Patent Application
20250112343
The present application claims priority to Japanese patent application no. 2023-170402, filed on Sep. 29, 2023, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a battery.
The battery can extract energy due to chemical change or the like as electric energy, and is used for various applications. For example, the batteries are used in mobile devices such as mobile phones, smart phones, and notebook computers.
The present disclosure relates to a battery. More specifically, the present disclosure relates to a battery including an electrode assembly made of an electrode-constituting layer including a positive electrode, a negative electrode, and a separator.
The safety of the battery is required. For example, a battery including a safety valve capable of achieving current interruption at the time of abnormality can be considered.
The inventor of the present application has studied and determined, for example, that there is still room for development of a safety valve for achieving current interruption at the time of abnormality in terms of interruption variation.
The present disclosure has been made in view of the above problems and relates to providing a battery having an interruption characteristic in which an interruption variation is reduced as a safety valve according to an embodiment.
A battery according to the present disclosure, in an embodiment, includes:
A battery according to the present disclosure, in an embodiment, includes:
In the battery according to the present disclosure, current interruption at the time of abnormality can be more suitably achieved. Specifically, in the battery according to the present disclosure, two corner portions having different shapes and angles as sectional views are provided inside the groove of the metal member constituting the safety valve, and current interruption variation is reduced by the action of the safety valve.
In recent years, along with a long life, a high output, and the like, performance improvement regarding reliability of a battery is required.
The inventor of the present application has found, for example, that a certain battery safety valve can achieve current interruption and the like at the time of abnormality and can cope with high output and the like, but still has room for development from another viewpoint. For example, the inventor of the present application has focused on the fact that a safety valve combined from a plurality of members is not necessarily satisfactory from the viewpoint of current interruption at the time of abnormality, and the current interruption at the time of abnormal increase in battery internal pressure may occur as undesired interruption.
For example, in a battery provided with a safety valve including a combination of a safety cover, a stripper disk, and an insulating member therebetween, a groove provided in the stripper disk can be used for current interruption at the time of abnormality such as an increase in internal pressure. More specifically, the current is interrupted by cleaving the stripper disk by the battery internal pressure at the time of abnormality with the corner portion of the groove as a starting point. Since the cleavage occurs based on the groove, the groove of the stripper disk can be referred to as a “cleavage groove”. The inventors of the present application have found the need to increase the reliability of the cleavage of the stripper disk during the verification of current interruption. Specifically, the inventor of the present application has found that the “interruption variation” may increase when the stripper disk is broken.
In particular, in the case where current conduction was still observed after generation of a breaking sound that can correspond to break of the stripper disk, there was a tendency that the current interruption sites of the cleavage groove after breaking varied, or there was a tendency that the interruption pressure varied (for example, the interruption pressure tends to vary as a higher interruption pressure). That is, it has been found that the case in which the conduction of the current is observed after the breaking sound has large interruption variation in the break site and/or the interruption pressure as compared with the desired case in which the conduction of the current is not observed after the breaking sound.
The inventor of the present application have attempted to solve such a problem and with a battery that reduces or avoids interruption variation at the time of abnormality such as an increase in battery internal pressure, and further increases reliability of a safety valve according to an embodiment.
Hereinafter, one or more embodiments of the present disclosure will be described in further details. It should be noted the following description and examples are provided for those skilled in the art to fully understand the present disclosure, and these are not intended to limit the subject matter described herein. That is, the present disclosure is not particularly limited to the preferred embodiments and the like described herein, and can be appropriately modified. Further, embodiments and the like may be separately described for convenience, but partial replacement and/or combination of configurations described in different embodiments and the like are possible. In the description of such an embodiment, descriptions of matters common to those described above may be omitted, and only different points may be described. For example, similar functions and effects achieved by similar configurations may not be mentioned sequentially for each embodiment.
In the description of the present specification, reference to a direction, an orientation, or the like is merely for convenience of description, and is not intended to limit the scope of the present disclosure unless otherwise explicitly described. For example, relative terms, such as “out (or outer side, outer portion or outer circumference)”, “in (or inner side, inner portion or inner circumference)”, “bottom”, and the like, as well as derivative terms thereof, should be understood to refer to directions as described or illustrated. That is, unless otherwise explicitly described, the invention is not required to be limited only to a specific direction, orientation, form, or the like. In addition, terms such as “provided”, “disposed”, “connected”, and “adhered”, and derivative terms thereof are also similar, and are not limited to a direct mode, and may be a mode in which another element such as an inclusion is interposed unless otherwise explicitly described. The various numerical ranges mentioned in the present specification are intended to include the lower and upper numerical values themselves, unless otherwise stated. More specifically, when a numerical range such as 1 to 10 is taken as an example, the example can be interpreted as including the lower limit of “1” and also including the upper limit of “10”.
The term “battery” as used herein includes not only a so-called “secondary battery” but also a “primary battery” capable of only discharging. That is, the “battery” in the present specification may be a “secondary battery” that can be repeatedly charged and discharged, or a “primary battery” that is substantially only discharged. The “secondary battery” is not excessively bound by the name, and may include an “electric storage device”, for example.
The battery according to the present disclosure, in an embodiment, will be described below in further detail including with reference to a secondary battery as an example.
The secondary battery according to the present disclosure includes an electrode assembly formed of electrode-constituting layers, the electrode-constituting layers including a positive electrode, a negative electrode, and a separator. In the secondary battery according to the present disclosure, such an electrode-constituting layer may have a wound structure (hereinafter, also referred to as a “wound electrode body” or a “wound structure”) wound in a roll shape.
The positive electrode is formed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, the positive electrode material layer is provided on at least one surface of the positive electrode current collector. The positive electrode material layer contains a positive electrode active material as an electrode active material. For example, for each of a plurality of positive electrodes in the electrode assembly, the positive electrode material layer may be provided on both surfaces of the positive electrode current collector, or may be provided only on one surface of the positive electrode current collector.
The negative electrode is formed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode, the negative electrode material layer is provided on at least one surface of the negative electrode current collector. The negative electrode material layer contains a negative electrode active material as an electrode active material. For example, for each of a plurality of negative electrodes in the electrode assembly, the negative electrode material layer may be provided on both surfaces of the negative electrode current collector, or may be provided only on one surface of the negative electrode current collector.
The electrode active materials included in the positive electrode and the negative electrode, that is, the positive electrode active material and the negative electrode active material are substances directly involved in the transfer of electrons in the secondary battery, and are main substances of the positive and negative electrodes, which are responsible for charge-discharge, that is, a battery reaction. More specifically, ions are brought in 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, thereby performing charging and discharging. The positive electrode material layer and the negative electrode material layer may be layers particularly capable of occluding and releasing lithium ions. More specifically, the secondary battery according to the present disclosure may be a non-aqueous electrolyte secondary battery in which lithium ions move between the positive electrode and the negative electrode with a non-aqueous electrolyte interposed therebetween, thereby charging and discharging the battery. In a case where lithium ions are involved in charge and discharge, the secondary battery according to the present disclosure corresponds to a so-called “lithium ion battery”, and includes electrodes capable of occluding and releasing lithium ions as a positive electrode and a negative electrode, and preferably includes layers capable of occluding and releasing lithium ions.
In view of a lithium ion battery, the positive electrode active material may be a material that contributes to occlusion and release of lithium ions. That is, the positive electrode layer may contain any one kind or two or more kinds among positive electrode materials capable of occluding and releasing lithium. From such a viewpoint, the positive electrode active material may be, for example, a lithium-containing compound. The lithium-containing compound is not particularly limited in its type, and can be, for example, a lithium-containing composite oxide, a lithium-containing phosphate compound, or the like. This is because a high energy density can be obtained.
The lithium-containing composite oxide is a generic name of oxides containing lithium and one or more of other elements (elements other than lithium) as constituent elements, and may have, for example, one of crystal structures such as a layered rock-salt type crystal structure and a spinel type crystal structure. The lithium-containing phosphate compound is a generic name of phosphate compounds that contain lithium and one or more of the other elements as constituent elements, and may have, for example, a crystal structure such as an olivine crystal structure. The kind of the other element is not particularly limited as long as the element is any one or two or more of arbitrary elements. Among them, the other element is one or two or more of elements belonging to Groups 2 to 15 in a long-period periodic table. More specific examples of other elements are nickel (Ni), cobalt (Co), manganese (Mn) and iron (Fe). This is because a high voltage can be easily obtained.
The lithium-containing composite oxide having a layered rock salt type crystal structure may be compounds represented by the following respective Formulas (1) to (3).
LiaMn(1−b−c)NibM11cO(2−d)Fe (1)
LiaNi(1−b−c)M12bO(2−c)Fd (2)
LiaCo(1−b)M13bO(2−c)Fd (3)
For example, specific examples of the lithium-containing composite oxide having a layered rock salt type crystal structure include LiNiO2, LiCoO2, LiCo0.98Al0.01Mg0.01O2, LiNi0.5CO0.2Mn0.3O2, LiNi0.8CO0.15Al0.05O2, LiNi0.33CO0.33Mn0.33O2, Li1.2Mn0.52CO0.175Ni0.1O2, and Li1.15(Mn0.65Ni0.22CO0.13)O2.
In a case in which 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. This is because a high energy density can be obtained.
The lithium-containing composite oxide having a spinel type crystal structure may be a compound represented by the following Formula (4).
LiaMn(2-b)M14bOcFd (4)
As specific examples, the lithium-containing composite oxide having a spinel type crystal structure may be LiMn2O4 and the like.
Examples of the lithium-containing phosphate compound having an olivine type crystal structure include a compound represented by the following Formula (5).
LiaM15PO4 (5)
As specific examples, the lithium-containing phosphate compound having an olivine type crystal structure may be LiFePO4, LiMnPO4, LiFe0.5Mn0.5PO4, LiFe0.3Mn0.7PO4, and the like.
Incidentally, the lithium-containing composite oxide may be a compound represented by the following Formula (6).
(Li2MnO3)x(LiMnO2)1−x (6)
In addition to these, the positive electrode material may be any one kind or two or more kinds among, for example, oxides, disulfides, chalcogenides, and conductive polymers. The oxide may be, for example, titanium oxide, vanadium oxide, manganese dioxide, or the like. Examples of the disulfide include titanium disulfide and molybdenum sulfide. The chalcogenide is, for example, niobium selenide or the like. The conductive polymer is, for example, sulfur, polyaniline, polythiophene, or the like. However, the positive electrode material is not particularly limited, and other materials other than the above materials may be used.
The positive electrode material layer may contain a binder. In addition, a positive electrode conductive agent may be contained in the positive electrode material layer in order to facilitate transmission of electrons promoting a battery reaction. The positive electrode binder contains, for example, any one or two or more types of synthetic rubbers and polymer compounds. The synthetic rubber is, for example, styrene-butadiene rubber, fluorine rubber, ethylene propylene diene, or the like. The polymer compound is, for example, polyvinylidene fluoride, polyimide, or the like. The positive electrode conductive agent may include, for example, any one of, or two or more of carbon materials. The carbon material is, for example, graphite, carbon black, acetylene black, ketjen black, or the like. However, the positive electrode conductive agent may be a metal material, a conductive polymer and the like as long as they are materials exhibiting conductivity.
Similarly, the negative electrode active material of the negative electrode material layer may be a material that contributes to occlusion and release of lithium ions. That is, the negative electrode layer may contain any one kind or two or more kinds among negative electrode materials capable of occluding and releasing lithium. From such a viewpoint, the negative electrode active material may be, for example, various carbon materials, metal-based materials, and/or other materials.
When a carbon material is used as the negative electrode active material, a change in the crystal structure at the time of occlusion of lithium and at the time of release of lithium is very small, so that a high energy density is easily obtained stably. In addition, since the carbon material also functions as a negative electrode conductive agent, the conductivity of the negative electrode layer is easily improved.
Specific examples of the carbon material 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 fired body, activated carbon, carbon blacks, or the like. The cokes may include pitch coke, needle coke, and petroleum coke. The organic polymer compound fired body is, for example, a material obtained by firing (carbonizing) a polymer compound such as phenol resin and furan resin at appropriate temperature. In addition, the carbon material may be low crystalline carbon subjected to a heat treatment 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 a fibrous shape, a spherical shape, a granular shape, and a scaly shape.
The “metal-based material” used as the negative electrode active material is a generic term for materials containing any one kind or two or more kinds among metal elements and metalloid elements as constituent elements. When a carbon material is used as the negative electrode active material, a high energy density is easily obtained. The metal-based material may be a simple substance, an alloy, a compound, two or more of these, or a material at least a part of which has phases formed of one or more of these. However, the alloy may include a material containing one or more kinds of metal elements and one or more kinds of metalloid elements in addition to a material formed of two or more kinds of metal elements. The alloy may also contain a non-metallic element. The construction of this metal-based material may be, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and a material in which two or more kinds among these coexist. Such metal element and metalloid element may be, for example, any one kind or two or more kinds among metal elements and metalloid elements capable of forming an alloy with lithium. Specific examples of the metal element and the metalloid element may include 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 aspect, the metal element or metalloid element is silicon and tin. This is because the ability to store and release lithium is excellent and thus a higher energy density is obtained. A material containing silicon as a constituent element may be a simple substance of silicon, an alloy of silicon, or a compound of silicon, may be two or more thereof selected therefrom, or may include one or more phases thereof in part or all thereof. Similarly, a material containing tin as a constituent element may be a simple substance of tin, an alloy of tin, or a compound of tin, may be two or more thereof, or may include one or more phases thereof in part or all thereof. The “simple substance” described in the present specification is a simple substance in a general sense to the utmost, and thus the simple substance may contain a small amount of impurities. That is, the purity of the simple substance is not necessarily limited to 100%. The alloy of silicon may contain, for example, any one or two or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, or the like as constituent elements other than silicon. The compound of silicon may contain, for example, any one or two or more of carbon, oxygen or the like as constituent elements other than silicon. The compound of silicon may contain, for example, any one or two or more of a series of elements described in the alloy of silicon as constituent elements other than silicon. As specific examples of the alloy of silicon and the compound of silicon, SiB4, SiB6, MgSi, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiOv (0<v≤2), and/or LiSiO can be exemplified. In SiOv, v may be 0.2<v<1.4. The alloy of tin may contain, for example, any one or two or more types of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, and the like, as constituent elements other than tin. The compound of tin may contain, for example, any one or two or more types of carbon, oxygen, and the like, as constituent elements other than tin. The compound of tin may contain any one or two or more of a series of elements described in the alloy of tin, for example, as constituent elements other than tin. As specific examples of the alloy of tin and the compound of tin, SnOw (0<w≤2), SnSiO3, LiSnO, and/or Mg2Sn can be exemplified. Particularly, the material containing tin as a constituent element may be, for example, a material (tin-containing material) containing a second constituent element and a third constituent element together with tin which is a first constituent element. The second constituent element may be, for example, any one or two 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, silicon, or the like. The third constituent element may be, for example, any one or two or more of boron, carbon, aluminum, phosphorus, or the like. This is because a high battery capacity, excellent cycle characteristics and the like can be easily obtained. Among these, the tin-containing material may be a material (tin cobalt carbon-containing material) containing tin, cobalt, and carbon as constituent elements. This is because a high energy density can be obtained. In the tin cobalt carbon-containing material, at least a part of carbon which is a constituent element may be bonded to a metal element or metalloid element which is another constituent element. This is because the aggregation of tin, crystallization of tin, and the like can be easily suppressed. The tin cobalt carbon-containing material is not limited to the material (SnCoC) that contains only tin, cobalt, and carbon as constituent elements. This tin cobalt carbon-containing material may further contain, for example, any one or two or more of silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth or the like as a constituent element in addition to tin, cobalt, and carbon. 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 employed.
In addition to these, the negative electrode material may be any one kind or two or more kinds among, for example, metal oxides and polymer compounds. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.
The negative electrode material layer may contain a binder. Furthermore, a negative electrode conductive agent may be contained in the negative electrode material layer in order to facilitate transfer of electrons promoting the battery reaction. The binder which can be contained in the negative electrode material layer is not particularly limited, but examples thereof include at least one kind selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, a polyimide-based resin, and a polyamideimide-based resin. The negative conductive agent that can be contained in the negative electrode material layer is not particularly limited, but examples thereof can include at least one selected from carbon blacks such as thermal black, furnace black, channel black, ketjen black, and acetylene black, carbon fibers such as graphite, carbon nanotube, and vapor-grown carbon fiber, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives. Note that the negative electrode material layer may contain a component derived from a thickener component (for example, a carboxymethyl cellulose) used at the time of manufacturing the battery.
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. In addition, the electrode current collector may have a porous or perforated form. For example, the current collector may be a metal foil, a punching metal, a net, an expanded metal, or the like. The positive electrode current collector that is used for the positive electrode may be made of, for example, a metal foil containing at least one selected from the group consisting of aluminum, nickel, stainless steel, and the like. On the other hand, the negative electrode current collector that is used for the negative electrode may be made of, for example, a metal foil containing at least one selected from the group consisting of copper, aluminum, nickel, stainless steel, and the like.
The separator used for the positive electrode and the negative electrode is a member provided from the viewpoints of the prevention of short circuit due to contact between the positive and negative electrodes and the holding of the electrolyte and the like. In other words, the separator is a member that separates the positive electrode and the negative electrode, and allows ions (for example, lithium ions) to pass while preventing a short circuit of a current due to contact between both electrodes. For example, the separator may be a porous or microporous insulating member, which may have a film form due to its small thickness.
This separator may be, for example, any one kind or two or more kinds among porous films of synthetic resins and/or ceramics and may be a stacked film of two or more kinds of porous films. The synthetic resin used for the separator is, for example, polytetrafluoroethylene, polypropylene, polyethylene, or the like. For example, the separator may include the porous film (substrate layer) and a polymer compound layer provided on one side or both sides of the base layer. This is because the close contact property of the separator with respect to the positive electrode is improved as well as the close contact property of the separator with respect to the negative electrode can be improved, and thus the distortion of the wound electrode body is likely to be suppressed. The polymer compound layer may contain, for example, any one or two or more types of polymer compounds such as polyvinylidene fluoride. It is excellent in physical strength and easily becomes electrochemically stable. It should be understood that the polymer compound layer may contain any one or two or more types of insulating particles such as an inorganic particle. The kind of inorganic particles may include aluminum oxide and/or aluminum nitride. In the present disclosure, the separator is not to be particularly limited by its name, and may be, for example, a solid electrolyte, a gel-like electrolyte, and/or an insulating inorganic particle having a similar function.
In the secondary battery of the present disclosure, the electrode assembly including the electrode-constituting layer including the positive electrode, the negative electrode, and the separator may be enclosed in the outer case together with an electrolyte. The electrolyte may be a so-called “non-aqueous” electrolyte.
The electrolyte may typically be an electrolytic solution. The electrolytic solution contains a solvent and an electrolyte salt. The electrolytic solution may further contain any one or two or more of other materials such as additives. In a preferred aspect, the separator may be impregnated with an electrolytic solution, and the positive electrode and/or the negative electrode may also be impregnated with an electrolytic solution.
The solvent may contain any one or two or more of non-aqueous solvents such as organic solvents. The electrolytic solution containing a nonaqueous solvent may be a so-called nonaqueous electrolytic solution. Examples of the non-aqueous solvent include a cyclic carbonate ester, a chain carbonate ester, a lactone, a chain carboxylate ester, and/or a nitrile (for example, mononitrile). This is because more excellent battery capacity, cycle characteristics and/or storage characteristics can be easily obtained. Examples of the cyclic carbonate ester may include 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 methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and/or ethyl trimethylacetate. The nitrile may be acetonitrile, methoxyacetonitrile, and/or 3-methoxypropionitrile. The non-aqueous solvent may be 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 nonaqueous solvent preferably contains one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and the like. This is because higher battery capacity, more excellent cycle characteristics, and/or more excellent storage characteristics are easily provided. In addition, the non-aqueous solvent may be an unsaturated cyclic carbonate ester, a halogenated carbonate ester, a sulfonate ester, an acid anhydride, a dicyano compound (dinitrile compound), a diisocyanate compound, a phosphate ester, and/or a chain compound having a carbon-carbon triple bond. This is because chemical stability of the electrolytic solution is easily improved. The “unsaturated cyclic carbonate ester” as used herein is a cyclic carbonate ester having one or more unsaturated bonds (carbon-carbon double bonds or carbon-carbon triple bonds). As this unsaturated cyclic carbonate ester, vinylene carbonate, vinyl ethylene carbonate, and/or methylene ethylene carbonate can be exemplified. The “halogenated carbonate ester” is a cyclic carbonate ester having one or more halogen elements as constituent elements or a chain carbonate ester having one or more halogen elements as constituent elements. In a case in which the halogenated carbonate ester contains two or more halogens as a constituent element, the kind of the two or more halogens may be one kind or two or more kinds. As the cyclic halogenated carbonate ester, for example, 4-fluoro-1, 3-dioxolan-2-one, and/or 4,5-difluoro-1,3-dioxolan-2-one can be exemplified. The chain halogenated carbonate ester may be, for example, fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, and/or difluoromethyl methyl carbonate. The sulfonate ester may be a monosulfonate ester and/or a disulfonate ester. The monosulfonate ester may be a cyclic monosulfonate ester or a chain monosulfonate ester. The cyclic monosulfonate ester may be sultones such as 1,3-propane sultone, and/or 1,3-propene sultone. Examples of the chain monosulfonate ester include a compound in which a cyclic monosulfonate ester is cleaved in the middle. The disulfonate ester may be a cyclic disulfonate ester or a chain disulfonate ester. The acid anhydride may be, for example, carboxylic acid anhydride, disulfonic acid anhydride, and/or carboxylic acid sulfonic acid anhydride. The carboxylic acid anhydride may be, for example, succinic anhydride, glutaric anhydride, and/or maleic anhydride. The disulfonic acid anhydride may be, for example, ethanedisulfonic anhydride, and/or propanedisulfonic anhydride. The carboxylic acid sulfonic acid anhydride may be, for example, sulfobenzoic anhydride, sulfopropionic anhydride, and/or sulfobutyric anhydride. A dinitrile compound is, for example, a compound represented by NC—R1-CN (R1 represents either of an alkylene group or an arylene group). The dinitrile compound may include succinonitrile (NC—C2H4—CN), glutaronitrile (NC-C3H6—CN), adiponitrile (NC—C4H8—CN), and phthalonitrile (NC—C6H4—CN). A diisocyanate compound is, for example, a compound represented by OCN—R2-NCO (R2 represents either of an alkylene group or an arylene group). The diisocyanate compound may be hexamethylene diisocyanate (OCN—C6H12—NCO) or the like. The phosphate ester may be trimethyl phosphate and triethyl phosphate. A chain compound having a carbon-carbon triple bond is a chain compound having one or two or more carbon-carbon triple bonds (—C═C—). This chain compound having a carbon-carbon triple bond may be propargyl methyl carbonate (CH═C—CH2—O—C(═O)—O—CH3) and propargyl methanesulfonate (CH═C—CH2—O—S(═O)2—CH3).
For example, the electrolyte salt included in the electrolytic solution may be any one or two or more of salts such as a lithium salt. The electrolyte salt may contain a salt other than a lithium salt, for example. The salt other than lithium may be, for example, salts of light metals other than lithium. Examples of the lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethane sulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SiF6), lithium chloride (LiCl), and/or lithium bromide (LiBr). This is because more excellent battery capacity, cycle characteristics and/or storage characteristics can be easily obtained. Among these, any one kind or two or more kinds among lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate may be employed.
A battery can used in a secondary battery corresponds to a member enclosing an electrode assembly in which electrode-constituting layers including a positive electrode, a negative electrode, and a separator are stacked as a battery package. The battery can may have, for example, a hollow structure in which one end portion is closed and the other end portion is opened (opened as an open end portion). The battery can is not particularly limited, but may be a metal can containing any one of, or two or more of metal materials such as iron, aluminum, stainless steel, and alloys thereof. One or more of metal materials such as nickel may be plated on the surface of the battery can, for example. A safety valve may be provided at the opening end of the battery can. Although it is merely an example, a safety valve may be provided at the opening end of the battery can together with a thermal resistor or the like with a gasket interposed therebetween (that is, the battery safety valve may be provided together with a caulking mechanism).
The battery of the present disclosure has features related to its safety mechanism. In particular, it has a feature related to a safety valve provided on a battery can (particularly, an opening end thereof) of a battery.
The safety valve provided in the battery of the present disclosure includes at least a first metal member, a second metal member, and an insulating member positioned therebetween. The first metal member is positioned relatively outside in the battery axial direction, while the second metal member is positioned 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 across the insulating member. Each of the first metal member and the second metal member may be a disk-shaped or plate-shaped member (that is, it may have a form extending on the same plane as a whole). The insulating member preferably has an opening part or a hollow portion in an inner or central region thereof, and may have a plate shape (for example, a flat plate shape) or a flat shape as a whole, as will be described later. In the present disclosure, the first metal member, the second metal member, and the insulating member are preferably disposed so as to be directly stacked on each other, and constitute a thin safety valve.
Further, in the safety valve according to the present disclosure, a groove is provided in the second metal member. The groove of the second metal member includes a corner portion having a specific form inside the groove. Specifically, the groove of the second metal member has at least two corner portions inside the groove in the sectional view, and the shapes of the two corner portions are different from each other. In the sectional view of the second metal member, it can also be said that two corner portions different from each other are provided as contours in a sectional view inside the groove.
As will be described later, since the groove of the second metal member contributes to the breakage of the second metal member subjected to the battery internal pressure at the time of abnormality, the groove can be regarded as a “cleavage groove”. However, due to the specific form of such a cleavage groove, a safety valve with reduced interruption variation can be provided. That is, when the current interruption is performed at the time of abnormality such as an increase in internal pressure using the cleavage groove of the second metal member, it is possible to further reduce variation in break sites of the cleavage groove of the second metal member and/or it is possible to further reduce variation in interruption pressure due to the “a cleavage groove having at least two corner portions therein in a sectional view, the two corner portions having different shapes from each other”. As a result, a battery in which the reliability of the safety valve is further improved is obtained. For example, in the battery having a small variation, the predictability when the internal pressure abnormally increases is improved, and a battery having a higher degree of freedom in design can be realized. Alternatively, it is easy to realize a battery in which the conduction of the current is desirably avoided thereafter so as to more suitably cope with the breaking sound of the second metal member and the like.
Hereinafter, such a battery of the present disclosure will be described in detail with appropriate reference to the drawings. A configuration of a safety valve of a battery according to the present disclosure includes at least a first metal member, a second metal member, and an insulating member positioned therebetween. As one specific exemplary embodiment, an aspect in which the first metal member corresponds to a safety cover and the second metal member corresponds to a stripper disk will be described below as an example.
As illustrated in
Each member constituting the safety valve 100 will be described in detail. The safety valve 100 contributes to a battery terminal (that is, one of the positive electrode terminal and the negative electrode terminal as the external terminal of the battery) and has, as a battery safety mechanism, a mechanism that can be displaced according to an excessive the battery internal pressure. Therefore, the safety valve 100 includes the safety cover 110 and the stripper disk 130 that can be displaced according to the excessive battery internal pressure, and at least includes the insulating member 120 therebetween as a component. Such a safety valve 100 may be provided at one end portion of the battery can, and is provided at an opening end 51 in the battery can 50 of
The safety cover 110 provided as the first metal member mainly corresponds to a displaceable member that can close the opening end 51 of the battery can 50 and can be displaceable and/or openable in response to an increase in the internal pressure of the battery can. The internal pressure of the battery can increases due to a side reaction such as a decomposition reaction of the electrolytic solution, for example. That is, since a gas such as carbon dioxide is generated inside the battery can when a side reaction such as a decomposition reaction of the electrolytic solution occurs, the internal pressure of the battery can undesirably increases according to an increase of the generation amount of the gas.
The safety cover 110 may be a metal member. For example, the safety cover 110 may include any one of, or two or more of metal materials such as iron (Fe), aluminum (for example, aluminum metal or aluminum alloy, such as A1050, A3203, and/or A5052), titanium (Ti), platinum (Pt), and gold (Au). In other words, it can be said that the safety cover 110 may be a member made of such a conductive material. A planar shape of the safety cover 110, particularly an outer ring contour shape in a plan view (hereinafter, also referred to as an “outer contour shape in a plan view”) is not particularly limited, but may be, for example, a circular shape, a polygonal shape, or another shape. The circular shape is, for example, a true circle (perfect circle), an ellipse, a substantial circle, or the like. The substantial circle is, for example, a generic name of a some or all distorted shape of a true circle. The polygons are, for example, triangles, squares, pentagons and hexagons. The other shapes are, for example, shapes other than a circle whose contour is formed only by a curve, shapes in which two or more types of polygons are combined, and shapes in which one or more types of circles and one or more types of polygons are combined. Such a definition of “circular” and the like is the same hereinafter. In the illustrated exemplary embodiment, the outer contour shape of the safety cover 110 in a plan view is circular.
The safety cover 110 may have, for example, a flat plate shape as a whole. That is, the safety cover 110 may have a form extending on the same plane as a whole. Although it is merely an example, the thickness of the safety cover 110 may be substantially constant except for a groove (for example, a displacement groove that contributes to displacement, deformation, breakage, or the like of the safety cover) provided in the safety cover. The safety cover 110 having such a form extending on the same plane as a whole contributes to thinning of the battery safety valve.
The insulating member 120 is interposed between the safety cover 110 and the stripper disk 130, and corresponds to a member that enables at least 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 shape of the insulating member 120 in a plan view may be a loop shape, a ring shape, or the like. Due to such a loop shape or ring shape, the inner region of the insulating member 120 forms a hollow portion or an opening region 120C (that is, “cavity” described later). An 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 loop shape or ring shape of the insulating member 120 may be provided as the whole member, or the loop shape or ring shape may be locally divided (refer to
Since the insulating member 120 has an insulating property, electrical conduction via the insulating member 120 is preferably prevented. The term “insulation” as used herein may have an electrical resistivity, that is, the insulation property of a general insulator, and therefore may have an electrical resistivity of the general insulator, and may have a resistivity of at least 1.0×105 Ω·m or more, preferably 1.0×106 Ω·m or more, and more preferably 1.0×107 Ω·m or more (room temperature: 20° C.) although it is merely an example.
In a preferred aspect, the insulating member 120 interposed between the safety cover 110 and the stripper disk 130 may contribute to insulation, and may not necessarily be bonded thereto. 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. Note that 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 the region including the battery axis.
The insulating member 120 is preferably made of a resin material. That is, the main component of the insulating member may be a resin material, or the insulating member may be configured to include at least a resin in the material of the member. When formed of a resin material as described above, the insulating member 120 more suitably contributes to the adhesiveness between the safety cover 110 and the stripper disk 130 while securing the insulating property, and furthermore, the insulating member 120 contributes to the realization of a thinner safety valve. For example, the insulating member 120 may be made of a thermosetting resin, a thermoplastic resin, and/or a UV curable resin. In a case where a viewpoint of connectivity is particularly emphasized, the insulating member 120 may be a member including a resin adhesive having insulating properties. Examples of such a resin adhesive include an acrylic-based resin adhesive such as acrylic acid ester copolymers, a rubber-based resin adhesive such as natural rubber, a silicone-based resin adhesive such as silicone rubber, a urethane-based resin adhesive such as a urethane resin, an α-olefin-based resin adhesive, an ether-based resin adhesive, an ethylene-vinyl acetate resin-based resin adhesive, an epoxy resin-based resin adhesive, a vinyl chloride resin-based resin adhesive, a chloroprene rubber-based resin adhesive, a cyanoacrylate-based resin adhesive, an aqueous polymer-isocyanate-based resin adhesive, a styrene-butadiene rubber-based resin adhesive, a nitrile rubber-based resin adhesive, a nitrocellulose-based resin adhesive, a reactive hot-melt-based resin adhesive, a phenol resin-based resin adhesive, a modified silicone-based resin adhesive, a polyamide resin-based resin adhesive, a polyimide-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 polyvinyl pyrrolidone 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.
The insulating member 120 has a cavity 120C at a position corresponding to a central region 110C of the safety cover 110 (refer to
The stripper disk 130 provided as the second metal member is disposed relatively inside the battery with respect to the safety cover 110 with the insulating member 120 interposed therebetween, and corresponds to a member that contributes to current interruption at the time of abnormality and/or, for example, passage or release of gas inside the battery can.
The stripper disk 130 may be a metal member. For example, the stripper disk 130 may include any one of, or two or more of metal materials such as iron (Fe), aluminum (for example, 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 or different 110 from the material of the safety cover 110. The contour shape of the stripper disk 130 in a plan view is not particularly limited, but is, for example, similar to the outer contour shape of the safety cover 110 in a plan view. In the illustrated exemplary embodiment, the outer contour shape of the stripper disk 130 in a plan view is circular.
The stripper disk 130 may have, for example, a flat plate shape as a whole. That is, the stripper disk 130 may have a form of extending on the same plane. Such a stripper disk extending on the same plane as a whole contributes to thinning of the battery safety valve. For example, the stripper disk 130 may have a substantially constant thickness as a whole except for a central region or the like. A central region 130C of the stripper disk 130 may be relatively raised (preferably raised outward along the battery axis) with respect to a region other than the region to contribute to connection with the safety cover 110. In other words, although the stripper disk 130 has a plate shape as a whole, at least the central portion of the region including the battery axis may be relatively protruded.
The stripper disk 130 may be provided with a plurality of cavities 130K. The plurality of cavities 130K mainly correspond to ventilation ports that contribute to passage or release of gas inside the battery can. For example, the plurality of cavities 130K may be provided in a region on the outer peripheral side of the central region 130C.
In the safety valve, the safety cover 110 and the stripper disk 130 are integrated as a whole by interposing the insulating member 120 therebetween, but the safety cover 110 and the stripper disk 130 may be electrically connected to each other in a central region thereof. 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 illustrated in
As described above, the safety valve may further include the top cover 150. That is, the top cover 150 may be further provided relatively outside the safety cover 110 provided as the first metal member in the battery axial direction. 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 opening 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 forming an external terminal of the battery. As illustrated in
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 (in particular, one of the positive electrode and the negative electrode), and contributes to electrical connection between the electrode assembly 10 and the safety valve (in particular, 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, particularly, a region (that is, a region positioned on a side farther from the cleavage groove 135 with respect to the battery axis) on the outer peripheral side of the cleavage groove 135. In the safety valve, the stripper disk 130 is electrically connected to the safety cover 110 with the central region 130C interposed therebetween, and the safety cover 110 is connected to the top cover 150 forming an external terminal of the battery. Therefore, the electrode assembly 10 such as the wound structure is electrically connected to the battery external terminal with the conductive member 15 interposed therebetween. In the present specification, the conductive member 15 may be a member containing metal, and preferably may be a metal member having an elongated shape. For example, the conductive member may include an electrode current collector of the electrode assembly, or may be a current collecting lead (that is, the lead) provided in the electrode assembly (in particular, the electrode). When the conductive member is made of the electrode current collector, the conductive member may be made of a metal portion of the electrode current collector where the electrode material is not provided. When the conductive member is formed of a current collecting lead, the conductive member may be formed of a metal member having a thin form and/or a long form. In the present disclosure, the conductive member electrically connecting the electrode assembly and the electrode terminal to each other can also be referred to as a “tab”. The conductive member used for such a secondary battery preferably has flexibility, and may be provided in a bent form and/or a bent form.
In the safety valve according to the secondary battery of the present disclosure, 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 each other. More specifically, as illustrated in
In the present specification, the “at least two corner portions inside the groove” means corner portions positioned closer to the groove bottom side than the surface of the second metal member (the surface of the member forming the groove opening contour) in the sectional view of the groove. That is, “at least two corner portions inside the groove” in the sectional view. It refers to a corner portion provided in the groove except for the corner portion that is flush with the surface of the second metal member.
The groove 135 having such a specific sectional view shape contributes to breakage of the stripper disk 130 when an abnormal increase in the battery internal pressure occurs, and contributes to disadvantageous current interruption thereafter. The groove 135 provided in the stripper disk 130 of the second metal member may be a groove having an opening toward the outside when viewed along the battery axis (that is, the groove 135 may be a groove opened on a surface of the member surface of the second metal member on a side relatively proximal to the first metal member). The opening of the groove may be a surface on a side proximal to the element side (that is, the opening of the groove may be on the surface on the side relatively proximal to the electrode assembly side). It is assumed that the pressure inside the battery can increases due to side reactions such as a decomposition reaction of the electrolytic solution or other factors.
The inventor of the present application has noted the need to increase the reliability of the breakage of the stripper disk 130. In particular, in the case where current conduction was still observed after generation of a breaking sound that can correspond to breaking of the stripper disk, there was a tendency that the interruption site of the cleavage groove after breaking was more uneven (for example, a groove breakage point and/or a broken shape after breakage vary) or the breaking pressure was uneven (for example, the interruption pressure varies as a higher interruption pressure). That is, it has been found that the case in which the conduction of the current is observed after the breaking sound has large interruption variation in the break site and/or the interruption pressure as compared with the desired case in which the conduction of the current is not observed after the breaking sound.
On the other hand, the inventor of the present application have made studies to arrive at a battery, in an embodiment, capable of suppressing or avoiding the above-described interruption variation at the time of abnormality such as an increase in battery internal pressure. For example, it has been found that it is possible to reduce or avoid the interruption variation by providing the stripper disk 130 with grooves having at least two corner portions inside the grooves and having different shapes of the two corner portions in a sectional view. That is, it has been found that providing such a specific groove can provide a battery in which the reliability of the safety valve is further improved.
In the following, such a specific groove will be described in more detail with reference to the drawings.
In the present specification, the “sectional view” related to the expression “sectional view of the groove” and the like is based on a cross section that can be obtained by cutting the safety valve in a plane along the battery axis. It is based on a cross section obtained by cutting each member constituting the safety valve along the thickness direction thereof, that is, for example, when a stripper disk or the like is cut along the thickness direction thereof.
As illustrated in
Without being bound by a specific theory, it is considered that such reduction or avoidance of the interruption variation can be achieved because the stress acting on the groove of the second metal member when the internal pressure of the battery can abnormally increases can more suitably act due to the “groove having corner portions of different shapes inside”. In particular, it is considered that due to such shape anisotropy inside the groove, the stress involved in the groove cutting of the second metal member when the internal pressure of the battery can abnormally increases suitably acts on the suppression of the interruption variation. For example, it is considered that at least an occurrence in which a breaking stress is more effectively easily applied to the vicinity of any corner portion due to the shape anisotropy of the inside of the groove, such as “the groove having the corner portions of mutually different shapes”, can occur, whereby the reduction and avoidance of the interruption variation of the safety valve at the time of abnormality can be achieved. Note that, in the case of a groove having no such shape anisotropy, it can be said that the groove is easily affected by variation in parts and members of the safety valve and variation in assembly, and it can also be said that variation in break sites easily occur with respect to break due to stress acting on the groove of the second metal member. In this regard, in an embodiment, of the present application, it can be said that the cleavage groove is relatively less likely to be affected by variation in parts and members and assembly of the safety valve, and it can also be said that the cleavage groove can contribute to reduction and avoidance of in the interruption variation.
In a preferred aspect, an angle of one of the two corner portions in the groove portion of the second metal member in a sectional view is relatively larger than an angle of the other of the two corner portions. That is, the angle formed by the contour of one corner portion in the sectional view of the second metal member is preferably larger than the angle formed by the contour of the other corner portions. In the aspect illustrated in
In the second metal member, the angle at the relatively large corner portion 135A is preferably larger than the angle at the relatively small corner portion 135B by 5° to 60°. That is, in the sectional view of the groove of the stripper disk 130 corresponding to the second metal member, the difference between the relatively large angle of the angles formed by the two corner portions and the relatively small angle of the two corner portions is preferably 5° to 60°. As illustrated in
From another perspective, it is preferable that the angle at the relatively large corner portion 135A in the second metal member is an obtuse angle, and it is particularly preferable that the angle is more than 100° and 170° or less. That is, in the sectional view of the groove of the stripper disk 130 corresponding to the second metal member, the relatively large angle of the angles formed by the two corner portions is preferably more than 100° and 170° or less. Referring to
The corner portion 135A having a relatively large angle is preferably positioned relatively closer to the battery center side in the second metal member. That is, as illustrated in
In a preferred aspect, the angle formed by the corner portion positioned relatively distally with respect to the battery axis is an acute angle. That is, it is preferable that the groove angle positioned relatively farther from the battery axis forms an acute angle. For example, in the sectional view of the groove, when one corner portion having a relatively large angle is positioned relatively closer to the battery axis side than the other corner portion, the angle at the other corner portion preferably forms an acute angle. Referring to
In the above description, different shapes of two corner portions inside the groove 135 have been described from the viewpoint of “angle” and “relative positional relationship”, but can also be described from the viewpoint of a characteristic contour formed by the second metal member. Specifically, in the present disclosure, the separation distance between the bottom surface contour of the groove and the inner main surface contour of the second metal member may be non-constant in the sectional view of the second metal member.
As illustrated in
Preferably, the separation distance gradually decreases in a direction away from the battery axis. That is, in the sectional view of the second metal member, the separation distance between the bottom surface contour of the groove and the inner main surface contour of the second metal member may gradually decrease toward the peripheral edge side of the member. Referring to
As can be seen from the aspect illustrated in
In a preferred aspect, in a sectional view of the groove, one of the two corner portions of the object forms a rounded corner portion. That is, only one of the two corner portions in the groove portion of the second metal member may be rounded corner portions particularly when viewed in a sectional view. In the stripper disk 130 corresponding to the second metal member, only one of the two corner portions 135A and 135B does not have an angular shape in the sectional view, and may have a rounded shape. For example, in the aspect illustrated in
When one of the two corner portions forms a rounded corner portion, the rounded corner portion is preferably provided relatively closer to the inner peripheral side than a non-rounded corner portion that is not rounded in the second metal member. That is, it is preferable that the rounded corner portion among the two corner portions in the groove portion of the second metal member is positioned relatively closer to the battery axis side. In the stripper disk 130 illustrated in
In the battery of the present disclosure, the groove can correspond to a cleavage groove that contributes to an abnormal increase in the internal pressure of the battery can in the safety valve. In order to act as a more suitable cleavage groove in the safety valve, the installation position thereof is preferably separated from the battery axis. In a preferred aspect, while the interconnection point between the first metal member and the second metal member is positioned on the battery axis, a groove of the second metal member may be provided at a position spaced apart from the battery axis corresponding to the interconnection point between the first metal member and the second metal member. Referring to
A method for producing a battery according to the present disclosure will be described by employing a method for producing a secondary battery as an example according to an embodiment. This secondary battery is produced, for example, by the following procedure.
In the production of the positive electrode, first, the positive electrode active material is, as necessary, mixed with the positive electrode binder, the positive electrode conductive agent, and the like to obtain a positive electrode mixture. Subsequently, the positive electrode mixture is dispersed in, for example, an organic solvent to obtain paste positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to one surface or both surfaces of the positive electrode current collector and then dried to form a positive electrode active material layer. Thereafter, the positive electrode active material layer is compression-molded using a roll press or the like, if necessary. In this case, the positive electrode active material may be heated, or compression molding may be repeated multiple times. In the same manner, a negative electrode can be produced. Specifically, the negative electrode active material, and, for example, a negative positive electrode binder and the negative electrode conductive agent are mixed to obtain a negative electrode mixture. Subsequently, the negative electrode mixture is dispersed in, for example, an organic solvent to obtain paste negative electrode mixture slurry. Then, the negative electrode mixture slurry is applied to one surface or both surfaces of the negative electrode current collector and then dried to form a negative electrode active material layer. Thereafter, the negative electrode active material layer is compression-molded using a roll press or the like, if necessary.
In the case of assembling a secondary battery, for example, the positive electrode lead is connected to the positive electrode current collector by a welding method and the like as well as the negative electrode lead is connected to the negative electrode current collector by a welding method and the like. Subsequently, the positive electrode and the negative electrode are stacked with the separator interposed therebetween, and then, the positive electrode, the negative electrode, and the separator are wound to form the wound electrode body. Subsequently, the center pin is inserted in the winding space of the wound electrode body. Then, the wound electrode body is sandwiched between a pair of insulating plates, and is contained inside the battery can together with the pair of insulating plates. In this case, one end of the positive electrode lead is coupled to the safety valve by, for example, a welding method, and similarly, one end of the negative electrode lead is coupled to the battery can by, for example, a welding method. Next, an electrolytic solution is injected into the battery can, and the wound electrode body is impregnated with the electrolytic solution. Finally, a safety valve is provided at the opening end portion of the battery can with, for example, a holder member interposed therebetween. Thereby, a secondary battery provided with the safety valve is completed.
The groove (that is, the cleavage groove that acts when the internal pressure of the battery can abnormally increases) provided in the second metal member according to the present disclosure can be provided through press die molding when the second metal member is press die molded. In the present disclosure, the cleavage groove of the second metal member has corner portions having shapes different from each other in a sectional view, which is advantageous in that a decrease in the die life can be further suppressed as compared with a case where the groove has a V shape in a sectional view. That is, in the case of a groove having a contour in a sectional view corresponding to a so-called V-notch shape, die wear is relatively fast, but in the present disclosure, such an occurrence can be suitably suppressed.
Although embodiments of the present disclosure have been described herein, in the safety valve provided in the present disclosure, the first metal member, the second metal member, and the insulating member are combined so as to be stacked together with the top cover, the first metal member, the second metal member, and the insulating member are plate-like or disk-like members, the insulating member has a hollow portion or a cavity, and the first metal member and the second metal member are connected with the hollow portion or the cavity of the insulating member interposed therebetween. Due at least to such a configuration, a thin safety valve is provided, which, together with the characteristic of the “two corner portions of different shapes and angles inside the groove”, reduces or avoids variation in break sites of the stripper disk, and/or reduces or avoids variation in interruption pressure (for example, variation in the interruption pressure resulting as a higher interruption pressure). Note that embodiments of the present disclosure described herein are merely exemplary. Therefore, the present disclosure is not limited to those embodiments, and those skilled in the art will readily understand that various aspects can be conceived.
For example, in the safety valve according to the present disclosure, the groove provided in the second metal member may be provided together with the opening part adjacent thereto. That is, an opening part may be provided in the second metal member, and the opening part and the groove may be adjacent to each other in the second metal member. The effect of reducing or avoiding the variation in the break sites as the safety valve is easily revealed, and/or the effect of reducing or avoiding the variation in the interruption pressure (for example, variation in the interruption pressure resulting as a higher interruption pressure) is easily revealed. That is, it is easy to realize a battery in which the reliability of the safety valve is improved from the viewpoint of the interruption variation. For example, in the exemplary embodiment illustrated in
In addition, while the safety valve according to the present disclosure has at least two corner portions inside the groove of the second metal member, the above description mainly refers to the drawing having two corner portions inside the groove. In the present disclosure, since “at least two”, for example, four corner portions may be provided inside the groove of the second metal member. For example, as illustrated in the sectional view of
In the present disclosure, such die press molding may be performed on the premise of a so-called “warpage returning” process. That is, the second metal member is taken out from the die at the time of die press molding, but it may be premised that warpage is corrected prior to such demolding. More specifically, the groove of the second metal member finally obtained through the process of correcting the warpage of the second metal member together with the die used for molding may be regarded as a “groove” in the invention of the present application, that is, such a groove may be regarded as a “cleavage groove having at least two angles having different shapes inside in a sectional view”.
Although the cylindrical battery has been described herein, the present disclosure is not necessarily limited thereto. For example, the battery according to the present disclosure may be a battery having another shape such as a prismatic battery, and the effect of the present disclosure can be similarly exhibited.
The battery can, that is, the exterior body of the battery has been mentioned in the description of the present disclosure, but such an exterior body may have a beadless structure without a beading portion. Since the beadless exterior body does not have a narrowed or constricted portion inside the exterior body (particularly, near the battery axis side), it is possible to secure a wider space for arranging the electrode assembly inside the exterior body. That is, a beadless exterior can or the like in which the inner diameter dimension of the battery can is substantially constant along the battery axis can contribute to realization of a battery having a higher energy density.
Aspects of the battery of the present disclosure are as follows.
Hereinafter, the present disclosure will be described according to Examples in an embodiment. Note that the present disclosure is not limited to the following Examples.
The present disclosure was verified using the following software which is general-purpose software widely used in various technical fields and has high reliability.
Examples 1 to 4 correspond to a “a safety valve case including a stripper disk having at least two corner portions therein in a sectional view and having cleavage grooves having different shapes of the two corner portions”, whereas Comparative Example 1 is a safety valve case including a stripper disk not subjected to this condition.
The battery safety valves were evaluated for “variation in break site” and “variation in interruption pressure”.
Evaluation of variation in break site: A safety valve lid member (top cover) was pressed with a resin part, and a fuel pressure was applied from the second metal member side to interrupt the safety valve. (n=12) At that time, 12 break sites×3 break sites were visually confirmed, the break portions were classified, and the ratio (%) was examined. “0%” indicates that all the three break portions were cut at “breakage on the proximal side of the battery axis”, and there was no groove broken at “breakage on the distal side of the battery axis”, and “100%” indicates that all the three break sites were cut at “breakage on the distal side of the battery axis” or cut (torn) on both the outer side and the inner side.
The evaluation criteria regarding the variation in break sites (variation in break sites accompanied by “breakage on the proximal side of the battery axis”, “breakage on the distal side of the battery axis”, “tearing”, and the like as break sites, shapes, and the like of grooves) are as follows.
Evaluation of variation in interruption pressure: When a case (A) in which variation in break sites was observed in the evaluation of the “variation in break sites” was compared with a case (B) in which variation in interruption sites was not observed, there was a tendency that the interruption pressure was generated as a higher pressure in the case (A) than in the case (B). The average interruption pressure of a predetermined run number was PA (kgf/cm2) with respect to the interruption pressure in the case (A) where the variation in the break sites was observed, and the average interruption pressure PB (kgf/cm2) of a predetermined run number was used with respect to the interruption pressure in the case where there was no variation in the interruption sites, and an index was obtained by comparing them. Specifically, when |PA−PB|≥1 kgf/cm2, it was evaluated that “the interruption pressure greatly varies to 1 kgf/cm2 or more”, when 0.5<|PA−PB|<1 kgf/cm2, it was evaluated that “the interruption pressure is more than 0.5 kgf/cm2 and less than 1 kgf/cm2”, and when 0<|PA−PB|≤0.5 kgf/cm2, it was evaluated that “the variation in the interruption pressure is within 0.5 kgf/cm2”. It is to be noted that when there was no variation in the break sites described above, it was evaluated as “no variation derived from the break sites”.
The evaluation criteria regarding the interruption pressure variation are as follows.
The comprehensive evaluation was evaluated according to the following criteria.
The results are shown in Table 1 below.
From the results in Table 1, it has been found that when the two corner portions inside the groove of the cleavage groove of the stripper disk are different from each other, the stripper disk can exhibit the interruption characteristic in which the interruption variation is reduced in terms of the break site and/or the interruption pressure. That is, it has been found that, in the safety valve according to the present disclosure, the interruption variation at the time of abnormality such as an increase in a battery internal pressure can be suppressed or avoided, and a battery having higher reliability of the safety valve can be more suitably provided from the viewpoint of the interruption variation.
Note that the effects and the like of the embodiments are merely an example. Therefore, the present disclosure is not limited thereto, and may have an additional effect.
The battery (battery such as a primary battery or a secondary battery) according to the present disclosure can be typically used for applications in which use of electric energy is required in an embodiment. For example, a secondary battery according to the present disclosure can be used in various fields in which electric storage is assumed. The battery of the present disclosure can be used in the fields of electricity, information, and communication in which electrical/electronic equipment and the like are used (for example, the fields of electrical/electronic equipment and mobile equipment including mobile phones, smartphones, notebook computers, digital cameras, activity meters, arm computers, electronic paper, wearable devices, and small electronic machines such as RFID tags, card type electronic money, and smartwatches), home and small industrial applications (for example, the fields of electric tools, golf carts, and home, nursing, and industrial robots), large industrial applications (for example, the fields of forklifts, elevators, and harbor cranes), transportation system fields (for example, the fields of hybrid vehicles, electric vehicles, buses, trains, power-assisted bicycles, electric two-wheeled vehicles), power system applications (for example, the fields of various types of power generation, road conditioners, smart grids, and household power storage systems), medical applications (the field of medical equipment such as earphone hearing aids), pharmaceutical applications (the fields of dosage management systems and the like), IoT fields, space and deep sea applications (for example, the fields of space probes and submersibles), and the like, as merely examples.
It should be understood that various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and diminishing without its intended advantages. It is therefore: intended that such changes and modifications be covered by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-170402 | Sep 2023 | JP | national |
