Cover plate assembly and battery

Abstract

The invention belongs to the technical field of batteries, and discloses a cover plate assembly and a battery, the cover plate assembly is connected with a pole group, the pole group is connected with a tab, the cover plate assembly comprises a cover plate body, a pole, lower plastic and a connecting piece, and the pole is arranged on the cover plate body; the lower plastic is arranged on one side, facing the pole group, of the cover plate body; the connecting piece is arranged on the side, facing the pole group, of the lower plastic, the connecting piece comprises a first welding part, a second welding part and a fusing part, the first welding part is connected with the pole, the second welding part is connected with the tab, the fusing part is arranged at the minimum section of the connecting position of the first welding part and the second welding part, and the tab is electrically connected with the pole through the connecting piece. Thus, the fusing part is located at the minimum cross section, the fusing part can be fused at the first time under the condition of abnormal overcurrent or high temperature, further accumulation of heat is prevented, electric connection between the pole group and an external circuit is rapidly cut off, and the safety performance of the high-capacity battery cell is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a cover plate assembly and a battery. Background Art

[0002] Lithium-ion batteries are one of the most widely used high-performance batteries due to their high operating voltage, high specific energy, large capacity, low self-discharge, good cycle performance, long service life, light weight and small size.

[0003] The long-cell lithium-ion battery includes a cover, a shell, an electrode group, an electrolyte, etc. The cover is connected to a connecting piece, the pole ear of the electrode group is welded to the connecting piece, and then the connecting piece is welded to the pole bottom plate set on the cover, which can lead the current out of the shell and achieve electrical connection with the external circuit. After the cover and the shell are welded, a closed space with a certain mechanical strength can be formed to protect the electrode group.

[0004] In the existing technology, the capacity of single battery cells has gradually increased, which has led to a gradual increase in fast charging requirements, and the structural overcurrent requirements and battery cell safety requirements have gradually increased. Existing large-capacity battery cells are difficult to cut off the internal circuit in time when thermal runaway occurs, which poses a safety hazard to the battery cells. Summary of the Invention

[0005] The object of the present invention is to provide a cover plate assembly and a battery to solve the problem of poor safety performance of large-capacity battery cells.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, a cover plate assembly is connected to a pole group, and the pole group is connected to a pole lug. The cover plate assembly includes a cover plate body, a pole post, a lower plastic, and a connecting piece. The pole post is arranged on the cover plate body; the lower plastic is arranged on the side of the cover plate body facing the pole group; the connecting piece is arranged on the side of the lower plastic facing the pole group, and the connecting piece includes a first welding portion, a second welding portion, and a fuse portion. The first welding portion is connected to the pole post, and the second welding portion is connected to the pole lug. The fuse portion is arranged at the minimum cross-section of the connection position between the first welding portion and the second welding portion, and the pole lug and the pole post are electrically connected through the connecting piece.

[0008] Preferably, the first welding portion, the second welding portion and the fuse portion are integrally formed.

[0009] Preferably, one of the second welding portions is connected to a corresponding fuse portion.

[0010] Preferably, the connecting piece includes one first welding portion and two second welding portions, and the fuse portions corresponding to the two second welding portions are symmetrically arranged on both sides of a symmetry axis in the length direction of the cover plate body.

[0011] Preferably, the cross-sectional area of ​​the fuse portion in the thickness direction of the connecting piece is S and meets the requirement of 30mm 2 ≤S≤35mm 2 , or, meet 20mm 2 ≤S≤30mm 2 .

[0012] Preferably, the minimum distance between the tab and the fuse part is W1, and satisfies W1≥2mm; the minimum distance between the pole and the fuse part is W2, and satisfies W2≥2mm.

[0013] Preferably, the second welding portion is welded to the tab to form a weld mark, and the fuse portion is spaced apart between the weld mark and the pole.

[0014] Preferably, the extending direction of the fuse portion is arranged obliquely to the length direction of the cover plate body.

[0015] Preferably, the connection between the first welding portion side wall and the second welding portion side wall is smoothly transitioned.

[0016] In a second aspect, a battery comprises a pole group, a shell, and the cover plate assembly as described above, wherein the cover plate body is connected to the shell, and the pole group is disposed inside the shell.

[0017] Beneficial effects of the present invention:

[0018] A cover plate assembly is connected to a pole group, and the pole group is connected to a pole lug. The cover plate assembly includes a cover plate body, a pole, a lower plastic and a connecting piece. The pole is arranged on the cover plate body; the lower plastic is arranged on the side of the cover plate body facing the pole group; the connecting piece is arranged on the side of the lower plastic facing the pole group. The connecting piece includes a first welding part, a second welding part and a fuse part. The first welding part is connected to the pole, and the second welding part is connected to the pole lug. The fuse part is arranged at the minimum cross-section of the connection position between the first welding part and the second welding part. The pole lug and the pole are electrically connected through the connecting piece.

[0019] In this way, the fuse part is set at the smallest cross-section. When the battery cell is working normally, the connecting piece can stably transmit the current inside the battery cell to the external circuit to ensure the current transmission capacity of the connecting piece. When the battery cell has abnormal overcurrent or high temperature, since the fuse part has the smallest cross-sectional area and the weakest structure, the fuse part can melt first and cut off the electrical connection between the electrode group and the external circuit in time, preventing further accumulation of heat and the occurrence of fire and explosion, reducing the safety hazards caused by thermal runaway, and improving the safety performance of large-capacity battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a partial front view of a battery in one embodiment of the present invention;

[0021] Figure 2 is a front view of a cover plate body according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic structural diagram of a cover plate body according to an embodiment of the present invention;

[0023] Figure 4 2 is a schematic structural diagram of a connecting piece in one embodiment of the present invention.

[0024] In the picture:

[0025] 1. Cover plate body; 2. Pole; 3. Lower plastic; 4. Connecting piece; 41. First welding part; 42. Second welding part; 421. Welding mark; 43. Fuse part; 5. Pole group; 51. Pole ear. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0027] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0028] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0029] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0030] See Figure 1 The present invention provides a cover plate assembly, which is connected to the pole group 5, and the pole group 5 is connected to the pole ear 51. The cover plate assembly includes a cover plate body 1, a pole 2, a lower plastic 3 and a connecting piece 4. The pole 2 is arranged on the cover plate body 1; the lower plastic 3 is arranged on the side of the cover plate body 1 facing the pole group 5; the connecting piece 4 is arranged on the side of the lower plastic 3 facing the pole group 5, and the connecting piece 4 includes a first welding portion 41, a second welding portion 42 and a fuse portion 43. The first welding portion 41 is connected to the pole 2, and the second welding portion 42 is connected to the pole ear 51. The fuse portion 43 is arranged at the minimum cross-section of the connection position of the first welding portion 41 and the second welding portion 42. The pole ear 51 and the pole 2 are electrically connected through the connecting piece 4.

[0031] In this embodiment, the first welding portion 41 is fixedly connected to the pole 2 by welding, and the second welding portion 42 is fixedly connected to the pole tab 51 by welding, and the second welding portion 42 and the pole tab 51 are arranged in a one-to-one correspondence. The current is transmitted to the external circuit through the pole group 5, the pole tab 51, the second welding portion 42, the fuse portion 43, the first welding portion 41, and the pole 2 in sequence.

[0032] In this way, since the fuse part 43 is arranged at the minimum cross-section of the connection position of the first welding part 41 and the second welding part 42, when the battery cell is working normally, the connecting piece 4 can stably transmit the current generated inside the battery cell to the external circuit, ensuring the current transmission capacity of the connecting piece, and in the case of abnormal overcurrent or high temperature, the fuse part 43 can be melted first to prevent further accumulation of heat, thereby quickly cutting off the electrical connection between the electrode group 5 and the external circuit, reducing the battery safety risks caused by thermal runaway, and improving the safety performance of large-capacity battery cells.

[0033] It can be understood that the positions of the first welding portion 41 and the second welding portion 42 can be adjusted according to the positions of the pole 2 and the pole lug 51, so as to achieve stable electrical connection between the pole 2 and the pole lug 51, and to make the connecting piece 4 have sufficient structural strength to improve the connection stability between the pole 2 and the pole lug 51. No further details will be given here.

[0034] See Figure 1 In some embodiments, the first welding portion 41, the second welding portion 42 and the fuse portion 43 are integrally formed.

[0035] In this way, the production and processing of the connecting piece 4 can be facilitated, and the internal resistance of the connecting piece 4 can be reduced, avoiding problems such as poor contact and uneven internal resistance caused by insufficient welding strength due to the split design, improving the stability of current transmission and conductivity of the connecting piece 4, and thus improving the safety performance of large-capacity battery cells.

[0036] It can be understood that the connection method of the first welding part 41, the second welding part 42 and the fuse part 43 can be adjusted according to actual needs, and the fuse part 43 can also be embedded between the first connection part and the second connection part. The one-piece molding setting is adopted in this embodiment to facilitate current transmission.

[0037] See Figure 1 In some embodiments, one second welding portion 42 is connected to a corresponding fuse portion 43 .

[0038] In this embodiment, the cross-section of the fuse portion 43 is also the cross-section of the connection between the first welding portion 41 and the second welding portion 42, so that when thermal runaway occurs in the battery cell, the fuse portion 43 can completely melt and block current transmission, thereby cutting off the internal circuit in time and avoiding the existence of residual current due to incomplete local melting.

[0039] In this way, when there are multiple electrode groups 5, when one of the electrode groups 5 has thermal runaway, the corresponding fuse 43 can cut off the current in time, thereby accurately cutting off the power to the runaway battery cell, avoiding affecting other electrode groups 5, and improving the safety performance of large-capacity battery cells.

[0040] See Figure 1 In some embodiments, the connecting piece 4 includes a first welding portion 41 and two second welding portions 42 , and the fuse portions 43 corresponding to the two second welding portions 42 are symmetrically arranged on both sides of the symmetry axis in the length direction of the cover body 1 .

[0041] In this embodiment, the two second welding portions 42 have the same shape and are symmetrically arranged on both sides of the symmetry axis in the length direction of the cover body 1 so that the two second welding portions 42 are respectively connected to the pole tabs 51 of the two pole groups 5 .

[0042] In this way, two second welding parts 42 are provided, so that one connecting piece 4 can be electrically connected to the pole ears 51 of two electrode groups 5 at the same time, thereby improving the current carrying capacity. The two second welding parts 42 on the same connecting piece 4 are symmetrically provided, which can make the current distribution more balanced and avoid uneven resistance of the connecting piece 4. In addition, the two fuse parts 43 are symmetrically provided, which can independently perform fuse protection on the electrode groups 5 connected thereto, thereby avoiding fuse failure caused by unreasonable position of the fuse part 43 and improving the reliability of the fuse part 43. When thermal runaway occurs in one of the electrode groups 5, the corresponding fuse part 43 is blown in time, which can avoid the abnormal current from affecting other electrode groups 5 and improve the overall safety performance of the large-capacity battery cell.

[0043] It is understandable that the number and location of the second welding portions 42 can be flexibly adjusted according to actual design, as long as a stable electrical connection between the pole 2 and the tab 51 can be achieved, and details will not be given here.

[0044] See Figure 1 In some embodiments, when the cell current range is 2500A-3000A, the cross-sectional area of ​​the fuse portion 43 in the thickness direction of the connecting piece 4 is S, and meets the 30mm 2 ≤S≤35mm 2 , which can make the fusing time range 30s-60s, meeting the fusing requirements.

[0045] In this embodiment, the cross-sectional area S of the fuse portion 43 can be 30 mm 2 -35mm 2 Any value between or a range between any two values, such as 30mm 2 , 31mm 2 , 32mm 2 , 33mm 2 , 34mm 2 , 35mm 2 wait.

[0046] Alternatively, in some other embodiments, when the cell current range is 3000A-3500A, the 20mm 2 ≤S≤30mm 2 , which can make the fusing time less than 30s and meet the fusing requirements.

[0047] In this embodiment, the cross-sectional area S of the fuse portion 43 can be 20 mm 2 -30mm 2 Any value between or a range between any two values, such as 20mm 2 , 22mm 2 , 24mm 2 , 26mm 2 , 28mm 2 , 30mm 2 wait.

[0048] In this way, the larger the cross-sectional area S of the fuse part 43, the stronger the overcurrent capacity, and the longer the required melting time. Setting the cross-sectional area S of the fuse part 43 according to the current range of the battery cell can make the fuse part 43 have a suitable internal resistance, and can stably transmit current under normal working conditions and maintain good current transmission capacity. In the case of abnormal overcurrent or thermal runaway, the fuse part 43 can melt within the specified time to cut off the internal circuit, avoid further loss of control of the battery cell, and improve the safety performance of large-capacity battery cells.

[0049] It can be understood that the cross-sectional area S of the fuse part 43 can be adjusted according to the current range of the battery cell and the dimensions of the connecting piece 4, the pole 2, and the pole ear 51. The cross-sectional area S of the fuse part 43 cannot be too small, otherwise it will cause premature melting and affect the normal operation of the large-capacity battery cell. The cross-sectional area S of the fuse part 43 cannot be too large, otherwise it will cause the melting time to be too long and increase the risk of thermal runaway of the battery cell.

[0050] See Figure 1 and Figure 2 In some embodiments, the minimum distance between the tab 51 and the fuse 43 is W1, and W1 ≥ 2 mm. The minimum distance between the terminal 2 and the fuse 43 is W2, and W2 ≥ 2 mm. For example, the minimum distance W1 between the tab 51 and the fuse 43 can be 2 mm, 3 mm, 4 mm, 5 mm, etc., and the minimum distance W2 between the terminal 2 and the fuse 43 can be 2 mm, 3 mm, 4 mm, 5 mm, etc.

[0051] In this way, the fuse part 43 can have an appropriate distance from the tab 51 and the pole 2, so that the tab 51 and the pole 2 are not easily affected by the melting heat when the fuse part 43 melts, avoiding the risks of local overheating, melting failure, short circuit, etc. caused by the tab 51 or the pole 2 being too close to the fuse part 43, improving the heat dissipation performance of the connecting piece 4, avoiding heat concentration, and improving the overall safety performance of the large-capacity battery cell.

[0052] It can be understood that the minimum distance W1 between the tab 51 and the fuse part 43 cannot be too small, otherwise the tab 51 will be affected by the fuse part 43 and damaged. The minimum distance W2 between the pole 2 and the fuse part 43 cannot be too small, otherwise it will cause the pole 2 to short-circuit, thereby reducing the safety performance of the battery. The minimum distance W1 between the tab 51 and the fuse part 43 and the minimum distance W2 between the pole 2 and the fuse part 43 can be adjusted according to actual needs, and no further examples will be given here.

[0053] See Figure 1 In some embodiments, the second welding portion 42 is welded to the tab 51 to form a welding mark 421 , and the fuse portion 43 is spaced apart and arranged between the welding mark 421 and the electrode 2 .

[0054] In this embodiment, the length direction of the weld mark 421 is parallel to the length direction of the cover body 1, and the edge of the weld mark 421 is spaced apart from the edge of the tab 51 to avoid the weld mark 421 being too close to the edge of the tab 51 and affecting the welding effect between the tab 51 and the second welding portion 42.

[0055] In this way, interference between the fuse part 43 and the weld mark 421 area during the welding process can be avoided, the welding quality can be improved, and the connection stability between the pole tab 51 and the second welding part 42, and the connection stability between the pole 2 and the first welding part 41 can be improved, thereby achieving a stable electrical connection between the pole tab 51 and the pole 2, and improving the safety performance of large-capacity battery cells; the edge of the weld mark 421 and the edge of the pole tab 51 are spaced apart, which can avoid the heat generated during the welding process from affecting the fuse part 43, thereby ensuring the reliability of the fuse part 43.

[0056] It is understandable that the position of the weld mark 421 can be adjusted according to the relative position of the tab 51 and the second welding portion 42, which will not be listed in detail here; it should be noted that the distance between the weld mark 421 and the edge of the tab 51 cannot be too small, as a too small distance will increase the risk of welding defects.

[0057] See Figure 2 In some embodiments, the extension direction of the fuse portion 43 is obliquely arranged to intersect the length direction of the cover body 1 .

[0058] In this embodiment, one end of the fuse portion 43 toward the pole 2 extends toward the edge of the lower plastic 3 , and one end of the fuse portion 43 toward the tab 51 extends away from the edge of the lower plastic 3 .

[0059] In this way, the fusible portion 43 is arranged at an angle, which can reasonably utilize the space of the lower plastic 3 and reduce the influence of the heat generated during the melting process on the lower plastic 3, the pole 2 and the tab 51. The end of the fusible portion 43 facing the tab 51 extends in a direction away from the edge of the lower plastic 3, which can keep the fusible portion 43 at an appropriate distance from the tab 51, thereby preventing the heat generated by welding the tab 51 and the second welding portion 42 from affecting the fusible portion 43, causing the fusible portion 43 to melt prematurely and affect the current transmission capacity.

[0060] It is understandable that the extension direction and the inclination angle of the fuse portion 43 can be adjusted according to actual needs, which will not be elaborated here.

[0061] See Figure 3 and Figure 4 In some embodiments, the connection between the side wall of the first welding portion 41 and the side wall of the second welding portion 42 is smoothly transitioned.

[0062] In this embodiment, the connection between the two second welding portions 42 on the same connecting piece 4 is smoothly transitioned, so that the side wall of the connecting piece 4 is smooth as a whole.

[0063] In this way, the stability of the connecting piece 4 can be improved, and the presence of sharp corners at the connection point that cause stress concentration, uneven resistance and other problems can be avoided. The structural strength and conductivity of the connecting piece 4 can be improved, and the overcurrent capacity and current transmission efficiency of the fuse part 43 can be improved. The pole ear 51 is stably electrically connected to the pole 2, and when thermal runaway occurs in the battery cell, the internal circuit can be cut off in time. It is also beneficial to assemble the connecting piece 4 to the lower plastic 3, reduce assembly interference and scratches with other components, and improve the safety performance and reliability of large-capacity battery cells.

[0064] It is understandable that the shape of the connecting piece 4 can be adjusted according to actual needs, as long as it can facilitate assembly and achieve stable electrical connection between the tab 51 and the pole 2, and will not be elaborated here.

[0065] In order to verify the rationality of the range of the cross-sectional area S of the fuse part 43, as shown in Table 1, this embodiment provides four groups of embodiments and three groups of comparative examples for illustration. By designing different cross-sectional areas S of the fuse part 43, the safety test effect of the battery cell is verified. The battery cell capacity is 880Ah, and the short-circuit current range is 3000A-3500A. The safety test requires that the battery cell does not catch fire, explode, or tear the shell, and there is no electrolyte leakage.

[0066] Table 1

[0067]

[0068] It can be seen from Examples 1 to 4 in Table 1 that after satisfying the range limitation, when the short-circuit current range is 3000A-3500A, the cross-sectional area S of the fuse portion 43 satisfies 30mm 2 ≤S≤35mm 2 , the fuse part 43 can only be blown during the battery cell safety test, and as the cross-sectional area S of the fuse part 43 decreases, the blowing time is also shortened.

[0069] From Comparative Examples 1 to 3 in Table 1, it can be seen that when the cross-sectional area S of the fuse portion 43 exceeds 35 mm 2 , the fuse part 43 cannot be melted in time, which leads to thermal runaway of the battery cell and causes problems such as fire, shell explosion and tearing, pole 2 melting, electrolyte leakage, etc., affecting the safety performance of the battery.

[0070] In order to verify the rationality of the minimum distance W1 between the tab 51 and the fuse part 43 and the minimum distance W2 between the pole 2 and the fuse part 43, as shown in Table 2, by designing different minimum distances W1 between the tab 51 and the fuse part 43 and the minimum distances W2 between the pole 2 and the fuse part 43, the safety test effect of the battery cell is verified. The battery cell capacity is 880Ah, and the short-circuit current range is 3000A-3500A. The safety test requires that the battery cell does not catch fire, explode, or have a shell that is not torn or leak electrolyte.

[0071] Table 2

[0072]

[0073] It can be seen from Examples 1 to 3 in Table 2 that after meeting the range limit, W1 ≥ 2 mm and W2 ≥ 2 mm need to be met at the same time, so that the battery cell safety test can pass, the fuse part 43 can be fully melted, and there is no abnormal overlap inside the battery cell.

[0074] It can be seen from Comparative Examples 1 to 4 in Table 2 that when one of the minimum distance W1 between the tab 51 and the fuse part 43 and the minimum distance W2 between the pole 2 and the fuse part 43 does not meet the range limit, the tab 51 will overlap with the pole 2, making it difficult to achieve timely circuit disconnection and the battery cell safety test will fail.

[0075] See Figure 1 The present invention also provides a battery, including a pole group 5, a shell and a cover assembly, the cover body 1 is connected to the shell, and the pole group 5 is arranged inside the shell.

[0076] In this embodiment, the electrode group 5 is connected to the electrode tab 51 , the electrode tab 51 is electrically connected to the electrode column 2 via the connecting piece 4 , and the cover body 1 is sealed and connected to the housing by welding.

[0077] It should be noted that by connecting the pole ears 51 of the two pole groups 5 to the corresponding second welding parts 42 respectively, the current of the pole group 5 can be transmitted to the external circuit, and since the pole ears 51 and the pole posts 2 are both connected to the connecting piece 4, the assembly and positioning of the cover body 1 and the pole group 5 can be facilitated, thereby improving the stability and safety performance of the large-capacity battery cell.

[0078] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A cover plate assembly, characterized in that: Connected to the electrode group (5), the electrode group (5) is connected to the electrode lug (51), and the cover plate assembly includes: A cover plate body (1) and a pole (2), wherein the pole (2) is arranged on the cover plate body (1); A lower plastic (3), the lower plastic (3) being arranged on a side of the cover plate body (1) facing the electrode group (5); A connecting piece (4), the connecting piece (4) is arranged on the side of the lower plastic (3) facing the pole group (5), the connecting piece (4) comprises a first welding portion (41), a second welding portion (42) and a fuse portion (43), the first welding portion (41) is connected to the pole (2), the second welding portion (42) is connected to the pole lug (51), the fuse portion (43) is arranged at the minimum cross-section of the connection position between the first welding portion (41) and the second welding portion (42), and the pole lug (51) is electrically connected to the pole (2) through the connecting piece (4).

2. The cover plate assembly according to claim 1, wherein: The first welding portion (41), the second welding portion (42) and the fuse portion (43) are integrally formed.

3. The cover plate assembly according to claim 1, wherein: One of the second welding portions (42) is correspondingly connected to one of the fuse portions (43).

4. The cover plate assembly according to claim 3, wherein: The connecting piece (4) comprises a first welding portion (41) and two second welding portions (42), and the fuse portions (43) corresponding to the two second welding portions (42) are symmetrically arranged on both sides of a symmetry axis in the length direction of the cover plate body (1).

5. The cover plate assembly according to claim 1, wherein: The cross-sectional area of ​​the fuse portion (43) in the thickness direction of the connecting piece (4) is S and meets the requirement of 30mm 2 ≤S≤35mm 2 , or, meet 20mm 2 ≤S≤30mm 2 .

6. The cover plate assembly according to claim 1, wherein: The minimum distance between the pole lug (51) and the fuse part (43) is W1, and satisfies W1≥2mm; the minimum distance between the pole (2) and the fuse part (43) is W2, and satisfies W2≥2mm.

7. The cover plate assembly according to any one of claims 1 to 6, characterized in that: The second welding portion (42) is welded to the pole tab (51) to form a welding mark (421), and the fuse portion (43) is spaced apart and arranged between the welding mark (421) and the pole (2).

8. The cover plate assembly according to any one of claims 1 to 6, characterized in that: The extension direction of the fuse portion (43) is arranged obliquely to the length direction of the cover plate body (1).

9. The cover plate assembly according to any one of claims 1 to 6, characterized in that: The connection between the side wall of the first welding portion (41) and the side wall of the second welding portion (42) is smoothly transitioned.

10. A battery, characterized in that: It comprises a pole group (5), a shell and a cover plate assembly according to any one of claims 1 to 9, wherein the cover plate body (1) is connected to the shell, and the pole group (5) is arranged inside the shell.

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