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 includes: a case; the electrode assembly is accommodated in the shell and 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; in the winding direction of the winding structure, the positive electrode uncoated area sequentially comprises a first positive electrode uncoated area, a second positive electrode uncoated area and a third positive electrode uncoated area, and the negative electrode uncoated area sequentially comprises a first negative electrode uncoated area, a second negative electrode uncoated area and a third negative electrode uncoated area; the number of winding turns of the third positive electrode uncoated area is larger than that of winding turns of the third negative electrode uncoated area, so that the energy density of the secondary battery is improved, and the internal resistance of the battery is reduced.

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] The current secondary battery includes an electrode assembly and a housing. The electrode assembly generally includes a positive electrode, a negative electrode and a separator. After the positive electrode tab and the negative electrode tab of the electrode assembly of the secondary battery are welded to the corresponding current collector plate, since the current collector plate will be pressed during installation and then the tab is welded to the current collector plate, different materials are generally selected for the positive electrode tab and the negative electrode tab. Due to the different hardnesses of the positive electrode tab and the negative electrode tab, the pressing during installation will cause different distances of outward expansion of the positive electrode tab and the negative electrode tab along the radial direction of the secondary battery, occupying the space inside the battery housing, thereby affecting the energy density of the secondary battery. Summary of the Utility Model

[0004] The technical problem to be solved by the utility model is to provide a secondary battery, a battery pack and an electronic device in order to overcome the above technical problems in the prior art.

[0005] The utility model solves the above technical problems through the following technical solutions:

[0006] A secondary battery, characterized in that it includes:

[0007] A housing;

[0008] An electrode assembly accommodated in the housing, the electrode assembly including 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 current collector, and the negative electrode sheet includes a negative current collector; along the axial direction of the winding structure, the positive current collector includes a positive coated area covered by a positive active material layer and a positive uncoated area not covered by the positive active material layer, and the negative current collector includes a negative coated area covered by a negative active material layer and a negative uncoated area not covered by the negative active material layer; the direction from the positive coated area to the positive uncoated area is the first direction, and the direction from the negative coated area to the negative uncoated area is the second direction;

[0009] Along the winding direction of the winding structure, the positive uncoated area sequentially includes a first positive uncoated area, a second positive uncoated area, and a third positive uncoated area, and the negative uncoated area sequentially includes a first negative uncoated area, a second negative uncoated area, and a third negative uncoated area;

[0010] Along the first direction, the second positive uncoated area includes a positive electrode tab and a positive connection area connected between the positive electrode tab and the positive coated area, and neither the first positive uncoated area nor the third positive uncoated area includes the positive electrode tab;

[0011] Along the second direction, the second negative uncoated area includes a negative electrode tab and a negative connection area connected between the negative electrode tab and the negative coated area, and neither the first negative uncoated area nor the third negative uncoated area includes the negative electrode tab;

[0012] 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.

[0013] Preferably, the number of winding turns of the third positive uncoated area ranges from 3 to 6, or,

[0014] The number of winding turns of the third negative uncoated area ranges from 1 to 3.

[0015] Preferably, along the axial direction of the winding structure, among the winding turns of the second positive uncoated area, the outermost second positive uncoated area includes a first bending portion, and the positive projection of the first bending portion is located within the outer peripheral edge of the winding structure, or,

[0016] Along the axial direction of the winding structure, among the winding turns of the second negative uncoated area, the outermost second negative uncoated area includes a second bending portion, and the positive projection of the second bending portion is located within the outer peripheral edge of the winding structure.

[0017] 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,

[0018] 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,

[0019] The ratio of the length of the third positive uncoated area to the length of the third negative uncoated area is 1.5 - 2.5.

[0020] Preferably, 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 along the radial direction of the winding structure. Wherein, at least part of the first side and / or the second side is covered with an insulating layer; the insulating layer includes a color developer.

[0021] Preferably, the insulating layer covers the entire area of the first side of the positive electrode connection area; and / or,

[0022] the insulating layer covers the entire area of the second side of the positive electrode connection area; and / or,

[0023] Along the first direction, the maximum width of the insulating layer is greater than or equal to the width of the positive electrode connection area.

[0024] Preferably, along the first direction, the width of the positive electrode connection area is 1.5 mm - 2.5 mm; and / or,

[0025] Along the second direction, the width of the negative electrode connection area is 1 mm - 2 mm.

[0026] Preferably, along the first direction, the positive electrode tab includes a positive electrode tab transition portion and a positive electrode tab body. The positive electrode tab transition portion is connected between the positive electrode connection area and the positive electrode tab body, and the positive electrode tab transition portion is a bent area of the positive electrode tab;

[0027] Along the second direction, the negative electrode tab includes a negative electrode tab transition portion and a negative electrode tab body. The negative electrode tab transition portion is connected between the negative electrode connection area and the negative electrode tab body, and the negative electrode tab transition portion is a bent area of the negative electrode tab;

[0028] 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.

[0029] 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,

[0030] 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.

[0031] 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 close to the opening includes a crimping portion recessed into the interior of the housing;

[0032] The secondary battery further includes:

[0033] A cover plate, which is installed on the opening;

[0034] An insulating seal, which is disposed around the periphery of the cover plate to insulate and seal the cover plate and the housing;

[0035] A current collector plate, which is disposed between the electrode assembly and the cover plate and is electrically connected to the housing. 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;

[0036] And / or

[0037] The secondary battery is a cylindrical battery, the positive electrode tab is a cut and stacked tab, and the negative electrode tab is a cut and stacked tab.

[0038] A battery pack, characterized in that it includes the secondary battery described above.

[0039] An electronic device, characterized in that it includes the battery pack described above.

[0040] The positive and progressive effects of the present utility model are as follows:

[0041] By setting the number of winding turns of the third positive uncoated area to be greater than the number of winding turns of the third negative uncoated area, the present utility model makes the outward expansion along the radial direction of the winding structure of the second positive uncoated area and the second negative uncoated area after bending as consistent as possible, thereby avoiding the influence on the energy density of the secondary battery; at the same time, the number of winding turns of the third negative uncoated area is reduced as little as possible, thereby being able to avoid the increase in the internal resistance of the secondary battery. That is, the energy density of the secondary battery is increased and the internal resistance of the battery is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic cross-sectional structure view of a secondary battery according to a preferred embodiment of the present utility model.

[0043] Figure 2 is Figure 1 A partial enlarged structure view of part A in

[0044] Figure 3 It is a schematic three-dimensional structure view of an electrode assembly of a secondary battery according to a preferred embodiment of the present utility model.

[0045] Figure 4 It is a schematic cross-sectional structure view of an electrode assembly of a secondary battery according to a preferred embodiment of the present utility model.

[0046] Figure 5Schematic diagram of the structure of the positive electrode sheet of a secondary battery according to a preferred embodiment of the present invention when it is not wound.

[0047] Figure 6 Partial sectional structure schematic diagram (one) of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0048] Figure 7 Schematic diagram of the structure of the negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention when it is not wound.

[0049] Figure 8 Partial sectional structure schematic diagram (two) of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0050] Figure 9 Partial sectional structure schematic diagram (three) of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0051] Figure 10 For Figure 9 Partial enlarged structure schematic diagram of part B in

[0052] Figure 11 For Figure 9 Partial enlarged structure schematic diagram of part C in

[0053] Figure 12 Partial sectional structure schematic diagram (one) of a single-turn positive electrode sheet of a secondary battery according to a preferred embodiment of the present invention.

[0054] Figure 13 Partial sectional structure schematic diagram (two) of a single-turn positive electrode sheet of a secondary battery according to a preferred embodiment of the present invention.

[0055] Figure 14 Partial sectional structure schematic diagram (one) of a single-turn negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention.

[0056] Figure 15 Partial sectional structure schematic diagram (two) of a single-turn negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention.

[0057] Figure 16 Schematic diagram of the structure of a battery pack according to a preferred embodiment of the present invention.

[0058] Figure 17 Schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention.

[0059] Description of reference numerals

[0060] 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 sheet 21; positive current collector 211; positive active material layer 2111; positive coating area 212; positive non - coating area 213; first positive non - coating area 214; second positive non - coating area 215; positive tab 2151; positive tab transition part 21511; positive tab body 21512; positive connection area 2152; third positive non - coating area 216; starting position of positive electrode sheet 217; ending position of positive electrode sheet 218; separator 22; starting position of separator 221; ending position of separator 222; negative electrode sheet 23; negative current collector 231; negative active material layer 2311; negative coating area 232; negative non - coating area 233; first negative non - coating area 234; second negative non - coating area 235; negative tab 2351; negative tab transition part 21511; negative tab body 23512; negative connection area 2352; third negative non - coating area 236; starting position of negative electrode sheet 237; ending position of negative electrode sheet 238; insulating layer 24; insulating film 25; crimping part 30; cover plate 40; insulating seal 50; first current collector plate 61; second current collector plate 62; terminal 70; length a1 of the first positive non - coating area; length a2 of the second positive non - coating area; length a3 of the third positive non - coating area; length b1 of the first negative non - coating area; length b2 of the second negative non - coating area; length b3 of the third negative non - coating 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; 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; width direction W1 of the positive current collector; width direction W2 of the negative current collector. Detailed implementation manners

[0061] The following is a preferred embodiment, and the present utility model will be described more clearly and completely in conjunction with the accompanying drawings.

[0062] In the prior art, the outer expansion of the positive tab along the radial direction of the electrode assembly is larger than that of the negative tab along the radial direction of the electrode assembly, which affects the energy density of the secondary battery. However, in order to avoid an increase in the outer diameter of the electrode assembly, the number of turns of the tabs of the electrodes located in the outer circle of the electrode assembly is correspondingly reduced, and the outer - circle electron path becomes longer, resulting in a relatively large internal resistance of the battery.

[0063] Such as Figure 1 and Figure 2As 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.

[0064] As Figure 3 and Figure 4 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.

[0065] As Figure 5 and Figure 6 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 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.

[0066] As Figure 7 and Figure 8 shown, the negative electrode sheet 23 includes a negative electrode current collector 231. 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 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.

[0067] As Figure 12 shown, the direction from the positive electrode coated area 212 to the positive electrode uncoated area 213 is the first direction Q1. Along the first direction Q1, the second positive electrode uncoated area 215 includes a positive electrode tab 2151 and a positive electrode connection area 2152 connecting the positive electrode tab 2151 and the positive electrode coated area 212. Neither the first positive electrode uncoated area 214 nor the third positive electrode uncoated area 216 includes a positive electrode tab. As Figure 14 shown, the direction from the negative electrode coated area 232 to the negative electrode uncoated area 233 is the second direction Q2. Along the second direction Q2, the second negative electrode uncoated area 235 includes a negative electrode tab 2351 and a negative electrode connection area 2352 connecting the negative electrode tab 2351 and the negative electrode coated area 232. Neither the first negative electrode uncoated area 234 nor the third negative electrode uncoated area 236 includes the negative electrode tab. Among them, the number of winding turns of the third positive electrode uncoated area 216 is greater than the number of winding turns of the third negative electrode uncoated area 236.

[0068] In this way, by setting the number of winding turns of the third positive uncoated area 216 to be greater than that of the third negative uncoated area 236, the outward expansion along the radial direction R of the winding structure 201 after bending the second positive uncoated area 215 and the second negative uncoated area 235 is made as consistent as possible, thus avoiding the influence on the energy density of the secondary battery 1; at the same time, the number of winding turns of the third negative uncoated area 236 is reduced as little as possible, so as to avoid the increase in 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.

[0069] As Figures 9 to 11 shown, the winding structure 201 formed by laminating and winding the positive electrode sheet 21, the separator 22 and the negative electrode sheet 23 usually has a central hole 2011 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. The separator 22 is made of an insulating material, specifically, it can be PP (polypropylene), PE (polyethylene), etc.

[0070] Please refer back to Figure 4 , in the winding structure 201, the positive electrode sheet 21 includes a positive electrode sheet starting position 217 and a positive electrode sheet ending position 218; the negative electrode sheet 23 includes a negative electrode sheet starting position 237 and a negative electrode sheet ending position 238; the separator 22 includes a separator starting position 221 and a separator ending position 222. 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.

[0071] 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 positive uncoated area 214, the second positive uncoated area 215 and the third positive uncoated area 216 are as Figure 5 shown; and after the winding structure 201 is formed, the positions of the first positive uncoated area 214, the second positive uncoated area 215 and the third positive uncoated area 216 are as Figure 6 shown. Similarly, when the negative electrode sheet 23 is in the unwound state, along the winding direction P of the winding structure 201, the positions of the first negative uncoated area 234, the second negative uncoated area 235 and the third negative uncoated area 236 are as Figure 7 shown; and after the winding structure 201 is formed, the positions of the first negative uncoated area 234, the second negative uncoated area 235 and the third negative uncoated area 236 are as Figure 8 shown.

[0072] 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 area 2152 to the positive electrode tab 2151.

[0073] 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 area 2352 to the negative electrode tab 2351.

[0074] It should be noted that the number of winding turns of the third positive electrode uncoated area 216 refers to the number of overlapping turns of the third positive electrode uncoated area 216 along the radial direction R of the wound structure 201 after winding and forming. Similarly, the number of winding turns of the third negative electrode uncoated area 236 refers to the number of overlapping turns of the third negative electrode uncoated area 236 along the radial direction R of the wound structure 201 after winding and forming. In addition, the housing 10 may contain one or more electrode assemblies 20.

[0075] 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.

[0076] Specifically, the value range of the number of winding turns of the third positive electrode uncoated area 216 is 3 - 6. In this way, by setting the value range of the number of winding turns of the third positive electrode uncoated area 216, on the one hand, it can avoid that the number of winding turns of the third positive electrode uncoated area 216 is too small, and after the second positive electrode uncoated area 215 is bent, it expands too much along the radial direction R of the wound structure 201, which has an adverse effect on the energy density of the secondary battery 1; on the other hand, it can avoid that the number of winding turns of the third positive electrode uncoated area 216 is too large, resulting in too large battery internal resistance.

[0077] The value range of the number of winding turns of the third negative electrode uncoated area 236 is 1 - 3. In this way, by setting the value range of the number of winding turns of the third negative electrode uncoated area 236, on the one hand, it can avoid that the number of winding turns of the third negative electrode uncoated area 236 is too small, and after the second negative electrode uncoated area 235 is bent, it expands too much along the radial direction R of the wound structure 201, which has an adverse effect on the energy density of the secondary battery 1; on the other hand, it can avoid that the number of winding turns of the third negative electrode uncoated area 236 is too large, resulting in too large battery internal resistance.

[0078] Along the axial direction O of the winding structure 201, in the winding turns of the second positive uncoated area 215, the outermost second positive uncoated area 215 includes a first bending portion, and the orthographic projection of the first bending portion is located within the outer peripheral edge of the winding structure 201, so as to ensure that the second positive 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.

[0079] Along the axial direction O of the winding structure 201, in the winding turns of the second negative uncoated area 235, the outermost second negative uncoated area 235 includes a second bending portion, and the orthographic projection of the second bending portion is located within the outer peripheral edge of the winding structure 201, so as to ensure that the second positive 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.

[0080] Preferably, please refer back to Figure 5 , along the winding direction P of the winding structure 201, the length a1 of the first positive 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 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 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.

[0081] Please refer back to Figure 7 , along the winding direction P of the winding structure 201, the length b1 of the first negative uncoated area 234 is 300 mm - 500 mm, for example, it can be 300 mm, 350 mm, 400 mm, 420 mm, 480 mm or 500 mm, etc. The length b2 of the second negative uncoated area 235 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 b3 of the third negative uncoated area 236 is 100 mm - 300 mm, for example, it can be 100 mm, 150 mm, 200 mm, 220 mm, 280 mm or 300 mm, etc.

[0082] In this way, by setting the value ranges of the lengths a1 of the first positive electrode uncoated area 214, a2 of the second positive electrode uncoated area 215, a3 of the third positive electrode uncoated area 216, b1 of the first negative electrode uncoated area 234, b2 of the second negative electrode uncoated area 235, and 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.

[0083] 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. For example, it can be 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 be a suitable ratio, not only can the number of turns of the third positive electrode uncoated area 216 be greater than that of the third negative electrode uncoated area 236, but also the lengths of both can be within a suitable range, and the internal resistance of the battery can be within a suitable range.

[0084] The positive electrode connection area 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. In this way, by covering at least part of the first side and / or the second side of the positive electrode connection area 2152 with the insulating layer 24, the deformation risk of the positive electrode connection area 2152 can be reduced, and the insulation performance of the positive electrode connection area 2152 can be improved, 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 1.5 μm - 2.5 μm. For example, it can be 1.5 μm, 1.7 μm, 2 μm, 2.1 μm, 2.3 μm, or 2.5 μm, 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, resulting in difficulty in obtaining 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 the possibility of 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 2 μm.

[0085] Please refer back to Figure 10 and Figure 12 , in this embodiment, both the first side and the second side of the positive electrode connection area 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 area 2152 is covered with the insulating layer 24, or only the second side of the positive electrode connection area 2152 is covered with the insulating layer 24. It can be adjusted according to design requirements.

[0086] 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 the surface density and other situations 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.

[0087] 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 of the positive electrode sheet 21 by using the color development effect of the developer in the insulating layer 24. Because sometimes it is necessary to distinguish the front and back of the positive electrode sheet 21, including but not limited to the surface density and other situations 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.

[0088] 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.

[0089] Please refer back to Figure 12 , 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.

[0090] Please refer back to Figure 14 , 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.

[0091] 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, when pressed 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.

[0092] Please refer back to Figure 12 , 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 the extension direction of the positive electrode connection area 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 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 13 shown.

[0093] Please refer back to Figure 14, preferably, along the second direction Q2, the width d1 of the negative electrode tab transition portion 23511 is 0.1 mm - 1 mm, and can be, for example, 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 endpoint B1 and a second negative electrode tab transition endpoint B2. The first negative electrode tab transition endpoint B1 is the position where the tangent of the negative electrode tab transition portion 23511 intersects the extension direction of the negative electrode connection region 2352, and the second negative electrode tab transition endpoint B2 is the position where the tangent of the negative electrode tab transition portion 23511 intersects the extension direction of the negative electrode tab body 23512. After being pressed, the negative electrode tab transition portion 23511 will be deformed and expand outward along the winding structure, and the formed structure is as Figure 15 shown.

[0094] , preferably, along the first direction Q1, the width c2 of the positive electrode tab body 21512 is 4.5 mm - 5.5 mm, and can be, for example, 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, and can be, for example, 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 may not provide enough reserved space and 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.

[0095] , preferably, along the first direction Q1, the width c3 of the positive electrode connection region 2152 is 1.5 mm - 2.5 mm, and can be, for example, 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.

[0096] 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 2311 is ensured, the thermal influence during welding is avoided, and the safety performance is improved.

[0097] 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.

[0098] Please refer back to Figure 1 and Figure 2 Referring back to, 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 near the opening 12 includes a crimping portion 30 that is recessed into the housing 10. The secondary battery 1 further includes: a cover plate 40, an insulating seal 50, and a 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 between 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 between the tab and the current collector plate can be prevented, and thus the welding strength between the tab and the current collector plate can be improved.

[0099] 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.

[0100] The secondary battery 1 further includes a pole column 70, and the pole column 70 passes through the end wall 13 and is insulated from the end wall 13.

[0101] 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, the first current collector plate 61 corresponds to the positive electrode tab 2151, and the positive electrode tab 2151 is electrically connected to the pole column 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.

[0102] 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 may also be a square battery or other shaped batteries. In this embodiment, the positive electrode tab 2151 is a cut and stacked tab. When welding the tab of the cylindrical battery and 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. Similarly, the negative electrode tab 2351 is also a cut and stacked tab.

[0103] 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 is as follows: 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 virtual soldering); weld the first current collector plate 61 using linear welding instead of spot welding. This is 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.

[0104] As Figure 16 shown, 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 electric cabinet, etc.; details are not elaborated here one by one.

[0105] As Figure 17 shown, 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, and the vehicle 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 the electrical components in the vehicle. 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 power planer, etc. The embodiments of the present application do not impose special restrictions on the above-mentioned electronic device 1000.

[0106] 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 accommodated in the housing, the electrode assembly including 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; the direction from the positive electrode coated area to the positive electrode uncoated area is the first direction, and the direction from the negative electrode coated area to the negative electrode uncoated area is the second direction; Along the winding direction of the winding structure, the positive electrode uncoated area sequentially includes a first positive electrode uncoated area, a second positive electrode uncoated area, and a third positive electrode uncoated area, and the negative electrode uncoated area sequentially includes a first negative electrode uncoated area, a second negative electrode uncoated area, and a third negative electrode uncoated area; Along the first direction, the second positive electrode uncoated area 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 positive electrode uncoated area nor the third positive electrode uncoated area includes the positive electrode tab; Along the second direction, the second negative electrode uncoated area 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 negative electrode uncoated area nor the third negative electrode uncoated area includes the negative electrode tab; The number of winding turns of the third positive electrode uncoated area is greater than the number of winding turns of the third negative electrode uncoated area.

2. The secondary battery according to claim 1, wherein The number of winding turns of the third positive electrode uncoated area ranges from 3 to 6, or The number of winding turns of the third negative electrode uncoated area ranges from 1 to 3.

3. The secondary battery according to claim 1, characterized in that, Along the axial direction of the winding structure, in the winding turns of the second positive electrode uncoated area, the outermost second positive electrode 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 Along the axial direction of the winding structure, in the winding turns of the second negative electrode uncoated area, the outermost second negative electrode 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.

4. The secondary battery according to claim 1, characterized in that, Along the winding direction of the winding structure, the length of the first positive electrode uncoated area is 400 mm - 600 mm, the length of the second positive electrode uncoated area is 3000 mm - 5000 mm, the length of the third positive electrode uncoated area is 200 mm - 500 mm, or Along the winding direction of the winding structure, the length of the first negative electrode uncoated area is 300 mm - 500 mm, the length of the second negative electrode uncoated area is 3000 mm - 5000 mm, the length of the third negative electrode uncoated area is 100 mm - 300 mm, or The ratio of the length of the third positive electrode uncoated area to the length of the third negative electrode uncoated area is 1.5 - 2.

5.

5. The secondary battery according to claim 1, characterized in that, The positive electrode connection region includes a first side radially away from the central hole of the winding structure and a second side close to the central hole along the winding structure. 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.

6. The secondary battery according to claim 5, wherein the insulating layer covers the entire region of the first side of the positive electrode connection region; and / or, the insulating layer covers the entire region of the second side of the positive electrode connection region; and / or, along the first direction, the maximum width of the insulating layer is greater than or equal to the width of the positive electrode connection region.

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

8. The secondary battery according to claim 1, wherein along the first direction, the positive electrode tab includes a positive electrode tab transition portion and a positive electrode tab body. The positive electrode tab transition portion is connected between the positive electrode connection region and the positive electrode tab body, and the positive electrode tab transition portion is a bent region of the positive electrode tab; along the second direction, the negative electrode tab includes a negative electrode tab transition portion and a negative electrode tab body. The negative electrode tab transition portion is connected between the negative electrode connection region and the negative electrode tab body, and the negative electrode tab transition portion is a bent region of the negative electrode tab; 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.

9. The secondary battery according to claim 8, 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.

10. The secondary battery according to any one of claims 1-9, characterized in that, The housing includes a surrounding side wall, and one end of the side wall forms an opening; one end of the housing close to the opening includes a crimping portion recessed into the interior of the housing; The secondary battery further includes: a cover plate installed at 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, which is disposed between the electrode assembly and the cover plate and is electrically connected to the housing. 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, the positive electrode tab is a cut and stacked tab, and the negative electrode tab is a cut and stacked tab.

11. A battery pack, characterized in that, Including the secondary battery according to any one of claims 1 to 10.

12. An electronic device, characterized in that, Including the battery pack according to claim 11.

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