Secondary battery cap assembly, secondary battery, battery pack, and vehicle

Abstract

The present invention relates to a cap assembly for a secondary battery, comprising a top cap electrically connected to the outside and a gasket surrounding an outer periphery of the top cap, the top cap having a thermally conductive layer on one surface.

Description

[Technical Field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2023-0100295, filed with 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 means of transportation. [Background technology]

[0003] In general, a secondary battery is a battery that can be charged and discharged, unlike a primary battery that cannot be charged. Such secondary batteries are widely used in cutting-edge electronic devices such as mobile phones, laptops, and camcorders.

[0004] The stability of the secondary battery can be ensured by undergoing a stability test in which one side of the secondary battery is crimped with a crimping machine and internal short circuits are measured.

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

[0006] The electrode assembly housed in the battery case is a chargeable and dischargeable power generating element consisting of a laminated structure of a positive electrode, a separator, and a negative electrode. It is classified into a folded electrode assembly (jelly roll) in which a separator is interposed between a long sheet-type positive electrode and a negative electrode coated with an active material and the electrode is wound up, and a stacked electrode assembly in which multiple positive and negative electrodes of a predetermined size are stacked one on top of the other with a separator interposed between them. Of these, jelly rolls have the advantages of being easy to manufacture and having a high energy density per weight, and there is a growing demand for cylindrical batteries that include electrode assemblies with a jelly roll structure.

[0007] A cylindrical battery includes a jelly-roll structured electrode assembly, a battery case, and a cap assembly. The cap assembly is a structure that is attached to the opening of the battery case into which the electrode assembly is inserted. Because the cap assembly blocks the battery case, gas inside the battery may not normally be released to the outside.

[0008] A cylindrical battery may experience thermal runaway due to 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, the internal heat of the battery case may damage the separator, cause a short circuit between the positive and negative electrodes, or generate excessive current due to an internal short circuit, which may result in a fire or even an explosion.

[0009] Furthermore, the internal heat and gas of the battery case cannot be released, which increases the internal pressure of the battery case, potentially causing the battery case to burst. Summary of the Invention [Problem to be solved by the invention]

[0010] In view of the above-mentioned problems in the prior art, an object of the present invention is to provide a cap assembly for a secondary battery, a secondary battery, a battery pack, and a means of transportation. [Means for solving the problem]

[0011] One embodiment of the present invention provides a cap assembly for a secondary battery, comprising: a top cap electrically connected to the outside; and a gasket surrounding an outer periphery of the top cap, wherein the top cap has a thermally conductive layer on one surface.

[0012] One embodiment of the present invention provides a secondary battery including: an electrode assembly in which electrodes and a separator are wound; a case having an open side and a space for receiving the electrode assembly; and the cap assembly coupled to the open side of the case.

[0013] One embodiment of the present invention provides a battery pack including the secondary battery.

[0014] One embodiment of the present invention provides a means of transportation including the battery pack. [Effects of the Invention]

[0015] The secondary battery cap assembly, secondary battery, battery pack, and transportation means according to the embodiments of the present invention can prevent the battery case from exploding by preventing a thermal runaway phenomenon caused by heat generated by the decomposition reaction of the electrode active material melting the top cap. [Brief explanation of the drawings]

[0016] [Figure 1a] 1 is a cross-sectional view of a cap assembly according to an embodiment of the present invention. [Figure 1b] FIG. 1 is a perspective view of a top cap and gasket according to one embodiment of the present invention. [Figure 2a] FIG. 4 is a cross-sectional view showing a secondary battery according to another embodiment of the present invention. [Figure 2b] FIG. 10 is a plan view showing a top cap and a battery case according to another embodiment of the present invention. [Figure 3] 1 is a cross-sectional view showing a secondary battery according to an embodiment of the present invention; [Figure 4] 1 is a perspective view showing a battery pack according to an embodiment of the present invention; [Figure 5] 1 is a perspective view showing a moving means according to an embodiment of the present invention; [Explanation of symbols]

[0017] 1...Secondary battery 2-pack housing 3 Battery pack 100...electrode assembly 200 Battery Case 210 Beading section 220 Crimping section 300a, 300b Cap assembly 310a, 310b Top cap 311...Protrusion 312 Frame 313 Bridge 314 Venting section 320 Safety Vent 330 Gasket 340 CID 350 CID gasket C Core H: Thermally conductive layer or material DETAILED DESCRIPTION OF THE INVENTION

[0018] The detailed description of the present invention is intended to fully explain the present invention to those skilled in the art. Throughout the specification, when a part is described as "comprising" a certain element or as "featuring" a certain structure and shape, this does not mean that other elements, structures, and shapes are excluded, but that other elements, structures, and shapes may be included, unless otherwise specified to the contrary.

[0019] The present invention can be modified in various ways and can have various embodiments, so specific examples will be presented and described in detail in the detailed description. However, this is not intended to limit the content of the invention according to the embodiments, and it should be understood that the present invention includes all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0020] The present invention will be described in detail below with reference to the drawings. However, the drawings are for illustrative purposes only and the scope of the present invention is not limited by the drawings.

[0021] The secondary battery 1 according to the present invention includes an electrode assembly 100, a battery case 200, and cap assemblies 300a and 300b. The secondary battery 1 according to the present invention is a cylindrical secondary battery, and in one embodiment, the cap assembly 300a is coupled to an upper portion of the battery case 200, and the positive and negative uncoated regions provided on the positive and negative electrodes of the electrode assembly 100 may be provided in the minor axis direction of the positive and negative current collectors, respectively.

[0022] In the secondary battery 1 according to another embodiment, the cap assembly 300b may be coupled to the lower part of the battery case 200. The positive electrode uncoated portion and the negative electrode uncoated portion of the electrode assembly 100 may be provided in the longitudinal direction of the positive electrode current collector and the negative electrode current collector, respectively.

[0023] When the cap assembly 300a is coupled to the upper part of the battery case 200, the cap assembly 300a may include a top cap 310a, a safety vent 320, and a gasket 330. When the cap assembly 300b is coupled to the lower part of the battery case 200, the cap assembly 300b may include a top cap 310b and a gasket 330.

[0024] The top cap 310 a may be located at the top of the cap assembly 300 a and protrude in a direction away from the center of the battery case 200 .

[0025] According to an embodiment, the top cap 310a may serve as an electrode terminal such that the protruding portion is electrically connected to the outside. For example, the top cap 310a may serve as a positive electrode terminal.

[0026] 1a and 1b, the top cap 310a includes a protrusion 311 protruding from the upper portion, a frame 312 that contacts or is surrounded by a safety vent 320 (described later), and a bridge 313 that connects the protrusion 311 and the frame 312.

[0027] 2a and 2b, a top cap 310b according to another embodiment may include a venting portion 314 that prevents the pressure resistance from increasing beyond a preset value due to gas generated inside the battery case 200. In particular, the top cap 310b may include a protrusion 311, a frame 312, and a venting portion 314, and the venting portion 314 may be located between the protrusion 311 and the frame 312.

[0028] The venting portion 314 is a region of the top cap 310b that is thinner than the surrounding region. The venting portion 314 is structurally weaker than the surrounding region. Therefore, if an abnormality occurs in the cylindrical secondary battery and the internal pressure of the battery case 200 increases above a predetermined level, the venting portion 314 may break, causing gas generated inside the battery case 200 to be released to the outside.

[0029] For example, the venting portion 314 may be formed by notching one or both surfaces of the top cap 310b to partially reduce the thickness of the top cap 310b.

[0030] A thermally conductive layer H is provided on the lower surface of the top caps 310a and 310b, i.e., the surface facing the electrode assembly 100, and the thermally conductive layer H may include a material having a higher thermal conductivity or thermal conductivity than the top caps 310a and 310b.

[0031] In other words, the cap assembly 300 has the bottom surfaces of the top caps 310a and 310b coated with a thermally conductive material, and the thermally conductive material may be a material having a higher thermal conductivity or rate of thermal conductivity than the top caps 310. For example, the top caps 310a and 310b 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 or rate of thermal conductivity than the iron or stainless steel.

[0032] Preferably, the top caps 310a, 310b may include iron, and the thermally conductive layer may include a material having a thermal conductivity higher than or equal to that of iron.

[0033] The thermally conductive layer H or a thermally conductive material may be coated or laminated on the lower surfaces of the protrusions 311 of the top caps 310a and 310b. The area coated with the thermally conductive material may be the same as or smaller than the area of ​​the lower surfaces of the protrusions 311. Preferably, the area coated with the thermally conductive material may be smaller than the area of ​​the lower surfaces of the protrusions 311. For example, based on 100% of the lower surface area of ​​the protrusions 311, the area coated with the thermally conductive material may be the entire protrusion or 30% to 70% or less.

[0034] Alternatively, the thermally conductive layer H may have a thermal conductivity of 50 W / mxK or more. The thermal conductivity refers to the thermal conductivity of the thermally conductive layer H itself, regardless of the type, amount, thickness, etc., of the material that constitutes the thermally conductive layer H.

[0035] Since the thermally conductive layer H or the thermally conductive material satisfies the thermal conductivity, when heat is generated in the electrode assembly 100, the portion coated with the thermally conductive material melts or explodes before the portion not coated with the thermally conductive material, thereby allowing the heat inside the electrode case 200 to be dissipated to the outside.

[0036] In an embodiment, 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.

[0037] 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.

[0038] The thermally conductive layer or the thermally conductive material may further include an electrically conductive material.

[0039] The gasket 330 may be positioned inside the crimping portion 220 of the battery case 200, which will be described later. The gasket 330 can increase the sealing force between the top caps 310a and 310b and the battery case 200.

[0040] The safety vent 320 may further be included. The safety vent 320 may be located at the bottom of the top cap 310a and electrically connected to the top cap 310a. At least a portion of the surface of the safety vent 320 facing the top cap 310a may be in contact with the top cap 310a. The safety vent 320 may be in contact with the top cap 310a for a predetermined length from the frame, and the portion excluding the contact length may be spaced apart from the top cap 310a. The portion of the safety vent 320 that is in contact with the top cap 310a may be coupled to a gasket 330.

[0041] In this case, the gasket 330 may be positioned inside the crimping portion 220 of the battery case 200. The gasket 330 can increase the sealing force between the safety vent 320 and the battery case 200.

[0042] The safety vent 320 may have a distance from the top cap 310a that increases toward the center of the safety vent 320 in a region that comes into contact with the top cap 310a.

[0043] The safety vent 320 may include a contact portion that contacts the top cap 310a, a central portion that is located at the center of the safety vent 320 and that contacts the current interrupting device, and a connecting portion that connects the contact portion and the central portion. The safety vent 320 may also include bent portions (or notches) at the portions where the contact portion and the connecting portion and the connecting portion and the central portion contact each other.

[0044] In one embodiment, the safety vent 320 may be provided with an end portion perpendicular to the axial direction of the battery case 200. In this case, the top cap 310a may be provided perpendicular to the axial direction of the battery case 200, just like the safety vent 320. That is, the safety vent 320 and the top cap 310a may be positioned horizontally.

[0045] In another embodiment, the safety vent 320 may be provided in a form in which the end portion is bent and surrounds the outer periphery of the top cap 310a.

[0046] In the secondary battery 1 according to the present invention, the electrode assembly 100 housed inside the battery case 200 reacts with the electrolyte, generating gas and heat, and causing an increase in internal pressure.

[0047] When the pressure inside the secondary battery 1 increases, the safety vent 320 receives a force in the direction of the top cap 310a, causing the bent portion to burst, thereby discharging the internal gas of the secondary battery 1.

[0048] A current interruptive device (CID) 340 may be located below the safety vent 320 and at least a portion thereof may be connected to the safety vent 320 .

[0049] When the safety vent 320 bursts due to an increase in the internal pressure of the secondary battery 1, the current interruption device 340 is separated from the safety vent 320 to interrupt the current.

[0050] More specifically, the current interruption device 340 may include a central portion connected to the safety vent 320, a connecting portion protruding in the direction of the safety vent 320, a peripheral portion excluding the connecting portion, and a joining portion connecting the connecting portion and the peripheral portion. A plurality of joining portions may be provided, and the plurality of joining portions may be spaced apart from one another.

[0051] When the safety vent 320 is deformed in the direction in which the top cap 310a is positioned, the joint breaks and the connecting portion can be separated from the edge portion. That is, the connecting portion can be separated in the direction of the top cap 310a while still connected to the safety vent 320.

[0052] The CID gasket 350 surrounds the edge of the current interrupting element 340 and can electrically isolate the edge of the current interrupting element 340 other than the connecting portion and the connecting portion from the safety vent 320 .

[0053] The electrode assembly 100 includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes. The electrode assembly 100 is a power generating element that is wound into a jelly-roll shape and can be charged and discharged.

[0054] In one embodiment, the electrode assembly 100 may be a jelly roll 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.

[0055] The positive electrode includes a positive electrode active material portion in which a positive electrode active material is coated on one or both surfaces of a positive electrode current collector, and a positive electrode non-coating portion in which the positive electrode active material is not coated.

[0056] The positive electrode current collector is a thin metal plate with excellent conductivity, and may include, for example, aluminum (Al) foil.

[0057] The positive electrode active material may include lithium cobalt oxide, which has a high working voltage and excellent capacity characteristics; lithium nickel oxide, which has a high reversible capacity and can easily realize a large-capacity battery; lithium nickel cobalt oxide, in which nickel is partially substituted with cobalt; lithium nickel cobalt metal oxide, in which nickel is partially substituted with manganese, cobalt, or aluminum; lithium manganese-based oxide, which is excellent in thermal stability and inexpensive; and lithium iron phosphate, which is excellent in stability.

[0058] The negative electrode includes a negative electrode active material portion in which a negative electrode active material is coated on one or both surfaces of a negative electrode current collector, and a negative electrode uncoated portion in which the negative electrode active material is not coated.

[0059] The negative electrode current collector may include a thin metal plate with high conductivity, such as copper (Cu) or nickel (Ni) foil.

[0060] The negative electrode active material may be, for example, a carbon material such as crystalline carbon, amorphous carbon, carbon composite, or carbon fiber, or lithium metal or a lithium alloy. In this case, the negative electrode active material may further include, for example, non-graphite-based silica (SiO) or silicon carbide (SiC) for a high capacity design.

[0061] In one embodiment, the electrode assembly 100 may include positive and negative uncoated regions on both ends or in the middle of the positive and negative electrodes, respectively, in one direction of the electrode current collectors. In addition, positive and negative tabs may be attached to the positive and negative uncoated regions.

[0062] The positive electrode tab and the negative electrode tab transfer electrons collected on the current collector to an external circuit, and may protrude in the same direction or in opposite directions relative to the electrode assembly of the jelly roll structure.

[0063] In another embodiment of the electrode assembly 100, the positive and negative uncoated regions may be provided in the longitudinal direction of the positive and negative current collectors, or may be located at both ends of the positive and negative current collectors in a single direction.

[0064] At least a portion of the positive electrode uncoated region and the negative electrode uncoated region may include a plurality of segments separated along the winding direction of the electrode assembly 100. The plurality of segments may be banded in the direction in which the core portion of the electrode assembly 100 is positioned. The banded plurality of segments may be overlapped in multiple layers. In this case, the first current collector and the second current collector may be joined in a region where the plurality of segments are overlapped in multiple layers.

[0065] In this case, the first current collector and the second current collector are all included in the secondary battery 1 according to one embodiment and other embodiments, and may be located on opposing surfaces positioned in the height direction of the electrode assembly 100, i.e., the upper and lower surfaces.

[0066] The first current collector and the second current collector are electrically connected to the battery case 200. The first current collector may function as a medium for electrical connection between the electrode assembly 100 and the battery case 200. Either the first current collector or the second current collector may be fixed to the inner wall of the battery case 200 by welding.

[0067] The separator prevents an internal short circuit that may occur when the positive electrode and the negative electrode come into contact with each other, and may include a porous material to facilitate the movement of ions between the electrodes.

[0068] In one embodiment, the separator may include a substrate layer made of a porous material, such as polyethylene (PE), polystyrene (PS), polypropylene (PP), or a copolymer of polyethylene (PE) and polypropylene (PP).

[0069] In another embodiment, the separator may include a safety-reinforced separator (SRS). That is, the separator may include a substrate layer made of a porous material and a coating layer formed by coating the substrate layer with 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, which are the active layer components, along with the pore structure contained in the separator substrate itself.

[0070] The coating layer may include ceramic particles including at least one selected from the group consisting of alumina, silica, TiO2, SiC, and MgAl2O4. The inclusion of such a coating layer can enhance the safety of the electrode assembly. The coating layer may further include a lithium salt.

[0071] The battery case 200 may have a columnar structure with a space formed therein. The battery case 200 may accommodate the electrode assembly 100 including electrodes and a separator, and an electrolyte (not shown) in the space.

[0072] The battery case 200 of the secondary battery 1 according to an embodiment may have a structure in which one side is open (hereinafter, referred to as an opening) and the other side is sealed.

[0073] The battery case 200 of the secondary battery 1 according to another embodiment may have a structure (sealed portion) that is open on one side and sealed on the other side except for a through-hole in the center.

[0074] Here, one side and the other side of the battery case 200 refer to the ends located at the upper and lower parts along the height direction of the electrode assembly 100 or the secondary battery 1 .

[0075] One side of the open 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 also be provided with a crimping portion 220 between the beading portion 210 and the opening.

[0076] The battery case 200 may be made of a lightweight conductive metal material such as aluminum or an aluminum alloy.

[0077] In the secondary battery 1 according to another embodiment, the electrode terminals may be coupled to through-holes provided on the other side of the battery case 200. For example, the electrode terminals may be fixed to the inner surface of the closing part of the battery case 200 by riveting.

[0078] The battery case 200 and the cap assembly have the same pole, and the electrode terminal has a different pole from the battery case 200 and the cap assembly. For example, if the electrode terminal is a positive pole, the battery case 200 and the cap assembly can be a negative pole.

[0079] According to an embodiment of the present invention, a battery pack 3 including any one of the above-described secondary batteries is provided.

[0080] In relation to this embodiment, referring to FIG. 4, a battery pack 3 including a secondary battery 1 in a pack housing 2 is shown.

[0081] The battery pack according to this embodiment has high output and high capacity.

[0082] According to an embodiment of the present invention, there is provided a vehicle including the battery pack described above.

[0083] In relation to this embodiment, referring to FIG. 5, a vehicle V including a battery pack 3 is shown.

[0084] The vehicle according to the embodiment uses a battery pack with high output / high capacity, and is therefore excellent in terms of stability and safety.

[0085] Although the present invention has been described above with reference to preferred embodiments, it should be understood that those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims

1. a top cap electrically connected to the outside; and a gasket surrounding the outer periphery of the top cap; Including, The cap assembly for a secondary battery, wherein the top cap has a thermally conductive layer on one surface thereof.

2. The cap assembly for a secondary battery according to claim 1 , wherein the thermally 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 thermally conductive layer has a higher thermal conductivity or a higher thermal conductivity than the top cap.

4. the top cap includes a protrusion, a frame portion that is an outer periphery of the top cap and is in contact with the gasket, and a connecting portion that connects the protrusion and the frame portion, The cap assembly for a secondary battery according to claim 1 , wherein the thermally conductive layer is provided on one surface of the protrusion.

5. further comprising a safety vent located below the top cap; The cap assembly for a secondary battery according to claim 1 , wherein the gasket surrounds an outer periphery of at least one of the top cap and the safety vent.

6. The secondary battery cap assembly according to claim 1 , further comprising a current interrupting device (CID) and a current interrupting device gasket.

7. The cap assembly for a secondary battery according to claim 1 , wherein the top cap includes a venting portion that is relatively thinner than a peripheral region.

8. an electrode assembly in which the electrode and the separator are wound up; a case having a space into which the electrode assembly is inserted and at least one side of which is open; and A cap assembly according to any one of claims 1 to 7, coupled to one open side of the case; A secondary battery comprising:

9. A battery pack comprising the secondary battery according to claim 8.

10. A means of transportation comprising the battery pack of claim 9.

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