Battery

Abstract

To provide a battery having improved breaking reliability as a safety valve.SOLUTION: A battery including a safety valve, the safety valve including a first metal member located on an outer side, a second metal member located on an inner side, and an insulating member located between the first metal member and the second metal member, the first metal member and the second metal member being connected to each other such that the first metal member and the second metal member straddle the insulating member, the first metal member has a step portion and a thin portion located on an inner peripheral side of the step portion, the first metal member has a first groove, the second metal member has a second groove, and the first groove is provided in an outer surface of the first metal member.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] Batteries can extract energy from chemical reactions and other processes as electrical energy and are used in a variety of applications, including mobile devices such as cell phones, smartphones, and laptops. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2022 / 131558 issue Summary of the Invention [Problem to be solved by the invention]

[0004] Safety is a requirement for batteries. For example, a battery equipped with a safety valve that can cut off current in the event of an abnormality is considered. The present inventors have diligently investigated whether there is still room for development of battery safety valves. As a result, they have found that there is still room for development in terms of cut-off characteristics of safety valves that cut off current in the event of an abnormality.

[0005] The present invention has been made in view of the above problems, and a main object of the present invention is to provide a battery in which the cutoff characteristics of the safety valve can be improved. [Means for solving the problem]

[0006] The inventors of the present application attempted to solve the above problems by taking a new approach rather than simply extending the conventional technology, and as a result, they have invented a battery that achieves the above-mentioned main object.

[0007] The battery according to the present invention has a safety valve, the safety valve comprises a first metal member located on the outside, a second metal member located on the inside, and an insulating member located between the first metal member and the second metal member, the first metal member and the second metal member being connected to each other so as to straddle the insulating member, the first metal member has a stepped portion and a thin-walled portion positioned more inwardly than the stepped portion, The first metal member has a first groove and the second metal member has a second groove, the first groove being provided on an outer surface of the first metal member. [Effects of the Invention]

[0008] The battery according to the present invention can more effectively interrupt current in the event of an abnormality. That is, the interruption characteristics can be improved by the safety valve in which "the first metal member has a stepped portion and a thin-walled portion, and the first groove, particularly the first groove is provided on the outer surface of the first metal member, and the second groove is provided in the second metal member." [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view showing the appearance of a secondary battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the internal configuration of a secondary battery according to one embodiment of the present invention. [Figure 3] FIG. 3 is a schematic perspective view showing components and related members of a safety valve of a secondary battery according to one embodiment of the present invention in an expanded state. [Figure 4] FIG. 4 is a schematic perspective view showing the components of the safety valve of the secondary battery according to one embodiment of the present invention in a half-split and developed state. [Figure 5] FIG. 5 is a schematic perspective view showing a half-cut safety valve of a secondary battery according to one embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view of a safety valve of a secondary battery according to one embodiment of the present invention. [Figure 7] FIG. 7 is a schematic cross-sectional view of the safety valve and a partially enlarged schematic view of the stepped portion of the first metal member. [Figure 8] FIG. 8 is a schematic cross-sectional view of a safety cover corresponding to the first metal member and a partially enlarged view thereof. [Figure 9A] FIG. 9A is a schematic exploded cross-sectional view of a safety valve (excluding a top cover) of a secondary battery according to one embodiment, and a schematic cross-sectional view of an assembled state. [Figure 9B] FIG. 9B is a schematic exploded cross-sectional view of a safety valve (excluding a top cover) of a secondary battery according to another embodiment, and a schematic cross-sectional view of the assembled state. [Figure 10] FIG. 10 is a schematic enlarged cross-sectional view of a foil portion and a step portion of the first metal member. [Figure 11A] FIG. 11A is a partial cross-sectional view and a partially enlarged cross-sectional view of a safety valve that can correspond to a comparative example. [Figure 11B] FIG. 11B is a partial cross-sectional view and a partially enlarged cross-sectional view of the safety valve of the present invention. [Figure 12] FIG. 12 is a schematic cross-sectional view of a 2D half-split model. [Figure 13] 13(a) and 13(b) are schematic cross-sectional views showing the states of the activated safety valves in Examples 1 and 2. Fig. 13(c) and 13(d) are schematic cross-sectional views showing the states of the activated safety valves in Comparative Examples 1 and 2. [Figure 14] Fig. 14(a) is a schematic cross-sectional view showing the displacement ratio of the stripper disc when the safety valve is activated in Examples 1 and 2. Fig. 14(b) is a schematic cross-sectional view showing the displacement ratio of the stripper disc when the safety valve is activated in Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Knowledge and other information that formed the basis of this disclosure] In recent years, with the trend toward longer life and higher output, there has been a demand for improved performance in terms of battery reliability.

[0011] The inventors of the present application have found that while certain battery safety valves are capable of interrupting current in the event of an abnormality and can accommodate higher output, there is still room for development from another perspective. Specifically, the inventors have noticed that safety valves made up of multiple components are not necessarily satisfactory in terms of interrupting current in the event of an abnormality, and that there are cases in which component deformation and displacement due to an abnormal rise in internal battery pressure, etc., are insufficient.

[0012] A battery safety valve can interrupt current and / or reduce internal can pressure in the event of an abnormality by rupturing or breaking its components. For example, in a battery equipped with a safety valve that includes a combination of a safety cover, a stripper disk, and an insulating member between them, the interruption pressure can be controlled by the deflection of the safety cover, and the timing of the groove rupture between the safety cover and the stripper disk can affect the interruption pressure.

[0013] In such a safety valve, it is expected that the stripper disk that has been ruptured or broken will move outward (outward along the battery axis) due to the internal pressure of the battery. However, we have found that such displacement is not always desired. In particular, we have found that the amount of displacement of the stripper disk may not be sufficient. Such insufficient displacement of the stripper disk is likely to cause undesired re-conduction.

[0014] Undesired re-conduction due to insufficient displacement is likely to become apparent when melting occurs. When a break is caused by groove rupture, melting may occur due to heat generated by the passage of a large current. Although a break may initially function due to melting of the stripper disk, molten metal that may be produced by melting is likely to induce re-conduction. For example, if molten metal produced by melting adheres to the safety cover and the stripper disk, there is a concern that an undesirable event such as re-conduction may occur. The inventors of the present application have realized that such an undesirable event is likely to become apparent when the displacement of the stripper disk when the safety valve is activated is insufficient.

[0015] The inventors of the present application attempted to solve these problems by taking a new approach rather than simply extending the conventional technology, and as a result, they improved the amount of displacement of the stripper disk in the safety valve mechanism that operates in the event of an abnormality, resulting in a more reliable battery that can reduce or avoid undesired re-conduction in the safety valve mechanism.

[0016] The following describes specific embodiments of the present invention. The applicant provides the following description and examples to enable those skilled in the art to fully understand the present invention, and it should be noted that these are not intended to limit the subject matter described in the claims. In other words, the present invention is not particularly limited to the preferred embodiments described below, and can be implemented with appropriate modifications within the scope of its intended purpose. For convenience, the present invention may be divided into embodiments and examples to facilitate explanation or understanding of the main points. However, partial substitution and / or combination of the configurations shown in different embodiments is possible. In describing such embodiments, descriptions of matters common to the above may be omitted, and only differences may be described. In particular, similar effects resulting from similar configurations may not be mentioned in each embodiment.

[0017] References to directions or orientations in the description of this specification are merely for the convenience of explanation and are not intended to limit the scope of the present invention unless otherwise expressly stated. For example, relative terms such as "outside (or outer, external, or outer circumference)," "inside (or inner, internal, or inner circumference)," "bottom," and their derivatives should be understood to refer to the direction as described or illustrated. In other words, unless otherwise expressly stated, the invention is not necessarily limited to a specific direction, orientation, or configuration. The same applies to terms such as "provided," "disposed," "connected," and "bonded," and their derivatives. Unless otherwise expressly stated, they may refer not only to a direct configuration but also to a configuration in which other elements, such as intervening elements, are present.

[0018] [Basic battery configuration] The term "battery" as used herein includes not only so-called "secondary batteries" but also "primary batteries" that can only be discharged. In other words, the term "battery" as used herein may refer to either a "secondary battery" that can be repeatedly charged and discharged, or a "primary battery" that essentially only discharges. Note that the term "secondary battery" should not be overly limited to its name, and may also include, for example, an "electricity storage device."

[0019] For convenience of explanation, the battery according to the present invention will be described below mainly using a secondary battery as an example.

[0020] The secondary battery according to the present invention includes an electrode assembly made up of electrode constituent layers including a positive electrode, a negative electrode, and a separator. The secondary battery according to the present invention may have a wound structure in which such electrode constituent layers are wound into a roll (hereinafter also referred to as a "wound electrode body" or "wound structure"). FIG. 1 shows an exemplary external view of a secondary battery 1000, and FIG. 2 shows an exemplary internal structure thereof. As shown in the figure, an electrode assembly 10 is housed inside a battery can 50. In the exemplary embodiment shown in FIG. 2, the electrode assembly 10 is configured by winding a positive electrode 11, a negative electrode 12, and a separator 13 disposed between the positive and negative electrodes. In the secondary battery 1000, the electrode assembly 10 is enclosed in a battery can 50 together with an electrolyte (e.g., a non-aqueous electrolyte).

[0021] The positive electrode is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, the positive electrode material layer is provided on at least one surface of the positive electrode current collector. The positive electrode material layer contains a positive electrode active material as an electrode active material. For example, each of the multiple positive electrodes in the electrode assembly may have a positive electrode material layer provided on both surfaces of the positive electrode current collector, or may have a positive electrode material layer provided on only one surface of the positive electrode current collector.

[0022] The negative electrode is composed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode, the negative electrode material layer is provided on at least one surface of the negative electrode current collector. The negative electrode material layer contains a negative electrode active material as an electrode active material. For example, each of the multiple negative electrodes in the electrode assembly may have a negative electrode material layer provided on both surfaces of the negative electrode current collector, or may have a negative electrode material layer provided on only one surface of the negative electrode current collector.

[0023] The electrode active materials contained in the positive and negative electrodes, i.e., the positive and negative electrode active materials, respectively, are materials directly involved in the transfer of electrons in a secondary battery and are the main materials of the positive and negative electrodes responsible for charge and discharge, i.e., the battery reaction. More specifically, the "positive electrode active material contained in the positive electrode layer" and the "negative electrode active material contained in the negative electrode layer" provide ions to the electrolyte, and these ions move between the positive and negative electrodes, transferring electrons and causing charge and discharge. The positive and negative electrode layers may be layers capable of absorbing and desorbing lithium ions. In other words, the secondary battery according to the present invention may be a nonaqueous electrolyte secondary battery in which lithium ions move between the positive and negative electrodes via a nonaqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charge and discharge, the secondary battery according to the present invention corresponds to a so-called "lithium ion battery," and has electrodes capable of absorbing and desorbing lithium ions as the positive and negative electrodes, preferably layers capable of absorbing and desorbing lithium ions.

[0024] In the case of a lithium-ion battery, the positive electrode active material may be a material that contributes to the absorption and desorption of lithium ions. That is, the positive electrode layer may contain one or more positive electrode materials that can absorb and desorb lithium. From this perspective, the positive electrode active material may be, for example, a lithium-containing compound. The type of lithium-containing compound is not particularly limited, but examples include lithium-containing composite oxides and lithium-containing phosphate compounds. This is because a high energy density can be easily obtained.

[0025] 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), and iron (Fe), etc. This is because a high voltage can be easily obtained.

[0026] 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) (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) (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 the following conditions: 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 a fully discharged state.) Li a Co (1-b) M13 b O (2-c) F d ···(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 the following conditions: 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 a fully discharged state.) Specific examples of lithium-containing composite oxides having a layered rock salt type crystal structure include LiNiO2, LiCoO2, and 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 Li 1.15 (Mn 0.65 Ni0.22 Co 0.13 )O2, etc. When the lithium-containing composite oxide having a layered rock-salt crystal structure contains nickel, cobalt, manganese, and aluminum as constituent elements, the atomic ratio of nickel is preferably 50 atomic % or more, because a high energy density is easily obtained.

[0027] 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) (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 the following conditions: 0.9≦a≦1.1, 0≦b≦0.6, 3.7≦c≦4.1, and 0≦d≦0.1. However, the lithium composition varies depending on the charge / discharge state, and a is the value in a fully discharged state.) A specific example of the lithium-containing composite oxide having a spinel-type crystal structure may be LiMn2O4.

[0028] 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) (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 composition of lithium varies depending on the charge / discharge state, and a is the value in a fully discharged state.) Specific examples of lithium-containing phosphate compounds having an olivine-type crystal structure include LiFePO4, LiMnPO4, and LiFe 0.5 Mn 0.5 PO4 and LiFe 0.3 Mn 0.7 It may be PO4, etc.

[0029] The lithium-containing composite oxide may be a compound represented by the following formula (6). (Li2MnO3) x (LiMnO2) 1-x ···(6) (x satisfies the condition 0≦x≦1. However, the lithium composition varies depending on the charge / discharge state, and x is the value in a fully discharged state.)

[0030] Alternatively, the positive electrode material may be one or more of oxides, disulfides, chalcogenides, and conductive polymers. Examples of oxides include titanium oxide, vanadium oxide, and manganese dioxide. Examples of disulfides include titanium disulfide and molybdenum sulfide. Examples of chalcogenides include niobium selenide. Examples of conductive polymers include sulfur, polyaniline, and polythiophene. However, the positive electrode material is not particularly limited and may be a material other than those listed above.

[0031] The positive electrode layer may contain a binder. The positive electrode layer may also contain a positive electrode conductive agent to facilitate the transfer of electrons that drive the battery reaction. The positive electrode binder may contain, for example, one or more of synthetic rubbers and polymeric compounds. Examples of synthetic rubbers include styrene-butadiene rubbers, fluorine-containing rubbers, and ethylene propylene dienes. Examples of polymeric compounds include polyvinylidene fluoride and polyimides. The positive electrode conductive agent may contain, for example, one or more of carbon materials. Examples of carbon materials include graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may also be a metal material or a conductive polymer, as long as it is a conductive material.

[0032] Similarly, the negative electrode active material of the negative electrode layer may be a material that contributes to the absorption and desorption of lithium ions. That is, the negative electrode layer may contain one or more negative electrode materials that can absorb and desorb lithium. From this perspective, the negative electrode active material may be, for example, various carbon materials, metal materials, and / or other materials.

[0033] When a carbon material is used as the negative electrode active material, the change in the crystal structure during lithium absorption and desorption is very small, so a high energy density can be easily obtained stably. In addition, the carbon material also functions as a negative electrode conductive agent, so the conductivity of the negative electrode layer can be easily improved.

[0034] Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and / or graphite. More specifically, the carbon material may be, for example, pyrolytic carbon, cokes, glassy carbon fiber, organic polymer compound calcined bodies, activated carbon, and carbon blacks. Examples of cokes include pitch coke, needle coke, and petroleum coke. Examples of organic polymer compound calcined bodies are substances obtained by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. Alternatively, the carbon material may be low-crystalline carbon heat-treated at a temperature of approximately 1000°C or less, or amorphous carbon. The shape of the carbon material is not particularly limited and may be at least one of fibrous, spherical, granular, and flaky.

[0035] The term "metal-based material" used as the negative electrode active material is a general term for materials containing one or more 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 simple substance, an alloy, a compound, or two or more of these, or may be a material containing at least one or more phases of these. However, alloys may include materials containing one or more metal elements and one or more metalloid elements in addition to materials consisting of two or more metal elements. The alloy may also contain nonmetallic elements. The structure of this metal-based material may be, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a mixture of two or more of these. Such metal elements and metalloid elements may be, for example, one or more metal elements and metalloid elements that can form an alloy with lithium. Specifically, the metal element and the metalloid element may be, for example, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium (Y), palladium (Pd), and / or platinum (Pt). In a preferred embodiment, the metal element or the metalloid element is silicon or tin. This is because they have excellent lithium absorption and desorption capabilities, making it easier to obtain a higher energy density. The material containing silicon as a constituent element may be silicon itself, a silicon alloy, a silicon compound, or two or more types selected from these, or may be a material that at least partially contains one or more phases of these. Similarly, a material containing tin as a constituent element may be tin alone, a tin alloy, a tin compound, or two or more of these, or may be a material that contains one or more of these phases at least in part. The term "simple element" used in this specification refers only to a simple element in the general sense, and the simple element may contain trace amounts of impurities.That is, the purity of the single substance is not necessarily limited to 100%. Silicon alloys 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. Silicon compounds may contain, for example, any one or more of carbon and oxygen as constituent elements other than silicon. Note that silicon compounds may also contain any one or more of the series of elements described for silicon alloys as constituent elements other than silicon. Specific examples of silicon alloys and silicon compounds 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 mentioned. Note that for SiO v the v in it may be 0.2 < v < 1.4. Tin alloys 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. Tin compounds may contain, for example, any one or more of carbon and oxygen as constituent elements other than tin. Note that tin compounds may also contain any one or more of the series of elements described for tin alloys as constituent elements other than tin. Specific examples of tin alloys and tin compounds 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 and excellent cycle characteristics, etc. are easily obtained. 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 a high energy density is easily obtained. 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 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, for example, contain, 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.

[0036] In addition, the negative electrode material may be, for example, any one or more of metal oxides and polymer compounds. The metal oxide may be, for example, iron oxide, ruthenium oxide, and molybdenum oxide. The polymer compound may be, for example, polyacetylene, polyaniline, and polypyrrole.

[0037] The negative electrode layer may contain a binder. Furthermore, the negative electrode layer may contain a negative electrode conductive agent to facilitate the transfer of electrons that promote the battery reaction. Binders that may be contained in the negative electrode layer include, but are not limited to, at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resins, and polyamide-imide resins. Negative electrode conductive agents that may be contained in the negative electrode layer include, but are not limited to, at least one selected from the group consisting of carbon blacks such as thermal black, furnace black, channel black, ketjen black, and acetylene black; carbon fibers such as graphite, carbon nanotubes, and vapor-grown carbon fibers; metal powders such as copper, nickel, aluminum, and silver; and polyphenylene derivatives. The negative electrode layer may also contain components derived from thickeners (e.g., carboxymethyl cellulose) used during battery production.

[0038] The positive electrode current collector and the negative electrode current collector used in the positive electrode and the negative electrode are components that contribute to collecting and supplying electrons generated in the electrode active material due to the battery reaction. Such electrode current collectors may be sheet-shaped metal components. The electrode current collectors may be single-layer or multi-layer. Furthermore, the electrode current collectors may be porous or perforated. For example, the current collectors may be metal foil, punched metal, mesh, expanded metal, or the like. The positive electrode current collector used in the positive electrode may be made of, for example, a metal foil containing at least one selected from the group consisting of aluminum, nickel, stainless steel, and the like. On the other hand, the negative electrode current collector used in the negative electrode may be made of, for example, a metal foil containing at least one selected from the group consisting of copper, aluminum, nickel, stainless steel, and the like.

[0039] The separator used for the positive electrode and the negative electrode is a member provided from the viewpoint of preventing short circuits due to contact between the positive and negative electrodes and maintaining electrolyte retention. In other words, the separator is a member that separates the positive electrode and the negative electrode and allows ions (e.g., lithium ions) to pass through while preventing short circuits of current due to contact between the two electrodes. For example, the separator may be a porous or microporous insulating member, and may have a membrane form due to its small thickness.

[0040] The separator may be, for example, one or more types of porous membranes made of synthetic resins and / or ceramics, or may be a laminated membrane of two or more types of porous membranes. Examples of synthetic resins used for the separator include polytetrafluoroethylene, polypropylene, and polyethylene. For example, the separator may include a porous membrane (substrate layer) and a polymer compound layer provided on one or both sides of the substrate layer. This improves the adhesion of the separator to the positive electrode and the negative electrode, thereby making it easier to suppress distortion of the wound electrode assembly. The polymer compound layer may include, for example, one or more types of polymer compounds such as polyvinylidene fluoride. This provides excellent physical strength and electrochemical stability. The polymer compound layer may also include, for example, one or more types of insulating particles such as inorganic particles. The inorganic particles may be, for example, aluminum oxide and / or aluminum nitride. In the present invention, the separator should not be limited to a particular name, and may be a solid electrolyte, a gel electrolyte, and / or insulating inorganic particles, which have similar functions.

[0041] In the secondary battery of the present invention, an electrode assembly consisting of electrode constituent layers including a positive electrode, a negative electrode, and a separator may be enclosed in an exterior body together with an electrolyte, which may be a so-called "non-aqueous" electrolyte.

[0042] The electrolyte may typically be an electrolytic solution. The electrolytic solution contains a solvent and an electrolyte salt. The electrolytic solution may further contain one or more of other materials such as additives. In a preferred embodiment, the separator is impregnated with the electrolytic solution, and the positive electrode and / or the negative electrode may also be impregnated with the electrolytic solution.

[0043] The solvent may contain one or more non-aqueous solvents such as organic solvents. An electrolyte containing a non-aqueous solvent can be a so-called non-aqueous electrolyte. The non-aqueous solvent may be, for example, a cyclic carbonate, a chain carbonate, a lactone, a chain carboxylic acid ester, and / or a nitrile (e.g., mononitrile). This is because it is easier to obtain better battery capacity, cycle characteristics, and / or storage characteristics. The cyclic carbonate may be, for example, ethylene carbonate, propylene carbonate, and / or butylene carbonate. The chain carbonate may be, for example, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and / or methyl propyl carbonate. The lactone may be, for example, γ-butyrolactone and / or γ-valerolactone. 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. The nitrile may be, for example, acetonitrile, methoxyacetonitrile, and / or 3-methoxypropionitrile. Other examples of the nonaqueous solvent include 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. Among these, it is preferable that the nonaqueous solvent contains one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. This is because higher battery capacity, better cycle characteristics, and / or better storage characteristics can be achieved. Furthermore, the non-aqueous solvent may be, for example, an unsaturated cyclic carbonate, a halogenated carbonate, a sulfonate, an acid anhydride, a dicyano compound (a dinitrile compound), a diisocyanate compound, a phosphate ester, and / or a chain compound having a carbon-carbon triple bond.This is because the chemical stability of the electrolyte solution is easily improved. The term "unsaturated cyclic carbonate" as used herein refers to a cyclic carbonate having one or more unsaturated bonds (carbon-carbon double bonds or carbon-carbon triple bonds). Examples of such unsaturated cyclic carbonates include vinylene carbonate, vinylethylene carbonate, and / or methyleneethylene carbonate. The term "halogenated carbonate" refers to a cyclic or chain carbonate containing one or more halogen elements as constituent elements. When a halogenated carbonate contains two or more halogens as constituent elements, the two or more halogens may be of one type or two or more types. Examples of cyclic halogenated carbonates include 4-fluoro-1,3-dioxolan-2-one and / or 4,5-difluoro-1,3-dioxolan-2-one. Examples of chain halogenated carbonates include fluoromethylmethyl carbonate, bis(fluoromethyl)carbonate, and / or difluoromethylmethyl carbonate. The sulfonate ester may be, for example, a monosulfonate ester and / or a disulfonate ester. The monosulfonate ester may be a cyclic monosulfonate ester or a chain monosulfonate ester. The cyclic monosulfonate ester may be, for example, a sultone such as 1,3-propane sultone and / or 1,3-propene sultone. The chain monosulfonate ester is, for example, a compound in which a cyclic monosulfonate ester is cleaved midway. The disulfonate ester may be a cyclic disulfonate ester or a chain disulfonate 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, ethane disulfonic acid anhydride and / or propane disulfonic acid anhydride. The carboxylic acid sulfonic acid anhydride may be, for example, sulfobenzoic anhydride, sulfopropionic anhydride, and / or sulfobutyric anhydride. The dinitrile compound may be, for example, N-C—R—CN (R is either an alkylene group or an arylene group).) is a compound represented by the formula: The dinitrile compound may be, for example, succinonitrile (NC-C2H4-CN), glutaronitrile (NC-C3H6-CN), adiponitrile (NC-C4H8-CN), phthalonitrile (NC-C6H4-CN), etc. The diisocyanate compound is, for example, a compound represented by the formula: OCN-R2-NCO (R2 is either an alkylene group or an arylene group). The diisocyanate compound is, for example, hexamethylene diisocyanate (OCN-C6H). 12 The phosphate ester may be, for example, trimethyl phosphate and triethyl phosphate. The chain compound having a carbon-carbon triple bond is a chain compound having one or more carbon-carbon triple bonds (-C≡C-). The chain compound having a carbon-carbon triple bond may be, for example, propargyl methyl carbonate (CH≡C-CH2-OC(=O)-O-CH3) and propargyl methylsulfonate (CH≡C-CH2-OS(=O)2-CH3).

[0044] The electrolyte salt contained in the electrolyte solution may include, for example, one or more salts such as lithium salts. The electrolyte salt may include, for example, a salt other than lithium salt. Such salts other than lithium may be, for example, salts of light metals other than lithium. Examples of lithium salts include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium hexafluoroarsenate (LiAsF), 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 better battery capacity, cycle characteristics, and / or storage characteristics. Among these, any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate may be used.

[0045] The battery can used in a secondary battery corresponds to a battery exterior member that encases an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are stacked. The battery can may have, for example, a hollow structure with one end closed and the other end open (open as an open end). The battery can is not particularly limited, but may be a metal can containing one or more metal materials such as iron, aluminum, stainless steel, and alloys thereof. The surface of the battery can may be plated with one or more metal materials such as nickel. A safety valve may be provided at the open end of the battery can. By way of example only, the safety valve may be provided at the open end of the battery can together with a thermosensitive resistor or the like via a gasket (i.e., the battery safety valve may be provided together with a crimping mechanism, for example).

[0046] [Characteristics of the Battery of the Present Invention] The battery of the present invention has features related to its safety mechanism, particularly a safety valve provided in the battery can (particularly at its open end).

[0047] The safety valve provided in the battery of the present invention comprises at least a first metal member, a second metal member, and an insulating member positioned therebetween. The first metal member is located relatively outward in the battery axial direction, while the second metal member is located relatively inward in the battery axial direction, and they are electrically connected to each other. Preferably, the first metal member and the second metal member are connected to each other in a manner that straddles the insulating member. The first metal member and the second metal member may each be a disk-shaped member. For example, each of the first metal member and the second metal member may have a shape that extends as a whole in the battery width direction. That is, each of the first metal member and the second metal member may have a shape that extends as a whole in a direction perpendicular to the battery axial direction. As described below, the insulating member preferably has an opening or hollow portion in its inner or central region and may be plate-shaped (e.g., flat) or flat as a whole. In the present invention, such first metal member, second metal member, and insulating member are preferably arranged so as to be directly stacked on top of each other, thereby forming a thin safety valve.

[0048] In the safety valve according to the present invention, both the first metal member and the second metal member have unique portions. Specifically, the first metal member has a stepped portion and a thin-walled portion and has a first groove, and the second metal member has a second groove.

[0049] The first metal member contributes to the function of the safety valve by being displaced by the internal battery pressure in the event of an abnormality. More specifically, if the second metal member breaks starting from the second groove, the first metal member may bend along with the broken second metal member, and this displacement causes current interruption. In the present invention, the above-mentioned unique elements (at least the above four elements) of the first metal member and the second metal member contribute to improving the interruption characteristics in the function of such a safety valve.

[0050] In the event of an abnormal current interruption, a safety valve according to the present invention, in which "the first metal member has a stepped portion and a thin-walled portion, and the first metal member has a first groove, particularly the first groove on the outer surface of the first metal member (the outer surface as viewed along the battery axis), and the second metal member has a second groove," can improve the amount of displacement of the stripper disk during operation. As a result, unintended re-conduction after fracture of the second metal member, which contributes to current interruption, is reduced or easily avoided, improving interruption characteristics. In other words, a more reliable battery can be achieved. Furthermore, such increased reliability improves predictability of behavior during abnormal increases in internal pressure, etc., allowing for greater design flexibility in batteries.

[0051] The battery of the present invention will be described in detail below with reference to the drawings as appropriate. The safety valve of the battery of the present invention is configured to have at least a first metal member, a second metal member, and an insulating member positioned therebetween. As a specific example embodiment, the first metal member corresponds to a safety cover and the second metal member corresponds to a stripper disk.

[0052] 1 and 2 show a schematic view of the appearance and cross section of a secondary battery according to one embodiment of the present invention. As shown in the figures, a secondary battery 1000 of the present invention may be a cylindrical secondary battery (e.g., a cylindrical nonaqueous secondary battery). In other words, the secondary battery of the present invention may include a cylindrical case, i.e., a cylindrical battery can 50. A safety valve 100 may be provided at the cylindrical end of the secondary battery 1000 (particularly, at the open end of the battery can). FIG. 3 shows the safety valve 100 together with its associated members (or peripheral members) in an expanded state, and FIG. 4 shows each component of the safety valve 100 as a half-split perspective view.

[0053] As shown in Figures 3 and 4, the safety valve 100 has a configuration in which a safety cover 110 provided as a first metal member, an insulating member 120, and a stripper disk 130 provided as a second metal member are combined in this order along a battery axis P. When viewed along the axial direction of the cylindrical shape of the battery, the safety cover 110 of the first metal member is positioned relatively outside the battery (i.e., the side farther from an electrode assembly such as a wound structure), while the stripper disk 130 of the second metal member is positioned relatively inside the battery (i.e., the side closer to an electrode assembly such as a wound structure), with the insulating member 120 interposed between the safety cover 110 and the stripper disk 130. In this specification, the term "battery axis" refers to an axis P that passes through the center of the battery can, which corresponds to the battery exterior, and extends in a direction perpendicular to the end face (particularly the imaginary planar end face) of the battery can (see Figures 1 and 2). For example, the battery axis can be said to refer to an axis that passes through the center of the exterior body 50 and extends in a direction perpendicular to the extension direction of the safety valve 100. The battery axis can also be said to be an axis that extends between the two terminals so as to pass through the centers of both terminals. Therefore, expressions such as "battery axis direction" described above and below refer to the direction along the battery axis.

[0054] The components constituting the safety valve 100 will be described in detail. The safety valve 100 serves as a battery terminal (i.e., one of the positive and negative terminals as the battery's external terminals) and has a mechanism that can be displaced in response to excessive battery internal pressure. Therefore, the safety valve 100 includes a safety cover 110 and a stripper disk 130 that can be displaced in response to excessive battery internal pressure, and at least an insulating member 120 as a component between them. Such a safety valve 100 may be provided at one end of the battery can, such as at the open end 51 of the battery can 50 in FIGS. 1 and 2. Furthermore, in the safety valve 100, a top cover 150 may be provided on the outer side of the safety cover 110, which is provided as the first metal member, in the battery axial direction (see FIGS. 3 and 4).

[0055] The safety cover 110 provided as the first metal member mainly corresponds to a displaceable member that can close the open end 51 of the battery can 50 and can deform and / or open in response to an increase in the internal pressure of the battery can. The internal pressure of the battery can may increase due to a side reaction such as a decomposition reaction of the electrolyte. That is, when a side reaction such as a decomposition reaction of the electrolyte occurs, gas such as carbon dioxide is generated inside the battery can, and the internal pressure of the battery can may increase undesirably as the amount of gas generated increases.

[0056] The safety cover 110 may be a metal member. For example, the safety cover 110 may include one or more of the following metal materials: aluminum (e.g., aluminum metal or aluminum alloy such as A1050, A3203, and / or A5052), iron (Fe), titanium (Ti), platinum (Pt), and gold (Au). In other words, the safety cover 110 may be a member made of such a conductive material. The planar shape of the safety cover 110, particularly its outer contour shape in a planar view (hereinafter also referred to as the "outer contour shape in a planar view"), is not particularly limited, and may be, for example, a circle, a polygon, or other shape. Examples of a circle include a perfect circle (perfect circle), an ellipse, and an approximate circle. An approximate circle is a general term for a shape that is partially or entirely distorted from a perfect circle. Examples of a polygon include a triangle, a rectangle, a pentagon, and a hexagon. Other shapes include, for example, shapes other than circles whose outlines are formed only by curves, shapes that combine two or more types of polygons, and shapes that combine one or more types of circles with one or more types of polygons. The same definitions of "circle" and the like will be used hereinafter. In the illustrated exemplary embodiment, the external outline shape of the safety cover 110 in a plan view is circular.

[0057] The safety cover 110 may be, for example, plate-shaped as a whole. In other words, the safety cover 110 may have a shape that extends as a whole in a direction perpendicular to the battery axis direction. Such a safety cover 110 that extends as a whole in the battery width direction contributes to making the battery safety valve thinner. As just one example, the safety cover 110 may have a substantially constant thickness except for localized areas such as stepped portions, thin-walled portions, and grooves provided therein.

[0058] The insulating member 120 is interposed between the safety cover 110 and the stripper disk 130 and corresponds to a member that at least enables the safety cover 110 and the stripper disk 130 to be connected to each other. The insulating member 120 may have an overall annular shape. That is, the insulating member 120 may have a ring-like or annular shape in a planar view. Due to such a ring-like or annular shape, the inner region of the insulating member 120 forms a hollow or an open region 120C (i.e., an "opening" described below). The outer contour shape of the insulating member 120 in a planar view is not particularly limited, but may be the same as the outer contour shape of the safety cover 110 in a planar view, for example, a circle. The annular or ring shape of the insulating member 120 may be present throughout the entire member (see FIG. 3), or the annular or ring shape may be locally interrupted. The insulating member 120 may also have an overall flat plate shape, for example. That is, the insulating member 120 may have a shape that extends on the same plane as a whole. Such an insulating member 120 that extends on the same plane contributes to reducing the thickness of the battery safety valve. By way of example only, the insulating member 120 may have a substantially constant thickness between the safety cover 110 and the stripper disk 130. Preferably, the insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 so that the opening region 120C of the insulating member 120 is positioned in a region that includes the battery shaft.

[0059] Since the insulating member 120 has insulating properties, electrical conduction through the insulating member 120 is preferably prevented. In this specification, "insulating" may mean having the insulating properties of a general insulator and therefore the electrical resistivity of a general insulator, and while this is merely an example, it may be at least 1.0×10 5 Ω·m or more, preferably 1.0×10 6 Ω·m or more, preferably 1.0×10 7 It may have a resistivity of Ω·m or more (at room temperature of 20°C).

[0060] In a preferred embodiment, the insulating member 120 interposed between the safety cover 110 and the stripper disk 130 may be a member that contributes to insulation and does not necessarily have to be adhered to them. On the other hand, for example, if they are adhered, the insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 as an adhesive layer. Note that the insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 so that the opening region 120C of the insulating member 120 is positioned in a region that includes the battery shaft.

[0061] The insulating member 120 is preferably made of a resin material. That is, the insulating member may be primarily composed of a resin material, or may be made to contain at least a resin. When made of such a resin material, the insulating member 120 can more effectively contribute to the adhesion between the safety cover 110 and the stripper disk 130 while maintaining its insulating properties, thereby contributing to the realization of a thinner safety valve. In particular, the present invention facilitates the realization of a thinner safety valve that can easily suppress or avoid undesired current re-conduction. When the insulating member 120 is made of a resin material, the insulating member 120 may be made of, for example, a thermosetting resin, a thermoplastic resin, and / or a UV-curable resin. When connectivity is particularly important, the insulating member 120 may be made of a resin adhesive that exhibits insulating properties. Examples of such resin adhesives include acrylic resin adhesives such as acrylic acid ester copolymers, silicone resin adhesives such as silicone rubber, urethane resin adhesives such as urethane resin, α-olefin resin adhesives, ether resin adhesives, ethylene-vinyl acetate resin adhesives, epoxy resin adhesives, vinyl chloride resin adhesives, chloroprene rubber resin adhesives, cyanoacrylate resin adhesives, aqueous polymer-isocyanate resin adhesives, styrene-butadiene rubber resin adhesives, nitrile rubber resin adhesives, nitrocellulose resin adhesives, and reactive hot melt resin adhesives. Examples of the adhesive include a phenolic resin adhesive, a silicone resin adhesive, a polyamide resin adhesive, a polyimide resin adhesive, a polyurethane resin adhesive, a polyolefin resin adhesive, a polyvinyl acetate resin adhesive, a polystyrene resin solvent-based resin adhesive, a polyvinyl alcohol resin adhesive, a polyvinylpyrrolidone resin adhesive, a polyvinyl butyral resin adhesive, a polybenzimidazole resin adhesive, a polymethacrylate resin adhesive, a melamine resin adhesive, a urea resin adhesive, and / or a resorcinol resin adhesive.

[0062] The insulating member 120 has an opening 120C at a location corresponding to the central portion 110C of the safety cover 110 (see FIGS. 3 and 4). The opening 120C corresponds to an inner opening region or hollow region of the insulating member that provides the insulating member 120 with an annular (hoop or ring) shape. The opening 120C of the insulating member 120 may be provided in a region that includes the battery shaft. The opening shape of the opening 120C of the insulating member 120 (particularly the opening shape in a plan view) is not particularly limited and may be the same as the outer contour shape of the safety cover 110 in a plan view. In the illustrated exemplary embodiment, the opening shape of the opening 120C of the insulating member 120 is circular.

[0063] The stripper disk 130 provided as the second metal member is positioned relatively closer to the battery inside the safety cover 110 via the insulating member 120, and corresponds to a member that contributes to current interruption in the event of an abnormality and / or the passage or release of gas, for example, inside the battery can.

[0064] The stripper disk 130 may be a metal member. For example, the stripper disk 130 may include one or more of the following metal materials: aluminum (e.g., aluminum metal or aluminum alloy such as A1050, A3203, and / or A5052), iron (Fe), titanium (Ti), platinum (Pt), and gold (Au). In other words, the stripper disk 130 may be a member made of such a conductive material. The material of the stripper disk 130 may be the same as or different from the material of the safety cover 110. The outer contour shape of the stripper disk 130 in a plan view is not particularly limited, and may be, for example, the same as the outer contour shape of the safety cover 110 in a plan view. In the illustrated exemplary embodiment, the outer contour shape of the stripper disk 130 in a plan view is circular.

[0065] The stripper disk 130 may have a shape extending in the width direction of the battery, such as a disk shape as a whole. That is, the stripper disk 130 may have a shape extending as a whole in a direction perpendicular to the axial direction of the battery. Such a stripper disk extending as a whole in the width direction of the battery contributes to making the battery safety valve thinner. For example, the stripper disk may have a substantially constant thickness.

[0066] The stripper disk 130 may be provided with a plurality of openings 130K. These openings 130K mainly serve as vents that allow gas inside the battery can to pass through or be released. For example, the openings 130K may be provided in a region that is closer to the outer periphery than the central region 130C.

[0067] In the safety valve, the safety cover 110 and the stripper disk 130 are integrated as a whole with the insulating member 120 interposed therebetween, but the safety cover 110 and the stripper disk 130 may be electrically connected to each other in their central regions. For example, the safety cover 110 may be directly connected to the central region 130C of the stripper disk 130 so as to straddle the insulating member 120. More specifically, as shown in Figures 5 and 6, the central region 110C of the safety cover 110 and the central region 130C of the stripper disk 130 may be directly connected to each other through the opening 120C of the insulating member 120.

[0068] As described above, the safety valve may further include a top cover 150. That is, the top cover 150 may be provided further outward in the battery axis direction than the safety cover 110 provided as the first metal member. In the safety valve, the top cover 150 is preferably electrically connected to the safety cover 110. The top cover, together with other components of the safety valve, corresponds to a battery cover that is provided to cover the open end of the battery can. In other words, the safety cover 110 is connected to the top cover 150, which forms the external terminal of the battery. As shown in Figures 3 and 4, the top cover 150 has a protrusion 150A that protrudes (e.g., curved) outward in the battery axis direction. In particular, the protrusion 150A is provided in the central region of the top cover. The protrusion 150A of the top cover 150 has a shape in which the annular region of the top cover is at least partially protruded (e.g., curved), and the central or inner region of the top cover protrudes or projects outward from the battery. Thus, the top cover 150 includes at least one bent portion 150C extending from the flat portion 150B toward the outside of the battery, and the bent portions 150C are spaced apart from one another (see FIG. 3). The spacing of the bent portions creates an opening 150D in the top cover 150. Such a top cover 150 can function favorably as a battery terminal. For example, the top cover 150 can function as the positive terminal of the battery, and the battery can can function as the negative terminal. In such a case, the top cover and the battery can can be insulated from each other. For example, the top cover can be insulated from the battery can by providing an insulating material between the top cover and the battery can. As merely one example, a safety valve including the top cover can be provided for the battery can via an insulating material provided between the top cover and the battery can, which has a partially constricted or narrowed portion.As another example, the top cover and the battery can may be insulated from each other by the presence of a holder member (particularly an insulating holder member, not shown) that is provided to support the first metal member at the periphery of the safety cover provided as the first metal member (in such a case, the battery can does not need to be the "battery can having a partially constricted or narrowed portion" described above, and therefore may be a non-constricted or non-necked battery can). The opening 150D of the top cover 150 may function as a vent hole for discharging gas generated inside the battery to the outside of the battery. The top cover 150 may be made of a metal. For example, the top cover 150 may be made of a conductive material such as iron (Fe), steel such as SPCC, stainless steel (SUS) such as SUS430 or SUS304, nickel (Ni), aluminum (Al), and / or titanium (Ti).

[0069] A conductive member 15 extending from the electrode assembly 10 is connected to the safety valve. The conductive member 15 is electrically connected to the electrode assembly 10 (particularly, one of the positive and negative electrodes) and contributes to the electrical connection between the electrode assembly 10 and the safety valve (particularly, the stripper disk 130). More preferably, the conductive member 15 may be connected to a region outside the central region 130C of the stripper disk 130, which corresponds to the second metal member, preferably a region on the outer periphery of the groove (particularly, the cutoff groove) (i.e., a region located farther from the cutoff groove relative to the battery axis). In the safety valve, the stripper disk 130 is electrically connected to the safety cover 110 via its central region 130C, and the safety cover 110 is connected to the top cover 150, which forms the external terminal of the battery. Therefore, the electrode assembly 10, such as a wound structure, is electrically connected to the external terminal of the battery via the conductive member 15. In this specification, the conductive member 15 may be a member containing metal, preferably a metal member having an elongated shape. For example, the conductive member may be an electrode current collector of an electrode assembly, or a current collecting lead (i.e., a lead) provided to the electrode assembly (particularly, its electrode). When the conductive member is an electrode current collector, the conductive member may be formed from a metal portion of the electrode current collector that is not provided with electrode material. When the conductive member is a current collecting lead, the conductive member may be formed from a metal member having a thin and / or elongated shape. In the present invention, a conductive member that electrically connects an electrode assembly and an electrode terminal to each other may also be referred to as a "tab." The conductive member used in such a secondary battery is preferably flexible and may be provided in a bent and / or curved shape.

[0070] In the safety valve of the secondary battery of the present invention, the safety cover 110, insulating member 120, and stripper disk 130 provided as the first metal member, as described above, are combined so as to be stacked on top of each other. More specifically, as shown in FIGS. 5 and 6 , the safety cover 110 and insulating member 120 provided as the first metal member are arranged so as to be stacked on top of each other, and the insulating member 120 and stripper disk 130 provided as the second metal member are also arranged so as to be stacked on top of each other. Furthermore, a top cover 150 is arranged so as to be stacked on top of the safety cover 110 provided as the first metal member. In this safety valve combination, the stripper disk 130 provided as the second metal member is provided with a groove, i.e., a second groove 135, that contributes to current interruption in the event of an abnormality. Note that an opening may be provided in a portion of the second groove 135.

[0071] In the event of an abnormal increase in the internal pressure of the battery can, the stripper disk 130 can break at its second groove 135, thereby interrupting subsequent undesirable current flow. Consider a case in which the internal pressure of the battery can increases due to a side reaction, such as the decomposition of the electrolyte, or other factors. First, when the internal pressure of the battery, i.e., the internal pressure of the battery can, is within a normal range, the battery safety valve does not operate. That is, the stripper disk 130 and the safety cover 110 have not yet displaced. If gas is generated inside the battery can due to a side reaction, such as the decomposition of the electrolyte, the gas accumulates inside the battery can, causing the internal pressure of the battery can to increase. If the internal pressure of the battery can continues to increase, the safety cover 110 will be affected by this increase in internal pressure. This is because the stripper disk 130 has multiple openings 130K (see Figures 3 and 4), which allow fluid communication between the safety cover 110 and the interior of the battery can 50. When the internal pressure of the battery can exceeds a predetermined pressure, the stripper disk 130 is pulled by the safety cover 110, causing the stripper disk 130 to break at the groove 135. The stripper disk 130 and the safety cover 110 are connected to each other at their central regions, and the force exerted by the safety cover 110, which attempts to displace due to the internal pressure, pulls the stripper disk 130, particularly the central region 130C, outward in the axial direction of the battery. In other words, when the tensile force acting on the central region 130C exceeds a certain limit, the stripper disk 130 breaks at the second groove 135 located around the central region. When the stripper disk 130 breaks, the safety cover 110 is electrically isolated from the non-central region 130E of the stripper disk 130 (particularly the peripheral non-central region 130E to which conductive members such as tabs and leads extending from the electrode assembly are still connected). This cuts off the electrical connection between the top cover 150 and the electrode assembly, thereby interrupting the path of current flowing between the electrode assembly and the top cover 150. In this way, current can be interrupted in the event of an abnormality such as an increase in internal pressure.

[0072] As described above, when the safety valve is activated, the stripper disk 130 may break, but the inventors have discovered that there is a concern that current may be re-conducted even after such a break. In particular, although the stripper disk may be displaced outward (outward in the battery axial direction) upon breakage, if this displacement is insufficient, unintended re-conduction may occur after the stripper disk breaks. More specifically, the amount of displacement of the stripper disk after breakage may be insufficient, which may result in undesired current re-conduction.

[0073] The inventors of the present application conducted extensive research into these issues and ultimately arrived at the present invention, which can reduce the amount of displacement when the safety valve is activated. Specifically, they found that by configuring the safety valve so that "the first metal member has both a stepped portion and a thin-walled portion, the first groove is provided on the outer surface of the first metal member, and the second metal member is provided with a second groove," it is possible to reduce the amount of displacement of the stripper disk associated with the stripper disk breaking, which contributes to current interruption. In other words, this unique safety valve configuration can result in a more reliable battery that more easily suppresses or avoids undesired re-conduction when the safety valve is activated.

[0074] This unique configuration will be described in more detail below with reference to the drawings. Figure 7 shows a cross-sectional view of the safety cover 110 and the stripper disk 130, along with their surrounding components. As shown in the figure, the safety cover 110 has a stepped portion 111, a thin-walled portion 116 spaced apart from the stepped portion 111, and a first groove 118. Meanwhile, the stripper disk 130 has a second groove 135. The first groove 118 of the safety cover 110 is a groove portion provided on the outside of the safety cover. That is, the first groove 118 is provided on the outer surface of the safety cover 110, particularly on the battery axial outer surface 110M, which is the outer side when viewed along the battery axial direction. This configuration of the safety cover and stripper disk can improve the amount of stripper disk displacement when the safety valve is activated. This makes it easier to suppress and avoid re-conduction when the safety valve is activated. For example, the displacement of the stripper disk upon actuation of the relief valve may be greater, thereby making it easier to suppress and avoid re-conduction.

[0075] In this specification, the "cross-sectional view" in expressions such as "cross-sectional view of the safety valve" is based on a cross-section obtained by cutting the safety valve along a plane parallel to the battery axis. It is based on a virtual cross-section obtained by cutting each component constituting the safety valve along its thickness direction, such as a safety cover or a stripper disk, along their thickness direction.

[0076] As shown in the cross-sectional view of FIG. 8 , the safety cover 110 corresponding to the first metal member has a stepped portion 111 in the cross-sectional view. In a preferred embodiment, the stepped portion 111 is provided so that the outer contour of the first metal member has a stepped contour, and the inner contour of the first metal member also has a stepped contour. More specifically, in the cross-sectional view of the safety valve, the outer contour of the first metal member positioned relatively outward in the battery axial direction has a stepped contour, and the inner contour of the first metal member positioned relatively inward in the battery axial direction also has a stepped contour. In the embodiment shown in the lower right of FIG. 8 , the outer contour of the safety cover 110 corresponding to the first metal member is a contour 111A positioned relatively outward in the battery axial direction, and the inner contour is a contour 111B positioned relatively inward in the battery axial direction. The outer contour 111A has a stepped contour 111Aa in part, and the inner contour 111B also has a stepped contour 111Bb in part. The step portion may be provided, for example, circumferentially on the first metal member, i.e., the step portion may be provided continuously or intermittently so as to form a ring-shaped outline in a plan view of the first metal member (e.g., the safety cover).

[0077] The provision of such a step 111 allows stress to be effectively applied to the safety valve when the safety valve is activated. In particular, in combination with the "thin-walled portion," the "first groove provided in the outer surface of the first metal member," and the "second groove provided in the second metal member," the step can effectively apply stress to the displacement of the stripper disk, contributing to improving the amount of displacement of the stripper disk when the safety valve is activated.

[0078] As shown in the cross-sectional view of Figure 8, the safety cover 110, which corresponds to the first metal member, also has a thin-walled portion 116 at a position separate from the stepped portion. In the first metal member, the thin-walled portion is positioned more inward than the stepped portion, i.e., closer to the battery axis. In other words, as shown in Figure 8, in the safety cover 110, the thin-walled portion 116 is positioned closer to the battery axis P than the stepped portion 111, while the stepped portion 111 is positioned farther from the battery axis P than the thin-walled portion 116.

[0079] The thin-walled portion 116 is a portion of the first metal member where the thickness is relatively reduced. Therefore, it is a portion where the member thickness is relatively reduced compared to other portions of the first metal member (excluding grooves, for example, excluding the first groove and step portions). For example, as shown in FIG. 8, the thin-walled portion 116 may have a thickness dimension smaller than that of a predetermined portion 116A of the first metal member located on the outer circumferential side of the thin-walled portion.

[0080] The provision of such thin-walled portion 116 allows stress to be effectively applied to the safety valve when the safety valve is activated. In particular, in combination with the presence of the "step portion," the "first groove provided in the outer surface of the first metal member," and the "second groove provided in the second metal member," thin-walled portion 116 can apply stress that is effective for displacement of the stripper disk, contributing to improving the amount of displacement of the stripper disk when the safety valve is activated.

[0081] For example, the thin-walled portion 116 of the first metal member preferably has a predetermined thickness range. More specifically, the thickness of the thin-walled portion 116 may have a thickness ratio of 0.7 or less to the non-thin thickness of the adjacent member region. That is, in the first metal member, the thickness of the thin-walled portion 116 may have a thickness ratio of 0.7 or less to the thickness of an adjacent member portion that does not have the thin-walled shape (e.g., the adjacent member portion 116A on the outer periphery). The lower limit of such a thin-walled thickness is not particularly limited, but may be, for example, 0.2, 0.3, 0.4, 0.5, or 0.6 relative to the non-thin thickness.

[0082] 8, the safety cover 110 corresponding to the first metal member has a first groove 118. The first groove 118 may be positioned in the first metal member between the stepped portion 111 and the thin-walled portion 116. That is, in the safety cover 110, the first groove 118 may be positioned closer to the battery axis P than the stepped portion 111, and further away from the battery axis P than the thin-walled portion 116. It can also be said that the first groove 118 may be positioned closer to the inner periphery than the stepped portion 111 and closer to the outer periphery than the thin-walled portion 116.

[0083] The first groove 118 may have a notched or recessed shape in cross-sectional view. Because the first groove 118 is a groove, it may have a paired shoulder contour in cross-sectional view (see the lower left of FIG. 8 ). It can also be said that the first groove may have an outline that is line-symmetric in cross-sectional view. For example, the first groove 118 may be a so-called "stamped groove" or a groove formed through press molding. Such a first groove 118 may have a gradually changing width. That is, the distance between opposing groove contours in cross-sectional view may gradually decrease toward the groove bottom. Furthermore, because it is a groove, the first groove may have a depth that is more than half the thickness of the member. That is, the groove depth of the first groove may be more than half the thickness of the first metal member. The thickness of the first metal member here refers specifically to the thickness of the member at locations other than the stepped portion and thin-walled portion.

[0084] Such a first groove is provided on the outer surface of the first metal member (i.e., the inner surface in the battery axial direction). In other words, the first groove is not provided on the inner main surface of the first metal member, but is particularly provided on the outer main surface (the surface located on the outside when viewed along the battery axial direction). As shown in the cross-sectional view of FIG. 8, it can also be said that the first groove 118 in the safety cover 110 opens upward or toward the outside of the battery. This first groove provided on the outer surface of the first metal member, in combination with the presence of the "step portion," "thin-walled portion," and "second groove provided in the second metal member," can provide an effective stress for displacement of the stripper disk, contributing to improving the amount of displacement of the stripper disk when the safety valve is activated.

[0085] 9A and 9B, the stripper disk 130, which corresponds to the second metal member, has second grooves 135. As will be described later, in one example, as shown in FIG. 9A, the second grooves 135 are provided on the inner surface of the stripper disk 130, particularly on a battery axial direction inner surface 130N that is on the inside when viewed along the battery axial direction. In another example, as shown in FIG. 9B, second grooves 135 are provided on the outer surface of the stripper disk 130, particularly on the battery axial direction outer surface 130M which is on the outer side when viewed along the battery axial direction.

[0086] The second groove may be located on the outer periphery of the interconnection point between the first metal member and the second metal member in the second metal member. That is, in the stripper disk 130 corresponding to the second metal member, the second groove 135 may be located more distally with respect to the battery axis than the interconnection point J between the safety cover 110 and the stripper disk 130.

[0087] The second groove 135 may also have a notched or recessed shape in cross section. Similarly, because the second groove 135 is a groove, it may have a shoulder contour that forms a pair in cross section (see FIGS. 9A and 9B). It can also be said that the second groove may have an outline that is line-symmetric in cross section. For example, the second groove 135 may be a so-called "stamped groove" or a groove formed through press molding. Also, because it is a groove, the second groove may have a depth that is more than half the thickness of the member. In other words, the groove depth dimension of the second groove may be more than half the thickness dimension of the second metal member. The thickness of the second metal member here refers to the member thickness at a location located on the outer periphery of the second groove. Such a second groove, in combination with the presence of the "step portion," the "thin-walled portion," and the "first groove provided on the outer surface of the first metal member," can provide effective stress for the displacement of the stripper disc, and contributes to improving the amount of displacement of the stripper disc when the safety valve is activated.

[0088] In this way, a safety valve having a configuration in which "the first metal member has a stepped portion and a thin-walled portion, the first groove is provided on the inner surface of the first metal member, and the second metal member is provided with a second groove" can improve the amount of displacement of the stripper disk due to rupture when current is interrupted. For example, as can be seen from the results of the examples described below, the amount of displacement of the second metal member when the safety valve is activated can be increased, thereby making it easier to suppress and avoid re-conduction. More specifically, for example, the amount of displacement of the stripper disk due to rupture when the safety valve is activated can be increased, thereby making it easier to suppress and avoid re-conduction between the stripper disk and the safety cover. In other words, the unique safety valve configuration described above makes it easier to suppress or avoid undesired re-conduction when the safety valve is activated, and therefore makes it easier to produce a more reliable battery.

[0089] This effect of facilitating the prevention and avoidance of undesirable re-conduction is likely to become apparent in the event of meltdown. If meltdown of the second metal member occurs during operation of the safety valve (e.g., meltdown due to the passage of a large current), re-conduction may occur due to the molten metal resulting from meltdown being undesirably routed between the first and second metal members. However, if the displacement of the second metal member is greater during operation of the safety valve, such undesirable route of the molten metal is more effectively prevented or avoided, thereby also making re-conduction easier to prevent. In other words, if the displacement of the stripper disk after meltdown during operation of the safety valve is greater, it becomes easier to prevent or avoid the undesirable event of "molten metal possibly resulting from meltdown being routed between the first and second metal members," thereby making it easier to effectively prevent and avoid re-conduction.

[0090] In a preferred embodiment, the first metal member has a central convex portion inwardly of the thin-walled portion, protruding toward the inside of the battery (i.e., toward the inside when viewed along the battery axis), and the second metal member has a second groove positioned more radially outward than the central convex portion. That is, the second groove may be positioned outside the central convex portion of the second metal member, which is located further away from the central convex portion in the battery axis direction. More specifically, as shown in FIGS. 9A and 9B , the safety cover 110 corresponding to the first metal member has a central convex portion 113 that protrudes relatively inwardly in the battery axis direction in its central region, and the second groove 135 may be provided in a region (the region of the stripper disk 130 corresponding to the second metal member) that is more radially outward than the central convex portion 113. This embodiment facilitates the reduction or avoidance of undesirable displacement during safety valve operation, which in turn facilitates the suppression or avoidance of re-conduction involving molten metal resulting from meltdown. More specifically, the effect of improving the amount of displacement of the stripper disk due to the fracture of the second metal member when current is interrupted is more likely to become apparent, and therefore the suppression and avoidance of re-conduction involving molten metal from the melting is also more likely to become apparent.

[0091] In a preferred embodiment, the second groove is provided on the inner surface of the second metal member (i.e., the inner surface in the battery axis direction). In other words, the second groove provided on the second metal member may be a groove that opens toward the inside when viewed along the battery axis. That is, the second groove may be a groove that opens on the surface of the second metal member that is relatively closer to the electrode assembly. More specifically, as shown in FIG. 9A , a second groove 135 is provided on the inner surface 130N of the stripper disk 130, which corresponds to the second metal member. As shown in the figure, the engraved surface of such a second groove on the second metal member faces upward. In this embodiment, the amount of displacement of the safety valve when activated can be improved. In particular, the second groove provided on the inner surface of the second metal member, in combination with the presence of the "step portion," "thin-walled portion," and "first groove provided on the outer surface of the first metal member," can provide effective stress for displacement of the stripper disk, contributing to improving the amount of displacement of the stripper disk when the safety valve is activated. In other words, the second groove provided on the inner surface of the second metal member in the battery axial direction contributes to improving the amount of displacement of the safety valve, which in turn makes it easier to more effectively suppress and avoid re-conduction caused by molten metal after fusing. More specifically, it can more effectively reduce the amount of displacement of the stripper disk caused by fracture of the second metal member when current is interrupted, thereby making it easier to more effectively suppress and avoid re-conduction caused by molten metal after fusing.

[0092] In another preferred embodiment, the second groove is provided on the outer surface of the second metal member (i.e., the outer surface in the battery axis direction). In other words, the second groove provided on the second metal member may be a groove that opens outward when viewed along the battery axis. That is, the second groove may be a groove that opens on a surface of the second metal member that is relatively closer to the top cover. More specifically, as shown in FIG. 9B , a second groove 135 is provided on the outer surface 130M of the stripper disk 130 corresponding to the second metal member. As shown in the figure, the engraved surface of such a second groove on the second metal member faces downward. This embodiment can improve the displacement of the safety valve when the safety valve is activated. In particular, the second groove provided on the outer surface of the second metal member, in combination with the presence of the "step portion," "thin-walled portion," and "first groove provided on the outer surface of the first metal member," can provide effective stress for stripper disk displacement, contributing to improving the displacement of the stripper disk when the safety valve is activated. In other words, the second groove provided on the outer surface of the second metal member in the battery axial direction contributes to improving the displacement of the safety valve, which in turn makes it easier to more effectively suppress and avoid re-conduction caused by molten metal after fusing. More specifically, it makes it easier to more effectively suppress and avoid re-conduction caused by molten metal after fusing.

[0093] The first metal member may have a two-stage protrusion toward the inside of the battery. More specifically, the first metal member may protrude toward the inside of the battery from a stepped portion, and the above-mentioned central protrusion may be provided so that the central region protrudes further toward the inside of the battery. In the embodiment shown in FIG. 7, the safety cover 110 protrudes toward the inside of the battery from a stepped portion 111, forming a protrusion 112. A central protrusion 113 is additionally provided on the protrusion 112. That is, the central protrusion 113 protrudes from the protrusion 112 on the inner periphery side of the thin-walled portion. This embodiment is desirable because it ensures the first metal member and the second metal member are connected to each other in their central region while more appropriately maintaining the separation between the first metal member and the second metal member in other regions. In other words, the two-stage protrusion of the safety cover can contribute to improving the shutoff reliability of the thin-type safety valve.

[0094] The second metal member may also have a shape that protrudes toward the inside of the battery. More specifically, a region of the second metal member that is inward from its peripheral edge may protrude toward the inside of the battery. In the embodiment shown in FIG. 7, the stripper disk 130 corresponding to the second metal member has a convex portion 133 that protrudes from a region that is inward from its peripheral edge 132. A central convex portion of the first metal member, preferably a central convex portion 113 provided on the protruding portion 112 (see FIG. 7), may be connected to the convex portion of the stripper disk. That is, in one embodiment, the second metal member has a convex portion that protrudes toward the inside of the battery, and the central convex portion of the first metal member may be connected to the convex portion of the second metal member (particularly its upper side surface). In such an embodiment, the above-mentioned feature that "the first metal member and the second metal member are connected to each other in their central region while the first metal member and the second metal member are more suitably separated from each other in other regions" may be more clearly realized. In other words, the connection between the protrusions of the two metal members can more significantly improve the shutoff reliability of the thin safety valve.

[0095] In a preferred embodiment, the thin-walled portion of the first metal member is positioned so as to at least partially overlap the second groove of the second metal member in the battery axis direction. In other words, the thin-walled portion of the first metal member and the second groove of the second metal member are positioned so as to be side-by-side in the battery axis direction. In the embodiment shown in FIG. 7, the second groove 135 of the stripper disk 130, which corresponds to the second metal member, is aligned or side-by-side in the battery axis direction with the thin-walled portion 116 of the safety cover 110, which corresponds to the first metal member. In this embodiment, the first metal member and the second groove of the second metal member, where melting occurs, can be positioned farther apart, making it easier to more effectively suppress and avoid re-conduction, particularly due to molten metal. In other words, if the thin-walled portion of the first metal member is positioned so as to at least partially overlap the second groove of the second metal member in the battery axial direction, it becomes easier to suppress or avoid an undesirable event such as "molten metal from the fuse being disposed so as to pass through the first metal member and the second metal member" when the safety valve is activated, and re-conduction can be more effectively suppressed and avoided.

[0096] In the safety valve provided in the battery of the present invention, as described above, the first metal member, the second metal member, and the insulating member are stacked together with the top cover, and the insulating member has a hollow portion or opening, and the first metal member and the second metal member are connected via the hollow portion or opening of the insulating member. This configuration at least results in a thin safety valve, which, combined with the feature of "the first metal member has a stepped portion and a thin portion, and a first groove is provided on the outer surface of the first metal member, and a second groove is provided in the second metal member," can improve the amount of displacement of the safety valve when the safety valve is activated, thereby making it easier to suppress and avoid re-conduction involving molten metal that may occur due to melting. In other words, a suitable thin safety valve according to the present invention makes it easier to suppress or avoid an undesirable event such as "molten metal from melting being disposed between the first metal member and the second metal member" during activation, making it easier to more effectively suppress and avoid re-conduction.

[0097] In a preferred embodiment, the top cover, which is provided outside the first metal member, has a protrusion that protrudes outward in the battery axis direction, and the second groove in the second metal member is positioned inward from the protrusion start point of the top cover and outward from the central connection point between the first metal member and the second metal member. That is, when a top cover is provided that is provided relatively outward from the first metal member in the battery axis direction and has a protrusion whose annular region partially protrudes outward in the battery axis direction, the second groove may be suitably provided in the second metal member in consideration of the top cover. Specifically, the second groove may be positioned in a region of the second metal member that is inward from the protrusion start point of the protrusion on the top cover and outward from the central connection point between the first metal member and the second metal member.

[0098] In a preferred embodiment, the first metal member may have a unique stepped portion shape, and the thin-walled portion may also have a unique shape. Specifically, the stepped portion of the first metal member may have a thin-walled shape, and the thin-walled portion may also have a stepped shape. In the embodiment of the safety cover 110 shown in FIG. 10 , the stepped portion 111 includes a thin-walled portion 114 that is relatively thinner than other portions. The thin-walled portion, i.e., the thin-walled portion in the stepped portion 111 that is relatively thinner, is the portion indicated by reference numeral 114, and the stepped portion 111 is formed in combination with the thin-walled portion. Due to at least the provision of such a stepped portion, a suitable displacement of the stripper disk corresponding to the second metal member when the safety valve is activated is easily achieved.

[0099] Similarly, in the embodiment of the safety cover shown in FIG. 10 , the thin-walled portion 116 located more inward than the stepped portion may be configured to be included in another stepped portion 117. In the illustrated embodiment, the thin-walled portion is the portion designated by reference numeral 116, and another stepped portion 117 is formed to include or be integrated with the portion 116. As can be seen from the illustrated embodiment, the other stepped portion 117 may be configured such that the outer contour 116A of the first metal member located relatively outward in the battery axis direction has a stepped contour 116Aa, and the inner contour 116B of the first metal member located relatively inward in the battery axis direction also has a stepped contour 116Bb (see the lower left diagram in FIG. 10 ). Such a thin-walled portion including another stepped portion is desirable because it more appropriately ensures the first metal member and the second metal member are separated from each other in regions other than the central region while making it easier to ensure their connection in the central region.

[0100] 10, a stepped portion is formed with a thin-walled configuration, and a thin-walled portion can be formed with a stepped portion. The stepped portion causes the first metal member to form a convex portion toward the battery body, and the stepped portion of the "thin-walled portion" further forms a convex portion toward the battery body, resulting in a two-step convex portion.

[0101] Here, the effects of the first groove will be described. Specifically, the effects of the first groove being provided not on the inner main surface of the first metal member but on its outer main surface (the surface located on the outside when viewed along the battery axis direction) will be described in detail. When the safety valve is activated, the safety cover, which corresponds to the first metal member, may deform and flex. Here, if the first groove 118 is provided on the inner main surface 110NX of the safety cover 110, stress may act in a contracting direction on the inner side of the groove, while stress may act in an expanding direction on the outer side of the groove (see FIG. 11A). This ultimately makes it difficult for the groove to rupture, which may increase the variability in rupture pressure. Furthermore, the safety cover itself is more likely to deform linearly, making it more likely to come into contact with the top cover, ultimately increasing the likelihood that the safety cover will not rupture. In contrast, when the first groove 118 is provided on the outer main surface 110M of the safety cover 110, stress can act in the direction of extension on both the inner and outer sides of the groove (see FIG. 11B). This makes the groove more likely to split open, potentially reducing the variation in splitting pressure. Furthermore, because the safety cover itself deforms while flexing more, it is easier to maintain a separation from the top cover, effectively avoiding the "event where the safety cover fails to split due to contact with the top cover."

[0102] (battery manufacturing) The method for manufacturing a battery according to the present invention will be described below by taking a method for manufacturing a secondary battery as an example. The secondary battery according to the present invention can be manufactured, for example, by the following procedure.

[0103] To fabricate a positive electrode, a positive electrode active material is mixed with, if necessary, a positive electrode binder and a positive electrode conductor to obtain a positive electrode mixture. The positive electrode mixture is then dispersed in an organic solvent or the like to obtain a paste-like positive electrode mixture slurry. The positive electrode mixture slurry is then applied to one or both sides of a positive electrode current collector, and the positive electrode mixture slurry is dried to form a positive electrode active material layer. The positive electrode active material layer may then be compression-molded using a roll press or the like, if necessary. In this case, the positive electrode active material layer may be heated, or the compression molding may be repeated multiple times. A negative electrode can be fabricated in a similar manner. Specifically, a negative electrode active material is mixed with a negative electrode binder and a negative electrode conductor to obtain a negative electrode mixture, and the negative electrode mixture is then dispersed in an organic solvent or the like to obtain a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to one or both surfaces of the negative electrode current collector, and 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.

[0104] When assembling a secondary battery, for example, a positive electrode lead is connected to a positive electrode current collector using a welding method or the like, and a negative electrode lead is connected to a negative electrode current collector using a welding method or the like. Next, the positive electrode and negative electrode are stacked via a separator, and the positive electrode, negative electrode, and separator are wound to form a wound electrode body. Next, a center pin is inserted into the winding space of the wound electrode body. Then, the wound electrode body is sandwiched between a pair of insulating plates and housed inside a battery can together with the pair of insulating plates. In this case, one end of the positive electrode lead is connected to a safety valve using a welding method or the like, and one end of the negative electrode lead is connected to the battery can similarly using a welding method or the like. Next, an electrolyte is injected into the battery can, and the electrolyte is impregnated into the wound electrode body. Finally, a safety valve is provided at the open end of the battery can, for example, via a holder member. This completes a secondary battery equipped with a safety valve.

[0105] The step portion, foil portion, and groove (i.e., first groove) provided in the first metal member and the groove (i.e., second groove) provided in the second metal member according to the present invention can be provided when the first metal member and the second metal member are formed using a press die. Furthermore, the elements can be formed by other methods, such as mechanical grinding and laser processing, without being limited to press forming.

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

[0107] For example, although the above description has focused on cylindrical batteries, the present invention is not necessarily limited to this. For example, the battery according to the present invention may be a battery of other shapes, such as a prismatic battery, and the effects of the present invention can be similarly achieved.

[0108] Furthermore, while the present invention has been described above with reference to a battery can, i.e., a battery exterior body, such an exterior body may have a beadless structure without a beading portion. A beadless exterior body does not have any narrowed or constricted portions inside (particularly near the battery axis), so a larger space can be secured inside the exterior body for arranging an electrode assembly. In other words, a beadless exterior can in which the inner diameter of the battery can is substantially constant along the battery axis can contribute to the realization of a battery with a higher energy density.

[0109] The present invention aims to provide a safety valve having a configuration that has not been previously known, and the battery of the present invention has the following features. <1> A battery (e.g., a primary battery or a secondary battery) having a safety valve (or safety valve structure, battery safety valve, or safety valve structure), the safety valve comprises a first metal member located on the outside, a second metal member located on the inside, and an insulating member located between the first metal member and the second metal member, the first metal member and the second metal member being connected to each other so as to straddle the insulating member, the first metal member has a stepped portion and a thin-walled portion positioned more inwardly than the stepped portion, A battery, wherein the first metal member has a first groove and the second metal member has a second groove, the first groove being provided on an outer surface of the first metal member. <2> The second groove is provided on the inner surface of the second metal member. <1> The battery described in <3> The second groove is provided on the outer surface of the second metal member. <1> The battery described in <4> the first metal member has a central convex portion that protrudes toward the inside of the battery in a central region that is on the inner circumferential side of the thin-walled portion, and the second groove of the second metal member is positioned on the outer circumferential side of the central convex portion. <1> ~ <3> 1. The battery according to any one of the preceding claims. <5> an inner peripheral region of the first metal member protrudes from the stepped portion toward the inside of the battery, and the central convex portion is provided so that the central region protrudes further toward the inside of the battery than the protrusion; <4> The battery described in <6> The thin-walled portion of the first metal member has a positional relationship in which it at least partially overlaps the second groove of the second metal member in the battery axial direction. <1> ~ <5> 1. The battery according to any one of the preceding claims. <7> In the safety valve, the first metal member, the second metal member, and the insulating member are combined together with a top cover so as to be stacked on top of each other, the insulating member has a hollow portion or an opening, and the first metal member and the second metal member are connected via the hollow portion or the opening of the insulating member. <1> ~ <6> 1. The battery according to any one of the preceding claims. <8> a top cover provided on the outside of the first metal member has a protrusion that protrudes outward in the battery axis direction; the second groove is positioned on the inner circumferential side of a protrusion start point of the convex portion of the top cover and on the outer circumferential side of a central connection point between the first metal member and the second metal member; <1> ~ <7> 1. The battery according to any one of the preceding claims. <9> The insulating member is made of a resin material. <1> ~ <8> 1. The battery according to any one of the preceding claims. <10> The battery includes a positive electrode and a negative electrode capable of absorbing and desorbing lithium ions. <1> ~ <9> 1. The battery according to any one of the preceding claims. [Example]

[0110] The present invention will be described below using examples, but the present invention is not limited to the following examples.

[0111] The present invention was verified using the following general-purpose software, which is widely used in various technical fields and has high reliability. ANSYS's coupled analysis software: Ansys Mechanical Verification target: Safety valve with static structure (2D semi-divided model shown in Figure 12) Material requirements for each part of the safety valve Top cover (safety valve cover material): structural steel Safety cover (first metal part): Aluminum alloy Stripper disc (second metal member): Aluminum alloy Insulation material: PBT (polybutylene terephthalate) resin Pressure setting: 0.1MPa / s Displacement rating pressure: 10 MPa

[0112] Example 1 Basic configuration: A safety valve having the basic configuration shown in FIG. 13, which includes a safety cover 110 arranged on the outside in the axial direction of the battery, a stripper disk 130 arranged on the inside in the axial direction of the battery, and an insulating member 120 arranged between the safety cover and the stripper disk. As shown in FIG. 13, the safety cover 110 has a step portion 111 and a thin portion 116 positioned on the inner circumferential side of the step portion. Groove configuration: A case in which a second groove 135 is provided in a stripper disk 130 corresponding to the second metal member, and the orientation and position of the second groove 135 is on an inner surface 130N in the battery axis direction that faces “upward” / “upper surface,” and a first groove 118 is provided in a safety cover 110 corresponding to the first metal member, and the orientation and position of the first groove 118 is on an outer surface 110M in the battery axis direction that faces “downward” / “lower surface” (see Figures 12 and 13(a)). Example 2 This safety valve is the same as that of Example 1, except that the groove configuration is changed as follows. Groove configuration: A second groove is provided in a stripper disk corresponding to the second metal member, and the orientation and position of the second groove is provided on the outer surface 130M in the battery axis direction facing "downward" / "lower surface" (see FIG. 12), and a first groove is provided in a safety cover corresponding to the first metal member, and the orientation and position of the first groove is provided on the outer surface 110M in the battery axis direction facing "downward" / "lower surface" (see FIG. 12 and FIG. 13(b)). Comparative Example 1 This safety valve is the same as that of Example 1, except that the groove configuration is changed as follows. Groove configuration: A second groove is provided in the stripper disk corresponding to the second metal member, and the orientation / position of the second groove is provided on the inner surface 130NX in the battery axis direction that faces "upward" / "upper surface", and a first groove is provided in the safety cover corresponding to the first metal member, and the orientation of the first groove is provided on the inner surface 110NX in the battery axis direction that faces "upward" / "upper surface" (see Figure 13(c)). Comparative Example 2 This safety valve is the same as that of Example 1, except that the groove configuration is changed as follows. Groove configuration: A second groove is provided in the stripper disk corresponding to the second metal member, and the orientation and position of the second groove is "downward" / "lower surface" on the outer surface 130MX in the battery axial direction, and a first groove is provided in the safety cover corresponding to the first metal member, and the orientation and position of the first groove is "upward" / "upper surface" on the inner surface 110NX in the battery axial direction (see Figure 13(d)).

[0113] The following displacement and deformation ratio were used as evaluation indicators. Displacement S [mm]: Displacement distance based on the center of the lower surface (inner surface in the battery axial direction) of the stripper disk, which corresponds to the second metal member (see Figure 14) Deformation ratio R [-]: Deformation ratio based on the base material thickness (0.4 mm) of the stripper disc corresponding to the second metal member (i.e., R = 0.4 / S)

[0114] The results are shown in Table 1 below. [Table 1]

[0115] The results in Table 1 reveal the following: In a safety valve in which "the first metal member (stripper disk) has a stepped portion and a thin-walled portion located more inward than the stepped portion," the first metal member has a first groove, the second metal member has a second groove, and the first groove is provided on the outer surface of the first metal member in the battery axis direction (Examples 1 and 2), the deformation ratio is relatively large (the deformation ratio increases by 82% to 92%) compared to when this is not the case (Comparative Examples 1 and 2), and therefore it is easier to suppress or avoid the undesirable decrease in the displacement amount of the stripper disk due to fracture. In other words, it is easier to suppress or avoid undesired re-conduction when the safety valve is activated, resulting in a more reliable battery. In particular, Example 1 is a case in which "the second groove is provided on the inner surface of the second metal member (safety cover) in the battery axis direction," while Example 2 is a case in which "the second groove is provided on the outer surface of the second metal member (safety cover) in the battery axis direction." When such second grooves are provided on the outer surface and on the inner surface, the deformation ratio is relatively larger than in Comparative Examples 1 and 2 (see FIG. 14(b)). In Examples 1 and 2 (see FIG. 14(a)), it is easier to suppress or avoid the undesirable decrease in the displacement of the stripper disk due to fracture. In other words, it is easier to suppress or avoid undesired re-conduction when the safety valve is activated, resulting in a more reliable battery.

[0116] The effects of the above embodiment are merely exemplary, and the present invention is not limited to the above, and may have additional effects. [Industrial Applicability]

[0117] The battery (primary battery, secondary battery, etc.) according to the present invention can be typically used in applications requiring the use of electrical energy. For example, the secondary battery according to the present invention can be used in various fields where power storage is expected. By way of example only, the battery of the present invention can be used in fields such as electricity, information, and communications where electrical and electronic devices are used (for example, electrical and electronic devices or mobile devices including mobile phones, smartphones, laptop computers, digital cameras, activity monitors, arm computers, electronic paper, wearable devices, and small electronic devices such as RFID tags, card-type electronic money, and smart watches), household and small industrial applications (for example, power tools, golf carts, and household, nursing care, and industrial robots), large industrial applications (for example, forklifts, elevators, and harbor cranes), transportation systems (for example, hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (for example, various power generation systems, road conditioners, smart grids, and general household power storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (dose management systems), IoT, and space and deep-sea applications (for example, space probes and submersible research vessels). [Explanation of symbols]

[0118] 10 Electrode assembly 11 Positive electrode 12 Negative electrode 13 Separator 15 Conductive material 50 battery cans 51 Open end of battery can 52 Battery can closure end 100 Safety valve 110 First metal member (e.g., safety cover) 110C Central region of first metal member (e.g., safety cover) 110M outer surface 111 Step 112 Protrusion 113 Central convex part 115 Step portion configured with a thin-walled shape with a relatively reduced thickness 116 Thin-walled section 116A Outer contour of the first metal member located relatively outward in the battery axial direction 116Aa Step contour of outer contour 116B Inner contour of the first metal member located relatively inward in the battery axial direction 116Bb Stepped contour of inner contour 118 First groove (groove of first metal member (e.g., safety cover)) 120 Insulating material 120C Openings / Open Areas in Insulating Members 130 Second metal member (e.g., stripper disk) 130C Central region of second metal member (e.g., stripper disk) 130K Opening of second metal member (e.g. stripper disk) 130E Non-central region of second metal member (e.g., stripper disk) 132 Peripheral edge of second metal member 135 Second groove (groove of second metal member (e.g., stripper disk)) J Interconnection between a first metal member (e.g., a safety cover) and a second metal member (e.g., a stripper disk) 150 top cover 150A Protrusion on top cover 150B Top cover flat part 150C Top cover bend 150D Top cover opening 1000 secondary battery P battery axis

Claims

1. A battery having a safety valve, the safety valve comprises a first metal member located on the outside, a second metal member located on the inside, and an insulating member located between the first metal member and the second metal member, the first metal member and the second metal member being connected to each other so as to straddle the insulating member, the first metal member has a stepped portion and a thin-walled portion positioned more inwardly than the stepped portion, The battery, wherein the first metal member has a first groove and the second metal member has a second groove, the first groove being provided on an outer surface of the first metal member.

2. The battery according to claim 1 , wherein the second groove is provided on an inner surface of the second metal member.

3. The battery according to claim 1 , wherein the second groove is provided on an outer surface of the second metal member.

4. The battery described in claim 1, wherein the first metal member has a central convex portion in a central region that is inner than the thin-walled portion and protrudes toward the inside of the battery, and the second groove of the second metal member is positioned outer than the central convex portion.

5. The battery according to claim 4 , wherein the first metal member has an inner peripheral region that protrudes from the stepped portion toward the inside of the battery, and the central convex portion is provided so that the central region protrudes further toward the inside of the battery than the protrusion.

6. The battery according to claim 1 , wherein the thin portion of the first metal member is positioned so as to at least partially overlap the second groove of the second metal member in the battery axial direction.

7. 2. The battery of claim 1, wherein the safety valve includes a top cover and the first metal member, the second metal member, and the insulating member are stacked together, the insulating member has a hollow portion or an opening, and the first metal member and the second metal member are connected via the hollow portion or the opening of the insulating member.

8. the top cover provided on the outside of the first metal member has a protrusion that protrudes outward in the battery axis direction, The battery according to claim 1 , wherein the second groove is positioned on the inner side of the protrusion start point of the convex portion of the top cover and on the outer side of the central connection point between the first metal member and the second metal member.

9. The battery according to claim 1 , wherein the insulating member is made of a resin material.

10. The battery according to any one of claims 1 to 9, comprising a positive electrode and a negative electrode capable of absorbing and desorbing lithium ions.

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