one side edge along the axial direction of the winding shaft WL. Conversely, a negative electrode tab group 44, in which multiple negative electrode tabs 22t are stacked, is formed on the other side edge along the axial direction of the wound electrode body 40. Moreover, a core portion 46 is formed at the central portion along the axial direction, with the positive electrode active material layer 14 and the negative electrode active material layer 24 facing each other. This core portion 46 becomes the main site where the charge and discharge reactions of the secondary battery occur.

[0113] When manufacturing a wound electrode body 40 with electrode tabs (positive electrode tab 12t, negative electrode tab 22t) having the above-described structure, there is a tendency for the cutting length to increase when laser cutting the protective layer forming region and the negative electrode active material layer forming region. Therefore, the protective layer 16 of the positive electrode plate 10 and the negative electrode active material layer 24 of the negative electrode plate 20 are prone to detachment or peeling. However, the manufacturing method of this embodiment can appropriately prevent the detachment or peeling of the negative electrode active material layer 24 and the protective layer 16 during laser cutting of the protective layer forming region and the negative electrode active material layer forming region. Therefore, the manufacturing method of this embodiment is particularly preferred for applications having… Figure 6 as well as Figure 7 The manufacturing of a secondary battery with a wound electrode body 40 having electrode tabs is shown.

[0114] Next, the wound electrode 40, manufactured through the above process, is housed together with the electrolyte inside the battery casing. The wound electrode 40 is then connected to the electrode terminals, thereby enabling the manufacture of a secondary battery. It should be noted that the specific steps for constructing a secondary battery using the wound electrode 40 can be employed without particular restriction using conventionally known manufacturing methods, and are not limited to the technology disclosed herein; therefore, detailed descriptions are omitted.

[0115] As described above, in the manufacturing method of this embodiment, since the protective layer forming area is cut with a continuously oscillating laser in the positive electrode cutting process S20, it is possible to prevent the protective layer 16 from being blown away from the positive electrode plate 10 during laser irradiation. Therefore, the internal short-circuit prevention function based on the protective layer 16 can be appropriately utilized. On the other hand, in this embodiment, since the negative electrode active material layer forming area is cut with a pulsed laser in the negative electrode cutting process S40, it is possible to prevent the molten negative electrode core 22 from mixing into the negative electrode active material layer 24. As a result, it is possible to prevent a portion of the negative electrode active material layer 24 from peeling off inside the secondary battery and becoming a conductive foreign object that could cause an internal short circuit. As described above, according to the manufacturing method of this embodiment, the detachment and peeling of the negative electrode active material layer 24 and the protective layer 16 at the laser-cut portion of the electrode plate can be prevented, thus enabling the manufacture of a secondary battery with high safety.

[0116] Secondary batteries

[0117] Next, the structure of the secondary battery manufactured by the manufacturing method of this embodiment will be described in detail. Figure 8 This is a perspective view schematically representing the secondary battery of this embodiment. Figure 9 It is along Figure 8 A schematic longitudinal section view of the IX-IX line. Figure 10 It is along Figure 8 A schematic longitudinal section view of the XX line. Figure 11 It is along Figure 8 A schematic cross-sectional view of the XI-XI line. Figure 12 It is a schematic three-dimensional view of the electrode body installed on the sealing plate. Figure 13 It is a schematic three-dimensional view of an electrode body with a positive second collector and a negative second collector installed. Figure 14 yes Figure 7 The XIV-XIV views in the diagram. Figures 8 to 14 In the attached figures, reference numeral X indicates the "short side direction" of the secondary battery 100, reference numeral Y indicates the "long side direction," and reference numeral Z indicates the "vertical direction." Furthermore, in the short side direction X, F indicates "front," and Rr indicates "rear." In the long side 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.

[0118] like Figure 9 As shown, the secondary battery 100 includes a wound electrode body 40, a battery casing 50, a positive terminal 60, a negative terminal 65, a positive current collector 70, and a negative current collector 75. Although not shown in the figure, a non-aqueous electrolyte is contained inside the battery casing 50 of the secondary battery 100, in addition to the wound electrode body 40. This non-aqueous electrolyte is prepared by dissolving a supporting 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.

[0119] (Battery casing)

[0120] The battery casing 50 is a frame that houses the wound electrode body 40. The battery casing 50 has a flat, bottomed cuboid shape (square). The material of the battery casing 50 can be the same as conventionally used materials, without particular limitation. The battery casing 50 is preferably made of metal, more preferably of materials such as aluminum, aluminum alloy, iron, or iron alloy. Figure 9As shown, the battery casing 50 includes an outer body 52 and a sealing plate 54.

[0121] The outer casing 52 is a flat, bottomed, square container with an opening 52h on its upper surface. For example... Figure 8 As shown, the outer casing 52 includes: a bottom wall 52a with a generally rectangular planar shape; a pair of long side walls 52b extending from the long side of the bottom wall 52a along the height direction Z; and a pair of short side walls 52c extending from the short side of the bottom wall 52a along the height direction Z. On the other hand, the sealing plate 54 is a plate-shaped member with a generally rectangular planar shape that blocks the opening 52h of the outer casing 52. Furthermore, the outer periphery of the sealing plate 54 is joined (e.g., welded) to the outer periphery of the opening 52h of the outer casing 52. Thus, a battery casing 50 with its interior airtightly sealed (sealed) is manufactured. 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. It should be noted that the injection hole 55 is sealed by the sealing member 56 after the non-aqueous electrolyte is injected. In addition, the gas discharge valve 57 is a thin-walled part designed such that when a large amount of gas is generated inside the battery housing 50, it breaks (opens) under a predetermined pressure to discharge the gas inside the battery housing 50.

[0122] (Electrode terminals)

[0123] Additionally, one side of the sealing plate 54 in the long side direction Y of the secondary battery 100 ( Figure 8 , Figure 9 A positive terminal 60 is installed at the left end of the battery casing 50. This positive terminal 60 is connected to a plate-shaped external positive electrode conductive member 62 on the outside of the battery casing 50. On the other hand, the sealing plate 54 on the other side of the secondary battery 100 in the long side direction Y... Figure 8 , Figure 9 A negative terminal 65 is installed at the right end of the battery. A plate-shaped external conductive component 67 is also installed on the negative terminal 65. These external conductive components (positive external conductive component 62 and negative external conductive component 67) are connected to other secondary batteries and external devices via external connection components (busbars, etc.). It should be noted that the external conductive components are preferably made of a metal with excellent conductivity (aluminum, aluminum alloy, copper, copper alloy, etc.).

[0124] (Electrode current collector)

[0125] Moreover, such as Figures 10-12As shown, in the secondary battery 100 of this embodiment, 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 the plurality of wound electrode bodies 40 via a positive current collector 70 housed inside 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 9 as well as Figure 12 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 height 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 is connected to the first positive electrode current collector 71 (see reference). Figure 9 On the other hand, such as Figures 11-13 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 11 as well as Figure 12 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.

[0126] On the other hand, the negative terminal 65 is connected to a plurality of wound electrode bodies 40 via a negative electrode current collector 75 housed within the battery casing 50. The connection structure on the negative electrode side is substantially the same as the connection structure on the positive electrode side. Specifically, the negative electrode current collector 75 includes: a plate-shaped conductive member extending along the inner surface of the sealing plate 54, namely a first negative electrode current collector 76; and plate-shaped conductive members extending along the height direction Z, namely a plurality of second negative electrode current collectors 77 (see reference). Figure 9 as well as Figure 12 Furthermore, the lower end 65c of the negative terminal 65 extends into the interior of the battery casing 50 through the terminal insertion hole 59 and connects to the negative first current collector 76 (see reference). Figure 9 On the other hand, 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). Figures 11-13 Furthermore, the negative electrode tab assembly 44 is bent such that the second negative electrode current collector 77 faces the other side 40b of the wound electrode body 40. As a result, the upper end of the second negative electrode current collector 77 is electrically connected to the first negative electrode current collector 76.

[0127] (Insulating components)

[0128] Furthermore, in the secondary battery 100 of this embodiment, various insulating components are installed to prevent the winding electrode body 40 from conducting through the battery casing 50. Specifically, an external insulating component 92 (see reference 67) is sandwiched between the positive electrode external conductive component 62 (negative electrode external conductive component 67) and the outer surface of the sealing plate 54. Figure 8 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 9 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 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. The internal insulating member 94 also has a protrusion 94b protruding from the inner surface of the sealing plate 54 toward the winding electrode body 40 (see reference). Figure 9 as well as Figure 10 This restricts the movement of the wound electrode body 40 in the height direction Z, preventing direct contact between the wound electrode body 40 and the sealing plate 54. Furthermore, the wound electrode body 40 is held by an electrode body holder 98 made of an insulating resin sheet (see reference). Figure 10 The 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. It should be noted that the materials of the aforementioned insulating components are not particularly limited as long as they possess the specified insulating properties. For 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.

[0129] (Wound electrode body)

[0130] Furthermore, in the secondary battery 100 of this embodiment, a wound electrode body 40 manufactured by the above-described manufacturing method is used. It should be noted that in this secondary battery 100, the wound electrode body 40 is housed inside the battery housing 50 such that the winding axis WL of the wound electrode body 40 is aligned with the long side direction Y of the battery housing 50. That is, in the secondary battery 100 of this embodiment, Figures 2-7 The “width direction S of the electrode plate” shown is related to Figures 8 to 14The "long side direction Y" of the secondary battery shown is essentially the same direction. It should be noted that "essentially the same direction" here means that slight deviations in direction due to manufacturing deviations are allowed.

[0131] Here, in the wound electrode body 40, as Figure 14 As shown, at the end edge of the positive electrode plate 10 adjacent to the protective layer 16 (the left end edge in the long side direction Y), a first thick-walled portion 12b is formed at the end of the positive electrode core 12, with a thickness greater than that of the positive electrode core 12 in the central region (near the core 46) of the positive electrode plate 10. This first thick-walled portion 12b is a trace left by continuous oscillating laser irradiation during the aforementioned positive electrode cutting process S20. This first thick-walled portion 12b is formed by solidifying the positive electrode core 12, which has been partially melted by the heat from the continuous oscillating laser. In addition, at the end face 16c of the protective layer 16 of the positive electrode plate 10, a ceramic sintered body is sometimes formed in a manner that covers the protective layer 16 (see reference). Figure 15 (The black portion in the image). With this ceramic sintered body formed, the peeling and detachment of the protective layer 16 can be more effectively prevented. On the other hand, at the end of the negative electrode core 22 located on the shorter side (the right side of the longer side in the Y direction) of one of the two end edges of the negative electrode plate 20 adjacent to the negative electrode active material layer 24, a second thick-walled portion 22b with a thickness greater than that of the negative electrode core 22 in the central region of the negative electrode plate 20 is provided. This second thick-walled portion 22b is a trace left by pulsed laser irradiation during the aforementioned negative electrode cutting process S40. This second thick-walled portion 22b is formed by solidifying the negative electrode core 22, which was partially melted by the heat from the pulsed laser. Furthermore, a coating layer 24b is attached to the surface of this second thick-walled portion 22b. The coating layer 24b is a layer of the negative electrode active material layer 24 that has deteriorated due to the heat from the pulsed laser. Specifically, the coating layer 24b is formed by densifying the negative electrode active material in the negative electrode active material layer 24 with carbon materials (or compounds containing carbon elements) such as carbonized additives (binders, etc.). The coating layer 24b has excellent adhesion to the surface of the negative electrode core 22 (second thick-walled portion 22b), thus effectively preventing the generation of internal short circuits caused by the peeling or shedding of conductive foreign matter.

[0132] In addition, such as Figure 14 As shown, a first thick-walled portion 12b with a generally spherical cross-sectional shape is formed. This is because the end of the positive electrode core 12, which was once melted by continuous oscillating laser, solidifies, thereby forming the first thick-walled portion 12b. On the other hand, the second thick-walled portion 22b has a claw shape, which has the following characteristics: in the thickness direction of the negative electrode core 22 ( Figure 14The negative electrode core 22 has a cap portion 22b1 protruding from both sides or one side in the short side direction (X); and a recess 22b2 formed between the cap portion 22b1 and the negative electrode core 22. Unlike the first thick-walled portion 12b of the positive electrode core 12, the second thick-walled portion 22b is formed by cutting with a pulsed laser. Therefore, the amount of melting in the negative electrode core 22 is less, and it sometimes becomes a claw shape as described above. The coating layer 24b enters the interior of the recess 22b2 of the claw-shaped second thick-walled portion 22b. As a result, the coating layer 24b can be firmly held in place with excellent anchoring effect. Consequently, it is possible to more effectively prevent conductive foreign matter (negative electrode active material layer 24, coating layer 24b) from falling off or peeling off. It should be noted that when such a claw-shaped second thick-walled portion 22b is formed in the negative electrode core 22, the diaphragm 30 in contact with the second thick-walled portion 22b may be damaged. However, in this embodiment, since the second thick-walled portion 22b is covered by the covering layer 24b, damage to the diaphragm 30 caused by the hook-shaped second thick-walled portion 22b can be appropriately prevented.

[0133] It should be noted that the thickness of the cap 22b1 of the second thick-walled portion 22b 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. It should be noted that the "thickness of the cap" mentioned above refers to the thickness of one side of the cap 22b1 with the core surface as a reference. Figure 14 The dimension in the short side direction X). Furthermore, from the viewpoint of more reliably preventing damage to the diaphragm 30, the upper limit of the thickness of the cap 22b1 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 22b1 ( Figure 14 The dimension (in the Y direction of the longer side) is not particularly limited. For example, the width of the cap portion 22b1 can be 1μm to 30μm, 5μm to 25μm, or 10μm to 20μm. Furthermore, the height of the entrance to the recess 22b2 of the second thick-walled portion 22b ( Figure 14 The dimension in the short side direction X of the middle part is preferably 1 μm to 10 μm, more preferably 2.5 μm to 7.5 μm. On the other hand, the depth of the recess 22b2 of the second thick-walled part 22b ( Figure 14 The dimension (in the long side direction Y) 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 24b to be maintained inside the recess 22b2, resulting in a more suitable anchoring effect. Furthermore, the angle at which the cap portion 22b1 rises from the surface of the negative electrode core 22 is preferably greater than 0° and less than 90°.

[0134] Furthermore, the first thick-walled portion 12b preferably extends outward from the end face 16c of the protective layer 16. Figure 14The first thick-walled portion 12b protrudes to the left of the long side direction Y. This first thick-walled portion 12b is thicker than other areas of the positive electrode core 12, therefore, when protruding outward from the end face 16c of the protective layer 16, it can restrict the movement of the protective layer 16 in the long side direction Y. As a result, it is possible to properly prevent the protective layer 16 from falling off outward in the long side direction Y. It should be noted that, from the viewpoint of more appropriately utilizing this first thick-walled portion 12b to hold the protective layer 16, the thickness of the first thick-walled portion 12b ( Figure 14 The dimension along the short side (X) of the winding electrode body is preferably 15 μm to 50 μm. It should be noted that the "thickness of the first thick-walled portion" in this specification refers to the thickness direction of the wound electrode body. Figure 14 The maximum dimension of the first thick-walled portion in the short side direction (X) is determined. On the other hand, the ratio of the thickness of the coating layer of the second thick-walled portion 22b to the thickness of the negative electrode active material layer 24 is preferably 0.01 to 0.2.

[0135] Furthermore, while not intended to limit the technology disclosed herein, the thickness of the second thick-walled portion 22b of the negative electrode core 22 in the secondary battery 100 manufactured by the above-described manufacturing method can be smaller than the thickness of the first thick-walled portion 12b of the positive electrode core 12. In the positive electrode cutting step S20 of the above-described manufacturing method, the positive electrode core 12 is gradually melted while being cut using a continuously oscillating laser. On the other hand, in the negative electrode cutting step S40, the amount of melting of the negative electrode core 22 is reduced by using a pulsed laser. Thus, the second thick-walled portion 22b of the negative electrode core 22 is formed with less metal than the first thick-walled portion 12b of the positive electrode core 12, and therefore, its thickness is easily smaller than that of the first thick-walled portion 12b.

[0136] Furthermore, in the electrode body 40 of this embodiment, the stacking position of each sheet component is determined such that the boundary between the coating layer 24b of the negative electrode plate 20 and the negative electrode active material layer 24 is located outside the long side direction Y of the side edge of the positive electrode active material layer 14. This prevents capacity reduction caused by charge carrier deposition during charging and discharging. Specifically, as described above, the coating layer 24b formed on the negative electrode plate 20 has the advantage of being difficult to peel off from the negative electrode core 22; however, due to its thin-film nature, it has the disadvantage of low functionality as a negative electrode active material layer (charge carrier absorption and release capacity). Therefore, when the coating layer 24b faces the positive electrode active material layer 14, the distribution of the charging and discharging reaction in the reaction surface (the flat surface of the core 46) of the electrode body 40 becomes uneven, and charge carrier deposition may occur. Therefore, it is preferable to arrange the boundary between the coating layer 24b and the negative electrode active material layer 24 in a region that is not facing the positive electrode active material layer 14, so that the coating layer 24b does not contribute to the charge and discharge reaction.

[0137] <Other Implementation Methods>

[0138] The above describes one embodiment of the technology disclosed herein. It should be noted that the above embodiment illustrates an example of the application of the technology disclosed herein and is not intended to limit the scope of the technology disclosed herein.

[0139] For example, 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 it includes a positive electrode plate, a negative electrode plate, and a separator. As another example of this electrode body, a stacked electrode body formed by sequentially stacking multiple positive and negative electrode plates while clamping a separator can be cited. To manufacture the positive electrode plate for such a stacked electrode body, it can be implemented with 12t for each positive electrode tab. Figure 3 double-dotted line L P3 The cutting is done along the width direction S as shown. Similarly, to fabricate the negative electrode plate for the laminated electrode body, it can be implemented with each negative electrode tab being 22t. Figure 5 double-dotted line L N3 The electrode is cut along the width direction S as shown. Then, the positive electrode tabs 12t of the positive electrode plate are stacked in the same position, and the negative electrode tabs 22t of the negative electrode plate are stacked in the same position, while the separator is sandwiched, thereby fabricating a stacked electrode body. Furthermore, in the manufacturing process of a secondary battery having this stacked electrode body, sometimes a laser is used to separately cut the protective layer formation region of the positive electrode precursor and the negative electrode active material layer formation region of the negative electrode precursor; therefore, the technology disclosed herein can be applied.

[0140] Furthermore, in the above embodiment, a high-capacity secondary battery 100 with three wound electrode bodies 40 housed inside the battery casing 50 is taken as the object. However, the number of electrode bodies housed in one battery casing is not particularly limited, and can be two or more, or even one. Also, the secondary battery 100 of the above embodiment is a lithium-ion secondary battery with lithium ions as the charge carrier. However, the secondary battery disclosed herein is not limited to lithium-ion secondary batteries. In the manufacturing process of other secondary batteries (e.g., nickel-metal hydride batteries), lasers are sometimes used to separately cut the protective layer forming region of the positive electrode precursor and the negative electrode active material layer forming region of the negative electrode precursor; therefore, the technology disclosed herein can be applied.

[0141] 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 between the positive and negative electrode plates. In this all-solid-state battery, the separator and the electrolyte are integrated and contained within the electrode body, thus preventing electrolyte leakage. In the manufacturing process of such an all-solid-state battery, sometimes a laser is used to separately cut the protective layer forming region of the positive electrode precursor and the negative electrode active material layer forming region of the negative electrode precursor; therefore, the technology disclosed herein can be applied.

[0142] [Experimental Example]

[0143] 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.

[0144] 1. Preparation of each sample

[0145] (1) Sample 1

[0146] In Sample 1, a positive electrode precursor with a thickness of 62 μm was first prepared, forming a positive electrode active material layer on both sides of a 13 μm thick positive electrode core (aluminum foil). This positive electrode precursor's positive electrode active material layer contained positive electrode active material, conductive material, and binder in a ratio of 97.5:1.5:1.0. It should be noted that the positive electrode active material used was lithium nickel cobalt manganese composite oxide (NCM). Additionally, acetylene black (AB) was used as the conductive material. Furthermore, polyvinylidene fluoride (PVdF) was used as the binder. Furthermore, a 30 μm thick protective layer was formed adjacent to the positive electrode active material layer in this positive electrode precursor. This protective layer contained ceramic particles (alumina particles), conductive material (graphite), and binder (PVdF) in a ratio of 83:3:14.

[0147] Next, the region where the protective layer of the aforementioned positive electrode precursor is formed (the protective layer forming region) is cut off to cut out a positive electrode plate of a specified size. Here, in sample 1, a continuous oscillating laser (CW laser) is used to cut the protective layer forming region. It should be noted that the output of the continuous oscillating laser is set to 1000W. In addition, the scanning speed is set to 6000mm / sec, and the spot diameter is set to 20μm.

[0148] (2) Sample 2

[0149] In Sample 2, the positive electrode plate was fabricated under the same conditions as in Sample 1, except that a pulsed laser was used when cutting the protective layer forming region of the positive electrode precursor. It should be noted that the average output of the pulsed laser was set to 20W, and the scanning speed was set to 350mm / sec. Furthermore, the pulse width of the pulsed laser was set to 30ns, the repetition frequency was set to 100kHz, and the spot diameter of the pulsed laser was set to 30μm.

[0150] (3) Sample 3

[0151] In Sample 3, the cutting target was changed to the negative electrode precursor. Specifically, firstly, a negative electrode precursor with a negative electrode active material layer of 80 μm thickness was prepared on both sides of the negative electrode core (copper foil). This negative electrode precursor's negative electrode active material layer contained negative electrode active material, a tackifier, 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 tackifier, and styrene-butadiene rubber (SBR) as the binder. Furthermore, in Sample 3, the negative electrode active material layer forming area of ​​the above-described negative electrode precursor was cut using a continuous oscillating laser to fabricate a negative electrode plate of a specified size. It should be noted that the continuous oscillating laser conditions in this sample were the same as those in Sample 1.

[0152] (4) Sample 4

[0153] In Sample 4, the negative electrode plate was fabricated under the same conditions as in Sample 3, except that a pulsed laser was used when cutting the region where the negative electrode active material layer of the negative electrode precursor was formed. It should be noted that the average output of the pulsed laser was set to 210 W, and the scanning speed was set to 1000 mm / sec. Furthermore, the pulse width of the pulsed laser was set to 120 ns, the repetition frequency was set to 400 kHz, and the spot diameter of the pulsed laser was set to 30 μm.

[0154] 2. Evaluation Test

[0155] In this experiment, a scanning electron microscope (SEM) was used to observe the laser-cut areas (protective layer formation areas or negative electrode active material layer formation areas) in the above samples at 1000x magnification. The observation results are as follows: Figures 15-18 As shown. Figure 15 This is a cross-sectional SEM image of the protective layer formation area of ​​sample 1. Figure 16 This is a cross-sectional SEM image of the protective layer formation area of ​​sample 2. Figure 17 This is a cross-sectional SEM image of the region where the negative electrode active material layer is formed in sample 3. Figure 18 This is a cross-sectional SEM image of the region where the negative electrode active material layer is formed in sample 4.

[0156] First, such as Figure 16 As shown, in sample 2, the protective layer peeled off at the location irradiated by the pulsed laser, exposing the positive electrode core. This can be understood as a result of using a pulsed laser that cuts through the protective layer formation area of ​​the positive electrode precursor, causing the protective layer to be blown away by the impact of the laser irradiation. On the other hand, as... Figure 15 As shown, in sample 1, the protective layer at the laser-irradiated area remained intact and peeled off from the surface of the positive electrode core. This demonstrates that, even when the protective layer forming area of ​​the positive electrode precursor is cut off, the impact of laser irradiation can be mitigated by using a continuously oscillating laser, thus preventing the protective layer from detaching or peeling off.

[0157] Additionally, when observing the laser irradiation position in sample 1, at the end of the positive electrode core ( Figure 15 The left end of the core has a first thick-walled portion that is thicker than other areas of the positive electrode core. It is presumed that this first thick-walled portion is formed by solidifying the end of a once-molten positive electrode core, and its cross-sectional shape is approximately circular. This first thick-walled portion restricts the movement of the protective layer outwards in the width direction, and therefore, it is expected to help prevent the protective layer from peeling off. Furthermore, at the end of the protective layer irradiated by a continuous oscillating laser, a ceramic sintered body (formed by sintering the protective layer) is formed. Figure 15 (The black portion in the image). Since the ceramic sintered body is formed by covering a protective layer, it is conceivable that the protective layer can be more effectively prevented from peeling off.

[0158] On the other hand, such as Figure 17 As shown, in sample 3, at the location irradiated by the continuously oscillating laser ( Figure 17 At the left end of the core, there is a negative electrode active material layer that is more shrunken than other negative electrode active material layers. Analysis of this shrunken negative electrode active material layer reveals that copper from the molten negative electrode core is incorporated and solidified, making it easy to detach and peel off due to minor impacts. On the other hand, as... Figure 18 As shown, in sample 4, a coating layer covering the negative electrode core was formed at the area irradiated by the pulsed laser. Confirmation of this coating layer revealed that carbon materials from the negative electrode active material, carbonized binder, etc., were densely attached to the negative electrode core. Furthermore, the coating layer contained almost no copper from the negative electrode core. Therefore, it can be concluded that when cutting the region where the negative electrode active material layer of the negative electrode precursor is formed, cutting the negative electrode core using a pulsed laser that rapidly raises the temperature of the negative electrode core can prevent the negative electrode active material layer from detaching or peeling off.

[0159] Furthermore, when observing the laser irradiation position in sample 4, a second thick-walled portion, thicker than other areas, was formed at the end of the negative electrode core. This second thick-walled portion of the negative electrode core is similar to the first thick-walled portion of the positive electrode core (see reference). Figure 15 Unlike the positive electrode core, the negative electrode core has a cap protruding on one side in the thickness direction and a hook-shaped portion formed between the cap and the negative electrode core. This can be understood as the amount of melting in the second thick-walled portion of the negative electrode core cut by a pulsed laser is reduced compared to the first thick-walled portion of the positive electrode core cut by a continuous wave laser. Moreover, the hook-shaped second thick-walled portion provides excellent anchoring effect and firmly holds the coating layer, thus more effectively preventing the shedding or peeling of conductive foreign matter. In addition, if such a hook-shaped second thick-walled portion is formed in the negative electrode core, the diaphragm in contact with the second thick-walled portion may be damaged. However, in sample 4, since the second thick-walled portion is covered by the coating layer, it is foreseeable that damage to the diaphragm caused by the hook-shaped second thick-walled portion can be appropriately prevented.

[0160] 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 above specific examples.

Claims

1. A method for manufacturing a secondary battery, the secondary battery comprising an electrode body, the electrode body including a positive electrode plate, a negative electrode plate, and a separator, wherein, The method for manufacturing the secondary battery includes: In the process of preparing the positive electrode precursor, a positive electrode active material layer containing positive electrode active material and a protective layer with lower conductivity than the positive electrode active material layer are formed on the surface of the positive electrode core, which is a strip-shaped metal foil. The process of cutting off the region of the positive electrode precursor where the protective layer is formed using a continuous oscillating laser; The process of preparing a negative electrode precursor, wherein a negative electrode precursor has a negative electrode active material layer containing a negative electrode active material formed on the surface of a negative electrode core, which is a strip-shaped metal foil; and The process of using a pulsed laser to cut off the region of the negative electrode precursor where the negative electrode active material layer is formed. The negative electrode active material contains carbon materials. In at least one of the end edges of the negative electrode plate adjacent to the negative electrode active material layer, a second thick-walled portion with a thickness greater than that of the negative electrode core in the central region of the negative electrode plate is provided at the end of the negative electrode core. A coating layer is attached to the surface of the second thick-walled portion, the coating layer containing carbon material or a compound containing carbon. The ratio of the thickness of the coating layer in the second thick-walled portion to the thickness of the negative electrode active material layer is 0.01 to 0.

2. The second thick-walled portion of the negative electrode core has a hook shape, the hook shape having a cap protruding to both sides or one side in the thickness direction and a recess formed between the cap and the negative electrode core.

2. The method for manufacturing a secondary battery as described in claim 1, wherein, The output of the continuously oscillating laser that cuts off the positive electrode precursor is 500W to 2000W.

3. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The scanning speed of the continuously oscillating laser that cuts off the positive electrode precursor is 2000 mm / sec to 10000 mm / sec.

4. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The diameter of the spot of the continuously oscillating laser that cuts off the positive electrode precursor is 10 μm to 60 μm.

5. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The average output of the pulsed laser that cuts off the negative electrode precursor is 80W to 300W.

6. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The scanning speed of the pulsed laser that cuts off the negative electrode precursor is less than 5000 mm / sec.

7. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The pulse width of the pulsed laser that cuts off the negative electrode precursor is 30ns to 240ns.

8. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The repetition frequency of the pulsed laser that cuts off the negative electrode precursor is 100KHz to 2000KHz.

9. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The diameter of the pulsed laser spot that cuts off the negative electrode precursor is 10μm to 60μm.

10. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The positive electrode core is made of aluminum or aluminum alloy.

11. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The positive electrode active material is a lithium transition metal composite oxide.

12. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The negative electrode core is made of copper or a copper alloy.

13. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The negative electrode active material is a carbon material.

14. The method for manufacturing a secondary battery as described in claim 1 or 2, wherein, The protective layer comprises ceramic particles and an adhesive.

15. A secondary battery comprising an electrode body, said electrode body including a positive electrode plate, a negative electrode plate, and a separator, wherein, The positive electrode plate includes: Positive electrode core, wherein the positive electrode core is a foil-shaped metal component; A positive electrode active material layer, the positive electrode active material layer being formed on the surface of the positive electrode core and comprising positive electrode active material; and A protective layer is formed on the surface of the positive electrode core adjacent to at least one end edge of the positive electrode core, and has a lower conductivity than the positive electrode active material layer. The negative electrode plate includes: A negative electrode core, wherein the negative electrode core is a foil-shaped metal component; and A negative electrode active material layer is formed on the surface of the negative electrode core, adjacent to at least one end edge of the negative electrode core, and contains negative electrode active material. In at least one of the end edges of the positive electrode plate adjacent to the protective layer, a first thick-walled portion with a thickness greater than that of the positive electrode core in the central region of the positive electrode plate is provided at the end of the positive electrode core. In at least one of the end edges of the negative electrode plate adjacent to the negative electrode active material layer, a second thick-walled portion with a thickness greater than that of the negative electrode core in the central region of the negative electrode plate is provided at the end of the negative electrode core. A coating layer is attached to the surface of the second thick-walled portion, the coating layer containing carbon material or a compound containing carbon. The ratio of the thickness of the coating layer in the second thick-walled portion to the thickness of the negative electrode active material layer is 0.01 to 0.

2. The second thick-walled portion of the negative electrode core has a hook shape, the hook shape having a cap protruding to both sides or one side in the thickness direction and a recess formed between the cap and the negative electrode core.

16. The secondary battery as claimed in claim 15, wherein, The first thick-walled portion of the positive electrode core protrudes outward from the end face of the protective layer.

17. The secondary battery as claimed in claim 15 or 16, wherein, The thickness of the second thick-walled portion of the negative electrode core is smaller than the thickness of the first thick-walled portion of the positive electrode core.

18. The secondary battery as claimed in claim 15 or 16, wherein, The boundary between the coating layer and the negative electrode active material layer protrudes outward from the end face of the positive electrode active material layer.

19. The secondary battery as described in claim 15 or 16, wherein, The electrode body is a wound electrode body formed by winding the strip-shaped positive electrode plate and the strip-shaped negative electrode plate together with a strip-shaped separator. The positive electrode plate has a plurality of positive electrode tabs protruding outward from one end face in the direction of the winding axis of the wound electrode body. The negative electrode plate has a plurality of negative electrode tabs protruding outward from the end face opposite to the winding axis of the wound electrode body.

20. The secondary battery as claimed in claim 15 or 16, wherein, The positive electrode core is made of aluminum or aluminum alloy.

21. The secondary battery as described in claim 15 or 16, wherein, The negative electrode core is made of copper or a copper alloy.

22. The secondary battery as described in claim 15 or 16, wherein, The protective layer comprises ceramic particles and an adhesive.

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