Battery cell and battery pack

Abstract

The invention relates to the technical field of batteries, in particular to a single battery and a battery pack. The battery cell provided by the embodiment of the invention comprises a shell, a first electrode terminal, a first electrode assembly and a first tab part, the shell is used for accommodating the first electrode assembly, and the shell is provided with a first wall; the first electrode terminal is arranged on the first wall; the first tab part comprises at least two first tab pieces, the first tab pieces extend out from at least one end of the first electrode assembly, and the first tab part is electrically connected with the first electrode terminal; a first welding mark and a second welding mark are arranged on the first tab part, the orthographic projection of the second welding mark falls into the orthographic projection of the first welding mark along the projection on the large surface of the first tab part, and the second welding mark is used for welding the first electrode terminal and the first tab part; wherein the roughness of the second welding mark is greater than that of the first welding mark. The technical effect of improving the welding strength between the tab and the electrode terminal is achieved.

Description

Technical Field

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

[0002] In the related art, the battery includes an electrode assembly and a cover assembly, and the cover assembly is connected to the pole lug of the electrode assembly. When the pole lug and the cover assembly are torque welded, due to the gaps between the pole lugs, after the ultrasonic welding equipment completes the surface pressure welding of the pole lug, the edge of the weld mark will rise to form a bulge, which can easily cause the pole piece to tear and prone to cold welding, resulting in insufficient welding strength between the pole posts of the pole lug after welding, thereby affecting the reliability of the connection between the pole post and the pole lug. Summary of the invention

[0003] The present application provides a battery cell and a battery pack, which achieve the technical effect of improving the welding strength between the tab and the electrode terminal.

[0004] In order to achieve the above objectives, the main technical solutions adopted in this application include:

[0005] An embodiment of the present application provides a battery cell, comprising a shell, a first electrode terminal, a first electrode assembly and a first pole ear portion, wherein the shell is used to accommodate the first electrode assembly, and the shell has a first wall; the first electrode terminal is arranged on the first wall; the first pole ear portion comprises at least two first pole ear sheets, the first pole ear sheets extend from at least one end of the first electrode assembly, and the first pole ear portion is electrically connected to the first electrode terminal; a first weld mark and a second weld mark are arranged on the first pole ear portion, and along the projection on the large surface of the first pole ear portion, the orthographic projection of the second weld mark falls within the orthographic projection of the first weld mark, and the second weld mark is used to weld the first electrode terminal and the first pole ear portion; wherein the roughness of the second weld mark is greater than the roughness of the first weld mark.

[0006] In the battery cell proposed in the embodiment of the present application, the first pole ear sheet extends out from at least one end of the first electrode assembly, and at least two first pole ear sheets are stacked and pre-welded and pressed to form a first weld mark, so as to reduce the gap between the first pole ear sheets, and also reduce the warping of the welding edge of the first pole ear sheet or the formation of a convex bulge. Then, the first pole ear portion is welded to the first electrode terminal at the first weld mark to form a second weld mark, wherein, along the projection on the large surface of the first pole ear portion, the orthographic projection of the second weld mark falls within the orthographic projection of the first weld mark, which means that the second weld mark is located in the first weld mark area, thereby improving the welding strength between the first pole ear portion and the first electrode terminal.

[0007] That is, when connecting the first electrode assembly and the first electrode terminal, first connect one end of the first pole ear portion to the first electrode assembly, overlap the other end of the first pole ear portion, and perform pre-welding to form a first weld mark, and then weld the first pole ear portion and the first electrode terminal in the region of the first weld mark to form a second weld mark. That is, the first pole ear portion is pre-welded so that the metal sheets of the first pole ear portion are combined together, and the structural strength of the first pole ear portion is improved by pre-welding, so that when the first pole ear portion and the first electrode terminal are welded again, even if the welding energy is relatively large, the structural strength of the first pole ear portion is enhanced due to the presence of the first weld mark, so when the first pole ear portion and the first electrode terminal are welded, the damage to the first pole ear portion can be reduced.

[0008] In order to fully weld the first pole ear portion and the first electrode terminal and improve the welding strength, the roughness of the second weld mark needs to be greater than the roughness of the first weld mark. If the roughness of the first weld mark is too large, the second weld mark cannot fully contact each first pole ear piece when the first pole ear portion is welded to the first electrode terminal, and a cold weld problem is likely to occur, thereby reducing the welding strength between the first pole ear portion and the first electrode terminal.

[0009] The present application also provides a battery cell, comprising a shell, a first electrode terminal, a first electrode assembly, a first pole ear portion, a second electrode assembly and a second pole ear portion, the shell being used to accommodate the first electrode assembly and the second electrode assembly, the shell having a first wall; the first electrode terminal being arranged on the first wall; the first pole ear portion comprising at least two first pole ear sheets, the first pole ear sheets extending from at least one end of the first electrode assembly, the first pole ear portion being electrically connected to the first electrode terminal; the second pole ear portion comprising at least two second pole ear sheets, the second pole ear sheets extending from at least one end of the second electrode assembly, the second pole ear portion being electrically connected to the first electrode terminal; the first pole ear portion and the second pole ear portion being overlapped and welded to form a first weld mark and a second weld mark, the orthographic projection of the second weld mark falling within the orthographic projection of the first weld mark along the projection on the large surface of the first pole ear portion or the second pole ear portion, the second weld mark being used to weld at least one of the first pole ear portion and the second pole ear portion to the first electrode terminal; wherein the roughness of the second weld mark is greater than the roughness of the first weld mark.

[0010] In the battery cell provided in the embodiment of the present application, when the first electrode assembly and the second electrode assembly are connected to the first electrode terminal, firstly, one end of the first pole ear portion is connected to the first electrode assembly, and one end of the second pole ear portion is connected to the second electrode assembly, and then the other end of the first pole ear portion and the other end of the second pole ear portion are overlapped and pre-welded to form a first weld mark, and then the first pole ear portion and the second pole ear portion are overlapped and welded to form a first weld mark, and then the first pole ear portion and the second pole ear portion are welded to the first electrode terminal in the first weld mark area to form a second weld mark. Since the thickness of the first pole ear portion and the second pole ear portion after overlapping is relatively thick, in order to prevent the first pole ear portion and the second pole ear portion from generating a cold weld with the first electrode terminal, it is necessary to increase the depth of the second weld mark, that is, to increase the roughness of the second weld mark, so that the first pole ear portion and the second pole ear portion are fully in contact with the first electrode terminal, thereby improving the connection strength between the first pole ear portion and the second pole ear portion and the first electrode terminal.

[0011] The present application also provides a battery pack, comprising the battery cell described in any of the above embodiments.

[0012] In the battery pack provided by the embodiment of the present application, the first pole ear portion is first pre-welded to form a first weld mark, and then the first pole ear portion is welded to the first electrode terminal in the region of the first weld mark to form a second weld mark, thereby reducing the probability of the first pole ear portion outside the region of the first weld mark being lifted or torn. The roughness of the first weld mark is less than that of the second weld mark, so that the first pole ear portion is in full contact with the first electrode terminal, thereby improving the connection strength between the first pole ear portion and the first electrode terminal, and thus improving the structural stability of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the specific implementation methods of the present application 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 application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 This is a schematic diagram of the structure of the battery cell of this application;

[0015] Figure 2 This is a schematic diagram of the partial structure of a battery cell in one embodiment of the present application;

[0016] Figure 3 It is a schematic diagram of the projection area of ​​the first weld mark and the second weld mark on the large surface along the first pole ear portion in the present application;

[0017] Figure 4 This is a schematic diagram of a partial structure of a battery cell in another embodiment of the present application;

[0018] Figure 5 This is a schematic diagram of a partial structure of a battery cell in another embodiment of the present application;

[0019] Figure 6 for Figure 5 The projection on the large surface along the first pole ear portion, the schematic diagram of the projection area of ​​the first weld mark, the second weld mark, the third weld mark and the fourth weld mark;

[0020] Figure 7 This is a schematic diagram of the structure of the first wall in this application;

[0021] Figure 8 It is a schematic diagram of the structure of the first pole ear in this application.

[0022] [Description of Reference Numerals]

[0023] 1: housing; 11: first wall; 12: electrode terminal;

[0024] 2: first electrode assembly;

[0025] 3: first pole ear portion; 31: first end; 32: second end; 33: first portion; 34: second portion; 35: bending portion;

[0026] 4: first weld mark; 41: first edge; 5: second weld mark; 51: second edge;

[0027] 6: second electrode assembly;

[0028] 7: second pole ear; 71: third end; 72: fourth end;

[0029] 8: third weld mark; 9: fourth weld mark. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0031] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0032] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0033] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0035] The term "multiple" as used in this application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple sheets" refers to more than two sheets (including two sheets).

[0036] In the related art, the battery includes an electrode assembly and a cover assembly, and the cover assembly is connected to the pole ear of the electrode assembly. Currently, the pole ear and the cover assembly are welded by torque welding. Since there are gaps between the pole ears, after the press welding is completed, the edge of the weld mark will rise up to form a bulge, which can easily cause the pole piece to tear and prone to cold welding, resulting in insufficient welding strength between the pole columns of the pole ears after welding.

[0037] In view of this, reference Figure 1 , Figure 2 and Figure 7 The present application provides a battery cell, which includes a shell 1, a first electrode terminal 12, a first electrode assembly 2 and a first pole ear portion 3, the shell is used to accommodate the first electrode assembly 2, the shell 1 has a first wall 11; the first electrode terminal 12 is arranged on the first wall 11; the first pole ear portion 3 includes at least two first pole ear sheets, the first pole ear sheets extend from at least one end of the first electrode assembly 2, and the first pole ear portion 3 is electrically connected to the first electrode terminal 12; a first weld mark 4 and a second weld mark 5 are arranged on the first pole ear portion 3, along the projection on the large surface of the first pole ear portion 3, the orthographic projection of the second weld mark 5 falls within the orthographic projection of the first weld mark 4, and the second weld mark 5 is used to weld the first electrode terminal 12 and the first pole ear portion 3; wherein the roughness of the second weld mark 5 is greater than the roughness of the first weld mark 4.

[0038] The housing is made of metal and is used to accommodate the first electrode assembly 2. The housing 1 has a first wall 11, and the first electrode terminal 12 is arranged on the first wall 11. Each first pole ear portion 3 has a first end 31 and a second end 32. The first end 31 of the first pole ear portion 3 is connected to the first electrode assembly 2. The second end 32 of each first pole ear portion 3 is overlapped and welded to form a first weld mark 4. The first weld mark 4 is used to press the first pole ear portion 3. The first weld mark 4 is connected to the first electrode terminal 12 to form a second weld mark 5. The second weld mark 5 is used to weld the first electrode terminal 12 and the first pole ear portion 3; wherein, along the overlapping direction of the plurality of second ends 32, the projection of the second weld mark 5 falls within the projection of the first weld mark 4, and the roughness of the second weld mark 5 is greater than the roughness of the first weld mark 4.

[0039] In the battery cell proposed in the embodiment of the present application, the first end 31 of the first pole ear portion 3 is connected to the first electrode assembly 2, and the second end 32 of the first pole ear portion 3 is stacked and pre-welded and pressed to form a first weld mark 4, so as to reduce the gap between the multiple first pole ear sheets in the first pole ear portion 3, and also reduce the warping or convexity of the welding edges of the multiple first pole ear sheets. Then, the first pole ear portion 3 is welded to the first electrode terminal 12 at the first weld mark 4 to form a second weld mark 5, wherein, along the stacking direction of the multiple second ends 32, the projection of the second weld mark 5 falls within the projection of the first weld mark 4, which means that the second weld mark 5 is located in the area of ​​the first weld mark 4, thereby improving the welding strength between the first pole ear portion 3 and the first electrode terminal 12.

[0040] That is, when the first electrode assembly 2 is connected to the first electrode terminal 12, the first end 31 of the first pole ear portion 3 is first connected to the first electrode assembly 2, the second end 32 of the first pole ear portion 3 is overlapped, and pre-welded to form a first weld mark 4, and then the first pole ear portion 3 and the first electrode terminal 12 are welded in the region of the first weld mark 4 to form a second weld mark 5. That is, the second end 32 of the first pole ear portion 3 is overlapped and pre-welded, so that the metal sheets of the first pole ear portion 3 are combined together, and the structural strength of the first pole ear portion 3 is improved by pre-welding, so that when the first pole ear portion 3 and the first electrode terminal 12 are welded again, even if the welding energy is relatively large, the structural strength of the first pole ear portion 3 is enhanced due to the presence of the first weld mark 4, so when the first pole ear portion 3 and the first electrode terminal 12 are welded, the damage to the first pole ear portion 3 can be reduced.

[0041] In order to fully weld the first pole ear portion 3 and the first electrode terminal 12 and improve the welding strength, the roughness of the second weld mark 5 needs to be greater than the roughness of the first weld mark 4. If the roughness of the first weld mark 4 is too large, the second weld mark 5 cannot fully contact each first pole ear sheet when welding the first pole ear portion 3 and the first electrode terminal 12, and a cold weld problem is likely to occur, thereby reducing the welding strength between the first pole ear portion 3 and the first electrode terminal 12.

[0042] In the present application, the large surface of the first pole ear portion 3 is the surface of the first pole ear portion 3 formed by stacking a plurality of first pole ear sheets after being flattened along the lead-out direction. Figure 8 The first pole ear portion 3 includes a first portion 33 connected to the first electrode assembly 2 , a second portion 34 connected to the first electrode terminal 12 , and a bending portion 35 connected between the first portion 33 and the second portion 34 , wherein the second portion 34 is a large surface of the first pole ear portion 3 .

[0043] In the present application, the first electrode terminal 12 refers to the pole, and the first electrode assembly 2 refers to the battery cell. One end of the first electrode terminal 12 is electrically connected to the busbar, and one end is electrically connected to the first pole ear portion 3. The first electrode assembly 2 refers to a unit formed by winding or laminating a stacked portion, and the stacked portion includes a first electrode, a separator, and a second electrode. When the first electrode is a positive electrode, the second electrode is a negative electrode.

[0044] Optionally, the roughness of the second weld mark 5 is a1, and the roughness of the first weld mark 4 is a2, satisfying: 5≤a1 / a2≤300, for example, a1 / a2 can be equal to 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290 or 300, etc. The roughness of the second weld mark 5 is greater than that of the first weld mark 4, reducing the problem of cold welding between the first pole ear portion 3 and the first electrode terminal 12, so as to enhance the welding between the first pole ear portion 3 and the first electrode terminal 12 to be more firm. However, if the roughness of the second weld mark 5 is too large, it is easy to cause the second weld mark 5 to weld through the first pole ear portion 3.

[0045] Optionally, the roughness of the second weld mark 5 satisfies: 300 μm≤a1≤3000 μm; and the roughness of the first weld mark 4 satisfies: 10 μm≤a2≤500 μm.

[0046] The roughness a1 of the second weld mark 5 can be 300 μm, 400 μm 、 500μm, 600μm, 700μm, 800μm, 1000μm, 1100μm, 1200μm, 1300μm, 1400μm, 1500μm, 1600μm, 1700μm, 1800μm , 1900μm, 2000μm, 2100μm, 2200μm, 2300μm, 2400μm, 2500μm, 2600μm, 2700μm, 2800μm, 2900μm or 3000μm, etc.

[0047] The roughness a2 of the first soldering mark 4 may be 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm m, 330μm, 340μm, 350μm, 360μm, 380μm, 400μm, 410μm, 420μm, 430μm, 440μm, 450μm, 470μm, 480μm, 490μm or 500μm, etc.

[0048] Optionally, the first weld mark 4 is formed by a toothless welding structure. The second end 32 of the first pole ear portion 3 is formed by toothless welding to form the first weld mark 4 to improve the flatness of the surface of the first pole ear portion 3. When the first pole ear portion 3 and the first electrode terminal 12 are welded, the first weld mark 4 formed by the toothless welding can reduce the stress of the second welding on the first pole ear portion 3, thereby reducing the damage to the first pole ear portion 3 during the second welding.

[0049] Among them, toothless welding is performed using a nearly toothless welding head. The depth of the teeth of the toothless welding head is relatively shallow, and a relatively shallow concave point will be formed in the welding area after the welding is completed.

[0050] Optionally, the second weld mark 5 includes a first welding area and a second welding area, the second welding area is arranged on the circumferential outside of the first welding area, a plurality of square weld marks are arranged in the first welding area, and a plurality of circular weld marks are arranged in the second welding area.

[0051] The second weld mark 5 formed by welding the first pole ear portion 3 and the electrode terminal includes two different forms of welding areas, a first welding area and a second welding area located outside the first welding area in the circumferential direction. The first welding area has a plurality of square weld marks, and the square weld marks of the first welding area are deeper to strengthen the connection strength between the first pole ear portion 3 and the first electrode terminal 12; the second welding area has a plurality of circular weld marks, and the circular weld marks are outside the second weld marks 5, which can relieve the stress between the second weld marks 5 and the first pole ear portion 3 outside the second weld marks 5, and reduce the risk of tearing the first pole ear portion 3.

[0052] Optionally, refer to Figure 3 , along the projection on the large surface of the first pole ear portion 3, the projection area of ​​the first weld mark 4 is S1, and the projection area of ​​the second weld mark 5 is S2, satisfying: 1≤S1 / S2≤10. That is, along the stacking direction of the second end 32 of the first pole ear portion 3, the projection area of ​​the first weld mark 4 is S1, and the projection area of ​​the second weld mark 5 is S2. Among them, S1 / S2 can be 1, 1.3, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, 3.2, 3.3, 3.5, 3.7, 4.0, 4.3, 4.5, 4.8, 5.0, 5.3, 5.6, 5.8, 6.0, 6.3, 6.5, 6.8, 7.2, 7.8, 8.0, 8.2, 8.6, 9.0, 9.3, 9.5, 9.8, 9.9 or 10, etc. After the first electrode assembly 2 and the first electrode terminal 12 are connected, in order to ensure sufficient current flow capacity and reduce the risk of tearing of the first pole ear portion 3, the connection area between the first pole ear portion 3 and the first electrode terminal 12 needs to satisfy: 1≤S1 / S2≤10.

[0053] If the area ratio between the second weld mark 5 and the first weld mark 4 is too small, it means that the area of ​​the second weld mark 5 is too small, and the connection area between the first pole ear portion 3 and the first electrode terminal 12 is small, which affects the current capacity; if the area ratio between the second weld mark 5 and the first weld mark 4 is too large, the area of ​​the second weld mark 5 is too large, and the effect of the first weld mark 4 in alleviating the stress of the first pole ear portion 3 at the edge of the first weld mark 4 will be affected, and there may be a problem of tearing of the first pole ear portion 3.

[0054] Optionally, the projection area of ​​the first weld mark 4 satisfies: 100mm2 ≤S1≤2000mm 2 , the projection area of ​​the second weld mark 5 satisfies: 20mm 2 ≤S2≤120mm 2 .

[0055] The projection area S1 of the first weld mark 4 can be 100 mm 2 , 200mm 2 、300mm 2 , 400mm 2 , 500mm 2 、600mm 2 、700mm 2 , 800mm 2 , 900mm 2 , 1000mm 2 、1100mm 2 、1200mm 2 、1300mm 2 、1400mm 2 、1500mm 2 、1600mm 2 、1700mm 2 、1800mm 2 、1900mm 2 or 2000mm 2 wait.

[0056] The projection area S2 of the second weld mark 5 can be 20 mm 2 , 25mm 2 , 30mm 2 , 35mm 2 , 40mm 2 , 45mm 2 , 50mm 2 , 55mm 2 、60mm 2 、65mm 2 , 70mm 2 , 75mm 2 , 80mm 2 、85mm 2 、90mm 2 、95mm 2 , 100mm 2 、105mm 2 、110mm 2 、115mm 2 or 120mm 2 wait.

[0057] Optionally, the first weld mark 4 has a first edge 41 , the second weld mark 5 has a second edge 51 , and the minimum distance between the first edge 41 and the second edge 51 is c, satisfying: 0.5 mm≤c≤10 mm. The minimum distance c between the first edge 41 and the second edge 51 can be 0.5mm, 0.8mm, 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.8mm, 2.0mm, 2.2mm, 2.5mm, 2.7mm, 2.8mm, 3.0mm, 3.2mm, 3.5mm, 3.8mm, 4.0mm, 4.1mm, 4.3mm, 4.5mm, 4.8mm, 5.0mm, 5.2mm, 5.6mm, 5.8mm, 6.0mm, 6.3mm, 6.7mm, 7.0mm, 7.3mm, 7.8mm, 8.1mm, 8.4mm, 8.6mm, 8.9mm, 9.1mm, 9.4mm, 9.6mm, 9.8mm or 10mm, etc.

[0058] In order to ensure sufficient connection strength between the first pole ear portion 3 and the first electrode terminal 12 and alleviate the tearing of the first pole ear portion 3, the minimum distance between the first edge 41 and the second edge 51 should satisfy: 0.5mm≤c≤10mm. If the second edge 51 of the second weld mark 5 is too close to the first edge 41 of the first weld mark 4, a certain compression effect will be exerted on the first pole ear portion 3 outside the first weld mark 4 during the second torque welding, causing the first pole ear portion 3 outside the first weld mark 4 to warp, and then cause the tearing problem. If the second edge 51 of the second weld mark 5 is too far from the first edge 41 of the first weld mark 4, it means that the welding area between the first pole ear portion 3 and the first electrode terminal 12 is too small, which affects the current capacity between the first electrode assembly 2 and the first electrode terminal 12.

[0059] Optionally, refer to Figure 5 and Figure 6 The battery cell further includes a second electrode assembly 6 and a second pole ear portion 7, both of which are arranged in the housing 1, the second pole ear portion 7 includes at least two second pole ear sheets, the second pole ear sheets extend from at least one end of the second electrode assembly 6, and the second pole ear portion 7 is electrically connected to the first electrode terminal 12; a third weld mark 8 and a fourth weld mark 9 are arranged on the second pole ear portion 7, and the projection area of ​​the first weld mark 4 along the large surface of the first pole ear portion 3 is S1, and the projection area of ​​the third weld mark 8 along the large surface of the second pole ear portion 7 is S3, and the sum of the projection area of ​​the second weld mark 5 and the projection area of ​​the fourth weld mark 9 is S4, satisfying: S1+S3>S4.

[0060] The second pole ear portion 7 has a third end 71 and a fourth end 72, a plurality of three ends 71 ​​are connected to the second electrode assembly 6, and the fourth end 72 is overlapped and welded to form a third weld mark 8, and the third weld mark 8 is connected to the first electrode terminal 12 to form a fourth weld mark 9. The projection direction along the large surface of the first pole ear portion 3 is the same as the projection direction along the large surface of the second pole ear portion 7.

[0061] The first pole ear portion 3 of the first electrode assembly 2 is pre-welded to form a first weld mark 4, the second pole ear portion 7 of the second electrode assembly 6 is pre-welded to form a third weld mark 8, and then the first electrode terminal 12 and the first pole ear portion 3 are welded in the region of the first weld mark 4 to form a second weld mark 5, and the first electrode terminal 12 and the second pole ear portion 7 are welded in the region of the third weld mark 8 to form a fourth weld mark 9. In other words, the first pole ear portion 3 of the first electrode assembly 2 and the second pole ear portion 7 of the second electrode assembly 6 are respectively welded to different regions of the first electrode terminal 12. Compared with stacking the first pole ear portion 3 and the second pole ear portion 7, welding the first pole ear portion 3 and the second pole ear portion 7 to different regions of the first electrode terminal 12 can reduce the connection thickness between the first pole ear portion 3 and the second pole ear portion 7, thereby reducing the virtual welding between the first pole ear portion 3 and the second pole ear portion 7 and the first electrode terminal 12.

[0062] In addition, the area of ​​the first weld mark 4 formed after the pre-welding of the first pole ear portion 3 should be larger than the area of ​​the second weld mark 5 formed by welding the first pole ear portion 3 and the first electrode terminal 12, that is, the second weld mark 5 is within the area of ​​the first weld mark 4; the area of ​​the third weld mark 8 formed after the pre-welding of the second pole ear portion 7 should be larger than the area of ​​the fourth weld mark 9 formed by welding the second pole ear portion 7 and the plurality of first electrode terminals 12, that is, the fourth weld mark 9 is within the area of ​​the third weld mark 8. That is, the sum of the projected area of ​​the first weld mark 4 and the projected area of ​​the third weld mark 8 is larger than the sum of the projected area of ​​the second weld mark 5 and the projected area of ​​the fourth weld mark 9, so as to meet the connection strength between the first pole ear portion 3 and the second pole ear portion 7 and the first electrode terminal 12, while alleviating the problem of bulges or tears in the first pole ear portion 2 outside the first weld mark 4 and the second pole ear portion 7 outside the third weld mark 8.

[0063] Specifically, the first pole ear portion 3 is pre-welded to form a first weld mark 4, the second pole ear portion 7 is pre-welded to form a third weld mark 8, and then the first pole ear portion 3 and the second pole ear portion 7 are spliced, that is, the first weld mark 4 and the third weld mark 8 do not overlap, and then the first pole ear portion 3 and the second pole ear portion 7 are welded to the first electrode terminal 12, and the second weld mark 5 formed by welding the first pole ear portion 3 to the first electrode terminal 12 and the fourth weld mark 9 formed by welding the second pole ear portion 7 to the second electrode terminal can be spaced apart or connected.

[0064] In an optional embodiment, the second end 32 of the first pole ear portion 3 is pre-welded to form a first weld mark 4, and the third end 72 of the second pole ear portion 7 is pre-welded to form a third weld mark 8. The first weld mark 4 and the third weld mark 8 are rectangular. Then, the first pole ear portion 3 and the second pole ear portion 7 are welded to the first electrode terminal 12 to form a second weld mark 5 and a fourth weld mark 9 respectively. The second weld mark 5 and the fourth weld mark 9 together form a circular weld mark, thereby realizing the welding of the first pole ear portion 3 and the second pole ear portion 7 to the first electrode terminal 12.

[0065] Optionally, the roughness of the second weld mark 5 is a1, the roughness of the first weld mark 4 is a2, the roughness of the fourth weld mark 9 is d1, and the roughness of the third weld mark 8 is d2, satisfying: 5≤a1 / a2≤280, 5≤d1 / d2≤280.

[0066] Among them, a1 / a2 can be 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 275 or 280, etc.

[0067] d1 / d2 can be 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 275 or 280, etc.

[0068] Since the first pole ear portion 3 and the second pole ear portion 7 are spliced ​​after pre-welding and are welded to the first electrode terminal 12 without overlapping, the thickness of the first pole ear portion 3 and the second pole ear portion 7 welded to the first electrode terminal 12 is relatively small, and the first pole ear portion 3 and the second pole ear portion 7 can be easily welded to the first electrode terminal 12 and achieve sufficient welding strength, so the roughness of the second weld mark 5 and the fourth weld mark 9 can be relatively reduced.

[0069] Optionally, the roughness of the second weld mark 5 satisfies: 300μm≤a1≤2800μm; the roughness of the first weld mark 4 satisfies: 10μm≤a2≤500μm; the roughness of the fourth weld mark 9 satisfies: 300μm≤d1≤2800μm; the roughness of the third weld mark 8 satisfies: 10μm≤d2≤500μm, etc.

[0070] The roughness a1 of the second weld print 5 may be 300 μm 、 400μm 、500μm, 600μm, 700μm, 800μm, 1000μm, 1100μm, 1200μm, 1300μm, 1400μm, 1500μm, 1600μm, 1700μm, 18 00μm, 1900μm, 2000μm, 2100μm, 2200μm, 2300μm, 2400μm, 2500μm, 2600μm, 2700μm, 2750μm or 2800μm, etc.

[0071] The roughness a2 of the first soldering mark 4 may be 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm m, 330μm, 340μm, 350μm, 360μm, 380μm, 400μm, 410μm, 420μm, 430μm, 440μm, 450μm, 470μm, 480μm, 490μm or 500μm, etc.

[0072] The roughness d1 of the third weld mark 8 can be 300 μm, 400 μm 、 500μm, 600μm, 700μm, 800μm, 1000μm, 1100μm, 1200μm, 1300μm, 1400μm, 1500μm, 1600μm, 1700μm, 18 00μm, 1900μm, 2000μm, 2100μm, 2200μm, 2300μm, 2400μm, 2500μm, 2600μm, 2700μm, 2750μm or 2800μm, etc.

[0073] The roughness d2 of the fourth welding mark 9 can be 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm m, 330μm, 340μm, 350μm, 360μm, 380μm, 400μm, 410μm, 420μm, 430μm, 440μm, 450μm, 470μm, 480μm, 490μm or 500μm, etc.

[0074] Optionally, 0.9≤S1 / S3≤1.1 is satisfied, wherein S1 / S3 may be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09 or 1.1, etc.

[0075] The projection area of ​​the first weld mark 4 formed after the pre-welding of the first pole ear portion 3 is S1, and the projection area of ​​the third weld mark 8 formed after the pre-welding of the second pole ear portion 7 is S3. In order to meet the overcurrent requirements between the first electrode assembly 2 and the second electrode assembly 6 and the first electrode terminal 12, the projection area of ​​the first weld mark 4 is S1 and the projection area of ​​the third weld mark 8 is S3, which should satisfy: 0.9≤S1 / S3≤1.1. Preferably, the projection area S1 of the first weld mark 4 and the projection area S3 of the third weld mark 8 are approximately equal.

[0076] Optionally, the first weld mark 4 is a rectangle. The first weld mark 4 is configured as a rectangle to increase the connection area between the first pole lugs 3, thereby reducing the gap between the plurality of first pole lug sheets, and further reducing the risk of the first pole lugs 3 being torn.

[0077] Optionally, the second weld mark 5 is circular. The first pole ear portion 3 is welded to the first electrode terminal 12 to form the second weld mark 5. Since the first pole ear portion 3 at the edge of the first weld mark 4 is pressed thin by the first weld mark 4 and the strength is reduced, when the second weld mark 5 is circular, the edge of the circular second weld mark 5 is rounded, and the stress on the first pole ear portion 3 at the edge of the first weld mark 4 is reduced, thereby reducing the risk of the first pole ear portion 3 being torn.

[0078] Optionally, along the projection on the large surface of the first pole ear portion 3, the area of ​​the second weld mark 5 is S2, and the end surface area of ​​the end of the electrode terminal connected to the first pole ear portion 3 is S5, satisfying: 0.25≤S2 / S5≤0.95. That is, along the stacking direction of the second end 32 of the first pole ear portion 3, the area of ​​the second weld mark 5 is S2, and the end surface area of ​​the end of the electrode terminal connected to the first pole ear portion 3 is S5. Among them, S2 / S5 can be 0.25, 0.28, 0.3, 0.32, 0.33, 0.35, 0.36, 0.38, 0.4, 0.42, 0.45, 0.47, 0.49, 0.51, 0.53, 0.56, 0.58, 0.6, 0.65, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.83, 0.86, 0.88, 0.9, 0.91, 0.93, 0.94 or 0.95, etc. The area of ​​the second weld mark 5 should allow sufficient current flow capacity between the first electrode assembly 2 and the first electrode terminal 12, so it is necessary to meet the following conditions: 0.25≤S2 / S5≤0.95.

[0079] Optionally, the area of ​​the second weld mark 5 satisfies: 20 mm 2 ≤S2≤120mm 2 The end surface area of ​​the electrode terminal connected to the first pole ear portion 3 satisfies: 50mm 2 ≤S5≤300mm 2 .

[0080] The projection area S2 of the second weld mark 5 can be 20 mm 2 , 25mm 2 , 30mm 2 , 35mm 2 , 40mm 2 , 45mm 2 , 50mm 2 , 55mm 2 、60mm 2 、65mm 2 , 70mm 2 , 75mm 2 , 80mm 2 、85mm 2 、90mm 2 、95mm 2 , 100mm 2 、105mm 2 、110mm 2 、115mm 2 or 120mm 2 wait.

[0081] The end surface area S5 of the electrode terminal connected to the first electrode ear portion 3 may be 50 mm 2 , 55mm 2 、60mm 2 、65mm 2 , 70mm 2 , 75mm 2 , 80mm 2 、85mm 2 、90mm 2 、95mm 2 , 100mm 2 、105mm 2 、110mm 2 、115mm 2 , 120mm 2 、140mm 2 、160mm 2 、180mm 2 , 200mm 2 , 210mm 2 , 220mm 2 , 230mm 2 , 240mm 2 , 250mm 2 、260mm 2 、270mm 2 、280mm 2 、290mm 2 or 300mm 2wait.

[0082] The present application also provides a battery cell, referring to Figure 4 The battery cell comprises a housing 1, a first electrode terminal 12, a first electrode assembly 2, a first pole ear portion 3, a second electrode assembly 6, and a second pole ear portion 7. The housing 1 is used to accommodate the first electrode assembly 2 and the second electrode assembly 6. The housing 1 has a first wall 11. The first electrode terminal 12 is disposed on the first wall 11. The first pole ear portion 3 comprises at least two first pole ear sheets, the first pole ear sheet extends from at least one end of the first electrode assembly 2, and the first pole ear portion 3 is electrically connected to the first electrode terminal 12. The second pole ear portion 7 comprises at least two second pole ear sheets. The second pole ear sheet extends from at least one end of the second electrode assembly 6, and the second pole ear portion 3 is electrically connected to the first electrode terminal 12; the first pole ear portion 3 and the second pole ear portion 7 are overlapped and welded to form a first weld mark 4 and a second weld mark 5, and along the projection on the large surface of the first pole ear portion 3 or the second pole ear portion 7, the orthographic projection of the second weld mark 5 falls within the orthographic projection of the first weld mark 4, and the second weld mark 5 is used to weld at least one of the first pole ear portion 3 and the second pole ear portion 7 to the first electrode terminal 12; wherein, the roughness of the second weld mark 5 is greater than the roughness of the first weld mark 4.

[0083] The first pole ear portion 3 extends from the end of the first electrode assembly 2 and is electrically connected to the first electrode terminal 12. The first electrode assembly 2 and the first pole ear portion 3 are both arranged in the housing 1. The first pole ear portion 3 has a first end 31 and a second end 32. The first end 31 of the first pole ear portion 3 is connected to the first electrode assembly 2. The second pole ear portion 7 extends from the end of the second electrode assembly 6 and is electrically connected to the first electrode terminal 12. The second electrode assembly 6 and the second pole ear 7 are both arranged in the housing 1. The second pole ear portion 7 has a third end 71 and a fourth end 72. The third end 71 of the second pole ear portion 7 is connected to the second electrode assembly 2. The components 6 are connected; the second end 32 of the first pole ear portion 3 and the fourth end 72 of the second pole ear portion 7 are overlapped and welded to form a first weld mark 4, the first weld mark 4 is used to press the first pole ear portion 3 and the second pole ear portion 7, the first weld mark 4 is connected to the first electrode terminal 12 to form a second weld mark 5, the second weld mark 5 is used to weld the first pole ear portion 3 and the first pole ear portion 3 to the first electrode terminal 12; along the overlapping direction of the second end 32 of the first pole ear portion 3 and the fourth end 72 of the second pole ear portion 7, the projection of the second weld mark 5 falls within the projection of the first weld mark 4, and the roughness of the second weld mark 5 is greater than the roughness of the first weld mark 4.

[0084] In the battery cell provided in the embodiment of the present application, when connecting the first electrode assembly 2 and the second electrode assembly 6 with the first electrode terminal 12, the first end 31 of the first pole ear portion 3 is first connected to the first electrode assembly 2, and the third end 71 of the second pole ear portion 7 is connected to the second electrode assembly 6, and then the second end 32 of the first pole ear portion 3 and the fourth end 72 of the second pole ear portion 7 are overlapped and pre-welded to form a first weld mark 4, and then the overlapped first pole ear portion 3 and the second pole ear portion 7 are welded to the first electrode terminal 12 in the area of ​​the first weld mark 4 to form a second weld mark 5. Since the thickness of the first pole ear portion 3 and the second pole ear portion 7 after overlapping is relatively thick, in order to prevent the first pole ear portion 3 and the second pole ear portion 7 from generating a cold weld with the first electrode terminal 12, it is necessary to increase the depth of the second weld mark 5, that is, increase the roughness of the second weld mark 5, so that the first pole ear portion 3 and the second pole ear portion 7 are fully in contact with the first electrode terminal 12, thereby improving the connection strength between the first pole ear portion 3 and the second pole ear portion 7 and the first electrode terminal 12.

[0085] Optionally, the roughness of the second weld mark 5 is a1, and the roughness of the first weld mark 4 is a2, satisfying: 6≤a1 / a2≤300. Wherein, a1 / a2 can be 6, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290 or 300, etc. The roughness of the second weld mark 5 is greater than that of the first weld mark 4, reducing the problem of cold welding between the first pole ear portion 3 and the first electrode terminal 12, so as to enhance the welding between the first pole ear portion 3 and the first electrode terminal 12 to be more firm.

[0086] Optionally, the roughness of the second weld mark 5 satisfies: 280 μm≤a1≤3000 μm; and the roughness of the first weld mark 4 satisfies: 10 μm≤a2≤500 μm.

[0087] The roughness a1 of the second weld mark 5 can be 280 μm, 300 μm, 400 μm 、 500μm, 600μm, 700μm, 800μm, 1000μm, 1100μm, 1200μm, 1300μm, 1400μm, 1500μm, 1600μm, 1700μm, 1800μm , 1900μm, 2000μm, 2100μm, 2200μm, 2300μm, 2400μm, 2500μm, 2600μm, 2700μm, 2800μm, 2900μm or 3000μm, etc.

[0088] The roughness a2 of the first soldering mark 4 may be 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm m, 330μm, 340μm, 350μm, 360μm, 380μm, 400μm, 410μm, 420μm, 430μm, 440μm, 450μm, 470μm, 480μm, 490μm or 500μm, etc.

[0089] Specifically, since the first pole ear portion 3 and the second pole ear portion 7 are thick after being stacked, in order to prevent the first pole ear portion 3 and the second pole ear portion 7 from having a cold weld with the first electrode terminal 12, it is necessary to increase the roughness of the second weld mark 5 so that the first pole ear portion 3 and the second pole ear portion 7 are in full contact with the first electrode terminal 12. However, if the roughness of the second weld mark 5 is too large, it is easy to cause the second weld mark 5 to weld through the first pole ear portion 3 and the second pole ear portion 7.

[0090] The present application also provides a battery pack, comprising a battery cell as described in any of the above embodiments. In the battery pack provided in the embodiment of the present application, the first pole ear portion 3 is first pre-welded to form a first weld mark 4, and then the first pole ear portion 3 is welded to the first electrode terminal 12 in the area of ​​the first weld mark 4 to form a second weld mark 5, thereby reducing the probability of the first pole ear portion 3 outside the area of ​​the first weld mark 4 being lifted or torn. The roughness of the first weld mark 4 is less than that of the second weld mark 5, so that the first pole ear portion 3 is in full contact with the first electrode terminal 12, thereby improving the connection strength between the first pole ear portion 3 and the first electrode terminal 12, and thereby improving the structural stability of the battery pack.

[0091] The present application also provides an electrical device, including the battery pack described in the above embodiment. The electrical device provided in the embodiment of the present application includes the first electrode assembly 2 and the first electrode terminal 12 in the above battery pack, the first electrode assembly 2 and the second electrode terminal are connected through the first pole ear portion 3, the first pole ear portion 3 is pre-welded to form a first weld mark 4, and the first pole ear portion 3 is welded to the first electrode terminal 12 in the area of ​​the first weld mark 4 to form a second weld mark 5, so as to reduce the probability of the first pole ear portion 3 outside the area of ​​the first weld mark 4 being lifted or torn. The roughness of the first weld mark 4 is less than that of the second weld mark 5, so that the first pole ear portion 3 is in full contact with the first electrode terminal 12, and the connection strength between the first pole ear portion 3 and the first electrode terminal 12 is improved, thereby improving the performance of the electrical device.

[0092] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0093] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0094] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0095] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that: include: a housing for accommodating the first electrode assembly, the housing having a first wall; A first electrode terminal, disposed on the first wall; A first electrode assembly and a first pole ear portion, wherein the first pole ear portion includes at least two first pole ear sheets, the first pole ear sheets extend from at least one end of the first electrode assembly, and the first pole ear portion is electrically connected to the first electrode terminal; A first welding mark and a second welding mark are provided on the first pole ear portion, and along the projection on the large surface of the first pole ear portion, the orthographic projection of the second welding mark falls within the orthographic projection of the first welding mark, and the second welding mark is used to weld the first electrode terminal and the first pole ear portion; Wherein, the roughness of the second weld mark is greater than the roughness of the first weld mark.

2. The battery cell according to claim 1, characterized in that: The roughness of the second weld mark is a1, and the roughness of the first weld mark is a2, satisfying: 5≤a1 / a2≤300.

3. The battery cell according to claim 2, characterized in that: The roughness of the second weld mark satisfies: 300 μm≤a1≤3000 μm; the roughness of the first weld mark satisfies: 10 μm≤a2≤500 μm.

4. The battery cell according to claim 1, characterized in that: The first weld mark is formed by a toothless weld configuration.

5. The battery cell according to claim 1, characterized in that: The second welding mark includes a first welding area and a second welding area, the second welding area is arranged on the circumferential outer side of the first welding area, a plurality of square welding marks are arranged in the first welding area, and a plurality of circular welding marks are arranged in the second welding area.

6. The battery cell according to claim 1, characterized in that: Along the projection on the large surface of the first pole ear portion, the projection area of ​​the first weld mark is S1, and the projection area of ​​the second weld mark is S2, satisfying: 1≤S1 / S2≤10.

7. The battery cell according to claim 6, characterized in that: The projection area of ​​the first weld mark meets the following requirements: 100 mm 2 ≤S1≤2000mm 2 The projection area of ​​the second weld mark satisfies: 20mm 2 ≤S2≤120mm 2 .

8. The battery cell according to claim 1, characterized in that: The first weld mark has a first edge, the second weld mark has a second edge, and a minimum distance between the first edge and the second edge is c, which satisfies: 0.5 mm ≤ c ≤ 10 mm.

9. The battery cell according to claim 1, characterized in that: The battery cell further includes a second electrode assembly and a second pole ear portion, wherein the second electrode assembly and the second pole ear portion are both disposed in the housing, the second pole ear portion includes at least two second pole ear sheets, the second pole ear sheet extends from at least one end of the second electrode assembly, and the second pole ear portion is electrically connected to the first electrode terminal; A third weld mark and a fourth weld mark are provided on the second pole ear portion. The projection area of ​​the first weld mark along the large surface of the first pole ear portion is S1, the projection area of ​​the third weld mark along the large surface of the second pole ear portion is S3, and the sum of the projection areas of the second weld mark and the fourth weld mark is S4, satisfying: S1+S3>S4.

10. The battery cell according to claim 9, characterized in that: The roughness of the second weld mark is a1, the roughness of the first weld mark is a2, the roughness of the fourth weld mark is d1, and the roughness of the third weld mark is d2, satisfying: 5≤a1 / a2≤280, 5≤d1 / d2≤280.

11. The battery cell according to claim 10, characterized in that: The roughness of the second weld mark satisfies: 300μm≤a1≤2800μm; the roughness of the first weld mark satisfies: 10μm≤a2≤500μm; the roughness of the fourth weld mark satisfies: 300μm≤d1≤2800μm; the roughness of the third weld mark satisfies: 10μm≤d2≤500μm.

12. The battery cell according to claim 9, characterized in that: Satisfies: 0.9≤S1 / S3≤1.

1.

13. The battery cell according to claim 1, characterized in that: The first weld mark is rectangular.

14. The battery cell according to any one of claims 1 to 13, characterized in that: The second weld mark is circular.

15. The battery cell according to claim 1, characterized in that: Along the projection on the large surface of the first pole ear portion, the area of ​​the second weld mark is S2, and the end surface area of ​​one end of the electrode terminal connected to the first pole ear portion is S5, satisfying: 0.25≤S2 / S5≤0.

95.

16. The battery cell according to claim 15, characterized in that: The area of ​​the second weld mark meets the following requirements: 20 mm 2 ≤S2≤120mm 2 The end surface area of ​​the electrode terminal connected to the first pole ear portion satisfies: 50mm 2 ≤S5≤300mm 2 .

17. A battery cell, characterized in that: include: a housing for accommodating the first electrode assembly and the second electrode assembly, the housing having a first wall; A first electrode terminal, disposed on the first wall; A first electrode assembly and a first pole ear portion, wherein the first pole ear portion includes at least two first pole ear sheets, the first pole ear sheets extend from at least one end of the first electrode assembly, and the first pole ear portion is electrically connected to the first electrode terminal; A second electrode assembly and a second pole ear portion, the second pole ear portion includes at least two second pole ear sheets, the second pole ear sheets extend from at least one end of the second electrode assembly, and the second pole ear portion is electrically connected to the first electrode terminal; The first pole ear portion and the second pole ear portion are overlapped and welded to form a first weld mark and a second weld mark, along the projection on the large surface of the first pole ear portion or the second pole ear portion, the orthographic projection of the second weld mark falls within the orthographic projection of the first weld mark, and the second weld mark is used to weld at least one of the first pole ear portion and the second pole ear portion to the first electrode terminal; Wherein, the roughness of the second weld mark is greater than the roughness of the first weld mark.

18. The battery cell according to claim 17, characterized in that: The roughness of the second weld mark is a1, and the roughness of the first weld mark is a2, satisfying: 6≤a1 / a2≤300.

19. The battery cell according to claim 18, characterized in that: The roughness of the second weld mark satisfies: 280 μm≤a1≤3000 μm; the roughness of the first weld mark satisfies: 10 μm≤a2≤500 μm.

20. A battery pack, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 19.

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