WO2023054579A1 - Secondary battery - Google Patents

Abstract

The present invention provides a secondary battery formed as a result of including an electrode winding comprising: a positive electrode; a negative electrode; and a separator that is arranged between the positive electrode and the negative electrode. For at least one of the ends of the electrode winding, either the positive electrode or negative electrode has a current collector extension portion that extends outward beyond the other electrode. The current collector extension portion has a high-density region in which the density of the current collector extension portion is relatively high and a low-density region where said density is relatively low.

Description

secondary battery

The present disclosure relates to secondary batteries. In particular, the present invention relates to a secondary battery having an electrode assembly composed of electrode layers including a positive electrode, a negative electrode and a separator.

A secondary battery can be charged and discharged repeatedly and is used for various purposes. For example, secondary batteries are used in mobile devices such as mobile phones, smart phones, and laptop computers.

Japanese Patent Application Publication No. 2015-519689

The inventor of the present application realized that there were problems to be overcome with conventional secondary batteries, and found the need to take measures to address them. Specifically, the inventors of the present application have found that there are the following problems.

Patent Document 1 discloses a secondary battery in which a current collector is welded to a foil-shaped body at the end of an electrode plate in an electrode winding body. 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 foils of the electrode plates are softened and shaped so that the foils are intertwined with each other.

With respect to such shaping treatment, the inventors of the present application have found that the mutually entangled foil-like bodies can bring about an inconvenient phenomenon in the electrode winding body. Specifically, the inventors have found that since the ends of the electrode winding body are covered by the mutually entangled foil-like bodies, the injection of the electrolytic solution into the electrode winding body may be hindered during battery production.

The present disclosure has been made in view of such problems. That is, a main object of the present disclosure is to provide a secondary battery having a more suitable structure in terms of electrolyte injection.

A secondary battery according to the present disclosure includes a positive electrode, a negative electrode, and an electrode roll composed of a separator disposed between the positive electrode and the negative electrode. In at least one of the parts, either one of the positive electrode and the negative electrode has a current collector extension part in which a current collector extends outside the other electrode, and the current collector The body extension portion has a high density region where the density of the current collector extension portion is relatively high and a low density region where the density is relatively low, and the high density region has voids. .

The secondary battery according to the present disclosure has a more suitable structure in terms of electrolyte injection.

Specifically, in the secondary battery of the present disclosure, at the end of the electrode winding body, either one of the positive electrode and the negative electrode current collector extends beyond the other electrode. consists of The end portion of the electrode winding body has two regions, a high-density region and a low-density region, in which the densities of the extended portions of the current collector are different from each other, and the high-density region has voids. With such a structure, when the electrolyte is injected during the manufacture of the secondary battery, the injected electrolyte can flow into the pores in the high-density region, and the electrolyte can be injected more efficiently. can be realized.

FIG. 1 is a schematic cross-sectional view showing an example of an electrode-constituting layer. FIG. 2 is a schematic perspective view showing the appearance of an example of the secondary battery of the present disclosure. FIG. 3 is a schematic cross-sectional view of the secondary battery of FIG. 2 when the cross-section taken along line AA passing through the winding axis is viewed in the direction of the arrow. FIG. 4 is a schematic perspective view showing an electrode winding body after end face shaping according to an embodiment of the present disclosure. FIG. 5 is a schematic partial cross-sectional enlarged view of the BB cross section of the electrode winding body of FIG. 4 when viewed in the direction of the arrow. FIG. 6 is a schematic diagram for explaining assembly of an electrode winding body and a current collector according to an embodiment of the present disclosure. FIG. 7 is a schematic partial cross-sectional enlarged view showing the electrode winding body before the current collector plate is thermally bonded according to one embodiment of the present disclosure. FIG. 8 is a schematic partial cross-sectional enlarged view showing the electrode winding body after the current collector plate is thermally bonded according to one embodiment of the present disclosure. FIG. 9 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. FIG. 10 is a schematic perspective view for explaining the winding mode of the electrode winding body according to one embodiment of the present disclosure. FIG. 11 is a schematic perspective view showing an electrode winding body after winding according to an embodiment of the present disclosure. FIG. 12 is a schematic cross-sectional view of the electrode winding body of FIG. 11, taken along line CC passing through the winding axis, viewed in the direction of the arrow. FIG. 13 is a schematic plan view for explaining end face shaping according to an embodiment of the present disclosure.

Below, the secondary battery according to one embodiment of the present disclosure will be described in more detail. Although the description will be made with reference to the drawings as necessary, the various elements in the drawings are only schematically and exemplarily shown for understanding of the present disclosure, and the appearance, dimensional ratio, etc. may differ from the actual ones. .

The "vertical direction" and "horizontal direction" directly or indirectly described in this specification correspond to the vertical direction and the horizontal direction in the drawings. In addition, the “cross-sectional view” described directly or indirectly in this specification refers to a direction along the winding axis of the electrode winding body constituting the secondary battery, or a direction perpendicular to the winding axis. It is based on a virtual cross section of the secondary battery cut along. Further, the term “planar view” used in this specification is based on a sketch of the object viewed from above or below along the direction of the winding axis. Unless otherwise specified, the same reference numerals or symbols indicate the same members or parts or the same meanings.

In addition, the terms “perpendicular to the winding axis” and “substantially perpendicular” as used herein do not necessarily have to be perfectly “perpendicular”, and are slightly deviated from it (for example, the angle formed with the winding axis is in the range of 90°±20°, eg up to 90°±10°).

In addition, the term “substantially parallel” as used herein does not necessarily mean perfect “parallel”, and a slightly deviated form (for example, a range of ±20° from perfect parallel, for example, up to ±10° range).

[Basic configuration of secondary battery]
A "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 overly bound by its name, and can include, for example, power storage devices.

FIG. 1 shows a schematic cross-sectional view of an exemplary electrode winding body 50. FIG. A secondary battery according to the present disclosure comprises an electrode roll 50 having an electrode configuration layer 5 including a positive electrode 1 , a negative electrode 2 and a separator 3 . As illustrated, the electrode winding body 50 may have a winding structure in which the electrode configuration layer 5 is wound in a winding shape. That is, the electrode winding body 50 includes the electrode-constituting layer 5 extending relatively long in a belt-like or elongated shape including the positive electrode 1, the negative electrode 2, and the separator 3 disposed between the positive electrode 1 and the negative electrode 2, which is a roll. It may have a winding structure wound in a shape. In the secondary battery according to the present disclosure, such electrode-wound body 50 is enclosed in an exterior body together with an electrolyte (eg, non-aqueous electrolyte).

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 a 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 be provided with positive electrode material layers on both sides of the positive electrode current collector, or may be provided with a positive electrode material layer only on one side of the positive electrode current collector. good. The positive current collector does not have to have a layer of positive material on both sides or all over one side. For example, a positive electrode material layer is formed on both sides so that a “collector extension portion” described later is provided at one end or both ends located on the long side (before winding) of the positive electrode current collector. It may have a portion that is not provided.

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 be provided with a negative electrode material layer on both sides of the negative electrode current collector, or may be provided with a negative electrode material layer only on one side of the negative electrode current collector. good. The negative electrode current collector does not have to have a layer of negative electrode material on both sides or the entire surface of one side. For example, one side end or both ends located on the long side (before winding) of the negative electrode current collector is provided with a negative electrode material layer on both sides so that a "current collector extension part" is provided. may have parts that are not

The electrode active material contained in the positive electrode 1 and the negative electrode 2, that is, the positive electrode active material and the negative electrode active material, is a substance directly involved in the transfer of electrons in the secondary battery, and is the main component of the positive and negative electrodes responsible for charging and discharging, that is, the battery reaction. It is matter. More specifically, ions are brought to the electrolyte due to the “positive electrode active material contained in the positive electrode material layer” and the “negative electrode active material contained in the negative electrode material layer”, and such ions are applied to the positive electrode 1 and the negative electrode 2. Electrons are transferred (or conducted) between them to charge and discharge. The positive electrode material layer and the negative electrode material layer may be layers capable of intercalating and deintercalating lithium ions. In other words, the secondary battery according to the present disclosure may be a non-aqueous electrolyte secondary battery in which charging and discharging of the battery are performed by moving lithium ions between the positive electrode 1 and the negative electrode 2 via the non-aqueous electrolyte. . When lithium ions are involved in charging and discharging, the secondary battery according to the present disclosure corresponds to a so-called "lithium ion battery", and the positive electrode 1 and the negative electrode 2 have layers capable of intercalating and deintercalating lithium ions.

When the positive electrode active material of the positive electrode layer is composed of, for example, granules, the positive electrode layer may contain a binder for sufficient contact between particles and shape retention. Furthermore, the positive electrode material layer may contain a conductive aid in order to facilitate the transfer of electrons that promote the battery reaction. Similarly, when the negative electrode active material of the negative electrode layer is composed of, for example, granules, a binder may be included for more sufficient contact and shape retention between the particles, thereby promoting electron transfer that promotes the battery reaction. A conductive aid may be included in the negative electrode material layer for smoothing. Because of such a configuration in which a plurality of components are contained, the positive electrode material layer and the negative electrode material layer can also be called "positive electrode material layer" and "negative electrode material layer", respectively.

The positive electrode active material may be a material that contributes to absorption and release of lithium ions. From this point of view, 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. That is, the positive electrode material layer of the secondary battery according to the present disclosure may contain such a lithium-transition metal composite oxide as a positive electrode active material. For example, the positive electrode active material may be lithium cobaltate, lithium nickelate, lithium manganate, lithium iron phosphate, or a transition metal thereof partially replaced by another metal. Although such a positive electrode active material may be contained as a single species, it may be contained in combination of two or more species.

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

The conductive aid that can be contained in the positive electrode material layer is not particularly limited. For example, the conductive additive for the positive electrode layer includes carbon black such as thermal black, furnace black, channel black, ketjen black and acetylene black, graphite, carbon fiber such as carbon nanotube and vapor growth carbon fiber, copper, nickel, and the like. , metal powders such as aluminum and silver, and at least one selected from the group consisting of polyphenylene derivatives and the like.

The negative electrode active material may be a material that contributes to intercalation and deintercalation of lithium ions. From this point of view, the negative electrode active material may be, for example, various carbon materials, oxides and/or lithium alloys.

Examples of various carbon materials for the negative electrode active material include graphite (eg, natural graphite and/or artificial graphite), hard carbon, soft carbon, and/or diamond-like carbon. In particular, graphite has high electron conductivity and excellent adhesion to the negative electrode current collector. As the oxide of the negative electrode active material, at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide and lithium oxide can be used. The lithium alloy of the negative electrode active material may be any metal that can be alloyed with lithium, such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn and/or may be binary, ternary or higher alloys of lithium with metals such as La. Such oxides may, for example, be amorphous in their structural form. This is because deterioration due to non-uniformity such as grain boundaries or defects is less likely to occur.

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

The conductive aid that can be contained in the negative electrode material layer is not particularly limited. Conductive agents for the negative electrode layer include, for example, carbon blacks 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 aluminum and silver, and at least one selected from the group consisting of polyphenylene derivatives and the like. In addition, the negative electrode material layer may contain a component resulting from a thickening agent component (for example, carboxylmethyl cellulose) used in manufacturing the battery.

The positive electrode current collector and negative electrode current collector used for the positive electrode and negative electrode are members that contribute to collecting and supplying electrons generated in the active material due to the battery reaction. Such a current collector may be a sheet metal member and may have a perforated or perforated morphology. For example, the current collector may be metal foil, perforated metal, mesh and/or expanded metal, and the like. The positive electrode current collector used for the positive electrode may be made of metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel, and the like. For example, the positive electrode current collector may be aluminum foil. On the other hand, the negative electrode current collector used for the negative electrode may be made of metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel, and the like. For example, the negative electrode current collector may be copper foil.

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/or retaining the electrolyte. In other words, the separator is a member that allows ions to pass through while preventing electronic contact between the positive electrode and the negative electrode. For example, a separator is a porous or microporous insulating member that has a membrane morphology due to its small thickness. By way of example only, a polyolefin microporous membrane 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 coat layer, an adhesive layer, or the like. Moreover, the surface of the separator may have adhesiveness. In the present disclosure, the separator should not be specifically bound by its name. For example, the separator may be a solid electrolyte, a gel electrolyte, insulating inorganic particles, or the like having similar functions.

In the secondary battery of the present disclosure, an electrode winding body composed of electrode configuration 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 the negative electrode have layers capable of intercalating and deintercalating lithium ions, the electrolyte may be a “non-aqueous” electrolyte such as an organic electrolyte or an organic solvent. That is, the electrolyte may be a non-aqueous electrolyte. The electrolyte will have metal ions released from the electrodes (positive and/or negative electrodes) and will therefore assist in the movement of metal ions in the battery reaction.

A non-aqueous electrolyte is an electrolyte containing a solvent and a solute. A specific solvent for the non-aqueous electrolyte may contain at least carbonate. Such carbonates may be cyclic carbonates and/or linear carbonates. Although not particularly limited, cyclic carbonates include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC) and vinylene carbonate (VC). be able to.

Examples of chain carbonates include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC) and dipropyl carbonate (DPC). By way of example only, a combination of cyclic carbonates and linear carbonates may be used as the non-aqueous electrolyte, for example, a mixture of ethylene carbonate and diethyl carbonate may be used. The solute of the non-aqueous electrolyte can be any conventional solute. As a specific non-aqueous electrolyte solute, for example, Li salts such as LiPF ₆ and/or LiBF ₄ may be used.

FIG. 2 is a schematic perspective view showing the appearance of an example of the secondary battery 100 of the present disclosure. The exterior body 60 that accommodates the electrode wound body may be a hard case, and may be composed of two members such as a body portion 61 and a lid portion 62 . For example, the body portion 61 may be a cup-shaped member that includes the side surface of the exterior body 60 and a main surface (typically, for example, a bottom surface or a lower surface) continuous therewith. The lid portion 62 is a member combined to cover the cup-shaped main body portion 61 (preferably provided so as to block the hollow portion inside the main body portion 61 from the outside). good. When the exterior body 60 is composed of the main body portion 61 and the lid portion 62, the main body portion 61 and the lid portion 62 are sealed after accommodating the wound electrode body, the electrolyte, and optionally the electrode terminals. A method for sealing the exterior body 60 is not particularly limited, and examples thereof include a laser irradiation method.

As materials for forming the body portion 61 and the lid portion 62, any material capable of forming a hard case-type exterior body in the field of secondary batteries can be used. Such materials may be conductive materials in which electron transfer may be achieved, or insulating materials in which electron transfer may not be achieved. The material of the exterior body is preferably a conductive material from the viewpoint of electrode extraction.

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 polyesters (eg, polyethylene terephthalate), polyimides, polyamides, polyamideimides, and/or polyolefins (eg, polyethylene and/or polypropylene).

In terms of conductivity and rigidity, both the body and lid may be constructed of stainless steel. As defined in "JIS G 0203 Iron and Steel Terms", stainless steel is an alloy steel containing chromium or chromium and nickel. refers to steel. Examples of such stainless steels include martensitic stainless steels, ferritic stainless steels, austenitic stainless steels, austenitic-ferritic stainless steels and/or precipitation hardening stainless steels.

The dimensions of the main body and lid of the outer package are determined mainly according to the dimensions of the electrode winding body. For example, the outer package may have dimensions that prevent the electrode-wound body from moving within the outer package when the electrode-wound body is accommodated. By preventing the movement of the electrode winding body, damage to the electrode winding body due to impact or the like can be prevented, and the stability of the secondary battery can be further improved.

The exterior body may be a flexible case such as a pouch made of laminated film. The laminate film has a configuration in which at least a metal layer (e.g., aluminum) and an adhesive layer (e.g., polypropylene and/or polyethylene) are laminated, and additionally a protective layer (e.g., nylon and/or polyamide, etc.) ) may be laminated.

The thickness dimension (that is, thickness dimension) of the exterior body 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 average value of the measured values at arbitrary 10 points is used as the thickness dimension of the outer package.

A secondary battery is generally provided with an electrode terminal. As for such electrode terminals, for example, a positive electrode terminal and a negative electrode terminal may be provided on different surfaces of the exterior body. Specifically, the electrode terminals of the positive electrode and the negative electrode may be provided on two opposite end surfaces of the outer package in the direction of the winding axis of the electrode winding body.

A material with high conductivity may be used for the electrode terminals. The material of the electrode terminal is not particularly limited, but at least one selected from the group consisting of silver, gold, copper, iron, tin, platinum, aluminum, nickel and stainless steel can be used.

The electrode terminal is not particularly limited and may have any configuration. For example, the electrode terminals may be constructed from a single material or may be constructed from multiple materials. Electrode terminals made of multiple materials (hereinafter also referred to as "electrode terminal structures") may consist of, for example, a rivet portion, an inner terminal and/or a gasket portion.

The rivet part and the inner terminal need only be made of a material that allows electron transfer. For example, the rivet portion and inner terminal are each constructed from 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 is constructed from an insulating polymeric material such as polyester (eg, polyethylene terephthalate), polyimide, polyamide, polyamideimide, and/or polyolefin (eg, polyethylene and/or polypropylene).

Although the electrode terminal structure is not particularly limited, for example, it may be fitted and inserted through the opening of the exterior body. The electrode terminal structure mainly includes a conductive rivet portion for leading the electrode to the outside, an outer gasket portion for preventing electrolyte leakage 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 winding body, and an inner gasket portion for preventing electrolyte leakage while ensuring electrical insulation between the inner terminal and the exterior body. may contain.

[Characteristics of the secondary battery of the present disclosure]
FIG. 2 is a schematic perspective view showing the appearance of an example of the secondary battery 100 of the present disclosure. Also, FIG. 4 is a schematic perspective view showing the appearance of an example of the electrode-wound body 50 that constitutes the secondary battery of the present disclosure. In the drawing, the secondary battery 100 and the electrode winding body 50 have a substantially cylindrical shape, but they are not necessarily limited to this. For example, the electrode winding body 50 may have a substantially cylindric shape. In other words, the cross-sectional shape of the electrode wound body 50 as seen from the direction along the winding axis is not particularly limited, and may be, for example, substantially circular, substantially elliptical, or substantially rectangular. In the present specification, the term "substantially rectangular" includes shapes having chamfered or rounded corners or corners regardless of the accuracy of the corners or surfaces of the shape.

FIG. 3 is a schematic cross-sectional view of the secondary battery of FIG. 2 when the AA cross section passing through the winding axis is viewed in the direction of the arrow. The secondary battery 100 according to the present disclosure is a secondary battery comprising an electrode winding body 50, an exterior body 60 that accommodates the electrode winding body 50, and an electrode terminal forming member 80 that is used for connection with an external device. At least the structure of the ends of the electrode winding body is characterized. The features are described below.

FIG. 4 shows a schematic perspective view of an electrode wound body 50 around which the electrode configuration layer 5 (see FIG. 1) of the secondary battery according to one embodiment of the present disclosure is wound. FIG. 5 is a schematic cross-sectional view of the BB line cross section passing through the winding axis P of the electrode winding body 50 shown in FIG. 4 as viewed in the direction of the arrow. As shown, the secondary battery of the present disclosure includes an electrode construction layer 5 composed of a positive electrode 1, a negative electrode 2 and a separator 3 disposed therebetween, and typically further includes an electrolyte. Further, in the electrode winding body 50 of the secondary battery according to the embodiment of the present disclosure, either one of the positive electrode 1 and the negative electrode 2 has the current collector extension portion 40 .

In the present disclosure, the term "current collector extension" means a portion of the electrode where the current collector having no electrode material layer extends along the edge of the electrode (see FIG. 5). In other words, the “collector extension portion” refers to an exposed portion of the current collector extending from one of the end faces forming the end faces of the electrode winding body 50 (preferably, a portion where the electrode material layer is provided). not part). Further, as described above, in the secondary battery of the present disclosure, the current collector of the positive electrode and/or the negative electrode may be metal foil. Therefore, the "collector extension portion" can also be referred to as "current collector exposed portion" or "collector foil extension portion".

A secondary battery according to an embodiment of the present disclosure includes current collector extensions 40 of the positive electrode 1 and/or the negative electrode 2 at the ends of the electrode winding body 50 . Here, the "end" of the electrode winding body 50 means the end through which the winding axis P passes (see FIG. 3). That is, the “end portion” of the electrode-wound body 50 includes the end face of the electrode-wound body 50 . For example, the “end portion” of the electrode winding body 50 means an end portion including an end face on the side of the electrode terminal forming member 80 and an end portion including an end face opposite to the end face. Therefore, one of the positive electrode 1 and the negative electrode 2 may have the current collector extension portion 40 on at least one of the end surfaces of the electrode winding body 50 . In other words, the current collector of one electrode (collector extension part 40) may extend further outward than the other electrode on the end surface having the current collector extension part 40 .

"Outside" in this specification means the outside of the electrode wound body 50 in the winding axis P direction. That is, in the secondary battery of the present disclosure, the positive electrode current collector extension portion 41 extending longer than the negative electrode 2 and the negative electrode current collector extending longer than the positive electrode 1 in the direction of the winding axis P It may comprise at least one body extension 42 (see FIG. 12). In one embodiment, the electrode winding 50 may include both the positive electrode current collector extension portion 41 and the negative electrode current collector extension portion 42 . That is, each of the positive electrode current collector extension portion 41 and the negative electrode current collector extension portion 42 may extend on different end surfaces of the electrode wound body 50 . This means that the positive electrode current collector extension portion 41 and the negative electrode current collector extension portion 42 extend in directions facing each other along the winding axis P direction.

At least part of the current collector extension 40 has a curved shape. In the present disclosure, bending includes at least bending and/or bending. In the present disclosure, bending means bending in a curved (or arcuate) shape (that is, bending roughly curvilinearly) in a cross-sectional view, which results in rounded bending and also includes flexion. In addition, the term "bending" in the present disclosure refers to bending at an acute angle or angular shape (that is, bending substantially linearly) in a cross-sectional view.

As shown in FIG. 5, the end portion of the electrode winding body 50 has at least two regions in which the densities of the bent current collector extension portions 40 are different from each other. Specifically, the current collector extension portion 40 has a high density region 40a where the density of the current collector extension portion 40 is relatively high and a low density region 40b where the density is relatively low. . That is, in the present disclosure, the terms "high density region" and "low density region" refer to a relatively dense region and a relatively sparse region of the current collector extension, respectively. In other words, the end portion of the electrode winding body 50 has two regions, and the current collector extension portions 40 are arranged so that one region is dense and the other region is sparse. can be By providing two types of regions with different densities in the current collector extension, it is possible to obtain a secondary battery that is more excellent in terms of electrolyte pourability while more preferably protecting the end faces of the electrode winding body. obtain.

As shown in FIG. 5, in a cross-sectional view, the current collector extension part 40 in the high-density region 40a may have a shape that bends in a folded manner. For example, the current collector extension portion 40 may have a shape that is greatly curved to form a convex shape in a cross-sectional view. More specifically, the current collector extension portion 40 may have a curved shape that protrudes in a direction substantially perpendicular to the winding axis P in at least a portion of the high density region 40a. In other words, at least part of the current collector extending portion in the high density region 40 a may have a curved shape that is convex toward the inner or outer peripheral side of the electrode wound body 50 . It can also be understood that such a bent shape is bent so as to provide a flat portion on the end surface of the electrode winding body 50 .

Such a 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 having a maximum point”, or a “sharp-angled shape”. is. Further, in one embodiment of the present disclosure, the current collector extension can also be regarded as having a wave shape that repeats a plurality of curved shapes. That is, in a cross-sectional view passing through the winding axis P, the current collector extension portion may extend in a meandering manner due to the curved shape in the high-density region.

In addition, as shown in FIG. 5, the high-density region 40a has voids 45. In the present disclosure, the pore portion means a space portion formed by at least a part of the bent current collector extension portion 40, and includes a gap portion inside the high-density region 40a and a concave portion existing on the end face. can include For example, the vacancies 45 may be positioned at bends of the current collector extension 40, between adjacent current collector extensions, and the like.

The pore 45 may be defined by the bent current collector extension 40 . The holes 45 can exist in various shapes depending on the bent shape of the current collector extension portion 40 . For example, the hole portion 45 may have a flat shape or an elongated shape in a cross-sectional view. In a preferred example, the shape of the hole portion 45 may be a flat shape or an elongated shape along the direction perpendicular to the winding axis P in a cross-sectional view. In addition, the shape of the hole portion 45 is not limited to such a shape, and the shape of the hole portion 45 may be, for example, a substantially circular shape, a substantially elliptical shape, a substantially rectangular shape, a polygonal shape, and/or an indefinite shape in a cross-sectional view passing through the winding axis P. It may be in shape.

The voids 45 may be distributed throughout the high-density region 40a. That is, the high density region 40a may have a plurality of voids 45 distributed throughout. In a cross-sectional view, the plurality of holes 45 may be arranged irregularly throughout the high-density region 40a, and may have different shapes and/or sizes. With the above-described structure, when the electrolytic solution is injected into the electrode winding body, the electrolytic solution can flow into the inside of the holes 45, so that the injection speed of the electrolytic solution is further improved, and the injection is more suitable. can be realized.

In one embodiment of the present disclosure, the high density region 40a has at least a portion of a structure in which a plurality of current collector extension portions 40 are folded over each other. That is, the plurality of current collector extension portions 40 may have a structure in which a plurality of bent current collector extension portions 40 are laminated in at least a portion of the high density region 40a. In other words, the plurality of current collector extension portions 40 may be folded in an overlapping manner so as to form a gap. That is, the plurality of current collector extension portions 40 may be bent so as to overlap each other in at least a part of the high density region 40a, and the void portions 45 may be formed between the current collector extension portions 40. .

In one aspect, in at least a part of the plurality of current collector extension portions 40, the adjacent current collector extension portions 40 are bent at the same degree of curvature, and the bent portion (for example, a portion where the curvature is relatively large or It may be folded while leaving a space at a substantially U-shaped portion (see FIGS. 5 and 7). In such a structure, the hole portion 45 can be positioned at the bent portion of the adjacent current collector extension portion 40, and can have at least a part of the same contour as the bent portion in a cross-sectional view. The voids 45 existing between the plurality of current collector extensions 40 are present along the bent current collector extensions 40 and help the electrolytic solution to flow smoothly into the electrode wound body 50. Therefore, more efficient electrolyte injection can be realized.

As shown in FIG. 5 , at least part of the bent current collector extension portion 40 may be exposed on the end surface of the electrode wound body 50 . In other words, the end face of the electrode winding body 50 may be configured by at least a portion of the bent current collector extension portion 40 . That is, at least a portion of the current collector extension portion 40 may be bent so as to provide a substantially plane substantially perpendicular to the winding axis P at the end face of the electrode wound body 50 . By forming a substantially flat surface on the end face of the electrode winding body 50, a collector plate 70 (see FIG. 6), which will be described later, and the end face of the electrode winding body 50 can be connected with a wider connection area.

Here, "substantially planar" simply means that it is planar when viewed macroscopically. In other words, it is not a flat surface in a strict physical sense, but when viewed microscopically, it means that it includes a shape with minute unevenness, or a case where there is minute distortion in whole or part. . Since the current collector extension part 40 of the high-density region 40 a has a folded structure, the current collector extension part 40 has a surface portion that is aligned with the end face of the electrode winding body 50 . folded so that it is exposed to Therefore, a larger bonding area can be provided when the collector plate and the electrode winding body 50 are bonded to each other, which will be described later. Therefore, the electrode winding body of the present disclosure can also contribute to stronger connection between the current collector extension and the current collector plate.

In one embodiment of the present disclosure, the high density region 40 a is in fluid communication from the end of the electrode winding 50 to the interior of the electrode winding 50 via the voids 45 . That is, in the electrode-wound body 50 of the present disclosure, fluid can enter and exit between the outside and the inside of the electrode-wound body 50 via the pores 45 of the high-density region 40a. Such a structure can be useful when infiltrating the electrolyte into the wound electrode body 50 using vacuum injection or the like in manufacturing a secondary battery. Specifically, the hole portion 45 can be useful not only as an injection path for the electrolytic solution, but also as a degassing path during the injection. That is, in the secondary battery of the present disclosure, fluid such as electrolytic solution and gas (for example, air) flows through the electrode winding through the pores 45 of the high-density region 40a formed by the bent current collector extension 40. The inside of the rotating body 50 may be accessible. As described above, the holes 45 positioned at the ends of the electrode-wound body 50 can further improve the injection efficiency of the electrolytic solution into the electrode-wound body 50 .

In one aspect, the high-density region 40a extends from the end of the electrode winding body 50 to the inside through a plurality of holes 45 (for example, a plurality of holes that can be grasped in a cross-sectional view). may be in fluid communication with the Specifically, at least some of the pore portions 45 positioned in the high density region 40 a may be connected to each other through gaps formed between the current collector extension portions 40 . That is, the high-density region 40 a may be in fluid communication with the end portion of the electrode winding body 50 to the inside through at least one of the holes 45 . In such a structure, the fluid communication passages in the high density region 40a may have a serpentine shape. That is, fluid such as electrolyte and/or air can enter and exit along the gaps between the plurality of curved current collector extensions via at least one of the pores. Therefore, the structure described above facilitates smooth inflow of the injected electrolyte, so that more efficient injection of the electrolyte can be achieved.

The high density region 40 a may be positioned at the end of the electrode winding body 50 . That is, in one embodiment of the present disclosure, the high density region 40 a is positioned at the end of the current collector extension 40 . In other words, the high-density region 40 a may be formed at the end of the electrode wound body 50 by having a bent shape such that the end portion of the current collector extension portion 40 is compressed. The electrode winding body 50 having the high-density region 40a at the end portion is provided with one or more holes 45 provided in the high-density region 40a to inject the electrolytic solution and/or remove the inside of the electrode winding body. can be made more suitable. In addition, since the current collector extension portions 40 are present at the ends at high density, a wider connection effective area can be ensured in the electrical connection between the end surfaces of the electrode winding body 50 and the electrode terminals 81 . . Furthermore, it can contribute to reducing the occurrence of breakage of the electrode winding body 50 due to joining heat during assembly of the secondary battery and/or external impact that may be applied to the secondary battery. Therefore, the secondary battery including the high-density region 40a at the end of the electrode-wound body 50 is more suitable for reducing the influence on the inside of the electrode-wound body due to heat and shock that may be applied from the outside. Injectability of the electrolytic solution can be realized.

In a preferred embodiment, the end of the electrode winding body 50 having the high-density region 40a is the end on the electrode terminal side. That is, the high density region 40a may be positioned at the end of the electrode winding body 50 on the electrode terminal 81 (see FIG. 3) side. In other words, the high density region 40 a may be positioned at the end of the current collector extension that is more proximal to the electrode terminal 81 . Further, it is more preferable that the high-density region 40a be positioned at the extreme end of the electrode-wound body 50, as shown in FIG. That is, at the end of the electrode-wound body 50 , the high-density region 40 a may be positioned outside the low-density region 40 b and constitute the end face of the electrode-wound body 50 . In such a structure, the extreme end of the electrode winding body 50 may be composed of a plurality of current collector extension portions 40 that are folded over each other. The presence of the high-density region 40 a at the extreme end of the electrode-wound body 50 ensures a wider connection effective area in the electrical connection between the end face of the electrode-wound body 50 and the electrode terminal 81 .

As shown in FIG. 5, the low density regions 40b may have voids 46 between the current collector extensions 40 while the high density regions 40a have voids 45 as described above. . In a cross-sectional view passing through the winding axis P, the voids 46 can have a relatively larger cross-sectional area than the void portions 45 of the high-density region 40a. The voids 46 of the low-density region 40b are defined by the current collector extending portions 40 extending from the electrode winding body 50, and are elongated in the winding axis direction in a cross-sectional view passing through the winding axis P. may have. In one embodiment of the present disclosure, the voids 46 may be arranged substantially regularly between adjacent current collector extensions 40 . Additionally, at least a portion of cavity 45 may be in fluid communication with cavity 46 . In other words, the electrode windings 50 may be in fluid communication from the ends of the electrode windings 50 to the inside via the cavities 45 and voids 46 . With such a structure, fluids such as electrolyte and air can enter and exit the electrode winding body 50 through the holes 45 and the gaps 46 in the liquid injection process.

At least a portion of the current collector extension portion 40 defining the voids 46 of the low density region 40b may be substantially linear in a cross-sectional view passing through the winding axis. Here, the term “substantially linear” is not limited to a linear shape, and as shown in FIG. including. For example, "substantially linear" includes bending and continuing at an internal angle of about 150° or more, or about 160° or more. On the other hand, at least a portion of the current collector extension portion 40 may be bent in the low density region 40b. Specifically, the current collector extension 40 forming the void 46 may be bent in the vicinity of the high density region 40a. That is, the current collector extension portion 40 of the low density region 40b may extend substantially linearly and be bent in the vicinity of the high density region 40a.

Further, the curvature of the current collector extension portion 40 in the low density region 40b may be smaller than the curvature of the current collector extension portion 40 in the high density region 40a. Due to the structure described above, the impact that may be applied from the high density region 40a side can be more preferably absorbed by the low density region 40b. Furthermore, in the low-density region 40b, the current collector extension portion 40 has a portion that bends with a relatively small curvature and extends substantially linearly, so that the voids 46 can be made wider, so that the electrolytic solution and fluids such as air can be more preferably fluidly communicable.

The terms "high density region" and "low density region" in the present disclosure can be defined from the area ratio occupied by the current collector extension part 40 in a cross-sectional view passing through the winding axis P. That is, the area ratio of the current collector extending portion observed in a cross-sectional view passing through the winding axis P is, for example, about 30% or more, about 40% or more, about 50% or more, or about 60% or more. It may be referred to as a "high density area". In other words, the area ratio of the current collector extending portion observed in a cross-sectional view passing through the winding axis P is, for example, less than about 30%, less than about 40%, less than about 50%, or less than about 60%. A region may be referred to as a "low density region." When the area occupied by the current collector extending portion in the high-density region and the low-density region is within the above range, an electrode winding body more suitable in terms of impact resistance and liquid pourability can be realized.

For example, the "high density region" may be a region in which the current collector extension portion occupies an area ratio of about 30% or more and about 95% or less in a cross-sectional view passing through the winding axis P, for example, about 40%. % to about 95%, about 50% to about 95%, or about 60% to about 95%. When the area occupied by the current collector extending portion in the high-density region is within the above range, an electrode winding body more suitable in terms of impact resistance and liquid pourability can be realized.

On the other hand, the "low-density region" may be a region in which the current collector extension portion occupies an area ratio of about 3% or more and less than about 60% in a cross-sectional view passing through the winding axis P. For example, about The area may range from 3% to less than about 50%, from about 5% to less than about 40%, or from about 5% to less than about 60%.

In a cross-sectional view passing through the winding axis P, the area ratio occupied by the current collector extension can be calculated, for example, by imaging and image processing the cross section of the current collector extension. Specifically, after the electrode winding body is resin-hardened, the section of the current collector extending portion is cut out by polishing the section. It can then be measured by imaging and processing the cross-sections using an electron microscope.

For example, the current collector extending portion of the electrode winding body is cut out and hardened with resin. Here, a dicer (ISOMET 4000/manufactured by Buehler) can be used for the cutting. Epofix resin (manufactured by Struers) can be used as the resin used for resin hardening, and Epofix curing agent (manufactured by Struers) can be used as the curing agent.

After solidifying the cut-out current collector extension part with resin, it is cut to the vicinity of the observation surface, and then the observation surface is leveled using abrasive paper or the like. The polishing method is not particularly limited, but rough polishing can be performed using coarse abrasive paper, and then polishing can be performed using abrasive paper or an abrasive having a small abrasive grain size. For polishing, an automatic polishing machine Ecomet 300 (manufactured by Buehler), polishing paper and/or chemical mechanical polishing (CMP) may be used. Preferably, the cross section is polished with abrasive paper No. 220 and/or No. 500 or the like, and then polished using CMP to level the surface. By taking an image of the surface-exposed polished surface with an electron microscope and binarizing it using image processing software, the area ratio occupied by the current collector extension part in the cross section of the electrode winding body can be calculated. An example of an electron microscope used for imaging a polished surface is VHX-5000 (Keyence). Image processing software includes GIMP 2.1.0, for example. As image processing, an image captured by an electron microscope is grayscaled, then binarized, and the white-black ratio is calculated, whereby the area ratio occupied by the extended portion of the current collector can be calculated.

In a cross-sectional view passing through the winding axis P, the thickness of the high density region 40a may be relatively smaller or larger than the thickness of the low density region 40b. In other words, the low density regions 40b may have a relatively greater thickness than the high density regions 40a, or they may be thinner than the high density regions 40a. Note that when the thickness of the low-density region 40b is larger than that of the high-density region 40a, the injection amount of the electrolytic solution that flows into the electrode wound body 50 can be increased, and more suitable electrolytic solution injection can be performed. can be realized. Furthermore, the thicker low-density region 40b can more preferably absorb impacts applied from the outside, which can contribute to improving the impact resistance of the secondary battery.

For example, the thickness of the high-density region 40a is preferably about 5% or more and about 40% or less, for example, about 5% or more and about 30% or less, with respect to the thickness of the low-density region 40b. When the thickness of the high-density region 40a with respect to the thickness of the low-density region 40b is within the above range, an electrode winding body more suitable in terms of impact resistance and liquid pourability can be realized.

Further, in one embodiment of the present disclosure, the separator 3 may extend in the low density region 40b. In other words, the separator 3 extending at the end of the electrode winding 50 may be positioned inside the void 46 of the low density region 40b. In such an embodiment, the separator 3 extends outward in the direction along the winding axis P than the other electrode, which is different from either one of the positive electrode and the negative electrode having the current collector extension portion 40. . The current collector extension portion 40 extends further outward than the separator 3 . Since the separator 3 extends further than the other electrode, electrical continuity between the electrode having the current collector extension portion 40 and the other electrode is inhibited, so that short circuits can be more suitably prevented. Furthermore, since the current collector extension part 40 extends outside the separator 3, the separator 3 is prevented from being sandwiched between the adjacent current collector extension parts 40 in the high-density region 40a. , it may be possible to secure a larger pore volume. Therefore, the volume of fluid that can pass through the holes 45 can be increased, and more efficient electrolyte injection can be achieved.

FIG. 3 is a schematic cross-sectional view showing a cross section passing through the winding axis P of the secondary battery 100 according to one embodiment of the present disclosure. As described above, the secondary battery 100 of the present disclosure includes the electrode terminal 81 electrically connected to the electrode wound body 50 and the exterior body 60 enclosing the electrode wound body 50 . In one embodiment of the present disclosure, the lid portion 62 of the exterior body 60 may have an opening in the center. An electrode terminal structure 80 may be provided to cover the opening. In the present disclosure, the electrode terminal structure 80 is not particularly limited in its structure and configuration. For example, the electrode terminal structure 80 may include a gasket portion 82 provided between the electrode terminal 81 and the lid portion 62 . Further, for example, a center pin 90 may be inserted into the cavity provided at the winding center of the electrode winding body 50 .

In the present disclosure, the shape and configuration of the gasket portion 82 are not particularly limited. Although it is only an example, the gasket part 82 is provided so as to fill the gap between the electrode terminal 81 and the outer package 60 as shown in FIG. can also As shown in FIG. 3 , the gasket portion 82 may have a shape along the cover portion 62 so as to extend to the area outside the electrode terminal 81 . That is, the gasket portion 82 may be provided on the lid portion 62 so as to protrude from the electrode terminal 81 to the outside. The material of the gasket portion is not particularly limited as long as it exhibits insulating properties.

In the present disclosure, the electrode terminal 81 is not particularly limited in its shape and configuration. The electrode terminal 81 may have, for example, a rivet shape or a plate shape. The material of the electrode terminal is not particularly limited, and may contain at least one metal selected from the group consisting of aluminum, nickel, and copper. As shown in FIG. 3 , the electrode terminal 81 may have a shape along the lid portion 62 . The shape of the electrode terminal in plan view is also not particularly limited, and may be, for example, a substantially circular shape or a substantially rectangular shape.

As shown in FIG. 3 , the secondary battery of the present disclosure further includes a current collector plate 70 (71, 72) electrically connecting one of the electrode terminal 81 and the outer package 60 to the electrode winding body 50. You can have it. FIG. 6 is a schematic diagram for explaining assembly of the electrode winding body 50 and the current collector plate 70 according to an embodiment of the present disclosure. As illustrated, the current collector plate 70 may be electrically connected to the current collector extensions 40 (41, 42) at the ends of the electrode winding body 50. FIG. That is, the positive electrode and the negative electrode that constitute the electrode winding body 50 are electrically connected to the electrode terminal 81 and/or the exterior body 60 via the current collector plate 70 connected to the current collector extension portion 40, respectively. may be That is, the positive and negative current collector plates 70 may be electrically led out to the outside via the electrode terminals 81 and/or the exterior body 60 (see FIG. 3).

The current collector plate 70 may be made of a material that allows electron transfer to be achieved. For example, current collector plate 70 may be composed of conductive materials such as silver, gold, copper, iron, tin, platinum, aluminum, nickel, and/or stainless steel. The shape of the current collector plate 70 is not particularly limited, and may be, for example, strip-shaped, flat plate-shaped, or disc-shaped. In addition, as shown in FIG. 6, the current collector plate 70 (71, 72) may include a long portion 76 for connection with the electrode terminal 81 and/or the exterior body 60. As shown in FIG. The long portion 76 may be configured as an integral member with the current collector plate 70 . By configuring as an integral member, it is possible to omit the step of connecting the elongated portion 76 and the current collector plate 70 in the assembly of the secondary battery.

The current collector plates 70 on the side of the positive electrode current collector extension 41 and on the side of the negative electrode current collector extension 42 are electrically connected to the current collector extension 40 exposed on the endmost surface of the electrode wound body 50, respectively. may be For example, as shown in FIGS. 3 and 6, the positive electrode current collector extension 41 may be connected to the electrode terminal 81 via the current collector plate 71, and in such embodiments, the electrode terminal 81 is connected to the secondary battery. acts as the positive electrode of On the other hand, the negative electrode current collector extension 42 may be connected to the package 60 via the current collector plate 72, and in this embodiment, the package 60 acts as the negative electrode of the secondary battery. That is, the electrical connection between the electrode winding body 50 and the collector plates 71 and 72 is achieved by directly connecting the collector plates 71 and 72 to the collector extensions 41 and 42, respectively. you can

With such a structure, the extension of the current collector extending from the electrode and the current collector plate are connected without requiring a separate connection member such as a lead wire or tab for connecting the electrode and the current collector plate. can do. Therefore, the manufacturing process of the connecting member and the connecting process of the connecting member in the assembly of the secondary battery can be omitted, and the manufacturing efficiency of the secondary battery can be further improved. Furthermore, by providing current collecting plates 71 and 72 between the electrode winding body 50 and the electrode terminal 81 and/or between the electrode winding body 50 and the exterior body 60, the end face of the electrode winding body 50 and the electrode terminal 81/the exterior body 60 can be provided with a space. As a result, the internal space of the secondary battery is increased, and it is possible to increase the injection amount of the electrolytic solution when the electrolytic solution is injected.

7 and 8 are schematic partial cross-sectional enlarged views showing the electrode winding body 50 including the current collector plate 70 according to one embodiment of the present disclosure. As shown, the current collector plate 70 may be joined together with the high density region 40a of the current collector extension 40 . That is, the connection between the current collector plate 70 and the current collector extension 40 is achieved by connecting the current collector extension 40 and the current collector plate 70 at the end surface of the electrode winding body 50 to form the high-density region 40a. may be implemented such that the are attached to each other. With such a structure, the current collector plate 70 is connected to the current collector extension portion 40 present at the end face at a higher density, and a larger bonding area can be secured. Therefore, the current collector plate 70 and the current collector extension portion 40 are more firmly connected, and the durability of the secondary battery can be further improved.

As shown in FIG. 7, the holes 45 of the high density region 40a may be positioned near the inner surface of the current collector plate 70. As shown in FIG. Here, the "inner surface" means the joint surface of the current collector plate 70 with the high-density region 40a. The inventors of the present disclosure have found that such a structure contributes to the formation of through holes in the current collector plate 70 when the current collector extension portion 40 and the current collector plate 70 are thermally bonded.

Specifically, when connecting the current collector plate 70 and the current collector extension 40 , heat applied for joining (for example, welding) causes the hole portion 45 near the inner surface of the current collector plate 70 to open. The internal gas (eg, air) of is heated. As the temperature inside the hole portion 45 rises, the volume of the internal air expands, and the expanded air escapes to the outside so as to push away the current collector plate 70 melted by the joining heat (for example, welding heat). The pushed-out portion of the metal solidifies as it is, and a through hole 75 is formed in the collector plate 70 (see FIG. 8). That is, when the current collector plate 70 is joined, the air in the hole 45 heated by the heat of joining can be discharged to the outside while forming the through hole 75 in the melted current collector plate 70 .

The through hole 75 formed in this manner may be in fluid communication with the inside of the electrode winding body 50 via the hole portion 45 . Therefore, the through hole 75 can contribute to injection and degassing of the electrolytic solution, and can function as an injection port for the electrolytic solution. From the above, the thermal joint (for example, welded portion) with the current collector plate 70 and/or the hole portion 45 existing in the vicinity of the thermal joint can realize more suitable electrolyte injection. . Furthermore, since the step of providing the liquid injection port in the current collector plate 70 can be omitted, the above structure can contribute to improving the manufacturing efficiency of the secondary battery.

Here, the "nearby" broadly means a range that can be affected by the heat applied when the current collector plate 70 and the current collector extension portion 40 are joined together. In a narrow sense, the “neighborhood” in the present disclosure is a range in which at least part of the current collector extension portion 40 forming the hole portion 45 can be melted by heat applied during bonding. Specifically, on the inner surface of the current collector plate 70, the radial distance from the welding point is, for example, 0 mm or more (excluding 0 mm) and about 3 mm or less, 0 mm or more (excluding 0 mm) and about 2 mm or less, or 0 mm. A range of about 1 mm or less (not including 0 mm) may be regarded as the vicinity. Although it is more preferable that the hole portion 45 is positioned immediately below the thermal joint portion, the hole portion 45 is not particularly limited as long as the effect of forming the through hole described above can be obtained.

A through hole 75 formed in the current collector plate 70 may be in fluid communication with the hole portion 45 . Also, the through holes 75 may be in fluid communication with a plurality of voids 45 in the high density region. Such through-holes 75 include at least one of the through-holes 75 previously formed in the current collector plate 70 before thermal bonding with the current collector extension portion 40 and the through-holes 75 formed during thermal bonding. In other words, the through hole 75 may be formed in advance before the current collector 70 is thermally bonded. Due to the structure in which the through holes 75 and the holes 45 are in fluid communication, the electrolytic solution can flow into the holes through the through holes 75 at the time of injection. can be realized.

Further, the through hole 75 fluidly communicating with the hole portion 45 may further fluidly communicate with the inside of the electrode wound body 50 . That is, the through holes 75 of the current collector plate 70 may be in fluid communication with the inside of the electrode winding body 50 via the holes 45 . In addition, the through holes 75 are in fluid communication with the inside of the electrode wound body 50 via a plurality of holes 45 (preferably a plurality of holes that can be seen in cross section) in the high-density region 40a. may In such a structure, the electrolyte may be injected into the electrode winding body 50 from the through hole 75 via one or more holes 45 . Further, the gas inside the electrode-wound body 50 may be degassed to the outside of the electrode-wound body 50 from the through-hole 75 via one or a plurality of holes 45 at the time of liquid injection. Therefore, the holes 45 formed in the high-density region 40 a can act as fluid paths between the inside of the electrode winding body 50 and the through holes 75 of the current collector plate 70 . Therefore, the flow of fluid between the inside and the outside of the electrode winding body 50 is made more efficient, and more suitable electrolyte injection can be realized.

The thickness of the current collector 70 is not particularly limited as long as thermal bonding with the current collector extension portion 40 is possible. More specifically, in a cross-sectional view passing through the winding axis P, the thickness of the current collector plate 70 is not particularly limited as long as the above-described through holes 75 can be formed during thermal bonding. For example, in a cross-sectional view passing through the winding axis P, the thickness of the current collector plate 70 may be about 0.2 times or more and about 10 times or less the thickness of the high-density region 40a, for example, about 0.5 times. Values can range from greater than or equal to about 5 times less. In other words, in a cross-sectional view passing through the winding axis P, the thickness of the high-density region 40a may be about 0.1 times or more and about 5 times or less the thickness of the current collector plate 70, for example, about 0.5 times. It can be a value in the range of greater than or equal to 5 times and less than or equal to about 4 times.

In one aspect, as shown in FIGS. 7 and 8, the thickness of the high-density region 40a may be relatively greater than the thickness of the current collector 70 in a cross-sectional view passing through the winding axis P. That is, in one embodiment of the present disclosure, the current collector extensions 40 are folded over each other so as to form a high-density region 40a having a thickness greater than that of the current collector 70 in cross-sectional view. For example, in a cross-sectional view passing through the winding axis, the thickness of the high-density region 40a may be about 1.05 times or more and about 5 times or less the thickness of the current collector plate 70, for example, about 1.5 times or more. Values in the range of about 4 times or less can be used.

The electrode winding body 50 having the high-density region 40a with a sufficient thickness can reduce the influence of heat for bonding on the components of the electrode winding body 50 when thermally bonding with the current collector plate 70. can. In particular, the heat applied during bonding can cause damage to the separators 3 forming the electrode winding body 50 . Therefore, the secondary battery of the present embodiment, in which bonding heat is less likely to be transferred to the inside of the electrode, can contribute to further improving the durability of the secondary battery. Furthermore, when the through hole 75 is formed by joining the current collector extending portion 40 and the current collector plate 70 , the high density region 40 a having a thickness larger than the current collector plate 70 expands from the melted portion of the current collector plate 70 . It can also contribute to preferentially degassing the air that has been degassed. Therefore, having the high-density region 40a have a greater thickness than the current collector facilitates the formation of the through-holes 75 and can assist in more suitable electrolyte injection.

[Manufacturing method of secondary battery according to the present disclosure]
Next, a method for manufacturing the secondary battery of the present disclosure will be described with reference to FIGS. 9 to 13. FIG. Note that the method described below is merely an example, and the method for manufacturing a secondary battery according to the embodiment of the present disclosure is not limited to the following method.

A secondary battery according to the present disclosure can be manufactured by a manufacturing method including the following steps. That is, the method for manufacturing a secondary battery according to the present disclosure includes a step of winding the positive electrode 1, the negative electrode 2, and the separator 3 disposed therebetween to form the electrode-wound body 50 (electrode-wound body forming step ), a step of shaping the end surface of the electrode winding body 50 having the current collector extension portion (end face shaping step), and a step of attaching a current collector plate to the electrode winding body 50 (current collector mounting step), A step of injecting an electrolyte into the exterior body 60 while housing the electrode wound body 50 in the exterior body 60 (accommodation process) is included.

(Step of Forming Electrode Winding Body)
FIG. 9 is a schematic diagram for explaining constituent members of the electrode-wound body 50 that constitutes the secondary battery according to one embodiment of the present disclosure. Moreover, FIG. 10 is a schematic perspective view for explaining the winding mode of the electrode wound body 50 according to one embodiment of the present disclosure. In this step, the electrode winding body 50 is obtained by winding the positive electrode 1, the negative electrode 2 and the separator 3 having a rectangular shape so as to overlap each other in a predetermined order. A process of forming an electrode winding body according to an embodiment of the present disclosure will be described below.

In this process, first, the positive electrode 1, the negative electrode 2, and the two separators 3 are arranged in a predetermined order. As shown in FIG. 9, the positive electrode 1 or the negative electrode 2 has a positive electrode current collector extension portion 41 where the current collector is exposed at one of the long sides (before winding). Alternatively, it has the negative electrode current collector extension portion 42 . At that time, as shown in FIG. 10, the separator 3 is superimposed between the positive electrode 1 and the negative electrode 2, and the positive electrode current collector extension part 41 extends outside the negative electrode 2 and the separator 3, and the negative electrode current collector The body extension part 42 is arranged so as to extend outside the positive electrode and the separator 3 . That is, the positive electrode material layer and the negative electrode material layer are stacked so that they face each other with the separator interposed therebetween, and the positive electrode current collector is placed on one of the long sides (before winding) of the electrode configuration layer. The extension part 41 is extended and the negative electrode current collector extension part 42 is extended at the other end side, and the electrode is arranged and wound.

FIG. 11 is a schematic perspective view showing the electrode winding body 50 after winding according to one embodiment of the present disclosure. 12 is a schematic cross-sectional view of the wound electrode body 50 of FIG. 11, taken along the line CC passing through the winding axis P, viewed in the direction of the arrow. The length w1 (see FIG. 9) of the current collector extending portion 40 in the winding axis direction is not particularly limited as long as a desired electrode winding can be obtained. For example, the length dimension w1 of the current collector extension portion 40 in the direction of the winding axis (particularly, the length dimension before winding or before end face shaping, which will be described later) is usually about 0.5 mm or more and about 20 mm or less. is preferably about 1 mm or more and about 15 mm or less. The positive electrode current collector extension portion 41 and the negative electrode current collector extension portion 42 may each have the same length dimension w1, or may have mutually different length dimensions w1.

The dimensions of the separator 3 and the positive and negative electrodes to be used are not particularly limited as long as the desired electrode winding body can be obtained. For example, the length dimension of the separator 3 in the longitudinal direction may be appropriately determined according to the dimensions of the intended secondary battery (in particular, the number of windings of the electrode winding body).

(End face shaping process)
At the end of the electrode winding body 50 obtained in the previous step, at least a portion of the current collector extending portion 40 is bent to obtain a shaped end face of the electrode winding body 50 . Bending may be performed by pressing the current collector extension 40 . When shaping the end face, the end portion of the electrode winding body 50 is bent inside the electrode winding body 50 so that the current collector extension portion 40 does not protrude outside the outer circumference of the electrode winding body 50 . It may be bent so as to fold the current collector extension portion 40 toward the circumferential side. Moreover, in order to make the connection with the current collector plate 70 (see FIG. 6) stronger in subsequent steps, at least a portion of the bent current collector extension portion 40 is bent in a direction perpendicular to the winding axis P. The end faces may be shaped to provide a substantially flat surface to the . The term "substantially flat" in the present disclosure means that it is not a flat surface in a strict physical sense, but includes a shape with fine unevenness, or a case where there is a fine distortion entirely or partially. . That is, at least a portion of the hole may be exposed on the shaped end face.

Shaping may be performed, for example, by pressing the current collector extension 40 from the outside. FIG. 13 is a schematic plan view for explaining an example of end face shaping according to an embodiment of the present disclosure; The current collector extension part 40 may be spirally pressed from the outer peripheral side to the inner peripheral side of the electrode wound body 50 in plan view. By such a pressing method, the current collector extension part 40 can be laid down so as to be folded over at the end surface, and can provide a substantially flat surface in a direction perpendicular to the winding axis P. As shown in FIG.

The means for shaping the end face of the electrode winding body 50 is not particularly limited as long as the desired end face can be obtained. For example, by pressing a pressing member against the end face of the electrode wound body 50 from the outside and moving the electrode wound body 50 and/or the pressing member in a direction perpendicular to the winding axis P, the end face is may be shaped. The structure, material, number, etc. of the pressing member are not particularly limited as long as a desired end surface of the wound electrode body 50 can be obtained. Examples of the pressing member include a pressing roller and a pressing plate.

(Mounting process of current collector)
A collector plate 70 is electrically connected to the end surface of the electrode winding body 50 shaped in the previous step (see FIGS. 6 to 8). The current collector plate 70 may be attached so as to join with the flat surface formed on the electrode winding body 50 . The joining may be performed by thermal bonding, for example by welding, welding or the like. As an example, the current collector plate 70 and the electrode winding body 50 may be welded by a laser irradiation method. For example, by irradiating the current collector plate 70 with a laser, the current collector plate 70 and the current collector extension portion 40 immediately below the current collector plate 70 are melted and alloyed to obtain electrical continuity. In addition, by applying laser heat to the holes 45 existing in the vicinity of the inner surface of the current collector plate 70 (preferably, the thermal joint and/or the vicinity of the thermal joint), the air in the holes 45 is removed. A through hole 75 may be formed in the current collector plate 70 by thermal expansion.

(Accommodation process)
While the electrode winding body to which the current collector plate is attached is accommodated in the outer insert, the current collector plate is electrically connected to the electrode terminal or the outer package, and the electrolytic solution is injected into the outer package. An example of a case where the exterior body is composed of a main body portion and a lid portion and electrode terminals are provided on the lid portion will be described below by way of example.

First, the lid, the electrode terminals, and an insulating member (for example, a gasket) provided to fill the gap between the lid and the electrode terminals are adhered. Next, after preliminarily bending the elongated portion extending from the current collector plate toward the electrode terminal or the exterior body to fix the shape, the elongated portion is connected to the electrode terminal or the exterior body. Next, the main body and the lid of the outer package are bonded together. Finally, the electrolytic solution is injected from an injection port (not shown) of the outer package, and the injection port is closed with a sealing plug (not shown). Adhesion may be achieved by any method known in the field of secondary batteries, for example laser irradiation may be used.

Although the embodiments of the present disclosure have been described above, they are merely examples of typical examples. A person skilled in the art will easily understand that the present disclosure is not limited to this, and that various aspects are conceivable without changing the gist of the present disclosure.

The secondary battery according to the present disclosure can be used in various fields where power storage is assumed. Although it is only an example, the secondary battery of the present disclosure is used in the electric, information, and communication fields where mobile devices are used (for example, mobile phones, smartphones, laptops and digital cameras, activity meters, arm computers, electronic Paper, RFID tags, card-type electronic money, electric and electronic equipment fields including small electronic devices such as smart watches, or mobile device fields), household and small industrial applications (e.g., power tools, golf carts, household and nursing care・Industrial robot field), large industrial applications (e.g. forklifts, elevators, harbor cranes), transportation system fields (e.g. hybrid vehicles, electric vehicles, buses, trains, power-assisted bicycles, electric motorcycles, etc.) ), power system applications (for example, fields such as various power generation, load conditioners, smart grids, and general household electrical storage systems), medical applications (medical device fields such as earphone hearing aids), pharmaceutical applications (medication management systems, etc.) field), IoT field, space/deep-sea applications (for example, fields of space probes, submersible research vessels, etc.), and the like.

1 Positive Electrode 11 Positive Electrode Current Collector 12 Positive Electrode Material Layer 2 Negative Electrode 21 Negative Electrode Current Collector 22 Negative Electrode Material Layer 3 Separator 5 Electrode Configuration Layer 50 Electrode Winding Body 40 Current Collector Extension 40a High Density Region 40b Low Density Region 41 Positive Electrode Current collector extension portion 42 Negative electrode current collector extension portion 45 Hole portion 46 Air gap 60 Exterior body 61 Body portion 62 Lid portion 70 Current collector plate 71 Positive electrode current collector plate 72 Negative electrode current collector plate 75 Penetration hole 76 Elongated portion 80 electrode terminal structure 81 electrode terminal 82 gasket portion 90 center pin 100 secondary battery

Claims (13)

1. comprising an electrode winding body composed of a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode;
   At least one of the ends of the electrode winding body, either one of the positive electrode and the negative electrode has a current collector extension portion in which a current collector extends outside the other electrode. formed by
   The current collector extension has a high density region where the density of the current collector extension is relatively high and a low density region where the density is relatively low,
   The secondary battery, wherein the high-density region has pores in a cross-sectional view.
2. The secondary battery according to claim 1, wherein the high-density region is positioned at the end of the current collector extension.
3. the current collector extension is bent in the high density region,
   3. The secondary battery according to claim 1, wherein said void is defined by said bent current collector extension.
4. The secondary battery according to any one of claims 1 to 3, wherein the high-density region is in fluid communication from the end of the electrode winding body to the inside through the void.
5. The secondary battery according to any one of claims 1 to 4, wherein the area ratio of the high-density region in the extended portion of the current collector is 40% or more and 95% or less in a cross-sectional view.
6. The secondary battery according to any one of claims 1 to 5, wherein the current collector extending portion extends outside the separator.
7. an electrode terminal electrically connected to the electrode winding body; an exterior body enclosing the electrode winding body; and electrically connecting at least one of the electrode terminal and the exterior body to the electrode winding body. and a current collector plate for
   7. The secondary battery according to claim 1, wherein said current collector plate is electrically connected to said current collector extension.
8. The secondary battery according to claim 7, wherein the current collector plate and the high-density region are bonded to each other.
9. The secondary battery according to claim 7 or 8, wherein the holes are positioned at least in the vicinity of the inner surface of the current collector plate.
10. The secondary battery according to claim 9, wherein the current collector plate has a through hole, and the through hole is in fluid communication with the hole.
11. 11. The secondary battery according to claim 10, wherein the through hole is in fluid communication with the inside of the electrode winding body through the hole.
12. The secondary battery according to any one of claims 7 to 11, wherein the thickness of the high-density region is relatively larger than the thickness of the current collector plate in a cross-sectional view.
13. The secondary battery according to any one of claims 1 to 12, wherein the high-density region has, at least in part, a structure in which a plurality of current collector extension portions are folded over each other.

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