Battery Cells and Battery Packs

Abstract

The present invention relates to the field of battery technology, and more particularly to a battery cell and a battery pack. The battery cell comprises: a shell; a cover plate welded to the shell to form a welding portion between the shell and the cover plate, the projection area of ​​the welding portion on the cross section of the shell perpendicular to its depth direction is S1, a boss portion extending into the shell is formed on the cover plate, the area enclosed by the outer edge of the boss portion is S2, and the tensile strength of the cover plate is U, ≥1. The present invention limits the relationship between S1, S2 and U to satisfy ≥1, thereby ensuring the welding strength of the shell and the cover plate, avoiding cracking of the welding portion, thereby ensuring the airtightness of the battery cell, and then ensuring the safety of the battery cell, and improving the safety of the battery pack.

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] case;

[0007] The cover plate is welded to the shell to form a welded portion between the shell and the cover plate, and the projection area of ​​the welded portion on the cross section of the shell perpendicular to its depth direction is S1, in mm 2 The cover plate is formed with a boss portion extending into the shell, and the area enclosed by the outer edge of the boss portion is S2, in units of mm 2 ; The tensile strength of the cover plate is U, in MPa; ≥1.

[0008] Preferably, the shell is formed into a rectangular structure; a rounded corner is arranged between two adjacent faces of the shell, and the radii of the rounded corner located outside the shell in the circumferential direction of the shell are R1, R2, R3 and R4 respectively, in units of mm.

[0009] Preferably, R1=R2=R3=R4=R, S1= 2×(A+B)×t-π×t 2 +(2×π-8)×R×t, where t is the effective penetration depth of the weld on the shell, in mm; A is the width dimension of the shell in the first direction, in mm; and B is the length dimension of the shell in the second direction, in mm.

[0010] Preferably, the effective penetration depth of the weld portion is t=350 μm~2000 μm.

[0011] Preferably, the effective weld width K of the welding 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 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≤200 μm.

[0014] 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≤200 μm.

[0015] Preferably, the cover plate is arranged at the end of the shell, so that the outer edge of the cover plate in the circumferential direction is arranged flush with the outer wall of the shell.

[0016] A second aspect of the present invention provides a battery pack, comprising the battery cell described in any of the above technical solutions.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] In the battery cell of the present invention, the shell and the cover are welded to form a welding portion, the projection area of ​​the welding portion on the cross section of the shell is S1, a boss portion extending into the interior of the shell is formed on the cover, and the area surrounded by the outer edge of the boss portion is S2. By defining the relationship between S1, S2 and the tensile strength U of the cover plate, ≥1, which can ensure the welding strength of the shell and the cover plate and avoid cracking of the welding part, thereby ensuring the airtightness of the battery cell, and then ensuring the safety of the battery cell and improving the safety of the battery pack.

[0019] 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

[0020] 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.

[0021] Figure 1 A schematic diagram of the assembly structure of the shell and the cover plate of the battery cell before welding provided in an embodiment of the present invention;

[0022] Figure 2 For along Figure 1 The cross-section taken at AA in the middle;

[0023] Figure 3 A schematic diagram of the S1 region on the shell of a battery cell provided in an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of the S2 region on the cover plate of a battery cell provided in an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of the assembly structure of the shell and the cover plate of the battery cell after welding provided by an embodiment of the present invention;

[0026] Figure 6 for Figure 5 Schematic diagram of the enlarged structure at G in the middle.

[0027] Icon: 10 - shell; 20 - cover plate; 21 - boss portion; 30 - welding portion; D1 - first direction; D2 - second direction. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more items.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 .

[0038] Hereinafter, a specific structure of the battery cell according to this embodiment will be described.

[0039] In this embodiment, if Figure 1 and Figure 5 As shown, the interior of the housing 10 is hollow for containing the battery cell electrode group; the cover plate 20 is welded to the housing 10 to form a welding portion 30 between the housing 10 and the cover plate 20, and the welding portion 30 is formed into a closed annular structure to ensure the sealing inside the housing 10. The welding portion 30 is a weld formed between the cover plate 20 and the housing 10 under the welding process, and the weld has a penetration depth and a penetration width. The welding strength of the welding portion 30 affects the assembly reliability of the cover plate 20 and the housing 10, thereby affecting the airtightness and safety of the battery cell.

[0040] Furthermore, in this embodiment, the cover plate 20 includes a top cover sheet, a pole and a pressure relief member. The top cover sheet is a plate-like structure. A through hole for installing the pole and the pressure relief member is provided on the top cover sheet. The pole is connected to the battery cell pole group to realize the introduction or export of current. The pole includes a positive pole and a negative pole. The pressure relief member can be an explosion-proof valve. The pressure relief member and the top cover sheet can be connected by welding. When the battery cell fails and a large amount of gas is generated inside, the pressure relief member can be opened at a preset pressure to achieve the purpose of timely exhaust, thereby ensuring the safety of the battery cell.

[0041] In this embodiment, if Figures 1 to 3 As shown, the projection area of ​​the welding portion 30 on the cross section of the housing 10 perpendicular to its depth direction is S1, in mm 2It should be noted that the depth direction of the housing 10 is the direction in which the battery cell is assembled into the housing 10, that is, Figure 1 The vertical direction under the viewing angle, S1 is Figure 3 The area of ​​the shaded portion on the cross section of the housing 10. The cover plate 20 is formed with a boss portion 21 extending into the interior of the housing 10. The area enclosed by the outer edge of the boss portion 21 is S2, in mm. 2 , Figure 4 The area inside the dotted line is area S2, and the tensile strength of the cover plate 20 is U, in MPa. ≥1, thus ensuring the welding strength between the housing 10 and the cover plate 20 and avoiding cracking of the welding portion 30, thereby ensuring the airtightness of the battery cell and further ensuring the safety of the battery cell.

[0042] In a preferred embodiment, Figure 1 As shown, the circumferential side wall of the boss portion 21 abuts against the inner wall of the housing 10 to ensure that the cover plate 20 and the housing 10 are tightly and reliably assembled before welding. When the circumferential side wall of the boss portion 21 abuts against the inner wall of the housing 10, S2 is equal to the area enclosed by the inner wall of the housing 10, that is, Figure 2 The area enclosed by the inner ring in the annular structure shown.

[0043] Next, the cover plates 20 and the housing 10 of different sizes and materials are welded and assembled, and the welded portion 30 formed by welding is tested to verify the ≥1, whether it is possible to avoid the problem of the battery cell being unable to ensure safe use due to cracking of the welding part 30, etc., the test results are shown in Table 1.

[0044] Table 1

[0045]

[0046] 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.

[0047] As shown in Table 1, the welding strength of the welding portion 30 is insufficient due to the relatively small area of ​​S1 in the embodiment 1-1. Less than 1, resulting in cracking of the welding part 30 during the test, the safety of the battery cell cannot be guaranteed; By comparing Example 1-3 with Example 1-4, it can be seen that in Example 1-3, due to the low tensile strength of the cover plate 20, the welding part 30 cracks, and the safety of the battery cell cannot be guaranteed; In Example 1-2, Example 1-4 to Example 1-15, all meet are greater than 1 or equal to 1, the weld 30 does not crack, and the test result is qualified, so it can be proved that Whether the air tightness requirements of the battery cell can be met during use under the limited condition of ≥1, thereby ensuring the safety of the battery cell.

[0048] Furthermore, in this embodiment, if Figure 1 and Figure 2 As shown, the battery cell is a square battery cell or a blade battery cell, and the shell 10 is formed into a rectangular structure; a rounded corner is arranged between two adjacent faces of the shell 10, and the radii of the rounded corners located on the outside of the shell 10 in the circumferential direction of the shell 10 are R1, R2, R3 and R4, respectively, and the unit is mm.

[0049] In a preferred embodiment, Figure 2 , Figure 3 and Figure 6 As shown, R1=R2=R3=R4=R, S1= 2×(A+B)×t-π×t 2 +(2×π-8)×R×t, where t is the effective penetration depth of the welding portion 30 on the shell 10, in mm; the effective penetration depth is the depth of the welding portion 30 embedded in the wall thickness of the shell 10 measured with the outer surface of the shell 10 as the initial position, that is, it does not include the portion of the welding portion 30 protruding from the outer surface of the shell 10; A is the width dimension of the shell 10 in the first direction D1, in mm, and B is the length dimension of the shell 10 in the second direction D2, in mm. The first direction D1 is perpendicular to the second direction D2, the first direction D1 is perpendicular to the thickness direction of the cover plate, and the second direction D2 is perpendicular to the thickness direction of the cover plate. The plane formed by the first direction D1 and the second direction D2 is parallel or coplanar with the cross section of the shell 10 as described above.

[0050] The first direction D1 , the second direction D2 , and the depth direction of the housing are perpendicular to each other.

[0051] Furthermore, if Figure 6 As shown, the effective penetration depth of the welding portion 30 is t=350 μm-2000 μm, thereby improving the connection 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.

[0052] Furthermore, if Figure 6 As shown, the effective weld width K of the welding part 30 is 400μm~2000μm, thereby further improving the connection strength of the welding part 30, avoiding cracking of the welding part 30, and ensuring that the airtightness of the battery cell meets the use requirements. It should be noted that the effective weld width is the width dimension of the welding part 30 within the wall thickness of the shell 10 and the thickness of the cover plate 20, that is, it does not include the part of the welding part 30 protruding from the surface of the shell 10 and / or the cover plate 20.

[0053] In this embodiment, if Figure 1 and Figure 5As shown, the cover plate 20 is arranged at the end of the shell 10 so that the outer edge of the cover plate 20 in the circumferential direction is flush with the outer wall of the shell 10 , so that the welding equipment can weld the cover plate 20 and the shell 10 in the thickness direction of the shell 10 .

[0054] In this embodiment, if Figure 5 and Figure 6 As shown, the welding portion 30 protrudes toward the outside of the battery cell, so that part of the welding portion 30 extends out of the outer surface of the cover plate 20 and / or the shell 10. When the blue film is coated on the outside of the battery cell, the protruding part of the welding portion 30 can easily cause the blue film to warp or become thinner, thereby affecting the insulation performance.

[0055] Furthermore, in this 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≤200μm, so as to avoid the problem that after the battery cell is coated with the blue film, the portion of the welding portion 30 protruding from the shell 10 causes the thickness of the blue film to become thinner, thereby affecting the insulation performance. It should be noted that when the circumferential edge of the cover plate 20 is flush with the outer surface of the shell 10, the height dimension of the welding portion 30 protruding from the outer surface of the shell 10 is also the height dimension of the welding portion 30 protruding from the cover plate 20.

[0056] 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 whether there is any performance that may affect the insulation performance after the blue film is assembled is tested. The test results are shown in Table 2.

[0057] Table 2

[0058]

[0059] Referring to Examples 2-1 to 2-6 in Table 2, it can be seen that the height dimension E of the welding portion 30 protruding from the outer surface of the shell 10 is less than 200μm or equal to 200μm, and the protruding position of the welding portion 30 does not show any whitish blue film, which means that the insulation performance is not affected and the safety requirements for the use of the battery cell are met; while in Examples 2-7 and 2-8, the height dimension E of the welding portion 30 protruding from the outer surface of the shell 10 exceeds 200μm, and the protruding position covered by the blue film turns white, indicating that the insulation performance is reduced and the safety of the battery cell cannot be guaranteed.

[0060] Furthermore, in this embodiment, if Figure 5 and Figure 6 As shown, 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≤200μm, so as to avoid the protrusion of the welding portion 30 on the cover plate 20 which may easily cause the blue film to warp up and affect the assembly quality of the battery cell and the blue film.

[0061] Next, the battery cells with different height dimensions D of the welding portion 30 protruding from the outer surface of the cover plate 20 are coated with blue film, and whether the blue film is warped after assembly is tested. The test results are shown in Table 3.

[0062] Table 3

[0063]

[0064] Referring to Examples 3-1 to 3-6 in Table 3, it can be seen that the height dimension D of the welding portion 30 protruding from the outer surface of the cover plate 20 is less than 200μm or equal to 200μm, and there is no warping after coating with the blue film, which meets the safety requirements for the use of the battery cell; while in Examples 3-7 and 3-8, the height dimension D of the welding portion 30 protruding from the outer surface of the cover plate 20 exceeds 200μm, and the blue film cannot be effectively fitted to the outer surface of the battery cell, resulting in slight warping of the blue film. Therefore, there is a risk of reduced insulation performance, and it is not recommended for use.

[0065] According to a battery cell provided by the present invention, a shell and a cover plate are welded to form a welding portion, the projection area of ​​the welding portion on the cross section of the shell is S1, a boss portion extending into the interior of the shell is formed on the cover plate, and the area surrounded by the outer edge of the boss portion is S2, and the relationship between S1, S2 and the tensile strength U of the cover plate is satisfied by defining ≥1, so that the welding strength of the shell and the cover plate can be guaranteed, and cracking of the welding part 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 effective melting depth t of the welding part to be within the range of 350μm~2000μm, and the effective melting width K of the welding part to be within the range of 400μm~2000μm, the strength of the welding part 30 can be further improved, and cracking of the welding part 30 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 shell to ≤200μm, and the height dimension E of the welding part protruding from the outer surface of the cover plate to ≤200μm, the battery cell can avoid the blue film covering the welding part to a certain extent. The area warping and thinning, thereby ensuring the insulation performance, further ensures the safety of the battery cell.

[0066] 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 a plurality of battery cells are provided, at least some of the battery cells are connected in series and / or in parallel. The battery cells inside the battery pack have reliable air tightness and insulation, thereby improving the overall safety performance of the battery pack.

[0067] 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: case; The cover plate is welded to the shell to form a welded portion between the shell and the cover plate, and the projection area of ​​the welded portion on the cross section of the shell perpendicular to its depth direction is S1, in mm 2 The cover plate is formed with a boss portion extending into the shell, the circumferential side wall of the boss portion abuts against the inner wall of the shell, and the area enclosed by the outer edge of the boss portion is S2, which is equal to the area enclosed by the inner wall of the shell, in units of mm 2 ; The tensile strength of the cover plate is U, in MPa; ≥1MPa; The shell is formed into a rectangular structure; a fillet is provided between two adjacent faces of the shell, and the radii of the fillet located outside the shell in the circumferential direction of the shell are R1, R2, R3 and R4 respectively, in units of mm; R1=R2=R3=R4=R, S1= 2×(A+B)×t-π×t 2 +(2×π-8)×R×t, where t is the effective penetration depth of the weld on the shell, in mm; A is the width of the shell in the first direction, in mm; B is the length of the shell in the second direction, in mm; The effective penetration depth of the welding part is t=350μm~2000μm; The effective weld width K of the welding portion is 400 μm to 2000 μm.

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 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≤200 μm.

4. 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≤200 μm.

5. The battery cell according to claim 1, characterized in that: The cover plate is arranged at the end of the shell, so that the outer edge of the cover plate in the circumferential direction is arranged flush with the outer wall of the shell.

6. A battery pack, characterized in that: The invention comprises a battery cell as described in any one of claims 1 to 5.

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