Secondary battery and electric device

Abstract

The application relates to the technical field of energy storage, in particular to a secondary battery and a power utilization device. The secondary battery comprises a shell, an electrode assembly, a first lug group and a first adapter. The shell has a cavity, and the electrode assembly is accommodated in the cavity. The first lug group is connected to the electrode assembly, and the first lug group comprises a first outer lug, an inner lug and a second outer lug arranged in sequence along a third direction, and the inner lug is provided with at least one. The first adapter comprises a first extension part and a first adapter part. The first extension part extends out of the shell along a first direction, and the first adapter part is located in the shell. When viewed along the first direction, the first adapter part is located on a side of the second outer lug away from the inner lug, the first adapter part is connected to the second outer lug, the first direction is perpendicular to the third direction, and the third direction is a thickness direction of the electrode assembly.

Description

TECHNICAL FIELD

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

[0002] The core component of a secondary battery is an electrode group. For a fast-charging electrode group, the transmission path of electrons can be shortened by a multi-tab design, and the internal resistance of the secondary battery can be reduced by multiple tabs, thereby reducing the temperature rise of the secondary battery during fast charging. The electrode group with a multi-tab structure needs to be welded with an adapter as an electrode terminal for charging and discharging. For a multi-tab structure ultra-thin fast-charging electrode group, the thickness of the electrode group is reduced, so that during packaging, the adapter welding needs to adopt a straight-out scheme, that is, the multi-layer tabs are directly drawn out from the shell and then welded with the adapter. However, in the related technical scheme, the straight-out scheme has the problem of tab position interference failure under stress test conditions such as collision and drop, which affects the safety of the secondary battery. SUMMARY

[0003] Therefore, the present application provides a secondary battery and a power utilization 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, which includes a shell, an electrode group, a first tab group, and a first adapter. The shell has a cavity, and the electrode group is accommodated in the cavity. The first tab group is connected to the electrode group, and the first tab group includes a first outer layer tab, an inner layer tab, and a second outer layer tab arranged in a third direction in sequence, and the inner layer tab is provided with at least one. The first adapter includes a first extension part and a first adapter part. The first extension part extends out of the shell along a first direction, and the first adapter part is located in the shell. When viewed along the first direction, the first adapter part is located on a side of the second outer layer tab away from the inner layer tab, the first adapter part is connected to the second outer layer tab, the first direction is perpendicular to the third direction, and the third direction is the thickness direction of the electrode group. The first outer layer tab and the second outer layer tab refer to the tabs located at the outermost layer in the third direction, that is, only one side has an adjacent inner layer tab, and both sides of the inner layer tab have adjacent outer layer tabs or other inner layer tabs.

[0005] In the secondary battery, the first lug group includes the first outer lug, the inner lug and the second outer lug arranged in the third direction in sequence, the first protruding part of the first adapter protrudes from the shell in the first direction, the first adapter part of the first adapter is connected with the second outer lug to form an adapter welding scheme, and the first adapter part is located on the side of the second outer lug away from the inner lug when viewed in the first direction, so that the first adapter is located on the side of the first lug group as a whole away from the first outer lug in the third direction. When the secondary battery is subjected to vibration or impact in the first direction for multiple times, the first adapter part is difficult to interfere with the first lug group, thereby improving the safety of the secondary battery.

[0006] In the above embodiment, the part of the first outer lug and the inner lug away from the electrode assembly converges and is stacked toward the side where the second outer lug is located to form a first stacking part, the first stacking part is parallel to the first direction, the first adapter part is welded with the first stacking part to form a first welding area, and the secondary battery further includes an edge sealing member arranged at least partially between the shell and the first adapter part to form a first edge sealing area, and the first welding area and the first edge sealing area are arranged in the first direction.

[0007] In the above secondary battery, the edge sealing member is used to seal the gap between the shell and the first adapter part to improve the sealing performance. The first welding area and the first edge sealing area are arranged in the first direction, thereby reducing the occupation in the thickness direction of the secondary battery and facilitating the reduction of the thickness of the secondary battery.

[0008] In one or more of the above embodiments, in the first direction, the total length of the first adapter part is L, the length of the first welding area is L1, the length of the end of the first welding area away from the electrode assembly and the end of the first stacking part away from the electrode assembly is L2, the length of the end of the first welding area close to the electrode assembly and the end of the first adapter part close to the electrode assembly is L3, the length of the end of the first edge sealing area close to the electrode assembly and the end of the first stacking part away from the electrode assembly is L4, the total length of the first edge sealing area is L5, and L=L1+L2+L3+L4+L5.

[0009] Wherein, the length relationship satisfies at least one of the following a1 to e1 conditions:

[0010] a1. 0.2mm≤L1≤3mm;

[0011] b1. 0.01mm≤L2≤1.0mm;

[0012] c1. 0.01mm≤L3≤1.0mm;

[0013] d1. 0.01mm≤L4≤1.0mm;

[0014] e 1.3.5mm≤L5≤5.5mm.

[0015] In the secondary battery described above, when the length LI of the first welding area, the length L2 of the first welding area from the end of the electrode assembly away from the first stacking portion, the length L3 of the first welding area from the end of the electrode assembly close to the first adapter portion, the length L4 of the first sealing edge area from the end of the electrode assembly close to the first stacking portion, and the total length L5 of the first sealing edge area all meet the respective length requirements, it is beneficial to reduce the occupation 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 embodiments described above, the first adapter portion is partially folded to form a first adapter section and a second adapter section, the second adapter section is connected with the first extension portion, and the first adapter section and the second adapter section are arranged in overlap along the third direction; the first adapter section is connected with a surface of the second outer layer tab away from the inner layer tab and welded with the first stacking portion, forming the first welding area.

[0017] In the secondary battery described above, the first adapter portion is partially folded to form a first adapter section and a second adapter section, the second adapter section is connected with the first extension portion, and the first adapter section and the second adapter section are arranged in overlap along the third direction, so that the end of the first adapter portion toward the electrode assembly is rounded, which is beneficial to reduce the impact of the first adapter portion on the first tab group when the secondary battery is subjected to vibration or impact along the first direction.

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

[0019] In the secondary battery described above, the end of the first adapter 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 sealing edge area close to the electrode assembly, thereby reducing the spatial occupation of the first adapter portion in the first direction and being beneficial to further improve the energy density of the secondary battery.

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

[0021] In the secondary battery described above, the projection of the first adapter section is located within the projection of the second adapter section, which reduces the spatial occupation of the first adapter along the first direction, thereby improving the energy density of the secondary battery.

[0022] In one or more of the embodiments above, in the first direction, the total length of the second adapter section is S, the length of the first welding area is S1, the length from the end of the first welding area close to the electrode assembly to the end of the first adapter section close to the electrode assembly is S2, the length from the end of the first welding area away from the electrode assembly to the 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] wherein the length relationship satisfies at least one of the following 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 secondary battery described above, when the length S1 of the first welding area, the length S2 from the end of the first welding area close to the electrode assembly to the end of the first adapter section close to the electrode assembly, the length S3 from the end of the first welding area away from the electrode assembly to the end of the first edge sealing area close to the electrode assembly, and the total length S4 of the first edge sealing area all satisfy the respective length requirements, it is beneficial to further reduce the occupation 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 embodiments above, the secondary battery further comprises a reinforcing sheet, the reinforcing sheet is connected to the surface of the first outer layer tab away from the inner layer tab and is welded with the first stacking part to form a second welding area.

[0030] In the secondary battery described above, by connecting the reinforcing sheet to the surface of the first outer layer tab away from the inner layer tab and welding the reinforcing sheet with the first stacking part, 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 tab and the inner layer tab and reducing the risk of electrical connection failure caused by the first outer layer tab being subjected to tensile stress concentration.

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

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

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

[0034] In the secondary battery described above, the length of the second welding area is equal to the length of the first welding area, so that the first welding area and the first welding area can be machined simultaneously on the same device, improving the processing convenience.

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

[0036] In the secondary battery described above, the length of the second welding area away from the one end of the electrode assembly and the one end of the first stacking part is greater than or equal to 0.01mm and less than or equal to 1mm, so as to limit the length of the reinforcing sheet, which is conducive to improving the problem of the secondary battery being too long to interfere with the edge sealing member, and improving the safety of the secondary battery.

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

[0038] In the secondary battery described above, the length of the second welding area close to the electrode assembly and the one end of the first stacking part close to the electrode assembly is greater than or equal to 0.01mm and less than or equal to 1mm, so as to limit the length of the reinforcing sheet, which is conducive to improving the problem of the secondary battery being too long to interfere with the first tab group, and improving the safety of the secondary battery.

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

[0040] In the secondary battery described above, the difference between the width of the reinforcing sheet and the width of the second welding area is greater than or equal to 0.1mm and less than or equal to 5mm, so that the second welding area is formed inside the reinforcing sheet, which is conducive to improving the connection stability of the reinforcing sheet and the first stacking part.

[0041] In one or more of the embodiments above, the first outer tab is partially folded to form a first tab section and a second tab section, the second tab section is connected to the electrode assembly, and the first tab section and the second tab section are arranged in the third direction; the first tab section is arranged on the side of the second tab section away from the second outer tab and is welded to the first adapter part to form a first welding area.

[0042] In the secondary battery described above, by folding back the first outer tab portion, the first tab section is arranged on the side of the second tab section away from the second outer tab and is welded with the first adapter, so that the first tab section directly contacts with the welding head or the welding seat, the problem of weak connection strength between the second tab section and the inner tab is improved, and the risk of electrical connection failure caused by stress concentration of the second tab section is reduced.

[0043] In a second aspect, the embodiments of the present application provide a power consuming device comprising the secondary battery in one or more of the above embodiments. BRIEF DESCRIPTION OF DRAWINGS

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

[0045] Figure 2 is a schematic diagram of the structure of the secondary battery after disassembly in an embodiment of the present application.

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

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

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

[0049] Figure 6 is a schematic diagram of the connection structure of the first tab group and the first adapter in another embodiment of the present application. Figure 5 is a top view of the connection structure of the first tab group and the first adapter in another embodiment of the present application.

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

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

[0052] Figure 9 is a schematic diagram of the structure of the power consuming device in an embodiment of the present application.

[0053] MAIN ELEMENT SYMBOL EXPLANATION

[0054] 001 secondary battery

[0055] 100 electrode assembly

[0056] 110 first tab sheet

[0057] 111 first current collector

[0058] 112 first active material layer

[0059] 120 second electrode tab

[0060] 121 second current collector

[0061] 122 second active material layer

[0062] 130 separator

[0063] 200 first tab group

[0064] 210 first outer tab

[0065] 211 first tab section

[0066] 212 second tab section

[0067] 220 inner tab

[0068] 230 second outer tab

[0069] 240 first stacking portion

[0070] 250 reinforcing sheet

[0071] 300 second tab group

[0072] 400 case

[0073] 410 cavity

[0074] 500 first adapter

[0075] 510 first extension

[0076] 520 first adapter portion

[0077] 521 first adapter section

[0078] 522 second adapter section

[0079] 600 second adapter

[0080] 710 first welding area

[0081] 720 second welding area

[0082] 730 first edge sealing area

[0083] 800 edge sealer

[0084] 900 protective adhesive tape

[0085] 910 adhesive layer

[0086] 910a first adhesive layer

[0087] 910b second adhesive layer

[0088] 920 substrate layer

[0089] 002 electrical device

[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 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 of them.

[0094] It should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected. When a component is considered to be "connected" to another component, it can be directly connected to another component or there can be a middle component. When a component is considered to be "provided on" another component, it can be directly provided on another component or there can be a middle component.

[0095] Unless otherwise specified, the term "a plurality of" as used herein refers to two or more.

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

[0097] The term "vertical" is used to describe the ideal state between two components. In the actual production or use state, there can be an approximate vertical state between the two components. For example, in combination with numerical description, vertical can refer to the included angle between two straight lines in the range of 90°±10°, vertical can also refer to the dihedral angle between two planes in the range of 90°±10°, and vertical can also refer to the included angle between a straight line and a plane in the range of 90°±10°.

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

[0099] A first direction X, including a positive direction along the first direction X and an opposite direction opposite to the first direction X, a second direction Y, including a positive direction along the second direction Y and an opposite direction opposite to the second direction Y, and a third direction Z, including a positive direction along the third direction Z and an opposite direction opposite to the third direction Z.

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

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

[0102] 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 specification of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0103] An embodiment of the present application provides a secondary battery, comprising a shell, an electrode assembly, a first tab group, and a first adapter. The shell has a cavity, and the electrode assembly is received in the cavity. The first tab group is connected to the electrode assembly, and the first tab group comprises a first outer layer tab, an inner layer tab, and a second outer layer tab arranged in sequence along a third direction, and the inner layer tab is provided with at least one. The first adapter comprises a first extension portion and a first adapter portion, the first extension portion extends out of the shell along a first direction, and the first adapter portion is located in the shell. In the first direction, the first adapter portion is located on a side of the second outer layer tab away from the inner layer tab, the first adapter portion is connected to the second outer layer tab, the first direction is perpendicular to the third direction, and the third direction is a thickness direction of the electrode assembly.

[0104] The first lug group includes a first outer layer lug, an inner layer lug and a second outer layer lug arranged in sequence along the third direction. The first extension part of the first adapter part extends out of the shell along the first direction. The first adapter part is connected with the second outer layer lug to form a direct welding scheme. When viewed along the first direction, the first adapter part is located on the side of the second outer layer lug away from the inner layer lug, so that the first adapter part is located on the side of the first lug group away from the first outer layer lug along the third direction. When the secondary battery is subjected to vibration or impact along the first direction multiple times, the first adapter part is located on the side of the first lug group away from the first outer layer lug along the third direction, and the first adapter part is difficult to cause impact interference to the first lug group, thereby improving the safety of the secondary battery.

[0105] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The features in the following embodiments and examples can be combined with each other without conflict.

[0106] Please refer to Figure 1 and Figure 2 The embodiments of the present application provide a secondary battery 001, which includes an electrode assembly 100 and a first lug group 200 connected with the electrode assembly 100. The secondary battery 001 further includes a second lug group 300 connected with the electrode assembly 100, and the polarities of the first lug group 200 and the second lug group 300 are different.

[0107] In some embodiments, the secondary battery 001 further includes a shell 400 having a cavity 410, and the electrode assembly 100 is received in the cavity 410 in the shell 400. The first lug group 200 is connected with a conductive first adapter part 500, and the first adapter part 500 partially extends out of the shell 400 and is used to be electrically connected with an external structure. The second lug group 300 is connected with a conductive second adapter part 600, and the second adapter part 600 partially extends out of the shell 400 and is used to be electrically connected with 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] Please refer to 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 separator 130. The separator 130 is arranged between the first electrode sheet 110 and the second electrode sheet 120. The first electrode sheet 110, the second electrode sheet 120 and the separator 130 are stacked and wound to form a winding structure.

[0110] In some embodiments, the electrode assembly 100 comprises a first tab 110, a second tab 120, and a separator 130 arranged between the first tab 110 and the second tab 120, and the first tab 110 and the second tab 120 are sequentially stacked to form a stacked structure.

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

[0112] In some embodiments, the first tab group 200 is electrically connected to the electrode assembly 100.

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

[0114] In some embodiments, the second tab group 300 is electrically connected to the electrode assembly 100.

[0115] The following describes the connection structure of the first tab group 200 and the first adapter 500 in detail. In some embodiments, the connection structure of the second tab group 300 and the second adapter 600 is the same as the connection structure of the first tab group 200 and the first adapter 500; in other embodiments, the connection structure of the second tab group 300 and the second adapter 600 is the same as the connection structure of the first tab group 200 and the first adapter 500, only the difference is the arrangement size.

[0116] Please refer to Figure 2 and Figure 3 In some embodiments, the first tab group 200 is located on 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 comprises a first outer layer tab 210, an inner layer tab 220, and a second outer layer tab 230 arranged sequentially along the third direction Z, and the inner layer tab 220 is provided with at least one. 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, the inner layer tab 220 is provided with N, and N is a positive integer and greater than or equal to 2.

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

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

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

[0122] The first stacked portion 240 is parallel to the first direction X, the first adapter portion 520 connects a surface of the second outer tab 230 away from the inner tab 220 and is welded with the first stacked portion 240 to form a first welding area 710.

[0123] The first tab group 200 includes the first outer tab 210, the inner tab 220, and the second outer tab 230 arranged in sequence along the third direction Z, the first outer tab 210 and the inner tab 220 are folded away from a portion of the electrode assembly 100 toward a side where the second outer tab 230 is located, and are stacked to form a first stacked portion 240. The first stacked portion 240 is parallel to the first direction X, after the first stacked 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 an adapter welding straight out solution. Since the first outer tab 210 and the inner tab 220 are folded away from a portion of the electrode assembly 100 toward a side where the second outer tab 230 is located, and the first adapter portion 520 connects a surface of the second outer tab 230 away from the inner tab 220, the first adapter 500 is located on a side of the first tab group 200 as a whole away from the first outer tab 210 along the third direction Z. When the secondary battery 001 is subjected to vibration or impact along the first direction X multiple times, the first stacked portion 240 is stretched along the first direction X, and the first adapter 500 is located on a side of the first tab group 200 as a whole away from the first outer tab 210 along the third direction Z, the first adapter portion 520 is difficult to interfere with the first tab group 200 to cause impact, thereby improving the safety of the secondary battery 001.

[0124] In some embodiments, the secondary battery 001 further includes an edge sealing member 800, the edge sealing member 800 is at least partially arranged between the housing 400 and the first adapter portion 520 to form a first edge sealing area 730, and the first welding area 710 and the first edge sealing area 730 are arranged along the first direction X.

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

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

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

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

[0129] In some embodiments, the length of the first sealing edge area 730 close to the one end of the electrode assembly 100 and the one end of the first stacking portion 240 along the first direction X is L4, 0.01mm≤L4≤1.0mm.

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

[0131] In some embodiments, the total length of the first adapter portion 520 along the first direction X is L, L=L1+L2+L3+L4+L5. The length of the first welding area 710 close to the one end of the electrode assembly 100 and the one end of the first adapter portion 520 can share the space along the first direction X with the part of the first tab group 200 where the tabs are bent, at the same time, the one end of the first adapter portion 520 close to the one end of the electrode assembly 100 can extend to the area where the one side of the first stacking portion 240 close to the one end of the electrode assembly 100 is located for accommodation 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, the two surfaces of the first welding area 710 are covered by a protective piece.

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

[0134] In some embodiments, the protective adhesive 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, the other side of the adhesive layer 910 is bonded to the substrate layer 920, and the substrate layer 920 is in contact with the shell 400, thereby playing an isolating and insulating role.

[0135] In some embodiments, the protective adhesive tape 900 comprises 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. The substrate layer 920 plays a role of insulation and isolation, and also plays a role of fixing the relative positions of the first welding area 710 and the shell 400, thereby improving the position stability of the first welding area 710.

[0136] Referring to Figure 2 and Figure 4 In some embodiments, the first adapter 520 is partially folded to form a first adapter segment 521 and a second adapter segment 522, the second adapter segment 522 is connected to the first extension 510, and the first adapter segment 521 and the second adapter segment 522 are arranged in an overlapping manner along the third direction Z. The first adapter segment 521 is connected to a surface of the second outer tab 230 away from the inner tab 220 and is welded to the first stacking portion 240 to form the first welding area 710.

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

[0138] In some embodiments, one end of the first adapter segment 521 away from the electrode assembly 100 is flush with one end of the first welding area 710 away from the electrode assembly 100. It should be noted that the above-mentioned "flush" means that along the first direction X, the distance between one end of the first adapter segment 521 away from the electrode assembly 100 and one end of the first welding area 710 away from the electrode assembly 100 is close to 0mm to 1.0mm; and / or along the first direction X, the distance between one end of the first stacking portion 240 away from the electrode assembly 100 and one end of the first welding area 710 away from the electrode assembly 100 is close to 0mm to 1.0mm.

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

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

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

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

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

[0144] In some embodiments, along the first direction X, the total length of the second adapter section 522 is S, S=S1+S2+S3+S4. Wherein the one end of the first adapter section 521 away from the electrode assembly 100 is flush with the one end of the first welding area 710 away from the electrode assembly 100, so that the one end of the first welding area 710 away from the electrode assembly 100 is closer to the one 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] Please refer to Figure 2 and Figure 5 In some embodiments, the secondary battery 001 further comprises a reinforcing sheet 250, the reinforcing sheet 250 is connected to the surface of the first outer layer tab 210 away from the inner layer tab 220 and welded with the first laminated part 240 to form a second welding area 720. During the welding process, the first outer layer tab 210 is directly in contact with the welding head or welding seat, so the connection strength of the first outer layer tab 210 and the inner layer tab 220 is weak. By connecting the reinforcing sheet 250 to the surface of the first outer layer tab 210 away from the inner layer tab 220 and welding with the first laminated part 240, the reinforcing sheet 250 is directly in contact with the welding head or welding seat, thereby improving the problem of weak connection strength of 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 of the first outer layer tab 210.

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

[0147] In some embodiments, along the first direction X, the length of the second welding area 720 away from the one end of the electrode assembly 100 and the one end of the first laminated part 240 away from the electrode assembly 100 is P2, 0.01mm≤P2≤1mm.

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

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

[0150] Please see Figure 2 , Figure 5 and Figure 6 In some embodiments, along the second direction Y, the width of the reinforcing sheet 250 is Y5, and the width of the second welding area 720 is Y1, where 0.1mm ≤ Y5 - Y1 ≤ 5mm. 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 all perpendicular to each other.

[0151] Along the second direction Y, the difference between the width of the reinforcing piece 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 piece 250, which is beneficial to improving the connection stability between the reinforcing piece 250 and the first stacked portion 240.

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

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

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

[0155] Please see Figure 2 and Figure 7 In some embodiments, the first adapter portion 520 is partially folded back to form a first adapter segment 521 and a second adapter segment 522. The second adapter segment 522 is connected to the first protrusion portion 510, and the first adapter segment 521 and the second adapter segment 522 are overlapped along a third direction Z. The first adapter segment 521 is connected to a surface of the second outer tab 230 away from the inner tab 220 and welded to the first stacked portion 240 to form a first welding area 710.

[0156] The secondary battery 001 also includes a reinforcing sheet 250, which is connected to a surface of the first outer electrode 210 away from the inner electrode 220 and welded to the first stacked portion 240 to form a second welding area 720.

[0157] The first transition section 521 is flush with the first welding area 710 away from the electrode assembly 100 at one end, so that the first welding area 710 away from the electrode assembly 100 is closer to 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 the surface of the first outer layer tab 210 away from the inner layer tab 220 and welding with the first stacking part 240, the reinforcing sheet 250 is directly in contact with the welding head or welding seat, 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 the first outer layer tab 210 under the stress concentration of pulling.

[0158] Referring to Figure 2 and Figure 8 In some embodiments, the first outer layer tab 210 is partially folded to form a first tab section 211 and a second tab section 212, the second tab section 212 is connected to the electrode assembly 100, and the first tab section 211 and the second tab section 212 are arranged in an overlapping manner along the third direction Z.

[0159] The first tab section 211 is arranged on the side of the second tab section 212 away from the second outer layer tab 230 and is welded with the first transition section 520 to form the first welding area 710. During the welding process, the first outer layer tab 210 is directly in 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 weak. By partially folding the first outer layer tab 210, the first tab section 211 is arranged on the side of the second tab section 212 away from the second outer layer tab 230 and is welded with the first transition section 520, so that the first tab section 211 is directly in contact with the welding head or welding seat, improving the problem of weak connection strength between the second tab section 212 and the inner layer tab 220, and reducing the risk of electrical connection failure caused by the second tab section 212 under the stress concentration of pulling.

[0160] In some embodiments, along the first direction X, the length of the first tab section 211 is greater than the length of the first welding area 710, so that the first welding area 710 is formed inside the first tab section 211, which is beneficial to improve the connection stability of the first tab section 211 and the first stacking part 240.

[0161] Referring to Figure 2 , Figure 4 and Figure 8In some embodiments, the first adapter 520 is partially folded to form a first adapter section 521 and a second adapter section 522, the second adapter section 522 is connected to the first extension 510, and the first adapter section 521 and the second adapter section 522 are arranged in an overlapping manner along the third direction Z. The first adapter section 521 is connected to a surface of the second outer tab 230 away from the inner tab 220 and is welded to the first stacking part 240 to form a first welding area 710.

[0162] The first outer tab 210 is partially folded to form a first tab section 211 and a second tab section 212, the second tab section 212 is connected to the electrode assembly 100, and the first tab section 211 and the second tab section 212 are arranged in an overlapping manner along the third direction Z.

[0163] The first tab section 211 is arranged on a side of the second tab section 212 away from the second outer tab 230 and is welded to the first adapter 520 to form the first welding area 710.

[0164] In some embodiments, the first outer tab 210 is partially folded to form a first tab section 211 and a second tab section 212, the first adapter 500 is welded to the first stacking part 240 to form the first welding area 710 before being folded, and a side of the first adapter 500 and the first stacking part 240 away from the electrode assembly 100 is cut flat, and the cutting position is designed to be -1.0 mm to 1.0 mm from the first welding area 710. Then the first adapter 500 is folded.

[0165] The first adapter section 521 is flush with the first welding area 710 at an end of the first adapter section 521 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 the first outer tab 210, the first tab section 211 is arranged on a side of the second tab section 212 away from the second outer tab 230 and is welded to the first adapter 520, so that the first tab section 211 is directly in contact with the welding head or the welding seat, thereby improving the problem of weak connection strength between the second tab section 212 and the inner tab 220 and reducing the risk of electrical connection failure caused by stress concentration of the second tab section 212.

[0166] For example, the first adapter 500 is partially folded to form a first adapter section 521 and a second adapter section 522, the second adapter section 522 is connected to the first extension 510, and the first adapter section 521 and the second adapter section 522 are arranged in an overlapping manner along the third direction Z. Figure 9 An embodiment of the present application also provides a power consuming device 002 comprising the secondary battery 001 of one or more embodiments described above.

[0167] In order to verify the effect of the position and connection structure of the first adapter 500 on the safety of the tabs in the secondary battery 001, the following tests were conducted:

[0168] (1) Drop test: 10 secondary batteries 001 in each group of comparative examples and each group of examples were tested, and the secondary batteries 001 of the examples and comparative examples were dropped from a height of 1.5 meters, after which the secondary batteries 001 were disassembled, and whether the tabs in the first tab group 200 were loose was observed with the naked eye, and whether the tabs were broken or had cracks was observed using a microscope.

[0169] (2) Cycle test test: After the drop test, 10 secondary batteries 001 in each group of comparative examples and each group of examples were subjected to a cycle test, and each secondary battery 001 was placed in a 25°C environment for 30 minutes, and then subjected to charging and discharging according to the following steps. 5C constant current charging to 4.2V, then 4C constant current charging to 4.3V, then 3C constant current charging to 4.45V, then 4.45V constant voltage charging to 0.05C, standing for 5 minutes, 1C constant current discharging to 3V, standing for 5 minutes, which is one cycle. According to the above cycle steps, 1000 cycles were cycled. The capacity retention rate of a single secondary battery 001 was calculated after the cycle test. The capacity retention rate is the ratio of the discharge capacity after 1000 cycles to the discharge capacity of the first cycle. The capacity retention rate of 10 secondary batteries 001 in each group of comparative examples and each group of examples after 1000 cycles was recorded, and the average value was calculated.

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

[0171] Example 1:

[0172] A secondary battery 001 was assembled as follows:

[0173] (1) Preparation of anode electrode sheet: Anode active material artificial graphite, conductive carbon black (Super P), and butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, deionized water was added as a solvent, and an anode active material slurry with a weight percentage of 70wt% was prepared and uniformly stirred for use. A copper foil with a thickness of 10μm was used as an anode current collector, and the above-mentioned anode active material slurry was uniformly coated on one surface of the anode current collector in the thickness direction, and an empty foil area without an anode active material layer was reserved at one end of the anode current collector in the width direction, and was dried at 110°C to obtain an anode electrode sheet substrate with an anode active material layer coated on one side. Then the above steps were repeated on the other side of the anode current collector in the thickness direction, and an empty foil area without an anode active material layer was reserved at one end of the anode current collector in the width direction, to obtain an anode electrode sheet substrate with anode active material layers coated on both sides, wherein the density of the anode active material layer is 1.70g / cm 3The anode tab substrate is punched using a die and a die cutter to obtain a single anode tab, wherein the position of the empty foil area where the anode active material layer is not arranged forms an anode tab. The anode tab is provided with a plurality of anode tabs.

[0174] (2) Preparation of the cathode tab: lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, N-methyl pyrrolidone (NMP) is added as a solvent, a cathode active material slurry with a solid content of 75wt% is prepared, and the mixture is stirred uniformly for use. An aluminum foil with a thickness of 10μm is used as the cathode current collector, the above-mentioned cathode active material slurry is uniformly coated on one surface of the cathode current collector along its thickness direction using a slot coater, wherein an empty foil area where the cathode active material layer is not arranged is reserved at one end of the cathode current collector in the width direction, and the cathode current collector is dried at 90℃ to obtain a cathode tab substrate coated with a cathode active material layer on one side. Then the above-mentioned step is repeated on the other side of the cathode current collector along its thickness direction, and an empty foil area where the cathode active material layer is not arranged is reserved at one end of the cathode current collector in the width direction to obtain a cathode tab substrate coated with a cathode active material layer on both sides. The cathode tab substrate is punched using a die and a die cutter to obtain a single cathode tab, wherein the position of the empty foil area where the cathode active material layer is not arranged forms a cathode tab, and the cathode tab is provided with a plurality of cathode tabs.

[0175] (3) Preparation of the electrolyte: in a dry argon atmosphere, first, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC: EMC: DEC = 30:50:20 to form a basic organic solvent, then lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix uniformly to obtain an electrolyte with a lithium salt concentration of 1.15mol / L, wherein the conductivity of the electrolyte is 8.0S / m.

[0176] (4) Preparation of the separator 130: the separator 130 adopts a three-layer structure, with a thickness of 5um, which includes a first adhesive layer, a first substrate layer 920, and a second adhesive layer arranged in layers. The first substrate layer 920 is made of polyethylene (PE), and the first adhesive layer and the second adhesive layer each contain a first adhesive and boehmite.

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

[0178] (6) Electrode assembly 100 assembly: Place the punched aluminum plastic film into the assembly fixture with the pit surface facing up, place the electrode assembly 100 into the pit, and apply external force to compress it. Then cover another punched aluminum plastic film with the pit surface facing down on the electrode assembly 100, and heat seal the periphery of the two aluminum plastic films by hot pressing to obtain the assembled electrode assembly 100.

[0179] (7) Liquid injection packaging: Inject electrolyte into the assembled electrode assembly 100, and go through vacuum packaging, standing, hot pressing formation, shaping and other processes to obtain the secondary battery 001.

[0180] Comparative Example 1: The first outer tab 210 and the inner tab 220 away from the electrode assembly 100 are bent towards the side where the second outer tab 230 is located, and are collected, stacked and formed into a first stacking portion 240, and the second outer tab 230 is not bent. The difference from Example 1 is that the first adapter 520 connects a surface of the first outer tab 210 away from the inner tab 220 and is welded with the first stacking portion 240 (in the table, simply referred to as above the first stacking portion 240).

[0181] Example 2: The difference from Example 1 is that the first adapter 500 is welded with the first stacking portion 240 to form the first welding area 710 before being folded, 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 cutting position is designed to be -1.0mm to 1.0mm away from the first welding area 710. Then the first adapter 500 is folded to form the first adapter segment 521 and the second adapter segment 522, and the second adapter segment 522 is connected with the first extension portion 510, and the first adapter segment 521 and the second adapter segment 522 are arranged in overlap along the third direction Z. Along the first direction X, the length of the overlap of the first adapter segment 521 and the second adapter segment 522 is C1. The first adapter segment 521 is connected with a surface of the second outer layer tab 230 away from the inner layer tab 220 and welded with the first stacking portion 240 to form the first welding area 710.

[0182] Example 3: The difference from Example 1 is that the reinforcing sheet 250 is connected with a surface of the first outer layer tab 210 away from the inner layer tab 220 and welded with the first stacking portion 240 to form the second welding area 720.

[0183] Example 4: The difference from Example 3 is that the first adapter 500 is welded with the first stacking portion 240 to form the first welding area 710 before being folded, 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 cutting position is designed to be -1.0mm to 1.0mm away from the first welding area 710. Then the first adapter 500 is folded to form the first adapter segment 521 and the second adapter segment 522, and the second adapter segment 522 is connected with the first extension portion 510, and the first adapter segment 521 and the second adapter segment 522 are arranged in overlap along the third direction Z. The first adapter segment 521 is connected with a surface of the second outer layer tab 230 away from the inner layer tab 220 and welded with the first stacking portion 240 to form the first welding area 710.

[0184] Example 5: The difference from Example 1 is that the first outer layer tab 210 is partially folded to form the first tab segment 211 and the second tab segment 212, and the second tab segment 212 is connected with the electrode assembly 100, and the first tab segment 211 and the second tab segment 212 are arranged in overlap along the third direction Z. 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 with the first adapter portion 520 to form the first welding area 710. Along the first direction X, the length of the overlap of the first tab segment 211 and the second tab segment 212 is C2.

[0185] Example 6: The difference between Example 5 and Example 6 is that the first adapter 500 is welded with the first stacking part 240 to form a first welding area 710 before being folded, and then the first adapter 500 and the first stacking part 240 are cut away from the side of the electrode assembly 100, and the cutting position is designed to be -1.0mm to 1.0mm away from the first welding area 710. Then the first adapter 500 is folded to form a first adapter section 521 and a second adapter section 522, the second adapter section 522 is connected with the first extension part 510, and the first adapter section 521 and the second adapter section 522 are arranged in an overlapping manner along the third direction Z. The first adapter section 521 is connected with a surface of the second outer layer tab 230 away from the inner layer tab 220 and welded with the first stacking part 240 to form the first welding area 710.

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

[0187] Table 1

[0188]

[0189] Note: " / " represents no value.

[0190] Example 1: Compared with Comparative Example 1, the first adapter section 520 is connected with a surface of the second outer layer tab 230 away from the inner layer tab 220 and welded with the first stacking part 240, and since the first adapter section 520 is offset towards the electrode assembly 100, the energy density is improved by about 0.5%. When the secondary battery 001 is subjected to vibration or impact along the first direction X multiple times, the first adapter section 520 is located on the side of the first tab group 200 away from the first outer layer tab 210 along the third direction Z, and the first adapter section 520 is difficult to interfere with the first tab group, and the safety of the first tab group 200 is higher. In this embodiment, after 10 secondary batteries 001 are subjected to drop test, the risk of interference failure of the first tab group 200 is reduced when the cycle test experiment is performed again, and the average capacity retention rate is improved from 78% to 82%, and the improvement effect is obvious.

[0191] Example 2: Compared with Example 1, the first adapter 520 is partially folded to form a first adapter section 521 and a second adapter section 522, the second adapter section 522 is connected with the first extension 510, and the first adapter section 521 and the second adapter section 522 are arranged in overlap along the third direction Z. The first adapter section 521 is connected with a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded with the first stacking portion 240 to form a first welding area 710. Since an end of the first adapter section 521 away from the electrode assembly 100 is flush with an 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, further saving the space in the first direction, and thus the energy density is improved by 1.2%. After the first adapter section 521 and the second adapter section 522 are arranged in overlap along the third direction Z, compared with Example 1, the connection stability of the first adapter 520 and the first stacking portion 240 is similar, the average capacity retention rate is improved from 82% to 84%, and the improvement effect is not obvious.

[0192] Example 3: Compared with Example 1, the reinforcing sheet 250 is connected with a surface of the first outer layer tab 210 away from the inner layer tab 220 and is welded with the first stacking portion 240 to form a second welding area 720, so that the reinforcing sheet 250 directly contacts with the welding head or the welding seat during the welding process, the problem of weak connection strength between the first outer layer tab 210 and the inner layer tab 220 is improved, the risk of electrical connection failure caused by the tensile stress concentration of the first outer layer tab 210 is reduced, the connection stability of the first adapter 520 and the first stacking portion 240 is further improved, and the average capacity retention rate is improved from 82% to 85%, and the improvement effect is obvious.

[0193] Example 4: Compared with Example 3, the first adapter 520 is partially folded to form a first adapter section 521 and a second adapter section 522, the second adapter section 522 is connected with the first extension 510, and the first adapter section 521 and the second adapter section 522 are arranged in overlap along the third direction Z. The first adapter section 521 is connected with a surface of the second outer layer tab 230 away from the inner layer tab 220 and is welded with the first stacking portion 240 to form a first welding area 710. Since an end of the first adapter section 521 away from the electrode assembly 100 is flush with an 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, further saving the space in the first direction, and thus the energy density is improved from 0.5% to 1.2%, and the improvement effect is obvious.

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

[0195] Example 6: Compared with Example 5, the first adapter portion 520 is partially folded back to form a first adapter segment 521 and a second adapter segment 522. The second adapter segment 522 is connected to the first protrusion portion 510. The first adapter segment 521 and the second adapter segment 522 are overlapped along the third direction Z. The first adapter segment 521 is connected to the surface of the second outer electrode tab 230 away from the inner electrode tab 220 and welded to the first stacked portion 240 to form a first welding area 710. Since the end of the first adapter segment 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 stacked portion 240 away from the electrode assembly 100 is close to 0, further saving space in the first direction. Therefore, the energy density is increased from 0.5% to 1.2%, with a significant improvement effect.

[0196] Furthermore, those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of this application's disclosure.

Claims

1. A secondary battery characterized by comprising: The secondary battery comprises: a housing having a cavity; an electrode assembly accommodated in the cavity; a first tab group connected to the electrode assembly, the first tab group comprising a first outer layer tab, an inner layer tab, and a second outer layer tab arranged in sequence along a third direction, the inner layer tab being provided with at least one; a first adapter comprising a first extension portion and a first adapter portion, the first extension portion extending out of the housing along a first direction, the first adapter portion being located in the housing, and viewed along the first direction, the first adapter portion being located on a side of the second outer layer tab away from the inner layer tab, the first adapter portion being connected to the second outer layer tab, the first direction being perpendicular to the third direction, and the third direction being a thickness direction of the electrode assembly.

2. The secondary battery according to claim 1, wherein The first outer layer tab and the inner layer tab away from the electrode assembly converge and overlap to form a first overlapping portion on a side where the second outer layer tab is located, the first overlapping portion being parallel to the first direction, the first adapter portion being welded to the first overlapping portion to form a first welding area, and the secondary battery further comprising an edge sealing member at least partially arranged between the housing and the first adapter portion to form a first edge sealing area, the first welding area and the first edge sealing area being arranged along the first direction.

3. The secondary battery according to claim 2, wherein Along the first direction, a total length of the first adapter portion is L, a length of the first welding area is L1, a length from an end of the first welding area away from the electrode assembly to an end of the first overlapping portion away from the electrode assembly is L2, a length from an end of the first welding area close to the electrode assembly to an end of the first adapter portion close to the electrode assembly is L3, a length from an end of the first edge sealing area close to the electrode assembly to the end of the first overlapping portion away from the electrode assembly is L4, and a total length of the first edge sealing area is L5, L=L1+L2+L3+L4+L5; wherein 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, wherein The first adapter portion is partially folded to form a first adapter segment and a second adapter segment, the second adapter segment being connected to the first extension portion, and the first adapter segment and the second adapter segment being arranged in overlap along the third direction; the first adapter segment being connected to a surface of the second outer layer tab away from the inner layer tab and welded to the first overlapping portion to form the first welding area.

5. The secondary battery according to claim 4, wherein An end of the first adapter segment away from the electrode assembly is flush with an end of the first welding area away from the electrode assembly.

6. The secondary battery according to claim 5, wherein Along the third direction, a projection of the first adapter segment is located within a projection of the second adapter segment.

7. The secondary battery according to claim 6, wherein the positive electrode is a lithium ion secondary electrode. In the first direction, a total length of the second adapter section is S, a length of the first welding area is S1, a length from an end of the first welding area close to the electrode assembly to an end of the first adapter section close to the electrode assembly is S2, a length from an end of the first welding area away from the electrode assembly to an end of the first edge sealing area close to the electrode assembly is S3, and a total length of the first edge sealing area is S4, S=S1+S2+S3+S4; wherein 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, wherein The secondary battery further comprises a reinforcing sheet connected to a surface of the first outer tab away from the inner tab and welded with the first stacking part, forming a second welding area.

9. The secondary battery according to claim 8, wherein The reinforcing sheet has a thickness of 10μm to 40μm.

10. The secondary battery according to claim 8, wherein the negative electrode is a lithium metal electrode. The second welding area has a length of P1, P1=L1.

11. The secondary battery according to claim 10, wherein In the first direction, a length from an end of the second welding area away from the electrode assembly to an end of the first stacking part away from the electrode assembly is P2, 0.01mm≤P2≤1mm; and / or In the first direction, a distance from an end of the second welding area close to the electrode assembly to an end of the reinforcing sheet close to the electrode assembly is P3, 0.01mm≤P3≤3mm.

12. The secondary battery according to claim 11, wherein In the second direction, the reinforcing sheet has a width of Y5, the second welding area has a width of Y1, 0.1mm≤Y5-Y1≤5mm, 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, wherein The first outer tab is partially folded to form a first tab section and a second tab section, the second tab section is connected to the electrode assembly, and the first tab section and the second tab section are arranged in overlapping manner along the third direction; the first tab section is arranged on a side of the second tab section away from the second outer tab and welded with the first adapter section, forming a first welding area.

14. An electrical device, comprising: The secondary battery comprises the secondary battery as claimed in any one of claims 1 to 13. The secondary battery comprises the secondary battery as claimed in any one of claims 1 to 13.

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