Secondary battery

Abstract

The present invention relates to a secondary battery, and addresses the technical problem of providing a secondary battery in which a first breaking portion can operate to gradually reduce internal pressure when the internal pressure increases due to heat exposure or an electrical short circuit, and a second breaking portion can operate to discharge an internal heat source to the outside when thermal runaway begins and the internal pressure increases further. To this end, the present invention provides a secondary battery comprising: a case; an electrode assembly accommodated in the case; and a cap plate for sealing the case, wherein the cap plate includes a first breaking portion and a second breaking portion provided around the first breaking portion.

Description

secondary battery

[0001] The present invention relates to an interest battery.

[0002] These are possible batteries. Low-capacity secondary batteries are used in small, portable electronic devices such as smartphones, feature phones, laptop computers, digital cameras, and camcorders, while large-capacity secondary batteries are widely used as power sources for driving motors in hybrid and electric vehicles, as well as for power storage. These secondary batteries include an electrode assembly consisting of a positive and negative electrode, a case housing the electrode assembly, and electrode terminals connected to the electrode assembly.

[0003] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0004] The present invention provides a secondary battery in which a first rupture unit operates to gradually reduce the internal pressure when the internal pressure increases due to heat exposure or an electrical short circuit, and a second rupture unit operates to discharge the internal heat source to the outside when the internal pressure further increases due to the start of thermal runaway.

[0005] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0006] According to one embodiment of the present invention for solving the above technical problem, a secondary battery includes a case; an electrode assembly accommodated in the case; and a cap plate sealing the case, wherein the cap plate may include a first break portion and a second break portion provided around the first break portion, and a break pressure of the first break portion and a break pressure of the second break portion may be different from each other.

[0007] In one or more embodiments, the breaking pressure of the first breaking portion may be less than the breaking pressure of the second breaking portion.

[0008] In one or more embodiments, the depth of the first fracture portion and the depth of the second fracture portion may be different from each other.

[0009] In one or more embodiments, the depth of the first fracture portion may be deeper than the depth of the second fracture portion.

[0010] In one or more embodiments, the thickness of the first fracture portion and the thickness of the second fracture portion may be different from each other.

[0011] In one or more embodiments, the thickness of the first fracture portion may be thinner than the thickness of the second fracture portion.

[0012] In one or more embodiments, the first break portion may include a plurality of notches provided in a mutually intersecting manner at the center of the cap plate.

[0013] In one or more embodiments, the second breaking portion may include a notch provided in the form of a circle or arc along the perimeter of the cap plate.

[0014] In one or more embodiments, the cap plate may include a first surface facing the electrode assembly and a second surface opposite the first surface, and the first break portion and the second break portion may be provided on the first surface or the second surface.

[0015] In one or more embodiments, the first break portion may be provided in a central region or an eccentric region of the cap plate.

[0016] In one or more embodiments, the diameter of the second break portion may be 40% to 95% of the diameter of the electrode assembly.

[0017] In one or more embodiments, the first fracture portion may include a slope that gradually deepens from the surface of the cap plate.

[0018] In one or more embodiments, the first fracture portion may include a flat surface extending from the inclined surface and parallel to the surface of the cap plate.

[0019] In one or more embodiments, the case may include a beading portion recessed inwardly in a region between the electrode assembly and the cap plate and a crimping portion bent inwardly to cover the cap plate, wherein the cap plate may be joined by interposing an insulating gasket between the beading portion and the crimping portion.

[0020] In one or more embodiments, the cap plate may include a first flat portion provided in an area corresponding to the center of the electrode assembly, a first bent portion bent in a direction away from the electrode assembly along a periphery of the first flat portion, a second flat portion extending horizontally from the periphery of the first bent portion, a second bent portion bent in a direction closer to the electrode assembly from the second flat portion, and a third flat portion extending horizontally from the periphery of the second bent portion and coupled between a beading portion and a crimping portion of the case by interposing an insulating gasket therebetween.

[0021] In one or more embodiments, when the thickness of the second break portion is less than 10% of the total thickness of the cap plate, the second break portion may be spaced apart from the second bend portion by 2 mm to 3 mm.

[0022] In one or more embodiments, when the thickness of the second break portion is 10% to 20% of the total thickness of the cap plate, the second break portion may be spaced apart from the second bend portion by 0.5 mm to 2 mm.

[0023] In one or more embodiments, the second breaking portion may be spaced apart from the inner end of the beading portion, the crimping portion, or the insulating gasket.

[0024] In one or more embodiments, the cap plate may be welded to the case.

[0025] In one or more embodiments, the electrode assembly may include a first tab and a second tab facing the cap plate, the first tab being electrically connected to a rivet terminal penetrating the case through the first collector plate, and the second tab being electrically connected to the case through the second collector plate.

[0026] According to the present invention, a secondary battery is provided, which provides a first rupture unit that operates at a first internal pressure and a second rupture unit that operates at a second internal pressure higher than the first internal pressure, so that when the internal pressure reaches the first internal pressure due to heat exposure or an electrical short, the first rupture unit operates to gradually reduce the internal pressure, and when thermal runaway starts and the internal pressure reaches the second internal pressure higher than the first internal pressure, the second rupture unit operates to discharge the internal heat source to the outside.

[0027] However, the effects that can be obtained through the present invention are not limited to the effects described above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0028] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0029] FIG. 1a and FIG. 1b are a perspective view and a cross-sectional view illustrating an exemplary cylindrical secondary battery according to the present invention.

[0030] FIGS. 2A to 2C are cross-sectional views illustrating a portion of an exemplary cylindrical secondary battery according to the present invention, and FIG. 2D is a bottom view.

[0031] FIG. 3a is a bottom view illustrating a portion of an exemplary cylindrical secondary battery according to the present invention, and FIG. 3b is a plan view.

[0032] FIGS. 4A and 4B are bottom views illustrating a portion of an exemplary cylindrical secondary battery according to the present invention.

[0033] FIG. 5 is a cross-sectional view illustrating a portion of an exemplary cylindrical secondary battery according to the present invention.

[0034] FIGS. 6A to 6D are bottom views illustrating a cap plate of an exemplary cylindrical secondary battery according to the present invention.

[0035] FIGS. 7A to 7C are cross-sectional views illustrating a portion of an exemplary cylindrical secondary battery according to the present invention.

[0036] FIG. 8 is a cross-sectional view illustrating a portion of an exemplary cylindrical secondary battery according to the present invention.

[0037] FIG. 9 is a drawing illustrating the vent operation of an exemplary cylindrical secondary battery according to the present invention.

[0038] FIGS. 10A and 10B are a cross-sectional view and a cross-sectional perspective view illustrating a cap plate of an exemplary cylindrical secondary battery according to the present invention.

[0039] FIGS. 11a and 11b are a cross-sectional view and a cross-sectional perspective view illustrating a cap plate of an exemplary cylindrical secondary battery according to the present invention.

[0040] FIGS. 12A and 12B are perspective views illustrating a battery pack including an exemplary cylindrical secondary battery according to the present invention.

[0041] FIGS. 13A and 13B are perspective and side views illustrating a vehicle including an exemplary battery pack according to the present invention.

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of a term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as substitutes for them at the time of filing this application.

[0043] Additionally, when used herein, the terms "comprise", "include" and / or "comprising", "including" specify the presence of stated features, numbers, steps, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, elements and / or groups thereof.

[0044] Additionally, to facilitate understanding of the invention, the attached drawings may not be drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0045] The statement that two compared objects are "identical" means "substantially identical." Therefore, "substantially identical" may include deviations considered low in the art, such as deviations of less than 5%. Furthermore, uniformity of a parameter over a given region may imply uniformity on average.

[0046] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0047] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0048] Any configuration being placed "on (or under)" or "above (or below)" a component may mean not only that any configuration is placed in contact with the upper surface (or lower surface) of said component, but also that other configurations may intervene between said component and any configuration placed on (or below) said component.

[0049] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to each other, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component. Furthermore, when it is said that a part is electrically coupled to another part, this includes not only cases where they are directly connected, but also cases where they are connected with another element in between.

[0050] When reference is made throughout the specification to "A and / or B," this means A, B, or A and B, unless otherwise stated. In other words, "and / or" includes all or any combination of the listed items. When reference is made to "C through D," this means C or more and D or less, unless otherwise stated.

[0051] The terminology used herein is for the purpose of describing embodiments of the present disclosure and is not intended to be limiting of the present disclosure.

[0052] FIGS. 1A and 1B are perspective views and cross-sectional views illustrating an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in FIGS. 1A and 1B, the exemplary secondary battery (100) according to the present invention may include a case (110), an electrode assembly (120), and a cap plate (130). In one or more embodiments, the exemplary secondary battery (100) according to the present invention may further include a first collector plate (141), a second collector plate (142), and a rivet terminal (150).

[0053] The case (110) accommodates the electrode assembly (120) and the electrolyte, and together with the cap plate (130), can form the outer shape of the secondary battery (100). The case (110) can include a base portion (111) having a substantially circular shape and a cylindrical side wall portion (112) extending downward from the base portion (111). The case (110) can include or be referred to as a can, an outer material, or a housing. In one or more embodiments, the case (110) can be configured in various shapes, such as a pouch shape, in addition to a circular shape. In addition, the case (110) can include a metal, such as steel, nickel-plated steel, a steel alloy, aluminum, an aluminum alloy, a cooling sheet for deep drawing (SPCE), or a laminate film or plastic that constitutes a pouch. In one or more embodiments, the side wall portion (112) of the case (110) may further include a beading portion (113) that is recessed inwardly in a region between the electrode assembly (120) and the cap plate (130) and a crimping portion (114) that is bent inwardly to cover the cap plate (130). The electrode assembly (120) can be stably fixed inside the case (110) by the base portion (111) of the case (110) and the beading portion (113), and the cap plate (130) can be stably fixed by the crimping portion (114).

[0054] The electrode assembly (120) may include a first electrode plate (121), a second electrode plate (122), and a separator (123) between the first electrode plate (121) and the second electrode plate (122), and may be wound in a jelly-roll shape. In one or more embodiments, a hollow core (124) may be provided longitudinally at the center of the electrode assembly (120). The electrode assembly (120) may include or be referred to as an electrode group, an electrode body, or an electrode. The electrode assembly (120) may be connected to an external device to be charged or discharged. In one or more embodiments, a center pin (optional) may be coupled to the core (124).

[0055] The first electrode plate (121) may include a first substrate (1211) and a first active material layer (1212) positioned on the first substrate (1211). A first non-conductive portion or first tab (1213) of the first substrate (1211) where the first active material layer (1212) is not positioned may extend outward (e.g., upward), and the first tab (1213) may be electrically connected to the first current collector plate (141).

[0056] The second electrode plate (122) may include a second substrate (1221) and a second active material layer (1222) positioned on the second substrate (1221). A second non-conductive portion or second tab (1223) of the second substrate (1221) where the second active material layer (1222) is not positioned may extend outward (e.g., downward), and the second tab (1223) may be electrically connected to the second collector plate (142). In one or more embodiments, the first tab (1213) and the second tab (1223) may extend in opposite directions.

[0057] The first electrode plate (121) can function as an anode. In this case, the first substrate (1211) can be composed of, for example, aluminum foil, and the first active material layer (1212) can include, for example, a transition metal oxide. The second electrode plate (122) can function as an anode. In this case, the second substrate (1221) can be composed of, for example, copper foil or nickel foil, and the second active material layer (1222) can include, for example, graphite and / or silicon.

[0058] The separator (123) can prevent short circuiting between the first electrode plate (121) and the second electrode plate (122) while allowing movement of lithium ions. In one or more embodiments, the separator (123) can be positioned on opposite sides of the first electrode plate (121), or on opposite sides of the second electrode plate (122).

[0059] In one or more embodiments, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used as the positive electrode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0060] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0061] As an example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li aNiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0062] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0063] A positive electrode for a lithium secondary battery may include a current collector (e.g., a first substrate) and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material.

[0064] The content of the positive electrode active material may be 90 wt% to 99.5 wt% with respect to 100 wt% of the positive electrode active material layer, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0065] Aluminum may be used as the current collector, but is not limited thereto.

[0066] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0067] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0068] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x ≤ 2), a Si-based alloy, or a combination thereof.

[0069] The above silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles.

[0070] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0071] A negative electrode for a lithium secondary battery may include a current collector (e.g., a second substrate) and a negative electrode active material layer formed on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0072] For example, the negative electrode active material layer may include 90 to 99 wt% of the negative electrode active material, 0.5 to 5 wt% of the binder, and 0 to 5 wt% of the conductive material.

[0073] The above binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof. When an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included.

[0074] The current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0075] An electrolyte for a lithium secondary battery may include a non-aqueous organic solvent and a lithium salt.

[0076] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0077] The above non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof, and may be used alone or in combination of two or more thereof.

[0078] Additionally, when using a carbonate solvent, a mixture of cyclic carbonate and chain carbonate can be used.

[0079] As described above, a lithium secondary battery may have a separator between the positive and negative electrodes. Such a separator may be a multilayer film of polyethylene, polypropylene, polyvinylidene fluoride, or two or more layers thereof.

[0080] The above separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof, positioned on one or both sides of the porous substrate.

[0081] The above organic material may include a polyvinylidene fluoride-based antibody or a (meth)acrylic polymer.

[0082] The above inorganic materials are Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, It may include inorganic particles selected from, but not limited to, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0083] The organic and inorganic substances may be mixed and present in one coating layer, or a coating layer including an organic substance and a coating layer including an inorganic substance may be present in a laminated form.

[0084] The cap plate (130) may be coupled to the lower side of the case (110) to seal the case (110). The cap plate (130) may be provided in a generally circular shape. In one or more embodiments, the periphery of the cap plate (130) may be coupled to the side wall portion (112) of the case (110) to seal the case (110). In one or more embodiments, the periphery of the cap plate (130) may be coupled by interposing an insulating gasket (115) between the beading portion (113) and the crimping portion (114). The cap plate (130) may include or be referred to as a vent plate, a cover plate, or a sealing plate. The cap plate (130) may be composed of iron, nickel-plated iron, stainless steel, aluminum, or an aluminum alloy. When the secondary battery (100) is exposed to heat or is electrically short-circuited (e.g., internal short-circuit or external short-circuit) and the internal pressure is higher than the reference pressure, the cap plate (130) can be opened to reduce the internal pressure and discharge the internal heat source to the outside.

[0085] In one or more embodiments, the cap plate (130) may include a first break portion (131) provided in a central region or an eccentric region and a second break portion (132) provided around the first break portion (131). In one or more embodiments, the break pressure of the first break portion (131) and the break pressure of the second break portion (132) may be different from each other. In one or more embodiments, the break pressure of the first break portion (131) may be less than the break pressure of the second break portion (132). In one or more embodiments, the break pressure of the second break portion (132) may be greater than the break pressure of the first break portion (131). In one or more embodiments, the depth of the first break portion (131) and the depth of the second break portion (132) may be different from each other. In one or more embodiments, the depth of the first fracture portion (131) may be deeper than the depth of the second fracture portion (132). In one or more embodiments, the depth of the second fracture portion (132) may be shallower than the depth of the first fracture portion (131). In one or more embodiments, the thickness of the first fracture portion (131) and the thickness of the second fracture portion (132) may be different from each other. In one or more embodiments, the thickness of the first fracture portion (131) may be thinner than the thickness of the second fracture portion (132). In one or more embodiments, the thickness of the second fracture portion (132) may be thicker than the thickness of the first fracture portion (131).

[0086] A first collector plate (141) may be interposed between the electrode assembly (120) and the base portion (111) of the case (110). The first collector plate (141) may have an approximately circular shape. In one or more embodiments, a first tab (1213) of the electrode assembly (120) may be electrically connected (e.g., laser welded) to a lower surface of the first collector plate (141). In one or more embodiments, an upper surface of the first collector plate (141) may be electrically connected (e.g., laser welded) to a rivet terminal (150). The first collector plate (141) may include or be referred to as a current collector, a current collector member, or a conductor. The first collector plate (141) may include aluminum, an aluminum alloy, steel, nickel-plated steel, or a steel alloy. The first collector plate (141) can provide a current flow path between the electrode assembly (120) and the rivet terminal (150).

[0087] A second collector plate (142) may be interposed between the electrode assembly (120) and the cap plate (130). The second collector plate (142) may have a substantially circular shape. In one or more embodiments, a second tab (1223) of the electrode assembly (120) may be electrically connected (e.g., laser welded) to an upper surface of the second collector plate (142). In one or more embodiments, a perimeter of the second collector plate (142) may be electrically connected to a side wall (112) of the case (110). In one or more embodiments, a perimeter of the second collector plate (142) may be electrically connected to a lower side of the beading portion (113). In one or more embodiments, a perimeter of the second collector plate (142) may be interposed between a lower side of the beading portion (113) and an upper side of the insulating gasket (115). The second collector plate (142) may include or be referred to as a current collector, a current collector member, or a conductor. The second collector plate (142) may include copper, a copper alloy, steel, nickel-plated steel, a steel alloy, aluminum, or an aluminum alloy. The second collector plate (142) may provide a current flow path between the electrode assembly (120) and the case (110).

[0088] The rivet terminal (150) may include a rivet body portion (151), a rivet inner plate (152), and a rivet outer plate (153). The rivet body portion (151) may be coupled by penetrating the base portion (111), and a sealing gasket (1511) may surround the periphery of the rivet body portion (151). The rivet inner plate (152) may be electrically connected (e.g., laser welding) to the first collector plate (141), and an inner insulating member (1521) may be interposed between the rivet inner plate (152) and the base portion (111). The rivet outer plate (153) may be positioned on the base portion (111), and an outer insulating member (1531) may be interposed between the rivet outer plate (153) and the base (111). The rivet terminal (150) may include or be referred to as an external terminal or a battery terminal. The rivet terminal (150) may include aluminum, an aluminum alloy, copper, a copper alloy, nickel, or a nickel alloy. The rivet terminal (150) may function as an external terminal (e.g., a positive terminal), and the base portion (111) may also function as an external terminal (e.g., a negative terminal).

[0089] In this way, the secondary battery (100) according to the present invention provides a cap plate (130) including a first rupture unit (131) that operates at a first internal pressure (e.g., 10 kgf) and a second rupture unit (132) that operates at a second internal pressure (e.g., 20 kgf) higher than the first internal pressure, so that when the internal pressure reaches the first internal pressure due to heat exposure or an electrical short, the first rupture unit (131) operates to gradually reduce the internal pressure, and when thermal runaway starts and the internal pressure reaches a second internal pressure higher than the first internal pressure, the second rupture unit (132) operates to discharge the internal heat source to the outside.

[0090] FIGS. 2A to 2C are cross-sectional views illustrating a portion of an exemplary cylindrical secondary battery (100) according to the present invention, and FIG. 2D is a bottom view. As illustrated in FIGS. 2A to 2C, the cap plate (130) may include a first surface (1301) that is approximately flat and faces the electrode assembly (120), and a second surface (1302) that is approximately flat and is opposite to the first surface (1301). The first break portion (131) and / or the second break portion (132) may be provided on the first surface (1301) or the second surface (1302) of the cap plate (130). In one or more embodiments, as illustrated in FIG. 2a, the first break portion (131) and the second break portion (132) may be provided on the second surface (1302) of the cap plate (130), and as illustrated in FIG. 2b, the first break portion (131) and the second break portion (132) may be provided on the first surface (1301) of the cap plate (130). Meanwhile, as illustrated in FIG. 2d, the first break portion (131) may include a plurality of notches provided in a mutually intersecting shape at approximately the center of the cap plate (130), and further, the second break portion (132) may include a notch provided in the shape of a circle or an arc along the perimeter of the cap plate (130).

[0091] In one or more embodiments, the first fracture portion (131) and the second fracture portion (132) may have a fracture depth (or a residual thickness after fracture) and / or a fracture length controlled to set a fracture pressure. As described above, the fracture pressure of the first fracture portion (131) may be set to be smaller than the fracture pressure of the second fracture portion (132), or in other words, the fracture pressure of the second fracture portion (132) may be set to be larger than the fracture pressure of the first fracture portion (131). In addition, as described above, the depth of the first fracture portion (131) may be set to be deeper than the depth of the second fracture portion (132), or in other words, the depth of the second fracture portion (132) may be set to be shallower than the depth of the first fracture portion (131). In addition, as described above, the thickness of the first fracture portion (131) may be set thinner than the thickness of the second fracture portion (132), or, in other words, the thickness of the second fracture portion (132) may be set thicker than the thickness of the first fracture portion (131).

[0092] FIG. 3a is a bottom view showing a part of an exemplary cylindrical secondary battery (100) according to the present invention, and FIG. 3b is a plan view. As illustrated in FIGS. 3A and 3B, the cap plate (130) may include a first flat portion (1331) relatively close to the electrode assembly (120), a first bent portion (1332) bent along the periphery of the first flat portion (1331) in a direction away from the electrode assembly (120), a second flat portion (1333) extending horizontally from the periphery of the first bent portion (1332), a second bent portion (1334) bent from the second flat portion (1333) in a direction closer to the electrode assembly (120), and a third flat portion (1335) extending horizontally from the periphery of the second bent portion (1334) and coupled to the side wall portion (112) of the case (110) (i.e., coupled by interposing an insulating gasket (115) between the beading portion (113) and the crimping portion (114). In one or more embodiments, the first rupture portion (131) may be provided on the first flat portion (1331), and the second rupture portion (132) may be provided on the second flat portion (1333). In one or more embodiments, the first rupture portion (131) may be provided on the first surface (1301) of the first flat portion (1331), and the second rupture portion (132) may be provided on the first surface (1301) of the second flat portion (1333). Accordingly, the first rupture portion (131) and the second rupture portion (132) may not be observed from the outside of the secondary battery (100). In one or more embodiments, the first rupture portion (131) may be provided on the second surface (1302) of the first flat portion (1331), and the second rupture portion (132) may be provided on the second surface (1302) of the second flat portion (1333). In one or more embodiments, the cross-sectional shape of the first rupture portion (131) may be approximately rectangular and approximately V-shaped, and the cross-sectional shape of the second rupture portion (132) may be approximately V-shaped.

[0093] FIGS. 4A and 4B are bottom views illustrating a portion of an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in FIGS. 4A and 4B, the second break portion (132) may be provided in a circular or arc shape along the periphery of the second flat portion (1333). The second break portion (132) illustrated in FIG. 4A may be completely separated from the cap plate (130) when broken, but the second break portion (132) illustrated in FIG. 4B may remain connected to the cap plate (130) when broken. In other words, as illustrated in FIG. 4B, since the second break portion (132) is provided in an arc shape, the second flat portion (1333) may be connected to the second bent portion (1334) via the bridge (1321). Therefore, when the second rupture portion (132) is broken, the first flat portion (1331), the first bent portion (1332), and the second flat portion (1333) can still be connected to the second bent portion (1334) through the bridge (1321).

[0094] FIG. 5 is a cross-sectional view illustrating a portion of an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in FIG. 5, a cap plate (130) may be welded (e.g., laser welded) to a side wall portion (112) of a case (110). In one or more embodiments, a second break portion (132) may be provided spaced apart from the side wall portion (112) of the case (110) by about 1 mm to about 2 mm so as not to be damaged by welding. In one or more embodiments, a diameter of the second break portion (132) may be about 40% to about 95% of a diameter of the electrode assembly (120). When the diameter of the second rupture portion (132) is approximately 40% to approximately 95% of the diameter of the electrode assembly (120), the electrode assembly (120) can be easily ejected to the outside of the case (110) due to an increase in internal pressure when the battery is exposed to heat or short-circuited. In one or more embodiments, the first rupture portion (131) may be provided at the center of the cap plate (130) where swelling most easily occurs, but may also be provided at an eccentric position from the center of the cap plate (130) as required for the process.

[0095] FIGS. 6A to 6D are bottom views illustrating a cap plate (130) of an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in FIG. 6A, the first break portion (131) may include three notches extending radially from the center of the cap plate (130), as illustrated in FIG. 6B, the first break portion (131) may include four notches extending radially from the center of the cap plate (130), as illustrated in FIG. 6C, the first break portion (131) may include five notches extending radially from the center of the cap plate (130), and as illustrated in FIG. 6D, the first break portion (131) may include six notches extending radially from the center of the cap plate (130). In addition, the first breaking portion (131) may be provided in a circular, triangular, square, pentagonal, hexagonal or polygonal shape, and in particular, may be provided in any shape as long as it has a breaking pressure lower than that of the second breaking portion (132).

[0096] FIGS. 7A to 7C are cross-sectional views illustrating a portion of an exemplary cylindrical secondary battery (100) according to the present invention. Here, FIGS. 7A to 7C illustrate the relationship between the second break portion (132) and the hinge (134). As illustrated in FIGS. 7A to 7C, the cap plate (130) may include a first flat portion (1331), a first bent portion (1332), a second flat portion (1333), a second bent portion (1334), and a third flat portion (1335), and here, the second bent portion (1334) may be defined as the hinge (132) of the second break portion (132). As illustrated in FIG. 7a, when the thickness of the second fracture portion (132) is less than approximately 10% (e.g., less than approximately 0.1 mm) of the total thickness of the cap plate (130) and the second fracture portion (132) is provided near the hinge (134), the second fracture portion (132) is cracked during or after the manufacturing process of the secondary battery (100). However, as illustrated in FIG. 7b, when the thickness of the second fracture portion (132) is less than approximately 10% (e.g., less than approximately 0.1 mm) of the total thickness of the cap plate (130) and the second fracture portion (132) is provided spaced apart from the hinge (134) by approximately 2 mm to approximately 3 mm, the second fracture portion (132) is not cracked during or after the manufacturing process of the secondary battery (100). In addition, as illustrated in FIG. 7c, when the thickness of the second fracture portion (132) is approximately 10% to approximately 20% of the total thickness of the cap plate (130) (e.g., approximately 0.15 mm to approximately 0.2 mm) and the second fracture portion (132) is provided at a distance of approximately 0.5 mm to approximately 2 mm from the hinge (134), the second fracture portion (132) is not cracked during or after the manufacturing process of the secondary battery (100).In this way, in the present invention, by controlling the depth of the second break portion (132) provided in the cap plate (130) and the distance between the hinge (134) and the second break portion (132), cracking of the second break portion (132) can be prevented, for example, under stress provided when forming the beading portion (113) and / or the crimping portion (114).

[0097] FIG. 8 is a cross-sectional view illustrating a portion of an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in FIG. 8, in the case of a hinge-less secondary battery (100), the second break portion (132) may be provided spaced apart from the inner end of the bead portion (113), the inner end of the insulating gasket (115), and / or the inner end of the crimping portion (114). In one or more embodiments, the second break portion (132) may be provided spaced apart from the aforementioned inner end by approximately 1 mm or more. However, the diameter of the second break portion (132) should be greater than approximately 40% of the diameter of the electrode assembly (120) as described above. Under these conditions, when the secondary battery (100) is exposed to heat or is short-circuited, the second rupture portion (132) operates so that the electrode assembly (120) can be easily discharged to the outside of the case (110). In one or more embodiments, the positions of the lower inner end provided at the bottom and the upper inner end provided at the top of the insulating gasket (115) may be different from each other, and even in this case, the position of the second rupture portion (132) may be provided spaced apart from the lower inner end and the upper inner end. In one or more embodiments, the lower inner end of the insulating gasket (115) may be longer than the upper inner end of the insulating gasket (115).

[0098] FIG. 9 is a diagram illustrating a vent operation of an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in (A) of FIG. 9, when the secondary battery (100) has a normal internal pressure, the first rupture portion (131) and the second rupture portion (132) provided on the cap plate (130) remain unbroken. However, as illustrated in (B) of FIG. 9, when the secondary battery (100) is exposed to heat or electrically shorted, the internal pressure increases, and when the internal pressure becomes higher than a preset first internal pressure, the first rupture portion (131) is broken first. Accordingly, the internal pressure of the secondary battery (100) gradually decreases. Subsequently, as illustrated in (C) of FIG. 9, when the internal pressure of the secondary battery (100) becomes higher than a preset second internal pressure that is higher than the first internal pressure, the second rupture portion (132) is broken. Accordingly, a heat source (e.g., electrode assembly (120) and electrolyte, etc.) located inside the secondary battery (100) can be discharged to the outside of the case (110). That is, when the first rupture part (131) operates, the internal pressure decreases gradually, and when the second rupture part (132) operates, the internal pressure decreases rapidly. However, since a bridge (1321) is provided between the second rupture parts (132), some areas of the cap plate (130) may not be completely separated to the outside.

[0099] FIGS. 10A and 10B are a cross-sectional view and a cross-sectional perspective view illustrating a cap plate (130) of an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in FIGS. 10A and 10B, the first break portion (131) may include an inclined surface (1311) that gradually deepens from a surface (e.g., a first surface (1301) or a second surface (1302)) of the cap plate (130). FIGS. 11A and 11B are a cross-sectional view and a cross-sectional perspective view illustrating a cap plate (130) of an exemplary cylindrical secondary battery (100) according to the present invention. As illustrated in FIGS. 11A and 11B, the first fracture portion (131) may include an inclined surface (1311) that gradually deepens from a surface of the cap plate (130) (e.g., the first surface (1301) or the second surface (1302)), and a flat surface (1312) (e.g., the first surface (1301) or the second surface (1302)) that extends from the inclined surface (1311) and is parallel to the surface of the cap plate (130). In this way, the present invention can control the fracture pressure and / or fracture path of the first fracture portion (131) by gradually varying the depth and / or thickness of the first fracture portion (131) along the radial or diametrical direction of the cap plate (130).

[0100] FIGS. 12A and 12B are perspective views illustrating a battery pack (300) including an exemplary cylindrical secondary battery according to the present invention. Referring to FIGS. 11A and 11B , the battery pack (300) may include a plurality of battery modules (200) and a housing (310) for accommodating the plurality of battery modules (200). For example, the housing (310) may include first and second housings (311, 312) that are coupled in a direction facing each other with the plurality of battery modules (200) interposed therebetween. The plurality of battery modules (210) may be electrically connected to each other using a bus bar (251), and the plurality of battery modules (200) may be electrically connected to each other in a series / parallel or series-parallel hybrid manner to obtain a required electrical output. In the drawings, for convenience of illustration, components such as a bus bar, a cooling unit, and an external terminal for electrically connecting battery cells are omitted. In one or more embodiments, the battery pack (300) may be mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may include a four-wheel vehicle or a two-wheel vehicle.

[0101] Figures 13a and 13b are perspective views and side views illustrating a vehicle (400, 500) including an exemplary battery pack (300) according to the present invention. In Figure 12a, the battery pack (300) may include a battery pack cover (311) (which may correspond to the first housing) which is a part of a vehicle underbody (410) and a pack frame (312) (which may correspond to the second housing) which is disposed at a lower portion of the vehicle underbody (410). The battery pack cover (311) and the pack frame (312) may be formed integrally with the vehicle floor (420). The vehicle underbody (410) separates the interior and exterior of the vehicle, and the pack frame (312) may be disposed at the exterior of the vehicle.

[0102] As illustrated in FIG. 12b, the vehicle (500) may be formed by combining additional components, such as a hood (510) at the front of the vehicle and fenders (520) positioned at the front and rear of the vehicle, respectively, with the vehicle body (400). The vehicle (500) includes a battery pack (300) including a battery pack cover (311) and a pack frame (312), and the battery pack (300) may be combined with the vehicle body component (400).

[0103] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. Case; An electrode assembly accommodated in the above case; and Including a cap plate sealing the above case, A secondary battery, wherein the cap plate includes a first fracture portion and a second fracture portion provided around the first fracture portion, and the fracture pressure of the first fracture portion and the fracture pressure of the second fracture portion are different from each other.

2. In paragraph 1, A secondary battery, wherein the breaking pressure of the first breaking portion is lower than the breaking pressure of the second breaking portion.

3. In paragraph 1, A secondary battery in which the depth of the first fracture portion and the depth of the second fracture portion are different from each other.

4. In paragraph 3, A secondary battery, wherein the depth of the first fracture portion is deeper than the depth of the second fracture portion.

5. In paragraph 1, A secondary battery in which the thickness of the first fracture portion and the thickness of the second fracture portion are different from each other.

6. In paragraph 5, A secondary battery, wherein the thickness of the first fracture portion is thinner than the thickness of the second fracture portion.

7. In paragraph 1, A secondary battery, wherein the first rupture portion includes a plurality of notches provided in a mutually intersecting manner at the center of the cap plate.

8. In paragraph 1, A secondary battery, wherein the second breaking portion includes a notch provided in the form of a circle or an arc along the periphery of the cap plate.

9. In paragraph 1, A secondary battery, wherein the cap plate includes a first surface facing the electrode assembly and a second surface opposite the first surface, and the first break portion and the second break portion are provided on the first surface or the second surface.

10. In paragraph 1, A secondary battery, wherein the first breaking portion is provided in the central region or eccentric region of the cap plate.

11. In paragraph 1, A secondary battery, wherein the diameter of the second rupture portion is 40% to 95% of the diameter of the electrode assembly.

12. In paragraph 1, A secondary battery, wherein the first fracture portion includes a slope that gradually deepens from the surface of the cap plate.

13. In paragraph 12, A secondary battery, wherein the first fracture portion includes a flat surface extending from the inclined surface and parallel to the surface of the cap plate.

14. In paragraph 1, A secondary battery, wherein the case includes a beading portion sunk inwardly in the area between the electrode assembly and the cap plate and a crimping portion bent inwardly to cover the cap plate, and the cap plate is joined by interposing an insulating gasket between the beading portion and the crimping portion.

15. In paragraph 1, A secondary battery, wherein the cap plate includes a first flat portion provided in an area corresponding to the center of the electrode assembly, a first bent portion bent in a direction away from the electrode assembly along the periphery of the first flat portion, a second flat portion extending horizontally from the periphery of the first bent portion, a second bent portion bent in a direction closer to the electrode assembly from the second flat portion, and a third flat portion extending horizontally from the periphery of the second bent portion and joined by interposing an insulating gasket between a beading portion and a crimping portion of the case.

16. In paragraph 15, A secondary battery, wherein the second breaking portion is spaced apart from the second bend portion by 2 mm to 3 mm when the thickness of the second breaking portion is less than 10% of the total thickness of the cap plate.

17. In paragraph 15, A secondary battery, wherein the second breaking portion is spaced apart from the second bend portion by 0.5 mm to 2 mm when the thickness of the second breaking portion is 10% to 20% of the total thickness of the cap plate.

18. In paragraph 14, A secondary battery, wherein the second breaking portion is spaced apart from the inner end of the beading portion, the crimping portion or the insulating gasket.

19. In paragraph 1, The above cap plate is welded to the case, a secondary battery.

20. In paragraph 1, The electrode assembly includes a first tab and a second tab facing the cap plate, A secondary battery, wherein the first tab is electrically connected to a rivet terminal penetrating the case through the first collector plate, and the second tab is electrically connected to the case through the second collector plate.

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