Secondary battery

Abstract

To provide a secondary battery having a more excellent vibration resistance.SOLUTION: A secondary battery comprises: a battery element; a housing member that houses the battery element; and a safety valve attached to the housing member. The safety valve has at least a structure that includes: a safety cover having a projection part at a center; a disc holder having an opening at the center; a stripper disc having an opening part at the center; and a sub disc that is bonded to the projection part extended via the opening of the disc holder and the opening part of the stripper disc so that they are combined in order relatively toward an inner side from an outer side of the housing member. The stripper disc includes a concave part on a surface positioned to a relative inner side of the housing member, and the concave part houses the sub disc.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to secondary batteries. In particular, it relates to a secondary battery including an electrode assembly including a positive electrode, a negative electrode, and a separator.

Background Art

[0002] A secondary battery can extract energy such as chemical change as electrical energy. A secondary battery can also be repeatedly charged and discharged because it is a so-called storage battery, and is used in various applications. For example, a battery is used in mobile devices such as mobile phones, smartphones, and notebook personal computers.

[0003] Conventionally, such a secondary battery is disclosed in, for example, Patent Document 1. The secondary battery described in Patent Document 1 includes a battery element including a positive electrode, a negative electrode, and an electrolytic solution, a housing member that houses the battery element, and a safety valve mechanism attached to the housing member. This safety valve mechanism includes a valve member having an opening valve portion that can be opened. The safety valve mechanism attempts to cut off the current during an abnormality and suppresses the generation of further gas inside the battery. Thereby, an increase in the internal pressure of the battery can be suppressed, and damage to the housing member can be avoided.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, as a result of intensive studies, the inventor has found that, while the secondary battery described in Patent Document 1 operates the safety valve mechanism during an abnormality to avoid risks such as damage to the housing member, there is still room for development regarding the functions of the battery that require the safety valve not to operate during normal times.

[0006] The present disclosure has been made in view of the above problems. That is, the main object of the present disclosure is to provide a secondary battery with excellent vibration resistance.

[0007] The inventor of the present application has tried to solve the above problems by dealing with them in a new direction instead of following the prior art. As a result, the inventor has completed the invention of a secondary battery in which the above main object is achieved. That is, the present disclosure includes the following embodiments.

Means for Solving the Problems

[0008] To solve the above problems, a secondary battery according to an embodiment of the present disclosure is a secondary battery including a battery element, a housing member that houses the battery element, and a safety valve attached to the housing member, wherein the safety valve includes a safety cover having a protrusion at the center, a disk holder having an opening at the center, a stripper disk having an opening at the center, and a sub-disk that joins with the protrusion extending through the opening of the disk holder and the opening of the stripper disk, and has at least a configuration in which they are combined in order from the relatively outer side to the inner side of the housing member, wherein the stripper disk has a concave portion on a surface that is relatively located inside the housing member, and the concave portion houses the sub-disk.

Effects of the Invention

[0009] The battery according to an embodiment of the present disclosure can provide a secondary battery with excellent vibration resistance.

Brief Description of the Drawings

[0010]

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DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be specifically described. It should be noted that the applicant provides the following description and examples for those skilled in the art to fully understand the present disclosure, and does not intend to limit the subject matter described in the claims by these. That is, the present disclosure is not particularly limited to the preferred modes described below, etc., and can be implemented with appropriate changes within the scope of its purpose. For the convenience of explanation or ease of understanding of the key points, the present invention may be shown separately in embodiments, examples, etc. However, partial substitution and / or combination of the configurations shown in different embodiments, etc. are possible. In the description of such embodiments, duplicate explanations may be omitted for substantially the same matters, and only the different points may be explained. In particular, for the same operational effects due to the same configuration, they may not be sequentially mentioned for each embodiment.

[0012] In addition, in the description of this specification, references to directions or orientations, etc. are for the convenience of explanation only and are not intended to limit the scope of the present disclosure unless specifically stated otherwise. For example, relative terms such as "outer (or outside, external or outer periphery)", "inner (or inside, internal or inner periphery)", and their derivative terms, etc. should be understood as referring to the directions as described or illustrated. Similarly, "above" an element includes not only the case of contacting the upper surface of the element but also the case of not contacting the upper surface of the element. That is, "above" an element includes not only a position above and separated from the element, i.e., an upper position via another object on the element or an upper position with a gap, but also a position immediately above in contact with the element. Also, "above" does not necessarily mean the upper side in the vertical direction. "Above" only indicates the relative positional relationship of an element. That is, unless specifically stated otherwise, the invention does not need to be limited to a specific direction, orientation, form, etc. Also, terms such as "provided", "arranged", and "connected", and their derivative terms are the same. Unless specifically stated otherwise, they are not limited to a direct mode, and other elements such as intervening objects may be intervening.

[0013] Each of the various numerical ranges referred to in this specification is intended to include the numerical values of the lower and upper limits themselves, unless otherwise specified, such as "less than". That is, for example, taking a numerical range of 0.35 to 0.45 mm as an example, it is interpreted as including the lower limit value of 0.35 mm and also including the upper limit value of 0.45 mm.

[0014] [Basic Configuration of Secondary Battery] The "secondary battery" referred to in this specification can be repeatedly charged and discharged. Note that the "secondary battery" is not overly restricted by its name, and for example, "power storage device" and the like can also be included in the scope.

[0015] Referring to FIGS. 1 and 2, a secondary battery according to an embodiment as a basic configuration of the present disclosure will be described. FIG. 1 is a schematic perspective view showing the appearance of the secondary battery according to this embodiment. FIG. 2 is a schematic diagram showing the internal configuration of the secondary battery according to this embodiment. In FIGS. 1 to 2, the Z-axis is parallel to the battery axis. The battery axis corresponds to the central axis of the cylindrical exterior body in this specification. The forward Z direction means vertically upward and is parallel to the battery axis in this specification. The reverse Z direction means vertically downward and is parallel to the battery axis in this specification. In the vertical direction (Z direction), relatively, the forward Z direction is referred to as the upper side, and relatively, the reverse Z direction is referred to as the lower side. The R direction is perpendicular to the Z direction and means the direction (radial direction) away from the battery axis in a plan view. The "cylinder" in this specification means that the ratio (aspect ratio) of the height to the equivalent diameter of the circle of the bottom surface in the cylindrical shape is large (for example, an aspect ratio of 1 or more). Here, the equivalent diameter of the circle of the bottom surface means the diameter of a circle having the same area as the area of the bottom surface.

[0016] As shown in FIGS. 1 to 2, the secondary battery 1000 according to this embodiment includes a battery assembly (battery element) 10, a battery can (outer package, housing member) 50 that houses the battery element 10, and a safety valve 100 attached to the battery can 50. In the secondary battery 1000, such a battery assembly 10 is enclosed (housed) in the outer package 50 together with an electrolyte (for example, a non-aqueous electrolyte). The battery assembly 10 includes a positive electrode 11, a negative electrode 12, and a separator 13 disposed between the positive electrode 11 and the negative electrode 12. In the secondary battery 1000 according to this embodiment, the battery assembly 10 may have a wound structure (hereinafter, also referred to as a "wound electrode body" or a "wound structure body") wound in a roll shape with the separator 13 disposed between the positive electrode 11 and the negative electrode 12.

[0017] The secondary battery 1000 may be a cylindrical secondary battery (for example, a cylindrical non-aqueous secondary battery). In other words, the secondary battery 1000 may include a cylindrical case, that is, a cylindrical battery can 50. The safety valve 100 may be provided at the cylindrical end of the secondary battery 1000 (particularly, on the side of the open end 51 of the battery can 50).

[0018] (Positive electrode and negative electrode) The positive electrode 11 is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode 11, 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, in the plurality of positive electrodes 11 in the battery assembly 10, the positive electrode material layers may be provided on both sides of the positive electrode current collector, or the positive electrode material layer may be provided only on one side of the positive electrode current collector.

[0019] The negative electrode 12 is composed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode 12, 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, in the plurality of negative electrodes 12 in the battery assembly 10, the negative electrode material layers may be provided on both sides of the negative electrode current collector, or the negative electrode material layer may be provided only on one side of the negative electrode current collector.

[0020] The electrode active materials contained in the positive electrode 11 and the negative electrode 12, that is, the positive electrode active material and the negative electrode active material respectively, are substances that are directly involved in the transfer of electrons in the secondary battery 1000, and are the main substances of the positive electrode 11 and the negative electrode 12 that are responsible for charge and discharge, that is, the battery reaction. More specifically, ions are brought into 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 move between the positive electrode 11 and the negative electrode 12 to transfer electrons and charge and discharge is performed. The positive electrode material layer and the negative electrode material layer may be layers that can particularly occlude and release lithium ions. That is, the secondary battery 1000 according to the present embodiment may be a non-aqueous electrolyte secondary battery in which lithium ions move between the positive electrode 11 and the negative electrode 12 through a non-aqueous electrolyte to perform charge and discharge of the secondary battery 1000. When lithium ions are involved in charge and discharge, the secondary battery 1000 according to the present embodiment corresponds to a so-called "lithium ion battery" and has layers capable of occluding and releasing lithium ions as the positive electrode 11 and the negative electrode 12.

[0021] When the secondary battery 1000 according to the present embodiment is a lithium ion battery, the positive electrode active material may be a substance that contributes to the occlusion and release of lithium ions. That is, the positive electrode layer may contain any one or two or more kinds of positive electrode materials capable of occluding and releasing lithium. From this point of view, the positive electrode active material may be, for example, a lithium-containing compound. The type of the lithium-containing compound is not particularly limited, and examples thereof include a lithium-containing composite oxide and a lithium-containing phosphate compound. This is because a high energy density is easily obtained.

[0022] Lithium-containing composite oxides are a general term for oxides containing lithium and one or more other elements (elements other than lithium) as constituent elements, and may have any crystal structure such as a layered rock salt type and a spinel type, for example. Lithium-containing phosphate compounds are a general term for phosphate compounds containing lithium and one or more other elements as constituent elements, and may have a crystal structure such as an olivine type, for example. The type of other element is not particularly limited as long as it is any one or more of arbitrary elements. Among them, it is preferable that the other element is any one or more of the elements belonging to Groups 2 to 15 in the long-period type 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 by these additive elements.

[0023] The lithium-containing composite oxide having a layered rock salt type crystal structure may be, for example, a compound represented by each of the following formulas (1) to (3). Li a Mn (1-b-c) Ni b M11 c O (2-d) F e ···(1) (In formula (1), M11 is at least one of cobalt (Co), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to e satisfy 0.8 ≦ a ≦ 1.2, 0 < b < 0.5, 0 ≦ c ≦ 0.5, (b + c) < 1, -0.1 ≦ d ≦ 0.2, and 0 ≦ e ≦ 0.1. However, the composition of lithium varies depending on the charge-discharge state, and a is the value in the fully discharged state.) Li a Ni (1-b) M12 b O (2-c) F d ···(2) (In formula (2), M12 is at least one of cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to d satisfy 0.8 ≤ a ≤ 1.2, 0.005 ≤ b ≤ 0.5, -0.1 ≤ c ≤ 0.2, and 0 ≤ d ≤ 0.1. However, the lithium composition varies depending on the charge-discharge state, and a is the value in the fully discharged state.) Li a Co (1-b) M13 b O (2-c) F d ···(3) (In formula (3), M13 is at least one of nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to d satisfy 0.8 ≤ a ≤ 1.2, 0 ≤ b < 0.5, -0.1 ≤ c ≤ 0.2, and 0 ≤ d ≤ 0.1. However, the lithium composition varies depending on the charge-discharge state, and a is the value in the fully discharged state.)

[0024] Specific examples of the lithium-containing composite oxide having a layered rock salt-type crystal structure include LiNiO2, LiCoO2, LiCo 0.98 Al 0.01 Mg 0.01 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O2 and Li1.15 (Mn 0.65 Ni 0.22 Co 0.13 )O₂ and the like can be mentioned. In addition, when the lithium-containing composite oxide having a layered rock salt type crystal structure contains nickel, cobalt, manganese, and aluminum as constituent elements, the atomic ratio of the nickel is preferably 50 atomic% or more. This is because a high energy density can be easily obtained.

[0025] The lithium-containing composite oxide having a spinel type crystal structure may be, for example, a compound represented by the following formula (4). Li a Mn (2-b) M₁₄ b O c F d ···(4) (In formula (4), M₁₄ is at least one of cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to d satisfy 0.9 ≤ a ≤ 1.1, 0 ≤ b ≤ 0.6, 3.7 ≤ c ≤ 4.1, and 0 ≤ d ≤ 0.1. However, the composition of lithium varies depending on the charge and discharge state, and a is the value in the fully discharged state.) Specific examples of the lithium-containing composite oxide having a spinel type crystal structure may be LiMn₂O₄ and the like.

[0026] The lithium-containing phosphate compound having an olivine type crystal structure is, for example, a compound represented by the following formula (5). Li a M₁₅PO₄···(5) (In formula (5), M15 is at least one of cobalt (Co), manganese (Mn), iron (Fe), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), niobium (Nb), copper (Cu), zinc (Zn), molybdenum (Mo), calcium (Ca), strontium (Sr), tungsten (W), and zirconium (Zr). a satisfies 0.9 ≦ a ≦ 1.1. However, the lithium composition varies depending on the charge-discharge state, and a is the value in the fully discharged state.) Specific examples of the lithium-containing phosphate compound having an olivine-type crystal structure include LiFePO4, LiMnPO4, LiFe 0.5 Mn 0.5 PO4, and LiFe 0.3 Mn 0.7 PO4, etc. may be used.)

[0027] In addition, the lithium-containing composite oxide may be a compound represented by the following formula (6). (Li2MnO3) x (LiMnO2) 1-x ···(6) (In formula (6), x satisfies 0 ≦ x ≦ 1. However, the lithium composition varies depending on the charge-discharge state, and x is the value in the fully discharged state.)

[0028] In addition, the positive electrode material may be, for example, any one or two or more of oxides, disulfides, chalcogenides, and conductive polymers. The oxides may be, for example, titanium oxide, vanadium oxide, and manganese dioxide. The disulfides may be, for example, titanium disulfide and molybdenum sulfide. The chalcogenides may be, for example, niobium selenide. The conductive polymers may be, for example, sulfur, polyaniline, and polythiophene. However, the positive electrode material is not particularly limited, and other materials other than the above may be used.)

[0029] The positive electrode material layer may contain a binder. Further, in order to smoothly promote the transfer of electrons that drive the battery reaction, the positive electrode material layer may contain a positive electrode conductive agent. The binder of the positive electrode 11 may contain, for example, any one or two or more of synthetic rubber and polymer compounds. The synthetic rubber may be, for example, styrene-butadiene rubber, fluorine rubber, and ethylene propylene diene. The polymer compound may be, for example, polyvinylidene fluoride and polyimide. The positive electrode conductive agent may contain, for example, any one or two or more of carbon materials. This carbon material may be, for example, graphite, carbon black, acetylene black, and ketjen black. However, as long as the positive electrode conductive agent is a material having conductivity, it may be a metal material, a conductive polymer, or the like.

[0030] Similarly, the negative electrode active material of the negative electrode material layer may be a material that contributes to the intercalation and deintercalation of lithium ions. That is, the negative electrode layer may contain any one or two or more of negative electrode materials capable of storing and releasing lithium. From this perspective, the negative electrode active material may be, for example, various carbon materials, metal-based materials, and / or other materials.

[0031] When a carbon material is used as the negative electrode active material, the change in crystal structure during lithium intercalation and lithium deintercalation is very small, so a high energy density is easily and stably obtained. In addition, since the carbon material also functions as a negative electrode conductive agent, the conductivity of the negative electrode layer is easily improved.

[0032] Specific carbon materials include, for example, graphitizable carbon, non-graphitizable carbon, and / or graphite. More specifically, the carbon material may be, for example, pyrolytic carbons, cokes, glassy carbon fibers, fired organic polymer compounds, activated carbon, and carbon blacks. The cokes may include pitch coke, needle coke, and petroleum coke. The fired organic polymer compound is a substance obtained by firing (carbonizing) a polymer compound such as a phenol resin and a furan resin at an appropriate temperature. In addition, the carbon material may be low-crystalline carbon heat-treated at a temperature of about 1000°C or lower, or may be amorphous carbon. Note that the shape of the carbon material is not particularly limited and may be at least one of fibrous, spherical, granular, and scaly.

[0033] The "metal-based material" used as the negative electrode active material is a general term for materials containing any one or two or more of metal elements and metalloid elements as constituent elements. When a carbon material is used as the negative electrode active material, a high energy density is easily obtained. The metal-based material may be a single substance, an alloy, a compound, two or more of them, or a material containing at least a part of one or two or more of their phases. However, the alloy may include, in addition to materials composed of two or more metal elements, materials containing one or more metal elements and one or more metalloid elements. Further, the alloy may contain a non-metal element. The structure of this metal-based material may be, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and a coexistence of two or more of them. Such metal elements and metalloid elements may be any one or two or more of, for example, metal elements and metalloid elements capable of forming an alloy with lithium. Specifically, the metal elements and metalloid elements 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 (Zn), hafnium (Hf), zirconium, yttrium (Y), palladium (Pd) and / or platinum (Pt). In a certain preferred embodiment, the metal elements are silicon and tin. This is because these metal elements have excellent ability to occlude and release lithium, and a higher energy density is easily obtained. The material containing silicon as a constituent element may be a single substance of silicon, an alloy of silicon, a compound of silicon, two or more selected from them, or a material containing at least a part of one or two or more of their phases. Similarly, the material containing tin as a constituent element may be a single substance of tin, an alloy of tin, a compound of tin, two or more of them, or a material containing at least a part of one or two or more of their phases. The "single substance" described in this specification is only a single substance in a general sense, so the single substance may contain trace amounts of impurities.That is, the purity of the single substance is not necessarily limited to 100%. The silicon alloy may contain, for example, any one or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than silicon. The silicon compound may contain, for example, any one or more of carbon and oxygen as constituent elements other than silicon. Note that the silicon compound may contain any one or more of the series of elements described for the silicon alloy as constituent elements other than silicon. Specific examples of the silicon alloy and specific examples of the silicon compound include SiB4, SiB6, MgSi, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiO. v (0 < v ≤ 2), and / or LiSiO, etc. can be cited. Note that for SiO v the v in it may be 0.2 < v < 1.4. The tin alloy may contain, for example, any one or more of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than tin. The tin compound may contain, for example, any one or more of carbon and oxygen as constituent elements other than tin. Note that the tin compound may contain any one or more of the series of elements described for the tin alloy as constituent elements other than tin. Specific examples of the tin alloy and specific examples of the tin compound include SnO w(0 < w ≤ 2), SnSiO3, LiSnO, and / or Mg2Sn, etc. can be mentioned. In particular, a material containing tin as a constituent element may be, for example, a material (tin-containing material) containing a second constituent element and a third constituent element together with tin which is the first constituent element. The second constituent element may be, for example, any one or more of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, silver, indium, cesium (Ce), hafnium (Hf), tantalum, tungsten, bismuth, and silicon. The third constituent element may be, for example, any one or more of boron, carbon, aluminum, and phosphorus. This is because high battery capacity, excellent cycle characteristics, etc. are easily obtained by these elements. Among them, the tin-containing material may be a material (tin-cobalt-carbon-containing material) containing tin, cobalt, and carbon as constituent elements. This is because high energy density is easily obtained by these materials. In the tin-cobalt-carbon-containing material, at least a part of the carbon which is a constituent element may be bonded to a metal element or a metalloid element which is another constituent element. This is because aggregation of tin and crystallization of tin, etc. are easily suppressed. Such a tin-cobalt-carbon-containing material is not limited to a material (SnCoC) whose constituent elements are only tin, cobalt, and carbon. This tin-cobalt-carbon-containing material may contain, for example, in addition to tin, cobalt, and carbon, any one or more of silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, and bismuth as constituent elements. In addition to the tin-cobalt-carbon-containing material, a material (tin-cobalt-iron-carbon-containing material) containing tin, cobalt, iron, and carbon as constituent elements may also be used.

[0034] In addition, the negative electrode material may be, for example, any one or two or more of metal oxides and polymer compounds. The metal oxide may be, for example, iron oxide, ruthenium oxide, molybdenum oxide, etc. The polymer compound may be, for example, polyacetylene, polyaniline, polypyrrole, etc.

[0035] The negative electrode material layer may contain a binder. Furthermore, a negative electrode conductive agent may be contained in the negative electrode material layer in order to smoothly promote the transfer of electrons for the battery reaction. The binder that can be contained in the negative electrode material layer is not particularly limited, and examples thereof include at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide-based resin, and polyamide-imide-based resin. The negative electrode conductive agent that can be contained in the negative electrode material layer is not particularly limited, and examples thereof include 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. In addition, the negative electrode material layer may contain components resulting from a thickening agent component (such as carboxymethyl cellulose, etc.) used during battery manufacturing.

[0036] 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 an electrode current collector may be a sheet-like metal member. Also, the electrode current collector may be a single layer or may be multilayered. Furthermore, the electrode current collector may have a porous or perforated form. For example, the current collector may be a metal foil, punching metal, a net, or expanded metal, etc. The positive electrode current collector used for the positive electrode 11 may be made of a metal foil containing at least one selected from the group consisting of, for example, aluminum, nickel, and stainless steel. On the other hand, the negative electrode current collector used for the negative electrode 12 may be made of a metal foil containing at least one selected from the group consisting of, for example, copper, aluminum, nickel, and stainless steel.

[0037] (Separator) The separator 13 used for the positive electrode 11 and the negative electrode 12 is a member provided from the viewpoints of preventing short circuit due to contact between the positive electrode 11 and the negative electrode 12 and retaining the electrolyte. In other words, the separator 13 is a member that isolates the positive electrode 11 and the negative electrode 12 and allows ions (for example, lithium ions) to pass through while preventing a short circuit of the current caused by contact between the two electrodes. For example, the separator 13 may be a porous or microporous insulating member and may have a film form due to its small thickness.

[0038] The separator 13 may be any one or two or more of porous membranes such as synthetic resin and / or ceramic, and may be a laminated membrane of two or more porous membranes. The synthetic resin used for the separator 13 is, for example, polytetrafluoroethylene, polypropylene, polyethylene, etc. For example, the separator 13 may include a porous membrane (base material layer) and a polymer compound layer provided on one or both sides of the base material layer. Thereby, the adhesion of the separator to the positive electrode is improved, and the adhesion of the separator to the negative electrode can be improved, so that the distortion of the wound electrode body is easily suppressed. The polymer compound layer may include any one or two or more of polymer compounds such as polyvinylidene fluoride. Thereby, it is excellent in physical strength and tends to be electrochemically stable. Note that the polymer compound layer may include any one or two or more of insulating particles such as inorganic particles. The type of inorganic particles may be, for example, aluminum oxide and / or aluminum nitride. In the present invention, the separator should not be particularly restricted by its name, and may be a solid electrolyte, a gel electrolyte, and / or insulating inorganic particles having the same function.

[0039] (Electrolyte) In the secondary battery 1000 according to the present embodiment, the battery assembly 10 including the positive electrode 11, the negative electrode 12, and the separator 13 may be enclosed in the exterior body 50 together with the electrolyte. The electrolyte may be a so-called "non-aqueous" electrolyte.

[0040] The electrolyte (typically, the electrolytic solution) includes a solvent and an electrolyte salt. The electrolytic solution may further include any one or two or more of other materials such as additives. In a certain preferred embodiment, the separator 13 is impregnated with the electrolytic solution, and further, the positive electrode 11 and / or the negative electrode 12 may also be impregnated with the electrolytic solution.

[0041] - Solvent - The solvent may contain any one or two or more of non-aqueous solvents such as organic solvents. The electrolyte containing a non-aqueous solvent can be a so-called non-aqueous electrolyte. The non-aqueous solvent is, for example, a cyclic carbonate, a chain carbonate, a lactone, a chain carboxylic acid ester and / or a nitrile (e.g., mononitrile), etc. Thereby, it becomes easier to obtain more excellent battery capacity, cycle characteristics and / or storage characteristics, etc. The cyclic carbonate may be, for example, ethylene carbonate, propylene carbonate and / or butylene carbonate, etc. The chain carbonate may be, for example, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and / or methyl propyl carbonate, etc. The lactone may be, for example, γ-butyrolactone and / or γ-valerolactone, etc. The chain carboxylic acid ester may be, for example, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate and / or ethyl trimethylacetate, etc. The nitrile may be, for example, acetonitrile, methoxyacetonitrile and / or 3-methoxypropionitrile, etc. In addition, the non-aqueous solvent may be, for example, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate and / or dimethyl sulfoxide, etc. Among them, the non-aqueous solvent preferably contains any one or two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, etc. This is because it becomes easier to bring about higher battery capacity, more excellent cycle characteristics and / or more excellent storage characteristics, etc. Furthermore, the non-aqueous solvent may be, for example, an unsaturated cyclic carbonate, a halogenated carbonate, a sulfonic acid ester, an acid anhydride, a dicyano compound (dinitrile compound), a diisocyanate compound, a phosphate ester and / or a chain compound having a carbon-carbon triple bond, etc.This makes it easier to improve the chemical stability of the electrolytic solution. The "unsaturated cyclic carbonate" mentioned here refers to a cyclic carbonate having one or more unsaturated bonds (carbon-carbon double bonds or carbon-carbon triple bonds). Examples of this unsaturated cyclic carbonate include vinylene carbonate, vinyl ethylene carbonate, and / or methylene ethylene carbonate. The "halogenated carbonate" refers to a cyclic or chain carbonate containing one or more halogen elements as constituent elements. When the halogenated carbonate contains two or more halogens as constituent elements, the types of the two or more halogens may be only one type or two or more types. Examples of the cyclic halogenated carbonate include 4-fluoro-1,3-dioxolan-2-one and / or 4,5-difluoro-1,3-dioxolan-2-one. The chain halogenated carbonate may be, for example, fluoromethyl methyl carbonate, bis(fluoromethyl) carbonate, and / or difluoromethyl methyl carbonate. The sulfonic acid ester may be, for example, a monosulfonic acid ester and / or a disulfonic acid ester. The monosulfonic acid ester may be a cyclic monosulfonic acid ester or a chain monosulfonic acid ester. The cyclic monosulfonic acid ester may be a sultone such as 1,3-propanesultone and / or 1,3-propenesultone. The chain monosulfonic acid ester may be, for example, a compound in which the cyclic monosulfonic acid ester is cut in the middle. The disulfonic acid ester may be a cyclic disulfonic acid ester or a chain disulfonic acid ester. The acid anhydride may be, for example, a carboxylic acid anhydride, a disulfonic acid anhydride, and / or a carboxylic acid sulfonic acid anhydride. The carboxylic acid anhydride may be, for example, succinic anhydride, glutaric anhydride, and / or maleic anhydride. The disulfonic acid anhydride may be, for example, ethanedisulfonic anhydride and / or propanedisulfonic anhydride. The carboxylic acid sulfonic acid anhydride may be, for example, sulfobenzoic anhydride, sulfopropionic anhydride, and / or sulfobutyric anhydride.The dinitrile compound is, for example, a compound represented by NC-R1-CN (where R1 is either an alkylene group or an arylene group). This dinitrile compound may be, for example, succinonitrile (NC-C2H4-CN), glutaronitrile (NC-C3H6-CN), adiponitrile (NC-C4H8-CN), phthalonitrile (NC-C6H4-CN), and the like. The diisocyanate compound is, for example, a compound represented by OCN-R2-NCO (where R2 is either an alkylene group or an arylene group). This diisocyanate compound may be, for example, hexamethylene diisocyanate (OCN-C6H. 12 -NCO), and the like. The phosphate ester may be, for example, trimethyl phosphate, triethyl phosphate, and the like. The chain compound having a triple bond between carbons is a chain compound having one or more triple bonds between carbons (-C≡C-). This chain compound having a triple bond between carbons may be, for example, propargyl methyl carbonate (CH≡C-CH2-O-C(=O)-O-CH3), propargyl methyl sulfonate (CH≡C-CH2-O-S(=O)2-CH3), and the like.

[0042] -Electrolyte salt- The electrolyte salt contained in the electrolyte may include any one or two or more of salts such as lithium salts. The electrolyte salt may include, for example, salts other than lithium salts. Such salts other than lithium may be, for example, salts of light metals other than lithium. Lithium salts include, for example, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SiF6), lithium chloride (LiCl) and / or lithium bromide (LiBr). This is because it is easier to obtain more excellent battery capacity, cycle characteristics and / or storage characteristics. Among them, it may be any one or two or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate and lithium hexafluoroarsenate.

[0043] (Battery can) The exterior body 50 used in the secondary battery 1000 corresponds to a member that houses the battery assembly 10 including the positive electrode 11, the negative electrode 12, and the separator 13 as a battery exterior body (housing member). Such an exterior body 50 can also be referred to as, for example, a "battery can". The exterior body 50 may have, for example, a hollow structure in which one end is closed and the other end is provided with an opening. The opening may be a through hole formed at one end of the exterior body. The structure of the exterior body having such an opening can also be understood as a structure having an open end with one end released. A safety valve 100 is provided at the open end 51 of the exterior body 50.

[0044] (Conductive member) The electrode assembly 10 may have a conductive member as a terminal. The conductive member is electrically connected to one of the positive electrode and the negative electrode in the electrode assembly 10, and contributes to the electrical connection between the electrode assembly 10 and the safety valve 100. The electrode assembly 10 such as a wound structure is electrically connected to an external battery terminal via the conductive member. In this specification, the conductive member may be a member containing a metal, and preferably may be a metal member having a long shape. For example, the conductive member may be composed of the current collector of the electrode assembly 10, or may be a current collecting lead (i.e., a lead) provided on the electrode assembly (particularly, its electrode). When the conductive member is composed of the current collector of the electrode, the conductive member may be formed from a metal portion of the current collector where the electrode material is not provided. When the conductive member is composed of the current collecting lead, the conductive member may be formed from a metal member having a thin form and / or a long form. In the present embodiment, the conductive member that electrically connects the electrode assembly 10 and the electrode terminal may also be referred to as a "tab". The conductive member used in the secondary battery 1000 preferably has flexibility and may be provided in a bent form and / or a curved form.

[0045] <First Embodiment: Secondary Battery> The first embodiment of the present disclosure relates to a secondary battery 1000. In addition to FIGS. 1 to 2, the secondary battery 1000 will be described with reference to FIGS. 3 to 7. FIG. 3 is a schematic perspective view showing the components and related components of the safety valve 100 of the secondary battery 1000 according to the first embodiment in a developed state. FIG. 4 is a schematic perspective view showing the components of the safety valve 100 of the secondary battery 1000 according to the first embodiment in a half-divided and developed state. FIG. 5 is a schematic perspective view showing the safety valve 100 of the secondary battery 1000 according to the first embodiment in a half-divided state. FIG. 6 is a schematic cross-sectional view of the safety valve 100 of the secondary battery 1000 according to the first embodiment. FIG. 7 is a schematic diagram showing a preferred combination state (connection state) of the members in the safety valve 100.

[0046] (Safety Valve) The secondary battery 1000 according to the first embodiment has features related to a safety mechanism. In particular, it has features regarding the safety valve 100 provided at the open end 51 of the secondary battery 1000 of the first embodiment. Specifically, in the secondary battery 1000, the safety valve 100 includes a safety cover 110 having a protruding portion 110T (protruding relatively inward toward the battery axis) at the center, a disk holder 120 having an opening at the center, a stripper disk 130 having an opening 130C at the center, and a sub-disk 140 joined to the protruding portion 110T extending through the opening of the disk holder and the opening of the stripper disk, and at least has a configuration in which they are combined in order from the relatively outer side to the inner side of the housing member (in the battery axis direction). The stripper disk 130 has a recess 130A on the surface located relatively inside the housing member (of the battery axis), and the recess 130A houses the sub-disk 140.

[0047] The safety valve 100 does not operate during normal use and operates during abnormal times. Specifically, the safety valve 100 can suppress and avoid battery smoking and / or battery ignition caused by it, for example, when an abnormal situation occurs in which the temperature undesirably rises due to a short circuit or the like (during abnormal times). Details of the operation of the safety valve will be described later.

[0048] The secondary battery 1000 according to the first embodiment is excellent in vibration resistance. The reason is presumed as follows. First, for the purpose of deepening the understanding of the secondary battery 1000 according to the first embodiment, the prior art will be described first with further reference to FIG. 9, and the above reason will be explained. FIG. 9 is a schematic cross-sectional view showing the safety valve 100 of a conventional secondary battery. As shown in FIG. 9, in the prior art secondary battery 1000z, the stripper disk 130z does not have a recess. The sub-disk 140 is arranged in contact with the lower surface of the stripper disk 130z. When vibration is applied to such a secondary battery 1000z, the battery assembly collides with the sub-disk 140 inside the secondary battery 1000z, so that stress concentrates on the joint portion between the safety cover 110 and the sub-disk 140 and its periphery. As a result, the joint portion between the safety cover 110 and the sub-disk 140 may be damaged.

[0049] In contrast, the sub-disk 140 of the secondary battery 1000 according to the first embodiment is accommodated in the recess 130A of the stripper disk 130. Thus, when vibration is applied to the secondary battery 1000, the battery assembly collides not only with the sub-disk 140 but also with the stripper disk 130 inside the secondary battery 1000. Therefore, the stress is dispersed to the stripper disk 130, and the stress on the joint between the safety cover 110 and the sub-disk 140 and its periphery is reduced. From the above, the secondary battery according to the first embodiment is excellent in vibration resistance.

[0050] Since the secondary battery 1000 is excellent in vibration resistance in this way, the secondary battery 1000 is less likely to be damaged during normal use. The proper operation of the safety valve 100 in case of an abnormality can be more reliably ensured.

[0051] As a result of the present inventor's intensive study of the prior art (for example, the secondary battery disclosed in Patent Document 1), it has been found that there is room for improving the vibration resistance. In the prior art, when an external stress is applied to the safety valve 100 due to an impact applied to the secondary battery 1000 by dropping or the like and vibration applied to the secondary battery 1000 during transportation or the like, the applied external stress is concentrated on the joint between the safety cover 110 and the sub-disk 140 and its periphery (the location where the safety valve 100 acts in case of an abnormality (more specifically, the location where the safety cover 110 and the sub-disk 140 are displaced or broken)), and it has been found that the joint and its periphery may be damaged.

[0052] Based on such technical knowledge, the inventor of the present invention conceived of suppressing the concentration of external stress at the joint between the safety cover 110 and the sub-disk 140 and its periphery and dispersing the external stress. Based on such a concept, the inventor further intensively studied and provided a recess 130A in the stripper disk 130 and accommodated the sub-disk 140 in the recess 130A, thereby succeeding in suppressing the concentration of external stress (particularly, the component in the Z direction among the external stresses) around the joint. In this way, the secondary battery 1000 according to the first embodiment, in which the stripper disk 130 having excellent vibration resistance has a recess 130A on the relatively inner surface of the battery axis and the recess 130A accommodates the sub-disk 140, was conceived.

[0053] As shown in FIGS. 3 and 4, the safety valve 100 has a configuration in which the safety cover 110, the disk holder 120, the stripper disk 130, and the sub-disk 140 are combined with each other in that order along the Z direction. When viewed along the axial direction of the cylindrical shape of the battery, the safety cover 110 is positioned relatively outside the battery (i.e., on the side farther from the electrode assembly 10 such as a wound structure), while the sub-disk 140 is positioned relatively inside the battery (i.e., on the side closer to the electrode assembly such as a wound structure). In other words, the disk holder 120 is positioned on the inner side of the battery with respect to the safety cover 110, the stripper disk 130 is positioned on the inner side of the battery with respect to the disk holder 120, and the sub-disk 140 is positioned on the inner side of the battery with respect to the stripper disk 130.

[0054] The components that make up the safety valve 100 will be described. The safety valve 100 is provided at a battery terminal (i.e., one of the positive and negative terminals as the external terminals of the battery), and has at least a mechanism that can be displaced and broken due to excessive internal battery pressure (for example, the safety cover 110 and / or the sub-disk 140 can be displaced and broken). Therefore, the safety valve 100 at least has the safety cover 110, the disk holder 120, the stripper disk 130, and the sub-disk 140 as components. The safety valve 100 may be provided at the open end of the battery can 50 (the open end 51 in the battery can 50 of FIGS. 1 and 2).

[0055] (Safety cover) The safety cover 110 is disposed relatively outside the battery axis of the disk holder 120. The safety cover 110 closes the open end 51 of the battery can 50, and can be deformed and / or displaced to open in response to an increase in the internal pressure of the battery can 50. The internal pressure of the battery can 50 may increase due to side reactions such as the decomposition reaction of the electrolytic solution. When side reactions such as the decomposition reaction of the electrolytic solution occur, gas such as carbon dioxide is generated inside the battery can 50, so the internal pressure of the battery can 50 may undesirably increase in response to an increase in the amount of gas generated.

[0056] The safety cover 110 has a substantially circular central portion 110Y and an outer peripheral portion 110X disposed at the periphery of the central portion 110Y. The central portion 110Y is recessed inwardly relative to the ring-shaped outer peripheral portion 110X in the direction of the battery axis (i.e., toward the disk holder 120). The central portion 110Y is closer to the disk holder 120 side than the outer peripheral portion 110X.

[0057] -Central portion- The planar shape of the central portion 110Y, particularly the outer contour shape in plan view (hereinafter also referred to as the "outer contour shape in plan view") is not particularly limited. For example, it is the same as the outer contour shape of the safety cover 110 in plan view. In the illustrated embodiment, the outer contour shape of the central portion 110Y in plan view is circular. Such a central portion 110Y is displaceable in response to an increase in the internal pressure of the battery can 50. When the internal pressure of the battery can 50 rises beyond a predetermined pressure such as during an abnormal time, the central portion 110Y of the safety cover 110 can be deformed and / or broken (cracked), for example. A substantially central portion of such a central portion 110Y is recessed further toward the disk holder 120, for example. In other words, the central portion 110Y is provided with a protruding portion 110T that protrudes relatively toward the inside of the battery (i.e., the direction in which an electrode assembly such as a wound structure is positioned). That is, in the secondary battery 1000, the protruding portion 110T protrudes toward the sub-disk 140.

[0058] The central portion 110Y has a protruding portion 110T that protrudes from the central portion 110Y relatively inward toward the battery axis at its center. The protruding portion 110T joins with the sub-disk 140 through the openings 120Z, 130C of the disk holder 120 and the stripper disk 130. For this reason, the safety cover 110 is electrically connected to the sub-disk 140 through the joining portion. During an abnormality of the secondary battery 1000, the internal pressure increases inside the battery sealed by the gas generated inside the potential. The increased internal pressure causes the central portion 110Y of the safety cover 110 to displace relatively outward toward the battery axis. When the internal pressure further increases, it breaks at the groove 115 of the safety cover 110 and a part of the central portion 110Y displaces relatively outward toward the battery axis. As a result, the electrical connection between the broken central portion 110Y and the outer peripheral portion 110X is interrupted.

[0059] The outer contour shape of the safety cover 110 in plan view is not particularly limited and may be, for example, circular, polygonal, or other shapes. The circular shape includes, for example, a perfect circle (true circle), an ellipse, and a substantially circular shape. The substantially circular shape is a general term for shapes in which a perfect circle is partially or entirely distorted. The polygonal shape includes, for example, a triangle, a quadrilateral, a pentagon, and a hexagon. Other shapes include, for example, shapes other than circular shapes whose contours are formed only by curves, shapes formed by combining two or more polygons, and shapes formed by combining one or more circular shapes and one or more polygons. Such definitions of "circular" and the like will be the same hereinafter. In the illustrated exemplary embodiment, the outer contour shape of the safety cover 110 in plan view is circular.

[0060] The safety cover 110 may be a metal member. For example, the safety cover 110 may contain any one or two or more of metal materials such as aluminum and aluminum alloys.

[0061] The central portion 110Y of the safety cover 110 can be fitted into the disk holder 120 (especially its recess). That is, while the safety cover 110 is aligned with the disk holder 120, the safety cover 110 can be fixed to the disk holder 120. Since the disk holder 120 also contributes to the fixation of the stripper disk 130, the safety cover 110 and the stripper disk 130 are fixed to each other via such a disk holder 120.

[0062] (Disk Holder) The disk holder 120 is interposed between the safety cover 110 and the stripper disk 130 and insulates the electrical connection between their outer peripheral portions 110X and 130X. Thereby, the electrical connection between the safety cover 110 and the stripper disk 130 in the safety valve 100 is limited to only the connection via the joint portion, and in the safety mechanism of the safety valve 100 described later, the joint portion can be displaced during an abnormal time to cut off the electrical connection.

[0063] The disk holder 120 is also interposed between the safety cover 110 and the stripper disk 130, and can align the stripper disk 130 with respect to the safety cover 110.

[0064] The disk holder 120 has a substantially circular opening 120Z at the center, a ring-shaped inner peripheral portion 120Y disposed at the periphery of the opening 120Z, and a ring-shaped outer peripheral portion 120X disposed at the periphery of the inner peripheral portion 120Y.

[0065] The disk holder 120 may have an annular shape (more specifically, in a plan view, a ring shape or a circular shape) having an opening at the center. The annular shape of the disk holder 120 is not particularly limited, but may be the same as the outer contour shape of the safety cover 110 in a plan view. The outer edge of the disk holder 120 may be, for example, circular.

[0066] The inner peripheral portion 120Y is disposed so as to be recessed relatively inwardly of the battery axis (toward the stripper disk 130 in the safety valve 100) with respect to the outer peripheral portion 120X. That is, the inner peripheral portion 120Y is closer to the stripper disk 130 side than the outer peripheral portion 120X. The outer contour shape and the inner contour shape of the inner peripheral portion 120Y in a plan view are not particularly limited, but may each be the same as, for example, the outer contour shape of the safety cover 110 in a plan view. In the illustrated exemplary embodiment, each of the outer contour shape and the inner contour shape of the inner peripheral portion 120Y in a plan view is circular.

[0067] The members constituting the disk holder 120 include an insulating member (for example, a resin member). The insulating member is, in a preferred embodiment, a resin member. Examples of the resin member include thermoplastic resins (more specifically, polypropylene (PP) and polybutylene terephthalate (PBT)). When the insulating member is a resin member in a preferred embodiment, when an external stress is applied to the secondary battery 100, the shape of the disk holder 120 can be deformed and mutated. Therefore, the concentration of the external stress on specific members and locations is reduced and dispersed, and undesired breakage during normal times is suppressed.

[0068] The disk holder 120 has an opening 120Z at a position corresponding to the central portion 110Y of the safety cover 110. The opening 120Z corresponds to an opening region that provides an annular shape to the disk holder 120. The opening shape of the opening 120Z (particularly the planar view opening shape in a planar view) is not particularly limited, and for example, it may be the same as the outer contour shape of the safety cover 110 in a planar view. In the illustrated exemplary embodiment, the opening shape of the opening 120Z in the disk holder 120 is circular.

[0069] The disk holder 120 is preferably a resin member. That is, it is preferable that the disk holder 120 comprises a resin component. Thereby, when manufacturing the safety valve 100, it becomes more easily displaceable by an external stress. That is, the disk holder 120 becomes more easily displaceable by the pressing force caused by the protrusion of the stripper disk 130, and the safety cover 110 and the stripper disk 130 are more easily fixed to each other via the displaced disk holder 120. The specific resin component of the disk holder 120 is not particularly limited, but examples include at least one selected from the group consisting of polyethylene resin, polypropylene resin, polystyrene resin, ABS resin (acrylonitrile (A) - butadiene (B) - styrene (S) resin), vinyl chloride resin, polymethyl methacrylate resin, polyethylene terephthalate resin, polyamide resin, polycarbonate resin, polyacetal resin, polybutylene terephthalate resin, modified polyphenylene ether resin, polyphenylene sulfide resin, liquid crystal polymer, polyarylate resin, polysulfone resin, polyether sulfone resin, and polyether ether ketone resin. In a preferred embodiment, the disk holder 120 comprises polybutylene terephthalate resin (PBT).

[0070] (Stripper Disk) The stripper disk 130 is interposed between the disk holder 120 and the sub-disk 140 and contributes to the passage or release of the gas generated inside the battery can 50.

[0071] As shown in FIG. 12, the stripper disk 130 has a substantially circular central portion 130Y and an outer peripheral portion 130X disposed at the periphery of the central portion 130Y so as to surround the central portion 130Y in plan view.

[0072] In a preferred embodiment, the thickness of the stripper disk 130 is 0.35 to 0.40 mm. When the thickness of the stripper disk is 0.35 mm or more, the stripper disk 130 has appropriate strength, and it is less likely that an undesired safety mechanism will operate during normal times. As a result, in such a case, the vibration resistance is further improved. When the thickness of the stripper disk is 0.40 mm or less, since the thickness of the material of the stripper disk 130 is appropriately thin, the punching machine is less likely to wear out the stripper disk 130, and the cost is excellent.

[0073] In a preferred embodiment, the material constituting the stripper disk 130 has a tensile strength of 230 to 290 N / mm obtained in a tensile test conforming to Japanese Industrial Standard (JIS) Z2241. 2 When the material constituting the stripper disk 130 has the above tensile strength of 230 N / mm or more, the stripper disk 130 has appropriate strength, and it is less likely that an undesired safety valve 100 will operate during normal times. As a result, in such a case, the vibration resistance is further improved. 2 When the material constituting the stripper disk 130 has the above tensile strength of 290 N / mm or less, since the thickness of the material of the stripper disk 130 is appropriately thin, the punching machine is less likely to wear out the stripper disk 130, and the cost is excellent. On the other hand, 2 When the material constituting the stripper disk 130 has the above tensile strength of 290 N / mm or less, since the thickness of the material of the stripper disk 130 is appropriately thin, the punching machine is less likely to wear out the stripper disk 130, and the cost is excellent.

[0074] The thickness of the stripper disk 130 is substantially constant. In this specification, the thickness of the stripper disk 130 refers to the length from the upper surface to the lower surface of the stripper disk 130 in the Z direction. The thickness of the stripper disk 130 is, for example, the length in the Z direction from the outer upper surface 130B to the inner lower surface 130E.

[0075] (Central part) The central part 130Y has a substantially circular opening 130C whose center coincides with the battery axis, a recess 130A disposed at the periphery of the opening 130C so as to surround the opening 130C, a plurality of openings 130K disposed concentrically at the periphery of the recess 130A, and a plurality of protrusions 130T and a plurality of openings 130P disposed near the interface between the central part 130Y and the outer peripheral part 130X.

[0076] (Outer peripheral part) The outer peripheral part 130X is disposed at the periphery of the central part 130Y so as to surround the central part 130Y. The outer peripheral part 130X is disposed relatively outside the battery axis compared to the central part 130Y. The outer peripheral part 130X is connected to the central part 130Y by a stepped portion.

[0077] -Recess- The recess 130A is provided on the second surface side of the stripper disk 130. The recess 130A is disposed so as to surround the periphery of the opening 130C of the stripper disk 130. The recess 130A is disposed so as to bulge relatively outside the battery axis compared to the central part 130Y other than the recess 130A. The recess 130A (inner space) is defined by the inner lower surface 130E and the inner side surface 130F of the recess 130A. The disk holder 120 is housed in the recess 130A (inner space).

[0078] The recess 130A of the stripper disk 130 houses the disk holder 120. When an external stress is applied to the secondary battery 1000, the thickness in the Z direction decreases by the amount that the disk holder 120 is housed in the recess 130A. For this reason, the external stress (particularly, the Z-direction component of the external stress) is reduced, and it is suppressed that the external stress concentrates on the joint part of the safety valve 100. For this reason, the secondary battery 1000 has excellent vibration resistance.

[0079] In a preferred embodiment, the inner diameter of the recess 130A is larger than the diameter (outer diameter) of the sub-disk 140 as shown in the enlarged cross-sectional view of FIG. 6. That is, when the diameter of the sub-disk 140 is less than the inner diameter of the recess 130A (the inner diameter of the recess) and the inner diameter of the recess 130A is less than the outer diameter of the disk holder 120, the difference (gap or clearance) between the inner diameter of the recess 130A and the outer diameter of the disk holder 120 functions as "play". In such a case, when an external stress is applied to the safety valve 100 of the secondary battery 1000, the disk holder 120 can move in the radial direction. Therefore, the applied external stress is less likely to concentrate on a specific portion (for example, the joint portion and its periphery) of the safety valve 100, making it less likely to break, and the vibration resistance is further improved. The inner diameter of the recess 130A may be, for example, 99%, 98%, 97%, 96%, or 95% smaller with the outer diameter of the sub-disk 140 taken as 100%.

[0080] In a preferred embodiment, the inner diameter of the recess 130A increases relatively inwardly toward the battery axis. That is, the inner surface 130F of the recess 130A is inclined with respect to the battery axis in a cross-sectional view such that the inner diameter of the recess 130A increases relatively inwardly toward the battery axis. Thus, the recess 130A can have a tapered shape. In such a case, when an external stress (particularly, the radial component of the external stress) is applied to the safety valve 100 of the secondary battery 1000, the disk holder 120 can move more easily in the radial direction. Therefore, the applied stress is less likely to concentrate on a specific portion (for example, the joint portion and its periphery) of the safety valve 100, and it is even less likely to break, further improving the vibration resistance. The inclination angle may be, for example, 100°, 110°, 120°, 130°, 140°, or 150° with respect to the inner lower surface 130E of the recess 130A for the inner surface 130F of the recess 130A.

[0081] The inner surface 130F is a straight line in FIG. 6 in a cross-sectional view, but at least a part thereof may be a curved surface.

[0082] The stripper disk 130 has a plurality of openings 130K arranged radially from the center point (opening center point) P of the stripper disk 130 in a plan view, and a plurality of protrusions 130T and a plurality of openings 130P arranged on the outer edge side of the opening 130K in the radial direction from the center point P. Note that the center point P of the stripper disk 130 is a point that overlaps the battery axis in a plan view in this specification.

[0083] The plurality of openings 130K, the plurality of protrusions 130T, and the plurality of openings 130P are arranged concentrically with respect to the center point P.

[0084] The opening 130K is composed of two straight lines parallel to a straight line extending in the radial direction from the center point P, a part (curve) of a circle having predetermined radii r1 and r2 with respect to the center point P, and a connecting portion. The connecting portion connecting the straight line and the curve is rounded. The two straight lines constituting the opening 130K intersect when rotated by an angle θ2 with respect to the center point P. The two straight lines constituting the opening 130K are arranged at a distance from each other by the rotation of the angle θ2 with respect to the center point P. That is, the opening 130K has an angular width of the angle θ2 with respect to the center point P. The two curves constituting the opening 130K are parts of two circles having different predetermined radii r1 and r2 with respect to the center point P. The two curves constituting the opening 130K are arranged facing each other and separated from each other by the above-mentioned radius difference (r2 - r1) in the radial direction. That is, the opening 130K has a radial width of the above-mentioned two radius differences.

[0085] The plurality of openings 130K have the same shape as each other. The plurality of openings 130K are arranged at equal angular intervals with respect to the center point P, and when the opening 130K is rotated by an angle θ1 with respect to the center point P, it overlaps with the adjacent opening 130K. In other words, the arrangement of the plurality of openings 130K is three-fold symmetric C3. The adjacent openings 130K are separated from the adjacent openings 130K at an angular rotation interval of the angle θ3 with respect to the center point P.

[0086] The plurality of openings 130P and the plurality of protrusions 130T are formed together, for example, by punching out a part of a two-dimensional material (a concave shape in plan view in FIG. 12). Therefore, when such a forming method is adopted, the openings 130P and the protrusions 130T exist in pairs.

[0087] There are six pairs of the openings 130P and the protrusions 130T. These six pairs are arranged at equal angles with respect to the center point P, and when any pair is rotated by an angle θ1 / 2 with respect to the center point P, it overlaps with the adjacent pair. That is, in other words, the arrangement of the plurality of openings 130P and the plurality of protrusions 130T has six-fold symmetry C6.

[0088] The six pairs include three pairs having a three-fold symmetry C3 arrangement relationship and the other three pairs having a three-fold symmetry C3 arrangement relationship. One of the three pairs is arranged to face the opening 130K in the radial direction. The number of the openings 130K is three, and the number of the protrusions 130T is six, and these numbers are different from each other.

[0089] The center point 130Tp of the protrusion 130T and the center point 130Pp of the opening 130P are located on a broken line extending radially from the center point P through the center point 130Kp of the opening 130K. Here, the broken line is a line (the line denoted by the broken line in FIG. 12) located at an angle θ2 / 2, which is half of the angle θ2 formed by the two straight lines constituting the opening 130K, when the stripper disk 130 is viewed in plan view. The center point 130Kp of the opening 130K is the intersection of the above-mentioned broken line and a part of a circle having a radius of (r1 + r2) / 2, which is the intermediate value of the radii (r1 and r2: r1 < r2) of the two curves constituting the opening 130K. The center point 130Tp of the protrusion 130T is the intersection of the above-mentioned broken line and the protrusion 130T, and is the point closest to the center point P.

[0090] The stripper disk 130 may be a metal member. For example, the stripper disk 130 may contain any one or two or more of metal materials such as aluminum and aluminum alloys. In a preferred embodiment, it is aluminum or an aluminum alloy. When the material of the stripper disk 130 is aluminum or an aluminum alloy, the strength of the stripper disk 130 can be further improved, the operation of the normally undesired safety valve 100 can be suppressed, and the vibration resistance of the secondary battery 1000 can be improved.

[0091] Note that the material of the stripper disk 130 may be the same as that of the safety cover 110, or may be different from that of the safety cover 110. The outer contour shape of the stripper disk 130 in plan view is not particularly limited. For example, it is the same as the outer contour shape of the safety cover 110 in plan view. In the illustrated exemplary embodiment, the outer contour shape of the stripper disk 130 in plan view is circular.

[0092] The outer contour shape of the central portion 130Y in plan view is not particularly limited, but may be the same as the outer contour shape of the safety cover 110 in plan view, for example, circular. Since the central portion 130Y of the stripper disk 130 is lower than the outer peripheral portion 130X, such a central portion 130Y is closer to the sub-disk 140 than the outer peripheral portion 130X. The inner peripheral portion 120Y of the disk holder 120 can be fitted into the stripper disk 130 (especially its recessed portion). Thereby, the stripper disk 130 can be aligned with the disk holder 120, and thus can be fixed to the safety cover 110 via the disk holder 120.

[0093] In the central portion 130Y of the stripper disk 130, in the region facing the central portion 110Y of the safety cover 110, for example, a plurality of openings 130K are provided. These plurality of openings 130K mainly correspond to vents that contribute to the passage or release of gas inside the battery can 50. Also, in the stripper disk 130, on the outer peripheral portion 130X, a plurality of protrusions 130T protruding toward the center of the disk (the center of the member as viewed in plan) are provided. Such a plurality of protrusions 130T are arranged outside the plurality of openings 130K. As shown in the drawing, such protrusions 130T have a form that protrudes or bulges in a "claw" shape in the stripper disk 130. The plurality of protrusions 130T are mainly used to preferably fix the stripper disk 130 to the disk holder 120. In this case, for example, as shown in FIG. 7, due to the pressing action of the plurality of protrusions 130T on the outer surface of the disk holder 120, the inner surface of the disk holder 120 provides a pressing action on the safety cover 110. Thereby, a suitable fitting force via the disk holder 120 is generated between a part of the stripper disk 130 (particularly the plurality of protrusions 130T) and the safety cover 110, and the stripper disk 130 and the safety cover 110 are preferably fixed to each other by that fitting force.

[0094] The illustrated stripper disk 130 has a form in which the stripper disk 130 is partially removed, for example, in the range from the outer peripheral portion 130X to the central portion 130Y. That is, an opening 130P (particularly an opening 130P that exists so as to extend from the outer peripheral portion 130X to the central portion 130Y) is provided in the stripper disk 130. In a certain preferred embodiment, the opening 130P is provided in connection with the installation of the protrusion 130T (for example, it can be provided when press-molding the stripper disk 130 provided with the protrusion 130T). Therefore, in the stripper disk 130, the opening 130P is provided adjacent to the inner peripheral side portion of the outer peripheral portion 130X, and the protrusion 130T can be provided adjacent to the opening 130P. In other words, it can be said that a plurality of openings 130P are respectively provided so as to correspond to the plurality of protrusions 130T. In the stripper disk 130, the number of the openings 130P is not particularly limited, and the number of the protrusions 130T is also not particularly limited. In the illustrated embodiment, the number of the openings 130P is, for example, six, and the number of the protrusions 130T is also, for example, six.

[0095] In the central portion 130Y of the stripper disk 130, for example, at a location corresponding to the protruding portion 110T of the safety cover 110, an opening 130C (particularly an opening different from the openings 130K and 130P) for allowing the protruding portion 110T to pass through is provided. Therefore, the protruding portion 110T of the safety cover 110 is physically connected to the sub-disk 140 through the opening 130C (particularly through passing through the stripper disk in a non-contact state). The opening shape of the opening 130C (particularly the planar view opening shape in a planar view) is not particularly limited, but for example, it may be the same as the outer contour shape of the safety cover 110 in a planar view. In the illustrated embodiment, the opening shape of the opening 130C of the stripper disk 130 is circular. Each of the plurality of openings 130K, the plurality of protrusions 130T, and the plurality of openings 130P may be arranged, for example, at positions on concentric circles centered on the opening 130C.

[0096] (Sub-disk) The sub-disk 140 is a member that can be disposed between the stripper disk 130 and the electrode assembly 10. The sub-disk 140 has a first surface 140C disposed relatively outward with respect to the battery axis and a second surface 140D disposed relatively inward with respect to the battery axis and facing the first surface 140C. The first surface 140C of the sub-disk 140 is joined to the protruding portion 110T of the safety cover 110. The second surface 140D of the sub-disk 140 contacts the conductive member 15. Thereby, the sub-disk 140 is electrically connected to the safety cover 110 and the conductive member 15. In other words, the sub-disk 140 electrically connects the electrode assembly (particularly the conductive member 15 such as its tabs and leads) 10 and the safety cover 110 (particularly its protruding portion 110T) to each other.

[0097] Since the sub-disk 140 is housed in the recess 130A of the stripper disk 130, it may have a shape corresponding to the internal space of the recess 130A of the stripper disk 130. The sub-disk 140 is, for example, circular.

[0098] The diameter of the sub-disk 140 is larger than the opening diameter of the opening 130C of the stripper disk 130. Thus, the stripper disk 130 and the sub-disk 140 block the communication of the internal space of the secondary battery 1000, allowing the safety valve 100 described later to operate due to an increase in internal pressure.

[0099] In a preferred embodiment, the diameter of the sub-disk 140 is less than the recess diameter of the recess 130A of the stripper disk 130. Here, the recess diameter refers to the inner diameter of the recess 130A in this specification, that is, the diameter of the inner upper surface of the recess 130A. When the diameter of the sub-disk 140 is less than the recess diameter of the recess 130A of the stripper disk 130, a clearance exists between the outer edge of the stripper disk 130 and the inner side surface 130F of the recess 130A. Therefore, when an external stress is applied to the secondary battery 1000, the sub-disk 140 can slide relative to the recess 130A. In this way, the safety valve 100 can reduce and disperse the external stress applied to the safety valve 100 (especially the joint between the safety cover 110 and the sub-disk 140 and its periphery) against the external stress (especially the radial component of the external stress). By suppressing such stress concentration, the vibration resistance is improved.

[0100] In a preferred embodiment, the terminal (conductive member) 15 of the battery element 10 contacts the second surface 140D of the sub-disk 140 and the outer lower surface 130D of the recess 130A of the stripper disk 130. In this way, since the sub-disk 140 is accommodated in the recess 130A, the conductive member 15 contacts not only the sub-disk 140 but also the stripper disk 130. On the other hand, in the conventional secondary battery 1000z, as shown in FIG. 9, the sub-disk 140 contacts only the sub-disk 140. In this way, since the conductive member 15 can increase the contact area with other members, the electrical connection can be made more reliable than in the conventional secondary battery 1000z.

[0101] In a preferred embodiment, the second surface 140D of the sub-disk 140 and the outer lower surface 130D of the recess 130A of the stripper disk 130 are flush. The second surface 140D of the sub-disk 140 and the outer lower surface 130D of the recess 130A of the stripper disk 130 contact the conductive member 15 and are electrically connected. Therefore, when they are flush as described above, the conductive member 15 can easily contact the second surface 140D of the sub-disk 140 and the outer lower surface 130D of the recess 130A of the stripper disk 130, and a more reliable electrical connection can be realized.

[0102] The sub-disk 140 may be a metal member. The sub-disk 140 may contain, for example, any one or two or more of metal materials such as aluminum and aluminum alloys. Note that the material of the sub-disk 140 may be the same as that of the safety cover 110, or may be different from that of the safety cover 110.

[0103] (Joining mode of the safety valve) The safety valve 100 has a configuration in which a plurality of members are combined, and this embodiment has specific matters related to the combination. As described above, in the safety valve 100, a fitting method using the protrusion 130T of the stripper disk 130 is preferably adopted. More specifically, due to the pressing force and fitting force caused by the protrusion 130T of the stripper disk 130, the safety cover 110 and the stripper disk 130 are fixed to each other via the disk holder 120. Taking the aspect shown in FIG. 7 as an example, due to the pressing force provided by the protrusion 130T with the opening 130P (for example, a claw-like part as shown in the figure), the safety cover 110 and the stripper disk 130 are fixed while being insulated from each other via the disk holder 120. Here, it is preferable that the side wall of the safety cover 110 (more specifically, the side wall portion between the outer peripheral part 110X and the central part 110Y) is provided at an angle with respect to the axis of the secondary battery 1000. In short, it preferably has the form of a "Z-fold" 112. Such a "Z-fold" 112 of the safety cover 110 contributes to more effectively applying the pressing force caused by the protrusion 130T of the stripper disk 130, and the safety cover 110 and the stripper disk 130 can be more effectively fixed via the disk holder 120. As described above, an opening 130P is provided in the vicinity of the protrusion 130T of the stripper disk 130 so as to be adjacent to the protrusion. This is related to the fact that the stripper disk 130 provided with the protrusion 130T is manufactured by press forming. That is, the stripper disk 130 is preferably a press part, and the opening 130P is formed when providing a protrusion 130T as shown in the figure as such a press part.

[0104] (Operation of the safety valve (safety mechanism)) In addition to FIG. 6, with reference mainly to FIGS. 10 and 11, the effects of the secondary battery 1000 according to the present embodiment in the event of an abnormality in the secondary battery 1000 will be described in further detail. FIG. 10 is a schematic cross-sectional view showing the state of the activated safety valve. FIG. 11 is a schematic cross-sectional view showing the state of the safety valve further activated from the state shown in FIG. 10.

[0105] As described above, when an abnormal temperature rise occurs inside the battery due to a short circuit or the like, it may occur in combination with an abnormality such as an increase in internal pressure. That is, assume a case where the pressure increase inside the battery can 50 caused by side reactions such as the decomposition reaction of the electrolyte or other factors becomes excessive together with the undesired temperature rise inside the battery 1000. FIG. 6 also shows a case where the internal pressure of the battery (that is, the internal pressure of the battery can 50) is within the normal range during normal use, and the safety valve 100 is not activated. As shown in FIG. 6, the safety cover 110 has not yet been displaced, and the gas flow path or discharge path itself through the plurality of openings 130K in the stripper disk 130 is not particularly functioning.

[0106] When gas is generated inside the battery can 50 due to a side reaction such as the decomposition reaction of the electrolytic solution, for example, the gas accumulates inside the battery can 50, so the internal pressure of the battery can 50 increases. Also, an excessive increase in the internal temperature of the battery due to an undesired short circuit or the like can also cause an increase in the internal pressure of the battery can 50. When the internal pressure of the battery can 50 exceeds a certain predetermined pressure, as shown in FIGS. 10 to 11, the sub-disk 140 will be cracked and severed. Although not particularly limited, for example, the sub-disk 140 cracks or is severed due to its thinness (small thickness), and its central portion 140Y is separated from the peripheral portion (i.e., the outer peripheral portion 140X). Then, due to the internal pressure of the battery can 50, the safety cover 110 is displaced so that at least a part of the safety cover 110 is lifted while maintaining the state where the separated central portion 140Y of the sub-disk 140 is connected to the protruding portion 110T of the safety cover 110. In particular, the safety cover 110 is displaced so that the central portion 110Y of the safety cover 110 bends outward (for example, bends like a bow) (see FIG. 10), and the internal pressure of the battery is reduced. The bending of the safety cover 110 can preferably act on the groove when the safety cover is provided with a groove (for example, the portion with reference numeral "115" in the embodiment shown in FIG. 10). The groove 115 is provided on the relatively outer surface of the safety cover 110 with respect to the battery axis and near the peripheral edge portion 110Y' of the central portion.

[0107] The safety cover 110 and the outer peripheral portion 140X of the sub-disk 140 (particularly, the outer peripheral portion 140X to which the conductive member 15 such as a tab or a lead extending from the electrode assembly is still connected) will be physically separated from each other. As a result, the electrical connection between the battery cover 170 and the electrode assembly is cut off, and the current path flowing between the electrode assembly 10 and the battery cover 170 is blocked. By cutting off the current, the generation of gas inside the battery can be suppressed. During normal use, the safety cover 110 is electrically connected to the battery cover 170 that forms the external terminal of the secondary battery 1000.

[0108] When the internal pressure inside the secondary battery 1000 further increases and the displacement of the safety cover 110 further progresses, as shown in FIG. 11, the safety cover 110 itself cracks or breaks. The break point 115’ of the safety cover 110 is derived from, for example, the groove 115 of the safety cover 110. Thereby, the inside and the outside of the battery communicate with each other, and a gas release path through the plurality of openings 130K of the stripper disk 130 is opened. The gas accumulated inside the battery is discharged to the outside of the battery via the openings 130K. The internal pressure of the battery is further reduced.

[0109] (Manufacture of Secondary Battery) An exemplary description will be given regarding the manufacturing method of the secondary battery 1000. The secondary battery 1000 can be manufactured, for example, by the following procedure.

[0110] - Fabrication of Electrodes - When fabricating the positive electrode 11, a positive electrode mixture is obtained by mixing a positive electrode active material and, if necessary, a positive electrode binder, a positive electrode conductive agent, etc. Next, a paste-like positive electrode mixture slurry is obtained by dispersing the positive electrode mixture in an organic solvent or the like. Then, the positive electrode mixture slurry is applied to one or both sides of the positive electrode current collector, and the positive electrode mixture slurry is dried to form a positive electrode active material layer. Thereafter, if necessary, the positive electrode active material layer may be compression-molded using a roll press or the like. In such a case, the positive electrode active material layer may be heated, or the compression molding may be repeated a plurality of times. Similarly, the negative electrode 12 can be fabricated. Specifically, a negative electrode mixture is obtained by mixing a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, etc., and then a paste-like negative electrode mixture slurry is obtained by dispersing the negative electrode mixture in an organic solvent or the like. Next, after applying the negative electrode mixture slurry to one or both sides of the negative electrode current collector, the negative electrode mixture slurry is dried to form a negative electrode active material layer. Thereafter, if necessary, the negative electrode active material layer is compression-molded using a roll press or the like.

[0111] - Assembly - When assembling the secondary battery 1000, the positive electrode lead is connected to the positive electrode current collector using a welding method or the like, and the negative electrode lead is connected to the negative electrode current collector using a welding method or the like. Next, after laminating the positive electrode 11 and the negative electrode 12 via the separator 13, the positive electrode 11, the negative electrode 12, and the separator 13 are wound to form a wound electrode body 10. Next, a center pin is inserted into the winding space of the wound electrode body 10. Then, while sandwiching the wound electrode body with a pair of insulating plates, the wound electrode body 10 together with the pair of insulating plates is housed inside the battery can 50. In this case, for example, as shown in FIG. 8, one end of the positive electrode lead (conductive member 15) is connected to the safety valve 100 using a welding method or the like, and similarly, one end of the negative electrode lead is connected to the battery can 50 using a welding method or the like. Next, an electrolytic solution is injected into the battery can 50, and the electrolytic solution is impregnated into the wound electrode body 10. Finally, a battery lid member (battery cover), a thermal resistance element, and a safety valve are provided through caulking at the open end of the battery can via a gasket. Thereby, the secondary battery 1000 equipped with the safety valve 100 is completed.

[0112] <Second Embodiment: Secondary Battery> The secondary battery according to the second embodiment has a different stripper disk 130a compared to the secondary battery 1000 according to the first embodiment. Hereinafter, the different configuration will be mainly described. In the second embodiment, the same reference numerals as those in the first embodiment denote the same configuration as that in the first embodiment, and thus the description thereof will be omitted in principle.

[0113] Hereinafter, with reference to FIG. 13, the secondary battery according to the second embodiment will be described. FIG. 13 shows the stripper disk 130a in the secondary battery 1000 according to the second embodiment.

[0114] The number of the openings 130K is the same as the number of the protrusions 130T. The number of the plurality of openings 130K is the same as the number of the plurality of protrusions 130T, and the plurality of protrusions 130T are all arranged so as to be radially opposed to each of the plurality of openings 130K. That is, the protrusions 130T are arranged so as to be radially opposed to the same number of openings 130K one by one. More specifically, the protrusion 130T has a center point 130Tp linearly extending from the center point P through the center point 130Kp of the opening 130K in the radial direction.

[0115] When the stripper disk 130a has such a shape (that is, the number of the openings 130K and the protrusions 130T is the same, and each pair of the openings 130K and the protrusions 130T is arranged on a straight line extending radially from the center point P), the strength is increased as compared with the stripper disk 130 of the first embodiment. Therefore, in such a case, the vibration resistance of the secondary battery 1000 according to the second embodiment is further improved.

[0116] As described above, the embodiments of the present invention have been described, but they are merely illustrative of typical examples. Therefore, it will be easily understood by those skilled in the art that the present invention is not limited thereto, and various aspects are conceivable.

[0117] <Other Embodiments> In the second embodiment, the arrangement of the plurality of openings 130K is six-fold symmetry C6, but it is not limited thereto. For example, the arrangement of the plurality of openings 130K may be n-fold symmetry Cn (n≠6: two-fold symmetry C2, three-fold symmetry C3, four-fold symmetry C4, five-fold symmetry C5, and eight-fold symmetry C8).

[0118] In addition, the safety valve 100 is provided with a battery lid member (i.e., a battery cover), and the safety valve 100 can bear a battery terminal (i.e., one of the positive and negative terminals as the external terminals of the secondary battery 1000), and in particular, it may bear the positive terminal. That is, the safety valve 100 may be provided on the positive terminal side of the battery can 50, and the safety valve 100 may be provided at the open end 51 of the battery can 50 where the positive terminal is provided. In such a case, the safety valve 100 is preferably combined with the positive terminal, improving the convenience of the secondary battery 1000 and contributing to the realization of a more practically preferable secondary battery 1000.

[0119] In addition, in the above embodiment, the description has been particularly centered on the cylindrical secondary battery 1000, but the present disclosure is not necessarily limited thereto. For example, the secondary battery 1000 according to the first embodiment may be a battery of other shapes such as a rectangular battery, and similarly, the effects of the present disclosure can be achieved.

[0120] Aspects of the secondary battery of the present disclosure are as follows. <1> A secondary battery including a battery element, an exterior member that houses the battery element, and a safety valve attached to the exterior member, wherein the safety valve has a safety cover with a protruding portion at the center, a disk holder with an opening at the center, a stripper disk with an opening at the center, and a sub-disk that joins the protruding portion extending through the opening of the disk holder and the opening of the stripper disk, and at least has a configuration in which they are combined in order from the relatively outer side to the inner side of the housing member, wherein the stripper disk has a concave portion on the relatively inner surface of the housing member, and the concave portion houses the sub-disk. <2> The secondary battery according to <1>, wherein a terminal electrically connected to the battery element contacts a second surface facing the first surface of the sub-disk joined to the protruding portion and an outer lower surface of the concave portion of the stripper disk. <3> The battery according to <2>, wherein the second surface of the sub-disk and the outer lower surface of the concave portion of the stripper disk are flush. <4> The secondary battery according to any one of <1> to <3>, wherein the thickness of the stripper disk is 0.35 to 0.40 mm. <5> The material constituting the stripper disk has a tensile strength of 230 to 290 N / mm obtained from a tensile test conforming to JIS Z2241 2 The secondary battery according to any one of <1> to <4>. <6> The secondary battery according to <5>, wherein the material is aluminum or an aluminum alloy. <7> The stripper disk has a plurality of openings arranged radially from the center of the stripper disk in a plan view, and a plurality of protrusions arranged on the outer edge side of the opening in the radial direction from the center and The number of the plurality of openings is the same as the number of the plurality of protrusions, and the plurality of protrusions are arranged so as to face each of the plurality of openings in the radial direction perpendicular to the battery axis. The secondary battery according to any one of <1> to <6>. <8> The diameter of the sub-disk is less than the recess diameter of the recess of the stripper disk. The secondary battery according to any one of <1> to <7>. <9> The inner diameter of the concave portion of the stripper disk increases toward the relatively inner side of the battery axis. The secondary battery according to any one of <1> to <8>. <10> The member constituting the disk holder includes a resin member. The secondary battery according to any one of <1> to <9>.

Example

[0121] Hereinafter, the present invention will be described more specifically with reference to examples. The present disclosure is not limited by the following examples at all.

[0122] <Example 1> [1. Preparation of Test Battery] A secondary battery having the following specifications was prepared. The configuration of Example 1 is summarized in Table 1. · Shape: Cylindrical shape (diameter dimension: about 22 cm, axial length: about 70 mm) · Positive and negative electrodes of the electrode assembly: Positive and negative electrodes capable of intercalating and deintercalating lithium ions · Nominal capacity: about 4100 mAh · Nominal voltage: 3.6 V · Safety valve: Composed of a safety cover, a disk holder, a stripper disk, and a sub-disk (Materials of each member) · Safety cover: Made of metal (metal containing aluminum) · Disk holder: Made of thermoplastic resin (polypropylene (PP)) · Outer body and sub-disk: Made of metal (metal containing aluminum)

[0123]

Table 1

[0124] [2. Measurement Method] (2-1. Measurement Method of Tensile Strength) The tensile strength of the material constituting the stripper disk was measured by a tensile test in accordance with Japanese Industrial Standard (JIS) Z2241.

[0125] [3. Evaluation Method] (3-1. Evaluation of Vibration Resistance: Vibration Test) A vibration test in accordance with UN38.3 standard was carried out at normal temperature and pressure (23 ± 2 °C, 1 atm). The battery of Example 1 was fully discharged. Specifically, it was discharged to a constant voltage of 2.5 V at a temperature of 23 ± 2 °C and a constant current of 4.0 A. Using a battery tester, the electrical resistance value (AC resistance value) of the secondary battery after discharge was measured (number of measurements n = 100). Specifically, an AC constant current with a measurement frequency of 1 kHz was passed, and the voltage value was measured. The internal resistance value of the battery was calculated from the obtained voltage value. The average value of the plurality of internal resistance values was calculated, and the obtained average value was taken as the "electrical resistance value before vibration application".

[0126] A sweep-type vibration was applied to the secondary battery after discharge. Specifically, the vibration frequency was swept from 7 Hz (minimum value) → 200 Hz (maximum value) → 7 Hz (minimum value) over 15 minutes. Considering this change in vibration frequency as one cycle, it was performed 12 times for each of the three directions of the XYZ axes (the XYZ axes shown in Figure 1). The amplitude was 0.8 (mm). The electrical resistance value of the battery after vibration application was measured (number of measurements n = 100). The average value of the plurality of electrical resistance values was calculated, and the obtained average value was taken as the "electrical resistance value after vibration application".

[0127] From the obtained electrical resistance values before and after vibration application: The increase rate of electrical resistance (%) = [(electrical resistance value after vibration application - electrical resistance value before vibration application) / electrical resistance value before vibration application] × 100 ··· (1) Using the formula represented by (1), the increase rate of the electrical resistance value due to vibration application was calculated. Based on the increase rate of the electrical resistance value, the vibration resistance of the secondary battery of Example 1 was evaluated according to the following evaluation criteria. The evaluation results of the vibration resistance are summarized in Table 1. [Evaluation Criteria] A (Pass: Good): The increase rate of the electrical resistance value is less than 10%. B (Fail: Bad): The increase rate of the electrical resistance value is 10% or more. ※ The increase in the electrical resistance value is caused by the weakening or partial breakage of the joint between the safety cover 110 and the sub-disc 140.

[0128] <Examples 2 to 9 and Comparative Examples 1 to 2> [1. Preparation of Test Batteries] A test battery was fabricated in the same manner as in Example 1, except that the configuration of the secondary battery was changed to the configuration described in Table 1. As specific changes, in Comparative Examples 1 and 2, no concave portion was provided on the second surface of the stripper disk, and the sub-disk was not housed in the concave portion. Also, in Examples 2 to 5 and Comparative Example 1, the thickness of the stripper disk was changed. Further, in Examples 6 to 9, the tensile strength of the stripper disk was changed.

[0129] [2. Measurement Method] and [3. Evaluation Method] For the batteries of Examples 2 to 9 and Comparative Examples 1 and 2, a vibration test was conducted in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0130] <Results: Examples 1 to 9 and Comparative Examples 1 and 2> In the secondary batteries of Examples 1 to 9, as shown in Table 1, a concave portion was provided on the second surface of the stripper disk, and the stripper disk was housed in the concave portion. The results of the vibration tests for the secondary batteries of Examples 1 to 9 were all A (pass). On the other hand, in the secondary batteries of Comparative Examples 1 and 2, as shown in Table 1, no concave portion was provided on the second surface of the stripper disk, and the stripper disk was not housed in the concave portion. The results of the vibration tests for the secondary batteries of Comparative Examples 1 and 2 were all B (fail).

[0131] From the above, it is clear that the secondary batteries of Examples 1 to 9 included in the scope of the invention according to claim 1 have better vibration resistance than Comparative Examples 1 and 2 located outside the scope of the invention according to claim 1.

[0132] Note that the effects of the above examples are merely illustrative. Therefore, the present disclosure is not limited to the above matters, and there may be additional effects.

Industrial Applicability

[0133] The secondary battery according to the present disclosure can typically be used in applications where the utilization of electrical energy is required. For example, the secondary battery according to the present disclosure can be used in various fields where power storage is assumed. Although it is merely an example, the secondary battery according to the present disclosure can be used in the electrical, information, and communication fields (e.g., the fields of electrical and electronic devices such as mobile phones, smartphones, notebook computers, digital cameras, activity monitors, arm computers, electronic paper, wearable devices, etc., and small electronic devices such as RFID tags, card-type electronic money, smartwatches, etc. or mobile device fields), home and small industrial applications (e.g., the fields of power tools, golf carts, home, care, and industrial robots), large industrial applications (e.g., the fields of forklifts, elevators, port cranes), transportation system fields (e.g., the fields of hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles, etc.), power system applications (e.g., the fields of various power generations, load conditioners, smart grids, general household installed energy storage systems, etc.), medical applications (the fields of medical devices such as earphone hearing aids), pharmaceutical applications (the fields of medication management systems, etc.), as well as the IoT field, space and deep sea applications (e.g., the fields of space exploration vehicles, submersible survey ships, etc.).

Explanation of Signs

[0134] 10 Electrode assembly 11 Positive electrode 12 Negative electrode 13 Separator 15 Conductive member 50 Battery can 51 Open end of the battery can 100 Safety valve 110 Safety cover 110T Protrusion of the safety cover 110X Outer peripheral part 110Y Central part 110Y’ Peripheral part of the central part 112 Z-folded part of the safety cover 115 Groove provided in the safety cover (especially its central part) 120 Disk Holder 120X Outer Periphery 120Y Inner Periphery 120Z Opening 130 Stripper Disk 130A Concave Portion 130B Outer Upper Surface (of the Concave Portion) 130C Opening (through which the protruding portion of the safety cover passes) 130D Outer Lower Surface (of the Concave Portion) 130E Inner Lower Surface (of the Concave Portion) (Second Surface of the Stripper Disk) 130F Inner Side Surface (of the Concave Portion) 130K Opening (mainly for gas passage or release) 130P Opening (adjacent to the protrusion) 130T Protrusion (adjacent to the opening) 130X Outer Periphery 130Y Central Portion 132 Inner Side Surface of the Central Portion of the Stripper Disk (especially the inner main surface in the recessed portion located inside in plan view compared to the outer periphery of the stripper disk) 130z Conventional Stripper Disk 140 Sub - Disk 140C First Surface (of the Sub - Disk) 140D Second Surface (of the Sub - Disk) 170 Battery Cover (Top Cover / Battery Lid Member) 1000 Secondary Battery 1000z Conventional Secondary Battery

Claims

1. A secondary battery comprising a battery element, a housing member for housing the battery element, and a safety valve attached to the housing member, wherein the safety valve comprises a safety cover having a protrusion at the center, a disk holder having an opening at the center, a stripper disk having an opening at the center, and a sub-disk joined to the protrusion extending through the opening of the disk holder and the opening of the stripper disk, and at least has a configuration in which they are combined in order from the relatively outer side to the inner side of the housing member, wherein the stripper disk has a recess on a surface located relatively inside the housing member, and the recess houses the sub-disk. The secondary battery.

2. The terminal electrically connected to the battery element faces the second surface facing the first surface of the sub-disk joined to the protrusion, and contacts the outer lower surface of the recess of the stripper disk. The secondary battery according to claim 1.

3. The secondary battery according to claim 2, wherein the second surface of the sub-disk and the outer lower surface of the recess of the stripper disk are flush.

4. The thickness of the stripper disk is 0.35 to 0.40 mm. The secondary battery according to claim 1 or 2.

5. The material constituting the stripper disk has a tensile strength of 230 to 290 N / mm obtained from a tensile test conforming to JIS Z2241 ２ The secondary battery according to claim 1 or 2, having the same

6. The material is aluminum or an aluminum alloy. The secondary battery according to claim 5.

7. The stripper disk has a plurality of openings arranged radially from the center point of the stripper disk in a plan view, and a plurality of protrusions arranged on the outer edge side of the opening in the radial direction from the center point, and the number of the plurality of openings is the same as the number of the plurality of protrusions, and the plurality of protrusions are all arranged so as to face the respective ones of the plurality of openings in the radial direction perpendicular to the battery axis. The secondary battery according to claim 1 or 2.

8. The diameter of the sub-disk is larger than the opening diameter of the opening and smaller than the recess diameter of the recess. The secondary battery according to claim 1 or 2.

9. The inner diameter of the recess of the disk in the stripper increases toward the relatively inner side of the battery axis. The secondary battery according to claim 1 or 2.

10. The member constituting the disk holder includes a resin member. The secondary battery according to claim 1 or 2.

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