Cell, secondary battery, and electronic device

Abstract

The invention discloses a battery cell, a secondary battery and an electronic device. The battery cell comprises an electrode assembly, a first tab and a second tab, the electrode assembly comprises a first straight section, a first bent section, a second straight section and a second bent section which are connected in sequence. The electrode assembly further comprises a first pole piece, a second pole piece and a diaphragm. The first pole piece comprises a first current collector, a first active material layer and a second active material layer. The first active material layer is connected to the first inner surface, and the second active material layer is connected to the first outer surface. The first tab comprises a first connecting part connected with the first pole piece; and the second tab comprises a second connecting part connected with the second pole piece. In the first direction, the projection of the first starting end and / or the projection of the second starting end are / is located on the side, away from the first bent section, of the first connecting part, and / or the projection of the first ending end and / or the projection of the second ending end are / is located on the side, away from the second bent section, of the second connecting part, and the battery cell is beneficial to improving the energy density.

Description

Battery cell, secondary battery and electronic device TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a battery cell, a secondary battery and an electronic device. BACKGROUND

[0002] The existing wound battery cell is prone to uneven thickness, which can cause unevenness of the outer surface of the battery cell, and can cause deformation of the battery cell during charging and discharging, affecting the normal use of the battery cell.

[0003] SUMMARY

[0004] In view of the above, the present application provides a battery cell, which is beneficial to improve the uniformity of the thickness of the battery cell.

[0005] The embodiment of the present application provides a battery cell, which comprises an electrode assembly, a first tab and a second tab. The electrode assembly comprises a first flat section, a first bending section, a second flat section and a second bending section connected in sequence. The first flat section and the second flat section are oppositely arranged along a first direction. The first bending section and the second bending section are oppositely arranged along a second direction. The first tab and the second tab extend out of the electrode assembly along a third direction. The first direction is the thickness direction of the battery cell, and the first direction, the second direction and the third direction are perpendicular to each other. The electrode assembly further comprises a first pole piece, a second pole piece and a separator, and the separator is arranged between the first pole piece and the second pole piece. The electrode assembly is wound by the first pole piece, the separator and the second pole piece around a winding center axis. The first pole piece comprises a first current collector, a first active material layer and a second active material layer. The first current collector comprises a first inner surface and a first outer surface, the first inner surface faces the winding center axis, and the first outer surface faces away from the winding center axis. The first active material layer is connected to the first inner surface, and the first active material layer comprises a first starting end and a first ending end. The second active material layer is connected to the first outer surface, and the second active material layer comprises a second starting end and a second ending end. In the third direction, the first tab is located in the first flat section or the second flat section, and the second tab is located in the first flat section or the second flat section. The first tab comprises a first connecting portion connected to the first pole piece, and the first connecting portion is closer to the first bending section than to the second bending section. The second tab comprises a second connecting portion connected to the second pole piece, and the second connecting portion is closer to the second bending section than to the first bending section. In the first direction, a projection of the first starting end and / or a projection of the second starting end is located on a side of the first connecting portion away from the first bending section, and / or a projection of the first ending end and / or a projection of the second ending end is located on a side of the second connecting portion away from the second bending section.

[0006] In the above battery cell, for the first connecting portion, the projection of the first starting end and / or the projection of the second starting end is located on the side of the first connecting portion away from the first bending section in the first direction, so as to reduce the space waste caused by the uneven outer surface of the battery cell due to the overlap of the first starting end and / or the second starting end with the first connecting portion, and to improve the uniformity of the thickness of the battery cell. For the second connecting portion, the projection of the first ending end and / or the projection of the second ending end is located on the side of the second connecting portion away from the second bending section in the first direction, so as to reduce the space waste caused by the uneven outer surface of the battery cell due to the overlap of the first ending end and / or the second ending end with the second connecting portion, and to improve the uniformity of the thickness of the battery cell.

[0007] In some embodiments of the present application, the distance L1 between the first starting end and the first connecting portion in the second direction satisfies 2mm≤L1≤5mm, so as to improve the uniformity of the thickness of the battery cell and to increase the energy density of the battery cell. And / or the distance L2 between the second starting end and the first connecting portion in the second direction satisfies 2mm≤L2≤5mm, so as to improve the uniformity of the thickness of the battery cell and to increase the energy density of the battery cell.

[0008] In some embodiments of the present application, the distance L3 between the first ending end and the second connecting portion in the second direction satisfies 2mm≤L3≤5mm, so as to improve the uniformity of the thickness of the battery cell and to increase the energy density of the battery cell. And / or the distance L4 between the second ending end and the second connecting portion in the second direction satisfies 2mm≤L4≤5mm, so as to improve the uniformity of the thickness of the battery cell and to increase the energy density of the battery cell.

[0009] In some embodiments of the present application, the first inner surface includes a first uncoated area beyond the first starting end, and the first outer surface includes a second uncoated area beyond the second starting end. The first connecting portion connects the first uncoated area or the second uncoated area. The battery cell further includes a first insulating member and a second insulating member. The first insulating member covers the first uncoated area and the first starting end, and the second insulating member covers the second uncoated area and the second starting end, so as to reduce the risk of the first starting section of the first tab contacting the adjacent second tab and causing short circuit, thereby improving the safety of the battery cell. The first insulating member includes a first overlapping portion covering the first active material layer, and the length W1 of the first overlapping portion in the second direction satisfies 0.2mm≤W1≤2mm, so as to reduce the risk of the first insulating member deviating from the first starting end and to improve the cycle performance of the electrode assembly. The second insulating member includes a second overlapping portion covering the second active material layer, and the length W2 of the second overlapping portion in the second direction satisfies 0.2mm≤W2≤2mm, so as to reduce the risk of the second insulating member deviating from the first starting end and to improve the cycle performance of the electrode assembly.

[0010] In some embodiments of the present application, the first inner surface includes a third uncoated area beyond the first end, and the first outer surface includes a fourth uncoated area beyond the second end. The battery cell further includes a third insulating member and a fourth insulating member. The third insulating member covers the third uncoated area and the first end, and the fourth insulating member covers the second uncoated area and the second end. The third insulating member and the fourth insulating member are configured to reduce the risk of the end section of the first tab contacting the adjacent second tab and causing a short circuit, thereby improving the safety of the battery cell. The third insulating member includes a third overlapping portion covering the first active material layer. In the second direction, the length W3 of the third overlapping portion satisfies 0.2 mm≤W3≤2 mm, so as to reduce the risk of the third insulating member deviating from the first end and improve the cycle performance of the electrode assembly. The fourth insulating member includes a fourth overlapping portion covering the second active material layer. In the second direction, the length W4 of the fourth overlapping portion satisfies 0.2 mm≤W4≤2 mm, so as to reduce the risk of the fourth insulating member deviating from the first end and improve the cycle performance of the electrode assembly.

[0011] In some embodiments of the present application, in the third direction, the first reference line passes through the first bending point of the first tab in the first direction, and the second reference line passes through the first bending point of the second tab in the first direction. The first reference line is closer to the first bending section than the second bending section, and the second reference line is closer to the second bending section than the first bending section. In the second direction, the first connecting portion and the first reference line are spaced apart, so as to reduce the risk of the first connecting portion interfering with the separator located at the first bending section and facilitate the tab adhesive covering the first connecting portion. And / or in the second direction, the second connecting portion and the second reference line are spaced apart, so as to reduce the risk of the second connecting portion interfering with the separator located at the second bending section and facilitate the tab adhesive covering the second connecting portion.

[0012] In some embodiments of the present application, the second tab includes a second current collector and a third active material layer. The second current collector includes a second outer surface, and the third active material layer is connected to the second outer surface. The third active material layer includes a third starting end. In the third direction, the third starting end is located between the first connecting portion and the first reference line in the second direction, so as to facilitate the third active material layer compensating for the thin area of the battery cell caused by the first starting end and / or the second starting end, and to improve the uniformity of the thickness of the battery cell.

[0013] In some embodiments of the present application, along the second direction, the distance L5 between the third starting end and the first reference line, and the distance L6 between the third starting end and the first connecting portion satisfy: L5≥2mm, and L6≥1mm. Wherein, L5≥2mm, so as to compensate the thin part of the battery cell caused by the first starting end and / or the second starting end by the third active material layer. L6≥1mm, so as to reserve a tolerance between the third starting end and the first connecting portion, reduce the space waste caused by the uneven surface of the battery cell due to the overlap between the third starting end and the first connecting portion, and improve the uniformity of the thickness of the battery cell.

[0014] In some embodiments of the present application, the battery cell further comprises a transition tab. The transition tab comprises a first extension segment and a second extension segment. One end of the first extension segment is connected to the first tab or the second tab, and the other end of the first extension segment is connected to the second extension segment. The second extension segment extends outward from the first extension segment along a third direction, so as to adapt to and connect with the connection position of the external circuit.

[0015] In some embodiments of the present application, the transition tab and the first tab are integrally formed, so as to improve the connection stability of the transition tab and the first tab. Or the transition tab and the second tab are integrally formed, so as to improve the connection stability of the transition tab and the second tab.

[0016] In some embodiments of the present application, the battery cell further comprises a packaging bag, a first tab adhesive and a second tab adhesive. The packaging bag comprises a main body portion and a top sealing edge. The electrode assembly is arranged in the main body portion, the main body portion comprises a top wall, and the top sealing edge is connected to the top wall. The first tab and the second tab respectively extend from the top sealing edge. The first tab adhesive is located on the top sealing edge and covers part of the first tab, so as to improve the sealing stability of the first tab and the top sealing edge. The second tab adhesive is located on the top sealing edge and covers part of the second tab, so as to improve the sealing stability of the first tab and the top sealing edge.

[0017] In some embodiments of the present application, along the first direction, the thickness of the battery cell is less than or equal to 2mm, so as to meet the size requirement of the ultra-thin battery cell.

[0018] The embodiments of the present application also provide a secondary battery, which comprises any one of the battery cells in the above embodiments.

[0019] The embodiments of the present application also provide an electronic device, which comprises any one of the secondary batteries in the above embodiments.

[0020] In the above electric chip, secondary battery and electronic device, for the first connecting part, the projection of the first starting end and / or the projection of the second starting end is located on the side of the projection of the first connecting part away from the first bending section in the first direction, so as to reduce the space waste caused by the uneven outer surface of the electric chip due to the overlapping of the first starting end and / or the second starting end with the first connecting part, and to improve the uniformity of the thickness of the electric chip. For the second connecting part, the projection of the first ending end and / or the projection of the second ending end is located on the side of the second connecting part away from the second bending section in the first direction, so as to reduce the space waste caused by the uneven outer surface of the electric chip due to the overlapping of the first ending end and / or the second ending end with the second connecting part, and to improve the uniformity of the thickness of the electric chip. BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION BRIEF DESCRIPTION OF DRAWINGS

[0021] Fig. 1 is a structural schematic diagram of an electric chip in an embodiment of the present application viewed in a third direction.

[0022] Fig. 2 is a structural schematic diagram of an electric chip in another embodiment of the present application viewed in a third direction.

[0023] Fig. 3 is a structural schematic diagram of an electric chip in another embodiment of the present application viewed in a third direction.

[0024] Fig. 4 is a structural schematic diagram of an electric chip in another embodiment of the present application viewed in a third direction.

[0025] Fig. 5 is a structural schematic diagram of an electric chip in another embodiment of the present application viewed in a third direction.

[0026] Fig. 6 is a structural schematic diagram of a transition tab of an electric chip in an embodiment of the present application.

[0027] Fig. 7 is a structural schematic diagram of a packaging bag, a first tab adhesive and a second tab adhesive of an electric chip in an embodiment of the present application.

[0028] Fig. 8 is a structural schematic diagram of a secondary battery assembled into an electronic device in an embodiment of the present application.

[0029] MAIN ELEMENT SYMBOL EXPLANATION

[0030] Electric chip 100

[0031] Secondary battery 200

[0032] Electronic device 300

[0033] Electrode assembly 10

[0034] First straight section 10A

[0035] First curved section 10B

[0036] Second straight section 10C

[0037] Second curved section 10D

[0038] Winding center axis O

[0039] First reference line E

[0040] Second reference line F

[0041] Third reference line G

[0042] First pole piece 11

[0043] First bending point 11A

[0044] Second bending point 11B

[0045] First current collector 111

[0046] First inner surface 111A

[0047] First uncoated region 1111

[0048] Third uncoated region 1113

[0049] First outer surface 111B

[0050] Second uncoated region 1112

[0051] Fourth uncoated region 1114

[0052] first active material layer 112

[0053] first starting end 112A

[0054] first ending end 112B

[0055] second active material layer 113

[0056] second starting end 113A

[0057] second ending end 113B

[0058] second tab 12

[0059] first bending point 12A

[0060] second bending point 12B

[0061] second current collector 121

[0062] second outer surface 121A

[0063] second inner surface 121B

[0064] third active material layer 122

[0065] third starting end 122A

[0066] fourth active material layer 123

[0067] fourth starting end 123A

[0068] separator 13

[0069] first tab 20

[0070] First connecting portion 21

[0071] Second tab 30

[0072] Second connecting portion 31

[0073] First insulating member 41

[0074] First overlapping portion 411

[0075] Second insulating member 42

[0076] Second overlapping portion 421

[0077] Third insulating member 43

[0078] Third overlapping portion 431

[0079] Fourth insulating member 44

[0080] Fourth overlapping portion 441

[0081] Adapter tab 50

[0082] First extension 51

[0083] Second extension 52

[0084] Packaging bag 60

[0085] Body portion 61

[0086] Top wall 611

[0087] Top seal 62

[0088] First tab adhesive 71

[0089] Second tab adhesive 72

[0090] First direction Z

[0091] Second direction X

[0092] Third direction Y

[0093] The following detailed description will further describe the present application with reference to the above drawings. DETAILED DESCRIPTION

[0094] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application.

[0095] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or can exist simultaneously with a middle element. When an element is considered to be "provided" on another element, it can be directly provided on the other element or can exist simultaneously with a middle element.

[0096] When a numerical value is considered to be "equal" to another numerical value, it means that both are equal within a set deviation, and the set deviation range is within 5%, that is, when at least one of the two numerical values fluctuates within the set deviation range, even if the values are not equal, it is still determined that they are approximately equal. When a numerical value is considered to be "1:1" to another numerical value, it means that both are equal within a set deviation, and the set deviation range is within 5%, that is, when at least one of the two numerical values fluctuates within the set deviation range, even if the values are not equal, it is still determined that the proportion is equal.

[0097] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. As used herein, the term "overlap" means that the projected portions of two components overlap or the projections of two components coincide.

[0098] An embodiment of the present application provides an electric core, which comprises an electrode assembly, a first tab and a second tab. The electrode assembly comprises a first flat section, a first bending section, a second flat section and a second bending section connected in sequence. The first flat section and the second flat section are oppositely arranged along a first direction. The first bending section and the second bending section are oppositely arranged along a second direction. The first tab and the second tab extend out of the electrode assembly along a third direction. The first direction is a thickness direction of the electric core, and the first direction, the second direction and the third direction are perpendicular to each other. The electrode assembly further comprises a first pole piece, a second pole piece and a separator, and the separator is arranged between the first pole piece and the second pole piece. The electrode assembly is wound by the first pole piece, the separator and the second pole piece around a winding center axis. The first pole piece comprises a first current collector, a first active material layer and a second active material layer. The first current collector comprises a first inner surface and a first outer surface, the first inner surface faces the winding center axis, and the first outer surface faces away from the winding center axis. The first active material layer is connected to the first inner surface, and the first active material layer comprises a first starting end and a first ending end. The second active material layer is connected to the first outer surface, and the second active material layer comprises a second starting end and a second ending end. In the third direction, the first tab is located in the first flat section or the second flat section, and the second tab is located in the first flat section or the second flat section. The first tab comprises a first connecting portion connected to the first pole piece, and the first connecting portion is closer to the first bending section than to the second bending section. The second tab comprises a second connecting portion connected to the second pole piece, and the second connecting portion is closer to the second bending section than to the first bending section. In the first direction, a projection of the first starting end and / or a projection of the second starting end is located on a side of the first connecting portion away from the first bending section, and / or a projection of the first ending end and / or a projection of the second ending end is located on a side of the second connecting portion away from the second bending section.

[0099] In the above electric core, for the first connecting portion, in the first direction, the projection of the first starting end and / or the projection of the second starting end is located on a side of the projection of the first connecting portion away from the first bending section, so as to reduce the space waste caused by the uneven outer surface of the electric core due to the overlap of the first starting end and / or the second starting end and the first connecting portion, and to improve the uniformity of the thickness of the electric core. For the second connecting portion, in the first direction, the projection of the first ending end and / or the projection of the second ending end is located on a side of the second connecting portion away from the second bending section, so as to reduce the space waste caused by the uneven outer surface of the electric core due to the overlap of the first ending end and / or the second ending end and the second connecting portion, and to improve the uniformity of the thickness of the electric core.

[0100] The embodiments of the present application are further described below with reference to the drawings.

[0101] Referring to FIG. 1, an embodiment of the present application provides an electric core 100. The electric core 100 comprises an electrode assembly 10, a first tab 20 and a second tab 30. The electrode assembly 10 is used to convert chemical energy into electrical energy. The first tab 20 and the second tab 30 are opposite in polarity and are used to electrically connect the electrode assembly 10 with an external circuit.

[0102] The electrode assembly 10 comprises a first flat section 10A, a first bending section 10B, a second flat section 10C and a second bending section 10D connected in sequence. The first flat section 10A and the second flat section 10C are oppositely arranged along a first direction Z, and the first bending section 10B and the second bending section 10D are oppositely arranged along a second direction X. The first tab 20 and the second tab 30 extend out of the electrode assembly 10 along a third direction Y. The first direction Z is a thickness direction of the electric core 100, and the first direction Z, the second direction X and the third direction Y are perpendicular to each other. Optionally, the second direction X is a width direction of the electric core 100, and the third direction Y is a length direction of the electric core 100.

[0103] The electrode assembly 10 further comprises a first pole piece 11, a second pole piece 12 and a separator 13. The separator 13 is arranged between the first pole piece 11 and the second pole piece 12, and the electrode assembly 10 is wound by the first pole piece 11, the separator 13 and the second pole piece 12 around a winding center axis O. The winding direction can be clockwise or counterclockwise, and the present application takes the counterclockwise winding as an example for description. The starting end refers to one end adjacent to the winding center axis O along the winding direction, and the ending end refers to one end away from the winding center axis O along the winding direction.

[0104] The first pole piece 11 comprises a first current collector 111, a first active material layer 112 and a second active material layer 113. The first current collector 111 comprises a first inner surface 111A and a first outer surface 111B. The first inner surface 111A faces the winding center axis O, and the first outer surface 111B is away from the winding center axis O. The first active material layer 112 is connected to the first inner surface 111A, and the first active material layer 112 comprises a first starting end 112A and a first ending end 112B. The second active material layer 113 is connected to the first outer surface 111B, and the second active material layer 113 comprises a second starting end 113A and a second ending end 113B. Along the winding direction, the first starting end 112A and the second starting end 113A are adjacent to the winding center axis O, and the first ending end 112B and the second ending end 113B are away from the winding center axis O.

[0105] The first pole piece 11 is of positive polarity, and the second pole piece 12 is of negative polarity. The starting end of the second pole piece 12 exceeds the starting end of the first pole piece 11. The part of the first pole piece 11 adjacent to the starting end of the first pole piece 11 is connected to the first tab 20. The part of the second pole piece 12 exceeding the starting end of the first pole piece 11 is connected to the second tab 30.

[0106] In the third direction Y, the first tab 20 is located at the first flat section 10A or the second flat section 10C, and the second tab 30 is located at the first flat section 10A or the second flat section 10C. The first tab 20 comprises a first connecting portion 21 connected with the first tab 11, and the first connecting portion 21 is closer to the first bending section 10B than the second bending section 10D. The second tab 30 comprises a second connecting portion 31 connected with the second tab 12, and the second connecting portion 31 is closer to the second bending section 10D than the first bending section 10B. In the first direction Z, the projection of the first connecting portion 21 and the projection of the second connecting portion 31 are spaced apart in the second direction X. The first connecting portion 21, the first starting end 112A and the second starting end 113A are all located at the innermost circle of the first tab 11, the first ending end 112B is located at the outermost circle of the first tab 11, and the second ending end 113B is located at the second outermost circle of the first tab 11; and the second connecting portion 31 is located at the innermost circle of the second tab 12.

[0107] Specifically, in the third direction Y, the edge of the first current collector 111 in the third direction Y is provided with a blank area, and the first tab 20 is connected to the blank area of the first current collector 111. The blank area refers to the area where the first inner surface 111A is not coated with the first active material layer 112, or the area where the first outer surface 111B is not coated with the second active material layer 113. Optionally, the first tab 20 is connected to the blank area of the first current collector 111 by welding. It can be understood that the connection structure of the second tab 30 and the second tab 12 is similar to that of the first tab 20 and the first tab 11.

[0108] Referring to FIG. 2, in some embodiments, in the first direction Z, the projection of the first starting end 112A is located on the side of the projection of the first connecting portion 21 away from the first bending section 10B, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the first starting end 112A and the first connecting portion 21, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100. The projection of the second starting end 113A, the projection of the first ending end 112B and the projection of the second ending end 113B are not limited.

[0109] Referring to FIG. 3, in some embodiments, in the first direction Z, the projection of the second starting end 113A is located on the side of the projection of the first connecting portion 21 away from the first bending section 10B, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the second starting end 113A and the first connecting portion 21, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100. The projection of the first starting end 112A, the projection of the first ending end 112B and the projection of the second ending end 113B are not limited.

[0110] Referring to FIG. 4, in some embodiments, the projection of the first end 112B is located on the side of the second connecting portion 31 away from the second bending section 10D, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the first end 112B and the second connecting portion 31, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100. The projection of the second end 113B, the projection of the first end 112A, and the projection of the second end 113A are not limited.

[0111] Referring to FIG. 5, in some embodiments, the projection of the second end 113B is located on the side of the second connecting portion 31 away from the second bending section 10D, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the second end 113B and the second connecting portion 31, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100. The projection of the first end 112B, the projection of the first end 112A, and the projection of the second end 113A are not limited.

[0112] In the above battery cell 100, for the first connecting portion 21, along the first direction Z, the projection of the first end 112A and / or the projection of the second end 113A is located on the side of the projection of the first connecting portion 21 away from the first bending section 10B, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the first end 112A and / or the second end 113A and the first connecting portion 21, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100. For the second connecting portion 31, along the first direction Z, the projection of the first end 112B and / or the projection of the second end 113B is located on the side of the second connecting portion 31 away from the second bending section 10D, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the first end 112B and / or the second end 113B and the second connecting portion 31, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100.

[0113] Referring to FIG. 1, in some embodiments, along the first direction Z, the projection of the first end 112A and the projection of the second end 113A are located on the side of the projection of the first connecting portion 21 away from the first bending section 10B, and the projection of the first end 112B and the projection of the second end 113B are located on the side of the second connecting portion 31 away from the second bending section 10D, so as to further improve the uniformity of the thickness of the battery cell 100.

[0114] Please refer to FIG. 2 again, in some embodiments, along the second direction X, the distance L1 between the first starting end 112A and the first connecting part 21 satisfies: 2mm≤L1≤5mm. When L1 is too small (less than 2mm), the tolerance reserved between the first starting end 112A and the first connecting part 21 is small, and in the process of connecting the first tab 20 and the first pole piece 11 or winding the electrode assembly 10, the first starting end 112A is easy to overlap with the first connecting part 21, resulting in uneven surface of the battery cell 100 and space waste, and further resulting in uneven thickness of the battery cell 100. When L1 is too large (greater than 5mm), the energy density of the battery cell 100 is reduced. By limiting 2mm≤L1≤5mm, the uniformity of the thickness of the battery cell 100 can be improved, and the energy density of the battery cell 100 can be improved.

[0115] Optionally, L1 is one of 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm and any other value within the range of 2mm≤L1≤5mm.

[0116] Further, 2mm≤L1≤3mm, so as to further improve the uniformity of the thickness of the battery cell 100 and improve the energy density of the battery cell 100.

[0117] Please refer to FIG. 3 again, in some embodiments, along the second direction X, the distance L2 between the second starting end 113A and the first connecting part 21 satisfies: 2mm≤L2≤5mm. When L2 is too small (less than 2mm), the tolerance reserved between the second starting end 113A and the first connecting part 21 is small, and in the process of connecting the first tab 20 and the first pole piece 11 or winding the electrode assembly 10, the second starting end 113A is easy to overlap with the first connecting part 21, resulting in uneven surface of the battery cell 100 and space waste, and further resulting in uneven thickness of the battery cell 100. When L2 is too large (greater than 5mm), the energy density of the battery cell 100 is reduced. By limiting 2mm≤L2≤5mm, the uniformity of the thickness of the battery cell 100 can be improved, and the energy density of the battery cell 100 can be improved.

[0118] Optionally, L2 is one of 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm and any other value within the range of 2mm≤L2≤5mm.

[0119] Further, 2mm≤L2≤3mm, so as to further improve the uniformity of the thickness of the battery cell 100 and improve the energy density of the battery cell 100.

[0120] In some embodiments, L1=L2, that is, along the first direction Z, the projection of the first starting end 112A and the projection of the second starting end 113A overlap.

[0121] Please refer to FIG. 4 again, in some embodiments, along the second direction X, the distance L3 between the first end 112B and the second connecting part 31 satisfies: 2mm≤L3≤5mm. When L3 is too small (less than 2mm), it will cause that the tolerance reserved between the first end 112B and the second connecting part 31 is small, and in the process of connecting the second tab 30 to the second electrode sheet 12 or winding the electrode assembly 10, the first end 112B is easy to overlap with the second connecting part 31, resulting in that the outer surface of the battery cell 100 is uneven and space is wasted, and then the thickness of the battery cell 100 is uneven. When L2 is too large (greater than 5mm), it will cause that the energy density of the battery cell 100 is reduced. By limiting 2mm≤L3≤5mm, the uniformity of the thickness of the battery cell 100 can be improved, and the energy density of the battery cell 100 is improved.

[0122] Optionally, L3 is one of 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm and any other value within the range of 2mm≤L3≤5mm.

[0123] Further, 2mm≤L3≤3mm, so as to further improve the uniformity of the thickness of the battery cell 100, and improve the energy density of the battery cell 100.

[0124] Please refer to FIG. 5 again, in some embodiments, along the second direction X, the distance L4 between the second end 113B and the second connecting part 31 satisfies: 2mm≤L4≤5mm. When L4 is too small (less than 2mm), it will cause that the tolerance reserved between the second end 113B and the second connecting part 31 is small, and in the process of connecting the second tab 30 to the second electrode sheet 12 or winding the electrode assembly 10, the second end 113B is easy to overlap with the second connecting part 31, resulting in that the outer surface of the battery cell 100 is uneven and space is wasted, and then the thickness of the battery cell 100 is uneven. When L4 is too large (greater than 5mm), it will cause that the energy density of the battery cell 100 is reduced. By limiting 2mm≤L4≤5mm, the uniformity of the thickness of the battery cell 100 can be improved, and the energy density of the battery cell 100 is improved.

[0125] Optionally, L4 is one of 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm and any other value within the range of 2mm≤L4≤5mm.

[0126] Further, 2mm≤L4≤3mm, so as to further improve the uniformity of the thickness of the battery cell 100, and improve the energy density of the battery cell 100.

[0127] In some embodiments, L3=L4, that is, along the first direction Z, the projection of the first end 112B and the projection of the second end 113B overlap.

[0128] Please refer to FIG. 1 again, in some embodiments, the first inner surface 111A includes a first uncoated area 1111 beyond the first starting end 112A, the first outer surface 111B includes a second uncoated area 1112 beyond the second starting end 113A, and the first connecting portion 21 connects the first uncoated area 1111 or the second uncoated area 1112. The uncoated area refers to an area where the surface of the current collector is not coated with the current collector.

[0129] The battery cell 100 further includes a first insulating member 41 and a second insulating member 42. The first insulating member 41 covers the first uncoated area 1111 and the first starting end 112A, and the second insulating member 42 covers the second uncoated area 1112 and the second starting end 113A. The first insulating member 41 and the second insulating member 42 are used to reduce the risk of the starting section of the first tab 11 contacting the adjacent second tab 12 and causing a short circuit, thereby improving the safety of the battery cell 100. In addition, the first insulating member 41 or the second insulating member 42 also covers the first connecting portion 21, so as to improve the stability of the connection between the first tab 20 and the first tab 11.

[0130] In some embodiments, the first insulating member 41 includes a first overlapping portion 411 covering the first active material layer 112, and the length W1 of the first overlapping portion 411 satisfies: 0.2mm≤W1≤2mm in the second direction X. When W1 is too small (less than 0.2mm), it is easy to cause the first insulating member 41 to deviate from the first starting end 112A. When W2 is too large (greater than 2mm), it will reduce the area of the first active material layer 112 being soaked by the electrolyte, resulting in a decrease in the cycle performance of the electrode assembly 10. By limiting 0.2mm≤W1≤2mm, the risk of the first insulating member 41 deviating from the first starting end 112A can be reduced, and the cycle performance of the electrode assembly 10 can be improved.

[0131] Optionally, W1 is one of 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 2mm, and any other value within the range of 0.2mm≤W1≤2mm.

[0132] Further, 0.8mm≤W1≤1.4mm, so as to further reduce the risk of the first insulating member 41 deviating from the first starting end 112A, and improve the cycle performance of the electrode assembly 10.

[0133] In some embodiments, the second insulating member 42 includes a second overlapping portion 421 covering the second active material layer 113, and a length W2 of the second overlapping portion 421 satisfies: 0.2mm≤W2≤2mm in the second direction X. When W2 is too small (less than 0.2mm), the second insulating member 42 is prone to deviate from the second starting end 113A. When W2 is too large (greater than 2mm), the area of the second active material layer 113 being impregnated by the electrolyte solution is reduced, resulting in a decrease in the cycle performance of the electrode assembly 10. By limiting 0.2mm≤W2≤2mm, the risk of the second insulating member 42 deviating from the second starting end 113A is reduced, and the cycle performance of the electrode assembly 10 is improved.

[0134] Optionally, W2 is one of 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 2mm, and any other value within the range of 0.2mm≤W2≤2mm.

[0135] Further, 0.8mm≤W2≤1.4mm, so as to further reduce the risk of the second insulating member 42 deviating from the second starting end 113A, and improve the cycle performance of the electrode assembly 10.

[0136] Please continue to refer to FIG. 1. In some embodiments, the first inner surface 111A includes a third uncoated area 1113 beyond the first end 112B, and the first outer surface 111B includes a fourth uncoated area 1114 beyond the second end 113B.

[0137] The battery cell 100 further includes a third insulating member 43 and a fourth insulating member 44. The third insulating member 43 covers the third uncoated area 1113 and the first end 112B, and the fourth insulating member 44 covers the fourth uncoated area 1114 and the second end 113B. The third insulating member 43 and the fourth insulating member 44 are used to reduce the risk of the end segment of the first tab 11 contacting the adjacent second tab 12 and generating a short circuit, thereby improving the safety of the battery cell 100.

[0138] In some embodiments, the third insulating member 43 includes a third overlapping portion 431 covering the first active material layer 112, and a length W3 of the third overlapping portion 431 satisfies: 0.2mm≤W3≤2mm in the second direction X. When W3 is too small (less than 0.2mm), the third insulating member 43 is prone to deviate from the first end 112B. When W3 is too large (greater than 2mm), the area of the first active material layer 112 being impregnated by the electrolyte solution is reduced, resulting in a decrease in the cycle performance of the electrode assembly 10. By limiting 0.2mm≤W3≤2mm, the risk of the third insulating member 43 deviating from the first end 112B is reduced, and the cycle performance of the electrode assembly 10 is improved.

[0139] Optionally, W3 is one of 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 2 mm, and any other value within the range of 0.2 mm≤W3≤2 mm.

[0140] Further, 0.8 mm≤W3≤1.4 mm, to further reduce the risk of the third insulating member 43 deviating from the first end 112B and improve the cycle performance of the electrode assembly 10.

[0141] In some embodiments, the fourth insulating member 44 includes a fourth overlapping portion 441 covering the second active material layer 113, and the length W4 of the fourth overlapping portion 441 satisfies 0.2 mm≤W4≤2 mm in the second direction X. When W4 is too small (less than 0.2 mm), the fourth insulating member 44 is prone to deviate from the second end 113B. When W4 is too large (greater than 2 mm), the area of the second active material layer 113 soaked by the electrolyte solution is reduced, resulting in a decrease in the cycle performance of the electrode assembly 10. By limiting 0.2 mm≤W4≤2 mm, the risk of the fourth insulating member 44 deviating from the second end 113B is reduced, and the cycle performance of the electrode assembly 10 is improved.

[0142] Optionally, W4 is one of 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 2 mm, and any other value within the range of 0.2 mm≤W4≤2 mm.

[0143] Further, 0.8 mm≤W4≤1.4 mm, to further reduce the risk of the fourth insulating member 44 deviating from the second end 113B and improve the cycle performance of the electrode assembly 10.

[0144] Please continue to refer to FIG. 1. In some embodiments, the first reference line E passes through the first bending point 11A of the first tab 11 in the first direction Z, and the second reference line F passes through the first bending point 12A of the second tab 12 in the first direction Z, as viewed in the third direction Y. The first reference line E is closer to the first bending section 10B than the second bending section 10D, and the second reference line F is closer to the second bending section 10D than the first bending section 10B. It should be noted that, in the absence of production tolerances in the battery cell 100, the first reference line E also passes through the second bending point 11B of the first tab 11, and the second reference line F also passes through the second bending point 12B of the second tab 12.

[0145] In some embodiments, along the second direction X, the first connecting portion 21 and the first reference line E are spaced apart to reduce the risk of the first connecting portion 21 interfering with the diaphragm 13 located at the first bending section 10B, and facilitate the tab adhesive covering the first connecting portion 21.

[0146] In some embodiments, along the second direction X, the second connecting portion 31 and the second reference line F are spaced apart to reduce the risk of the second connecting portion 31 interfering with the diaphragm 13 located at the second bending section 10D, and facilitate the tab adhesive covering the second connecting portion 31.

[0147] In some embodiments, the second tab 12 includes a second current collector 121 and a third active material layer 122, the second current collector 121 includes a second outer surface 121A, and the third active material layer 122 is connected to the second outer surface 121A. The third active material layer 122 includes a third starting end 122A, and the third starting end 122A is adjacent to the winding center axis O. In the third direction Y, the third starting end 122A is located between the first connecting portion 21 and the first reference line E in the second direction X, so as to facilitate the third active material layer 122 to compensate for the thinning of the battery cell 100 due to the first starting end 112A and / or the second starting end 113A, i.e., the position between the first connecting portion 21 and the first reference line E, and improve the uniformity of the thickness of the battery cell 100.

[0148] In some embodiments, along the second direction X, the distance L5 between the third starting end 122A and the first reference line E, and the distance L6 between the third starting end 122A and the first connecting portion 21 satisfy: L5≥2mm, and L6≥1mm. Wherein, L5≥2mm, so as to facilitate the third active material layer 122 to compensate for the thinning of the battery cell 100 due to the first starting end 112A and / or the second starting end 113A. L6≥1mm, so as to reserve a tolerance between the third starting end 122A and the first connecting portion 21, reduce the space waste caused by the unevenness of the outer surface of the battery cell 100 due to the overlap of the third starting end 122A and the first connecting portion 21, and improve the uniformity of the thickness of the battery cell 100.

[0149] Optionally, L5 is one of 2mm, 2.5mm, 3mm, and other arbitrary values within the range of L5≥2mm.

[0150] Optionally, L6 is one of 1mm, 1.5mm, 2mm, and other arbitrary values within the range of L6≥1mm.

[0151] In some embodiments, the second current collector 121 further comprises a second inner surface 121B and a fourth active material layer 123 connected to the second inner surface 121B. The fourth active material layer 123 comprises a fourth starting end 123A adjacent to the winding center axis O. The third starting end 122A is located at the innermost circle of the second tab 12, and the fourth starting end 123A is located at the second inner circle of the second tab 12. In the first direction Z, the projection of the fourth starting end 123A is located between the projection of the first connecting part 21 and the first reference line E, so as to compensate for the thin part of the battery cell 100 caused by the first starting end 112A and / or the second starting end 113A, and to improve the uniformity of the thickness of the battery cell 100.

[0152] Please continue to refer to FIG. 1. In some embodiments, as viewed in the third direction Y, a third reference line G is defined along the first direction Z passing through the winding center axis O. The first connecting part 21, the first starting end 112A and the second starting end 113A are located on one side of the third reference line G toward the first bending section 10B, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the first insulating part 41 or the second insulating part 42 with the second connecting part 31, and to improve the uniformity of the thickness of the battery cell 100. The second connecting part 31, the first ending end 112B and the second ending end 113B are located on one side of the third reference line G toward the second bending section 10D, so as to reduce the space waste caused by the uneven outer surface of the battery cell 100 due to the overlap of the first insulating part 41 or the second insulating part 42 with the first connecting part 21, and to improve the uniformity of the thickness of the battery cell 100.

[0153] Please refer to FIG. 6. In some embodiments, the battery cell 100 further comprises a transition tab 50 comprising a first extension 51 and a second extension 52. One end of the first extension 51 is connected to the first tab 20 or the second tab 30, and the other end of the first extension 51 is connected to the second extension 52. The second extension 52 extends outward from the first extension 51 in the third direction Y, so as to adapt to and connect with the connection position of the external circuit. Optionally, the first extension 51 extends in the second direction X.

[0154] In some embodiments, the transition tab 50 and the first tab 20 are integrally formed, so as to improve the connection stability of the transition tab 50 and the first tab 20.

[0155] In some embodiments, the transition tab 50 and the second tab 30 are integrally formed, so as to improve the connection stability of the transition tab 50 and the second tab 30.

[0156] Referring to FIG. 7, in some embodiments, the battery cell 100 further includes a packaging bag 60, a first tab adhesive 71 and a second tab adhesive 72. The packaging bag 60 includes a main body 61 and a top seal edge 62, and the electrode assembly 10 is disposed in the main body 61. The main body 61 includes a top wall 611 disposed in the third direction Y, and the top seal edge 62 is connected to the top wall 611. The first tab 20 and the second tab 30 respectively extend out of the top seal edge 62 along the third direction Y. The first tab adhesive 71 is located on the top seal edge 62 and covers part of the first tab 20, so as to improve the sealing stability of the first tab 20 and the top seal edge 62. The second tab adhesive 72 is located on the top seal edge 62 and covers part of the second tab 30, so as to improve the sealing stability of the second tab 30 and the top seal edge 62.

[0157] It can be understood that when the adapter tab 50 is connected to the first tab 20 or the second tab 30, the first extension section 51 is located in the top seal edge 62, and the corresponding first tab adhesive 71 or second tab adhesive 72 covers the first extension section 51, so as to improve the sealing stability of the adapter tab 50 and the top seal edge 62.

[0158] In some embodiments, along the first direction Z, the thickness of the battery cell 100 is less than or equal to 2 mm, so as to meet the size requirement of the ultra-thin battery cell. Generally, the number of tab layers of the ultra-thin battery cell is small, and the length of the tab needs to reach a corresponding value to ensure a high winding rate. By locating the projection of the first starting end 112A and / or the projection of the second starting end 113A on the side of the projection of the first connecting portion 21 away from the first bending section 10B, and / or locating the projection of the first ending end 112B and / or the projection of the second ending end 113B on the side of the projection of the second connecting portion 31 away from the second bending section 10D, the space waste can be reduced, which is conducive to increasing the number of tab layers and prolonging the length of the tab, and improving the winding rate and manufacturability.

[0159] Referring to FIG. 8, an embodiment of the present application further provides a secondary battery 200, which includes the battery cell 100 in any of the above embodiments. After discharging, the secondary battery 200 can be used continuously by activating the active material through charging.

[0160] An embodiment of the present application further provides an electronic device 300, which includes the secondary battery 200 in any of the above embodiments. Optionally, the electronic device 300 can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool, etc.

[0161] The specific embodiments of the battery cell 100 in the examples and comparative examples are described below.

[0162] 1. Battery cell thickness difference test:

[0163] Place the battery cell flat. Select five measurement points on the battery cell, for example, for battery cell 100, the five measurement points are: the position of battery cell 100 corresponding to the first reference line E; the position of battery cell 100 corresponding to the first connecting portion 21; the position of battery cell 100 corresponding to the position between the first connecting portion 21 and the second connecting portion 31; the position of battery cell 100 corresponding to the second connecting portion 31; and the position of battery cell 100 corresponding to the second reference line F. Measure the thickness of the battery cell at the five measurement points using a micrometer, and take the range of the five measurement points as the thickness difference.

[0164] 2. Battery cell energy density test:

[0165] The battery cell volume energy density test method is to divide the energy value by the volume of the battery cell. The energy value is the product of the battery cell capacity and the voltage, and the volume of the battery cell is the product of the length, width and thickness of the battery cell. The thickness of the battery cell is measured by PPG (Parallel Plate Gauge), which is to place the battery cell between two flat plates and apply a certain pressure, usually 650±50g, and then measure the distance between the two flat plates, which is the thickness of the battery cell.

[0166] 3. Battery cell cycle performance test:

[0167] Charge the battery cell at 25degC using a conventional 0.5C constant current, charge to 0.05C cutoff, stand for 5min, then discharge at 0.5C constant current, and observe whether there is lithium precipitation after 300 cycles. If lithium precipitation is found, it is judged as not passing. The test number is 10.

[0168] Example 1:

[0169] A battery cell 100, 50% SOC initial thickness 1.4mm, length 110mm, width 50mm, the assembly process is as follows:

[0170] (1) Preparation of negative electrode sheet: mix negative active material artificial graphite, conductive carbon black (Super P), and butadiene rubber (SBR) according to a weight ratio of 96:1.5:2.5, add deionized water as a solvent, and adjust to a slurry with a weight percentage of 50wt%, and stir uniformly. Pre-paste foam on part of the surface of the negative current collector copper foil with a thickness of 6μm, then uniformly coat the slurry on one surface of the copper foil, heat to make the foam fall off to expose part of the surface of the copper foil, and then dry at 110°C to obtain a negative electrode sheet with a negative active material layer coated on one side. When preparing a double-sided coated negative electrode sheet, repeat the above steps on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet with a negative active material layer. Then cold-press the coated sheet to a thickness of 105μm, and weld negative tabs on the copper foil exposed by the foam. The material of the negative tabs is copper.

[0171] (2) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5, and N-methyl pyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the slurry was stirred uniformly. The slurry was uniformly coated on one surface of an aluminum foil, and then dried at 90°C to obtain a positive electrode sheet coated with a positive electrode active material on one surface. When a double-coated positive electrode sheet was prepared, the above coating step was repeated on the other surface of the aluminum foil. The coated sheet was then cold-pressed to a thickness of 95 μm, and the negative electrode tab was welded to the positive electrode tab at the blank area of the edge of the aluminum foil, and the positive electrode tab was made of aluminum.

[0172] (3) Preparation of the electrolyte: In a dry argon atmosphere, first, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC: EMC: DEC = 30:50:20 to form a base organic solvent, and then lithium salt lithium hexafluorophosphate (LiPF6) was added to the base organic solvent to dissolve and mix uniformly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0173] (4) Preparation of the separator film: A 7-micron-thick polyethylene porous polymer film was used as the separator film.

[0174] (5) Preparation of the electrode assembly 10: The positive electrode sheet, the separator film, and the negative electrode sheet were wound and arranged.

[0175] (6) Assembly of the electrode assembly 10: The punched aluminum-plastic film was placed in the assembly jig with the pit surface facing upward, and the electrode assembly was placed in the pit and pressed tightly. Then, the other punched aluminum-plastic film was placed on the electrode assembly with the pit surface facing downward, and the four sides of the two aluminum-plastic films were heat-sealed by hot pressing to obtain an assembled electrode group.

[0176] (7) Liquid injection packaging: The electrolyte was injected into the assembled electrode assembly, and the secondary battery was obtained after vacuum packaging, standing, hot pressing, shaping, and other processes.

[0177] Table 1

[0178] (Except for the parameters involved in Table 1, the other parameters of Comparative Example 1 and Examples 1-15 were the same as those of Example 1.)

[0179] As can be seen from Comparative Example 1 and Examples 1-15, in the following four cases, the projection of the first starting end 112A is located on the side of the projection of the first connecting portion 21 away from the first bending section 10B, the projection of the second starting end 113A is located on the side of the projection of the first connecting portion 21 away from the first bending section 10B, the projection of the first ending end 112B is located on the side of the second connecting portion 31 away from the second bending section 10D, and the projection of the second ending end 113B is located on the side of the second connecting portion 31 away from the second bending section 10D, as long as at least one of the four cases is met, the thickness difference of the battery cell can be reduced, and the uniformity of the thickness of the battery cell 100 can be improved.

[0180] Table 2

[0181] (Example 18 is the same as Example 8, and Examples 16-17 and 19-32 are the same as Example 18 except for the parameters involved in Table 2.)

[0182] As can be seen from Examples 16-20, by limiting 2mm≤L1≤5mm, the energy density of the battery cell 100 can be improved. It should be noted that Example 16 is prone to cause a smaller tolerance reserved between the first starting end 112A and the first connecting portion 21, and in the process of connecting the first tab 20 to the first pole piece 11 or winding the electrode assembly 10, the first starting end 112A is prone to overlap with the first connecting portion 21, resulting in a space waste caused by the uneven outer surface of the battery cell 100.

[0183] As can be seen from Examples 21-24, by limiting 2mm≤L2≤5mm, the energy density of the battery cell 100 can be improved. It should be noted that Example 21 is prone to cause a smaller tolerance reserved between the second starting end 113A and the first connecting portion 21, and in the process of connecting the first tab 20 to the first pole piece 11 or winding the electrode assembly 10, the second starting end 113A is prone to overlap with the first connecting portion 21, resulting in a space waste caused by the uneven outer surface of the battery cell 100.

[0184] As can be seen from Examples 25-28, by limiting 2mm≤L3≤5mm, the energy density of the battery cell 100 can be improved. It should be noted that Example 25 is prone to cause a smaller tolerance reserved between the first ending end 112B and the second connecting portion 31, and in the process of connecting the second tab 30 to the second pole piece 12 or winding the electrode assembly 10, the first ending end 112B is prone to overlap with the second connecting portion 31, resulting in a space waste caused by the uneven outer surface of the battery cell 100.

[0185] It can be seen from Examples 29-32 that by limiting 2mm≤L4≤5mm, the energy density of the battery cell 100 can be improved. It should be noted that Example 29 is prone to cause a small tolerance reserved between the second end 113B and the second connecting portion 31, and in the process of connecting the second tab 30 to the second electrode piece 12 or the electrode assembly 10 winding, the second end 113B and the second connecting portion 31 are prone to overlap, resulting in a space waste caused by the uneven outer surface of the battery cell 100.

[0186] Table 3

[0187] (Example 35 is the same as Example 18, and Examples 33-34, 36-49 are the same as Example 35 except for the parameters involved in Table 3.)

[0188] It can be seen from Examples 33-37 that by limiting 0.2mm≤W1≤2mm, the cycle performance of the battery cell 100 can be improved. When W1>2mm, the first insulating piece covers more of the first active material layer, resulting in a loss of capacity and a loss of energy density.

[0189] It can be seen from Examples 38-41 that by limiting 0.2mm≤W2≤2mm, the cycle performance of the battery cell 100 can be improved. When W2>2mm, the first insulating piece covers more of the first active material layer, resulting in a loss of capacity and a loss of energy density.

[0190] It can be seen from Examples 42-45 that by limiting 0.2mm≤W3≤2mm, the cycle performance of the battery cell 100 can be improved. When W3>2mm, the first insulating piece covers more of the first active material layer, resulting in a loss of capacity and a loss of energy density.

[0191] It can be seen from Examples 46-49 that by limiting 0.2mm≤W4≤2mm, the cycle performance of the battery cell 100 can be improved. When W4>2mm, the first insulating piece covers more of the first active material layer, resulting in a loss of capacity and a loss of energy density.

[0192] Table 4

[0193] (Example 51 is the same as Example 35, and Examples 50, 52-57 are the same as Example 51 except for the parameters involved in Table 4.)

[0194] It can be seen from Examples 50-53 that by limiting L5≥2mm, the thickness difference of the battery cell can be reduced, which is conducive to improving the uniformity of the thickness of the battery cell 100.

[0195] It can be seen from Examples 54-57 that by limiting L6≥1mm, the thickness difference of the battery cell can be reduced, which is conducive to improving the uniformity of the thickness of the battery cell 100.

[0196] In summary, in the above-mentioned battery cell 100, secondary battery 200, and electronic device 300, for the first connecting portion 21, along the first direction Z, the projection of the first starting end 112A and / or the projection of the second starting end 113A is located on the side of the projection of the first connecting portion 21 away from the first bending section 10B, so as to reduce the space waste caused by the unevenness of the outer surface of the battery cell 100 due to the overlap of the first starting end 112A and / or the second starting end 113A with the first connecting portion 21, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100. For the second connecting portion 31, along the first direction Z, the projection of the first ending end 112B and / or the projection of the second ending end 113B is located on the side of the second connecting portion 31 away from the second bending section 10D, so as to reduce the space waste caused by the unevenness of the outer surface of the battery cell 100 due to the overlap of the first ending end 112B and / or the second ending end 113B with the second connecting portion 31, and to facilitate the improvement of the uniformity of the thickness of the battery cell 100.

Claims

1. An electric cell, characterized by, The battery cell comprises an electrode assembly, a first tab and a second tab; The electrode assembly comprises a first flat section, a first bent section, a second flat section and a second bent section connected in sequence, the first flat section and the second flat section are oppositely arranged along a first direction, the first bent section and the second bent section are oppositely arranged along a second direction, the first tab and the second tab extend out of the electrode assembly along a third direction, the first direction is a thickness direction of the battery cell, the first direction, the second direction and the third direction are perpendicular to each other; The electrode assembly further comprises a first tab, a second tab and a separator, the separator is arranged between the first tab and the second tab, the electrode assembly is wound by the first tab, the separator and the second tab around a winding center axis, the first tab comprises a first current collector, a first active material layer and a second active material layer, the first current collector comprises a first inner surface and a first outer surface, the first inner surface faces the winding center axis, the first outer surface faces away from the winding center axis, the first active material layer is connected to the first inner surface, the first active material layer comprises a first starting end and a first ending end, the second active material layer is connected to the first outer surface, the second active material layer comprises a second starting end and a second ending end; In the third direction, the first tab is located in the first flat section or the second flat section, the second tab is located in the first flat section or the second flat section, the first tab comprises a first connecting part connected to the first tab, the first connecting part is closer to the first bent section than the second bent section, the second tab comprises a second connecting part connected to the second tab, the second connecting part is closer to the second bent section than the first bent section; In the first direction, a projection of the first starting end and / or a projection of the second starting end is located on a side of the first connecting part away from the first bent section, and / or a projection of the first ending end and / or a projection of the second ending end is located on a side of the second connecting part away from the second bent section.

2. The cell of claim 1, wherein, In the second direction, a distance L1 between the first starting end and the first connecting part satisfies: 2mm≤L1≤5mm; and / or a distance L2 between the second starting end and the first connecting part satisfies: 2mm≤L2≤5mm.

3. The cell of any one of claims 1 to 2, wherein, In the second direction, a distance L3 between the first ending end and the second connecting part satisfies: 2mm≤L3≤5mm; and / or a distance L4 between the second ending end and the second connecting part satisfies: 2mm≤L4≤5mm.

4. The battery cell of any one of claims 1 to 3, wherein, The first inner surface comprises a first non-coating area beyond the first starting end, the first outer surface comprises a second non-coating area beyond the second starting end, the first connecting part is connected to the first non-coating area or the second non-coating area; The battery cell further comprises a first insulating member and a second insulating member; The first insulating member covers the first uncoated area and the first starting end, and includes a first overlapping portion covering the first active material layer, a length W1 of the first overlapping portion along the second direction satisfying 0.2 mm≤W1≤2 mm. The second insulating member covers the second uncoated area and the second starting end, and includes a second overlapping portion covering the second active material layer, a length W2 of the second overlapping portion along the second direction satisfying 0.2 mm≤W2≤2 mm. The first inner surface includes a third uncoated area beyond the first end, and the first outer surface includes a fourth uncoated area beyond the second end; 5. The battery cell of any one of claims 1 to 4, wherein, The battery cell further includes a third insulating member and a fourth insulating member; The third insulating member covers the third uncoated area and the first end, and includes a third overlapping portion covering the first active material layer, a length W3 of the third overlapping portion along the second direction satisfying 0.2 mm≤W3≤2 mm. The fourth insulating member covers the second uncoated area and the second end, and includes a fourth overlapping portion covering the second active material layer, a length W4 of the fourth overlapping portion along the second direction satisfying 0.2 mm≤W4≤2 mm. A first reference line passes through a first bending point of the first tab along the first direction, and a second reference line passes through a first bending point of the second tab along the first direction, the first reference line being closer to the first bending segment than the second bending segment, and the second reference line being closer to the second bending segment than the first bending segment; 6. The battery cell of any one of claims 1 to 5, wherein, The first connecting portion and the first reference line are spaced apart along the second direction; and / or The second connecting portion and the second reference line are spaced apart along the second direction. The second tab includes a second current collector and a third active material layer, the second current collector including a second outer surface, and the third active material layer connecting the second outer surface, the third active material layer including a third starting end; 7. The cell of claim 6, wherein, The third starting end is located between the first connecting portion and the first reference line along the second direction as viewed along the third direction. A distance L5 between the third starting end and the first reference line, and a distance L6 between the third starting end and the first connecting portion along the second direction satisfy L5≥2 mm and L6≥1 mm.

8. The cell of claim 7, wherein, The battery cell further includes an adapter tab, the adapter tab including a first extension segment and a second extension segment, one end of the first extension segment being connected to the first tab or the second tab, the other end of the first extension segment being connected to the second extension segment, and the second extension segment extending outward from the first extension segment along a third direction.

9. The battery cell of any one of claims 1 to 8, wherein, The adapter tab and the first tab are integrally formed; or the adapter tab and the second tab are integrally formed.

10. The cell of claim 9, wherein, The battery cell further includes a packaging bag, a first tab adhesive, and a second tab adhesive; 11. The battery cell of any one of claims 1 to 10, wherein, The packaging bag includes a main body portion and a top sealing edge, the electrode assembly being arranged in the main body portion, and the ​ The body portion includes a top wall, the top seal edge connects the top wall, the first tab and the second tab respectively extend from the top seal edge, the first tab adhesive is located on the top seal edge and covers part of the first tab, and the second tab adhesive is located on the top seal edge and covers part of the second tab.

12. The battery cell of any one of claims 1 to 11, wherein, In the first direction, the thickness of the battery cell is less than or equal to 2 mm.

13. A secondary battery characterized by comprising: The secondary battery includes the battery cell according to any one of claims 1 to 12.

14. An electronic device, comprising: The electronic device includes the battery cell according to any one of claims 1 to 12 or the secondary battery according to claim 13.

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