End plate, cover plate assembly and cylindrical lithium battery

Abstract

The utility model provides an end plate, a cover plate assembly and a cylindrical lithium battery, the end plate is circular, the end plate sequentially comprises a fixing part, a first connecting part and a second connecting part from outside to inside along the radial direction, and an annular first hole is formed between the first connecting part and the second connecting part; the first hole is disconnected by a fusing connection part connecting the first connection part and the second connection part, the fusing connection part is used for electrical conduction between the first connection part and the second connection part, and the fusing connection part is fused when the current flowing through the fusing connection part reaches a set value. By utilizing the characteristic that the first connecting part and the second connecting part are fused due to large current during short circuit, the CID is prevented from being broken in advance during an external small resistor short circuit test in a battery production process, so that the cylindrical lithium battery smoothly passes through the external small resistor short circuit test.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an end plate, a cover plate assembly and a cylindrical lithium battery. Background Art

[0002] In related technologies, lithium batteries can be divided into three types based on packaging: prismatic, cylindrical, and pouch. Cylindrical lithium batteries have become a hot topic in lithium battery research due to their consistent performance, high production efficiency, and strong system-level heat dissipation. Cylindrical batteries are typically packaged in a cylindrical steel shell. Bare cells are manufactured using a winding process to form a cylindrical core. The cover assembly sits on top of the battery and connects to the positive electrode in the core electrode assembly via a positive current collector.

[0003] In the related art, in existing cylindrical lithium-ion batteries, the safety protection devices of the cover plate are explosion-proof plates and CID breakage protection mechanisms. After the battery cells are made, they are tested for national standard projects. When a small external resistor is used for short-circuit testing, the CID may break prematurely, the explosion-proof valve may open prematurely, and other phenomena may occur, resulting in the failure of the external small resistor short-circuit test.

[0004] To solve this problem later, the conventional method is to add a fuse to the positive electrode connector to ensure that the small resistance short circuit test can pass. However, this method requires an additional protection mechanism (fuse) to be added to the positive electrode connector, which increases the manufacturing cost. Adding a protection device to the positive current collector has high requirements for the position. When the equipment bends the positive electrode adapter, the fuse of the positive electrode connector is the weakest area of the entire structure and the most easily bent place. Therefore, when the equipment bends the positive electrode connector into the shell, it is easy to bend at the fuse. The bending position does not match the actual bending position, which eventually causes the cover plate to be unable to enter the shell, resulting in scrap and increased manufacturing costs. After a large number of subsequent verifications, it was found that even after the fuse position was fixed, this problem would occur again due to changes or optimizations in the equipment tooling. The bending of the positive terminal connecting piece at the fuse would concentrate some stress there, and the aluminum material is relatively soft and easy to break, causing the fuse protection device here to fail directly; or after the fuse is bent, cracks that are invisible to the naked eye may appear in the weak area here, etc., causing the battery cell to melt during normal use, causing the battery cell to fail before thermal runaway occurs, reducing the battery cell's service life and increasing the cost of use. Utility Model Content

[0005] The embodiment of the present application provides an end plate to at least solve the technical problem that the fuse structure of the existing cylindrical lithium battery breaks the CID prematurely during the external small resistance short circuit test, resulting in failure of the external small resistance short circuit test.

[0006] The first embodiment of the present application provides an end plate for a cylindrical lithium battery, wherein the end plate is circular and includes:

[0007] From the outside to the inside in radial direction, it includes a fixing part, a first connecting part and a second connecting part, wherein the fixing part is used to connect to the sealing ring of the cylindrical lithium battery, the first connecting part is used to connect to the positive current collecting disk of the cylindrical lithium battery, and the second connecting part is used to connect to the explosion-proof disk of the cylindrical lithium battery, and an annular first hole is formed between the first connecting part and the second connecting part, and the first hole is disconnected by a fusible connecting part connecting the first connecting part and the second connecting part. The fusible connecting part is used to electrically conduct between the first connecting part and the second connecting part, and the fusible connecting part melts when the current flowing through it reaches a set value.

[0008] The end plate according to the embodiment of the present application has at least the following beneficial effects:

[0009] In the end plate of the embodiment of the present application, the current allowed to pass through the fusible connection portion meets the current required by the cylindrical lithium battery during the production process, and will not cause accidental breakage during testing during the production process. At the same time, during the use of the cylindrical lithium battery, if the current passing through the fusible connection portion is too large, the fusible connection portion will melt, disconnecting the connection between the first connection portion and the second connection portion, thereby ensuring battery safety. The fusible connection portion is fused based on the current, allowing the cylindrical lithium battery to successfully pass the external low-resistance short-circuit test.

[0010] In one possible embodiment, the area of the first hole is S1, and the area of the end plate is S2, and 5%≤S1 / S2≤15%. If S1 / S2 is lower than 5%, a large amount of gas will be generated during the abuse test of the battery cell. When the gas is exhausted through the first hole of the end plate, the exhaust rate is affected due to the low S1 / S2, and the exhaust rate is reduced. At this time, a safety problem arises, and the safety of the battery cannot be guaranteed. If S1 / S2 is greater than 15%, the fuse connection is too long, which reduces the structural strength. When producing end plate parts, the fuse connection is prone to breakage, twisting, deformation and other adverse phenomena, which reduces the yield rate and increases the cost. If S1 / S2 is too large, it will occupy the welding area, resulting in a smaller welding area, thereby affecting the pressing and positioning of the welding tooling, and reducing the production yield.

[0011] In one possible embodiment, a second hole in the shape of an annular ring is formed between the fixing portion and the first connecting portion, and the second hole is disconnected by a plurality of connectors spaced apart from each other, and the connector connects the fixing portion to the first connecting portion. The provision of multiple second holes helps to quickly discharge gas when the battery produces gas during use. The second hole is arranged around the first hole, that is, in the radial direction of the end plate, the positions of the first hole and the second hole are different, and the first hole is closer to the center of the end plate, which helps to discharge gas at the same time when gas is produced at different positions in the radial direction of the battery, thereby improving exhaust efficiency and reducing the safety risks of cylindrical lithium batteries.

[0012] In one possible embodiment, the area of the second hole is S3, 15%≤S3 / S2≤25%. Since S3 / S2 is relatively low, the exhaust rate is affected. When the exhaust rate is reduced, safety issues will arise. Can the safety of the battery cell be guaranteed? If S3 / S2 is greater than 25%, the structural strength of the end plate will be reduced. When producing end plate parts, the connector of the second hole will be too long and the strength will be reduced. During production, the connector is prone to breakage, twisting, deformation and other adverse phenomena, which will reduce the yield rate and increase the cost. In addition, the increase in S3 / S2 will occupy the welding area, resulting in a smaller welding area, thereby affecting the pressing and positioning of the welding tooling and reducing the production yield rate.

[0013] In one possible embodiment, the fusible connection portion includes a first arc-shaped edge and a second arc-shaped edge symmetrically distributed along the circumference of the end plate, the shortest distance between the first edge and the second edge along the circumferential direction of the first hole is L1, the maximum length of the first hole in the circumferential direction is L2, and 2%≤L1 / L2≤5%.

[0014] In one possible embodiment, the length of the fusible connection along the radial direction of the end plate is L3, and 0.9≤L3 / L1≤1.1. If L3 / L1 is too low, the structural strength of the second connection portion is too low, and problems such as bending, deformation, and breakage of the fusible connection portion may occur during production, transportation, and sample preparation, increasing the manufacturing cost of the battery and reducing the yield. When L3 / L1 is too high, the width of the fusible connection area is wide and does not play a protective role. The overcurrent area is wide, and when a short circuit occurs in the battery, this area is not easy to melt and perform power-off protection, which reduces safety performance. Designing L3 / L1 to be 0.9~1.1 helps to balance the safety of the battery and the overall structural strength of the fusible connection.

[0015] In one possible embodiment, the thickness of the fusible connection portion is 0.3-0.5 mm. Designing the thickness of the fusible connection portion to be 0.3-0.5 mm helps to balance the overall structural strength of the end plate and the safety of the battery.

[0016] In one possible embodiment, the fusible link includes a first side and a second side symmetrically distributed along the circumference of the end plate. A line connecting the midpoint of the first side and the center of the end plate and a line connecting the midpoint of the second side and the center of the end plate form an angle α, where 6°≤α≤16°. Designing the angle α to be between 6° and 16° helps balance the structural strength of the fusible link and the safety of the battery.

[0017] A second embodiment of the present application provides a cover plate assembly for a cylindrical lithium battery, comprising:

[0018] The cover plate assembly is sequentially provided with a cover plate, an explosion-proof disc, a sealing ring and an end plate provided in any of the aforementioned embodiments along the thickness direction of the cover plate assembly, the sealing ring is provided with a third hole, the explosion-proof disc and the second connecting part of the end plate are connected via the third hole, and the sealing ring is connected to the fixing part.

[0019] The second embodiment of the present application provides a cylindrical lithium battery, comprising: a cover plate assembly, an outer shell, a positive current collecting disc, a winding core and a negative current collecting disc provided in any of the aforementioned embodiments, wherein the positive current collecting disc is arranged between the cover plate assembly and the winding core, and the positive current collecting disc is connected to the surface of the first connecting portion of the end plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 is a schematic top view of an end plate provided in an embodiment of the present application;

[0022] Figure 2 is a cross-sectional schematic diagram of a cover plate assembly provided in an embodiment of the present application;

[0023] Figure 3 This is a schematic diagram of an exploded view of a cover assembly provided in an embodiment of the present application.

[0024] Reference numerals:

[0025] 100 - end plate, 110 - fixing portion, 120 - first connection portion, 130 - second connection portion, 140 - first hole, 150 - fusible connection portion, 151 - first side, 152 - second side, 160 - second hole, 170 - connector;

[0026] 200-seal ring, 210-third hole;

[0027] 300 explosion-proof disk;

[0028] 400 cover. DETAILED DESCRIPTION

[0029] Examples of the present embodiment are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present embodiment and are not to be construed as limiting the present embodiment.

[0030] In the description of this embodiment, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this embodiment.

[0031] In the description of this embodiment, "several" means one or more, "many" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and is not to be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0032] In the description of this embodiment, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this embodiment based on the specific content of the technical solution.

[0033] The following combination Figures 1 to 3 The end plate of the first embodiment of the present application is described in detail.

[0034] The cylindrical lithium battery includes an outer shell, a negative electrode current collector, a winding core, a positive electrode current collector and a cover assembly. The outer shell forms a cavity with an opening at one end. The negative electrode current collector, the winding core and the positive electrode current collector are assembled into the cavity through the opening. The winding core is located between the negative electrode current collector and the positive electrode current collector. The positive electrode of the winding core is connected to the positive electrode current collector, the negative electrode of the winding core is connected to the negative electrode current collector, and the negative electrode current collector is connected to the outer shell. The cover assembly seals the cavity at the open end of the outer shell, and the cover assembly is connected to the positive electrode current collector.

[0035] In existing cylindrical batteries, the cover assembly's safety protection devices include explosion-proof discs and CID breakage protection mechanisms. However, after the battery cell is manufactured and tested for national standard projects, when a small external resistor is connected for short-circuit testing, the CID may break prematurely, the explosion-proof valve may open prematurely, and other phenomena may cause the external small resistor short-circuit test to fail. To solve this problem, the current conventional method is to add a fuse structure to the positive electrode connector to ensure that the small resistor short-circuit test can pass. However, this method requires an additional protection mechanism (fuse) on the positive electrode connector, which increases manufacturing costs. Adding a protective device to the positive current collector has high positioning requirements. When the equipment bends the positive electrode adapter, the fuse of the positive electrode connector is the weakest area of the entire structural component and is also the place most prone to bending. Therefore, when the equipment bends the positive electrode connector into the shell, it is easy to bend at the fuse. The bending position does not match the actual bending position, ultimately preventing the cover from entering the shell, resulting in scrap and increasing manufacturing costs. After a large number of subsequent verifications, it was found that even after the fuse position was fixed, this problem would occur again due to changes or optimizations in the equipment tooling. The bending of the positive terminal connecting piece at the fuse would concentrate some stress there, and the aluminum material is relatively soft and easy to break, causing the fuse protection device here to fail directly; or after the fuse is bent, cracks that are invisible to the naked eye may appear in the weak area here, etc., causing the battery cell to melt during normal use, causing the battery cell to fail before thermal runaway occurs, reducing the battery cell's service life and increasing the cost of use.

[0036] The embodiment of the present application discloses an end plate 100 for a cylindrical lithium battery. The end plate 100 is circular and includes a fixing portion, a first connecting portion, and a second connecting portion in sequence from the outside to the inside along the radial direction of the end plate 100. The fixing portion is used to connect to the sealing ring 200 of the cylindrical lithium battery, the first connecting portion is used to connect to the positive current collecting disk of the cylindrical lithium battery, and the second connecting portion is used to connect to the explosion-proof disk 300 of the cylindrical lithium battery. A first annular hole is formed between the first connecting portion and the second connecting portion, and the first hole is disconnected by a fuse connecting the first connecting portion and the second connecting portion. The fuse connecting portion is used to electrically conduct between the first connecting portion and the second connecting portion. The fuse connecting portion melts when the current flowing through it reaches a set value. The current allowed to pass through the fuse connecting portion meets the current size required by the cylindrical lithium battery during the production process and will not cause accidental breakage during testing during the production process. At the same time, during the use of the cylindrical lithium battery, if the current passing through the fuse connecting portion is too large, the fuse connecting portion melts, disconnecting the connection between the first connecting portion and the second connecting portion, ensuring battery safety. The fusible connection part is fused based on the current, so that the cylindrical lithium battery can successfully pass the external small resistance short circuit test.

[0037] In some embodiments, the first connection part 120, the fuse connection part 150, and the second connection part 130 are integrally formed and are all made of aluminum. When the end plate 100 is manufactured, the end plate 100 is a whole circular thin aluminum plate, which is cut based on the shape of the first hole 140 to obtain the end plate 100 including the first connection part 120, the fuse connection part 150, and the second connection part 130. In some embodiments, the first hole 140 is in the shape of a notched circular ring, and the position of the notch is the fuse connection part 150. It is understandable that the first hole 140 can also be in other shapes, for example, the shape of the first hole 140 is a "C" shape, and there is no specific limitation. The first hole 140 is used for electrolyte infiltration and timely discharge of gas when gas is produced during use.

[0038] In some embodiments, the first connecting portion 120 is annular, the second connecting portion 130 is circular, and the second connecting portion 130 is located at the center of the first connecting portion 120. In some embodiments, the first connecting portion 120 includes an upper surface and a lower surface that are opposed to each other along the thickness direction of the first connecting portion 120. The lower surface is used to connect to the positive electrode current collecting disk, and the connection method can be laser welding, which is not limited to this. The upper surface refers to the surface facing away from the winding core, and the lower surface refers to the surface facing the winding core.

[0039] In some embodiments, the fixing portion 110 is located at the outer edge of the end plate 100 , and the shape of the fixing portion 110 matches the shape of the sealing ring 200 , so that the fixing portion 110 and the sealing ring 200 can be combined in a subsequent assembly process.

[0040] In some embodiments, the area of the first hole 140 is S1, the area of the end plate 100 is S2, and 5% ≤ S1 / S2 ≤ 15%. The area of the end plate 100 refers to the square of the radius of the end plate 100 multiplied by π, that is, it includes the area of any opening on the end plate 100. If the ratio of S1 / S2 is too low, when a large amount of gas is produced during the battery cell test, when the gas is exhausted through the first hole 140 of the end plate 100, the exhaust rate is affected due to the low ratio of S1 / S2, and the exhaust rate is reduced. At this time, safety problems will arise, and whether the safety of the battery can be guaranteed. If S1 / S2 is greater than 15%, the length of the fuse connection 150 is too long, which reduces the structural strength. When the end plate 100 is produced, the fuse connection 150 is prone to breakage, distortion, deformation and other defects, which reduces the yield rate and increases the cost. In addition, if S1 / S2 is too large, it will occupy the area of the welding area, resulting in a smaller welding area, thereby affecting the pressing and positioning of the welding tooling, and reducing the production yield.

[0041] In some embodiments, S1 / S2 is preferably 6.3% to 11.2%.

[0042] In some embodiments, a second hole 160 in the shape of an annular ring is formed between the fixing portion 110 and the first connecting portion 120. The second hole 160 is interrupted by a number of connectors 170 spaced apart from each other, and the connector 170 connects the fixing portion 110 to the first connecting portion 120. The provision of multiple second holes 160 helps to quickly discharge gas when the battery produces gas during use. The second holes 160 are arranged around the first hole 140, that is, in the radial direction of the end plate 100, the positions of the first hole 140 and the second hole 160 are different, and the first hole 140 is closer to the center of the end plate 100, which helps to discharge gas at the same time when gas is produced at different positions in the radial direction of the battery, thereby improving exhaust efficiency and reducing the safety risks of cylindrical lithium batteries. In some embodiments, the second holes 160 are fan-shaped and symmetrically distributed with the center of the end plate 100 as the center. The number of second holes 160 is 6. In some embodiments, the connector 170 is integrally formed with the fixing portion 110 and the first connecting portion 120. When the end plate 100 is manufactured, the end plate 100 is a whole circular thin aluminum plate. The circular thin aluminum plate is cut into the shape of the second hole 160, and the thin aluminum plate in the shape of the second hole 160 is discarded to obtain the end plate 100 with the shape of the second hole 160.

[0043] In some embodiments, the area of the second hole 160 is S3, 15% ≤ S3 / S2 ≤ 25%. If S3 / S2 is too large, when the battery cell is tested and a large amount of gas is produced, when the gas is exhausted through the second hole 160 of the end plate 100, the exhaust rate is affected due to the low S3 / S2, and the exhaust rate is reduced. At this time, safety problems will arise, and the safety of the battery cell cannot be guaranteed. If S3 / S2 is greater than 25%, the structural strength of the end plate 100 will be reduced. When the end plate 100 is produced, the connector 170 of the second hole 160 is too long and the strength becomes low. During production, the connector 170 is prone to breakage, twisting, deformation and other adverse phenomena, resulting in a reduced yield and increased costs. If S3 / S2 increases, it will occupy the welding area, resulting in a smaller welding area, thereby affecting the pressing and positioning of the welding tooling, and reducing the production yield. Further, S3 / S2 is preferably 18% to 23%.

[0044] In some embodiments, the fusible link 150 includes a first side 151 and a second side 152 symmetrically distributed along the circumference of the end plate 100. The shortest distance between the first side 151 and the second side 152 along the circumference of the first hole 140 is L1, and the maximum length of the first hole 140 along the circumference is L2. 2% ≤ L1 / L2 ≤ 5%. If L1 / L2 is too low, the structural strength of the second connection portion 130 is too low, and the fusible link 150 may bend, deform, or break during production, transportation, and sample preparation, increasing battery manufacturing costs and reducing battery yield. If L1 / L2 is too high, the fusible link 150 is too wide, failing to provide protection. The overcurrent region is wide, making it difficult for this region to fuse and provide power-off protection when a battery short circuit occurs, reducing safety performance.

[0045] In some embodiments, the shape of the first edge 151 and the second edge 152 on one side close to the first connection portion 120 and the second connection portion 130 is a rounded chamfered shape. Designing the shape of the first edge 151 and the second edge 152 to include a rounded chamfer helps reduce stress at the connection and make the structure more stable.

[0046] In some embodiments, the length of the fusible link 150 along the radial direction of the end plate 100 is L3, and 0.9≤L3 / L1≤1.1. When L3 / L1 is too small, heat can diffuse between the first connection portion 120 and the second connection portion 130 through the fusible link 150, reducing the ability of the fusible link 150 to accumulate heat. In the event of an internal short circuit in the battery, the fusible link 150 cannot accumulate heat and thus cannot reach the temperature required for melting. In other words, the purpose of power-off protection cannot be achieved, and safety performance is reduced. When L3 / L1 is too large, the length of the fusible link 150 is too long, reducing the overall strength of the structure. This can easily cause the fusible link 150 to bend, deform, or break during the production of individual parts, reducing the yield of the parts and increasing costs. When the end plate 100 is assembled into the cover plate assembly, assembly becomes more difficult and prone to deformation. If the fusible link 150 breaks or deforms during or after the assembly and welding of the end plate 100, the cover plate assembly will be scrapped, resulting in waste, increased manufacturing costs, and reduced yield. Designing L3 / L1 to 0.9 to 1.1 helps balance battery safety and the overall structural strength of the fusible link 150.

[0047] In some embodiments, the thickness of the fuse connection 150 is 0.3-0.5 mm. In some embodiments, the thickness of the fuse connection 150 is preferably 0.3-0.4 mm. If the thickness of the fuse connection 150 is too thick, the current allowed to pass through the fuse connection 150 is too large, which is not conducive to timely melting and cutting off the connection between the first connection part 120 and the second connection part 130 when a short circuit occurs inside the battery, and is likely to cause a safety accident. If the thickness of the fuse connection 150 is too thin, it is not conducive to the overall structural strength of the end plate 100, and it is easy to curl during the production process, and it is easy to cause desoldering and broken welding problems during the subsequent welding process. Designing the thickness of the fuse connection 150 to be 0.3-0.5 mm helps to balance the overall structural strength of the end plate 100 and the safety of the battery.

[0048] In some embodiments, the fusible link 150 includes a first side 151 and a second side 152 symmetrically distributed along the circumference of the end plate 100. The line connecting the midpoint of the first side 151 and the center of the end plate 100 and the line connecting the midpoint of the second side 152 and the center of the end plate 100 form an angle α, with 6°≤α≤16°. If the angle α is too small, the structural strength of the fusible link 150 is too weak, and problems such as bending, deformation, and breakage may occur during production, transportation, and sample preparation, increasing the manufacturing cost of the battery and reducing the yield. If the angle α is too large, the fusible link 150 is too wide and cannot provide protection. The overcurrent area is wide, and when a short circuit occurs in the battery, this area is not easily fused and power is cut off, reducing safety performance. Designing the angle α to be 6° to 16° helps to balance the structural strength of the fusible link 150 and the safety of the battery.

[0049] In some embodiments, the angle α is preferably 8-14°, which is more conducive to balancing overcurrent protection and structural strength.

[0050] Example 2:

[0051] like Figure 2 and 3 As shown, this embodiment provides a cover plate assembly. The difference between this embodiment and the first embodiment mainly lies in the different subjects of protection. The first embodiment protects the end plate 100, and this embodiment protects the cover plate assembly having the end plate 100 of the first embodiment.

[0052] Specifically, the cover plate assembly provided in the second embodiment is used for a cylindrical lithium battery and includes a cover plate 400, a bursting disc 300, a sealing ring 200, and an end plate 100 provided in any of the aforementioned embodiments, arranged in sequence along the thickness direction of the cover plate assembly. The sealing ring 200 is provided with a third hole 210. The bursting disc 300 and the second connecting portion 130 of the end plate 100 are connected via the third hole 210. The sealing ring 200 is connected to the fixing portion 110. Except for the above differences, the rest of this embodiment can refer to the first embodiment and will not be described in detail here.

[0053] Example 3:

[0054] This embodiment provides a cylindrical lithium battery. The difference between this embodiment and the second embodiment mainly lies in the different protected subjects. The second embodiment protects the cover plate assembly, and this embodiment protects the cylindrical lithium battery having the cover plate assembly of the second embodiment.

[0055] Specifically, the cylindrical lithium battery provided in Example 3 includes the cover plate assembly, housing, positive electrode current collecting disc, winding core, and negative electrode current collecting disc provided in Example 2. The positive electrode current collecting disc is disposed between the cover plate assembly and the winding core, and is connected to the surface of the first connecting portion 120 of the end plate 100. Aside from the above differences, the rest of this embodiment can be referred to in Example 1 and Example 2 and will not be described in detail here.

[0056] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present embodiment. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0057] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and intent of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. An end plate for a cylindrical lithium battery, characterized in that: The end plate is circular and comprises a fixing portion (110), a first connecting portion (120) and a second connecting portion (130) in sequence from the outside to the inside in the radial direction, wherein the fixing portion (110) is used to connect with the sealing ring (200) of the cylindrical lithium battery, the first connecting portion (120) is used to connect with the positive electrode current collecting disk of the cylindrical lithium battery, and the second connecting portion (130) is used to connect with the explosion-proof disk (300) of the cylindrical lithium battery, and an annular first hole (140) is formed between the first connecting portion (120) and the second connecting portion (130), and the first hole (140) is disconnected by a fuse connecting portion (150) connecting the first connecting portion (120) and the second connecting portion (130), and the fuse connecting portion (150) is used for electrical conduction between the first connecting portion (120) and the second connecting portion (130), and the fuse connecting portion (150) is melted when the current flowing through it reaches a set value.

2. The end plate according to claim 1, characterized in that The area of the first hole (140) is S1, the area of the end plate is S2, and 5%≤S1 / S2≤15%.

3. The end plate according to claim 2, characterized in that A second hole (160) in the form of an annular ring is formed between the fixing portion (110) and the first connecting portion (120). The second hole (160) is interrupted by a plurality of connecting bodies (170) spaced apart from each other. The connecting bodies (170) connect the fixing portion (110) and the first connecting portion (120).

4. The end plate according to claim 3, characterized in that The area of the second hole (160) is S3, 15%≤S3 / S2≤25%.

5. The end plate according to any one of claims 1 to 4, characterized in that: The fusible connection portion (150) includes a first side (151) and a second side (152) in an arc shape symmetrically distributed along the circumference of the end plate, the shortest distance between the first side (151) and the second side (152) along the circumferential direction of the first hole (140) is L1, the maximum length of the first hole (140) in the circumferential direction is L2, and 2%≤L1 / L2≤5%.

6. The end plate according to claim 5, characterized in that The length of the fusible connection portion (150) in the radial direction of the end plate is L3, and 0.9≤L3 / L1≤1.

1.

7. The end plate according to claim 5, characterized in that The thickness of the fusible connection part (150) is 0.3-0.5 mm.

8. The end plate according to any one of claims 1 to 4, characterized in that: The fusible connection portion (150) comprises a first side (151) and a second side (152) in an arc shape symmetrically distributed along the circumference of the end plate, and a line connecting the midpoint of the first side (151) and the center of the end plate and a line connecting the midpoint of the second side (152) and the center of the end plate form an angle α, 6°≤α≤16°.

9. A cover plate assembly for a cylindrical lithium battery, characterized in that: The cover plate assembly is provided with a cover plate (400), an explosion-proof disk (300), a sealing ring (200) and the end plate (100) according to any one of claims 1 to 8 in sequence along the thickness direction of the cover plate assembly, the sealing ring (200) is provided with a third hole (210), the explosion-proof disk (300) and the second connecting portion (130) of the end plate are connected via the third hole (210), and the sealing ring (200) is connected to the fixing portion (110).

10. A cylindrical lithium battery, characterized in that: The invention comprises the cover plate assembly according to claim 9, a housing, a positive current collecting disc, a winding core and a negative current collecting disc, wherein the positive current collecting disc is arranged between the cover plate assembly and the winding core, and the positive current collecting disc is connected to the surface of the first connecting portion (120) of the end plate.

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