Secondary battery manufacturing method

Abstract

A method for manufacturing a secondary battery, according to one embodiment of the present invention, includes: a step for providing an electrode assembly inside of a cup-shaped exterior member; a step for pouring an electrolytic solution inside the cup-shaped exterior member; a step for putting a lid on an opening of the cup-shaped exterior member and providing a lid-shaped exterior member in the opening, so as to fit in at least a portion thereof; and a step for forming a welded portion by irradiating a border section between the cup-shaped exterior member and the lid-shaped exterior member with a laser. In particular, in the present invention, each of the cup-shaped and lid-shaped exterior members is formed having a first extended surface constituting the border section, and a second extended surface that is separated from and faces the first extended surface, and a laser is irradiated from the second extended surface of one of the cup-shaped exterior member and lid-shaped exterior member, with the border section therebetween, toward the second extended surface of the other of the cup-shaped exterior member and lid-shaped exterior member.

Description

[Technical field]

[0001] The present invention relates to a secondary battery and a manufacturing method thereof, and more particularly to a manufacturing method of a secondary battery including an electrode assembly including a positive electrode, a negative electrode, and a separator. [Background technology]

[0002] Secondary batteries are storage batteries that can be repeatedly charged and discharged, and are used in a variety of applications, including mobile devices such as mobile phones, smartphones, and laptops. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-46639 A [Patent Document 2] JP 2016-038991 A [Patent Document 3] JP 2005-183360 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application realized that there were problems to be overcome with conventional secondary batteries, and found the need to take measures to address these problems. Specifically, the inventors of the present application found the following problems (see FIG. 11).

[0005] The secondary battery comprises an electrode assembly 10' including a positive electrode, a negative electrode and a separator therebetween, and an exterior body 50' that encases the electrode assembly 10'. The exterior body 50' of the secondary battery is composed of, for example, two exterior members (a cup-shaped member and a lid-shaped member) connected to each other by a welded portion 20'.

[0006] The welded portion 20' may be formed, for example, by disposing a lid-shaped exterior member 52' ​​so as to fit into the opening of a cup-shaped exterior member 51', and irradiating a boundary portion 53' between an end of the lid-shaped exterior member 52' ​​and an end of the cup-shaped exterior member 51' with a laser L'. The laser L' is usually irradiated along the extension direction of the boundary portion 53' between the lid-shaped exterior member 52' ​​and the cup-shaped exterior member 51' located at the boundary portion 53'.

[0007] Since the laser L' is irradiated along the extending direction of the boundary portion 53', the sputter 90' is likely to penetrate into the electrode assembly 10' through the boundary portion 53'. The penetration of the sputter 90' into the electrode assembly 10' may damage the electrode assembly 10', which may cause deterioration of the battery characteristics.

[0008] The present invention has been made in view of the above problems. That is, a main object of the present invention is to provide a method for manufacturing a secondary battery that can prevent spatter generated during welding of an exterior member by a laser from entering an electrode assembly. [Means for solving the problem]

[0009] In order to achieve the above object, in one embodiment of the present invention, Providing an electrode assembly within a cup-shaped exterior member; A step of injecting an electrolyte into the cup-shaped exterior member; A step of covering the opening of the cup-shaped exterior member and providing a lid-shaped exterior member so that at least a portion of the lid-shaped exterior member fits into the opening; and The step of providing the lid-shaped exterior member includes a step of irradiating a laser toward a boundary portion between the cup-shaped exterior member and the lid-shaped exterior member that face each other to form a welded portion, Each of the cup-shaped and lid-shaped exterior members has a first extending surface constituting the boundary portion and a second extending surface facing and spaced apart from the first extending surface, A method for manufacturing a secondary battery is provided, in which the laser is irradiated from the second extended surface of one of the cup-shaped and lid-shaped exterior members, via the boundary portion, toward the second extended surface of the other of the cup-shaped and lid-shaped exterior members. Effect of the Invention

[0010] According to the method for manufacturing a secondary battery according to one embodiment of the present invention, it is possible to prevent spatters generated during welding of exterior members by laser from entering the electrode assembly. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A is a schematic cross-sectional view showing a step of installing an electrode assembly in a cup-shaped exterior member, in a method for manufacturing a secondary battery according to one embodiment of the present invention. [Figure 1B] FIG. 1B is a schematic cross-sectional view showing a step of connecting a current collecting tab drawn out from an electrode assembly to an external connection terminal provided on a lid-shaped exterior member, in a method for manufacturing a secondary battery according to one embodiment of the present invention. [Figure 1C] FIG. 1C is a schematic cross-sectional view showing an electrolyte injection step in a method for producing a secondary battery according to one embodiment of the present invention. [Figure 1D] FIG. 1D is a schematic cross-sectional view showing a process of covering an opening of a cup-shaped exterior member, providing a lid-shaped exterior member so that at least a portion of the lid-shaped exterior member fits into the opening, and irradiating a laser toward a boundary portion between the cup-shaped exterior member and the lid-shaped exterior member that face each other to form a weld, in a manufacturing method for a secondary battery according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic enlarged cross-sectional view of FIG. 1D. [Diagram 3] FIG. 3 is a schematic enlarged cross-sectional view showing a process of forming a welded portion when the laser irradiation direction is different from the laser irradiation direction shown in FIG. 1D. [Figure 4] FIG. 4 is a schematic perspective view showing a specific configuration of a secondary battery obtained according to a method for producing a secondary battery according to one embodiment of the present invention. [Diagram 5]FIG. 5 is a schematic cross-sectional view showing a specific configuration of a secondary battery obtained according to a method for producing a secondary battery according to one embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a state in which a force is acting on the outer peripheral edge portion forming the opening of the cup-shaped exterior member when a lid-shaped exterior member is provided to cover the opening of the cup-shaped exterior member and to fit at least a portion of the opening into the opening. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an embodiment in which a lid-like exterior member having a protruding portion is used. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an embodiment in which a cup-shaped exterior member having a step portion is used. [Figure 9] FIG. 9 is a schematic cross-sectional view showing an embodiment in which a cup-shaped exterior member is used in which the outer periphery forming the opening is curved away from the rising side portion of the lid-shaped exterior member. [Figure 10A] FIG. 10A is a cross-sectional view that illustrates an electrode configuration layer having a planar laminated structure. [Figure 10B] FIG. 10B is a cross-sectional view that illustrates a schematic diagram of an electrode configuration layer having a wound structure. [Figure 11] FIG. 11 is a cross-sectional view that illustrates a mode in which a laser is irradiated along the extending direction of the boundary portion between the end of a cup-shaped exterior member and the end of a lid-shaped exterior member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described in more detail. Although the description will be made with reference to the drawings as necessary, various elements in the drawings are merely shown as schematic and illustrative elements for understanding the present invention, and the appearance and / or dimensional ratios may differ from the actual ones.

[0013] The "cross-sectional view" described directly or indirectly in this specification is based on a virtual cross section of the secondary battery cut along the height direction. The "upper-lower direction" and "left-right direction" used directly or indirectly in this specification correspond to the upper-lower direction and left-right direction in the figure, respectively. Unless otherwise specified, the same reference numerals or symbols indicate the same members or parts or the same meanings. In a preferred embodiment, the vertical downward direction (i.e., the direction in which gravity acts) can be considered to correspond to the "downward direction", and the opposite direction to the "upward direction".

[0014] [Basic structure of secondary batteries] In this specification, the term "secondary battery" refers to a battery that can be repeatedly charged and discharged. Therefore, the secondary battery according to the present invention is not limited to the name, and may also include, for example, a power storage device.

[0015] A secondary battery according to an embodiment of the present invention includes an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are stacked. An electrode assembly 10 is illustrated in FIG. 10A and FIG. 10B. As illustrated in FIG. 10A and FIG. 10B, a positive electrode 1 and a negative electrode 2 are stacked with a separator 3 interposed therebetween to form an electrode constituent layer 5, and at least one such electrode constituent layer 5 is stacked to form an electrode assembly. In FIG. 10A, the electrode constituent layer 5 has a planar laminated structure in which the electrode constituent layer 5 is not wound but is laminated in a planar shape. On the other hand, in FIG. 10B, the electrode constituent layer 5 has a wound laminated structure in which the electrode constituent layer 5 is wound in a wound shape. That is, in FIG. 10B, the electrode constituent layer including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode has a wound structure in which the electrode constituent layer is wound in a roll shape. In a secondary battery, such an electrode assembly is enclosed in an exterior body together with an electrolyte (e.g., a non-aqueous electrolyte). In addition, the structure of the electrode assembly is not necessarily limited to a planar laminated structure or a wound structure. For example, the electrode assembly may have a so-called stack-and-folded type structure in which a positive electrode, a separator, and a negative electrode are laminated on a long film and then folded.

[0016] The positive electrode is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, the positive electrode material layer is provided on at least one side of the positive electrode current collector. The positive electrode material layer contains a positive electrode active material as an electrode active material. For example, each of the multiple positive electrodes in the electrode assembly may have a positive electrode material layer provided on both sides of the positive electrode current collector, or may have a positive electrode material layer provided only on one side of the positive electrode current collector.

[0017] The negative electrode is composed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode, the negative electrode material layer is provided on at least one side of the negative electrode current collector. The negative electrode material layer contains a negative electrode active material as an electrode active material. For example, each of the multiple negative electrodes in the electrode assembly may have a negative electrode material layer provided on both sides of the negative electrode current collector, or may have a negative electrode material layer provided only on one side of the negative electrode current collector.

[0018] The electrode active materials contained in the positive and negative electrodes, that is, the positive and negative active materials, are materials directly involved in the transfer of electrons in the secondary battery, and are the main materials of the positive and negative electrodes that are responsible for charging and discharging, i.e., the battery reaction. More specifically, ions are brought to the electrolyte due to the "positive electrode active material contained in the positive electrode material layer" and the "negative electrode active material contained in the negative electrode material layer", and these ions move between the positive and negative electrodes to transfer electrons and charge and discharge. The positive and negative electrode material layers may be layers that can absorb and release lithium ions in particular. In other words, the secondary battery according to the present invention may be a non-aqueous electrolyte secondary battery in which lithium ions move between the positive and negative electrodes via the non-aqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charging and discharging, the secondary battery according to the present invention corresponds to a so-called "lithium ion battery", and the positive and negative electrodes have layers that can absorb and release lithium ions.

[0019] The positive electrode active material of the positive electrode layer is, for example, composed of granules, and a binder may be included in the positive electrode layer to ensure sufficient contact between the particles and shape retention. Furthermore, a conductive assistant may be included in the positive electrode layer to facilitate the transfer of electrons that promote the battery reaction. Similarly, the negative electrode active material of the negative electrode layer is, for example, composed of granules, and a binder may be included in the positive electrode layer to ensure sufficient contact between the particles and shape retention, and a conductive assistant may be included in the negative electrode layer to facilitate the transfer of electrons that promote the battery reaction. In this way, since a plurality of components are contained, the positive electrode layer and the negative electrode layer can also be referred to as a "positive electrode mixture layer" and a "negative electrode mixture layer", respectively.

[0020] The positive electrode active material may be a material that contributes to the absorption and release of lithium ions. From this perspective, the positive electrode active material may be, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material may be a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese, and iron. In other words, in the positive electrode material layer of the secondary battery according to the present invention, such a lithium transition metal composite oxide is preferably contained as the positive electrode active material. For example, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium iron phosphate, or a material in which a part of the transition metal is replaced with another metal. Such a positive electrode active material may be contained as a single type, or may be contained in a combination of two or more types.

[0021] The binder that may be included in the positive electrode layer is not particularly limited, but may include at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, etc. The conductive assistant that may be included in the positive electrode layer is not particularly limited, but may include at least one selected from carbon black such as thermal black, furnace black, channel black, ketjen black, and acetylene black, carbon fibers such as graphite, carbon nanotubes, and vapor-grown carbon fibers, metal powders such as copper, nickel, aluminum, and silver, and polyphenylene derivatives.

[0022] The thickness of the positive electrode layer is not particularly limited, but may be 1 μm or more and 300 μm or less, for example, 5 μm or more and 200 μm or less. The thickness of the positive electrode layer is the thickness inside the secondary battery, and may be the average value of measurements at any 10 points.

[0023] The negative electrode active material may be a material that contributes to the absorption and release of lithium ions. From this perspective, the negative electrode active material may be, for example, various carbon materials, oxides, and / or lithium alloys.

[0024] Examples of various carbon materials for the negative electrode active material include graphite (natural graphite and / or artificial graphite), hard carbon, soft carbon, and / or diamond-like carbon. In particular, graphite has high electronic conductivity and excellent adhesion to the negative electrode current collector. Examples of the negative electrode active material include at least one selected from the group consisting of silicon, silicon oxide, tin oxide, tin alloy, titanium oxide such as lithium titanate, metallic lithium, indium oxide, zinc oxide and lithium alloy, silicon alloy, and the like. The lithium alloy for the negative electrode active material may be any metal that can form an alloy with lithium, and may be, for example, a binary, ternary or more alloy of lithium and a metal such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, etc. Such an active material may have an amorphous structure. This is because deterioration caused by non-uniformity such as grain boundaries or defects is less likely to occur.

[0025] The binder that may be included in the negative electrode material layer is not particularly limited, but may be at least one selected from the group consisting of styrene butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resin, and polyamideimide resin. The binder included in the negative electrode material layer may be styrene butadiene rubber. The conductive assistant that may be included in the negative electrode material layer is not particularly limited, but may be at least one selected from carbon black such as thermal black, furnace black, channel black, ketjen black, and acetylene black, carbon fibers such as graphite, carbon nanotubes, and vapor-grown carbon fibers, metal powders such as copper, nickel, aluminum, and silver, and polyphenylene derivatives. The negative electrode material layer may contain a component resulting from a thickener component (e.g., carboxymethyl cellulose) used during battery production.

[0026] The thickness of the negative electrode layer is not particularly limited, but may be 1 μm or more and 300 μm or less, for example, 5 μm or more and 200 μm or less. The thickness of the negative electrode layer is the thickness inside the secondary battery, and the average value of the measurements at any 10 points may be used.

[0027] The positive electrode current collector and the negative electrode current collector used for the positive electrode and the negative electrode are members that contribute to collecting and supplying electrons generated in the electrode active material due to the battery reaction. Such an electrode current collector may be a sheet-shaped metal member. The electrode current collector may also have a porous or perforated form. For example, the current collector may be a metal foil, a punched metal, a net, an expanded metal, or the like. The positive electrode current collector used for the positive electrode is preferably made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel, and the like, and may be, for example, an aluminum foil. On the other hand, the negative electrode current collector used for the negative electrode is preferably made of a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel, and the like, and may be, for example, a copper foil.

[0028] The thickness of each of the positive electrode current collector and the negative electrode current collector is not particularly limited, but may be 1 μm or more and 100 μm or less, for example, 10 μm or more and 70 μm or less. The thickness of the positive electrode current collector and the negative electrode current collector is the thickness inside the secondary battery, and the average value of the measurements at any 10 points may be used.

[0029] The separator used for the positive and negative electrodes is a member provided from the viewpoint of preventing short circuit due to contact between the positive and negative electrodes and maintaining electrolyte. In other words, the separator is a member that allows ions to pass while preventing electronic contact between the positive and negative electrodes. For example, the separator is a porous or microporous insulating member, and has a membrane form due to its small thickness. Although it is merely an example, a microporous membrane made of polyolefin may be used as the separator. In this regard, the microporous membrane used as the separator may contain, for example, only polyethylene (PE) or only polypropylene (PP) as polyolefin. Furthermore, the separator may be a laminate composed of a "microporous membrane made of PE" and a "microporous membrane made of PP". The surface of the separator may be covered with an inorganic particle coating layer and / or an adhesive layer. The surface of the separator may have adhesive properties. In the present invention, the separator should not be limited to a particular name, and may be a solid electrolyte, a gel electrolyte, and / or insulating inorganic particles having similar functions.

[0030] The thickness of each separator is not particularly limited, but may be 1 μm or more and 100 μm or less, for example, 2 μm or more and 20 μm or less. The thickness of the separator is the thickness inside the secondary battery (particularly the thickness between the positive electrode and the negative electrode), and the average value of the measurements at any 10 points may be used.

[0031] In the secondary battery according to one embodiment of the present invention, an electrode assembly consisting of electrode constituent layers including a positive electrode, a negative electrode, and a separator may be enclosed in an exterior body together with an electrolyte. The electrolyte may be a "non-aqueous" electrolyte containing an organic electrolyte and an organic solvent, or may be an "aqueous" electrolyte containing water. When the positive electrode and the negative electrode have a layer capable of absorbing and releasing lithium ions, the electrolyte is preferably a "non-aqueous" electrolyte such as an organic electrolyte and an organic solvent. In other words, it is preferable that the electrolyte is a non-aqueous electrolyte. In the electrolyte, metal ions released from the electrodes (positive electrode and / or negative electrode) are present, and therefore the electrolyte can assist the movement of metal ions in the battery reaction. The electrolyte may be in the form of a liquid or gel.

[0032] The non-aqueous electrolyte is an electrolyte containing a solvent and a solute. The solvent may be an organic solvent. A specific organic solvent for the non-aqueous electrolyte may contain at least a carbonate. Such a carbonate may be a cyclic carbonate and / or a chain carbonate. Although not particularly limited, the cyclic carbonate may be at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC) and vinylene carbonate (VC). The chain carbonate may be at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC). As an example, a combination of cyclic carbonates and chain carbonates may be used as the non-aqueous electrolyte, for example, a mixture of ethylene carbonate and diethyl carbonate may be used. In addition, as a specific solute of the non-aqueous electrolyte, for example, Li salts such as LiPF6 and / or LiBF4 may be used.

[0033] The exterior body of the secondary battery is a member that encases an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are laminated. Such an exterior body may be made of at least one metal selected from the group consisting of stainless steel (SUS) and / or aluminum and iron. Note that "stainless steel" in this specification refers to stainless steel as defined in "JIS G 0203 Iron and Steel Terminology," for example, and may be an alloy steel containing chromium or chromium and nickel.

[0034] [Characteristics of the present invention] (Method of Manufacturing Secondary Battery of the Present Invention) The characteristic features of the present invention will be described below.

[0035] The present inventors have conducted extensive research into a solution for preventing spatters generated during welding of exterior members with a laser from entering an electrode assembly, and have come up with a method for manufacturing a secondary battery according to an embodiment of the present invention.

[0036] FIG. 1A is a schematic cross-sectional view showing a step of installing an electrode assembly on a cup-shaped exterior member in a method for producing a secondary battery according to an embodiment of the present invention. FIG. 1B is a schematic cross-sectional view showing a step of connecting a current collecting tab drawn out from the electrode assembly to an external connection terminal provided on a lid-shaped exterior member in a method for producing a secondary battery according to an embodiment of the present invention. FIG. 1C is a schematic cross-sectional view showing a step of injecting an electrolyte in a method for producing a secondary battery according to an embodiment of the present invention. FIG. 1D is a schematic cross-sectional view showing a step of covering an opening of a cup-shaped exterior member, providing a lid-shaped exterior member so that at least a part of the lid-shaped exterior member fits into the opening, and irradiating a laser toward a boundary between the cup-shaped exterior member and the lid-shaped exterior member facing each other to form a welded portion in a method for producing a secondary battery according to an embodiment of the present invention. FIG. 2 is a schematic enlarged cross-sectional view of FIG. 1D. FIG. 3 is a schematic enlarged cross-sectional view showing a step of forming a welded portion when the laser irradiation direction is different from the laser irradiation direction shown in FIG. 1D.

[0037] The method for producing a secondary battery according to one embodiment of the present invention roughly includes the following steps (i) to (iv) in this order. (i) providing the electrode assembly 10 in a cup-shaped exterior member 51 (see FIG. 1A ); (ii) A step of injecting the electrolyte 30 into the cup-shaped exterior member 51 (see FIG. 1C ); (iii) a step of covering the opening of the cup-shaped exterior member 51 and providing a lid-shaped exterior member 52 so as to at least partially fit into the opening (see FIG. 1D ); and (iv) The process of providing the lid-shaped exterior member includes a process of irradiating a laser L toward a boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52 which face each other, to form a weld 20 (see FIG. 1D).

[0038] The manufacturing method of the secondary battery according to one embodiment of the present invention is characterized by the above-mentioned step (iv). Specifically, each of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 has a first extending surface 51a, 52a constituting a boundary portion 53 and a second extending surface 51b, 52b spaced apart from the first extending surface 51a, 52a, and a laser L is irradiated from one of the second extending surfaces of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 toward the other of the second extending surfaces of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 through the boundary portion 53 (see FIG. 1D and FIG. 2). That is, when forming the welded portion 20, the laser L is irradiated so as to straddle the boundary portion 53 to form the welded portion 20. In other words, when forming the welded portion 20, the laser L is irradiated so as to cross the boundary portion 53.

[0039] The term "cup-shaped exterior member" as used herein means a member having a side wall or side surface corresponding to a body portion and a main surface (for example, a bottom portion in a typical embodiment) that is continuous therewith, and a hollow portion is formed inside. The cup-shaped exterior member 51 may be circular as shown in FIG. 2. The term "circular" as used herein is not limited to a perfect circle (i.e., simply a "circle" or a "perfect circle"), but also includes an approximately circular shape that may be normally included in a "round shape" as recognized by those skilled in the art, even if it has been modified from the perfect circle. For example, it may be not only a circle or a perfect circle, but also a shape whose arc curvature varies locally, and may further be a shape derived from a circle or a perfect circle, such as an ellipse. The opening of the cup-shaped exterior member 51 may be, for example, circular. The term "circular" as used herein is the same as the "circular" described in the cup-shaped exterior member.

[0040] In this specification, the term "lid-shaped exterior member" refers to a member that is provided to cover the opening of a cup-shaped exterior member. The lid-shaped exterior member may be provided with an external output terminal 60 and an insulating member 70, as shown in Fig. 2. The lid-shaped exterior member 52 may be, for example, circular, as shown in Fig. 2. The "circular" here is the same as the "circular" described for the cup-shaped exterior member.

[0041] The "opening of the cup-shaped exterior member" in this specification may be, for example, circular in plan view. The "circular" here is the same as the "circular" described for the cup-shaped exterior member.

[0042] In this specification, "providing a lid-shaped exterior member so that at least a part of it fits into the opening of the cup-shaped exterior member" means providing the lid-shaped exterior member so that a predetermined part (part) of the cup-shaped exterior member that forms the opening by the fitting and at least a part of the lid-shaped exterior member face each other. "Facing each other" may mean, for example, that the extending surface of the cup-shaped exterior member and the extending surface of the lid-shaped exterior member have a relationship of being approximately parallel to each other. Note that the lid-shaped exterior member may be provided so that the entirety of the lid-shaped exterior member fits into the opening of the cup-shaped exterior member, as shown in FIG. 1D.

[0043] The term "first extending surface" as used herein means the extending surfaces of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 that constitute the boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52. Specifically, as shown in FIG. 2, the first extending surface 51a of the cup-shaped exterior member 51 means the extending surface of the cup-shaped exterior member 51 at the boundary portion 53. The first extending surface 52a of the lid-shaped exterior member 52 means the extending surface of the lid-shaped exterior member 52 at the boundary portion 53. In one embodiment, as shown in FIG. 2, at the boundary portion 53, the first extending surface 51a of the cup-shaped exterior member 51 and the first extending surface 52a of the lid-shaped exterior member 52 face each other in close proximity or in contact with each other.

[0044] The term "second extending surface" as used herein refers to the extending surface of the cup-shaped exterior member 51 or the extending surface of the lid-shaped exterior member 52 on the side not constituting the boundary portion 53, and is the extending surface opposite to the side on which the first extending surface is formed. Specifically, as shown in FIG. 2, the second extending surface 51b of the cup-shaped exterior member 51 means an extending surface that is separated from and faces the first extending surface 51a of the cup-shaped exterior member 51. The second extending surface 52b of the lid-shaped exterior member 52 means an extending surface that is separated from and faces the first extending surface 52a of the cup-shaped exterior member 52. In one embodiment, as shown in FIG. 2, the first extending surface and the second extending surface of each exterior member may be parallel to each other. Here, "parallel" may mean, for example, that the separation distance between the first extending surface and the second extending surface is substantially constant in the surface direction.

[0045] In this specification, "separate" means that objects are separated from each other and are not physically or spatially continuous with each other. In other words, "facing each other at a distance" means that objects are positioned to face each other and are separated from each other. For example, as shown in FIG. 2, a first extending surface 51a of a cup-shaped exterior member 51 faces a second extending surface 51b of the cup-shaped exterior member 51, but is separated from the second extending surface 51b by the thickness of the cup-shaped exterior member 51. In other words, the first extending surface 51a of the cup-shaped exterior member 51 faces the second extending surface 51b of the cup-shaped exterior member 51 at a distance.

[0046] In one embodiment of the present invention, each of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 has first extending surfaces 51a, 52a constituting a boundary portion 53 and second extending surfaces 51b, 52b spaced apart and facing the first extending surfaces 51a, 52a. A laser L is irradiated from one of the second extending surfaces of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 toward the other second extending surface through the boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52, thereby forming a welded portion 20.

[0047] Specifically, when the laser L is incident on one of the second extending surfaces of the cup-shaped exterior member 51 and the lid-shaped exterior member 52, the welded portion 20 is first formed at the laser incident portion L1 on one of the second extending surfaces. After that, the welded portion 20 can be formed while passing through the boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52 and extending toward the other second extending surface. That is, the welded portion 20 can be formed while the laser L is incident on one of the cup-shaped exterior member 51 and the lid-shaped exterior member 52, passes through the boundary portion 53, and extends toward the other of the cup-shaped exterior member 51 and the lid-shaped exterior member 52. Finally, the welded portion 20 can be formed so as to connect both the cup-shaped exterior member 51 and the lid-shaped exterior member 52.

[0048] According to the above-mentioned features, the laser L is not irradiated along the extending direction of the boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52. As a result, the following effects can be achieved.

[0049] Conventionally, in the manufacture of an exterior body 50' of a secondary battery, a laser L' is irradiated along the extension direction of a boundary portion 53' between a cup-shaped exterior member 51' and a lid-shaped exterior member 52' ​​to form a welded portion 20'. In other words, the boundary portion 53' becomes an incident portion L1' of the laser. Therefore, spatter 90' generated during the formation of the welded portion 20' is likely to penetrate into the electrode assembly 10' through the boundary portion 53'.

[0050] In one embodiment of the present invention, the welded portion 20 can be formed by irradiating the laser L from the second extending surface of one of the cup-shaped and lid-shaped exterior members toward the second extending surface of the other of the cup-shaped and lid-shaped exterior members via the boundary portion 53. That is, the laser L is not irradiated along the extending direction of the boundary portion between the cup-shaped exterior member 51 and the lid-shaped exterior member 52. This makes it possible to prevent spatters generated when forming the welded portion 20 from entering the electrode assembly 10.

[0051] The direction of irradiation of the laser L may be any direction that intersects with the extending direction of the boundary portion 53. The intersecting direction means a direction perpendicular or non-perpendicular to the second extending surface 51b of the cup-shaped exterior member 51 and / or the second extending surface 52b of the lid-shaped exterior member 52 in a cross-sectional view. For example, as shown in Fig. 2, irradiation may be performed from the outer periphery side of the cup-shaped or lid-shaped exterior member toward the inner periphery side via the boundary portion, or as shown in Fig. 3, irradiation may be performed from the inner periphery side of the cup-shaped or lid-shaped exterior member toward the outer periphery side via the boundary portion.

[0052] Due to the above-mentioned characteristics, one embodiment of the present invention can further achieve the following effects.

[0053] In one embodiment of the present invention, as described above, the laser L can be irradiated from one of the second extending surfaces of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 toward the other second extending surface of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 via the boundary portion 53. In such an embodiment, the irradiation direction of the laser L is unlikely to be toward the electrode assembly 10. Therefore, even if the irradiation range and / or the intensity of the laser L are increased to more reliably form the welded portion, the formed welded portion is unlikely to be toward the electrode assembly 10, so that the risk of the spatter 90 penetrating into the electrode assembly 10 is low. For example, even if the intensity of the laser L is increased relatively to the thickness of the cup-shaped and lid-shaped exterior members, the risk of the spatter 90 penetrating into the electrode assembly 10 is low.

[0054] In addition, as shown in FIG. 1, the laser L is irradiated not along the extending direction of the boundary portion 53, so that the laser L is not irradiated toward the electrode assembly 10. In other words, it is difficult to form a weld toward the electrode assembly 10. Therefore, the heat of the laser L that forms the weld is also difficult to propagate toward the electrode assembly 10. In other words, it is possible to avoid the propagation of the heat of the laser L to the electrode assembly 10, and it is possible to strengthen the strength of the laser L and form the weld 20 firmly, and it is difficult for the exterior body 50 to be separated into the lid-shaped and cup-shaped exterior members due to impact, etc. In addition, it is possible to avoid damage to the electrode assembly 10 due to the heat of the laser L, so that it is possible to prevent deterioration of the performance characteristics of the secondary battery.

[0055] 11, even if a gap G exists at a boundary portion 53' between the cup-shaped and lid-shaped exterior members, the laser L' is not irradiated along the extending direction of the boundary portion 53', so there is a low risk that the sputters 90 will enter the electrode assembly 10' through the gap G. Therefore, measures to prevent the gap G from occurring, such as highly accurate design dimensions for the cup-shaped and lid-shaped exterior members, are not required.

[0056] In the conventional manufacture of an exterior body 50' of a secondary battery, the welded portion 20' is formed on the end portion, particularly the end face, of the cup-shaped and lid-shaped exterior member. When the welded portion 20' is formed on the end face, the end face becomes uneven due to the welded portion 20, so that the flatness (or smoothness) is increased. In this regard, in one embodiment of the present invention, the laser L is not irradiated toward the end face, so that the flatness and parallelism of the end face can be maintained at a low level even after the welded portion 20 is formed. This can suppress variation in the height of the obtained secondary battery.

[0057] In one embodiment of the present invention, the effects described above can be achieved, and therefore it becomes possible to design a product in which the variation in height of the secondary battery, the flatness and parallelism of the end faces of the end parts of the exterior components, and the dimensional tolerances are small when packaging the secondary battery in a smaller and thinner size.

[0058] Hereinafter, the secondary battery obtained by the method for producing a secondary battery according to one embodiment of the present invention including the above step (iv) will be specifically described with reference to FIGS.

[0059] Fig. 4 is a schematic perspective view showing a specific configuration of a secondary battery obtained according to a manufacturing method for a secondary battery according to an embodiment of the present invention. Fig. 5 is a schematic cross-sectional view showing a specific configuration of a secondary battery obtained according to a manufacturing method for a secondary battery according to an embodiment of the present invention. As shown in Figs. 4 and 5, a secondary battery 100 obtained by the manufacturing method according to an embodiment of the present invention described above includes an electrode assembly 10 and an exterior body 50 that houses the electrode assembly 10.

[0060] The exterior body 50 includes a cup-shaped exterior member 51 and a lid-shaped exterior member 52 connected to each other by a welded portion 20. The welded portion 20 is formed so as to connect the boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52 without welding the ends of the cup-shaped and lid-shaped exterior members. As described above, in one embodiment of the present invention, the welded portion 20 is formed by irradiating the laser L from one of the second extending surfaces of the cup-shaped and lid-shaped exterior members toward the other second extending surface of the cup-shaped and lid-shaped exterior members through the boundary portion 53. That is, the laser L is not irradiated along the extending direction of the boundary portion 53. Therefore, compared to the boundary portion 53' of the conventional secondary battery 100', no welded portion is formed at the end of the lid-shaped and cup-shaped exterior members at the boundary portion 53, and therefore the boundary surface between the end of the lid-shaped exterior member 52 and the end of the cup-shaped exterior member 51 may remain. In addition, since the conventional secondary battery irradiates a laser along the boundary portion 53', a welded portion 20' is formed at the end of the lid-shaped and cup-shaped exterior member at the boundary portion 53' of the conventional secondary battery 100'. As a result, the flatness of the surface of the exterior member around the boundary portion 53' is lost, and the surface of the exterior member may become uneven. In this regard, the welded portion 20 is not formed around the end of the cup-shaped and lid-shaped exterior members of the secondary battery 100 of the present invention, and the flatness can be maintained. In this specification, the "end of the cup-shaped exterior member" means the end portion or edge portion of the cup-shaped exterior member where no welded portion is formed. The same can be applied to the "end of the lid-shaped exterior member".

[0061] The obtained secondary battery 100 can be a coin-type secondary battery. A coin-type secondary battery is typically approximately circular in plan view. A coin-type secondary battery does not need to be entirely approximately circular in plan view, and can be irregular in shape including a straight line portion (for example, D-shaped in plan view). When the secondary battery is approximately circular in plan view, the electrode assembly 10 and / or the exterior body 50 that contains it can also be approximately circular in plan view. The term "approximately circular (approximately circular shape)" as used herein does not necessarily mean a perfect circle (i.e., simply a "circle" or "perfect circle"), but may mean a shape whose curvature varies locally. For example, it may be a shape derived from a circle or a perfect circle, such as an ellipse, or an oval. The size of a coin-type secondary battery is typically small, and its thickness is smaller than the diameter or width of the coin-type secondary battery. The term "coin type" is merely used by those skilled in the art to refer to the above-mentioned appearance as "coin type". Therefore, it can be variously referred to as a button battery, a bean battery, or a cylindrical, flat, flat, or cylinder-shaped battery, depending on its appearance. That is, if it has the shape and appearance as mentioned above, it can be called a "coin-type" secondary battery, for example. The obtained battery may also be a cylindrical can-type secondary battery. The size of a cylindrical can-type secondary battery is typically small, and its height is greater than the diameter or width of the cylindrical can-type secondary battery.

[0062] (Specific embodiment of the manufacturing method of the present invention) Possible embodiments of the production method of the present invention will be specifically described below.

[0063] In one embodiment of the present invention, the second extending surface is preferably the side surface 51B of the cup-shaped exterior member 51 and the side surface 52B of the lid-shaped exterior member 52 (see Figs. 1A to 1D, 2, and 3, etc.). The term "side surface" in this specification means a surface extending in a direction relatively perpendicular to the upper surface or the lower surface. The side surface 51B of the cup-shaped exterior member 51 in this specification may be a surface forming an opening of the cup-shaped exterior member 51, as shown in Fig. 2, for example, and may be a surface extending in a direction substantially perpendicular to the bottom surface (or lower surface) of the cup-shaped exterior member 51. The side surface 52B of the lid-shaped exterior member 52 in this specification may be a surface extending in a direction substantially perpendicular to the bottom of the lid-shaped exterior member 52, as shown in Fig. 2, for example.

[0064] By adopting such a configuration, the laser L can be irradiated toward the second extended surface, which is the "side surface", and therefore it is possible to easily form the welded portion 20 by irradiating the laser L. For example, a cup-shaped exterior member 51 is placed on a smooth surface, a lid-shaped exterior member is provided to cover the opening and to fit at least a portion of the opening, and then the cup-shaped exterior member 51 is rotated to irradiate the laser L, the irradiation direction of which is fixed, toward the second extended surface located at the "side surface".

[0065] When the laser L penetrates the cup-shaped exterior member 51 or the lid-shaped exterior member 52 during the formation of the welded portion 20 by irradiation with the laser L, spatter 90 may adhere to the surface of the exterior member around the penetration point. If the spatter 90 adheres to the surface of the exterior body 50 after the welded portion 20 is formed, the attached spatter 90 may become a so-called "hooked portion." In particular, if the spatter 90 adheres to the outer peripheral surface of the cup-shaped exterior member 51, there is a risk that the "hooked portion" may scratch other secondary batteries during a process after the formation of the welded portion 20, such as a transport process by a belt conveyor or a packing process into a container. In addition, if the spatter 90 adheres to the outer peripheral surface of the exterior body, the surface becomes uneven, which may impair the appearance.

[0066] From the viewpoint of preventing problems caused by sputters 90 adhering to the surface of the exterior body 50, in one embodiment of the present invention, it is preferable to irradiate the laser L from the outer periphery side of the cup-shaped exterior member 51 or the lid-shaped exterior member 52 toward the inner periphery side via the boundary portion. By adopting such a form, when the laser L penetrates each exterior member, the sputters 90 can adhere to the inner periphery side of the cup-shaped exterior member 51 or the lid-shaped exterior member 52. In other words, it is possible to prevent the sputters 90 from adhering to the surface on the outer periphery side of the cup-shaped exterior member 51 or the lid-shaped exterior member 51.

[0067] In one embodiment of the present invention, each of the cup-shaped and lid-shaped exterior members further has a third extending surface connecting an end of the first extending surface and an end of the second extending surface, and the laser L may be irradiated toward the cup-shaped or lid-shaped second extending surface so that the welded portion 20 is formed apart from the third extending surface of the cup-shaped or lid-shaped exterior member. In other words, the laser L may be irradiated so as not to directly intersect with the third extending surface.

[0068] The term "third extending surface" as used herein means an extending surface that directly connects the end portions of the first extending surfaces 51a, 52a of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 to the end portions of the second extending surfaces 51b, 52b that face the first extending surfaces 51a, 52a at a distance. In this case, the thickness of the third extending surface corresponds to the thickness of the cup-shaped exterior member 51 and the lid-shaped exterior member 52. For example, as shown in FIG. 2, the third extending surface 51c of the cup-shaped exterior member 51 directly connects the end portion of the first extending surface 51a of the cup-shaped exterior member to the end portion of the second extending surface 51b of the cup-shaped exterior member. The third extending surface 52c of the lid-shaped exterior member 52 directly connects the end portion of the first extending surface 51a of the lid-shaped exterior member 52 to the end portion of the second extending surface 51b of the lid-shaped exterior member 52.

[0069] By adopting such a configuration, when forming the welded portion 20 by irradiating the laser L, it is possible to prevent the welded portion 20 from being formed on the third extended surface of each of the cup-shaped exterior member 51 and the lid-shaped exterior member 52. If the welded portion 20 is formed on the third extended surface, the third extended surface becomes uneven due to the welded portion 20, making it difficult to maintain flatness. In addition, when the welded portion 20 is formed, "shrinkage" may occur, in which each molten exterior member is significantly deformed by surface tension. If "shrinkage" occurs, a catch may be formed on the periphery of the end face, or the product dimensions may change, which may cause the quality to be unstable.

[0070] The third extension surface may be, for example, an end surface of the end of the cup-shaped exterior member 51 and / or the lid-shaped exterior member 52. The "end surface of the end" here may be, for example, a two-dimensional surface forming the edge of the cup-shaped exterior member 51. In other words, it may be a surface that connects an end of one main surface and an end of the other main surface among the main surfaces that form the cup-shaped exterior member 51. The above can also be applied to the lid-shaped exterior member 52. Even by adopting such a form, it is possible to achieve the same effect as when the laser L is irradiated toward the cup-shaped or lid-shaped second extension surface so that the welded portion 20 is formed apart from the third extension surface of the cup-shaped or lid-shaped exterior member.

[0071] In FIG. 2 and the like, the third extension surface 51c of the cup-shaped exterior member and the third extension surface 52c of the lid-shaped exterior member 52 are each flat, but other surface shapes may be adopted. For example, the third extension surface 51c of the cup-shaped exterior member and / or the third extension surface 52c of the lid-shaped exterior member 52 may be a curved surface, an inclined surface, or a plurality of surfaces. In one embodiment of the present invention, the laser L is irradiated toward the cup-shaped or lid-shaped second extension surface so that the welded portion 20 is formed apart from the third extension surface, so that the quality of the welded portion formed is easily made constant regardless of the shape of the third extension surface. In other words, in one embodiment of the present invention, even if the third extension surface takes any shape (for example, as described below, a shape in which it is difficult to make the welding quality constant in the past), the welded portion 20 can be formed while avoiding welding of such a third extension surface.

[0072] The third extension surface in a form that makes it difficult to make the welding quality constant may be, for example, a positional relationship in which the third extension surfaces 51c and 52c of the cup-shaped exterior member and the lid-shaped exterior member are not aligned (i.e., not flush) with each other. Alternatively, the third extension surfaces 51c and 52c of the cup-shaped exterior member and the lid-shaped exterior member are spaced from each other, and a gap is generated between the third extension surfaces 51c and 52c. When welding the exterior members including the third extension surfaces in the above form, it is difficult to make the shape of the welded portion constant. In one embodiment of the present invention, even with the third extension surface in the above form, the quality of the welded portion 20 formed is easily made constant by irradiating the laser L so that the welded portion 20 is formed at a distance from the third extension surface.

[0073] In one embodiment of the present invention, as shown in FIG. 6, a lid-shaped exterior member 52 may be used that has a bottom portion 55 and rising side portions 54 configured to rise from the outer periphery of the bottom portion 55, and in which an outer curved surface 56 is formed by the bottom portion 55 and the rising side portions 54 when viewed in cross section.

[0074] In this specification, the "raised side portion" refers to a portion where the outer periphery of the lid-shaped exterior member 52 is raised relative to the bottom portion 55. In addition, since the raised portion can be seen as a side portion relative to the bottom portion 55 in terms of the overall appearance, the raised portion can be referred to as a "raised side portion."

[0075] In this specification, the term "outside" refers to, for example, the outer periphery side of the lid-shaped exterior member 52. The "outer periphery side" refers to, of the two surfaces that define the thickness of the lid-shaped exterior member 52 and are spaced apart from each other and face each other, the surface on the distal side as viewed from the space surrounded by the bottom portion 55 and the rising side portion 54 can be said to be the "outer periphery side" and the surface on the proximal side can be said to be the "inner periphery side". In addition, the "outer curved surface" refers to a curved surface that is curved so as to be convex toward the outer periphery side of the lid-shaped exterior member 52.

[0076] As shown in FIG. 6, the diameter of the lid-shaped exterior member 52 in which the bottom portion 55 and the rising side portion 54 form the outer curved surface 56 can have the following configuration due to the presence of the outer curved surface 56 curved in an R shape. Specifically, as shown in FIG. 6, the outer diameter R2 of the opening of the lid-shaped exterior member 52 is larger than the diameter R1 of the bottom portion 55 of the flat portion of the lid-shaped exterior member 52 that does not include the curved portion. In addition, the diameter R1 of the bottom portion 55 is smaller than the inner diameter R3 of the opening of the cup-shaped exterior member 52. The inner diameter R3 of the opening of the cup-shaped exterior member 52 and the outer diameter R2 of the opening of the lid-shaped exterior member may be approximately the same. In other words, the inner diameter R3 of the opening of the cup-shaped exterior member 52 and the outer diameter R2 of the opening of the lid-shaped exterior member may each be large enough to allow the lid-shaped exterior member 52 to fit into the opening of the cup-shaped exterior member 51. In this embodiment, when the lid-shaped exterior member 52 is provided to cover the opening of the cup-shaped exterior member 51, the bottom 55 of the lid-shaped exterior member 52 can be easily positioned at the opening of the cup-shaped exterior member 51.

[0077] Furthermore, the rising side portion 54 of the lid-shaped exterior member 52 has a shape in which the end is a free end and is continuous with the outer curved surface 56 before being fitted into the cup-shaped exterior member 51. Furthermore, the outer diameter R2 of the opening of the lid-shaped exterior member 52 is slightly larger than the inner diameter R3 of the opening of the cup-shaped exterior member 51. Due to this configuration, the outer diameter R2 of the opening of the lid-shaped exterior member 52 can change during fitting to approach the inner diameter R3 of the opening of the cup-shaped exterior member, which is slightly smaller than R2. As a result, during fitting, the rising side portion 54 can deform relatively inwardly with the outer curved surface 56 as a starting point. As a result, the rising side portion 54 of the lid-shaped exterior member 52 can deform so that the inner diameter R3 and the outer diameter R2 become approximately the same. This means that, since the raised side portion 54 of the lid-shaped exterior member 52 has an "outer curved surface," the cup-shaped exterior member 51 and the lid-shaped exterior member 52 can fit together without having to design highly accurate dimensions.

[0078] Furthermore, when the lid-shaped outer casing member 52 is fitted into the cup-shaped outer casing member 51 under the above-described conditions, the outer circumferential diameter of the cup-shaped outer casing member 51 at the portion in contact with the lid-shaped outer casing member 52 can be larger than the outer circumferential diameter of the portion of the bottom 55 of the lid-shaped outer casing member 52 where the lid-shaped outer casing member 52 and the cup-shaped outer casing member 51 do not contact.

[0079] Furthermore, when the lid-shaped exterior member 52 having the raised side portion 54 including the above-mentioned "outer curved surface" is fitted into the cup-shaped exterior member 51, a stress F may act on the outer circumferential edge forming the opening of the cup-shaped exterior member 51 due to the fitting of the lid-shaped exterior member 52. More specifically, the stress F may act in the circumferential direction of the opening of the cup-shaped exterior member 51.

[0080] These problems arise because the outer peripheral edge forming the opening of the cup-shaped exterior member 51 is pushed out in the circumferential direction of the opening by the fitted lid-shaped exterior member 52 as described above. By adopting such a configuration, the opening of the cup-shaped exterior member 51 is covered and the lid-shaped exterior member 52 is provided so that at least a portion of the lid-shaped exterior member 52 is fitted into the opening, and this can improve the sealing performance. In addition, the presence of the rising side portion 54 of the lid-shaped exterior member 52 increases the opposing portion between the cup-shaped exterior member 51 and the lid-shaped exterior member 52 when fitted together, which can contribute to improving the sealing performance.

[0081] By adopting such a configuration, the lid-shaped exterior member 52 can be held in the cup-shaped exterior member 51 by merely fitting them together. As a result, when forming the welded portion 20 by irradiating the laser L, it is not necessary to perform a process of preparing and fixing a new jig to prevent the lid-shaped exterior member 52 from shifting from the welding position, and / or a process of spot welding and fixing a part of the boundary portion 53 of each exterior member, and the like, and it is possible to simplify the welding process.

[0082] Furthermore, by adopting such a configuration, the boundary surface between the cup-shaped and lid-shaped exterior members can be brought into contact without any gaps by simply fitting the lid-shaped exterior member 51 to the cup-shaped exterior member 52 before irradiating the laser L to form the welded portion 20. Specifically, by making the outer diameter R2 of the lid-shaped exterior member 51 larger than the inner diameter R3 of the cup-shaped exterior member 52, the lid-shaped exterior member 51 can be "pushed" into the cup-shaped exterior member 52, and the main surface having the rising side portion 54 including the outer curved surface 56 of the lid-shaped exterior member 51 can be pressed against the cup-shaped exterior member 52. By pressing, the boundary surface between the cup-shaped and lid-shaped exterior members can be brought into contact without any gaps, and the state in which the lid-shaped exterior member 51 is fitted into the cup-shaped exterior member 52 can be maintained. As a result, it is no longer necessary to provide a fixing means for preventing the lid-shaped and cup-shaped exterior members from moving before irradiating the laser L, which can contribute to simplifying the manufacturing method of the secondary battery. In addition, by adjusting the depth of the "pushing", the end face of the end of the lid-shaped exterior member 51 can be easily positioned so as to be flush with the end face of the end of the cup-shaped exterior member 52.

[0083] When using a lid-shaped exterior member 51 having a raised side portion 54 including an outer curved surface 56 in a cross-sectional view, an external output terminal 60 may be further provided on the lid-shaped exterior member 51. In a cross-sectional view, the lid-shaped exterior member 51 having the raised side portion 54 including the outer curved surface 56 has a concave structure like a bowl. Therefore, for example, even if the external output terminal 60 is provided on the lid-shaped exterior member 51, the external output terminal 60 fits into the concave structure of the lid-shaped exterior member 51, so that the external output terminal 60 does not protrude in a convex shape from the lid-shaped exterior member 51 when viewed as a whole secondary battery. In addition, since the internal volume of the secondary battery can be maximized, the volumetric energy density of the secondary battery can be maximized.

[0084] In one embodiment of the present invention, the lid-shaped exterior member 52 and the cup-shaped exterior member 51 may have a step 51S provided on the inner peripheral side of at least one of the lid-shaped exterior member 52 and the cup-shaped exterior member 51, as shown in FIG. 8.

[0085] By adopting such a configuration, when the lid-shaped exterior member 52 is provided to cover the opening of the cup-shaped exterior member 51 and to be at least partially fitted into the opening, the lid-shaped exterior member 52 can come into contact with and engage with the step 51S as shown in FIG. 8. This makes it possible to limit the insertion depth of the lid-shaped exterior member 52 into the cup-shaped exterior member 51. In other words, the insertion depth of the lid-shaped exterior member 52 into the cup-shaped exterior member 51 can be positioned constant. That is, the cup-shaped exterior member 51 can function as a mechanism for limiting the insertion depth of the lid-shaped exterior member 52. As a result, the quality of the manufactured exterior body 50 can be stabilized, and the manufacturing yield of the secondary battery can be improved.

[0086] In one embodiment of the present invention, it is preferable that the boundary portion 53 has a contact region 53a where the cup-shaped exterior member 51 and the lid-shaped exterior member 52 are in contact with each other, and that the contact region 53a is irradiated with the laser L. Specifically, when a lid-shaped exterior member 52 having a rising side portion 54 including an outer curved surface 56 as shown in FIG. 7 is used, the boundary portion 53 has a contact region 53a where the cup-shaped exterior member 51 and the lid-shaped exterior member 52 are in contact with each other and a separation region 53b that is separated from each other. Of the contact region 53a and the separation region 53b, it is preferable that the laser L is irradiated from the second extending surface of one of the cup-shaped and lid-shaped exterior members toward the second extending surface of the other of the cup-shaped and lid-shaped exterior members via the contact region 53a.

[0087] When forming the welded portion 20 by irradiating the laser L, if the laser L is irradiated toward the separation region 53b, the welded portion 20 is formed so as to be exposed inside each exterior sealing structure, which increases the possibility of spatter 90 penetrating into the electrode assembly 10. In this regard, by irradiating the laser L toward the contact region 53a of the boundary portion 53, it is possible to prevent the spatter from penetrating into the electrode assembly 10. In addition, as described above, the use of the lid-shaped exterior member 52 having the raised side portion 54 including the outer curved surface 56 can also improve sealing performance.

[0088] In one embodiment of the present invention, as shown in FIG. 7, the lid-shaped exterior member 52 may further include a protruding portion 52p that is continuous with the rising side portion 54 of the lid-shaped exterior member 52 and extends in a direction different from the extending direction of the rising side portion 54. In other words, the lid-shaped exterior member 52 may have a "third extending surface 52c of the lid-shaped exterior member 52" that further includes a protruding portion 52p that protrudes toward the outer periphery of the lid-shaped exterior member 52. By adopting such a form, the protruding portion 52p comes into contact with the end of the cup-shaped exterior member 51. As shown in FIG. 7, the protruding portion 52p comes into contact with the end of the cup-shaped exterior member 51, so that the protruding portion 52p can engage with the end of the cup-shaped exterior member 51. This makes it possible to limit the insertion depth of the lid-shaped exterior member 52 into the cup-shaped exterior member 51. In other words, when the lid-shaped exterior member 52 is provided to cover the opening of the cup-shaped exterior member 51 and to be at least partially fitted into the opening, the insertion depth of the lid-shaped exterior member 52 can be positioned constant. That is, the cup-shaped exterior member 51 can function as an insertion depth limiting mechanism for the lid-shaped exterior member 52. In addition, since the protruding portion 52p is positioned so as to cover the end face of the end of the cup-shaped exterior member 51, the boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52 is not exposed to the outside. Therefore, the flatness of the end face of the end of the manufactured exterior body 50 can be improved.

[0089] From the viewpoint of increasing the volumetric energy density of the secondary battery, the thicknesses of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 may be thin. Specifically, the thickness of the cup-shaped exterior member 51 may be 10 μm or more and 500 μm or less, for example, 10 μm or more and 300 μm or less, 10 μm or more and 150 μm or less, 10 μm or more and 100 μm or less, or 10 μm or more and 75 μm or less. The thickness of the lid-shaped exterior member 52 may be 10 μm or more and 500 μm or less, for example, 10 μm or more and 300 μm or less, 10 μm or more and 150 μm or less, or 10 μm or more and 75 μm or less.

[0090] As described above, the volumetric energy density of the secondary battery can be increased by reducing the thickness of the exterior member. However, by reducing the thickness of the exterior member, the exterior member is more likely to "shrink" due to melting when the welded portion 20 is formed. In particular, if "shrinkage" occurs when the end of the cup-shaped or lid-shaped exterior member 52 is irradiated with the laser L, it may cause the formation of a catch due to the "shrinkage" and cause variations in product dimensions. The occurrence of "shrinkage" can be suppressed by weakening the strength of the laser L, but on the other hand, there is a possibility that the formation of the welded portion 20 may be insufficient, and there is a risk that the sealing property cannot be ensured.

[0091] In one embodiment of the present invention, the laser L is not irradiated along the extending direction of the boundary portion 53 between the cup-shaped exterior member 51 and the lid-shaped exterior member 52. This makes it possible to suppress the occurrence of "shrinkage" of the welded portion 20 when the end portions of the cup-shaped and lid-shaped exterior members 52 are irradiated with the laser L, thereby making it possible to reduce the thickness of the exterior member.

[0092] In one embodiment of the present invention, as shown in Fig. 9, a cup-shaped exterior member 51 can be used in which the outer peripheral edge portion of the cup-shaped exterior member is curved so that the end of the cup-shaped exterior member is separated from the end of the lid-shaped exterior member in a cross-sectional view. Specifically, this means that the outer peripheral edge portion forming the opening of the cup-shaped exterior member 51 is curved in an R-shape toward the outer periphery of the cup-shaped exterior member 51 in a cross-sectional view. When a lid-shaped exterior member 52 is fitted into the cup-shaped exterior member 51 in which the outer peripheral edge portion forming the opening is curved in an R-shape toward the outer periphery, a gap W is formed between the end of the opening of the cup-shaped exterior member 51 and the end of the lid-shaped exterior member 52.

[0093] In this embodiment, when the laser L is irradiated along the extending direction of the boundary portion 53, the gap W exists at the boundary portion 53, so that the spatter 90 generated by the formation of the welded portion 20 is more likely to penetrate into the electrode assembly.

[0094] As described above, in the present invention, the laser L is irradiated not along the direction in which the boundary portion 53 extends, so that even if the welded portion 20 is formed using a cup-shaped exterior member 51 in which the outer peripheral edge portion forming the opening is curved toward the outer periphery of the cup-shaped exterior member 51, there is a low risk of the spatter 90 penetrating into the electrode assembly 10. Also, for the same reason, it is possible to prevent "shrinkage" due to melting of the ends of each exterior member. In other words, even if the exterior member has the above-mentioned gap W in the conventional method, the problem of the present invention can be solved by applying the features of the present invention even if the gap W exists.

[0095] Furthermore, when the outer peripheral edge portion forming the opening of the cup-shaped exterior member 51 is curved toward the outer periphery of the cup-shaped exterior member 51, the inner diameter of the curved opening becomes large, making it easier to fit the lid-shaped exterior member 52. Even if a cup-shaped exterior member 51 in which the outer peripheral edge portion forming the opening is curved in an R shape is manufactured in the manufacturing process of the cup-shaped exterior member 51, it can be used as it is according to the present invention, and therefore productivity can be improved. EXAMPLES

[0096] Examples of the present invention will now be described.

[0097] [Comparative Example] (Preparation of cup-shaped exterior member and lid-shaped exterior member) A cup-shaped exterior member and a lid-shaped exterior member were prepared. 、 The container used had, in cross-sectional view, a bottom portion and rising side portions configured to rise from the outer peripheral edge of the bottom portion, and an outer curved surface was formed by the bottom portion and the rising side portions.

[0098] A cup-shaped exterior member with an inner diameter of 12 mm and a height of 5.4 mm and a lid-shaped exterior member with an outer diameter of 12.05 mm and an inner circumferential height of 0.4 mm were prepared. The thicknesses of the cup-shaped exterior member and the lid-shaped exterior member were prepared in four types: 0.3 mm, 0.15 mm, 0.1 mm, and 0.075 mm, as shown in the table.

[0099] (Formation of exterior body) An electrode assembly was provided, and a lid-shaped exterior member was placed over the opening of a cup-shaped exterior member into which an electrolyte had been poured, and the lid-shaped exterior member was inserted so that at least a portion of the lid-shaped exterior member was fitted into the opening (as shown in FIG. 2). The cup-shaped and lid-shaped exterior members were inserted to a depth such that their end faces were on the same plane (flush). Thereafter, as shown in FIG. 11, a laser was aimed from above the cup-shaped and lid-shaped exterior members at the end faces of the cup-shaped and lid-shaped exterior members, and irradiated along the boundary surface between the cup-shaped and lid-shaped exterior members to perform welding. In this way, the boundary surface between the cup-shaped and lid-shaped exterior members was welded to form an exterior body.

[0100] [Measurement of side height dimensional variation] The side height dimension was measured at eight points on each sample using a flat terminal Digimatic Indicator (manufactured by Mitutoyo), and the maximum value was used as the side height of that sample. The CV value was calculated by dividing the standard deviation of the 32 data points by the average value.

[0101] (Results of side height dimensional variation in the comparative example) The results of the side height dimension variation of the comparative examples are shown in Table 1. The cases where the thicknesses of the cup-shaped and lid-shaped exterior members were 0.3 mm, 0.15 mm, 0.1 mm, and 0.075 mm were designated Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, respectively. As can be seen from Table 1, the value of the side height dimension variation increased as the thickness became thinner. Specifically, as the thickness became thinner, the value of the side height dimension variation increased to 0.27, 1.5, 1.9, and 2.2. In particular, compared to the result of a thickness of 0.3 mm, the value of the side height dimension variation of a thickness of 0.15 mm was about 5 times, that of a thickness of 0.1 mm was about 7 times, and that of a thickness of 0.075 mm was about 8 times.

[0102] [Table 1]

[0103] [Example] As shown in Fig. 2, the laser was irradiated from the outer periphery (horizontal direction) of the side surface of the cup-shaped exterior member to the side surface of the cup-shaped exterior member, and welding was performed under the same irradiation conditions, except that the exterior body was produced under the same conditions as the comparative example, and the side height dimension variation was measured in the same manner. The cases where the thicknesses of the cup-shaped and lid-shaped exterior members were 0.3 mm, 0.15 mm, 0.1 mm, and 0.075 mm are designated as Example 1, Example 2, Example 3, and Example 4, and the results are shown in Table 1. As can be seen from Table 1, the value of the side height dimension variation hardly changed even when the thicknesses of the cup-shaped and lid-shaped exterior members were reduced.

[0104] [Comparison between Comparative Example and Example] Based on the results shown in Table 1, the comparative examples and the examples were compared. First, comparing the side height dimension variation (CV%) values ​​of Example 1 and Comparative Example 1, in which the thickness of the cup-shaped and lid-shaped exterior members is 0.3 mm, the value was 0.14 for Example 1 and 0.27 for Comparative Example 1. The value of Example 1 was smaller than that of Comparative Example 1, and the value of the side height dimension variation of Comparative Example 1 was about twice that of Example 1. When the thickness was 0.15 mm, the value of Example 2 was 0.13 and the value of Comparative Example 2 was 1.5, so that Example 2 was smaller, and the difference between the two was about 10 times or more. When the thickness was 0.1 mm, the value of Example 3 was 0.15 and the value of Comparative Example 3 was 1.9, so that Example 3 was smaller, and the difference between the two was 10 times or more. When the thickness was 0.075 mm, the value of Example 4 was 0.18 and the value of Comparative Example 4 was 2.2, so that Example 4 was smaller, and the difference between the two was 10 times or more. A small value of the side height dimension variation (CV%) means that the exterior body has a uniform side height. That is, it can be said that the example in which welding was performed by irradiating a laser toward the side surface of the cup-shaped exterior member from the outer periphery (horizontal direction) of the side surface resulted in an exterior body with a more uniform side surface height than the comparative example.

[0105] The welded portion formed in the example was formed from the side surface of the cup-shaped exterior member to the side surface of the lid-shaped exterior member, and was not formed on the end surfaces of the cup-shaped and lid-shaped exterior members. This is because the welding was performed by irradiating the laser from the outer periphery (horizontal direction) of the side surface of the cup-shaped exterior member toward the side surface of the cup-shaped exterior member. Therefore, the end surfaces of the cup-shaped and lid-shaped exterior members were able to maintain the same surface (flush) state at the time of insertion. In other words, the side height was able to be maintained uniform.

[0106] On the other hand, the welds formed in the comparative example were formed on the boundary surface located at the end faces of the cup-shaped and lid-shaped exterior members. This is because the laser was aimed at the end faces of the cup-shaped and lid-shaped exterior members from above the cup-shaped and lid-shaped exterior members, and was irradiated along the boundary surface of the cup-shaped and lid-shaped exterior members to perform welding. The surface of the welds was uneven and the shape was non-uniform, and the welds were formed as convex parts on the end faces, so the side height of the comparative example in which the welds were formed on the end faces of the cup-shaped and lid-shaped exterior members was no longer uniform.

[0107] In the comparative example, when forming the welded portion, the laser was irradiated along the boundary surface between the cup-shaped and lid-shaped exterior members as described above, and welding was performed. In other words, since the welded portion was formed toward the electrode assembly located on the inner periphery side of the exterior body, it was found that there was a risk of spatter penetrating into the electrode assembly. In this regard, in the example, the laser was not irradiated along the boundary surface between the cup-shaped and lid-shaped exterior members as described above, and it was found that there was no risk of spatter penetrating into the electrode assembly.

[0108] Also, as shown in Table 1, the side height dimensional variation (CV%) for thicknesses of 0.15 mm (Comparative Example 2), 0.1 mm (Comparative Example 3), and 0.075 mm (Comparative Example 4) was larger than that for a thickness of 0.30 mm (Comparative Example 1). This is because the thinner the thickness, the larger the thermal energy of the laser irradiation that the exterior member received, causing the entire end face to melt, and as a result, the end face was significantly deformed due to surface tension. This is thought to have caused the dimensional variation of the finished product to increase.

[0109] On the other hand, the side height dimension variation (CV%) of Examples 2, 3, and 4 was similar to that of Example 1, and was smaller than that of the Comparative Example. This shows that even when the thickness of the exterior member is reduced, the side height dimension variation (CV%) can be suppressed from increasing and high dimensional accuracy can be maintained by forming a weld by irradiating a laser from the side of the exterior member.

[0110] Although the embodiments of the present invention have been described above, they are merely typical examples. Therefore, it will be easily understood by those skilled in the art that the present invention is not limited to these, and that various embodiments are possible. [Industrial Applicability]

[0111] The secondary battery according to one embodiment of the present invention can be used in various fields where power storage is required. Although merely illustrative, the secondary battery of the present invention can be used in the electrical, information, and communication fields in which electrical and electronic devices are used (for example, electrical and electronic devices fields or mobile device fields including mobile phones, smartphones, notebook computers, digital cameras, activity meters, arm computers, electronic paper, wearable devices, and small electronic devices such as RFID tags, card-type electronic money, and smart watches), household and small industrial applications (for example, electric tools, golf carts, household, nursing care, and industrial robots), large industrial applications (for example, forklifts, elevators, and port cranes), transportation systems (for example, hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (for example, various power generation, road conditioners, smart grids, and general household installation-type power storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (medical management systems), and the IoT field, and space and deep sea applications (for example, space probes, submersible research vessels, and the like). [Explanation of symbols]

[0112] 1 positive electrode 2 negative electrode 3. Separator 5 Electrode composition layer 10, 10' electrode assembly 20, 20' welded section 30 Electrolyte 41 Positive electrode current collecting tab 42 Negative electrode current collecting tab 50, 50' exterior body 51, 51' Cup-shaped exterior member 51a: First extending surface (cup-shaped exterior member side) 51B Side of cup-shaped exterior member 51b Second extending surface (cup-shaped exterior member side) 51c Third extension surface (cup-shaped exterior member side) 51s Step 52, 52' Lid-shaped exterior member 52a: First extending surface (lid-shaped exterior member side) 52B Side of lid-shaped exterior member 52b Second extending surface (lid-shaped exterior member side) 52c Third extension surface (lid-shaped exterior member side) 52p protruding part 53 Boundary part 53a Contact area 53b Separate area 54, 54' raised side 55, 55' bottom 56 Outer curved surface 60 External output terminal 70 Insulating materials 90' Spatter 100, 100' secondary battery F Stress G Boundary gap L, L' Laser L1, L1' laser entrance area R1 Diameter of the bottom of the flat part of the lid-shaped exterior part, excluding the curved part R2 Outer shape of the opening of the lid-shaped exterior part R3: Inner diameter of the opening of the cup-shaped exterior member 52 Gap between the end of the W-cup lid-shaped exterior member and the end of the lid-shaped member

Claims

1. Providing an electrode assembly within a cup-shaped exterior member; A step of injecting an electrolyte into the cup-shaped exterior member; A step of covering the opening of the cup-shaped exterior member and providing a lid-shaped exterior member so that at least a portion of the lid-shaped exterior member fits into the opening; and The step of installing the lid-shaped exterior member includes a step of irradiating a laser toward a boundary portion between the cup-shaped exterior member and the lid-shaped exterior member that face each other to form a welded portion, Each of the cup-shaped and lid-shaped exterior members has a first extending surface constituting the boundary portion and a second extending surface facing and spaced apart from the first extending surface, The laser is irradiated from the second extension surface of one of the cup-shaped and the lid-shaped exterior members toward the second extension surface of the other of the cup-shaped and the lid-shaped exterior members through the boundary portion; The method for manufacturing a secondary battery uses, as the exterior member, a cup-shaped exterior member and / or a lid-shaped exterior member having a step on the inner periphery side.

2. The method for manufacturing a secondary battery according to claim 1 , wherein the laser is irradiated so as to straddle the boundary portion.

3. The method for producing a secondary battery according to claim 1 , wherein the laser is irradiated so as to intersect the boundary portion.

4. The method for manufacturing a secondary battery according to claim 1 , wherein the second extension surface is a side surface of the cup-shaped exterior member and a side surface of a lid-shaped exterior member.

5. The method for manufacturing a secondary battery according to claim 1 , wherein the second extending surface of the one of the cup-shaped and lid-shaped exterior members is an incident portion of the laser.

6. The method for producing a secondary battery according to any one of claims 1 to 5, wherein the laser is irradiated from an outer periphery side of the cup-shaped or lid-shaped exterior member toward an inner periphery side through the boundary portion.

7. Each of the cup-shaped and lid-shaped exterior members further includes a third extension surface connecting an end of the first extension surface and an end of the second extension surface, The method for manufacturing a secondary battery according to any one of claims 1 to 6, wherein a laser is irradiated to the cup-shaped or lid-shaped exterior member so that a weld is formed away from the third extension surface of the cup-shaped or lid-shaped exterior member.

8. The method for manufacturing a secondary battery according to any one of claims 1 to 7, wherein the lid-shaped exterior member has a bottom and a rising side portion configured to rise from an outer periphery of the bottom when viewed in cross section, and an outer curved surface is formed by the bottom and the rising side portion.

9. The method for manufacturing a secondary battery according to claim 8 , wherein the boundary portion has at least a contact area where the cup-shaped exterior member and the lid-shaped exterior member are in contact with each other, and the laser is irradiated to the contact area.

10. 10. The method for manufacturing a secondary battery according to claim 8, wherein the lid-shaped exterior member further includes a protruding portion that is continuous with the rising side portion of the lid-shaped exterior member and extends in a direction different from the extending direction of the rising side portion.

11. The method for manufacturing a secondary battery according to any one of claims 1 to 10, wherein the cup-shaped exterior member and the lid-shaped exterior member each have a thickness of 300 µm or less.

12. The method for manufacturing a secondary battery according to any one of claims 1 to 11, wherein the cup-shaped exterior member has an outer peripheral edge portion curved so that an end of the cup-shaped exterior member is separated from an end of the lid-shaped exterior member in a cross-sectional view.

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