Battery cell and battery pack

Abstract

The present application relates to the technical field of batteries, and in particular to a battery cell and a battery pack. The battery cell comprises: a casing, in which an accommodating cavity is formed; and a cover plate, welded to the casing to seal the accommodating cavity, wherein after welding, a weld portion is formed between the cover plate and the casing; formula (I), wherein C is the perimeter of the cover plate and is expressed in mm, S is the area of the cover plate and is expressed in mm2, K is the shear strength of the cover plate and is expressed in Mpa, and B is the fusion depth of the weld portion and is expressed in mm. In the present invention, the perimeter C of the cover plate, the area S of the cover plate, the shear strength K of the cover plate, and the fusion depth B of the weld portion are defined to satisfy the condition C / S×B×K≥1.25, so that the welding strength between the casing and the cover plate can be ensured, and the weld portion is prevented from cracking, thereby ensuring the airtightness of the battery cell, and further ensuring the use safety of the battery cell.

Description

Battery cell and battery pack

[0001] Cross Reference to Related Applications

[0002] The present application claims priority to the Chinese patent application No. CN202411237650.8, filed on September 5, 2024, and entitled "Battery cell and battery pack", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of battery, in particular to a battery cell and a battery pack. BACKGROUND

[0004] With the increasing maturity of lithium ion battery technology, power batteries as a new type of battery are widely used in electric vehicles and energy storage fields, and the performance and safety requirements of power batteries are increasingly high.

[0005] A lithium ion power battery generally includes a battery internal structure and a battery external structure. The battery internal structure mainly includes a battery cell pole group, and the battery external structure mainly includes a battery cell cover plate and a battery cell shell. The battery cell shell provides a containing space for the battery cell pole group, and the battery cell cover plate and the battery cell shell are fixed in the internal space by welding. At present, if the welding strength of the battery cell cover plate and the battery cell shell is insufficient, the weld formed by welding will crack, thereby affecting the air tightness of the battery and failing to ensure the safe operation of the battery cell. In addition, the modules in the battery pack are wrapped with a blue film outside the battery cell to insulate the battery cell. After the battery cell cover plate and the battery cell shell are welded, the blue film at the welded part is prone to warping and thinning due to the protrusion of the weld, thereby affecting the insulation performance.

[0006] SUMMARY

[0007] Therefore, the purpose of the present application is to provide a battery cell and a battery pack to solve the problem that the welding strength of the existing battery cell cover plate and the battery cell shell at the welding connection is insufficient, which leads to the cracking of the weld between the battery cell cover plate and the battery cell shell, thereby affecting the air tightness of the battery cell and failing to ensure the safe operation of the battery cell.

[0008] In a first aspect, the present application provides a battery cell, wherein the battery cell comprises:

[0009] a shell, an accommodating cavity being formed in the interior of the shell;

[0010] a cover plate, the cover plate being welded with the shell to close the accommodating cavity, a welding part being formed between the cover plate and the shell after welding;

[0011] wherein C is the circumference of the cover plate, in mm; S is the area of the cover plate, in mm 2K is the shearing strength of the cover plate, in Mpa; B is the penetration of the welding part, in mm.

[0012] Beneficial effects: the application can guarantee the welding strength of the shell and the cover plate, avoid the cracking of the welding part, guarantee the air tightness of the battery cell, further guarantee the safety of the battery cell, and improve the safety of the battery pack.

[0013] In an alternative embodiment, the penetration B of the welding part is 500-1450 μm.

[0014] In an alternative embodiment, the width A of the welding part is 400-2000 μm.

[0015] In an alternative embodiment, the welding part protrudes outward from the battery cell, so that part of the welding part protrudes out of the outer surface of the cover plate and / or the shell.

[0016] In an alternative embodiment, in the thickness direction of the cover plate, the height dimension of the welding part protruding out of the outer surface of the cover plate is D, and D≤300 μm.

[0017] In an alternative embodiment, in the thickness direction of the shell, the height dimension of the welding part protruding out of the outer surface of the shell is E, and E≤150 μm.

[0018] In an alternative embodiment, the outer wall of the cover plate in the circumferential direction abuts against the inner wall of the shell.

[0019] In an alternative embodiment, the cover plate comprises a cover plate body formed as a plate structure, C is the circumference of the outer edge of the cover plate body, and S is the area enclosed by the outer edge of the cover plate body.

[0020] In an alternative embodiment, the cover plate further comprises:

[0021] a pole column mounted on the cover plate body, part of the pole column protruding out of the side of the cover plate body facing the outside of the battery cell;

[0022] a first insulating member arranged on the side of the cover plate body facing the inside of the battery cell.

[0023] In a second aspect, the application provides a battery pack comprising the battery cell according to any of the above technical solutions. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the specific embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and those of ordinary skill in the art can obtain other drawings without creative effort based on these drawings.

[0025] Fig. 1 is a structural schematic diagram of an electric core provided by an embodiment of the present application;

[0026] Fig. 2 is an exploded structural schematic diagram of an electric core provided by an embodiment of the present application;

[0027] Fig. 3 is a structural schematic diagram of a cover plate in an electric core provided by an embodiment of the present application;

[0028] Fig. 4 is a structural schematic diagram of an electric core provided by an embodiment of the present application from another perspective;

[0029] Fig. 5 is a sectional view along Q-Q in Fig. 4;

[0030] Fig. 6 is a partial structural sectional view of a cover plate and a shell after welding in an electric core provided by an embodiment of the present application;

[0031] Fig. 7 is an enlarged structural schematic diagram of P in Fig. 6.

[0032] Reference signs: 10 - shell; 11 - accommodating cavity; 101 - boss; 20 - cover plate; 21 - cover plate body; 211 - liquid injection hole; 22 - pole column; 231 - first insulating piece; 232 - second insulating piece; 24 - pressure relief piece; 30 - welding part. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in detail below, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0034] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples. Such repetition is for the purpose of simplification and clarity, and in itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art can realize the applicability of other processes and / or the use of other materials.

[0035] According to a first aspect of the present application, an electric core is provided, which specifically comprises a shell 10 and a cover plate 20.

[0036] In the following, the specific structure of the electric core according to the present embodiment will be described.

[0037] In the present embodiment, as shown in FIGS. 1-5, the inside of the shell 10 is formed with a receiving cavity 11 for accommodating components such as the electric core pole group, when the electric core is a square electric core or a blade electric core, the shell 10 is formed as a rectangular thin-walled hollow structure, and when the electric core is a cylindrical electric core, the shell 10 is a cylindrical thin-walled hollow structure. The cover plate 20 is welded with the shell 10 to close the receiving cavity 11, and a welding portion 30 is formed between the cover plate 20 and the shell 10 after welding. The welding portion 30 can be understood as a weld formed between the cover plate 20 and the shell 10 under the welding process, and the weld includes a depth of penetration and a width of penetration, which are well-known techniques in the art and will not be described in detail here. The welding strength of the welding portion 30 directly affects the assembly reliability of the cover plate 20 and the shell 10, thereby affecting the sealing of the electric core.

[0038] The welding portion 30 is formed as a closed annular structure, so that the assembly reliability of the cover plate 20 and the shell 10 can guarantee the sealing of the electric core.

[0039] In the present embodiment, the cover plate 20 and the shell 10 after welding satisfy wherein C is the circumference of the cover plate 20, in mm; S is the area of the cover plate 20, in mm 2 ; K is the shear strength of the cover plate 20, in Mpa; and B is the depth of penetration of the welding portion 30, in mm. By limiting the circumference C of the cover plate 20, the area S of the cover plate 20, the shear strength K of the cover plate 20, and the depth of penetration B of the welding portion 30 to satisfy the condition of C / S x B x K≥1.25, the welding strength of the shell 10 and the cover plate 20 can be guaranteed, and the cracking of the welding portion 30 can be avoided, thereby guaranteeing the air tightness of the electric core, further guaranteeing the safety of the electric core in use, and improving the safety of the battery pack.

[0040] It should be noted that the circumference of the cover plate 20 is the length of the portion shown by the dashed line in FIG. 3, and the area of the cover plate 20 is the area of the region enclosed by the dashed line in FIG. 3.

[0041] Further, in a preferred embodiment, as shown in FIG. 6, the depth of penetration B of the welding portion 30 is 500 μm-1450 μm, thereby further improving the strength of the welding portion 30, avoiding the cracking of the welding portion 30, and thereby guaranteeing the air tightness of the electric core to meet the use requirements.

[0042] Further, in the preferred embodiment, as shown in FIG. 6, the welding portion 30 has a fusion width A of 400-2000 μm, so as to further improve the strength of the welding portion 30, avoid cracking of the welding portion 30, and ensure that the air tightness of the battery cell meets the use requirements.

[0043] In the preferred embodiment, as shown in FIGS. 2, 5-7, the outer wall of the cover plate 20 in the circumferential direction abuts against the inner wall of the shell 10, specifically, the side wall of the cover plate body 21 abuts against the inner wall of the shell 10, so that the cover plate body 21 is embedded in the shell 10 and then welded on the side of the cover plate 20 facing away from the accommodating cavity 11. Further, in the present embodiment, as shown in FIG. 2, the inner wall of the shell 10 is formed with a protruding boss 101, so as to limit and support the cover plate body 21, and ensure that the side of the cover plate body 21 facing the outside of the battery cell is flush with the end of the shell 10 after the cover plate 20 is assembled with the shell 10.

[0044] In the present embodiment, as shown in FIG. 2, the cover plate 20 comprises a cover plate body 21 formed in a plate structure, which can be formed in a rectangular plate structure, and C is the circumference of the outer edge of the cover plate body 21, and S is the area enclosed by the outer edge of the cover plate body 21. In addition, the cover plate body 21 is provided with a liquid injection hole 211, which is a through hole, so that electrolyte can be injected into the battery cell through the liquid injection hole 211 after the cover plate 20 and the shell 10 are welded.

[0045] Further, in the present embodiment, as shown in FIG. 2, the cover plate 20 further comprises a pole 22, a first insulating member 231, a second insulating member 232, and a pressure relief member 24; the pole 22 is mounted on the cover plate body 21, one end of the pole 22 is connected to the tab on the pole group inside the battery cell, and part of the pole 22 extends out of the side of the cover plate body 21 facing the outside of the battery cell, for connecting to a charging or power consuming device, so as to realize current conduction. The pole 22 in the cover plate 20 is provided with at least one, which can be a positive pole or a negative pole when there is one pole 22; when there are multiple poles 22, optionally, at least part of the multiple poles 22 are positive poles, and the rest are negative poles.

[0046] The first insulating member 231 and the second insulating member 232 are both made of insulating materials, so as to play a role of insulation and protection, and avoid short circuit of the battery cell; specifically, the first insulating member 231 is arranged on the side of the cover plate body 21 facing the inside of the battery cell, i.e., the first insulating member 231 is arranged in the accommodating cavity 11; the second insulating member 232 is arranged between the pole 22 and the cover plate body 21, and the second insulating member 232 is arranged in one-to-one correspondence with the pole 22.

[0047] The pressure relief member 24 can be an explosion-proof notch engraved on the cover plate body 21 or an explosion-proof valve installed at a through hole of the cover plate body 21, and can be opened at a preset pressure when the battery cell fails to produce gas inside, so as to connect the inside and outside of the battery cell, timely exhaust the gas, and ensure the safety of the battery cell.

[0048] The cover plate 20 and the shell 10 of different sizes and materials are welded and assembled, and the welding portion 30 formed by welding is detected to verify whether the cracking of the welding portion 30 can be avoided under the condition of C / S×B×K≥1.25, which can ensure the safety of the battery cell. The test results are shown in Table 1.

[0049] Table 1

[0050] Note: OK in the table means that the detection result is qualified, and NG in the table means that the detection result is unqualified.

[0051] As shown in Table 1, examples 1-1 to 1-14, examples in which C / S×B×K-1.25 is less than 0 all have the cracking of the welding portion 30, and thus it can be proved that the cracking of the welding portion 30 can be avoided under the condition of C / S×B×K≥1.25 to a certain extent.

[0052] In the embodiment, as shown in FIGS. 6 and 7, under the influence of the welding process, the welding portion 30 protrudes outward from the battery cell, and part of the welding portion 30 protrudes outward from the outer surface of the cover plate 20 and / or the shell 10.

[0053] It should be noted that the outer surface of the cover plate 20 and / or the shell 10 refers to the surface of the cover plate 20 and / or the shell 10 facing the outside of the battery cell.

[0054] Further, in the thickness direction of the cover plate 20, the height dimension of the welding portion 30 protruding outward from the outer surface of the cover plate 20 is D, and D≤300μm, so as to avoid the warping of the blue film after the battery cell is covered with the blue film under the influence of the protruding welding portion 30.

[0055] The battery cell with different height dimensions D of the welding portion 30 protruding outward from the outer surface of the cover plate 20 is covered with the blue film, and whether the blue film is warped is detected, and the test results are shown in Table 2.

[0056] Table 2

[0057] As can be seen from the above Table 2, in the cases of Examples 2-1 to 2-6, the height dimension D of the welding portion 30 protruding from the outer surface of the cover plate 20 is less than or equal to 300 μm, and no lifting of the blue film occurs; in the cases of Examples 2-7 and 2-8, the height dimension D of the welding portion 30 protruding from the outer surface of the cover plate 20 is greater than 300 μm, and the blue film is easily lifted, resulting in slight lifting of the blue film.

[0058] Further, in the present embodiment, in the thickness direction of the shell 10, the height dimension E of the welding portion 30 protruding from the outer surface of the shell 10 is less than or equal to 150 μm, so that the thickness of the blue film is not reduced due to the protruding welding portion 30 after the battery cell is wrapped with the blue film, thereby avoiding the problem of affecting the insulation performance.

[0059] In the following, the blue film wrapped battery cell with different height dimensions E of the welding portion 30 protruding from the outer surface of the shell 10 is detected to see whether the insulation performance is affected, and the test results are shown in Table 3.

[0060] Table 3

[0061] As can be seen from the above Table 3, in the cases of Examples 3-1 to 3-6, the height dimension E of the welding portion 30 protruding from the outer surface of the shell 10 is less than or equal to 150 μm, and no whitening of the blue film occurs, i.e. the insulation performance is not affected, and the safety requirement for the battery cell is met; in the cases of Examples 3-7 and 3-8, the height dimension E of the welding portion 30 protruding from the outer surface of the shell 10 is greater than 150 μm, and the protruding height is too high, resulting in whitening of the blue film when the blue film is wrapped, which indicates that the insulation performance is reduced and the safety requirement for the battery cell cannot be met.

[0062] According to the battery cell provided by the present application, the shell and the cover plate are welded to form a welding portion, and the welding strength of the shell and the cover plate is ensured by limiting the perimeter C of the cover plate, the area S of the cover plate, the shearing strength K of the cover plate and the penetration B of the welding portion under the condition of C / S x B x K≥1.25, so that the cracking of the welding portion is avoided, the air tightness of the battery cell is ensured, and the safety requirement for the battery cell is met. Furthermore, the strength of the welding portion is further improved by further limiting the penetration B of the welding portion in the range of 500 μm to 1450 μm and the width A of the welding portion in the range of 400 μm to 2000 μm, so that the cracking of the welding portion is avoided, the air tightness of the battery cell is ensured, and the safety requirement for the battery cell is met. In addition, the height dimension D of the welding portion protruding from the outer surface of the cover plate is limited to be less than or equal to 300 μm, and the height dimension E of the welding portion protruding from the outer surface of the shell is limited to be less than or equal to 150 μm, so that the lifting and thinning of the blue film in the area of the welding portion after the battery cell is wrapped with the blue film is avoided to some extent, the insulation performance is ensured, and the safety requirement for the battery cell is further met.

[0063] According to the battery pack provided by the application, the battery pack comprises the battery cell as described above, the battery cell is provided with at least one, when the battery cell is provided with a plurality of battery cells, at least part of the battery cells are arranged in series and / or parallel, the air tightness and insulation of each battery cell can be guaranteed, and the safety of the battery pack is effectively improved.

[0064] Although the embodiments of the application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and purposes of the application, and the scope of the application is defined by the claims and their equivalents. Industrial applicability

[0065] The application can guarantee the welding strength of the shell and the cover plate, avoid the cracking of the welding part, guarantee the air tightness of the battery cell, further guarantee the safe use of the battery cell, and improve the safety of the battery pack.

Claims

1. An electric cell, characterized by, The electric core comprises: a shell, an accommodation cavity is formed inside the shell; A cover plate is welded with the shell to close the accommodating cavity, and a welding portion is formed between the cover plate and the shell after welding. Wherein, C is the perimeter of the cover plate, unit: mm; S is the area of the cover plate, unit: mm 2 ; K is the shear strength of the cover plate, unit: Mpa; B is the penetration of the welding part, unit: mm.

2. The electric cell of claim 1, wherein, a depth B of the welding part is 500-1450 μm.

3. The electric cell of claim 1, wherein, a width A of the welding part is 400-2000 μm.

4. The electric cell of claim 1, wherein, The welding part protrudes outside the electric core, so that part of the welding part protrudes outside the cover plate and / or the shell.

5. The electric cell of claim 4, wherein, In the thickness direction of the cover plate, the height of the welding part protruding outside the cover plate is D, and D≤300 μm.

6. The electric cell of claim 4, wherein, In the thickness direction of the shell, the height of the welding part protruding outside the shell is E, and E≤150 μm.

7. The electric cell of claim 1, wherein, The outer wall of the cover plate in the circumferential direction abuts against the inner wall of the shell.

8. The electric cell of claim 1, wherein, The cover plate comprises a cover plate body in a plate structure, C is the circumference of the outer edge of the cover plate body, and S is the area surrounded by the outer edge of the cover plate body.

9. The electric cell of claim 8, wherein, The cover plate further comprises: a pole, which is installed on the cover plate body and part of which protrudes outside the cover plate body; a first insulating part, which is arranged on the side of the cover plate body facing the inside of the electric core.

10. A battery pack, characterized by, The electric core comprises the electric core according to any one of claims 1-9.

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