Battery cell assembly and battery comprising same

Abstract

The invention relates to the technical field of batteries, and particularly provides a battery cell assembly and a battery comprising the same. The battery cell assembly comprises a first diaphragm, a negative plate, a second diaphragm and a positive plate which are sequentially stacked and wound; the first diaphragm and the second diaphragm are respectively bonded with the negative plate to form a first composite region; at least partial areas of the positive plate and the second diaphragm are mutually bonded to form at least one second composite area; the length of the second composite area is smaller than that of the first composite area. In the application, the positive plate, the negative plate and the diaphragm are pressed together, so that the winding core is prevented from being wound tightly due to respective tension during winding, the first composite area can reinforce the adhesion of the diaphragm and the negative plate, so that the diaphragm and the negative plate do not slide relatively, and the second composite area can fix the positive plate at a set position to form a compensation area; a certain gap is reserved between the positive plate and the negative plate in the non-composite area, so that the pole piece gap in the circular arc area of the roll core is increased, a space is reserved for cyclic expansion of the battery, and the problem of cyclic expansion deformation of the battery is effectively solved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and specifically proposes a battery cell assembly and a battery comprising the same. Background Art

[0002] With the development of lithium-ion battery technology, the market has put forward higher requirements on the fast charging capability and energy density of batteries. In particular, the improvement of battery energy density has reached a bottleneck. The more effective method at present is to use new materials, such as high-capacity silicon-based materials for the negative electrode. However, during the use of wound batteries, the volume of silicon-based negative electrode materials expands greatly during circulation, which can easily squeeze the positive electrode sheet and cause the curved section of the positive electrode sheet to break. Summary of the invention

[0003] The purpose of this application is to solve at least part of the technical problems mentioned above, and this purpose is achieved through the following technical solutions:

[0004] In the first aspect, the present application proposes a battery cell assembly, which includes a first separator, a negative electrode sheet, a second separator and a positive electrode sheet stacked and wound in sequence, and the battery cell assembly has a straight section and a curved section; along the length direction of the negative electrode sheet, the first separator and the second separator are respectively bonded to the negative electrode sheet to form a first composite area; along the length direction of the positive electrode sheet, at least part of the positive electrode sheet and the second separator are bonded to each other to form at least one bonding portion, and the positive electrode sheet and the second separator at the bonding portion and the negative electrode sheet and the first separator corresponding to the bonding portion together form a second composite area; the second composite area is located in the straight section, and along the length direction of the negative electrode sheet, the size of the second composite area is smaller than the size of the first composite area.

[0005] In some embodiments, along the width direction of the battery cell assembly, the distance between two points where the innermost layer of the curved section of the battery cell assembly has the maximum curvature and where the outermost layer of the curved section of the battery cell assembly has the maximum curvature is R, and 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.

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

[0007] In some embodiments, at least one second composite region is provided on the straight section of the innermost circle layer of the battery cell assembly to the straight section of the fourth outermost circle layer of the battery cell assembly.

[0008] In some embodiments, along the thickness direction of the battery cell assembly, the projections of the second composite areas on the straight sections of two adjacent layers of the battery cell assembly do not overlap; or, along the thickness direction of the battery cell assembly, the projections of the second composite areas on the straight sections of two adjacent layers of the battery cell assembly partially overlap.

[0009] In some embodiments, reference Figure 4 Along the winding direction of the battery cell assembly, the sizes of two adjacent second composite regions increase successively, or the sizes of all the second composite regions are equal.

[0010] In some embodiments, the positive electrode sheet has a positive electrode sheet starting end located at the innermost circle layer of the battery cell assembly, the innermost circle layer has a first positive electrode straight section and a first positive electrode curved section connected to the first positive electrode straight section, the positive electrode sheet starting end is the starting position of the first positive electrode straight section, and the first positive electrode straight section has a first second composite area; along the winding direction of the battery cell assembly, the starting end of the first second composite area is flush with the starting end of the positive electrode sheet; or, the distance between the starting end of the first second composite area and the starting end of the positive electrode sheet is D, and satisfies 0mm<D≤3mm; and / or, along the winding direction of the battery cell assembly, the end end of the first second composite area is located at the junction of the first positive straight section and the first positive curved section.

[0011] In some embodiments, the area of ​​a single second composite region is S; the projections of the second composite regions on the straight sections of two adjacent layers of the battery cell assembly on the negative electrode sheet along the thickness direction of the battery cell assembly at least partially overlap, and the overlapping area is S1, satisfying 0.2≤S1 / S≤1.

[0012] In some embodiments, the battery cell assembly also includes a positive electrode ear connected to the positive electrode sheet and a negative electrode ear connected to the negative electrode sheet, and both the positive electrode ear and the negative electrode ear are arranged on the straight section of the battery cell assembly; the orthographic projections of the second composite region and the positive electrode ear arranged on the straight section where the second composite region is located in the thickness direction of the battery cell assembly do not overlap; and / or the orthographic projections of the second composite region and the negative electrode ear arranged on the straight section where the second composite region is located in the thickness direction of the battery cell assembly do not overlap.

[0013] In some embodiments, the straight section where the positive electrode ear is located has a second composite area, and along the width direction of the battery cell assembly, the distance between one end of the second composite area close to the positive electrode ear and one end of the positive electrode ear close to the second composite area is d1, and d1≥0.5mm is satisfied; and / or, the straight section where the negative electrode ear is located has a second composite area, and along the width direction of the battery cell assembly, the distance between one end of the second composite area close to the negative electrode ear and one end of the negative electrode ear close to the second composite area is d2, and d2≥0.5mm is satisfied.

[0014] In some embodiments, the battery cell assembly further includes a positive electrode ear connected to the positive electrode sheet, and the bonding strength between the positive electrode ear and the second separator is F; the bonding strength between the positive electrode sheet and the second separator in the second composite region is F2, satisfying F2≥F.

[0015] 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 closest curved segment is D1, and D1≥0.5 mm is satisfied.

[0016] In some embodiments, along the length direction of the negative electrode sheet, the size of a single straight section is L, the size of a single second composite area is L1, and 3mm≤L1≤L is satisfied; and / or, along the width direction of the negative electrode sheet, the size of the second composite area is W1, the size of the positive electrode sheet is W, and 5mm≤W1≤W is satisfied.

[0017] In some embodiments, along the length direction of the negative electrode sheet, the size of the third composite area near the leading end or the tail end of the negative electrode sheet is L2, and satisfies 0.5mm≤L2≤2L; and / or, along the width direction of the negative electrode sheet, third composite areas are respectively provided on both sides of the negative electrode sheet, and the size of the third composite area on one side along the width direction of the negative electrode sheet is W2, and satisfies 0.2mm≤W2≤2mm.

[0018] In some embodiments, the bonding strength between the first separator or the second separator in the first composite region and the negative electrode sheet is F1, the bonding strength between the positive electrode sheet and the second separator in the second composite region is F2, and the bonding strength between the first separator and the second separator in the third composite region is F3, wherein F2≥F1 is satisfied between F1 and F2; and / or F3≥F1 is satisfied between F1 and F3; and / or 1N / m≤F1≤15N / m; and / or 1.5N / m≤F2≤30N / m; and / or 1N / m≤F3≤15N / m.

[0019] In some embodiments, the positive electrode sheet has a positive electrode active coating, the positive electrode active coating has a functional structure area, at least part of the functional structure area is located in the curved section, the surface density of the positive electrode active coating in the functional structure area is ρ1, the surface density of the positive electrode active coating in the straight section is ρ2, and ρ1<ρ2 is satisfied.

[0020] In some embodiments, along the winding direction of the battery cell assembly, at least two curved sections connected to the straight section with the positive electrode tab are provided with a functional structure area.

[0021] In some embodiments, the curved section where at least part of the functional structure area is located and the straight section where the second composite area is located are located in the same circle layer of the battery core component.

[0022] In some embodiments, the positive electrode sheet in the functional structure area is provided with a recess; the recess has at least two holes, the depth of the hole is h, the diameter of the hole is d, the distance between two adjacent holes is m, and 0mm≤m≤5mm is satisfied; and / or, 2μm≤h≤80μm; and / or, 10μm≤d≤200μm; and / or, the recess has at least one groove, and the dimension of the groove along the length direction of the positive electrode sheet is L3, satisfying: 2mm≤L3≤12mm; and / or, the dimension of the groove along the width direction of the positive electrode sheet is greater than or equal to 2mm and less than or equal to the width of the positive electrode sheet; and / or, the groove along the thickness direction 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.

[0023] In some embodiments, along the length direction of the positive electrode sheet, the size L1 of a single second composite area and the depth h of the hole in the recess satisfy: 1.5≤L1 / h≤20000; and / or, along the length direction of the positive electrode sheet, the size L1 of a single second composite area and the size L3 of the groove in the recess satisfy 0.3≤L1 / L3≤20.

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

[0025] In a second aspect, the present application proposes a battery, which includes the battery cell assembly of the first aspect.

[0026] The technical solution proposed in this application has at least the following technical effects:

[0027] In the present application, the positive electrode sheet is pressed together with the negative electrode sheet and the diaphragm to avoid the winding core being wound very tightly due to the respective tension during winding, thereby increasing the gap between the positive and negative electrode sheets. Specifically, the negative electrode sheet forms a first composite area with the first diaphragm and the second diaphragm, which can strengthen the bonding between the diaphragm and the negative electrode sheet to form a composite sheet with higher strength, which is conducive to the positive electrode sheet and the composite sheet forming a second composite area without relative sliding between the electrode sheet and the diaphragm, and the second composite area can fix the positive electrode sheet at a set position on the negative electrode sheet, so that the positive electrode sheet forms a compensation area between two adjacent second composite areas, that is, a certain gap is left between the positive electrode sheet and the negative electrode sheet in the uncomposite area, thereby increasing the electrode sheet gap in the arc area of ​​the winding core, reserving space for battery cycle expansion, and effectively solving the problem of battery cycle expansion and deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to better combine the contents shown in the drawings of the specification with the contents described in the specific implementation methods, the drawings of the specification are briefly introduced below. It can be understood that the drawings of the specification mentioned below only schematically show some embodiments of the relevant technical solutions and the technical solutions of this application. Without paying creative labor, those skilled in the art can also make drawings showing other embodiments.

[0029] Specifically, the annotations of the drawings in the specification are as follows:

[0030] Figure 1 It is a first cross-sectional schematic diagram of the battery cell assembly described in some embodiments of the present application in a stacked state along the length direction of the negative electrode sheet;

[0031] Figure 2 A schematic cross-sectional view of a battery cell assembly in some embodiments of the present application in a stacked state along the width direction of a negative electrode sheet;

[0032] Figure 3 A second cross-sectional schematic diagram of the battery cell assembly described in some embodiments of the present application in a stacked state along the length direction of the negative electrode sheet;

[0033] Figure 4 It is a schematic structural diagram of the first battery cell assembly in a wound state described in some embodiments of the present application;

[0034] Figure 5 It is a schematic structural diagram of the second battery cell assembly in a wound state described in some embodiments of the present application;

[0035] Figure 6 It is a schematic structural diagram of the third battery cell assembly in a wound state described in some embodiments of the present application;

[0036] Figure 7 It is a schematic diagram of the structure of the battery cell assembly described in the comparative example in a wound state.

[0037] Specifically, the annotations of the accompanying drawings in the specification are as follows:

[0038] 100, battery cell assembly; 110, positive electrode sheet; 111, positive electrode current collector; 112, positive electrode active coating; 120, negative electrode sheet; 121, negative electrode current collector; 122, negative electrode active coating; 130, first separator; 140, second separator; 150, positive electrode ear; 160, negative electrode ear; Q1, first composite area; Q2, second composite area; Q3, third composite area; Q4, functional structure area; A1, straight section; A2, curved section; B, compensation area; X, width direction of battery cell assembly; Y, length direction of battery cell assembly; Z, thickness direction of battery cell assembly. DETAILED DESCRIPTION

[0039] In order to make the contents of the embodiments of the present application clearer, the following description will be made in conjunction with the accompanying drawings. It can be understood that the contents mentioned below are only some embodiments of the present application, and all embodiments are listed in detail. Therefore, without paying creative work, other embodiments obtained based on the following embodiments fall within the protection scope of the present application.

[0040] It should be understood that the terms used herein are only for the purpose of describing specific embodiments and are not intended to strictly limit the technical solutions unless the context clearly indicates otherwise. For example, the use of "a", "an" and "the" to modify a feature does not exclude that the feature may also be plural in other embodiments.

[0041] It should be understood that the terms "include", "comprises", and "have" are open ended, indicating the presence of the stated features, but not excluding the possibility that the embodiment may have other features. Similarly, the use of the terms first, second, etc. in the text to describe multiple features only means to distinguish one feature from another, and unless the context clearly indicates otherwise, such terms do not imply an order or sequence.

[0042] It should be understood that, unless the context clearly indicates otherwise, the terms "dispose", "connect", and "install" should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or integrally connected; they can be directly connected or indirectly connected through a medium. For those skilled in the art, the specific meanings of the above terms in the text can be understood according to the specific circumstances.

[0043] In addition, for the convenience of description, the text will use terms of spatial relative relationships to illustrate the position of one feature relative to another feature, for example, "inside", "outside", "end", "side", "top", "middle", "bottom", "high", "low", "axial", "circumferential", "radial", "horizontal", "vertical", "first direction", "second direction", etc. It can be understood that the spatial relative relationship between two features should include other specific situations in addition to those shown in the drawings of the specification.

[0044] The background technology of this application is further described below.

[0045] With the development of lithium-ion battery technology, the market has put forward higher requirements for the fast charging capability and energy density of batteries, especially the current improvement of battery energy density has reached a bottleneck. The more effective method at present is to use new materials. For example, the negative electrode sheet uses high-capacity silicon-based materials, which can store a large amount of lithium ions, thereby providing higher energy density. However, the silicon-based material on the negative electrode sheet will undergo a large volume expansion when the lithium is deintercalated during the battery charging and discharging process, so that the negative electrode sheet will cause compression on the positive electrode sheet. In the wound battery cell, the different forces inside and outside the curved section of the battery cell are prone to stress concentration. After the negative electrode sheet expands, the stress concentration phenomenon of the curved section will be further aggravated. Furthermore, the positive electrode sheet of the inner circle layer of the battery cell is coated with a positive electrode active coating on both sides along its thickness direction to form a double-sided area, and the positive electrode sheet of the outer circle layer of the battery cell is coated with a positive electrode active coating on one side along its thickness direction to form a single-sided area. It can be understood that the structural strength of the single-sided area is less than that of the double-sided area. Due to the characteristics of the winding structure, the curved section has a greater outward expansion and compression force than the straight section. The part of the wound cell close to the outer ring is the single-sided area of ​​the positive electrode sheet, and due to the characteristics of the winding structure, the closer to the outer ring of the wound cell, the more uneven the force on the curved section, the greater the expansion force from the inside to the outside, and the smaller the restraining force from the outside to the inside. Therefore, the curved section in the single-sided area of ​​the positive electrode sheet is more likely to break due to the compression of the negative electrode sheet, and the positive electrode sheet in the single-sided area of ​​the outer ring has no restraining force, which can easily lead to the positive electrode sheet in the curved section, especially the curved section in the single-sided area of ​​the outer ring, being very easy to break after the cell is cycled, which ultimately affects the cycle life and performance of the battery.

[0046] In response to the above problems, the existing solution is to perform local processing on the positive electrode sheet of the battery's curved section, such as setting multiple micropores and recessed areas to reduce the positive electrode lithium content in this area, reduce the amount of lithium embedded in the corresponding negative electrode sheet coating, and thus slow down the volume expansion of the negative electrode sheet coating. However, due to the large expansion of silicon-based negative electrode materials, this technology still cannot completely solve the problem of battery deformation or even electrode sheet breakage caused by volume expansion when the battery is cycled to the later stage.

[0047] 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 lithium-ion batteries with high reliability and high energy density.

[0048] The embodiments of the present application are described below in conjunction with the accompanying drawings.

[0049] First, refer to Figure 1 and Figure 2The present application proposes a battery cell assembly 100, which includes a first separator 130, a negative electrode sheet 120, a second separator 140 and a positive electrode sheet 110 which are sequentially stacked and wound, and the battery cell assembly 100 has a straight section A1 and a curved section A2; along the length direction of the negative electrode sheet 120, the first separator 130 and the second separator 140 are respectively bonded to the negative electrode sheet 120 to form a first composite area Q1; along the length direction of the positive electrode sheet 110, at least part of the positive electrode sheet 110 and the second separator 140 are bonded to each other to form at least one bonding portion, and the positive electrode sheet 110 and the second separator 140 at the bonding portion and the negative electrode sheet 120 and the first separator 130 corresponding to the bonding portion jointly form a second composite area Q2; the second composite area Q2 is located in the straight section A1, and along the length direction of the negative electrode sheet 120, the size of the second composite area Q2 is smaller than the size of the first composite area Q1.

[0050] In the above embodiment, referring to Figure 3 , the positive electrode sheet 110 is pressed together with the negative electrode sheet 120 and the separator to avoid the winding core being wound too tightly due to the respective tensions during winding, thereby increasing the gap between the positive and negative electrode sheets 120. Specifically, the negative electrode sheet 120 and the first separator 130 and the second separator 140 form a first composite area Q1, which can strengthen the bonding between the separator and the negative electrode sheet 120, forming a composite sheet with higher strength, which is conducive to the positive electrode sheet 110 and the composite sheet forming the second composite area Q2 without relative sliding between the electrode sheet and the separator, and the second composite area Q2 can fix the positive electrode sheet 110 at a set position on the negative electrode sheet 120, so that the positive electrode sheet 110 forms a compensation area B between two adjacent second composite areas Q2, that is, a certain gap is left between the positive electrode sheet 110 and the negative electrode sheet 120 in the uncomposite area, so that the positive electrode sheet 110 has a compensation length, thereby increasing the electrode sheet gap in the winding core bending section A2, reserving space for battery cycle expansion, and effectively solving the problem of battery cycle expansion and deformation.

[0051] It should be noted that Figure 1 It is only used to show the relative position relationship of each part, and the compensation area B is not shown. Figure 3 The bulge of compensation area B can be clearly seen.

[0052] In addition, in the present application, the extending direction of the stacked positive electrode sheet 110 is consistent with that of the negative electrode sheet 120, which is the length direction thereof; and after being wound to form the battery cell assembly 100, the battery cell assembly 100 has a straight section A1 and a curved section A2, wherein the length direction of the straight section A1 is consistent with the length direction of the negative electrode sheet 120, which is also the width direction X of the battery cell assembly, and the length direction Y of the battery cell assembly is the extending direction of the positive electrode ear 150 or the negative electrode ear 160 on the straight section A1, which is also the width direction of the negative electrode sheet 120. Therefore, it can be understood that the battery cell assembly 100 has a length direction, a width direction, and a thickness direction that are perpendicular to each other, the thickness direction Z of the battery cell assembly is consistent with the thickness direction of the negative electrode sheet 120 and the positive electrode sheet 110, the width direction X of the battery cell assembly is consistent with the length direction of the negative electrode sheet 120 and the positive electrode sheet 110, and the length direction Y of the battery cell assembly is consistent with the width direction of the negative electrode and the positive electrode sheet 110.

[0053] In some embodiments, reference Figure 4 , along the width direction X of the battery cell assembly, the distance between the two points where the innermost curvature of the curved section A2 of the battery cell assembly 100 is the maximum and where the outermost curvature of the curved section A2 of the battery cell assembly 100 is the maximum is R, and along the thickness direction Z of the battery cell assembly, the thickness of the battery cell assembly 100 is H, satisfying 1.05≤R:(H / 2)≤1.3.

[0054] In the above embodiment, the distance between the two points where the curvature of the innermost layer and the outermost layer of the curved section A2 of the battery cell assembly 100 is the largest can be understood as the distance between the two points where the curvature of the inner diaphragm of the innermost layer of the stacked body of the battery cell assembly 100 and the outer positive electrode sheet 110 of the outermost layer of the stacked body is the largest in the curved section A2. H / 2 can be understood as the distance between the diaphragm at the winding center of the battery cell and the outermost electrode sheet of the battery cell along the thickness direction of the battery cell. It should be further explained that there are curved sections A2 on both the left and right sides of the width direction of the battery cell. The R values ​​of the curved sections A2 on the left and right sides of the battery cell can be the same or different. When the innermost curved sections A2 on the left and right sides of the battery cell are When the distance R between the two points at the maximum layer curvature and the maximum outermost layer curvature of the curved section A2 of the battery cell assembly 100 is different, H / 2 of half the battery cell thickness corresponding to the left curved section A2 and the right curved section A2 is also different. In a specific embodiment, if R is the distance between the two points at the maximum innermost layer curvature of the left curved section A2 of the battery cell and the maximum outermost layer curvature of the curved section A2 of the battery cell assembly 100, then H / 2 corresponds to the distance along the battery cell thickness direction between the outermost pole piece of the battery cell in the straight section A1 area close to the curved section A2 on the left side of the battery cell and connected to the curved section A2 on the left side of the battery cell and the diaphragm of the straight section A1 in the winding center of the battery cell.

[0055] It can be understood that if the value of R:(H / 2) is too small, it means that the gap between the positive electrode sheet 110 and the negative electrode sheet 120 in the curved section A2 is too small, and the problem of cyclic expansion of the negative electrode sheet 120 cannot be effectively addressed; and if the value of R:(H / 2) is too large, it means that the gap between the positive electrode sheet 110 and the negative electrode sheet 120 in the curved section A2 is too large, which will cause the lithium ions in the electrolyte to be free and reach the negative electrode sheet 120 more slowly, and the transmission path for lithium ion deintercalation is longer, the transmission speed is slow, and even lithium plating may be caused, resulting in a reduction in battery capacity. Therefore, the value of R:(H / 2) should be moderate. For example, R:(H / 2) can be any one of 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, 1.30, or the range between any two of them.

[0056] In some embodiments, the first separator 130 and the second separator 140 extend beyond the negative electrode sheet 120 along the length direction and / or the width direction of the negative electrode sheet 120, and the portions of the first separator 130 and the second separator 140 that extend beyond the negative electrode sheet 120 along the length direction and / or the width direction of the negative electrode sheet 120 are bonded to each other to form a third composite region Q3.

[0057] It should be understood that the first diaphragm 130 and the second diaphragm 140 are equivalent to the two sides of the packaging bag, and the negative electrode sheet 120 is packaged therein. The excess edge portions of the first diaphragm 130 and the second diaphragm 140 compared to the negative electrode sheet 120 constitute the third composite area Q3, and the third composite area Q3 further increases the bonding strength between the diaphragm and the negative electrode sheet 120.

[0058] In some embodiments, at least one second composite region Q2 is provided on the straight segment A1 of the innermost circle layer of the battery cell assembly 100 to the straight segment A1 of the fourth outer circle layer from the end of the battery cell assembly 100 .

[0059] It should be noted that the starting layer or the innermost layer of the winding core must be provided with a second composite area Q2, and the four outermost layers may not have a composite area; in addition, in some embodiments, the outermost layer, the second outermost layer and / or the third outermost layer of the battery cell assembly 100 may also be provided with a second composite area Q2. It can be understood that in the present application, the winding direction of the battery cell assembly 100 refers to the direction of winding from the inside of the battery cell to the outside, and can also be understood as the length direction of the positive electrode sheet 110 and / or the negative electrode sheet 120 (that is, the extension direction of the positive electrode sheet 110 and the negative electrode sheet 120 after winding).

[0060] Specifically, along the winding direction of the battery cell assembly 100, the second outer layer is connected to the outermost layer, the third outer layer from the end is connected to the inner side of the second outer layer, and the fourth outer layer from the end is connected to the inner side of the third outer layer from the end.

[0061] In addition, the number of the second composite region Q2 on the straight segment A1 is at least one, that is, a plurality of second composite regions Q2 may be spaced apart on one straight segment A1.

[0062] In particular, the above scheme is only a partial implementation method. If one or several straight sections A1 from the innermost circle to the fourth outer circle are not provided with the second composite area Q2, it should also fall within the protection scope of the present application.

[0063] In some embodiments, reference Figure 6 , along the thickness direction Z of the battery cell assembly, the projections of the second composite area Q2 on the straight sections A1 of two adjacent layers of the battery cell assembly 100 do not overlap; or, referring to Figure 4 and Figure 5 , along the thickness direction Z of the cell assembly, the projections of the second composite area Q2 on the straight sections A1 of two adjacent layers of the cell assembly 100 partially overlap. In some embodiments, the area of ​​a single second composite area Q2 is S; the projections of the second composite area Q2 on the straight sections A1 of two adjacent layers of the cell assembly 100 along the thickness direction Z of the cell assembly on the negative electrode sheet 120 at least partially overlap, and the overlapping area is S1, satisfying 0.2≤S1 / S≤1.

[0064] It should be noted that the projection here refers to the orthographic projection along the thickness direction of the battery cell assembly 100, or it can be said to be the projection on the projection surface of the negative electrode sheet 120 along the thickness direction of the battery cell assembly 100; the projections described in this application are all orthographic projections.

[0065] In summary, the projections of the second composite areas Q2 on the straight segments A1 of two adjacent ring layers may not overlap, partially overlap, or completely overlap. The above solutions are better than not setting the second composite area Q2 and are also within the protection scope of this application.

[0066] In some embodiments, reference Figure 4 , along the winding direction of the battery cell assembly 100, the sizes of the two adjacent second composite areas Q2 increase successively, or refer to Figure 5 , the sizes of all second composite regions Q2 are equal.

[0067] In the above embodiment, the lengths of all the second composite areas Q2 gradually increase, or the lengths of all the second composite areas Q2 are the same. It should be explained that during the winding process of the core, the length of the curved section A2 from the inside to the outside gradually increases. In order to match the length of the curved section A2 and to ensure that the distance between two adjacent second composite areas Q2 is consistent as much as possible, and considering the difficulty of the process operation, the length of the second composite area Q2 should be gradually increased as much as possible.

[0068] In particular, the present application should also protect the following schemes: the lengths of all second composite areas Q2 tend to increase as a whole, wherein the lengths of some two adjacent second composite areas Q2 are the same; and the length of the latter second composite area Q2 is slightly smaller than the length of the former second composite area Q2 along the winding direction of the core.

[0069] In some embodiments, the positive electrode sheet 110 has a positive electrode sheet starting end located at the innermost circle layer of the battery cell assembly 100, the innermost circle layer has a first positive straight section and a first positive curved section connected to the first positive straight section, the positive electrode sheet starting end is the starting position of the first positive straight section, and the first positive straight section has a first second composite area Q2; along the winding direction of the battery cell assembly 100, the starting end of the first second composite area Q2 is flush with the starting end of the positive electrode sheet; or, the distance between the starting end of the first second composite area Q2 and the starting end of the positive electrode sheet is D, and satisfies 0mm<D≤3mm; and / or, along the winding direction of the battery cell assembly 100, the end end of the first second composite area Q2 is located at the junction of the first positive straight section and the first positive curved section.

[0070] In the above embodiment, the first second composite area Q2 starts at the starting end of the positive electrode sheet and ends at the junction of the first straight section of the positive electrode sheet 110 and the first bending area; that is, the head of the positive electrode sheet 110 must be composited with the second diaphragm 140, on the one hand, to prevent the head of the positive electrode sheet 110 from being easily warped and folded when the tape passes through the roller if it is not composited, and on the other hand, if the positive electrode head is not fixed and composited, then when winding is performed later, the position of other second composite areas Q2 will fluctuate or the second composite areas Q2 behind will be stretched by the tension of the head of the positive electrode sheet 110, causing the second composite areas Q2 to fail, and thus making it impossible to achieve compensation for the bending section A2. In summary, the distance D between the starting end of the first second composite area Q2 and the starting end of the positive electrode sheet should preferably not exceed 3 mm.

[0071] In some embodiments, the battery cell assembly 100 also includes a positive electrode ear 150 connected to the positive electrode sheet 110 and a negative electrode ear 160 connected to the negative electrode sheet 120, and the positive electrode ear 150 and the negative electrode ear 160 are both arranged on the straight section A1 of the battery cell assembly 100; the second composite area Q2 and the positive electrode ear 150 arranged on the straight section A1 where the second composite area Q2 is located do not overlap in the thickness direction of the battery cell assembly 100; and / or the second composite area Q2 and the negative electrode ear 160 arranged on the straight section A1 where the second composite area Q2 is located do not overlap in the thickness direction of the battery cell assembly 100.

[0072] Specifically, the above embodiment can effectively prevent the positive electrode tab 150 and the negative electrode tab 160 from being damaged when forming the second composite region Q2 , and prevent the burrs of the positive electrode tab 150 and the negative electrode tab 160 from piercing the separator of the second composite region Q2 .

[0073] In some embodiments, the straight section A1 where the positive electrode ear 150 is located has a second composite area Q2, and along the width direction X of the battery cell assembly, the distance between one end of the second composite area Q2 close to the positive electrode ear 150 and one end of the positive electrode ear 150 close to the second composite area Q2 is d1, and d1≥0.5mm is satisfied; and / or, the straight section A1 where the negative electrode ear 160 is located has a second composite area Q2, and along the width direction X of the battery cell assembly, the distance between one end of the second composite area Q2 close to the negative electrode ear 160 and one end of the negative electrode ear 160 close to the second composite area Q2 is d2, and d2≥0.5mm is satisfied.

[0074] In the above embodiment, the distance between the edge of the second composite area Q2 and the edge of the positive electrode ear 150 and the negative electrode ear 160 cannot be too close, otherwise the electrode ear is easily damaged during the composite process in the second composite area Q2, or the burr at the electrode ear is easy to puncture the diaphragm under the action of the composite roller, making the second composite area Q2 ineffective. Specifically, d1 and d2 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc.

[0075] In some embodiments, the battery cell assembly 100 further includes a positive electrode tab 150 connected to the positive electrode sheet 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 sheet 110 and the second separator 140 in the second composite region Q2 is F2, satisfying F2≥F.

[0076] In the above embodiment, the setting of F2≥F can ensure that the positive electrode sheet 110 and the negative electrode sheet 120 have sufficient bonding strength with the diaphragm, and at the same time can reduce the increase of the welding protrusion on the positive electrode ear 150 due to excessive bonding strength when the positive electrode ear 150 is formed at the position corresponding to the second composite area Q2, thereby avoiding scratching or puncturing the diaphragm to cause safety problems.

[0077] In some embodiments, along the length direction of the negative electrode sheet 120 , the distance between the end of the second composite region Q2 and the edge of the closest curved segment A2 is D1, and D1≧0.5 mm is satisfied.

[0078] It should be noted that the edge of the curved section A2 refers to the junction of the curved section A2 and the straight section A1.

[0079] In the above embodiment, the second composite area Q2 is at a certain distance from the curved section A2 to prevent the second composite area Q2 from being located at the curved section A2, where the positive electrode sheet 110 and the negative electrode sheet 120 are in close contact with each other, thus failing to increase the gap between the positive and negative electrode sheets 120. In addition, the present embodiment defines the lower limit of D1, i.e., to ensure that the distance between the second composite area Q2 and the curved section A2 is far enough to ensure the bonding strength between the positive electrode sheet 110 and the negative electrode sheet 120, otherwise the winding tension of the curved section A2 is too large, which may easily cause the bonding failure of the second composite area Q2.

[0080] In some embodiments, along the length direction of the negative electrode sheet 120, the size of a single straight segment A1 is L, the size of a single second composite area Q2 is L1, and 3mm≤L1≤L is satisfied; and / or, along the width direction of the negative electrode sheet 120, the size of the second composite area Q2 is W1, the size of the positive electrode sheet 110 is W, and 5mm≤W1≤W is satisfied.

[0081] In the above embodiment, the length and width of the second composite area Q2 cannot exceed the length and width of the straight section A1, and the length and width of the second composite area Q2 cannot be too small, otherwise the bonding strength will be affected. For example, the length L1 of the second composite area Q2 can be 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc., and the width of the second composite area Q2 can be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, etc.

[0082] In some embodiments, along the length direction of the negative electrode sheet 120, the size of the third composite area Q3 near the beginning or the end of the negative electrode sheet 120 is L2, and satisfies 0.5mm≤L2≤2L; and / or, along the width direction of the negative electrode sheet 120, the third composite areas Q3 are respectively provided on both sides of the negative electrode sheet 120, and the size of the third composite area Q3 on one side along the width direction of the negative electrode sheet 120 is W2, and satisfies 0.2mm≤W2≤2mm.

[0083] It can be understood that the third composite region Q3 provides the key bonding force for the diaphragm and the negative electrode sheet 120 to be composited into a whole. Limiting the size of the third composite region Q3 can improve the bonding strength of the third composite region Q3, and cooperate with the first composite region Q1 to improve the overall strength of the negative electrode composite sheet, ensuring that the diaphragm and the electrode sheet are not separated when the second composite region Q2 is formed, thereby improving the stability of the gap formed in the bending section A2 after winding.

[0084] In the above embodiment, along the length direction of the negative electrode sheet 120, the dimension of the separator beyond the head or / and tail of the negative electrode does not exceed the length of two straight sections A1, otherwise the third composite area Q3 there will be too long and wound on the outside of the winding core, increasing the thickness of the battery cell assembly 100, thereby reducing the energy density of the battery; on the contrary, if the length of the third composite area Q3 at the end is too short, it will be difficult to ensure the bonding strength. Therefore, the length L2 of the third composite area Q3 near the head or tail end of the negative electrode sheet 120 should be moderate, for example, L2 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc.

[0085] Similarly, the width W2 of the third composite area Q3 located on the side of the negative electrode sheet 120 cannot be too wide, otherwise it will increase the size of the negative electrode sheet 120 in the width direction, that is, the size of the battery cell assembly in the length direction Y, which is not conducive to improving the battery energy density; on the contrary, if the width of the third composite area Q3 located on the side of the negative electrode sheet 120 is too narrow, it is difficult to ensure the bonding strength. Therefore, the width W2 of the third composite area Q3 located on one side of the width direction of the negative electrode sheet 120 should be moderate. For example, W2 can be 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, 2.0mm, any one of them or a range between any two of them.

[0086] In some embodiments, the bonding strength between the first separator 130 or the second separator 140 of the first composite region Q1 and the negative electrode sheet 120 is F1, the bonding strength between the positive electrode sheet 110 and the second separator 140 of the second composite region Q2 is F2, and the bonding strength between the first separator 130 and the second separator 140 of the third composite region Q3 is F3, wherein F2≥F1 is satisfied between F1 and F2; and / or, F3≥F1 is satisfied between F1 and F3; and / or, 1N / m≤F1≤15N / m; and / or, 1.5N / m≤F2≤30N / m; and / or, 1N / m≤F3≤15N / m.

[0087] In the above embodiment, the bonding strength between the two layers of the separator at the edge of the negative electrode sheet 120 is greater than the bonding strength between the separator and the negative electrode; and the bonding strength between the positive electrode sheet 110 and the separator in the second composite area Q2 is greater than the bonding strength between the negative electrode sheet 120 and the separator, ensuring that the positive electrode sheet 110 will not detach during the winding process, which is conducive to the formation of a gap between the two adjacent second composite areas Q2, i.e., the uncomposite area, between the positive and negative electrode sheets 120, thereby increasing the gap between the positive and negative electrode sheets 120 in the winding core bending section A2.

[0088] In some embodiments, the positive electrode sheet 110 has a positive electrode active coating 112, the positive electrode active coating 112 has a functional structure area Q4, at least part of the functional structure area Q4 is located in the curved section A2, the surface density of the positive electrode active coating 112 in the functional structure area Q4 is ρ1, and the surface density of the positive electrode active coating 112 in the straight section A1 is ρ2, and ρ1<ρ2 is satisfied.

[0089] In the above embodiment, the active coating surface density of the functional structure area Q4 is relatively small, and the lithium content is relatively small, thereby reducing the amount of lithium embedded in the positive electrode functional structure area Q4 corresponding to the negative electrode sheet 120 and reducing the expansion of the negative electrode sheet 120 after lithium embedding.

[0090] In some embodiments, along the winding direction of the battery cell assembly 100 , at least two curved sections A2 connected to the straight section A1 having the positive electrode tab 150 are provided with a functional structure area Q4 .

[0091] Furthermore, in some embodiments, along the winding direction of the battery cell assembly 100 (winding from the inside to the outside), with the straight section A1 having the positive electrode ear 150 as a reference, at least the following conditions are satisfied: a functional structure area Q4 is provided on both of the two curved sections A2 of the positive electrode sheets 110 connected to the straight section A1 where the positive electrode ear 150 is located, and a functional structure area Q4 is also provided on the positive bent sections adjacent to the two positive curved sections A2 connected to the straight section A1 where the positive electrode ear 150 is located; in another embodiment, along the width direction of the battery cell, at least the two outer curved sections A2 of the two positive curved sections A2 connected to the straight section A1 where the positive electrode ear 150 are located are also provided with a functional structure area Q4; that is, along the winding direction of the battery cell assembly 100, with the straight section A1 having the positive electrode ear 150 as a reference, a functional structure area Q4 is provided on at least one inner curved section A2 and three outer curved sections A2.

[0092] It should be noted that the straight section A1 where the positive electrode ear 150 is located and the electrode ring area connected to the straight section A1 where the positive electrode ear 150 is located have a large current density and a concentrated charge. The problem of lithium insertion and expansion of the negative electrode sheet 120 is relatively serious. Therefore, it is necessary to set a functional structure area Q4 in the positive electrode curved section A2 in these areas to improve the negative electrode expansion and the resulting breakage problem of the positive electrode curved section A2.

[0093] In some embodiments, the curved section A2 where at least part of the functional structure region Q4 is located and the straight section A1 where the second composite region Q2 is located are located in the same circle layer of the battery cell assembly 100 .

[0094] In the above embodiment, the functional structure area Q4 and the second composite area Q2 are located in the same winding layer and can work synergistically, that is, reducing the expansion of the charging and discharging electrode sheet while increasing the gap of the bending section A2, thereby preventing the positive electrode sheet 110 of the bending section A2 from being squeezed and stretched and causing fracture.

[0095] In particular, the second composite region Q2 and the functional structure region Q4 can be separately designed in different winding cores, or combined and arranged in the same winding core, both of which can solve the problem of cyclic expansion of the negative electrode sheet 120, all of which fall within the protection scope of this application.

[0096] In some embodiments, the positive electrode sheet 110 of the functional structure area Q4 is provided with a recess; the recess has at least two holes, the depth of the hole is h, the diameter of the hole is d, and the distance between two adjacent holes is m, satisfying 0mm≤m≤5mm; and / or, 2μm≤h≤80μm; and / or, 10μm≤d≤200μm; and / or, the recess has at least one groove, and the dimension of the groove along the length direction of the positive electrode sheet 110 is L3, satisfying: 2mm≤L3≤12mm; and / or, the dimension of the groove along the width direction of the positive electrode sheet 110 is greater than or equal to 2mm and less than or equal to the width of the positive electrode sheet 110; and / or, the groove along the thickness direction of the positive electrode sheet 110 is greater than or equal to 2μm and less than or equal to the thickness of the positive electrode sheet 110.

[0097] It should be noted that by setting holes and / or grooves on the concave portion in the curved section A2 of the positive electrode sheet 110, the amount of active material in the positive electrode coating of the curved section A2 is reduced, the deintercalation of lithium ions is reduced, the wettability to the electrolyte is improved, the amount of lithium intercalation in the negative electrode sheet 120 corresponding to this location is reduced, and the problem of breakage caused by the expansion of the negative electrode sheet 120 after charging and discharging of the battery is improved; at the same time, the holes and grooves on the concave portion can also release part of the stress on the curved section A2, thereby improving the problem of breakage of the positive electrode sheet 110 in the curved section A2 caused by excessive stress during charging and discharging.

[0098] Specifically, the concave portion may be on the positive electrode active layer, on the positive electrode current collector 111, or on both the positive electrode current collector 111 and the positive electrode active layer. The concave portion may be a through hole provided on the positive electrode sheet 110, or a depression formed on the positive electrode sheet 110 by rolling, and the other side surface of the positive electrode sheet 110 opposite to the depression may be provided with a protrusion corresponding to the depression, or may not have a protrusion.

[0099] In the above embodiment, the size parameters of the holes and grooves on the concave portion should be moderate, not too large, otherwise it will affect the strength of the positive electrode sheet 110, and not too small, otherwise it will be difficult to achieve the effect of improving the expansion of the negative electrode sheet 120. Specifically, the distance m between the edges of the two holes can be any value of 0mm, 1mm, 2mm, 3mm, 4mm, 5mm or a range between any two values; the hole depth h can be any value of 2μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm or a range between any two values; the pore diameter d can be any value of 10μm, 50μm, 100μm, 150μm, 200μm or a range between any two values. The length L3 of the groove can be any value among 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm or a range between any two values; in addition, if the width of the positive electrode sheet 110 is W, the thickness of the positive electrode sheet 110 is G1, the width of the groove is W3, and the depth of the groove is h1, then 2mm≤W3≤W, and / or 2μm≤h1≤G1 are satisfied.

[0100] In some embodiments, along the length direction of the positive electrode sheet 110, the size L1 of a single second composite area Q2 and the depth h of the hole in the recess satisfy: 1.5≤L1 / h≤20000; and / or, along the length direction of the positive electrode sheet 110, the size L1 of a single second composite area Q2 and the size L3 of the groove in the recess satisfy 0.3≤L1 / L3≤20.

[0101] In the above embodiment, when the hole or groove on the concave portion is cooperatively arranged with the second composite area Q2, it is necessary to ensure that the fragmentation effect is improved while avoiding over-compensation, so that the curved section A2 cannot perform lithium insertion and extraction reaction, resulting in lithium deposition in the curved section A2. Therefore, the ratio L1 / h of the length of the second composite area Q2 to the hole depth should be moderate, for example, L1 / h can be any value among 1.5, 10, 100, 1000, 10000, 20000 or a range between any two values; similarly, the ratio L1 / L3 of the length of the second composite area Q2 to the groove length should also be moderate, for example, L1 / L3 can be any value among 0.3, 1, 5, 10, 15, 20 or a range between any two values.

[0102] In some embodiments, in the battery cell assembly 100, the thickness of the negative electrode sheet 120 is G, the thickness of the first separator 130 is g1, the thickness of the second separator 140 is g2, and in the bending section A2 of the battery cell assembly 100, the distance between two adjacent layers of positive electrode sheets 110 is the positive electrode sheet gap, and the size of at least one positive electrode sheet gap in the bending section A2 is H1, satisfying: G+g1+g2+5μm≤H1≤G+g1+g2+30μm.

[0103] In the above embodiment, at least one positive electrode sheet gap is larger than other positive electrode sheet gaps, and the larger positive electrode sheet gap H1 needs to satisfy G+g1+g2+5μm≤H1≤G+g1+g2+30μm, where g1 and g2 can be equal. It can be seen that the size of the positive electrode sheet gap minus the thickness of the first diaphragm 130, the second diaphragm 140 and the negative electrode sheet 120 is H'=H1-(G+g1+g2), that is, 5μm≤H'≤30μm.

[0104] It can be understood that since G, g1 and g2 are all preset values, the size change trends of H' and H1 are consistent. H' cannot be too small, that is, H1 cannot be too small, otherwise the gap between the positive electrode sheet 110 and the negative electrode sheet 120 is too small, and the problem of cyclic expansion of the negative electrode sheet 120 cannot be effectively dealt with; and if H' is too large, it means that the gap between the positive electrode sheet 110 and the negative electrode sheet 120 in the bending section A2 is too large, which will cause the lithium ions in the electrolyte to be free and reach the negative electrode sheet 120 more slowly, and the negative electrode sheet 120 will have less lithium embedded, and the capacity will be reduced. Therefore, the value of H' should be moderate, for example, H' can be any value of 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 15μm, 20μm, 25μm, 30μm, or a range between any two values.

[0105] It should be noted that the positive electrode sheet gap can be obtained using the gap test method. Specifically, CT is used to scan the cross section of the core roll. The brighter the color, the whiter it is, which is the positive electrode sheet coating. The distance between two adjacent positive electrode sheet coatings measured using CT test software is the positive electrode sheet gap.

[0106] Specifically, some detailed embodiments and comparative examples are listed below to illustrate the present application:

[0107] 1. Preparation of batteries

[0108] General steps: (1) Preparation of positive electrode sheet: 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, 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 an aluminum foil, and then rolled and cut to form a positive electrode sheet.

[0109] (2) Preparation of negative electrode sheet: artificial graphite, silicon-carbon material, styrene-butadiene rubber and conductive carbon black are mixed uniformly in a certain mass ratio, deionized water is added to prepare a negative electrode active coating slurry, the negative electrode active coating slurry is evenly coated on both sides of the copper foil, and after drying and roller pressing, a negative electrode sheet is obtained.

[0110] (3) preparing a battery: winding the positive electrode sheet prepared in step (1), the separator (the two sides of the polyethylene base film are respectively a boehmite ceramic layer and a polyvinylidene fluoride adhesive layer) and the negative electrode sheet prepared in step (2) to form a winding core; after injecting the electrolyte, the battery is formed, sorted, and OCV tested to obtain a battery.

[0111] Specifically, comparative example 1: referring to Figure 7 According to the existing conventional winding technology, the negative electrode sheet, the separator, and the positive electrode sheet are stacked in sequence and wound into a core, and then the battery is prepared through processes such as core hot pressing, packaging, baking, liquid injection, formation, vacuum sealing, and capacity division.

[0112] Comparative Example 2: First, the first diaphragm, the negative electrode sheet, and the second diaphragm are stacked and compounded in sequence (compounding temperature 80°C, compounding pressure 3500N, and compounding speed 200mm / s) to form a negative electrode composite sheet (including a first composite area and a third composite area), and then the positive electrode sheet and the negative electrode composite sheet are wound according to the existing winding technology to form a core, and then the core is hot pressed, packaged, baked, injected, formed, vacuum sealed, and capacity divided to prepare a battery.

[0113] Embodiment 1: First, the first separator, the prepared negative electrode sheet and the second separator are stacked in sequence, and then hot-pressed and composited together (composite temperature 80°C, composite pressure 3500N, composite speed 200mm / s) to form a negative electrode composite sheet (including the first composite area and the third composite area); then the positive electrode sheet and the negative electrode composite sheet are intermittently composited together to form multiple second composite areas (the second composite area is located in the straight section of the winding core, composite temperature 80°C, composite pressure 250kg, composite speed 250mm / s), and then wound to prepare a winding core. Among them, the distance D between the starting end of the first second composite area and the starting end of the positive electrode sheet is 3mm; the distance d1 between one end of the positive electrode ear and the end of the positive electrode ear close to the second composite area is 0.5mm, and the distance d2 between the end of the second composite area close to the negative electrode ear and the end of the negative electrode ear close to the second composite area is 0.5mm; the distance D1 between the end of the second composite area and the edge of the closest curved section is 0.5mm. In particular, the length L1 of a single second composite area is 3 mm, the length L' of the first composite area is 1250 mm, the length L of the straight section is 59 mm, the distance R between the maximum curvature of the innermost layer of the curved section and the maximum curvature of the outermost circle is 2.58 mm, the thickness H of the battery cell assembly is 3.97 mm, and the area S of a single second composite area is 270 mm2 The projected overlapping area S1 of the second composite zone on the straight section of two adjacent ring layers is 54mm 2 The width W of the positive electrode sheet is 90 mm, and the width W1 of the second composite area is 90 mm.

[0114] Example 2: The same core preparation method as in Example 1 is used, 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 other parameters are consistent with those in Example 1.

[0115] Example 3: The same core preparation method as in Example 1 is used, wherein 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 other parameters are consistent with those in Example 1.

[0116] Example 4: The same core preparation method as in Example 1 is 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 other parameters are consistent with those in Example 2.

[0117] Example 5: The same core preparation method as in Example 1 is 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 other parameters are consistent with those in Example 2.

[0118] Example 6: The same core preparation method as in Example 1 is adopted, wherein R is 2.43 mm, H is 3.99 mm, and the other parameters are consistent with those in Example 2.

[0119] Example 7: The active coating area of ​​the positive electrode sheet located in the bending section close to the inner side of the winding center and away from the outer side of the winding center is punched (such as laser ablation, chemical corrosion, convex roller rolling, etc.), and the remaining steps of preparing the core are the same as Example 1; wherein, the hole depth h is 15μm, the hole diameter d is 100μm, the pore gap m is 180μm, and R is 2.48mm, H is 4.02mm, and the other parameters are consistent with Example 2, so L1 / h is 1000.

[0120] Example 8: A groove is set on the inner side of the curved section of the positive electrode sheet, and the remaining steps for preparing the winding core are the same as those in Example 1; wherein, the groove depth is 20 μm, the dimension L3 of the groove along the length direction of the positive electrode sheet is 5 mm, the dimension along the width direction of the positive electrode sheet is 5 mm, and R is 2.45 mm, H is 3.98 mm, and the other parameters are consistent with those in Example 2, so L1 / L3 is 3.

[0121] After the winding core of the above embodiment is manufactured, it is packaged, injected, formed, and divided into different capacities according to the same technical requirements to manufacture a finished battery.

[0122] 2. Test results

[0123] 5 pcs of batteries of the embodiment and the comparative example were randomly selected for charge and discharge cycle test (3C constant current charging to 4.3V, 1.8C constant current charging to 4.4V, 1C constant current constant voltage charging to 4.5V, 0.035C cut-off, and then 0.5C discharge to 3.0V), the cycle was 1000 times and CT was used to monitor the fragmentation of the electrode inside the battery during the process.

[0124] Specifically, the "whether it is broken" in the last column of Table 2 refers to whether the positive electrode sheet in the outermost curved section of the battery cell assembly is broken. It should be understood that in practice, in addition to the outermost curved section of the positive electrode sheet, the fracture may also occur in the curved sections of other layers of the positive electrode sheet. In the following table and analysis, only the outermost curved section of the positive electrode sheet is used as an example to illustrate whether it will be broken.

[0125] Table 1

[0126] project L1(mm) L'(mm) L1 / L' R(mm) H(mm) R / (H / 2) L(mm) L1 / L Example 1 3 1250 0.0024 2.58 3.97 1.3 59 0.05 Example 2 15 1250 0.012 2.52 3.95 1.28 59 0.25 Example 3 55 1250 0.044 2.11 4.01 1.05 59 0.93 Example 4 15 1250 0.012 2.12 3.75 1.13 59 0.25 Example 5 15 1250 0.012 2.51 4.03 1.25 59 0.25 Example 6 15 1250 0.012 2.43 3.99 1.22 59 0.25 Example 7 15 1250 0.012 2.48 4.02 1.23 59 0.25 Example 8 15 1250 0.012 2.45 3.98 1.23 59 0.25 Comparative Example 1 / 1250 / 2.01 4.03 1.00 59 / Comparative Example 2 / 1250 / 2.04 4.05 1.01 59 /

[0127] Table 2

[0128] project <![CDATA[S(mm 2 )]]> <![CDATA[S1(mm 2 )]]> S1 / S W1(mm) W(mm) W1 / W Capacity retention rate Thickness expansion rate Is it broken? Example 1 270 54 0.2 90 90 1 82.81％ 14.48％ no Example 2 1350 1174.5 0.87 90 90 1 83.86％ 13.38％ no Example 3 4950 4950 1 90 90 1 80.41％ 15.73％ no Example 4 75 65.3 0.87 5 90 0.06 84.06％ 12.85％ no Example 5 750 652.5 0.87 50 90 0.56 81.17％ 13.26％ no Example 6 1350 1174.5 0.87 90 90 1 83.84％ 16.41％ no Example 7 1350 1174.5 0.87 90 90 1 85.08％ 13.15％ no Example 8 1350 1174.5 0.87 90 90 1 85.12％ 12.87％ no Comparative Example 1 / / / / 90 / 75.97％ 18.36％ yes Comparative Example 2 / / / / 90 / 74.45％ 19.02％ yes

[0129] According to the experimental results in Table 1 and Table 2, it can be seen that when the first composite area, the third composite area and the second composite area are set in the battery cell assembly, the positive electrode sheet in the battery cell assembly does not break, and the capacity retention rate is also high, specifically referring to Examples 1 to 8. Among them, Examples 7 and 8 are not only provided with the above-mentioned composite area, but also provided with a functional structure area in the curved section of the positive electrode sheet, that is, an opening or a groove is set. According to the data in the table, it can be seen that the positive electrode sheets of Examples 7 and 8 do not break, and the capacity retention rate of the batteries in these two embodiments is the highest among all the above embodiments. On the contrary, referring to Comparative Example 1 and Comparative Example 2, the battery cell assembly in Comparative Example 1 does not have any composite area, and only the first composite area and the third composite area are set in Comparative Example 2, but there is no second composite area. Specifically, the outermost curved section positive electrode sheet of the battery cell assembly in Comparative Example 1 breaks after 500 cycles, and the outermost curved section positive electrode sheet of the battery cell assembly in Comparative Example 2 breaks after 530 cycles. The positive electrode sheets in these two embodiments not only break, but also have low capacity retention rates of the batteries. Therefore, providing the above-mentioned composite area, especially the second composite area, in the battery cell assembly can effectively prevent the positive electrode sheet from breaking and increase the battery capacity retention rate.

[0130] In a second aspect, the present application proposes a battery, which includes the battery cell assembly of the first aspect.

[0131] Therefore, the battery of the second aspect has at least all the technical effects of the battery cell assembly of the first aspect, and its specific technical effects are not described in detail here. In addition, the embodiments of the present application only illustrate the structure of the battery of the second aspect related to the improvement of the present application, but it does not mean that it does not have other structures. For example, the battery also includes a shell, a cover plate, etc., and other structures are not described one by one here.

[0132] In particular, the term "and / or" in this application should be understood as follows:

[0133] In the first case, the term "and / or" located between a first subject and a second subject includes any one of the following meanings: (1) only the first subject; (2) only the second subject; and (3) the first subject and the second subject.

[0134] In the second case, the term "and / or" between the last two subjects among three or more subjects means including at least any one of the multiple subjects. For example, "the first subject, the second subject and / or the third subject" has the same meaning as "the first subject and / or the second subject and / or the 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 but not the third subject; (5) the first subject and the third subject but not the second subject; (6) the second subject and the third subject but not the first subject; and (7) the first subject, the second subject and the third subject.

[0135] Finally, although the above content describes the embodiments of the present application in conjunction with the accompanying drawings, those skilled in the art can also make various modifications and variations without departing from the concept of the present application, and such modifications and variations shall fall within the scope of protection of the present application.

Claims

1. A battery cell assembly, characterized in that: It comprises a first separator, a negative electrode sheet, a second separator and a positive electrode sheet which are sequentially stacked and wound, and the battery core assembly has a straight section and a curved section; Along the length direction of the negative electrode sheet, the first separator and the second separator are respectively bonded to the negative electrode sheet to form a first composite area; Along the length direction of the positive electrode sheet, at least a portion of the positive electrode sheet and the second separator are bonded to each other to form at least one bonding portion, and the positive electrode sheet and the second separator at the bonding portion and the negative electrode sheet and the first separator corresponding to the bonding portion together form a second composite area; The second composite region is located in the straight section 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: Along the width direction of the battery cell assembly, the distance between the two points where the innermost layer of the curved section of the battery cell assembly has the maximum curvature and the outermost layer of the curved section of the battery cell assembly has the maximum curvature is R, and 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 battery core assembly according to claim 1, characterized in that: The first separator and the second separator extend beyond the negative electrode sheet along the length direction and / or the width direction of 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 the width direction of the negative electrode sheet are bonded to each other to form a third composite region.

4. The battery core assembly according to claim 1, characterized in that: At least one of the second composite areas is provided on the straight section from the innermost circle layer of the battery cell assembly to the straight section of the fourth outer circle layer from the end of the battery cell assembly.

5. The battery cell assembly according to claim 4, characterized in that: Along the thickness direction of the battery core assembly, projections of the second composite area on the straight sections of two adjacent coil layers of the battery core assembly do not overlap; Alternatively, along the thickness direction of the battery cell assembly, projections of the second composite areas on the straight sections of two adjacent coils of the battery cell assembly partially overlap.

6. The battery cell assembly according to claim 4, characterized in that: Along the winding direction of the battery core assembly, the sizes of two adjacent second composite regions increase successively, or the sizes of all the second composite regions are equal.

7. The battery cell assembly according to claim 1, characterized in that: The positive electrode sheet has a positive electrode sheet starting end located at the innermost circle of the battery cell assembly, the innermost circle has a first positive electrode straight section and a first positive electrode curved section connected to the first positive electrode straight section, the positive electrode sheet starting end is the starting position of the first positive electrode straight section, and the first positive electrode straight section has the first second composite area; Along the winding direction of the battery cell assembly, the starting end of the first second composite area is flush with the starting end of the positive electrode sheet; Alternatively, the distance between the starting end of the first second composite region and the starting end of the positive electrode sheet is D, and satisfies 0mm<D≤3mm; And / or, along the winding direction of the battery cell assembly, the end of the first second composite region is located at the farthest point at the junction of the first positive electrode straight section and the first positive electrode curved section.

8. The battery cell assembly according to claim 5, characterized in that: The area of ​​a single second composite zone is S; The projections of the second composite areas on the straight sections of two adjacent coils of the battery cell assembly on the negative electrode sheet along the thickness direction of the battery cell assembly at least partially overlap, and the overlapping area is S1, satisfying 0.2≤S1 / S≤1.

9. The battery core assembly according to claim 1, characterized in that: The battery cell assembly further comprises a positive electrode ear connected to the positive electrode sheet and a negative electrode ear connected to the negative electrode sheet, and the positive electrode ear and the negative electrode ear are both arranged in the straight section of the battery cell assembly; The orthographic projections of the second composite area and the positive electrode tab arranged on the straight section where the second composite area is located in the thickness direction of the battery cell assembly do not overlap; And / or the second composite area and the negative electrode ear arranged on the straight section where the second composite area is located do not overlap in the thickness direction of the battery core assembly.

10. The battery core assembly according to claim 9, characterized in that: The straight section where the positive electrode ear is located has the second composite area, and along the width direction of the battery cell assembly, the distance between one end of the second composite area close to the positive electrode ear and one end of the positive electrode ear close to the second composite area is d1, and d1≥0.5mm is satisfied; And / or, the straight section where the negative electrode ear is located has the second composite area, and along the width direction of the battery cell assembly, the distance between one end of the second composite area close to the negative electrode ear and one end of the negative electrode ear close to the second composite area is d2, and d2≥0.5mm.

11. The battery core assembly according to claim 1, characterized in that: The battery cell assembly further includes a positive electrode ear connected to the positive electrode sheet, and the bonding strength between the positive electrode ear and the second separator is F; The bonding strength between the positive electrode sheet and the second separator in the second composite region is F2, satisfying F2≥F.

12. The battery core assembly according to claim 1, characterized in that: Along the length direction of the negative electrode sheet, the distance between the end of the second composite region and the edge of the curved section closest thereto is D1, and D1≥0.5 mm.

13. The battery cell assembly according to claim 1, characterized in that: Along the length direction of the negative electrode sheet, the size of a single straight section is L, the size of a single second composite area is L1, and 3mm≤L1≤L is satisfied; And / or, along the width direction of the negative electrode sheet, the size of the second composite area is W1, the size of the positive electrode sheet is W, and 5mm≤W1≤W is satisfied.

14. The battery core assembly according to claim 3, characterized in that: Along the length direction of the negative electrode sheet, the size of the third composite area close to the leading end or the trailing end of the negative electrode sheet is L2, and satisfies 0.5 mm ≤ L2 ≤ 2L; And / or, along the width direction of the negative electrode sheet, the third composite area is respectively provided on both sides of the negative electrode sheet, and the size of the third composite area on one side along the width direction of the negative electrode sheet is W2, and satisfies 0.2mm≤W2≤2mm.

15. The battery core assembly according to claim 3, characterized in that: The bonding strength between the first separator or the second separator in the first composite region and the negative electrode sheet is F1, the bonding strength between the positive electrode sheet 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, 1.5 N / m ≤ F2 ≤ 30 N / m; And / or, 1N / m≤F3≤15N / m.

16. The battery cell assembly according to claim 9, characterized in that: The positive electrode sheet has a positive electrode active coating, and the positive electrode active coating has a functional structure area. At least part of the functional structure area is located in the curved section. The surface density of the positive electrode active coating in the functional structure area is ρ1, and the surface density of the positive electrode active coating in the straight section is ρ2, and ρ1<ρ2 is satisfied.

17. The battery core assembly according to claim 16, characterized in that: Along the winding direction of the battery core assembly, at least two of the curved sections connected to the straight section with the positive electrode tab are provided with the functional structure area.

18. The battery core assembly according to claim 17, characterized in that: The curved section where at least part of the functional structure area is located and the straight section where the second composite area is located are located in the same circle layer of the battery core component.

19. The battery core assembly according to claim 16, characterized in that: The positive electrode sheet in the functional structure area is provided with a recess; The recess has at least two holes, the depth of the hole is h, the diameter of the hole is d, the distance between two adjacent holes is m, and 0mm≤m≤5mm is satisfied; and / or, 2 μm ≤ h ≤ 80 μm; and / or, 10 μm ≤ d ≤ 200 μm; And / or, the recess has at least one groove, and the size of the groove along the length direction of the positive electrode sheet is L3, satisfying: 2mm≤L3≤12mm; And / or, the dimension of the groove along the width direction of the positive electrode sheet is greater than or equal to 2 mm and less than or equal to the width of the positive electrode sheet; And / or, the groove is greater than or equal to 2 μm and less than or equal to the thickness of the positive electrode sheet along the thickness direction of the positive electrode sheet.

20. The battery cell assembly according to claim 19, characterized in that: Along the length direction of the positive electrode sheet, the size L1 of a single second composite area and the depth h of the hole in the recess satisfy: 1.5≤L1 / h≤20000; And / or, along the length direction of the positive electrode sheet, a size L1 of a single second composite area and a size L3 of a groove in the recessed portion satisfy 0.3≤L1 / L3≤20.

21. The battery core assembly according to claim 20, 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, the thickness of the second separator is g2, and in the curved section of the battery cell assembly, the distance between two adjacent layers of positive electrode sheets is the positive electrode sheet gap. The size of at least one positive electrode sheet gap in the curved section is H1, satisfying: G+g1+g2+5μm≤H1≤G+g1+g2+30μm.

22. A battery, characterized in that: Comprising the battery core assembly according to any one of claims 1 to 21.

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