Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell and an electrode assembly accommodated in the shell, wherein the electrode assembly comprises a winding structure formed by laminating and winding a positive plate, a diaphragm and a negative plate; in the axial direction of the winding structure, a positive current collector of the positive plate comprises a positive coated region and a positive uncoated region, and a negative current collector of the negative plate comprises a negative coated region and a negative uncoated region; one part of the positive electrode uncoated area is bent to form a positive electrode tab stacking area, the positive electrode tab stacking area comprises a positive electrode tab stacking number stabilizing area, and the stacking number of positive electrode tabs in the positive electrode tab stacking number stabilizing area is m; one part of the negative electrode uncoated area is bent to form a negative electrode tab lamination area, the negative electrode tab lamination area comprises a negative electrode tab lamination number stabilizing area, and in the negative electrode tab lamination number stabilizing area, the lamination number of negative electrode tabs is n; wherein, mgt; and n, the energy density of the secondary battery is improved, and meanwhile, the diaphragm is prevented from being scalded.

Description

Technical Field

[0001] The utility model relates to a secondary battery, a battery pack and an electronic device. Background Art

[0002] With the development of social economy, more and more electrical equipment uses secondary batteries as energy storage and supply devices, such as new energy vehicles, communication base stations, energy storage containers, etc.

[0003] Current secondary batteries consist of an electrode assembly and a casing. The electrode assembly generally includes a positive electrode, a negative electrode and a separator. The positive electrode tab and the negative electrode tab of the electrode assembly are respectively protruded from both sides of the electrode assembly, and after being cut and stacked, they are flattened and then welded to the corresponding current collecting plates.

[0004] Specifically, the positive electrode tab and the current collector plate made of metal aluminum are usually welded with red light, and the negative electrode tab and the current collector plate made of metal copper are welded with green light. This is because the absorption rate of metal aluminum to green laser is not high, but it absorbs red light highly, so metal aluminum is generally welded with red laser; while metal copper absorbs green light highly, so metal copper is generally welded with green laser.

[0005] However, due to the poor stability of red light compared to green light, the green light requires fewer layers of welding tabs, while the red light requires more layers of welding tabs. The number of layers of the positive and negative tabs of existing secondary batteries after bending is usually the same. If the number of layers set in the weldable area of the positive and negative tabs is too small, and there is not enough reserved unwelded layers, the diaphragm will be burned during the welding process; if the number of layers set in the weldable area of the positive and negative tabs is too large, the energy density of the battery will be reduced.

[0006] Therefore, how to balance the number of tab stacking and battery energy density within the weldable area of the positive and negative tabs is a technical problem that needs to be solved urgently in this field. Utility Model Content

[0007] The technical problem to be solved by the utility model is to overcome the above technical problems and provide a secondary battery, a battery pack and an electronic device.

[0008] The utility model solves the above technical problems through the following technical solutions:

[0009] A secondary battery, characterized in that it comprises:

[0010] case;

[0011] An electrode assembly is accommodated in the housing. The electrode assembly includes a winding structure formed by laminating and winding a positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector, and the negative electrode sheet includes a negative electrode current collector. Along the axial direction of the winding structure, the positive electrode current collector includes a positive electrode coated area covered by a positive electrode active material layer and a positive electrode uncoated area not covered by the positive electrode active material layer. The negative electrode current collector includes a negative electrode coated area covered by a negative electrode active material layer and a negative electrode uncoated area not covered by the negative electrode active material layer.

[0012] Along the radial direction of the winding structure, a part of the positive electrode uncoated area is bent towards the central hole of the winding structure, and the positive electrode uncoated areas of different winding turns are laminated with each other to form a positive electrode tab lamination area. The positive electrode tab lamination area includes a positive electrode tab lamination number stable area, in which the lamination number of the positive electrode tabs is m.

[0013] Along the radial direction of the winding structure, a part of the negative electrode uncoated area is bent towards the central hole, and the negative electrode uncoated areas of different winding turns are laminated with each other to form a negative electrode tab lamination area. The negative electrode tab lamination area includes a negative electrode tab lamination number stable area, in which the lamination number of the negative electrode tabs is n.

[0014] Wherein, m > n.

[0015] Preferably, along the radial direction of the winding structure, from the outer periphery to the central hole, the positive electrode tab lamination area sequentially includes a positive electrode tab lamination number increasing area, the positive electrode tab lamination number stable area, and a positive electrode tab lamination number decreasing area. The negative electrode tab lamination area sequentially includes a negative electrode tab lamination number increasing area, the negative electrode tab lamination number stable area, and a negative electrode tab lamination number decreasing area.

[0016] Along the radial direction of the winding structure, the length of the positive electrode tab lamination number stable area is greater than the length of the negative electrode tab lamination number stable area.

[0017] Preferably, along the axial direction of the winding structure, the lamination number of the positive electrode tabs in the positive electrode tab lamination number stable area is 15 - 22 layers, or

[0018] along the axial direction of the winding structure, the lamination number of the negative electrode tabs in the negative electrode tab lamination number stable area is 12 - 18 layers, or

[0019] The ratio of m to n is 1.05 - 1.5.

[0020] Preferably, the secondary battery further includes a current collecting plate, which includes a first current collecting plate and a second current collecting plate. The first current collecting plate is welded to the stable stacking number area of the positive electrode tab and forms a first welding mark. The second current collecting plate is welded to the stable stacking number area of the negative electrode tab and forms a second welding mark;

[0021] Axially along the winding structure, the stacking number of the positive electrode tabs connecting the first welding mark is 8 - 12 layers, or,

[0022] Axially along the winding structure, the stacking number of the negative electrode tabs connecting the second welding mark is 8 - 12 layers, or,

[0023] Axially along the winding structure, within the stable stacking number area of the positive electrode tabs, the ratio i of the stacking number of the positive electrode tabs connecting the first welding mark to the stacking number of the positive electrode tabs located in the stable stacking number area of the positive electrode tabs is 0.4 - 0.65; or,

[0024] Axially along the winding structure, within the stable stacking number area of the negative electrode tabs, the ratio j of the stacking number of the negative electrode tabs connecting the second welding mark to the stacking number of the negative electrode tabs located in the stable stacking number area of the negative electrode tabs is 0.5 - 0.8.

[0025] Preferably, i < j.

[0026] Preferably, radially along the winding structure, the ratio of the length of the stable stacking number area of the positive electrode tabs to the diameter of the central hole is 0.5 - 1.4, or,

[0027] Radially along the winding structure, the ratio of the length of the stable stacking number area of the negative electrode tabs to the diameter of the central hole is 0.5 - 1.4, or,

[0028] The diameter of the central hole is 4 mm - 8 mm.

[0029] Preferably, the direction from the positive electrode coating area to the non - coated area of the positive electrode is the first direction, and the direction from the negative electrode coating area to the non - coated area of the negative electrode is the second direction;

[0030] Axially along the winding direction of the winding structure, the non - coated area of the positive electrode sequentially includes a first non - coated area of the positive electrode, a second non - coated area of the positive electrode, and a third non - coated area of the positive electrode. The non - coated area of the negative electrode sequentially includes a first non - coated area of the negative electrode, a second non - coated area of the negative electrode, and a third non - coated area of the negative electrode;

[0031] Radially along the winding structure, the second positive uncoated area is bent towards the central hole, and the second positive uncoated areas with different winding turns are stacked on top of each other to form the positive tab stacking area. The second negative uncoated area is bent towards the central hole, and the second negative uncoated areas with different winding turns are stacked on top of each other to form the negative tab stacking area;

[0032] Along the first direction, the second positive uncoated area includes a positive tab and a positive connection area connecting the positive tab and the positive coated area. Neither the first positive uncoated area nor the third positive uncoated area includes the positive tab;

[0033] Along the second direction, the second negative uncoated area includes a negative tab and a negative connection area connecting the negative tab and the negative coated area. Neither the first negative uncoated area nor the third negative uncoated area includes the negative tab;

[0034] The number of winding turns of the third positive uncoated area is greater than the number of winding turns of the third negative uncoated area.

[0035] Preferably, the number of winding turns of the third positive uncoated area ranges from 3 to 6, or,

[0036] The number of winding turns of the third negative uncoated area ranges from 1 to 2.

[0037] Preferably, axially along the winding structure, among the winding turns formed by the second positive uncoated area, the outermost second positive uncoated area includes a first bent portion, and the orthographic projection of the first bent portion is located within the outer peripheral edge of the winding structure, or,

[0038] Axially along the winding structure, among the winding turns formed by the second negative uncoated area, the outermost second negative uncoated area includes a second bent portion, and the orthographic projection of the second bent portion is located within the outer peripheral edge of the winding structure.

[0039] Preferably, along the winding direction of the winding structure, the length of the first positive uncoated area is 400 mm - 600 mm, the length of the second positive uncoated area is 3000 mm - 5000 mm, the length of the third positive uncoated area is 200 mm - 500 mm, or,

[0040] Along the winding direction of the winding structure, the length of the first negative uncoated area is 300 mm - 500 mm, the length of the second negative uncoated area is 3000 mm - 5000 mm, the length of the third negative uncoated area is 100 mm - 300 mm, or,

[0041] The ratio of the length of the third uncoated anode region to the length of the third uncoated cathode region is 1.5 - 2.5.

[0042] Preferably, the anode tab is a cut and stacked tab; when the anode sheet is unfolded, the anode current collector is in a flat state, and a first acute angle is formed between the extending direction of the anode tab and the length direction of the anode current collector, and the first acute angle is 30 degrees - 85 degrees;

[0043] The cathode tab is a cut and stacked tab; when the cathode sheet is unfolded, the cathode current collector is in a flat state, and a second acute angle is formed between the extending direction of the cathode tab and the length direction of the cathode current collector, and the second acute angle is 30 degrees - 85 degrees.

[0044] Preferably, along the radial direction of the winding structure, the anode connection region includes a first side away from the central hole of the winding structure and a second side close to the central hole, wherein at least a partial region of the first side and / or the second side is covered with an insulating layer; the insulating layer includes a color developer.

[0045] Preferably, the insulating layer covers the entire region of the first side of the anode connection region; and / or,

[0046] The insulating layer covers the entire region of the second side of the anode connection region; and / or,

[0047] Along the first direction, the maximum width of the insulating layer is greater than or equal to the width of the anode connection region.

[0048] Preferably, along the first direction, the width of the anode connection region is 1.5 mm - 2.5 mm; and / or,

[0049] Along the second direction, the width of the cathode connection region is 1 mm - 2 mm.

[0050] Preferably, along the first direction, the anode tab includes an anode tab transition portion and an anode tab body, the anode tab transition portion is connected between the anode connection region and the anode tab body, and the anode tab transition portion is a bent region of the anode tab;

[0051] Along the second direction, the cathode tab includes a cathode tab transition portion and a cathode tab body, the cathode tab transition portion is connected between the cathode connection region and the cathode tab body, and the cathode tab transition portion is a bent region of the cathode tab;

[0052] The width of the positive electrode tab transition portion of the positive electrode tab located in the outermost circle is greater than the width of the positive electrode tab transition portion of the negative electrode tab located in the outermost circle.

[0053] Preferably, along the first direction, the width of the positive electrode tab transition portion is 1 mm - 2 mm, and the width of the positive electrode tab body is 4.5 mm - 5.5 mm; the thickness of the positive electrode tab is 12 μm - 20 μm; and / or,

[0054] Along the second direction, the width of the negative electrode tab transition portion is 0.1 mm - 1 mm, and the width of the negative electrode tab body is 4 mm - 5 mm; the thickness of the negative electrode tab is 4 μm - 11 μm.

[0055] Preferably, the housing includes a surrounding side wall, and one end of the side wall is formed with an opening; one end of the housing near the opening includes a crimping portion recessed into the interior of the housing;

[0056] The secondary battery further includes:

[0057] A cover plate, mounted on the opening;

[0058] An insulating seal, which surrounds the periphery of the cover plate to insulate and seal the cover plate and the housing;

[0059] A current collector plate, disposed between the electrode assembly and the cover plate and electrically connected to the housing, and the connecting piece of the current collector plate is located on the side of the crimping portion facing the electrode assembly and is welded to the crimping portion;

[0060] and / or,

[0061] The secondary battery is a cylindrical battery.

[0062] A battery pack, characterized in that it includes the secondary battery as described above.

[0063] An electronic device, characterized in that it includes the battery pack as described above.

[0064] The positive progressive effect of the present utility model is that:

[0065] By setting the number of stacked layers of the positive electrode tab in the stable area of the positive electrode tab stack number to be greater than the number of stacked layers of the negative electrode tab in the stable area of the negative electrode tab stack number, the present utility model can ensure that there are sufficient un-welded tab stacked layers both in the stable area of the positive electrode tab stack number and in the stable area of the negative electrode tab stack number, thereby preventing the separator from being scalded during the welding process; at the same time, the number of stacked layers of the negative electrode tab is increased as little as possible, thereby avoiding the influence on the energy density of the secondary battery. That is, while improving the energy density of the secondary battery, the separator is prevented from being scalded. Brief Description of the Drawings

[0066] Figure 1 It is a schematic cross-sectional structure diagram of a secondary battery according to a preferred embodiment of the present utility model.

[0067] Figure 2 It is Figure 1 a partially enlarged structural schematic diagram of part A in

[0068] Figure 3 It is a three-dimensional structural schematic diagram of an electrode assembly of a secondary battery according to a preferred embodiment of the present utility model.

[0069] Figure 4 It is a cross-sectional structural schematic diagram of an electrode assembly of a secondary battery according to a preferred embodiment of the present utility model.

[0070] Figure 5 It is a structural schematic diagram of an unrolled positive electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0071] Figure 6 It is a partial structural schematic diagram of an unfolded negative electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0072] Figure 7 It is a partial cross-sectional structural schematic diagram (one) of an electrode assembly of a secondary battery according to a preferred embodiment of the present utility model.

[0073] Figure 8 It is a structural schematic diagram of an unrolled negative electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0074] Figure 9 It is a partial structural schematic diagram of an unfolded negative electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0075] Figure 10 It is a partial cross-sectional structural schematic diagram (two) of an electrode assembly of a secondary battery according to a preferred embodiment of the present utility model.

[0076] Figure 11 It is a partial cross-sectional structural schematic diagram (three) of an electrode assembly of a secondary battery according to a preferred embodiment of the present utility model.

[0077] Figure 12 It is Figure 11 a partially enlarged structural schematic diagram of part B in

[0078] Figure 13 It is Figure 11 a partially enlarged structural schematic diagram of part C in

[0079] Figure 14Partial cross-sectional structural schematic diagram (1) of the single-turn positive electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0080] Figure 15 Partial cross-sectional structural schematic diagram (2) of the single-turn positive electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0081] Figure 16 Partial cross-sectional structural schematic diagram (1) of the single-turn negative electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0082] Figure 17 Partial cross-sectional structural schematic diagram (2) of the single-turn negative electrode sheet of a secondary battery according to a preferred embodiment of the present utility model.

[0083] Figure 18 Structural schematic diagram of a battery pack according to a preferred embodiment of the present utility model.

[0084] Figure 19 Structural schematic diagram of an electronic device according to a preferred embodiment of the present utility model.

[0085] Description of reference numerals

[0086] Electronic device 1000; battery pack 100; working section 300; box body 310; box cover 320; secondary battery 1; housing 10; side wall 11; opening 12; end wall 13; electrode assembly 20; winding structure 201; central hole 2011; positive electrode plate 21; positive current collector 211; positive active material layer 2111; positive coating area 212; positive uncoated area 213; positive tab stacking area 2131; positive tab stacking number increasing area 21311; positive tab stacking number stable area 21312; positive tab stacking number decreasing area 21313; first positive uncoated area 214; second positive uncoated area 215; positive tab 2151; positive tab transition part 21511; positive tab body 21512; positive connection area 2152; third positive uncoated area 216; positive electrode plate starting position 217; positive electrode plate ending position 218; separator 22; separator starting position 221; separator ending position 222; negative electrode plate 23; negative current collector 231; negative active material layer 2311; negative coating area 232; negative uncoated area 233; negative tab stacking area 2331; negative tab stacking number increasing area 23311; negative tab stacking number stable area 23312; negative tab stacking number decreasing area 23313; first negative uncoated area 234; second negative uncoated area 235; negative tab 2351; negative tab transition part 23511; negative tab body 23512; negative connection area 2352; third negative uncoated area 236; negative electrode plate starting position 237; negative electrode plate ending position 238; insulating layer 24; insulating film 25; crimping part 30; cover plate 40; insulating seal 50; first current collecting plate 61; second current collecting plate 62; terminal post 70; length a1 of the first positive uncoated area; length a2 of the second positive uncoated area; length a3 of the third positive uncoated area; length b1 of the first negative uncoated area; length b2 of the second negative uncoated area; length b3 of the third negative uncoated area; width c1 of the positive tab transition part; width c2 of the positive tab body; width c3 of the positive connection area; width d1 of the negative transition part; width d2 of the negative tab; width d3 of the negative connection area; length f1 of the positive tab stacking number stable area; length f2 of the negative tab stacking number stable area; diameter f3 of the central hole; thickness t1 of the positive tab; thickness t2 of the negative tab; axial direction O of the winding structure; radial direction R of the winding structure; winding direction P of the winding structure; first direction Q1; second direction Q2; length direction L1 of the positive current collector; length direction L2 of the negative current collector; first acute angle α; second acute angle β; width direction W1 of the positive current collector; width direction W2 of the negative current collector. Detailed implementation manners

[0087] A preferred embodiment is given below and the present utility model will be more clearly and completely described in conjunction with the accompanying drawings.

[0088] In the prior art, the number of layers after bending of the positive electrode tab and the negative electrode tab of a secondary battery is usually the same. If the number of layers provided in the weldable areas of the positive and negative electrode tabs is too small and there is not enough reserved number of non-welded layers, the separator will be scalded during the welding process; while if the number of layers provided in the weldable areas of the positive and negative electrode tabs is too large, the energy density of the battery will be reduced.

[0089] As Figure 1 and Figure 2 shown, this embodiment provides a secondary battery 1. The secondary battery 1 includes: a housing 10 and an electrode assembly 20, and the electrode assembly 20 is accommodated in the housing 10.

[0090] As Figure 3 , Figure 4 , Figures 11 to 13 shown, the electrode assembly 20 includes a winding structure 201 formed by laminating and winding a positive electrode sheet 21, a separator 22, and a negative electrode sheet 23. A winding structure 201 is formed by laminating and winding the positive electrode sheet 21, the separator 22, and the negative electrode sheet 23, and a central hole 2011 is usually formed in the middle. The axial direction of the central hole 2011 is the axial direction O of the winding structure 201, and the axial direction O of the winding structure 201 is the same as the height direction of the secondary battery 1.

[0091] As Figures 5 to 7 shown, the positive electrode sheet 21 includes a positive electrode current collector 211. Along the axial direction O of the winding structure 201, the positive electrode current collector 211 includes a positive electrode coated area 212 covered by a positive electrode active material layer 2111 and a positive electrode uncoated area 213 not covered by the positive electrode active material layer 2111. Along the radial direction R of the winding structure 201, a part of the positive electrode uncoated area 213 is bent towards the central hole 2011 of the winding structure 201, and the positive electrode uncoated areas 213 of different winding turns are laminated with each other to form a positive electrode tab lamination area 2131. The positive electrode tab lamination area 2131 includes a positive electrode tab lamination number stable area 21312, and within the positive electrode tab lamination number stable area 21312, the number of layers of the positive electrode tab 2151 is m.

[0092] As Figures 8 to 10 shown, the negative electrode sheet 23 includes a negative electrode current collector 231. Along the axial direction O of the winding structure 201, the negative electrode current collector 231 includes a negative electrode coated area 232 covered by a negative electrode active material layer 2311 and a negative electrode uncoated area 233 not covered by the negative electrode active material layer 2311. Along the radial direction R of the winding structure 201, a part of the negative electrode uncoated area 233 is bent towards the central hole 2011, and the negative electrode uncoated areas 233 of different winding turns are laminated with each other to form a negative electrode tab lamination area 2331. The negative electrode tab lamination area 2331 includes a negative electrode tab lamination number stable area 23312, and within the negative electrode tab lamination number stable area 23312, the number of layers of the negative electrode tab 2351 is n.

[0093] Wherein, m > n.

[0094] In this way, by setting the number of stacked layers m of the positive electrode tab 2151 within the stable region 21312 of the number of stacked layers of the positive electrode tab to be greater than the number of stacked layers n of the negative electrode tab 2351 within the stable region 23312 of the number of stacked layers of the negative electrode tab, it is possible to ensure that there are sufficient un-welded stacked layers of tabs both within the stable region 21312 of the number of stacked layers of the positive electrode tab and within the stable region 23312 of the number of stacked layers of the negative electrode tab, thereby preventing the separator 22 from being scalded during the welding process; at the same time, the number of stacked layers of the negative electrode tab 2351 is increased as little as possible, thereby avoiding an impact on the energy density of the secondary battery 1. That is, while improving the energy density of the secondary battery 1, the separator 22 is prevented from being scalded. It should be noted that the stable region 21312 of the number of stacked layers of the positive electrode tab, that is, the weldable region of the positive electrode tab, the number of stacked layers of the positive electrode tab 2151 in the weldable region of the positive electrode tab is positively correlated with the thicknesses of the positive electrode active material layer 2111, the positive electrode current collector 211, and the separator 22. The number of stacked layers of the positive electrode tab 2151 in this weldable region of the positive electrode tab includes the number of stacked layers welded to the first current collecting plate 61 and the number of stacked layers not welded to the first current collecting plate 61. These numbers of stacked layers not welded to the first current collecting plate 61 are the redundant stacked layers of the reserved positive electrode tab 2151, which play a role in preventing the separator 22 from being scalded during the welding process; similarly, the stable region 23312 of the number of stacked layers of the negative electrode tab, that is, the weldable region of the negative electrode tab, the number of stacked layers of the negative electrode tab 2351 in the weldable region of the negative electrode tab is negatively correlated with the thicknesses of the negative electrode active material layer 2311, the negative electrode current collector 231, and the separator 22. The number of stacked layers of the negative electrode tab 2351 in this weldable region of the negative electrode tab includes the number of stacked layers welded to the second current collecting plate 62 and the number of stacked layers not welded to the second current collecting plate 62. The separator 22 is made of an insulating material, specifically, it can be PP (polypropylene) or PE (polyethylene), etc.

[0095] Please refer back to Figure 7 , along the radial direction R of the winding structure 201, from the outer periphery to the central hole 2011, the positive electrode tab stacking region 2131 sequentially includes a positive electrode tab number of stacked layers increasing region 21311, the aforementioned stable region 21312 of the number of stacked layers of the positive electrode tab, and a positive electrode tab number of stacked layers decreasing region 21313; please refer back to Figure 10 , along the radial direction R of the winding structure 201, from the outer periphery to the central hole 2011, the negative electrode tab stacking region 2331 sequentially includes a negative electrode tab number of stacked layers increasing region 23311, the aforementioned stable region 23312 of the number of stacked layers of the negative electrode tab, and a negative electrode tab number of stacked layers decreasing region 23313.

[0096] Along the radial direction R of the winding structure 201, a part of the uncoated area 213 of the positive electrode bends towards the central hole 2011 of the winding structure 201, such that from the outer periphery of the winding structure 201 to the central hole 2011, there is a change in the number of stacked layers from gradually increasing to stable and then to gradually decreasing. Correspondingly, a positive electrode tab stacking area 2131 is formed, which sequentially includes a positive electrode tab stacking number increasing area 21311, a positive electrode tab stacking number stable area 21312, and a positive electrode tab stacking number decreasing area 21313. The number of layers in the positive electrode tab stacking number stable area 21312 is the largest and relatively uniform. Similarly, a negative electrode tab stacking area 2331 is formed, which sequentially includes a negative electrode tab stacking number increasing area 23311, a negative electrode tab stacking number stable area 23312, and a negative electrode tab stacking number decreasing area 23313. The number of layers in the negative electrode tab stacking number stable area 23312 is the largest and relatively uniform.

[0097] Along the radial direction R of the winding structure 201, the length f1 of the positive electrode tab stacking number stable area 21312 is greater than the length f2 of the negative electrode tab stacking number stable area 23312. The longer the length f1 of the positive electrode tab stacking number stable area 21312 and the length f2 of the negative electrode tab stacking number stable area 23312, the more the number of tab layers in the weldable area formed after stacking. Thus, by setting the length f1 of the positive electrode tab stacking number stable area 21312 to be greater than the length f2 of the negative electrode tab stacking number stable area 23312, it indirectly realizes that the stacking number of the positive electrode tabs 2151 in the positive electrode tab stacking number stable area 21312 is greater than the stacking number of the negative electrode tabs 2351 in the negative electrode tab stacking number stable area 23312, thereby achieving the improvement of the energy density of the secondary battery 1 while preventing the separator 22 from being scalded.

[0098] Specifically, along the axial direction O of the winding structure 201, the stacking number of the positive electrode tabs 2151 in the positive electrode tab stacking number stable area 21312 is 15 - 22 layers. For example, it can be 15 layers, 17 layers, 18 layers, 20 layers, or 22 layers, etc. In this way, by setting the value range of the stacking number of the positive electrode tabs 2151 in the positive electrode tab stacking number stable area 21312, on the one hand, it can avoid too few stacking numbers of the positive electrode tabs 2151, without reserving enough un-welded stacking numbers, resulting in scalding of the separator 22; on the other hand, it can avoid too many stacking numbers of the positive electrode tabs 2151, which have an adverse impact on the energy density of the secondary battery 1.

[0099] Along the axis O of the winding structure 201, the number of layers of the negative electrode tab 2351 located in the stable region 23312 of the number of layers of the negative electrode tab is 12 - 18 layers. For example, it can be 12 layers, 13 layers, 15 layers, 16 layers, or 18 layers, etc. In this way, by setting the value range of the number of layers of the negative electrode tab 2351 located in the stable region 23312 of the number of layers of the negative electrode tab, on the one hand, it can avoid the situation where the number of layers of the negative electrode tab 2351 is too small and there is not enough number of un-welded layers reserved, resulting in scalding the separator 22; on the other hand, it can avoid the situation where the number of layers of the negative electrode tab 2351 is too large and having an adverse impact on the energy density of the secondary battery 1.

[0100] Along the axis O of the winding structure 201, the ratio of the number of layers m of the positive electrode tab 2151 located in the stable region 21312 of the number of layers of the positive electrode tab to the number of layers n of the negative electrode tab 2351 located in the stable region 23312 of the number of layers of the negative electrode tab is 1.05 - 1.5. For example, it can be 1.05, 1.17, 1.2, 1.3, 1.41, or 1.5, etc. In this way, by setting the value range of the ratio of the number of layers m of the positive electrode tab 2151 located in the stable region 21312 of the number of layers of the positive electrode tab to the number of layers n of the negative electrode tab 2351 located in the stable region 23312 of the number of layers of the negative electrode tab, making this ratio a suitable ratio, not only can the number of layers m of the positive electrode tab 2151 located in the stable region 21312 of the number of layers of the positive electrode tab be greater than the number of layers n of the negative electrode tab 2351 located in the stable region 23312 of the number of layers of the negative electrode tab, but also the number of layers of both can be within a suitable range, so as to achieve preventing scalding the separator 22 while improving the energy density of the secondary battery 1.

[0101] Please refer back to Figure 1 Preferably, the secondary battery 1 further includes a current collector plate, and the current collector plate includes a first current collector plate 61 and a second current collector plate 62. The first current collector plate 61 is welded to the stable region 21312 of the number of layers of the positive electrode tab and forms a first welding mark, and the second current collector plate 62 is welded to the stable region 23312 of the number of layers of the negative electrode tab and forms a second welding mark.

[0102] Along the axis O of the winding structure 201, the number of layers of the positive electrode tab 2151 connecting the first welding mark is 8 - 12 layers. For example, it can be 8 layers, 10 layers, or 12 layers, etc. Along the axis O of the winding structure 201, the number of layers of the negative electrode tab 2351 connecting the second welding mark is 8 - 12 layers. For example, it can be 8 layers, 10 layers, or 12 layers, etc. In this way, by setting the value range of the number of layers of the positive electrode tab 2151 connecting the first welding mark and the number of layers of the negative electrode tab 2351 connecting the second welding mark, the welding strength between the positive electrode tab 2151 and the first current collector plate 61 and the welding strength between the negative electrode tab 2351 and the second current collector plate 62 can be effectively guaranteed.

[0103] Along the axial direction O of the winding structure 201, within the positive electrode tab stacking number stable region 21312, the ratio i of the stacking number of the positive electrode tabs 2151 connected to the first welding mark to the stacking number m of the positive electrode tabs 2151 located in the positive electrode tab stacking number stable region 21312 is 0.4 - 0.65. For example, it can be 0.4, 0.45, 0.55, 0.6, or 0.65, etc. The stacking number of the positive electrode tabs 2151 connected to the first welding mark, that is, the stacking number welded to the first current collector plate 61 within the positive electrode tab stacking number stable region 21312; by setting the value range of the ratio i of it to the stacking number m of the positive electrode tabs 2151 located in the positive electrode tab stacking number stable region 21312 to make this ratio a suitable ratio, on the one hand, it can avoid too few stacking numbers of the positive electrode tabs 2151 not connected to the first welding mark, and there is not enough un-welded stacking number reserved, resulting in scalding the separator 22; on the other hand, it can avoid too many stacking numbers of the positive electrode tabs 2151, which has an adverse effect on the energy density of the secondary battery 1.

[0104] Along the axial direction O of the winding structure 201, within the negative electrode tab stacking number stable region 23312, the ratio j of the stacking number of the negative electrode tabs 2351 connected to the second welding mark to the stacking number n of the negative electrode tabs 2351 located in the negative electrode tab stacking number stable region 23312 is 0.5 - 0.8. For example, it can be 0.5, 0.55, 0.65, 0.7, or 0.8, etc. The stacking number of the negative electrode tabs 2351 connected to the second welding mark, that is, the stacking number welded to the second current collector plate 62 within the negative electrode tab stacking number stable region 23312; by setting the value range of the ratio j of it to the stacking number n of the negative electrode tabs 2351 located in the negative electrode tab stacking number stable region 23312 to make this ratio a suitable ratio, on the one hand, it can avoid too few stacking numbers of the negative electrode tabs 2351 not connected to the second welding mark, and there is not enough un-welded stacking number reserved, resulting in scalding the separator 22; on the other hand, it can avoid too many stacking numbers of the negative electrode tabs 2351, which has an adverse effect on the energy density of the secondary battery 1.

[0105] Preferably, i < j, so as to ensure that there are enough un-welded tab stacking numbers reserved both within the positive electrode tab stacking number stable region 21312 and within the negative electrode tab stacking number stable region 23312, and prevent scalding the separator 22 during the welding process; at the same time, the stacking number of the negative electrode tabs 2351 is increased as little as possible, thus avoiding the impact on the energy density of the secondary battery 1.

[0106] Please refer back to Figure 7 and Figure 11, preferably, along the radial direction R of the winding structure 201, the ratio of the length f1 of the positive electrode tab stacking number stable area 21312 to the diameter f3 of the central hole 2011 is 0.5 - 1.4, and can be, for example, 0.5, 0.64, 0.7, 0.95, 1.23 or 1.4, etc. By setting the value range of the ratio of the length f1 of the positive electrode tab stacking number stable area 21312 to the diameter f3 of the central hole 2011, on the one hand, it avoids the length f1 of the positive electrode tab stacking number stable area 21312 being too long and causing the tabs near the position of the central hole 2011 to interfere with each other. On the other hand, it avoids the length f1 of the positive electrode tab stacking number stable area 21312 being too short and not being able to provide enough area for welding with the first current collector plate 61, thus affecting the welding strength.

[0107] Please refer back to Figure 8 and Figure 11 , similarly, along the radial direction R of the winding structure 201, the ratio of the length f2 of the negative electrode tab stacking number stable area 23312 to the diameter f3 of the central hole 2011 is 0.5 - 1.4, and can be, for example, 0.5, 0.64, 0.7, 0.95, 1.23 or 1.4, etc. By setting the value range of the ratio of the length f2 of the negative electrode tab stacking number stable area 23312 to the diameter f3 of the central hole 2011, on the one hand, it avoids the length f2 of the negative electrode tab stacking number stable area 23312 being too long and causing the tabs near the position of the central hole 2011 to interfere with each other. On the other hand, it avoids the length f2 of the negative electrode tab stacking number stable area 23312 being too short and not being able to provide enough area for welding with the second current collector plate 62, thus affecting the welding strength.

[0108] The diameter f3 of the central hole 2011 is 4 mm - 8 mm. By setting the value range of the diameter f3 of the central hole 2011, it avoids the diameter f3 of the central hole 2011 being too small, resulting in too large a torque during the winding of the winding needle and being inconvenient for winding. At the same time, it avoids the diameter f3 of the central hole 2011 being too large, causing the overall volume to increase and reducing the energy density of the secondary battery 1.

[0109] Please refer back to Figure 5 , along the winding direction P of the winding structure 201, the positive electrode uncoated area 213 sequentially includes a first positive electrode uncoated area 214, a second positive electrode uncoated area 215, and a third positive electrode uncoated area 216.

[0110] Please refer back to Figure 8 , along the winding direction P of the winding structure 201, the negative electrode uncoated area 233 sequentially includes a first negative electrode uncoated area 234, a second negative electrode uncoated area 235, and a third negative electrode uncoated area 236.

[0111] Such as Figure 14As shown, the direction from the positive electrode coated area 212 to the uncoated area 213 of the positive electrode is the first direction Q1. Along the first direction Q1, the second uncoated area 215 of the positive electrode includes the positive electrode tab 2151 and the positive electrode connection area 2152 connecting the positive electrode tab 2151 and the positive electrode coated area 212. Neither the first uncoated area 214 nor the third uncoated area 216 of the positive electrode includes a positive electrode tab. As Figure 16 shown, the direction from the negative electrode coated area 232 to the uncoated area 233 of the negative electrode is the second direction Q2. Along the second direction Q2, the second uncoated area 235 of the negative electrode includes the negative electrode tab 2351 and the negative electrode connection area 2352 connecting the negative electrode tab 2351 and the negative electrode coated area 232. Neither the first uncoated area 234 nor the third uncoated area 236 of the negative electrode includes the negative electrode tab. Among them, the number of winding turns of the third uncoated area 216 of the positive electrode is greater than the number of winding turns of the third uncoated area 236 of the negative electrode.

[0112] In this way, by setting the number of winding turns of the third uncoated area 216 of the positive electrode to be greater than the number of winding turns of the third uncoated area 236 of the negative electrode, the outward expansion along the radial direction R of the winding structure 201 after the second uncoated area 215 of the positive electrode is bent and the second uncoated area 235 of the negative electrode is bent is made as consistent as possible, thereby avoiding the influence on the energy density of the secondary battery 1; at the same time, the number of winding turns of the third uncoated area 236 of the negative electrode is reduced as little as possible, so as to avoid the increase of the internal resistance of the secondary battery 1. That is, the energy density of the secondary battery 1 is increased and the internal resistance of the battery is reduced.

[0113] Please refer back to Figure 4 , in the winding structure 201, the positive electrode sheet 21 includes the starting position 217 and the ending position 218 of the positive electrode sheet; the negative electrode sheet 23 includes the starting position 237 and the ending position 238 of the negative electrode sheet; the separator 22 includes the starting position 221 and the ending position 222 of the separator. The outside of the winding structure 201 is also coated with an insulating film 25, and the insulating film 25 can be synthesized from PP, PE, PET, PVC or other polymer materials.

[0114] When the positive electrode sheet 21 is in the unwound state (when the positive electrode sheet 21 is unfolded), that is, in the state before winding, along the winding direction P of the winding structure 201, the positions of the first uncoated area 214, the second uncoated area 215 and the third uncoated area 216 of the positive electrode are as Figure 5 shown; and after the winding structure 201 is formed, the positions of the first uncoated area 214, the second uncoated area 215 and the third uncoated area 216 of the positive electrode are as Figure 7 shown. Similarly, when the negative electrode sheet 23 is in the unwound state (when the negative electrode sheet 23 is unfolded), along the winding direction P of the winding structure 201, the positions of the first uncoated area 234, the second uncoated area 235 and the third uncoated area 236 of the negative electrode are as Figure 8As shown; after the winding structure 201 is formed, the positions of the first uncoated negative electrode region 234, the second uncoated negative electrode region 235, and the third uncoated negative electrode region 236 are as Figure 10 shown.

[0115] When the positive electrode sheet 21 is unfolded, the positive electrode current collector 211 is in a flat state, and the first direction Q1 is the same as the width direction W1 of the positive electrode current collector 211; when the positive electrode sheet 21 is wound and the positive electrode tab 2151 is bent, the first direction Q1 changes with the bending of the positive electrode tab 2151. At this time, the first direction Q1 is the direction from the positive electrode connection region 2152 to the positive electrode tab 2151.

[0116] Similarly, when the negative electrode sheet 23 is unfolded, the negative electrode current collector 231 is in a flat state, and the second direction Q2 is the same as the width direction W2 of the negative electrode current collector 231; when the negative electrode sheet 23 is wound and the negative electrode tab 2351 is bent, the second direction Q2 changes with the bending of the negative electrode tab 2351. At this time, the second direction Q2 is the direction from the negative electrode connection region 2352 to the negative electrode tab 2351.

[0117] It should be noted that the number of winding turns of the third uncoated positive electrode region 216 refers to the number of overlapping turns of the third uncoated positive electrode region 216 along the radial direction R of the wound winding structure 201 after winding. Similarly, the number of winding turns of the third uncoated negative electrode region 236 refers to the number of overlapping turns of the third uncoated negative electrode region 236 along the radial direction R of the wound winding structure 201 after winding. In addition, the housing 10 may contain one or more electrode assemblies 20.

[0118] In this embodiment, the housing 10 contains one electrode assembly 20, but it is not limited thereto. In other embodiments, the number of electrode assemblies 20 contained in the housing 10 may also be two, three, four, or other values, which can be adjusted according to design requirements.

[0119] Specifically, the value range of the number of winding turns of the third uncoated positive electrode region 216 is 3 - 6. In this way, by setting the value range of the number of winding turns of the third uncoated positive electrode region 216, on the one hand, it can avoid the number of winding turns of the third uncoated positive electrode region 216 being too small, resulting in excessive outward expansion along the radial direction R of the winding structure 201 after the second uncoated positive electrode region 215 is bent, which has an adverse effect on the energy density of the secondary battery 1; on the other hand, it can avoid the number of winding turns of the third uncoated positive electrode region 216 being too large, resulting in too large internal resistance of the battery.

[0120] The number of winding turns formed by the third negative electrode uncoated area 236 ranges from 1 to 3. In this way, by setting the range of the number of winding turns formed by the third negative electrode uncoated area 236, on the one hand, it can avoid too few winding turns of the third negative electrode uncoated area 236, and excessive outward expansion along the radial direction R of the winding structure 201 after the second negative electrode uncoated area 235 is bent, which has an adverse effect on the energy density of the secondary battery 1; on the other hand, it can avoid too many winding turns formed by the third negative electrode uncoated area 236, resulting in too large internal resistance of the battery.

[0121] Along the axial direction O of the winding structure 201, in the winding turns of the second positive electrode uncoated area 215, the outermost second positive electrode uncoated area 215 includes a first bent portion, and the orthographic projection of the first bent portion is located within the outer peripheral edge of the winding structure 201, so as to ensure that the second positive electrode uncoated area 215 after bending does not expand beyond the outer peripheral edge of the winding structure 201 along the radial direction R of the winding structure 201, thereby avoiding affecting the energy density of the secondary battery 1.

[0122] Along the axial direction O of the winding structure 201, in the winding turns of the second negative electrode uncoated area 235, the outermost second negative electrode uncoated area 235 includes a second bent portion, and the orthographic projection of the second bent portion is located within the outer peripheral edge of the winding structure 201, so as to ensure that the second positive electrode uncoated area 215 after bending does not expand beyond the outer peripheral edge of the winding structure 201 along the radial direction R of the winding structure 201, thereby avoiding affecting the energy density of the secondary battery 1.

[0123] Preferably, please refer back to Figure 5 Along the winding direction P of the winding structure 201, the length a1 of the first positive electrode uncoated area 214 is 400 mm - 600 mm, for example, it can be 400 mm, 450 mm, 500 mm, 520 mm, 580 mm or 600 mm, etc. The length a2 of the second positive electrode uncoated area 215 is 3000 mm - 5000 mm, for example, it can be 3000 mm, 3500 mm, 4000 mm, 4200 mm, 4800 mm or 5000 mm, etc. The length a3 of the third positive electrode uncoated area 216 is 200 mm - 500 mm, for example, it can be 200 mm, 250 mm, 300 mm, 400 mm, 450 mm or 500 mm, etc.

[0124] Please refer back to Figure 8, along the winding direction P of the winding structure 201, the length b1 of the first negative electrode uncoated area 234 is 300 mm - 500 mm, and can be, for example, 300 mm, 350 mm, 400 mm, 420 mm, 480 mm or 500 mm, etc. The length b2 of the second negative electrode uncoated area 235 is 3000 mm - 5000 mm, and can be, for example, 3000 mm, 3500 mm, 4000 mm, 4200 mm, 4800 mm or 5000 mm, etc. The length b3 of the third negative electrode uncoated area 236 is 100 mm - 300 mm, and can be, for example, 100 mm, 150 mm, 200 mm, 220 mm, 280 mm or 300 mm, etc.

[0125] In this way, by setting the value ranges of the length a1 of the first positive electrode uncoated area 214, the length a2 of the second positive electrode uncoated area 215, the length a3 of the third positive electrode uncoated area 216, the length b1 of the first negative electrode uncoated area 234, the length b2 of the second negative electrode uncoated area 235, and the length b3 of the third negative electrode uncoated area 236, the energy density can be better improved and the internal resistance of the battery can be reduced.

[0126] The ratio of the length a3 of the third positive electrode uncoated area 216 to the length b3 of the third negative electrode uncoated area 236 is 1.5 - 2.5, and can be, for example, 1.5, 1.7, 2, 2.1, 2.3 or 2.5, etc. In this way, by setting the value range of the ratio of the length a3 of the third positive electrode uncoated area 216 to the length b3 of the third negative electrode uncoated area 236 to make this ratio a suitable ratio, it can be ensured that not only the number of turns of the third positive electrode uncoated area 216 is greater than that of the third negative electrode uncoated area 236, but also the lengths of both are within a suitable range, and the internal resistance of the battery can be within a suitable range.

[0127] The positive electrode tab 2151 is located within the positive electrode tab stacking area 2131, and the negative electrode tab 2351 is located within the negative electrode tab stacking area 2331.

[0128] In this embodiment, the secondary battery 1 is a cylindrical battery. The cylindrical battery has advantages such as high energy density, long cycle life, and good safety performance. However, it is not limited thereto. In other embodiments, the secondary battery 1 can also be a square battery or other shaped batteries.

[0129] In this embodiment, the positive electrode tab 2151 is a cut and stacked tab. When the tab of the cylindrical battery is welded to the current collector plate, the pre-treatment steps of the tab include two different treatment methods. One is the tab flattening treatment method, and the other is the cut and stacked tab treatment method adopted by the positive electrode tab 2151 in this embodiment. Please refer back to Figure 6, when the positive electrode sheet 21 is unfolded, the positive electrode current collector 211 is in a flat state, and a first acute angle α is formed between the extending direction of the positive electrode tab 2151 and the length direction L1 of the positive electrode current collector 211. The first acute angle α is 30 degrees to 85 degrees. By setting the value range of the first acute angle α, the length of the positive electrode tab 2151 can be extended within a certain range while ensuring the connection strength of the positive electrode tab 2151.

[0130] The negative electrode tab 2351 is also a cut and folded tab. Please refer back to Figure 9 , when the negative electrode sheet 23 is unfolded, the negative electrode current collector 231 is in a flat state, and a second acute angle β is formed between the extending direction of the negative electrode tab 2351 and the length direction L2 of the negative electrode current collector 231. The second acute angle β is 30 degrees to 85 degrees. By setting the value range of the second acute angle β, the length of the negative electrode tab 2351 can be extended within a certain range while ensuring the connection strength of the negative electrode tab 2351.

[0131] The positive electrode connection region 2152 includes a first side away from the central hole 2011 of the winding structure 201 and a second side close to the central hole 2011 along the radial direction R of the winding structure 201. Among them, at least part of the first side and / or the second side is covered with an insulating layer 24 to reduce the deformation risk of the positive electrode connection region 2152 and improve the insulation performance of the positive electrode connection region 2152, thereby greatly improving the safety and reliability of the battery performance. The main components of the insulating layer 24 are: boehmite and PVDF (full English name: polyvinylidene difluoride, Chinese name: polyvinylidene fluoride). The proportion of boehmite is 80%; the proportion of PVDF is 20%. The thickness of the insulating layer 24 is 1.5μm - 2.5μm, and for example, it can be 1.5μm, 1.7μm, 2μm, 2.1μm, 2.3μm or 2.5μm, etc. By setting the thickness range of the insulating layer 24, it is avoided that the coating thickness of the insulating layer 24 is too thin to obtain the required electrical insulation and support strength; at the same time, it is avoided that the thickness of the insulating layer 24 is too thick, resulting in a longer curing time of the coating layer and an increase in the thickness of the overall structure. Preferably, the thickness of the insulating layer 24 is 2μm.

[0132] Please refer back to Figure 12 and Figure 14 , in this embodiment, both the first side and the second side of the positive electrode connection region 2152 are covered with the insulating layer 24. However, it is not limited to this. In other embodiments, it may also be that only the first side of the positive electrode connection region 2152 is covered with the insulating layer 24, or only the second side of the positive electrode connection region 2152 is covered with the insulating layer 24. It can be adjusted according to the design requirements.

[0133] The insulating layer 24 includes a developer, and through the color development effect of the developer, it can be distinguished whether the side coated with the insulating layer 24 is the front or the back of the positive electrode sheet 21, including but not limited to cases such as the surface density for distinguishing the front and back of the positive electrode sheet 21. The main component of the developer is bismuth vanadate, and the color is yellow.

[0134] In this embodiment, it can be that the first side of the positive electrode connection area 2152 is covered with the insulating layer 24 containing the developer; the second side of the positive electrode connection area 2152 is covered with the insulating layer 24 not containing the developer, so that the front and back sides of the positive electrode sheet 21 have different colors. Thus, it can be quickly distinguished whether the front and back sides of the positive electrode sheet 21 by using the color development effect of the developer in the insulating layer 24. Because it is sometimes necessary to distinguish the front and back sides of the positive electrode sheet 21, including but not limited to cases such as the surface density for distinguishing the front and back of the positive electrode sheet 21, so it is necessary to add a developer to the insulating layer 24 on one side to achieve the purpose of quick distinction. In other embodiments, it can also be that the second side of the positive electrode connection area 2152 is covered with the insulating layer 24 containing the developer; the first side of the positive electrode connection area 2152 is covered with the insulating layer 24 not containing the developer, and it can also make the front and back sides of the positive electrode sheet 21 have different colors.

[0135] Preferably, the insulating layer 24 covers all areas of the first side of the positive electrode connection area 2152; the insulating layer 24 covers all areas of the second side of the positive electrode connection area 2152. Along the first direction Q1, the maximum width of the insulating layer 24 is greater than or equal to the width of the positive electrode connection area 2152. In this way, it can better prevent the deformation of the positive electrode connection area 2152 and improve the insulation performance of this area. It should be noted that if a part of the insulating layer 24 covers the positive electrode tab 2151, at this time, the width of the insulating layer 24 is the maximum width.

[0136] Please refer back to Figure 14 , further, along the first direction Q1, the positive electrode tab 2151 includes a positive electrode tab transition portion 21511 and a positive electrode tab body 21512. The positive electrode tab transition portion 21511 is connected between the positive electrode connection area 2152 and the positive electrode tab body 21512, and the positive electrode tab transition portion 21511 is the bending area of the positive electrode tab 2151.

[0137] Please refer back to Figure 16 , along the second direction Q2, the negative electrode tab 2351 includes a negative electrode tab transition portion 23511 and a negative electrode tab body 23512. The negative electrode tab transition portion 23511 is connected between the negative electrode connection area 2352 and the negative electrode tab body 23512, and the negative electrode tab transition portion 23511 is the bending area of the negative electrode tab 2351.

[0138] The width c1 of the positive electrode tab transition portion 21511 of the positive electrode tab 2151 located in the outermost circle is greater than the width d1 of the positive electrode tab transition portion 21511 of the negative electrode tab 2351 located in the outermost circle. In this way, since the hardness of the positive electrode tab 2151 is greater than that of the negative electrode tab 2351, during the pressing during installation, the outward expansion of the positive electrode tab 2151 along the radial direction R of the winding structure 201 will be greater than the outward expansion of the negative electrode tab 2351 along the radial direction R of the electrode assembly. By setting the width c1 of the positive electrode tab transition portion 21511 of the positive electrode tab 2151 located in the outermost circle to be greater than the width d1 of the positive electrode tab transition portion 21511 of the negative electrode tab 2351 located in the outermost circle, the positive electrode tab 2151 can have more bending regions compared to the negative electrode tab 2351, thereby avoiding the influence of pressing on the size of the positive electrode tab body 21512 formed after bending, and making the sizes of the positive electrode tab body 21512 and the negative electrode tab body 23512 formed after bending equivalent.

[0139] Please refer back to Figure 14 , preferably, along the first direction Q1, the width c1 of the positive electrode tab transition portion 21511 is 1 mm - 2 mm, and for example, it can be 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 1.9 mm or 2 mm, etc. In this way, by setting the value range of the width c1 of the positive electrode tab transition portion 21511, the positive electrode tab 2151 can have more bending regions compared to the negative electrode tab 2351 to avoid affecting the size of the positive electrode tab body 21512 formed after bending. It should be noted that the positive electrode tab transition portion 21511 is arc-shaped, and the positive electrode tab transition portion 21511 includes a first positive electrode tab transition endpoint A1 and a second positive electrode tab transition endpoint A2. The first positive electrode tab transition endpoint A1 is the position where the tangent of the positive electrode tab transition portion 21511 intersects with the extension direction of the positive electrode connection region 2152, and the second positive electrode tab transition endpoint A2 is the position where the tangent of the positive electrode tab transition portion 21511 intersects with the extension direction of the positive electrode tab body 21512. After being pressed, the positive electrode tab transition portion 21511 will be deformed and expand outward along the winding structure, and the formed structure is as Figure 15 shown.

[0140] Please refer back to Figure 16, preferably, along the second direction Q2, the width d1 of the negative electrode tab transition portion 23511 is 0.1 mm - 1 mm, for example, it can be 0.1 mm, 0.2 mm, 0.5 mm, 0.7 mm, 0.9 mm or 1 mm, etc. In this way, by setting the value range of the width d1 of the negative electrode tab transition portion 23511, the negative electrode tab 2351 has fewer bending regions compared to the positive electrode tab 2151, saving the material cost of the tab. It should be noted that the negative electrode tab transition portion 23511 is arc-shaped. The negative electrode tab transition portion 23511 includes a first negative electrode tab transition end point B1 and a second negative electrode tab transition end point B2. The first negative electrode tab transition end point B1 is the position where the tangent of the negative electrode tab transition portion 23511 intersects with the extending direction of the negative electrode connection region 2352, and the second negative electrode tab transition end point B2 is the position where the tangent of the negative electrode tab transition portion 23511 intersects with the extending direction of the negative electrode tab body 23512. After being pressed, the negative electrode tab transition portion 23511 will deform and expand outward along the winding structure, and the formed structure is as Figure 17 shown.

[0141] , preferably, along the first direction Q1, the width c2 of the positive electrode tab body 21512 is 4.5 mm - 5.5 mm, for example, it can be 4.5 mm, 4.7 mm, 5 mm, 5.1 mm, 5.3 mm or 5.5 mm, etc.; along the second direction Q2, the width d2 of the negative electrode tab body 23512 is 4 mm - 5 mm, for example, it can be 4 mm, 4.2 mm, 4.5 mm, 4.7 mm, 4.9 mm or 5 mm, etc. In this way, by setting the value ranges of the width c2 of the positive electrode tab body 21512 and the width d2 of the negative electrode tab body 23512, a reasonable positive electrode tab stacking area and negative electrode tab stacking area can be formed, avoiding too many tab layers in the stacking area and reducing the energy density of the battery; while too few tab layers in the stacking area cannot provide enough reserved space, which may scald the surrounding components (such as the separator 22, etc.) during the welding process, that is, form a thermal influence on the surrounding components, thereby damaging the surrounding components.

[0142] , preferably, along the first direction Q1, the width c3 of the positive electrode connection region 2152 is 1.5 mm - 2.5 mm, for example, it can be 1.5 mm, 1.7 mm, 2 mm, 2.1 mm, 2.3 mm or 2.5 mm, etc. In this way, by setting the value range of the width c3 of the positive electrode connection region 2152, the distance from the welding surface of the positive electrode current collector plate and the positive electrode tab 2151 to the positive electrode coating region 212 covered with the positive electrode active material layer 2111 can be ensured, avoiding the thermal influence during welding and improving the safety performance.

[0143] Along the second direction Q2, the width d3 of the negative electrode connection region 2352 is 1 mm - 2 mm, and for example, it can be 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 1.9 mm, or 2 mm, etc. In this way, by setting the value range of the width of the negative electrode connection region 2352, the distance from the welding surface of the negative electrode current collector plate and the negative electrode tab 2351 to the negative electrode coating region 232 covered with the negative electrode active material layer can be ensured, avoiding the thermal influence during welding and improving the safety performance.

[0144] The thickness t1 of the positive electrode tab 2151 is 12 μm - 20 μm, and for example, it can be 12 μm, 14 μm, 16 μm, 17.5 μm, 19.5 μm, or 20 μm, etc. The thickness t2 of the negative electrode tab 2351 is 4 μm - 11 μm, and for example, it can be 4 μm, 6 μm, 7.5 μm, 8 μm, 9 μm, or 11 μm, etc. Since the material of the positive electrode tab 2151 is usually aluminum and the material of the negative electrode tab 2351 is usually copper, the hardness of the positive electrode tab 2151 is higher than that of the negative electrode tab 2351. By setting the value range of the thickness t1 of the positive electrode tab 2151, it is avoided that the thickness is too thin and it is easily torn during press-fitting, and the thickness is too thick and the manufacturing cost is increased. By setting the value range of the thickness t2 of the negative electrode tab 2351, on the basis of ensuring the installation requirements of the negative electrode tab 2351, the use of materials can be minimized to achieve the beneficial technical effect of cost saving.

[0145] Please refer back Figure 1 and Figure 2 Referring again, in this embodiment, the housing 10 includes a surrounding side wall 11, and an opening 12 is formed at one end of the side wall 11; one end of the housing 10 close to the opening 12 includes a crimping portion 30 recessed into the interior of the housing 10. The secondary battery 1 further includes: a cover plate 40, an insulating seal 50, and the aforementioned current collector plate. The cover plate 40 is installed at the opening 12. The insulating seal 50 is disposed around the periphery of the cover plate 40 to insulate and seal the cover plate 40 and the housing 10. The current collector plate is disposed between the electrode assembly 20 and the cover plate 40 and is electrically connected to the housing 10. The connecting piece of the current collector plate is located on the side of the crimping portion 30 facing the electrode assembly 20 and is welded to the crimping portion 30. In this way, by setting the connecting piece of the current collector plate to be located on the side of the crimping portion 30 facing the electrode assembly 20 and welded to the crimping portion 30, that is, the welding area of the current collector plate and the tab is located at a position closer to the electrode assembly 20 than the crimping portion 30, the influence of the crimping portion 30 on the welding area of the tab and the current collector plate can be prevented, and thus the welding strength of the tab and the current collector plate can be improved.

[0146] Further, the housing 10 further includes an end wall 13, and the side wall 11 is disposed around the end wall 13 and is located at one end of the side wall 11 away from the opening 12. The end wall 13 and the side wall 11 enclose a receiving cavity within the housing 10 for receiving the electrode assembly 20, the electrolyte, and other necessary battery components. The connection between the end wall 13 and the side wall 11 can be achieved in various ways, such as integral stamping, integral casting, or split welding.

[0147] The secondary battery 1 further includes a terminal post 70, and the terminal post 70 passes through the end wall 13 and is insulated from the end wall 13.

[0148] As described above, the current collector plate includes a first current collector plate 61 and a second current collector plate 62. Among them, the first current collector plate 61 is disposed between the electrode assembly 20 and the cover plate 40; the second current collector plate 62 is disposed between the electrode assembly and the end wall 13. In this embodiment, as described above, the first current collector plate 61 corresponds to the positive electrode tab 2151, and the positive electrode tab 2151 is electrically connected to the terminal post 70 through the first current collector plate 61; the second current collector plate 62 corresponds to the negative electrode tab 2351, and the negative electrode tab 2351 is electrically connected to the housing 10 through the second current collector plate 62. However, it is not limited thereto. In other embodiments, it may also be that the first current collector plate 61 corresponds to the positive electrode tab 2151 and the second current collector plate 62 corresponds to the negative electrode tab 2351.

[0149] The welding sequence of the first current collector plate 61 and the second current collector plate 62 of the secondary battery 1 in this embodiment with the electrode assembly 20 respectively: First, place the first current collector plate 61; then, press the electrode assembly 20 together on both the positive and negative sides (the pressing process can increase the contact between the current collector plate and the electrode assembly 20 and avoid false soldering); weld the first current collector plate 61 using linear welding instead of spot welding because the negative electrode tab 2351 is relatively soft. After two presses, the distance between the second current collector plate 62 and the electrode assembly 20 will be relatively close. Using spot welding, due to the concentrated heat, it will cause damage to the separator 22. Using linear welding, the heat is small, which can avoid damaging the separator 22 and causing a short circuit between the positive and negative electrodes; then, place the second current collector plate 62; press the electrode assembly 20 together on both the positive and negative sides again; finally, weld the second current collector plate 62.

[0150] As Figure 18As shown in the figure, the present utility model also provides a battery pack 100. The battery pack 100 includes the above-mentioned secondary battery 1. In an embodiment of the battery pack 100 of the present utility model, the battery pack 100 includes a box body 310, a box cover 320 and a plurality of secondary batteries 1. The plurality of secondary batteries 1 are placed in the box body 310 and are connected in series or in parallel with each other, or in a mixed connection of series and parallel. The box cover 320 covers the box body 310 to protect the plurality of secondary batteries 1. It should be noted that in addition to the secondary battery 1 of the present utility model, the battery pack 100 may also include parts such as a battery pack 100 thermal management system and a circuit board. The battery pack 100 may be a battery module or a battery pack, an energy storage electrical cabinet, etc.; details will not be elaborated here one by one.

[0151] As Figure 19 shown in the figure, the present utility model also provides an electronic device 1000. The electronic device 1000 includes the above-mentioned battery pack 100. The working part 300 is electrically connected to the battery pack 100 to obtain electrical energy support. As an example, the electronic device 1000 is a vehicle, which may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited thereto. The working part 300 is the vehicle body, and the battery pack 100 is arranged at the bottom of the vehicle body and provides electrical energy support for the running of the vehicle or the operation of in-vehicle electrical components. However, in some other embodiments, the electronic device 1000 may also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spaceship, etc.; the working part 300 may be a unit component that can obtain the electrical energy of the battery pack 100 and perform corresponding work, such as the fan blade rotation unit of a fan, the dust suction working unit of a vacuum cleaner, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle toy, an electric ship toy and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact electric drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not impose special restrictions on the above-mentioned electronic device 1000.

[0152] Although the specific embodiments of the present utility model have been described above, those skilled in the art should understand that this is only an example. The protection scope of the present utility model is defined by the appended claims. Without departing from the principles and essence of the present utility model, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present utility model.

Claims

1. A secondary battery, characterized in that, It includes: a housing; an electrode assembly, which is accommodated in the housing, and the electrode assembly includes a winding structure formed by laminating and winding a positive electrode sheet, a separator, and a negative electrode sheet; the positive electrode sheet includes a positive electrode current collector, and the negative electrode sheet includes a negative electrode current collector; along the axial direction of the winding structure, the positive electrode current collector includes a positive electrode coated area covered by a positive electrode active material layer and a positive electrode uncoated area not covered by the positive electrode active material layer, and the negative electrode current collector includes a negative electrode coated area covered by a negative electrode active material layer and a negative electrode uncoated area not covered by the negative electrode active material layer; Along the radial direction of the winding structure, a part of the positive electrode uncoated area is bent towards the central hole of the winding structure, and the positive electrode uncoated areas of different winding turns are laminated with each other to form a positive electrode tab laminated area, and the positive electrode tab laminated area includes a positive electrode tab lamination number stable area, in which the lamination number of the positive electrode tabs is m; Along the radial direction of the winding structure, a part of the negative electrode uncoated area is bent towards the central hole, and the negative electrode uncoated areas of different winding turns are laminated with each other to form a negative electrode tab laminated area, and the negative electrode tab laminated area includes a negative electrode tab lamination number stable area, in which the lamination number of the negative electrode tabs is n; wherein, m > n.

2. The secondary battery according to claim 1, characterized in that Along the radial direction of the winding structure, from the outer periphery to the central hole, the positive electrode tab laminated area sequentially includes a positive electrode tab lamination number increasing area, the positive electrode tab lamination number stable area, and a positive electrode tab lamination number decreasing area, and the negative electrode tab laminated area sequentially includes a negative electrode tab lamination number increasing area, the negative electrode tab lamination number stable area, and a negative electrode tab lamination number decreasing area; Along the radial direction of the winding structure, the length of the positive electrode tab lamination number stable area is greater than the length of the negative electrode tab lamination number stable area.

3. The secondary battery according to claim 1, characterized in that Along the axial direction of the winding structure, the lamination number of the positive electrode tabs located in the positive electrode tab lamination number stable area is 15 - 22 layers, or Along the axial direction of the winding structure, the lamination number of the negative electrode tabs located in the negative electrode tab lamination number stable area is 12 - 18 layers, or the ratio of m to n is 1.05 - 1.

5.

4. The secondary battery according to claim 1, wherein The secondary battery further includes a current collecting plate, and the current collecting plate includes a first current collecting plate and a second current collecting plate. The first current collecting plate is welded to the positive electrode tab lamination number stable area and forms a first welding mark, and the second current collecting plate is welded to the negative electrode tab lamination number stable area and forms a second welding mark; Along the axial direction of the winding structure, the lamination number of the positive electrode tabs connecting the first welding mark is 8 - 12 layers, or Along the axial direction of the winding structure, the lamination number of the negative electrode tabs connecting the second welding mark is 8 - 12 layers, or Along the axial direction of the winding structure, in the positive electrode tab lamination number stable area, the ratio i of the lamination number of the positive electrode tabs connecting the first welding mark to the lamination number of the positive electrode tabs located in the positive electrode tab lamination number stable area is 0.4 - 0.65; or Axially along the winding structure, within the stable region of the number of stacked negative electrode tabs, the ratio j of the number of stacked negative electrode tabs connecting the second weld mark to the number of stacked negative electrode tabs within the stable region of the number of stacked negative electrode tabs is 0.5 - 0.

8.

5. The secondary battery according to claim 1, characterized in that, i < j.

6. The secondary battery according to claim 1, wherein Radially along the winding structure, the ratio of the length of the stable region of the number of stacked positive electrode tabs to the diameter of the central hole is 0.5 - 1.4, or Radially along the winding structure, the ratio of the length of the stable region of the number of stacked negative electrode tabs to the diameter of the central hole is 0.5 - 1.4, or The diameter of the central hole is 4 mm - 8 mm.

7. The secondary battery according to claim 1, wherein The direction from the positive electrode coated area to the uncoated area of the positive electrode is the first direction, and the direction from the negative electrode coated area to the uncoated area of the negative electrode is the second direction; Axially along the winding direction of the winding structure, the uncoated area of the positive electrode sequentially includes a first uncoated area of the positive electrode, a second uncoated area of the positive electrode, and a third uncoated area of the positive electrode, and the uncoated area of the negative electrode sequentially includes a first uncoated area of the negative electrode, a second uncoated area of the negative electrode, and a third uncoated area of the negative electrode; Radially along the winding structure, the second uncoated area of the positive electrode is bent towards the central hole, and the second uncoated areas of different winding turns are stacked on top of each other to form the stacked area of the positive electrode tabs, the second uncoated area of the negative electrode is bent towards the central hole, and the second uncoated areas of different winding turns are stacked on top of each other to form the stacked area of the negative electrode tabs; Axially along the first direction, the second uncoated area of the positive electrode includes a positive electrode tab and a positive electrode connection area connecting the positive electrode tab and the positive electrode coated area, and neither the first uncoated area of the positive electrode nor the third uncoated area of the positive electrode includes the positive electrode tab; Axially along the second direction, the second uncoated area of the negative electrode includes a negative electrode tab and a negative electrode connection area connecting the negative electrode tab and the negative electrode coated area, and neither the first uncoated area of the negative electrode nor the third uncoated area of the negative electrode includes the negative electrode tab; The number of winding turns of the third uncoated area of the positive electrode is greater than the number of winding turns of the third uncoated area of the negative electrode.

8. The secondary battery according to claim 7, wherein The value range of the number of winding turns of the third uncoated area of the positive electrode is 3 - 6, or The value range of the number of winding turns of the third uncoated area of the negative electrode is 1 - 2.

9. The secondary battery according to claim 7, wherein Axially along the winding structure, among the winding turns of the second uncoated area of the positive electrode, the outermost second uncoated area of the positive electrode includes a first bent portion, and the orthographic projection of the first bent portion is located within the outer periphery of the winding structure, or Axially along the winding structure, among the winding turns of the second uncoated area of the negative electrode, the outermost second uncoated area of the negative electrode includes a second bent portion, and the orthographic projection of the second bent portion is located within the outer periphery of the winding structure.

10. The secondary battery according to claim 7, wherein In the winding direction of the winding structure, the length of the first uncoated area of the positive electrode is 400 mm - 600 mm, the length of the second uncoated area of the positive electrode is 3000 mm - 5000 mm, the length of the third uncoated area of the positive electrode is 200 mm - 500 mm, or, In the winding direction of the winding structure, the length of the first uncoated area of the negative electrode is 300 mm - 500 mm, the length of the second uncoated area of the negative electrode is 3000 mm - 5000 mm, the length of the third uncoated area of the negative electrode is 100 mm - 300 mm, or, The ratio of the length of the third uncoated area of the positive electrode to the length of the third uncoated area of the negative electrode is 1.5 - 2.

5.

11. The secondary battery according to claim 7, wherein, The positive electrode tab is a cut and stacked tab; when the positive electrode sheet is unfolded, the positive electrode current collector is in a flat state, and a first acute angle is formed between the extending direction of the positive electrode tab and the length direction of the positive electrode current collector, and the first acute angle is 30 degrees - 85 degrees; The negative electrode tab is a cut and stacked tab; when the negative electrode sheet is unfolded, the negative electrode current collector is in a flat state, and a second acute angle is formed between the extending direction of the negative electrode tab and the length direction of the negative electrode current collector, and the second acute angle is 30 degrees - 85 degrees.

12. The secondary battery according to claim 7, wherein, In the radial direction of the winding structure, the positive electrode connection area includes a first side away from the central hole of the winding structure and a second side close to the central hole, wherein at least part of the area of the first side and / or the second side is covered with an insulating layer; the insulating layer includes a color developer.

13. The secondary battery according to claim 12, wherein, The insulating layer covers the entire area of the first side of the positive electrode connection area; and / or, The insulating layer covers the entire area of the second side of the positive electrode connection area; and / or, In the first direction, the maximum width of the insulating layer is greater than or equal to the width of the positive electrode connection area.

14. The secondary battery according to claim 7, wherein, In the first direction, the width of the positive electrode connection area is 1.5 mm - 2.5 mm; and / or, In the second direction, the width of the negative electrode connection area is 1 mm - 2 mm.

15. The secondary battery according to claim 7, wherein, In the first direction, the positive electrode tab includes a positive electrode tab transition part and a positive electrode tab body, the positive electrode tab transition part is connected between the positive electrode connection area and the positive electrode tab body, and the positive electrode tab transition part is a bent area of the positive electrode tab; In the second direction, the negative electrode tab includes a negative electrode tab transition part and a negative electrode tab body, the negative electrode tab transition part is connected between the negative electrode connection area and the negative electrode tab body, and the negative electrode tab transition part is a bent area of the negative electrode tab; The width of the positive electrode tab transition part of the positive electrode tab located in the outermost circle is greater than the width of the positive electrode tab transition part of the negative electrode tab located in the outermost circle.

16. The secondary battery according to claim 15, wherein: Along the first direction, the width of the positive electrode tab transition portion is 1 mm - 2 mm, and the width of the positive electrode tab body is 4.5 mm - 5.5 mm; the thickness of the positive electrode tab is 12 μm - 20 μm; and / or, Along the second direction, the width of the negative electrode tab transition portion is 0.1 mm - 1 mm, and the width of the negative electrode tab body is 4 mm - 5 mm; the thickness of the negative electrode tab is 4 μm - 11 μm.

17. The secondary battery according to any one of claims 1-16, characterized in that, The housing includes a surrounding sidewall, and one end of the sidewall is formed with an opening; one end of the housing near the opening includes a crimping portion recessed into the interior of the housing; The secondary battery further includes: A cover plate, mounted on the opening; An insulating seal, which is disposed around the periphery of the cover plate to insulate and seal the cover plate and the housing; A current collector plate, disposed between the electrode assembly and the cover plate and electrically connected to the housing, and the connecting piece of the current collector plate is located on the side of the crimping portion facing the electrode assembly and is welded to the crimping portion; and / or, The secondary battery is a cylindrical battery.

18. A battery pack, characterized in that, Including the secondary battery according to any one of claims 1 to 17.

19. An electronic device, characterized in that, Including the battery pack according to claim 18.

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