Secondary battery and manufacturing method thereof

Abstract

Provided is a secondary battery comprising an electrode wound body formed by winding an electrode-constituting layer configured from a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The electrode wound body includes a central cavity which extends centrally along a winding axis, and any one of the positive electrode and the negative electrode is provided, at an end surface of the electrode wound body, with a current collecting foil extended portion in which a current collector extends further outward than the other electrode. The current collecting foil extended portion in the vicinity of the central cavity is bent so as to be folded back toward the central cavity, and the electrode-constituting layer is offset from the end surface toward an interior of the electrode wound body.

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Special Publication No. 2015-519689 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have realized that conventional secondary batteries have problems to be overcome and have found the need to take measures to address these problems. Specifically, the present inventors have found the following problems.

[0005] Patent Document 1 discloses a secondary battery in which a current collector is welded to a foil-like body at the end of an electrode plate in an electrode winding. In such a secondary battery, the foil-like body is subjected to a shaping process using high-frequency vibration, and the current collector is welded to the shaped foil-like body. By using high-frequency vibration during the shaping process, the foil-like body of the electrode plate is softened and shaped so that the foil-like bodies become entangled with each other.

[0006] The inventors of the present application have found that such a shaping process can cause problems for the electrode winding when the foil is compressed by high-frequency vibrations. Specifically, they have found that when the foil is compressed, it can enter the cavity in the center of the electrode winding, causing contact between the electrodes and resulting in a short circuit.

[0007] The present disclosure has been made in view of the above-mentioned problems. That is, a main object of the present disclosure is to provide a secondary battery having a structure more suitable for preventing short circuits, and a method for manufacturing the same. [Means for solving the problem]

[0008] The secondary battery according to the present disclosure comprises an electrode winding body formed by winding an electrode constituent layer composed of a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, the electrode winding body having a central cavity extending centrally along the winding axis, and at an end face of the electrode winding body, one of the positive electrode and the negative electrode has a current collector foil extension portion in which the current collector extends outward more than the other electrode, the current collector foil extension portion near the central cavity is bent so as to fold back toward the central cavity, and the electrode constituent layer is shifted from the end face toward the interior of the electrode winding body.

[0009] Furthermore, a manufacturing method according to the present disclosure includes a step of winding an electrode configuration layer composed of a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode to form an electrode wound body while leaving a central cavity, and a step of shaping an end surface of the electrode wound body, wherein the step of forming the electrode wound body includes winding the electrode so that, at the end surface, a current collector extension portion of one of the positive electrode and the negative electrode extends outward more than that of the other electrode, and winding the electrode configuration layer such that, near the central cavity, the electrode configuration layer is shifted from the end surface toward the interior of the electrode wound body, and the shaping step includes bending the current collector foil extension portion near the central cavity so as to fold it back. [Effects of the Invention]

[0010] The secondary battery according to the present disclosure has a structure that is more suitable for preventing short circuits.

[0011] Specifically, at the end face of the electrode winding, one of the positive and negative electrodes has a current collector extension portion in which the current collector extends further outward than the other electrode. This current collector extension portion has a bent shape that folds back toward a central cavity provided in the center of the electrode winding. The electrode component layer located near the central cavity is arranged so as to be shifted inward from the end face of the electrode winding. With this structure, the bent current collector extension portion and the electrode component layer are spaced apart near the central cavity, making it possible to more effectively prevent short circuits in the electrode winding.

[0012] In addition, in the method for manufacturing a secondary battery according to the present disclosure, in the electrode winding process, the electrode is wound so that the electrode constituent layer constituting the vicinity of the central cavity is shifted toward the inside of the electrode winding body while the current collector extension of one electrode extends from the end face of the electrode winding body. Next, in the shaping process, the current collector extension is bent to shape the end face of the electrode winding body. Through the above process, the current collector extension and the electrode constituent layer are spaced apart from each other, thereby obtaining a secondary battery that can more effectively prevent short circuits. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of an electrode configuration layer. [Figure 2] FIG. 2 is a schematic perspective view showing the appearance of an example of a secondary battery according to the present disclosure. [Figure 3] FIG. 3 is a schematic cross-sectional view of the secondary battery of FIG. 2 taken along line AA passing through the winding axis and viewed in the direction of the arrow. [Figure 4] FIG. 4 is a schematic perspective view showing an electrode winding body constituting a secondary battery according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a schematic enlarged partial cross-sectional view of the BB cross section near the center of the electrode winding body of FIG. 4, as viewed in the direction of the arrow. [Figure 6]FIG. 6 is a schematic diagram for explaining constituent members of an electrode winding body that constitutes a secondary battery according to an embodiment of the present disclosure. [Figure 7] FIG. 7 is a schematic perspective view for explaining the winding mode of an electrode winding body according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a schematic perspective view showing a wound electrode body according to an embodiment of the present disclosure after winding. [Figure 9] FIG. 9 is a schematic cross-sectional view of the electrode winding body taken along line CC near the center of the electrode winding body of FIG. 8, viewed in the direction of the arrow. [Figure 10] FIG. 10 is a schematic partial enlarged cross-sectional view of the vicinity of the center of an electrode winding body after winding according to an embodiment of the present disclosure. [Figure 11] FIG. 11 is a schematic diagram showing constituent members of an electrode winding body according to an embodiment of the present disclosure. [Figure 12] FIG. 12 is a schematic plan view for explaining end face shaping according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] A secondary battery according to an embodiment of the present disclosure will be described in more detail below. While the description will be made with reference to drawings as needed, various elements in the drawings are merely shown schematically and for illustrative purposes to facilitate understanding of the present disclosure, and the appearance or dimensional ratios may differ from those of the actual objects.

[0015] The "vertical direction" and "horizontal direction" directly or indirectly described in this specification correspond to the vertical direction and horizontal direction in the drawings. Furthermore, the "cross-sectional view" directly or indirectly described in this specification is based on a virtual cross section of the secondary battery cut along the direction along the winding axis of the electrode winding body that constitutes the secondary battery, or along a direction perpendicular to the winding axis. Furthermore, the "plan view" used in this specification is based on a sketch of the object as seen from above or below along the direction of the winding axis. Unless otherwise specified, the same symbols or symbols indicate the same components or parts or the same meanings.

[0016] Furthermore, in this specification, "perpendicular to the winding axis" and "substantially perpendicular" do not necessarily mean completely "perpendicular" and include situations where the angle is slightly different from the winding axis (for example, the angle formed with the winding axis is in the range of 90°±20°, e.g., up to 90°±10°).

[0017] Furthermore, in this specification, "substantially parallel" does not necessarily mean completely "parallel," but includes a state where the parallelism is slightly deviated from the parallelism (for example, within a range of ±20° from completely parallelism, e.g., within a range of ±10°).

[0018] [Basic structure of secondary batteries] 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 disclosure is not limited to the name, and may also include, for example, an electricity storage device.

[0019] FIG. 1 shows a schematic cross-sectional view of an exemplary electrode wound body 50. A secondary battery according to the present disclosure includes an electrode wound body 50 including an electrode configuration layer 5 including a positive electrode 1, a negative electrode 2, and a separator 3. As shown in the figure, the electrode wound body 50 may have a wound structure in which the electrode configuration layer 5 is wound in a spiral shape. In other words, the electrode wound body 50 may have a wound structure in which the electrode configuration layer 5, which is relatively long and extends in a strip or long shape and includes the positive electrode 1, the negative electrode 2, and the separator 3 disposed between the positive electrode 1 and the negative electrode 2, is wound in a roll shape. In a secondary battery according to the present disclosure, such an electrode wound body 50 is enclosed in an exterior body together with an electrolyte (e.g., a non-aqueous electrolyte).

[0020] The positive electrode 1 is composed of at least a positive electrode material layer 12 and a positive electrode current collector 11 (see FIG. 5). In the positive electrode 1, a positive electrode material layer is provided on at least one side of the positive electrode current collector, and the positive electrode material layer contains a positive electrode active material as an electrode active material. For example, the positive electrode in the electrode winding body may have a positive electrode material layer provided on both sides of the positive electrode current collector, or may have a positive electrode material layer provided on only one side of the positive electrode current collector. The positive electrode current collector does not necessarily have to have a positive electrode material layer on the entire surface of both sides or one side. For example, one end or both ends located on the long side of the positive electrode current collector (before winding) may have a portion on both sides where no positive electrode material layer is provided, to provide a "current collector extension" described below.

[0021] The negative electrode 2 is composed of at least a negative electrode material layer 22 and a negative electrode current collector 21 (see FIG. 5). In the negative electrode 2, a negative electrode material layer is provided on at least one side of the negative electrode current collector, and the negative electrode material layer contains a negative electrode active material as an electrode active material. For example, the negative electrode in the electrode winding body may have a negative electrode material layer provided on both sides of the negative electrode current collector, or may have a negative electrode material layer provided on only one side of the negative electrode current collector. The negative electrode current collector does not necessarily have to have a negative electrode material layer on the entire surface of both sides or one side. For example, one end or both ends located on the long side of the negative electrode current collector (before winding) may have a portion on both sides where no negative electrode material layer is provided, to provide a "current collector extension."

[0022] The electrode active materials contained in the positive electrode 1 and the negative electrode 2, i.e., the positive electrode active material and the negative electrode active material, are materials directly involved in the transfer of electrons in the 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 material layer" and the "negative electrode active material contained in the negative electrode material layer" provide ions to the electrolyte, and these ions move between the positive electrode 1 and the negative electrode 2, transferring electrons and causing charge and discharge. The positive electrode material layer and the negative electrode material layer may be layers capable of absorbing and desorbing lithium ions. In other words, the secondary battery according to the present disclosure may be a nonaqueous electrolyte secondary battery in which lithium ions move between the positive electrode 1 and the negative electrode 2 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 disclosure corresponds to a so-called "lithium ion battery," in which the positive electrode 1 and the negative electrode 2 have layers capable of absorbing and desorbing lithium ions.

[0023] 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.

[0024] 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 may be preferably included as the positive electrode active material in the positive electrode layer of the secondary battery according to the present disclosure. 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 included as a single species or in combination of two or more species.

[0025] The binder that can be contained in the positive electrode material layer is not particularly limited, and can be, for example, at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, etc.

[0026] The conductive additive that can be contained in the positive electrode layer is not particularly limited, and may be at least one selected from the group consisting of carbon black such as thermal black, furnace black, channel black, ketjen black, and acetylene black, graphite, carbon fibers such as carbon nanotubes and vapor-grown carbon fibers, metal powders such as copper, nickel, aluminum, and silver, and polyphenylene derivatives.

[0027] 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.

[0028] Examples of various carbon materials for the negative electrode active material include graphite (e.g., natural graphite and / or artificial graphite), hard carbon, soft carbon, and / or diamond-like carbon. Graphite, in particular, has high electronic conductivity and excellent adhesion to the negative electrode current collector. Examples of oxides for the negative electrode active material include at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide, and lithium oxide. The lithium alloy for the negative electrode active material may be any metal capable of forming an alloy with lithium, such as 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, and / or La. Such oxides may have an amorphous structure, for example. This is because they are less susceptible to degradation due to inhomogeneities such as grain boundaries or defects.

[0029] The binder that can be contained in the negative electrode layer is not particularly limited, and can be, for example, at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resins, and polyamide-imide resins.

[0030] The conductive additive that can be contained in the negative electrode material layer is not particularly limited. For example, the conductive additive can be at least one selected from the group consisting of carbon black such as thermal black, furnace black, channel black, ketjen black, and acetylene black; graphite; carbon fibers such as carbon nanotubes and vapor-grown carbon fibers; metal powders such as copper, nickel, aluminum, and silver; and polyphenylene derivatives. The negative electrode material layer may also contain a component derived from a thickener component (e.g., carboxymethyl cellulose) used during battery production.

[0031] The positive electrode current collector and the negative electrode current collector used in the positive electrode and the negative electrode are components that contribute to collecting and supplying electrons generated in the active material due to the battery reaction. Such current collectors may be sheet-shaped metal components and may be porous or perforated. For example, the current collectors may be metal foil, punched metal, mesh, and / or expanded metal. The positive electrode current collector used in the positive electrode may be made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel, etc. For example, the positive electrode current collector may be aluminum foil. On the other hand, the negative electrode current collector used in the negative electrode may be made of a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel, etc. For example, the negative electrode current collector may be copper foil.

[0032] The separator used between the positive electrode and the negative electrode is a member provided from the viewpoint of preventing short circuits due to contact between the positive and negative electrodes and maintaining electrolyte retention. In other words, the separator is a member that allows ions to pass through while preventing electrical contact between the positive electrode and the negative electrode. For example, the separator is a porous or microporous insulating member that 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 "microporous membrane made of PE" and a "microporous membrane made of PP."

[0033] The surface of the separator may be covered with an inorganic particle coating layer, an adhesive layer, or the like. The surface of the separator may have adhesive properties. In the present disclosure, the separator should not be limited to a particular name. For example, the separator may be a solid electrolyte, a gel electrolyte, insulating inorganic particles, or the like having similar functions.

[0034] In the secondary battery disclosed herein, an electrode winding consisting of electrode constituent layers including a positive electrode, a negative electrode, and a separator is enclosed in an exterior body together with an electrolyte. When the positive electrode and negative electrode have layers capable of absorbing and releasing lithium ions, the electrolyte may be a "non-aqueous" electrolyte such as an organic electrolyte or an organic solvent. In other words, the electrolyte may be 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 assists the migration of metal ions in the battery reaction.

[0035] The nonaqueous electrolyte is an electrolyte containing a solvent and a solute. Specific examples of the solvent for the nonaqueous electrolyte include a solvent containing at least a carbonate. The carbonate may be a cyclic carbonate and / or a chain carbonate. The cyclic carbonate may be, but is not limited to, at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC).

[0036] 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 non-aqueous electrolyte, such as a mixture of ethylene carbonate and diethyl carbonate. The solute of the non-aqueous electrolyte may be a conventional solute. Specific examples of the solute of the non-aqueous electrolyte include Li salts such as LiPF6 and / or LiBF4.

[0037] FIG. 2 is a schematic perspective view showing the appearance of an example of a secondary battery 100 according to the present disclosure. The exterior body 60 that houses the electrode winding may be a hard case and may be composed of components such as a main body 61 and a lid 62. For example, the main body 61 may be a cup-shaped component having a side surface of the exterior body 60 and a main surface (typically, a bottom or lower surface) that is continuous with the side surface. The lid 62 may be a component that is combined with the cup-shaped main body 61 to cover it (preferably, is provided so as to isolate the hollow space inside the main body 61 from the outside). When the exterior body 60 is composed of the main body 61 and the lid 62, the main body 61 and the lid 62 are sealed together after housing the electrode winding, the electrolyte, and, if desired, electrode terminals, etc. The method for sealing the exterior body 60 is not particularly limited, and examples thereof include laser irradiation.

[0038] Any material that can be used to form a hard case-type exterior body in the field of secondary batteries can be used as the material for the main body 61 and the lid 62. Such a material may be a conductive material through which electrons can move, or an insulating material through which electrons cannot move. From the perspective of electrode extraction, the material for the exterior body is preferably a conductive material.

[0039] Conductive materials include, for example, conductive materials such as silver, gold, copper, iron, tin, platinum, aluminum, nickel, and / or stainless steel. Insulating materials include, for example, insulating polymeric materials such as polyester (e.g., polyethylene terephthalate), polyimide, polyamide, polyamideimide, and / or polyolefin (e.g., polyethylene and / or polypropylene).

[0040] From the standpoint of electrical conductivity and rigidity, both the body and the lid may be constructed of stainless steel. As defined in JIS G 0203, "Terminology of Iron and Steel," stainless steel is an alloy steel containing chromium or chromium and nickel, generally with a chromium content of approximately 10.5% or more. Examples of such stainless steel include martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, austenitic-ferritic stainless steel, and / or precipitation-hardening stainless steel.

[0041] The dimensions of the main body and lid of the exterior body are determined mainly according to the dimensions of the electrode winding body. For example, the exterior body may have dimensions that prevent the electrode winding body from moving within the exterior body when the electrode winding body is housed therein. Preventing movement of the electrode winding body prevents damage to the electrode winding body due to impacts and improves the stability of the secondary battery.

[0042] The exterior may be a flexible case such as a pouch made of a laminate film. The laminate film may be configured to have at least a metal layer (e.g., aluminum) and an adhesive layer (e.g., polypropylene and / or polyethylene) laminated together, with an additional protective layer (e.g., nylon and / or polyamide) laminated on top.

[0043] The thickness of the exterior body (i.e., the wall thickness) is not particularly limited, but may be 10 μm or more and 200 μm or less, for example, 50 μm or more and 100 μm or less. The thickness of the exterior body is calculated by averaging the values ​​measured at any 10 points.

[0044] Secondary batteries are generally provided with electrode terminals. For example, the electrode terminal for the positive electrode and the electrode terminal for the negative electrode may be provided on different surfaces of the exterior body. In other words, the electrode terminals for the positive electrode and the negative electrode may be provided at opposite ends of the exterior body in the winding axis direction of the electrode winding body.

[0045] The electrode terminals may be made of a material with high electrical conductivity, and may be made of at least one material selected from the group consisting of silver, gold, copper, iron, tin, platinum, aluminum, nickel, and stainless steel, although the material is not particularly limited thereto.

[0046] The electrode terminal is not particularly limited and may have any configuration. For example, the electrode terminal may be made of a single material or may be made of multiple materials. An electrode terminal made of multiple materials (hereinafter also referred to as an "electrode terminal structure") may be made of, for example, a rivet portion, an inner terminal, and / or a gasket portion.

[0047] The rivet portion and the inner terminal may be made of a material through which electrons can be transferred. For example, the rivet portion and the inner terminal may each be made of a conductive material such as silver, gold, copper, iron, tin, platinum, aluminum, nickel, and / or stainless steel. The gasket portion may be made of an insulating material. For example, the gasket portion may be made of an insulating polymer material such as polyester (e.g., polyethylene terephthalate), polyimide, polyamide, polyamideimide, and / or polyolefin (e.g., polyethylene and / or polypropylene).

[0048] The electrode terminal structure is not particularly limited, and may be, for example, fitted into and inserted into an opening in the exterior body. The electrode terminal structure may include a conductive rivet portion mainly for leading the electrode to the outside, an outer gasket portion for preventing leakage of electrolyte while ensuring electrical insulation between the rivet portion and the exterior body, an inner terminal for ensuring electrical connection between the rivet portion and the electrode wound body, and an inner gasket portion for preventing leakage of electrolyte while ensuring electrical insulation between the inner terminal and the exterior body.

[0049] [Features of the Secondary Battery Disclosed Herein] FIG. 2 is a schematic perspective view showing the appearance of an example of a secondary battery 100 according to the present disclosure. FIG. 4 is a schematic perspective view showing the appearance of an example of an electrode winding 50 constituting a secondary battery according to the present disclosure. In the figure, the secondary battery 100 and the electrode winding 50 have a substantially cylindrical shape, but this is not necessarily limited thereto. For example, the electrode winding 50 may have a substantially elliptical cylindrical shape. That is, the cross-sectional shape of the electrode winding 50 as viewed from the direction along the winding axis is not particularly limited and can be, for example, a substantially circular, substantially elliptical, or substantially rectangular shape. In this specification, a substantially rectangular shape includes a shape having chamfered or rounded corners, regardless of the accuracy of the corners or surfaces of the shape.

[0050] FIG. 3 is a schematic cross-sectional view of the secondary battery of FIG. 2 taken along line AA passing through the winding axis P and viewed in the direction of the arrow. The electrode wound body 50 housed in the outer casing has a central cavity 55 (see FIG. 5) extending centrally along the winding axis. In other words, in one embodiment of the present disclosure, the electrode configuration layer 5 (see FIG. 5) may be wound so that a hollow portion is provided at the center of the winding. The central cavity 55 may have a substantially cylindrical shape that is elongated in the direction of the winding axis P. The shape of the central cavity 55 in plan view may be, for example, a substantially circular shape or a substantially elliptical shape having a predetermined inner diameter and centered approximately on the winding axis P. As shown in FIG. 3, for example, a center pin 90 may be inserted into the central cavity 55.

[0051] The center pin 90 may be open at both ends in the direction of the winding axis P and may have a length extending from one end of the electrode winding body 50 to the other. The cross-sectional shape of the center pin 90 in a plan view is not particularly limited and may be, for example, approximately circular, approximately elliptical, or approximately C-shaped. The diameter of the center pin 90 may be constant along the winding axis direction, or may have a tapered shape at least at one end in the axial direction. The material of the center pin 90 is not particularly limited, but may include at least one selected from the group consisting of copper, iron, aluminum, nickel, titanium, and stainless steel.

[0052] The center pin 90, which is inserted through the center of the winding of the electrode winding body 50, contributes to improving the safety of the secondary battery. Specifically, it can suppress deformation of the electrode winding body 50 caused by expansion of the electrode due to external impact or repeated charging and discharging. Furthermore, if gas is generated inside the secondary battery, the gas is vented in the direction of the winding axis through the opening at the end of the center pin 90, thereby suppressing deformation and explosion of the secondary battery.

[0053] As shown in FIG. 3 , the secondary battery of the present disclosure may further include current collector plates 70 (71, 72) that electrically connect either the electrode terminal 81 or the exterior housing 60 to the electrode winding body 50. As shown in the figure, the current collector plate 70 may be electrically connected to at least a portion of the end surface of the electrode winding body 50. In other words, the current collector plate 70 may be combined with the electrode winding body 50 so as to cover at least a portion of the end surface of the electrode winding body 50. That is, the positive and negative electrodes that constitute the electrode winding body 50 may be electrically connected to the electrode terminal 81 or the exterior housing 60, respectively, via the current collector plate 70 that is connected to at least a portion of the end surface of the electrode winding body 50. That is, the positive and negative current collector plates 70 may be electrically led to the outside via the electrode terminal 81 and / or the exterior housing 60.

[0054] The current collector 70 may be made of a material that allows electron transfer. For example, the current collector 70 may be made of a conductive material such as silver, gold, copper, iron, tin, platinum, aluminum, nickel, and / or stainless steel. The shape of the current collector is not particularly limited and may be, for example, strip-shaped, flat, or substantially circular. As shown in FIG. 3 , the current collector 70 may include an elongated portion 76 for connection to an electrode terminal 81 and / or the outer casing 60. The elongated portion 76 may be formed as an integral member with the current collector 70. By forming the elongated portion 76 as an integral member, the step of connecting the elongated portion 76 and the current collector can be omitted during the assembly of the secondary battery.

[0055] FIG. 4 shows a schematic perspective view of an electrode winding 50 of a secondary battery according to an embodiment of the present disclosure. FIG. 5 is a schematic enlarged cross-sectional view of a section taken along line BB passing through the winding axis P in the vicinity of the center 50′ of the electrode winding 50 of FIG. 4, as viewed in the direction of the arrow. As shown in FIG. 5, the secondary battery according to the present disclosure includes an electrode layer 5 composed of a positive electrode 1, a negative electrode 2, and a separator 3 disposed between the positive electrode 1 and the negative electrode 2, and typically further includes an electrolyte (not shown). In addition, in the electrode winding 50 of the secondary battery according to an embodiment of the present disclosure, at least one of the positive electrode 1 and the negative electrode 2 has a current collector extension 40. In the present disclosure, the term “current collector extension” refers to a portion of the electrode in which the current collector does not have an electrode material layer and extends from an end edge of the electrode. In other words, the “current collector extension” may be an exposed portion of the current collector (preferably, a portion where no electrode material layer is provided) extending from one of the end edges constituting the end face of the electrode winding. As described above, in the secondary battery of the present disclosure, the current collectors of the positive electrode and / or negative electrode may be metal foils. Therefore, the "current collector extension" can also be referred to as an "exposed current collector portion" or an "extended current collector foil portion."

[0056] A secondary battery according to an embodiment of the present disclosure includes a current collector extension 40 of either the positive electrode 1 or the negative electrode 2 at an end of an electrode winding 50. More specifically, at an end of the electrode winding 50, either the positive electrode 1 or the negative electrode 2 has a current collector extension 40 in which the current collector extends further outward than the other electrode. Here, "outward" refers to the outside of the electrode winding 50 in the direction of the winding axis P. In other words, the secondary battery according to the present disclosure includes either a positive electrode current collector extension 41 that extends further in the direction of the winding axis P than the negative electrode 2, or a negative electrode current collector extension 42 that extends further in the direction of the winding axis P than the positive electrode 1. Furthermore, in one embodiment, the electrode winding body 50 may include both the positive electrode current collector extension portion 41 and the negative electrode current collector extension portion 42, and the positive electrode current collector extension portion 41 and the negative electrode current collector extension portion 42 may extend at different ends of the electrode winding body 50. In other words, the positive electrode current collector extension portion 41 and the negative electrode current collector extension portion 42 may extend in directions facing each other along the winding axis P.

[0057] As shown in FIG. 5 , in a cross-sectional view passing through the winding axis P, at least a portion of the current collector extension 40 may be substantially linear. Here, "substantially linear" is not limited to a straight line and includes a current collector extension that is bent at a small angle (an interior angle close to 180°) and continues, as shown in FIG. 5 . For example, "substantially linear" includes a current collector extension that is bent at an interior angle of approximately 150° or more, or approximately 160° or more, and continues. As shown in FIG. 5 , in one embodiment of the present disclosure, the current collector extension 40 may extend substantially linearly and bend near the end surface 51. At least a portion of the bent current collector extension 40 may be exposed at the end surface 51 of the electrode winding. In other words, the end surface 51 of the electrode winding may be constituted by at least a portion of the bent current collector extension 40. That is, at least a portion of the current collector extension 40 may be bent at the end surface 51 of the electrode winding body so as to provide a substantially flat surface that is substantially perpendicular to the winding axis P. By forming a substantially flat surface on the end surface 51 of the electrode winding body, the current collector plate 70 (see FIG. 3) and the end surface 51 of the electrode winding body can be connected over a wider contact area. Here, in this specification, "substantially flat" simply means a planar shape when viewed macroscopically. In other words, it does not refer to a surface that is flat in the strict physical sense, but rather includes a shape that has minute irregularities when viewed microscopically, or a case where there is slight distortion overall or partially.

[0058] In the present disclosure, "bending" includes at least curvature and / or folding. "Bending" refers to bending in a bay-like (or bow-like) shape in a cross-sectional view (i.e., bending in a substantially curved line), meaning a rounded bend, and also includes flexure. "Bending" refers to bending at an acute or angular angle in a cross-sectional view (i.e., bending in a substantially linear line). In the secondary battery of the present disclosure, the current collector extension 40 may have a wave shape that repeats multiple bends. That is, in a cross-sectional view passing through the winding axis P, the current collector extension 40 may extend in a serpentine manner due to the bent shape.

[0059] The current collector extension 40 located near the central cavity 55 may be bent toward the winding center of the electrode winding 50. Furthermore, the current collector extension 40 located near the central cavity 55 may have a larger curvature than the current collector extension 40 located on the outer periphery of the electrode winding 50. Specifically, the current collector extension 40 may be bent so as to turn back toward the central cavity 55 near the central cavity 55. That is, near the central cavity 55, the current collector extension 40 may have a shape that extends from the end face 51 of the electrode winding in the direction of the winding axis P, bends toward the inner periphery, and then bends toward the interior of the electrode winding 50. The end of the current collector extension 40 bent toward the interior may be located within the central cavity 55. More specifically, the inner side surface (i.e., inner wall surface) of the central cavity 55 located on the end face 51 side of the electrode winding may be formed by the folded current collector extension 40. In particular, the current collector extension 40 closest to the central cavity 55 may be greatly bent so as to form a convex shape toward the end face 51 of the electrode winding. In other words, the tip of the current collector extension 40 closest to the central cavity 55 may be positioned more inward than the tips of the current collector extensions 40 on the more outer periphery side.

[0060] With this shape, the current collector extension 40 can help maintain the shape of the opening of the central cavity 55 at the end surface 51 of the electrode winding. The opening of the central cavity 55 can be defined by the current collector extension 40 bent inward at the end surface 51 of the electrode winding. This bent shape can also be referred to as, for example, a "folded shape," a "substantially U-shaped (or substantially V-shaped) shape," a "curved shape with a maximum point," or a "shape bent at an acute angle." By defining the opening of the central cavity 55 with the current collector extension 40 bent back, the density of the current collector extension 40 at the opening can be further increased in the cross-sectional view shown in FIG. 5 . This can more effectively prevent deformation of the opening of the central cavity 55 due to external impact, etc.

[0061] Furthermore, in a cross-sectional view, the electrode configuration layer 5 composed of the positive electrode 1, the negative electrode 2, and the separator 3 may be offset toward one end in the direction of the winding axis P near the central cavity 55. Specifically, in a cross-sectional view, the electrode configuration layer 5 may have a structure in which it is offset inward from the end surface 51 of the electrode winding body near the central cavity 55. Here, in this specification, the term "offset structure" refers to a structure in which the position of the end edge of the electrode configuration layer 5 is not constant in the direction of the winding axis P. In a cross-sectional view passing through the winding axis P, at least one end of the electrode configuration layer 5 located near the central cavity 55 may be positioned closer to the interior of the battery than an end of the electrode configuration layer 5 located closer to the outer periphery.

[0062] In this specification, the term "inner side" refers to the inside of the wound electrode body 50 along the direction of the winding axis P. For example, as shown in FIG. 5, the electrode configuration layer 5 located on the innermost periphery of the wound electrode body 50 may be positioned shifted more inward (i.e., downward in FIG. 5) than the electrode configuration layer 5 located on the more outer periphery. This can also be referred to as the side of a central cavity 55 extending to the center along the winding axis P of the wound electrode body 50. In other words, the electrode configuration layer 5 located on the outer periphery of the wound electrode body 50 may be disposed closer to the end face (i.e., upward in FIG. 5) than the electrode configuration layer 5 located near the central cavity 55. This means that the electrode configuration layer 5 located on the more outer periphery is shifted toward the end face 51 relative to the electrode configuration layer 5 located on the innermost periphery of the wound electrode body 50.

[0063] The above-described "shift" of the electrode configuration layer 5 can separate the tip of the current collector extension portion 40 folded back toward the central cavity 55 from the electrode configuration layer 5. Specifically, the electrode configuration layer 5 has an "shift" toward the inside of the wound electrode body 50, which makes it possible to ensure a longer length of the current collector extension portion 40 extending in a substantially linear manner along the winding axis P in a cross-sectional view (i.e., the length along the winding axis P). This makes it possible to more appropriately ensure a distance between either the positive or negative electrode including the current collector extension portion 40 and the other electrode included in the electrode configuration layer 5 near the central cavity 55. This makes it possible to more appropriately prevent the occurrence of a short circuit in the wound electrode body in the secondary battery of the present disclosure.

[0064] Here, "the vicinity of the central cavity" may be, in plan view, 0% or more (excluding 0%) and 30% or less of the diameter of the electrode winding 50, for example, a distance of 0% or more (excluding 0%) and 20% or less. The above range may be changed as appropriate depending on the size of the electrode winding, the diameter of the central cavity, and / or the thicknesses of the positive and negative electrodes and separators. As merely one example, "the vicinity of the central cavity" may be, in plan view, a radial distance from the outer periphery of the central cavity of 0 mm or more (excluding 0 mm) and approximately 3 mm or less, or 0 mm or more (excluding 0 mm) and approximately 2 mm or less.

[0065] In a secondary battery according to an embodiment of the present disclosure, either the positive electrode or the negative electrode may include a current collector extension 40, and the other electrode may be an electrode disposed at the innermost periphery of the electrode winding 50. That is, on one end face of the electrode winding 50, the electrode including the current collector extension 40 and the electrode positioned at the innermost periphery of the electrode winding 50 may be different electrodes. For example, as shown in FIG. 5 , in an embodiment in which the positive electrode 1 includes the current collector extension 40 on the end face 51 of the electrode winding 50, the electrode positioned at the innermost periphery may be the negative electrode 2. The above-described misalignment of the electrode configuration layer 5 separates the electrode positioned at the innermost periphery from the current collector extension 40, which can more effectively prevent conduction between different electrodes.

[0066] Furthermore, as will be described later, the degree of inward displacement of the electrode configuration layer 5 can be greatest at the innermost periphery of the electrode winding 50. In such an electrode winding, the electrode positioned at the innermost periphery and the electrode including the current collector extension portion 40 are different electrodes, so that a longer distance can be ensured between the positive and negative electrodes near the central cavity 55. Therefore, the positive and negative electrodes at the innermost periphery are suitably spaced apart, and the occurrence of a short circuit in the electrode winding can be more suitably prevented.

[0067] In one embodiment of the present disclosure, in a cross-sectional view passing through the winding axis P, the distance L between the end edge of the electrode that does not include the current collector extension portion 40 and the end face 51 of the electrode winding near the central cavity 55 of the electrode winding is different from the distance L' on the outer periphery of the electrode winding. In other words, in the end face 51 of either the positive or negative electrode that has the current collector extension portion 40, the distance between the end face 51 near the central cavity 55 and the other electrode is different on the inner periphery and outer periphery of the electrode winding 50. More specifically, the distance L between the end edge of the positive electrode or the negative electrode that does not include the current collector extension portion 40 near the central cavity 55 and the end face 51 of the electrode winding may be relatively longer than the distance L' on the outer periphery of the electrode winding 50.

[0068] As described above, in the present disclosure, the end surface 51 of the electrode winding may be a substantially flat surface formed by the bent current collector extension 40. Therefore, as shown in FIG. 5 , the "end surface" here may also be interpreted as an "end surface level," which is a virtual straight line connecting the exposed portions of the bent current collector extension 40 at the end surface 51 of the electrode winding. For example, as shown in FIG. 5 , when the positive electrode 1 has the current collector foil extension 40, the distance L from the end surface level 51 near the central cavity 55 to the end edge of the negative electrode 2 may be longer than the distance L' on the outer periphery of the electrode winding 50. In other words, the end surface 51 (or end surface level) of the electrode winding and the electrode that does not have the current collector extension 40 on the side of the end surface 51 may be spaced farther apart near the central cavity 55. As described above, the current collector extension 40 located near the central cavity 55 can bend more than the current collector extension 40 located on the outer periphery of the electrode winding 50, in order to maintain the shape of the central cavity 55. By having a structure in which an electrode other than the electrode having the current collector extension 40 is positioned farther away from the end face 51 near the central cavity 55, the occurrence of a short circuit due to the bent current collector extension 40 can be more effectively prevented.

[0069] In a cross-sectional view passing through winding axis P, if the distance from end surface 51 of the electrode wound body 50 on the outermost side to the edge of the electrode that does not have current collector extension 40 is L' and the same distance on the innermost side is L, then distance L on the innermost side may be in the range of about 1.05 to about 3 times, for example, about 1.05 to about 2 times, or about 1.05 to about 1.5 times, distance L' on the outermost side. Note that the above range can be changed as appropriate depending on the length of the current collector extension and / or the thicknesses of the positive and negative electrodes and separator.

[0070] Furthermore, in one embodiment of the present disclosure, the distance from the end face 51 of the electrode winding to the electrode that does not have the current collector extension 40 gradually decreases from the inner periphery toward the outer periphery of the electrode winding 50. In other words, the distance between the electrode that does not have the current collector extension 40 and the end face 51 of the electrode winding may gradually increase from the outer periphery toward the central cavity 55 of the electrode winding 50. With this structure, the tip of the current collector extension 40 of either the positive or negative electrode can be more appropriately spaced from the other electrode near the central cavity 55.

[0071] Furthermore, by gradually changing the distance between the end surface 51 of the electrode winding and the end of the electrode, it is possible to further reduce misalignment between adjacent electrodes. This ensures a larger electrode reaction area where the positive and negative electrodes face each other via the separator. In addition, since the portion of the positive electrode material layer that protrudes beyond the negative electrode material layer is further reduced, the occurrence of short circuits due to the deposition of metallic lithium can be further suppressed. For these reasons, the structure of the electrode winding of the present disclosure, in which the distance between the end surface and the electrode end gradually increases from the outer periphery to the inner periphery, can more effectively prevent short circuits in the electrode winding.

[0072] In the electrode wound body 50 constituting the secondary battery of the present disclosure, the electrode configuration layer 5 described above may be offset such that the end contour 5a of the electrode configuration layer is inclined in a cross section passing through the winding axis P. Here, the "end contour of the electrode configuration layer" refers to the contour formed by the end edges of the layer where the positive electrode 1 and the negative electrode 2 face each other with the separator 3 interposed therebetween in a cross section passing through the winding axis P. In other words, the end contour 5a of the electrode configuration layer is a virtual contour line connecting the multiple end edges of the layer where the positive electrode 1 and the negative electrode 2 face each other with the separator 3 interposed therebetween, on one end face of the electrode wound body. As shown in FIG. 5 , in a cross section passing through the winding axis P, the end contour 5a of the electrode configuration layer may be inclined toward the interior of the electrode wound body 50 with respect to the end face 51 of the electrode wound body. In other words, the end contour 5a of the electrode configuration layer may be inclined at an angle with respect to the end face 51 of the electrode wound body and may be inclined toward the central cavity 55 so as to gradually move away from the end face 51.

[0073] Here, "inclined" refers to an aspect in which the angle formed by the end contour 5a with respect to the end surface 51 of the electrode winding is not zero in absolute value. Furthermore, the inclination angle of the end contour 5a does not have to be constant as long as it is shaped so that it gradually moves away from the end surface toward the inside. This means that the end contour of the electrode configuration layer does not have to be a line that is uniformly inclined from the outermost circumference to the innermost circumference. In other words, the end contour may be linear, or may have a bent and / or curved curved shape and / or a stepped shape.

[0074] In one embodiment of the present disclosure, the end contour of the electrode configuration layer near the central cavity 55 is inclined at a different angle from the end contour on the more outer periphery side. That is, the end contour near the central cavity 55 and the end contour on the more outer periphery side may have different inclination angles with respect to the end face 51 of the electrode winding. Specifically, the inclination angle formed by the end contour of the electrode configuration layer located near the central cavity 55 with respect to the end face 51 of the electrode winding body is preferably larger than the inclination angle of the end contour on the more outer periphery side. Therefore, in one embodiment of the present disclosure, the degree of inward displacement of the electrode configuration layer 5 may be greatest near the central cavity 55.

[0075] As described above, the current collector extension 40 located near the central cavity 55 may be bent more than the current collector extension 40 located on the outer periphery of the electrode winding 50, from the viewpoint of maintaining the shape of the central cavity 55. In this case, the tip of the current collector extension 40 located near the central cavity 55 may be positioned further inside the electrode winding 50, and therefore needs to be sufficiently spaced apart from the electrode configuration layer 5. As described above, by having the electrode configuration layer 5 have a more inclined end contour 5a near the central cavity 55, the tip of the bent current collector extension 40 near the central cavity and the electrode configuration layer 5 can be more appropriately spaced apart.

[0076] Furthermore, the end contour 5a may be inclined inward with respect to the end surface 51 of the electrode winding near the central cavity 55. For example, the electrode configuration layer 5 may be arranged so that it is inclined only near the central cavity 55 and is substantially parallel to the end surface 51 on the outer periphery. By making the end contour 5a of the electrode configuration layer inclined only on a portion of the end surface 51, it is possible to ensure a larger area where the positive and negative electrodes face each other with the separator 3 interposed therebetween. This ensures a larger electrode reaction area for the electrode configuration layer 5, and the charge / discharge capacity of the secondary battery can be further improved. In other words, by making the end contour 5a of the electrode configuration layer inclined near the central cavity 55, it may be possible to further improve the performance of the secondary battery and more effectively prevent the occurrence of a short circuit in the electrode winding.

[0077] [Method of manufacturing a secondary battery according to the present disclosure] Next, a method for manufacturing a secondary battery according to the present disclosure will be described with reference to Fig. 6 to Fig. 11. Note that the method described below is merely an example, and the method for manufacturing a secondary battery according to an embodiment of the present disclosure is not limited to the following method.

[0078] The secondary battery according to the present disclosure can be manufactured by a manufacturing method including the following steps: That is, the manufacturing method for the secondary battery according to the present disclosure includes a step of winding an electrode component layer composed of a positive electrode, a negative electrode, and a separator disposed therebetween to form an electrode wound body while leaving a central cavity along the winding axis (electrode wound body forming step), a step of shaping the end of the electrode wound body having a current collector extension (end surface shaping step), and a step of housing the electrode wound body in an exterior body and injecting an electrolyte into the exterior body (enclosing step).

[0079] (Electrode Wound Body Forming Process) Fig. 6 is a schematic diagram illustrating components of an electrode winding that constitutes a secondary battery according to an embodiment of the present disclosure. Fig. 7 is a schematic perspective view illustrating a winding mode of an electrode winding 50 according to an embodiment of the present disclosure. In this process, a rectangular positive electrode 1, a negative electrode 2, and a separator 3 are wound so as to overlap one another in a predetermined order to obtain the electrode winding 50. The process of forming the electrode winding according to an embodiment of the present disclosure will be described below.

[0080] In this process, first, a positive electrode 1, a negative electrode 2, and two separators 3 are arranged in a predetermined order. As shown in FIG. 6, the positive electrode 1 or the negative electrode 2 has a positive electrode current collector extension 41 or a negative electrode current collector extension 42 where the current collector is exposed at one end edge located on the long side (before winding). In this case, a separator 3 is overlapped between the positive electrode 1 and the negative electrode 2, and the current collector extension 40 of either the positive electrode 1 or the negative electrode 2 is arranged so that it extends further outward than the other electrode. In other words, the positive electrode material layer and the negative electrode material layer are overlapped so as to face each other with the separator 3 interposed therebetween, and are arranged so that the positive electrode current collector extension 41 extends at one end edge of the long side (before winding) of the electrode component layer, and the negative electrode current collector extension 42 extends at the other end edge.

[0081] The length dimension w1 (see FIG. 6) of the current collector extension in the direction of the winding axis is not particularly limited as long as the desired electrode winding can be obtained. For example, the length dimension w1 of the current collector extension in the direction of the winding axis (particularly the length dimension before winding or before end face shaping, as described below) may typically be from about 1 mm to about 20 mm, for example, from about 2 mm to about 15 mm. The positive electrode current collector extension 41 and the negative electrode current collector extension 42 may each have the same length dimension w1, or may have different length dimensions w1.

[0082] Next, the electrode configuration layer is wound around the winding core. During winding, the electrode configuration layer is wound so that it is shifted from the end face having the current collector extension portion toward the inside of the electrode wound body near the winding core, which forms the central cavity 55. In other words, when winding from the vicinity of the winding core to the outer periphery, the position of the edge of the electrode configuration layer may be shifted toward the end face having the current collector extension portion. After winding, the winding core is removed, forming a central cavity 55 that penetrates the electrode wound body along the winding axis P.

[0083] FIG. 8 is a schematic perspective view showing a wound electrode body 50 according to an embodiment of the present disclosure. FIG. 9 is a schematic enlarged cross-sectional view of a cross section taken along line CC passing through the winding axis P in the direction of the arrow near the center 50′ of the wound electrode body 50 in FIG. 8 . As shown in FIG. 8 , one end face 51 of the wound electrode body after winding may be concave near the winding axis P, and the other end face 51 may be convex near the winding axis P. Also, as shown in FIG. 9 , the positive electrode 1, the negative electrode 2, and the separator 3 may each be shifted toward the interior of the wound electrode body 50 in the central cavity 55. By winding the electrode component layers with a shift in this manner, a wound electrode body having a structure in which the electrode component layers 5 near the central cavity 55 are shifted toward the interior can be obtained. By forming this offset, the collector extension portion 40, which is folded back significantly inside the electrode winding body in the shaping process described below, and the electrode configuration layer 5 are further separated, making it possible to more effectively prevent short circuits in the electrode winding body.

[0084] In one embodiment of the present disclosure, the electrode configuration layers are wound so that the end contour 5a (see FIG. 9) of the electrode configuration layers at the end surface 51 including the current collector extension 40 is inclined toward the inside of the wound electrode body 50. That is, at the end surface 51 having the current collector extension 40, the electrode configuration layers may be wound while being gradually shifted so that the inner peripheral portion of the end surface of the wound electrode body is recessed in a generally conical shape from the outer peripheral portion. By shifting the electrode configuration layers so that the end contours 5a of the electrode configuration layers are inclined, a wound electrode body can be obtained that can more suitably suppress the occurrence of short circuits while minimizing misalignment with adjacent electrodes.

[0085] Furthermore, when shifting the electrode configuration layer, the electrode configuration layer may be spirally wound at the end of the electrode wound body including the current collector extension portion 40. More specifically, the electrode configuration layer may be spirally wound so as to gradually shift in the winding axis direction while the positive electrode 1 and the negative electrode 2 face each other via the separator 3. In other words, the electrode configuration layer may be wound while gradually shifting the end of the electrode configuration layer outward. FIG. 10 is an enlarged partial cross-sectional view of an electrode wound body obtained by spirally winding the electrode configuration layer, taken through the winding axis P near the center 50′. As shown in the figure, in the spirally wound electrode wound body, the positive electrode 1 and the negative electrode 2 face each other via the separator 3, while the electrode configuration layer 5 is shifted in steps. In other words, by spirally winding, the electrode configuration layer 5 can be gradually shifted while the positive electrode 1 and the negative electrode 2 face each other via the separator 3. Therefore, the above-described method can provide an electrode wound body that can more effectively prevent short circuits while maintaining a larger electrode reaction area.

[0086] In one embodiment of the present disclosure, both the positive and negative electrodes may have current collector extensions. In such an embodiment, as shown in FIG. 7 , winding may be performed in a state in which the positive electrode current collector extension 41 extends outward from the negative electrode 2 and separator 3, and the negative electrode current collector extension 42 extends outward from the positive electrode and separator 3. During winding, the electrode constituent layers may be shifted toward either side of the winding axis near the winding core. From the perspective of more appropriately separating the positive and negative electrodes, the electrode constituent layers may be wound so that the end face having the current collector extension of the electrode located at the innermost periphery of the electrode wound body 50 is convex and protrudes outward near the central cavity 55, and the other opposing end face is concave and recessed inward.

[0087] The dimensions of the positive electrode 1, negative electrode 2, and separator 3 used are not particularly limited as long as the desired electrode winding body can be obtained. For example, the longitudinal length of the separator 3 may be determined appropriately depending on the dimensions of the desired secondary battery (particularly the number of turns of the electrode winding body).

[0088] Furthermore, in the above-described process for forming the wound electrode body, a wound electrode body in which the electrode constituent layers are misaligned may be obtained by using a positive electrode, a negative electrode, and / or a separator having a shape different from that of the above-described embodiment. Here, the "shape" of the positive electrode, the negative electrode, and / or the separator refers to the shape of the electrode and / or the separator in a plan view when unwound, for example, the shape when viewed from above when placed on the surface with the largest area.

[0089] 11 is a schematic perspective view showing components of an electrode winding according to an embodiment of the present disclosure. The positive electrode 1, the negative electrode 2, and the separator 3 may each have a shape in which at least a portion of one of their end edges in the longitudinal direction S is inclined, and the length dimension in the width direction R gradually increases in the longitudinal direction S. Either the positive or negative electrode may have a current collector extension on the inclined end edge. The other electrode may have a current collector extension on the non-inclined end edge. In other words, the electrode material layers of the positive electrode 1 and the negative electrode 2 may have a shape in which the length dimension in the width direction R gradually increases in the longitudinal direction S.

[0090] During winding, winding begins from the end where the length dimension in the width direction R of the positive electrode 1, negative electrode 2, and separator 3 is relatively short. That is, at one end of the electrode winding body, the length dimension in the winding axis direction of the positive electrode 1 and negative electrode 2 gradually increases in the winding direction. Therefore, the obtained electrode winding body has a shape in which, at one end face of the electrode winding body, the portion where the electrode material layers of the positive electrode 1 and negative electrode 2 face each other via the separator 3 is shifted spirally toward the inside of the electrode winding body. In other words, by using a component with a slope on at least a portion of the end side, it is possible to obtain a desired electrode winding body without performing an operation to shift the electrode component layers during winding.

[0091] (End surface shaping process) At least a portion of the current collector extension 40 is bent at the end surface 51 (see FIG. 8 ) of the electrode winding obtained in the previous step, to obtain a shaped end surface of the electrode winding. The end surface of the electrode winding 50 may be bent by folding the current collector extension 40 over so that the bent current collector extension 40 does not protrude outside the outer periphery of the electrode winding 50. Furthermore, to further strengthen the connection with the current collector in the subsequent step, the end surface may be shaped so that at least a portion of the bent current collector extension 40 presents a substantially flat surface in a direction perpendicular to the winding axis at the end surface of the electrode winding. The bending may be performed, for example, by pressing the current collector extension from the outside.

[0092] During shaping, first, the current collector extension near the central cavity is pressed from the outside. The current collector extension near the central cavity may be pressed separately before pressing the current collector extension on the outer periphery to maintain the shape of the opening of the central cavity. The current collector extension near the central cavity may be pressed so as to be folded inward toward the central cavity. Next, the end of the current collector extension may be bent toward the inside of the electrode winding 50 to conform to the shape of the opening of the central cavity. That is, the current collector extension may be folded toward the central cavity 55, and then bent so as to fold back toward the inside of the electrode winding 50 along the central cavity 55 (see FIG. 5 ). By bending the current collector extension near the central cavity in this manner, a substantially flat surface can be formed at the end face of the electrode winding while maintaining the shape of the central cavity.

[0093] Next, the current collector extension portion located closer to the outer periphery is pressed. Fig. 12 is a schematic plan view illustrating end face shaping according to an embodiment of the present disclosure. As shown in the figure, the current collector extension portion 40 may be pressed spirally from the outer periphery toward the inner periphery of the electrode winding body 50 in a plan view. By this pressing method, the current collector extension portion is folded over at the end face, and can present a substantially flat surface in a direction perpendicular to the winding axis.

[0094] The above-described electrode winding formation process and end surface shaping process can provide an electrode winding 50 in which, in a cross-sectional view passing through the winding axis P, the end contour 5a of the electrode configuration layer is inclined toward the interior of the electrode winding with respect to the end face of the electrode winding, as shown in FIG. That is, in the electrode winding 50 obtained by the above-described process, in a cross-sectional view passing through the winding axis P, the end contour 5a of the electrode configuration layer near the central cavity 55 forms an angle with respect to the end face of the electrode winding and is gradually spaced apart from the end face. Therefore, the current collector extension 40 near the central cavity 55 can be folded back more slightly than the current collector extension 40 on the more outer periphery. Therefore, near the central cavity, the tip of the current collector extension bent back can be more appropriately spaced from the electrode configuration layer, providing an electrode winding that can more appropriately prevent short circuits.

[0095] The means for shaping the end surface of the wound electrode body is not particularly limited as long as the desired end surface can be obtained. For example, the end surface may be shaped by pressing a pressing member against the end surface of the wound electrode body from the outside and moving the wound electrode body and / or the pressing member in a direction perpendicular to the winding axis. The structure, material, and number of pressing members are not particularly limited as long as the desired end surface of the wound electrode body can be obtained. Examples of pressing members include a pressing roller and a pressing plate.

[0096] (Current collector plate installation process) A current collector plate is electrically connected to the end face of the electrode winding that was shaped in the previous process. The current collector plate may be attached so as to join to the flat surface formed on the end face of the electrode winding. As an example, the current collector plate and the electrode winding may be welded by laser irradiation. By irradiating a laser from the current collector plate side, the current collector plate and the current collector extension directly below the current collector plate are melted and alloyed, thereby achieving conductivity.

[0097] (Storage process) The electrode winding body with the current collector plate attached is housed in the outer shell, and the current collector plate is electrically connected to the electrode terminal or the exterior body, and an electrolyte is poured into the exterior body. Below, an example will be described of an embodiment in which the exterior body is composed of a main body and a lid, and the electrode terminal is provided on the lid.

[0098] First, the lid, the electrode terminal, and an insulating member provided to fill the gap between the lid and the electrode terminal are bonded together. Next, the long portion extending from the current collector plate is pre-bent toward the electrode terminal or the exterior body to adjust its shape, and then the long portion is connected to the electrode terminal or the exterior body. Next, the main body and the lid of the exterior body are bonded together. Finally, the electrolyte is injected through an injection port (not shown) in the exterior body, and the injection port is closed with a sealing plug (not shown). Bonding may be achieved by any method known in the field of secondary batteries, such as laser irradiation.

[0099] Although the embodiments of the present disclosure have been described above, they are merely typical examples. Those skilled in the art will readily understand that the present disclosure is not limited thereto, and that various modifications are possible within the scope of the present disclosure. [Industrial Applicability]

[0100] The secondary battery according to the present disclosure can be used in various fields where power storage is expected. Although merely illustrative, the secondary battery of the present disclosure can also be used in the electrical, information, and communications fields where mobile devices and the like are used (for example, the electrical and electronic equipment fields or mobile device fields including small electronic devices such as mobile phones, smartphones, laptop computers, digital cameras, activity monitors, arm computers, electronic paper, RFID tags, card-type electronic money, and smart watches), home and small industrial applications (for example, power tools, golf carts, and home, 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 types of power generation, road conditioners, smart grids, and general home-installed power storage systems), medical applications (for medical devices such as earphone hearing aids), pharmaceutical applications (for example, medication management systems), IoT, and space and deep-sea applications (for example, space probes and submersible research vessels). [Explanation of symbols]

[0101] 1 positive electrode 11 Positive electrode current collector 12 Cathode material layer 2 negative electrode 21 Negative electrode current collector 22 Negative electrode material layer 3 Separator 40 Current collector extension part 41 Positive electrode current collector extension part 42 Negative electrode current collector extension part 5 Electrode composition layer 5a Edge contour 50 Electrode winding body 51 End face 55 Central Cavity 60 Exterior body 61 Main body 62 Lid 70 Current collector plate 76 Long section 80 Electrode terminal structure 81 Electrode terminal 82 Gasket part 90 center pin 100 Secondary battery

Claims

1. the battery includes an electrode winding body formed by winding an electrode configuration layer including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; the electrode winding has a central cavity extending centrally along a winding axis; At an end surface of the electrode winding body, one of the positive electrode and the negative electrode includes a current collector extension portion in which a current collector extends further outward than the other electrode, the current collector extension portion in the vicinity of the central cavity is bent so as to fold back toward the central cavity, and the electrode configuration layer is shifted from the end surface toward the inside of the electrode winding body, the current collector extension portion is bent at the end surface to form a plane perpendicular to the winding axis direction, a tip of the current collector extension portion bent so as to return toward the central cavity and the other electrode are spaced apart from each other.

2. The secondary battery according to claim 1 , wherein the electrode disposed on the innermost periphery of the electrode winding body is the other electrode.

3. The secondary battery according to claim 1 , wherein, in a cross-sectional view, the distance between the end face and the other electrode near the central cavity is relatively longer than the distance on a more outer circumferential side of the electrode winding body.

4. The secondary battery according to claim 3 , wherein the distance gradually decreases from the inner periphery of the electrode winding body toward the outer periphery.

5. The secondary battery according to claim 1 , wherein, in a cross-sectional view, an edge profile of the electrode configuration layer is inclined toward the inner side with respect to the edge surface.

6. The secondary battery according to claim 5 , wherein the edge contour near the central cavity and the edge contour on the outer periphery have different inclination angles.

7. a step of winding an electrode configuration layer including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode to form an electrode wound body while leaving a central cavity; and a step of shaping the end surface of the electrode winding body, The step of forming the electrode winding body includes: the positive electrode and the negative electrode are wound in a state in which a current collector extension portion of one of the positive electrode and the negative electrode extends outward at the end surface of the other electrode; and winding the electrode configuration layer so that the electrode configuration layer is shifted from the end surface toward the inside of the electrode winding body in the vicinity of the central cavity, the shaping step includes bending the current collector extension portion near the central cavity back toward the central cavity so that the end surface of the current collector extension portion forms a plane perpendicular to the winding axis direction and a tip of the current collector extension portion and the other electrode are spaced apart.

8. The method for manufacturing a secondary battery according to claim 7 , wherein the deviation of the electrode configuration layer causes an edge contour of the electrode configuration layer to be inclined toward the inner side.

9. The method for manufacturing a secondary battery according to claim 7 , wherein the misalignment is caused by spirally winding the electrode configuration layer from the inner side toward the end face.

10. 8. The method for producing a secondary battery according to claim 7, wherein the shaping step comprises pressing the current collector extension from outside to form a flat surface perpendicular to the winding axis direction.

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