Battery Cells and Battery Packs

Abstract

The present invention relates to the field of battery technology, and in particular to a battery cell and a battery pack. The battery cell comprises: a housing is provided with a receiving cavity; a cover plate is welded to the housing to close the receiving cavity, and a welding portion is formed between the cover plate and the housing after welding; #imgabs0#; wherein C is the circumference of the cover plate, in mm; S is the area of ​​the cover plate, in mm 2 ; K is the shear strength of the cover plate, in MPa; B is the penetration of the weld, in mm. The present invention can ensure the welding strength of the shell and the cover plate and avoid cracking of the weld by limiting the perimeter C of the cover plate, the area S of the cover plate, the shear strength K of the cover plate and the penetration B of the weld under the condition of satisfying C / S×B×K≥1.25, thereby ensuring the airtightness of the battery cell and further ensuring the safety of the battery cell.

Description

Technical Field

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

[0002] As lithium-ion battery technology becomes increasingly mature, power batteries are widely used as new types of batteries in electric vehicles and energy storage fields, and the performance and safety requirements of power batteries are increasing.

[0003] Lithium-ion power batteries generally include an internal battery structure and an external battery structure. The internal battery structure mainly includes a battery cell pole group, and the external battery structure mainly includes a battery cell cover and a battery cell shell. The battery cell shell provides a storage space for the battery cell pole group, and the battery cell cover and the battery cell shell are welded together to fix the pole group in the internal space. At present, the insufficient welding strength of the battery cell cover and the battery cell shell will cause cracks in the weld formed by welding, 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 will be coated with a blue film on the outside of the battery cell to insulate the battery cell. After welding, the battery cell cover and the battery cell shell are prone to warping and thinning of the blue film due to the protrusion of the weld, thereby affecting the insulation performance. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a battery cell and a battery pack to solve the problem that the existing battery cell cover and the battery cell shell have insufficient strength at the welding connection, which causes the weld between the battery cell cover and the battery cell shell to easily crack, thereby affecting the air tightness of the battery cell and failing to ensure the safe operation of the battery cell.

[0005] A first aspect of the present invention provides a battery cell, wherein the battery cell comprises:

[0006] A housing having an accommodating cavity formed therein;

[0007] A cover plate, welded to the shell to close the accommodating cavity, a welding portion being formed between the cover plate and the shell after welding;

[0008] ;

[0009] Wherein, C is the perimeter of the cover plate, in mm; S is the area of ​​the cover plate, in mm 2 ; K is the shear strength of the cover plate, in MPa; B is the penetration depth of the weld, in mm.

[0010] Preferably, the penetration depth B of the weld portion is 500 μm to 1450 μm.

[0011] Preferably, the weld width A of the weld portion is 400 μm to 2000 μm.

[0012] Preferably, the welding portion protrudes toward the outside of the battery cell, so that a portion of the welding portion extends out of the outer surface of the cover plate and / or the shell.

[0013] Preferably, in the thickness direction of the cover plate, the height dimension of the welding portion protruding from the outer surface of the cover plate is D, and D≤300 μm.

[0014] Preferably, in the wall thickness direction of the shell, the height dimension of the welding portion protruding from the outer surface of the shell is E, and E≤150 μm.

[0015] Preferably, an outer wall of the cover plate in the circumferential direction abuts against an inner wall of the shell.

[0016] Preferably, the cover plate comprises a cover plate body formed as a plate-like structure, C is the perimeter of the outer edge of the cover plate body, and S is the area enclosed by the outer edge of the cover plate body.

[0017] Preferably, the cover plate further comprises:

[0018] A pole, mounted on the cover body, with part of the pole extending out of a side of the cover body facing the outside of the battery cell;

[0019] The first insulating member is arranged on a side of the cover body facing the inside of the battery cell.

[0020] A second aspect of the present invention provides a battery pack, comprising the battery cell described in any of the above technical solutions.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The battery cell of the present invention comprises a shell and a cover plate, which are welded to form a welding portion. By limiting the circumference C of the cover plate, the area S of the cover plate, the shear strength K of the cover plate and the penetration B of the welding portion under the condition of satisfying C / S×B×K≥1.25, the welding strength of the shell and the cover plate can be ensured, and cracking of the welding portion can be avoided, thereby ensuring the airtightness of the battery cell, and further ensuring the safety of the battery cell, thereby improving the safety of the battery pack.

[0023] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of the structure of a battery cell provided in an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of the exploded structure of a battery cell provided in an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the structure of a cover plate in a battery cell provided in an embodiment of the present invention;

[0028] Figure 4 A schematic diagram of the structure of a battery cell provided by an embodiment of the present invention from another perspective;

[0029] Figure 5 For along Figure 4 The cross-section taken at QQ in the middle;

[0030] Figure 6 A cross-sectional view of the local structure of a battery cell after the cover plate and the shell are welded in an embodiment of the present invention;

[0031] Figure 7 for Figure 6 Schematic diagram of the enlarged structure at P in the middle.

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

[0033] The following specific embodiments are provided to help the reader obtain a comprehensive understanding of the methods, devices and / or systems described herein. However, after understanding the disclosure of the present application, various changes, modifications and equivalents of the methods, devices and / or systems described herein will be apparent. For example, the order of operations described herein is merely an example, and is not limited to the order set forth herein, but in addition to the operations that must occur in a particular order, changes that will be apparent after understanding the disclosure of the present application may be made. In addition, in order to improve clarity and brevity, descriptions of features known in the art may be omitted.

[0034] The features described herein may be implemented in different forms and should not be interpreted as being limited to the examples described herein. Rather, the examples described herein have been provided only to illustrate some of the many possible ways of implementing the methods, devices and / or systems described herein that will be apparent after understanding the disclosure of the present application.

[0035] Throughout the specification, when an element (such as a layer, a region, or a substrate) is described as being “on”, “connected to”, “bound to”, “over”, or “covering” another element, it may be directly “on”, “connected to”, “bound to”, “over”, or “covering” another element, or one or more other elements may be present between them. In contrast, when an element is described as being “directly on”, “directly connected to”, “directly bound to”, “directly over”, or “directly covering” another element, there may be no other elements present between them.

[0036] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more items.

[0037] Although terms such as "first," "second," and "third" may be used herein to describe various members, components, regions, layers, or portions, these members, components, regions, layers, or portions are not limited by these terms. Rather, these terms are only used to distinguish one member, component, region, layer, or portion from another member, component, region, layer, or portion. Therefore, without departing from the teachings of the examples described herein, the first member, component, region, layer, or portion referred to may also be referred to as the second member, component, region, layer, or portion.

[0038] For ease of description, spatial relational terms such as "above", "upper", "below", and "lower" may be used herein to describe the relationship of one element to another element as shown in the accompanying drawings. Such spatial relational terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the accompanying drawings. For example, if the device in the accompanying drawings is turned over, an element described as being "above" or "upper" relative to another element will subsequently be "below" or "lower" relative to the other element. Therefore, the term "above" includes both "above" and "below" orientations depending on the spatial orientation of the device. The device may also be positioned in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relational terms used herein will be interpreted accordingly.

[0039] The terms used herein are only used to describe various examples and are not used to limit the present disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms "include", "comprise" and "have" list the stated features, quantities, operations, components, elements and / or their combinations that exist, but do not exclude the existence or addition of one or more other features, quantities, operations, components, elements and / or their combinations.

[0040] Variations in the shapes shown in the drawings may occur due to manufacturing techniques and / or tolerances. Therefore, the examples described herein are not limited to the specific shapes shown in the drawings but include variations in shapes that occur during manufacturing.

[0041] The features of the examples described herein may be combined in various ways that will be apparent after understanding the disclosure of the present application. In addition, although the examples described herein have various configurations, other configurations are possible as will be apparent after understanding the disclosure of the present application.

[0042] According to a first aspect of the present invention, a battery cell is provided, which specifically includes a housing 10 and a cover plate 20 .

[0043] Hereinafter, a specific structure of the battery cell according to this embodiment will be described.

[0044] In this embodiment, if Figures 1 to 5 As shown, a receiving cavity 11 is formed inside the shell 10 for containing components such as the cell pole group. When the cell is a square cell or a blade cell, the shell 10 is formed into a rectangular thin-walled hollow structure. When the cell is a cylindrical cell, the shell 10 is a cylindrical thin-walled hollow structure. The cover plate 20 is welded to the shell 10 to close the receiving cavity 11. 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. The weld includes the depth of penetration and the width of penetration, which are well known in the art, and its specific definition is not repeated 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 cell.

[0045] The welding portion 30 is formed into a closed annular structure, so that the cover plate 20 and the housing 10 can be assembled reliably and the sealing of the battery cell can be ensured.

[0046] In this embodiment, the welded cover plate 20 and the housing 10 meet the following conditions: ; Wherein, C is the perimeter 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; B is the penetration depth of the weld 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 penetration depth B of the weld 30 and satisfying the condition of C / S×B×K≥1.25, the welding strength of the shell 10 and the cover plate 20 can be guaranteed, and cracking of the weld 30 can be avoided, thereby ensuring the airtightness of the battery cell, and then ensuring the safety of the battery cell, thereby improving the safety of the battery pack.

[0047] It should be noted that the perimeter of the cover plate 20 is Figure 3 The dashed line shows the length of the portion, and the area of ​​the cover plate 20 is Figure 3 The area enclosed by the middle dotted line.

[0048] Further, in a preferred embodiment, as Figure 6 As shown, the penetration depth B of the welding portion 30 is 500 μm-1450 μm, thereby further improving the strength of the welding portion 30 and avoiding cracking of the welding portion 30, thereby ensuring that the airtightness of the battery cell meets the use requirements.

[0049] Further, in a preferred embodiment, as Figure 6 As shown, the weld width A of the welding portion 30 is 400 μm-2000 μm, thereby further improving the strength of the welding portion 30 , avoiding cracking of the welding portion 30 , and ensuring that the airtightness of the battery cell meets the use requirements.

[0050] In a preferred embodiment, Figure 2 , Figures 5 to 7 As shown, 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 described below 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 this embodiment, Figure 2 As shown, the inner wall of the shell 10 is formed with a protruding boss 101 to limit and support the cover body 21, ensuring that after the cover 20 and the shell 10 are assembled, the side of the cover body 21 facing the outside of the battery cell is flush with the end of the shell 10.

[0051] In this embodiment, if Figure 2 As shown, the cover plate 20 includes a cover plate body 21 formed into a plate-like structure. The cover plate body 21 can be formed into a rectangular plate-like structure. As mentioned above, C is the perimeter of the outer edge of the cover plate body 21, and S is the area surrounded by the outer edge of the cover plate body 21. In addition, a liquid injection hole 211 is opened on the cover plate body 21. The liquid injection hole 211 is a through hole, so that after the cover plate 20 and the shell 10 are welded, the electrolyte can be injected into the interior of the battery cell through the liquid injection hole 211.

[0052] Furthermore, in this embodiment, if Figure 2 As shown, the cover plate 20 also includes a pole 22, a first insulating member 231, a second insulating member 232 and a pressure relief member 24; the pole 22 is installed on the cover plate body 21, one end of the pole 22 is connected to the pole ear on the pole group located 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, which is used to connect charging or power-consuming equipment, so as to achieve current conduction. There is at least one pole 22 in the cover plate 20. When one pole 22 is provided, the pole 22 can be a positive pole or a negative pole; when multiple poles 22 are provided, optionally, at least part of the poles 22 among the multiple poles 22 are positive poles, and the rest are negative poles.

[0053] Both the first insulating member 231 and the second insulating member 232 are made of insulating materials to provide insulation protection to prevent the battery cell from short circuiting. Specifically, the first insulating member 231 is arranged on the side of the cover body 21 facing the inside of the battery cell, that is, 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 body 21, and the second insulating member 232 is arranged one-to-one with the pole 22.

[0054] The pressure relief member 24 can be an explosion-proof notch engraved on the cover body 21 or an explosion-proof valve installed at a through hole on the cover body 21. When the battery cell fails and produces gas inside, the pressure relief member 24 can be opened under a preset pressure to connect the inside and outside of the battery cell and exhaust gas in time to ensure the safe use of the battery cell.

[0055] The cover plates 20 and the shell 10 of different sizes and materials are welded and assembled, and the welded portion 30 formed by welding is tested to verify whether the problem of cracking of the welded portion 30 and the like that may result in failure to ensure the safety of the battery cell can be avoided under the condition of C / S×B×K≥1.25. The test results are shown in Table 1.

[0056] Table 1

[0057]

[0058] Note: The test result in the table is OK, which means the test result is qualified, and the test result is NG, which means the test result is unqualified.

[0059] Referring to Examples 1-1 to 1-14 in Table 1, it can be seen that the examples where C / S×B×K -1.25 is less than 0 all have cracks in the weld 30 . This proves whether cracks in the weld 30 can be avoided under the condition of C / S×B×K≥1.25 to a certain extent.

[0060] In this embodiment, if Figure 6 and Figure 7As shown, under the influence of the welding process, the welding portion 30 protrudes toward the outside of the battery cell, so that a portion of the welding portion 30 extends out of the outer surface of the cover plate 20 and / or the shell 10 .

[0061] It should be noted that the outer surface of the cover plate 20 and / or the housing 10 refers to the surface of the cover plate 20 and / or the housing 10 facing the outside of the battery cell.

[0062] Furthermore, in the thickness direction of the cover plate 20 , the height dimension of the welding portion 30 protruding from the outer surface of the cover plate 20 is D, D≤300μm, so as to avoid the situation where the blue film is warped due to the protruding welding portion 30 after the battery cell is coated with the blue film.

[0063] Next, the cells with different heights D of the welding portions 30 protruding from the outer surface of the cover plate 20 are coated with blue films, and the blue films are tested to see if they are warped. The test results are shown in Table 2.

[0064] Table 2

[0065]

[0066] Referring to Examples 2-1 to 2-6 in Table 2 above, it can be seen that when the height dimension D of the welding portion 30 protruding from the outer surface of the cover plate 20 is ≤300μm, the blue film does not warp; while in 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 exceeds 300μm, which easily lifts up the blue film, resulting in slight warping of the blue film.

[0067] Furthermore, in the present embodiment, in the wall thickness direction of the shell 10, the height dimension of the welding portion 30 protruding from the outer surface of the shell 10 is E, E≤150μm, thereby preventing the blue film from becoming thinner due to the protruding welding portion 30 after the battery cell is coated with the blue film, thereby affecting the insulation performance.

[0068] Next, the battery cells with different height dimensions E of the welding portion 30 protruding from the outer surface of the shell 10 are coated with blue film, and the coating is tested to see whether the insulation performance is affected. The test results are shown in Table 3.

[0069] Table 3

[0070]

[0071] Referring to Examples 3-1 to 3-6 in Table 3 above, it can be seen that when the height dimension E of the welding portion 30 protruding from the outer surface of the shell 10 is ≤150μm, the blue film does not turn white, that is, the insulation performance is not affected, and the safety requirements for the use of the battery cell are met; while in Examples 3-7 and 3-8, the height dimension E of the welding portion 30 protruding from the outer surface of the shell 10 exceeds 150μm, and the excessive protrusion causes the blue film to turn white when covering this area, indicating that the insulation performance is reduced and the safety of the battery cell cannot be guaranteed.

[0072] A battery cell provided by the present invention comprises a shell and a cover plate, which are welded to form a welding portion. By limiting the circumference C of the cover plate, the area S of the cover plate, the shear strength K of the cover plate and the penetration B of the welding portion under the condition of C / S×B×K≥1.25, the welding strength of the shell and the cover plate can be ensured, and cracking of the welding portion can be avoided, thereby ensuring the airtightness of the battery cell and further ensuring the safety of the battery cell; further, by further limiting the penetration B of the welding portion to within the range of 500μm~1450μm and the penetration width A of the welding portion to within the range of 400μm~2000μm, the strength of the welding portion can be further improved, cracking of the welding portion can be avoided, thereby ensuring that the airtightness of the battery cell meets the use requirements. In addition, by limiting the height dimension D of the welding part protruding from the outer surface of the cover plate to ≤300μm, and the height dimension E of the welding part protruding from the outer surface of the shell to ≤150μm, the battery cell can, after being coated with the blue film, to a certain extent avoid the warping and thinning of the area covered by the blue film on the welding part, thereby ensuring the insulation performance and further ensuring the safety of the battery cell.

[0073] A battery pack provided according to the present invention includes the battery cell as described above, wherein at least one battery cell is provided. When multiple battery cells are provided, at least some of the battery cells are connected in series and / or in parallel. The air tightness and insulation of each battery cell can be guaranteed, thereby effectively improving the safety of the battery pack.

[0074] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The protection scope of the present application is not limited thereto. Although the present application is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed in the present application, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A battery cell, characterized in that: The battery cell comprises: A housing having an accommodating cavity formed therein; A cover plate is welded to the shell to close the accommodating cavity, a welding portion is formed between the cover plate and the shell after welding, and a weld width A of the welding portion is 400 μm to 2000 μm; ； Wherein, C is the perimeter of the cover plate, in mm; S is the area of ​​the cover plate, in mm 2 ; K is the shear strength of the cover plate, in MPa; B is the penetration depth of the weld, in the formula, the unit of B is mm, B=500μm~1450μm.

2. The battery cell according to claim 1, characterized in that: The welding portion protrudes toward the outside of the battery cell, so that a portion of the welding portion extends out of the outer surface of the cover plate and / or the shell.

3. The battery cell according to claim 2, characterized in that: In the thickness direction of the cover plate, the height dimension of the welding portion protruding from the outer surface of the cover plate is D, and D≤300 μm.

4. The battery cell according to claim 2, characterized in that: In the wall thickness direction of the shell, the height dimension of the welding portion protruding from the outer surface of the shell is E, and E≤150 μm.

5. The battery cell according to claim 1, characterized in that: An outer wall of the cover plate in a circumferential direction abuts against an inner wall of the housing.

6. The battery cell according to claim 1, characterized in that: The cover plate includes a cover plate body formed into a plate-like structure, C is the perimeter of the outer edge of the cover plate body, and S is the area surrounded by the outer edge of the cover plate body.

7. The battery cell according to claim 6, characterized in that: The cover plate also includes: A pole, mounted on the cover body, with part of the pole extending out of a side of the cover body facing the outside of the battery cell; The first insulating member is arranged on a side of the cover body facing the inside of the battery cell.

8. A battery pack, characterized in that: A battery cell comprising the battery cell described in any one of claims 1 to 7.

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