Secondary batteries, battery packs, and electronic devices

Abstract

The present invention provides a secondary battery, a battery pack, and an electronic device that improve the energy density of the secondary battery and reduce the internal resistance of the battery. [Solution] The secondary battery includes a case and an electrode assembly housed within the case, the electrode assembly including 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, and the negative electrode current collector of the negative electrode sheet includes a negative electrode coated region and a negative electrode uncoated region. Along the winding direction of the winding structure, the positive electrode uncoated region includes, in order, a first positive electrode uncoated region, a second positive electrode uncoated region, and a third positive electrode uncoated region, and the negative electrode uncoated region includes, in order, a first negative electrode uncoated region, a second negative electrode uncoated region, and a third negative electrode uncoated region. The number of winding layers in the third positive electrode uncoated region is greater than the number of winding layers in the third negative electrode uncoated region.

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 are adopting secondary batteries as energy storage and supply devices such as new energy vehicles, communication base stations, and energy storage containers.

[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 of the secondary battery are welded to the corresponding current collector plate, and then the current collector plate is crimped during installation, and then the tab and the current collector plate are welded. Generally, different materials are selected for the positive electrode tab and the negative electrode tab, and the hardness of the positive electrode tab and the negative electrode tab is different. Therefore, due to the crimping during installation, the distances that the positive electrode tab and the negative electrode tab spread outward in the radial direction of the secondary battery are different, occupying the space inside the battery case, thereby affecting the energy density of the secondary battery.

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0005] The present invention solves the above technical problems by the following technical means.

[0006] A case, and an electrode assembly housed in the case, and includes the electrode assembly includes a winding structure in which a positive electrode sheet, a separator, and a negative electrode sheet are laminated and wound. 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, with the direction from the positive electrode coated region to the positive electrode uncoated region being the first direction and the direction from the negative electrode coated region to the negative electrode uncoated region being 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 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 the first uncoated negative electrode region and the third uncoated negative electrode region do not include the negative electrode tab. A secondary battery characterized in that the number of winding layers in the uncoated region of the third positive electrode is greater than the number of winding layers in the uncoated region of the third negative electrode.

[0007] Preferably, the numerical range of the number of winding layers in the uncoated third positive electrode region is 3 to 6, or The numerical range for the number of winding layers in the uncoated third negative electrode region is 1 to 3.

[0008] 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 folded portion, and the orthographic projection of the first folded portion is located within 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 folded portion, and the orthographic projection of the second folded portion is located within the outer peripheral edge of the winding structure.

[0009] 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.

[0010] Preferably, the positive electrode connection region includes a first side along the radial direction of the winding structure, away from the central hole of the winding structure, and a second side adjacent to the central hole, wherein at least a portion of the first side and / or the second side is covered with an insulating layer, the insulating layer containing a color developer.

[0011] Preferably, the insulating layer covers the entire area on the first side of the positive electrode connection area, and / or The insulating layer covers the entire area on the second side of the positive electrode connection area, and / or Along the first direction, the maximum width of the insulating layer is greater than or equal to the width of the positive electrode connection region.

[0012] Preferably, along the first direction, the width of the positive electrode connection area is 1.5 mm to 2.5 mm, and / or Along the second direction, the width of the negative electrode connection area is 1 mm to 2 mm.

[0013] Preferably, along the first direction, the positive electrode tab includes a positive electrode tab transition portion and a positive electrode tab body, the positive electrode tab transition portion is connected between the positive electrode connection 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 bending area of ​​the negative electrode tab. The width of the transition portion of the positive electrode tab located in the outermost layer is greater than the width of the transition portion of the negative electrode tab located in the outermost layer.

[0014] 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 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 body is 4 mm to 5 mm, and the thickness of the negative electrode tab is 4 μm to 11 μm.

[0015] Preferably, the case includes an annular side wall, with an opening at one end of the side wall, and the case includes a crimping portion at one end adjacent to the opening, which is recessed toward the inside of the case. 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 and insulating and sealing the cover plate and the case, A current collector is provided between the electrode assembly and the cover plate and electrically connected to the case, wherein the connecting piece of the current collector is located on the side of the crimping portion facing the electrode assembly and is welded to the crimping portion, and the current collector is provided between the electrode assembly and the case, including and / or, The secondary battery is a cylindrical battery, the positive electrode tab is a cut and stacked tab, and the negative electrode tab is a cut and stacked tab.

[0016] A battery pack comprising the secondary battery described above.

[0017] An electronic device comprising the battery pack described above.

Advantages of the Invention

[0018] The positive progressive effects of the present invention are as follows. The present invention sets the number of winding layers in the third uncoated region of the positive electrode to be more than the number of winding layers in the third uncoated region of the negative electrode, so as to make the outward spread along the radial direction of the winding structure after bending of the second uncoated region of the positive electrode and the second uncoated region of the negative electrode coincide as much as possible, thereby avoiding the influence on the energy density of the secondary battery. At the same time, by reducing the number of winding layers in the third uncoated region of the negative electrode as much as possible, an increase in the internal resistance of the secondary battery can be avoided. That is, the energy density of the secondary battery can be improved and the internal resistance of the battery can be reduced.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic cross-sectional structure diagram of a secondary battery according to a preferred embodiment of the present invention. [Figure 2] It is a schematic enlarged partial structure diagram of part A in FIG. 1. [Figure 3] It is a schematic three-dimensional structure diagram of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 4] It is a schematic cross-sectional structure diagram of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 5] It is a schematic structure diagram of an unrolled positive electrode sheet of a secondary battery according to a preferred embodiment of the present invention. [Figure 6] It is a schematic partial cross-sectional structure diagram (one) of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 7] It is a schematic structure diagram of an unrolled negative electrode sheet of a secondary battery according to a preferred embodiment of the present invention. [Figure 8]This is a schematic diagram (2) of the local cross-sectional structure of an electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 9] This is a schematic diagram (3) of the local cross-sectional structure of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention. [Figure 10] This is a schematic diagram of a localized, enlarged view of section B in Figure 9. [Figure 11] This is a schematic diagram of a localized enlarged structure of part C in Figure 9. [Figure 12] This is a schematic diagram (1) 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 13] This is a schematic diagram (2) 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 14] This is a schematic diagram (1) 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 15] This is a schematic diagram (2) 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 16] This is a schematic diagram of the structure of a battery pack according to a preferred embodiment of the present invention. [Figure 17] 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]

[0020] The present invention will be described more clearly and completely below with reference to preferred embodiments and the drawings.

[0021] In existing technologies, the distance over which the positive electrode tab extends radially outward from the electrode assembly is greater than the distance over which the negative electrode tab extends radially outward from the electrode assembly, thus affecting the energy density of the secondary battery. However, if the number of turns of the electrode tabs located on the outer circle is reduced to avoid increasing the outer diameter of the electrode assembly, the electron path on the outer circle becomes longer, increasing the resistance within the battery.

[0022] 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.

[0023] As shown in Figures 3 and 4, the electrode assembly 20 includes a wound structure 201 formed by laminating and winding a positive electrode sheet 21, a separator 22, and a negative electrode sheet 23.

[0024] As shown in Figures 5 and 6, 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 with a positive electrode active material layer 2111 and a positive electrode uncoated region 213 not covered with the positive electrode active material layer 2111. Along the winding direction P of the winding structure 201, the positive electrode uncoated region 213 includes, in order, a first positive electrode uncoated region 214, a second positive electrode uncoated region 215, and a third positive electrode uncoated region 216.

[0025] As shown in Figures 7 and 8, the negative electrode sheet 23 includes a negative electrode current collector 231, which includes a negative electrode coated region 232 covered with a negative electrode active material layer 2311 and a negative electrode uncoated region 233 not covered with the negative electrode active material layer 2311. Along the winding direction P of the winding structure 201, the negative electrode uncoated region 233 includes, in order, a first negative electrode uncoated region 234, a second negative electrode uncoated region 235, and a third negative electrode uncoated region 236.

[0026] As shown in Figure 12, 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 neither the first negative electrode uncoated area 214 nor the third negative electrode uncoated area 216 includes the positive electrode tab. As shown in Figure 14, 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 connecting the negative electrode tab 2351 and the negative electrode coated area 232, while neither the first negative electrode uncoated area 234 nor the third negative electrode uncoated area 236 includes 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.

[0027] 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 outward spreading of the winding structure 201 along the radial R after bending the second uncoated second positive electrode region 215 and the second uncoated second negative electrode region 235 can be 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 as much as possible, an increase in the internal resistance of the secondary battery 1 can be avoided. In other words, the energy density of the secondary battery 1 is improved and the internal resistance of the battery is reduced.

[0028] As shown in Figures 9 to 11, the winding structure 201, formed by laminating and winding a positive electrode sheet 21, a separator 22, and a negative electrode sheet 23, typically has a central hole 2011 in the middle. The axial direction of the central hole 2011 is the axial direction O of the winding structure 201, and the axial direction O of the winding structure 201 is the same direction as the height direction of the secondary battery 1. The separator 22 is an insulating material, specifically PP (polypropylene) or PE (polyethylene), etc.

[0029] Referring 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.

[0030] When the positive electrode sheet 21 is not yet wound (when the positive electrode sheet 21 is unfolded), i.e., in the state before winding, 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 6. Similarly, when the negative electrode sheet 23 is not yet wound, 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 7. 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 8.

[0031] 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.

[0032] 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 folding the negative electrode tab 2351, the second direction Q2 changes in accordance with the folding of the negative electrode tab 2351, and at this time, the second direction Q2 is in the direction from the negative electrode connection region 2352 to the negative electrode tab 2351.

[0033] The number of winding layers in the uncoated third positive electrode region 216 refers to the number of circles that overlap with the winding structure 201 formed after the third positive electrode region 216 has been wound and molded, along the radial direction R. Similarly, the number of winding layers in the uncoated third negative electrode region 236 refers to the number of circles that overlap with the winding structure 201 formed after the third negative electrode region 236 has been wound and molded, along the radial direction R. The case 10 also contains one or more electrode assemblies 20.

[0034] In this embodiment, one electrode assembly 20 is included in the case 10, but the invention is not limited to this. In other embodiments, the number of electrode assemblies 20 included in the case 10 may be two, three, four, or other values, and can be adjusted according to the design requirements.

[0035] Specifically, the numerical range for the number of winding layers in the uncoated third positive electrode region 216 is 3 to 6. By setting this numerical range for the number of winding layers in the uncoated third positive electrode region 216, it is possible to avoid, on the one hand, excessive outward spreading along the radial R of the winding structure 201 after bending of the uncoated second positive electrode region 215 due to too few winding layers, thereby adversely affecting the energy density of the secondary battery 1. On the other hand, it is possible to avoid excessive resistance within the battery due to too many winding layers in the uncoated third positive electrode region 216.

[0036] The numerical range for the number of winding layers in the uncoated third negative electrode region 236 is 1 to 3. By setting a numerical range for the number of winding layers in the uncoated third negative electrode region 236 in this way, it is possible to avoid, on the one hand, excessive outward spreading along the radial R of the winding structure 201 after bending of the uncoated second negative electrode region 235 due to too few winding layers, thereby adversely affecting the energy density of the secondary battery 1. On the other hand, it is possible to avoid excessive resistance within the battery due to too many winding layers in the uncoated third negative electrode region 236.

[0037] 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 bent portion, and the orthographic projection of the first bent portion is located within the outer peripheral edge of the winding structure 201, so that the extent to which the second positive electrode uncoated region 215 extends outward along the radial direction R of the winding structure 201 after bending does not exceed the outer peripheral edge of the winding structure 201, thereby avoiding affecting the energy density of the secondary battery 1.

[0038] 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 folded portion, and the orthographic projection of the second folded portion is located within the outer peripheral edge of the winding structure 201, so that the extent to which the second uncoated negative electrode region 235 extends outward along the radial direction R of the winding structure 201 after folding does not exceed the outer peripheral edge of the winding structure 201, thereby avoiding affecting the energy density of the secondary battery 1.

[0039] Preferably, referring 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.

[0040] Referring to Figure 7, 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.

[0041] By setting numerical ranges 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, the energy density can be improved and the internal resistance of the battery can be reduced.

[0042] 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 numerical 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 set this ratio to an appropriate value, ensuring that the number of circles in the uncoated third positive electrode region 216 is greater than the number of circles in the uncoated third negative electrode region 236, and also to set the lengths of both regions within an appropriate range, thereby setting the internal resistance of the battery within an appropriate range.

[0043] The positive electrode connection region 2152 includes a first side that moves away from the central hole 2011 of the winding structure 201 along the radial direction R of the winding structure 201, and a second side that is close to the central hole 2011, where at least a portion of the first side and / or the second side is covered with an insulating layer 24. By covering at least a portion of the first side and / or the second side of the positive electrode connection region 2152 with an insulating layer 24 in this way, the risk of deformation of the positive electrode connection region 2152 can be reduced, the insulation performance of the positive electrode connection region 2152 can be improved, and thereby the safety and reliability of the battery performance can be greatly improved. 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 obtaining the necessary electrical insulation and support strength due to the coating thickness of the insulating layer 24 being too thin, while at the same time avoiding the possibility of the curing time of the coating layer being prolonged and the overall thickness of the structure increasing due to the insulating layer 24 being too thick. Preferably, the thickness of the insulating layer 24 is 2 μm.

[0044] Referring to Figures 10 and 12, in this embodiment, both the first and second sides of the positive electrode connection region 2152 are covered with the insulating layer 24. However, the embodiment 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 as needed for the design.

[0045] The insulating layer 24 contains a color developer, and the color-developing action of the color developer distinguishes whether the side to which the insulating layer 24 is applied is the front or back surface of the positive electrode sheet 21, including situations where the distinction between the front and back surface densities of the positive electrode sheet 21 is not limited. The main component of the color developer is bismuth vanadate, and its color is yellow.

[0046] 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. The positive electrode sheet 21 may need to be distinguished from its front and back surfaces, and this includes situations where the distinction between the surface density of the front and back surfaces of the positive electrode sheet 21 is not limited. Therefore, a color developer is added to one of the insulating layers 24 to achieve quick differentiation. 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.

[0047] 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 better prevents deformation of the positive electrode connection region 2152 and improves the insulation performance of this region. Note that if the insulating layer 24 covers a portion of the positive electrode tab 2151, the width of the insulating layer 24 will be its maximum width.

[0048] Referring to Figure 12, further along the first direction Q1, the positive electrode tab 2151 includes a positive electrode tab transition portion 21511 and a positive electrode tab body 21512, the positive electrode tab transition portion 21511 being connected between the positive electrode connection region 2152 and the positive electrode tab body 21512, and the positive electrode tab transition portion 21511 is the bent region of the positive electrode tab 2151.

[0049] Referring to Figure 14, 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 area 2352 and the negative electrode tab body 23512, and the negative electrode tab transition section 23511 is the folded area of ​​the negative electrode tab 2351.

[0050] The width c1 of the positive electrode tab transition portion 21511 of the outermost positive electrode tab 2151 is greater than the width d1 of the positive electrode tab transition portion 21511 of the outermost negative electrode tab 2351. Thus, because the hardness of the positive electrode tab 2151 is higher than that of the negative electrode tab 2351, the outward expansion of the positive electrode tab 2151 along the radial R of the winding structure 201 due to the crimping during installation is greater than the outward expansion of the negative electrode tab 2351 along the radial R of the electrode assembly. 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 positive electrode tab transition portion 21511 of the outermost negative electrode tab 2351, the positive electrode tab 2151 has a larger bending area than the negative electrode tab 2351, thereby avoiding the effect of crimping on the dimensions of the positive electrode tab body 21512 after bending, and making the dimensions of the positive electrode tab body 21512 and the negative electrode tab body 23512 after bending to be reasonable.

[0051] Referring to Figure 12, 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 a numerical range 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 this avoids affecting the dimensions of the positive electrode tab body 21512 after bending. 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. Upon crimping, the positive electrode tab transition section 21511 deforms and spreads outward along the winding structure, forming the structure shown in Figure 13.

[0052] Referring to Figure 14, 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 a numerical range 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 the cost of tab material. 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. Upon crimping, the negative electrode tab transition section 23511 deforms and spreads outward along the winding structure, forming the structure shown in Figure 15.

[0053] 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 numerical ranges of 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. This avoids a decrease in the energy density of the battery due to too many layers of tabs in the stacking region, and avoids the possibility of damaging surrounding components (e.g., separator 22, etc.) during the welding process by not providing sufficient spare space due to too few layers of tabs in the stacking region.

[0054] 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 a numerical range 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.

[0055] 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 numerical range for the width of the negative electrode connection area 2352 in this way, the distance 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 is ensured, thereby avoiding thermal effects during welding and improving safety performance.

[0056] 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, and the hardness of the positive electrode tab 2151 is higher than that of the negative electrode tab 2351. By setting a numerical range for the thickness t1 of the positive electrode tab 2151, it is possible to avoid the tab being too thin, which would make it prone to tearing during crimping, and to avoid the increased manufacturing cost caused by the tab being too thick. By setting a numerical range for the thickness t2 of the negative electrode tab 2351, it is possible to achieve beneficial technical effects such as maximizing material usage and saving costs, while ensuring the mounting requirements of the negative electrode tab 2351 are met.

[0057] Referring to Figures 1 and 2, in this embodiment, the case 10 includes an annular side wall 11, with an opening 12 at one end of the side wall 11, and the case 10 includes a crimped portion 30 at the end adjacent to the opening 12, which is recessed toward the interior of the case 10. The secondary battery 1 further includes a cover plate 40, an insulating sealing component 50, and a current collector. The cover plate 40 is attached to the opening 12. The insulating sealing component 50 is provided around the periphery of the cover plate 40, insulating and sealing the cover plate 40 from the case 10. The current collector is provided between the electrode assembly 20 and the cover plate 40 and is electrically connected to the case 10, and the connecting piece of the current collector 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 connecting piece of the current collector is located on the side of the crimping portion 30 facing the electrode assembly 20, and is welded to the crimping portion 30. As a result, the welding area between the current collector tab and the current collector tab is positioned closer to the electrode assembly 20 than the crimping portion 30, preventing the crimping portion 30 from affecting the welding area between the tab and the current collector, thereby improving the welding strength between the tab and the current collector.

[0058] Furthermore, the case 10 includes an end wall 13, and the side wall 11 is provided surrounding the end wall 13 and 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, which is used to house the electrode assembly 20, electrolyte, and other necessary battery components. The connection between the end wall 13 and the side wall 11 can be achieved by several methods, such as integral press molding, integral casting, or partial welding.

[0059] The secondary battery 1 further includes a terminal post 70, which penetrates the end wall 13 and is insulated from the end wall 13.

[0060] 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, the first current collector panel 61 corresponds to the positive electrode tab 2151, which 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, which 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.

[0061] 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. In this embodiment, the positive electrode tab 2151 is a cut and laminated tab. When welding the tab of the cylindrical battery to the current collector, there are two different processing methods for the tab pretreatment process: one is a tab flattening process, and the other is a tab cutting and lamination process, which is used for the positive electrode tab 2151 in this embodiment. Similarly, the negative electrode tab 2351 is also a cut and laminated tab.

[0062] The welding sequence between the electrode assembly 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 assembly 20 is crimped simultaneously on both the positive and negative electrodes (the crimping process increases contact between the current collector and the electrode assembly 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 crimpings, the distance between the second current collector 62 and the electrode assembly 20 becomes shorter. Spot welding would concentrate heat and burn the separator 22. Linear welding generates less heat, and burns to the separator 22 can be avoided, thus preventing short circuits due to contact between the positive and negative electrodes. Subsequently, the second current collector 62 is placed, and the electrode assembly 20 is crimped again simultaneously on both the positive and negative electrodes, and finally the second current collector 62 is welded.

[0063] As shown in Figure 16, 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 also include a thermal management system for the battery pack 100, a circuit board, etc., and the battery pack 100 may also be a battery module, a battery package, an energy storage cabinet, etc. These will not be described in detail here.

[0064] As shown in Figure 17, 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 a fan rotation unit for a fan or a dust collection operation unit for 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. This embodiment does not impose any special limitations on the electronic devices 1000 described above.

[0065] 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]

[0066] This invention can avoid increasing the internal resistance of a secondary battery, improve the energy density of the secondary battery, and reduce the internal resistance. [Explanation of Symbols]

[0067] 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 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 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 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 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 case, 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, with the direction from the positive electrode coated region to the positive electrode uncoated region being the first direction and the direction from the negative electrode coated region to the negative electrode uncoated region being 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 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 the first uncoated negative electrode region and the third uncoated negative electrode region do not include the negative electrode tab. A secondary battery characterized in that the number of winding layers in the uncoated region of the third positive electrode is greater than the number of winding layers in the uncoated region of the third negative electrode.

2. The numerical 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 numerical range of the number of winding layers in the uncoated third negative electrode region is 1 to 3.

3. 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 folded portion, and the orthographic projection of the first folded portion is located within the outer peripheral edge of the winding structure, or The secondary battery according to claim 1, characterized in that, along the axial direction of the winding structure, the second uncoated negative electrode region located in the outermost layer of the winding layer includes a second folded portion, and the orthographic projection of the second folded portion is located within the outer peripheral edge of the winding structure.

4. 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 1, 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.

5. The positive electrode connection region includes a first side that is radially adjacent to the central hole of the winding structure and a second side that is close to the central hole. At least a portion of the first side and / or the second side is covered with an insulating layer. The secondary battery according to claim 1, characterized in that the insulating layer contains a color developer.

6. The insulating layer covers the entire area on the first side of the positive electrode connection area, 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 5, characterized in that, along the first direction, the maximum width of the insulating layer is greater than or equal to the width of the positive electrode connection region.

7. 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 1, characterized in that the width of the negative electrode connection region along the second direction is 1 mm to 2 mm.

8. 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 portion and a negative electrode tab body, the negative electrode tab transition portion is connected between the negative electrode connection region and the negative electrode tab body, and the negative electrode tab transition portion is the folding region of the negative electrode tab. The secondary battery according to claim 1, 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.

9. 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 8, 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.

10. The case includes an annular side wall, with an opening at one end of the side wall, and the case includes a crimping portion at one end adjacent to the opening, which is recessed toward the inside of the case. 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 and insulating and sealing the cover plate and the case, A current collector is provided between the electrode assembly and the cover plate and electrically connected to the case, wherein the connecting piece of the current collector is located on the side of the crimping portion facing the electrode assembly and is welded to the crimping portion, and the current collector is provided between the electrode assembly and the case, including and / or, The secondary battery according to claim 1, characterized in that the secondary battery is a cylindrical battery, the positive electrode tab is a cut and stacked tab, and the negative electrode tab is a cut and stacked tab.

11. A battery pack characterized by including a secondary battery according to any one of claims 1 to 10.

12. An electronic device characterized by including the battery pack described in claim 11.

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