Cylindrical battery

Abstract

To provide a cylindrical battery equipped with a safety valve that can suitably suppress unintentional current interruption and re-conduction after current interruption in the event of a battery abnormality.SOLUTION: A cylindrical battery includes a top cover and a safety valve, the safety valve having a safety cover and a stripper disk located inward of the safety cover in the battery axial direction, and a predetermined portion of the safety cover located between the contact point between the safety cover and the top cover and the contact point between the safety cover and the stripper disk is an inclined portion that is inclined inward in the battery axial direction with respect to the contact surface between the safety cover and the top cover.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a cylindrical battery. [Background technology]

[0002] Cylindrical batteries and other batteries can extract energy from chemical reactions as electrical energy and are used in a variety of applications, such as in mobile devices such as laptops.

[0003] Safety is a requirement for cylindrical batteries. To ensure this safety, there are cylindrical batteries equipped with a safety valve that can cut off current in the event of an abnormality (see Patent Document 1). This cylindrical battery has a top cover and a safety valve, and the safety valve has a safety cover with a stepped structure and a stripper disk located inward of the safety cover in the axial direction of the battery. The stepped structure of the safety cover makes it possible to control deformation of the safety cover due to an increase in internal pressure in the event of a battery abnormality. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent No. 2016 / 0028058 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present application have found that there are some issues that can be improved regarding conventional cylindrical batteries. Specifically, if the safety cover only has a stepped structure, the center of the safety cover may deform under low pressure when there is no battery abnormality. As a result, the amount of displacement of the safety cover increases under such low pressure, which may result in an unintended current interruption. Furthermore, if the safety cover only has a stepped structure, the amount of displacement of the safety cover required for current interruption is small, which may result in contact between the safety cover and the stripper disk after current interruption in the event of a battery abnormality, leading to the re-establishment of current conduction.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a cylindrical battery equipped with a safety valve that can effectively suppress unintended current interruption and re-conduction after current interruption in the event of a battery abnormality. [Means for solving the problem]

[0007] In order to achieve the above object, in one embodiment of the present invention, A top cover and a safety valve are provided. the safety valve has a safety cover and a stripper disc located inward of the safety cover in the battery axial direction, A cylindrical battery is provided in which a predetermined portion of the safety cover located between the portion where the safety cover and the top cover contact and the portion where the safety cover and the stripper disk contact is an inclined portion that is inclined inward in the battery axial direction relative to the contact surface where the safety cover and the top cover contact. [Effects of the Invention]

[0008] The cylindrical battery according to the present invention can effectively prevent unintended current interruption and re-conduction after current interruption in the event of a battery abnormality. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view showing the appearance of a cylindrical battery. [Figure 2] FIG. 2 is a schematic diagram showing the internal structure of a cylindrical battery. [Figure 3] FIG. 3 is a schematic perspective view showing the components and related members of the safety valve of the cylindrical battery in an expanded state. [Figure 4] FIG. 4 is a schematic cross-sectional view showing the configuration of a safety valve of a cylindrical battery according to one embodiment of the present invention. [Figure 5] FIG. 5 is a graph showing the relationship between the displacement of the safety cover and the pressure applied to the safety cover, depending on whether or not the safety cover has an inclined portion. [Figure 6] FIG. 6 is a schematic cross-sectional view for explaining the amount of displacement of the safety cover. [Figure 7] FIG. 7 is a schematic cross-sectional view for explaining the mechanism of action when pressure is applied to the inclined portion of the safety cover. [Figure 8A] FIG. 8A is a schematic cross-sectional view showing a first pattern of a step portion in the thickness direction of the safety cover. [Figure 8B] FIG. 8B is a schematic cross-sectional view showing a second pattern of a step portion in the thickness direction of the safety cover. [Figure 8C] FIG. 8C is a schematic cross-sectional view showing a third pattern of a step portion in the thickness direction of the safety cover. [Figure 9] FIG. 9 is a table showing the measurement results for the examples and comparative examples of the present application. [Figure 10] FIG. 10 is a graph showing the relationship between the pressure on the safety cover and the amount of displacement of the safety cover due to differences in the thickness of the thin-walled portion of the first step portion of the safety cover. [Figure 11] FIG. 11 is a graph showing the relationship between the pressure on the safety cover and the amount of displacement of the safety cover depending on the shape of the first step portion of the safety cover. [Figure 12]FIG. 12 is a graph showing the relationship between the pressure on the safety cover and the amount of displacement of the safety cover depending on the shape of the second step portion of the safety cover. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a cylindrical battery according to one embodiment of the present invention will be specifically described with reference to the drawings.

[0011] [Basic structure of cylindrical battery] The cylindrical "battery" referred to in this specification includes not only so-called "secondary batteries" but also "primary batteries" that can only be discharged. In other words, the "battery" referred to in this specification may be a "secondary battery" that can be repeatedly charged and discharged, or a "primary battery" that is essentially only discharged. Note that the term "secondary battery" is not overly restrictive and may also include, for example, "electricity storage devices."

[0012] For convenience of explanation, the cylindrical battery according to the present invention will be described below mainly using a secondary battery as an example. Fig. 1 is a schematic perspective view showing the appearance of a cylindrical battery. Fig. 2 is a schematic view showing the internal structure of the cylindrical battery. Fig. 3 is a schematic perspective view showing the components of the safety valve and related components of the cylindrical battery in an expanded state.

[0013] A secondary battery includes an electrode assembly made up of electrode constituent layers including a positive electrode, a negative electrode, and a separator. The secondary battery may have a wound structure in which such electrode constituent layers are wound into a roll (hereinafter also referred to as a "wound electrode body" or "wound structure"). As shown in the figure, an electrode assembly 10 is housed inside a cylindrical battery can 50. In the exemplary embodiment shown in FIG. 2, the electrode assembly 10 has a configuration in which a positive electrode 11, a negative electrode 12, and a separator 13 disposed between the positive electrode and the negative electrode are wound together. In a secondary battery 1000, such an electrode assembly 10 is enclosed in a cylindrical battery can 50 together with an electrolyte (e.g., a non-aqueous electrolyte).

[0014] The positive electrode 11 is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, the positive electrode material layer is provided on at least one side of the positive electrode current collector. The positive electrode material layer contains a positive electrode active material as an electrode active material. For example, each of the multiple positive electrodes in the electrode assembly may have a positive electrode material layer provided on both sides of the positive electrode current collector, or may have a positive electrode material layer provided on only one side of the positive electrode current collector.

[0015] The negative electrode 12 is composed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode, the negative electrode material layer is provided on at least one side of the negative electrode current collector. The negative electrode material layer contains a negative electrode active material as an electrode active material. For example, each of the multiple negative electrodes in the electrode assembly may have a negative electrode material layer provided on both sides of the negative electrode current collector, or may have a negative electrode material layer provided on only one side of the negative electrode current collector.

[0016] The electrode active materials contained in the positive electrode 11 and the negative electrode 12, i.e., the positive electrode active material and the negative electrode active material, respectively, 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 layer" and the "negative electrode active material contained in the negative electrode layer" provide ions to the electrolyte, and these ions move between the positive electrode and the negative electrode, transferring electrons and causing charge and discharge. The positive electrode layer and the negative electrode layer may be layers capable of absorbing and desorbing lithium ions. In other words, the secondary battery of the present invention may be a nonaqueous electrolyte secondary battery in which lithium ions move between the positive electrode and the negative electrode via a nonaqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charge and discharge, the secondary battery of the present invention corresponds to a so-called "lithium ion battery," and has electrodes capable of absorbing and desorbing lithium ions as the positive electrode and the negative electrode, preferably layers capable of absorbing and desorbing lithium ions.

[0017] In the case of a lithium-ion battery, the positive electrode active material may be a material that contributes to the absorption and desorption of lithium ions. That is, the positive electrode layer may contain one or more positive electrode materials that can absorb and desorb lithium. From this perspective, the positive electrode active material may be, for example, a lithium-containing compound. The type of lithium-containing compound is not particularly limited, but examples include lithium-containing composite oxides and lithium-containing phosphate compounds. This is because a high energy density can be easily obtained.

[0018] The lithium-containing composite oxide is a general term for oxides containing lithium and one or more other elements (elements other than lithium) as constituent elements, and may have, for example, a layered rock salt type or a spinel type crystal structure. The lithium-containing phosphate compound is a general term for phosphate compounds containing lithium and one or more other elements as constituent elements, and may have, for example, an olivine type crystal structure. The type of the other element is not particularly limited as long as it is one or more of any element. In particular, the other element is preferably one or more of elements belonging to Groups 2 to 15 of the long period periodic table. More specifically, the other element is, for example, nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), etc. This is because a high voltage can be easily obtained.

[0019] The positive electrode layer may contain a binder. The positive electrode layer may also contain a positive electrode conductive agent to facilitate the transfer of electrons that drive the battery reaction. The positive electrode binder may contain, for example, one or more of synthetic rubbers and polymeric compounds. Examples of synthetic rubbers include styrene-butadiene rubbers, fluorine-containing rubbers, and ethylene propylene dienes. Examples of polymeric compounds include polyvinylidene fluoride and polyimides. The positive electrode conductive agent may contain, for example, one or more of carbon materials. Examples of carbon materials include graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer, as long as it is a conductive material.

[0020] Similarly, the negative electrode active material of the negative electrode layer may be a material that contributes to the absorption and desorption of lithium ions. That is, the negative electrode layer may contain one or more negative electrode materials that can absorb and desorb lithium. From this perspective, the negative electrode active material may be, for example, various carbon materials, metal materials, and / or other materials.

[0021] When a carbon material is used as the negative electrode active material, the change in the crystal structure during lithium absorption and desorption is very small, so a high energy density can be easily obtained stably. In addition, the carbon material also functions as a negative electrode conductive agent, so the conductivity of the negative electrode layer can be easily improved.

[0022] Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and / or graphite. More specifically, the carbon material may be, for example, pyrolytic carbon, cokes, glassy carbon fiber, organic polymer compound calcined bodies, activated carbon, and carbon blacks. Examples of cokes include pitch coke, needle coke, and petroleum coke. Examples of organic polymer compound calcined bodies are substances obtained by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. Alternatively, the carbon material may be low-crystalline carbon heat-treated at a temperature of approximately 1000°C or less, or amorphous carbon. The shape of the carbon material is not particularly limited and may be at least one of fibrous, spherical, granular, and flaky.

[0023] The term "metallic material" used as the negative electrode active material is a general term for materials containing one or more of metal elements and semimetal elements as constituent elements. When a carbon material is used as the negative electrode active material, a high energy density is easily obtained. The metallic material may be a simple substance, an alloy, a compound, or two or more of these, or may be a material that at least partially contains one or more of these phases.

[0024] Specifically, the metal element and the metalloid element may be, for example, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium (Y), palladium (Pd), and / or platinum (Pt).

[0025] The negative electrode layer may contain a binder. Furthermore, the negative electrode layer may contain a negative electrode conductive agent to facilitate the transfer of electrons that promote the battery reaction. Binders that may be contained in the negative electrode layer include, but are not limited to, at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resins, and polyamide-imide resins. Negative electrode conductive agents that may be contained in the negative electrode layer include, but are not limited to, at least one selected from the group consisting of carbon blacks such as thermal black, furnace black, channel black, ketjen black, and acetylene black; carbon fibers such as graphite, carbon nanotubes, and vapor-grown carbon fibers; metal powders such as copper, nickel, aluminum, and silver; and polyphenylene derivatives. The negative electrode layer may also contain components derived from thickeners (e.g., carboxymethyl cellulose) used during battery production.

[0026] The positive electrode current collector and the negative electrode current collector used for the positive electrode 11 and the negative electrode 12 are members that contribute to collecting and supplying electrons generated in the electrode active material due to the battery reaction. Such electrode current collectors may be sheet-shaped metal members. The electrode current collectors may be single-layer or multi-layer. Furthermore, the electrode current collectors may be porous or perforated. For example, the current collectors may be metal foil, punched metal, mesh, expanded metal, or the like. The positive electrode current collector used for the positive electrode may be made of, for example, a metal foil containing at least one selected from the group consisting of aluminum, nickel, stainless steel, and the like. On the other hand, the negative electrode current collector used for the negative electrode may be made of, for example, a metal foil containing at least one selected from the group consisting of copper, aluminum, nickel, stainless steel, and the like.

[0027] The separator 13 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 separates the positive and negative electrodes and allows ions (e.g., lithium ions) to pass through while preventing short circuits of current due to contact between the two electrodes. For example, the separator may be a porous or microporous insulating member, and may have a membrane form due to its small thickness. The separator 13 may be, for example, one or more types of porous membranes made of synthetic resin and / or ceramic, or may be a laminated membrane of two or more types of porous membranes.

[0028] The electrolyte may typically be an electrolytic solution. The electrolytic solution contains a solvent and an electrolyte salt. The electrolytic solution may further contain one or more of other materials such as additives. In a preferred embodiment, the separator is impregnated with the electrolytic solution, and the positive electrode and / or the negative electrode may also be impregnated with the electrolytic solution.

[0029] The solvent may include one or more non-aqueous solvents such as organic solvents. An electrolyte solution containing a non-aqueous solvent can be a so-called non-aqueous electrolyte solution. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, lactones, chain carboxylic acid esters, and / or nitriles (e.g., mononitriles).

[0030] The cylindrical battery can 50 corresponds to a battery exterior member that encases the electrode assembly 10, which is made up of laminated electrode constituent layers including a positive electrode 11, a negative electrode 12, and a separator 13. The battery can 50 may have, for example, a hollow structure with one end closed and the other end open (open as an open end). The battery can 50 is not particularly limited, but may be a metal can containing one or more of metal materials such as iron, aluminum, stainless steel, and alloys thereof. The surface of the battery can 50 may be plated with one or more of metal materials such as nickel.

[0031] Furthermore, a safety valve 100 may be provided at the open end 51 of the cylindrical battery can 50. By way of example only, the safety valve 100 may be provided at the open end of the battery can 50 via a gasket (that is, the battery safety valve 100 may be provided together with, for example, a crimping mechanism).

[0032] The configuration of the safety valve 100 will be described below (see FIG. 3).

[0033] The safety valve 100 serves as a battery terminal (i.e., one of the positive and negative terminals as the battery's external terminals) and is equipped with a mechanism that can be displaced in response to excessive battery internal pressure. The safety valve 100 comprises at least a safety cover 110, a stripper disk 130, and an insulating member 120 positioned therebetween. The safety valve 100 may further be provided with a top cover 150 on the outer side of the safety cover 110 in the battery axis direction. Here, the outer side in the battery axis direction refers to the side opposite the side on which the electrode assembly 10 is located, relative to the position of the safety cover 110, in the battery axis direction.

[0034] The safety cover 110 is positioned relatively outward in the battery axial direction, while the stripper disk 130 is positioned relatively inward in the battery axial direction, and they are electrically connected to each other. Preferably, the safety cover 110 and the stripper disk 130 are connected to each other in a manner that straddles the insulating member 120.

[0035] In this specification, the term "battery axis" refers to an axis P that passes through the center of the battery can, which corresponds to the battery exterior, and extends in a direction perpendicular to the end face or bottom face of the battery can (see FIGS. 1 to 3). For example, the battery axis refers to an axis that passes through the center of the battery can 50 and extends in a direction perpendicular to the radial direction of the bottom face of the battery can. Alternatively, the battery axis may be an axis that extends between both terminals and passes through the centers of both terminals. For these reasons, the term "battery axis direction" refers to the direction in which the above-mentioned battery axis extends.

[0036] The safety cover 110 and the stripper disk 130 may each be a disk-shaped member. Each of the safety cover 110 and the stripper disk 130 may have a shape that extends, for example, as a whole in the battery width direction (a direction corresponding to the radial direction of the battery in a cylindrical battery). In other words, each of the safety cover 110 and the stripper disk 130 may have a shape that extends as a whole in a direction perpendicular to the battery axial direction. The insulating member 120 may have an opening or a hollow portion in its inner or central region and may be plate-shaped (e.g., plate-shaped) or flat as a whole.

[0037] The safety cover 110, stripper disk 130, and insulating member 120 having the above-described configuration are directly stacked on top of each other to form a safety valve. The safety cover 110 contributes to the function of the safety valve by displacing when subjected to internal battery pressure during an abnormality. Specifically, when the stripper disk 130 breaks at a groove formed therein, the safety cover 110 bends along with the broken stripper disk 130, and this displacement interrupts the current. Note that the scope of application of the present invention also includes safety valves 100 that include components other than the safety cover 110, stripper disk 130, and insulating member 120.

[0038] The safety cover 110 provided as a safety cover mainly corresponds to a displaceable member that can close the open end 51 of the battery can 50 and is deformable and / or openable in response to an increase in the internal pressure of the battery can. The internal pressure of the battery can may increase due to a side reaction such as a decomposition reaction of the electrolyte. That is, when a side reaction such as a decomposition reaction of the electrolyte occurs, gas such as carbon dioxide is generated inside the battery can, and the internal pressure of the battery can may increase undesirably as the amount of generated gas increases.

[0039] The safety cover 110 may have, for example, multiple stepped portions 111, 112 as an ideal shape for preventing unintended interruption and re-establishment of conduction between a portion X where the safety cover 110 and the top cover 150 contact each other and a portion Y where the safety cover 110 and the stripper disk 130 contact each other. Specifically, the safety cover 110 may have a first stepped portion 111 located on the outer periphery and a second stepped portion 112 located on the inner periphery. A first groove 118 that contributes to the cleavage of the safety cover 110 is formed between the first stepped portion 111 and the second stepped portion 112. The inner periphery and outer periphery referred to here correspond to the inner and outer radial sides of the battery can 50, respectively, relative to the battery axis P (an axis that passes through the center of the battery can 50 and extends in a direction perpendicular to the radial direction of the bottom surface of the battery can).

[0040] The safety cover 110 may be a metal member. For example, the safety cover 110 may include one or more of metal materials such as aluminum (e.g., aluminum metal or aluminum alloy such as A1050, A3203, and / or A5052), iron (Fe), titanium (Ti), platinum (Pt), and gold (Au). In other words, the safety cover 110 may be a member made of such a conductive material.

[0041] The planar shape of the safety cover 110, particularly the outer contour shape in a planar view (hereinafter also referred to as the "outer contour shape in a planar view"), is not particularly limited, and may be, for example, a circle, a polygon, or other shapes. Examples of circles include perfect circles (perfect circles), ellipses, and approximate circles. An approximate circle is a general term for shapes that are partially or entirely distorted from a perfect circle. Examples of polygons include triangles, quadrilaterals, pentagons, and hexagons. Examples of other shapes include shapes other than circles whose contours are formed solely by curves, shapes that combine two or more types of polygons, and shapes that combine one or more types of circles with one or more types of polygons. This definition of "circle" and the like will apply hereinafter. In the illustrated exemplary embodiment, the outer contour shape in a planar view of the safety cover 110 is circular.

[0042] The safety cover 110 may be, for example, plate-shaped as a whole. That is, the safety cover 110 may have a shape that extends as a whole in a direction perpendicular to the battery axis direction. As an example, the safety cover 110 may have a substantially constant thickness except for localized areas such as stepped portions, thin-walled portions, and grooves.

[0043] The insulating member 120 is interposed between the safety cover 110 and the stripper disk 130, and corresponds to a member that at least enables the safety cover 110 and the stripper disk 130 to be connected to each other. The insulating member 120 may have an overall annular shape. That is, the insulating member 120 may have a circular or ring shape in plan view. Due to such a circular or ring shape, the inner region of the insulating member 120 forms a hollow portion or an opening region 120C (i.e., an "opening" described below).

[0044] The outer contour shape of the insulating member 120 in a plan view is not particularly limited, but may be the same as the outer contour shape of the safety cover 110 in a plan view, for example, circular. The annular or ring shape of the insulating member 120 may be present throughout the entire member (see FIG. 3 ), or the annular or ring shape may be locally interrupted. The insulating member 120 may also be, for example, flat. That is, the insulating member 120 may extend on the same plane as a whole. As an example, the insulating member 120 may have a substantially constant thickness between the safety cover 110 and the stripper disk 130. Preferably, the insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 so that the opening region 120C of the insulating member 120 is positioned in a region including the battery shaft.

[0045] Since the insulating member 120 has insulating properties, electrical conduction through the insulating member 120 is preferably prevented. In this specification, "insulating" may mean having the insulating properties of a general insulator and therefore the electrical resistivity of a general insulator, and while this is merely an example, it may be at least 1.0×10 5 Ω·m or more, preferably 1.0×10 6 Ω·m or more, preferably 1.0×10 7 It may have a resistivity of Ω·m or more (at room temperature of 20°C).

[0046] The insulating member 120 may be any member that contributes to insulation and does not necessarily have to be adhered to them. On the other hand, if they are adhered, the insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 as an adhesive layer. The insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 so that the opening region 120C of the insulating member 120 is positioned in the region that includes the battery shaft.

[0047] The insulating member 120 is preferably made of a resin material. That is, the insulating member may be mainly made of a resin material, or may be made of at least a resin material. If the insulating member 120 is made of such a resin material, the insulating member 120 can more effectively contribute to the adhesion between the safety cover 110 and the stripper disk 130 while still ensuring insulation.

[0048] When the insulating member 120 is made of a resin material, the insulating member 120 may be made of, for example, a thermosetting resin, a thermoplastic resin, and / or a UV-curable resin. When connectivity is particularly important, the insulating member 120 may be made of a resin adhesive that exhibits insulating properties. Examples of such resin adhesives include acrylic resin adhesives such as acrylic acid ester copolymers, silicone resin adhesives such as silicone rubber, urethane resin adhesives such as urethane resin, α-olefin resin adhesives, ether resin adhesives, ethylene-vinyl acetate resin adhesives, epoxy resin adhesives, vinyl chloride resin adhesives, chloroprene rubber resin adhesives, cyanoacrylate resin adhesives, aqueous polymer-isocyanate resin adhesives, styrene-butadiene rubber resin adhesives, nitrile rubber resin adhesives, nitrocellulose resin adhesives, and reactive hot-melt resin adhesives. Examples of the adhesive include a phenolic resin adhesive, a silicone resin adhesive, a polyamide resin adhesive, a polyimide resin adhesive, a polyurethane resin adhesive, a polyolefin resin adhesive, a polyvinyl acetate resin adhesive, a polystyrene resin solvent-based resin adhesive, a polyvinyl alcohol resin adhesive, a polyvinylpyrrolidone resin adhesive, a polyvinyl butyral resin adhesive, a polybenzimidazole resin adhesive, a polymethacrylate resin adhesive, a melamine resin adhesive, a urea resin adhesive, and / or a resorcinol resin adhesive.

[0049] In addition, the stripper disk 130 is positioned relatively closer to the battery inside than the safety cover 110 via the insulating member 120, and corresponds to a member that contributes to current interruption in the event of an abnormality and / or the passage or release of gas inside the battery can, for example.

[0050] The stripper disk 130 may be a metal member. For example, the stripper disk 130 may include one or more of the following metal materials: aluminum (e.g., aluminum metal or aluminum alloy such as A1050, A3203, and / or A5052), iron (Fe), titanium (Ti), platinum (Pt), and gold (Au). In other words, the stripper disk 130 may be a member made of such a conductive material. The material of the stripper disk 130 may be the same as or different from the material of the safety cover 110. The outer contour shape of the stripper disk 130 in a plan view is not particularly limited, and may be, for example, the same as the outer contour shape of the safety cover 110 in a plan view. In the illustrated exemplary embodiment, the outer contour shape of the stripper disk 130 in a plan view is circular.

[0051] The stripper disk 130 may have a shape extending in the battery width direction, such as a disk shape as a whole. That is, the stripper disk 130 may have a shape extending as a whole in a direction perpendicular to the battery axial direction. For example, the stripper disk may have a substantially constant thickness.

[0052] The stripper disk 130 may be provided with a plurality of openings 130K. These openings 130K mainly serve as vents that allow gas inside the battery can to pass through or be released. For example, the openings 130K may be provided in a region that is closer to the outer periphery than the central region 130C.

[0053] In the safety valve, safety cover 110 and stripper disk 130 are integrated as a whole with insulating member 120 interposed therebetween, but safety cover 110 and stripper disk 130 may be electrically connected to each other in their central regions. For example, safety cover 110 may be directly connected to central region 130C of stripper disk 130 so as to straddle insulating member 120.

[0054] The top cover 150 is electrically connected to the safety cover 110. The top cover, together with other components of the safety valve, corresponds to a battery cover that is provided to cover the open end of the battery can. In other words, the safety cover 110 is connected to the top cover 150, which forms the external terminal of the battery. As shown in FIG. 3, the top cover 150 has a protrusion 150A that protrudes (for example, curvedly protrudes) outward in the battery axis direction. The protrusion 150A is provided particularly in the central region of the top cover.

[0055] The convex portion 150A of the top cover 150 has a shape in which the annular region of the top cover is at least partially raised (e.g., raised in a curved manner), and the central or inner region of the top cover is raised or protruded toward the outside of the battery. Thus, the top cover 150 includes at least one bent portion 150C extending from the flat portion 150B toward the outside of the battery, and the bent portions 150C are spaced apart from each other (see FIG. 3 ). The spacing of the bent portions results in an opening 150D in the top cover 150. Such a top cover 150 can suitably function as a battery terminal. For example, the top cover 150 can function as the positive terminal of the battery, and the battery can can function as the negative terminal. In such a case, the top cover and the battery can can be insulated from each other. For example, the top cover can be insulated from the battery can by interposing an insulating material between them.

[0056] Opening 150D of top cover 150 can act as a vent hole for discharging gas generated inside the battery to the outside of the battery. Top cover 150 may be made of a metal. For example, top cover 150 may be made of a conductive material such as iron (Fe), steel such as SPCC, stainless steel (SUS) such as SUS430 or SUS304, nickel (Ni), aluminum (Al), and / or titanium (Ti).

[0057] A conductive member 15 extending from the electrode assembly 10 is connected to the safety valve 100. The conductive member 15 is electrically connected to the electrode assembly 10 (particularly, one of its positive and negative electrodes) and contributes to the electrical connection between the electrode assembly 10 and the safety valve (particularly, the stripper disk 130). In the safety valve, the stripper disk 130 is electrically connected to the safety cover 110 via its central region 130C, and the safety cover 110 is connected to the top cover 150, which forms the external terminal of the battery. Therefore, the electrode assembly 10, such as a wound structure, is electrically connected to the external terminal of the battery via the conductive member 15.

[0058] In this configuration, if the internal pressure of the battery can 50 increases abnormally, the stripper disk 130 can break at the second groove 135 formed in the central region, thereby interrupting any subsequent undesirable current flow. For example, if gas is generated inside the battery can 50 due to a side reaction, such as the decomposition reaction of the electrolyte, the gas accumulates inside the battery can 50, causing the internal pressure of the battery can 50 to increase. If the internal pressure of the battery can 50 continues to increase, the safety cover 110 is affected by this increase in internal pressure. If the internal pressure of the battery can 50 exceeds a certain pressure, the stripper disk 130 is pulled by the safety cover 110, causing the stripper disk 130 to break at the second groove 135. This is because the stripper disk 130 and the safety cover 110 are connected to each other at their central regions, and the force received from the safety cover 110, which is attempting to displace due to internal pressure, causes the stripper disk 130, particularly its central region, to be pulled outward in the battery axial direction.

[0059] In other words, when the tensile force exceeds a certain limit, the stripper disk 130 breaks from the second groove 135 located around the central region. When the stripper disk 130 breaks, the safety cover 110 is electrically isolated from the non-central regions of the stripper disk 130 (particularly the non-central regions of the peripheral edge to which conductive members such as tabs and leads extending from the electrode assembly are still connected). Specifically, when the stripper disk 130 breaks from the second groove 135, the safety cover 110 bends along with the broken stripper disk 130, and this displacement interrupts current. This breaks the electrical connection between the top cover 150 and the electrode assembly 10, interrupting the current path between the electrode assembly 10 and the top cover 150. In this way, current can be interrupted in the event of an abnormality such as an increase in internal pressure.

[0060] Here, the present invention has the following technical features. Specifically, in the safety valve 100, a predetermined portion 114 of the safety cover 110, which is located between a portion X where the safety cover 110 and the top cover 150 contact and a portion Y where the safety cover 110 and the stripper disk 130 contact, is an inclined portion 115 that is inclined inward in the battery axial direction with respect to a contact surface X1 where the safety cover 110 and the top cover 150 contact (see FIG. 4). Specifically, the inclined portion 115 can be located between the first step portion 111 and the second step portion 112 of the safety cover 110 described above.

[0061] This configuration allows the safety cover 110 to have a larger total length within a predetermined width region than if it did not have the inclined portion 115. As a result, when the safety cover 110 is subjected to low pressure (specifically, a pressure lower than the internal pressure value at which the safety valve 100 is desired to be opened, in other words, a pressure at which the safety valve 100 is desired not to be opened), and the central region 113 of the safety cover 110 (specifically, a central convex portion in the central region 113 that protrudes inward in the battery axial direction) may deform, the safety cover 110 has a tension force that can provide a force that resists deformation of the safety cover 110 (see FIG. 7 ). As a result, the amount of displacement of the safety cover 110 due to low pressure when there is no battery abnormality can be suppressed (see the displacement amount before interruption in FIG. 5 ). From the above, according to the present invention, it is possible to avoid so-called unintended current interruption.

[0062] On the other hand, as described above, the total length of the safety cover 110 in the predetermined width region can be increased compared to when the inclined portion 115 is not provided, and this allows the displacement of the safety cover 110 to maintain current interruption due to increased internal battery pressure that may occur in the event of a battery abnormality to be increased (see the displacement after interruption in FIG. 5). As a result, contact between the safety cover 110 and the stripper disk 130 can be avoided after current interruption in the event of a battery abnormality. From the above, according to the present invention, it is possible to avoid re-conduction of current.

[0063] The "amount of displacement of the safety cover 110" before and after the current is interrupted as mentioned above refers to the amount of change from the initial position of the central region 113 of the safety cover 110 (the position of the safety cover 110 before deformation when not affected by the internal pressure of the battery) to a predetermined position where the safety cover 110 is deformed outward in the battery axis direction.

[0064] In a preferred embodiment, the angle between the contact surface X1 where the safety cover 110 and the top cover 150 come into contact and the inclined portion 115 of the safety cover 110 is 3 degrees or more and 10 degrees or less. When the angle is in this range, the amount of displacement of the safety cover 110 at low pressure when there is no battery abnormality can be suppressed, and the amount of displacement of the safety cover 110 to maintain current interruption when there is a battery abnormality can be increased.

[0065] In a preferred embodiment, at least one of the first step region 111 and the second step region 112 of the safety cover 110 has a plurality of outer step surfaces 116 located on the outer side in the direction of the battery axis P, and one inner step surface 117 located on the inner side in the direction of the axis P (see FIG. 8A ). As described above, the outer side in the battery axis direction here refers to the side opposite the side on which the electrode assembly 10 is located, based on the position of the safety cover 110, in the direction of the battery axis P. On the other hand, the inner side in the battery axis direction refers to the side opposite the side on which the safety cover 110 is located, based on the position of the safety cover 110, in the direction of the battery axis P. With this configuration, the presence of a plurality of outer step surfaces 116 allows the surface area of ​​the first step region 111 and / or the second step region 112 to be increased.

[0066] When there is no battery abnormality, the tension force of the safety cover 110 can be increased, thereby increasing the force that resists deformation of the safety cover 110. As a result, the amount of displacement of the safety cover 110 at low pressure when there is no battery abnormality can be further suppressed.

[0067] Furthermore, compared to a case without inclined portion 115, the total length of safety cover 110 within a predetermined width region can be increased, and the surface area of ​​first step portion 111 and / or second step portion 112 can be increased, so that the amount of displacement of safety cover 110 required to maintain current interruption due to increased internal battery pressure that may occur in the event of a battery abnormality can be increased. As a result, contact between safety cover 110 and stripper disk 130 is more likely to be avoided after current interruption in the event of a battery abnormality, making it possible to more likely prevent current from re-conducting.

[0068] In view of the above, it is more preferable that both the first step portion 111 and the second step portion 112 of the safety cover 110 have a plurality of the outer step surfaces 116 and one inner step surface 117.

[0069] Without being limited to this, if at least one of the first step portion 111 and the second step portion 112 of the above-mentioned safety cover 110 has the configuration shown in Figure 8A, the other can have the configuration shown in Figure 8B or Figure 8C.

[0070] 8B, the other of the first step region 111 and the second step region 112 has one outer step surface 116 and one inner step surface 117, and the outer step surface 116 and the inner step surface 117 overlap in the thickness direction α of the safety cover 110. In addition, in the configuration shown in Fig. 8C, the other of the first step region 111 and the second step region 112 has one outer step surface 116 and one inner step surface 117, and the outer step surface 116 and the inner step surface 117 are offset from each other in the radial direction β of the safety cover.

[0071] Regarding the first step portion 111, it is preferable that the safety cover 110 displaces in one step between before and after current interruption, as indicated by the continuous solid curve in FIG. 5 . In this regard, the configurations shown in FIGS. 8A and 8C facilitate the above-described one-step displacement of the safety cover 110 compared to the configuration shown in FIG. 8B because the surface of the safety cover 110 can include a relatively larger horizontal portion 119. The horizontal portion 119 here refers to a substantially flat region (not limited to a completely flat region) extending radially between the outer step surface 116 and the inner step surface 117 in the radial direction β of the safety cover. The one-step displacement of the safety cover here refers to displacement from a pre-interruption state to a post-interruption state at a predetermined pressure without undergoing two-step behavior. This one-step behavior allows the first step portion 111 to displace before the first groove 118, thereby increasing the displacement of the safety cover 110 from before to after interruption. This more effectively prevents contact between the safety cover 110 and the stripper disc 130 after current is cut off in the event of a battery abnormality, making it possible to more effectively prevent current from being re-conducted.

[0072] In a preferred embodiment, at least the first step region 111 has a thin portion 111a (see FIG. 4), and the ratio of the thickness of the thin portion 111a to the thickness of the portions of the safety cover 110 other than the step regions 111 and 112 can be 50% or more and 80% or less. This is because a ratio below 50% makes molding difficult, and a ratio above 80% makes it difficult to achieve the desired displacement. In this case, the first step region 111 can exhibit one-stage behavior of the displacement curve of the safety cover 110 between before and after current interruption, as shown by the continuous solid line in FIG. 5.

[0073] The step portion, thin-walled portion, and groove (i.e., first groove) provided in the safety cover according to the present invention and the groove (i.e., second groove) provided in the stripper disk can be provided when the safety cover and the stripper disk are formed using a press die. Furthermore, the elements can be formed by other methods, such as mechanical grinding and laser processing, without being limited to press forming.

[0074] Although the embodiments of the present invention have been described above, the embodiments of the present invention described above are merely typical examples. Therefore, it will be readily understood by those skilled in the art that the present invention is not limited to these and that various other embodiments are possible.

[0075] The present invention aims to provide a safety valve having a configuration that has not been previously known, and the cylindrical battery of the present invention has the following features. [Example]

[0076] The present invention will be described below using examples, but the present invention is not limited to the following examples.

[0077] The present invention was verified using the following general-purpose software, which is widely used in various technical fields and has high reliability. ANSYS coupled analysis software: Ansys Mechanical (model: 2023 R1) -Verification target: Safety valve with static structure Material requirements for each part of the safety valve Top cover (safety valve cover material): structural steel Safety cover (safety cover): Aluminum alloy Stripper disc (stripper disc): Aluminum alloy Insulation material: PBT (polybutylene terephthalate) resin Pressure setting: 0.1MPa / s Displacement rating pressure: 10 MPa First step portion 111: the structure shown in FIG. 8A (corresponding to shape C in the table), FIG. 8B (corresponding to shape B in the table), and FIG. 8C (corresponding to shape B in the table) Second step portion 112: the structure shown in FIG. 8A (corresponding to shape C in the table), FIG. 8B (corresponding to shape B in the table), and FIG. 8C (corresponding to shape B in the table)

[0078] ■Examples 1 to 11 Basic configuration: A safety cover 110 arranged on the outer side in the axial direction of the battery and having an inclined portion 115, a stripper disk 130 arranged on the inner side in the axial direction of the battery, and a safety valve including an insulating member 120 arranged between the safety cover 110 and the stripper disk 130 (see Figure 4). 9 corresponds to the first step portion 111, and step 2 corresponds to the second step portion 112. In FIG. In each example, as shown in FIG. 9, the shapes of the two step portions were appropriately selected, and the inclination angle was changed and controlled within a range of 3 degrees to 10 degrees. In Examples 6 and 7, compared to Examples 1 to 5 and Examples 8 to 11, the thickness of the thin-walled portion 111a in the first step portion 111 (corresponding to step 1 in FIG. 9) of the safety cover 110 shown in FIG. 4 was set to 0.25 mm and 0.30 mm, respectively. Note that in Examples 1 to 5 and Examples 8 to 11, the thickness of the thin-walled portion 111a was set to 0.20 mm, respectively. Then, the relationship between the pressure on the safety cover 110 and the displacement of the safety cover 110 was confirmed in Examples 2, 6, and 7 (which differ in the thin-walled portion 111a) (see FIG. 10). Furthermore, the relationship between the pressure on the safety cover 110 and the amount of displacement of the safety cover 110 due to differences in the shape of the step 1 (corresponding to the first step portion 111) in FIG. 9 was confirmed (see FIG. 11). Furthermore, the relationship between the pressure on the safety cover 110 and the amount of displacement of the safety cover 110 due to differences in the shape of the step 2 (corresponding to the second step portion 112) in FIG. 9 was confirmed (see FIG. 12). Comparative Example 1 In comparison with the above embodiment, the safety cover 110 does not have the inclined portion 115.

[0079] For the evaluation, the displacement of the safety cover 110 before and after the current was interrupted was measured.

[0080] [result] The results are shown in Figures 9 to 12. First, the results in Figure 9 revealed the following: It was found that the example (with inclined portion) was able to reduce the amount of displacement before current interruption to less than 0.2 mm compared to comparative example 1 (without inclined portion). It was found that the example (with inclined portion) was able to achieve a displacement of 0.82 mm or more after current interruption compared to comparative example 1 (without inclined portion).

[0081] From the above, it was found that the displacement of the safety cover 110 at low pressure when there is no battery abnormality can be suppressed compared to Comparative Example 1 (without inclined portions), and as a result, it was found that the occurrence of so-called unintended current interruption can be avoided.

[0082] It was found that the displacement of the safety cover 110 to maintain current interruption during a battery abnormality can be increased. As a result, it was found that contact between the safety cover 110 and the stripper disc 130 can be avoided after current interruption during a battery abnormality, and that re-conduction of current can be prevented.

[0083] Furthermore, the measurement results in FIG. 10 show that when the thickness of the thin-walled portion 111a of the first step portion 111 (corresponding to step 1 in FIG. 9) is 0.20 mm, it is easier to achieve one-stage displacement of the safety cover 110 compared to when the thickness is 0.25 mm or 0.30 mm.

[0084] From the measurement results of Figure 11, it was found that if the shape of the first step portion 111 (corresponding to step 1 in Figure 9) is the configuration shown in Figures 8A and 8C (corresponding to shapes C and B in Figure 9), it is easier to achieve one-stage displacement of the safety cover 110 compared to the configuration shown in Figure 8B (corresponding to shape A in Figure 9).

[0085] From the measurement results in Figure 12, it was found that one stage of displacement of the safety cover 110 can be achieved regardless of the shape of the second step portion 112 (corresponding to step 2 in Figure 9) being any of the configurations shown in Figures 8A to 8C (corresponding to shapes C, A, and B in Figure 9, respectively).

[0086] The effects of the above embodiment are merely exemplary, and the present invention is not limited to the above, and may have additional effects. The cylindrical battery of the present invention can take the following forms. <1> A top cover and a safety valve are provided. the safety valve has a safety cover and a stripper disc located inward of the safety cover in the battery axial direction, A cylindrical battery, wherein a predetermined portion of the safety cover located between the portion where the safety cover and the top cover contact and the portion where the safety cover and the stripper disk contact is an inclined portion that is inclined inward in the battery axial direction with respect to the contact surface where the safety cover and the top cover contact. <2> The angle between the contact surface and the inclined portion is 3 degrees or more and 10 degrees or less. <1> The cylindrical battery according to claim 1. <3> the safety cover has a first step portion located on the outer circumferential side and a second step portion located on the inner circumferential side, and the first step portion and the second step portion are located between a portion where the safety cover and the top cover contact each other and a portion where the safety cover and the stripper disk contact each other. <1> or <2> The cylindrical battery according to claim 1. <4> The inclined portion is located between the first step portion and the second step portion. <3> The cylindrical battery according to claim 1. <5> At least one of the first step portion and the second step portion has a plurality of outer step surfaces located on the outer side in the axial direction of the battery, and has one inner step surface located on the inner side in the axial direction. <3> or <4> The cylindrical battery according to claim 1. <6> one of the first step portion and the second step portion has a plurality of outer step surfaces and one inner step surface; the other of the first step portion and the second step portion has one outer step surface and one inner step surface, and the outer step surface and the inner step surface overlap in the thickness direction of the safety cover. <5> The cylindrical battery according to claim 1. <7> one of the first step portion and the second step portion has a plurality of outer step surfaces and one inner step surface; the other of the first step portion and the second step portion has one outer step surface and one inner step surface, and the outer step surface and the inner step surface are provided so as to be shifted from each other in the radial direction of the safety cover. <5> The cylindrical battery according to claim 1. <8> At least the first step portion has a thin portion, and the ratio of the thickness of the thin portion to the thickness of the other portion of the safety cover other than the step portion is 50% or more and 80% or less. <3> ~ <7> 1. The cylindrical battery according to any one of claims 1 to 9. [Industrial Applicability]

[0087] The cylindrical battery (battery such as a primary battery or a secondary battery) according to the present invention can be typically used in applications requiring the use of electrical energy. By way of example only, the cylindrical battery of the present invention can be used in fields such as electricity, information, and communications where electrical and electronic devices are used (for example, electrical and electronic devices or mobile devices including mobile phones, smartphones, laptop computers, digital cameras, activity monitors, arm computers, electronic paper, wearable devices, and small electronic devices such as RFID tags, card-type electronic money, and smart watches), household and small industrial applications (for example, power tools, golf carts, and household, nursing care, and industrial robots), large industrial applications (for example, forklifts, elevators, and harbor cranes), transportation systems (for example, hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (for example, various power generation systems, road conditioners, smart grids, and general household power storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (dose management systems), IoT, and space and deep-sea applications (for example, space probes and submersible research vessels). [Explanation of symbols]

[0088] 10 Electrode assembly 11 Positive electrode 12 Negative electrode 13 Separator 15 Conductive material 50 battery cans 51 Open end of battery can 100 Safety valve 110 Safety Cover 110C Central area of ​​safety cover 111 First step area 111a Thin-walled portion of first step portion 112 Second step area 113 Central convex part 114 Safety cover designated area 115 Slope area 116 Outer step surface of safety cover 117 Inner step surface of safety cover 118 First groove of safety cover 120 Insulating material 120C Open area of ​​insulating material 130 Stripper disc 130C Stripper disc center area 130K Stripper disc opening 135 Second groove of stripper disc 150 top cover 150A Protrusion on top cover 1000 Cylindrical Battery P battery axis X Contact area between the safety cover and the top cover X1 Contact surface where the safety cover and top cover come into contact Y: The area where the safety cover and stripper disc come into contact α Thickness direction of safety cover β Radial direction of safety cover

Claims

1. A top cover and a safety valve are provided. the safety valve has a safety cover and a stripper disc located inward of the safety cover in the battery axial direction, A cylindrical battery, wherein a predetermined portion of the safety cover located between the portion where the safety cover and the top cover contact and the portion where the safety cover and the stripper disk contact is an inclined portion that is inclined inward in the battery axial direction with respect to the contact surface where the safety cover and the top cover contact.

2. The cylindrical battery according to claim 1 , wherein an angle between the contact surface and the inclined portion is equal to or greater than 3 degrees and equal to or less than 10 degrees.

3. 2. The cylindrical battery according to claim 1, wherein the safety cover has a first step portion located on the outer periphery side and a second step portion located on the inner periphery side, and the first step portion and the second step portion are located between a portion where the safety cover and the top cover contact and a portion where the safety cover and the stripper disk contact.

4. The cylindrical battery according to claim 3 , wherein the inclined portion is located between the first step portion and the second step portion.

5. 4. The cylindrical battery according to claim 3, wherein at least one of the first step portion and the second step portion has a plurality of outer step surfaces located on the axial outer side of the battery and one inner step surface located on the axial inner side.

6. one of the first step portion and the second step portion has a plurality of outer step surfaces and one inner step surface; 6. The cylindrical battery according to claim 5, wherein the other of the first step portion and the second step portion has one outer step surface and one inner step surface, and the outer step surface and the inner step surface overlap in the thickness direction of the safety cover.

7. one of the first step portion and the second step portion has a plurality of outer step surfaces and one inner step surface; 6. The cylindrical battery according to claim 5, wherein the other of the first step portion and the second step portion has one outer step surface and one inner step surface, and the outer step surface and the inner step surface are offset from each other in the radial direction of the safety cover.

8. 4. The cylindrical battery according to claim 3, wherein at least the first step portion has a thin-walled portion, and the ratio of the thickness of the thin-walled portion to the thickness of the portion of the safety cover other than the step portion is 50% or more and 80% or less.

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