Secondary battery and electric device

Abstract

The invention relates to the technical field of energy storage, in particular to a secondary battery and an electric device. The secondary battery comprises a shell, an electrode assembly, a first tab group and a first adapter, the shell is provided with a containing cavity, and the electrode assembly is contained in the containing cavity. The first tab group is connected with the electrode assembly, the first tab group comprises a first outer-layer tab, at least one inner-layer tab and a second outer-layer tab which are sequentially arranged in the third direction, and the number of the inner-layer tabs is at least one. The first adapter comprises a first extending part and a first adapter part, the first extending part extends out of the shell in the first direction, the first adapter part is located in the shell, the first adapter part is located on the side, away from the inner-layer tab, of the second outer-layer tab when observed in the first direction, the first adapter part is connected with the second outer-layer tab, and the first direction is perpendicular to the third direction; the third direction is the thickness direction of the electrode assembly.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a secondary battery and an electrical device. Background Art

[0002] The core component of a secondary battery is the battery cell. For a fast-charging cell, the multi-ear design can shorten the electron transmission path. Multiple ears can also reduce the internal resistance of the secondary battery, thereby reducing the temperature rise of the secondary battery during fast charging. The battery cell with a multi-ear structure needs to be welded with an adapter as the electrode terminal for charging and discharging. For the ultra-thin fast-charging cell with a multi-ear structure, since the thickness of the battery cell is reduced, the adapter welding needs to adopt a direct-out solution during packaging, that is, the multi-layer ears are directly led out from the shell and then welded to the adapter. However, in the related technical solutions, the direct-out solution has the problem of ear position interference failure under stress test conditions such as collision and falling, which affects the safety of the secondary battery. Summary of the invention

[0003] In view of this, the present application provides a secondary battery and an electrical device, which can improve the safety of the secondary battery.

[0004] In a first aspect, an embodiment of the present application provides a secondary battery, comprising a housing, an electrode assembly, a first tab group, and a first adapter. The housing has a cavity, and the electrode assembly is accommodated in the cavity. The first tab group is connected to the electrode assembly, and the first tab group includes a first outer tab, an inner tab, and a second outer tab arranged in sequence along a third direction, and at least one inner tab is provided. The first adapter includes a first extension and a first adapter, the first extension extends out of the housing along a first direction, the first adapter is located in the housing, and when viewed along the first direction, the first adapter is located on the side of the second outer tab away from the inner tab, and the first adapter is connected to the second outer tab, and the first direction is perpendicular to the third direction, and the third direction is the thickness direction of the electrode assembly. The first outer tab and the second outer tab refer to the tabs located at the outermost layer in the third direction, that is, only one side has an inner tab adjacent, and both sides of the inner tab have outer tabs or other inner tabs adjacent.

[0005] In the above-mentioned secondary battery, the first pole lug group includes a first outer pole lug, an inner pole lug and a second outer pole lug arranged in sequence along a third direction, the first extension portion of the first adapter extends out of the shell along the first direction, the first adapter portion of the first adapter is connected to the second outer pole lug to form an adapter welding direct-out scheme, and when observed along the first direction, the first adapter portion is located on the side of the second outer pole lug away from the inner pole lug, so that the first adapter is located on the side of the first pole lug group as a whole away from the first outer pole lug along the third direction. When the secondary battery is subjected to vibration or impact along the first direction for multiple times, the first adapter is located on the side of the first pole lug group as a whole away from the first outer pole lug along the third direction, and the first adapter portion is difficult to cause impact interference to the first pole lug group, thereby improving the safety of the secondary battery.

[0006] In the above embodiments, the first outer electrode tab and the portion of the inner electrode tab away from the electrode assembly are gathered and stacked toward the side where the second outer electrode tab is located to form a first stacking portion, the first stacking portion is parallel to the first direction, the first transition portion is welded to the first stacking portion to form a first welding area, the secondary battery also includes an edge sealing member, the edge sealing member is at least partially arranged between the shell and the first transition portion to form a first edge sealing area, and the first welding area and the first edge sealing area are arranged along the first direction.

[0007] In the above-mentioned secondary battery, the edge sealing member is used to seal the gap between the housing and the first adapter to improve the sealing performance. The first welding area and the first edge sealing area are arranged along the first direction, thereby reducing the occupation of the secondary battery in the thickness direction, which is conducive to reducing the thickness of the secondary battery.

[0008] In one or more of the above embodiments, along the first direction, the total length of the first transition portion is L, the length of the first welding area is L1, the length between one end of the first welding area away from the electrode assembly and one end of the first overlapping portion away from the electrode assembly is L2, the length between one end of the first welding area close to the electrode assembly and one end of the first transition portion close to the electrode assembly is L3, the length between one end of the first edge sealing area close to the electrode assembly and one end of the first overlapping portion away from the electrode assembly is L4, and the total length of the first edge sealing area is L5, L=L1+L2+L3+L4+L5;

[0009] The length relationship satisfies at least one of the following conditions a 1 to e 1:

[0010] a 1.0.2mm≤L 1≤3mm;

[0011] b 1.0.01mm≤L2≤1.0mm;

[0012] c 1.0.01mm≤L3≤1.0mm;

[0013] d 1.0.01mm≤L4≤1.0mm;

[0014] e 1.3.5mm≤L5≤5.5mm.

[0015] In the above-mentioned secondary battery, when the length L1 of the first welding area, the length L2 between one end of the first welding area away from the electrode assembly and one end of the first overlapping portion away from the electrode assembly, the length L3 between one end of the first welding area close to the electrode assembly and one end of the first adapter portion close to the electrode assembly, the length L4 between one end of the first edge sealing area close to the electrode assembly and one end of the first overlapping portion away from the electrode assembly, and the total length L5 of the first edge sealing area meet their respective length requirements at the same time, it is beneficial to reduce the occupancy of the first adapter portion in the length direction of the secondary battery under the premise of stable connection, so as to improve the energy density.

[0016] In one or more of the above embodiments, the first transition portion is partially folded back to form a first transition section and a second transition section, the second transition section is connected to the first extension portion, and the first transition section and the second transition section are overlapped along a third direction; the first transition section connects a surface of the second outer layer ear away from the inner layer ear and is welded to the first overlapping portion to form a first welding area.

[0017] In the above-mentioned secondary battery, the first transition portion is partially folded back to form a first transition section and a second transition section, the second transition section is connected to the first extension portion, and the first transition section and the second transition section are overlapped along the third direction so that one end of the first transition portion facing the electrode assembly is rounded, which is beneficial to reducing the impact of the first transition portion on the first pole lug group when the secondary battery is subjected to vibration or impact along the first direction.

[0018] In one or more of the above embodiments, an end of the first transition section away from the electrode assembly is flush with an end of the first welding region away from the electrode assembly.

[0019] In the above-mentioned secondary battery, the end of the first transition section away from the electrode assembly is flush with the end of the first welding area away from the electrode assembly, so that the end of the first welding area away from the electrode assembly is closer to the end of the first edge sealing area close to the electrode assembly, thereby reducing the space occupied by the first transition part in the first direction, which is conducive to further improving the energy density of the secondary battery.

[0020] In one or more of the above embodiments, along the third direction, the projection of the first transition segment is located within the projection of the second transition segment.

[0021] In the above-mentioned secondary battery, the projection of the first adapter section is located within the projection of the second adapter section, which reduces the space occupied by the first adapter along the first direction, thereby improving the energy density of the secondary battery.

[0022] In one or more of the above embodiments, along the first direction, the total length of the second transition section is S, the length of the first welding area is S1, the length between one end of the first welding area close to the electrode assembly and one end of the first transition section close to the electrode assembly is S2, the length between one end of the first welding area away from the electrode assembly and one end of the first edge sealing area close to the electrode assembly is S3, and the total length of the first edge sealing area is S4, S=S1+S2+S3+S4;

[0023] The length relationship satisfies at least one of the following conditions a2 to d2:

[0024] a2.0.2mm≤S1≤3mm;

[0025] b2.0.01mm≤S2≤1.0mm;

[0026] c2.0.01mm≤S3≤1.0mm;

[0027] d2.3.5mm≤S4≤5.5mm.

[0028] In the above-mentioned secondary battery, when the length S1 of the first welding area, the length S2 between one end of the first welding area close to the electrode assembly and one end of the first adapter section close to the electrode assembly, the length S3 between one end of the first welding area away from the electrode assembly and one end of the first edge sealing area close to the electrode assembly, and the total length S4 of the first edge sealing area meet their respective length requirements at the same time, it is beneficial to further reduce the occupancy of the first adapter section in the length direction of the secondary battery under the premise of stable connection, so as to improve the energy density.

[0029] In one or more of the above embodiments, the secondary battery further includes a reinforcing sheet, which is connected to a surface of the first outer electrode tab away from the inner electrode tab and is welded to the first overlapping portion to form a second welding region.

[0030] In the above-mentioned secondary battery, by connecting the reinforcing sheet to a surface of the first outer layer pole ear away from the inner layer pole ear and welding it to the first overlapping portion, the reinforcing sheet is directly in contact with the welding head or the welding seat, thereby improving the problem of weak connection strength between the first outer layer pole ear and the inner layer pole ear, and reducing the risk of electrical connection failure caused by concentrated tensile stress on the first outer layer pole ear.

[0031] In one or more of the above embodiments, the thickness of the reinforcing sheet is 10 μm to 40 μm.

[0032] In the above-mentioned secondary battery, the thickness of the reinforcing sheet is 10μm to 40μm, so as to improve the problem of over-melting during welding due to the reinforcing sheet being too thin, and also to improve the problem of insufficient welding stability due to insufficient welding between the reinforcing sheet and the first outer layer tab during welding due to the reinforcing sheet being too thick.

[0033] In one or more of the above embodiments, the length of the second welding region is P1, where P1=L1.

[0034] In the above-mentioned secondary battery, the length of the second welding region is equal to the length of the first welding region, so that the first welding region and the second welding region can be processed simultaneously on the same equipment, thereby improving processing convenience.

[0035] In one or more of the above embodiments, along the first direction, the length between one end of the second welding region away from the electrode assembly and one end of the first overlapping portion away from the electrode assembly is P2, and 0.01 mm≤P2≤1 mm.

[0036] In the above-mentioned secondary battery, the length of the second welding area away from one end of the electrode assembly and the length of the first overlapping portion away from one end of the electrode assembly is greater than or equal to 0.01 mm and less than or equal to 1 mm, thereby limiting the length of the reinforcing sheet, which is beneficial to improving the problem of the secondary battery being too long and interfering with the edge sealing member, thereby improving the safety of the secondary battery.

[0037] In one or more of the above embodiments, along the first direction, a distance between an end of the second welding region close to the electrode assembly and an end of the reinforcing sheet close to the electrode assembly is P3, and 0.01 mm≤P3≤3 mm.

[0038] In the above-mentioned secondary battery, the length between one end of the second welding area close to the electrode assembly and one end of the first overlapping portion close to the electrode assembly is greater than or equal to 0.01 mm and less than or equal to 1 mm, thereby limiting the length of the reinforcing sheet, which is beneficial to improving the problem of the secondary battery being too long and interfering with the first pole lug group, thereby improving the safety of the secondary battery.

[0039] In one or more of the above embodiments, along the second direction, the width of the reinforcing sheet is Y5, the width of the second welding area is Y1, 0.1 mm ≤ Y5 - Y 1 ≤ 5 mm, and the first direction, the second direction and the third direction are perpendicular to each other.

[0040] In the secondary battery, the difference between the width of the reinforcing sheet and the width of the second welding area is greater than or equal to 0.1 mm and less than or equal to 5 mm, so that the second welding area is formed inside the reinforcing sheet, which is beneficial to improve the connection stability between the reinforcing sheet and the first overlapping portion.

[0041] In one or more of the above embodiments, the first outer layer pole lug portion is folded back to form a first pole lug segment and a second pole lug segment, the second pole lug segment is connected to the electrode assembly, and the first pole lug segment and the second pole lug segment are overlapped along a third direction; the first pole lug segment is arranged on a side of the second pole lug segment away from the second outer layer pole lug and is welded to the first transition portion to jointly form a first welding area.

[0042] In the above-mentioned secondary battery, by folding back the first outer layer pole lug portion, the first pole lug segment is arranged on the side of the second pole lug segment away from the second outer layer pole lug and welded to the first transition portion, so that the first pole lug segment is directly in contact with the welding head or welding seat, thereby improving the problem of weak connection strength between the second pole lug segment and the inner layer pole lug, and reducing the risk of electrical connection failure caused by concentrated tensile stress on the second pole lug segment.

[0043] In a second aspect, an embodiment of the present application provides an electrical device, comprising a secondary battery in one or more of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the overall structure of a secondary battery in one embodiment of the present application.

[0045] Figure 2 It is a schematic diagram of the disassembled structure of a secondary battery in one embodiment of the present application.

[0046] Figure 3 It is a schematic diagram of the connection structure between the first tab group and the first adapter in an embodiment of the present application.

[0047] Figure 4 It is a schematic diagram of the connection structure between the first tab group and the first adapter in another embodiment of the present application.

[0048] Figure 5 It is a schematic diagram of the connection structure between the first tab group and the first adapter in another embodiment of the present application.

[0049] Figure 6 yes Figure 5 A top view of the connection structure between the first tab group and the first adapter.

[0050] Figure 7 It is a schematic diagram of the connection structure between the first tab group and the first adapter in another embodiment of the present application.

[0051] Figure 8 It is a schematic diagram of the connection structure between the first tab group and the first adapter in another embodiment of the present application.

[0052] Fig. 9 It is a schematic diagram of the structure of an electrical device in an embodiment of the present application.

[0053] Main component symbols

[0054] 001 Secondary battery

[0055] 100 Electrode Assembly

[0056] 110 First Pole

[0057] 111 First Collection

[0058] 112 first active material layer

[0059] 120 Second pole piece

[0060] 121 Second Episode of Fluid

[0061] 122 second active material layer

[0062] 130 Diaphragm

[0063] 200 First tab group

[0064] 210 First outer tab

[0065] 211 First lug segment

[0066] 212 Second pole ear segment

[0067] 220 Inner tab

[0068] 230 Second outer tab

[0069] 240 first overlapping portion

[0070] 250 Reinforcement sheet

[0071] 300 Second tab set

[0072] 400 Housing

[0073] 410 cavity

[0074] 500 First adapter

[0075] 510 First extension

[0076] 520 First Transfer Unit

[0077] 521 First transfer section

[0078] 522 Second transfer section

[0079] 600 Second adapter

[0080] 710 First welding area

[0081] 720 Second welding area

[0082] 730 First edge banding area

[0083] 800 Edge Banding

[0084] 900 Protective Tape

[0085] 910 Adhesive layer

[0086] 910a First adhesive layer

[0087] 910b Second adhesive layer

[0088] 920 base material layer

[0089] 002 Electrical equipment

[0090] X first direction

[0091] Y Second direction

[0092] Z third direction DETAILED DESCRIPTION

[0093] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0094] It should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 mechanical connection or an electrical connection. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component at the same time. When a component is considered to be "provided on" another component, it can be directly provided on the other component or there may be an intermediate component at the same time.

[0095] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0096] The terms "first", "second", etc. are only used to distinguish different objects and shall not be understood as indicating or implying relative importance or implying the quantity, specific order or primary and secondary relationship of the indicated technical features.

[0097] The term "perpendicular" is used to describe an ideal state between two components. In actual production or use, two components may be in a state that is approximately perpendicular to each other. For example, in combination with numerical descriptions, perpendicularity can refer to the angle between two straight lines being within the range of 90°±10°, perpendicularity can also refer to the dihedral angle between two planes being within the range of 90°±10°, and perpendicularity can also refer to the angle between a straight line and a plane being within the range of 90°±10°.

[0098] The term "parallel" is used to describe an ideal state between two components. In actual production or use, two components may be approximately parallel. For example, in combination with numerical descriptions, parallel can refer to the angle between two straight lines being within the range of 180°±10°, parallel can also refer to the dihedral angle between two planes being within the range of 180°±10°, and parallel can also refer to the angle between a straight line and a plane being within the range of 180°±10°.

[0099] The first direction X includes a positive direction along the first direction X and a direction opposite to the first direction X, the second direction Y includes a positive direction along the second direction Y and a direction opposite to the second direction Y, and the third direction Z includes a positive direction along the third direction Z and a direction opposite to the third direction Z.

[0100] It should be noted that when a parameter is greater than, equal to, or less than a certain endpoint value, it should be understood that the endpoint value is allowed to have a tolerance of ±5%.

[0101] It should be recognized that the dimensions of the structures shown in the drawings are provided for better understanding and more convenient description, and the present application is not limited to the dimensions shown in the drawings. In order to make the present application clear, elements not related to the description are omitted from the details of the present specification.

[0102] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0103] One embodiment of the present application provides a secondary battery, including a shell, an electrode assembly, a first tab group and a first adapter. The shell has a cavity, and the electrode assembly is accommodated in the cavity. The first tab group is connected to the electrode assembly, and the first tab group includes a first outer tab, an inner tab and a second outer tab arranged in sequence along a third direction, and at least one inner tab is provided. The first adapter includes a first extension and a first adapter, the first extension extends out of the shell along a first direction, the first adapter is located in the shell, and when viewed along the first direction, the first adapter is located on the side of the second outer tab away from the inner tab, and the first adapter is connected to the second outer tab, and the first direction is perpendicular to the third direction, and the third direction is the thickness direction of the electrode assembly.

[0104] The first pole lug group includes a first outer pole lug, an inner pole lug and a second outer pole lug which are arranged in sequence along a third direction. The first extension portion of the first adapter extends out of the shell along the first direction. The first adapter portion of the first adapter is connected to the second outer pole lug to form an adapter welding direct-out scheme. When observed along the first direction, the first adapter portion is located on the side of the second outer pole lug away from the inner pole lug, so that the first adapter is located on the side of the first pole lug group as a whole away from the first outer pole lug along the third direction. When the secondary battery is subjected to vibration or impact along the first direction for multiple times, the first adapter is located on the side of the first pole lug group as a whole away from the first outer pole lug along the third direction. The first adapter portion is unlikely to cause impact interference to the first pole lug group, thereby improving the safety of the secondary battery.

[0105] Some embodiments of the present application are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the features in the following embodiments and examples can be combined with each other.

[0106] See also Figure 1 and Figure 2 The embodiment of the present application provides a secondary battery 001, which includes an electrode assembly 100 and a first tab group 200, wherein the first tab group 200 is connected to the electrode assembly 100. The secondary battery 001 also includes a second tab group 300, wherein the second tab group 300 is connected to the electrode assembly 100, and the first tab group 200 and the second tab group 300 have different polarities.

[0107] In some embodiments, the secondary battery 001 further includes a housing 400, the housing 400 having a cavity 410, and the electrode assembly 100 is accommodated in the cavity 410 in the housing 400. The first tab group 200 is connected to a conductive first adapter 500, and the first adapter 500 partially extends out of the housing 400 and is used to be electrically connected to an external structure. The second tab group 300 is connected to a conductive second adapter 600, and the second adapter 600 partially extends out of the housing 400 and is used to be electrically connected to an external structure.

[0108] In some embodiments, the shell 400 includes at least one of a steel shell, a resin shell or an aluminum-plastic film. For example, when the secondary battery 001 is a hard-shell battery, the shell 400 includes a steel shell or a resin shell. When the secondary battery 001 is a soft-pack battery, the shell 400 includes an aluminum-plastic film.

[0109] See also Figure 2 and Figure 3 In some embodiments, the electrode assembly 100 includes a first electrode sheet 110, a second electrode sheet 120 and a diaphragm 130, the diaphragm 130 is disposed between the first electrode sheet 110 and the second electrode sheet 120, and the first electrode sheet 110, the second electrode sheet 120 and the diaphragm 130 are stacked and wound to form a winding structure.

[0110] In other embodiments, the electrode assembly 100 includes a first electrode plate 110, a second electrode plate 120 and a diaphragm 130, the diaphragm 130 is disposed between the first electrode plate 110 and the second electrode plate 120, and the first electrode plate 110 and the second electrode plate 120 are stacked in sequence to form a stacked structure.

[0111] In some embodiments, the first electrode tab group 200 is electrically connected to the electrode assembly 100 .

[0112] In some embodiments, the first electrode sheet 110 includes a first current collector 111 and a first active material layer 112 coated on a surface of the first current collector 111 , and the first electrode tab group 200 is formed by extending the first current collector 111 along a width direction of the first current collector 111 .

[0113] In some embodiments, the second tab group 300 is electrically connected to the electrode assembly 100 .

[0114] In some embodiments, the second electrode sheet 120 includes a second current collector 121 and a second active material layer 122 coated on a surface of the second current collector 121 , and the second electrode tab group 300 is formed by extending the second current collector 121 along a width direction of the second current collector 121 .

[0115] The following is a detailed description of the connection structure between the first tab group 200 and the first adapter 500. In some embodiments, the connection structure between the second tab group 300 and the second adapter 600 is the same as the connection structure between the first tab group 200 and the first adapter 500; in other embodiments, the connection structure between the second tab group 300 and the second adapter 600 is the same as the connection method between the first tab group 200 and the first adapter 500, with the only difference being the layout size.

[0116] See also Figure 2 and Figure 3 In some embodiments, the first electrode tab group 200 is located at one side of the electrode assembly 100 along the first direction X. The first direction X is the length direction of the secondary battery 001 .

[0117] In some embodiments, the first tab group 200 includes a first outer tab 210, an inner tab 220, and a second outer tab 230 sequentially arranged along a third direction Z, and at least one inner tab 220 is provided. The third direction Z is the thickness direction of the secondary battery 001, and the first direction X is perpendicular to the third direction Z.

[0118] In some embodiments, there are N inner tabs 220 , where N is a positive integer greater than or equal to 2.

[0119] In some embodiments, the first outer electrode tab 210 and the inner electrode tab 220 are bent away from the electrode assembly 100 toward the side where the second outer electrode tab 230 is located, and are stacked together to form a first stacking portion 240 .

[0120] In some embodiments, the second outer tab 230 is not bent.

[0121] In some embodiments, the first adapter 500 includes a first extending portion 510 and a first adapter portion 520 . The first extending portion 510 extends out of the housing 400 along the first direction X, and the first adapter portion 520 is located inside the housing 400 .

[0122] The first stacking portion 240 is parallel to the first direction X. The first transition portion 520 is connected to a surface of the second outer electrode tab 230 away from the inner electrode tab 220 and is welded to the first stacking portion 240 to form a first welding region 710 .

[0123] The first electrode tab group 200 includes a first outer electrode tab 210, an inner electrode tab 220, and a second outer electrode tab 230 arranged in sequence along the third direction Z. The first outer electrode tab 210 and the inner electrode tab 220 away from the electrode assembly 100 are gathered and stacked toward the side where the second outer electrode tab 230 is located to form a first stacking portion 240. The first stacking portion 240 is parallel to the first direction X. After the first stacking portion 240 is connected to the first adapter 500, the first extension portion 510 of the first adapter 500 extends out of the housing 400 along the first direction X to form a transfer welding direct-out solution. Since the first outer electrode tab 210 and the inner electrode tab 220 away from the electrode assembly 100 are gathered toward the side where the second outer electrode tab 230 is located, and the first adapter portion 520 is connected to a surface of the second outer electrode tab 230 away from the inner electrode tab 220, so that the first The adapter 500 is located on a side of the first pole tab group 200 that is away from the first outer pole tab 210 along the third direction Z. When the secondary battery 001 is subjected to vibration or impact along the first direction X for multiple times, the first stacking portion 240 is straightened along the first direction X, and the first adapter 500 is located on a side of the first pole tab group 200 that is away from the first outer pole tab 210 along the third direction Z. The first adapter portion 520 is unlikely to cause impact interference to the first pole tab group 200, thereby improving the safety of the secondary battery 001.

[0124] In some embodiments, the secondary battery 001 further includes an edge sealer 800 , which is at least partially disposed between the housing 400 and the first adapter 520 and forms a first edge sealer region 730 . The first welding region 710 and the first edge sealer region 730 are arranged along the first direction X.

[0125] In some embodiments, the edge sealing member 800 is tab glue.

[0126] In some embodiments, along the first direction X, the length of the first welding region 710 is L1, 0.2 mm≤L1≤3 mm.

[0127] In some embodiments, along the first direction X, a length between an end of the first welding region 710 away from the electrode assembly 100 and an end of the first overlapping portion 240 away from the electrode assembly 100 is L2, and 0.01 mm≤L2≤1.0 mm.

[0128] In some embodiments, along the first direction X, a length between an end of the first welding region 710 close to the electrode assembly 100 and an end of the first transition portion 520 close to the electrode assembly 100 is L3, and 0.01 mm≤L3≤1.0 mm.

[0129] In some embodiments, along the first direction X, a length between an end of the first edge sealing region 730 close to the electrode assembly 100 and an end of the first overlapping portion 240 away from the electrode assembly 100 is L4, and 0.01 mm≤L4≤1.0 mm.

[0130] In some embodiments, along the first direction X, the total length of the first edge-sealed area 730 is L5, and 3.5 mm≤L5≤5.5 mm.

[0131] In some embodiments, along the first direction X, the total length of the first transition portion 520 is L, L=L1+L2+L3+L4+L5. The length of the end of the first welding area 710 close to the electrode assembly 100 and the end of the first transition portion 520 close to the electrode assembly 100 can share the space along the first direction X with the bent portion of the first tab group 200. At the same time, the end of the first transition portion 520 close to the electrode assembly 100 can extend to the area where the first stacking portion 240 close to the electrode assembly 100 is located and does not occupy the overall thickness of the battery cell, thereby improving the energy density of the secondary battery 001.

[0132] In some embodiments, two surfaces of the first welding region 710 are covered with protective members respectively.

[0133] In some embodiments, the protective member is a protective adhesive tape 900 .

[0134] In some embodiments, the protective tape 900 includes an adhesive layer 910 and a substrate layer 920. One side of the adhesive layer 910 is bonded to the first welding area 710, and the other side of the adhesive layer 910 is bonded to the substrate layer 920. The substrate layer 920 is in contact with the shell 400, thereby playing an isolation and insulation role.

[0135] In some embodiments, the protective adhesive tape 900 includes a first adhesive layer 910a, a substrate layer 920 and a second adhesive layer 910b. The substrate layer 920 is disposed between the first adhesive layer 910a and the second adhesive layer 910b. The first adhesive layer 910a is bonded to the first welding area 710, and the first adhesive layer 910a is bonded to the shell 400. While playing the role of isolation and insulation, it also plays the role of fixing the relative position of the first welding area 710 and the shell 400, thereby improving the position stability of the first welding area 710.

[0136] See also Figure 2 and Figure 4 In some embodiments, the first transition portion 520 is partially folded back to form a first transition section 521 and a second transition section 522, the second transition section 522 is connected to the first extension portion 510, and the first transition section 521 and the second transition section 522 are overlapped along the third direction Z. The first transition section 521 is connected to a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded to the first overlapping portion 240 to form a first welding area 710.

[0137] In some embodiments, the projection of the first transition segment 521 is located within the projection of the second transition segment 522 , that is, along the first direction X, the length of the first transition segment 521 is less than the length of the second transition segment 522 .

[0138] In some embodiments, the end of the first transition section 521 away from the electrode assembly 100 is flush with the end of the first welding region 710 away from the electrode assembly 100. It is worth noting that the above-mentioned "flush" means that along the first direction X, the distance between the end of the first transition section 521 away from the electrode assembly 100 and the end of the first welding region 710 away from the electrode assembly 100 is close to 0mm to 1.0mm; and / or along the first direction X, the distance between the end of the first stacking portion 240 away from the electrode assembly 100 and the end of the first welding region 710 away from the electrode assembly 100 is close to 0mm to 1.0mm.

[0139] The first adapter 500 is welded to the first stacking portion 240 before being folded back to form a first welding area 710, and then the first adapter 500 and the first stacking portion 240 are cut flat on a side away from the electrode assembly 100, and the tolerance of the cutting position from the first welding area 710 is designed to be -1.0 mm to 1.0 mm. Then the first adapter 500 is folded back.

[0140] In some embodiments, along the first direction X, the length of the first welding region 710 is S1, and 0.2 mm≤S1≤3 mm.

[0141] In some embodiments, along the first direction X, a length between an end of the first welding region 710 close to the electrode assembly 100 and an end of the first transition section 522 close to the electrode assembly 100 is S2, and 0.01 mm≤S2≤1.0 mm.

[0142] In some embodiments, along the first direction X, a length between an end of the first welding region 710 away from the electrode assembly 100 and an end of the first edge sealing region 730 close to the electrode assembly 100 is S3, and 0.01 mm≤S 3≤1.0 mm.

[0143] In some embodiments, along the first direction X, the total length of the first edge-sealed area 730 is S4, and 3.5 mm≤S4≤5.5 mm.

[0144] In some embodiments, along the first direction X, the total length of the second transition section 522 is S, S=S1+S2+S3+S4. Among them, the end of the first transition section 521 away from the electrode assembly 100 is flush with the end of the first welding area 710 away from the electrode assembly 100, so that the end of the first welding area 710 away from the electrode assembly 100 is closer to the end of the first edge sealing area 730 close to the electrode assembly 100, thereby further improving the energy density of the secondary battery 001.

[0145] See also Figure 2 and Figure 5 In some embodiments, the secondary battery 001 further includes a reinforcing sheet 250, which is connected to a surface of the first outer layer tab 210 away from the inner layer tab 220 and welded to the first overlapping portion 240 to form a second welding area 720. During the welding process, the first outer layer tab 210 is in direct contact with the welding head or welding seat, so the connection strength between the first outer layer tab 210 and the inner layer tab 220 is relatively weak. By connecting the reinforcing sheet 250 to a surface of the first outer layer tab 210 away from the inner layer tab 220 and welding it to the first overlapping portion 240, the reinforcing sheet 250 is directly in contact with the welding head or welding seat, thereby improving the problem of the weak connection strength between the first outer layer tab 210 and the inner layer tab 220, and reducing the risk of electrical connection failure caused by tensile stress concentration on the first outer layer tab 210.

[0146] In some embodiments, along the first direction X, the length of the second welding region 720 is P1, P1=L1, that is, the length of the second welding region 720 is equal to the length of the first welding region 710.

[0147] In some embodiments, along the first direction X, a length between an end of the second welding region 720 away from the electrode assembly 100 and an end of the first overlapping portion 240 away from the electrode assembly 100 is P2, and 0.01 mm≤P2≤1 mm.

[0148] In some embodiments, along the first direction X, a distance between an end of the second welding region 720 close to the electrode assembly 100 and an end of the reinforcing sheet 250 close to the electrode assembly 100 is P3, and 0.01 mm≤P3≤3 mm.

[0149] In some embodiments, the thickness of the reinforcement sheet 250 is 10 μm to 40 μm.

[0150] See also Figure 2 , Figure 5 and Figure 6 In some embodiments, along the second direction Y, the width of the reinforcing sheet 250 is Y5, the width of the second welding area 720 is Y1, 0.1 mm ≤ Y5 - Y 1 ≤ 5 mm. The second direction Y is the width direction of the secondary battery 001, and the first direction X, the second direction Y and the third direction Z are perpendicular to each other.

[0151] Along the second direction Y, the difference between the width of the reinforcing sheet 250 and the width of the second welding area 720 is greater than or equal to 0.1 mm and less than or equal to 5 mm, so that the second welding area 720 is formed inside the reinforcing sheet 250, which is beneficial to improve the connection stability between the reinforcing sheet 250 and the first overlapping portion 240.

[0152] In some embodiments, the material of the reinforcing sheet 250 is the same as that of the first tab group 200 .

[0153] In some embodiments, the first electrode sheet 110 is a positive electrode sheet, and the reinforcing sheet 250 is made of aluminum foil.

[0154] In some embodiments, the first electrode sheet 110 is a negative electrode sheet, and the reinforcing sheet 250 is made of copper foil or nickel foil.

[0155] See also Figure 2 and Figure 7 In some embodiments, the first transition portion 520 is partially folded back to form a first transition section 521 and a second transition section 522, the second transition section 522 is connected to the first extension portion 510, and the first transition section 521 and the second transition section 522 are overlapped along the third direction Z. The first transition section 521 is connected to a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded to the first overlapping portion 240 to form a first welding area 710.

[0156] The secondary battery 001 further includes a reinforcing sheet 250 . The reinforcing sheet 250 is connected to a surface of the first outer electrode tab 210 away from the inner electrode tab 220 and is welded to the first overlapping portion 240 to form a second welding region 720 .

[0157] The end of the first transition section 521 away from the electrode assembly 100 is flush with the end of the first welding area 710 away from the electrode assembly 100, so that the end of the first welding area 710 away from the electrode assembly 100 is closer to the end of the first edge sealing area 730 close to the electrode assembly 100, thereby further improving the energy density of the secondary battery 001. By connecting the reinforcing sheet 250 to a surface of the first outer layer tab 210 away from the inner layer tab 220 and welding it to the first overlapping portion 240, the reinforcing sheet 250 is directly in contact with the welding head or welding seat, thereby improving the problem of weak connection strength between the first outer layer tab 210 and the inner layer tab 220, and reducing the risk of electrical connection failure caused by tensile stress concentration on the first outer layer tab 210.

[0158] See also Figure 2 and Figure 8 In some embodiments, the first outer electrode tab 210 is partially folded back to form a first electrode tab segment 211 and a second electrode tab segment 212. The second electrode tab segment 212 is connected to the electrode assembly 100. The first electrode tab segment 211 and the second electrode tab segment 212 are overlapped along the third direction Z.

[0159] The first pole lug segment 211 is arranged on the side of the second pole lug segment 212 away from the second outer pole lug 230 and is welded to the first transition portion 520 to form a first welding area 710. During the welding process, the first outer pole lug 210 is in direct contact with the welding head or welding seat, so the connection strength between the first outer pole lug 210 and the inner pole lug 220 is relatively weak. By partially folding back the first outer pole lug 210, the first pole lug segment 211 is arranged on the side of the second pole lug segment 212 away from the second outer pole lug 230 and is welded to the first transition portion 520, so that the first pole lug segment 211 is in direct contact with the welding head or welding seat, thereby improving the problem of the weak connection strength between the second pole lug segment 212 and the inner pole lug 220 and reducing the risk of electrical connection failure caused by the tensile stress concentration of the second pole lug segment 212.

[0160] In some embodiments, along the first direction X, the length of the first pole lug segment 211 is greater than the length of the first welding region 710 , so that the first welding region 710 is formed inside the first pole lug segment 211 , which is beneficial to improve the connection stability between the first pole lug segment 211 and the first stacking portion 240 .

[0161] See also Figure 2 , Figure 4 and Figure 8In some embodiments, the first transition portion 520 is partially folded back to form a first transition section 521 and a second transition section 522, the second transition section 522 is connected to the first extension portion 510, and the first transition section 521 and the second transition section 522 are overlapped along the third direction Z. The first transition section 521 is connected to a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded to the first overlapping portion 240 to form a first welding area 710.

[0162] The first outer electrode tab 210 is partially folded back to form a first electrode tab segment 211 and a second electrode tab segment 212 . The second electrode tab segment 212 is connected to the electrode assembly 100 . The first electrode tab segment 211 and the second electrode tab segment 212 are overlapped along the third direction Z.

[0163] The first electrode tab segment 211 is disposed on a side of the second electrode tab segment 212 away from the second outer electrode tab 230 and is welded to the first transition portion 520 to form a first welding region 710 .

[0164] The first outer layer tab 210 is partially folded back to form the first tab segment 211 and the second tab segment 212, the first adapter 500 is welded to the first stacking portion 240 before being folded back to form the first welding area 710, and then the first adapter 500 and the first stacking portion 240 are cut flat on the side away from the electrode assembly 100, and the tolerance of the cutting position from the first welding area 710 is designed to be -1.0 mm to 1.0 mm. Then the first adapter 500 is folded back.

[0165] The end of the first transition section 521 away from the electrode assembly 100 is flush with the end of the first welding area 710 away from the electrode assembly 100, so that the end of the first welding area 710 away from the electrode assembly 100 is closer to the end of the first edge sealing area 730 close to the electrode assembly 100, thereby further improving the energy density of the secondary battery 001. By partially folding back the first outer layer tab 210, the first tab segment 211 is arranged on the side of the second tab segment 212 away from the second outer layer tab 230 and welded to the first transition portion 520, so that the first tab segment 211 is directly in contact with the welding head or welding seat, improving the problem of weak connection strength between the second tab segment 212 and the inner layer tab 220, and reducing the risk of electrical connection failure caused by tensile stress concentration on the second tab segment 212.

[0166] See also Fig. 9 An embodiment of the present application further provides an electric device 002, comprising the secondary battery 001 in one or more of the above embodiments.

[0167] In order to verify the influence of the position and connection structure of the first adapter 500 on the safety of the tab in the secondary battery 001, the following test was conducted:

[0168] (1) Drop test: 10 secondary batteries 001 were taken from each group of comparative examples and each group of examples for testing. The secondary batteries 001 of the examples and comparative examples were dropped from a height of 1.5 meters. The secondary batteries 001 were then disassembled and the tabs in the first tab group 200 were observed with the naked eye to see whether they were loose. A microscope was used to observe whether the tabs were broken or cracked.

[0169] (2) Cycle test: After 10 secondary batteries 001 are taken from each group of comparative examples and each group of examples for drop test, each secondary battery 001 is subjected to cycle test, each secondary battery 001 is placed in a 25°C environment for 30 minutes, and then charged and discharged according to the following steps. Charge to 4.2V at 5C constant current, then charge to 4.3V at 4C constant current, then charge to 4.45V at 3C constant current, then charge to 0.05C at 4.45V constant voltage, stand for 5 minutes, discharge to 3V at 1C constant current, stand for 5 minutes, this is one cycle. Cycle 1000 times according to the above cycle steps. After the cycle test, calculate the capacity retention rate of a single secondary battery 001. The capacity retention rate is the ratio of the discharge capacity after 1000 cycles to the discharge capacity of the first cycle. Record the capacity retention rate of 10 secondary batteries 001 in each group of comparative examples and each group of examples after 1000 cycles, and calculate its average value.

[0170] The specific implementation of the secondary battery 001 in the embodiment and the comparative example is described below.

[0171] Embodiment 1:

[0172] A secondary battery 001, the assembly process is as follows:

[0173] (1) Preparation of anode pole piece: The anode active material artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96:1.5:2.5, and deionized water is added as a solvent to prepare an anode active material slurry with a weight percentage of 70wt%, and stirred evenly for use. A copper foil with a thickness of 10μm is used as the anode current collector, and the above-mentioned anode active material slurry is evenly coated on one surface of the anode current collector along its thickness direction using a slit coater, wherein an empty foil area without an anode active material layer is reserved at one end in the width direction of the anode current collector, and dried at 110°C to obtain an anode pole piece substrate coated with an anode active material layer on one side. Then, the above steps are repeated on the other side of the anode current collector along its thickness direction, and an empty foil area without an anode active material layer is reserved at one end in the width direction of the anode current collector to obtain an anode pole piece substrate coated with an anode active material layer on both sides, wherein the compression of the anode active material layer is 1.70g / cm 3The anode plate substrate is punched out using a mold and a die cutter to obtain a single anode plate, wherein the empty foil area where the anode active material layer is not provided forms an anode tab. There are multiple anode tabs.

[0174] (2) Preparation of cathode electrode: The cathode active material lithium cobalt oxide (LiCoO 2 ), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a cathode active material slurry with a solid content of 75wt%, and stirred evenly for use. A 10μm thick aluminum foil is used as the cathode current collector, and a slit coater is used to evenly coat the above cathode active material slurry on one surface of the cathode current collector along its thickness direction, wherein an empty foil area without a cathode active material layer is reserved at one end in the width direction of the cathode current collector, and dried at 90°C to obtain a cathode pole sheet substrate coated with a cathode active material layer on one side. Then repeat the above steps on the other side of the cathode current collector along its thickness direction, and reserve an empty foil area without a cathode active material layer at one end in the width direction of the cathode current collector to obtain a cathode pole sheet substrate coated with a cathode active material layer on both sides. A single cathode pole piece is obtained by punching the cathode pole piece substrate using a mold and a die cutter, wherein a cathode pole ear is formed at an empty foil area where no cathode active material layer is provided, and a plurality of cathode pole ears are provided.

[0175] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed at a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF4) was added to the basic organic solvent. 6 ) are dissolved and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L, wherein the conductivity of the electrolyte is 8.0 S / m.

[0176] (4) Preparation of the diaphragm 130: The diaphragm 130 has a three-layer structure and a thickness of 5 μm, and includes a first adhesive layer, a first substrate layer 920, and a second adhesive layer stacked in layers. The first substrate layer 920 is made of polyethylene (PE), and both the first adhesive layer and the second adhesive layer contain a first adhesive and boehmite.

[0177] (5) Preparation of electrode assembly 100: A first electrode sheet 110, a separator 130 and a second electrode sheet 120 are stacked along a third direction Z to form a winding layer, and the winding layer is wound to form a winding structure. After winding, the pole tabs on the first electrode sheet 110 form a first pole tab group 200, and the first pole tab group 200 includes a first outer layer pole tab 210, an inner layer pole tab 220 and a second outer layer pole tab 230 arranged in sequence along the third direction Z, and a plurality of inner layer pole tabs 220 are provided. The first outer layer pole tab 210 and the inner layer pole tab 220 are bent away from the electrode assembly 100 toward the side where the second outer layer pole tab 230 is located, and are gathered and stacked to form a first stacking portion 240, and the second outer layer pole tab 230 is not bent. The first adapter 500 includes a first extension portion 510 and a first adapter portion 520. The first adapter portion 520 connects a surface of the second outer electrode tab 230 away from the inner electrode tab 220 and is welded to the first stacking portion 240 to form a first welding area 710 (referred to as below the first stacking portion 240 in the table).

[0178] (6) Assembly of the electrode assembly 100: Place the aluminum-plastic film with the holes punched and formed in an assembly fixture, with the holes facing upward, place the electrode assembly 100 in the holes, and apply external force to press it. Then, place another aluminum-plastic film with the holes punched and formed on the electrode assembly 100 with the holes facing downward, and heat-seal the four sides of the two aluminum-plastic films by hot pressing to obtain an assembled electrode assembly 100.

[0179] (7) Liquid injection packaging: The electrolyte is injected into the assembled electrode assembly 100, and the secondary battery 001 is obtained through processes such as vacuum packaging, static standing, hot pressing, and shaping.

[0180] Comparative Example 1: The first outer layer tab 210 and the inner layer tab 220 are bent toward the side where the second outer layer tab 230 is located, and are stacked together to form a first stacking portion 240, and the second outer layer tab 230 is not bent. The difference from Example 1 is that the first transition portion 520 connects a surface of the first outer layer tab 210 away from the inner layer tab 220 and is welded to the first stacking portion 240 (referred to as the upper portion of the first stacking portion 240 in the table).

[0181] Embodiment 2: The difference from Embodiment 1 is that the first adapter 500 is welded to the first overlapping portion 240 before being folded back to form a first welding area 710, and then the first adapter 500 and the first overlapping portion 240 are cut flat on the side away from the electrode assembly 100, and the tolerance of the cutting position from the first welding area 710 is designed to be -1.0mm to 1.0mm. Then the first adapter 500 is folded back to form a first transfer section 521 and a second transfer section 522, and the second transfer section 522 is connected to the first extension portion 510, and the first transfer section 521 and the second transfer section 522 are overlapped along the third direction Z. Along the first direction X, the overlapping length of the first transfer section 521 and the second transfer section 522 is C1. The first transfer section 521 connects to a surface of the second outer layer pole ear 230 away from the inner layer pole ear 220 and is welded to the first overlapping portion 240 to form a first welding area 710.

[0182] Embodiment 3 is different from Embodiment 1 in that the reinforcing sheet 250 is connected to a surface of the first outer electrode tab 210 away from the inner electrode tab 220 and is welded to the first overlapping portion 240 to form a second welding area 720 .

[0183] Embodiment 4: The difference from Embodiment 3 is that the first adapter 500 is welded to the first overlapping portion 240 before being folded back to form the first welding area 710, and then the first adapter 500 and the first overlapping portion 240 are cut flat on the side away from the electrode assembly 100, and the tolerance of the cutting position from the first welding area 710 is designed to be -1.0mm to 1.0mm. Then the first adapter 500 is folded back to form a first transfer section 521 and a second transfer section 522, and the second transfer section 522 is connected to the first extension portion 510, and the first transfer section 521 and the second transfer section 522 are overlapped along the third direction Z. The first transfer section 521 is connected to a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded to the first overlapping portion 240 to form the first welding area 710.

[0184] Embodiment 5: The difference from Embodiment 1 is that the first outer layer pole lug 210 is partially folded back to form a first pole lug segment 211 and a second pole lug segment 212, the second pole lug segment 212 is connected to the electrode assembly 100, and the first pole lug segment 211 and the second pole lug segment 212 are overlapped along the third direction Z. The first pole lug segment 211 is arranged on a side of the second pole lug segment 212 away from the second outer layer pole lug 230 and is welded to the first transition portion 520 to form a first welding area 710. Along the first direction X, the first pole lug segment 211 and the second pole lug segment 212 overlap by a length C2.

[0185] Embodiment 6: The difference from Embodiment 5 is that the first adapter 500 is welded to the first overlapping portion 240 before being folded back to form the first welding area 710, and then the first adapter 500 and the first overlapping portion 240 are cut flat on the side away from the electrode assembly 100, and the tolerance of the cutting position from the first welding area 710 is designed to be -1.0mm to 1.0mm. Then the first adapter 500 is folded back to form a first transfer section 521 and a second transfer section 522, and the second transfer section 522 is connected to the first extension portion 510, and the first transfer section 521 and the second transfer section 522 are overlapped along the third direction Z. The first transfer section 521 is connected to a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded to the first overlapping portion 240 to form the first welding area 710.

[0186] The main parameter control and test results of each embodiment and comparative example are shown in Table 1:

[0187] Table 1

[0188]

[0189] Note: “ / ” means no value.

[0190] Embodiment 1: Compared with comparative example 1, the first adapter 520 connects a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded to the first stacking portion 240. Since the first adapter 520 is offset toward the electrode assembly 100, the energy density is increased by about 0.5%. When the secondary battery 001 is subjected to vibration or impact along the first direction X for many times, the first adapter 520 is located on the side of the first tab group 200 as a whole away from the first outer layer tab 210 along the third direction Z. The first adapter 520 is unlikely to cause impact interference to the first tab group, and the first tab group 200 is safer. In this embodiment, after 10 secondary batteries 001 were subjected to a drop test, when a cycle test experiment was conducted, the risk of interference failure of the first tab group 200 was reduced, and the average capacity retention rate was increased from 78% to 82%, with a significant improvement effect.

[0191] Embodiment 2: Compared with Embodiment 1, the first transition portion 520 is partially folded back to form a first transition section 521 and a second transition section 522, the second transition section 522 is connected to the first extension portion 510, the first transition section 521 and the second transition section 522 are overlapped along the third direction Z, the first transition section 521 is connected to a surface of the second outer layer pole ear 230 away from the inner layer pole ear 220 and is welded to the first stacking portion 240 to form a first welding area 710. Since the end of the first transition section 521 away from the electrode assembly 100 is flush with the end of the first welding area 710 away from the electrode assembly 100, the length of the end of the first welding area 710 away from the electrode assembly 100 and the end of the first stacking portion 240 away from the electrode assembly 100 is close to 0, which further saves space in the first direction, and thus the energy density is increased to 1.2%. After the first transition section 521 and the second transition section 522 are overlapped along the third direction Z, compared with Example 1, the connection stability between the first transition portion 520 and the first overlapping portion 240 is similar, and the average capacity retention rate is increased from 82% to 84%, but the improvement effect is not obvious.

[0192] Embodiment 3: Compared with Embodiment 1, the reinforcing sheet 250 is connected to a surface of the first outer layer pole ear 210 away from the inner layer pole ear 220 and is welded to the first overlapping portion 240 to form a second welding area 720, so that during the welding process of the first outer layer pole ear 210, the reinforcing sheet 250 is in direct contact with the welding head or the welding seat, thereby improving the problem of weak connection strength between the first outer layer pole ear 210 and the inner layer pole ear 220, reducing the risk of electrical connection failure caused by tensile stress concentration on the first outer layer pole ear 210, and further improving the connection stability between the first adapter portion 520 and the first overlapping portion 240, and the average capacity retention rate is increased from 82% to 85%, with a significant improvement effect.

[0193] Embodiment 4: Compared with Embodiment 3, the first transition portion 520 is partially folded back to form a first transition section 521 and a second transition section 522, the second transition section 522 is connected to the first extension portion 510, the first transition section 521 and the second transition section 522 are overlapped along the third direction Z, the first transition section 521 is connected to a surface of the second outer layer pole ear 230 away from the inner layer pole ear 220 and is welded to the first overlapping portion 240 to form a first welding area 710. Since the end of the first transition section 521 away from the electrode assembly 100 is flush with the end of the first welding area 710 away from the electrode assembly 100, the length of the end of the first welding area 710 away from the electrode assembly 100 and the end of the first overlapping portion 240 away from the electrode assembly 100 is close to 0, which further saves space in the first direction, so the energy density is increased from 0.5% to 1.2%, and the improvement effect is obvious.

[0194] Embodiment 5: Compared with Embodiment 1, the first outer layer pole lug 210 is partially folded back to form a first pole lug segment 211 and a second pole lug segment 212, and the second pole lug segment 212 is connected to the electrode assembly 100. The first pole lug segment 211 and the second pole lug segment 212 are overlapped along the third direction Z. During the welding process of the first outer layer pole lug 210, the first pole lug segment 211 directly contacts the welding head or the welding seat, thereby improving the problem of weak connection strength between the second pole lug segment 212 and the inner layer pole lug 220, and reducing the risk of electrical connection failure caused by tensile stress concentration on the second pole lug segment 212. The connection stability between the first transition portion 520 and the first overlapping portion 240 is further improved, and the average capacity retention rate is increased from 82% to 86%, with a significant improvement effect.

[0195] Embodiment 6: Compared with Embodiment 5, the first transition portion 520 is partially folded back to form a first transition section 521 and a second transition section 522, the second transition section 522 is connected to the first extension portion 510, the first transition section 521 and the second transition section 522 are overlapped along the third direction Z, the first transition section 521 is connected to a surface of the second outer layer pole ear 230 away from the inner layer pole ear 220 and is welded to the first overlapping portion 240 to form a first welding area 710. Since the end of the first transition section 521 away from the electrode assembly 100 is flush with the end of the first welding area 710 away from the electrode assembly 100, the length of the end of the first welding area 710 away from the electrode assembly 100 and the end of the first overlapping portion 240 away from the electrode assembly 100 is close to 0, which further saves space in the first direction, so the energy density is increased from 0.5% to 1.2%, and the improvement effect is obvious.

[0196] In addition, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of the present application.

Claims

1. A secondary battery, characterized in that: include: A housing having a cavity; an electrode assembly, wherein the electrode assembly is accommodated in the cavity; A first electrode tab group, the first electrode tab group is connected to the electrode assembly, the first electrode tab group comprises a first outer electrode tab, an inner electrode tab and a second outer electrode tab arranged in sequence along a third direction, and the inner electrode tab is provided with at least one; A first adapter, the first adapter includes a first extension portion and a first adapter portion, the first extension portion extends out of the shell along a first direction, the first adapter portion is located in the shell, and when observed along the first direction, the first adapter portion is located on a side of the second outer layer pole ear away from the inner layer pole ear, the first adapter portion is connected to the second outer layer pole ear, and the first direction is perpendicular to the third direction, and the third direction is the thickness direction of the electrode assembly.

2. The secondary battery according to claim 1, wherein: The first outer electrode tab and the portion of the inner electrode tab away from the electrode assembly are gathered and stacked toward the side where the second outer electrode tab is located to form a first stacking portion, the first stacking portion is parallel to the first direction, the first transition portion is welded to the first stacking portion to form a first welding area, the secondary battery also includes an edge sealing member, the edge sealing member is at least partially arranged between the shell and the first transition portion to form a first edge sealing area, and the first welding area and the first edge sealing area are arranged along the first direction.

3. The secondary battery according to claim 2, characterized in that: Along the first direction, the total length of the first transition portion is L, the length of the first welding area is L1, the length between one end of the first welding area away from the electrode assembly and one end of the first overlapping portion away from the electrode assembly is L2, the length between one end of the first welding area close to the electrode assembly and one end of the first transition portion close to the electrode assembly is L3, the length between one end of the first edge sealing area close to the electrode assembly and one end of the first overlapping portion away from the electrode assembly is L4, and the total length of the first edge sealing area is L5, L=L1+L2+L3+L4+L5; The length relationship satisfies at least one of the following conditions a1 to e1: a1.0.2mm≤L1≤3mm; b1.0.01mm≤L2≤1.0mm; c1.0.01mm≤L3≤1.0mm; d1.0.01mm≤L4≤1.0mm; e1.3.5mm≤L5≤5.5mm.

4. The secondary battery according to claim 2, characterized in that: The first transition portion is partially folded back to form a first transition section and a second transition section, the second transition section is connected to the first extension portion, and the first transition section and the second transition section are overlapped along the third direction; the first transition section is connected to a surface of the second outer layer pole ear away from the inner layer pole ear and is welded to the first overlapping portion to form the first welding area.

5. The secondary battery according to claim 4, characterized in that: One end of the first transition section away from the electrode assembly is flush with one end of the first welding region away from the electrode assembly.

6. The secondary battery according to claim 5, characterized in that: Along the third direction, a projection of the first transition section is located within a projection of the second transition section.

7. The secondary battery according to claim 6, characterized in that: Along the first direction, the total length of the second transition section is S, the length of the first welding area is S1, the length between one end of the first welding area close to the electrode assembly and one end of the first transition section close to the electrode assembly is S2, the length between one end of the first welding area away from the electrode assembly and one end of the first edge sealing area close to the electrode assembly is S3, and the total length of the first edge sealing area is S4, S=S1+S2+S3+S4; The length relationship satisfies at least one of the following conditions a2 to d2: a2.0.2mm≤S1≤3mm; b2.0.01mm≤S2≤1.0mm; c2.0.01mm≤S3≤1.0mm; d2.3.5mm≤S4≤5.5mm.

8. The secondary battery according to any one of claims 2 to 7, characterized in that: The secondary battery further includes a reinforcing sheet connected to a surface of the first outer electrode tab away from the inner electrode tab and welded to the first overlapping portion to form a second welding region.

9. The secondary battery according to claim 8, characterized in that The thickness of the reinforcing sheet is 10 μm to 40 μm.

10. The secondary battery according to claim 8, wherein The length of the second welding area is P1, P1=L1.

11. The secondary battery according to claim 10, characterized in that: Along the first direction, a length between an end of the second welding region away from the electrode assembly and an end of the first overlapping portion away from the electrode assembly is P2, 0.01 mm ≤ P2 ≤ 1 mm; and / or Along the first direction, a distance between an end of the second welding region close to the electrode assembly and an end of the reinforcing sheet close to the electrode assembly is P3, and 0.01 mm≤P3≤3 mm.

12. The secondary battery according to claim 11, wherein: Along the second direction, the width of the reinforcing sheet is Y5, the width of the second welding area is Y1, 0.1 mm≤Y5-Y1≤5 mm, and the first direction, the second direction and the third direction are perpendicular to each other.

13. The secondary battery according to any one of claims 1 to 7, characterized in that: The first outer layer pole lug portion is folded back to form a first pole lug segment and a second pole lug segment, the second pole lug segment is connected to the electrode assembly, and the first pole lug segment and the second pole lug segment are overlapped along the third direction; the first pole lug segment is arranged on a side of the second pole lug segment away from the second outer layer pole lug and is welded to the first transition portion to jointly form a first welding area.

14. An electrical device, characterized in that: Comprising the secondary battery according to any one of claims 1 to 13.

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