Cylindrical lithium secondary battery

Abstract

The cylindrical lithium secondary battery pack of the present invention includes: a battery can housing an electrode assembly through an opening formed on one side thereof; a cover plate for covering the opening; and a current collector disposed between the electrode assembly and the cover plate and electrically connecting the electrode assembly and the battery can, wherein the current collector has a tensile strength of 200 N / mm² to 370 N / mm².

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2023-0190267, filed on December 22, 2023, and Korean Patent Application No. 10-2024-0096753, filed on July 22, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This invention relates to a cylindrical lithium secondary battery. Background Technology

[0005] With recent advancements in electric vehicle technology, the increased demand for high-capacity batteries necessitates the development of large-volume, large-size cylindrical batteries. In the case of small cylindrical batteries commonly used in existing technology (i.e., cylindrical batteries with a form factor of 1865 or 2170), resistance or heat generation has no significant impact on battery performance due to their small capacity. However, applying the specifications of conventional small cylindrical batteries directly to large cylindrical batteries could lead to serious safety issues.

[0006] As battery size increases, the amount of heat and gas generated inside the battery also increases. This heat and gas cause the internal temperature and pressure to rise, potentially leading to battery fire or explosion. To prevent these problems, the heat and gas inside the battery must be properly vented to the outside, and the battery's cross-sectional area (which serves as a channel for heat dissipation) must increase proportionally to the increase in volume. However, since the increase in cross-sectional area is often mismatched with the increase in volume, as batteries become larger, the amount of heat generated inside the battery may increase, leading to an increased risk of explosion and reduced output. Furthermore, when fast charging at high voltages, there is a risk of battery fire due to the large amount of heat generated around the electrode terminals in a short period of time.

[0007] To prevent the risk of fire or explosion, safety devices are provided within the secondary battery according to relevant technologies. For example, a safety vent is primarily installed within the cylindrical secondary battery. According to these technologies, when the internal pressure of the secondary battery increases, a path can be formed through which gas is released as a portion of the safety vent ruptures. Therefore, gas within the secondary battery can be released to the outside through this path, preventing the risk of explosion.

[0008] However, even when the safety vent is operating, if the flame continues and the electrode assembly is not ejected from the outside of the can, a problem arises where the flame is sprayed to the side of the can. When cylindrical lithium secondary batteries are used in vehicles, battery packs with multiple cylindrical lithium secondary batteries connected together can be applied. However, there is a problem that a break in the side surface of the battery can cause a continuous flame in other surrounding cell units. Summary of the Invention

[0009] Technical issues

[0010] The cylindrical lithium secondary battery of the present invention can be provided as a cylindrical battery with a large volume to achieve high capacity, and improves the problem of side surface cracking of the can in the event of fire to achieve high safety.

[0011] Technical solution

[0012] [1] In a first aspect, the present invention provides a cylindrical lithium secondary battery comprising: an electrode assembly in which a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes are wound in one direction; a battery can configured to receive the electrode assembly through an opening defined on one side thereof; a cover plate configured to cover the opening; and a current collector disposed between the electrode assembly and the cover plate to electrically connect the electrode assembly to the battery can, wherein the current collector has a current density of 200 N / mm². 2 Up to 370 N / mm 2 Tensile strength.

[0013] [2] In a second aspect, the present invention can provide a battery including a beading part as a support member, a cover plate disposed on the beading part, wherein the current collector can be connected to the beading part.

[0014] [3] In a third aspect, in the first or second aspect of the present invention, the current collector may have a strength of 230 N / mm². 2 Up to 350 N / mm 2 Tensile strength.

[0015] [4] In a fourth aspect, in any one of the first to third aspects of the present invention, the current collector may have a thickness of 50 μm to 500 μm.

[0016] [5] In a fifth aspect, in any one of the first to fourth aspects of the present invention, the pressing portion may have a thickness of 0.4 mm to 0.6 mm.

[0017] [6] In a sixth aspect, in any one of the first to fifth aspects of the present invention, the current collector may be a negative current collector.

[0018] [7] In a seventh aspect, in the sixth aspect of the invention, the current collector may be a copper thin film.

[0019] [8] In an eighth aspect, in any one of the first to seventh aspects of the invention, each of the positive electrode and the negative electrode may include an uncoated portion without an active material layer, and at least a portion of the uncoated portion of the positive electrode or the uncoated portion of the negative electrode may have a connectorless structure defining an electrode connector.

[0020] [9] In a ninth aspect, in an eighth aspect of the invention, the positive electrode uncoated portion and the negative electrode uncoated portion may be respectively disposed on one end of the positive electrode and one end of the negative electrode along the winding direction of the electrode assembly, the current collector may be connected to each of the positive electrode uncoated portion and the negative electrode uncoated portion, and the current collector may be connected to the electrode terminal.

[0021]

[10] In a tenth aspect, in an eighth or ninth aspect of the invention, each of the positive electrode uncoated portion and the negative electrode uncoated portion may be processed into a plurality of independently bendable segments, and at least a portion of the plurality of segments may be bent toward the winding center of the electrode assembly.

[0022]

[11] In an eleventh aspect, in a tenth aspect of the invention, at least some of the plurality of curved segments may overlap each other at the upper and lower ends of the electrode assembly, and the current collector may be connected to the plurality of overlapping segments.

[0023]

[12] In a twelfth aspect, in any one of the first to eleventh aspects of the invention, the cylindrical lithium secondary battery may have a form factor ratio of 0.4 or greater.

[0024]

[13] In a thirteenth aspect, in any one of the first to twelfth aspects of the present invention, the cylindrical lithium secondary battery may be a 46110 cell, a 4875 cell, a 48110 cell, a 4880 cell, a 4680 cell, or a 4695 cell.

[0025]

[14] In a fourteenth aspect, the present invention may provide a battery pack comprising the cylindrical lithium secondary battery described in any one of the first to thirteenth aspects.

[0026] Beneficial effects

[0027] The cylindrical lithium secondary battery of the present invention has the following effects: even if the secondary battery is decomposed to generate a flame, no holes or tears will appear in the side surface of the cell, and the flame can be guided toward the vent to prevent the flame from being directly transmitted to the adjacent cell cells.

[0028] Therefore, battery packs using the cylindrical lithium secondary battery of the present invention as unit cells can have high safety. Attached Figure Description

[0029] The following accompanying drawings illustrate preferred embodiments of the present disclosure and are used to further understand the technical spirit of the disclosure in conjunction with the detailed description thereof. This disclosure should not be construed as being limited to the drawings.

[0030] Figure 1 This is a perspective view of a cylindrical lithium secondary battery according to an embodiment of the present invention.

[0031] Figure 2 This is a cross-sectional view of a cylindrical lithium secondary battery according to an embodiment of the present invention.

[0032] Figure 3 yes Figure 2 The enlarged cross-sectional view of the first collector plate and its surroundings is shown. Detailed Implementation

[0033] Preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings, enabling those skilled in the art to readily practice the invention. However, the invention may be implemented in several different forms and is not limited to or construed as follows.

[0034] To clearly explain the invention, detailed descriptions of related known technologies that are irrelevant to the description or may unnecessarily obscure the essence of the invention have been omitted, and reference numerals have been added to the components in each drawing throughout this specification. In this case, the same or similar reference numerals are assigned to the same or similar elements throughout the specification.

[0035] Furthermore, the terms or words used in this specification and claims should not be construed as having a general meaning or a dictionary-based meaning, but rather should be interpreted as meanings and concepts within the scope of the invention based on the inventor's ability to appropriately define the concepts of the terms in order to best describe and explain the principles of his or her invention.

[0036] The invention will be described in more detail below.

[0037] The cylindrical lithium secondary battery and / or battery pack according to the present invention may include at least one of the configurations disclosed below, and may include any combination of technically possible configurations of the configurations disclosed below.

[0038] Figure 1 This is a perspective view of a cylindrical lithium secondary battery according to an embodiment of the present invention, and Figure 2 This is a cross-sectional view of a cylindrical lithium secondary battery according to an embodiment of the present invention.

[0039] The cylindrical lithium secondary battery 1 (hereinafter referred to as "secondary battery") according to an embodiment of the present invention may include an electrode assembly 10 and a battery can 20 for accommodating the electrode assembly 10.

[0040] The electrode assembly 10 may include a positive electrode, a negative electrode, and a diaphragm inserted between the positive and negative electrodes. Furthermore, the electrode assembly 10 may be provided with a first electrode connector 11 connected to one of the positive and negative electrodes and a second electrode connector 12 connected to the other of the positive and negative electrodes.

[0041] More specifically, the electrode assembly 10 can be configured as a wound core. The electrode assembly 10 can be manufactured by winding a stack in which the positive electrode, separator, negative electrode, and separator are sequentially stacked. A hollow portion C extending in the height direction can be formed at the center of the electrode assembly 10. To insulate the electrode assembly 10 from the inner circumference of the battery canister 20, the separator can be disposed on the outermost side of the electrode assembly 10.

[0042] The first electrode connector 11 and the second electrode connector 12 can be respectively disposed at both ends of the electrode assembly 10 in the height direction. More specifically, one uncoated portion of the positive and negative electrodes can be disposed at one end of the electrode assembly 10 to serve as the first electrode connector 11. The other uncoated portion of the positive and negative electrodes can be disposed at the other end of the electrode assembly 10 to serve as the second electrode connector 12.

[0043] Each of electrode connectors 11 and 12 may extend along the winding direction of electrode assembly 10.

[0044] Alternatively, each of electrode connectors 11 and 12 may include a plurality of foil markings disposed along the winding direction of electrode assembly 10.

[0045] The first current collector 50, which will be described later, can be connected to the first electrode connector 11, and the second current collector 60, which will be described later, can be connected to the second electrode connector 12. With the current collectors 50 and 60 connected to the electrode connectors 11 and 12 respectively, the electrode assembly 10 can be housed in the battery canister 20.

[0046] For example, the first electrode connector 11 can be the uncoated portion of the negative electrode, and the second electrode connector 12 can be the uncoated portion of the positive electrode. In this case, the first current collector 50 can be named the negative current collector, and the second current collector 60 can be named the positive current collector. This could be an example of a connectorless structure, which will be described later.

[0047] The battery canister 20 may have an approximately cylindrical shape. A surface 20a may be provided on one side of the battery canister 20 in the height direction, and an opening may be formed on the other side.

[0048] The electrode assembly 10 and the electrolyte can be contained together in the battery canister 20 through an opening.

[0049] The battery canister 20 may be made of a conductive material, such as a metal. The battery canister 20 may be electrically connected to the first electrode connector 11 via the first current collector 50, which will be described later. The battery canister 20 may have the same polarity as the first electrode connector 11.

[0050] A pressing edge 21 and a rolled edge 22 can be provided in the battery can 20. The pressing edge 21 and the rolled edge 22 can be provided adjacent to the opening of the battery can 20.

[0051] The pressing edge 21 can be provided by pressing the circumference of the battery can 20 inward in the radial direction. The inner diameter of the pressing edge 21 can be smaller than the inner diameter of the battery can 20.

[0052] The clamping portion 21 can be provided while the electrode assembly 10 is housed in the battery can 20. The electrode assembly 10 can be confined in the height direction of the battery can 20 between a surface 20a of the battery can 20 and the clamping portion 21. The clamping portion 21 can prevent the electrode assembly 10 from separating from the opening of the battery can 20. Furthermore, the clamping portion 21 can be connected to the first current collector 50. For example, the first current collector 50 can be welded to the clamping portion 21. Therefore, the first current collector 50 can electrically connect the first electrode connector 11 to the battery can 20.

[0053] The rolled edge portion 22 may be provided adjacent to the pressing edge portion 21. The rolled edge portion 22 may be provided by bending the end of the circumferential surface of the battery can 20 inward in the radial direction. The rolled edge portion 22 may be provided after the first current collector 50 is attached to the pressing edge portion 21. The rolled edge portion 22 may, together with the pressing edge portion 21, constrain the cover plate 30, which will be described later.

[0054] The secondary battery 1 may include a cover 30 that covers the opening of the battery canister 20.

[0055] The cover plate 30 may have an approximately circular plate shape. The cover plate 30 may define the appearance of the secondary battery 1 together with the battery canister 20. The edge of the cover plate 30 may be confined between the pressing edge portion 21 and the rolled edge portion 22 of the battery canister 20.

[0056] The cover plate 30 can be made of a highly rigid material, such as metal. The cover plate 30 can be insulated from the battery canister 20 and can be non-polarized. More specifically, the sealing portion 72 of the spacer 70, which will be described later, can be inserted between the cover plate 30 and the battery canister 20. This will be described in detail later.

[0057] The secondary battery 1 may include a terminal 40 fixed via a surface 20a of the battery canister 20.

[0058] Terminal 40 may pass through a surface 20a of battery can 20, more specifically, through the central portion of surface 20a. A portion of terminal 40 may be exposed on the outside of battery can 20, and another portion may be disposed inside battery can 20. For example, terminal 40 may be riveted to a surface 20a of battery can 20.

[0059] Terminal 40 may be made of a conductive material such as metal.

[0060] Terminal 40 can be connected to a second current collector 60, which will be described later. For example, the second current collector 60 can be soldered to terminal 40. Thus, the second current collector 60 can electrically connect the second electrode connector 12 to terminal 40.

[0061] Terminal 40 may be insulated from battery canister 20. More specifically, an insulating gasket G may be inserted between terminal 40 and battery canister 20. However, it is not limited to this, but may be applied to form an insulating coating on a portion of terminal 40 or to structurally fix terminal 40 while separating terminal 40 and battery canister 20 from each other.

[0062] The insulating gasket G can deform during the riveting of the terminal 40 and bend toward the inner surface of one surface 20a of the battery can 20. The insulating gasket G can seal the gap between the terminal 40 and the battery can 20.

[0063] Due to the insulating liner G, the battery canister 20 and the terminal 40 can have opposite polarities. More specifically, the battery canister 20 can have the same polarity as the first electrode connector 11, and the terminal 40 can have the same polarity as the second electrode connector 12. Therefore, one side 2a of the battery canister 20 can be used as a first terminal with a first polarity, and the terminal 40 can be used as a second terminal with a second polarity. Since one side 2a of the battery canister 20 and the terminal 40 are arranged adjacent to each other, the internal space required to install the busbar in the battery module comprising multiple secondary batteries 1 can be reduced, and the energy density of the battery module can be increased.

[0064] The secondary battery 1 may include a first current collector 50, which electrically connects a first electrode connector 11 to the battery canister 20. For example, the first electrode connector 11 may be connected to the negative terminal of the electrode assembly 10, and the first current collector 50 may be referred to as a negative current collector.

[0065] The secondary battery 1 may include a second current collector 60, which electrically connects the second electrode connector 11 to the terminal 40. For example, the second electrode connector 12 may be connected to the positive terminal of the electrode assembly 10, and the second current collector 60 may be referred to as the positive current collector.

[0066] The first current collector 50 and the second current collector 60 can be installed inside the battery tank 20.

[0067] The first current collector 50 can be disposed between the electrode assembly 10 and the cover plate 30 in the height direction of the battery can 20. The first current collector 50 can be connected to the first electrode connector 11. More specifically, the first current collector 50 can be welded to the first electrode connector 11. In addition, the first current collector 50 can be welded to the battery can 20, more specifically, to the pressure edge portion 21.

[0068] The second current collector 60 can be disposed between the electrode assembly 10 and a surface 20a of the battery can 20 in the height direction of the battery can 20. The second current collector 60 can be connected to the second electrode connector 12. More specifically, the second current collector 60 can be soldered to the second electrode connector 12. In addition, the second current collector 60 can be soldered to the terminal 40.

[0069] The secondary battery 1 may include a spacer 70 disposed between the cover plate 30 and the electrode assembly 10. More specifically, the spacer 70 may be disposed between the cover plate 30 and the first current collector 50.

[0070] The height of the spacer 70 can correspond to the distance between the cover plate 30 and the electrode assembly 10. The spacer 70 can prevent the electrode assembly 10 from moving or shaking within the battery canister 20.

[0071] The secondary battery 1 may include an insulator 80 disposed between the electrode assembly 10 and the battery canister 20. More specifically, the insulator 80 may be disposed between the second current collector 60 and the battery canister 20.

[0072] The insulator 80 can insulate the second current collector 60 and the electrode assembly 10 from the battery canister 20. The insulator 80 may be made of a resin material that has insulating properties.

[0073] A hole through which terminal 40 passes can be defined in the central portion of insulator 80. Terminal 40 can pass through this hole and be connected to second current collector 60.

[0074] The insulator 80 may have an approximate cap shape. In this case, a portion of the insulator 80 may be disposed between one surface 20a of the battery can 20 and the second current collector 60, while another portion may be disposed between the outer circumference of the second current collector 60 and the inner circumference of the battery can 20.

[0075] However, it is not limited to this; the insulator 80 may also be plate-shaped and disposed between a surface 20a of the battery can 20 and the second current collector 60. In this case, an insulating strip separate from the insulator 80 may be inserted between the outer circumference of the second current collector 60 and the inner circumference of the battery can 20.

[0076] The height of the insulator 80 can correspond to the vertical distance between a surface 20a of the battery can 20 and the electrode assembly 10. The insulator 80, together with the spacer 70, can prevent the electrode assembly 10 from moving or shaking within the battery can 20.

[0077] Figure 3 yes Figure 2 The enlarged cross-sectional view of the first collector plate and its surroundings is shown.

[0078] As described above, the first current collector 50 can be connected to the first electrode connector 11. More specifically, at least a portion of the first electrode connector 11 can be bent toward the hollow portion C of the electrode assembly 10, and the first current collector 50 can be connected to the bent portion of the first electrode connector 11. Although Figure 3 Not shown, but the curved portions of a plurality of adjacent first electrode connectors 11 may overlap each other.

[0079] Therefore, the height of the first electrode connector 11 can be reduced to increase the energy density of the secondary battery 1. In addition, since the connection area between the first electrode connector 11 and the first current collector 50 is increased, the connection force between the first electrode connector 11 and the first current collector 50 can be improved, and the resistance can be reduced.

[0080] More specifically, the first current collector 50 may include a central portion 51, a connector connection portion 52 extending outward from the central portion 51 and connected to the first electrode connector 11, a can connection portion 53 connected to the battery can 20 and spaced apart from the connector connection portion 52, and a bridging portion 54 connecting the can connection portion 53 to the central portion 51.

[0081] The center portion 51 may be disposed at the center of one side (e.g., the lower side) of the electrode assembly 10. The center portion 51 may have an approximately circular shape.

[0082] A central hole 51a may be defined in the central portion 51. The central hole 51a may face the hollow portion C of the electrode assembly 10. The central hole 51a, together with the hollow portion C, may serve as a channel for inserting a welding rod or introducing laser irradiation to connect the terminal 40 to the second current collector 60. Furthermore, the central hole 51a may serve as a channel to allow the electrolyte to smoothly impregnate the interior of the electrode assembly 10 during electrolyte injection.

[0083] The connector connection portion 52 can extend radially outward from the center portion 51. The connector connection portion 52 can be connected to the first electrode connector 11. Multiple connector connection portions 52 can be provided, and multiple connector connection portions 52 can extend radially from the center portion 51.

[0084] The width of the connector connection portion 52 can become wider as it moves away from the center portion 51. Therefore, the connector connection portion 52 can extensively cover the curved portion of the first electrode connector 11 and prevent the curved portion of the first electrode connector 11 from being lifted.

[0085] The connector connection portion 52 may not overlap with the pressing edge portion 21 in the height direction of the battery can 20. That is, the connector connection portion 52 may not be provided between the electrode assembly 10 and the pressing edge portion 21. Therefore, damage to the connector connection portion 52 due to it getting stuck between the electrode assembly 10 and the pressing edge portion 21 during the sizing process can be prevented. Sizing can refer to a compression process in which the height of the pressing edge portion 21 is reduced to decrease the height of the secondary battery 1 after the pressing edge portion 21 and the rolled edge portion 22 are formed in the battery can 20 housing the electrode assembly 10.

[0086] The can connection portion 53 can be connected to the battery can 20, and more specifically, to the pressing edge portion 21. The can connection portion 53 can be connected to the surface of the pressing edge portion 21 that is relatively far away from the electrode assembly 10.

[0087] The can connection portion 53 may have a predetermined height difference relative to the center portion 51 and the connector connection portion 52. This height difference may represent the distance between the connector connection portion 52 and the can connection portion 53 in the height direction of the battery can 20. This height difference may correspond to the height of the pressing edge portion 21. That is, the distance between the connector connection portion 52 and the can connection portion 53 in the height direction of the battery can 20 may be equal to or similar to the height of the pressing edge portion 21.

[0088] The can connection portion 53 can be pressed by the sealing portion 72, which will be described later. More specifically, the can connection portion 53 can be inserted and fixed between the sealing portion 72 and the pressing portion 21.

[0089] The can connection portion 53 may be spaced apart from the connector connection portion 52. More specifically, each of the can connection portion 53 and the connector connection portion 52 may be connected to the central portion 51, and the can connection portion 53 and the connector connection portion 52 may not be directly connected to each other. Therefore, when an impact or vibration is applied to the secondary battery 1, the stress acting on the connection portion between the connector connection portion 52 and the first electrode connector 11, and on the connection portion between the can connection portion 53 and the battery can 20, can be dispersed to minimize the possibility of damage to the first current collector 50.

[0090] Multiple tank connection parts 53 can be provided. The tank connection parts 53 and the connector connection parts 52 can be arranged alternately in the circumferential direction of the first manifold 50.

[0091] The can connection portion 53 can extend along the inner circumference of the battery can 20. That is, the can connection portion 53 can extend in the circumferential direction of the pressing edge portion 21. Therefore, since the contact area between the can connection portion 53 and the pressing edge portion 21 is increased, the connection between the can connection portion 53 and the pressing edge portion 21 can be stably formed, and the resistance between the can connection portion 53 and the pressing edge portion 21 can be reduced.

[0092] The edges on both sides of the tank connection 53 can be arranged in the radial direction of the first manifold 50. A virtual line extending along the two edges can pass through the center of the first manifold 50.

[0093] The can connection portion 53 and the connector connection portion 52 can be made to not overlap each other in the height direction of the battery can 20. Therefore, when multiple first current collectors 50 are stacked in the state of being connected to the electrode assembly 10, the can connection portion 53 of one first current collector 50 and the connector connection portion 52 of another first current collector 50 can be prevented from interfering with each other.

[0094] The connection strength between the can connector 53 and the battery can 20, more specifically, the connection strength between the can connector 53 and the pressing edge portion 21, can be greater than the connection strength between the connector connector 52 and the first electrode connector 11. Therefore, the can connector 53 can be stably connected to the rigid battery can 20.

[0095] The bridging portion 54 can connect the tank connection portion 53 to the center portion 51. The bridging portion 54 can extend radially outward from the center portion 51 and can be spaced apart from the connector connection portion 52 in the circumferential direction of the first manifold 50.

[0096] Similar to the tank connection portion 53, multiple bridging portions 54 can be provided, and the multiple bridging portions 54 can extend radially from the central portion 51. The bridging portions 54 and the connector connection portion 52 can be alternately arranged in the circumferential direction of the first manifold 50.

[0097] Because there is a height difference between the central portion 51 and the tank connection portion 53, the bridging portion 54 can be formed as an inclination. The bridging portion 54 can extend away from the electrode assembly 10 in an inclined direction when it moves away from the central portion 51.

[0098] The inclination of the bridging portion 54 can become gentler as it moves away from the center portion 51. More specifically, the bridging portion 54 may include a first inclined portion 54a extending from the center portion 51 and a second inclined portion 54b extending from the first inclined portion 54a and having a gentler inclination than the first inclined portion 54a.

[0099] However, it is not limited to this, and the bridging portion 54 can be formed to be circular in a direction that becomes more gradual as it moves away from the center portion 51.

[0100] Therefore, excessive deformation of the bridging portion 54 due to the sizing process can be prevented, and the central portion 51 and the first electrode connector 11 connected to the central portion 51 can be prevented from being lifted. During the sizing process, the pressing portion 21 can be compressed toward the electrode assembly 10, and its height can be reduced. Therefore, the connector connecting portion 53 connected to the pressing portion 21 can also move toward the electrode assembly 10. Therefore, a repulsive force can be applied to the central portion 51 connected to the connector connecting portion 53 and the bridging portion 54 in a direction away from the electrode assembly 10. If the inclination of the bridging portion 54 is constant or becomes steeper as it moves further away from the central portion 51, the repulsive force may be greatly applied to the central portion 51, and there is a risk that the central portion 51 and the first electrode connector 11 connected thereto will be lifted. On the other hand, the bridging portion 54 according to this embodiment can minimize the lifting phenomenon of the central portion 51 and the first electrode connector 11 caused by the sizing process.

[0101] Furthermore, the process of pressing the outer circumference of the battery can 20 inward to form the pressing edge portion 21 can be performed while the electrode assembly 10 connected to the first current collector 50 is housed within the battery can 20. During this process, since the bridging portion 54 has a gentle inclination as it moves away from the center portion 51, the pressing edge portion 21 can be easily formed without interfering with the bridging portion 54.

[0102] The edge of the cover plate 30 can be disposed between the pressing edge portion 21 and the rolled edge portion 22 of the battery can 20, and can be fixed by the sealing portion 72, which will be described later.

[0103] The cover plate 30 may not protrude relative to the battery canister 20. For example, when the cover plate 30 is located at the lower end of the battery canister 20, the bottom surface of the plate portion 31 of the cover plate 30 may be located on the same plane as or higher than the bottom surface of the battery canister 20. Therefore, it is possible to prevent the cover plate 30 from being pressed upward by the bottom surface supporting the battery canister 20, and it is possible to prevent the pressure required for the vent 34 to rupture due to the weight of the secondary battery 1 from being different from the design value.

[0104] The vent 34 can be disposed in the cover plate 30. The vent 34 can be configured to have a thickness thinner than the surrounding area. Therefore, the vent 34 can be structurally weaker than the surrounding area, and the vent 34 can preferentially rupture if the internal pressure of the battery tank 20 increases beyond a preset value.

[0105] The exhaust portion 34 may be arranged along the circumferential direction of the cover plate 30. For example, the exhaust portion 34 may be formed in a closed-loop shape, such as a ring. Therefore, when the exhaust portion 34 breaks, the area of ​​the cover plate 30 disposed inside the exhaust portion 34 can be easily separated to define an opening, and the gas inside the battery tank 20 can be quickly discharged.

[0106] The exhaust portion 34 can be provided by opening each of the two sides of the cover plate 30 to a predetermined depth, thereby partially reducing the thickness of the cover plate 30. However, it is not limited to this, and the exhaust portion 34 can also be formed by opening only one surface of the cover plate 30.

[0107] The spacer 70 may have an elastic material to effectively absorb the impact or vibration applied to the secondary battery 1.

[0108] The height of the spacer 70 can correspond to the distance between the first current collector 50 and the cover plate 30. In this case, the body 71 can effectively prevent the electrode assembly 10 from moving within the battery canister 20 due to the gap defined between the first current collector 50 and the cover plate 30. Therefore, the spacer 70 can prevent damage at the connection between the electrode assembly 10 and the first current collector 50 and / or at the connection between the first current collector 50 and the battery canister 20.

[0109] In the spacer 70, an opening may be defined to face the hollow portion C of the electrode assembly 10 through the central hole 51a of the first current collector 50. This opening, together with the central hole 51a and the hollow portion C, can be used as a channel for inserting welding rods or for laser irradiation. Additionally, this opening can serve as a channel allowing electrolyte to smoothly impregnate the interior of the electrode assembly 10.

[0110] The sealing part 72 may be integrated with the spacer 70. However, this embodiment is not limited to this.

[0111] The sealing portion 72 may have an annular shape extending along the inner circumference of the battery can 20. The sealing portion 72 may be fixed between the pressing portion 21 and the rolled edge portion 22 of the battery can 20. A portion of the sealing portion 72 may be bent together with the rolled edge portion 22 to surround the edge of the cover plate 30. Therefore, the sealing portion 72 can firmly seal the space between the cover plate 30 and the battery can 20. Thus, the sealing portion 72 can serve as a gasket to improve the fixing force of the cover plate 30 and the sealing force of the battery can 20.

[0112] The sealing part 72 can press the can connection part 53 of the first manifold 50 against the pressing edge part 21 to further strengthen the connection between the can connection part 53 and the pressing edge part 21. In addition, the sealing part 72 can insulate the can connection part 53 and the cover plate 30 from each other.

[0113] The tensile strength of the current collector included in the lithium secondary battery of the present invention can be 200 N / mm. 2 Up to 370 N / mm 2 230N / mm is preferred 2 Up to 350 N / mm 2 The optimal value is 250 N / mm. 2 Up to 330 N / mm 2 If the current collector included in the lithium secondary battery of the present invention has tensile strength within the above-mentioned range, then when a flame is generated in the lithium secondary battery, the flame may not point towards the side surface, but rather towards the top of the battery, thereby preventing the flame from spreading to the surrounding lithium secondary batteries. Furthermore, if the current collector included in the lithium secondary battery of the present invention has tensile strength within the above-mentioned range, it can prevent the current collector from being excessively stretched or broken during actual operation of the lithium secondary battery.

[0114] Tensile strength was measured using an elongation meter (manufacturer: Nanotech, product name: Universal Testing Machine (UTM)).

[0115] The tensile strength of manifolds can be affected by various factors, such as the heat treatment method, the rolling method, and whether or not electroplating is performed.

[0116] The thickness of the current collector can be from 50 μm to 500 μm, preferably from 100 μm to 400 μm, and more preferably from 150 μm to 350 μm. If the thickness of the current collector meets the above range, when a flame is generated in the lithium secondary battery, the flame may not point towards the side surface, but rather towards the top of the battery, thereby preventing the flame from spreading to the surrounding lithium secondary batteries. Furthermore, when the current collector included in the lithium secondary battery of the present invention has a thickness within the above range, the current collector can have a resistance level that provides suitable cell performance and exhibits minimal physical deformation during cell operation.

[0117] The pressing edge portion may have a thickness of 0.4 mm to 0.6 mm, preferably 0.4 mm to 0.5 mm. If the thickness of the pressing edge portion meets the above range, when a flame is generated in the lithium secondary battery, the flame may not point towards the side surface, but rather towards the top of the battery, thereby preventing the flame from spreading to the surrounding lithium secondary batteries.

[0118] The current collector can be made of copper film, nickel-plated copper film, etc., and can have an elongation of 2% to 50% at a temperature of 25°C, preferably 5% to 30%, and more preferably 5% to 20%. The elongation can be measured using an elongation meter (manufacturer: Nanotech, product name: Universal Material Testing Machine (UTM)).

[0119] Specifically, the electrode assembly of the present invention can have a structure in which a positive electrode, a negative electrode, and a separator inserted between the positive and negative electrodes are wound in one direction, and can be, for example, a wound-core type electrode assembly. The electrode assembly of the present invention can be manufactured by winding a stack provided by sequentially stacking a separator, a positive electrode, a separator, and a negative electrode at least once in one direction.

[0120] Here, each of the positive and negative electrodes may have a structure in which an active material layer is disposed on a sheet-like current collector, and may include uncoated portions in some areas of the current collector in which no active material layer is disposed.

[0121] When positive and negative electrodes, including uncoated portions, are used as described above, a battery with a connectorless structure can be realized, in which at least a portion of the uncoated portion of each of the positive and negative electrodes defines an electrode connector without providing a separate electrode connector.

[0122] Specifically, the uncoated portion can be configured to extend along the winding direction at one end of the current collector, and the current collector can be connected to each of the positive and negative uncoated portions. Then, the current collector can be connected to the electrode terminals to realize a battery with a connectorless structure.

[0123] For example, a battery with a jointless structure can be manufactured by the following method. First, a separator, a positive electrode, a separator, and a negative electrode can be stacked sequentially, with the uncoated portions of the positive and negative electrodes facing opposite directions, and then wound in one direction to manufacture an electrode assembly. Next, the uncoated portions of the positive and negative electrodes can be bent towards the winding center (i.e., in the direction of the hollow portion C), and a current collector can be welded and connected to the uncoated portions of the positive and negative electrodes to connect the current collector to the electrode terminals, thereby manufacturing a battery with a jointless structure. Since the current collector has a larger cross-sectional area compared to a strip electrode connector, and resistance is inversely proportional to the cross-sectional area of ​​the current flow path, the cell resistance can be significantly reduced when the secondary battery has the above structure.

[0124] The uncoated positive electrode portion and the uncoated negative electrode portion can be processed into multiple independently bendable segments, and at least a portion of the multiple segments can be bent toward the hollow portion C, which is the winding center of the electrode assembly.

[0125] These sections can be formed by processing the positive and negative current collectors through metal foil cutting processes such as laser opening, ultrasonic cutting, or stamping.

[0126] When the uncoated portions of the positive and negative electrodes are processed in multiple sections, the stress applied to the uncoated portions during bending can be reduced to prevent deformation or damage to the uncoated portions and improve the welding performance with the current collector.

[0127] The current collector and uncoated parts are typically joined by welding. To improve weldability, strong pressure must be applied to the weld area of ​​the uncoated part to bend it as flat as possible. However, during this bending process, the shape of the uncoated part may twist and deform, and the deformed portion may come into contact with an electrode of opposite polarity, causing internal short circuits or microcracks in the uncoated part. However, if the uncoated parts of the positive and negative electrodes are machined into multiple independently bendable segments, the stress applied to the uncoated part during bending can be reduced, minimizing deformation and damage to the uncoated part.

[0128] Furthermore, when the uncoated portion is processed in the form of segments as described above, multiple segments can overlap each other during bending to increase the welding strength with the current collector, and when using the latest technologies (such as laser welding), it can prevent the problem of laser penetration into the electrode assembly and melting the diaphragm or active material. Preferably, at least some of the multiple bent segments can overlap each other at the upper and lower ends of the electrode assembly, and the current collector can be attached to the multiple overlapping segments.

[0129] Cylindrical lithium secondary battery

[0130] Next, the cylindrical lithium secondary battery according to the present invention will be described. The cylindrical lithium secondary battery according to the present invention can be a high-capacity cylindrical secondary battery with a rated capacity of 25Ah or greater.

[0131] The cylindrical lithium secondary battery according to the present invention can be a large cylindrical battery with a shape factor ratio (defined as the ratio of the diameter Φ of the cylindrical battery to its height H) of 0.4 or greater. Here, the shape factor can refer to the value representing the diameter and height of the cylindrical battery.

[0132] The cylindrical battery according to the present invention can be, for example, a 46110 cell (diameter 46 mm, height 110 mm, shape factor ratio 0.418), a 4875 cell (diameter 48 mm, height 75 mm, shape factor ratio 0.640), a 48110 cell (diameter 48 mm, height 110 mm, shape factor ratio 0.436), a 4880 cell (diameter 48 mm, height 80 mm, shape factor ratio 0.600), a 4680 cell (diameter 46 mm, height 80 mm, shape factor ratio 0.575), or a 4695 cell (diameter 46 mm, height 95 mm, shape factor ratio 0.484). In the shape factor values, the first two digits may represent the diameter of the cell, and the next two or three digits may represent the height of the cell.

[0133] The cylindrical lithium secondary battery according to the present invention can significantly reduce the amount of gas generated compared with conventional batteries, and therefore can achieve excellent safety even in large cylindrical batteries with a shape factor ratio of 0.4 or greater.

[0134] The cylindrical battery according to the present invention can be a battery having a connectorless structure that does not include electrode terminals.

[0135] A battery with a connectorless structure can have a structure in which each of the positive and negative electrodes includes an uncoated portion on which no active material layer is formed, the positive and negative uncoated portions being disposed at the upper and lower ends of the electrode assembly, respectively, a current collector being connected to each of the positive and negative uncoated portions, and the current collector being connected to the electrode terminals.

[0136] Cylindrical lithium-ion batteries can be used in a variety of devices. For example, they can be used in electric vehicles, such as electric bicycles, electric vehicles, and hybrid electric vehicles (HEVs).

[0137] Therefore, according to another embodiment of the present invention, a battery module comprising a cylindrical lithium secondary battery as a unit cell and a battery pack comprising the battery module are provided.

[0138] Battery modules or battery packs can be used as power sources for at least one medium to large-sized device in power tools, vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), and systems for storing electricity.

[0139] The present invention will now be described in more detail through specific embodiments.

[0140] Example

[0141] Example 1

[0142] A wound-core electrode assembly is manufactured by inserting a separator between the positive and negative electrodes and stacking and winding the separator, positive electrode, and negative electrode in the order of separator / positive electrode / separator / negative electrode. After inserting the electrode assembly into a cylindrical battery can, electrolyte is injected, and the opening of the battery can is sealed with a cover plate.

[0143] A 200 μm thick copper plate was used as the negative electrode plate, and the cover plate and electrode assembly were welded together to electrically connect the cover plate to the electrode assembly. The tensile strength of the negative electrode plate was 275 N / mm². 2 And the elongation at 25°C is 20.0%.

[0144] Example 2

[0145] A wound-core electrode assembly is manufactured by inserting a separator between the positive and negative electrodes and stacking and winding the separator, positive electrode, and negative electrode in the order of separator / positive electrode / separator / negative electrode. After inserting the electrode assembly into a cylindrical battery can, electrolyte is injected, and the opening of the battery can is sealed with a cover plate.

[0146] A 200 μm thick copper plate was used as the negative electrode plate, and the cover plate and electrode assembly were welded together to electrically connect the cover plate to the electrode assembly. The tensile strength of the negative electrode plate was 325 N / mm². 2 And its elongation at 25°C is 6.5%.

[0147] Example 3

[0148] A wound-core electrode assembly is manufactured by inserting a separator between the positive and negative electrodes and stacking and winding the separator, positive electrode, and negative electrode in the order of separator / positive electrode / separator / negative electrode. After inserting the electrode assembly into a cylindrical battery can, electrolyte is injected, and the opening of the battery can is sealed with a cover plate.

[0149] A 300 μm thick copper plate was used as the negative electrode plate, and the cover plate and electrode assembly were welded together to electrically connect the cover plate to the electrode assembly. The tensile strength of the negative electrode plate was 238 N / mm². 2 And the elongation at 25°C is 46.0%.

[0150] Comparative Example 1

[0151] A wound-core electrode assembly is manufactured by inserting a separator between the positive and negative electrodes and stacking and winding the separator, positive electrode, and negative electrode in the order of separator / positive electrode / separator / negative electrode. After inserting the electrode assembly into a cylindrical battery can, electrolyte is injected, and the opening of the battery can is sealed with a cover plate.

[0152] A 200 μm thick copper plate was used as the negative electrode plate, and the cover plate and electrode assembly were welded together to electrically connect the cover plate to the electrode assembly. The tensile strength of the negative electrode plate was 175 N / mm². 2 And its elongation at 25°C is 42.5%.

[0153] Comparative Example 2

[0154] A wound-core electrode assembly is manufactured by inserting a separator between the positive and negative electrodes and stacking and winding the separator, positive electrode, and negative electrode in the order of separator / positive electrode / separator / negative electrode. After inserting the electrode assembly into a cylindrical battery can, electrolyte is injected, and the opening of the battery can is sealed with a cover plate.

[0155] A 300 μm thick copper plate was used as the negative electrode plate, and the cover plate and electrode assembly were welded together to electrically connect the cover plate to the electrode assembly. The tensile strength of the negative electrode plate was 380 N / mm². 2 And its elongation at 25°C is 3.5%.

[0156] Experimental Example

[0157] Overcharge experiments were conducted using lithium-ion batteries from Examples 1 to 3 and Comparative Examples 1 and 2. Specifically, the lithium-ion batteries were charged at 1 / 3C to the full charge voltage (4.2V) with a 1 / 50C cutoff, and then left to stand for 2 hours to stabilize the voltage. After overcharging five identically manufactured lithium-ion batteries at a current of 40A, the number of lithium-ion batteries that lost their negative current collectors was counted, and the results are shown in Table 1 below.

[0158] [Table 1]

[0159] [Description of reference numerals in the attached figures]

[0160] 1: Cylindrical lithium secondary battery

[0161] 10: Electrode assembly

[0162] 11: First electrode connector

[0163] 12: Second electrode connector

[0164] 20: Battery can

[0165] 21: Edge pressing section

[0166] 22: Rolled edge

[0167] 30: Cover plate

[0168] 34: Bend

[0169] 40. Terminal

[0170] 50: First manifold

[0171] 51: Central Section

[0172] 51a: Center hole

[0173] 52: Connector connection part

[0174] 53: Tank connection part

[0175] 54: Bridging section

[0176] 60: Second manifold

[0177] 70: Spacer

[0178] 72: Sealing part

Claims

1. A cylindrical lithium secondary battery, the cylindrical lithium secondary battery comprising: An electrode assembly in which a positive electrode, a negative electrode, and a diaphragm inserted between the positive and negative electrodes are wound in one direction; A battery canister configured to receive the electrode assembly through an opening defined on one side thereon; A cover plate, the cover plate being configured to cover the opening; as well as A current collector, disposed between the electrode assembly and the cover plate, for electrically connecting the electrode assembly to the battery canister. The current collector plate has a strength of 200 N / mm. 2 Up to 370 N / mm 2 Tensile strength.

2. The cylindrical lithium secondary battery according to claim 1, wherein, The battery can includes a pressing edge portion, which is a support member for mounting the cover plate. The current collector plate is connected to the pressure edge portion.

3. The cylindrical lithium secondary battery according to claim 1, wherein, The current collector has a strength of 230 N / mm. 2 Up to 350 N / mm 2 Tensile strength.

4. The cylindrical lithium secondary battery according to claim 1, wherein, The current collector has a thickness of 50 μm to 500 μm.

5. The cylindrical lithium secondary battery according to claim 2, wherein, The pressing edge has a thickness of 0.4 mm to 0.6 mm.

6. The cylindrical lithium secondary battery according to claim 1, wherein, The current collector is a negative current collector.

7. The cylindrical lithium secondary battery according to claim 6, wherein, The current collector is a thin copper film.

8. The cylindrical lithium secondary battery according to claim 1, wherein, Each of the positive and negative electrodes includes an uncoated portion without an active material layer, and At least a portion of the uncoated portion of the positive electrode or the uncoated portion of the negative electrode has a connectorless structure that defines an electrode connector.

9. The cylindrical lithium secondary battery according to claim 8, wherein, The uncoated positive electrode portion and the uncoated negative electrode portion are respectively disposed on one end of the positive electrode and one end of the negative electrode along the winding direction of the electrode assembly. The current collector is connected to each of the positive uncoated portion and the negative uncoated portion, and The current collector is connected to the electrode terminals.

10. The cylindrical lithium secondary battery according to claim 8, wherein, Each of the uncoated positive electrode portion and the uncoated negative electrode portion is processed into multiple segments that can be bent independently, and At least a portion of the plurality of segments bends toward the winding center of the electrode assembly.

11. The cylindrical lithium secondary battery according to claim 10, wherein, At least some of the multiple curved segments overlap each other at the upper and lower ends of the electrode assembly, and The manifold is connected to multiple overlapping sections.

12. The cylindrical lithium secondary battery according to claim 1, wherein, The cylindrical lithium secondary battery has a shape factor ratio of 0.4 or greater.

13. The cylindrical lithium secondary battery according to claim 1, wherein, The cylindrical lithium secondary battery is a 46110 cell, 4875 cell, 48110 cell, 4880 cell, 4680 cell, or 4695 cell.

14. A battery pack comprising a cylindrical lithium secondary battery according to any one of claims 1 to 13.

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