Secondary battery

Abstract

The present invention provides a secondary battery which comprises: an electrode assembly; an outer package that contains the electrode assembly; and an electrode terminal that is provided on the outer package and is electrically connected to the electrode assembly via a conductive member. With respect to this secondary battery, the electrode terminal and the outer package are bonded to each other by means of an insulating sealing member that is provided around an opening of the outer package, while being interposed between the electrode terminal and the outer package, through the opening the conductive member passing; when viewed in plan, the outline of a surface of the electrode terminal, the surface being in contact with the insulating sealing member, is composed of both a linear part and a curved part; when viewed in plan, the outline of a surface of the outer package, the surface being in contact with the insulating sealing member, includes a curvature; and the curved part of the electrode terminal and a part of the curvature of the outer package face each other.

Description

secondary battery

[0001] The present invention relates to a secondary battery, and more particularly to a secondary battery having an electrode assembly composed of electrode constituent layers including a positive electrode, a negative electrode, and a separator.

[0002] Secondary batteries are so-called 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.

[0003] JP 2019-046639 A JP 2020-202071 A

[0004] A secondary battery is composed of an electrode assembly in which electrode constituent layers, including a positive electrode, a negative electrode, and a separator between them, are stacked, and an exterior body encasing the electrode assembly. Such secondary batteries may be equipped with a rupture mechanism in case of an increase in internal cell pressure, etc., to prevent more serious accidents, such as unintended battery explosions.

[0005] On the other hand, secondary batteries must be provided with external terminals for electrical connection to the outside in order to be used.

[0006] The present inventors have conducted extensive research to determine whether there is still room for development of a battery configuration that satisfies both the installation of the battery external terminal and the cleavage mechanism, and as a result, have found that there is still room for development of a battery configuration that satisfies both the cleavage mechanism and the installation of the terminal.

[0007] The present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to provide a new battery configuration from the viewpoint of the cleavage mechanism and terminal placement.

[0008] The inventors of the present invention attempted to solve the above problems by taking a new approach rather than simply extending the conventional technology, and as a result, they have invented a secondary battery that achieves the above-mentioned main object.

[0009] The secondary battery of the present invention comprises an electrode assembly, an outer casing that houses the electrode assembly, and an electrode terminal that is disposed on the outer casing and electrically connected to the electrode assembly via a conductive member, wherein the electrode terminal and the outer casing are bonded to each other by an insulating seal member that is interposed between the electrode terminal and the outer casing and provided around an opening of the outer casing through which the conductive member passes, the planar outline of the electrode terminal at the surface where the electrode terminal contacts the insulating seal member is composed of both straight portions and curved portions, the planar outline of the outer casing at the surface where the outer casing contacts the insulating seal member includes a curve, and the curved portion of the electrode terminal and a part of the curve of the outer casing face each other.

[0010] The secondary battery of the present invention has a previously unseen battery configuration involving both terminal installation and a cleavage mechanism. This configuration facilitates the provision of an external lead-out member for external connection and facilitates the creation of a more suitable cleavage mechanism. More specifically, when the electrode terminal's planar outline is composed of both straight and curved portions, the proportion of the planar area of ​​the non-terminal region on the battery's main surface is more easily ensured than when the electrode terminal does not have such a contour configuration. This facilitates the provision of an external lead-out member in the non-terminal region, making the secondary battery of the present invention more suitable. Furthermore, when pressure is generated due to an abnormal increase in internal pressure of the exterior body, the electrode terminal can be cleaved open to prevent unintended battery explosion. In the secondary battery of the present invention, such cleavage occurs relatively easily from the "straight portion." In other words, the electrode terminal is more likely to cleave open from the straight portion of the electrode terminal's planar outline, improving the predictability of abnormal increases in cell internal pressure.

[0011] FIG. 1 is a cross-sectional view schematically illustrating electrode constituent layers (FIG. 1(A): planar laminated structure, FIG. 1(B): wound structure). FIG. 2 is a perspective view schematically illustrating the appearance of a secondary battery according to one embodiment of the present invention. FIG. 3 is a schematic diagram of a secondary battery according to one embodiment of the present invention (FIG. 3(A): cross-sectional view, FIG. 3(B): half-split perspective view). FIG. 4 is a schematic diagram illustrating representative elements constituting a secondary battery according to one embodiment of the present invention. FIGS. 5(A) to 5(D) are each schematic diagrams illustrating a plan view of the main surface of a secondary battery according to one embodiment of the present invention. FIGS. 6(A) to 6(D) are each schematic diagrams illustrating the plan view outline of an electrode terminal according to one embodiment of the present invention together with the plan view outline of an exterior body according to one embodiment of the present invention. FIGS. 7(A) to 7(D) are each schematic diagrams illustrating the plan view outline of an electrode terminal according to one embodiment of the present invention. FIG. 8 is a schematic diagram illustrating the plan view outline of an electrode terminal according to one embodiment of the present invention. FIGS. 9(A) to 9(D) are each schematic diagrams illustrating the plan view outline of an exterior body according to one embodiment of the present invention. FIG. 10 is a schematic diagram showing a configuration related to an exterior body opening of a secondary battery according to one embodiment of the present invention. FIG. 11 is a schematic diagram illustrating a vent mechanism related to the present invention. FIGS. 12(A) to 12(D) are each a schematic diagram showing the planar outline of an insulating seal member according to one embodiment of the present invention. FIG. 13 is a schematic diagram illustrating the deflection or distortion of the exterior body when an abnormal increase in cell internal pressure occurs. FIGS. 14(A) and 14(B) are schematic perspective views illustrating the "installation mode of the external lead-out member." FIGS. 15(A) and 15(B) are schematic diagrams illustrating a virtual battery that serves as the base for the [Example]. FIG. 16(A) is a schematic diagram modeling the configurations of the Example and Comparative Example, and FIG. 16(B) is a schematic diagram illustrating the non-terminal region area for the modeled configuration. FIG. 17 is a graph showing the results of a simulation.

[0012] A secondary battery according to one embodiment of the present invention will be described in more detail below. While the description will be made with reference to drawings as necessary, various elements in the drawings are merely shown schematically and illustratively for the purpose of understanding the present invention, and the appearance and / or dimensional ratios may differ from those of the actual battery. The secondary battery described below is intended to embody the technical concept of the present invention, and unless otherwise specified, the present invention is not limited to the following. For convenience, the present invention may be divided into embodiments and examples to facilitate explanation or understanding of the main points. However, partial substitution or combination of the configurations shown in different embodiments is possible. In describing such embodiments, descriptions of matters common to the above may be omitted, and only differences may be described. In particular, similar effects resulting from similar configurations may not be mentioned in each embodiment.

[0013] The "cross-sectional view" directly or indirectly described in this specification is based on a virtual cross section of a secondary battery cut along the stacking direction of the electrode assembly or electrode component layers that constitute the secondary battery. The "thickness" direction directly or indirectly described in this specification is based on the stacking direction of the electrode materials that constitute the secondary battery or the direction along the winding axis of a wound stacked structure. For example, in the case of a "plate-like thick secondary battery" such as a button-type or coin-type, the "thickness" direction may correspond to the plate thickness direction of such a secondary battery. Furthermore, the "planar view" may correspond to, for example, a view obtained when viewing an object along the normal or perpendicular direction to its main surface (e.g., the upper surface).

[0014] The terms "upper and lower directions" and "left and right directions" used directly or indirectly in this specification correspond to the upper and lower directions and left and right directions in the drawings, 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 that can be considered to correspond to the "upward direction."

[0015] Unless otherwise specified, the various numerical ranges mentioned herein are intended to include the lower and upper limit values ​​themselves. Furthermore, terms such as "approximately," "about," and "certain" mean that there may be a variation or difference of a few percent, for example, ±10%.

[0016] [Basic Structure of Secondary Battery] The term "secondary battery" as used herein 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, an electricity storage device.

[0017] A secondary battery according to the present invention includes an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are stacked. FIGS. 1A and 1B illustrate an example of an electrode assembly 10. As shown in the figure, 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 the electrode assembly 10. In FIG. 1A, the electrode constituent layer 5 has a planar laminate structure in which the electrode constituent layer 5 is not wound but stacked in a planar manner. In contrast, in FIG. 1B, the electrode constituent layer 5 has a wound laminate structure in which the electrode constituent layer 5 is wound in a spiral. That is, in FIG. 1B, the electrode constituent layer 5 including a positive electrode 1, a negative electrode 2, and a separator 3 disposed between the positive electrode 1 and the negative electrode 2 is wound into a roll. In a secondary battery, such an electrode assembly is enclosed in an exterior case together with an electrolyte (e.g., a nonaqueous electrolyte). The structure of the electrode assembly is not necessarily limited to a planar laminate structure or a wound structure. For example, the electrode assembly may have a so-called stack-and-fold type structure in which a positive electrode, a separator, and a negative electrode are stacked on a long film and then folded.

[0018] 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 surface 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 surfaces of the positive electrode current collector, or may have a positive electrode material layer provided on only one surface of the positive electrode current collector.

[0019] 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 surface 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 surfaces of the negative electrode current collector, or may have a negative electrode material layer provided on only one surface of the negative electrode current collector.

[0020] The electrode active materials contained in the positive and negative electrodes, i.e., the positive and negative electrode active materials, are materials directly involved in the transfer of electrons in a secondary battery and are the main materials of the positive and negative electrodes responsible for charge and discharge, i.e., the battery reaction. More specifically, the "positive electrode active material contained in the positive electrode layer" and the "negative electrode active material contained in the negative electrode layer" provide ions to the electrolyte, and these ions move between the positive and negative electrodes, transferring electrons and causing charge and discharge. The positive and negative electrode layers may be layers capable of absorbing and desorbing lithium ions. In other words, the secondary battery according to the present invention may be a nonaqueous electrolyte secondary battery in which lithium ions move between the positive and negative electrodes via the nonaqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charge and discharge, the secondary battery according to the present invention corresponds to a so-called "lithium ion battery," and has layers capable of absorbing and desorbing lithium ions as the positive and negative electrodes.

[0021] The positive electrode active material of the positive electrode material layer may be, for example, composed of granules, and a binder may be included in the positive electrode material layer to ensure better contact between the particles and to maintain the shape. Furthermore, a conductive additive may be included in the positive electrode material layer to facilitate the transfer of electrons that drive the battery reaction. Similarly, the negative electrode active material of the negative electrode material layer may be, for example, composed of granules, and a binder may be included in the negative electrode material layer to ensure better contact between the particles and to maintain the shape. A conductive additive may be included in the negative electrode material layer to facilitate the transfer of electrons that drive the battery reaction. Because they contain multiple components, the positive electrode material layer and the negative electrode material layer may also be referred to as a "positive electrode composite layer" and a "negative electrode composite layer," respectively.

[0022] The positive electrode active material may be a material that contributes to the absorption and desorption 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, such a lithium transition metal composite oxide is preferably contained as the positive electrode active material in the positive electrode layer of the secondary battery according to the present invention. For example, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, or a material in which part of the transition metal is replaced with another metal. Such positive electrode active materials may be contained as a single species or in a combination of two or more species.

[0023] The binder that can be contained in the positive electrode layer is not particularly limited, but can include at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, etc. The conductive additive that can be contained in the positive electrode layer is not particularly limited, but can include at least one selected from the group consisting of 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.

[0024] 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 taken at any 10 points.

[0025] The negative electrode active material may be a material that contributes to the absorption and desorption of lithium ions, such as various carbon materials, oxides, and / or lithium alloys.

[0026] 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. 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 any metal that can form an alloy with lithium, and may be, for example, a binary, ternary, or higher alloy of lithium with a metal such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, or La.

[0027] The binder that can be contained in the negative electrode material layer is not particularly limited, but can include at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resin, and polyamide-imide resin. The conductive additive that can be contained in the negative electrode material layer is not particularly limited, but can include at least one selected from the group consisting of carbon black such as thermal black, furnace black, channel black, ketjen black, and acetylene black; carbon fiber such as graphite, carbon nanotubes, and vapor-grown carbon fiber; metal powder such as copper, nickel, aluminum, and silver; and polyphenylene derivatives. The negative electrode material layer may also contain components derived from thickener components (e.g., carboxymethyl cellulose) used during battery production.

[0028] 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 measurements at any 10 points may be used.

[0029] The positive electrode current collector and the negative electrode current collector used in 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 electrode current collectors may be sheet-shaped metal members. Furthermore, the electrode current collectors may be porous or perforated. For example, the current collectors may be metal foil, punched metal, mesh, expanded metal, or the like. The positive electrode current collector used in 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, aluminum foil. On the other hand, the negative electrode current collector used in 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, copper foil.

[0030] 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 measurements taken at any 10 positions may be used.

[0031] The separator used for the positive and negative electrodes is a component provided primarily from the viewpoint of preventing short circuits due to contact between the positive and negative electrodes and maintaining electrolyte integrity. In other words, the separator is a component that allows ions to pass through while preventing electronic contact between the positive and negative electrodes. For example, the separator is a porous or microporous insulating component, and has a membrane shape due to its small thickness. By way of example only, 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 the polyolefin. Furthermore, the separator may be a laminate composed of a "PE microporous membrane" and a "PP microporous membrane." The surface of the separator may be covered with an inorganic particle coating layer and / or an adhesive layer, etc. 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, which have similar functions.

[0032] The thickness of the 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 measurements taken at any 10 points may be used.

[0033] In the secondary battery 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 outer casing together with an electrolyte. The electrolyte may be a "non-aqueous" electrolyte containing an organic electrolyte and an organic solvent, or an "aqueous" electrolyte containing water. When the positive electrode and negative electrode have layers capable of absorbing and releasing lithium ions, the secondary battery preferably contains a "non-aqueous" electrolyte. In other words, the electrolyte is preferably a non-aqueous electrolyte. Metal ions released from the electrodes (positive electrode and / or negative electrode) are present in the electrolyte, and therefore the electrolyte can assist the migration of metal ions during the battery reaction. The electrolyte may be in a liquid or gel form.

[0034] The nonaqueous electrolyte is an electrolyte containing a solvent and a solute. The solvent may be an organic solvent. Specific examples of the organic solvent for the nonaqueous electrolyte include those containing at least a carbonate. The carbonate may be a cyclic carbonate and / or a chain carbonate. While not particularly limited, the cyclic carbonate may include 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 include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dipropyl carbonate (DPC). By way of example only, a combination of a cyclic carbonate and a chain carbonate may be used as the nonaqueous electrolyte, such as a mixture of ethylene carbonate and diethyl carbonate. Specific examples of the solute of the non-aqueous electrolyte include LiPF ６ and / or LiBF ４ Li salts such as may be used.

[0035] 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 stacked. As will be described later, the exterior body may be a metal exterior body having a non-laminated structure.

[0036] [Characteristics of the Secondary Battery of the Present Invention] The secondary battery of the present invention is characterized at least in the configuration related to the opening of the exterior body that encases the electrode assembly, and in particular in the electrode terminal provided to cover the opening of the exterior body and the battery cleaving mechanism related thereto.

[0037] In the secondary battery of the present invention, the electrode terminal (positive or negative electrode terminal) disposed on the exterior body using an insulating seal member is electrically connected to the electrode assembly via a conductive member. The insulating seal member is interposed between the electrode terminal and the exterior body and is provided around the opening of the exterior body through which the conductive member passes. The electrode terminal and the exterior body are bonded to each other by the insulating seal member provided around the opening of the exterior body. The electrode terminal is preferably bonded to the insulating seal member, and the exterior body is also preferably bonded to the insulating seal member. In other words, the exterior body has an opening through which the conductive member passes, and the electrode terminal is provided on the exterior body surface (on the outer surface of the exterior body) corresponding to the surrounding area of ​​the opening by utilizing the adhesive force of the insulating seal member to cover the opening. Preferably, the electrode terminal is attached to the exterior body solely by the adhesive force of the insulating seal member, without relying on mechanical or structural action such as crimping (in short, the electrode terminal is attached to the exterior body without preferably being crimped to the electrode terminal and / or the exterior body).

[0038] In the present invention, the electrode terminal related to the battery cleavage mechanism is unique. In particular, the outline of the electrode terminal in plan view has a unique shape that is different from conventional shapes. Specifically, the outline of the electrode terminal in plan view is composed of both straight and curved portions.

[0039] More specifically, in the electrode terminal, the outline of the electrode terminal in plan view at the surface in contact with the insulating seal member is composed of both a straight portion and a curved portion. Also, in the exterior body, the outline of the exterior body in plan view at the surface in contact with the insulating seal member includes a curve. In such a secondary battery of the present invention, the curved portion of the electrode terminal and a part of the curve of the exterior body face each other.

[0040] Fig. 2 shows the appearance of a secondary battery 1000 according to one embodiment of the present invention, and Figs. 3(A) and 3(B) show a cross-sectional view and a half-split perspective view of the secondary battery 1000 according to one embodiment of the present invention. Fig. 4 also shows elements related to the features of the secondary battery of the present invention separately, in order to facilitate understanding of the present invention.

[0041] Figures 5(A) to 5(D) show plan views of the upper surface side (the side where the electrode terminals are installed) of the secondary battery, and in particular show the plan view outlines of the electrode terminals and the exterior body. Figures 6(A) to 6(D) show plan view outlines of the electrode terminals corresponding to Figures 5(A) to 5(D), respectively. Figures 5(A) and 6(A) show plan view outlines corresponding to Figures 2 to 4, and Figures 5(B) to 5(D) and 6(B) to 6(D) show plan view outlines of secondary batteries according to other preferred embodiments.

[0042] 5(A) to 5(D) and 6(A) to 6(D), the outline 250 of the electrode terminal 200 in a plan view when the secondary battery is viewed from the outside has a unique shape composed of two types of portions: a straight portion 252 and a curved portion 254. In other words, the outline of the electrode terminal in a plan view on the surface that contacts the insulating seal member is composed of both straight portions and curved portions (hereinafter, the outer outline or outer edge outline of the electrode terminal in the surface that contacts the insulating seal member will also be referred to as the "outline of the electrode terminal in a plan view" or simply the "outline of the electrode terminal").

[0043] 5A to 5D , the outline 160 of the exterior body 100 in a plan view, when the main surface of the secondary battery is viewed from the outside, is preferably curved. That is, the outline 160 of the exterior body 100 in a plan view at the surface that contacts the insulating seal member 300 (particularly the outer edge outline that forms the outer edge of the battery) includes a curve. For example, the outline 160 of the exterior body 100 in a plan view at the surface that directly contacts the insulating seal member 300 used to install the electrode terminal 200 includes a curve (hereinafter, the outer outline or outer edge outline of the exterior body when viewed as a whole from the outside will be referred to as the "outline of the exterior body in a plan view" or simply the "outline of the exterior body"). In a preferred embodiment, the outline 160 of the exterior body 100 in a plan view is curved as a whole; for example, the entire outline of the exterior body in a plan view is curved. The outline 160 of the exterior body 100 in a plan view may be, for example, circular.

[0044] In the secondary battery of the present invention, the curvature of the contour of the exterior body faces, preferably directly faces, the curved portion of the electrode terminal in a plan view. That is, for example, as shown in Figures 5(A) to 5(D), the curved portion 254 in the plan view contour 250 of the electrode terminal 200 and the curved portion 160a in the plan view contour 160 of the exterior body 100 face each other (preferably directly face each other). In a plan view when the secondary battery is viewed from the outside, it can also be said that the curved portion in the contour of the electrode terminal 200 and the curved portion in the contour of the exterior body 100 face each other or face each other. As used herein, "facing each other" means that, in the plan view contour of the secondary battery, the curved portion of the electrode terminal and the curved portion of the exterior body have a positional relationship adjacent to or side by side with each other (for example, a positional relationship in which they are adjacent to or side by side while being spaced apart from each other in a plan view of the battery when viewed from the outside), and preferably means that they have a positional relationship in which they are adjacent to or side by side more closely or more directly.

[0045] In the secondary battery of the present invention, the electrode terminal corresponds to an output terminal for external connection. In particular, the electrode terminal is provided on the main surface of the exterior body so as to cover an opening therein, and preferably the electrode terminal is adhered or attached via an insulating seal member provided around the opening. The electrode terminal 200 has, for example, a flat plate shape (see FIGS. 3 and 4). In other words, the electrode terminal 200 may be a flat plate-like member (for example, an electrode terminal 200 whose opposing main surfaces are planar). The flat plate-like electrode terminal may be, for example, a metal disk. Because of its flat plate shape, the electrode terminal may have a substantially uniform thickness.

[0046] The electrode terminal is electrically connected to the conductive member of the electrode assembly. The conductive member may be a member containing metal (e.g., simply a metal member), preferably a metal member having an elongated shape. For example, the conductive member may be an electrode current collector of the electrode assembly, or a current collecting lead provided on the electrode assembly (particularly, its electrode). When the conductive member is an electrode current collector, the conductive member may be formed from a metal portion of the electrode current collector that is not provided with electrode material. When the conductive member is a current collecting lead, the conductive member may be formed from a metal member having a thin and / or elongated shape. In the present invention, the conductive member electrically connecting the electrode assembly and the electrode terminal to each other may also be referred to as a "tab." The conductive member is preferably flexible and may be provided in a bent and / or curved shape to contribute to the cleaving mechanism described below.

[0047] In the present invention, only one electrode terminal may be provided for a battery. That is, as shown in FIGS. 2 and 3, a single electrode terminal 200 may be provided for one main surface of a battery. In the case of a single electrode terminal, the closed area formed by the planar view outline 250 of the electrode terminal may also be single, as shown in FIGS. 6(A) to 6(D), for example. That is, as shown in the plan views of FIGS. 6(A) to 6(D), the closed area of ​​the planar view outline 250 of the electrode terminal is formed as a single closed area inside the closed area formed by the planar view outline of the exterior body (particularly, the planar view outline 160 of the exterior body that forms the outer edge of the exterior body). There are no particular limitations on the material of the electrode terminal 200, as long as it is electrically conductive. The electrode terminal may be made of a metal material commonly used as a terminal material for secondary batteries. For example, the electrode terminal may contain at least one metal selected from the group consisting of iron, stainless steel, aluminum, nickel, and copper.

[0048] In this specification, the "contour of the electrode terminal in a plan view" refers to the contour of the electrode terminal when viewed in a plan view (e.g., the contour of the terminal shape obtained when the electrode terminal is viewed along the normal or perpendicular direction to the main surface of the electrode terminal). Preferably, the "contour of the electrode terminal in a plan view" may be considered to be the outer edge contour of the surface that directly contacts the insulating seal member used to install the electrode terminal (e.g., the electrode terminal surface that is in the same plane as the contact surface). Simply put, the "contour of the electrode terminal in a plan view" may correspond to the contour shape formed by the outer edge (preferably the outermost edge) of the electrode terminal. Similarly, the "contour of the exterior body in a plan view" refers to the contour of the exterior body when viewed in a plan view, as described above, and typically refers to the outer edge contour or outer contour of the exterior body. Preferably, the "planar view outline of the exterior body" may refer to the outline, outer outline, or outer edge outline (preferably, an outline that may be located outside the outline of the electrode terminal when viewed in plan, or the outer outline or outer edge outline) of the surface that directly contacts the insulating seal member used to install the electrode terminal (e.g., an exterior body surface that is on the same plane as the contacting surface) among the surfaces that make up the exterior body. In a preferred embodiment, the "planar view outline of the exterior body" in the present invention may be considered to be the outline formed by the exterior body when the secondary battery is viewed so that the electrode terminal is visible from a direction perpendicular to the main surface of the electrode terminal (e.g., it may be considered to be the outline of the exterior body that is located outside the electrode terminal, or the outer outline or outermost outline of the exterior body).

[0049] As described above, the planar outline of the electrode terminal in the present invention is composed of both straight and curved portions. This configuration facilitates the provision of a region other than the electrode terminal as a suitable region on one of the battery's main surfaces. For example, in the embodiment shown in Figures 6(A) to 6(D), this facilitates the provision of both the terminal region 110A and the non-terminal region 110B on the battery main surface where the electrode terminal is provided. In particular, the planar outline of the electrode terminal composed of straight and curved portions ensures a more suitable or larger proportion of the planar area of ​​the non-terminal region 110B on the battery main surface compared to a case where such an electrode terminal outline configuration is not provided. Therefore, the non-terminal region 110B provided together with the terminal region 110A on the battery main surface increases the design flexibility of the battery. For example, it is easier to provide an external lead-out member for external connection in the non-terminal region 110B, making the secondary battery of the present invention more suitable for use as a suitable battery (e.g., this may enable a compact battery design in which external circuits, etc., are provided on the main surface of the secondary battery of the present invention). Such a problem is likely to become apparent when the outline of the exterior body in plan view at the surface where the exterior body contacts the insulating seal member includes a curve, and the curved portion of the electrode terminal and a part of the curve of the exterior body face each other.

[0050] Furthermore, by having the electrode terminal have a planar outline composed of both straight and curved portions, it becomes easier to provide both terminal and non-terminal regions on the battery main surface, while also ensuring a suitable sealing area associated with the electrode terminal. In other words, it becomes easier to ensure a suitable proportion of the planar area of ​​the non-terminal region 110B on the battery main surface without adversely impairing sealing strength and / or longevity. In other words, by having the electrode terminal have a planar outline composed of both straight and curved portions, it becomes easier to provide a suitable terminal and non-terminal region on the battery main surface, while also ensuring a suitable sealing area (hereinafter also referred to as the "sealing area") associated with the electrode terminal via an insulating seal member on the exterior body. This also becomes apparent when the planar outline of the exterior body at the surface where the exterior body contacts the insulating seal member includes a curve, and the curved portion of the electrode terminal and a portion of the curve of the exterior body face each other.

[0051] The features of the electrode terminal's planar profile, which includes both straight and curved portions, also contribute favorably to a safety mechanism in the event of an increase in cell internal pressure, i.e., a battery rupture mechanism. In the event of an abnormal increase in cell internal pressure, the electrode terminal ruptures outward to prevent unintended battery explosions. In the secondary battery of the present invention, this rupture occurs relatively easily from the "straight portion." That is, the electrode terminal is more likely to rupture from the straight portion of the electrode terminal's planar profile (such rupture will be described later), increasing the predictability of an abnormal increase in cell internal pressure. In other words, the secondary battery of the present invention can be provided as a safer battery while minimizing the unpredictability of the rupture mode in the event of an excessive increase in cell internal pressure. This effect is also more pronounced when the planar profile of the exterior body at the surface where the exterior body contacts the insulating seal member includes a curve, and the curved portion of the electrode terminal and a portion of the curve of the exterior body face each other.

[0052] In the secondary battery of the present invention, the curved portion of the electrode terminal faces the curve of the exterior body. In a preferred embodiment, the straight portion of the electrode terminal also faces the curve of the exterior body (a curved portion different from the portion facing the curved portion of the electrode terminal). This will be described in more detail with reference to FIGS. 5(A) to 5(D). As described above, in the secondary battery of the present invention, the curved portion 254 in the planar view outline 250 of the electrode terminal 200 and the curved portion 160a in the planar view outline 160 of the exterior body 100 face each other. This opposing relationship between the electrode terminal and the exterior body may also be formed with respect to the straight portion of the electrode terminal. The curve in the planar view outline 160 of the exterior body 100 may have a portion facing the curved portion 254 of the planar view outline 250 of the electrode terminal 200 and a portion facing the straight portion 252. 5(A) to 5(D), the outline 160 of the exterior body 100 in plan view is curved as a whole, and a curved portion 160b of the exterior body, which is different from the "part 160a of the curve of the exterior body 100 that faces the curved portion 254 of the electrode terminal 200," faces the straight portion 252 of the electrode terminal 200. In such an embodiment, the effects of making it easier to provide the above-mentioned external lead-out member and / or making it easier to achieve a suitable cleavage mechanism, etc., are more likely to be realized.

[0053] In the secondary battery of the present invention, the curved portion of the electrode terminal and the curve of the exterior body face each other, but it is preferable that the curved portion of the electrode terminal in plan view be positioned closer to the outer contour of the exterior body in plan view than the other portions of the electrode terminal (non-curved contour portions). It can be said that it is preferable that the curved portion be positioned closer to the curvature of the outer contour of the exterior body in plan view than the straight portion of the outline of the electrode terminal in plan view. For example, in the plan views shown in Figures 5(A) to 5(D), the "separation distance between the curved portion 254 of the electrode terminal 200 and the opposing curved portion 160a of the exterior body 100 (the "shortest separation distance" described below)" may be smaller than the "separation distance between the straight portion 252 of the electrode terminal 200 and the opposing other portion 160b of the curve of the exterior body 100 (the curved portion 160b different from the first portion 160a)" (the "shortest separation distance"). This will be described in further detail using Figures 6(A) to 6(D). In the plan views of Figures 6(A) to 6(D), when comparing the "shortest distance Lw between the curved portion 254 of the plan view contour 250 of the electrode terminal 200 and the plan view outer contour 160 of the exterior body 100" with the "shortest distance Ls between the straight portion 252 of the plan view contour 250 of the electrode terminal 200 and the plan view outer contour 160 of the exterior body 100," Lw is smaller than Ls. It can also be said that the straight portion of the plan view contour of the electrode terminal is positioned relatively farther from the plan view outer contour of the exterior body than the curved portion. An electrode terminal having such a plan view contour more easily provides terminal and non-terminal regions on the main battery surface, making it easier to produce a desired secondary battery. For example, it becomes easier to provide an external lead-out member for external connection in the non-terminal region. Preferably, this facilitates ensuring a suitable seal area while also ensuring a suitable terminal and non-terminal region on the main battery surface. The "shortest separation distance Lw" refers to the shortest or shortest distance in a direction perpendicular to the tangent of the curved portion in a plan view. Similarly, the "shortest separation distance Ls" refers to the shortest or shortest distance in a direction perpendicular to the straight portion.

[0054] In a preferred embodiment, one end portion of the straight portion and one end portion of the curved portion are shared with each other so that the straight portion and the curved portion are continuous in the planar view outline of the electrode terminal (e.g., so that the planar view outline is continuous). In other words, the planar view outline of the electrode terminal is configured from an outline in which the straight portion and the curved portion are connected via their end portions. In the planar view outlines of the electrode terminals in FIGS. 7(A) to 7(D), which correspond to FIGS. 6(A) to 6(D), respectively, one end portion 252a of the straight portion 252 and one end portion 254a of the curved portion 254 may overlap so as to be shared with each other, thereby forming the planar view outline 250 so that the straight portion 252 and the curved portion 254 are connected to each other. An electrode terminal having such a planar view outline more easily ensures that terminal and non-terminal regions are properly defined on the battery main surface, making it easier to produce a desired secondary battery. For example, it is easier to provide an external lead-out member for external connection in the non-terminal region. Preferably, the sealing area is suitably secured, and the terminal area and the non-terminal area are suitably provided on the main surface of the battery.

[0055] In the planar view profile of the electrode terminal, the curved portion may be arc-shaped. That is, the planar view profile of the electrode terminal may include a shape equivalent to a portion of a circle. In the embodiment shown in Figures 7(A) to 7(D), the planar view profile 250 of the electrode terminal may be composed of an arc-shaped contour 254' as the curved portion 254 and a linear portion 252 combined with it. When the planar view profile of the electrode terminal includes such an arc-shaped curved portion, the terminal area and the non-terminal area are more easily secured on the main surface of the battery, preferably while securing a suitable sealing area, and the desired secondary battery is more easily obtained. This may be more apparent when the secondary battery is a button-type or coin-type battery. For example, it becomes easier to provide an external lead-out member for external connection in the non-terminal area, contributing to more optimal battery design. By way of example only, the outline of the electrode terminal in plan view may include an arc-shaped curved portion corresponding to a circumference of at least a semicircle, a quarter circle, a sixth circle, or a eighth circle.

[0056] When the curved portion has an arc shape and the outline of the exterior body in a plan view (particularly, the outer outline of the exterior body in a plan view forming the outer edge of the exterior body) is circular, the imaginary circle forming the arc of the curved portion and the circular outline of the exterior body in a plan view may be concentric with each other. That is, the arc outline of the electrode terminal and the circular outline of the exterior body may share the same center in a plan view. This makes it easier to ensure a more uniform and larger seal area between the electrode terminal and the exterior body, and ultimately, more favorably ensures the joint strength and long-term reliability of the sealing related to the electrode terminal (in short, the joining of the electrode terminal in the area surrounding the opening of the exterior body). Note that the term "concentric circles" in this specification does not necessarily mean perfectly concentric circles, but also includes approximately concentric circles that can be modified but are recognized by those skilled in the art as having a substantially concentric relationship (e.g., the center of the circle may be offset by, for example, 30%, 20%, 10%, 5%, or 3% of the diameter of the circular outline of the exterior body in a plan view).

[0057] In a preferred embodiment, the proportion of the curved portions in the outline of the electrode terminal in a plan view is relatively larger than the proportion of the straight portions. In other words, in the outline of the electrode terminal in a plan view, the total length of the curved portions may be relatively longer than the total length of the straight portions. In the embodiment shown in FIG. 8, the length of the straight portions 252 is L. ａ and the length of the curved portion 254 is L ｂ Then, L ａ <L ｂ In the case of such a planar view contour of the electrode terminal in which the proportion of the curved portion is greater than the proportion of the straight portion, it becomes easier to more suitably secure the terminal area and the non-terminal area on the main surface of the battery, and it becomes easier to obtain a desired battery. For example, it becomes easier to provide an external lead-out member for external connection in the non-terminal area. Preferably, it becomes easier to suitably provide the terminal area and the non-terminal area on the main surface of the battery while suitably securing the sealing area related to the electrode terminal. Although it is merely an example, the length L of the curved portion ｂ is the length of the straight section L ａ The length L of the curved portion may be 1.2 times or more, for example, 1.5 times or more. ｂ Although there is no particular restriction on the upper limit of the length of the straight part Lａ Therefore, by way of example only, the outline of the electrode terminal in plan view may be 1.2L ａ ≦L ｂ ≦3L ａ , 1.2L ａ ≦L ｂ ≦2.5L ａ , 1.2L ａ ≦L ｂ ≦2L ａ , 1.5L ａ ≦L ｂ ≦3L ａ , 1.5L ａ ≦L ｂ ≦2.5L ａ or 1.5L ａ ≦L ｂ ≦2L ａ The relative lengths may be:

[0058] In a preferred embodiment, the planar outline of the electrode terminal is composed only of straight and curved portions. For example, as shown in FIGS. 6A to 6D , the outline is composed only of two types of straight and curved portions: a straight portion 252 and a curved portion 254. In short, the planar outline of the electrode terminal may be composed only of a combination of straight and curved portions. In such a case, the features of the present disclosure are more prominent, and the effects of the present invention are more readily apparent. That is, the terminal area and the non-terminal area are more readily secured on the main surface of the battery, and the effect of, for example, facilitating the provision of an external lead-out member for external connection in the non-terminal area is more readily apparent. Preferably, the effect of providing a well-balanced and suitable terminal area and non-terminal area on the main surface of the battery is more readily apparent, while the sealing area associated with the electrode terminal is suitably secured.

[0059] In the secondary battery of the present invention, the electrode terminal is provided on the exterior body. The electrode terminal may be provided on a region including at least a portion of the main surface of the exterior body (preferably a portion of the planar main surface). In particular, the electrode terminal is provided on the exterior body so as to cover at least an opening (also referred to herein as an "exterior body opening") of the exterior body through which a conductive member electrically connected to the electrode terminal (i.e., a conductive member extending from the electrode assembly) passes. Preferably, the electrode terminal is provided on the exterior body so as to cover the entire opening of the exterior body, and preferably the electrode terminal is provided so as to extend over the planar surface of the exterior body around the opening of the exterior body. As used herein, the term "exterior body" refers to a member for housing or encasing an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are stacked. For example, the exterior body may be a metal exterior body having a non-laminated structure. This means that the exterior body is not a laminate member such as one consisting of a metal sheet / bonding layer / protective layer. The exterior body of the present invention may differ from the exterior body of a soft-case battery, which corresponds to a pouch made of a laminated film. A metal exterior body having a non-laminated structure is preferably constructed of a single metal member. For example, such a metal exterior body may be a single member made of a metal such as iron, stainless steel (SUS), and / or aluminum. The term "single metal member" as used herein broadly means that the exterior body does not have a so-called laminated structure, and in a narrow sense, means that the exterior body is a member made essentially of metal. Therefore, if the metal exterior body is a member made essentially of metal, the surface of the metal exterior body may be subjected to an appropriate surface treatment. For example, a cross section of such a metal exterior body cut in the thickness direction reveals a single metal layer, excluding the surface-treated portion. Note that "stainless steel" in this specification refers to stainless steel as defined in "JIS G 0203 Iron and Steel Terminology," and may be an alloy steel containing chromium or chromium and nickel. In a preferred embodiment, the exterior body may have a can shape (in which case the exterior body can be considered to be an "external can").

[0060] In the secondary battery of the present invention, the exterior body may be composed mainly of two parts. For example, the exterior body may be composed of two parts, a first metal exterior body and a second metal exterior body, which are metal members. In the case of an exterior body having a non-laminated configuration, each of the first metal exterior body and the second metal exterior body may be a single metal member. In the present invention, the exterior body may have a relatively thin thickness. For example, each of the first metal exterior body and the second metal exterior body may have a thickness dimension of 50 μm or more and less than 200 μm, such as 50 μm or more and 190 μm or less, 50 μm or more and 180 μm or less, or 50 μm or more and 170 μm or less.

[0061] In an exterior housing composed of two parts, a first metal exterior housing and a second metal exterior housing, the above-mentioned "exterior housing opening" may be provided in one of the first metal exterior housing and the second metal exterior housing. That is, an opening may be provided in either the first metal exterior housing or the second metal exterior housing, and an electrode terminal may be provided in one of the sub-exterior housings having that opening. Note that the first metal exterior housing and the second metal exterior housing, which are metal members, may be combined with each other by laser welding to form an exterior housing, or may be combined with each other by crimping to form an exterior housing.

[0062] One of the first metal outer packaging body and the second metal outer packaging body may be a cup-shaped member, and the other of the first metal outer packaging body and the second metal outer packaging body may be a lid-shaped member. In such a case, for example, the metal outer packaging bodies may be joined together by welding or crimping the peripheral edge of the lid-shaped member from the outside, which may enable relatively easy encapsulation. The term "cup-shaped member" refers to a member having a side wall or side surface corresponding to a body portion and a main surface portion (e.g., a bottom portion in a typical embodiment) continuous therewith, forming a hollow portion inside. The term "lid-shaped member" also refers to a member that is combined with the cup-shaped member to cover it (preferably, a member that is provided in contact with the side wall of the cup-shaped member to block the internal hollow portion of the cup-shaped member from the outside). The lid-shaped member may be, for example, a single member (typically a flat member) extending in a planar direction (particularly, a direction perpendicular to the direction in which the side wall of the cup-shaped member extends upright), and may particularly be a member that is provided in contact with the side wall of the cup-shaped member.

[0063] The above-mentioned "exterior body opening" may be provided in the lid-shaped member. In other words, the exterior body may be composed of a cup-shaped member 100A and a lid-shaped member 100B, and the lid-shaped member 100B, not the cup-shaped member 100A, may have the exterior body opening 150 (see FIG. 4). When the lid-shaped member has the exterior body opening, an electrode terminal is provided on the lid-shaped member. In such a case, a secondary battery can be manufactured by first obtaining an assembly in which the electrode terminal is provided on the lid-shaped member, and a secondary battery can be obtained relatively easily.

[0064] The "exterior body opening" may also be provided in the cup-shaped member. That is, the exterior body may be composed of a cup-shaped member and a lid-shaped member, and the exterior body opening may be provided in the cup-shaped member rather than the lid-shaped member (for example, the exterior body opening may be provided in a surface corresponding to the bottom of the cup-shaped member). When the cup-shaped member has an exterior body opening, an electrode terminal may be provided in the cup-shaped member (for example, in a surface corresponding to the bottom of the cup-shaped member).

[0065] When the metal exterior body is particularly composed of a cup-shaped member and a lid-shaped member, the cup-shaped member and the lid-shaped member may be hermetically sealed by joining together. In other words, the cup-shaped member and the lid-shaped member are not crimped together, and therefore, hermetic sealing by crimping is not required. This makes it easier to achieve a more space-saving secondary battery than a secondary battery with a crimped exterior body. In other words, the non-crimped configuration of the cup-shaped member and the lid-shaped member contributes favorably to miniaturizing the secondary battery and improving its energy density.

[0066] In the present invention, the exterior body opening may also have a contour shape similar to that of the electrode terminal. That is, in a secondary battery having a conductive member electrically connecting the electrode assembly and the electrode terminal, in which an insulating seal member is interposed between the electrode terminal and the exterior body surface around the exterior body opening through which the conductive member passes, the exterior body opening's planar-view contour may be composed of both straight and curved portions. Figures 9(A) to 9(D) show planar-view contours of the exterior body corresponding to Figures 5(A) to 5(D) or Figures 6(A) to 6(D), respectively. In the planar view of the exterior body 100 shown in Figures 9(A) to 9(D) (planar view excluding the electrode terminal), the contour 180 of the exterior body opening 150 is composed of two types: a straight portion 182 and a curved portion 184. That is, the shape of the opening edge forming the exterior body opening 150 is composed of a straight portion and a curved portion. In one preferred embodiment, the contour 180 of the exterior body opening 150 is composed of only two types of parts: a straight portion 182 and a curved portion 184, and therefore the shape of the opening edge that forms the exterior body opening 150 is composed of only straight portions and curved contours.

[0067] A secondary battery having such a planar outline can provide more suitable sealing. Specifically, the planar outline of the opening and the electrode terminal are likely to be similar in shape, which facilitates more uniform sealing of the electrode terminals around the opening (preferably, the width of the seal area formed around the opening is likely to be constant along the opening). In other words, a safer battery can be provided with a stable hermetic seal.

[0068] 9(A) to 9(D) , the shapes themselves are similar to the contour shapes 250 of the electrode terminals shown in Figures 6(A) to 6(D) . Therefore, the various features described above regarding the plan view contour 250 of the electrode terminal can also be applied to the plan view contour 180 of the exterior body opening 150.

[0069] In the secondary battery of the present invention, an insulating seal member is provided between the electrode terminal and the exterior body. Fig. 10 shows a cross-sectional view of the relative positions of the exterior body 100, electrode terminal 200, and insulating seal member 300. As can be seen from the configuration shown in Fig. 10, the insulating seal member 300 is interposed between the exterior body 100 and the electrode terminal 200. The exterior body 100 has an exterior body opening 150 as an opening, and the insulating seal member 300 is disposed on the exterior body surface 158 around the exterior body opening 150. Preferably, the electrode terminal 200 is bonded to the exterior body 100 via the insulating seal member 300 in the area surrounding the exterior body opening 150 due to the bonding properties of the insulating seal member 300. As shown in Fig. 10, the electrode terminal 200 is preferably attached to the insulating seal member 300 so as to externally close the exterior body opening 150. In a preferred embodiment of the secondary battery of the present invention, an insulating seal member 300 is interposed between the electrode terminal 200 and the exterior body surface 158 around the opening 150 of the exterior body through which the conductive member 400 passes. As can be seen from Fig. 10 , the insulating seal member 300 is sandwiched between the electrode terminal 200 and the exterior body 100 in the joint region between the electrode terminal 200 and the exterior body 100.

[0070] The insulating seal member 300 may be provided on the surface of the exterior body (preferably on the outer surface of the exterior body) so as to follow the periphery of the opening 150. To provide better insulation, the insulating seal member 300 may be provided so as to extend to an area outside the electrode terminal 200. That is, for example, as shown in FIG. 10 , the insulating seal member 300 may be provided on the exterior body 100 so as to protrude outward from the electrode terminal 200. Similarly, to provide better insulation, the insulating seal member 300 may be provided further inward beyond the edge of the opening 150 of the exterior body 100. That is, for example, as shown in FIG. 10 , the insulating seal member 300 may extend further inward beyond the edge portion 155 that defines the opening 150 in the exterior body 100, and therefore a portion of the insulating seal member 300 may reach the area of ​​the opening 150.

[0071] In this specification, the term "insulating seal member" refers to at least a member interposed between the exterior body and the electrode terminal, contributing to insulation therebetween, and also to battery sealing (more specifically, airtight sealing between the exterior body and the electrode terminal). The insulating seal member is not particularly limited in terms of the type of material as long as it exhibits insulating properties. "Insulating" in this specification means that the insulating properties possessed by a general insulator and therefore the electrical resistivity possessed by a general insulator are acceptable, and while this is merely an example, the insulating seal member may have an electrical resistivity of at least 1.0 x 10 ５ Ω·m or more, preferably 1.0×10 ６ Ω·m or more, more preferably 1.0×10 ７The insulating seal member may have a resistivity of Ω·m or more (at room temperature 20°C). Preferably, the insulating seal member has not only insulating properties but also fusible properties, as this makes it easier to improve sealing properties. For example, the insulating seal member may be made of a thermoplastic resin. Although this is merely one specific example, the insulating seal member may be made of a polyolefin such as polyethylene and / or polypropylene. From another perspective, the insulating seal member as an insulating bonding material may contain an adhesive component that exhibits insulating properties, as this may make it easier to expect improved sealing properties. Examples of such adhesives (i.e., materials for the insulating seal member) include acrylic adhesives such as acrylic acid ester copolymers, rubber adhesives such as natural rubber, silicone adhesives such as silicone rubber, urethane adhesives such as urethane resins, α-olefin adhesives, ether adhesives, ethylene-vinyl acetate resin adhesives, epoxy resin adhesives, vinyl chloride resin adhesives, chloroprene rubber adhesives, cyanoacrylate adhesives, aqueous polymer-isocyanate adhesives, styrene-butadiene rubber adhesives, nitrile rubber adhesives, nitrocellulose adhesives, reactive hot melt adhesives, phenolic resin adhesives, modified silicone adhesives, polyamide resin adhesives, polyimide adhesives, polyurethane resin adhesives, polyolefin resin adhesives, polyvinyl acetate resin adhesives, polystyrene resin solvent adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone resin adhesives, polyvinyl butyral resin adhesives, polybenzimidazole adhesives, polymethacrylate resin adhesives, melamine resin adhesives, urea resin adhesives, and / or resorcinol adhesives.

[0072] A secondary battery with an insulating seal member interposed between the electrode terminals and the exterior surface is likely to be used as a safer battery. In other words, if an abnormal situation occurs in which the internal pressure of the exterior body increases, the electrode terminals may split open (preferably so that the electrode terminals open toward the outside of the battery) to prevent more serious accidents, such as unintended battery explosions. In other words, to prevent a battery explosion caused by an increase in pressure inside the exterior body (also referred to herein as "internal cell pressure") due to gas generated by abnormal heat generation inside the battery due to overcharging or an internal short circuit, etc., the secondary battery preferably has a vent mechanism that releases internal gas when the internal cell pressure increases excessively. In this regard, the secondary battery of the present invention is preferably capable of displacing the electrode terminals so as to release the sealed state that blocks the exterior body opening when the internal cell pressure increases excessively. In other words, when the internal pressure of the cell rises abnormally, the electrode terminals are displaced so that they peel off from the insulating seal material on the surface of the exterior body and open (see Figure 11).As a result, the opening in the exterior body communicates with the outside, allowing the internal gas to escape to the outside and preventing battery explosion, etc.

[0073] In the present invention, the insulating seal member may also have a contour shape similar to that of the electrode terminal. That is, the contour of the insulating seal member in a plan view may be composed of both straight and curved portions. FIGS. 12(A) to 12(D) show the contour of the insulating seal member 300 in a plan view corresponding to FIGS. 5(A) to 5(D) or 6(A) to 6(D), respectively. As shown in FIGS. 12(A) to 12(D), the outer contour 350 of the insulating seal member 300 is composed of two types of contours: straight portions 352 and curved portions 354. That is, the contour of the outer edge of the insulating seal member 300 in a plan view is composed of straight and curved contours. In a preferred embodiment, the outer contour of the insulating seal member 300 is composed of only two types of contours: straight and curved portions. Therefore, the contour of the outer edge of the insulating seal member 300 in a plan view is composed of only straight and curved contours. The inner contour of the insulating seal member 300 may be similar. The inner contour 360 of the insulating seal member 300 is composed of two types of portions: a straight line portion 362 and a curved line portion 364. That is, the planar contour of the inner edge of the insulating seal member 300 is composed of a straight line portion and a curved line portion. In a preferred embodiment, the inner contour of the insulating seal member 300 is composed of only two types of portions: a straight line portion and a curved line portion, and therefore the planar contour of the inner edge of the insulating seal member 300 is composed of only a straight line portion and a curved line portion.

[0074] A secondary battery including an insulating seal member 300 having such a planar contour is likely to provide better sealing. Specifically, the planar contour of the outer edge and / or inner edge of the insulating seal member and the planar contour of the electrode terminal are likely to have a similar shape, which makes it easier for the insulating seal member and the electrode terminal to contribute to more uniform sealing of the area around the exterior body opening (preferably, the width of the seal area formed around the exterior body opening is likely to be constant along the periphery of the opening). In other words, a safer battery is likely to be provided with stable hermetic sealing.

[0075] 12A to 12D, the contour shapes of the insulating seal member 300 are similar to the contour shapes 250 of the electrode terminals shown in Figures 6A to 6D. Therefore, the various features described above regarding the plan view contour 250 of the electrode terminal can also be applied to the plan view contours 350, 360 of the insulating seal member.

[0076] In a preferred embodiment, the distance between the curved portion 254 of the planar view contour 250 of the electrode terminal 200 and the planar view outer contour 160 of the exterior body 100 is constant. This is particularly true when the curved portion 250 of the electrode terminal 200 has an arc shape and the planar view contour of the exterior body (particularly the planar view outer contour of the exterior body forming the outer edge of the exterior body) has a circular shape (see FIGS. 6(A) to 6(D)). In other words, the "shortest distance Lw" described using FIGS. 6(A) to 6(D) may be a constant distance in plan view. Such a constant distance contributes to more uniform sealing. In other words, the width dimension of the seal area formed around the exterior body opening tends to be constant along the periphery of the opening, which tends to result in a more stable hermetic seal.

[0077] In a preferred embodiment, the electrode terminal of the present invention is a non-crimped metal plate. Furthermore, because of this non-crimped metal plate, for example, the metal plate extends on the same plane in cross-section. In short, the electrode terminal serving as an external output terminal does not have a curved shape overall but has a flat plate-like form. For example, as shown in FIGS. 3(A) and 10 , the cross-sectional shape of the electrode terminal 200 may be rectangular. Such an electrode terminal 200 has not been subjected to a history of pressure deformation and is likely to have greater long-term stability from a material perspective. In other words, it is likely to become an external output terminal suitable for long-term use of a secondary battery. Because of this non-crimped configuration, for example, the insulating seal member 300 may also extend on the same plane in cross-section. In other words, the cross-sectional shape of the insulating seal member provided adjacent to the electrode terminal may not be curved but may be, for example, rectangular. As shown in FIGS. 3(A) and 10 , the insulating seal member 300 may have a substantially constant thickness. Such an insulating seal member 300 can be said to be an insulating member or insulating material that is less susceptible to deformation due to pressure when an electrode terminal is installed. The insulating seal member 300 may have a film shape. For example, the insulating seal member 300 may be provided using a precursor of a film-shaped insulating member having a shape close to the final shape.

[0078] Here, the cleavage mechanism associated with the electrode terminal, i.e., the vent mechanism, will be described in detail. As the internal cell pressure increases during battery use, such as charging and discharging, the force acting on the electrode terminal 200 due to the internal cell pressure also increases. In a preferred embodiment, when the internal cell pressure becomes excessively high, the force acting on the electrode terminal 200 exceeds the bonding force between the electrode terminal 200 and the exterior body 100 (i.e., the adhesive or fixing force of the electrode terminal 200 to the exterior body 100 via the insulating seal member 300), causing at least a portion of the electrode terminal 200 to detach from the exterior body 100. For example, the electrode terminal 200 is provided so as to cover the opening 150 of the exterior body 100, but the electrode terminal 200 can be displaced so that the cover opens (see FIG. 11 ). This displacement of the electrode terminal 200 releases excess gas inside the exterior body to the outside of the exterior body, preventing more serious accidents such as unintended battery explosions.

[0079] In this specification, the term "internal cell pressure" broadly refers to the pressure inside the exterior body of a secondary battery. In a narrower sense, the term "internal cell pressure" refers to the pressure inside an exterior body that is provided with an electrode assembly and is in an airtight sealed state (particularly the internal pressure when the battery is in use). Note that the "insulating seal member" in this embodiment contributes to the vent mechanism as described above, and can be referred to as an insulating seal that can be peeled off in the event of an abnormality in the internal cell pressure, i.e., a peelable member.

[0080] The secondary battery of the present invention can be used as a battery with high predictability in the event of an abnormal rise in cell internal pressure, since the electrode terminal has a planar outline that is composed of both straight and curved portions. Specifically, when an abnormal rise in cell internal pressure occurs, the electrode terminal is likely to split open starting from a point corresponding to the "straight portion" of the planar outline of the electrode terminal, which increases predictability and enables more suitable battery design.

[0081] When the internal pressure of a secondary battery increases, stress is exerted on the exterior body due to the internal pressure of the cell. In particular, when the internal pressure of the cell increases abnormally, deformation stress that causes deflection or distortion of the exterior body may act (see FIG. 13 ). Such deformation stress tends to cause greater deflection in the central region of the exterior body. In particular, the main surface of the exterior body, which extends substantially flat, is structurally more prone to deflection than the side surfaces of the exterior body, which may be curved or folded. Therefore, when the internal pressure of the cell increases abnormally, the widthwise center of the main surface of the battery is likely to have a greater curvature or bending than the outer portions, and the main surface of the exterior body (in the illustrated embodiment, its lid-shaped member 100B) may deform, for example, as shown in FIG. 13 . The location of the relatively large curvature for such deformation of the exterior body (i.e., battery deformation) or its vicinity (hereinafter also referred to as the “maximum curvature location”) is preferably located at or near the “straight line” of the planar profile of the electrode terminal. It can also be said that the straight portion 252 of the outline of the electrode terminal 200 in a plan view is located at the maximum curvature point U, relatively closer to the curved portion 254 (see FIG. 13 ). Therefore, the straight portion of the outline of the electrode terminal in a plan view is relatively more susceptible to the deformation stress of the exterior body than the curved portion, and the electrode terminal is more likely to tear apart, such as peeling off, from the straight portion of the outline of the electrode terminal in a plan view. This effect is likely to be apparent in the above-mentioned cases, such as "the curved portion of the electrode terminal and the curve of the exterior body face each other," "the straight portion of the electrode terminal also faces the curve of the exterior body (a curved outline portion different from the portion facing the curved portion of the electrode terminal)," "the curved portion is located relatively closer to the outline of the exterior body in a plan view than the straight portion," and / or "the proportion of the curved portion in the outline in a plan view is relatively larger than the proportion of the straight portion (i.e., the proportion of the straight portion in the outline in a plan view is relatively smaller than the proportion of the curved portion)."

[0082] In this way, when the cell ruptures due to an abnormal increase in internal cell pressure, the electrode terminals are displaced so as to open from a position corresponding to the straight portion of the outline of the electrode terminals in a plan view, and therefore the secondary battery of the present invention can be designed more appropriately with such rupture in mind. In other words, such a secondary battery is likely to be a battery in which unpredictability regarding the rupture mode related to the exterior body is avoided as much as possible, and can be provided as a safer battery.

[0083] [Method for Manufacturing Secondary Battery of the Present Invention] The secondary battery of the present invention can be obtained by enclosing an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are stacked in an exterior case.

[0084] The electrode assembly may be fabricated by a conventional method, and a secondary battery can be obtained by placing it inside an exterior housing. An insulating seal member is provided as a sealant in the area surrounding the exterior housing opening, and an electrode terminal is provided via the insulating seal member so as to close the exterior housing opening. For example, if the exterior housing is composed of the above-mentioned cup-shaped member and a lid-shaped member that is circular in plan view, a secondary battery can be obtained by the steps of: placing the electrode assembly inside the cup-shaped member and closing the open end of the cup-shaped member with the lid-shaped member (for example, the lid-shaped member and the cup-shaped member may be combined with each other by welding, etc.); and providing an insulating seal member in the area surrounding the exterior housing opening on the exterior housing; and providing an electrode terminal on the exterior housing via the insulating seal member so as to cover the exterior housing opening.

[0085] The electrode terminal itself, whose outline in plan view is composed of both straight and curved portions, can be obtained by a conventional metal processing method. The type of metal processing method itself is not particularly limited. For example, the electrode terminal can be obtained through machining (e.g., cutting and / or grinding), plastic processing (e.g., pressing and / or forging), and / or casting (sand casting and / or die casting). Alternatively, the electrode terminal may be manufactured using a metal 3D printer.

[0086] The present invention can be embodied in various forms, which will be described below.

[0087] (Aspects Relating to a Single Straight Portion and a Single Curved Portion) This aspect is characterized by the number of contour elements of the planar-view contour of the electrode terminal. Specifically, the planar-view contour of the electrode terminal is composed of a single straight portion and a single curved portion. In other words, the planar-view contour of the electrode terminal includes a single of each of the two types of contour elements.

[0088] 8 , the planar view contour 250 of the electrode terminal 200 includes only one straight portion 252 and only one curved portion 254. In this embodiment, it is preferable that, in the planar view contour 250 of the electrode terminal 200, one end portion 252 a of the straight portion 252 and one end portion 254 a of the curved portion 254 are shared with each other, and the other end portion 252 b of the straight portion 252 and the other end portion 254 b of the curved portion 254 are shared with each other, so that the straight portion 252 and the curved portion 254 are continuous.

[0089] In this embodiment, in the planar view outline, the center point of the straight portion and the center point of the curved portion may face each other so as to straddle the battery center. In the planar view shown in FIG. 8 , a center point 252c dividing the straight portion 252 in half and a center point 254c dividing the curved portion 254 in half face each other across the battery center M. The planar view outline 250 may be configured so that a single curved portion 254 and a single straight portion 252 form a closed region surrounding the battery center M. Note that the term "battery center M" as used herein refers broadly to the center of the main surface of the secondary battery, and narrowly to the center of the shape of the outer outline of the exterior body in a planar view (for example, if the outer outline of the exterior body in a planar view is circular, the center of the circle corresponds to the "battery center M").

[0090] When the planar outline of the electrode terminal is composed of a single straight portion and a single curved portion, it becomes easier to ensure that the terminal region and the non-terminal region are properly defined on the battery main surface, making it easier to obtain a desired battery. For example, it becomes easier to provide an external lead-out member for external connection (i.e., a member provided separately from the electrode terminal for external output) in the non-terminal region, contributing to more suitable battery design. Preferably, it becomes easier to ensure that both the terminal region and the non-terminal region are properly defined on the battery main surface while ensuring a suitable sealing area.

[0091] With regard to the exemplary embodiment of FIG. 8 , the electrode terminal may have a planar contour that is arch-shaped, D-shaped, and / or crescent-shaped. In particular, arch-shaped, D-shaped, and / or crescent-shaped electrode terminals may be provided on the main surface of the battery so as to extend to the above-described "battery center M." Furthermore, as can be seen from the exemplary embodiment of FIG. 8 , in the secondary battery of the present disclosure, electrode terminals that include both a linear and a curved contour in plan view may extend from the center of the battery toward one side of the battery. In other words, by providing electrode terminals with a contour that includes both a linear and a curved contour in plan view, it becomes easier to ensure a desired large sealing area while shifting the electrode terminal to one side of the center. This makes it easier to ensure a desired large exposed area of ​​the exterior body (particularly the area of ​​the non-terminal region on the main surface of the exterior body where the electrode terminal is provided) without compromising sealing strength and / or long life.

[0092] (Installation mode of external lead-out member) This mode relates to a battery configuration that contributes to more suitable connection with the outside. Specifically, both one external lead-out member and the other external lead-out member for external connection are provided on the same main battery surface. Here, the same main battery surface can correspond to the battery surface configured by the electrode terminals and the exterior body. In other words, on the battery main surface on which the electrode terminals are provided (hereinafter also referred to as the "terminal-installed battery surface"), both one external lead-out member and the other external lead-out member are provided on the battery main surface.

[0093] 14(A) and 14(B) show an embodiment in which a pair of external lead-out members 500A, 500B are provided on a terminal-installed battery surface 600 including a terminal region 110A and a non-terminal region 110B. As shown in FIG. 14(B), a positive-side external lead-out member 500A for connection to an external circuit and / or external device, and a negative-side external lead-out member 500B for connection to an external circuit and / or external device, are provided on the terminal-installed battery surface 600. This secondary battery configuration is due to the planar outline of the electrode terminals, which are composed of both straight and curved portions. In other words, the planar outline of the electrode terminals, which are composed of straight and curved portions, facilitates the terminal region 110A and the non-terminal region 110B to be more optimally provided on the terminal-installed battery surface. Such a planar outline allows the non-terminal region 110B to be a larger area (particularly compared to a case where the electrode terminal does not have both straight and curved portions in its planar outline), and the non-terminal region 110B can serve as an area where it is easy to provide an external lead-out member for external connection. Therefore, it is preferable that both one external lead-out member and the other external lead-out member be provided on the terminal-installed battery surface. In the secondary battery according to this embodiment, the external lead-out members are preferably concentrated on one main battery surface, making the battery more suitable for external connection.

[0094] Two external lead-out members may be provided on the terminal-mounted battery surface, one of which is provided on the electrode terminal and the other in the non-terminal region. That is, one external lead-out member may be provided on the electrode terminal, and the other external lead-out member may be provided on the non-terminal region of the battery main surface other than the electrode terminal. This allows the terminal-mounted battery surface to be more effectively utilized while maintaining the desired conductive function of the two external lead-out portions. As shown in FIG. 14(B) , one and the other external lead-out members may be provided side-by-side (preferably side-by-side so as to be adjacent to each other) on the battery main surface. As just one example, at least a portion of the positive electrode external lead-out member may be disposed on the electrode terminal to be electrically connected to the electrode terminal, and at least a portion of the negative electrode external lead-out member may be disposed on the non-terminal region to be electrically connected to the non-terminal region. Alternatively, the opposite configuration may be adopted, with at least a portion of the negative electrode side external lead-out member being positioned on the electrode terminal so as to be electrically connected to the electrode terminal, and at least a portion of the positive electrode side external lead-out member being positioned on the non-terminal region so as to be electrically connected to the non-terminal region.

[0095] The pair of lead-out members 500A, 500B may be members having the same form or shape. Alternatively, the pair of lead-out members 500A, 500B may be members having different forms or shapes. For example, as shown in FIG. 14(B), the lead-out members 500A, 500B may each have an elongated shape. The material of the lead-out members is not particularly limited as long as it is electrically conductive. For example, the material of the lead-out members 500A, 500B may be a metal material commonly used for electrical connection of batteries. For example, the lead-out members 500A, 500B may each be a member containing at least one metal selected from the group consisting of iron, SUS, aluminum, nickel, and copper. In the present disclosure, the external lead-out member is a member provided to suitably connect the battery to the outside (for example, an external circuit and / or an external device, or other element that requires the energy of the battery of the present disclosure), and therefore may also be referred to as an "external output tab" or an "external connection conductive member." Therefore, in the secondary battery of the present disclosure, an external lead-out member called an external output tab can be suitably attached to the same surface, thereby enabling a compact battery design that also includes the external circuit.

[0096] For example, the secondary battery of the present disclosure may include an external circuit above the terminal-equipped battery surface, and the external circuit and the terminal-equipped battery surface may be electrically connected by two external lead-out members provided on the terminal-equipped battery surface. Preferably, both of the external lead-out members are positioned between the terminal-equipped battery surface and the external circuit. An external circuit preferably disposed above the terminal-equipped battery surface contributes to the realization of a compact battery pack, due at least to the positive and negative lead-out members provided on the same battery main surface (the main surface at the upper end). Preferably, the planar size of the external circuit disposed above the terminal-equipped battery surface is the same as or smaller than the terminal-equipped battery surface.

[0097] (Secondary Battery with a Circular Plan View) In this embodiment, the overall shape of the secondary battery is circular in a plan view. That is, the secondary battery 1000 has a button-type or coin-type outer shape (see, for example, FIG. 2).

[0098] The secondary battery having a circular planar shape means that the electrode assembly and / or the exterior body enclosing it can have a circular shape when viewed from above or below.

[0099] The term "circular" as used herein does not necessarily mean a perfect circle (i.e., simply a "circle" or "perfect circle"), but also includes approximately circular shapes that may be modified from the circle and that are generally considered to be "round" by those skilled in the art. For example, the term "circular" does not only mean a circle or a perfect circle, but also means a shape whose arc curvature varies locally, and may also mean a shape derived from a circle or a perfect circle, such as an ellipse. A typical example of such a battery having a circular shape in plan view corresponds to a so-called button-type or coin-type battery. In one preferred embodiment, the secondary battery of the present invention is a cylindrical battery.

[0100] In such an embodiment of a secondary battery that is circular in plan view, the curve in the plan view outline of the exterior body is arc-shaped, and may have a portion facing the curved portion of the plan view outline of the electrode terminal, as well as a portion facing the straight portion of the plan view outline of the electrode terminal. That is, for example, as shown in the plan views of Figures 5(A) to 5(D), another arc portion 160b of the exterior body outline, different from the "arc portion 160a of the exterior body 100 facing the curved portion 254 of the electrode terminal 200," may face the straight portion 252 of the electrode terminal 200.

[0101] In a secondary battery having a circular shape in plan view, the outline of the exterior body opening in plan view (i.e., the outline of the opening in plan view) may be composed of both straight and curved portions. For example, the shape of the outline of such an exterior body opening in plan view is similar to the outline of the electrode terminal in plan view, and preferably has a similar shape with a smaller area than the outline of the electrode terminal in plan view. Note that in the present invention, although the outer outline of the exterior body in plan view (i.e., the outline of the portion forming the outer edge) is circular, the outline of the electrode terminal in plan view, the opening outline of the exterior body opening in plan view, the outer outline of the insulating seal member in plan view, and / or the inner outline of the insulating seal member in plan view may be non-circular, and preferably comprise both straight and curved portions.

[0102] In a preferred embodiment, because the secondary battery is a button-type or coin-type battery, the dimension in the axial direction (e.g., the normal direction to the main surface of the battery) is smaller than the width dimension (diameter dimension). However, the secondary battery of the present invention is not limited to this, and the dimension in the axial direction (e.g., the normal direction to the main surface of the battery) of the secondary battery may be the same as or larger than the width dimension (diameter dimension).

[0103] (Small Secondary Battery) In this embodiment, the entire secondary battery is relatively small. In other words, the secondary battery may be a small battery.

[0104] For example, the width dimension of the secondary battery or the exterior body (e.g., the dimension in a direction perpendicular to the normal or perpendicular direction of the battery main surface) may be on the order of millimeters. For example, the width dimension of the secondary battery or the exterior body (if the width dimension is not constant, the maximum dimension) may be approximately 5 mm to 50 mm, e.g., 5 mm to 40 mm, 5 mm to 30 mm, or 5 mm to 20 mm. Note that the lower limit is not limited to 5 mm and may be 10 mm (excluding 10 mm). That is, the width dimension of the secondary battery or the exterior body may be approximately greater than 10 mm and less than 50 mm, e.g., greater than 10 mm and less than 40 mm, greater than 10 mm and less than 30 mm, greater than 10 mm and less than 20 mm, or greater than 10 mm and less than 18 mm. In the case of a cylindrical battery, the width dimension of the secondary battery may correspond to the diameter dimension of the exterior body (e.g., its lid member).

[0105] In the secondary battery according to this embodiment, even though it is small, it is easier to ensure that the terminal region and the non-terminal region are properly defined on the battery main surface. That is, even in a small battery (e.g., a small cylindrical battery) on the order of millimeters, an external lead-out member for external connection can be properly provided in the non-terminal region. For example, such a small battery may have both a positive electrode side external lead-out member and a negative electrode side external lead-out member provided on a single battery main surface.

[0106] Although the embodiments of the present invention have been described above, they are merely typical examples. Therefore, it will be readily understood by those skilled in the art that the present invention is not limited to these and that various other embodiments are possible.

[0107] For example, the tearing mechanism, i.e., the vent mechanism, has been mentioned above. In the vent mechanism, the conductive member connected to the electrode terminal may have "slack" to allow the electrode terminal to open more smoothly. In other words, if the conductive member connected to the electrode terminal is not long enough, the presence of the conductive member itself may act as a resistance to the opening of the electrode terminal. Therefore, the length of the conductive member between the electrode assembly and the electrode terminal may be relatively long enough to not adversely hinder the opening of the electrode terminal (especially, it may be longer than the length of a conventional conductive member). In other words, the conductive member may have a length that does not create excessive tension between the electrode terminal and the electrode assembly that would hinder the opening of the electrode terminal. For example, the conductive member extending from the electrode assembly may be connected to the electrode terminal while being flexible and / or bent.

[0108] Furthermore, with regard to the vent mechanism, in the secondary battery of the present invention, the electrode terminals may have higher rigidity than the exterior body. In other words, at least a portion of the exterior body may have lower rigidity than the electrode terminals. For example, the exterior portion having the surface on which the electrode terminals are disposed may have lower rigidity than the electrode terminals. Conversely, the electrode terminals may have relatively higher rigidity than the exterior portion having the surface on which they are disposed. Such a difference in rigidity contributes to the realization of a more suitable vent mechanism. In the event of an abnormality, such as an excessive increase in internal cell pressure, the electrode terminals are less likely to deform due to their high rigidity, while the exterior portion forming the surface on which the electrode terminals are disposed can deform, making it easier for the bonding surface of the insulating seal member to peel off and the electrode terminals to open. By way of example only, the thickness of the exterior portion forming the surface on which the electrode terminals are disposed (e.g., the thickness of the lid-shaped member when the exterior body is composed of a lid-shaped member and a cup-shaped member) may be 170 μm or less. If the thickness of such an exterior portion is 170 μm or less, the exterior body is more likely to deform in the event of an abnormality, such as an excessive increase in cell internal pressure, and the electrode terminals are more likely to open as a vent mechanism. In other words, if the thickness of the exterior portion is greater than 170 μm (e.g., 200 μm or more), the exterior body is less likely to deform in the event of an abnormality, and the intended opening of the electrode terminals 200 is less likely to occur. The lower limit of the thickness of such a thin exterior portion is not particularly limited, but may be, for example, 50 μm or more and 170 μm or less. Note that, when an opening 150 is provided in the cover-shaped member 100B of the exterior body 100 shown in FIG. 4 and the electrode terminals 200 are disposed therein, the thickness of the cover-shaped member 100B may be smaller than the thickness of the electrode terminals 200. Because the cover-shaped member 100B alone constitutes the "exterior portion providing the surface on which the electrode terminals are disposed," it is easy to provide a thin member and, therefore, is likely to be a member that is easily deformed, such as by bending or distorting.

[0109] Although the above description refers to an embodiment in which the exterior body is composed of a cup-shaped member and a lid-shaped member, the present invention is not necessarily limited thereto. For example, the exterior body may be composed of two cup-shaped members. That is, the first metal exterior body and the second metal exterior body may each be cup-shaped members. In other words, the exterior body may be composed of at least a first metal exterior body that is a cup-shaped member and a second metal exterior body that is also a cup-shaped member. In this case, the first metal exterior body and the second metal exterior body that are cup-shaped members may be combined so that their side walls mate with each other to form the exterior body. The above-mentioned "exterior body opening" may be provided in the cup-shaped member of either the first metal exterior body or the second metal exterior body, and therefore, an electrode terminal and an insulating seal member may be provided in that cup-shaped member. Furthermore, when the exterior body is composed of a cup-shaped member and a lid-shaped member, although it has been mentioned that the exterior body opening is provided in the lid-shaped member, the present invention is not necessarily limited thereto. The exterior body opening may be provided in the cup-shaped member.

[0110] Although the above description refers to an embodiment in which the insulating seal member 300 is provided on the exterior body 100 so as to protrude outward from the electrode terminals 200 ( FIG. 10 ), the present invention is not necessarily limited to this. The insulating seal member may be provided so as to be hidden under the electrode terminals without protruding outward from the electrode terminals. For example, the insulating seal member may be provided only at a position approximately flush with or further inward from the outer edge of the electrode terminals.

[0111] Although the above description has been made regarding the electrode terminal having a planar outline in which the end portions of the straight and curved portions are shared, the shape of the shared portion between the straight and curved portions is not particularly limited. For example, the planar outline of the shared portion between the straight and curved portions may be rounded or angular.

[0112] In addition, although the non-terminal region has been mentioned above, it may specifically refer to the region mentioned in the later-described [Example]. In other words, the imaginary straight line L ｖand the outer contour 160 of the exterior body, a region R on the side not including the electrode terminal 200 may be regarded as the "non-terminal region" (see the right side of FIG. 16(B)). When there are multiple straight-line contours, the total region of the regions formed similarly for each of the straight-line contours (the total region including any one of the overlapping portions) may be regarded as the non-terminal region.

[0113] In the present disclosure, the "contour in a plan view of the electrode terminal at the surface where the electrode terminal contacts the insulating seal member" may be simply considered to be the "outer contour of the electrode terminal when the secondary battery is viewed from the outside." Similarly, the "contour in a plan view of the exterior body at the surface where the exterior body contacts the insulating seal member" may be simply considered to be the "outer contour of the exterior body when the secondary battery is viewed from the outside (particularly, the battery surface on which the electrode terminal is installed, from the outside)." For example, if the exterior body includes the above-mentioned lid-shaped member and the lid-shaped member has an opening (an opening through which a conductive member passes), the outline in a plan view, the outer outline in a plan view, or the outermost outline in a plan view of the lid-shaped member may be considered to be the "contour in a plan view of the exterior body at the surface where the exterior body contacts the insulating seal member." 3(A) and 3(B) and 10, the outline of the portion excluding the bent outer edge in a plan view can be considered to be "the outline of the exterior body in a plan view at the surface where the exterior body contacts the insulating seal member" (although this is merely an example, in FIG. 3, the outline indicated by reference number 160' can be considered to be the intended outline). Alternatively, the outline of the entire cover member in a plan view, including the bent outer edge (i.e., the outline of the cover member as a whole, including the outer edge, when viewed from the outside), can be considered to be "the outline of the exterior body in a plan view at the surface where the exterior body contacts the insulating seal member." Furthermore, when the lid-shaped member and the cup-shaped member in the outer casing are airtightly combined with each other, so that the outer edge contours of the lid-shaped member and the cup-shaped member can have the same shape (e.g., substantially the same or similar shapes) in a planar view, the outer edge contour of the cup-shaped member in a planar view may be considered to be "the planar view contour of the outer casing at the surface where the outer casing contacts the insulating seal member."

[0114] Aspects of the secondary battery disclosed herein are as follows: <1> A secondary battery comprising: an electrode assembly; an exterior housing that houses the electrode assembly; and an electrode terminal that is disposed on the exterior housing and electrically connected to the electrode assembly via a conductive member, wherein the electrode terminal and the exterior housing are bonded to each other by an insulating seal member (or insulating member) that is interposed between the electrode terminal and the exterior housing and provided around an opening of the exterior housing through which the conductive member passes, wherein a planar outline of the electrode terminal at a surface where the electrode terminal contacts the insulating seal member is composed of both straight portions and curved portions, and the planar outline of the exterior housing at a surface where the exterior housing contacts the insulating seal member includes a curve, and the curved portion of the electrode terminal and a portion of the curve of the exterior housing face each other. <2> The secondary battery described in <1>, wherein the straight portion of the electrode terminal faces a curve that is different from the portion of the exterior housing. <3> The secondary battery according to <1> or <2>, wherein one end portion of the straight portion and one end portion of the curved portion are shared so that the straight portion and the curved portion are continuous in the outline of the electrode terminal in a plan view. <4> The secondary battery according to any one of <1> to <3>, wherein the curved portion accounts for a relatively larger proportion of the outline of the electrode terminal in a plan view than the straight portion. <5> The secondary battery according to any one of <1> to <4>, wherein the curved portion is arc-shaped in the outline of the electrode terminal in a plan view. <6> The secondary battery according to any one of <1> to <5>, wherein the curved portion is positioned relatively closer to the curvature of the exterior body than the straight portion of the electrode terminal. <7> The secondary battery according to any one of <1> to <6>, which has two lead-out members for external connection, one of which is provided on the same main battery surface, and the same main battery surface corresponds to the battery surface formed by the electrode terminals and the exterior body. <8> The secondary battery according to <7>, wherein one of the lead-out members is provided on the electrode terminals, and the other of the lead-out members is provided on a non-terminal region of the same main battery surface other than the electrode terminals.<9> The secondary battery according to any one of <1> to <8>, wherein the outline of the electrode terminal in a plan view is composed of a single straight portion and a single curved portion. <10> The secondary battery according to any one of <1> to <9>, wherein the outline of the opening of the exterior body in a plan view is composed of both straight portions and curved portions. <11> The secondary battery according to any one of <1> to <10>, wherein the outline of the insulating seal member in a plan view is composed of both straight portions and curved portions. <12> The secondary battery according to any one of <1> to <11>, wherein the electrodes of the electrode assembly include a positive electrode and a negative electrode capable of absorbing and releasing lithium ions.

[0115] A model study was carried out in relation to the present invention. Specifically, a simulation was carried out on the area of ​​the non-terminal region on the main surface of the battery.

[0116] A hypothetical battery 1000', which served as the base for the design, is shown in Figures 15(A) and 15(B). The following assumptions were made for this hypothetical battery: The battery has an overall cylindrical shape. An electrode terminal is attached to the top surface of the cylindrical battery via an insulating seal member. The lid member is joined to the can member at its outer periphery by laser welding. The outer diameter (a) of the lid member is 12 mm. The distance (b) between the outer diameter of the lid member and the insulating seal member is 1 mm or more to prevent the insulating seal member from being affected by heat when the lid member's outer periphery is laser-welded. The insulating seal member is slightly larger than the electrode terminals, with a clearance (c) of 0.5 mm on each side. The seal distance (d) is 1.5 mm or more to ensure adhesive strength and long-term reliability. The lid hole size required to connect the internal conductive tab inside the cell is 4 mm or more in the short side distance (e) of the hole. Based on the above assumptions, a schematic diagram of the configurations of the example and comparative example is shown in Figure 16(A). In FIG. 16A, the can member is depicted in a simplified form, and the lid member is also depicted as a simple flat plate.

[0117] FIG. 16B is a schematic diagram comparing the effective area of ​​the non-terminal region of the lid member that can be substantially used for installing the external lead-out member (hereinafter simply referred to as the "non-terminal region area") between the Example and the Comparative Example, with reference to the model shown in FIG. 16A. As shown in FIG. 16B, it was found that the Example can achieve a larger non-terminal region area R, thereby ensuring a larger area for connecting the external lead-out member. Furthermore, FIG. 17 is a graph showing the change in the non-terminal region area when the dimension a (outer diameter of the lid member) under the preconditions is changed. As shown in the graph in FIG. 17, it was found that, under the preconditions, a dimension a greater than φ10 mm can be substantially significant in terms of the non-terminal region area, and this effect becomes more pronounced as the dimension a increases.

[0118] The effects of the above embodiment are merely exemplary, and the present invention is not limited to the above, and may have additional effects.

[0119] The secondary battery according to the present invention can be used in various fields where the use of batteries or the storage of electricity is expected. Although merely illustrative, the secondary battery of the present invention can be used in the fields of electricity, information, and communications where electric and electronic devices are used (for example, electric and electronic devices or mobile devices including mobile phones, smartphones, notebook computers, digital cameras, activity meters, arm computers, electronic paper, wearable devices, RFID tags, card-type electronic money, smart watches, and other small electronic devices), household and small industrial applications (for example, power tools, golf carts, and 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 systems, road conditioners, smart grids, and general household installation-type power storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (dose management systems), and the IoT field, and space and deep-sea applications (for example, space probes, submersible research vessels, and the like).

[0120] Finally, we would like to add a few words about the disclosures of Japanese Patent Laid-Open No. 2019-046639 (Patent Document 1) and Japanese Patent Laid-Open No. 2020-202071 (Patent Document 2). In the battery disclosed in Patent Document 1, the electrode terminal diameter is large, and the exposed area of ​​the exterior material on the battery surface where the electrode terminals are provided is small. Therefore, it is not generally expected that a component (e.g., a tab) for external output will be connected to the exterior material surface of the battery. Furthermore, in the structure disclosed in Patent Document 2, two circular electrode terminals are attached to the same surface of the battery, and each terminal is small, making it impossible to ensure a large sealing area for the insulating seal material for each terminal. In other words, even if the configuration disclosed in Patent Document 2 ensures initial airtight sealing of the battery, the two individually small terminals may increase the amount of electrolyte volatilization from inside the cell and the amount of moisture intrusion from outside the cell, which is thought to make it impossible to ensure long-term reliability of the battery. In addition, the adhesive strength of the electrode terminals cannot be increased.

[0121] 1 Positive electrode 2 Negative electrode 5 Electrode configuration 10 Electrode assembly 100 Exterior body 100A Cup-shaped member 100B Lid-shaped member 110A Terminal region 110B Non-terminal region 150 Exterior body opening 155 Exterior body opening edge 158 Exterior body surface 160 Plan view contour of exterior body / exterior contour of exterior body (exterior contour of secondary battery) 160' Plan view contour of exterior body / exterior contour of exterior body (exterior contour of secondary battery) 160a Curved portion of the exterior body outer contour facing the curved contour portion of the electrode terminal in plan view 160b Curved portion of the exterior body outer contour facing the linear contour portion of the electrode terminal in plan view 180 Contour of exterior body opening 182 Straight portion of the contour of the exterior body opening 184 Curved portion of the contour of the exterior body opening 200 Electrode terminal 250 Plan view contour of the electrode terminal 252 Straight portion 252a One end portion of straight portion 252b The other end portion of straight portion 252c Halving point of straight portion 254 Curved portion 254' Arc contour 254a One end portion of curved portion 254b The other end portion of curved portion 254c Halving point of curved portion 300 Insulating seal member 350 Outer contour of insulating seal member 352 Straight portion of outer contour of insulating seal member 354 Curved portion of outer contour of insulating seal member 360 Inner contour of insulating seal member 362 Straight portion of inner contour of insulating seal member 364 Curved portion of inner contour of insulating seal member 400 Conductive member 500A External lead-out member 500B External lead-out member 600 Terminal-mounted battery surface (same main battery surface) 1000 Secondary battery Lw Distance (shortest distance) between curved portion of electrode terminal and outer contour of exterior body Ls Distance (shortest distance) between the straight part of the electrode terminal and the outer contour of the exterior body Lv Virtual line extending from the straight contour M Center of the battery U Maximum curvature point 1000' Virtual battery assumed in the simulation 100' Exterior body of the virtual battery 100B' Lid-like member of the virtual battery 200' Electrode terminal of the virtual battery 300' Insulating seal member of the virtual battery

Claims

1. electrode assembly, an exterior housing that houses the electrode assembly; and An electrode terminal that is disposed on the exterior body and is electrically connected to the electrode assembly via a conductive member. and the electrode terminal and the exterior body are bonded to each other by an insulating seal member interposed between the electrode terminal and the exterior body and provided around an opening of the exterior body through which the conductive member passes, A secondary battery, wherein the planar view contour of the electrode terminal at the surface where the electrode terminal contacts the insulating seal member is composed of both straight portions and curved portions, the planar view contour of the outer casing at the surface where the outer casing contacts the insulating seal member includes a curve, and the curved portion of the electrode terminal and a portion of the curve of the outer casing face each other.

2. The secondary battery according to claim 1 , wherein the straight portion of the electrode terminal faces the curve that is different from the part of the exterior body.

3. 2. The secondary battery according to claim 1, wherein one end portion of the straight portion and one end portion of the curved portion are shared with each other so that the straight portion and the curved portion are continuous in the planar view contour of the electrode terminal.

4. The secondary battery according to claim 1 , wherein a proportion of the curved portion in the plan view outline of the electrode terminal is greater than a proportion of the straight portion.

5. The secondary battery according to claim 1 , wherein the curved portion is arc-shaped in the plan view contour of the electrode terminal.

6. The secondary battery according to claim 1 , wherein the curved portion is positioned relatively closer to the curvature of the exterior body than the straight portion of the electrode terminal.

7. 2. The secondary battery according to claim 1, comprising two external lead-out members for external connection, one and the other of the external lead-out members being provided on a same battery main surface, the same battery main surface corresponding to a battery surface constituted by the electrode terminal and the exterior body.

8. 8. The secondary battery according to claim 7, wherein the one of the external lead-out members is provided for the electrode terminal, and the other of the external lead-out members is provided for a non-terminal region of the same battery main surface that is a region other than the electrode terminal.

9. The secondary battery according to claim 1 , wherein the planar outline of the electrode terminal is formed by a single straight portion and a single curved portion.

10. The secondary battery according to claim 1 , wherein a contour of the opening of the exterior body in a plan view is made up of both straight lines and curved lines.

11. 2. The secondary battery according to claim 1, wherein the insulating seal member has a contour in a plan view that is made up of both straight portions and curved portions.

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