Secondary battery

Abstract

The present invention relates to a secondary battery in which a vent expansion part formed from a material having a lower melting point than a cap plate is provided on the outer side, in plan view, of a safety vent so as to melt when a flame occurs inside the secondary battery, thereby enabling an open area to be expanded compared to when only the safety vent ruptures, and thus facilitating the discharging of the flame. Disclosed, according to one embodiment, is a secondary battery comprising: an electrode assembly having a first electrode plate, a separator, and a second electrode plate; a case receiving the electrode assembly therein and having an open lower end portion; a terminal coupled by passing through the upper surface portion of the case; and a cap plate for sealing the lower end portion of the case, wherein the cap plate comprises a vent expansion part which is formed from a material having a lower melting point than the other areas of the cap plate, and which has a ring shape in plan view.

Description

secondary battery

[0001] The present disclosure relates to a secondary battery.

[0002] Rechargeable batteries are power storage systems that provide excellent energy density by converting electrical energy into the form of chemical energy for storage. Unlike primary batteries, which are non-rechargeable, rechargeable batteries are widely used in IT devices such as smartphones, cellular phones, laptops, and tablet PCs. Recently, interest in electric vehicles has increased due to the need to prevent environmental pollution, leading to the adoption of high-capacity rechargeable batteries in these vehicles. These rechargeable batteries require characteristics such as high density, high output, and stability.

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

[0004] The present invention provides a vent expansion portion made of a material having a lower melting point than that of a cap plate on the flat outer side of the safety vent, thereby expanding the open area to facilitate flame evacuation when a flame occurs inside a secondary battery and melts, compared to the case where only the safety vent is ruptured.

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

[0006] A secondary battery according to an embodiment of the present invention for solving the above technical problem comprises an electrode assembly having a first electrode plate, a separator, and a second electrode plate, a case having an open bottom end that accommodates the electrode assembly, a terminal coupled by penetrating the upper surface of the case, and a cap plate that seals the bottom end of the case, wherein the cap plate is made of a material having a melting point lower than that of other regions of the cap plate and may include a vent expansion portion formed in a planar ring shape.

[0007] The above cap plate may further include a safety vent that is thinner than other areas and is located inwardly in a planar manner compared to the vent extension.

[0008] The above safety vent may be in the shape of a flat ring.

[0009] The above vent extension may not overlap with the above safety vent in a planar manner.

[0010] The above cap plate may include a central region in the shape of a circular plate, a protruding region extending outward in a planar direction from the central region and protruding outward from the case relative to the central region, and an edge region extending outward in a planar direction from the protruding region and coupled to the case.

[0011] The above safety vent may be provided in the above protruding area.

[0012] The central region and the edge region may be concave toward the inside of the case relative to the protruding region.

[0013] The above vent extension may be provided in the above protruding area or the above edge area.

[0014] The above case may include a beading portion recessed into the interior of the case on the upper part of the cap plate, and a crimping portion on the lower part of the cap plate in which the lower part of the case is bent inward to fix the cap plate.

[0015] It further includes a cap gasket interposed between the cap plate and the beading portion and between the cap plate and the crimping portion, and the cap plate may be nonpolar.

[0016] The above-mentioned vent extension may be located in a first region between the outer periphery of the safety vent and the end of the cap gasket on the plane of the cap plate.

[0017] The above cap plate may be made of a magnetic metal.

[0018] The above cap plate may be made of steel, stainless steel, or nickel-plated iron.

[0019] The above vent expansion may be made of any one of aluminum (Al), copper (Cu), gold (Au), silver (Ag), brass, invar, and lead (Pb), which has a lower melting point compared to other areas of the cap plate.

[0020] The width of the above vent extension may be 5 mm to 5.5 mm.

[0021] The above vent extension may be any one of a circular ring shape, a polygonal ring shape, or a serrated ring shape.

[0022] If the above vent extension is in the shape of a polygonal ring, the number of corners may be 10 or more.

[0023] A first current collector plate interposed between the upper surface of the electrode assembly and the case, electrically connecting the first electrode plate and the terminal, and

[0024] It may further include a second current collector plate welded to the second electrode plate exposed to the lower surface of the electrode assembly, having a circular plate shape corresponding to the lower surface of the electrode assembly.

[0025] The above vent extension has the same thickness as other areas of the cap plate excluding the area where the safety vent is provided, and may be thicker than the safety vent.

[0026] According to the present invention, a secondary battery can be provided in which a vent expansion portion made of a material having a lower melting point than that of a cap plate is provided on the flat outer side of the safety vent, thereby expanding the open area and facilitating flame evacuation when a flame occurs inside the secondary battery, compared to the case where only the safety vent is ruptured by melting.

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

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

[0029] FIG. 1 is a perspective view illustrating a secondary battery according to the present invention.

[0030] Figure 2 is a cross-sectional view of the secondary battery shown in Figure 1.

[0031] FIG. 3 is a bottom view illustrating an example of a cap plate in the secondary battery of FIG. 1.

[0032] Figure 4 is a cross-sectional view of the cap plate shown in Figure 3.

[0033] Figure 5 is an enlarged view of part 5 of Figure 2.

[0034] FIG. 6 is a bottom view illustrating another example of a cap plate in the secondary battery shown in FIG. 1.

[0035] FIG. 7 is a bottom view illustrating another example of a cap plate in the secondary battery shown in FIG. 1.

[0036] FIGS. 8A and FIGS. 8B are perspective views illustrating a battery pack including an exemplary secondary battery according to the present invention.

[0037] FIGS. 9a and FIGS. 9b are a perspective view and a side view illustrating an automobile including an exemplary battery pack according to the present invention.

[0038] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe their invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. It should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0039] Additionally, as used herein, “comprise, include” and / or “comprising, including” specify the presence of the mentioned features, numbers, steps, actions, parts, elements, and / or groups thereof, and do not exclude the presence or addition of one or more other features, numbers, actions, parts, elements, and / or groups.

[0040] Additionally, to aid in understanding the invention, the attached drawings are not drawn to actual scale, and the dimensions of some components may be exaggerated. Furthermore, the same reference numerals may be assigned to identical components in different embodiments.

[0041] The statement that two subjects of comparison are 'identical' means that they are 'substantially identical.' Therefore, substantial identity may include deviations considered low in the industry, for example, deviations within 5%. Additionally, the statement that a parameter is uniform in a given area may mean that it is uniform from an average perspective.

[0042] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0043] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0044] The fact that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0045] Furthermore, where it is stated that one component is "connected," "coupled," or "connected" to another component, it should be understood that while said components may be directly connected or connected to each other, another component may be "interposed" between each component, or that each component may be "connected," "coupled," or "connected" through another component. Additionally, when it is stated that a part is electrically coupled with another part, this includes not only cases where they are directly connected but also cases where they are connected with another component in between.

[0046] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise. That is, "and / or" includes any combination or any combination of the enumerated items. "C to D" means C or more and D or less, unless specifically stated otherwise.

[0047] The terms used in this specification are intended to describe embodiments of the present disclosure and are not intended to limit the present disclosure.

[0048] FIG. 1 is a perspective view illustrating a secondary battery according to the present invention, and FIG. 2 is a cross-sectional view of the secondary battery illustrated in FIG. 1.

[0049] As illustrated in FIGS. 1 and 2, a secondary battery (100) according to the present invention may include an electrode assembly (110) and a case (120) that accommodates the electrode assembly (110) and an electrolyte (optional) inside. Additionally, the secondary battery (100) may include a terminal (150) coupled to a terminal hole (122a) provided at one end of the case (120), for example, at the upper end. Additionally, the secondary battery (100) may include a cap plate (160) that seals the other end of the case (110), for example, at the lower end. Here, since the cap plate (160) is coupled with the case (120) to accommodate the electrode assembly (110) inside, it can be considered as a part of the case (120).

[0050] The secondary battery (100) may further include a positive current collector plate (130) that electrically connects the positive plate (111) of the electrode assembly (110) and the terminal (150), and a negative current collector plate (140) that electrically connects the negative plate (112) of the electrode assembly (110) and the case (120).

[0051] The electrode assembly (110) may include a separator (113), an anode plate (111) and a cathode plate (112) positioned between the separator (113), and may be wound in the form of a jelly-roll.

[0052] The positive plate (111) may include a positive substrate and a positive active material layer located on at least one surface of the positive substrate. A positive tab (111aa) may extend outward from the positive non-positive portion of the positive substrate where the positive active material layer is not located, and the positive tab (111aa) may be electrically connected to a terminal (150) through a positive current collector plate (130). The negative plate (112) may include a negative substrate and a negative active material layer located on the negative substrate. A negative tab (112aa) may extend outward from the negative non-positive portion of the negative substrate where the negative active material layer is not located, and the negative tab (112aa) may be electrically connected to a case (120) through a negative current collector plate (140).

[0053] The positive electrode tab (111aa) and the negative electrode tab (112aa) may be located in opposite directions in the electrode assembly (110). The positive electrode substrate of the positive electrode plate (111) may be composed of aluminum foil, and the positive electrode active material layer may include, for example, a transition metal oxide. The negative electrode substrate of the negative electrode plate (112) may be composed of copper foil or nickel foil, and the negative electrode active material layer may include, for example, graphite.

[0054] The separator (113) functions to prevent a short circuit between the positive plate (111) and the negative plate (112) while allowing the movement of lithium ions. The separator (113) may be composed of, for example, a polyethylene film, a polypropylene film, a polyethylene-polypropylene film, etc.

[0055] In some examples, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used as the positive electrode active material. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0056] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0057] As an example, compounds represented by any one of the following chemical formulas may be used. LiaA1-bXbO2-cDc(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiaMn2-bXbO4-cDc(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiaNi1-b-cCobXcO2-αDα(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); LiaNi1-b-cMnbXcO2-αDα(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); LiaNibCocL1dGeO2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); LiaNiGbO2(0.90≤a≤1.8, 0.001≤b≤0.1); LiaCoGbO2(0.90≤a≤1.8, 0.001≤b≤0.1); LiaMn1-bGbO2 (0.90≤a≤1.8, 0.001≤b≤0.1); LiaMn2GbO4 (0.90≤a≤1.8, 0.001≤b≤0.1); LiaMn1-gGgPO4(0.90≤a≤1.8, 0≤g≤0.5); Li(3-f)Fe2(PO4)3(0≤f≤2); LiaFePO4(0.90≤a≤1.8).

[0058] 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; and L1 is Mn, Al, or a combination thereof.

[0059] 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 may include a positive electrode active material and may further include a binder and / or a conductive material.

[0060] The content of the positive active material is 90% to 99.5% by weight with respect to 100% by weight of the positive active material layer, and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer.

[0061] Aluminum may be used as the current collector mentioned above, but is not limited thereto.

[0062] 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.

[0063] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as 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, etc.

[0064] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The above 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.

[0065] The 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.

[0066] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0067] 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 may include a negative electrode active material and may further include a binder and / or a conductive material.

[0068] For example, the negative electrode active material layer may comprise 90% to 99% by weight of negative electrode active material, 0.5% to 5% by weight of binder, and 0% to 5% by weight of conductive material.

[0069] As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used. When an aqueous binder is used as the cathode binder, a cellulose-based compound capable of imparting viscosity may be further included.

[0070] As the current collector mentioned above, a material selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof may be used.

[0071] The electrolyte for a lithium secondary battery may include a non-aqueous organic solvent and a lithium salt.

[0072] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0073] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, a non-protic solvent, or a combination thereof, and may be used alone or in a mixture of two or more types.

[0074] In addition, when using carbonate-based solvents, cyclic carbonates and chain carbonates can be mixed and used.

[0075] As described above, a separator may be present between the positive and negative electrodes of a lithium secondary battery. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used.

[0076] The above separator may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0077] The above organic material may include a polyvinylidene fluoride-based antibody or a (meth)acrylic-based polymer.

[0078] The above inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but is not limited thereto.

[0079] The above organic and inorganic materials may exist mixed in a single coating layer, or may exist in a stacked form with a coating layer containing organic materials and a coating layer containing inorganic materials.

[0080] The case (120) accommodates the electrode assembly (110) and the electrolyte, and can form the external shape of the secondary battery (100) together with the terminal (150) and the cap plate (160). The case (120) may include a roughly cylindrical body portion (121) and an upper portion (122) connected to one side of the body portion (121). That is, the body portion (121) may extend downward from the edge of the upper portion (122). A beading portion (123) deformed toward the inside may be located on the body portion (121), and a crimping portion (124) bent toward the inside may be located at the opening end of the body portion (121). A terminal hole (122a) penetrating the center may be provided on the upper portion (122). The upper portion (122) can be coupled by inserting a terminal (150) into a terminal hole (122a). A terminal gasket (125) for sealing and electrical insulation may be further interposed between the terminal hole (122a) and the terminal (150). The upper portion (122) may further be provided with an insulating member (126) on its inner surface to prevent contact with the electrode assembly (110).

[0081] The beading portion (123) can prevent the electrode assembly (110) from moving inside the case (120) and facilitate the seating of the cap gasket (127) and the cap plate (160). The crimping portion (124) can firmly secure the cap plate (160) by pressing the edge of the cap plate (160) through the cap gasket (127). The case (123) may be composed of, for example, nickel-plated iron, aluminum, aluminum alloy, or stainless steel.

[0082] One side of the positive current collector plate (130) (e.g., bottom surface) may be in contact with and coupled to the positive tab (111aa) of the electrode assembly (110), and the other side opposite to the one side (e.g., top surface) may be in contact with and coupled to the terminal (150). The positive current collector plate (130) may be welded to the positive tab (111aa) of the electrode assembly (110) to be electrically connected. The positive current collector plate (130) may be welded to be electrically connected while the other side is in contact with the terminal (150).

[0083] The cathode collector plate (140) can generally have its center (141) in contact with and coupled to the cathode tab (112aa) of the electrode assembly (110), and its edge portion (142) in contact with and coupled to the body portion (121) of the case (120). The cathode collector plate (140) can be electrically connected by welding its center (141) to the cathode tab (112aa) of the electrode assembly (110). The cathode collector plate (140) can be electrically connected by welding its edge portion (142) in contact with the beading portion (123) of the case (120).

[0084] The terminal (150) may include a terminal plate (151) located on the outside of the case (120) and a fastening member (152) that is joined by penetrating the terminal plate (151) and the case (120). The terminal plate (151) may have a terminal hole (151a) penetrating the center. The fastening member (152) may be fixed by pressing the terminal plate (151) by penetrating the terminal hole (122a) of the upper portion (122) and the terminal hole (151a) of the terminal plate (151) from the inside of the case (120). A terminal gasket (125) for electrical insulation may be interposed between the terminal (150) and the case (120). Here, the terminal gasket (125) may separately be configured to be interposed between the terminal plate (151) and the case (120), and to be interposed between the terminal hole (122a) and the fastening member (152). Additionally, the fastening member (152) may be further provided with a terminal groove (153) extending inward from the center. The terminal (150) may be welded externally to the positive current collector plate (130) through the terminal groove (153). The terminal (150) may be electrically connected to the positive plate (111) of the electrode assembly (110) through the positive current collector plate (130). The terminal (150) may have a polarity different from that of the case (120).

[0085] As another example, the terminal (150) can be inserted integrally from the outer side of the case (120) inwardly through the terminal hole (122a) and joined by riveting inside the upper part (122).

[0086] The cap plate (160) can be fixed to the inside of the crimping portion (124) through the cap gasket (127) to seal the case (120).

[0087] FIG. 3 is a bottom view illustrating an example of a cap plate in the secondary battery of FIG. 1, FIG. 4 is a cross-sectional view of the cap plate illustrated in FIG. 3, and FIG. 5 is an enlarged view illustrating part 5 of FIG. 2. Below, the description of the cap plate (160) will be explained with reference to FIG. 3 to FIG. 5.

[0088] The cap plate (160) is a circular metal plate and can be attached to the opening at the bottom of the case (120). The cap plate (160) is attached to the bottom of the case (120) with a cap gasket (127) interposed therebetween, thereby preventing electrical connection with the case (120). Here, the outer end of the cap gasket (127) may protrude further toward the center of the cap plate (160) than the crimping portion (124). Since the cap plate (160) is not electrically connected to the positive or negative electrode of the electrode assembly (110), it may not have a separate electrical polarity.

[0089] The cap plate (160) can be fixed in such a state that its edge region (163) is positioned between the beading portion (123) and the crimping portion (124) of the case (120). More specifically, the cap plate (160) can be seated with a cap gasket (127) interposed at the bottom of the beading portion (123) of the case (120). Subsequently, the crimping portion (124) of the case (120) can be bent inward toward the cap plate (160) to press the cap gasket (127), thereby joining the cap plate (160) and the case (120).

[0090] The cap plate (160) may have a protruding area (162) that protrudes downward. For example, the protruding area (162) of the cap plate (160) may be located on the flat outer side from the center area (161) and may protrude downward to have a flat ring shape. The cap plate (160) may have a shape in which the center area (161) and the edge area (163) are concave inward toward the case (120) compared to the protruding area (162). For example, the lower surface of the protrusion (161) of the cap plate (160) may be located above the lower surface of the crimping portion (124) of the case (120). Therefore, when the secondary battery (100) is placed on a flat surface, the protrusion (161) of the cap plate (160) is spaced apart from the surface, and the crimping portion (124) of the case (120) may come into contact with the surface. The cap plate (160) may be provided with irregularities by the protruding area (162).

[0091] Such a cap plate (160) may be made of a magnetic metal. For example, the cap plate (160) may be made of iron, stainless steel, or nickel-plated iron. Since the cap plate (160) is made of a magnetic metal, when the secondary battery (100) is required to be transported, it can be easily transported by a magnetic object such as a magnet. In addition, the cap plate (160) can increase rigidity compared to when it is made of other metals such as aluminum.

[0092] Additionally, the cap plate (160) may further include a safety vent (165) so that it can be opened at a set pressure. The safety vent (165) may be a thinner area compared to other areas of the cap plate (160) by means of a notch. When gas is generated due to overcharging or abnormal operation of the secondary battery (100), the safety vent (165) may break to discharge the internal gas of the secondary battery (100) to the outside. That is, if excessive internal pressure is generated inside the case (110), the safety vent (165) may break due to the pressure to discharge the gas. The safety vent (165) may be provided to have a planar ring shape on the protrusion (161) of the cap plate (160). Also, the thickness of the vent extension (164) may be the same as other areas of the cap plate (160) and may be thicker than the safety vent (165). For example, the upper surface of the vent extension (164) may be located in the same plane as the upper surface of the adjacent cap plate (160), and the lower surface may be located in the same plane as the lower surface of the adjacent cap plate (160).

[0093] Such a cap plate (160) may further be provided with a vent extension (164) made of a material having a lower melting point than the cap plate (160) on the outer side of the safety vent (165) in a planar direction. Here, the vent extension (164) may be provided in a planar circular ring shape. That is, the outer periphery of the vent extension (164) may be larger than the outer periphery of the safety vent (165). Also, the vent extension (164) may not overlap with the safety vent (165) in a planar direction. This is to ensure that the vent extension (164) secures an additional open area by melting after the safety vent (165) is broken. Here, the vent extension (164) may be made of any one of aluminum (Al), copper (Cu), gold (Au), silver (Ag), brass, invar, or lead (Pb), which have a lower melting point than iron, stainless steel, or nickel-plated iron.

[0094] The inner diameter of the vent extension (164) is positioned adjacent to the safety vent (165), and the outer diameter may be located in the protruding area (162) or in the area exposed through the cap gasket (127) at the edge area (163). The diameter of the vent extension (164) may be larger than the diameter of the safety vent (165). That is, the vent extension (164) may be located within a first area (A) located between the outer side of the safety vent (165) on the plane of the cap plate (160) and the inner side of the cap gasket (127). The width (164w) of such a vent extension (164) may be 5mm to 5.5mm. Here, the width of the vent extension (164) may refer to the gap between the inner diameter and the outer diameter of the vent extension (164). If the width of the vent expansion portion (164) is less than 5 mm, the opening of the cap plate (160) may not be easy due to the reduction in the melting area. If the width of the vent expansion portion (164) is greater than 5.5 mm, the rigidity of the cap plate (160) may be reduced.

[0095] The vent expansion section (164) can melt and discharge the flame to the outside when a flame occurs after the internal pressure of the secondary battery (100) rises. That is, the vent expansion section (164) is made of a material with a high melting point, such as the cap plate (160), and can be provided to prevent heat discharge from being difficult due to the safety vent (165) not opening further after it is broken by the flame. When a flame occurs inside the secondary battery (100), the vent expansion section (164) can melt and expand the opening area compared to when the safety vent (165) is broken. That is, the vent expansion section (164) can make it easier to discharge the heat source and flame by expanding the opening area of ​​the cap plate (160) when a flame occurs inside the case (120).

[0096] A secondary battery (100) including such a cap plate (160) can induce heat sources and flames to be discharged through the cap plate (160), so that the case (120) is melted or destroyed to discharge the heat sources, thereby preventing heat propagation from rapidly being transmitted to adjacent secondary batteries in a battery module or battery pack containing multiple secondary batteries (100).

[0097] FIGS. 6 and FIGS. 7 are bottom views illustrating other examples of a cap plate in a secondary battery shown in FIG. 1.

[0098] First, as shown in FIG. 6, the cap plate (160A) may have a polygonal ring shape in the planar shape of the vent extension (164A). The position and width of the vent extension (164A) may be similar to the vent extension (164) shown in FIG. 3 to 5.

[0099] The vent extension (164) is illustrated as a dodecagonal ring shape, but the number of corners may be 10 or more. If the number of corners of the vent extension (164) is less than 10, it may be difficult to form it within the first area (A) of the cap plate (160).

[0100] As illustrated in FIG. 7, the cap plate (160B) may have a planar shape of the vent extension (164B) that has a sawtooth ring shape. Here, the vent extension (164B) may have both an inner circumference and an outer circumference that are sawtooth-shaped. Additionally, the sawtooth shape of the inner circumference and the sawtooth shape of the outer circumference of the vent extension (164B) may correspond in size and shape. The position and width of the vent extension (164B) may be similar to the vent extension (164) illustrated in FIG. 3 to FIG. 5.

[0101] The secondary battery according to the above-described embodiment can be used to manufacture a battery pack.

[0102] FIGS. 8A and 8B are perspective views illustrating a battery pack including an exemplary secondary battery (100) according to the present invention. Referring to FIGS. 8A and 8B, 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 (200) 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 mixed series / parallel manner to obtain the required electrical output. In the drawings, for convenience of illustration, components such as a bus bar for electrically connecting the battery cells, a cooling unit, and external terminals are omitted. In some examples, the battery pack (300) may be mounted in 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-wheeled vehicle or a two-wheeled vehicle.

[0103] FIGS. 9a and 9b are a perspective view and a side view illustrating an automobile (400, 500) including an exemplary battery pack (300) according to the present invention. In FIG. 9a, the battery pack (300) may include a battery pack cover (311) (which may correspond to the first housing) which is part of the vehicle under body (410) and a pack frame (312) (which may correspond to the second housing) disposed at the bottom of the vehicle under body (410). The battery pack cover (311) and the pack frame (312) may be structures formed integrally with the vehicle floor portion (420). The vehicle under body (410) separates the interior and exterior of the vehicle, and the pack frame (312) may be disposed on the exterior of the vehicle.

[0104] As illustrated in FIG. 9b, the vehicle (500) may be formed by combining additional parts, such as a hood (510) at the front of the vehicle and fenders (520) located at the front and rear of the vehicle, respectively, with the vehicle body (400). The vehicle (500) includes a battery pack (300) comprising a battery pack cover (311) and a pack frame (312), and the battery pack (300) may be combined with the vehicle body part (400).

[0105] The above description is merely one embodiment for implementing a secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment. The technical spirit of the present invention extends to the scope in which various modifications can be made by anyone with ordinary knowledge in the field to which the invention belongs, without departing from the gist of the invention as claimed in the following patent claims.

[0106] The above description is merely one embodiment for implementing a secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment. The technical spirit of the present invention extends to the scope in which various modifications can be made by anyone with ordinary knowledge in the field to which the invention belongs, without departing from the gist of the invention as claimed in the following patent claims.

Claims

1. An electrode assembly having a first electrode plate, a separator, and a second electrode plate; A case in which the above electrode assembly is accommodated and the lower end is open; A terminal coupled by penetrating the upper surface of the above case; and It includes a cap plate that seals the lower part of the above case, and A secondary battery comprising a cap plate made of a material with a melting point lower than that of other regions of the cap plate, and a vent expansion portion formed in a planar ring shape.

2. In Paragraph 1, A secondary battery comprising a cap plate that is thinner than other regions and further includes a safety vent located planar inward from the vent extension.

3. In Paragraph 2, The above safety vent is a secondary battery having a planar ring shape.

4. In Paragraph 2, The above vent extension is a secondary battery that does not overlap in plane with the above safety vent.

5. In Paragraph 2, The above cap plate has a central region in the shape of a circular plate; A protruding region extending outwardly in a planar direction from the central region and protruding outwardly from the central region compared to the case; and A secondary battery that extends outwardly in a planar direction from the above-mentioned protruding region and includes an edge region coupled with the above-mentioned case.

6. In Paragraph 5, The above safety vent is a secondary battery provided in the above protruding area.

7. In Paragraph 5, The above central region and the above edge region are concave toward the inside of the case compared to the above protruding region, in a secondary battery.

8. In Paragraph 5, The above vent extension is a secondary battery provided in the above protruding area or the above edge area.

9. In Paragraph 5, The above case is A beading portion recessed into the interior of the case on the upper part of the cap plate; and A secondary battery comprising a crimping portion that fixes the cap plate by bending the lower part of the case inwardly at the lower part of the cap plate.

10. In Paragraph 9, It further includes a cap gasket interposed between the cap plate and the beading portion, and between the cap plate and the crimping portion, and The above cap plate is a nonpolar secondary battery.

11. In Paragraph 10, The above vent extension is a secondary battery located in a first region between the outer periphery of the safety vent and the end of the cap gasket on the plane of the cap plate.

12. In Paragraph 1, The above cap plate is a secondary battery made of a magnetic metal.

13. In Paragraph 1, The above cap plate is a secondary battery made of steel, stainless steel, or nickel-plated iron.

14. In Paragraph 13, A secondary battery in which the vent extension portion is made of any one of aluminum (Al), copper (Cu), gold (Au), silver (Ag), brass, invar, and lead (Pb), which has a lower melting point compared to other regions of the cap plate.

15. In Paragraph 1, A secondary battery having a vent extension with a width of 5mm to 5.5mm.

16. In Paragraph 1, The above vent extension is a secondary battery that is one of a circular ring shape, a polygonal ring shape, or a sawtooth ring shape.

17. In Paragraph 16, A secondary battery having 10 or more corners when the above-mentioned vent extension is in the shape of a polygonal ring.

18. In Paragraph 1, A first current collector plate interposed between the upper surface of the electrode assembly and the case, and electrically connecting the first electrode plate and the terminal; and A secondary battery further comprising a second current collector plate welded to the second electrode plate exposed to the lower surface of the electrode assembly, having a circular plate shape corresponding to the lower surface of the electrode assembly.

19. In Paragraph 2, A secondary battery in which the vent extension portion has the same thickness as other regions excluding the area where the safety vent is provided in the cap plate, and is thicker than the safety vent.

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