Secondary batteries, battery packs, and electronic devices

Abstract

The present invention provides a secondary battery, battery pack, and electronic device that improve the energy density of the secondary battery while simultaneously preventing thermal damage to the separator. [Solution] The secondary battery includes a case and an electrode assembly housed within the case, the electrode assembly includes a winding structure formed by stacking and winding a positive electrode sheet, a separator and a negative electrode sheet, along the axial direction of the winding structure, the positive electrode current collector of the positive electrode sheet includes a positive electrode coated region and a positive electrode uncoated region, the negative electrode current collector of the negative electrode sheet includes a negative electrode coated region and a negative electrode uncoated region, a part of the positive electrode uncoated region is folded to form a positive electrode tab stacking region, the positive electrode tab stacking region includes a positive electrode tab stacking number stable region, within the positive electrode tab stacking number stable region, the number of stacked positive electrode tabs is m, a part of the negative electrode uncoated region is folded to form a negative electrode tab stacking region, the negative electrode tab stacking region includes a negative electrode tab stacking number stable region, within the negative electrode tab stacking number stable region, the number of stacked negative electrode tabs is n, where m > n.

Description

Technical Field

[0001] The present invention 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 devices, such as new energy vehicles, communication base stations, and energy storage containers, are adopting secondary batteries as energy storage and supply devices.

[0003] The current secondary battery is composed of an electrode assembly and a case. The electrode assembly generally includes a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode tab and the negative electrode tab of the electrode assembly protrude from both sides of the electrode assembly respectively, are flattened after being overlapped, and then are welded to the corresponding current collector.

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0005] The present invention solves the above technical problems by the following technical means. A case, and an electrode assembly accommodated in the case, wherein 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 region covered with a positive electrode active material layer and a positive electrode uncoated region not covered with the positive electrode active material layer, and the negative electrode current collector includes a negative electrode coated region covered with a negative electrode active material layer and a negative electrode uncoated region not covered with the negative electrode active material layer, Along the radial direction of the winding structure, a portion of the uncoated positive electrode region is bent toward the central hole of the winding structure, and the uncoated positive electrode regions with different winding layer counts are stacked on each other to form a positive electrode tab stacking region, the positive electrode tab stacking region includes a positive electrode tab stacking number stable region, and within the positive electrode tab stacking number stable region, the number of stacked positive electrode tabs is m. Along the radial direction of the winding structure, a portion of the uncoated negative electrode region is bent toward the central hole, and the uncoated negative electrode regions with different winding layer counts are stacked on each other to form a negative electrode tab stacking region, the negative electrode tab stacking region includes a negative electrode tab stacking number stable region, and within the negative electrode tab stacking number stable region, the number of stacked negative electrode tabs is n. A secondary battery characterized by m > n.

[0006] Preferably, along the radial direction of the winding structure, from the outer circumference to the central hole, the positive electrode tab stacking region includes, in order, a region where the number of stacked positive electrode tabs increases, a region where the number of stacked positive electrode tabs stabilizes, and a region where the number of stacked positive electrode tabs decreases, and the negative electrode tab stacking region includes, in order, a region where the number of stacked negative electrode tabs increases, a region where the number of stacked negative electrode tabs stabilizes, and a region where the number of stacked negative electrode tabs decreases. Along the radial direction of the winding structure, the length of the positive electrode tab stacking number stable region is longer than the length of the negative electrode tab stacking number stable region.

[0007] Preferably, along the axial direction of the winding structure, the number of stacked positive electrode tabs located in the positive electrode tab stacking stability region is 15 to 22 layers, or Along the axial direction of the winding structure, the number of stacked negative electrode tabs located in the stable stacking region of the negative electrode tabs is 12 to 18 layers, or The ratio of m to n is between 1.05 and 1.5.

[0008] Preferably, the secondary battery further includes a current collector, the current collector includes a first current collector and a second current collector, the first current collector is welded to the positive electrode tab stacking stability region and a first weld bead is formed, and the second current collector is welded to the negative electrode tab stacking stability region and a second weld bead is formed. Along the axial direction of the winding structure, the number of layers of the positive electrode tab connected to the first weld bead is 8 to 12, or Along the axial direction of the winding structure, the number of layers of the negative electrode tab connected to the second weld bead is 8 to 12, or Along the axial direction of the winding structure, within the positive electrode tab stacking stability region, the ratio i of the number of stacked positive electrode tabs connected to the first weld bead to the number of stacked positive electrode tabs located in the positive electrode tab stacking stability region is 0.4 to 0.65, or Along the axial direction of the winding structure, within the negative electrode tab stacking stability region, the ratio j of the number of stacks of the negative electrode tabs connected to the second weld bead to the number of stacks of the negative electrode tabs located in the negative electrode tab stacking stability region is 0.5 to 0.8.

[0009] Preferably, along the radial direction of the winding structure, the ratio of the length of the positive electrode tab stacking number stable region to the diameter of the central hole is 0.5 to 1.4, or Along the radial direction of the winding structure, the ratio of the length of the negative electrode tab stacking stability region to the diameter of the central hole is 0.5 to 1.4, or The diameter of the aforementioned central hole is 4 mm to 8 mm.

[0010] Preferably, the direction in which the coated positive electrode region extends to the uncoated positive electrode region is the first direction, and the direction in which the coated negative electrode region extends to the uncoated negative electrode region is the second direction. Along the winding direction of the winding structure, the uncoated positive electrode region includes, in order, a first uncoated positive electrode region, a second uncoated positive electrode region, and a third uncoated positive electrode region, and the uncoated negative electrode region includes, in order, a first uncoated negative electrode region, a second uncoated negative electrode region, and a third uncoated negative electrode region. Along the radial direction of the winding structure, the uncoated region of the second positive electrode is bent toward the central hole, and the uncoated regions of the second positive electrode with different winding layer counts are stacked on top of each other to form the positive electrode tab stacked region, and the uncoated region of the second negative electrode is bent toward the central hole, and the uncoated regions of the second negative electrode with different winding layer counts are stacked on top of each other to form the negative electrode tab stacked region, Along the first direction, the second uncoated positive electrode region includes a positive electrode tab and a positive electrode connection region connected between the positive electrode tab and the positive electrode coated region, while neither the first uncoated positive electrode region nor the third uncoated positive electrode region includes the positive electrode tab. Along the second direction, the second uncoated negative electrode region includes a negative electrode tab and a negative electrode connection region connected between the negative electrode tab and the negative electrode coated region, while neither the first uncoated negative electrode region nor the third uncoated negative electrode region includes the negative electrode tab. The number of winding layers in the uncoated third positive electrode region is greater than the number of winding layers in the uncoated third negative electrode region.

[0011] Preferably, the range of the number of winding layers in the uncoated third positive electrode region is 3 to 6, or The range of the number of winding layers in the uncoated third negative electrode region is 1 to 2.

[0012] Preferably, along the axial direction of the winding structure, in the winding layer of the second uncoated positive electrode region, the outermost layer of the second uncoated positive electrode region includes a first bend, and the orthographic projection of the first bend is located inside the outer peripheral edge of the winding structure, or Along the axial direction of the winding structure, in the winding layer of the second uncoated negative electrode region, the outermost layer of the second uncoated negative electrode region includes a second bend, and the orthographic projection of the second bend is located inside the outer peripheral edge of the winding structure.

[0013] Preferably, along the winding direction of the winding structure, the length of the first uncoated positive electrode region is 400 mm to 600 mm, the length of the second uncoated positive electrode region is 3000 mm to 5000 mm, and the length of the third uncoated positive electrode region is 200 mm to 500 mm, or Along the winding direction of the aforementioned winding structure, the length of the first uncoated negative electrode region is 300 mm to 500 mm, the length of the second uncoated negative electrode region is 3000 mm to 5000 mm, and the length of the third uncoated negative electrode region is 100 mm to 300 mm, or The ratio of the length of the uncoated region of the third positive electrode to the length of the uncoated region of the third negative electrode is 1.5 to 2.5.

[0014] Preferably, the positive electrode tab is a cut laminated tab. When the positive electrode sheet is unfolded, the positive electrode current collector is in a flat state. The stretching direction of the positive electrode tab and the length direction of the positive electrode current collector form a first acute angle, and the first acute angle is 30 degrees to 85 degrees. The negative electrode tab is a cut laminated tab. When the negative electrode sheet is unfolded, the negative electrode current collector is in a flat state. The stretching direction of the negative electrode tab and the length direction of the negative electrode current collector form a second acute angle, and the second acute angle is 30 degrees to 85 degrees.

[0015] Preferably, along the radial direction of the winding structure, the positive electrode connection region includes a first side far from the central hole of the winding structure and a second side close to the central hole. At least a part of the region on the first side and / or the second side is covered by an insulating layer, and the insulating layer contains a chromogenic agent.

[0016] Preferably, the insulating layer covers the entire region on the first side of the positive electrode connection region, and / or the insulating layer covers the entire region on the second side of the positive electrode connection region, and / or Along the first direction, the maximum width of the insulating layer is not less than the width of the positive electrode connection region.

[0017] Preferably, along the first direction, the width of the positive electrode connection region is 1.5 mm to 2.5 mm, and / or Along the second direction, the width of the negative electrode connection region is 1 mm to 2 mm.

[0018] Preferably, along 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 region and the positive electrode tab body, and the positive electrode tab transition part is a bending region of the positive electrode tab. Along 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 region and the negative electrode tab body, and the negative electrode tab transition part is a bending region of the negative electrode tab. The width of the positive electrode tab transition portion of the positive electrode tab located in the outermost layer is larger than the width of the negative electrode tab transition portion of the negative electrode tab located in the outermost layer.

[0019] Preferably, along the first direction, the width of the positive electrode tab transition portion is 1 mm to 2 mm, the width of the positive electrode tab main body is 4.5 mm to 5.5 mm, and the thickness of the positive electrode tab is 12 μm to 20 μm, and / or Along the second direction, the width of the negative electrode tab transition portion is 0.1 mm to 1 mm, the width of the negative electrode tab main body is 4 mm to 5 mm, and the thickness of the negative electrode tab is 4 μm to 11 μm.

[0020] Preferably, the case includes an annular side wall, an opening is formed at one end of the side wall, and the case includes a crimping portion recessed inside the case at one end close to the opening. The secondary battery further includes a cover plate attached to the opening, an insulating and sealing component provided surrounding the periphery of the cover plate to insulate and seal the cover plate and the case, a current collector provided between the electrode assembly and the cover plate and electrically connected to the case, wherein the connection sheet of the current collector is located on the side facing the electrode assembly of the crimping portion and is welded to the crimping portion, the current collector, including and / or The secondary battery is a cylindrical battery.

[0021] A battery pack comprising the secondary battery described above.

[0022] An electronic device comprising the battery pack described above.

Advantages of the Invention

[0023] The positive progressive effects of the present invention are as follows. This invention ensures a sufficient number of unwelded tabs within both the positive and negative electrode tab stacking stability regions by setting the number of stacked positive electrode tabs located within the positive electrode tab stacking stability region to be greater than the number of stacked negative electrode tabs located within the negative electrode tab stacking stability region. This prevents thermal damage to the separator during the welding process, while simultaneously minimizing the number of stacked negative electrode tabs and avoiding any impact on the energy density of the secondary battery. In other words, it improves the energy density of the secondary battery while preventing thermal damage to the separator. [Brief explanation of the drawing]

[0024] [Figure 1] This is a schematic diagram of the cross-sectional structure of a secondary battery according to a preferred embodiment of the present invention. [Figure 2] This is a schematic diagram of a localized, enlarged view of part A in Figure 1. [Figure 3] This is a schematic diagram of the three-dimensional structure of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 5] This is a schematic diagram of the structure of the positive electrode sheet of a secondary battery in an unwinded state according to a preferred embodiment of the present invention. [Figure 6] This is a schematic diagram of the local structure of the positive electrode sheet of a secondary battery in a preferred embodiment of the present invention when it is unfolded. [Figure 7] This is a schematic diagram of the local cross-sectional structure of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 8] This is a schematic diagram of the structure of the negative electrode sheet of a secondary battery in an unwound state according to a preferred embodiment of the present invention. [Figure 9] This is a schematic diagram of the local structure of the negative electrode sheet of a secondary battery in a preferred embodiment of the present invention when unfolded. [Figure 10] This is a schematic diagram of the local cross-sectional structure of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 11] This is a schematic diagram of the local cross-sectional structure of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 12]This is a schematic diagram of a localized, enlarged view of part B in Figure 11. [Figure 13] This is a schematic diagram of a localized enlarged structure of part C in Figure 11. [Figure 14] This is a schematic diagram of the local cross-sectional structure of a single-layer positive electrode sheet of a secondary battery according to a preferred embodiment of the present invention. [Figure 15] This is a schematic diagram of the local cross-sectional structure of a single-layer positive electrode sheet of a secondary battery according to a preferred embodiment of the present invention. [Figure 16] This is a schematic diagram of the local cross-sectional structure of a single-layer negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention. [Figure 17] This is a schematic diagram of the local cross-sectional structure of a single-layer negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention. [Figure 18] This is a schematic diagram of the structure of a battery pack according to a preferred embodiment of the present invention. [Figure 19] This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention. [Modes for carrying out the invention]

[0025] The present invention will be described more clearly and completely below with reference to preferred embodiments and the drawings.

[0026] In conventional technology, the number of layers of the positive and negative electrode tabs of a secondary battery after bending is usually the same. If the number of layers set in the weldable area of ​​the positive and negative electrode tabs is too small, a sufficient number of unwelded layers cannot be secured, and the separator will be burned during the welding process. On the other hand, if the number of layers is too large, the energy density of the battery decreases. Specifically, the positive electrode tab and current collector, which are typically made of metallic aluminum, are welded with red light, while the negative electrode tab and current collector, which are made of metallic copper, are welded with green light. This is because metallic aluminum has a low absorption rate of green light and a high absorption rate of red light, so metallic aluminum is typically welded with a red light laser, and metallic copper has a high absorption rate of green light, so metallic copper is typically welded with a green light laser.

[0027] However, because red light is less stable than green light, a smaller number of tabs need to be welded when using green light, and a larger number of tabs need to be welded when using red light. In conventional secondary batteries, the number of stacked tabs after bending the positive and negative electrode tabs is usually the same. If the number of stacked tabs set in the weldable area of ​​the positive and negative electrode tabs is too small, a sufficient number of unwelded stacked tabs cannot be secured, and the separator will be burned during the welding process. On the other hand, if the number of stacked tabs is too large, the energy density of the battery will decrease.

[0028] Therefore, appropriately balancing the number of tab stacks and the battery energy density within the weldable region of the positive and negative electrode tabs is a technical challenge that urgently needs to be addressed in this field.

[0029] As shown in Figures 1 and 2, this embodiment provides a secondary battery 1. This secondary battery 1 includes a case 10 and an electrode assembly 20, the electrode assembly 20 being housed inside the case 10.

[0030] As shown in Figures 3, 4, and 11-13, the electrode assembly 20 includes a winding structure 201 formed by stacking and winding a positive electrode sheet 21, a separator 22, and a negative electrode sheet 23. The winding structure 201, formed by stacking and winding a positive electrode sheet 21, a separator 22, and a negative electrode sheet 23, typically has a central hole 2011 in the center, and the axial direction of the central hole 2011 is the axial direction O of the winding structure 201, which is the same direction as the height direction of the secondary battery 1.

[0031] As shown in Figures 5 to 7, 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 region 212 covered by a positive electrode active material layer 2111 and a positive electrode uncoated region 213 not covered by the positive electrode active material layer 2111. Along the radial direction R of the winding structure 201, a portion of the positive electrode uncoated region 213 is bent toward the central hole 2011 of the winding structure 201, and positive electrode uncoated regions 213 with different winding layer counts are stacked with each other to form a positive electrode tab stacking region 2131, which includes a positive electrode tab stacking number stable region 21312, within which the number of stacked positive electrode tabs 2151 is m.

[0032] As shown in Figures 8 to 10, 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 region 232 covered by a negative electrode active material layer 2311 and a negative electrode uncoated region 233 not covered by the negative electrode active material layer 2311. Along the radial direction R of the winding structure 201, a portion of the negative electrode uncoated region 233 is bent toward the central hole 2011, and negative electrode uncoated regions 233 with different winding layer counts are stacked on top of each other to form a negative electrode tab stacking region 2331. The negative electrode tab stacking region 2331 includes a negative electrode tab stacking number stable region 23312, and within the negative electrode tab stacking number stable region 23312, the number of stacked negative electrode tabs 2351 is n.

[0033] Here, m > n.

[0034] In this way, by setting the number of stacked positive electrode tabs 2151 m located within the positive electrode tab stacking stability region 21312 to be greater than the number of stacked negative electrode tabs 2351 located within the negative electrode tab stacking stability region 23312, a sufficient number of unwelded tabs can be secured within both the positive electrode tab stacking stability region 21312 and the negative electrode tab stacking stability region 23312, preventing thermal damage to the separator 22 during the welding process. At the same time, by minimizing the number of stacked negative electrode tabs 2351, the impact on the energy density of the secondary battery 1 can be avoided. That is, the energy density of the secondary battery 1 can be improved while preventing thermal damage to the separator 22. The positive electrode tab stacking stability region 21312 is a positive electrode tab weldable region, and the number of stacked positive electrode tabs 2151 in the positive electrode tab weldable region has a positive correlation with the thickness of the positive electrode active material layer 2111, the positive electrode current collector 211, and the separator 22. The number of stacks of positive electrode tabs 2151 in this positive electrode tab weldable region includes the number of stacks welded to the first current collector 61 and the number of stacks not welded to the first current collector 61. These stacks not welded to the first current collector 61 serve as redundant stacks of spare positive electrode tabs 2151, preventing thermal damage to the separator 22 during the welding process. Similarly, the negative electrode tab stacking stability region 23312 is a negative electrode tab weldable region, and the number of stacks of negative electrode tabs 2351 in this negative electrode tab weldable region is negatively correlated with the thickness of the negative electrode active material layer 2311, the negative electrode current collector 231, and the separator 22. The number of stacks of negative electrode tabs 2351 in this negative electrode tab weldable region includes the number of stacks welded to the second current collector 62 and the number of stacks not welded to the second current collector 62. The separator 22 is an insulating material, specifically PP (polypropylene) or PE (polyethylene), etc.

[0035] Referring again to Figure 7, along the radial R of the winding structure 201, from the outer circumference to the central hole 2011, the positive electrode tab stacking region 21311 includes, in order, a region where the number of stacked positive electrode tabs increases 21311, a region where the number of stacked positive electrode tabs stabilizes 21312, and a region where the number of stacked positive electrode tabs decreases 21313. Referring again to Figure 10, along the radial R of the winding structure 201, from the outer circumference to the central hole 2011, the negative electrode tab stacking region 23311 includes, in order, a region where the number of stacked negative electrode tabs increases 23311, a region where the number of stacked negative electrode tabs stabilizes 23312, and a region where the number of stacked negative electrode tabs decreases 23313.

[0036] Along the radial R of the winding structure 201, a portion of the uncoated positive electrode region 213 is bent toward the central hole 2011 of the winding structure 201. As a result, from the outer circumference of the winding structure 201 to the central hole 2011, the number of layers gradually increases and stabilizes, then gradually decreases. Correspondingly, the positive electrode tab layering region 2131 includes, in order, a positive electrode tab layering increase region 21311, a positive electrode tab layering stability region 21312, and a positive electrode tab layering decrease region 21313, with the positive electrode tab layering stability region 21312 having the most layers and being relatively uniform. Similarly, the negative electrode tab layering region 23311 includes, in order, a negative electrode tab layering increase region 23311, a negative electrode tab layering stability region 23312, and a negative electrode tab layering decrease region 23313, with the negative electrode tab layering stability region 23312 having the most layers and being relatively uniform.

[0037] Along the radial R of the winding structure 201, the length f1 of the positive electrode tab stacking stability region 21312 is longer than the length f2 of the negative electrode tab stacking stability region 23312. The longer the lengths f1 of the positive electrode tab stacking stability region 21312 and f2 of the negative electrode tab stacking stability region 23312, the greater the number of tab layers in the weldable region formed after stacking. By setting the length f1 of the positive electrode tab stacking stability region 21312 to be greater than the length f2 of the negative electrode tab stacking stability region 23312, the number of stacked positive electrode tabs 2151 located within the positive electrode tab stacking stability region 21312 becomes greater than the number of stacked negative electrode tabs 2351 located within the negative electrode tab stacking stability region 23312, thereby improving the energy density of the secondary battery 1 while preventing burns to the separator 22.

[0038] Specifically, along the axial direction O of the winding structure 201, the number of stacked positive electrode tabs 2151 located in the positive electrode tab stacking stability region 21312 is 15 to 22 layers, for example, 15, 17, 18, 20, or 22 layers. By setting a range for the number of stacked positive electrode tabs 2151 located in the positive electrode tab stacking stability region 21312 in this way, it is possible to avoid, on the one hand, thermal damage to the separator 22 caused by insufficient securing of a sufficient number of unwelded layers due to too few stacked positive electrode tabs 2151, and on the other hand, to avoid adverse effects on the energy density of the secondary battery 1 due to too many stacked positive electrode tabs 2151.

[0039] Along the axial direction O of the winding structure 201, the number of stacked negative electrode tabs 2351 located in the negative electrode tab stacking stability region 23312 is 12 to 18, for example, 12, 13, 15, 16, or 18 layers. By setting a range for the number of stacked negative electrode tabs 2351 located in the negative electrode tab stacking stability region 23312 in this way, it is possible to avoid, on the one hand, thermal damage to the separator 22 caused by insufficient securing of a sufficient number of unwelded layers due to too few stacked negative electrode tabs 2351, and on the other hand, to avoid adverse effects on the energy density of the secondary battery 1 due to too many stacked negative electrode tabs 2351.

[0040] Along the axial direction O of the winding structure 201, the ratio of the number of stacked positive tabs 2151 located in the positive tab stacking stability region 21312 to the number of stacked negative tabs 2351 located in the negative tab stacking stability region 23312 is between 1.05 and 1.5, for example, 1.05, 1.17, 1.2, 1.3, 1.41, or 1.5. In this way, by setting a range for the ratio of the number of stacked positive electrode tabs 2151 located in the positive electrode tab stacking stability region 21312 to the number of stacked negative electrode tabs 2351 located in the negative electrode tab stacking stability region 23312, this ratio can be set to an appropriate value, ensuring that the number of stacked positive electrode tabs 2151 located in the positive electrode tab stacking stability region 21312 becomes greater than the number of stacked negative electrode tabs 2351 located in the negative electrode tab stacking stability region 23312. Furthermore, by setting the stacking numbers of both within an appropriate range, it is possible to improve the energy density of the secondary battery 1 while preventing thermal damage to the separator 22.

[0041] Referring again to Figure 1, preferably, the secondary battery 1 further includes a current collector, the current collector including a first current collector 61 and a second current collector 62. The first current collector 61 is welded to a positive electrode tab stacking number stable region 21312 to form a first weld bead, and the second current collector 62 is welded to a negative electrode tab stacking number stable region 23312 to form a second weld bead.

[0042] Along the axial direction O of the winding structure 201, the number of layers of the positive electrode tab 2151 connected to the first weld bead is 8 to 12, for example, 8 layers, 10 layers, or 12 layers. Along the axial direction O of the winding structure 201, the number of layers of the negative electrode tab 2351 connected to the second weld bead is 8 to 12, for example, 8 layers, 10 layers, or 12 layers. By setting the range of values ​​for the number of layers of the positive electrode tab 2151 connected to the first weld bead and the number of layers of the negative electrode tab 2351 connected to the second weld bead in this way, the welding strength between the positive electrode tab 2151 and the first current collector 61, and the welding strength between the negative electrode tab 2351 and the second current collector 62 can be effectively ensured.

[0043] Along the axial direction O of the winding structure 201, within the positive electrode tab stacking stability region 21312, the ratio i of the number of stacks of positive electrode tabs 2151 connected to the first weld bead to the number of stacks m of positive electrode tabs 2151 located in the positive electrode tab stacking stability region 21312 is 0.4 to 0.65, for example, 0.4, 0.45, 0.55, 0.6, or 0.65. The number of stacks of positive electrode tabs 2151 connected to the first weld bead is the number of stacks welded to the first current collector panel 61 located within the positive electrode tab stacking stability region 21312. By setting a range for the value of the ratio i to the number of stacked positive electrode tabs 2151 located in the positive electrode tab stacking stability region 21312, this ratio can be made to an appropriate value. On the one hand, it is possible to avoid burns to the separator 22 caused by insufficient securing of a sufficient number of unwelded stacked positive electrode tabs 2151 that are not connected to the first weld bead due to too few stacked positive electrode tabs 2151, and on the other hand, it is possible to avoid adverse effects on the energy density of the secondary battery 1 due to too many stacked positive electrode tabs 2151.

[0044] Along the axial direction O of the winding structure 201, within the negative electrode tab stacking stability region 23312, the ratio j of the number of stacks of negative electrode tabs 2351 connected to the second weld bead to the number of stacks n of negative electrode tabs 2351 located in the negative electrode tab stacking stability region 23312 is 0.5 to 0.8, for example, 0.5, 0.55, 0.65, 0.7, or 0.8. The number of stacks of negative electrode tabs 2351 connected to the second weld bead is the number of stacks welded to the second current collector 62 within the negative electrode tab stacking stability region 23312. By setting a range for the value of the ratio j of the number of stacks n of negative electrode tabs 2351 located in this negative electrode tab stacking stability region 23312, this ratio can be made to an appropriate value, while at the same time, burns to the separator 22 caused by insufficient securing of a sufficient number of unwelded stacks due to too few stacks of negative electrode tabs 2351 not connected to the second weld bead can be avoided. On the other hand, it is possible to avoid the adverse effect on the energy density of the secondary battery 1 caused by having too many stacked negative electrode tabs 2351.

[0045] Preferably, i < j. This ensures a sufficient number of unwelded tab layers within the positive tab layer number stable region 21312 and the negative tab layer number stable region 23312, preventing the separator 22 from being thermally damaged during the welding process. At the same time, by increasing the number of layers of the negative tab 2351 as little as possible, the impact on the energy density of the secondary battery 1 can be avoided.

[0046] Referring to FIGS. 7 and 11 again, preferably, along the radial direction R of the winding structure 201, the ratio of the length f1 of the positive tab layer number stable region 21312 to the diameter f3 of the central hole 2011 is 0.5 to 1.4, such as 0.5, 0.64, 0.7, 0.95, 1.23, or 1.4, etc. By setting the range of the ratio value of the length f1 of the positive tab layer number stable region 21312 to the diameter f3 of the central hole 2011, on the one hand, it avoids the mutual interference of the tabs at a position close to the central hole 2011 due to the length f1 of the positive tab layer number stable region 21312 being too long. On the other hand, it avoids the influence on the welding strength caused by the insufficient provision of a sufficient area for welding with the first current collector 61 due to the length f1 of the positive tab layer number stable region 21312 being too short.

[0047] Referring to FIGS. 10 and 11 again, similarly, along the radial direction R of the winding structure 201, the ratio of the length f2 of the negative tab layer number stable region 23312 to the diameter f3 of the central hole 2011 is 0.5 to 1.4, such as 0.5, 0.64, 0.7, 0.95, 1.23, or 1.4, etc. By setting the range of the ratio value of the length f2 of the negative tab layer number stable region 23312 to the diameter f3 of the central hole 2011, on the one hand, it avoids the mutual interference of the tabs at a position close to the central hole 2011 due to the length f2 of the negative tab layer number stable region 23312 being too long. On the other hand, it avoids the influence on the welding strength caused by the insufficient provision of a sufficient area for welding with the second current collector 62 due to the length f2 of the negative tab layer number stable region 23312 being too short.

[0048] The diameter f3 of the center hole 2011 is between 4mm and 8mm. By setting a range for the value of the diameter f3 of the center hole 2011, it is possible to avoid winding difficulties due to excessive torque during winding of the winding needle caused by the diameter f3 of the center hole 2011 being too small, and at the same time, to avoid a decrease in the energy density of the secondary battery 1 due to an increase in the overall volume caused by the diameter f3 of the center hole 2011 being too large.

[0049] Referring again to Figure 5, along the winding direction P of the winding structure 201, the uncoated positive electrode region 213 includes, in order, a first uncoated positive electrode region 214, a second uncoated positive electrode region 215, and a third uncoated positive electrode region 216.

[0050] Referring again to Figure 8, along the winding direction P of the winding structure 201, the uncoated negative electrode region 233 includes, in order, the first uncoated negative electrode region 234, the second uncoated negative electrode region 235, and the third uncoated negative electrode region 236.

[0051] As shown in Figure 14, the direction from the positive electrode coated area 212 to the negative electrode uncoated area 213 is the first direction Q1. Along the first direction Q1, the second negative electrode uncoated area 215 includes the positive electrode tab 2151 and the positive electrode connection area 2152 connected between the positive electrode tab 2151 and the positive electrode coated area 212, while the first negative electrode uncoated area 214 and the third negative electrode uncoated area 216 do not include the positive electrode tab. As shown in Figure 16, 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 the negative electrode tab 2351 and the negative electrode connection area 2352 connected between the negative electrode tab 2351 and the negative electrode coated area 232, while the first negative electrode uncoated area 234 and the third negative electrode uncoated area 236 do not include the negative electrode tab. Here, the number of winding layers in the uncoated third positive electrode region 216 is greater than the number of winding layers in the uncoated third negative electrode region 236.

[0052] In this way, by setting the number of winding layers in the uncoated third positive electrode region 216 to be greater than the number of winding layers in the uncoated third negative electrode region 236, the radial expansion of the winding structure 201 after bending the second uncoated second positive electrode region 215 and the second uncoated second negative electrode region 235 is made to match as much as possible, thereby avoiding an impact on the energy density of the secondary battery 1. At the same time, by reducing the number of winding layers in the uncoated third negative electrode region 236 to the minimum possible, an increase in the internal resistance of the secondary battery 1 is avoided. In other words, the energy density of the secondary battery 1 is improved and the internal resistance of the battery is reduced.

[0053] Referring again to Figure 4, in the winding structure 201, the positive electrode sheet 21 includes a positive electrode sheet start position 217 and a positive electrode sheet end position 218, the negative electrode sheet 23 includes a negative electrode sheet start position 237 and a negative electrode sheet end position 238, and the separator 22 includes a separator start position 221 and a separator end position 222. The outside of the winding structure 201 is further covered with an insulating film 25, which is made of PP, PE, PET, PVC or other polymer material.

[0054] When the positive electrode sheet 21 is unwound (when the positive electrode sheet 21 is unfolded), i.e., in the pre-winding state, the positions of the first uncoated positive electrode region 214, the second uncoated positive electrode region 215, and the third uncoated positive electrode region 216 along the winding direction P of the winding structure 201 are as shown in Figure 5. After the winding structure 201 is formed, the positions of the first uncoated positive electrode region 214, the second uncoated positive electrode region 215, and the third uncoated positive electrode region 216 are as shown in Figure 7. Similarly, when the negative electrode sheet 23 is unwound (when the negative electrode sheet 23 is unfolded), 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 along the winding direction P of the winding structure 201 are as shown in Figure 8. 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 shown in Figure 10.

[0055] 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 in the same direction as the width direction W1 of the positive electrode current collector 211. After winding the positive electrode sheet 21 and bending the positive electrode tab 2151, the first direction Q1 changes in accordance with the bending of the positive electrode tab 2151, and at this time, the first direction Q1 is in the direction from the positive electrode connection region 2152 to the positive electrode tab 2151.

[0056] 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 in the same direction as the width direction W2 of the negative electrode current collector 231. After winding the negative electrode sheet 23 and bending the negative electrode tab 2351, the second direction Q2 changes in accordance with the bending of the negative electrode tab 2351, and at this time, the second direction Q2 is the direction from the negative electrode connection region 2352 to the negative electrode tab 2351.

[0057] The number of winding layers in the uncoated third positive electrode region 216 refers to the number of circles that overlap with the third positive electrode region 216 along the radial direction R of the winding structure 201 formed after winding molding. Similarly, the number of winding layers in the uncoated third negative electrode region 236 refers to the number of layers that overlap with the third negative electrode region 236 along the radial direction R of the winding structure 201 formed after winding molding. Furthermore, one or more electrode assemblies 20 may be included within the case 10.

[0058] In this embodiment, the case 10 contains one electrode assembly 20, but it is not limited to this. In other embodiments, the number of electrode assemblies 20 contained in the case 10 may be two, three, four, or other values, and can be adjusted according to the design requirements.

[0059] Specifically, the range of the number of winding layers in the uncoated third positive electrode region 216 is 3 to 6. By setting a range for the number of winding layers in the uncoated third positive electrode region 216 in this way, it is possible to avoid, on the one hand, an adverse effect on the energy density of the secondary battery 1 due to excessive radial expansion of the winding structure 201 after bending of the second positive electrode uncoated region 215 caused by too few winding layers in the uncoated third positive electrode region 216, and on the other hand, an excessive increase in internal battery resistance due to too many winding layers in the uncoated third positive electrode region 216.

[0060] The range of the number of winding layers formed by the third uncoated negative electrode region 236 is 1 to 3. By setting a range for the number of winding layers formed by the third uncoated negative electrode region 236 in this way, it is possible to avoid, on the one hand, an adverse effect on the energy density of the secondary battery 1 due to excessive radial expansion of the winding structure 201 after bending of the second uncoated negative electrode region 235 caused by too few winding layers in the third uncoated negative electrode region 236, and on the other hand, an excessive increase in internal battery resistance due to too many winding layers formed by the third uncoated negative electrode region 236.

[0061] Along the axial direction O of the winding structure 201, in the winding layer of the second positive electrode uncoated region 215, the outermost layer of the second positive electrode uncoated region 215 includes a first bend, and the orthographic projection of this first bend is located inside the outer peripheral edge of the winding structure 201. By ensuring that the expansion of the second positive electrode uncoated region 215 in the radial direction R of the winding structure 201 after bending does not exceed the outer peripheral edge of the winding structure 201, the influence on the energy density of the secondary battery 1 is avoided.

[0062] Along the axial direction O of the winding structure 201, in the winding layer of the second uncoated negative electrode region 235, the outermost layer of the second uncoated negative electrode region 235 includes a second bend, and the orthographic projection of this second bend is located inside the outer peripheral edge of the winding structure 201. By ensuring that the expansion of the second uncoated negative electrode region 235 in the radial direction R of the winding structure 201 after bending does not exceed the outer peripheral edge of the winding structure 201, the influence on the energy density of the secondary battery 1 is avoided.

[0063] Preferably, referring again to Figure 5, along the winding direction P of the winding structure 201, the length a1 of the first uncoated positive electrode region 214 is 400 mm to 600 mm, for example 400 mm, 450 mm, 500 mm, 520 mm, 580 mm, or 600 mm. The length a2 of the second uncoated positive electrode region 215 is 3000 mm to 5000 mm, for example 3000 mm, 3500 mm, 4000 mm, 4200 mm, 4800 mm, or 5000 mm. The length a3 of the third uncoated positive electrode region 216 is 200 mm to 500 mm, for example 200 mm, 250 mm, 300 mm, 400 mm, 450 mm, or 500 mm.

[0064] Referring again to Figure 8, along the winding direction P of the winding structure 201, the length b1 of the first uncoated negative electrode region 234 is 300 mm to 500 mm, for example, 300 mm, 350 mm, 400 mm, 420 mm, 480 mm, or 500 mm. The length b2 of the second uncoated negative electrode region 235 is 3000 mm to 5000 mm, for example, 3000 mm, 3500 mm, 4000 mm, 4200 mm, 4800 mm, or 5000 mm. The length b3 of the third uncoated negative electrode region 236 is 100 mm to 300 mm, for example, 100 mm, 150 mm, 200 mm, 220 mm, 280 mm, or 300 mm.

[0065] In this way, by setting the range of values ​​for the lengths a1 of the first positive electrode uncoated region 214, a2 of the second positive electrode uncoated region 215, a3 of the third positive electrode uncoated region 216, b1 of the first negative electrode uncoated region 234, b2 of the second negative electrode uncoated region 235, and b3 of the third negative electrode uncoated region 236, it is possible to more effectively improve energy density and reduce internal battery resistance.

[0066] The ratio of the length a3 of the uncoated third positive electrode region 216 to the length b3 of the uncoated third negative electrode region 236 is between 1.5 and 2.5, for example, 1.5, 1.7, 2, 2.1, 2.3, or 2.5. By setting a range for the ratio of the length a3 of the uncoated third positive electrode region 216 to the length b3 of the uncoated third negative electrode region 236 in this way, it is possible to make this ratio an appropriate value, not only so that the number of layers in the uncoated third positive electrode region 216 is greater than the number of layers in the uncoated third negative electrode region 236, but also to make the internal resistance of the battery an appropriate range by setting the lengths of both within an appropriate range.

[0067] The positive electrode tab 2151 is located within the positive electrode tab stacking region 2131, and the negative electrode tab 2351 is located within the negative electrode tab stacking region 2331.

[0068] In this embodiment, the secondary battery 1 is a cylindrical battery. Cylindrical batteries have advantages such as high energy density, long cycle life, and good safety performance. However, they are not limited to this, and in other embodiments, the secondary battery 1 may be a battery of other shapes, such as a rectangular battery.

[0069] In this embodiment, the positive electrode tab 2151 is a cut and laminated tab. When welding the tab of a cylindrical battery to the current collector, there are two different processing methods for the tab pretreatment process: one is the tab flattening process, and the other is the cut and laminated tab cutting and lamination process used for the positive electrode tab 2151 in this embodiment. Referring again to Figure 6, when the positive electrode sheet 21 is unfolded, the positive electrode current collector 211 is in a flat state, and the extension direction of the positive electrode tab 2151 and the length direction L1 of the positive electrode current collector 211 form a first acute angle α, which is between 30 and 85 degrees. By setting the range of the value of the first acute angle α, the length of the positive electrode tab 2151 can be extended within a certain range, while simultaneously ensuring the connection strength of the positive electrode tab 2151.

[0070] The negative electrode tab 2351 is also a cut and laminated tab. Referring again to Figure 9, when the negative electrode sheet 23 is unfolded, the negative electrode current collector 231 is in a flat state, and the extension direction of the negative electrode tab 2351 and the length direction L2 of the negative electrode current collector 231 form a second acute angle β, which is between 30 and 85 degrees. By setting a range for the value of the second acute angle β, the length of the negative electrode tab 2351 can be extended within a certain range while simultaneously ensuring the connection strength of the negative electrode tab 2351.

[0071] The positive electrode connection region 2152 includes a first side far from the central hole 2011 of the winding structure 201 and a second side close to the central hole 2011, along the radial R of the winding structure 201, where at least a portion of the first side and / or the second side is covered with an insulating layer 24, reducing the risk of deformation of the positive electrode connection region 2152 and improving the insulating performance of the positive electrode connection region 2152, thereby significantly improving the safety and reliability of the battery performance. The main components of the insulating layer 24 are boehmite and PVDF (polyvinylidene difluoride). The proportion of boehmite is 80%, and the proportion of PVDF is 20%. The thickness of the insulating layer 24 is 1.5 μm to 2.5 μm, for example, 1.5 μm, 1.7 μm, 2 μm, 2.1 μm, 2.3 μm, or 2.5 μm. By setting a range for the thickness of the insulating layer 24, it is possible to avoid the difficulty in securing the necessary electrical insulation and support strength due to the coating thickness of the insulating layer 24 being too thin, while simultaneously avoiding the possibility of prolonged curing time of the coating layer and increased overall structure thickness due to the insulating layer 24 being too thick. Preferably, the thickness of the insulating layer 24 is 2 μm.

[0072] Referring again to Figures 12 and 14, in this embodiment, both the first and second sides of the positive electrode connection region 2152 are covered with the insulating layer 24. However, it is not limited to this, and in other embodiments, only the first side of the positive electrode connection region 2152 may be covered with the insulating layer 24, or only the second side of the positive electrode connection region 2152 may be covered with the insulating layer 24. This can be adjusted according to the design requirements.

[0073] The insulating layer 24 contains a color developer, and the color-developing action of the color developer allows us to distinguish whether the side to which the insulating layer 24 is applied is the front or back surface of the positive electrode sheet 21, but this is not limited to distinguishing the surface density of the front and back surfaces of the positive electrode sheet 21. The main component of the color developer is bismuth vanadate, and its color is yellow.

[0074] In this embodiment, the first side of the positive electrode connection region 2152 is covered with an insulating layer 24 containing a color developer, and the second side of the positive electrode connection region 2152 is covered with an insulating layer 24 that does not contain a color developer, thereby making the front and back surfaces of the positive electrode sheet 21 different in color. This allows for quick differentiation of the front and back surfaces of the positive electrode sheet 21 by utilizing the color-developing effect of the color developer in the insulating layer 24. In some cases, it is necessary to distinguish between the front and back surfaces of the positive electrode sheet 21, and this is not limited to distinguishing between the surface density of the front and back surfaces. Therefore, the purpose of quick differentiation is achieved by adding a color developer to one of the insulating layers 24. In other embodiments, the second side of the positive electrode connection region 2152 is covered with an insulating layer 24 containing a color developer, and the first side of the positive electrode connection region 2152 is covered with an insulating layer 24 that does not contain a color developer, thereby similarly making the front and back surfaces of the positive electrode sheet 21 different in color.

[0075] Preferably, the insulating layer 24 covers the entire area on the first side of the positive electrode connection region 2152, and the insulating layer 24 covers the entire area on the second side of the positive electrode connection region 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 region 2152. This makes it possible to more effectively prevent deformation of the positive electrode connection region 2152 and improve the insulation performance of this region. Note that if a part of the insulating layer 24 covers the positive electrode tab 2151, then the width of the insulating layer 24 becomes its maximum width.

[0076] Referring again to Figure 14, further along the first direction Q1, the positive tab 2151 includes a positive tab transition portion 21511 and a positive tab body 21512, the positive tab transition portion 21511 being connected between the positive connection region 2152 and the positive tab body 21512, and the positive tab transition portion 21511 is the bent region of the positive tab 2151.

[0077] Referring again to Figure 16, along the second direction Q2, the negative electrode tab 2351 includes a negative electrode tab transition section 23511 and a negative electrode tab body 23512, the negative electrode tab transition section 23511 is connected between the negative electrode connection region 2352 and the negative electrode tab body 23512, and the negative electrode tab transition section 23511 is the bent region of the negative electrode tab 2351.

[0078] The width c1 of the positive tab transition portion 21511 of the positive tab 2151 located in the outermost layer is greater than the width d1 of the negative tab transition portion 23511 of the negative tab 2351 located in the outermost layer. Thus, because the hardness of the positive electrode tab 2151 is higher than that of the negative electrode tab 2351, the expansion of the winding structure 201 of the positive electrode tab 2151 in the radial direction R due to compression during installation is greater than the expansion of the electrode assembly of the negative electrode tab 2351 in the radial direction R. By setting the width c1 of the positive electrode tab transition portion 21511 of the outermost positive electrode tab 2151 to be larger than the width d1 of the negative electrode tab transition portion 23511 of the outermost negative electrode tab 2351, the positive electrode tab 2151 has a larger bending area than the negative electrode tab 2351, avoiding the impact on the dimensions of the positive electrode tab body 21512 formed after bending due to compression, and making the dimensions of the positive electrode tab body 21512 and the negative electrode tab body 23512 equivalent after bending.

[0079] Referring again to Figure 14, preferably, along the first direction Q1, the width c1 of the positive electrode tab transition portion 21511 is 1 mm to 2 mm, for example, 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 1.9 mm, or 2 mm. By setting the range of values ​​for the width c1 of the positive electrode tab transition portion 21511 in this way, the positive electrode tab 2151 has a larger bending area than the negative electrode tab 2351, and the influence on the dimensions of the positive electrode tab body 21512 formed after bending is avoided. The positive electrode tab transition section 21511 is arc-shaped and 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 to the positive electrode tab transition section 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 to the positive electrode tab transition section 21511 intersects with the extension direction of the positive electrode tab body 21512. After compression, the positive electrode tab transition section 21511 deforms and spreads outwards from the winding structure, resulting in the structure shown in Figure 15.

[0080] Referring again to Figure 16, preferably, along the second direction Q2, the width d1 of the negative electrode tab transition portion 23511 is 0.1 mm to 1 mm, for example, 0.1 mm, 0.2 mm, 0.5 mm, 0.7 mm, 0.9 mm, or 1 mm. By setting the range of values ​​for the width d1 of the negative electrode tab transition portion 23511 in this way, the negative electrode tab 2351 has a smaller bending area compared to the positive electrode tab 2151, thereby saving on tab material costs. The negative electrode tab transition section 23511 is arc-shaped and 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 to the negative electrode tab transition section 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 to the negative electrode tab transition section 23511 intersects the extension direction of the negative electrode tab body 23512. After being compressed, the negative electrode tab transition section 23511 deforms and spreads outwards from the winding structure, resulting in the structure shown in Figure 17.

[0081] Preferably, along the first direction Q1, the width c2 of the positive electrode tab body 21512 is 4.5 mm to 5.5 mm, for example 4.5 mm, 4.7 mm, 5 mm, 5.1 mm, 5.3 mm, or 5.5 mm, and along the second direction Q2, the width d2 of the negative electrode tab body 23512 is 4 mm to 5 mm, for example 4 mm, 4.2 mm, 4.5 mm, 4.7 mm, 4.9 mm, or 5 mm. By setting the range of values ​​for the width c2 of the positive electrode tab body 21512 and the width d2 of the negative electrode tab body 23512 in this way, a reasonable positive electrode tab stacking region and a negative electrode tab stacking region can be formed, thereby avoiding a decrease in the energy density of the battery due to too many tab layers in the stacking region, while avoiding thermal damage to surrounding parts (e.g., separator 22, etc.) during the welding process due to insufficient spare space due to too few tab layers in the stacking region, that is, preventing thermal damage to surrounding parts.

[0082] Preferably, along the first direction Q1, the width c3 of the positive electrode connection area 2152 is 1.5 mm to 2.5 mm, for example, 1.5 mm, 1.7 mm, 2 mm, 2.1 mm, 2.3 mm, or 2.5 mm. By setting the range of values ​​for the width c3 of the positive electrode connection area 2152 in this way, a distance is secured from the welding surface of the positive electrode current collector and the positive electrode tab 2151 to the positive electrode coating area 212 covered with the positive electrode active material layer 2111, thereby avoiding thermal effects during welding and improving safety performance.

[0083] Along the second direction Q2, the width d3 of the negative electrode connection area 2352 is 1 mm to 2 mm, for example, 1 mm, 1.2 mm, 1.5 mm, 1.7 mm, 1.9 mm, or 2 mm. By setting a range of values ​​for the width of the negative electrode connection area 2352 in this way, a distance is ensured from the welding surface of the negative electrode current collector and the negative electrode tab 2351 to the negative electrode coating area 232 covered with the negative electrode active material layer 2311, thereby avoiding thermal effects during welding and improving safety performance.

[0084] The thickness t1 of the positive electrode tab 2151 is 12 μm to 20 μm, for example, 12 μm, 14 μm, 16 μm, 17.5 μm, 19.5 μm, or 20 μm. The thickness t2 of the negative electrode tab 2351 is 4 μm to 11 μm, for example, 4 μm, 6 μm, 7.5 μm, 8 μm, 9 μm, or 11 μm. The material of the positive electrode tab 2151 is usually aluminum, and the material of the negative electrode tab 2351 is usually copper, with the hardness of the positive electrode tab 2151 being higher than that of the negative electrode tab 2351. By setting a range for the thickness t1 of the positive electrode tab 2151, it is possible to avoid easy tearing during compression due to being too thin and to avoid increased manufacturing costs due to being too thick. By setting a range for the thickness t2 of the negative electrode tab 2351, the mounting requirements for the negative electrode tab 2351 can be ensured, thereby maximizing material usage and achieving beneficial technical effects of cost savings. Referring again to Figures 1 and 2, in this embodiment, the case 10 includes an annular side wall 11, with an opening 12 formed at one end of the side wall 11, and the case 10 includes a crimped portion 30 recessed into the interior of the case 10 at one end near the opening 12. The secondary battery 1 further includes a cover plate 40, an insulating sealing component 50, and the aforementioned current collector panel. The cover plate 40 is attached to the opening 12. The insulating sealing component 50 is provided surrounding the periphery of the cover plate 40, insulating and sealing the cover plate 40 and the case 10. The current collector panel is provided between the electrode assembly 20 and the cover plate 40 and is electrically connected to the case 10, and the connection sheet of the current collector panel is located on the side of the crimped portion 30 facing the electrode assembly 20 and is welded to the crimped portion 30. In this way, the connection sheet of the current collector panel is positioned on the side of the crimping portion 30 facing the electrode assembly 20 and is provided to be welded to the crimping portion 30. As a result, the welding area between the current collector panel and the tab is located closer to the electrode assembly 20 than to the crimping portion 30, preventing the crimping portion 30 from affecting the welding area between the tab and the current collector panel, and improving the welding strength between the tab and the current collector panel.

[0085] Furthermore, the case 10 includes an end wall 13, and the side wall 11 surrounds the end wall 13 and is located at one end furthest from the opening 12 of the side wall 11. The end wall 13 and the side wall 11 form a housing space within the case 10 that contains the electrode assembly 20, electrolyte, and other essential battery components. The connection between the end wall 13 and the side wall 11 can be achieved by multiple methods, such as integral press molding, integral casting, or partial welding.

[0086] The secondary battery 1 further includes a terminal post 70, the terminal post 70 penetrates the end wall 13 and is insulated from the end wall 13. As described above, the current collector panel includes a first current collector panel 61 and a second current collector panel 62, where the first current collector panel 61 is provided between the electrode assembly 20 and the end wall 13, and the second current collector panel 62 is provided between the electrode assembly and the cover plate 40. In this embodiment, as described above, the first current collector panel 61 corresponds to the positive electrode tab 2151, and the positive electrode tab 2151 is electrically connected to the terminal post 70 via the first current collector panel 61, and the second current collector panel 62 corresponds to the negative electrode tab 2351, and the negative electrode tab 2351 is electrically connected to the case 10 via the second current collector panel 62. However, it is not limited to this, and in other embodiments, the first current collector panel 61 may correspond to the negative electrode tab 2351 and the second current collector panel 62 may correspond to the positive electrode tab 2151.

[0087] The welding sequence between the electrode assemblies 20 of the first current collector 61 and the second current collector 62 of the secondary battery 1 in this embodiment is as follows. First, the first current collector 61 is placed. Next, the electrode assemblies 20 are compressed simultaneously on both the positive and negative sides (the compression process increases the contact between the current collector and the electrode assemblies 20, thus avoiding welding defects). The first current collector 61 is welded, using linear welding rather than spot welding. This is because the negative electrode tab 2351 is soft, and after two compressions, the distance between the second current collector 62 and the electrode assemblies 20 becomes shorter. Spot welding concentrates heat and burns the separator 22, while linear welding generates less heat, avoiding burns to the separator 22 and preventing short circuits between the positive and negative electrodes. Subsequently, the second current collector 62 is placed. Again, the electrode assemblies 20 are compressed simultaneously on both the positive and negative sides. Finally, the second current collector 62 is welded.

[0088] As shown in Figure 18, the present invention further provides a battery pack 100 which includes the above-mentioned secondary battery 1. In one embodiment of the battery pack 100 of the present invention, the battery pack 100 includes a housing 310, a housing cover 320, and a plurality of secondary batteries 1, which are arranged inside the housing 310 and connected to each other in series, parallel, or a combination of series and parallel, and the housing cover 320 seals the housing 310 and protects the plurality of secondary batteries 1. In addition to the secondary batteries 1 of the present invention, the battery pack 100 may include parts such as a thermal management system and a circuit board, and the battery pack 100 may be a battery module, a battery pack, an energy storage cabinet, etc. These will not be described in detail here.

[0089] As shown in Figure 19, the present invention further provides an electronic device 1000, which includes the battery pack 100 described above. The operating unit 300 is electrically connected to the battery pack 100 to obtain power. As an example, the electronic device 1000 is a vehicle, which is a fuel-fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle is a pure electric vehicle, a hybrid vehicle, or a range-extender vehicle, etc. The operating unit 300 is the vehicle body, and the battery pack 100 is located at the bottom of the vehicle body and provides power for the vehicle to run or for the operation of electrical components inside the vehicle. However, in some other embodiments, the electronic device 1000 may be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, a power tool, etc. Spacecraft include airplanes, rockets, space shuttles, etc., and the operating unit 300 is a unit component that obtains power from the battery pack 100 and performs a corresponding operation, such as the fan rotation unit of a fan or the dust collection operation unit of a vacuum cleaner. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys. Power tools include metal cutting power tools, polishing power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The embodiments of this application do not impose any special limitations on the above-mentioned electronic devices 1000.

[0090] Although specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative and that the scope of protection of the present invention is limited by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and all such changes and modifications are included within the scope of protection of the present invention. [Industrial applicability]

[0091] The secondary battery, battery pack, and electronic device of this application are applicable to the battery technology field. [Explanation of Symbols]

[0092] 1000 electronic devices 100 Battery Pack 300 Operating Unit 310 cabinets 320 Case Cover 1 Secondary battery 10 cases 11 Side wall 12 Openings 13 End wall 20 Electrode assembly 201 Winding structure 2011 center hole 21 Positive electrode sheet 211 Positive electrode current collector 2111 Cathode active material layer 212 Positive electrode coating area 213 Uncoated area of ​​the positive electrode 2131 Positive tab stacking region 21311 Increased number of positive electrode tab stacks region 21312 Stable region for the number of stacked positive tabs 21313 Region where the number of stacked positive tabs decreases 214 Uncoated area of ​​the first positive electrode 215 Second cathode uncoated area 2151 Positive Tab 21511 Positive Tab Transition Section 21512 Positive electrode tab body 2152 Positive electrode connection area 216 Third cathode uncoated area 217 Positive electrode sheet starting position 218 Positive electrode sheet end position 22 Separators 221 Separator start position 222 Separator end position 23 Negative electrode sheet 231 Negative electrode current collector 2311 Negative active material layer 232 Negative electrode coating area 233 Area without negative electrode coating 2331 Negative electrode tab stacking region 23311 Area where the number of stacked negative electrode tabs increases 23312 Negative electrode tab stacking number stable region 23313 Region where the number of stacked negative electrode tabs decreases 234 Uncoated area of ​​the first negative electrode 235 Second negative electrode uncoated area 2351 Negative Electrode Tab 23511 Negative electrode tab transition section 23512 Negative electrode tab body 2352 Negative electrode connection area 236 Third negative electrode uncoated area 237 Negative electrode sheet starting position 238 Negative electrode sheet end position 24 Insulating layer 25 Insulating film 30 Crimping section 40 Cover Plate 50 Insulated sealing components 61 First current collection panel 62 Second current collection panel 70 Terminal post a1 Length of the uncoated region of the first positive electrode a2 Length of the uncoated region of the second positive electrode a3 Length of the uncoated region of the third positive electrode b1 Length of the uncoated region of the first negative electrode b2 Length of the uncoated region of the second negative electrode b3 Length of the uncoated region of the third negative electrode c1 Width of the positive electrode tab transition area c2 Positive tab body width c3 Width of the positive electrode connection area d1 Width of the negative electrode tab transition area d2 Width of the negative electrode tab d3 Width of the negative electrode connection area f1 Length of the stacking stability region of the positive electrode tab f2 Length of the stacking stability region of the negative electrode tab f3 Diameter of the center hole t1 Thickness of the positive electrode tab t2 thickness of the negative electrode tab O Axial direction of the winding structure Radial direction of R winding structure Winding direction of the P winding structure Q1 First direction Q2 Second direction L1 Positive electrode current collector length direction L2 Negative electrode current collector length direction α First acute angle β second acute angle W1 Width direction of the positive electrode current collector W2 Width direction of the negative electrode current collector

Claims

1. The case and, The electrode assembly housed in the aforementioned case includes, The electrode assembly includes a wound structure formed by stacking 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 region covered with a positive electrode active material layer and a positive electrode uncoated region not covered with a positive electrode active material layer, and the negative electrode current collector includes a negative electrode coated region covered with a negative electrode active material layer and a negative electrode uncoated region not covered with a negative electrode active material layer. Along the radial direction of the winding structure, a portion of the uncoated positive electrode region is bent toward the central hole of the winding structure, and the uncoated positive electrode regions with different winding layer numbers are stacked on each other to form a positive electrode tab stacking region, the positive electrode tab stacking region includes a positive electrode tab stacking number stable region, and within the positive electrode tab stacking number stable region, the number of stacked positive electrode tabs is m. Along the radial direction of the winding structure, a portion of the uncoated negative electrode region is bent toward the central hole, and the uncoated negative electrode regions with different winding layer counts are stacked on each other to form a negative electrode tab stacking region, the negative electrode tab stacking region includes a negative electrode tab stacking number stable region, and within the negative electrode tab stacking number stable region, the number of stacked negative electrode tabs is n. A secondary battery characterized by m > n.

2. Along the radial direction of the winding structure, from the outer circumference to the central hole, the positive electrode tab stacking region includes, in order, a region where the number of stacked positive electrode tabs increases, a region where the number of stacked positive electrode tabs stabilizes, and a region where the number of stacked positive electrode tabs decreases, and the negative electrode tab stacking region includes, in order, a region where the number of stacked negative electrode tabs increases, a region where the number of stacked negative electrode tabs stabilizes, and a region where the number of stacked negative electrode tabs decreases. The secondary battery according to claim 1, characterized in that the length of the positive electrode tab stacking number stabilization region is longer than the length of the negative electrode tab stacking number stabilization region along the radial direction of the winding structure.

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

5.

4. The secondary battery further includes a current collector, the current collector includes a first current collector and a second current collector, the first current collector is welded to the positive electrode tab stacking number stabilization region and a first weld bead is formed, and the second current collector is welded to the negative electrode tab stacking number stabilization region and a second weld bead is formed. Along the axial direction of the winding structure, the number of layers of the positive electrode tab connected to the first weld bead is 8 to 12, or Along the axial direction of the winding structure, the number of layers of the negative electrode tab connected to the second weld bead is 8 to 12, or Along the axial direction of the winding structure, within the positive electrode tab stacking stability region, the ratio i of the number of stacked positive electrode tabs connected to the first weld bead to the number of stacked positive electrode tabs located in the positive electrode tab stacking stability region is 0.4 to 0.65, or The secondary battery according to claim 1, characterized in that, along the axial direction of the winding structure, within the negative electrode tab stacking stability region, the ratio j of the number of stacked negative electrode tabs connected to the second weld bead to the number of stacked negative electrode tabs located in the negative electrode tab stacking stability region is 0.5 to 0.

8.

5. Along the radial direction of the winding structure, the ratio of the length of the positive electrode tab stacking stability region to the diameter of the central hole is 0.5 to 1.4, or Along the radial direction of the winding structure, the ratio of the length of the negative electrode tab stacking stability region to the diameter of the central hole is 0.5 to 1.4, or The secondary battery according to claim 1, characterized in that the diameter of the central hole is 4 mm to 8 mm.

6. The direction in which the coated positive electrode region extends to the uncoated positive electrode region is the first direction, and the direction in which the coated negative electrode region extends to the uncoated negative electrode region is the second direction. Along the winding direction of the winding structure, the uncoated positive electrode region includes, in order, a first uncoated positive electrode region, a second uncoated positive electrode region, and a third uncoated positive electrode region, and the uncoated negative electrode region includes, in order, a first uncoated negative electrode region, a second uncoated negative electrode region, and a third uncoated negative electrode region. Along the radial direction of the winding structure, the uncoated region of the second positive electrode is bent toward the central hole, and the uncoated regions of the second positive electrode with different winding layer counts are stacked on top of each other to form the positive electrode tab stacked region, and the uncoated region of the second negative electrode is bent toward the central hole, and the uncoated regions of the second negative electrode with different winding layer counts are stacked on top of each other to form the negative electrode tab stacked region, Along the first direction, the second uncoated positive electrode region includes a positive electrode tab and a positive electrode connection region connected between the positive electrode tab and the positive electrode coated region, while neither the first uncoated positive electrode region nor the third uncoated positive electrode region includes the positive electrode tab. Along the second direction, the second uncoated negative electrode region includes a negative electrode tab and a negative electrode connection region connected between the negative electrode tab and the negative electrode coated region, while neither the first uncoated negative electrode region nor the third uncoated negative electrode region includes the negative electrode tab. The number of winding layers in the uncoated third positive electrode region is greater than the number of winding layers in the uncoated third negative electrode region. The range of the number of winding layers in the uncoated region of the third positive electrode is 3 to 6, or The secondary battery according to claim 1, characterized in that the value of the number of winding layers in the uncoated third negative electrode region is in the range of 1 to 2.

7. Along the axial direction of the winding structure, in the winding layer of the second uncoated positive electrode region, the outermost layer of the second uncoated positive electrode region includes a first bend, and the orthographic projection of the first bend is located inside the outer peripheral edge of the winding structure, or Along the axial direction of the winding structure, in the winding layer of the second uncoated negative electrode region, the outermost layer of the second uncoated negative electrode region includes a second bend, and the orthographic projection of the second bend is located inside the outer peripheral edge of the winding structure, and / or Along the winding direction of the winding structure, the length of the first uncoated positive electrode region is 400 mm to 600 mm, the length of the second uncoated positive electrode region is 3000 mm to 5000 mm, and the length of the third uncoated positive electrode region is 200 mm to 500 mm, or Along the winding direction of the winding structure, the length of the first uncoated negative electrode region is 300 mm to 500 mm, the length of the second uncoated negative electrode region is 3000 mm to 5000 mm, and the length of the third uncoated negative electrode region is 100 mm to 300 mm, or The secondary battery according to claim 6, characterized in that the ratio of the length of the uncoated region of the third positive electrode to the length of the uncoated region of the third negative electrode is 1.5 to 2.

5.

8. The positive electrode tab is a cut and laminated tab, and when the positive electrode sheet is unfolded, the positive electrode current collector is in a flat state, and the extension direction of the positive electrode tab and the longitudinal direction of the positive electrode current collector form a first acute angle, and the first acute angle is between 30 and 85 degrees. The secondary battery according to claim 6, characterized in that the negative electrode tab is a cut and laminated tab, when the negative electrode sheet is unfolded the negative electrode current collector is in a flat state, the stretching direction of the negative electrode tab and the longitudinal direction of the negative electrode current collector form a second acute angle, and the second acute angle is 30 degrees to 85 degrees.

9. Along the radial direction of the winding structure, the positive electrode connection region includes a first side far from the central hole of the winding structure and a second side close to the central hole, and at least a portion of the first side and / or the second side is covered with an insulating layer, the insulating layer contains a color developer, The insulating layer covers the entire area on the first side of the positive electrode connection region, and / or The insulating layer covers the entire area on the second side of the positive electrode connection region, and / or The secondary battery according to claim 6, characterized in that the maximum width of the insulating layer along the first direction is equal to or greater than the width of the positive electrode connection region.

10. Along the first direction, the width of the positive electrode connection region is 1.5 mm to 2.5 mm, and / or The secondary battery according to claim 6, characterized in that the width of the negative electrode connection region is 1 mm to 2 mm along the second direction.

11. 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 the bending region of the positive electrode tab. Along the second direction, the negative electrode tab includes a negative electrode tab transition section and a negative electrode tab body, the negative electrode tab transition section is connected between the negative electrode connection area and the negative electrode tab body, and the negative electrode tab transition section is the bent area of ​​the negative electrode tab. The secondary battery according to claim 6, characterized in that the width of the positive electrode tab transition portion of the positive electrode tab located in the outermost layer is greater than the width of the negative electrode tab transition portion of the negative electrode tab located in the outermost layer.

12. Along the first direction, the width of the positive electrode tab transition portion is 1 mm to 2 mm, the width of the positive electrode tab body is 4.5 mm to 5.5 mm, the thickness of the positive electrode tab is 12 μm to 20 μm, and / or The secondary battery according to claim 11, characterized in that, along the second direction, the width of the negative electrode tab transition portion is 0.1 mm to 1 mm, the width of the negative electrode tab body is 4 mm to 5 mm, and the thickness of the negative electrode tab is 4 μm to 11 μm.

13. The case includes an annular side wall, an opening is formed at one end of the side wall, and the case includes a crimping portion recessed into the interior of the case at one end near the opening. The aforementioned secondary battery further, A cover plate attached to the opening, An insulating sealing component is provided surrounding the periphery of the cover plate to insulate and seal the cover plate and the case, A current collector is provided between the electrode assembly and the cover plate and is electrically connected to the case, wherein the connection sheet of the current collector is located on the side of the crimping portion facing the electrode assembly and is welded to the crimping portion, including the current collector. and / or, The secondary battery according to claim 1, characterized in that the secondary battery is a cylindrical battery.

14. A battery pack characterized by including a secondary battery according to any one of claims 1 to 13.

15. An electronic device characterized by including the battery pack described in claim 14.

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