Battery cell assembly and battery

Abstract

The present application provides a battery cell assembly and a battery. The battery cell assembly comprises a first separator, a negative electrode sheet, a second separator, and a positive electrode sheet that are sequentially stacked and wound. The first separator and the second separator are separately bonded to the negative electrode sheet to form a first composite area. The positive electrode sheet is bonded to at least part of the second separator to form at least one second composite area. The length of the second composite area is less than that of the first composite area. In the present application, a positive electrode sheet, a negative electrode sheet, and a separator are stacked, so that a jelly roll is prevented from being tightly wound due to respective tensions during winding. A first composite area can strengthen the bonding between the separator and the negative electrode sheet, so that the separator and the negative electrode sheet do not slide relative to each other. A second composite area can fix the positive electrode sheet at a set position to form a compensation area, that is, a certain gap is reserved between the positive electrode sheet and the negative electrode sheet in a non-composite area, so that the gap between the electrode sheets in a circular arc-shaped area of the jelly roll is increased, and thus space is reserved for cycle expansion of the battery, thereby effectively solving the problem of cycle expansion and deformation of the battery.

Description

Battery cell assembly and battery Technical Field

[0001] This application relates to the field of battery technology, specifically to a cell assembly and a battery. Background Technology

[0002] With the development of lithium-ion battery technology, the market has placed higher demands on battery fast charging capabilities and energy density. Currently, improving battery energy density has reached a bottleneck, and the most effective method is to use new materials, such as high-capacity silicon-based materials for the negative electrode. However, during use, the silicon-based negative electrode material undergoes significant volume expansion during cycling, which can easily compress the positive electrode sheet, leading to breakage at the bending section of the positive electrode sheet. Summary of the Invention

[0003] In response to at least some of the technical problems mentioned above, this application provides the following technical solutions.

[0004] In a first aspect, embodiments of this application provide a battery cell assembly comprising a first separator, a negative electrode, a second separator, and a positive electrode arranged sequentially and wound together. The battery cell assembly has a straight portion and a curved portion. The positive electrode has a first straight section and a first curved section located in the straight portion and the curved portion, respectively. The negative electrode has a second straight section and a second curved section located in the straight portion and the curved portion, respectively. Along the length direction of the negative electrode, the first separator and the second separator are respectively bonded to each other to form a first composite region. Along the length direction of the positive electrode, the positive electrode and the second separator are bonded to each other in at least a portion to form at least one bonding portion. The positive electrode and the second separator at the bonding portion, together with the negative electrode and the first separator corresponding to the bonding portion, together form a second composite region. The second composite region is located in the straight portion, and along the length direction of the negative electrode, the size of the second composite region is smaller than the size of the first composite region.

[0005] In some embodiments, in the curved portion, along the width direction of the cell assembly, the distance between two points, from the point of maximum curvature of the innermost layer of the cell assembly to the point of maximum curvature of the outermost layer of the cell assembly, is R, and along the thickness direction of the cell assembly, the thickness of the cell assembly is H, satisfying 1.05≤R:(H / 2)≤1.3.

[0006] In some embodiments, along the length direction and / or width direction of the negative electrode sheet, the first separator and the second separator extend beyond the negative electrode sheet, and the portions of the first separator and the second separator extending beyond the negative electrode sheet along the length direction and / or width direction of the negative electrode sheet are bonded together to form a third composite region.

[0007] In some embodiments, a second composite region is provided on the flat portion, at least on the portion from the innermost layer of the cell assembly to the fourth outermost layer from the end of the cell assembly.

[0008] In some embodiments, in the flat portion, along the thickness direction of the cell assembly, the projected portions of the second composite regions on two adjacent layers of the cell assembly overlap.

[0009] In some embodiments, the area of ​​a single second composite region is S. In the flat portion, the projections of the second composite regions on two adjacent layers of the cell assembly onto the negative electrode sheet along the thickness direction of the cell assembly at least partially overlap, and have an overlapping area of ​​S1, where S1 satisfies: 0.2≤S1 / S≤1.

[0010] In some embodiments, along the thickness direction of the cell assembly, in the flat portion, the projections of the second composite regions on two adjacent layers of the cell assembly do not overlap.

[0011] In some embodiments, the dimensions of two adjacent second composite regions increase sequentially along the winding direction of the cell assembly.

[0012] In some embodiments, all second composite regions are of equal size.

[0013] In some embodiments, in the innermost layer, the positive electrode has a starting end, a first straight section, and a first curved section connected to the first straight section. The starting end of the positive electrode is at the starting position of the first straight section, and the first straight section has a first second composite region. Along the winding direction of the battery cell assembly, the starting end of the first second composite region is flush with the starting end of the positive electrode.

[0014] In some embodiments, in the innermost layer, the positive electrode has a starting end of the positive electrode, a first straight section, and a first curved section connected to the first straight section. The starting end of the positive electrode is the starting position of the first straight section, and the first straight section has a first second composite region. The distance between the starting end of the first second composite region and the starting end of the positive electrode is D, and D satisfies: 0mm < D ≤ 3mm.

[0015] In some embodiments, along the winding direction of the battery cell assembly, the farthest end of the first second composite region is located at the junction of the first first straight section and the first first curved section.

[0016] In some embodiments, the battery cell assembly further includes a positive electrode tab connected to the positive electrode plate and a negative electrode tab connected to the negative electrode plate, and both the positive and negative electrode tabs are disposed in the straight portion of the battery cell assembly. The second composite region and the positive electrode tab do not overlap in the orthographic projection along the thickness direction of the battery cell assembly.

[0017] In some embodiments, the positive electrode sheet has a positive active coating, the positive active coating has a functional structure region, at least a portion of the functional structure region is located at the first curved end, the areal density of the positive active coating in the functional structure region is ρ1, the areal density of the positive active coating in the first straight section is ρ2, and ρ1 < ρ2.

[0018] In some embodiments, functional structure regions are provided on at least two first curved sections connected to a first straight section having a positive tab along the winding direction of the cell assembly.

[0019] In some embodiments, the first curved section where at least a portion of the functional structural region is located and the first straight section where a second composite region is located are located in the same layer of the cell assembly.

[0020] In some embodiments, the portion of the positive electrode sheet having the functional structure region has a recess. The recess has at least two holes with a depth of h and a diameter of d, and the distance between two adjacent holes is m, where m satisfies 0 mm ≤ m ≤ 5 mm; and / or 2 μm ≤ h ≤ 80 μm; and / or 10 μm ≤ d ≤ 200 μm.

[0021] In some embodiments, the recess has at least one groove, the dimension of which along the length of the positive electrode sheet is L3, and L3 satisfies: 2mm≤L3≤12mm; and / or, the dimension of which along the thickness of the positive electrode sheet is greater than or equal to 2μm and less than or equal to the thickness of the positive electrode sheet.

[0022] In some embodiments, along the length of the positive electrode sheet, the size L1 of a single second composite region and the depth h of the hole in the recess satisfy: 1.5≤L1 / h≤20000.

[0023] In some embodiments, along the length direction of the positive electrode sheet, the size L1 of a single second composite region and the size L3 of the groove in the recess satisfy: 0.3≤L1 / L3≤20.

[0024] In some embodiments, in the cell assembly, the thickness of the negative electrode is G, the thickness of the first separator is g1, the thickness of the second separator is g2, and in the bent portion of the cell assembly, the distance between two adjacent positive electrode layers is the positive electrode gap. The size of at least one positive electrode gap in the bent section is H1, and H1 satisfies: G+g1+g2+5μm≤H1≤G+g1+g2+30μm.

[0025] In some embodiments, the orthogonal projections of the second composite region and the negative electrode tab disposed on the second straight segment where the second composite region is located in the cell assembly thickness direction do not overlap.

[0026] In some embodiments, the first straight section where the positive electrode tab is located has a second composite region. Along the width direction of the cell assembly, the distance between the end of the second composite region near the positive electrode tab and the end of the positive electrode tab near the second composite region is d1, where d1 ≥ 0.5 mm.

[0027] In some embodiments, the second straight section where the negative electrode tab is located has a second composite region. Along the width direction of the cell assembly, the distance between the end of the second composite region near the negative electrode tab and the end of the negative electrode tab near the second composite region is d2, where d2 ≥ 0.5 mm.

[0028] In some embodiments, the cell assembly further includes a positive electrode tab connected to the positive electrode plate, and the adhesion strength between the positive electrode tab and the second separator is F. The adhesion strength between the positive electrode plate and the second separator in the second composite region is F2, satisfying F2≥F.

[0029] In some embodiments, along the length direction of the negative electrode sheet, the distance between the end of the second composite region and the edge of the nearest second curved segment is D1, where D1 ≥ 0.5 mm.

[0030] In some embodiments, along the length direction of the negative electrode sheet, the size of a single second straight segment is L, the size of a single second composite region is L1, and L1 and L satisfy: 3mm≤L1≤L.

[0031] In some embodiments, along the width direction of the negative electrode sheet, the size of the second composite region is W1, and the size of the positive electrode sheet is W, where W and W1 satisfy: 5mm ≤ W1 ≤ W. In some embodiments, along the length direction of the negative electrode sheet, the size of the third composite region near the beginning or end of the negative electrode sheet is L2, where L2 satisfies: 0.5mm ≤ L2 ≤ 2L; and / or, along the width direction of the negative electrode sheet, third composite regions are respectively provided on both sides of the negative electrode sheet, and the size of the third composite region on each side along the width direction of the negative electrode sheet is W2, where W2 satisfies: 0.2mm ≤ W2 ≤ 2mm.

[0032] In some embodiments, the bonding strength between the first or second separator in the first composite region and the negative electrode is F1, the bonding strength between the positive electrode in the second composite region and the second separator is F2, and the bonding strength between the first separator and the second separator in the third composite region is F3, wherein F1 and F2 satisfy: F2≥F1; and / or, F1 and F3 satisfy: F3≥F1; and / or, 1N / m≤F1≤15N / m; and / or, 1.5N / m≤F2≤30N / m; and / or, 1N / m≤F3≤15N / m.

[0033] Secondly, this application proposes a battery that includes the cell assembly of the first aspect.

[0034] In this application, the positive and negative electrode sheets are pressed together with the separator to prevent the core from being wound too tightly due to their respective tensions during winding, thereby increasing the gap between the positive and negative electrode sheets. Specifically, the negative electrode sheet forms a first composite region with the first and second separators, which strengthens the adhesion between the separator and the negative electrode sheet, forming a composite sheet with higher strength. This helps prevent relative sliding between the electrode sheet and the separator when the positive electrode sheet and the composite sheet form a second composite region. The second composite region can fix the positive electrode sheet in a predetermined position on the negative electrode sheet, so that the positive electrode sheet forms a compensation region between two adjacent second composite regions. That is, a certain gap is left between the positive and negative electrode sheets in the uncomposite area, thereby increasing the electrode gap in the arc area of ​​the core and reserving space for battery cyclic expansion, which can effectively solve the problem of battery cyclic expansion deformation. Attached Figure Description

[0035] To better integrate the content illustrated in the accompanying drawings with the description of the specific embodiments, a brief introduction to the drawings is provided below. It is understood that the accompanying drawings mentioned below are merely schematic illustrations of some embodiments of the relevant technical solutions and the technical solutions of this application. Without creative effort, those skilled in the art can create drawings illustrating other embodiments.

[0036] Figure 1 is a first cross-sectional view of the battery cell assembly provided in some embodiments of this application in a stacked state along the length of the negative electrode sheet.

[0037] Figure 2 is a cross-sectional schematic diagram along the width direction of the negative electrode sheet in a stacked state of the cell assembly provided in some embodiments of this application.

[0038] Figure 3 is a second cross-sectional view of the battery cell assembly provided in some embodiments of this application in a stacked state along the length of the negative electrode sheet.

[0039] Figure 4 is a structural schematic diagram of a battery cell assembly in a wound state provided in some embodiments of this application.

[0040] Figure 5 is another structural schematic diagram of the battery cell assembly provided in some embodiments of this application in the wound state.

[0041] Figure 6 is another structural schematic diagram of the battery cell assembly provided in some embodiments of this application in the wound state.

[0042] Figure 7 is a schematic diagram of the structure of a positive electrode sheet with a functional structure region provided in some embodiments of this application.

[0043] Figure 8 is another structural schematic diagram of a positive electrode sheet with a functional structure region provided in some embodiments of this application.

[0044] Figure 9 is another structural schematic diagram of a positive electrode sheet with a functional structure region provided in some embodiments of this application.

[0045] Figure 10 is a schematic diagram of the structure of a battery cell assembly in the winding state in the related technology.

[0046] Reference numerals: 100, Cell assembly; 110, Positive electrode sheet; 111, Positive current collector; 112, Positive active coating; 113, First straight section; 114, First curved section; 116, Recess; 116a, Hole; 116b, Groove; 120, Negative electrode sheet; 121, Negative current collector; 122, Negative active coating; 123, Second straight section; 124, Second curved section; 130, First separator; 140, Second separator; 150, Positive tab; 160, Negative tab; Q1, First composite region; Q2, Second composite region; Q3, Third composite region; Q4, Functional structure region; A1, Straight section; A2, Curved section; B, Compensation region; C, Adhesive section; X, Width direction of cell assembly; Y, Length direction of cell assembly; Z, Thickness direction of cell assembly. Detailed Implementation

[0047] To make the embodiments of this application clearer, the embodiments will be described below with reference to the accompanying drawings. It is understood that the content mentioned below is only a part of the embodiments of this application, and does not exhaustively list all embodiments. Therefore, other embodiments obtained based on the following embodiments without creative effort all fall within the protection scope of this application.

[0048] It should be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to impose strict limitations on the technical solutions unless the context clearly indicates otherwise. For example, the use of "a," "an," and "the" to modify a feature does not preclude the possibility that the feature may be plural in other embodiments.

[0049] It should be understood that the terms "comprising," "including," and "having" are open-ended, indicating the presence of the stated features but not excluding the possibility of other features in the embodiment. Similarly, the use of terms such as "first," "second," etc., to describe multiple features only indicates the distinction between one feature and another, and such terms do not imply order or sequence unless explicitly stated in the context.

[0050] It should be understood that, unless the context clearly indicates otherwise, the terms "setup," "connection," and "installation" should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection via a medium. Those skilled in the art will understand the specific meaning of these terms in this document based on the specific circumstances.

[0051] In addition, for ease of description, the text will use terms of spatial relative relationship to describe the position of one feature relative to another feature, such as "inner", "outer", "end", "side", "upper", "middle", "lower", "high", "low", "axial", "circumferential", "radial", "horizontal", "vertical", "first direction" and "second direction", etc. Understandably, the spatial relative relationship between two features should include other specific situations besides those shown in the accompanying drawings of the specification.

[0052] With the development of lithium-ion battery technology, the market has placed higher demands on battery fast charging capabilities and energy density, especially since the improvement of battery energy density has reached a bottleneck. Currently, a relatively effective method is to use new materials, such as high-capacity silicon-based materials for the negative electrode, which can store a large number of lithium ions, thus providing higher energy density. However, the silicon-based material on the negative electrode undergoes significant volume expansion during the lithium insertion / extraction reaction during battery charging and discharging, causing the negative electrode to compress the positive electrode. In wound cells, the inner and outer sides of the curved section of the cell experience different forces, easily leading to stress concentration. The expansion of the negative electrode further exacerbates this stress concentration in the curved section. Furthermore, the positive electrode in the inner layers of the cell is coated with a positive active coating on both sides along its thickness, forming a double-sided region, while the positive electrode in the outer layers is coated with a positive active coating on only one side along its thickness, forming a single-sided region. Understandably, the structural strength of the single-sided region is less than that of the double-sided region. Due to the characteristics of the wound structure, the curved section experiences greater outward expansion and compression forces compared to the straight section. The portion of the wound cell near the outer ring is the single-sided area of ​​the positive electrode sheet. Furthermore, due to the characteristics of the wound structure, the closer to the outer ring of the wound cell, the more uneven the stress distribution at the curved section. The outward expansion force is greater, while the inward binding force is weaker. Therefore, the curved section of the positive electrode sheet in the single-sided area is more prone to breakage under the pressure of the negative electrode sheet. In particular, the outermost single-sided area of ​​the positive electrode sheet lacks binding force, making the curved section, especially the outermost single-sided area, highly susceptible to breakage after cell cycling, ultimately affecting the battery's cycle life and performance.

[0053] To address the aforementioned issues, related technologies offer solutions such as localized treatment of the positive electrode at the curved section of the battery, including the creation of multiple micropores or recessed areas to reduce the lithium content in that region. This, in turn, reduces the lithium intercalation amount in the corresponding negative electrode coating, thus mitigating the volume expansion of the negative electrode coating. However, due to the significant expansion of silicon-based negative electrode materials, this technology still cannot completely resolve the battery deformation or even electrode breakage caused by volume expansion during later battery cycles.

[0054] Therefore, it is necessary to study a new technology to solve the problem of battery deformation and even electrode breakage caused by cyclic expansion, so as to produce high-reliability and high-energy-density lithium-ion batteries.

[0055] The embodiments of this application will now be described with reference to the accompanying drawings.

[0056] In a first aspect, referring to Figures 1, 2, and 4, this application proposes a battery cell assembly 100, which includes a first separator 130, a negative electrode 120, a second separator 140, and a positive electrode 110 sequentially stacked and wound. The battery cell assembly 100 has a straight portion A1 and a bent portion A2. The positive electrode 110 has a first straight section 113 and a first bent section 114 located in the straight portion A1 and the bent portion A2, respectively. The negative electrode 120 has a second straight section 123 and a second bent section 124 located in the straight portion A1 and the bent portion A2, respectively. Along the length direction of the negative electrode 120, the first separator 130 and the second separator 140 are bonded to the negative electrode 120 to form a first composite region Q1. Along the length of the positive electrode 110, at least a portion of the positive electrode 110 and the second separator 140 are bonded together to form at least one bonding portion. The positive electrode 110 and the second separator 140 at the bonding portion location, together with the negative electrode 120 and the first separator 130 corresponding to the bonding portion location, together form a second composite region Q2. The second composite region Q2 is located in the straight portion A1, and along the length of the negative electrode 120, the size of the second composite region Q2 is smaller than the size of the first composite region Q1.

[0057] Referring to Figure 3, the positive electrode 110, the negative electrode 120, and the separator are pressed together to prevent the core from being wound too tightly due to their respective tensions during winding, thereby increasing the gap between the positive electrode 110 and the negative electrode 120. Specifically, the negative electrode 120, the first separator 130, and the second separator 140 form a first composite region Q1, which strengthens the bond between the separator and the negative electrode 120, forming a composite sheet with higher strength. This helps prevent the negative electrode 120 from sliding relative to the separator when the positive electrode 110 and the composite sheet form a second composite region Q2. The second composite region Q2 can fix the positive electrode 110 in a set position on the negative electrode 120, so that the positive electrode 110 forms a compensation region B between two adjacent second composite regions Q2. That is, a certain gap is left between the positive electrode 110 and the negative electrode 120 in the uncomposite area, so that the positive electrode 110 has a compensation length, thereby increasing the electrode gap of the core bending part A2, and thus reserving space for battery cycle expansion, which can effectively solve the problem of battery cycle expansion deformation.

[0058] It should be noted that Figure 1 is only used to show the relative positional relationship of the various parts and does not show the compensation area B. The protrusion of the compensation area B can be clearly seen in Figure 3.

[0059] Furthermore, in this application, the extended directions of the stacked positive electrode 110 and negative electrode 120 are consistent, which is their length direction. After being wound to form the cell assembly 100, the cell assembly 100 has a straight portion A1 and a bent portion A2. The length direction of the straight portion A1 is consistent with the length direction of the negative electrode 120, which is also the width direction X of the cell assembly 100. The length direction Y of the cell assembly 100 is the extension direction of the positive electrode tab 150 or the negative electrode tab 160 on the straight portion A1, which is also the width direction of the negative electrode 120. Therefore, it can be understood that the cell assembly 100 has two perpendicular length directions, width directions and thickness directions. The thickness direction Z of the cell assembly 100 is consistent with the thickness directions of the negative electrode 120 and the positive electrode 110. The width direction X of the cell assembly 100 is consistent with the length direction of the negative electrode 120 and the positive electrode 110. The length direction Y of the cell assembly 100 is consistent with the width direction of the negative electrode 120 and the positive electrode 110.

[0060] In some embodiments, referring to FIG4, the distance between the two points along the width direction X of the cell assembly 100, from the innermost point of the curved portion A2 of the cell assembly 100 with the maximum curvature to the outermost point of the curved portion A2 of the cell assembly 100 with the maximum curvature, is R, and along the thickness direction Z of the cell assembly 100, the thickness of the cell assembly 100 is H, and R and H satisfy 1.05≤R:(H / 2)≤1.3.

[0061] It is understood that the aforementioned bend A2 can be any bend A2 of the cell assembly 100; the figure is only used for example and for ease of understanding.

[0062] In the above embodiment, the distance R between the two points where the curvature is greatest at the innermost and outermost layers of the bent portion A2 of the cell assembly 100 can be understood as the distance between the two points with the greatest curvature on the innermost layer of the separator and the outermost layer of the positive electrode 110 in the bent portion A2. H / 2 can be understood as the distance along the thickness direction of the cell assembly 100 between the separator at the winding center of the cell assembly 100 and the outermost electrode 110. It should be further noted that the cell assembly 100 has bent portions A2 on both the left and right sides in the width direction, and the R values ​​of the left and right bent portions A2 can be the same or different. When the distance R between the two points from the innermost point of maximum curvature of the left and right curved portions A2 of the cell assembly 100 to the outermost point of maximum curvature of the curved portion A2 of the cell assembly 100 is different, the H / 2 corresponding to half of the cell thickness of the left and right curved portions A2 is also different.

[0063] In one embodiment, if R is the distance between the innermost point of the curved portion A2 on the left side of the cell with the maximum curvature and the outermost point of the curved portion A2 of the cell assembly 100 with the maximum curvature, then H / 2 corresponds to the distance along the thickness direction of the cell assembly 100 between the outermost electrode of the cell assembly 100 and the diaphragm of the straight portion A1 at the winding center of the cell assembly 100, which is close to and connected to the curved portion A2 on the left side of the cell.

[0064] Understandably, if the value of R:(H / 2) is too small, it means that the gap between the positive electrode 110 and the negative electrode 120 at the bend A2 is too small, which cannot effectively cope with the problem of the cyclic expansion of the negative electrode 120. On the other hand, if the value of R:(H / 2) is too large, it means that the gap between the positive electrode 110 and the negative electrode 120 at the bend A2 is too large, which will cause lithium ions to reach the negative electrode 120 more slowly in the electrolyte, resulting in a longer lithium ion insertion / extraction transport path, slower transport speed, and even lithium plating, thus reducing the battery capacity. Therefore, the value of R:(H / 2) should be moderate. For example, R:(H / 2) can be any one of the following values ​​or a range between any two of them: 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, 1.21, 1.22, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28, 1.29, or 1.30.

[0065] Referring to Figures 1 and 2, in some embodiments, along the length direction and / or width direction of the negative electrode 120, the first separator 130 and the second separator 140 extend beyond the negative electrode 120, and the portions of the first separator 130 and the second separator 140 extending beyond the negative electrode 120 along the length direction and / or width direction of the negative electrode 120 are bonded together to form a third composite region Q3.

[0066] It should be understood that the first separator 130 and the second separator 140 are equivalent to the two sides of the encapsulation bag and encapsulate the negative electrode 120 inside them. The portion of the first separator 130 and the second separator 140 that extends beyond the edge of the negative electrode 120 constitutes the third composite region Q3. The third composite region Q3 can further increase the bonding strength between the separator and the negative electrode 120.

[0067] In some embodiments, a second composite region Q2 is provided on at least the straight portion A1 of the innermost layer of the cell assembly 100 to the straight portion A1 of the fourth outermost layer from the end of the cell assembly 100.

[0068] It should be noted that the starting or innermost layer of the battery cell assembly 100 must have a second composite zone Q2, while the outermost four layers may not have a composite zone.

[0069] In some embodiments, a second composite region Q2 may also be provided on the straight portion A1 of the outermost layer, the second outermost layer, and / or the third outermost layer from the bottom of the cell assembly 100. It is understood that, in this application, the winding direction of the cell assembly 100 refers to the direction of winding from the inside of the cell assembly 100 outwards, and can also be understood as the length direction of the positive electrode 110 and / or the negative electrode 120 (i.e., the extension direction of the positive electrode 110 and the negative electrode 120 after winding).

[0070] Specifically, along the winding direction of the cell assembly 100, the second outermost layer of the cell assembly 100 is the layer connected to the outermost layer, the third outermost layer is the layer connected to the inner side of the second outermost layer, and the fourth outermost layer is the layer connected to the inner side of the third outermost layer.

[0071] Furthermore, the number of second composite regions Q2 on the aforementioned straight portion A1 is at least one, that is, a straight portion A1 may have multiple second composite regions Q2 spaced apart.

[0072] In particular, the above solution is only one implementation method. If one or more straight sections A1 from the innermost layer to the fourth outermost layer from the bottom are not provided with a second composite area Q2, they should also fall within the protection scope of this application.

[0073] In some embodiments, referring to FIG6, along the thickness direction Z of the cell assembly 100, the projections of the second composite region Q2 on the straight portion A1 of two adjacent layers of the cell assembly 100 do not overlap.

[0074] In some alternative embodiments, referring to Figures 4 and 5, along the thickness direction Z of the cell assembly 100, the projected portions of the second composite regions Q2 on the straight portions A1 of two adjacent layers of the cell assembly 100 overlap.

[0075] In some embodiments, the area of ​​a single second composite region Q2 is S; the projections of the second composite regions Q2 on the straight portion A1 of two adjacent layers of the cell assembly 100 along the thickness direction Z of the cell assembly onto the negative electrode sheet 120 at least partially overlap, and the overlapping area of ​​the two is S1, where S1 satisfies: 0.2≤S1 / S≤1.

[0076] It should be noted that the projection referred to here is an orthographic projection along the thickness direction of the cell assembly 100, or a projection onto the projection surface of the negative electrode sheet 120 along the thickness direction of the cell assembly 100. It should also be noted that all projections in this application are orthographic projections.

[0077] In summary, the projections of the second composite regions Q2 on the straight sections A1 of two adjacent concentric circles can be non-overlapping, partially overlapping, or completely overlapping. All of the above solutions are superior to not setting the second composite region Q2 and are within the protection scope of this application.

[0078] In some embodiments, referring to FIG4, the dimensions of two adjacent second composite regions Q2 increase sequentially along the winding direction of the cell assembly 100, or referring to FIG5, the dimensions of all second composite regions Q2 are equal.

[0079] In the above embodiments, the length of all second composite regions Q2 gradually increases, or the length of all second composite regions Q2 is the same. It should be explained that during the winding process of the cell assembly 100, the length of the curved portion A2 gradually increases from the inside to the outside. To match the length of the curved portion A2 and to ensure that the distance between two adjacent second composite regions Q2 is as consistent as possible, while also considering the ease of process operation, the length of the second composite region Q2 should be gradually increased as much as possible.

[0080] In particular, this application should also protect the following schemes: the length of all second composite regions Q2 generally increases, with some adjacent second composite regions Q2 having the same length; and the case where the length of the later second composite region Q2 is slightly smaller than the length of the earlier second composite region Q2 along the winding direction of the core.

[0081] In some embodiments, the positive electrode 110 has a starting end located in the innermost layer of the cell assembly 100. The innermost layer has a first positive electrode straight portion A11 and a first positive electrode bent portion A21 connected to the first positive electrode straight portion A11. The starting end of the positive electrode 110 is the starting position of the first positive electrode straight portion A11. The first positive electrode straight portion A11 has a first second composite region Q2. Along the winding direction of the cell assembly 100, the starting end of the first second composite region Q2 is flush with the starting end of the positive electrode 110.

[0082] In an alternative example, the distance between the starting end of the first second composite region Q2 and the starting end of the positive electrode 110 is D, and satisfies 0mm < D ≤ 3mm. Along the winding direction of the cell assembly 100, the farthest ending end of the first second composite region Q2 is located at the junction of the first positive electrode straight portion A11 and the first positive electrode curved portion A21.

[0083] In the above embodiment, the first second composite region Q2 begins at the starting end of the positive electrode sheet 110 and ends at the junction of the straight portion A11 and the curved portion A21 of the first positive electrode. That is, the head of the positive electrode sheet 110 must be composited with the second separator 140. This is to prevent the head of the positive electrode sheet 110 from warping or folding during conveyor belt travel if it is not composited. Furthermore, if the head of the positive electrode sheet 110 is not fixed and composited, the positions of other second composite regions Q2 will fluctuate during subsequent winding, or the subsequent second composite regions Q2 will be subjected to tension from the head of the positive electrode sheet 110, causing the second composite regions Q2 to fail and thus preventing compensation for the curved portion A2. Therefore, optionally, the distance D between the starting end of the first second composite region Q2 and the starting end of the positive electrode sheet 110 does not exceed 3 mm.

[0084] Referring to Figures 4 to 7, in some embodiments, the battery cell assembly 100 further includes a positive electrode tab 150 connected to the positive electrode plate 110 and a negative electrode tab 160 connected to the negative electrode plate 120, and both the positive electrode tab 150 and the negative electrode tab 160 are disposed on the flat portion A1 of the battery cell assembly 100. The orthographic projections of the second composite region Q2 and the positive electrode tab 150 disposed on the flat portion A1 where the second composite region Q2 is located do not overlap in the thickness direction of the battery cell assembly 100. In one example, the orthographic projections of the second composite region Q2 and the negative electrode tab 160 disposed on the flat portion A1 where the second composite region Q2 is located do not overlap in the thickness direction of the battery cell assembly 100.

[0085] Specifically, the above embodiments can effectively prevent damage to the positive electrode tab 150 and the negative electrode tab 160 when the second composite region Q2 is formed, and at the same time prevent the burrs of the positive electrode tab 150 and the negative electrode tab 160 from piercing the diaphragm of the second composite region Q2.

[0086] In some embodiments, the straight portion A1 where the positive electrode tab 150 is located has a second composite region Q2. Along the width direction X of the cell assembly 100, the distance between the end of the second composite region Q2 near the positive electrode tab 150 and the end of the positive electrode tab 150 near the second composite region Q2 is d1, which satisfies d1≥0.5mm.

[0087] In some embodiments, the straight portion A1 where the negative electrode tab 160 is located has a second composite region Q2. Along the width direction X of the cell assembly 100, the distance between the end of the second composite region Q2 near the negative electrode tab 160 and the end of the negative electrode tab 160 near the second composite region Q2 is d2, and satisfies d2≥0.5mm.

[0088] In the above embodiment, the distance between the edge of the second composite region Q2 and the edges of the positive electrode tab 150 and the negative electrode tab 160 should not be too close. Otherwise, the negative electrode tab 160 and the positive electrode tab 150 may be easily damaged during the composite process in the second composite region Q2, or the burrs on the negative electrode tab 160 may easily puncture the diaphragm under the action of the composite roller, causing the second composite region Q2 to fail. Optionally, d1 and d2 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm, etc.

[0089] In some embodiments, the cell assembly 100 further includes a positive electrode tab 150 connected to the positive electrode plate 110, and the bonding strength between the positive electrode tab 150 and the second separator 140 is F. The bonding strength between the positive electrode plate 110 and the second separator 140 in the second composite region Q2 is F2, and F and F2 satisfy: F2≥F.

[0090] In the above embodiment, the setting of F2≥F can ensure that the positive electrode 110 and the negative electrode 120 have sufficient bonding strength with the separator. At the same time, it can reduce the welding protrusion on the positive electrode 150 due to excessive bonding strength when the positive electrode tab 150 is formed at the position corresponding to the second composite region Q2, thus avoiding scratching or puncturing the separator and causing safety problems.

[0091] In this application, the test method for the relevant adhesive strength test (peel strength test) can be referred to the following description. After hot-pressing the diaphragm (25 mm wide) to the electrode (25 mm wide) or diaphragm to diaphragm under a certain pressure (e.g., 1 MPa) and temperature (e.g., 90 °C), it is cut into standard samples. Peel tests are performed on a universal tensile testing machine at a peel angle of 180° and a rate of 300 mm / min. The average force value during the stable peel phase is recorded, and the peel strength per unit width (N / m) is calculated accordingly. Each sample is tested at least three times, and the average value is taken.

[0092] In some embodiments, along the length direction of the negative electrode 120, the distance between the end of the second composite region Q2 and the edge of the nearest bend A2 is D1, and D1 ≥ 0.5 mm, for example 0.8 mm, 1 mm, 1.5 mm or 2 mm.

[0093] It should be noted that the edge of the curved part A2 refers to the junction of the curved part A2 and the straight part A1.

[0094] In the above embodiment, the second composite region Q2 needs to be a certain distance from the bending portion A2 to prevent the positive electrode 110 and negative electrode 120 from being in close contact at the bending portion A2, thus failing to increase the gap between them. Furthermore, this embodiment limits the lower limit of D1, ensuring a sufficiently large distance between the second composite region Q2 and the bending portion A2, thus guaranteeing the bonding strength between the positive electrode 110 and the negative electrode 120. Otherwise, excessive winding tension at the bending portion A2 could easily cause the bonding of the second composite region Q2 to fail.

[0095] In some embodiments, along the length direction of the negative electrode 120, the size of a single straight portion A1 is L, the size of a single second composite region Q2 is L1, and 3mm≤L1≤L is satisfied.

[0096] In some embodiments, along the width direction of the negative electrode 120, the size of the second composite region Q2 is W1, the size of the positive electrode 110 is W, and the condition 5mm≤W1≤W is met.

[0097] In the above embodiments, the length and width of the second composite region Q2 cannot exceed the length and width of the straight portion A1, and the length and width of the second composite region Q2 cannot be too small, otherwise the bonding strength will be affected. For example, the length L1 of the second composite region Q2 can be 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, etc., and the width of the second composite region Q2 can be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm or 13mm, etc.

[0098] In some embodiments, along the length direction of the negative electrode 120, the size of the third composite region Q3 near the first or last end of the negative electrode 120 is L2, and satisfies 0.5mm≤L2≤2L. In some embodiments, along the width direction of the negative electrode 120, a third composite region Q3 is provided on both sides of the negative electrode 120, and the size of the third composite region Q3 on each side along the width direction of the negative electrode 120 is W2, and satisfies 0.2mm≤W2≤2mm, for example, 0.5mm, 0.8mm, 1mm, 1.3mm, 1.5mm or 1.8mm.

[0099] Understandably, the third composite region Q3 can provide key adhesion for the diaphragm and the negative electrode 120 to be composited into a whole. By limiting the size of the third composite region Q3, the adhesion strength of the third composite region Q3 can be improved. It works in synergy with the first composite region Q1 to improve the overall strength of the negative electrode composite, ensuring that the diaphragm and the electrode do not detach when the second composite region Q2 is formed, and improving the stable formation of the gap of the bent portion A2 after winding.

[0100] In the above embodiment, along the length of the negative electrode 120, the length of the separator extending beyond the head or / and tail of the negative electrode 120 does not exceed the length of two straight portions A1. Otherwise, the third composite region Q3 at that location will be too long and wound around the outside of the core, increasing the thickness of the cell assembly 100 and thus reducing the energy density of the battery. Conversely, if the length of the third composite region Q3 at the end is too short, it will be difficult to guarantee the bonding strength. Therefore, the length L2 of the third composite region Q3 near the head or tail of the negative electrode 120 should be moderate. For example, L2 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm, etc.

[0101] Similarly, the width W2 of the third composite region Q3 located on the side of the negative electrode 120 should not be too wide, otherwise it will increase the dimension of the negative electrode 120 in the width direction, that is, the dimension of the cell assembly 100 in the length direction Y, which is not conducive to improving the energy density of the battery. Conversely, if the width of the third composite region Q3 located on the side of the negative electrode 120 is too narrow, it will be difficult to guarantee the bonding strength. Therefore, the width W2 of the third composite region Q3 located on one side of the width direction of the negative electrode 120 should be moderate. For example, W2 can be any value or a range between any two of the following: 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, or 2.0mm.

[0102] In some embodiments, the adhesion strength between the first separator 130 or the second separator 140 of the first composite region Q1 and the negative electrode 120 is F1; the adhesion strength between the positive electrode 110 and the second separator 140 of the second composite region Q2 is F2; ​​and the adhesion strength between the first separator 130 and the second separator 140 of the third composite region Q3 is F3. Here, F2 ≥ F1 satisfies F1 and F2. In one example, F3 ≥ F1 satisfies F3. In one example, 1 N / m ≤ F1 ≤ 15 N / m. In one example, 1.5 N / m ≤ F2 ≤ 30 N / m. In one example, 1 N / m ≤ F3 ≤ 15 N / m.

[0103] In the above embodiment, the bonding strength between the two layers of separator at the edge of the negative electrode 120 is greater than the bonding strength between the separator and the negative electrode 120. Moreover, the bonding strength between the positive electrode 110 and the separator in the second composite region Q2 is greater than the bonding strength between the negative electrode 120 and the separator, ensuring that the positive electrode 110 will not detach from the separator during the winding process. This is beneficial for the formation of the gap between the positive electrode 110 and the negative electrode 120 in the uncomposite region between two adjacent second composite regions Q2, thereby increasing the gap between the positive electrode 110 and the negative electrode 120 in the bent portion A2 of the electrode assembly 100.

[0104] In some embodiments, the positive electrode 110 has a positive active coating 112, the positive active coating 112 has a functional structure region Q4, at least a portion of the functional structure region Q4 is located in the curved portion A2, the areal density of the positive active coating 112 in the functional structure region Q4 is ρ1, the areal density of the positive active coating 112 in the straight portion A1 is ρ2, and ρ1 < ρ2.

[0105] In the above embodiments, the density of the active coating surface of the functional structure region Q4 is relatively small, and the lithium content is relatively small, thereby reducing the amount of lithium intercalation at the corresponding negative electrode 120 in the positive electrode functional structure region Q4, and reducing the expansion of the negative electrode 120 after lithium intercalation.

[0106] In some embodiments, along the winding direction of the cell assembly 100, at least two curved portions A2 connected to the straight portion A1 having the positive electrode tab 150 are provided with functional structure regions Q4.

[0107] Referring to FIG1, in some embodiments, along the winding direction of the cell assembly 100 (winding from the inside to the outside), taking the straight portion A1 with the positive electrode tab 150 as a reference, at least the following conditions are met: the two positive electrode plates 110 connected to the straight portion A1 where the positive electrode tab 150 is located are provided with functional structure regions Q4 on the portions of the curved portion A2, and the positive electrode plates 110 adjacent to the two positive electrode plates 110 connected to the straight portion A1 where the positive electrode tab 150 is located are also provided with functional structure regions Q4 on the portions of the curved portion A2.

[0108] In another embodiment, along the width direction of the electrode assembly 100, at least two portions of the two positive electrode plates 110 connected to the straight portion A1 where the positive electrode tab 150 is located, located on the outer side of the portions located on the curved portion A2, are also provided with functional structure regions Q4. That is, along the winding direction of the cell assembly 100, with the straight portion A1 having the positive electrode tab 150 as a reference, at least one portion located on the inner side of the curved portion A2 and three portions located on the outer side of the curved portion A2 are provided with functional structure regions Q4.

[0109] It should be noted that the current density is relatively high and the charge is relatively concentrated in the flat part A1 where the positive electrode tab 150 is located and the electrode ring area connected to the flat part A1 where the positive electrode tab 150 is located. The problem of lithium insertion expansion of the negative electrode 120 is relatively serious. Therefore, it is necessary to set the functional structure region Q4 in the bent part A2 of the positive electrode 110 in these areas to improve the negative electrode expansion and the resulting problem of breakage of the bent part A2 of the positive electrode 110.

[0110] In some embodiments, at least the curved portion A2 where the functional structural region Q4 is located and the straight portion A1 where the second composite region Q2 is located are located in the same layer of the cell assembly 100.

[0111] In the above embodiment, the functional structure region Q4 and the second composite region Q2 are located in the same winding layer and can work together to reduce the expansion of the negative electrode 120 during the charging and discharging process, while increasing the gap between the winding layers of the bending portion A2, thereby preventing the positive electrode 110 located in the bending portion A2 from being squeezed and stretched, which would lead to breakage.

[0112] Specifically, the second composite region Q2 or the functional structure region Q4 can be set separately in the cell assembly 100, or they can be arranged in combination in the cell assembly 100, which can solve the problem of cyclic expansion of the negative electrode 120. All of the above are within the protection scope of this application.

[0113] Referring to Figures 1 and 7 through 9, in some embodiments, the positive electrode 110 of the functional structure region Q4 is provided with a recess 116. The recess 116 has at least two holes 116a, the depth of which is h, the diameter of which is d, and the distance between two adjacent holes 116a is m, where m satisfies: 0 mm ≤ m ≤ 5 mm. In some embodiments, 2 μm ≤ h ≤ 80 μm. In some embodiments, 10 μm ≤ d ≤ 200 μm.

[0114] Referring to Figures 1 and 2, in some embodiments, the recess 116 has at least one groove 116b, the groove 116b having a dimension L3 along the length direction of the positive electrode 110, where L3 satisfies: 2mm ≤ L3 ≤ 12mm. In some embodiments, the dimension of the groove 116b along the width direction of the positive electrode 110 is greater than or equal to 2mm and less than or equal to the width of the positive electrode 110.

[0115] In some embodiments, the dimension of the groove 116b along the thickness direction of the positive electrode 110 is greater than or equal to 2 μm and less than or equal to the thickness of the positive electrode 110.

[0116] It should be noted that by providing holes 116a and / or grooves 116b on the recess 116 in the portion of the positive electrode 110 located at the bend A2, the amount of active material in the positive electrode active coating 112 in the portion of the positive electrode 110 located at the bend A2 is reduced, thereby reducing lithium ion insertion / extraction, improving wettability to the electrolyte, reducing the lithium insertion amount in the corresponding negative electrode 120, and improving the problem of electrode breakage caused by the expansion of the negative electrode 120 after battery charging and discharging. At the same time, the holes 116a and grooves 116b on the recess can also release some of the stress on the bend A2, improving the problem of breakage of the positive electrode 110 portion of the bend A2 caused by excessive stress during charging and discharging.

[0117] Specifically, the recess 116 can be formed on the positive electrode active coating 112, on the positive electrode current collector 111, or simultaneously on both the positive electrode current collector 111 and the positive electrode active coating 112. The recess 116 can be a through hole provided on the positive electrode sheet 110, or a recess formed on the positive electrode sheet 110 by roll forming. On the other side surface of the positive electrode sheet 110 opposite to the recess, a protrusion corresponding to the recess can be provided, or no protrusion may be provided.

[0118] In the above embodiments, the dimensional parameters of the holes 116a and grooves 116b on the recess 116 should be appropriate. If they are too large, it will affect the strength of the positive electrode 110; if they are too small, it will be difficult to improve the expansion of the negative electrode 120. Specifically, the distance m between the edges of the two holes 116a can be any one of 0mm, 1mm, 2mm, 3mm, 4mm, or 5mm, or a range between any two of these values. The depth h of the hole 116a can be any one of 2μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, or 80μm, or a range between any two of these values. The diameter d of the hole 116a can be any one of 10μm, 50μm, 100μm, 150μm, or 200μm, or a range between any two of these values. The length L3 of the groove 116b can be any one of 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, and 12mm, or a range between any two of these values. Furthermore, if the width of the positive electrode 110 is W, the thickness of the positive electrode 110 is G1, the width of the groove 116b is W3, and the depth of the groove 116b is h1, then 2mm ≤ W3 ≤ W, and / or 2μm ≤ h1 ≤ G1.

[0119] In some embodiments, along the length direction of the positive electrode 110, the size L1 of a single second composite region Q2 and the depth h of the hole 116a in the recess 116 satisfy: 1.5 ≤ L1 / h ≤ 20000. In some embodiments, along the length direction of the positive electrode 110, the size L1 of a single second composite region Q2 and the size L3 of the groove 116b in the recess 116 satisfy: 0.3 ≤ L1 / L3 ≤ 20.

[0120] In the above embodiments, when the hole 116a or groove 116b on the recess 116 is co-located with the second composite region Q2, it is necessary to ensure improved fragmentation effect while avoiding overcompensation, which would prevent the bent portion A2 from undergoing lithium insertion / extraction reaction, leading to lithium plating in the bent portion A2. Therefore, the ratio L1 / h of the length of the second composite region Q2 to the depth of the hole 116a should be appropriate. For example, L1 / h can be any one of 1.5, 10, 100, 1000, 10000, or 20000, or a range between any two of these values. Similarly, the ratio L1 / L3 of the length of the second composite region Q2 to the length of the groove 116b should also be appropriate. For example, L1 / L3 can be any one of 0.3, 1, 5, 10, 15, or 20, or a range between any two of these values.

[0121] In some embodiments, in the cell assembly 100, the thickness of the negative electrode 120 is G, the thickness of the first separator 130 is g1, the thickness of the second separator 140 is g2, and in the bent portion A2 of the cell assembly 100, the distance between two adjacent positive electrode layers 110 is the positive electrode gap. In the bent portion A2, at least one of the gaps has a size of H1, and H1 satisfies: G+g1+g2+5μm≤H1≤G+g1+g2+30μm.

[0122] In the above embodiments, at least one positive electrode gap is larger than the other positive electrode gaps. The larger gap H1 must satisfy: G + g1 + g2 + 5μm ≤ H1 ≤ G + g1 + g2 + 30μm, where g1 and g2 can be equal. Therefore, the size H' of the positive electrode gap after subtracting the thicknesses of the first separator 130, the second separator 140, and the negative electrode 120 is H1 - (G + g1 + g2), that is, 5μm ≤ H' ≤ 30μm.

[0123] Understandably, since G, g1, and g2 are all preset values, the changing trends of H' and H1 are consistent. H' cannot be too small, meaning H1 cannot be too small; otherwise, the gap between the positive electrode 110 and the negative electrode 120 will be too small, failing to effectively address the cyclic expansion problem of the negative electrode 120. Conversely, if H' is too large, it means the gap between the positive electrode 110 and the negative electrode 120 at the bend A2 will be too large, resulting in slower lithium ion ionization in the electrolyte and slower lithium intercalation into the negative electrode 120, leading to reduced capacity. Therefore, the value of H' should be moderate. For example, H' can be any one of 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 15μm, 20μm, 25μm, or 30μm, or a range between any two of these values.

[0124] It should be noted that the gap between the positive electrode plates can be obtained using a gap test method. Specifically, a CT scan is used to scan the cross-section of the cell assembly 100. The brighter white color indicates the coating of the positive electrode plate 110. The distance between the edges of the coatings of two adjacent positive electrode plates 110 is measured using CT testing software, which is the gap between the positive electrode plates.

[0125] The following detailed embodiments and comparative examples illustrate this application.

[0126] I. Battery Preparation

[0127] General steps: (1) Preparation of positive electrode 110: The positive electrode active material Li[Ni 0.83 Co 0.06 Mn 0.05 Fe 0.06 O2 ternary material, binder polyvinylidene fluoride, and conductive agent carbon black are mixed in a certain mass percentage (e.g., 98:1:1), and an appropriate amount of N-methylpyrrolidone is added as a solvent. The mixture is stirred evenly to form an electrode slurry. The prepared positive electrode slurry is evenly coated on aluminum foil and then rolled and cut to form a positive electrode sheet 110.

[0128] (2) Preparation of negative electrode 120: Artificial graphite, silicon carbide, styrene-butadiene rubber, polyacrylic acid and conductive carbon black are mixed evenly according to a certain mass percentage (e.g., 66:30:1.5:1.0:1.5), and deionized water is added to make a slurry for negative electrode active coating 122. The above slurry for negative electrode active coating 122 is evenly coated on both sides of copper foil, and after drying and compaction by a roller press, negative electrode 120 is obtained.

[0129] (3) Battery preparation: The positive electrode 110, separator (polyethylene base film with borosilicate ceramic layer and polyvinylidene fluoride adhesive layer on both sides) and negative electrode 120 prepared in step (1) are wound together to form a cell assembly 200; after injecting electrolyte, the battery is formed, sorted and tested by OCV to obtain the battery.

[0130] Comparative Example 1: Referring to Figure 10, according to the existing conventional winding technology, the negative electrode sheet, separator and positive electrode sheet are stacked and wound into a core in sequence, and then the core is hot-pressed, packaged, baked, injected with liquid, formed, degassing and sealed, and capacity tested to produce a battery.

[0131] Comparative Example 2: First, the first separator, the negative electrode sheet, and the second separator are stacked and laminated sequentially (laminarization temperature 80℃, lamination pressure 3500N, lamination speed 200mm / s) to form a negative electrode composite sheet (including the first composite region and the third composite region). Then, the positive electrode sheet and the negative electrode composite sheet are wound together using existing winding technology to form a core. After hot pressing, encapsulation, baking, liquid injection, formation, degassing and sealing, and capacity testing of the core, a battery is produced.

[0132] Example 1:

[0133] First, the first separator 130, the prepared negative electrode sheet 120, and the second separator 140 are sequentially stacked and then hot-pressed together (composite temperature 80℃, composite pressure 3500N, composite speed 200mm / s) to form a negative electrode composite sheet (including a first composite region Q1 and a third composite region Q3). Then, the positive electrode sheet 110 is intermittently composited with the negative electrode composite sheet to form multiple second composite regions Q2 (the second composite regions Q2 are located in the straight portion A1 of the cell assembly 100, composite temperature 80℃, composite pressure 250kg, composite speed 250mm / s), and then wound to form the cell assembly 100. The distance D between the starting end of the first second composite region Q2 and the starting end of the positive electrode sheet 110 is 3mm. The distance d1 between one end of the positive electrode tab 150 and the end of the positive electrode tab 150 near the second composite region Q2 is 0.5 mm; the distance d2 between the end of the second composite region Q2 near the negative electrode tab 160 and the end of the negative electrode tab 160 near the second composite region Q2 is 0.5 mm; the distance D1 between the end of the second composite region Q2 and the edge of the nearest curved portion A2 is 0.5 mm. Specifically, the length L1 of a single second composite region Q2 is 3 mm, the length L' of the first composite region Q1 is 1250 mm, the length L of the straight portion A1 is 59 mm, the distance R between the innermost curvature of the curved portion A2 and the outermost curvature of the curved portion A2 is 2.58 mm, the thickness H of the cell assembly 100 is 3.97 mm, and the area S of a single second composite region Q2 is 270 mm². 2The projected overlap area S1 of the second composite region Q2 on the straight portion A1 of two adjacent concentric circles is 54 mm. 2 The width W of the positive electrode 110 is 90mm, and the width W1 of the second composite region Q2 is 90mm.

[0134] Example 2:

[0135] The same method as in Example 1 was used to fabricate the battery cell assembly 100, wherein L1 is 15 mm, R is 2.52 mm, H is 3.95 mm, and S is 1350 mm. 2 S1 is 1174.5mm. 2 The remaining parameters are the same as in Example 1.

[0136] Example 3:

[0137] The same core preparation method as in Example 1 was used, where L1 is 55 mm, R is 2.11 mm, H is 4.01 mm, and S is 4950 mm. 2 S1 is 4950mm 2 The remaining parameters are the same as in Example 1.

[0138] Example 4:

[0139] The same core preparation method as in Example 1 was used, wherein R is 2.12 mm, H is 3.75 mm, W1 is 5 mm, and S is 75 mm. 2 S1 is 65.3mm. 2 The remaining parameters are the same as in Example 2.

[0140] Example 5:

[0141] The same core preparation method as in Example 1 was used, wherein R is 2.51 mm, H is 4.03 mm, W1 is 50 mm, and S is 70 mm. 2 S1 is 652.5mm 2 The remaining parameters are the same as in Example 2.

[0142] Example 6:

[0143] The same core preparation method as in Example 1 was used, wherein R was 2.43 mm, H was 3.99 mm, and the remaining parameters were the same as in Example 2.

[0144] Example 7:

[0145] The positive electrode sheet 110 is perforated 116a in the active coating area located on the inner side near the winding center and the outer side away from the winding center of the bending portion A2 (e.g., by laser ablation, chemical etching, bump roll pressing, etc.). The remaining steps for preparing the cell assembly 100 are the same as in Example 1. The hole depth h of hole 116a is 15μm, the hole diameter d of hole 116a is 100μm, the hole gap m of hole 116a is 180μm, and R is 2.48mm, H is 4.02mm, the other parameters are the same as in Example 2, and L1 / h is 1000.

[0146] Example 8:

[0147] A groove 116b is provided on the inner side of the portion of the positive electrode 110 located at the bend A2. The remaining steps for preparing the cell assembly 100 are the same as in Example 1. The groove 116b has a depth of 20 μm, a length L3 dimension L3 of the groove 116b along the positive electrode 110 of 5 mm, a width dimension L5 of the groove 116b along the positive electrode 110 of 5 mm, and R = 2.45 mm, H = 3.98 mm. The remaining parameters are the same as in Example 2, and L1 / L3 = 3.

[0148] After the core of the above embodiments is manufactured, it is packaged, injected with electrolyte, formed, and capacity tested according to the same technical requirements to produce a finished battery.

[0149] II. Test Results

[0150] Five cells were randomly selected from both the example and comparative batteries for charge-discharge cycle testing (3C constant current charging to 4.3V, 1.8C constant current charging to 4.4V, 1C constant current and constant voltage charging to 4.5V, cutoff at 0.035C, and then 0.5C discharge to 3.0V), 1000 cycles were performed, and CT was used to monitor the breakage of electrode plates inside the battery during the process.

[0151] Specifically, the "whether it is broken" item in the last column of Table 2 refers to whether the positive electrode 110 of the outermost bend A2 of the cell assembly 100 is broken. It should be understood that in reality, the breakage may occur not only at the outermost bend A2 of the positive electrode 110, but also at the bends A2 of other layers of the positive electrode 110. The following table and analysis will only use the example of whether the positive electrode 110 of the outermost bend A2 is broken to illustrate this point.

[0152] Table 1

[0153] Table 2

[0154] According to the experimental results in Tables 1 and 2, when the first composite region Q1, the third composite region Q3, and the second composite region Q2 are provided in the cell assembly 100, the positive electrode 110 in the cell assembly 100 does not break, and the capacity retention rate is also high, as specifically seen in Examples 1 to 8. Examples 7 and 8 not only have the aforementioned composite regions, but also have a functional structure region, i.e., an opening 116a or a groove 116b, in the portion of the positive electrode 110 located at the bend A2. According to the data in the tables, the positive electrode 110 in Examples 7 and 8 did not break, and the capacity retention rate of the battery in these two examples is the highest among all the above examples.

[0155] Conversely, referring to Comparative Examples 1 and 2, Comparative Example 1 did not have any composite region in its cell assembly, while Comparative Example 2 only had a first composite region and a third composite region, without a second composite region. Specifically, in Comparative Example 1, the positive electrode sheet at the outermost bent portion of the cell assembly broke after 500 cycles, and in Comparative Example 2, the positive electrode sheet at the outermost bent portion of the cell assembly broke after 530 cycles. In both embodiments, the positive electrode sheet not only broke, but the battery capacity retention rate was also low. Therefore, providing the aforementioned composite region, especially the second composite region Q2, in the cell assembly 100 can effectively prevent the positive electrode sheet 110 from breaking and increase the battery capacity retention rate.

[0156] Secondly, this application proposes a battery that includes the cell assembly 100 of the first aspect.

[0157] Therefore, the battery of the second aspect possesses at least all the technical effects of the cell assembly 100 of the first aspect, and its specific technical effects will not be elaborated here. Furthermore, the embodiments of this application only illustrate the structure of the battery of the second aspect related to the improvements of this application, but do not mean that it does not possess other structures. For example, the battery also includes a casing and a cover plate, etc., and other structures will not be described in detail here.

[0158] In particular, the term "and / or" in this application should be understood as follows:

[0159] In the first case, the term “and / or” located between the first subject and the second subject includes any of the following meanings: (1) only the first subject; (2) only the second subject; and (3) both the first subject and the second subject.

[0160] In the second case, the term "and / or" between the last two of three or more subjects means including at least any one of the subjects. For example, "first subject, second subject and / or third subject" has the same meaning as "first subject and / or second subject and / or third subject", specifically including the following combinations: (1) only the first subject; (2) only the second subject; (3) only the third subject; (4) the first subject and the second subject and no third subject; (5) the first subject and the third subject and no second subject; (6) the second subject and the third subject and no first subject; and (7) the first subject, the second subject and the third subject.

[0161] In addition, the character " / " in this application generally indicates that the objects before and after it are in an "or" relationship.

[0162] Finally, although the embodiments of this application have been described above in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the concept of this application, and such modifications and variations all fall within the scope of protection of this application.

Claims

1. A battery cell assembly, characterized in that, The battery cell assembly includes a first separator, a negative electrode, a second separator, and a positive electrode arranged in sequence and wound together. The battery cell assembly has a straight portion and a curved portion. The positive electrode has a first straight section and a first curved section located in the straight portion and the curved portion, respectively. The negative electrode has a second straight section and a second curved section located in the straight portion and the curved portion, respectively. Along the length of the negative electrode sheet, the first diaphragm and the second diaphragm are respectively bonded to the negative electrode sheet to form a first composite region; Along the length of the positive electrode sheet, the positive electrode sheet and the second separator are bonded together in at least a partial area to form at least one bonding portion. At the bonding portion, the positive electrode sheet and the second separator, along with the negative electrode sheet and the first separator corresponding to the bonding portion, together form a second composite region; and The second composite region is located in the straight portion and along the length direction of the negative electrode sheet, and the size of the second composite region is smaller than the size of the first composite region.

2. The battery cell assembly according to claim 1, characterized in that, In the curved portion, along the width direction of the battery cell assembly, the distance between the two points where the curvature of the innermost layer of the battery cell assembly is the maximum and the curvature of the outermost layer of the battery cell assembly is the maximum is R. Along the thickness direction of the battery cell assembly, the thickness of the battery cell assembly is H, satisfying 1.05≤R:(H / 2)≤1.

3.

3. The cell assembly according to claim 1 or 2, characterized in that, Along the length direction and / or width direction of the negative electrode sheet, the first separator and the second separator extend beyond the negative electrode sheet, and the portions of the first separator and the second separator extending beyond the negative electrode sheet along the length direction and / or width direction of the negative electrode sheet are bonded together to form a third composite region.

4. The cell assembly according to claim 3, characterized in that, The bonding strength between the first or second separator in the first composite region and the negative electrode is F1, and the bonding strength between the positive electrode in the second composite region and the second separator is F2, wherein F2 ≥ F1.

5. The cell assembly according to claim 4, characterized in that, The bonding strength between the first diaphragm and the second diaphragm in the third composite region is F3, and F1 and F3 satisfy the condition that F3 ≥ F1.

6. The cell assembly according to claim 5, characterized in that, 1N / m≤F3≤15N / m.

7. The cell assembly according to any one of claims 4 to 6, characterized in that, 1N / m≤F1≤15N / m.

8. The cell assembly according to any one of claims 4 to 7, characterized in that, 1.5N / m≤F2≤30N / m.

9. The cell assembly according to any one of claims 1 to 8, characterized in that, In the straight section, a second composite region is provided on at least the portion from the innermost layer of the cell assembly to the fourth outermost layer from the end of the cell assembly.

10. The cell assembly according to claim 9, characterized in that, In the straight section, along the thickness direction of the cell assembly, the projected portions of the second composite region on two adjacent layers of the cell assembly overlap.

11. The cell assembly according to claim 9 or 10, characterized in that, The area of ​​a single second composite region is S; and In the straight section, the projections of the second composite regions on two adjacent layers of the cell assembly onto the negative electrode sheet along the thickness direction of the cell assembly at least partially overlap, and have an overlapping area of ​​S1, where S1 satisfies: 0.2≤S1 / S≤1.

12. The cell assembly according to claim 9, characterized in that, Along the thickness direction of the battery cell assembly, in the straight section, the projections of the second composite region on two adjacent layers of the battery cell assembly do not overlap.

13. The cell assembly according to any one of claims 9 to 12, characterized in that, Along the winding direction of the battery cell assembly, the size of two adjacent second composite regions increases sequentially.

14. The cell assembly according to any one of claims 9 to 13, characterized in that, All of the second composite regions are of equal size.

15. The cell assembly according to any one of claims 1 to 14, characterized in that, In the innermost layer, the positive electrode has a starting end, a first straight section, and a first curved section connected to the first straight section. The starting end of the positive electrode is the starting position of the first straight section, and the first straight section has a first second composite region. as well as Along the winding direction of the battery cell assembly, the starting end of the first second composite region is flush with the starting end of the positive electrode sheet.

16. The cell assembly according to any one of claims 1 to 14, characterized in that, In the innermost layer, the positive electrode has a starting end, a first straight section, and a first curved section connected to the first straight section. The starting end of the positive electrode is the starting position of the first straight section, and the first straight section has a first second composite region. as well as The distance between the starting end of the first second composite region and the starting end of the positive electrode is D, and D satisfies: 0mm < D ≤ 3mm.

17. The cell assembly according to claim 15 or 16, characterized in that, Along the winding direction of the battery cell assembly, the farthest end of the first second composite region is located at the junction of the first straight section and the first curved section.

18. The cell assembly according to any one of claims 1 to 17, characterized in that, The battery cell assembly further includes a positive electrode tab connected to the positive electrode plate and a negative electrode tab connected to the negative electrode plate, and both the positive electrode tab and the negative electrode tab are disposed on the straight portion of the battery cell assembly; and The second composite region does not overlap with the positive electrode tab's orthogonal projection in the thickness direction of the cell assembly.

19. The cell assembly according to claim 18, characterized in that, The positive electrode sheet has a positive active coating, the positive active coating has a functional structure region, at least a portion of the functional structure region is located at the first bent end, the areal density of the positive active coating in the functional structure region is ρ1, the areal density of the positive active coating in the first straight section is ρ2, and ρ1 < ρ2.

20. The cell assembly according to claim 19, characterized in that, Along the winding direction of the battery cell assembly, the functional structure area is provided on at least two of the first curved segments connected to the first straight segment having the positive electrode tab.

21. The cell assembly according to claim 20, characterized in that, At least part of the functional structure area is located in the first curved section and a second composite area is located in the first straight section in the same layer of the cell assembly.

22. The cell assembly according to claim 21, characterized in that, The portion of the positive electrode plate having the aforementioned functional structure region is provided with a recess; and The recess has at least two holes, and the distance between two adjacent holes is m, where m satisfies: 0mm≤m≤5mm.

23. The cell assembly according to claim 22, characterized in that, The depth of the hole is h, where 2μm≤h≤80μm.

24. The cell assembly according to claim 22 or 23, characterized in that, The diameter of the hole is d, where 10μm≤d≤200μm.

25. The cell assembly according to any one of claims 22 to 24, characterized in that, The recess has at least one groove, and the dimension of the groove along the length direction of the positive electrode is L3, where L3 satisfies: 2mm≤L3≤12mm.

26. The cell assembly according to any one of claims 22 to 25, characterized in that, Along the length of the positive electrode sheet, the size L1 of a single second composite region and the depth h of the hole in the recess satisfy: 1.5≤L1 / h≤20000.

27. The cell assembly according to any one of claims 22 to 26, characterized in that, Along the length of the positive electrode sheet, the size L1 of a single second composite region and the size L3 of the groove in the recess satisfy: 0.3≤L1 / L3≤20.

28. The cell assembly according to any one of claims 1 to 27, characterized in that, In the battery cell assembly, the thickness of the negative electrode sheet is G, the thickness of the first separator is g1, and the thickness of the second separator is g2. In the bent portion of the battery cell assembly, the distance between two adjacent positive electrode sheets is the positive electrode sheet gap. The size of at least one positive electrode sheet gap in the bent section is H1, and H1 satisfies: G+g1+g2+5μm≤H1≤G+g1+g2+30μm.

29. The cell assembly according to any one of claims 1 to 28, characterized in that, The second composite area and the negative electrode tab disposed on the second straight section where the second composite area is located do not overlap in the orthogonal projection of the cell assembly in the thickness direction.

30. The cell assembly according to any one of claims 1 to 29, characterized in that, The first straight section where the positive electrode tab is located has a second composite region. Along the width direction of the cell assembly, the distance between the end of the second composite region near the positive electrode tab and the end of the positive electrode tab near the second composite region is d1, where d1 ≥ 0.5 mm.

31. The cell assembly according to any one of claims 1 to 30, characterized in that, The second straight section where the negative electrode tab is located has a second composite region. Along the width direction of the cell assembly, the distance between the end of the second composite region near the negative electrode tab and the end of the negative electrode tab near the second composite region is d2, where d2 ≥ 0.5 mm.

32. The cell assembly according to any one of claims 1 to 31, characterized in that, The battery cell assembly further includes a positive electrode tab connected to the positive electrode plate, wherein the adhesion strength between the positive electrode tab and the second separator is F; and The bonding strength between the positive electrode and the second separator in the second composite region is F2, which satisfies F2≥F.

33. The cell assembly according to any one of claims 1 to 31, characterized in that, Along the length of the negative electrode sheet, the distance between the end of the second composite region and the edge of the nearest second curved segment is D1, where D1 ≥ 0.5 mm.

34. The cell assembly according to any one of claims 1 to 33, characterized in that, Along the length of the negative electrode sheet, the size of a single second straight segment is L, and the size of a single second composite region is L1, and L1 and L satisfy: 3mm≤L1≤L.

35. The cell assembly according to any one of claims 1 to 34, characterized in that, Along the width direction of the negative electrode, the size of the second composite region is W1, the size of the positive electrode is W, and W and W1 satisfy: 5mm≤W1≤W.

36. A battery, characterized in that, Includes the battery cell assembly as described in any one of claims 1 to 35.

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