Wound electrode body and battery having same

Abstract

The utility model provides a wound electrode body and a battery having the same. The winding type electrode body comprises a positive plate, a diaphragm and a negative plate which are arranged in a stacked mode, the positive plate and the negative plate are wound across the diaphragm, the diaphragm is provided with a plurality of diaphragm straight sections and a plurality of diaphragm arc sections, and the diaphragm straight sections and the diaphragm arc sections are alternately arranged in the length direction of the diaphragm. One side, facing the positive plate, of at least one diaphragm arc section is provided with a bonding force weakening area, and the bonding force of the bonding force weakening area to the positive plate is smaller than that of other areas, facing one side of the positive plate, of the diaphragm to the positive plate. According to the winding type electrode body and the battery provided by the invention, when the negative plate expands and extends along the length direction of the diaphragm, the trend that the positive plate extends along the length direction of the diaphragm along with the extension of the negative plate is weakened, so that the risk of breakage of the positive plate is reduced, and the risk of unexpected capacity loss of the battery is reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of batteries, and in particular, to a wound electrode body and a battery having the same. Background Art

[0002] Batteries having wound electrode bodies (also referred to as cores) are known. Some wound electrode bodies, in terms of shape, include a pair of curved portions and a flat portion extending therebetween. However, such batteries suffer from capacity loss. Summary of the Utility Model

[0003] In view of this, the present disclosure provides a wound electrode body and a battery having the same to reduce the risk of capacity loss.

[0004] On the one hand, the present disclosure provides a wound electrode body. The wound electrode body includes a positive electrode sheet, a separator, and a negative electrode sheet arranged in a stacked manner. The positive electrode sheet and the negative electrode sheet are wound with the separator therebetween. The separator is provided with a plurality of separator straight sections and a plurality of separator arc sections, and the plurality of separator straight sections and the plurality of separator arc sections are alternately arranged along the length direction of the separator. At least one side of the separator arc section facing the positive electrode sheet is provided with an adhesion weakening region. The adhesion of the adhesion weakening region to the positive electrode sheet is less than the adhesion of other regions on the side of the separator facing the positive electrode sheet to the positive electrode sheet.

[0005] Supplementally or alternatively, the separator includes a base layer and a functional layer arranged in a stacked manner, the functional layer is provided on the side of the base layer facing the positive electrode sheet, and the functional layer is provided with a groove in the adhesion weakening region.

[0006] Supplementally or alternatively, the groove is provided with functionally dispersed particles.

[0007] Supplementally or alternatively, the functional layer includes a ceramic layer. The wound electrode body satisfies: 0.1 ≤ F1 / F2 ≤ 0.5; and / or 0.5 N / m ≤ F1 ≤ 10.5 N / m; and / or 5 N / m ≤ F2 ≤ 35 N / m; and / or 0.05 μm ≤ Dt ≤ 0.6 μm; and / or 0.5 μm ≤ D ≤ 8 μm. Here, F1 is the adhesion of the adhesion weakening region to the positive electrode sheet, F2 is the adhesion of other regions to the positive electrode sheet, Dt is the thickness difference between the adhesion weakening region and other regions, and D is the thickness of the functional layer in other regions.

[0008] Supplementally or alternatively, the functional layer is an adhesive layer. The wound electrode body satisfies: 0.2 ≤ F1 / F2 ≤ 0.6; and / or 2 N / m ≤ F1 ≤ 15 N / m; and / or 10 N / m ≤ F2 ≤ 30 N / m; and / or 0.05 μm ≤ Dt ≤ 0.5 μm; and / or 0.5 μm ≤ T1 ≤ 8 μm. Here, F1 is the adhesion force of the adhesion force weakening area to the positive electrode sheet, F2 is the adhesion force of other areas to the positive electrode sheet, Dt is the thickness difference between the adhesion force weakening area and other areas, and T1 is the thickness of the functional layer in other areas.

[0009] Supplementally or alternatively, the functional layer includes a ceramic layer, and the separator further includes an adhesive layer arranged in a stacked manner with the base layer and the ceramic layer. The adhesive layer is located on the side of the base layer facing the negative electrode sheet.

[0010] Supplementally or alternatively, the functional layer is an adhesive layer, and the separator further includes a ceramic layer arranged in a stacked manner with the base layer and the adhesive layer. The ceramic layer is located on the side of the base layer facing the negative electrode sheet.

[0011] Supplementally or alternatively, the groove penetrates the functional layer to expose the surface of the part of the base layer located within the adhesion force weakening area.

[0012] Supplementally or alternatively, the wound electrode body satisfies: H1 + 0.1 mm ≤ M1 ≤ H1 + 10 mm; and / or W1 = W2. Here, M1 is the size of the adhesion force weakening area in the length direction of the separator, H1 is the size of the corresponding separator arc segment in the length direction of the separator, W1 is the width of the separator, and W2 is the size of the adhesion force weakening area in the width direction of the separator.

[0013] Supplementally or alternatively, at least one separator arc segment includes the penultimate separator arc segment and / or the antepenultimate separator arc segment.

[0014] Supplementally or alternatively, the positive electrode sheet includes a plurality of positive electrode sheet straight segments and a plurality of positive electrode sheet arc segments. The plurality of positive electrode sheet straight segments and the plurality of positive electrode sheet arc segments are arranged alternately. A ductile tensile layer is provided on the side of the penultimate positive electrode sheet arc segment facing away from the separator.

[0015] Supplementally or alternatively, both ends of the ductile tensile layer in the length direction of the positive electrode sheet are located in the positive electrode sheet straight segments.

[0016] Supplementally or alternatively, the positive projection of the ductile tensile layer on the separator covers the adhesion force weakening area of the penultimate separator arc segment, such that the positive projections of both ends of the ductile tensile layer in the length direction of the positive electrode sheet on the separator are located outside the adhesion force weakening area of the penultimate separator arc segment.

[0017] Supplementary or alternatively, the wound electrode body satisfies: H2 + 3 mm ≤ M2 ≤ H2 + 25 mm; and / or 3 μm ≤ T2 ≤ 20 μm. Here, H2 is the size of the corresponding diaphragm arc segment in the length direction of the diaphragm, M2 is the size of the tough tensile layer in the length direction of the diaphragm, and T2 is the thickness of the tough tensile layer.

[0018] Supplementary or alternatively, the positive electrode sheet includes a plurality of flat positive electrode segments and a plurality of arc positive electrode segments arranged alternately along its length direction. The positive electrode sheet has a first active layer, a current collector, and a second active layer stacked along its thickness direction. The current collector is located between the first active layer and the second active layer. The end of the second active layer extends beyond the end of the first active layer. The end of the first active layer is located at the third-to-last arc positive electrode segment.

[0019] On the other hand, the present disclosure also provides a battery. The battery includes the above-mentioned wound electrode body.

[0020] During the charge and discharge cycle, the negative electrode sheet expands and extends along the length direction of the diaphragm, and the positive electrode sheet has a tendency to extend along the length direction of the diaphragm as the negative electrode sheet extends. According to the wound electrode body and the battery provided by the present disclosure, at least one diaphragm arc segment is provided with an adhesion weakening region, so that the tendency of the positive electrode sheet to extend along the length direction of the diaphragm as the negative electrode sheet extends is weakened, thereby reducing the risk of the positive electrode sheet breaking, and thus reducing the risk of capacity loss of the battery. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a battery according to an embodiment of the present disclosure.

[0022] Figure 2 It is a schematic structural diagram of a battery according to another embodiment of the present disclosure.

[0023] Figure 3 It is a schematic structural diagram of an electrode body according to an embodiment of the disclosure.

[0024] Figure 4 It is along Figure 3 The cross-sectional schematic diagram taken along the B-B line in

[0025] Figure 5 It is Figure 4 The partial structural schematic diagram of the positive electrode sheet in

[0026] Figure 6 It is Figure 4 The structural schematic diagram after the electrode body is unfolded along the width direction in

[0027] Figure 7 It is the structural schematic diagram after the electrode body according to another embodiment of the present disclosure is unfolded along the width direction.

[0028] Figure 8 It is a schematic cross-sectional view of an electrode body according to the related art.

[0029] Figure 9 is Figure 8 a partial structural schematic diagram of the positive electrode sheet in

[0030] Figure 10 is Figure 9 a structural schematic diagram of the positive electrode sheet in when passing through a pressure roller. Specific embodiments

[0031] Batteries with wound electrode bodies are known. Some wound electrode bodies have a pair of bent portions and a flat portion extending between them, making them generally flat in shape. For example, the width-to-thickness ratio of such wound electrode bodies can be from 1:1.1 to 1:200. However, batteries with such wound electrode bodies have a problem of capacity loss, especially after some number of cycles. This problem has troubled those skilled in the relevant art. For ease of understanding, first, in combination with Figures 8 to 10 , such a wound electrode body 10 and the problems it has will be illustrated by way of example.

[0032] Referring to Figure 8 , from the perspective of shape, the wound electrode body 10 includes two bent portions 11 and a flat portion 12, and the flat portion 12 is located between the two bent portions 11. From the perspective of composition, the electrode body 10 includes a positive electrode sheet 13, a negative electrode sheet 14, and a separator 15 arranged in a stacked manner. The positive electrode sheet 13 and the negative electrode sheet 14 are wound with the separator 15 in between.

[0033] Referring to Figure 8 and Figure 9 , the positive electrode sheet 13 includes a current collector 16, a first active layer 17, and a second active layer 18. The first active layer 17 and the second active layer 18 are respectively located on opposite sides in the thickness direction of the current collector 16. Specifically, the first active layer 17 is located on the side of the current collector 16 facing away from the winding center A of the wound electrode body 10, and the second active layer 18 is located on the side of the current collector 16 facing away from the first active layer 17.

[0034] It should be noted that in the present disclosure, the winding center of the wound electrode body may refer to the winding axis of the wound electrode body. It can be understood that in the winding process, the positive electrode sheet, the negative electrode sheet, the separator, etc. are wound around this winding axis.

[0035] Continuing to refer to Figure 8 and Figure 9, along the winding direction, that is, along the direction from the winding starting end 13a to the winding ending end 13b of the positive electrode sheet 13, the ending end of the second active layer 18 extends beyond the ending end of the first active layer 17, thereby forming a single-layer section and a double-layer section arranged in sequence along the winding direction. Due to the different thicknesses of the single-layer section and the double-layer section, a step will be formed at the boundary B between the single-layer section and the double-layer section, that is, at the ending end of the first active layer 17. At the boundary B between the single-layer section and the double-layer section, that is, the ending end of the first active layer 17 is located at the penultimate positive electrode arc section of the positive electrode sheet 13.

[0036] It can be understood that in this text, elements such as the positive electrode sheet, negative electrode sheet, separator, current collector, and active layer all have a starting end and an ending end. In the winding process, any element is wound from the starting end to the ending end. The winding direction refers to the direction from the starting end to the ending end. For the convenience of understanding, the winding direction is indicated by the arrow X in the figure.

[0037] It can be understood that in the case where the wound electrode body is unfolded, the winding direction of a certain element is consistent with its length direction, or rather, the direction from its starting end to its ending end is its length direction. Therefore, in the unfolded view, for example, in Figures 5 to 7 , Figure 9 and Figure 10 , the arrow X also indicates the length direction of the positive electrode sheet. For the convenience of understanding, in the drawings where the wound electrode body is unfolded, the thickness direction of elements such as the positive electrode sheet, negative electrode sheet, separator, current collector, and active layer is indicated by the arrow Y in the figure.

[0038] After being wound into a wound electrode body, elements such as the positive electrode sheet, negative electrode sheet, and core include multiple straight sections and multiple arc sections, and the multiple straight sections and multiple arc sections are arranged alternately. The straight section of a certain element is the part of the element located in the flat part of the wound electrode body, and the arc section is the part of the element located in the bent part of the wound electrode body.

[0039] In this text, the last arc section of a certain element is the arc section closest to its ending end. Along the direction from the ending end to the starting end, after the last arc section, there are successively the penultimate arc section, the third-to-last arc section..., and so on.

[0040] For some purposes, for example, to increase the bonding strength between the active material layer and the current collector and compact the active material layer, a rolling process is required. In the rolling process, referring to Figure 10 , when the step at the boundary B passes through a pair of rollers, due to the sharp change in thickness, the rollers will jump and then hit the electrode sheet 13. This will damage the current collector 16 and form micro-cracks on it.

[0041] According to the structural characteristics of the wound electrode body 10, the outermost positive electrode sheet arc segments are subject to more uneven forces. The expansion force acting on them from the inside out is large, while the restraint force from the outside in is small. Additionally, the boundary B between the single-layer section and the double-layer section is exactly located at the third-to-last positive electrode sheet arc segment, which leads to a higher likelihood of electrode sheet fracture in the area near the boundary B, that is, at the third-to-last positive electrode sheet arc segment and the second-to-last positive electrode sheet arc segment. Meanwhile, during the cycling process, on the one hand, the negative electrode sheet 14 expands in the thickness direction, and on the other hand, it extends in the length and width directions. The negative electrode sheet 14 causes the positive electrode sheet 13 to expand and extend, thereby leading to the expansion of microcracks and ultimately resulting in the fracture of the positive electrode sheet 13, causing capacity loss.

[0042] To solve the above problems existing in the related art, the present disclosure provides a wound electrode body and a battery having the same. The following will be described in conjunction with Figures 1 to 7 , and the embodiments provided in the disclosure will be described.

[0043] It should be understood that there can be multiple implementation manners of the present disclosure and should not be construed as being limited to the embodiments described herein. The embodiments described herein are only for a more thorough and clear understanding of the present disclosure.

[0044] <Exemplary Battery>

[0045] First, it should be noted that in the present disclosure, a "battery" refers to a rechargeable energy storage device, which can be interpreted as the concept of a "secondary battery". In the present disclosure, the concept of a "secondary battery" can, but is not limited to, include lithium-ion secondary batteries, sodium-ion secondary batteries, nickel-metal hydride batteries, etc.

[0046] The battery 100 according to an embodiment of the present disclosure is shown in Figure 1 . Referring to Figure 1 , the battery 100 may include an electrode body 20 and a packaging body 30. A cavity may be provided inside the packaging body 30, and one or more electrode bodies 20 may be received inside the cavity.

[0047] As Figure 1 shown, the packaging body 30 may be square. That is to say, the battery 100 may be a square battery. The material of the packaging body 30 may be the same as the materials used in the past and is not particularly limited. For example, the packaging body 30 may be made of metal, and in particular, may be made of aluminum (alloy) or iron (alloy), etc.

[0048] The battery 100 according to another embodiment of the present disclosure is shown in Figure 2 . As Figure 2 shown, in this embodiment, the packaging body 30 is flat and made of a relatively soft material, such as an aluminum-plastic film. That is to say, in this embodiment, the battery 100 may be a soft-pack battery.

[0049] It is contemplated that in other examples of the present disclosure, the battery 100 may also be implemented as other types besides a square battery and a soft pack battery.

[0050] It should be noted that other aspects of the structure of the battery 100 may be the same as the previous battery structure, and for the purpose of brevity, this disclosure will not elaborate on this.

[0051] <Exemplary wound electrode body>

[0052] refer to Figure 3 and Figure 4 The wound electrode body 20 may include a positive electrode sheet 23, a negative electrode sheet 24 and a separator 25 arranged in a stacked manner. The separator 25 is a member that insulates the positive electrode sheet 23 and the negative electrode sheet 24. The positive electrode sheet 23 and the negative electrode sheet 24 may be wound into a flat structure with the winding axis A as the winding center through the separator 25. In this article, flat means that the width is greater than the thickness. For example, the ratio B / C of the width B and the thickness C of the wound electrode body 20 may satisfy 1.1≤A / B≤200. The wound electrode body 20 may include two curved portions 21 and a flat portion 22, and the flat portion 22 is located between the two curved portions 21.

[0053] For the convenience of explanation, the present disclosure mentions the "width direction" and "thickness direction" of the electrode body, and the "length direction" of the electrode body will also be mentioned below. Here, the "width direction" refers to the direction from one bend to another bend, indicated by arrow U in the figure; the "thickness direction" refers to the thickness direction of the electrode sheet before winding, and the direction perpendicular to the "width direction", indicated by arrow V in the figure; the "length direction" refers to the direction parallel to the winding axis A, which is perpendicular to its "width direction" and "thickness direction", indicated by arrow R in the figure.

[0054] The positive electrode sheet 23 may include a current collector 26, a first active layer 27, and a second active layer 28 stacked along the thickness direction thereof. The first active layer 27 and the second active layer 28 may be disposed on opposite sides of the current collector 26. Specifically, the first active layer 27 may be disposed on a side of the current collector 26 away from the winding center A, and the second active layer 28 may be disposed on a side of the current collector 26 away from the first active layer 27. Similarly, the negative electrode sheet 24 may also include a current collector and two active material layers disposed on opposite sides thereof.

[0055] By way of example only, the current collector 26 may be a strip-shaped metal foil. The first active layer 27 and the second active layer 28 may include a positive electrode active material capable of reversibly absorbing and releasing charge carriers. In addition, they may further include a conductive material, a binder, and various additive components, etc. By way of example only, the metal foil mentioned here may be an aluminum foil, the positive electrode active material mentioned may be a lithium transition metal composite oxide such as lithium nickel cobalt manganese composite oxide, the conductive material mentioned may be a carbon material such as acetylene black, and the binder mentioned may be polyvinylidene fluoride, etc.

[0056] By way of example only, the current collector of the negative electrode sheet may be a strip-shaped metal foil, and its active material layer may include a negative electrode active material capable of reversibly absorbing and releasing charge carriers, a binder, a dispersant, and various additive components, etc. By way of example only, the metal foil mentioned here may be a copper foil, the negative electrode active material mentioned may be a carbon material such as graphite, the binder mentioned may be a rubber such as styrene-butadiene rubber, and the dispersant mentioned may be a cellulose such as carboxymethyl cellulose.

[0057] Reference Figure 4 and Figure 5 Along the winding direction, that is, along the direction from the winding start end 23a to the winding end end 23b of the positive electrode sheet 23, the end end of the second active layer 28 extends beyond the end end of the first active layer 27, thereby forming a single-layer section and a double-layer section arranged in sequence along the winding direction.

[0058] The positive electrode sheet 23 may include a plurality of positive electrode straight sections and a plurality of positive electrode arc sections, and the plurality of positive electrode straight sections and the plurality of positive electrode arc sections are alternately arranged along its length direction. The positive electrode straight section is the part of the positive electrode sheet 23 located in the flat part 22 of the wound electrode body 20. The positive electrode arc section is the part of the positive electrode sheet 23 located in the bent part 21 of the wound electrode body 20.

[0059] The boundary B between the single-layer section and the double-layer section, that is, the end end of the first active layer 27 may be located at the third-to-last positive electrode arc section. The end end of the second active layer 28 may be located at the second-to-last positive electrode arc section. The end end of the current collector 26 may be located in the last positive electrode straight section and is attached with a termination tape 291 to achieve the positive electrode termination.

[0060] The separator 25 may be provided with a plurality of separator arc sections and a plurality of separator straight sections, and the plurality of separator straight sections and the plurality of separator arc sections are alternately arranged along the length direction of the separator 25. The separator straight section is the part of the separator 25 located in the flat part 22 of the wound electrode body 20. The separator arc section is the part of the separator 25 located in the bent part 21 of the wound electrode body 20.

[0061] The penultimate Nth separator arc segment corresponds to the penultimate Nth positive electrode arc segment, where N is an integer greater than or equal to 1. This correspondence is reflected in the fact that both are located in the same bending portion 21. The positive projection of the penultimate Nth positive electrode arc segment on the separator 25 substantially coincides with the penultimate Nth separator arc segment.

[0062] Combined with Figure 6 , on one side of at least one separator arc segment facing the positive electrode 23, there is a bonding force weakening region 251, and the bonding force of the bonding force weakening region 251 to the positive electrode 23 is less than the bonding force of other regions on the side of the separator 25 facing the positive electrode 23 to the positive electrode 23. During the charge and discharge cycle, the negative electrode 24 expands and extends along the length direction of the separator 25, and the positive electrode 23 has a tendency to extend along the length direction of the separator as the negative electrode 24 extends. According to the wound electrode body 20 and the battery 100 provided by the present disclosure, at least one separator arc segment is provided with a bonding force weakening region 251, so that the tendency of the positive electrode 23 to extend along the length direction of the separator 25 as the negative electrode 24 extends is weakened, thereby reducing the risk of the positive electrode 23 breaking, and thus the risk of the battery 100 suffering from capacity loss will be reduced.

[0063] Reference Figure 4 and Figure 6 , the penultimate positive electrode arc segment is a single-layer segment of the positive electrode 23, and the charge and discharge process only occurs on one side, so the stress change during the charge and discharge process also only occurs on one side. In addition, the penultimate positive electrode arc segment is located on the outermost side and is subjected to an outward expansion force from the inside without a binding force from the outside. Therefore, the forces on the inner and outer sides are uneven, making the penultimate positive electrode arc segment prone to breakage. In view of this, in some examples, the penultimate separator arc segment may be provided with a bonding force weakening region 251a to significantly reduce the risk of breakage of the corresponding positive electrode arc segment, that is, the penultimate positive electrode arc segment.

[0064] Reference Figures 4 to 6 , the junction B of the positive electrode 23 from the double-layer segment to the single-layer segment is provided in the third-to-last positive electrode arc segment, which causes the pressing roller to jump at the junction B when passing through the pressing roller, resulting in the third-to-last positive electrode arc segment being damaged and generating microcracks. In view of this, in some examples, the third-to-last separator arc segment is provided with a bonding force weakening region 251b to significantly reduce the risk of breakage of the corresponding positive electrode arc segment, that is, the third-to-last positive electrode arc segment.

[0065] As a way of implementation, referring to Figure 6, the separator 25 may include a base layer 252 and a functional layer 253 arranged in a laminated manner. The functional layer 253 may be disposed on one side of the base layer 252 facing the positive electrode plate 23. In the current example, the functional layer 253 may include a ceramic layer. Optionally, the separator 25 may further include an adhesive layer 255 arranged in a laminated manner with the base layer 252 and the functional layer 254. The adhesive layer 255 may be disposed on one side of the base layer 252 facing away from the functional layer 254.

[0066] The material of the base layer of the separator may be one or more of polyethylene, polypropylene, polyethylene, polypropylene, polyamide, polyimide, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and aramid.

[0067] The material of the adhesive layer of the separator may be one or more of polymethyl methacrylate (PMMA), polymethyl methacrylate - hexafluoropropylene copolymer (PMMA - HFP), polyvinylidene fluoride (PVDF), and polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - HFP).

[0068] The material of the ceramic layer of the separator may be one or more of porous inorganic materials such as boehmite, alumina, magnesia, zirconia, and silica.

[0069] The functional layer 253 is provided with a groove 254 in the adhesion - weakening region 251. That is to say, the adhesion - weakening region 251 is the region of the separator 25 where the groove 254 is provided. Due to the existence of the groove 254, the adhesion of the adhesion - weakening region 251 to the positive electrode plate 23 will be weakened, being lower than the adhesion of other regions to the positive electrode plate 23. In this way, the tendency of the positive electrode plate 23 to extend along the length direction of the separator 25 as the negative electrode plate 24 extends can be weakened, thereby reducing the risk of the positive electrode plate 23 breaking. In addition, the ceramic layer 253 and the adhesive layer 255 of the separator 25 can fully absorb the electrolyte, facilitating the transfer of lithium ions on the opposite positive and negative electrode sides. When the adhesion - weakening region is realized as a groove, the electrolyte retention amount in the adhesion - weakening region can be reduced, the transfer speed of lithium ions from the positive electrode to the negative electrode during charging can be decreased, the amount of lithium ions embedded in the negative electrode in this region per unit time can be reduced, and thus the swelling force of the negative electrode plate in this region per unit time can be reduced.

[0070] As an implementation, the groove 254 can penetrate through the functional layer 253 to expose the surface of the part of the base layer 252 located within the adhesion weakening region 251. In other words, within the groove 254, that is, within the adhesion weakening region 251, the separator 25 only includes the base layer 252 and does not include the functional layer 253. In other words, the difference in the thickness of the separator 25 between the adhesion weakening region 251 and its other regions is the thickness of the functional layer 253. That is to say, within the adhesion weakening region 251, the separator 25 no longer provides adhesion to the positive electrode sheet 23. According to the implementation of the present disclosure, the tendency of the positive electrode sheet 23 to extend as the negative electrode sheet 24 expands can be weakened to the greatest extent, thereby reducing the risk of the positive electrode sheet 23 breaking.

[0071] As another implementation, functional layer particles can be dispersedly arranged within the groove 254. The material of the functional layer particles is the same as that of the functional layer 253. For example, in the current example, the functional layer particles are ceramic particles. Another example is that in the following example where the functional layer 253 is an adhesive layer, the functional layer particles are adhesive particles.

[0072] On the one hand, the adhesion provided by the dispersedly arranged functional layer 253 particles is less than the adhesion provided by the functional layer 253, and the groove 254 can still form an adhesion weakening region 251. On the other hand, the groove 254 is provided with dispersedly arranged functional layer 253 particles, so that there is no obvious thickness difference in the functional layer 253 of the separator 25. Therefore, during the winding process, local stress can be avoided from being formed between the positive electrode sheet 23 and the separator 25, thereby damaging the positive electrode sheet 23.

[0073] Furthermore, the wound electrode body 20 can satisfy: 0.1 ≤ F1 / F2 ≤ 0.5; and / or 0.5 N / m ≤ F1 ≤ 10.5 N / m; and / or 5 N / m ≤ F2 ≤ 35 N / m; and / or 0.05 μm ≤ Dt ≤ 0.6 μm; and / or 0.5 μm ≤ D ≤ 8 μm. Here, F1 is the adhesion of the adhesion weakening region 251 to the positive electrode sheet, F2 is the adhesion of other regions to the positive electrode sheet, Dt is the thickness difference between the adhesion weakening region 251 and other regions, and D is the thickness of the functional layer in other regions. It has been found that when the above conditions are met, the risk of the positive electrode sheet 23 breaking is relatively small.

[0074] The length of the bonding force weakening region 251, that is, the dimension of the bonding force weakening region 251 in the length direction of the separator 25, should not be too long or too short. If the length of the bonding force weakening region 251 is too long, the straight section will expand and deform due to poor bonding. If the length of the bonding force weakening region 251 is too short, the requirement for weakening the bonding force of the arc section cannot be met. As an example, the wound electrode body 20 can satisfy: H1 + 0.1 mm ≤ M1 ≤ H1 + 10 mm. H1 is the dimension of the corresponding separator arc section in the length direction of the separator 25, and M1 is the dimension of the bonding force weakening region 251 in the length direction of the separator. In this way, on the basis of avoiding the expansion and deformation of the straight section due to poor bonding, the arc section can lose the bonding force.

[0075] The width of the bonding force weakening region 251 can be approximately equal to the width of the separator 25. That is to say, the wound electrode body 20 can satisfy: W1 = W2, where W1 is the width of the separator and W2 is the dimension of the bonding force weakening region 251 in the width direction of the separator. In this way, the length of the first region is equal to the width of the separator, enabling it to fully play this role.

[0076] To further reduce the risk of fracture of the positive electrode sheet 23, refer to Figure 4 and Figure 6 , a ductile tensile layer 292 can be provided on the side of the penultimate positive electrode sheet arc section facing away from the separator 25. Considering that the penultimate positive electrode sheet arc section is unevenly stressed on the inner and outer sides, the positive electrode sheet 23 is prone to fracture at the penultimate positive electrode sheet arc section. Therefore, pasting the ductile tensile layer 292 on the side of the penultimate positive electrode sheet arc section facing away from the separator 25 can further reduce the risk of fracture of the positive electrode sheet 23.

[0077] Continue to refer to Figure 4 and Figure 6 , the two ends 292a, 292b of the ductile tensile layer 292 in the length direction of the positive electrode sheet 23 can be located in the straight section of the positive electrode sheet. The two ends 292a, 292b of the tensile layer are located in the straight section of the positive electrode sheet, and the two end portions of the ductile tensile layer 292 will be subject to the frictional force of the straight section, which can further increase the tensile strength and distribute the outward expansion force of the penultimate positive electrode sheet arc section, thereby further reducing the risk of fracture of the positive electrode sheet 23.

[0078] Refer to Figure 6, the positive projection of the ductile tensile layer 292 on the separator 25 can cover the adhesion weakening area 251a of the penultimate separator arc segment, so that the positive projections of both ends of the ductile tensile layer 292 in the length direction of the positive electrode sheet 23 on the separator 25 are located outside the adhesion weakening area 251a. The positive projections of both ends of the ductile tensile layer 292 in the length direction of the positive electrode sheet 23 on the separator 25 are located outside the adhesion weakening area 251a, that is, outside the groove 254a, which can prevent the ductile tensile layer 292 and the groove 254a from cooperating to form a shear force acting on the positive electrode sheet 23, thereby further reducing the risk of fracture of the positive electrode sheet 23.

[0079] The ductile tensile layer 292 should not be too long or too short. If the ductile tensile layer 292 is too long, the energy density will be excessively reduced. If the ductile tensile layer 292 is too short, the above requirements cannot be met. As an example, the wound electrode body 20 can satisfy: H2 + 3mm ≤ M2 ≤ H2 + 25mm, preferably, H2 + 5mm ≤ M2 ≤ H2 + 15mm. Wherein, H2 is the size of the penultimate separator arc segment in the length direction of the separator, M2 is the size of the ductile tensile layer in the length direction of the separator, and T2 is the thickness of the ductile tensile layer. In this way, the risk of fracture of the positive electrode sheet 23 can be reduced without excessively reducing the energy density.

[0080] The ductile tensile layer 292 should not be too thick or too thin. If the ductile tensile layer 292 is too thick, the energy density will be excessively reduced. If the ductile tensile layer 292 is too thin, sufficient tensile strength cannot be provided. As an example, the wound electrode body 20 can satisfy: μm ≤ T2 ≤ 20μm. It is found that under the condition of meeting the above conditions, the risk of fracture of the positive electrode sheet 23 can be reduced without increasing the width and thickness of the battery cell, that is, without affecting the energy density of the battery.

[0081] The material of the ductile tensile layer can be one or more of rubber adhesive paper, acrylic adhesive paper, acrylic adhesive paper, polypropylene adhesive paper, and styrene-isoprene-styrene adhesive paper.

[0082] Continue to refer to Figure 4 , the electrode body 20 may further include a first tab 295 and a second tab 296. The first tab 295 can be a part of the current collector 26 or an independent component fixed to the current collector 26. Correspondingly, the second tab 296 can be a part of the current collector of the negative electrode sheet 24 or an independent component fixed to the current collector of the negative electrode sheet 24.

[0083] It should be noted that although in Figure 4 , the electrode body 20 adopts a tab-centered structure, however, in other examples, the electrode body 20 can also adopt a multi-tab structure or a conventional structure. The present disclosure does not make special restrictions on the arrangement of the tabs.

[0084] In addition, referring to Figure 4 、 Figure 6 and Figure 7 , the electrode body 20 may further include termination tapes 293 and 294. The termination tape 293 may be adhered to the termination end of the first active layer 27, that is, adhered to the third last positive electrode sheet arc segment. The termination tape 294 may be adhered to the termination end of the second active layer 28, that is, adhered to the last positive electrode sheet arc segment.

[0085] Next, with reference to Figure 7 , a wound electrode body provided in another embodiment of the present disclosure will be exemplified. It should be noted that the foregoing embodiments and the embodiments described below have some common elements. In the following embodiments, these elements will use the same reference numerals as those in the foregoing embodiments to avoid repeated description.

[0086] Referring to Figure 7 , in the current embodiment, the functional layer 253 may be an adhesive layer. Further, in some examples, the separator 25 further includes a ceramic layer 255 laminated with the base layer 252 and the adhesive layer 253, and the ceramic layer 255 is located on the side of the base layer 252 facing the negative electrode sheet 24.

[0087] Further, in the current embodiment, functional layer particles may also be dispersedly arranged in the groove 254, and the functional layer particles may be adhesive particles.

[0088] Further, the wound electrode body 20a may satisfy: 0.2 ≤ F1 / F2 ≤ 0.6; and / or 2 N / m ≤ F1 ≤ 15 N / m; and / or 10 N / m ≤ F2 ≤ 30 N / m; and / or 0.05 μm ≤ Dt ≤ 0.5 μm; and / or 0.5 μm ≤ T1 ≤ 8 μm. Here, F1 is the adhesion force of the adhesion force weakening region 251 to the positive electrode sheet, F2 is the adhesion force of other regions to the positive electrode sheet, Dt is the thickness difference between the adhesion force weakening region 251 and other regions, and T1 is the thickness of the functional layer in other regions. It has been found that when the above conditions are met, the risk of the positive electrode sheet 23 breaking is small.

[0089] The above has given examples of the wound electrode body according to some embodiments of the present disclosure. It can be understood that the wound positive electrode body according to the present disclosure is not limited to the description above. For example, in a foreseeable example, a plurality of slits arranged at intervals may be provided in the adhesion weakening region to weaken the adhesion to the positive electrode sheet. Another example is that in another foreseeable example, a plurality of holes arranged in an array may be provided in the adhesion weakening region to weaken the adhesion to the positive electrode sheet. Another example is that in another foreseeable example, the adhesion weakening region may be made of a material different from other regions, so that the adhesion of the adhesion weakening region to the positive electrode sheet is less than that of other regions to the positive electrode sheet.

[0090] It should be understood that the term "including" and its variants used in the present disclosure are open-ended, that is, "including but not limited to". The term "according to" means "at least partially according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least another embodiment". The term "a plurality" means "more than one", which means covering two, three or more cases.

[0091] It should be understood that although terms such as "first" or "second" may be used in the present disclosure to describe various elements, for example, the first active layer and the second active layer, these elements are not defined by these terms, and these terms are only used to distinguish one element from another.

[0092] The protection scope of the present disclosure is not limited to the above embodiments. Any person skilled in the art within the technical scope disclosed in the present disclosure can think of changes or substitutions, which should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A wound electrode body, characterized in that: The invention comprises a positive electrode sheet, a separator and a negative electrode sheet which are stacked, wherein the positive electrode sheet and the negative electrode sheet are wound with the separator between them, the separator is provided with a plurality of separator straight sections and a plurality of separator arc sections, the plurality of separator straight sections and the plurality of separator arc sections are alternately arranged along the length direction of the separator, and a bonding weakening region is provided on a side of the separator arc section facing the positive electrode sheet, the bonding force of the bonding weakening region to the positive electrode sheet is less than the bonding force of other regions on the side of the separator facing the positive electrode sheet to the positive electrode sheet.

2. The wound electrode body according to claim 1, characterized in that: The separator includes a base layer and a functional layer which are stacked. The functional layer is disposed on a side of the base layer facing the positive electrode sheet. The functional layer is provided with a groove in the bonding weakened region.

3. The wound electrode body according to claim 2, characterized in that: Functional layer particles are dispersedly arranged in the groove.

4. The wound electrode body according to claim 3, characterized in that: The functional layer includes a ceramic layer, and the wound electrode body satisfies: 0.1≤F1 / F2≤0.5; and / or 0.5N / m≤F1≤10.5N / m; and / or 5N / m ≤ F2 ≤ 35N / m; and / or 0.05 μm ≤ Dt ≤ 0.6 μm; and / or 0.5μm≤D≤8μm, Among them, F1 is the bonding force of the weakened bonding area to the positive electrode sheet, F2 is the bonding force of the other area to the positive electrode sheet, Dt is the thickness difference between the weakened bonding area and the other area, and D is the thickness of the functional layer in the other area.

5. The wound electrode body according to claim 3, characterized in that: The functional layer is a glue layer, and the wound electrode body satisfies: 0.2≤F1 / F2≤0.6; and / or 2N / m ≤ F1 ≤ 15N / m; and / or 10N / m ≤ F2 ≤ 30N / m; and / or 0.05 μm ≤ Dt ≤ 0.5 μm; and / or 0.5μm≤T1≤8μm, Among them, F1 is the bonding force of the weakened bonding area to the positive electrode sheet, F2 is the bonding force of the other area to the positive electrode sheet, Dt is the thickness difference between the weakened bonding area and the other area, and T1 is the thickness of the functional layer in the other area.

6. The wound electrode body according to claim 2, characterized in that: The functional layer includes a ceramic layer, and the separator further includes a glue layer stacked with the base layer and the ceramic layer, and the glue layer is located on a side of the base layer facing the negative electrode sheet; or, The functional layer is a glue layer, and the separator further includes a ceramic layer stacked with the base layer and the glue layer, and the ceramic layer is located on a side of the base layer facing the negative electrode sheet.

7. The wound electrode body according to claim 2, characterized in that: The groove penetrates through the functional layer to expose a portion of the surface of the base layer located in the weakened adhesion region.

8. The wound electrode body according to claim 1, characterized in that: The wound electrode body satisfies: H1+0.1mm≤M1≤H1+10mm; and / or W1=W2, Among them, M1 is the size of the weakened adhesion area in the length direction of the diaphragm, H1 is the size of the corresponding diaphragm arc segment in the length direction of the diaphragm, W1 is the width of the diaphragm, and W2 is the size of the weakened adhesion area in the width direction of the diaphragm.

9. The wound electrode body according to any one of claims 1 to 8, characterized in that: The at least one diaphragm arc segment includes the second to last diaphragm arc segment and / or the third to last diaphragm arc segment.

10. The wound electrode body according to claim 9, characterized in that: The positive electrode sheet comprises a plurality of straight sections and a plurality of arc sections, which are arranged alternately, and a tough tensile layer is provided on the side of the penultimate arc section of the positive electrode sheet facing away from the diaphragm.

11. The wound electrode body according to claim 10, characterized in that: Both ends of the tough tensile layer in the length direction of the positive electrode sheet are located in the straight section of the positive electrode sheet.

12. The wound electrode body according to claim 10, characterized in that: The orthographic projection of the tough tensile layer on the diaphragm covers the weakened adhesion region of the penultimate diaphragm arc segment, so that the orthographic projections of the tough tensile layer at both ends in the length direction of the positive electrode sheet on the diaphragm are located outside the weakened adhesion region of the penultimate diaphragm arc segment.

13. The wound electrode body according to claim 10, characterized in that: The wound electrode body meets the following requirements: H2+3mm≤M2≤H2+25mm; and / or 3μm≤T2≤20μm, Among them, H2 is the size of the penultimate diaphragm arc segment in the length direction of the diaphragm, M2 is the size of the tough tensile layer in the length direction of the diaphragm, and T2 is the thickness of the tough tensile layer.

14. The wound electrode body according to claim 9, characterized in that: The positive electrode sheet comprises a plurality of positive electrode sheet straight sections and a plurality of positive electrode sheet arc sections alternately arranged along its length direction, and the positive electrode sheet comprises a first active layer, a current collector and a second active layer stacked along its thickness direction, the current collector is located between the first active layer and the second active layer, the tail end of the second active layer extends beyond the tail end of the first active layer, and the tail end of the first active layer is located at the third-to-last positive electrode sheet arc section.

15. A battery, characterized in that: The battery includes the wound electrode body according to any one of claims 1 to 14.

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