Secondary battery manufacturing method

Abstract

The present invention includes: a step for providing an electrode assembly inside a cup-shaped exterior member; a step for providing a lid-shaped exterior member so as to form a lid on an opening in the cup-shaped exterior member; and a step for irradiating a laser onto a facing portion at which the cup-shaped exterior member and the lid-shaped exterior member face each other, and forming a welded section, the facing portion being formed by positioning the end face of either the cup-shaped exterior member or the lid-shaped exterior member on the end face of the other of the cup-shaped exterior member or the lid-shaped exterior member, the end faces being in a non-stepped state.

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a secondary battery, and more particularly to a method for manufacturing a secondary battery having 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] International Publication No. 15 / 072010 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 FIGS. 12A and 12B).

[0005] The secondary battery comprises an electrode assembly 10' including a positive electrode, a negative electrode, and a separator between them, and an exterior body 50' that encases the electrode assembly 10'. The exterior body 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'. This welded portion 20' can be formed, for example, by arranging a stepped portion 54' provided at an end of a lid-shaped exterior member 52' ​​so as to fit against a stepped portion 55' provided at an end of a cup-shaped exterior member 51', and irradiating the facing portion 53' with a laser L'.

[0006] In this regard, it is preferable that the facing portion 53' is sealed without gaps from the viewpoint of improving the sealing property and preventing the intrusion of spatters 90' that may occur when the electrode assembly 10' is irradiated with the laser L'. However, the facing portions between the substantially vertical surfaces 54a', 55a' and between the substantially vertical surfaces 54c', 55c', which are components of the step portions 54', 55' of the cup-shaped exterior member 51' and the lid-shaped exterior member 52', are more likely to have gaps G' due to their shapes than the facing portions between the substantially horizontal surfaces 54b', 55b', which are components of the step portions 54', 55' of both. Therefore, measures such as highly accurate alignment adjustment are required to prevent gaps from occurring in the facing portions between the substantially vertical surfaces, but this is not preferable from the viewpoint of production efficiency.

[0007] 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 easily ensure the sealing performance of the opposing portions of a cup-shaped exterior member and a lid-shaped exterior member. [Means for solving the problem]

[0008] 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 providing a lid-shaped exterior member to cover the opening of the cup-shaped exterior member; and a step of irradiating a laser to a portion where the cup-shaped exterior member and the lid-shaped exterior member face each other to form a weld; A method for manufacturing a secondary battery is provided in which the opposing portion is formed by positioning an end face of one end of the cup-shaped exterior member and the lid-shaped exterior member on an end face of the other end of the cup-shaped exterior member and each end face has a non-step shape. Effect of the Invention

[0009] According to the method for manufacturing a secondary battery according to one embodiment of the present invention, it is possible to easily ensure the sealing performance of the opposing portions of the cup-shaped exterior member and the lid-shaped exterior member. [Brief description of the drawings]

[0010] [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 forming a welded portion by laser irradiation, in the method for producing a secondary battery according to one embodiment of the present invention. [Figure 1C] FIG. 1C is a schematic cross-sectional view showing a secondary battery obtained according to a method for producing a secondary battery according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic enlarged cross-sectional view of FIG. 1B. [Diagram 3] FIG. 3 is a schematic perspective view showing a specific configuration of FIG. 1C. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a specific configuration of FIG. 1C. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a process of forming a welded portion using a lid-shaped exterior member having an inclined side surface at an end thereof and a cup-shaped exterior member having an inclined end surface at an end thereof. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a process of forming a weld using a lid-shaped exterior member having an inclined side surface at an end thereof and a cup-shaped exterior member having an inclined side surface at an end thereof. [Figure 7] FIG. 7 is a schematic perspective view showing a secondary battery obtained through the step of forming the welded portion shown in FIG. [Figure 8A] FIG. 8A 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 another embodiment of the present invention. [Figure 8B] FIG. 8B is a schematic cross-sectional view showing a step of drawing the end of the cup-shaped exterior member, in the method for manufacturing a secondary battery according to another embodiment of the present invention. [Figure 8C] FIG. 8C is a schematic cross-sectional view showing a step of forming a welded portion by laser irradiation, in the method for producing a secondary battery according to another embodiment of the present invention. [Figure 9] FIG. 9 is a schematic cross-sectional view showing a step of forming a welded portion by laser irradiation in accordance with a method for producing a secondary battery according to still another embodiment of the present invention. [Figure 10] 10 is a schematic cross-sectional view showing a step of forming a welded portion by laser irradiation according to a method for producing a secondary battery according to still another embodiment of the present invention. [Figure 11A] FIG. 11A is a cross-sectional view that illustrates an electrode configuration layer having a planar laminated structure. [Figure 11B] FIG. 11B is a cross-sectional view that illustrates a schematic diagram of an electrode configuration layer having a wound structure. [Figure 12A] FIG. 12A is a schematic cross-sectional view showing a state in which a laser is irradiated to a stepped portion between an end of a cup-shaped exterior member and an end of a lid-shaped exterior member (prior art). [Figure 12B] FIG. 12B is a schematic cross-sectional view showing an embodiment of forming a weld via the laser irradiation embodiment of FIG. 12A (prior art). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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 examples for understanding the present invention, and the appearances and dimensional ratios may differ from the actual ones.

[0012] 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 drawing, 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 stacking direction of the electrode assembly may correspond to the upper-lower direction, and the vertical downward direction (i.e., the direction in which gravity acts) corresponds to the "downward direction", and the opposite direction corresponds to the "upward direction".

[0013] [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.

[0014] 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. 11A and FIG. 11B. As illustrated in FIG. 11A and FIG. 11B, 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. 11A, 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. 11B, 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. 11B, 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 oxides for the negative electrode active material include at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide, and lithium oxide. The lithium alloy for the negative electrode active material may be a metal that can form an alloy with lithium, and may be, for example, a binary, ternary, or higher alloy of lithium and a metal such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, or La. Such oxides may have an amorphous structure. This is because deterioration caused by non-uniformity such as grain boundaries or defects is less likely to occur.

[0024] 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 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, graphite, carbon fibers such as 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The exterior body of a 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 metal such as stainless steel (SUS) and / or aluminum. 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.

[0033] [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.

[0034] The present inventors have conducted extensive research into a solution for easily ensuring the sealing performance of the opposing portions of the cup-shaped exterior member and the lid-shaped exterior member, and as a result have devised a method for manufacturing a secondary battery according to an embodiment of the present invention.

[0035] 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 forming a welded portion by laser irradiation 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 secondary battery obtained according to the 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. 1B.

[0036] The term "cup-shaped exterior member" refers to a member having a side wall or side surface corresponding to a body portion and a main surface (e.g., a bottom portion in a typical embodiment) that is continuous with the side wall and has a hollow portion formed inside. The term "lid-shaped exterior member" refers to a member that is provided to cover the cup-shaped member (preferably, a member that covers the cup-shaped member so as to extend onto the side wall of the cup-shaped member).

[0037] Hereinafter, a method for manufacturing a secondary battery according to one embodiment of the present invention will be described with reference to the drawings. A method for producing a secondary battery according to one embodiment of the present invention mainly includes the following steps. (i) Step of providing the electrode assembly 10 in a cup-shaped exterior member 51 (see FIG. 1A). (ii) A process of finally providing a lid-shaped exterior member 52 to cover the opening of the cup-shaped exterior member 51 in a state in which the inside of the cup-shaped exterior member 51 is filled with the electrolyte 30. (iii) A step of irradiating a laser L to a portion 50A where the cup-shaped exterior member 51 and the lid-shaped exterior member 52 face each other to form a welded portion 20 (see Figs. 1B and 1C). Through the above steps, the secondary battery of the present invention can be obtained.

[0038] The manufacturing method of the secondary battery according to one embodiment of the present invention is characterized by steps (ii) and (iii) among the above steps. Specifically, before forming the welded portion 20 by irradiating the laser L, the above-mentioned facing portion 50A is formed by positioning the end face of one end of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 on the end face of the other end, and each end face has a non-step shape (see Fig. 1B, Fig. 1C, and Fig. 2). That is, the facing portion 50A is formed by positioning the non-step-shaped end face of the other end of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 on the non-step-shaped end face of the one end of the cup-shaped exterior member 51. As an example, the facing portion 50A is formed by positioning the non-step-shaped end face 52A of the end of the lid-shaped exterior member 52 on the non-step-shaped end face 51A of the end of the cup-shaped exterior member 51.

[0039] The term "end surface" in this specification refers to a surface constituting at least a part of the end of each exterior member that forms the opposing portion (i.e., the boundary portion) between the cup-shaped exterior member 51 and the lid-shaped exterior member 52. The term "non-stepped end surface" in this specification refers to an end surface that does not have a step shape (i.e., a shape composed of two faces with different heights and a face connecting the ends of the two faces), and examples thereof include an inclined shape, a horizontal surface shape, a curved shape, a tapered shape (tapering shape), a wavy shape, and the like.

[0040] In one embodiment of the present invention, the point is to position the end face of one exterior member on the end face of the other exterior member. In order to position (i.e., place) the other end face on the end face of one, it is necessary that each end face is not a surface extending in the direction of gravity. In view of this, each end face can also be said to be a surface extending in a direction different from the direction of gravity (i.e., a non-vertical direction or a non-gravity direction). Each end face of each exterior member may have a shape that is paired with each other. For example, if the end face of the cup-shaped exterior member 51 is inclined, the end face of the lid-shaped exterior member 52 may be inclined. Each end face of each exterior member may be a surface extending in the same direction. For example, if the end face of the cup-shaped exterior member 51 is an inclined extending surface, the end face of the lid-shaped exterior member 52 may be a surface extending in the same direction as the direction in which the end face of the cup-shaped exterior member 51 extends. By adopting such a form, it becomes easier to position the end face of the other exterior member on the end face of one exterior member.

[0041] According to the above-mentioned features, in a state where the facing portion 50A is formed, a force such as gravity can be applied downward from the end face 52A, which is a component of the end of the lid-shaped exterior member 52, to the end face 51A, which is a component of the end of the cup-shaped exterior member 51. As a result, it is possible to prevent a gap from being generated between the end faces 51A, 52A, which are components of the ends of the two exterior members, and as a result, it is possible to make both end faces 51A, 52A face to face and contact each other. Therefore, according to one embodiment of the present invention, it is possible to easily ensure the sealing property of the facing portion 50A of the cup-shaped exterior member 51 and the lid-shaped exterior member 52.

[0042] By simply ensuring the sealing performance of the facing portion 50A, the following effects can be achieved.

[0043] In the past, when manufacturing an exterior body 50' of a secondary battery, it was necessary to take additional measures to prevent gaps from occurring in the opposing portions between the approximately horizontal surfaces 54b', 55b' of the step portions 54', 55' provided at the ends of the cup-shaped exterior member 51' and the lid-shaped exterior member 52' ​​(see Figs. 12A and 12B). As a countermeasure, for example, high-precision alignment adjustment and manufacturing of the cup-shaped exterior member 51' and the lid-shaped exterior member 52' ​​with high dimensional accuracy are required so that the step portions 54', 55' can contact each other without gaps. Therefore, it takes time and cost to manufacture equipment to achieve high-precision alignment adjustment, and further takes time and cost to manufacture a mold itself to obtain an exterior member with high dimensional accuracy.

[0044] In one embodiment of the present invention, since it is possible to suppress the occurrence of gaps between the end faces 51A, 52A, which are components of the ends of the two exterior members, there is no need for highly accurate alignment adjustment and the manufacture of cup-shaped and lid-shaped exterior members with high dimensional accuracy, as in the previous embodiment. Therefore, there is no need to spend time and money on manufacturing equipment to achieve highly accurate alignment adjustment, and further there is no need to spend time and money on manufacturing a mold itself to obtain an exterior member with high dimensional accuracy.

[0045] In addition, in the past, when a gap occurs in the opposing portion, it is necessary to increase the output of the laser L' and irradiate the laser L over a wide area in order to fill the gap. As a result, the radiation heat energy of the laser L' is easily propagated to the electrode assembly 10', and the risk of thermal damage increases (see Figs. 12A and 12B). In contrast, in one embodiment of the present invention, it is possible to suppress the generation of a gap between the end faces 51A and 52A at the respective ends of both exterior members, so that it is possible to reduce the output of the laser L and irradiate a narrower area than before. As a result, it is possible to suitably suppress the propagation of the radiation heat energy of the laser L to the electrode assembly 10, and it is possible to suitably reduce thermal damage to the electrode assembly 10 and the intrusion of spatter that may occur when the welded portion 20 is formed.

[0046] When the lid-shaped exterior member 52 is provided to cover the opening of the cup-shaped exterior member 51, a force may be applied in the vertical direction (e.g., the direction of gravity) so as to sandwich the main surfaces of the cup-shaped and lid-shaped exterior members 51, 52. Specifically, in a state in which the end surface 52A of the lid-shaped exterior member 52 is placed on the end surface 51A of the cup-shaped exterior member 51, a force may be applied in the vertical direction (e.g., the direction of gravity) so as to sandwich the main surfaces of the exterior members. The force that sandwiches the main surfaces is a force that presses the end surfaces 51A, 52A of both exterior members against each other. Therefore, the end surfaces 51A, 52A can be more closely contacted with each other than when only the action of gravity or the like acts. By adopting such a form, it is possible to further suppress the occurrence of a gap between the end surfaces 51A, 52A of both exterior members.

[0047] 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 (iii) will be specifically described with reference to Fig. 3 and Fig. 4. Fig. 3 is a schematic perspective view showing a specific configuration of a secondary battery according to one embodiment of the present invention. Fig. 4 is a schematic cross-sectional view showing a specific configuration of a secondary battery according to one embodiment of the present invention.

[0048] Fig. 3 is a schematic perspective view showing a specific configuration of Fig. 1C. Fig. 4 is a schematic cross-sectional view showing a specific configuration of Fig. 1C. As shown in Fig. 3 and Fig. 4, a secondary battery 100 obtained by the manufacturing method according to one embodiment of the present invention includes an electrode assembly 10 and an exterior body 50 that houses the electrode assembly 10.

[0049] 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 to connect an end of the cup-shaped exterior member 51 and an end of the lid-shaped exterior member 52. In this regard, in the conventional secondary battery 100', as shown in FIG. 12A, a laser L' is irradiated so that both the substantially vertical surface and the substantially horizontal surface, which are components of the step portions 54' and 55' of the cup-shaped exterior member 51' and the lid-shaped exterior member 52' ​​before welding, are melted. Therefore, the size of the welded portion 20' (FIG. 12B) obtained after irradiation is relatively large. In contrast, as described above, in one embodiment of the present invention, the output of the laser L is suppressed during manufacturing, and the laser L is irradiated to a narrow range to form the welded portion 20. As a result, the size of the welded portion 20 can be reduced compared to the welded portion 20' of the conventional secondary battery 100'.

[0050] The small size of the welded portion 20 means that it is possible to preferably reduce thermal damage to the electrode assembly 10 during the formation of the welded portion 20 and the intrusion of spatter that may occur during the formation of the welded portion 20. Therefore, the battery characteristics of the obtained secondary battery 100 can be further stabilized as compared to the conventional secondary battery 100'.

[0051] Furthermore, the size of the welded portion 20 of the secondary battery obtained by the manufacturing method of the present invention is smaller than that of the welded portion 20' of the conventional secondary battery 100'. Therefore, as shown in Fig. 3 and Fig. 4, a facing contact area (a gap) between the end surface 52A, which is a component of the end of the lid-shaped exterior member 52, and the end surface 51A, which is a component of the end of the cup-shaped exterior member 51, may remain on both sides of the welded portion 20. In this respect, too, the obtained secondary battery 100 has the above-mentioned external appearance characteristics.

[0052] 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 an irregular 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, such as an ellipse, which is derived from a circle or a perfect circle. 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 being similar to a "coin type". Therefore, it can be variously referred to depending on its appearance, for example, as a button battery, a bean battery, or a cylindrical, flat, flat, cylindrical battery, etc. In other words, if it has the shape and appearance as mentioned above, it can be called a "coin type" secondary battery, for example.

[0053] (Specific embodiment of the manufacturing method of the present invention) The following is a specific description of possible forms of the manufacturing method of the present invention. In the following, an example is taken of the case where the facing portion 50A is formed by facing end faces 51A and 52A of a single surface shape extending in one direction. In the present specification, the term "single surface end face" refers to an end face consisting of a single surface in a broad sense, and to an end face that does not have a bending point and is therefore not composed of two or more continuous surfaces extending in different directions.

[0054] For example, as a possible embodiment, the facing portion 50A can be formed by overlapping the end surface 51A of the cup-shaped exterior member 51 and the end surface 52A of the lid-shaped exterior member 52 along the thickness direction. In other words, the facing portion 50A can be formed by overlapping the end surface 51A of the cup-shaped exterior member 51 and the end surface 52A of the lid-shaped exterior member 52 along the thickness direction. The "thickness direction" means a direction along the thickness of the exterior member, for example, a direction perpendicular to the surface constituting the exterior member. By adopting such an embodiment, the end surface 52A of the lid-shaped exterior member 52 and the end surface 51A of the cup-shaped exterior member 51 overlap each other in the thickness direction. Since the end surfaces overlap each other in the thickness direction, the cup-shaped and lid-shaped exterior members are less likely to move in the thickness direction. Therefore, after the lid-shaped exterior member 52 is provided to cover the opening of the cup-shaped exterior member 51, the lid-shaped exterior member 52 is less likely to shift in the thickness direction from the predetermined position until the laser L is irradiated, making it easier to form the welded portion 20 at the predetermined position.

[0055] As a specific embodiment, the end faces 51A, 52A, which are components of the end of each exterior member, may have an inclined shape. In this case, compared to a case where the end face 52A of the lid-shaped exterior member 52 and the end face 51A of the cup-shaped exterior member 51 are in contact with each other on one side, compared to a case where the end face 52A of the lid-shaped exterior member 52 is configured with two surfaces having a tapered shape (tapering shape), etc., this makes it possible to more suitably apply a force such as gravity downward from the end face 52A of the lid-shaped exterior member 52 to the end face 51A of the cup-shaped exterior member 51, and more suitably suppress the occurrence of a gap between the end faces 51A, 52A.

[0056] In one embodiment of the present invention, in a cross-sectional view, the end of each exterior member has side surfaces (i.e., the inner surface 51Xa and the outer surface 51Xb) facing each other and an end surface connecting the side surfaces, and the end surface can be inclined (see FIG. 2). Specifically, the end of each exterior member has side surfaces (i.e., the inner surface 51Xa and the outer surface 51Xb) facing each other and having substantially planar shapes, and inclined surfaces 51B, 52B connecting the side surfaces.

[0057] In this specification, the term "inclined surface" refers in a broad sense to a surface having a shape in which the thickness of the end forming the opening of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 becomes thinner from the bottom (i.e., the main surface side) toward the opening side in a cross-sectional view. In the narrow sense, the term "inclined surface" refers to a surface in which at least a part of the outer side surface 51Xb of the end of the cup-shaped exterior member 51 and at least a part of the inner side surface 52Xa of the end of the lid-shaped exterior member 52 are sloped.

[0058] In this embodiment, before the laser L irradiation, the inclined surfaces 51B and 52B that connect the mutually opposing and substantially planar side surfaces (the inner surface 51Xa and the outer surface 51Xb) are opposed to each other to form the facing portion 50A. This allows the inclined surface 52B, which is a component of the end of the lid-shaped exterior member 52, to be positioned directly above the inclined surface 51B, which is a component of the end of the cup-shaped exterior member 51. This allows a force such as gravity to be applied from the inclined surface 52B of the lid-shaped exterior member 52 to the inclined surface 51B of the cup-shaped exterior member 51 in a substantially vertically downward direction. As a result, it is possible to more suitably suppress the occurrence of a gap between the inclined surfaces 51B and 52B, which are components of the respective ends of both exterior members, and it is possible to more suitably face and contact both the inclined surfaces 51B and 52B. Therefore, it is possible to more easily ensure the sealing property of the facing portion 50A of the cup-shaped exterior member 51 and the lid-shaped exterior member 52.

[0059] In this embodiment, as shown in FIG. 2, the inclined surface 52B at the end of the lid-shaped exterior member 52 is positioned directly above the inclined surface 51B at the end of the cup-shaped exterior member 51. Therefore, if the thickness of the cup-shaped exterior member 51 and the lid-shaped exterior member 52, particularly the thickness of at least the lid-shaped exterior member 52, is relatively increased, the weight of the lid-shaped exterior member 52 increases by the amount of increase in thickness, and the force acting approximately vertically downward due to gravity and the like also increases. This makes it possible to further reduce the gap between the inclined surfaces 51B and 52B, and to make the inclined surfaces 51B and 52B contact each other more effectively. Furthermore, it is expected that the strength of the exterior body composed of both exterior members can be improved by relatively increasing the thickness of the exterior members 51 and 52.

[0060] 2, when the end faces of the cup-shaped exterior member and the lid-shaped exterior member are inclined, the inner side surface 51Xa of the cup-shaped exterior member and the inner side surface 52Xa of the lid-shaped exterior member may be on the same line or plane, and the outer side surface 51Xb of the cup-shaped exterior member and the outer side surface 52Xb of the lid-shaped exterior member may be on the same line or plane. By adopting such a configuration, the cup-shaped exterior member 51 and the lid-shaped exterior member 52 each having approximately the same thickness can be used, so that the balance of strength of the entire exterior body 50 consisting of the cup-shaped and lid-shaped exterior members is improved.

[0061] 2, the inclination angle θ formed between the inclined surface 51B and the inner side surface 51Xa of the cup-shaped exterior member 51 in a cross-sectional view is preferably 10 degrees or more and 70 degrees or less, preferably 20 degrees or more and 60 degrees or less, more preferably 30 degrees or more and 50 degrees or less, for example, 45 degrees, from the viewpoint of the insertion accuracy of the lid-shaped exterior member 52 into the opening of the cup-shaped exterior member 51. Similarly, the inclination angle formed between the inclined surface 52B and the outer side surface 52Xb of the lid-shaped exterior member 52 is preferably 10 degrees or more and 70 degrees or less, preferably 20 degrees or more and 60 degrees or less, more preferably 30 degrees or more and 50 degrees or less, for example, 45 degrees, from the viewpoint of the insertion accuracy of the lid-shaped exterior member 52 into the opening of the cup-shaped exterior member 51. The inclination angle may vary depending on the wall thickness of the can and the lid, the insertion accuracy, and the allowable length of the inclined portion, but if it is within the above range, the insertion accuracy of the lid-shaped exterior member 52 into the opening of the cup-shaped exterior member 51 can be improved.

[0062] Although not particularly limited, the inclined surfaces 51B, 52B at the ends of the cup-shaped and lid-shaped exterior members 51, 52 can be formed by shearing such as chamfering. In the present embodiment, the cup-shaped and lid-shaped exterior members 51, 52 can be manufactured by drawing a flat exterior plate. Due to its structure, the exterior member manufactured by drawing has a higher strength than the conventional flat-plate-structured lid-shaped exterior member. In addition, the exterior body 50 made of the cup-shaped and lid-shaped exterior members manufactured by drawing has a rounded edge 50a of the exterior body as shown in FIG. 4. Therefore, the exterior body can have a smoother shape than the edge 50a' of the exterior body of the conventional secondary battery as shown in FIG. 12, and it is easy to prevent the exterior body from being broken due to an external impact.

[0063] The inclined surface 51B of the cup-shaped exterior member 51 is formed on the outer surface 51Xb side, and the inclined surface 52B of the lid-shaped exterior member 52 is formed on the inner surface 52Xa side. However, without being limited thereto, the inclined surface 51B may be formed on the inner surface 51Xa side, and the inclined surface 52B may be formed on the inner surface 52Xa side. The secondary battery obtained by such formation also has the above-mentioned characteristics and effects achieved thereby, which have been exemplarily described with reference to FIG.

[0064] In another embodiment, the side surface 52X itself of one end of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 may have an inclined shape, and the other exterior member may have an inclined end face at its end (see FIG. 5). Specifically, in this embodiment, it is sufficient that the side surface itself of the end of one exterior member has an inclined shape, and it is sufficient that the other exterior member has a structure in which the ends face each other and have substantially flat side surfaces and an inclined surface connecting the side surfaces.

[0065] FIG. 5 is a schematic cross-sectional view showing a process of forming a welded portion 20 using a lid-shaped exterior member 52 having an inclined side surface at an end and a cup-shaped exterior member 52 having an inclined end face at an end. Hereinafter, with reference to FIG. 5, a case where the side surface of the end of the lid-shaped exterior member 52 itself has an inclined shape will be described as an example. In one example, as shown in FIG. 5, an inclined surface 51B is formed at the end located at the opening of the cup-shaped exterior member 51, and the inclined side surface 52X of the lid-shaped exterior member 52 is positioned on the inclined surface 51B. Specifically, the side surface of the cup-shaped exterior member 51 extends approximately perpendicularly from the main surface of the cup-shaped exterior member 51, and the inclined surface is provided at the end of the cup-shaped exterior member 51. The side surface 52X of the lid-shaped exterior member is not perpendicular to the planar main surface of the lid-shaped exterior member 52, and has an inclined structure such that the opening size of the lid-shaped exterior member 52 is large. The side surface 52X of the lid-shaped exterior member is inclined at an inclination angle θ with respect to a perpendicular line from the main surface of the lid-shaped exterior member 52. The inclination may be achieved by forming the exterior member by drawing, etc. Also, the inclination angle θ may be adjusted during drawing of the exterior member.

[0066] Even in this embodiment, the inclined side surface 52X of the lid-shaped exterior member 52 can be positioned on the inclined surface 51B at the end of the cup-shaped exterior member 51 before the laser L is irradiated. This allows a force such as gravity to act downward from the inclined side surface 52X of the lid-shaped exterior member 52 to the inclined surface 51B of the cup-shaped exterior member 51. As a result, it is possible to prevent a gap from being generated between the inclined surface 51B and the inclined side surface 52X, which are components of the ends of both exterior members, and it is possible to make the inclined surface 51B and the inclined side surface 52X face to face and contact each other. Therefore, it is possible to easily ensure the sealing property of the facing portion 50A of the cup-shaped exterior member 51 and the lid-shaped exterior member 52. Note that the above describes an embodiment in which the end of the cup-shaped exterior member 51 has an inclined surface and the side surface of the lid-shaped exterior member 52 itself has an inclined form, but the above description is not limited to the above embodiment. For example, even if the side surface of the end of the cup-shaped exterior member 51 itself has an inclined shape and the end of the lid-shaped exterior member has an inclined surface, it is possible to obtain the same features and effects as those of the above embodiment.

[0067] When an inclined surface is provided at the end of the exterior member to connect side surfaces (for example, inner surface 51Xa and outer surface 51Xb) that face each other and are substantially planar, the inclined surface can be formed by shearing the end of the exterior member, such as chamfering. When shearing the end of a relatively thin exterior member, such as chamfering, the end of the exterior member is cut off by shearing, and the thickness of the inclined surface formed becomes very thin. It may be technically difficult to form such an inclined surface. According to this embodiment, one of the two exterior members has a side surface that is inclined. As described above, an exterior member having a side surface that is inclined can be achieved by molding the exterior member by drawing or the like. That is, shearing or the like is not required to mold an exterior member having a side surface that is inclined. Therefore, even if the thickness of the exterior member is relatively thin, an exterior member having a side surface that is inclined can be obtained relatively easily. Therefore, in addition to suppressing the occurrence of gaps at the opposing portions 50A of the ends of both exterior members, the thickness (wall thickness) of one of the exterior members can be made thinner, compared to the embodiment shown in Fig. 2. Therefore, while ensuring easy sealing at the opposing portions 50A of the ends of the two exterior members, the obtained secondary battery 100 can be made thinner and smaller.

[0068] 5, as in the embodiment of FIG. 2, the inclination angle θ formed between the inclined surface 51B and the inner side surface 51Xa of the cup-shaped exterior member 51 in a cross-sectional view is preferably 10 degrees or more and 70 degrees or less, preferably 20 degrees or more and 60 degrees or less, more preferably 30 degrees or more and 50 degrees or less, for example, 45 degrees, from the viewpoint of the accuracy of insertion of the lid-shaped exterior member 52 into the opening of the cup-shaped exterior member 51. In addition, from the viewpoint of suitable opposing contact between the inclined surface 51B of the cup-shaped exterior member 51 and the inclined side surface 52X of the lid-shaped exterior member 52, the side surface 52X of the lid-shaped exterior member 52 may have an inclined structure that is not perpendicular to the planar main surface of the lid-shaped exterior member 52 but opens at an angle of 90+θ degrees from the planar main surface.

[0069] In yet another embodiment, both the side surface 51X at the end of the cup-shaped exterior member 51 and the side surface 52X at the end of the lid-shaped exterior member 52 may have an inclined shape (see FIG. 6).

[0070] Fig. 6 is a schematic cross-sectional view showing a process of forming a welded portion using a lid-shaped exterior member having an inclined side surface at an end and a cup-shaped exterior member having an inclined side surface at an end. Fig. 7 is a schematic perspective view showing a secondary battery obtained through the welded portion forming process shown in Fig. 6. As shown in Fig. 6, in this embodiment, the side surfaces 51X, 52X at the ends of both exterior members 51, 52 themselves have an inclined shape.

[0071] The side surface 52X of the lid-shaped exterior member shown in FIG. 6 is inclined outward with respect to the main surface of the lid-shaped exterior member, similar to the embodiment shown in FIG. 5. Furthermore, a part of the side surface 51X of the cup-shaped exterior member is inclined inward with respect to the main surface of the cup-shaped exterior member. Specifically, the end of the side surface 51X of the cup-shaped exterior member is inclined inward with respect to the extension direction of the side surface of the cup-shaped exterior member so that the opening diameter of the cup-shaped exterior member 51 becomes smaller. The side surface 51X of the cup-shaped exterior member is inclined at an inclination angle θ with respect to a perpendicular line from the main surface of the cup-shaped exterior member 51. The side surface 52X of the lid-shaped exterior member is inclined at an inclination angle θ with respect to a perpendicular line from the main surface of the lid-shaped exterior member 52. The inclination may be achieved by forming the exterior member by drawing or the like. The inclination angle θ may be adjusted during drawing of the exterior member.

[0072] Even in this embodiment, the inclined side surface 52X of the lid-shaped exterior member 52 can be positioned on the inclined side surface 51X of the end of the cup-shaped exterior member 51 before the laser L irradiation. This allows a force such as gravity to act downward from the inclined side surface 52X of the lid-shaped exterior member 52 to the inclined side surface 51X of the cup-shaped exterior member 51. As a result, it is possible to prevent a gap from being generated between the inclined side surfaces 51X and 52X, which are components of the ends of both exterior members, and it is possible to make the inclined side surfaces 51X and 52X face each other in contact with each other. Therefore, it is possible to easily ensure the sealing property of the facing portion 50A of the cup-shaped exterior member 51 and the lid-shaped exterior member 52.

[0073] According to this embodiment, both side surfaces of the two exterior members are inclined. The exterior member having the side surface itself inclined may be achieved by molding the exterior member by drawing or the like, as described above. That is, the molding of the exterior member having the side surface itself inclined does not require the use of shear processing or the like. Therefore, even if the thickness of the exterior member is relatively thin, the exterior member having the side surface itself inclined can be obtained relatively easily. Therefore, compared with the embodiment shown in FIG. 2 and FIG. 5, in addition to suppressing the occurrence of gaps in the facing portions 50A of the respective ends of the two exterior members, the thickness (wall thickness) of both exterior members can be made thin. Therefore, while ensuring easy sealing in the facing portions 50A of the respective ends of the two exterior members, the obtained secondary battery 100 can be made thinner and smaller (see FIG. 7). 6, similarly to the embodiment in Fig. 5, the inclination angle θ of the cup-shaped exterior member 51 in a cross-sectional view is preferably 10 degrees or more and 70 degrees or less, preferably 20 degrees or more and 60 degrees or less, more preferably 30 degrees or more and 50 degrees or less, for example, 45 degrees, from the viewpoint of the accuracy of insertion of the lid-shaped exterior member 52 into the opening of the cup-shaped exterior member 51. In addition, from the viewpoint of suitable opposing contact between the cup-shaped exterior member 51 and the lid-shaped exterior member 52, the side surface 52X of the lid-shaped exterior member may have an inclined structure that is not perpendicular to the planar main surface of the lid-shaped exterior member 52 but opens at an angle of 90+θ degrees from the planar main surface.

[0074] In addition, since the thicknesses of both exterior members can be made thin, when forming the welded portion 20 using the laser L, the laser irradiation output can be reduced and the irradiation range can be narrowed to form the welded portion 20. Therefore, the irradiation heat energy of the laser L can be made smaller, and the thermal damage to the electrode assembly 10 caused by the irradiation heat of the laser can be further reduced.

[0075] A method for producing the secondary battery 100 shown in FIG. 7 obtained in this embodiment will be described below with reference to FIGS. 8A to 8C.

[0076] Fig. 8A is a schematic cross-sectional view showing a step of placing an electrode assembly on a cup-shaped exterior member in a method for manufacturing a secondary battery according to another embodiment of the present invention. Fig. 8B is a schematic cross-sectional view showing a step of drawing an end of a cup-shaped exterior member in a method for manufacturing a secondary battery according to another embodiment of the present invention. Fig. 8C is a schematic cross-sectional view showing a step of forming a welded portion by laser irradiation in a method for manufacturing a secondary battery according to another embodiment of the present invention.

[0077] Hereinafter, a method for producing a secondary battery according to an embodiment of the present invention will be described with reference to the drawings. The method for producing a secondary battery according to an embodiment of the present invention mainly includes the following steps. (i) A step of providing the electrode assembly 10 in a cup-shaped exterior member 51 (see FIG. 8A). (ii) A step of drawing a part of the edge of the opening of the cup-shaped exterior member 51 (see FIG. 8B). (iii) A process of providing a lid-shaped exterior member to cover the opening of the cup-shaped exterior member 51 while the interior of the cup-shaped exterior member 51 is filled with the electrolyte 30. (iv) A process of irradiating a laser beam L to portion 50A where cup-shaped exterior member 51 and lid-shaped exterior member 52 face each other to form a welded portion (see FIG. 8C).

[0078] Since the method for producing a secondary battery of the present invention has already been described with reference to Figures 1A to 1C, only the steps that are characteristic of the embodiment shown in Figures 1 to 1C will be described. Specifically, this embodiment is characterized by the above step (ii). Step (ii) will be described in more detail below with reference to Figure 8B.

[0079] As shown in Fig. 8B, after placing the electrode assembly 10 in the cup-shaped exterior member 51, the end portion located at the opening of the cup-shaped exterior member 51 is subjected to drawing to provide an inclined shape to the side surface of the cup-shaped exterior member 51. Specifically, the inclined side surfaces of the end portion of the cup-shaped exterior member 51 and the end portion of the lid-shaped exterior member 52 are formed by locally bending a part of the planar extending surfaces of both exterior members by drawing. In other words, a taper angle is provided to the part of the side surface of the cup-shaped exterior member 51 that is close to the side surface of the lid-shaped exterior member 52.

[0080] 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.

[0081] In the above, the case where the "end faces" of the ends of both exterior members 51 and 52 are inclined has been described, but one embodiment of the present invention is not limited to this. For example, the "end faces" may also extend horizontally.

[0082] Specifically, as shown in Fig. 9, in the step of providing a lid-shaped exterior member 52 to cover the opening of a cup-shaped exterior member 51, horizontal surfaces 51C and 52C at the ends located at the openings of the cup-shaped exterior member 51 and the lid-shaped exterior member 52 are brought close to each other. Even in this case, it is possible to prevent a gap from being generated between the horizontal surfaces 51C and 52C at the ends of both exterior members 51 and 52. Furthermore, the embodiment shown in Fig. 9 can be said to be a simpler manufacturing method in that drawing is not required to mold the lid-shaped exterior member 52 and drawing is not required to mold the cup-shaped exterior member 51.

[0083] According to a manufacturing method of an embodiment of the present invention, the welded portion 20 can be formed on the side surface of the exterior body 50 as shown in Figs. 3 and 4. However, this embodiment is not limited to this, and the following embodiment can be adopted as long as it is possible to suppress the occurrence of a gap between the end faces of the respective ends of the exterior members 51 and 52. Specifically, as shown in Fig. 10, the end of the opening of the cup-shaped exterior member 51 can be provided on the upper surface side instead of the side surface, and the inclined surface of the opening end of the cup-shaped exterior member 52 can be provided so as to directly face this. In the embodiment shown in Fig. 10, the opening of the cup-shaped exterior member 51 is located on the upper surface side, so that the electrolyte 30 filled in the cup-shaped exterior member 51 is less likely to leak to the outside during the manufacturing process. [Industrial Applicability]

[0084] 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, and small electronic devices such as RFID tags, card-type electronic money, and smart watches), household and small industrial applications (for example, power 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 earphone 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]

[0085] 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 Exterior body 50a, 50a' Edge of exterior body 51, 51' Cup-shaped exterior member 51A End face 51B Slope 51C horizontal plane 51X side 51Xa inner surface 51Xb outer surface 52, 52' Lid-shaped exterior member 52A End face 52B Slope 52C horizontal plane 52X side 52Xa Inner surface 52Xb outer surface 53' Opposing parts of cup-shaped and lid-shaped exterior parts 54' Stepped part of cup-shaped exterior part 54a', 54c' Approximately vertical surface of the step 54b' Approximately horizontal surface of the step 55' Stepped part of the lid-shaped exterior part 55a', 54c' Approximately vertical surface of the step 55b' Approximately horizontal surface of the step 60 External output terminal 70 Insulating materials 90 Spatter 100, 100' secondary battery L, L' Laser

Claims

1. Providing an electrode assembly within a cup-shaped exterior member; A step of providing a lid-shaped exterior member to cover the opening of the cup-shaped exterior member; and a step of irradiating a laser to a portion where the cup-shaped exterior member and the lid-shaped exterior member face each other to form a weld; The facing portion is formed by positioning an end surface of one end of the cup-shaped exterior member and the lid-shaped exterior member on an end surface of the other end of the cup-shaped exterior member and each end surface has a non-step shape; The end surface is inclined, In a cross-sectional view, an extending direction of the cup-shaped exterior member from the facing portion and an extending direction of the lid-shaped exterior member from the facing portion are on the same straight line, A method for manufacturing a secondary battery, wherein the inclined end surface is a surface that is inclined with respect to an outer surface of the cup-shaped exterior member or an outer surface of the lid-shaped exterior member in a cross-sectional view.

2. The method for manufacturing a secondary battery according to claim 1 , wherein the facing portion is formed by facing the end faces of a single-sided shape extending in one direction in a cross section along the extension direction.

3. The method for manufacturing a secondary battery according to claim 1 , wherein the facing portion is formed by overlapping the end surface of the cup-shaped exterior member and the end surface of the lid-shaped exterior member with each other along a thickness direction.

4. The method for manufacturing a secondary battery according to any one of claims 1 to 3, wherein the end surface of the inclined configuration is an end surface of at least one end of the cup-shaped exterior member and the lid-shaped exterior member in a cross-sectional view, and the end surface is a surface that connects side surfaces of the exterior members that face each other.

5. 5. The method for manufacturing a secondary battery according to claim 4, wherein, when the end faces of the cup-shaped exterior member and the lid-shaped exterior member are inclined, in a cross-sectional view, the inner surface of the cup-shaped exterior member and the inner surface of the lid-shaped exterior member are on the same straight line, and the outer surface of the cup-shaped exterior member and the outer surface of the lid-shaped exterior member are on the same straight line.

6. The method for manufacturing a secondary battery according to any one of claims 1 to 4, wherein the end surface having the inclined shape is a side surface of the end portion of at least one of the cup-shaped exterior member and the lid-shaped exterior member in a cross-sectional view, and the side surface has an inclined shape.

7. 7. The method for manufacturing a secondary battery according to claim 6, wherein the inclined side surface of at least one of the end portion of the cup-shaped exterior member and the end portion of the lid-shaped exterior member is formed by locally bending a part of a planar exterior member by drawing.

8. 8. The method for manufacturing a secondary battery according to claim 1, wherein the facing portion is formed by facing a side surface of the cup-shaped exterior member and a side surface of the lid-shaped exterior member.

9. The method for producing a secondary battery according to any one of claims 1 to 8, wherein the end surface of the end portion is an end surface extending in a non-vertical direction.

10. The method for manufacturing a secondary battery according to any one of claims 1 to 9, wherein the facing portion is formed by opposing the end faces such that an inner surface of the cup-shaped exterior member and an inner surface of the lid-shaped exterior member are on the same plane, and an outer surface of the cup-shaped exterior member and an outer surface of the lid-shaped exterior member are on the same plane.

11. The method for producing a secondary battery according to any one of claims 1 to 10, wherein the secondary battery is a coin-type battery.

12. The method for manufacturing a secondary battery according to claim 1, wherein the electrode assembly includes a positive electrode and a negative electrode capable of absorbing and releasing lithium ions.

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