Battery

Abstract

To provide a battery having improved shutoff reliability as a safety valve.SOLUTION: In a battery having a safety valve, the safety valve includes 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 are connected to each other so as to straddle the insulating member, and the first metal member has a stepped portion including a thin-walled portion whose thickness is relatively reduced compared to other portions.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] Batteries can extract energy produced by chemical reactions or the like as electrical energy and are used in a variety of applications, including mobile devices such as mobile phones, smartphones, and laptops. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Patent Publication (WO) 2018 / 230148 Summary of the Invention [Problem to be solved by the invention]

[0004] Batteries are required to be safe. For example, a battery equipped with a safety valve capable of cutting off current in the event of an abnormality is considered. The inventors of the present application have earnestly examined 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 cutting off reliability of safety valves for cutting 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 having improved cutoff reliability as a safety valve. [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 are connected to each other so as to straddle the insulating member, The first metal member has a stepped portion including a thin portion whose thickness is relatively reduced compared to other portions. Effect of the Invention

[0008] In the battery according to the present invention, current interruption in the event of an abnormality can be more effectively achieved. Specifically, the outer first metal member provided in the safety valve has a stepped portion configured with a thin wall shape, which improves the interruption reliability of the safety valve of the battery. [Brief description 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. [Diagram 2] FIG. 2 is a schematic diagram showing the internal configuration of a secondary battery according to one embodiment of the present invention. [Diagram 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 a developed state. [Figure 4] FIG. 4 is a schematic perspective view showing components of a safety valve of a secondary battery according to one embodiment of the present invention in a half-split and developed state. [Diagram 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 a step 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 9] FIG. 9 is a schematic cross-sectional view of a safety cover corresponding to the first metal member, as well as a partially enlarged view and a partially enlarged contour view thereof. [Figure 10] FIG. 10 is a schematic cross-sectional view of the safety cover and top cover corresponding to the first metal member, as well as a partially enlarged view and a partially enlarged contour view thereof. [Figure 11] FIG. 11 is a schematic cross-sectional view of a safety valve and a first metal member and a second metal member constituting the safety valve. [Figure 12] FIG. 12 is a schematic cross-sectional view and a partially enlarged schematic view of a safety valve for explaining a preferred embodiment of the present invention. [Figure 13] FIG. 13 is a schematic cross-sectional view showing the state of the safety valve before it is activated. [Figure 14] FIG. 14 is a schematic cross-sectional view showing a state of an activated safety valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0011] The inventors of the present application have found that, although a certain battery safety valve can cut off current in the event of an abnormality and can accommodate high output, etc., there is still room for development from another perspective. Specifically, the inventors of the present application have noticed that a safety valve made up of a plurality of components is not necessarily satisfactory in terms of cutting off current in the event of an abnormality, and that there are cases in which undesirable component displacement may occur due to an abnormal rise in the battery internal pressure, etc.

[0012] The safety valve of a battery can cut off current and / or reduce internal pressure of the can when its components are ruptured or broken. For example, in a battery equipped with a safety valve including a combination of a safety cover, a stripper disk, and an insulating member between them, the groove provided in the safety cover at least acts to release pressure when an abnormality occurs, such as an increase in internal pressure of the battery. In other words, the safety cover that receives internal pressure of the battery in an abnormality is displaced and finally breaks starting from the groove, thereby releasing pressure. However, in the course of verifying the safety valve, the inventors of the present application noticed that even if the intended pressure release occurs, the current is not necessarily cut off appropriately, and there are cases in which current conduction is observed after the safety valve is ruptured.

[0013] More specifically, in the safety valve, a mechanism is assumed in which the safety cover is displaced so as to bend when the stripper disc (e.g., a cleaved or broken stripper disc) receives the battery internal pressure and moves outward (outward along the battery axis), but the inventors have found that such a mechanism is not as desired, and there are cases in which unintended current conduction occurs after the safety valve is cleaved. In particular, the inventors have found that a springback phenomenon occurs with respect to the displacement of the safety cover, and undesired current conduction may occur even after the stripper disc and / or the safety cover are broken.

[0014] The inventors of the present application attempted to solve such problems by taking a new approach rather than simply extending the conventional technology, and as a result, they invented a more reliable battery that reduces or avoids undesirable displacement of the safety cover in a safety valve mechanism that operates in response to an abnormal increase in the battery's internal pressure, and thus reduces or avoids undesirable conduction as a safety valve mechanism.

[0015] The following describes the embodiments of the present invention in detail. Please note that the applicant provides the following description and examples to allow those skilled in the art to fully understand the present invention, and does not intend 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 modified and implemented as appropriate within the scope of its purpose. In addition, in consideration of the explanation or ease of understanding of the main points, the present invention may be shown in separate embodiments and examples for convenience, but partial replacement and / or combination of the configurations shown in different embodiments is possible. In the description of such embodiments, the description of matters common to the above may be omitted, and only the differences may be described. In particular, the same action and effect due to the same configuration may not be mentioned in each embodiment.

[0016] In the description of the present specification, references to directions or orientations are merely for convenience of description and are not intended to limit the scope of the present invention unless otherwise expressly described. For example, relative terms such as "outer (or outer, external or outer circumference)", "inner (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 described, the invention does not need to be limited to a specific direction, orientation, form, etc. Similarly, terms such as "provided", "disposed", "connected" and "bonded" and their derivatives may be used in a form in which other elements such as intervening objects are present, rather than being limited to a direct form, unless otherwise expressly described.

[0017] [Basic battery configuration] The term "battery" in this specification includes not only so-called "secondary batteries" but also "primary batteries" that can only be discharged. In other words, the term "battery" in this specification may be a "secondary battery" that can be repeatedly charged and discharged, or a "primary battery" that can only be discharged. Note that the term "secondary battery" is not overly limited to its name, and may also include, for example, an "electricity storage device."

[0018] For convenience of explanation, the battery according to the present invention will be explained below mainly taking a secondary battery as an example.

[0019] The secondary battery according to the present invention has an electrode assembly composed 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 a "wound structure"). FIG. 1 shows an exemplary embodiment of the external appearance of a secondary battery 1000, and FIG. 2 shows an exemplary embodiment of its internal structure. As shown in the figure, an electrode assembly 10 is accommodated inside a battery can 50. In the exemplary embodiment shown in FIG. 2, the electrode assembly 10 has a configuration in which a positive electrode 11, a negative electrode 12, and a separator 13 arranged between the positive electrode and the negative electrode are wound. In the secondary battery 1000, such an electrode assembly 10 is enclosed in a battery can 50 together with an electrolyte (e.g., a non-aqueous electrolyte).

[0020] 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 side of the positive electrode current collector. The positive electrode material layer contains a positive electrode active material as an electrode active material. For example, each of the multiple positive electrodes in the electrode assembly may have a positive electrode material layer provided on both sides of the positive electrode current collector, or may have a positive electrode material layer provided only on one side of the positive electrode current collector.

[0021] 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 side of the negative electrode current collector. The negative electrode material layer contains a negative electrode active material as an electrode active material. For example, each of the multiple negative electrodes in the electrode assembly may have a negative electrode material layer provided on both sides of the negative electrode current collector, or may have a negative electrode material layer provided only on one side of the negative electrode current collector.

[0022] The electrode active materials contained in the positive electrode and the negative electrode, that is, the positive electrode active material and the negative electrode active material, respectively, are materials directly involved in the transfer of electrons in the secondary battery, and are the main materials of the positive and negative electrodes that are responsible for charging and discharging, i.e., the battery reaction. More specifically, ions are brought to the electrolyte due to the "positive electrode active material contained in the positive electrode material layer" and the "negative electrode active material contained in the negative electrode material layer", and such ions move between the positive electrode and the negative electrode to transfer electrons and charge and discharge. The positive electrode material layer and the negative electrode material layer may be layers capable of absorbing and releasing lithium ions in particular. In other words, the secondary battery according to the present invention may be a non-aqueous electrolyte secondary battery in which lithium ions move between the positive electrode and the negative electrode via the non-aqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charging and discharging, the secondary battery according to the present invention corresponds to a so-called "lithium ion battery", and has electrodes capable of absorbing and releasing lithium ions as the positive electrode and the negative electrode, and preferably has a layer capable of absorbing and releasing the lithium ions.

[0023] In view of the lithium ion battery, the positive electrode active material may be a material that contributes to the absorption and release of lithium ions. In other words, the positive electrode layer may contain any one or more of positive electrode materials that can absorb and release 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 thereof include lithium-containing composite oxides and lithium-containing phosphate compounds. This is because high energy density is easily obtained.

[0024] The lithium-containing composite oxide is a general term for oxides containing lithium and one or more other elements (elements other than lithium) as constituent elements, and may have any crystal structure such as a layered rock salt type and a spinel type, for example. The lithium-containing phosphate compound is a general term for phosphate compounds containing lithium and one or more other elements as constituent elements, and may have a crystal structure such as an olivine type, for example. The type of the other element is not particularly limited as long as it is any one or more of arbitrary elements. Among them, the other element is preferably any one or more of the elements belonging to Groups 2 to 15 in the long-period type periodic table. More specifically, the other element is, for example, nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), etc. This is because a high voltage can be easily obtained.

[0025] 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 0.8≦a≦1.2, 0.005≦b≦0.5, -0.1≦c≦0.2, and 0≦d≦0.1. However, the composition of lithium 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 0.8≦a≦1.2, 0≦b<0.5, -0.1≦c≦0.2, and 0≦d≦0.1. However, the composition of lithium 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 layered rock salt type crystal structure is LiNiO 2 , LiCoO 2 , LiCo 0.98 Al 0.01 Mg 0.01 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , Li 1.2 Mn 0.52Co 0.175 Ni 0.1 O 2 and Li 1.15 (M 0.65 Ni 0.22 Co 0.13 )O 2 And so on. 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.

[0026] 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 0.9≦a≦1.1, 0≦b≦0.6, 3.7≦c≦4.1, and 0≦d≦0.1. However, the composition of lithium varies depending on the charge / discharge state, and a is the value in a fully discharged state.) A specific example of a lithium-containing composite oxide having a spinel-type crystal structure is LiMn 2 O 4 etc.

[0027] The lithium-containing phosphate compound having an olivine type crystal structure is, for example, a compound represented by the following formula (5). Li a M15PO 4 (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.) A specific example of a lithium-containing phosphate compound having an olivine crystal structure is LiFePO 4 , LiMnPO 4 , Life 0.5 Mn 0.5 PO 4 and Life 0.3 Mn 0.7 PO 4 etc.

[0028] The lithium-containing composite oxide may be a compound represented by the following formula (6). (Li 2 MnO 3 ) x (LiMnO 2 ) 1-x (6) (x satisfies 0≦x≦1. However, the lithium composition varies depending on the charge / discharge state, and x is the value in a fully discharged state.)

[0029] In addition, the positive electrode material may be, for example, one or more of oxides, disulfides, chalcogenides, conductive polymers, etc. The oxides may be, for example, titanium oxide, vanadium oxide, manganese dioxide, etc. The disulfides may be, for example, titanium disulfide, molybdenum sulfide, etc. The chalcogenides may be, for example, niobium selenide, etc. The conductive polymers may be, for example, sulfur, polyaniline, polythiophene, etc. However, the positive electrode material is not particularly limited and may be other materials than those mentioned above.

[0030] The positive electrode layer may contain a binder. In addition, the positive electrode layer may contain a positive electrode conductive agent to facilitate the transfer of electrons that promote the battery reaction. The binder of the positive electrode may contain, for example, one or more of synthetic rubber and polymer compounds. Examples of synthetic rubber include styrene butadiene rubber, fluorine-based rubber, and ethylene propylene diene. Examples of polymer compounds include polyvinylidene fluoride and polyimide. The positive electrode conductive agent may contain, for example, one or more of carbon materials. Examples of the carbon materials may include graphite, carbon black, acetylene black, and ketjen black. However, the positive electrode conductive agent may be a metal material, a conductive polymer, or the like, as long as it is a material that has conductivity.

[0031] 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 any one or more types of 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.

[0032] 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 that a high energy density can be stably obtained. In addition, the carbon material also functions as a negative electrode conductive agent, so that the conductivity of the negative electrode layer can be easily improved.

[0033] Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and / or graphite. More specifically, the carbon material may be, for example, pyrolytic carbons, cokes, glassy carbon fiber, organic polymer compound sintered bodies, activated carbon, and carbon blacks. The cokes may include pitch coke, needle coke, and petroleum coke. The organic polymer compound sintered bodies are, for example, substances in which polymer compounds such as phenol resins and furan resins are sintered (carbonized) at an appropriate temperature. In addition, the carbon material may be low-crystalline carbon that has been heat-treated at a temperature of about 1000° C. or less, or may be amorphous carbon. The shape of the carbon material is not particularly limited, and may be at least one of fibrous, spherical, granular, and scaly shapes.

[0034] The "metal-based material" used as the negative electrode active material is a general term for a material containing one or more of metal elements and metalloid elements as constituent elements. When a carbon material is used as the negative electrode active material, a high energy density is easily obtained. The metal-based material may be a single substance, an alloy, a compound, or two or more of them, or may be a material containing at least one or more phases of them. However, the alloy may include a material containing one or more metal elements and one or more metalloid elements in addition to a material consisting of two or more metal elements. The alloy may also contain a nonmetallic element. The structure of this metal-based material may be, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a coexistence of two or more of them. Such a metal element and metalloid element may be, for example, one or more of 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 and tin. This is because they have excellent ability to absorb and release lithium, and therefore it is easy to obtain a higher energy density. The material containing silicon as a constituent element may be silicon alone, a silicon alloy, a silicon compound, or two or more types selected from them, or may be a material that contains one or more phases of them at least in a part. Similarly, a material containing tin as a constituent element may be a simple substance of tin, a tin alloy, a tin compound, or two or more of these, or may be a material that contains at least one or more of these phases in part. The term "simple substance" as used herein refers to a simple substance in the general sense, and may contain a trace amount of impurities.That is, the purity of the single substance is not necessarily limited to 100%. The silicon alloy may contain, for example, any one or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than silicon. The silicon compound may contain, for example, any one or more of carbon and oxygen as constituent elements other than silicon. Note that the silicon compound may contain any one or more of the series of elements described for the silicon alloy as constituent elements other than silicon. Specific examples of the silicon alloy and specific examples of the silicon compound include SiB. 4 , SiB 6 , MgSi, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , CaSi 2 , CrSi 2 , Cu 5 Si, FeSi 2 , MnSi 2 , NbSi 2 , TaSi 2 , VSi 2 , WSi 2 , ZnSi 2 , SiC, Si 3 N 4 , Si 2 N 2 O, SiO v (0 < v ≦ 2), and / or LiSiO, etc. can be mentioned. Note that SiO vIn this case, v may satisfy 0.2 < v < 1.4. The tin alloy may contain, for example, any one or more of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than tin. The tin compound may contain, for example, any one or more of carbon and oxygen as constituent elements other than tin. Note that the tin compound may contain any one or more of the series of elements described for the tin alloy as constituent elements other than tin. Specific examples of the tin alloy and the tin compound include SnO w (0 < w ≤ 2), SnSiO 3 , LiSnO and / or Mg 2Examples of the tin-containing material include Sn. In particular, the material containing tin as a constituent element may be, for example, a material containing tin as a first constituent element as well as a second and a third constituent element (tin-containing material). 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 a high battery capacity and excellent cycle characteristics are easily obtained. Among them, the tin-containing material may be a material containing tin, cobalt, and carbon as constituent elements (tin-cobalt-carbon containing material). 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 the aggregation of tin and the crystallization of tin 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. For example, in addition to tin, cobalt, and carbon, this tin-cobalt carbon-containing material may further contain 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 be used.

[0035] In addition, the negative electrode material may be, for example, one or more of metal oxides and polymer compounds. The metal oxide may be, for example, iron oxide, ruthenium oxide, molybdenum oxide, etc. The polymer compound may be, for example, polyacetylene, polyaniline, polypyrrole, etc.

[0036] The negative electrode material layer may contain a binder. Furthermore, the negative electrode material layer may contain a negative electrode conductive agent to facilitate the transfer of electrons that promote the battery reaction. The binder that may be contained in the negative electrode material layer is not particularly limited, but at least one selected from the group consisting of styrene butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resins, and polyamideimide resins can be mentioned. The negative electrode conductive agent that may be contained in the negative electrode material layer is not particularly limited, but at least one selected from carbon black 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 can be mentioned. The negative electrode material layer may contain a component resulting from a thickener component (e.g., carboxymethyl cellulose) used during battery production.

[0037] The positive electrode current collector and the negative electrode current collector used for the positive electrode and the negative electrode are members that contribute to collecting and supplying electrons generated in the electrode active material due to the battery reaction. Such an electrode current collector may be a sheet-shaped metal member. The electrode current collector may be a single layer or a multilayer. Furthermore, the electrode current collector may have a porous or perforated form. For example, the current collector may be a metal foil, a punched metal, a net, an expanded metal, or the like. The positive electrode current collector used for the positive electrode may be, for example, a metal foil containing at least one selected from the group consisting of aluminum, nickel, stainless steel, and the like. On the other hand, the negative electrode current collector used for the negative electrode may be, for example, a metal foil containing at least one selected from the group consisting of copper, aluminum, nickel, stainless steel, and the like.

[0038] The separator used for the positive and negative electrodes is a member provided from the viewpoint of preventing short circuit caused by contact between the positive and negative electrodes and retaining the electrolyte. In other words, the separator is a member that separates the positive and negative electrodes and allows ions (e.g., lithium ions) to pass through while preventing short circuit of current caused by 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.

[0039] The separator may be, for example, one or more of a porous film such as a synthetic resin and / or a ceramic, or may be a laminated film of two or more of the porous films. Examples of the synthetic resin used for the separator include polytetrafluoroethylene, polypropylene, and polyethylene. For example, the separator may include a porous film (substrate layer) and a polymer compound layer provided on one or both sides of the substrate layer. Since the adhesion of the separator to the positive electrode and the adhesion of the separator to the negative electrode can be improved, the distortion of the wound electrode body can be easily suppressed. The polymer compound layer may include, for example, one or more of a polymer compound such as polyvinylidene fluoride. The polymer compound layer has excellent physical strength and is easily electrochemically stable. The polymer compound layer may include, for example, one or more of insulating particles such as inorganic particles. The type of inorganic particles may be, for example, aluminum oxide and / or aluminum nitride. In the present invention, the separator should not be limited to a particular name, and may be a solid electrolyte, a gel electrolyte, and / or insulating inorganic particles having similar functions.

[0040] 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. The electrolyte may be a so-called "non-aqueous" electrolyte.

[0041] The electrolyte may typically be an electrolytic solution. The electrolytic solution includes a solvent and an electrolyte salt. The electrolytic solution may further include any 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.

[0042] The solvent may include any one or more of non-aqueous solvents such as organic solvents. An electrolyte solution including a non-aqueous solvent may be a so-called non-aqueous electrolyte solution. The non-aqueous solvent may be, for example, a cyclic carbonate ester, a chain carbonate ester, a lactone, a chain carboxylate ester, and / or a nitrile (e.g., mononitrile). This is because it is easy to obtain better battery capacity, cycle characteristics, and / or storage characteristics. The cyclic carbonate ester may be, for example, ethylene carbonate, propylene carbonate, and / or butylene carbonate. The chain carbonate ester 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 carboxylate ester may be, for example, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate, and / or ethyl trimethyl acetate. The nitrile may be, for example, acetonitrile, methoxyacetonitrile, and / or 3-methoxypropionitrile. In addition, the non-aqueous solvent may be, for example, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, and / or dimethyl sulfoxide. Among them, the non-aqueous solvent preferably contains one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. This is because it is easy to bring about a higher battery capacity, better cycle characteristics, and / or better storage characteristics. 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 the unsaturated cyclic carbonate include vinylene carbonate, vinylethylene carbonate, and / or methyleneethylene carbonate. The term "halogenated carbonate" refers to a cyclic or chain-like carbonate containing one or more halogen elements as constituent elements. When the halogenated carbonate contains two or more halogens as constituent elements, the type of the two or more halogens may be only one type or may be two or more types. Examples of the cyclic halogenated carbonate include 4-fluoro-1,3-dioxolane-2-one and / or 4,5-difluoro-1,3-dioxolane-2-one. Examples of the chain-like halogenated carbonate include fluoromethyl methyl carbonate, bis(fluoromethyl) carbonate, and / or difluoromethyl methyl carbonate. The sulfonate ester may be, for example, a monosulfonate ester and / or a disulfonate ester. The monosulfonate ester may be, for example, 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 cut in the middle. The disulfonate ester may be, for example, 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 acid anhydride, glutaric acid anhydride and / or maleic acid 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, etc. The dinitrile compound may be, for example, NC-R1-CN (R1 is either an alkylene group or an arylene group).) This dinitrile compound is, for example, succinonitrile (NC-C. 2 H 4 -CN), glutaronitrile (NC-C 3 H 6 -CN), adiponitrile (NC-C 4 H 8 -CN) and phthalonitrile (NC-C 6 H 4 The diisocyanate compound may be, for example, a compound represented by OCN-R2-NCO (R2 is either an alkylene group or an arylene group). The diisocyanate compound may be, for example, hexamethylene diisocyanate (OCN-C 6 H 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 is, for example, propargyl methyl carbonate (CH≡C-CH 2 -OC(=O)-O-CH 3 ) and propargyl methylsulfonate (CH≡C-CH 2 -OS(=O) 2 -CH 3 ) etc.

[0043] The electrolyte salt contained in the electrolytic solution may include, for example, one or more of salts such as lithium salt. The electrolyte salt may include, for example, a salt other than lithium salt. Such a salt other than lithium may be, for example, a salt of a light metal other than lithium. The lithium salt may be, for example, lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4), lithium methanesulfonate (LiCH 3 SO 3 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium tetrachloroaluminate (LiAlCl 4 ), dilithium hexafluorosilicate (Li 2 SiF 6 ), lithium chloride (LiCl) and / or lithium bromide (LiBr), etc. This is because it is easy to obtain better battery capacity, cycle characteristics and / or storage characteristics. Among them, any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate and lithium hexafluoroarsenate may be used.

[0044] The battery can used in the secondary battery corresponds to a member that, as a battery exterior, encloses an electrode assembly in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are laminated. 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 may be a metal can containing, but is not particularly limited to, any one or more of metal materials such as iron, aluminum, stainless steel, and alloys thereof. The surface of the battery can may be plated with, for example, any one or more of metal materials such as nickel. The open end of the battery can may be provided with a safety valve. Although this is merely an example, the open end of the battery can may be provided with a safety valve via a gasket together with a thermosensitive resistor or the like (that is, the safety valve of the battery may be provided together with, for example, a crimping mechanism).

[0045] [Characteristics of the Battery of the Present Invention] The battery of the present invention has features related to its safety mechanism, in particular, a safety valve provided in the battery can (particularly at the open end thereof).

[0046] 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 located between them. The first metal member is located relatively outside in the battery axial direction, while the second metal member is located relatively inside 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 form that straddles the insulating member. The first metal member and the second metal member may each be a disk-shaped or plate-shaped member (that is, may have a form that extends on the same plane as a whole). As will be mentioned later, the insulating member preferably has an opening or a 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 a first metal member, second metal member, and insulating member are preferably arranged so as to be directly stacked on each other, and a thin safety valve is formed.

[0047] In the safety valve according to the present invention, a specific stepped portion is provided in the first metal member. Specifically, in the safety valve according to the present invention, the first metal member has a stepped portion including a thin-walled portion whose thickness is relatively reduced compared to other portions.

[0048] The first metal member contributes to the function of the safety valve by being displaced by the battery internal pressure in the event of an abnormality. More specifically, when the second metal member breaks from its groove, the first metal member bends together with the broken second metal member, and current is interrupted through such displacement. In the present invention, the specific step portion of the first metal member contributes to improving the interruption reliability in the function of such a safety valve.

[0049] In the present invention, when current is interrupted in the event of an abnormality such as an increase in internal pressure of the can, the "step portion including the thin-walled portion having a relatively reduced thickness compared to other portions" can reduce or avoid undesirable displacement such as the springback phenomenon of the first metal member after the safety valve is ruptured. As a result, unintended current conduction after the rupture of the second metal member that contributes to current interruption can be avoided, resulting in a more reliable battery. Furthermore, such increased reliability improves the predictability of behavior in the event of an abnormal increase in internal pressure, making it easier to realize a battery with greater design freedom.

[0050] 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 located between them. As a specific example embodiment, the first metal member corresponds to a safety cover, and the second metal member corresponds to a stripper disk.

[0051] 1 and 2 are schematic diagrams showing the appearance and cross-sectional view of a secondary battery according to an embodiment of the present invention. As shown in the figures, the 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 have a cylindrical case, i.e., a cylindrical battery can 50. The safety valve 100 may be provided at the cylindrical end of the secondary battery 1000 (particularly, at the open end side of the battery can). FIG. 3 shows the safety valve 100 together with its related 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.

[0052] As shown in Fig. 3 and Fig. 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 with each other in that 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), and an insulating member 120 is interposed between the safety cover 110 and the stripper disk 130. In this specification, the "battery axis" refers to an axis P that extends in a direction perpendicular to an end face of the battery can (particularly an imaginary planar end face) so as to pass through the center of the battery can corresponding to the battery exterior body (see Figs. 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. Therefore, expressions such as "battery axis direction" described above or below refer to the direction along the battery axis.

[0053] Each member 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 external terminal of the battery) and has a mechanism that can be displaced in response to excessive internal battery pressure as a battery safety mechanism. Thus, the safety valve 100 has a safety cover 110 and a stripper disk 130 that can be displaced in response to excessive internal battery pressure, and at least an insulating member 120 between them as a component. Such a safety valve 100 may be provided at one end of the battery can, and is provided at the opening end 51 in the battery can 50 of Figs. 1 and 2. In addition, in the safety valve 100, a top cover 150 may be provided on the outside in the battery axis direction of the safety cover 110 provided as the first metal member (see Figs. 3 and 4).

[0054] The safety cover 110 provided as the first metal member corresponds mainly to a displaceable member that can close the open end 51 of the battery can 50 and can be deformed and / or opened 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 in response to an increase in the amount of gas generated.

[0055] The safety cover 110 may be a metal member. For example, the safety cover 110 may include one or more of metal materials such as iron (Fe), aluminum (e.g., aluminum metal or aluminum alloy such as A1050, A3203, and / or A5052), 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 the outer contour shape in plan view (hereinafter also referred to as "outer contour shape in plan 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 (correct circle), an ellipse, and an approximate circle. Examples of an approximate circle include a shape in which a perfect circle is partially or entirely distorted. Examples of a polygon include a triangle, a rectangle, a pentagon, and a hexagon. Other shapes include, for example, shapes other than a circle whose outline is formed only by curves, a shape in which two or more types of polygons are combined, and a shape in which one or more types of circles and one or more types of polygons are combined. The definition of "circle" will be the same hereinafter. In the illustrated embodiment, the outer outline shape of the safety cover 110 in a plan view is a circle.

[0056] The safety cover 110 may be, for example, flat as a whole. In other words, the safety cover 110 may have a shape that extends on the same plane as a whole. By way of example only, the safety cover 110 may have a substantially constant thickness except for steps and grooves (for example, grooves that contribute to the displacement, deformation, breakage, or cleavage of the safety cover) provided therein. Such a safety cover 110 that has a shape that extends on the same plane as a whole contributes to making the battery safety valve thinner.

[0057] The insulating member 120 corresponds to a member that is interposed between the safety cover 110 and the stripper disk 130 and 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 annular shape as a whole. That is, the insulating member 120 may have a ring shape or a ring shape in a plan view. Due to such a ring shape or ring shape, the insulating member 120 has an inner region that forms a hollow portion or an opening region 120C (i.e., an "opening" described later). The outer contour shape of such an insulating member 120 in a plan view is not particularly limited, but may be the same as the outer contour shape of the safety cover 110 in a plan view, and may be, for example, a circular shape. The insulating member 120 may have a ring shape or a ring shape as a whole member (see FIG. 3), or may have a form in which the ring shape or ring shape is locally divided. The insulating member 120 may have, for example, a flat plate shape as a whole. That is, the insulating member 120 may have a shape that extends on the same plane as a whole. The insulating member 120 having such a shape that extends on the same plane contributes to making the battery safety valve thinner. 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 such that the opening region 120C of the insulating member 120 is positioned in a region that includes the battery axis.

[0058] Since the insulating member 120 has insulating properties, electrical conduction through the insulating member 120 is preferably prevented. In this specification, "insulating" may have insulating properties that a general insulator has, and therefore may have an electrical resistivity that a general insulator has, 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).

[0059] In a preferred embodiment, the insulating member 120 interposed between the safety cover 110 and the stripper disk 130 may be one that contributes to insulation and may not necessarily be bonded to them. On the other hand, for example, when bonded, the insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 as an adhesive layer. The insulating member 120 may be interposed between the safety cover 110 and the stripper disk 130 so that the opening region 120C of the insulating member 120 is positioned in a region including the battery shaft.

[0060] The insulating member 120 is preferably made of a resin material. That is, the insulating member may be mainly made of a resin material, or may be made of at least a resin material. If made of such a resin material, the insulating member 120 will contribute more favorably to the adhesion between the safety cover 110 and the stripper disk 130 while ensuring insulation, and thus the insulating member 120 will favorably contribute to realizing a thinner safety valve. 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 the connectivity aspect is particularly important, the insulating member 120 may be a member containing a resin adhesive that exhibits insulation. 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 phenol resin-based resin adhesive, a silicone resin-based resin adhesive, a polyamide resin-based resin adhesive, a polyimide resin-based resin adhesive, a polyurethane resin-based resin adhesive, a polyolefin resin-based resin adhesive, a polyvinyl acetate resin-based resin adhesive, a polystyrene resin solvent-based resin adhesive, a polyvinyl alcohol-based resin adhesive, a polyvinylpyrrolidone resin-based resin adhesive, a polyvinyl butyral resin-based resin adhesive, a polybenzimidazole-based resin adhesive, a polymethacrylate resin-based resin adhesive, a melamine resin-based resin adhesive, a urea resin-based resin adhesive, and / or a resorcinol-based resin adhesive.

[0061] The insulating member 120 has an opening 120C at a position 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 a hollow region of the insulating member that provides the insulating member 120 with an annular shape (annular or ring shape). The opening 120C of the insulating member 120 may be provided in a region including the battery axis. The opening shape of the opening 120C of the insulating member 120 (particularly the planar opening shape in a planar view) is not particularly limited, and may be the same as the outer contour shape of the safety cover 110 in a planar view, for example. In the illustrated exemplary embodiment, the opening shape of the opening 120C of the insulating member 120 is circular.

[0062] 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.

[0063] The stripper disk 130 may be a metal member. For example, the stripper disk 130 may include one or more of metal materials such as iron (Fe), aluminum (e.g., aluminum metal or aluminum alloy such as A1050, A3203, and / or A5052), 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 the material of the safety cover 110, or may be different from the material of the safety cover 110. The outer contour shape of the stripper disk 130 in plan view is not particularly limited, but is, for example, the same as the outer contour shape of the safety cover 110 in plan view. In the illustrated exemplary embodiment, the outer contour shape of the stripper disk 130 in plan view is circular.

[0064] The stripper disk 130 may be, for example, flat as a whole. That is, the stripper disk 130 may have a shape extending on the same plane. Such a stripper disk extending on the same plane as a whole contributes to making the battery safety valve thinner. For example, the stripper disk 130 may have a substantially constant thickness as a whole except for a central region. The central region 130C of the stripper disk 130 may be raised relatively to the other regions (preferably raised outward along the battery axis) to contribute to connection with the safety cover 110. In other words, the stripper disk 130 may have a plate-like shape as a whole, but at least the central portion of the region including the battery axis may be relatively protruding.

[0065] The stripper disk 130 may have a plurality of openings 130K. The plurality of openings 130K mainly correspond to vents that allow gas inside the battery can to pass through or be released. For example, the plurality of openings 130K may be provided in a region that is closer to the outer periphery than the central region 130C.

[0066] 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 Figs. 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.

[0067] As described above, the safety valve may further include a top cover 150. That is, the top cover 150 may be provided relatively outward in the battery axial direction from 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 corresponds to a battery cover provided to cover the open end of the battery can together with other components of the safety valve. In other words, the safety cover 110 is connected to the top cover 150 that constitutes the external terminal of the battery. The top cover 150 has a protrusion 150A that protrudes outward in the battery axial direction, as shown in FIG. 3 and FIG. 4. The protrusion 150A is provided particularly in the central region of the top cover. The convex portion 150A of the top cover 150 has a shape that protrudes outward from the battery, and the top cover 150 includes at least one bent portion 150C extending from the flat portion 150B toward the outside of the battery, and the bent portions 150C are spaced apart from each other (see FIG. 3). The space between the bent portions results in an opening 150D in the top cover 150. Such a top cover 150 can function favorably as a terminal of the battery. For example, the top cover 150 can function as a positive terminal of the battery, and the battery can can function as a negative terminal. In such a case, the top cover and the battery can can be insulated from each other. For example, the top cover can be insulated from the battery can by interposing an insulating material between the top cover and the battery can. This is merely one example, but 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 having a partially narrowed or constricted 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) 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 may not be the above-mentioned "battery can having a narrowed or constricted portion in one portion," and therefore may be a non-narrowed or non-constricted battery can). The opening 150D of the top cover 150 may act as a vent hole for discharging gas generated inside the battery to the outside of the battery.The material of the top cover 150 may be 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 and SUS304, nickel (Ni), aluminum (Al), and / or titanium (Ti).

[0068] 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 corresponding to the second metal member, preferably a region on the outer periphery side of the groove (particularly the cleavage groove) (i.e., a region located on the side farther away from the cleavage groove with respect to the battery axis). In the safety valve, the stripper disk 130 is electrically connected to the safety cover 110 via the central region 130C, and the safety cover 110 is connected to the top cover 150 that constitutes the external terminal of the battery. Thus, the electrode assembly 10 such as the winding structure is electrically connected to the battery external terminal via the conductive member 15. In this specification, the conductive member 15 may be a member containing a metal, and may preferably be a metal member having an elongated shape. For example, the conductive member may be made of an electrode current collector of an electrode assembly, or may be a current collector lead (i.e., a lead) provided on an electrode assembly (particularly, its electrode). When the conductive member is made of an electrode current collector, the conductive member may be made of a metal portion of the electrode current collector on which no electrode material is provided. When the conductive member is made of a current collector lead, the conductive member may be made of a metal member having a thin-walled shape and / or an elongated shape. In the present invention, the conductive member that electrically connects the electrode assembly and the electrode terminal to each other may also be called 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.

[0069] In the safety valve of the secondary battery of the present invention, the safety cover 110 provided as the first metal member, the insulating member 120, and the stripper disk 130 provided as the second metal member are combined so as to be stacked on one another. More specifically, as shown in Fig. 5 and Fig. 6, the safety cover 110 and the insulating member 120 provided as the first metal member are arranged so as to be stacked on one another, and the insulating member 120 and the stripper disk 130 provided as the second metal member are arranged so as to be stacked on one another, and further, the top cover 150 is arranged so as to be stacked on the safety cover 110 provided as the first metal member. In such a safety valve combination, the stripper disk 130 provided as the second metal member is provided with a groove that contributes to current interruption in the event of an abnormality, i.e., a cutoff groove.

[0070] When the internal pressure of the battery can increases abnormally, the stripper disk 130 can break starting from the cutoff groove, and the subsequent undesirable current can be cut off. The groove 135 provided in the stripper disk 130 of the second metal member may be a groove that opens toward the outside when viewed along the battery axis (i.e., a groove that opens on the surface of the second metal member that is relatively closer to the first metal member). Let us assume that the pressure inside the battery can increases due to a side reaction such as a decomposition reaction of the electrolyte or other factors. Figure 13 shows a state in which the internal pressure of the battery, i.e., the internal pressure of the battery can, is within the normal range and the battery safety valve is not particularly operating. As shown in the figure, the stripper disk 130 and the safety cover 110 have not yet been displaced. When gas is generated inside the battery can due to a side reaction such as a decomposition reaction of the electrolyte, the gas accumulates inside the battery can, and the internal pressure of the battery can increases. When the internal pressure of the battery can continues to rise, the safety cover 110 is affected by the rise in internal pressure. This is because the stripper disk 130 has a plurality of openings 130K (see Figs. 3 and 4), and the safety cover 110 and the inside of the battery can 50 are in fluid communication with each other. When the internal pressure of the battery can exceeds a certain pressure, the stripper disk 130 is pulled by the safety cover 110, and the stripper disk 130 is broken starting from the groove 135 (see Figs. 13 and 14). The stripper disk 130 and the safety cover 110 are connected to each other in their central regions, and the stripper disk 130, particularly the central region 130C, is pulled outward in the battery axial direction due to the force received from the safety cover 110, which tries to displace under the internal pressure. In other words, when the tensile force acting on the central region 130C exceeds a certain limit, the stripper disk 130 will break starting from the grooves 135 located around the central region.As can be seen from the configurations shown in FIG. 13 and FIG. 14, when such a breakage of the stripper disk 130 occurs, the safety cover 110 is electrically separated from the non-center region 130E of the stripper disk 130 (particularly the non-center region 130E of the peripheral portion to which the conductive members such as the tabs and leads extending from the electrode assembly are still connected). Thus, the electrical connection between the top cover 150 and the electrode assembly is cut off, and the path of the current flowing between the electrode assembly and the top cover 150 is interrupted. In this way, the current is interrupted in the event of an abnormality such as an increase in internal pressure. If the displacement of the safety cover 110 progresses further and the safety cover itself is broken or torn open, the internal pressure of the battery can is more effectively reduced. For example, when a groove or the like is provided in the safety cover 110 corresponding to the first metal member (for example, when a breaking groove or cleavage groove such as the groove 118 described later is provided), the safety cover is broken or cleaved starting from the groove. In this case, the gas release path via the multiple openings 130K of the stripper disk 130 is particularly opened, and the gas can be released to the outside of the battery via these openings 130K.

[0071] When the safety valve is activated, the stripper disk 130 breaks as described above, but the inventors have now found that there are cases in which current conduction occurs after such breakage. In particular, the safety cover may be displaced so as to bend as the broken stripper disk moves outward (outward along the battery axis), but the displacement is ultimately not as desired, and unintended current conduction may occur after the stripper disk breaks. More specifically, the inventors have found that a springback phenomenon or the like occurs with respect to the displacement of the safety cover (for example, the safety cover is likely to spring back when the internal pressure of the can is reduced by the opening of the safety valve), which may cause undesired current conduction after the stripper disk breaks.

[0072] In response to this, the inventors of the present application conducted extensive research and finally arrived at an invention that can reduce or avoid the above-mentioned undesirable displacement when the safety valve is activated. Specifically, it was found that by providing "a step portion 115 including a thin-walled portion whose thickness is relatively reduced compared to other portions" in the safety cover 110, it is possible to more suitably reduce or avoid the undesirable displacement of the safety cover after the stripper disk that contributes to current interruption breaks (more specifically, the undesirable displacement after the safety valve is torn open, such as springback). In other words, by providing such a specific step portion, a more reliable battery is obtained that can reduce or avoid undesirable conduction when the safety valve is activated.

[0073] Such a specific step portion will be described in more detail below with reference to the drawings. FIG. 7 shows a cross-sectional view of the safety cover 110 together with its surrounding members. As shown in the figure, in the cross-sectional view, the safety cover 110 has a step portion 115, and in particular has a "step portion 115 including a thin portion whose thickness is relatively reduced compared to other portions." In other words, it can be said that the safety cover 110 has a "step portion 115 configured with a thin-walled form whose thickness is relatively reduced." Thus, the present invention is at least characterized in that the safety cover 110 corresponding to the first metal member has a step portion 115 with a reduced thickness.

[0074] In this specification, the "cross-sectional view" of the expression "cross-sectional view of the safety valve" is based on a cross section that can be obtained by cutting the safety valve along a plane along the battery axis, and is based on a cross section obtained by cutting each member constituting the safety valve along its thickness direction, for example, by cutting a safety cover along its thickness direction.

[0075] As shown in the cross-sectional view of FIG. 8, the safety cover 110 corresponding to the first metal member has a step portion 115 including a thin portion having a relatively reduced thickness compared to other portions in the cross-sectional view. That is, the safety cover 110 has the step portion 115 configured together with a thin-walled form having a relatively reduced thickness. In the safety cover 110, the thin portion, i.e., the thin portion having a relatively reduced thickness, is the portion indicated by reference number 112, and the step portion 115 is configured together with the thin portion. The safety cover 110 is provided so as to extend on the same plane as a whole, for example, based on the thin portion 112, and the step portion 115 is provided in the safety cover 110 extending on such a same plane. Such a step portion may be provided, for example, circumferentially, in the first metal member. That is, in a plan view of the first metal member (e.g., safety cover), "step portions 115 including thin-walled portions having a relatively reduced thickness compared to other portions" may be provided continuously or intermittently so as to form an annular contour. Due to at least the provision of such step portions, it is possible to reduce or avoid undesirable displacement when the safety valve is activated. More specifically, it is possible to reduce or avoid springback of the safety cover corresponding to the first metal member after the rupture of the stripper disk corresponding to the second metal member (more preferably, springback after the rupture / splitting of the first metal member, which is particularly conducive to reducing the internal pressure of the can), and thus it is possible to suitably reduce or avoid undesirable conduction when the safety valve is activated.

[0076] In a preferred embodiment, in a cross-sectional view of the safety valve, 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 a cross-sectional view of the safety valve, the outer contour of the first metal member located relatively outward in the battery axial direction has a stepped contour, and the inner contour of the first metal member located relatively inward in the battery axial direction also has a stepped contour. In the embodiment shown in FIG. 9, in the safety cover 110 corresponding to the first metal member, the outer contour is a contour 116A located relatively outward in the battery axial direction, while the inner contour is a contour 116B located relatively inward in the battery axial direction. The outer contour 116A has a stepped contour 116Aa in a part thereof, and the inner contour 116B also has a stepped contour 116Bb in a part thereof. Due to such a contour form, it is easy to suitably reduce or avoid undesirable displacement such as springback of the safety cover corresponding to the first metal member when the safety valve is operated. That is, undesired conduction during operation of the safety valve is reduced or easily avoided. Note that, as shown in the cross-sectional view of Fig. 9, the outer step contour 116Aa and the inner step contour 116Bb constituting the step portion may have a contour relationship that is point symmetrical to each other.

[0077] The thin-walled portion 112 directly or indirectly involved in the specific step of the first metal member is preferably within a predetermined range of thickness. More specifically, the thickness dimension of the thin-walled portion 112 has a thickness ratio of 0.7 or less to the non-thin-walled thickness dimension corresponding to the thickness dimension of the other portion. That is, in the first metal member, the thickness dimension of the thin-walled portion 112 brought about by the thin-walled form has a thickness ratio of 0.7 or less to the non-thin-walled thickness dimension of the portion not having the thin-walled form. The lower limit of such a thin-walled thickness dimension is not particularly limited, but may be, for example, 0.3, 0.4, or 0.5, etc., relative to the non-thin-walled thickness dimension. In the embodiment shown in FIG. 8, in the safety cover 110 corresponding to the first metal member, the thickness dimension of the thin-walled portion 112 is set to T 1 The thickness dimension of the non-thin portion 114 of the other portion is T 2 Then, T 1 ≦0.7T2 For example, 0.3T 2 ≦T 1 ≦0.7T 2 , 0.4T 2 ≦T 1 ≦0.7T 2 , 0.5T 2 ≦T 1 ≦0.7T 2 When the thickness ratio between the thin portion of the first metal member and the other portion (non-thin portion) has such a relationship, it is possible to suitably reduce or avoid the displacement of the safety cover, which corresponds to the first metal member, such as undesirable springback when the safety valve is activated. In other words, it is possible to reduce or avoid undesirable conduction when the safety valve is activated.

[0078] In the above, the "non-thin portion" corresponding to the "other portion" may be regarded as a portion of the safety cover located on the outer periphery side of the thin portion (thin portion) 112, but may also be regarded as a portion of the safety cover located on the inner periphery side of the thin portion 112. In other words, the thickness dimension of the non-thin portion 117 of the other portion located on the inner periphery side of the thin portion 112 is T 3 Then (see Figure 8), T 1 ≦0.7T 3 For example, 0.3T 3 ≦T 1 ≦0.7T 3 , 0.4T 3 ≦T 1 ≦0.7T 3 , 0.5T 3 ≦T 1 ≦0.7T 3 In addition, in the safety cover, the non-thin portion 114 located on the outer circumferential side of the thin portion 112 and the non-thin portion 117 located on the inner circumferential side of the thin portion 112 as other portions may have substantially the same thickness.

[0079] In a preferred embodiment, the battery includes a top cover that is provided further outside than the first metal member and has a convex portion that protrudes outward, and the step portion of the first metal member and the raised area of ​​the convex portion of the top cover have a positional relationship in which they at least partially overlap each other. That is, when the battery further includes a top cover that is provided relatively outside the first metal member in the battery axial direction and has a convex portion that protrudes outward in the battery axial direction, the step portion may be suitably provided on the first metal member in consideration of the top cover. Specifically, the step portion of the first metal member may be positioned so as to extend to the area of ​​the convex portion of the top cover (in other words, the step portion of the first metal member may be provided at a position that reaches the internal area of ​​the convex portion of the top cover in the battery transverse direction perpendicular to the battery axial direction). Preferably, the step portion of the first metal member and the raised area of ​​the convex portion of the top cover may have a positional relationship in which they at least partially overlap each other in the battery axial direction. In the embodiment shown in FIG. 10, the step portion 115 of the safety cover 110 corresponding to the first metal member at least partially overlaps with the raised area 151 that may correspond to the side portion of the protrusion 150A of the top cover 150. Due to such an overlapping relationship in the safety valve, it is easy to preferably reduce or avoid the displacement of the safety cover corresponding to the first metal member, such as undesirable springback, when the safety valve is activated. In this embodiment, the displacement of the first metal member is likely to cause a large deformation in which the protrusion of the top cover rises or bends from the periphery. Due to such a specific displacement, it is easy to more preferably suppress or avoid undesirable conduction when the safety valve is activated. The stepped portion of the present invention contributes to reducing or avoiding undesirable displacement such as springback, and even in the case of the overlapping relationship described above, the stepped portion has a thin-walled form, which makes it easier and preferable to avoid the first metal member, which deforms when the safety valve is activated, coming into contact with the top cover (particularly its raised area), and therefore undesirable fluctuations in the cut-off / break-off pressure can be suppressed or avoided.With regard to the overlapping relationship, the "raised region" may be considered to be the region provided by the boundary between the straight and curved portions of the cross-sectional contour from the outer edge portion of the top cover to the convex portion (in the cross-sectional view of FIG. 10, the portion between the outer boundary 151a and the inner boundary 151a', or the portion between the outer boundary 151b and the inner boundary 151b' in the battery transverse direction perpendicular to the battery axis direction), and the "step portion" may be considered to be the thin-walled portion 112. In the present invention, such specific portions may have a relationship of overlapping with each other in the battery axis direction.

[0080] The first metal member may have a groove on the inner circumferential side of the stepped portion in addition to the stepped portion. That is, the first metal member may further have a groove positioned relatively closer to the battery shaft side than the "step portion including a thin-walled portion having a relatively reduced thickness compared to other portions" (i.e., the "step portion configured together with a thin-walled form having a relatively reduced thickness"). With reference to Figs. 7 and 11, in the safety cover 110 corresponding to the first metal member, a groove 118 is provided closer to the battery shaft side than the stepped portion 115. As shown in the figures, the groove 118 provided in the first metal member may be a groove having an opening toward the outside when viewed along the battery shaft (i.e., a groove that opens on the surface of the first metal member that is relatively closer to the top cover side). In the illustrated embodiment, such a groove 118 is provided in a non-thin portion 117 (i.e., another portion) located on the inner circumferential side than the thin-walled portion 112. In this embodiment, the effect of reducing or avoiding the undesirable springback of the safety cover corresponding to the first metal member when the safety valve is activated can be more clearly seen. In other words, the effect of the safety valve, such as reducing or avoiding undesirable conduction when the safety valve is activated, can be more clearly seen. The groove 118 provided in the first metal member can also contribute to the rupture or cleavage of the first metal member when the internal pressure of the battery can abnormally increases, and therefore can also be called a "rupture groove" or a "cleavage groove". In the present invention, even if such a groove acts when the safety valve is activated, and the safety cover 110 corresponding to the first metal member is thereby ruptured or cleaved, thereby reducing the internal pressure of the battery can (for example, greatly reducing), the undesirable displacement such as the springback of the safety cover 110 after the rupture or cleavage is effectively reduced or avoided due to the step portion 115.

[0081] In terms of its relationship to the top cover, the groove of the first metal member overlaps the region of the protrusion in the battery axis direction. Preferably, the groove of the first metal member is provided at a location located inside the raised region corresponding to the side portion of the protrusion of the top cover in the battery cross direction perpendicular to the battery axis direction. In this embodiment, the distance R of the groove 118 of the safety cover 110 corresponding to the first metal member from the battery axis P is 1 and the raised area starting point 150C of the top cover 150 p (More specifically, the outer boundary 151a or 151b between the straight portion and the curved portion in the cross-sectional outline) 2 Then (see Figure 10), R 1 ≦0.7R 2 For example, 0.3R 2 ≦R 1 ≦0.7R 2 , 0.4R 2 ≦R 1 ≦0.7R 2 Such a relationship of the separation distance ratio makes it easy to suitably reduce or avoid undesirable displacement such as springback of the safety cover corresponding to the first metal member when the safety valve is activated. In other words, it makes it easy to reduce or avoid undesirable conduction when the safety valve is activated.

[0082] In the safety valve according to the present invention, the second metal member may have a groove that contributes to at least suitable shutoff when the safety valve is activated. In other words, the second metal member is preferably provided with a groove that contributes to the rupture of the second metal member when the internal pressure of the battery can abnormally rises, i.e., a cleavage groove. When such a groove is provided, the second metal member is more likely to be ruptured starting from the groove when the internal pressure of the battery can abnormally rises. In the present invention, the groove of the second metal member may have a suitable relative positional relationship with the groove and the step portion of the first metal member. Specifically, the groove provided in the second metal member may be positioned relatively closer to the battery axis than the groove and the step portion of the first metal member. In other words, the shutoff groove of the second metal member may be positioned on the inner circumferential side than the groove of the first metal member. 11, the cutoff groove 135 in the stripper disk 130 corresponding to the second metal member is positioned relatively closer to the battery shaft than both the groove 118 (preferably the groove 118 provided in the non-thin portion 117 located on the inner periphery side of the thin portion 112) provided in the safety cover 110 corresponding to the first metal member and the "step portion 115 including the thin portion having a relatively reduced thickness compared to other portions". In a safety valve having such characteristics, the effect of reducing or avoiding the undesirable springback of the safety cover corresponding to the first metal member when the safety valve is activated can be more clearly achieved. In other words, the effect of the safety valve, such as reducing or avoiding undesirable conduction when the safety valve is activated, can be more clearly achieved.

[0083] In the battery of the present invention, the groove provided in the second metal member is preferably located away from the battery axis so as to function as a more suitable cutoff groove in the safety valve. In a preferred embodiment, the interconnection point between the first metal member and the second metal member is located on the battery axis, and the groove in the second metal member may be located away from the battery axis where the interconnection point between the first metal member and the second metal member is located. Referring to FIG. 7, the groove 135 in the stripper disk 130 is located away from the interconnection point J (member connection point located on the battery axis P) between the safety cover 110 corresponding to the first metal member and the stripper disk 130 corresponding to the second metal member. This makes it easier for the groove provided in the second metal member to function as a cutoff groove when the internal pressure increases abnormally, and makes the effect brought about by the "step portion including a thin-walled portion having a relatively reduced thickness compared to other portions" more apparent. In other words, the effect of reducing or avoiding undesirable displacement such as springback of the safety cover corresponding to the first metal member when the safety valve is activated becomes more apparent, and the effect of the safety valve, such as reducing or avoiding undesirable conduction when the safety valve is activated, can be more favorable.

[0084] In a preferred embodiment, the first metal member has a preferred thickness relationship between its step portion and the groove. Specifically, the thickness of the thin portion provided at the step portion of the first metal member may be greater than the member thickness of the groove portion of the first metal member (i.e., the distance between the bottom surface contour of the groove and the inner main surface contour of the first metal member). With reference to FIG. 12 (upper part of a partially enlarged view), the thickness of the thin portion 112 forming the step portion of the safety cover 110 corresponding to the first metal member is set to t a The thickness of the groove 118 in the safety cover 110 (i.e., the distance between the bottom surface contour of the groove and the inner main surface contour of the first metal member) is t b Then, t a >t bWith such a relationship, the effect of reducing or avoiding undesirable springback of the safety cover corresponding to the first metal member when the safety valve is activated can be more clearly realized. In other words, the effect of the safety valve in which undesirable conduction when the safety valve is activated is reduced or avoided can be more clearly realized.

[0085] In another preferred embodiment, the first metal member has a preferred width relationship between its step portion and the groove. Specifically, the width of the thin portion provided at the step portion of the first metal member may be larger than the width of the groove in the first metal member (for example, the groove opening dimension at the surface of the first metal member). With reference to FIG. 12 (lower side of a partially enlarged view), the width of the thin portion 112 forming the step portion of the safety cover 110 corresponding to the first metal member is W a The thickness of the groove 118 of the safety cover 110 (for example, the groove opening dimension on the front surface side of the first metal member) is W b Then, W a >W b With this relationship, the thin-walled portion provided with the step portion has a longer extension, so that the first metal member is more likely to be suitably displaced when the internal pressure increases abnormally, and therefore the effect of the "step portion including the thin-walled portion having a relatively reduced thickness compared to other portions" described above is more likely to be realized. In other words, the effect of reducing or avoiding the displacement of the safety cover equivalent to the first metal member, such as undesirable springback, when the safety valve is activated is more likely to be realized, and the effect of the safety valve of reducing or avoiding undesirable conduction when the safety valve is activated can be more likely to be realized.

[0086] In the safety valve according to the present invention, the safety cover corresponding to the first metal member, the stripper disk corresponding to the second metal member, and the insulating member between them each have a disk or plate shape (e.g., flat plate shape) as a whole, and the first metal member is provided with a "step portion including a thin-walled portion whose thickness is relatively reduced compared to other portions" as described above. Therefore, it can be said that a thinner safety valve structure (a structure with a lower safety valve height dimension) is provided while the deformation amount for cutting off the current when the safety valve is activated is suitably ensured. Because of such a thin safety valve, it can be said that the internal volume of the battery (the electrode assembly inside the exterior body) can be effectively increased while maintaining the desired safety valve function, and the desired high capacity can be easily achieved.

[0087] (Battery manufacturing) The method for producing a battery according to the present invention will be described by taking a method for producing a secondary battery as an example. The secondary battery according to the present invention can be produced, for example, by the following procedure.

[0088] In preparing the positive electrode, a positive electrode active material is mixed with a positive electrode binder and a positive electrode conductor, etc., if necessary, to obtain a positive electrode mixture. Then, the positive electrode mixture is dispersed in an organic solvent, etc., to obtain a paste-like positive electrode mixture slurry. Then, the positive electrode mixture slurry is 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. Thereafter, the positive electrode active material layer may be compression molded using a roll press, etc., if necessary. In such a case, the positive electrode active material layer may be heated, or compression molding may be repeated multiple times. In the same manner, a negative electrode can be prepared. Specifically, a negative electrode active material is mixed with a negative positive electrode binder, a negative electrode conductor, etc., to obtain a negative electrode mixture, and then the negative electrode mixture is dispersed in an organic solvent, etc., to obtain a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to one or both sides of the negative electrode current collector, and then 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.

[0089] 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 the negative electrode are laminated via a separator, and then the positive electrode, the negative electrode, and the 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, while sandwiching the wound electrode body between a pair of insulating plates, the wound electrode body is stored inside the 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 similarly connected to the battery can using a welding method or the like. Next, an electrolyte is injected into the inside of 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 or the like. This completes a secondary battery equipped with a safety valve.

[0090] The groove provided in the first metal member according to the present invention (i.e., "a step portion including a thin-walled portion having a relatively reduced thickness compared to other portions") can be provided when the first metal member is molded using a press die. In addition, the step portion can be formed by other methods such as mechanical grinding and laser processing, without being limited to press molding.

[0091] The embodiments of the present invention have been described above. In the safety valve provided in the present invention, as described above, the first metal member, the second metal member, and the insulating member are combined together with the top cover so as to be stacked on top of each other, the first metal member, the second metal member, and the insulating member are plate-shaped or disk-shaped members, the insulating member has a hollow portion or an opening, and the first metal member and the second metal member are connected through the hollow portion or the opening of the insulating member. At least due to such a configuration, a thin safety valve is obtained, and in combination with the feature of the "step portion including a thin-walled portion whose thickness is relatively reduced compared to other portions", it is easy to suitably reduce or avoid undesirable displacement such as springback of the safety cover corresponding to the first metal member when the safety valve is operated (that is, it is easy to reduce or avoid undesirable conduction when the safety valve is operated). Note that the embodiments of the present invention described above are merely typical examples. Therefore, the present invention is not limited to this, and it will be easily understood by those skilled in the art that various aspects are possible.

[0092] For example, although the above description has focused on cylindrical batteries, the present invention is not necessarily limited thereto. For example, the battery according to the present invention may be a battery of another shape, such as a prismatic battery, and the effects of the present invention can be similarly achieved.

[0093] In addition, in the above description of the present invention, a battery can, i.e., a battery exterior body, was mentioned, but such an exterior body may have a beadless structure that does not have a beading portion. A beadless exterior body has no narrowed or constricted parts inside (particularly near the battery axis side), so a larger space can be secured inside the exterior body for disposing the electrode assembly. In other words, a beadless exterior can in which the inside diameter dimension of such a battery can is substantially constant along the battery axis can contribute to the realization of a battery with a higher energy density.

[0094] Furthermore, for example, in the safety valve according to the present invention, the groove (cutoff groove) provided in the second metal member may be provided together with an opening portion adjacent thereto. That is, an opening portion may be provided in the second metal member, and the opening portion and the groove may be adjacent to each other in the second metal member to form a cutoff portion. In other words, the groove and the opening portion may be formed in a relationship adjacent to each other, preferably directly adjacent to each other, to form a cutoff portion (i.e., a cutoff portion that acts when the internal pressure of the battery can increases abnormally). In such a case, the groove and the opening portion may be arranged adjacent to each other so that a ring-shaped contour is formed from the groove and the opening portion, and preferably they may be arranged so that they are alternately adjacent to each other.

[0095] The secondary battery of the present disclosure has the following features. <1> A battery (e.g., a primary battery or a secondary battery) having a safety valve (or a safety valve structure, a battery safety valve, or a safety valve structure), the safety valve comprising 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 are connected to each other so as to straddle the insulating member, A battery, wherein the first metal member has a stepped portion (i.e., a stepped portion formed together with a thin-walled shape having a relatively reduced thickness) that includes a thin-walled portion (thin portion) whose thickness is relatively reduced compared to other portions (non-thin portions). <2> In a cross-sectional view of the safety valve, the step portion is provided so that an outer contour of the first metal member has a stepped contour, and an inner contour of the first metal member also has a stepped contour. <1> 2. The battery according to claim 1 . <3> 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 first metal member, the second metal member, and the insulating member are plate-shaped or disk-shaped members, 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> or <2> 2. The battery according to claim 1 . <4> a top cover provided further outside than the first metal member and having a protrusion protruding outward; the step portion of the first metal member and the raised area of ​​the protrusion of the top cover have a positional relationship in which they overlap each other; <1> ~ <3> 13. The battery according to claim 12, <5> The first metal member further has a groove positioned relatively closer to the battery shaft than the step portion. <1> ~ <4> 13. The battery according to claim 12, <6> a groove is provided in the second metal member, and the groove of the second metal member is positioned relatively closer to a battery shaft side than the groove and the step portion of the first metal member; <5> 2. The battery according to claim 1 . <7> an interconnection point between the first metal member and the second metal member is positioned on a battery shaft, and the groove of the second metal member is provided at a position spaced apart from the battery shaft; <6> 2. The battery according to claim 1 . <8> In the first metal member, the thin-walled portion has a thickness ratio of 0.7 or less to the non-thin-walled portion. <1> ~ <7> 13. The battery according to claim 12, <9> The insulating member is made of a resin material. <1> ~ <8> 13. The battery according to claim 12, <10> The battery includes a positive electrode and a negative electrode capable of absorbing and releasing lithium ions, <1> ~ <9> 13. The battery according to claim 12, [Industrial Applicability]

[0096] The battery according to the present invention (such as a primary battery and a secondary battery) 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 in which power storage is expected. By way of example only, the battery of the present invention can be used in the electrical, information, and communication fields in which electrical and electronic devices are used (for example, electrical and electronic devices fields or mobile device fields including mobile phones, smartphones, notebook computers, digital cameras, activity meters, 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, household, nursing care, and industrial robots), large industrial applications (for example, forklifts, elevators, and port cranes), transportation systems (for example, hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (for example, various power generation, road conditioners, smart grids, and general household installation type power storage systems), medical applications (medical devices such as earphone hearing aids), pharmaceutical applications (medical management systems), as well as the IoT field, and space and deep sea applications (for example, space probes, submersible research vessels, and the like). [Explanation of symbols]

[0097] 10 Electrode assembly 11 Positive electrode 12 Negative electrode 13 Separator 15 Conductive materials 50 Battery Can 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) 112 Thin-walled area (thin-walled part) 114 Other parts, i.e. non-thin parts (non-thin parts located on the outer periphery side of the thin parts) 115 Step portion configured with a thin-walled shape with a relatively reduced thickness 116A: Outer contour of the first metal member located relatively outward in the battery axial direction 116Aa Step contour of outer contour 116B An inner contour of a first metal member located relatively inward in the battery axial direction 116Bb Stepped contour of inner contour 117 Other parts, i.e. non-thin parts (non-thin parts located on the inner side of the thin part) 118 Groove in first metal member (e.g., safety cover) 120 Insulating materials 120C Openings / Opening Areas in Insulating Materials 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) 135 Groove (especially cleavage groove) of second metal member (e.g. stripper disk) J: An interconnection point between a first metal member (e.g., a safety cover) and a second metal member (e.g., a stripper disk) 150 Top cover 150A Top cover protrusion 150B Top cover flat plate 150C Top cover bend 150C p Raised area start point / Top cover bending start point (outer bending start point) 150D Top cover opening 151: raised area of ​​the convex portion of the top cover 150 151a Boundary portion between straight and curved portions of cross-sectional contour (relatively outside in the battery axis direction and outside in the width direction) 151a' Boundary portion between straight and curved portions of the cross-sectional contour (relatively outside in the battery axis direction and inside in the width direction) 151b Boundary portion between straight and curved portions of cross-sectional contour (relatively inside in the battery axis direction and outside in the width direction) 151b' Boundary portion between straight and curved portions of the cross-sectional contour (relatively inside in the battery axis direction and inside in the width direction) 1000 secondary battery P battery axis

Claims

1. A battery having a safety valve, the safety valve comprises a first metal member located on an outside, a second metal member located on an 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 are connected to each other so as to straddle the insulating member, A battery, wherein the first metal member has a stepped portion including a thin-walled portion whose thickness is relatively reduced compared to other portions.

2. The battery according to claim 1 , wherein the step portion is provided such that, in a cross-sectional view of the safety valve, 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.

3. 2. The battery of claim 1, wherein in the safety valve, the first metal member, the second metal member and the insulating member are combined so as to be stacked together with a top cover, the first metal member, the second metal member and the insulating member are plate-shaped or disk-shaped members, 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.

4. a top cover provided further outwardly than the first metal member and having a protrusion protruding outwardly; The battery according to claim 1 , wherein the stepped portion of the first metal member and the raised area of ​​the convex portion of the top cover are in a positional relationship such that they at least partially overlap each other.

5. The battery according to claim 1 , wherein the first metal member further has a groove positioned relatively closer to the battery shaft than the stepped portion.

6. The battery according to claim 5 , wherein a groove is provided in the second metal member, and the groove of the second metal member is positioned relatively closer to the battery axis than the groove and the step portion of the first metal member.

7. The battery according to claim 6 , wherein an interconnection point between the first metal member and the second metal member is positioned on a battery shaft, and the groove of the second metal member is provided at a position spaced apart from the battery shaft.

8. The battery according to claim 1 , wherein in the first metal member, the thickness dimension of the thinned portion has a thickness ratio of 0.7 or less to a non-thinned thickness dimension of the other portion.

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 releasing lithium ions.

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