Cover assembly for secondary battery, secondary battery, battery pack, and sports tool

Abstract

The present invention relates to a cap assembly for a secondary battery, including a top cap electrically connected to an exterior and a gasket surrounding an outer peripheral portion of the top cap, in which the top cap has a thermally conductive layer provided on one surface thereof.

Description

Technical Field

[0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0100295 filed in the Korean Intellectual Property Office on August 1, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a cap assembly for a secondary battery, a secondary battery, a battery pack, and a vehicle. Background Art

[0003] Generally, a secondary battery refers to a chargeable and dischargeable battery unlike a non-chargeable primary battery, and is widely used in the field of high-tech electronic devices such as mobile phones, laptop computers, and camcorders.

[0004] The stability of the secondary battery can be ensured by a stability test in which one surface is compressed by a press to measure an internal short circuit.

[0005] According to the shape of the battery case, secondary batteries are classified into: cylindrical batteries and prismatic batteries in which the electrode assembly is built into a cylindrical or prismatic metal battery case, and pouch-type batteries in which the electrode assembly is built into a pouch-type battery case made of an aluminum laminate.

[0006] In addition, the electrode assembly built into the battery box is a rechargeable / dischargeable power generation device having a stacking structure of a positive electrode / separator / negative electrode, and is classified into: a folding electrode assembly (winding type), in which a long sheet of positive electrode and a negative electrode coated with an active material are wound with a separator interposed between the positive electrode and the negative electrode; and a stacked electrode assembly, in which a plurality of positive electrodes and negative electrodes of a predetermined size are stacked in sequence with a separator interposed between the positive electrode and the negative electrode. Among these electrode assemblies, the wound electrode assembly has the advantages of being easy to manufacture and having a high energy density per unit weight. Therefore, the demand for cylindrical batteries including electrode assemblies having a wound structure is increasing.

[0007] The cylindrical battery includes an electrode assembly having a wound structure, a battery case, and a cap assembly. The cap assembly is a structure coupled to an opening of the battery case into which the electrode assembly is inserted. Since the cap assembly seals the battery case, under normal circumstances, gas inside the battery cannot be discharged to the outside.

[0008] The cylindrical battery may experience thermal runaway due to the heat generated by the decomposition reaction of the electrode active material contained in the electrode assembly. If the cap assembly is not separated from the battery case at this time, the heat inside the battery case may damage the separator, causing a short circuit of the positive and negative electrodes, and an excessive current due to the internal short circuit, which may cause a fire or even an explosion.

[0009] Additionally, the internal pressure of the battery case may increase due to heat and gas within the battery case not being exhausted, which may cause the battery case to rupture. Summary of the invention

[0010] Technical issues

[0011] In view of the above-mentioned problems of the related art, the present invention is directed to providing a cap assembly for a secondary battery, a secondary battery, a battery pack, and a vehicle.

[0012] Technical Solutions

[0013] An exemplary embodiment of the present invention provides a cap assembly for a secondary battery, the cap assembly including a top cover electrically connected to the outside and a gasket configured to surround a peripheral portion of the top cover, wherein the top cover has a thermal conductive layer disposed on one surface.

[0014] An exemplary embodiment of the present invention provides a secondary battery including: an electrode assembly in which electrodes and separators are wound; a box having a space into which the electrode assembly is introduced and having one side opened; and the above-mentioned cap assembly coupled to the open side of the box.

[0015] An exemplary embodiment of the present invention provides a battery pack including a secondary battery.

[0016] An exemplary embodiment of the present invention provides a vehicle including a battery pack.

[0017] Beneficial Effects

[0018] The cap assembly for a secondary battery, the secondary battery, the battery pack, and the vehicle according to the exemplary embodiment of the present invention can prevent the battery case from being broken due to the top cover being melted by the heat generated by the decomposition reaction of the electrode active material and thereby prevent the runaway phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 (a) is a cross-sectional view showing a cap assembly according to an exemplary embodiment of the present invention, and Figure 1 (b) is a perspective view showing a top cover and a gasket according to an exemplary embodiment of the present invention.

[0020] Figure 2 (a) is a cross-sectional view showing a secondary battery according to another exemplary embodiment of the present invention, and Figure 2 (b) is a plan view showing a top cover and a battery box according to another exemplary embodiment of the present invention.

[0021] Figure 3 is a cross-sectional view showing a secondary battery according to an exemplary embodiment of the present invention.

[0022] Figure 4 is a perspective view showing a battery pack according to an exemplary embodiment of the present invention.

[0023] Figure 5 is a perspective view showing a vehicle according to an exemplary embodiment of the present invention.

[0024] Description of Reference Numerals and Symbols

[0025] 1: Secondary battery

[0026] 2: Battery pack housing

[0027] 3: Battery Pack

[0028] 100: Electrode assembly

[0029] 200: Battery box

[0030] 210: Curling part

[0031] 220: Crimping part

[0032] 300a, 300b: Cover assembly

[0033] 310a, 310b: Top cover

[0034] 311: The Prominence

[0035] 312: Edge

[0036] 313: Bridge

[0037] 314: Exhaust part

[0038] 320: Safety exhaust parts

[0039] 330: Pad

[0040] 340: CID

[0041] 350: CID gasket

[0042] C: Core part

[0043] H: Thermally conductive layer or thermally conductive material DETAILED DESCRIPTION

[0044] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. Throughout the entire specification, unless there is an explicit description to the contrary, when a component "includes (comprising)" another component or is "characterized by" having a certain structure and a certain shape, this means that other components, structures and shapes can be included and not excluded.

[0045] The present invention can be modified in various ways and can have various exemplary embodiments, and specific exemplary embodiments will be described in detail in the detailed description. However, the description of the exemplary embodiments is not intended to limit the content of the present invention, but it should be understood that the present invention will cover all modifications, equivalents and alternatives that fall within the spirit and technical scope of the present invention.

[0046] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. However, it should be noted that the accompanying drawings are provided for illustrating the present invention, and the scope of the present invention is not limited by the accompanying drawings.

[0047] The secondary battery 1 according to the exemplary embodiment of the present invention includes an electrode assembly 100, a battery box 200 and a cap assembly 300a, 300b. The secondary battery 1 according to the exemplary embodiment of the present invention is a cylindrical secondary battery. In the secondary battery 1 according to the exemplary embodiment, the cap assembly 300a can be connected to the upper portion of the battery box 200, and the positive electrode uncoated portion and the negative electrode uncoated portion provided on the positive electrode and the negative electrode of the electrode assembly 100 can be provided in the short axis direction of the positive electrode collector and the negative electrode collector, respectively.

[0048] In a secondary battery 1 according to another exemplary embodiment, a cap assembly 300b may be coupled to a lower portion of a battery case 200. Positive and negative uncoated portions of an electrode assembly 100 may be disposed in the long axis directions of positive and negative current collectors, respectively.

[0049] When the cap assembly 300a is coupled to the upper portion of the battery case 200, the cap assembly 300 may include the top cover 310, the safety vent 320, and the gasket 330. When the cap assembly 300 is coupled to the lower portion of the battery case 200, the cap assembly 300 may include the top cover 310 and the gasket 330.

[0050] The top cover 310 is located at the top of the cap assembly 300 and may protrude in a direction opposite to the center of the battery case 200 .

[0051] The top cover 310a according to the exemplary embodiment may be used as an electrode terminal so that the protruding portion is electrically connected to the outside. For example, the top cover 310a may be used as a positive electrode terminal.

[0052] Reference Figure 1 The top cover 310 a includes a protrusion 311 protruding upward, a rim portion 312 contacting or surrounded by a safety vent 320 described below, and a bridge portion 313 connecting the protrusion 311 and the rim portion 312 .

[0053] Reference Figure 2, the top cover 310b according to another exemplary embodiment may be provided with a vent portion 314 that prevents the internal pressure from increasing beyond a preset value due to the gas generated in the battery case 200. Specifically, the top cover 310b may include a protrusion 311, an edge portion 312, and the vent portion 314, and the vent portion 314 may be located between the protrusion 311 and the edge portion 312.

[0054] The exhaust portion 314 refers to an area of ​​the top cover 310b that has a thinner thickness than the surrounding area. The exhaust portion 314 is structurally fragile compared to the surrounding area. Therefore, if an abnormality occurs in the cylindrical secondary battery and the internal pressure of the battery box 200 increases to a certain level or more, the exhaust portion 314 may rupture, and the gas generated in the battery box 200 may be discharged to the outside.

[0055] For example, the exhaust portion 314 may be formed by grooves in any one side or both sides of the top cover 310 b to partially reduce the thickness of the top cover 310 b.

[0056] The top cover 310 is provided with a heat conductive layer (H) on a lower surface, ie, a surface facing the safety vent 320 , and the heat conductive layer (H) may include a material having a higher thermal conductivity than that of the top cover 310 .

[0057] In other words, the cap assembly 300 may have a thermally conductive material coated on the lower surface of the top cap 310, and the thermally conductive material may be a material having a higher thermal conductivity than the top cap 310. For example, the top cap 310 may include iron or stainless steel, and the thermally conductive layer (H) or the thermally conductive material may include a material having a higher thermal conductivity than iron or stainless steel.

[0058] Preferably, the top cover 310 may include iron, and the heat conductive layer may include a material having a higher thermal conductivity than that of iron.

[0059] The heat conductive layer (H) or the heat conductive material may be coated or laminated on the lower surface of the protrusion 311 of the top cover 310. The coating area of ​​the heat conductive material may be equal to or smaller than the lower surface area of ​​the protrusion 311. Preferably, the coating area of ​​the heat conductive material may be smaller than the lower surface area of ​​the protrusion 311. For example, the coating area of ​​the heat conductive material may be 30% to 70% based on 100% of the lower surface area of ​​the protrusion 311.

[0060] Alternatively, the thermal conductivity of the heat conductive layer (H) may be 50 W / m·K or higher. Thermal conductivity refers to the thermal conductivity of the heat conductive layer (H) itself, regardless of the type, amount, thickness, etc. of the material forming the heat conductive layer (H).

[0061] When the thermally conductive layer (H) or the thermally conductive material satisfies the above thermal conductivity, if heat is generated in the electrode assembly 100, the portion coated with the thermally conductive material melts or breaks earlier than the portion not coated with the thermally conductive material, thereby causing the heat in the electrode box 200 to be dissipated to the outside.

[0062] In exemplary embodiments, the thermally conductive material may include any one of a metal-based material, a ceramic-based material, a carbon-based material, and a polymer-based material.

[0063] For example, the metal-based material may include silver, copper, aluminum, etc., and the ceramic-based material may include silicon carbide (SiC), beryllium oxide (BeO), aluminum nitride (AlN), aluminum oxide (Al2O3), etc.

[0064] Furthermore, the heat conducting layer or the heat conducting material may also include an electrically conductive material.

[0065] The gasket 330 may be located inside the crimping portion 220 of the battery case 200 described below. The gasket 330 may increase the sealing force between the top cover 310 and the battery case 200.

[0066] A safety vent 320 may also be included. The safety vent 320 is located below the top cover 310 and may be electrically connected to the top cover 310. At least a portion of a surface of the safety vent 320 facing the top cover 310 may be in contact with the top cover 310. The safety vent 320 is in contact with the top cover 310 for a certain length from the edge of the safety vent 320, and a portion other than the contact length may be positioned away from the top cover 310. The portion of the safety vent 320 in contact with the top cover 310 may be coupled to the gasket 330.

[0067] In this case, the gasket 330 may be located inside the crimping portion 220 of the battery case 200. The gasket 330 may increase the sealing force between the safety vent 320 and the battery case 200.

[0068] The spacing distance between the safety vent 320 and the top cover 310 may increase from a region of the safety vent 320 that contacts the top cover 310 toward a center of the safety vent 320 .

[0069] The safety vent 320 may include a contact portion contacting the top cover 310, a central portion located at the center of the safety vent 320 and contacting the current interruption device, and a connection portion connecting the contact portion with the central portion. The safety vent 320 may be provided with a bent portion (or notch) at portions where the contact portion contacts the connection portion and where the connection portion contacts the central portion.

[0070] In an exemplary embodiment, the safety vent 320 may have an end portion perpendicular to the axial direction of the battery case 200. In this case, the top cover 310 may be disposed perpendicular to the axial direction of the battery case 200 similarly to the safety vent 320. That is, the safety vent 320 and the top cover 310 may be positioned horizontally.

[0071] In another exemplary embodiment, the safety vent 320 may have an end portion bent to surround the outer peripheral surface of the top cover 310 .

[0072] In the secondary battery 1 according to the exemplary embodiment of the present invention, when the electrode assembly 100 accommodated in the battery case 200 reacts with the electrolyte solution, gas or heat is generated, thereby increasing the internal pressure.

[0073] As the internal pressure of the secondary battery 1 increases, the safety vent 320 receives a force in the direction of the top cover 310 , and the bent portion is broken, thereby causing the gas within the secondary battery 1 to be discharged.

[0074] A current interrupt device (CID) 330 is located below the safety vent 320 , and at least a portion of the current interrupt device (CID) 330 may be connected to the safety vent 320 .

[0075] When the safety vent 320 is ruptured as the internal pressure of the secondary battery 1 increases, the current interruption device 330 is separated from the safety vent 320 to interrupt current.

[0076] More specifically, the current interruption device 330 may include a connection portion connected to the safety vent 320 at a central portion and protruding in a direction in which the safety vent 320 is positioned, an edge portion other than the connection portion, and a coupling portion connecting the connection portion and the edge portion. The coupling portion is provided in plurality, and the plurality of coupling portions may be positioned spaced apart from each other.

[0077] When the safety vent 320 is deformed in the direction where the top cover 310 is positioned, the coupling portion may be disconnected and the connecting portion may be separated from the edge portion. That is, the connecting portion is separated in the direction of the top cover 310 while being connected to the safety vent 320.

[0078] The CID gasket 350 surrounds the edge of the current interrupt device 330 and may electrically separate the safety vent 320 from the edge portion and the coupling portion of the current interrupt device 330 except for the connection portion.

[0079] The electrode assembly 100 includes a positive electrode, a separator, and a negative electrode. The electrode assembly 100 is a wound type chargeable / dischargeable power generating element, which includes a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode and is wound.

[0080] In exemplary embodiments, the electrode assembly 100 may be a wound structure in which a negative electrode, a separator, and a positive electrode are sequentially stacked and wound, or a first separator, a negative electrode, a second separator, and a positive electrode are sequentially stacked and wound.

[0081] The positive electrode includes a positive electrode active material portion having a positive electrode active material applied to one surface or both surfaces of a positive electrode current collector and a positive electrode uncoated portion having no positive electrode active material applied thereto.

[0082] The positive electrode current collector is a metal thin plate having excellent conductivity, and may include, for example, an aluminum (Al) foil.

[0083] The positive electrode active material may include lithium cobalt oxide having high operating voltage and excellent capacity characteristics, lithium nickel oxide having high reversible capacity and easy realization of large-capacity batteries, lithium nickel cobalt oxide in which a portion of nickel is replaced by cobalt, lithium nickel cobalt metal oxide in which a portion of nickel is replaced by manganese, cobalt or aluminum, lithium manganese-based oxide with excellent thermal stability and low cost, lithium iron phosphate with excellent stability, etc.

[0084] The negative electrode includes a negative electrode active material portion having a negative electrode active material applied to one surface or both surfaces of a negative electrode current collector and a negative electrode uncoated portion having no negative electrode active material applied thereto.

[0085] The negative electrode current collector may include a metal thin plate having excellent electrical conductivity, such as copper (Cu) or nickel (Ni) foil.

[0086] The negative electrode active material may be, for example, a carbon material such as crystalline carbon, amorphous carbon, a carbon composite material or carbon fiber, lithium metal, lithium alloy, etc. In this case, the negative electrode active material may also include, for example, non-graphite-based SiO (silicon dioxide), SiC (silicon carbide), etc. for high capacity design.

[0087] The electrode assembly 100 according to the exemplary embodiment may have a positive electrode uncoated portion and a negative electrode uncoated portion disposed at both ends or in the middle of the positive electrode and the negative electrode in the short direction of the electrode current collector. In addition, the positive electrode tab and the negative electrode tab may be provided by being bonded to the positive electrode uncoated portion and the negative electrode uncoated portion.

[0088] The positive electrode tab and the negative electrode tab serve to transfer electrons collected in the current collector to an external circuit, and may protrude in the same direction or in opposite directions with respect to the electrode assembly of the wound structure.

[0089] The electrode assembly 100 according to another exemplary embodiment may have positive and negative uncoated portions disposed along the long direction of the positive and negative current collectors. The positive and negative uncoated portions may be disposed at both ends in the short direction of the positive and negative current collectors.

[0090] At least a portion of the positive electrode uncoated portion and the negative electrode uncoated portion may include a plurality of segments divided along the winding direction of the electrode assembly 100. The plurality of segments may be bent in the direction in which the core portion of the electrode assembly 100 is located. The plurality of bent segments may overlap in a plurality of layers. In this case, the first current collector and the second current collector may be combined in an area where the plurality of segments overlap in a plurality of layers.

[0091] In this case, the first and second current collectors are included in two secondary batteries 1 according to the exemplary embodiment and according to another exemplary embodiment, and may be located on facing surfaces, ie, on upper and lower surfaces located in a height direction of the electrode assembly 100 .

[0092] The first current collector and the second current collector are electrically connected to the battery case 200. The first current collector may serve as a medium for electrical connection between the electrode assembly 100 and the battery case 200. The first current collector or the second current collector may be welded and fixed to the inner wall of the battery case 200.

[0093] The separator prevents an internal short circuit that may be generated when the positive electrode and the negative electrode contact each other, and may include a porous material to facilitate migration of ions between the electrodes.

[0094] In an exemplary embodiment, the separator may include a substrate layer made of a porous material. The substrate layer may include, for example, any one selected from the group consisting of polyethylene (PE), polystyrene (PS), polypropylene (PP), and a copolymer of polyethylene (PE) and polypropylene (PP).

[0095] In another exemplary embodiment, the separator may include a safety reinforced separator (SRS). That is, the separators 130, 140 may include a substrate layer made of a porous material and a coating layer coated and formed on the substrate layer by applying a mixed slurry of inorganic particles and a binder polymer. Preferably, the coating layer includes ceramic particles and has a uniform pore structure formed by the interstitial volume between the ceramic particles as a component of the active layer in addition to the pore structure of the separator substrate itself.

[0096] The coating may include ceramic particles including at least one selected from the group consisting of aluminum oxide, silicon dioxide, TiO2, SiC, and MgAl2O4. Such a coating is included so that the safety of the electrode assembly can be improved. The coating may also include a lithium salt.

[0097] The battery case 200 may have a columnar structure having a space formed therein. The battery case 30 may accommodate the electrode assembly 100 including electrodes and separators and an electrolyte solution (not shown) in the inner space.

[0098] The battery case 200 of the secondary battery 1 according to the exemplary embodiment may have a structure in which one side is opened (hereinafter referred to as an opening portion) and the other side is sealed.

[0099] The battery case 200 of the secondary battery 1 according to another exemplary embodiment may have a structure in which one side is open and the other side is sealed (sealed portion) except for a through hole at the center.

[0100] Here, one side and the other side of the battery case 200 refer to end portions located at an upper portion and a lower portion in a height direction of the electrode assembly 100 or the secondary battery 1 .

[0101] The opened one side of the battery case 200 may be provided with a beading portion 210 folded toward the center of the secondary battery 1. The battery case 200 may be provided with a crimping portion 220 between the beading portion 210 and the opening.

[0102] The battery case 200 may be made of a lightweight conductive metal material, such as aluminum or an aluminum alloy.

[0103] In the secondary battery 1 according to another exemplary embodiment, the electrode terminal may be coupled to a through hole provided on the other side of the battery case 200. For example, the electrode terminal may be fixed on the inner surface of the sealing portion of the battery case 200 by riveting.

[0104] The battery case 200 and the cap assembly 300 have the same polarity, and the electrode terminal has a different polarity from the battery case 200 and the cap assembly 300. For example, when the electrode terminal is a positive electrode, the battery case 200 and the cap assembly 300 may be a negative electrode.

[0105] According to an exemplary embodiment of the present invention, there is provided a battery pack 3 including any one of the above-described secondary batteries.

[0106] Regarding the above exemplary embodiments, refer to Figure 4 , shows a battery pack 3 including a secondary battery 1 in a battery pack case 2 .

[0107] The battery pack according to the above exemplary embodiment has high output / high capacity.

[0108] According to an exemplary embodiment of the present invention, there is provided a vehicle including the above-mentioned battery pack.

[0109] Regarding the above exemplary embodiments, refer to Figure 5 , a vehicle V including a battery pack 3 is shown.

[0110] Since the vehicle according to the above exemplary embodiment uses a battery pack having high output / high capacity, the vehicle is excellent in stability and safety.

[0111] While the present invention has been described with reference to preferred exemplary embodiments, it will be understood by those skilled in the art that various modifications and variations may be made to the present invention without departing from the technical spirit and scope of the present invention.

Claims

1. A cap assembly for a secondary battery, the cap assembly comprising: a top cover electrically connected to the outside; as well as a liner configured to surround an outer peripheral portion of the top cover, Wherein, the top cover has a heat conducting layer arranged on one surface.

2. The cap assembly for a secondary battery according to claim 1, wherein: The heat conductive layer includes at least one of a metal-based material, a ceramic-based material, a carbon-based material, and a polymer-based material.

3. The cap assembly for a secondary battery according to claim 1, wherein The thermal conductivity of the heat-conducting layer is higher than that of the top cover.

4. The cap assembly for a secondary battery according to claim 1, wherein The top cover includes: a protrusion, an edge portion, and a connection portion, wherein the edge portion is a peripheral portion in contact with the gasket, and the connection portion connects the protrusion and the edge portion, and Wherein, the heat conducting layer is arranged on a surface of the protrusion.

5. The cap assembly for a secondary battery according to claim 1, further comprising a safety vent at a lower side of the top cover, and in, The gasket surrounds a peripheral portion of at least one of the top cover and the safety vent. 6 . The cap assembly for a secondary battery according to claim 1 , further comprising a current interrupt device (CID) and a current interrupt device gasket.

7. The cap assembly for a secondary battery according to claim 1, wherein The top cover includes a vent portion having a relatively thin thickness compared to a surrounding area.

8. A secondary battery, comprising: an electrode assembly in which electrodes and separators are wound; a case having a space into which the electrode assembly is introduced and having at least one side portion opened; and A cover assembly according to any one of claims 1 to 7, coupled to an open side of the box. 9 . A battery pack comprising the secondary battery according to claim 8 .

10. A vehicle comprising the battery pack according to claim 9.

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