Secondary battery

Abstract

Provided is a secondary battery including an electrode assembly, in which a notch is provided in an upper cover such that the upper cover breaks under a set internal pressure, thereby easily discharging gas inside the battery, thereby improving stability of the battery, preventing chain breaking or explosion. The secondary battery includes: an electrode assembly; a can configured to accommodate the electrode assembly; and a cap assembly configured to seal an upper portion of the can and having an upper cap, the upper cap comprising: a substrate; a terminal portion protruding upward from an upper side of the substrate and disposed at a center of the upper cover; and a connection portion configured to connect the substrate to the terminal portion. A notch is provided in at least one of the substrate, the terminal portion, and the connection portion to break at a set pressure within the can.

Description

[0001] This application claims the priority and benefit of Korean Patent Application No. 10-2024-0010035, filed with the Korean Intellectual Property Office on January 23, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] Aspects of embodiments of the present disclosure relate to a secondary battery with improved stability. Background Art

[0003] Unlike non-rechargeable primary batteries, secondary batteries are rechargeable and dischargeable. Low-capacity batteries including battery cells in a group form can be used for small portable electronic devices such as smartphones and digital cameras, and high-capacity battery modules including dozens to hundreds of battery packs connected to each other can be used as a power source for driving motors of, for example, hybrid vehicles, electric vehicles, power tools, handheld vacuum cleaners, drones, etc.

[0004] In a secondary battery, due to abnormal usage conditions such as short circuit or overcharging, the internal temperature of the battery rises, gas is generated, and the pressure inside the battery increases.

[0005] For example, in a lithium secondary battery, if overcharging occurs, the electrolyte decomposes to release gases such as carbon dioxide or carbon monoxide, thereby increasing the internal pressure of the battery. Additionally, if an overcurrent flows due to over-discharge or short circuit, the temperature inside the battery rises, and the electrolyte turns into gas. Therefore, the pressure and temperature inside the battery increase, and there is a risk of fire in particular, which poses a safety risk. This phenomenon causes overall deterioration of the performance and life characteristics of the battery.

[0006] The above information disclosed in this background art section is for enhancing the understanding of the background art of the present disclosure, and thus, it may include information that does not constitute related (or prior) art. Summary of the Invention

[0007] Embodiments of the present disclosure provide a secondary battery that is advantageous in terms of stability by providing a notch in the upper cover to affect gas discharge by utilizing a function similar to that of a safety vent.

[0008] However, the technical problems to be solved by the present disclosure are not limited to the above problems, and those skilled in the art will clearly understand other problems not mentioned herein and aspects and features of the present disclosure for solving these problems from the following description of the present disclosure.

[0009] According to some embodiments, a secondary battery includes: an electrode assembly; a can configured to accommodate the electrode assembly; and a lid assembly configured to seal an upper portion of the can and provided with an upper lid, wherein the upper lid includes: a substrate; a terminal portion protruding upward from an upper side of the substrate and disposed at a center of the upper lid; and a connection portion configured to connect the substrate to the terminal portion, wherein a notch is provided in at least one of the substrate, the terminal portion, and the connection portion so as to break under a set pressure inside the can.

[0010] The notch may be provided in a multi-stage groove shape.

[0011] The substrate may be provided in a planar ring shape, and the notch may be provided in the substrate.

[0012] The notch may have an annular shape disposed along a circumference of the substrate.

[0013] The notch may include a plurality of notches spaced apart from each other at regular intervals along a circumference of the substrate.

[0014] The notch may include a plurality of notches provided in a linear shape radiating outward from an inner side of the substrate, and the plurality of notches are provided at regular intervals along a circumference of the substrate.

[0015] The notch may be disposed on at least one surface of the connection portion along a circumference of the connection portion.

[0016] The terminal portion may be provided in a planar circular shape, and the notch may be provided in the terminal portion.

[0017] The notch may have an annular shape disposed along a circumference of the terminal portion.

[0018] The notch may branch into at least three segments at a center of the terminal portion.

[0019] The notch may have a shape of at least two or more straight lines intersecting at a center of the terminal portion.

[0020] The notch may include a plurality of notches provided in a linear shape radiating outward from an inner side of the terminal portion, and the plurality of notches may be provided at regular intervals along a circumference of the terminal portion.

[0021] A portion of the upper lid provided with the notch may have a thickness less than about 0.34 times a thickness of the upper lid.

[0022] An angle of the notch may be in a range of about 35° to about 80°.

[0023] The notch may be provided as a two-stage or three-stage notch.

[0024] The secondary battery may further include a safety plate including a protrusion mounted at a lower portion of the upper cover to protrude downward to be electrically connected to the electrode assembly, wherein the safety plate may further include a curled portion coupled to the substrate in a shape surrounding an edge of the substrate.

[0025] The notch may be provided in the substrate, and the notch may be disposed at a position about 0.5 mm to about 0.7 mm from an end of the curled portion.

[0026] Each of the substrate, the connection part, and the terminal part may have a corresponding top surface and a corresponding bottom surface, the notch may be provided in the corresponding bottom surface of at least one of the substrate, the connection part, and the terminal part, and the notch may include: a first surface disposed between the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection part, and the terminal part; a pair of second surfaces disposed on opposite side portions of the first surface and spaced apart from each other; a pair of third surfaces disposed on side portions of the pair of second surfaces and spaced apart from each other; and a pair of fourth surfaces disposed on side portions of the pair of third surfaces and spaced apart from each other and configured to connect the pair of third surfaces to the corresponding bottom surface.

[0027] The first surface and the pair of third surfaces of the notch may be parallel to the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection part, and the terminal part, and the pair of second surfaces and the pair of fourth surfaces may be provided to be inclined.

[0028] Each of the substrate, the connection part, and the terminal part may have a corresponding top surface and a corresponding bottom surface, the notch may be provided in the corresponding bottom surface of at least one of the substrate, the connection part, and the terminal part, and the notch may include: a first surface disposed between the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection part, and the terminal part; a pair of second surfaces disposed on opposite side portions of the first surface and spaced apart from each other; a pair of third surfaces disposed on side portions of the pair of second surfaces and spaced apart from each other; a pair of fourth surfaces disposed on side portions of the pair of third surfaces and spaced apart from each other; a pair of fifth surfaces disposed on side portions of the pair of fourth surfaces and spaced apart from each other; and a sixth surface disposed on side portions of the pair of fifth surfaces and spaced apart from each other and configured to connect the pair of fifth surfaces to the bottom surface.

[0029] The first surface of the notch, the pair of third surfaces, and the pair of fifth surfaces may be parallel to the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection part, and the terminal part, and the pair of second surfaces, the pair of fourth surfaces, and the pair of sixth surfaces may be provided to be inclined. Description of the Drawings

[0030] The following drawings attached to the present specification illustrate embodiments of the present disclosure and further describe aspects and features of the present disclosure together with the detailed description of the present disclosure. Accordingly, the present disclosure should not be construed as being limited to the drawings:

[0031] Figure 1 is a perspective view of a secondary battery according to some embodiments;

[0032] Figure 2 is a cross-sectional view of a secondary battery according to some embodiments;

[0033] Figure 3A and Figure 3B is a rear view of an upper cover of a secondary battery having a notch provided in a substrate according to some embodiments;

[0034] Figure 4 is according to some embodiments of Figure 2 a cross-sectional view of a cover assembly of a secondary battery;

[0035] Figure 5A and Figure 5B is according to some embodiments of a Figure 4 magnified cross-sectional view of a portion '5' provided in the upper cover;

[0036] Figure 6 is a rear view of an upper cover having a notch provided in a substrate according to various embodiments of the present disclosure;

[0037] Figures 7A to 7D is a rear view of an upper cover of a secondary battery having a notch provided in a terminal part according to various embodiments of the present disclosure;

[0038] Figure 8 is a cross-sectional view of a cover assembly of a secondary battery according to some embodiments;

[0039] Figure 9 is a rear view of an upper cover of a secondary battery having a notch provided in a connection part according to various embodiments of the present disclosure;

[0040] Figure 10 is a cross-sectional view of a cover assembly of a secondary battery according to some embodiments; and

[0041] Figure 11Rear view of an upper cover with a notch provided for a secondary battery according to various embodiments of the present disclosure. Detailed Description

[0042] Hereinafter, some embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. The terms used in the following description and claims are not limited to their dictionary meanings, but are used only to enable a clear and consistent understanding of the present invention. Accordingly, it will be apparent to those skilled in the art that the following description of the embodiments of the present invention is provided for illustrative purposes only and not for the purpose of limiting the present invention defined by the appended claims and their equivalents. Therefore, since the embodiments described in this specification and the configurations shown in the drawings are only one most preferred embodiment of the present invention and do not represent all the technical concepts of the present invention, it should be understood that various equivalents and modifications that can replace them may exist in the present application.

[0043] Moreover, "comprising" and / or "including" used in this specification neither limit the mentioned shapes, quantities, steps, operations, components, elements, and / or groups thereof, nor exclude the existence or addition of one or more other different shapes, quantities, steps, operations, components, elements, and / or groups thereof, or their addition. The term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0044] In addition, for a more obvious description, the shapes and sizes of the elements in the drawings will be enlarged. In addition, in different embodiments, the same reference numerals may be assigned to the same components.

[0045] Referring to two comparison objects as "the same" means "substantially the same". Accordingly, substantially the same may include deviations considered to be at a low level in the art, such as deviations of less than 5%. In addition, the uniformity of a parameter over a certain region may mean uniformity from an average perspective.

[0046] It will be understood that although the terms first and second are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one component from another, and the first component may also be the second component, unless specifically stated to the contrary.

[0047] Throughout the specification, unless specifically stated to the contrary, each component may be singular or plural.

[0048] The arrangement of any component on the upper part (or lower part) of a component or on the top (or bottom) of a component means that any component is placed in contact with the top surface (or bottom surface) of the component and that other elements are interposed between the element and any element provided above (or below) the element.

[0049] In addition, if a component is described as being linked, coupled, or connected to another component, it should be understood that the above components can be directly connected or connected to each other, but other components can be "interposed" between each component, or each component can be linked, coupled, or connected through another component. Moreover, in the following description, if any part is referred to as being "electrically connected" to another part, it should be understood that the former can be "directly connected" to the latter, or "connected" to the latter via an intermediate member.

[0050] If "A and / or B" is mentioned throughout the description, this means A, B, or A and B, unless specifically stated to the contrary. That is, "and / or" includes all or any combination of the listed items. If "C~D" is mentioned, this means not less than C and not greater than D, unless otherwise specified.

[0051] The terms used in this description are for describing the embodiments of the present disclosure and are not intended to limit the present disclosure.

[0052] In some embodiments of a cylindrical battery according to an embodiment of the present disclosure, one of the cylindrical batteries is selected, and the selected battery is described as having a general structure, and for the technology commonly applied, the general structure of the cylindrical cell is described.

[0053] Figure 1 is a perspective view of a secondary battery according to some embodiments. Figure 2 is a cross-sectional view of a secondary battery according to some embodiments.

[0054] As Figure 1 and Figure 2 illustrated in, the secondary battery 100 may include an electrode assembly 110, a can 120 that houses the electrode assembly 110 and an electrolyte, a cap assembly 130 that is coupled to an opening of the can 120 to seal the can 120, and a first insulating plate 125 disposed between the electrode assembly 110 and the cap assembly 130 inside the can 120. In some embodiments, the secondary battery 100 may include a gasket 190 that insulates the cap assembly 130 from the body portion 121 that is a side portion of the can 120.

[0055] The electrode assembly 110 may include a separator 113 and a first electrode 111 and a second electrode 112, and the separator 113 is disposed between the first electrode 111 and the second electrode 112, and the electrode assembly 110 is wound into a pole core shape.

[0056] The first electrode 111 may include a first base material and a first active material layer disposed on the first base material. A first lead tab 114 may extend outward from a first uncoated portion on which no first active material layer is disposed in the first base material, and the first lead tab 114 may be electrically connected to the cap assembly 130.

[0057] The second electrode 112 may include a second substrate material and a second active material layer disposed on the second substrate material. The second lead tab 115 may extend outward from a second uncoated portion of the second substrate material on which the second active material layer is not disposed, and the second lead tab 115 may be electrically connected to the can 120. The first lead tab 114 and the second lead tab 115 may extend in opposite directions.

[0058] The first electrode 111 may serve as a positive electrode. In some embodiments, the first substrate material may be made of, for example, aluminum foil, and the first active material layer may include, for example, a transition metal oxide. The second electrode 112 may serve as a negative electrode. In some embodiments, the second substrate material may be made of, for example, copper foil or nickel foil, and the second active material layer may include, for example, graphite.

[0059] The separator 113 may be used to prevent a short circuit between the first electrode 111 and the second electrode 112 while allowing the movement of lithium ions. The separator 113 may be made of, for example, a polyethylene film, a polypropylene film, a polyethylene - polypropylene film, etc.

[0060] The can 120 may accommodate the electrode assembly 110 and the electrolyte, and may define the appearance of the secondary battery 100 together with the lid assembly 130. The can 120 may include a generally cylindrical body portion 121 and a bottom 122 connected to one side of the body portion 121. An inwardly deformed crimping portion 123 may be provided on the body portion 121, and an inwardly bent caulking portion 124 may be provided on the open - side end of the body portion 121.

[0061] The crimping portion 123 may prevent the electrode assembly 110 from moving inside the can 120 to facilitate the placement of the gasket 190 and the lid assembly 130. The caulking portion 124 may firmly fix the lid assembly 130 by pressing the edge of the lid assembly 130 via the gasket 190. The can 120 may be made of iron plated with, for example, nickel.

[0062] The first insulating plate 125 may be disposed under the crimping portion 123 to contact the electrode assembly 110, and a tab opening may be provided in the first insulating plate 123 through which the first lead tab 114 is drawn out. The lid assembly 130 electrically connected to the first electrode 111 via the first lead tab 114 faces the electrode assembly 110, and the first insulating plate 125 is between the first electrode 111 and the lid assembly 130, and the insulating state between the lid assembly 130 and the second electrode 112 may be maintained by the first insulating plate 125.

[0063] The first insulating plate 125 can be used to prevent the electrode assembly 110 from making electrical contact with the lid assembly 130. In some embodiments, the first insulating plate 125 can be used to prevent the second electrode 112 of the electrode assembly 110 from making electrical contact with the lid assembly 130. In some embodiments, if a large amount of gas is generated due to an abnormality in the secondary battery 100, a plurality of holes such as tab openings can be used to allow the gas to quickly move to the lid assembly 130. In some embodiments, the plurality of holes can be used to allow the electrolyte to quickly flow into the electrode assembly 110 during the process of injecting the electrolyte.

[0064] The second lead tab 115 of the electrode assembly 110 can be welded to the bottom 122 of the can 120. In some embodiments, the can 120 can serve as the second electrode 112. In other embodiments, the first lead tab 114 can be welded to the bottom 122 of the can 120. In some embodiments, the can 120 can serve as the first electrode 111.

[0065] In some embodiments, a second insulating plate 126 can be disposed between the electrode assembly 110 and the bottom 122. The second insulating plate 126 is coupled to the can 120 and has holes defined therein at its center and outer side. The second insulating plate 126 can be used to prevent the electrode assembly 110 from making electrical contact with the bottom 122 of the can 120. In some embodiments, the first insulating plate 126 can be used to prevent the first electrode 111 of the electrode assembly 110 from making electrical contact with the bottom 122.

[0066] The lid assembly 130 can be fixed to the inner side of the crimping portion 124 through a gasket 190 to seal the can 120. The lid assembly 130 can include, but is not limited to, an upper lid 140, a safety plate 150, a lower lid 160, an insulating member 170, and a sub-board 180, and various modifications can be made.

[0067] The upper lid 140 can be disposed at the uppermost side of the lid assembly 130. The upper lid 140 can include a terminal portion 141 that protrudes upward and is connected to an external circuit, and an outlet for discharging gas can be provided around the terminal portion 141.

[0068] The upper lid 140 can include a terminal portion 141, a connecting portion 142, and a substrate 143. In some embodiments, at least one of the terminal portion 141, the connecting portion 142, and the substrate 143 of the upper lid 140 can be provided with one or more notches 143a, 241a, 342a, 441a, and 441b that are provided to break at a set pressure.

[0069] The terminal portion 141 can protrude upward and be connected to an external circuit, and an outlet for discharging gas can be provided around the terminal portion 141. In some embodiments, the outlet can be a through hole 1421 of the connecting portion 142.

[0070] The substrate 143 may be flat, and the notch 143a may be provided in the substrate 143. The connecting portion 142 may connect the terminal portion 141 to the substrate 143.

[0071] The upper cover 140 may be made of steel and / or stainless steel, and nickel plating may be provided on the surface of the upper cover 140. In some embodiments, nickel may be plated on the upper cover 140 to prevent corrosion of the upper cover 140, and the electrode tab (not shown) of an external device may be easily welded to the upper cover 140.

[0072] The specific structure of the upper cover 140 and the structure of the notch will be described herein according to various embodiments.

[0073] The safety plate 150 may be disposed below the upper cover 140. The safety plate 150 may include a protrusion 151 that protrudes downward and is connected to the daughter board 180, and at least one safety vent 152 provided around the protrusion 151. The safety vent 152 may be a notch. In some embodiments, the safety plate 150 may include a curled portion 153 that is coupled to the substrate 143 in the form of surrounding the edge of the substrate 143 of the upper cover 140. The curled portion 153 may be provided along the end of the safety plate 150.

[0074] If gas is generated due to overcharging or abnormal operation of the secondary battery 100, the protrusion 151 may be deformed upward by pressure and may be separated from the daughter board 180, and the safety plate 150 may be cut along the safety vent 152. The cut safety plate 150 may prevent the explosion of the secondary battery 100 by discharging the gas to the outside.

[0075] The lower cover 160 may be disposed below the safety plate 150. An opening for exposing the protrusion 151 of the safety plate 150 and an opening for discharging gas may be defined in the lower cover 160. The insulating member 170 may be disposed between the safety plate 150 and the lower cover 160 to insulate the safety plate 150 and the lower cover 160 from each other.

[0076] The daughter board 180 may be disposed below the lower cover 160. The daughter board 180 may be fixed to the bottom surface of the lower cover 160. Although not specifically shown in the drawings, in some embodiments, the protrusion 151 of the safety plate 150 may be fixed to the daughter board 180. The first lead tab 114 drawn from the electrode assembly 110 may be fixed to the daughter board 180. In some embodiments, the upper cover 140, the safety plate 150, the lower cover 160, and the daughter board 180 may be electrically connected to the first electrode 111 of the electrode assembly 110.

[0077] The gasket 190 can be installed on the upper part of the can 120. In some embodiments, the gasket 190 can be pressed between the outer periphery of the safety plate 150 and the crimping part 123 and the caulking part 124 of the can 120. The gasket 190 can insulate the can 120 from the lid assembly 130 and prevent the lid assembly 130 from separating from the can 120.

[0078] However, the present disclosure is not limited thereto, and the can 120 can be provided in various shapes such as a prismatic shape or a bag shape. In some embodiments, the can 120 can be made of a metal such as aluminum, an aluminum alloy, or nickel-plated steel, or a laminated film or plastic forming the bag.

[0079] In some embodiments, a compound capable of reversibly embedding and de-embedding lithium (lithiated embedding compound) can be used as the positive electrode active material. In some embodiments, a composite oxide of lithium and one or more types of metals selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0080] The composite oxide can be a lithium transition metal composite oxide, and specific examples can include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel manganese-based oxides, or combinations thereof.

[0081] For example, a compound represented by any of the following chemical formulas can 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 L1 dG e O2 (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1); Li a NiG 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).

[0082] In the chemical formulas described above, A can be Ni, Co, Mn, or a combination thereof; X can be Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D can be O, F, S, P, or a combination thereof; G can be Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L1 can be Mn, Al, or a combination thereof.

[0083] The positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer disposed on the current collector. The positive electrode active material layer may contain a positive electrode active material and may further contain a binder and / or a conductive material.

[0084] Based on 100% by weight of the positive electrode active material layer, the content of the positive electrode active material may be about 90% to about 99.5% by weight, and based on 100% by weight of the positive electrode active material layer, the content of each of the binder and the conductive material may be about 0.5% to 5% by weight.

[0085] Al can be used as the current collector, but is not limited thereto.

[0086] In some embodiments, the negative electrode active material may include 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.

[0087] Materials capable of reversibly embedding / desorbing lithium ions can be carbonaceous negative electrode active materials and can include, for example, crystalline carbon, amorphous carbon, or combinations thereof. Examples of crystalline carbon can include graphite, such as natural graphite or artificial graphite, and examples of amorphous carbon can include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0088] Si-based negative electrode active materials or Sn-based negative electrode active materials can be used as materials capable of doping and de-doping lithium. The Si-based negative electrode active materials can be silicon, silicon-carbon composites, SiO x (0 < x < 2), Si-based alloys, or combinations thereof.

[0089] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to some embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of each silicon particle.

[0090] The silicon-carbon composite can further include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating provided on the surface of the core.

[0091] The negative electrode for a lithium secondary battery can include a current collector and a negative electrode active material layer provided on the current collector. The negative electrode active material layer contains a negative electrode active material and can further contain a binder and / or a conductive material.

[0092] For example, the negative electrode active material layer can contain about 90% to about 99% by weight of the negative electrode active material, about 0.5% to about 5% by weight of the binder, and about 0% to about 5% by weight of the conductive material.

[0093] The binder can be a non-aqueous binder, an aqueous binder, a dry powder binder, or a combination thereof. If an aqueous binder is used as the negative electrode binder, the negative electrode binder can further contain a cellulose-based compound capable of imparting viscosity.

[0094] The negative electrode current collector can be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer matrix material coated with a conductive metal, and combinations thereof.

[0095] The electrolyte for a lithium secondary battery can contain a non-aqueous organic solvent and a lithium salt.

[0096] The non-aqueous organic solvent can be used as a medium through which the ions involved in the electrochemical reaction of the battery move.

[0097] The non-aqueous organic solvent can be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof, and can be used alone or as a mixture of two or more.

[0098] In some embodiments, if a carbonate solvent is used, a mixture of a cyclic carbonate and a linear carbonate may be used.

[0099] Depending on the type of the lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used.

[0100] The separator may include a porous matrix material and a coating containing an organic material, an inorganic material, or a combination thereof provided on one or both sides of the porous matrix material.

[0101] The organic material may include a polyvinylidene fluoride-based heavy antibody or a (meth)acrylic acid-based polymer.

[0102] The 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.

[0103] The organic material and the inorganic material may be mixed in one coating, or may be present in a laminated form of a coating containing an organic material and a coating containing an inorganic material.

[0104] Hereinafter, the upper covers 140, 240, 340, and 440 will be described in detail. Notches 143a, 241a, 342a, 441a, and 441b are provided in the upper covers 140, 240, 340, and 440 to provide a secondary battery that is advantageous in terms of stability by affecting gas emission by utilizing a function similar to that of the safety plate 150.

[0105] Figure 3A and Figure 3B is a rear view of the upper cover 140 provided with the notch 143a in the substrate 143 of the secondary battery 100 according to some embodiments. Figure 4 is according to some embodiments Figure 2 of the secondary battery 100 of the cover assembly 130. Figure 5A and Figure 5B is according to some embodiments Figure 4 of the upper cover provided with the notch 143a (e.g., see part '5') of the secondary battery 100. Figure 6 is a rear view of the upper cover 140 provided with the notch 143a in the substrate according to various embodiments of the present disclosure.

[0106] First, referring to Figures 3A to 6 , the upper cover 140, in which the substrate 143 is provided with the notch 143a, will be described.

[0107] The substrate 143 may be disposed on the outer periphery of the upper cover 140 and may include a substantially flat top surface 1431 and a bottom surface 1432. In some embodiments, the substrate 143 may include an inner peripheral surface 1433 and an outer peripheral surface 1434 that connect the top surface 1431 to the bottom surface 1432. The inner peripheral surface 1433 may be a surface connected to the connecting portion 142, and the outer peripheral surface 1434 may be the outermost surface of the upper cover 140. The inner peripheral surface 1433 and the outer peripheral surface 1434 may be circular shapes having the same center, and the substrate 143 may be provided in an annular shape along the inner peripheral surface 1433 and the outer peripheral surface 1434. The substrate 143 may be electrically connected to the safety plate 150. In some embodiments, the gasket 190 may be disposed on the outer periphery of the substrate 143.

[0108] The terminal portion 141 may be provided to protrude from the substrate 143 and may be provided as flat. In some embodiments, the terminal portion 141 may be disposed at the center of the upper cover 140 and may be provided in a stepped manner from the substrate 143. The terminal portion 141 may be electrically connected to the first lead tab 114 of the electrode assembly 110 and ultimately serve as the first electrode 111. The terminal portion 141 may serve as a terminal for an electrode tab that is directly connected to an external device.

[0109] The connecting portion 142 may connect the substrate 143 to the terminal portion 141. In the connecting portion 142, the perimeter of the upper portion connected to the terminal portion 141 may be smaller than the perimeter of the lower portion connected to the substrate 143. In some embodiments, the connecting portion 142 may be provided as inclined. In some embodiments, a through hole 1421 may be defined in the connecting portion 142, and the gas generated inside the can 120 is discharged through the through hole 1421. The through hole 1421 may be defined as a plurality of through holes, but the number of through holes is not limited in the present disclosure.

[0110] Figure 3A and Figure 3B Illustrating the bottom surface 1432 of the substrate 143, and a notch 143a may be provided on the bottom surface 1432 of the substrate 143. In some embodiments, the notch 143a may have a multi-stage groove shape with a constant depth. However, in some embodiments, the notch 143a may be provided on the top surface 1431 of the substrate 143.

[0111] The notch 143a may be provided in a substantially annular shape (e.g., see Figure 3A ) along the circumference of the bottom surface 1432 of the substrate 143. In some embodiments, the notches 143a may be provided at regular intervals along the circumference of the substrate 143 (e.g., see Figure 3B ).

[0112] The notch 143a can be provided between the inner peripheral surface 1433 and the outer peripheral surface 1434 of the substrate 143. For example, referring to Figure 4 , the notch 143a can be provided at a position about 0.5 mm to about 0.7 mm from the end of the curled portion 153 of the safety plate 150. In some embodiments, the distance d1 between the center of the notch 143a and the end of the curled portion 153 can be about 0.5 mm to about 0.7 mm. In some embodiments, if the distance d1 between the center of the notch 143a and the end of the curled portion 153 is less than about 0.5 mm or greater than about 0.7 mm, the notch 143a may not break, and only deformations such as rising may occur.

[0113] Referring to Figure 4 , the thickness t1 of the portion of the upper cover 140 provided with the notch 143a can be less than about 0.34 times (e.g., 1 / 3 times) the thickness of the upper cover 140. For example, if the thickness of the upper cover 140 is about 0.6 mm, the thickness t1 of the portion of the upper cover 140 provided with the notch 143a can be about 0.05 mm to about 0.20 mm. In some embodiments, if the thickness t1 of the portion provided with the notch 143a is less than about 0.05 mm, the notch 143a may break before the desired rupture pressure is set. Additionally, if the thickness t1 of the portion provided with the notch 143a is about 0.20 mm or greater, the notch 143a may not break even at the set rupture pressure, and only deformations such as rising may occur, or the upper cover 140 may deform.

[0114] Referring to Figure 5A and Figure 5B , the depth of the notch 143a can be determined by the height between the bottom surface 1432 of the substrate 143 and the first surface 143a-1. For example, the depth of the notch 143a can be about 80% to about 90% of the height between the top surface 1431 and the bottom surface 1432 of the substrate 143. Here, if the depth of the notch 143a is greater than about 90% of the height between the top surface 1431 and the bottom surface 1432 of the substrate 143, the notch 143a may break at a relatively low internal battery pressure. In some embodiments, if the depth of the notch 143a is greater than about 90% of the height between the top surface 1431 and the bottom surface 1432 of the substrate 143, there is a risk that the notch 143a will break even under a relatively small external impact. In some embodiments, if the depth of the notch 143a is less than about 80% of the height between the top surface 1431 and the bottom surface 1432 of the substrate 143, the notch 143a may not break even under a relatively large internal battery pressure.

[0115] As described above, the deeper the depth of the notch 143a, the lower the internal pressure required to break the notch, and the shallower the depth of the notch 143b, the higher the pressure required to break the notch 143a. In some embodiments, if the depth of the notch 143a (the height of the first surface 143a-1 from the bottom surface 1432 of the substrate 143) is adjusted, the breaking pressure of the upper cover 140 can be adjusted. Here, the depth of the notch 143a can be a value obtained by subtracting the thickness t1 of the upper cover 140 at the portion where the notch 143a is provided from the total thickness of the upper cover 140.

[0116] Reference Figure 5A , to describe the notch 143a in more detail, the notch 143a may include a first surface 143a-1 provided between the top surface 1431 and the bottom surface 1432 of the substrate 143, and a pair of second surfaces 143a-2, 143a-3 provided at two opposite side portions of the first surface 143a-1 to be spaced apart from each other. In some embodiments, the notch 143a may include a pair of third surfaces 143a-4, 143a-5 provided at side portions of each of the pair of second surfaces 143a-2, 143a-3 to be spaced apart from each other. In some embodiments, the notch 143a may include a pair of fourth surfaces 143a-6, 143-7, the pair of fourth surfaces 143a-6, 143-7 being spaced apart from each other, provided at side portions of each of the pair of third surfaces 143a-4, 143a-5 and connected to the bottom surface 1432 of the substrate 143. Here, the first surface 143a-1 and the pair of third surfaces 143a-4, 143a-5 may be provided to be substantially parallel to the top surface 1431 and the bottom surface 1432 of the substrate 143.

[0117] In some embodiments, the angle θ1 between the pair of fourth surfaces 143a-6, 143a-7 may be about 35° to about 80°. If the angle θ1 between the pair of fourth surfaces 143a-6, 143a-7 is greater than about 80°, the notch 143a may break under a relatively low internal pressure. In some embodiments, if the angle θ1 between the pair of fourth surfaces 143a-6, 143a-7 is greater than about 80°, there may be a risk of the notch 143a breaking even by a relatively small external shock. In some embodiments, if the angle θ1 between the pair of fourth surfaces 143a-6, 143a-7 is less than about 35°, the notch 143a may not break even under a relatively high internal pressure.

[0118] In some embodiments, as the angle θ1 between a pair of fourth surfaces 143a-6 and 143a-7 increases, the internal pressure at which the notch 143a may rupture decreases, and as the angle θ1 between the pair of fourth surfaces 143a-6 and 143a-7 decreases, the internal pressure at which the notch 143b may rupture increases. In some embodiments, if the angle θ1 between the pair of fourth surfaces 143a-6 and 143a-7 is adjusted, the rupture pressure of the upper cover 140 can be adjusted.

[0119] In some embodiments, referring to Figure 5B , the notch 143a may include a pair of fifth surfaces 143a-8 and 143a-9, which are provided on the sides of each of the pair of fourth surfaces 143a-6 and 143a-7 and are spaced apart from each other. In some embodiments, the notch 143a may include a pair of sixth surfaces 143a-10 and 143a-11, which are provided on the sides of each of the pair of fifth surfaces 143a-8 and 143a-9 and are connected to the bottom surface 1432 of the substrate 143 and are spaced apart from each other. Here, the first surface 143a-1, the pair of third surfaces 143a-4 and 143a-5, and the pair of fifth surfaces 143a-8 and 143a-9 may be provided to be substantially parallel to the top surface 1431 and the bottom surface 1432 of the substrate 143.

[0120] The angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 may be from about 35° to about 80°. If the angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 is greater than about 80°, the notch 143a may rupture at a relatively low internal pressure. In some embodiments, if the angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 is greater than about 80°, there may be a risk of the notch 143a rupturing even by a relatively small external impact. In some embodiments, if the angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 is less than about 35°, the notch 143a may not rupture at a relatively high internal pressure. The angle θ1 between the pair of fourth surfaces 143a-6 and 143a-7 and the angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 may be referred to as the angles of the notch 143a.

[0121] In some embodiments, as the angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 increases, the internal pressure at which the notch 143a may rupture decreases, and as the angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 decreases, the internal pressure at which the notch 143b may rupture increases. In some embodiments, if the angle θ2 between the pair of sixth surfaces 143a-10 and 143a-11 is adjusted, the rupture pressure of the upper cover 140 can be adjusted.

[0122] In some embodiments, the notch 143a may be provided in a multi - stage manner such as a two - stage (e.g., see Figure 5A ) or a three - stage (e.g., see Figure 5B ).

[0123] Referring to Figure 6 , the notch 143a may be provided in a linear shape radiating outward from the inner side of the substrate 143. In some embodiments, the notch 143a may be provided in a linear shape radiating from the inner circumferential surface 1433 of the substrate 143 toward the outer circumferential surface 1434. The linear - shaped notch 143a may be provided at regular intervals along the circumference of the substrate 143. In some embodiments, the linear notch 143a may be provided from the inner circumferential surface 1433 to the position where the curling part 153 is joined.

[0124] In some embodiments, the notch 143a may be provided in the terminal part 141 or the connection part 142 of the upper cover 140. In some embodiments, the provision of the notch 143a in the terminal part 141 or the connection part 142 of the upper cover 140 will be described with reference to Figures 7A to 11 .

[0125] Figures 7A to 7D is a rear view of the upper cover 240 having a notch 241a provided in the terminal part 241 of the secondary battery 100 according to various embodiments of the present disclosure. Figure 8 is a cross - sectional view of the cover assembly 130 of the secondary battery 100 according to some embodiments.

[0126] Referring to Figures 7A to 8 , the terminal part 241 may be provided in a circular shape on a plane, and the notch 241a may be provided in the terminal part 241. In some embodiments, the notch 241a may be provided to branch into at least three segments from the center of the terminal part 241. In some embodiments, the notch 241a may be provided in the shape of at least two or more straight lines intersecting at the center of the terminal part 241. Here, the width t2 of the notch 241a provided in the bottom surface may be about 0.05 mm to about 0.20 mm. That is, the width t2 of the notch 241a provided in the bottom surface may be equal to the thickness t3 of the part of the upper cover 240 where the notch 241a is formed, but is not limited thereto.

[0127] In the illustrated embodiment, the upper cover 240 further includes a connection part 242 and a substrate 243.

[0128] In some embodiments, the thickness t3 of the portion of the upper cover 240 provided with the notch 241a may be less than about 0.34 times (e.g., 1 / 3 times) the thickness of the upper cover 240. For example, if the thickness of the upper cover 240 is about 0.6 mm, the thickness t3 of the portion of the upper cover 240 provided with the notch 241a may be about 0.05 mm to about 0.20 mm. The structure of the notch 241a may be the same as the structure of the notch 143a provided in the substrate 143, and thus its description will be omitted (e.g., see Figure 5A and Figure 5B ). In some embodiments, since the electrode tab of the external device is welded to the terminal portion 241, the notch 241a may be provided at a position where the electrode tab of the external device is not welded.

[0129] As described above, the notch 241a may be provided in the bottom surface of the terminal portion 241, but is not limited thereto. For example, the notch 241a may be provided in the top surface of the terminal portion 241.

[0130] Figure 9 is a rear view of the upper cover 340 provided with the notch 342a in the connection portion 342 of the secondary battery 100 according to various embodiments of the present disclosure. Figure 10 is a cross-sectional view of the cover assembly 130 of the secondary battery 100 according to some embodiments.

[0131] Referring to Figure 9 and Figure 10 , the notch 342a may be provided on at least one surface of the connection portion 342 along the circumference of the connection portion 342. In some embodiments, the thickness t4 of the portion of the upper cover 340 provided with the notch 342a may be less than about 0.34 times (e.g., 1 / 3 times) the thickness of the upper cover 340. For example, if the thickness of the upper cover 340 is about 0.6 mm, the thickness t4 of the portion of the upper cover 340 provided with the notch 342a may be about 0.05 mm to about 0.20 mm. The structure of the notch 342a may be the same as the structure of the notch 143a provided in the substrate 143, and thus its description will be omitted (e.g., see Figure 5A and Figure 5B ). In some embodiments, since the upper cover 340 provides the terminal portion 341 and the connection portion 342 by pressing the flat main board with a jig, if the notch 342a is provided in advance at the portion that will become the connection portion 342, there may be a risk that the notch 342a is broken due to being pressed by the jig. In some embodiments, the terminal portion 341 and the connection portion 342 may be provided by pressing the main board with a jig, and then, the notch 342a may be provided in the connection portion 342.

[0132] In the illustrated embodiment, the upper cover 340 further includes a substrate 343.

[0133] As described above, the notch 342a may be provided in the bottom surface of the connection part 342, but is not limited thereto. For example, the notch 342a may be provided in the top surface of the connection part 342.

[0134] Figure 11 It is a rear view of the upper cover 440 of the secondary battery 100 provided with notches 441a and 441b according to various embodiments of the present disclosure.

[0135] Reference Figure 11 , the notch 441a may have an annular shape provided along the circumference of the terminal part 441. Additionally, in some embodiments, the notch 441b may be provided in a linear shape radiating outward from the inside of the terminal part 441, and the linear-shaped notch 441b may be provided at regular intervals along the circumference of the terminal part 441. In some embodiments, two types of notches 441a and 441b may be applied to the terminal part 441.

[0136] In the illustrated embodiment, the upper cover 440 further includes a connection part 442 and a substrate 443.

[0137] If the internal pressure of the can 120 abnormally increases, the above-described notches 143a, 241a, 342a, 441a, and 441b may rupture to discharge the internal gas. If the notches 143a, 241a, 342a, 441a, and 441b rupture, the terminal part 141 and the connection part 142 of the upper cover 140 may be separated to the outside. In some embodiments, if the notches 143a, 241a, 342a, 441a, and 441b rupture, the terminal part 141 and the connection part 142 may be separated from the upper cover 140. In some embodiments, the portion of the substrate 143 provided inside the notch 143a may also be separated from the upper cover 140. Therefore, the notches 143a, 241a, 342a, 441a, and 441b according to the present disclosure can quickly discharge the internal gas to rapidly reduce the internal temperature.

[0138] In some embodiments, as described above, the secondary battery may include a safety plate and an upper cover. The safety plate blocks current and ruptures when the internal pressure of the canister abnormally increases. The upper cover has a through hole through which the internal gas is discharged. If the internal pressure of the canister abnormally increases, the internal temperature may rapidly rise to the extent that the safety plate melts. As a result, if the safety plate ruptures, the fragments may melt to block the through hole of the upper cover, making it difficult to discharge the internal gas. However, the secondary battery 100 according to the present disclosure may include one or more of notches 143a, 241a, 342a, 441a, and 441b provided in at least one of the terminal portion, the connection portion, and the substrate provided on the upper cover. Therefore, if the internal pressure of the canister 120 abnormally increases, the notch may rupture, separating the terminal portion and the connection portion to the outside, thereby quickly discharging the internal gas. Accordingly, the secondary battery 100 according to the present disclosure can prevent the risk of the ruptured safety plate 150 blocking the through holes 1421, 2421, 3421, and 4421.

[0139] According to an embodiment of the present disclosure, a groove may be provided in the upper cover such that if the safety vent operates, the upper cover ruptures, so that the gas inside the canister can be easily discharged, improving the stability of the battery itself and preventing the occurrence of chain ruptures or explosions.

[0140] According to an embodiment of the present disclosure, the multi-stage groove-shaped notches provided in the upper cover may be provided to easily discharge the gas generated in the canister, quickly reduce the internal temperature of the canister, and control the rupture pressure of the upper cover.

[0141] However, the aspects and features of the present disclosure are not limited to those described above, and other aspects and features not explicitly described herein will be clearly understood by those skilled in the art from the description of the exemplary embodiments of the present disclosure described below.

[0142] Although the present disclosure has been described with reference to the embodiments and the drawings illustrating its aspects, the present disclosure is not limited thereto. Those skilled in the art to which the present disclosure pertains can make various modifications and variations within the scope of the technical spirit of the present disclosure and the claims and their equivalents.

Claims

1. A secondary battery, comprising: an electrode assembly; a can configured to accommodate the electrode assembly; and a lid assembly configured to seal an upper portion of the can and provided with an upper lid, wherein the upper lid includes: a substrate; a terminal portion protruding upward from an upper side of the substrate and disposed at a center of the upper lid; and a connection portion configured to connect the substrate to the terminal portion, wherein a notch is provided in at least one of the substrate, the terminal portion, and the connection portion to break under a set pressure inside the can.

2. The secondary battery according to claim 1, wherein the notch is provided in a multi-stage groove shape.

3. The secondary battery according to claim 1, wherein the substrate is provided in a planar ring shape, and the notch is provided in the substrate.

4. The secondary battery according to claim 3, wherein the notch has a ring shape provided along a circumference of the substrate.

5. The secondary battery according to claim 3, wherein the notch includes a plurality of notches spaced apart from each other at regular intervals along the circumference of the substrate.

6. The secondary battery according to claim 3, wherein the notch includes a plurality of notches provided in a linear shape radiating outward from an inner side of the substrate, and the plurality of notches are provided at regular intervals along the circumference of the substrate.

7. The secondary battery according to claim 1, wherein the notch is provided along a circumference of the connection portion on at least one surface of the connection portion.

8. The secondary battery according to claim 1, wherein the terminal portion is provided in a planar circular shape, and the notch is provided in the terminal portion.

9. The secondary battery according to claim 8, wherein the notch has a ring shape provided along a circumference of the terminal portion.

10. The secondary battery according to claim 8, wherein the notch branches into at least three segments at a center of the terminal portion.

11. The secondary battery according to claim 8, wherein the notch has a shape of at least two or more straight lines intersecting at a center of the terminal portion.

12. The secondary battery according to claim 8, wherein the notch includes a plurality of notches provided in a linear shape radiating outward from an inner side of the terminal portion, and the plurality of notches are provided at regular intervals along the circumference of the terminal portion.

13. The secondary battery according to claim 1, wherein a portion of the upper lid provided with the notch has a thickness less than 0.34 times a thickness of the upper lid.

14. The secondary battery according to claim 1, wherein an angle of the notch is in a range of 35° to 80°.

15. The secondary battery according to claim 1, wherein the notch is provided in a two-stage or three-stage manner.

16. The secondary battery according to claim 1, further comprising a safety plate including a protrusion mounted on a lower portion of the upper lid to protrude downward to be electrically connected to the electrode assembly, wherein the safety plate further includes a curled portion coupled to the substrate in a shape surrounding an edge of the substrate.

17. The secondary battery according to claim 16, wherein the notch is provided in the substrate, and the notch is provided at a position 0.5 mm to 0.7 mm from the end of the curled portion.

18. The secondary battery according to claim 1, wherein each of the substrate, the connection portion, and the terminal portion has a corresponding top surface and a corresponding bottom surface, the notch is provided in the corresponding bottom surface of at least one of the substrate, the connection portion, and the terminal portion, and the notch includes: a first surface provided between the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection portion, and the terminal portion; a pair of second surfaces provided on opposite side portions of the first surface of the notch and spaced apart from each other; a pair of third surfaces provided on side portions of the pair of second surfaces and spaced apart from each other; and a pair of fourth surfaces provided on side portions of the pair of third surfaces and spaced apart from each other, and configured to connect the pair of third surfaces to the corresponding bottom surface.

19. The secondary battery according to claim 18, wherein the first surface and the pair of third surfaces of the notch are parallel to the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection portion, and the terminal portion, and the pair of second surfaces and the pair of fourth surfaces are provided to be inclined.

20. The secondary battery according to claim 1, wherein each of the substrate, the connection portion, and the terminal portion has a corresponding top surface and a corresponding bottom surface, the notch is provided in the corresponding bottom surface of at least one of the substrate, the connection portion, and the terminal portion, and the notch includes: a first surface provided between the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection portion, and the terminal portion; a pair of second surfaces provided on opposite side portions of the first surface and spaced apart from each other; a pair of third surfaces provided on side portions of the pair of second surfaces and spaced apart from each other; a pair of fourth surfaces provided on side portions of the pair of third surfaces and spaced apart from each other; a pair of fifth surfaces provided on side portions of the pair of fourth surfaces and spaced apart from each other; and a pair of sixth surfaces provided on side portions of the pair of fifth surfaces and spaced apart from each other, and configured to connect the pair of fifth surfaces to the corresponding bottom surface.

21. The secondary battery according to claim 20, wherein the first surface, the pair of third surfaces, and the pair of fifth surfaces of the notch are parallel to the corresponding top surface and the corresponding bottom surface of at least one of the substrate, the connection portion, and the terminal portion, and the pair of second surfaces, the pair of fourth surfaces, and the pair of sixth surfaces are provided to be inclined.

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