Battery cell and battery

Abstract

The utility model provides a battery cell and a battery, the battery cell comprises a winding structure formed by laminating a negative pole piece, a diaphragm and a positive pole piece, the negative pole piece is provided with a second negative pole bending part close to the end part of a first negative pole active layer, and the positive pole piece is provided with a second positive pole bending part corresponding to the second negative pole bending part; a first concave part is formed in a first area, located at the second positive electrode bending part, of the second positive electrode active layer, and an end part area of the second negative electrode active layer is close to the first negative electrode active layer and located at the second negative electrode bending part or close to the second negative electrode bending part. Therefore, the quality and the surface capacity of the second positive electrode active layer in the first region are reduced, the CB value of the region is improved, the potential of the negative electrode plate is improved, the lithium precipitation at the position is improved, the service life of the battery is prolonged, and the safety of the battery during use is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell and a battery. Background Art

[0002] With the rapid development of lithium-ion battery technology, the industry has higher and higher requirements for the performance of lithium-ion batteries, such as high energy density, super fast charging, high safety, etc. This also puts higher requirements on R&D personnel when designing lithium-ion batteries, and also puts higher requirements on the production and manufacturing of lithium-ion batteries to meet the performance requirements of lithium-ion batteries such as high energy density, super fast charging, and high safety.

[0003] In order to increase the energy density of the battery, it is necessary to apply greater pressure to the active layer of the electrode, which leads to a decrease in the porosity of the negative electrode active layer, and ultimately affects the lithium insertion capacity of the negative electrode active layer, which can easily cause lithium deposition in the negative electrode of the battery, affecting the service life of the battery. At the same time, there are also certain safety hazards. Utility Model Content

[0004] In view of this, the present application provides a battery cell, aiming to solve the problem of lithium deposition in lithium-ion batteries and affecting the battery life. The present application also provides a battery including the above-mentioned battery cell.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] A battery cell, comprising a winding structure of a negative electrode sheet, a separator and a positive electrode sheet, wherein:

[0007] The negative electrode sheet comprises a negative electrode current collector, along the length direction of the negative electrode current collector, a first negative electrode active layer and a second negative electrode active layer are provided on one side surface of the negative electrode current collector adjacent to each other, and a third negative electrode active layer is provided on the other side surface of the negative electrode current collector; in the orthographic projection of the plane where the negative electrode current collector is located, the second negative electrode active layer at least partially overlaps with the third negative electrode active layer, and the first negative electrode active layer is located outside the projection of the third negative electrode active layer; the third negative electrode active layer faces the center of the winding structure;

[0008] The positive electrode sheet comprises a positive electrode current collector, wherein along the length direction of the positive electrode current collector, a first positive electrode active layer and a second positive electrode active layer are provided on one side surface of the positive electrode current collector adjacent to each other, and a third positive electrode active layer is provided on the other side surface of the positive electrode current collector; in the orthographic projection of the plane where the positive electrode current collector is located, the second positive electrode active layer at least partially overlaps with the third positive electrode active layer, and the first positive electrode active layer is located outside the projection of the third positive electrode active layer; the first positive electrode active layer and the second positive electrode active layer face the center of the winding structure;

[0009] The negative electrode sheet has a second negative electrode bend portion close to the end of the first negative electrode active layer, the positive electrode sheet has a second positive electrode bend portion corresponding to the second negative electrode bend portion, the second positive electrode active layer is located in a first area of ​​the second positive electrode bend portion and a first recess is set, the end area of ​​the second negative electrode active layer is close to the first negative electrode active layer, the end area is located in the second negative electrode bend portion, or the end area is close to the second negative electrode bend portion.

[0010] Optionally, the negative electrode sheet has a first negative electrode bending portion, the positive electrode sheet has a first positive electrode bending portion corresponding to the first negative electrode bending portion, and the second positive electrode active layer is located in a second region of the first positive electrode bending portion to provide a first recess.

[0011] Optional,

[0012] In the length direction of the positive electrode current collector, the width of the first region is W; the arc length of the outermost bend of the winding structure is M; wherein W and M satisfy: M≤W≤M+10mm; and / or,

[0013] In the width direction of the positive electrode current collector, the length of the first region is equal to the width of the positive electrode plate; and or,

[0014] In the length direction of the positive electrode current collector, the width of the second region is P, and the arc length of the outermost bending portion of the winding structure is M, wherein P and M satisfy: M≤P≤M+10mm; and / or,

[0015] In the width direction of the positive electrode current collector, the length of the second region is equal to the width of the positive electrode sheet.

[0016] Optionally, the third positive electrode active layer includes a third region where a first recess is provided, and a difference between projection dimensions of the first region and the third region in the length direction of the positive electrode sheet is N, wherein N≤5 mm.

[0017] Optionally, a second recess is provided in a fourth region of the first negative electrode bending portion of the first negative electrode active layer;

[0018] Wherein, in the length direction of the negative electrode current collector, the width of the fourth region is R, wherein: R and P satisfy: P-2mm≤R≤P; and / or,

[0019] In the width direction of the negative electrode current collector, the length of the fourth region is not greater than the length of the second region.

[0020] Optionally, a second recess is formed in the fifth region of the second negative electrode active layer and the first negative electrode active layer;

[0021] Wherein, in the length direction of the negative electrode current collector, the width of the fifth region is S, and the width of the first region is W, wherein: S and W satisfy: W-2mm≤S≤W; and / or,

[0022] In the width direction of the negative electrode current collector, the length of the fifth region is not greater than the length of the first region.

[0023] Optionally, a second recess is provided in a sixth region of the second negative electrode active layer corresponding to the first negative electrode active layer, in the length direction of the negative electrode current collector:

[0024] The width of the sixth region is not less than 3 mm, and the overlapping width of the fifth region and the second negative electrode active layer is not less than 3 mm.

[0025] Optional,

[0026] In a direction perpendicular to the positive electrode current collector, the depth of the first recess is E; in a direction perpendicular to the negative electrode current collector, the depth of the second recess is F; wherein E and F satisfy: 1<E:F≤2; and / or,

[0027] The outer diameter of the first recess is H, and the outer diameter of the second recess is K, wherein H and K satisfy: 1<H:K≤2; and / or,

[0028] A plurality of the first recesses and a plurality of the second recesses are provided; wherein a groove spacing between adjacent first recesses is T, a groove spacing between adjacent second recesses is U, and T and U satisfy: 0.5≤T:U≤1.

[0029] Optional,

[0030] A groove pitch T between adjacent first recesses satisfies: 50 μm ≤ T ≤ 5000 μm, and a groove pitch U between adjacent second recesses satisfies: 50 μm ≤ U ≤ 5000 μm; and / or,

[0031] The depth of the first recess is E satisfying: 3μm≤E≤35μm, and the distance between the bottom of the first recess and the positive electrode collector is greater than 0; and the depth of the second recess is F satisfying: 3μm≤F≤35μm, and the distance between the bottom of the second recess and the negative electrode collector is greater than 0; and or,

[0032] The maximum distance between the first recess near the edge of the positive electrode sheet and the edge of the positive electrode sheet is 50μm to 970μm, and / or the minimum distance between the first recess near the edge of the positive electrode sheet and the edge of the positive electrode sheet is 10μm to 630μm; and the maximum distance between the second recess near the edge of the negative electrode sheet and the edge of the negative electrode sheet is 50μm to 970μm, and the minimum distance between the second recess near the edge of the negative electrode sheet and the edge of the negative electrode sheet is 10μm to 630μm.

[0033] Optionally, the inner diameter of the groove bottom of the first recess and the second recess is smaller than the outer diameter of the groove opening.

[0034] Optionally, the first negative electrode active layer, the second negative electrode active layer and the third negative electrode active layer have no recesses on the remaining negative electrode bends of the negative electrode sheet, and the first positive electrode active layer, the second positive electrode active layer and the third positive electrode active layer have no recesses on the remaining positive electrode bends of the positive electrode sheet.

[0035] A battery comprising any one of the above-mentioned cells.

[0036] The battery cell provided in the present application includes a winding structure, in which a first recess is provided in the first area where the second positive electrode active layer is located at the second positive electrode bending portion, and the end area of ​​the second negative electrode active layer is close to the first negative electrode active layer, and the end area is located at the second negative electrode bending portion, or the end area is close to the second negative electrode bending portion, thereby reducing the mass and surface capacity of the second positive electrode active layer located in the first area, thereby increasing the CB value of the area, increasing the potential of the negative electrode plate, improving lithium deposition at the position, and thereby increasing the service life of the battery and the safety of the battery during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0038] Figure 1 A front view of the winding structure provided for this embodiment;

[0039] Figure 2 It is a front view of the positive electrode sheet in the unfolded state;

[0040] Figure 3 A top view of the positive electrode sheet in the unfolded state;

[0041] Figure 4It is a bottom view of the positive electrode sheet in the unfolded state;

[0042] Figure 5 It is a front view of the negative electrode sheet in the unfolded state;

[0043] Figure 6 A top view of the negative electrode sheet in the unfolded state;

[0044] Figure 7 It is a bottom view of the negative electrode sheet in the unfolded state;

[0045] Figure 8 It is a partial enlarged view of the positive electrode active layer;

[0046] Fig. 9 for Figure 8 LL section view;

[0047] Fig.10 It is a partial enlarged view of the positive electrode active layer;

[0048] Fig.11 for Fig.10 Cross-sectional view at VV of .

[0049] exist Figure 1-Figure 11 middle:

[0050] 1-positive electrode sheet, 2-negative electrode sheet, 3-first negative electrode bending portion, 4-second negative electrode bending portion, 5-first positive electrode bending portion, 6-second positive electrode bending portion, 7-fourth negative electrode bending portion, 8-fifth negative electrode bending portion;

[0051] 11-positive electrode current collector, 12-positive electrode active layer, 13-first positive electrode active layer, 14-second positive electrode active layer, 15-third positive electrode active layer, 21-negative electrode current collector, 22-negative electrode active layer, 23-first negative electrode active layer, 24-second negative electrode active layer, 25-third negative electrode active layer, 26-end region;

[0052] 121 - first area, 122 - second area, 123 - third area, 124 - seventh area, 221 - fourth area, 222 - fifth area, 223 - sixth area. DETAILED DESCRIPTION

[0053] The present application provides a battery cell. The present application also provides a battery comprising the battery cell.

[0054] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0055] like Figures 1 to 11 As shown, the embodiment of the present application provides a battery cell, which mainly includes a winding structure in which a negative electrode sheet 2, a separator (not shown in the figure) and a positive electrode sheet 1 are stacked, and the negative electrode sheet 2 includes a negative electrode collector 21. Along the length direction of the negative electrode collector 21, one side surface of the negative electrode collector 21 is provided with a first negative electrode active layer 23 and a second negative electrode active layer 24 adjacent to each other, and the other side surface of the negative electrode collector is provided with a third negative electrode active layer 25; in the orthographic projection of the plane where the negative electrode collector 21 is located, the second negative electrode active layer 24 and the third negative electrode active layer 25 at least partially overlap, and the first negative electrode active layer 23 is located outside the projection of the third negative electrode active layer 25. Exemplarily, in the negative electrode sheet 2, the area where the first negative electrode active layer 23 is located is a single-sided area of ​​the negative electrode sheet 2, and the area where the second negative electrode active layer 24 and the third negative electrode active layer 25 are located is a double-sided area of ​​the negative electrode sheet 2; The third negative electrode active layer 25 faces the center of the winding structure; the positive electrode sheet 1 includes a positive electrode collector 11, along the length direction of the positive electrode collector 11, one side surface of the positive electrode collector 11 is provided with a first positive electrode active layer 13 and a second positive electrode active layer 14 adjacent to each other, and the other side surface of the positive electrode collector 11 is provided with a third positive electrode active layer 15; in the orthographic projection of the plane where the positive electrode collector 11 is located, the second positive electrode active layer 14 and the third positive electrode active layer 15 at least partially overlap, and the first positive electrode active layer 13 is located outside the projection of the third positive electrode active layer 15. Exemplarily, in the positive electrode sheet 1, the area where the first positive electrode active layer 13 is located is a single-sided area of ​​the positive electrode sheet 1, and the area where the second positive electrode active layer 14 and the third positive electrode active layer 15 are located is a double-sided area of ​​the positive electrode sheet 1; the first positive electrode active layer 13 and the second positive electrode active layer 14 face the center of the winding structure. Among them, the winding center of the winding structure refers to Figure 1 The area shown in A; the end of the first negative electrode active layer 23 refers to Figure 1 The length direction of the negative electrode current collector 21 refers to Figure 4 and Figure 5 The direction indicated by the double-headed arrow X2 is the length direction of the positive electrode current collector 11. Figure 2 and Figure 3 The direction is indicated by the double-headed arrow X1.

[0056] Specifically, in order to improve the energy density of the battery, the roller pressing device is required to apply a greater roller pressure to the active layer of the electrode sheet. The increase in roller pressure will cause the third negative electrode active layer 25 and the second negative electrode active layer 24 of the negative electrode sheet 2 to be subjected to a greater roller pressure in the end area 26 close to the first negative electrode active layer 23, which will cause the porosity between the active materials in the end area 26 to decrease, which will cause the battery composed of the above-mentioned negative electrode sheet 2 to have a reduced ability to insert lithium in the end area 26 during charging, resulting in the end area 26 being easy to precipitate lithium. Based on this, the negative electrode sheet 2 has a second negative electrode bend 4 close to the end of the first negative electrode active layer 23, the positive electrode sheet 1 has a second positive electrode bend 6 corresponding to the second negative electrode bend 4, the second positive electrode active layer 14 is located in the first area 121 of the second positive electrode bend 6 to set a first recess, the end area 26 of the second negative electrode active layer 24 is close to the first negative electrode active layer 23, the end area 26 is located in the second negative electrode bend 4, or the end area 26 is close to the second negative electrode bend 4. In this way, the first recess is opened in the first area 121 where the second positive electrode active layer 14 is located at the second positive electrode bend 6. When the end area 26 is located at the second negative electrode bend 4, when the battery cell composed of the above-mentioned winding structure is charged and discharged, a lithium ion migration reaction occurs between the first area 121 and the end area 26. The first recess is opened in the first area 121, which reduces the mass and surface capacity of the positive electrode active material in the first area 121, increases the liquid storage capacity of the area, increases the CB value of the position, and at the same time increases the potential of the end area 26, thereby improving the lithium precipitation of the end area 26; when the end area 26 is close to the second negative electrode bend 4, the position A first recess is provided in the first region 121 of the second positive electrode bend 6. Since the size of the first region 121 is larger than that of the second negative electrode bend 4, a first recess is also provided in the region of the second positive electrode active layer 14 corresponding to the end region 26. Thus, when the battery cell composed of the above-mentioned winding structure is charged and discharged, a lithium ion migration reaction occurs between the first region 121 and the end region 26. The first recess is provided in the first region 121, which reduces the mass and surface capacity of the positive electrode active material in the first region 121, increases the liquid storage capacity in the region, increases the CB value at the position, and at the same time increases the potential of the end region 26, thereby improving lithium deposition in the end region 26.

[0057] It should be noted that, in the winding structure formed by stacking the positive electrode sheet 1, the separator, the negative electrode sheet 2 and the separator, the bending times of the positive electrode sheet 1 and the negative electrode sheet 2 can be the same or different, wherein the second negative electrode bending portion 4 refers to the portion where the negative electrode sheet 2 is bent for the second time and can undergo a lithium ion migration reaction with the positive electrode sheet 1, and the second positive electrode bending portion 6 refers to the portion where the positive electrode sheet 1 is bent for the second time and can undergo a lithium ion migration reaction with the negative electrode sheet 2; correspondingly, the first negative electrode bending portion 3 refers to the portion where the negative electrode sheet 2 is bent for the first time and can undergo a lithium ion migration reaction with the positive electrode sheet 1, and the first positive electrode bending portion 5 refers to the portion where the positive electrode sheet 1 is bent for the first time and can undergo a lithium ion migration reaction with the negative electrode sheet 2. Among them, in some winding structures, although Figure 1 The negative electrode sheet 2 is also bent at the position O shown in the figure, but since there is no lithium ion migration reaction between this area and the positive electrode sheet 1, the negative electrode sheet 1 is bent at Figure 1 The bending at position O is not counted in the bending times of the negative electrode plate 2 .

[0058] It should also be noted that the positive electrode sheet 1 has a second positive electrode bend portion 6 corresponding to the second negative electrode bend portion 4, wherein the correspondence refers to the region where the positive electrode sheet 1 can undergo a lithium ion migration reaction with the second negative electrode bend portion 4. Correspondingly, the positive electrode sheet 1 hereinafter has a first positive electrode bend portion 5 corresponding to the first negative electrode bend portion 3, wherein the correspondence refers to the region where the positive electrode sheet 1 can undergo a lithium ion migration reaction with the first negative electrode bend portion 3.

[0059] It should also be noted that the first recess and the second recess mentioned below can both be grooves and / or holes, wherein the first recess and the second recess can both be provided with one or more recesses, and the first and second mentioned above do not represent the number of grooves and / or holes.

[0060] The winding structure of the above structure is achieved by setting a first recess in the first area 121 of the second positive electrode active layer 14 located at the second positive electrode bend 6, and the end area 26 of the second negative electrode active layer 24 is close to the first negative electrode active layer 23, the end area 26 is located at the second negative electrode bend 4, or the end area 26 is close to the second negative electrode bend 4, thereby reducing the mass and surface capacity of the second positive electrode active layer 14 located in the first area 121, thereby increasing the CB value of the area, increasing the potential of the negative electrode plate 2, improving lithium deposition at the position, and thereby increasing the service life of the battery and improving the safety of the battery during use.

[0061] In some embodiments, the negative electrode sheet 2 has a first negative electrode bend portion 3 away from the end of the first negative electrode active layer 23. In the winding structure, since the end of the first negative electrode active layer 23 is located at the winding center, the first negative electrode active layer 23 located in the first negative electrode bend portion 3 area needs to be bent nearly 360°, which can easily cause the active material of the first negative electrode active layer 23 located in the first negative electrode bend portion 3 area to fall off, resulting in insufficient CB value in the first negative electrode bend portion 3 area, making the first negative electrode active layer 23 located in the first negative electrode bend portion 3 prone to lithium deposition problems. Here, the positive electrode sheet 1 has a first positive electrode bend portion 5 corresponding to the first negative electrode bend portion 3, and a first recess is set in the second area 122 of the second positive electrode active layer 14 located at the first positive electrode bend portion 5. When the battery cell composed of the above-mentioned winding structure is charged and discharged, a lithium ion migration reaction occurs between the second area 122 located at the first positive electrode bend portion 5 and the first negative electrode active layer 23 located at the first negative electrode bend portion 3. The first recess is opened in the second area 122, which reduces the mass and surface capacity of the positive electrode active material in the second area 122, increases the CB value at this position, and improves the lithium deposition of the first negative electrode active layer 23 located at the first negative electrode bend portion 3.

[0062] In some embodiments, in the length direction of the positive electrode current collector 11, the width of the first region 121 is W; the arc length of the outermost bend of the winding structure is M; wherein W and M satisfy: M≤W≤M+10mm; and / or, in the width direction of the positive electrode current collector 11, the length of the first region 121 is equal to the width of the positive electrode sheet 1. Since the end of the third negative electrode active layer 25 close to the first negative electrode active layer 23 is located at the second negative electrode bend 4, the winding structure is formed by stacking the positive electrode sheet 1, the separator, the negative electrode sheet 2 and the separator, the outermost bend of the winding structure ( Figure 1 The arc length of the first region 121 (in the region shown in B) is greater than the arc length of the second negative electrode bend 4. Since the positive electrode sheet 1 and the negative electrode sheet 2 may be misaligned when winding when the positive electrode sheet 1 and the negative electrode sheet 2 form a winding structure, it is ensured that the width of the first region 121 is greater than or equal to the arc length of the outermost circle of the winding structure, and the arc length of the outermost circle of the winding structure is greater than the arc length of the second negative electrode bend 4 provided with the end region 26, so that it can be further ensured that the width of the first region 121 where the first recess is provided is greater than the arc length of the second negative electrode bend 4 provided with the end region 26, so that when the positive electrode sheet 1 and the negative electrode sheet 2 form a winding structure and there is a slight misalignment, it is further ensured that the first recess can alleviate the lithium deposition of the second negative electrode bend 4 provided with the end region 26. Moreover, it is ensured that the width of the first area 121 is less than or equal to the arc length of the outermost circle of the winding structure plus 10 mm, so as to avoid the first area 121 with the first recess being too large, and to avoid excessive reduction in the energy density of the battery while avoiding lithium deposition in the end area 26.

[0063] Since the area with smaller porosity in the end region 26 of the second negative electrode bend 4 is located in the entire area in the width direction of the negative electrode plate 2, it is ensured that in the width direction of the positive electrode plate 1, the length of the first area 121 is equal to the width of the positive electrode plate 1, thereby alleviating lithium deposition in the local area 26 of the width direction of the end region 26 of the negative electrode plate 2.

[0064] It should be noted that the length direction of the positive electrode current collector 11 refers to Figure 2 and Figure 3 The direction indicated by the double-headed arrow X1 in FIG. 1 is the width direction of the positive electrode current collector 11. Figure 3 The direction shown by Y1.

[0065] In some embodiments, in the length direction of the positive electrode current collector 11, the width of the second region 122 is P, and the arc length of the outermost bend of the winding structure is M, wherein P and M satisfy: M≤P≤M+10mm; and / or, in the width direction of the positive electrode current collector 11, the length of the second region 122 is equal to the width of the positive electrode sheet 1. Since the winding structure is formed by winding the positive electrode sheet 1 and the negative electrode sheet 2 layer by layer, the arc length of the outermost bend of the winding structure is greater than the arc length of the first positive bend 5. Since the positive electrode sheet 1 and the negative electrode sheet 2 may be misaligned when the winding structure is wound, it is ensured that the width of the second region 122 is greater than or equal to the arc length of the outermost circle of the winding structure, and the arc length of the outermost circle of the winding structure is greater than the arc length of the first positive electrode bend 5, so that the length of the second region 122 with the first recess is further ensured to be greater than the arc length of the first negative electrode bend 3, thereby further ensuring that the lithium deposition of the first negative electrode bend 3 can be alleviated. Moreover, it is also ensured that the width of the second region 122 is less than or equal to the arc length of the outermost circle of the winding structure plus 10mm, so that the size of the second region 122 with the first recess is avoided to be too large, and while avoiding the lithium deposition of the first negative electrode bend 3, the energy density of the battery can be avoided to be reduced too much.

[0066] Since there is a probability of negative active material falling in each area of ​​the first negative electrode bend 3 in the width direction of the negative electrode current collector 21, it is ensured that the length of the first area 121 in the width direction of the positive electrode current collector 11 is equal to the width of the positive electrode plate 1, so that the local lithium plating of the first negative electrode bend 3 in the width direction of the negative electrode active layer 22 can be alleviated.

[0067] In some embodiments, the third positive electrode active layer 15 includes a third region 123 where a first recess is provided. Preferably, the difference between the projection dimensions of the first region 121 and the third region 123 in the length direction of the positive electrode current collector 11 is N, where N≤5 mm. Specifically, a first recess is also provided in the third region 123 to increase the CB value of the third region 123 and the fifth negative electrode bend 8, which can further prevent lithium deposition in the negative electrode active layer 22 located at the fifth negative electrode bend 8 of the negative electrode sheet 2.

[0068] Correspondingly, a first recess may be provided in the seventh region 124 of the positive active layer 12 arranged opposite to the second region 122 on the other side of the positive current collector 11 , so as to alleviate lithium deposition in the fourth negative electrode bend 7 of the negative electrode sheet 2 arranged corresponding to the seventh region 124 .

[0069] It should be noted that the direction perpendicular to the positive electrode current collector 11 refers to Figure 2 the fourth negative electrode bending portion 7 is also the location where the negative electrode sheet 2 is bent for the fourth time, and the fifth negative electrode bending portion 8 is also the location where the negative electrode sheet 2 is bent for the fifth time.

[0070] It should also be noted that, when the electrode sheet is in the unfolded state, the aligned arrangement means that the first region 121 and the third region 123 are respectively located on both sides of the positive electrode current collector 11 in a direction perpendicular to the positive electrode sheet 1 .

[0071] In some embodiments, a first recess is provided in the second region 122, which increases the contact area between the positive electrode active layer 12 and the electrolyte, increases the porosity of the positive electrode active layer 12, increases the mobility of lithium ions at this position, and improves the dynamic performance of the second region 122. On the basis of the above, a second recess is provided in the fourth region 221 of the first negative electrode active layer 23 located at the first negative electrode bending portion 3, which correspondingly increases the contact area between the negative electrode active layer 22 and the electrolyte, increases the porosity of the negative electrode active layer 22, increases the mobility of lithium ions at this position, and improves the dynamic performance of the fourth region 221, thereby matching the dynamic performance of the positive electrode sheet 1 and the negative electrode sheet 2.

[0072] In the length direction of the negative electrode current collector 21, the width of the fourth region 221 is R, and R and P satisfy: P-2mm≤R≤P; in the width direction of the negative electrode current collector 21, the length of the fourth region 221 is not greater than the length of the second region 122. In this way, the opening size of the fourth region 221 of the negative electrode active layer 22 is smaller than the opening size of the second region 122 of the positive electrode active layer 12, ensuring that when the dynamic performance of the positive electrode plate 1 and the negative electrode plate 2 are matched, the opening area of ​​the fourth region 221 is prevented from being too large, and the lithium analysis of the fourth region 221 beyond the second region 122 is avoided, and the opening area of ​​the fourth region 221 is prevented from being too small, and the dynamic matching of the positive electrode plate 1 and the negative electrode plate 2 is not greatly improved.

[0073] It should be noted that the length direction of the negative electrode current collector 21 refers to Figure 5 and Figure 6 The direction indicated by the double-headed arrow X2 in FIG. 1 is the width direction of the negative electrode current collector 21. Figure 6 The direction is indicated by the double-headed arrow Y2.

[0074] In some embodiments, a first recess is provided in the first region 121, which increases the contact area between the positive electrode active layer 12 and the electrolyte, increases the porosity of the positive electrode active layer 12, increases the mobility of lithium ions at this position, and improves the kinetic performance of the first region 121. On the basis of the above, a second recess is provided in the fifth region 222 of the second negative electrode active layer 24 and the first negative electrode active layer 23, which correspondingly increases the contact area between the negative electrode active layer 22 and the electrolyte, increases the porosity of the negative electrode active layer 22, increases the mobility of lithium ions at this position, and improves the kinetic performance of the fifth region 222, thereby achieving kinetic matching between the positive electrode sheet 1 and the negative electrode sheet 2.

[0075] In the length direction of the negative electrode current collector 21, the width of the fifth region 222 is S, and the width of the first region 121 is W, wherein: S and W satisfy: W-2mm≤S≤W; and / or, in the width direction of the negative electrode current collector 21, the length of the fifth region 222 is not greater than the length of the first region 121. In this way, the opening size of the fifth region 222 is smaller than the opening size of the first region 121, ensuring that when the dynamic performance of the positive electrode plate 1 and the negative electrode plate 2 are matched, the opening area of ​​the fifth region 222 is prevented from being too large, thereby alleviating lithium deposition in the fifth region 222, and the opening area of ​​the fifth region 222 is prevented from being too small, thereby preventing the dynamic matching of the positive electrode plate 1 and the negative electrode plate 2 from being greatly improved.

[0076] In some embodiments, since the compaction density of the second negative electrode active layer 24 and the third negative electrode active layer 25 located in the end region 26 is relatively large, there is a situation where the active material is crushed to death. On the basis of opening a second recess in the fifth region 222, a second recess is set in the sixth region 223 located in the third negative electrode active layer 25 close to the first negative electrode active layer 23. This setting improves the porosity of the fifth region 222 and the sixth region 223, avoids the fifth region 222 and the sixth region 223 from being crushed to death, and improves the mobility rate of lithium ions during charging and discharging.

[0077] In this embodiment, further, in the length direction of the negative electrode current collector 21, the width of the sixth region 223 is ensured to be not less than 3 mm, and the overlap width of the fifth region 222 and the third negative electrode active layer 25 is not less than 3 mm, and the width of the fifth region 222 and the sixth region 223 can exceed the width of the corresponding grooved region of the first region 121. Such a configuration can increase the porosity of the surface of the fifth region 222 and the sixth region 223, allowing lithium ions to more easily penetrate the dense layer on the surface of the negative electrode and embed into the graphite in the thickness direction when the battery is charged, thereby improving lithium precipitation.

[0078] It should be noted that the overlapping width between the fifth region 222 and the third negative electrode active layer 25 refers to the width of the overlapping region in a direction perpendicular to the negative electrode current collector 21 .

[0079] Illustratively, in the length direction of the negative electrode current collector 21, the width of the fifth region 222 may be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 10 mm, 15 mm, etc.; correspondingly, the width of the sixth region 223 may be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 10 mm, 15 mm, etc.

[0080] In some embodiments, in the direction perpendicular to the current collector, the depth of the first recess is E; in the direction perpendicular to the negative electrode current collector 21, the depth of the second recess is F; wherein E and F satisfy: 1<E:F≤2; the outer diameter of the first recess is H, and the outer diameter of the second recess is K, wherein H and K satisfy: 1<H:K≤2; multiple first recesses and second recesses are provided, that is, multiple first recesses are opened in the first region 121, the second region 122, the third region 123 and the seventh region 124, and multiple second recesses are opened in the fourth region 221, the fifth region 222 and the sixth region 223; wherein the groove spacing between adjacent first recesses is T, the groove spacing between adjacent second recesses is U, and T and U satisfy: 0.5≤T:U≤1. In order to improve the lithium deposition of the negative electrode plate 2, it is necessary to ensure that the content of the positive electrode active layer 12 is less than the content of the corresponding negative electrode active layer 22, and a first recess is opened on the positive electrode active layer 12 and a second recess is opened on the corresponding negative electrode active layer 22, so that the dynamic performance of the above-mentioned areas matches. Here, it is ensured that the depth, outer diameter and groove spacing of the first recess and the second recess meet the above relationship, which can improve the porosity of the negative electrode active layer 22 and improve the mobility efficiency of lithium ions, so that the dynamic performance of the positive and negative electrodes is matched, and it can also ensure that the lithium deposition at the above-mentioned position is alleviated, and the ability to store electrolyte at the position where the groove is set is improved.

[0081] It should be noted that the direction perpendicular to the positive electrode current collector 11 refers to Figure 2 The direction indicated by the double-headed arrow Z1 in FIG. 2 is perpendicular to the negative electrode current collector 21. Figure 5 The direction is indicated by the double-headed arrow Z2.

[0082] It should also be noted that there are multiple first recesses and multiple second recesses, and the values ​​of the depth of the first recess, the depth of the second recess, the outer diameter of the first recess, the outer diameter of the second recess, the groove spacing between adjacent first recesses, and the groove spacing between adjacent second recesses are the average values ​​of the multiple values ​​measured.

[0083] Exemplarily, the ratio of the depth of the first recess to the depth of the second recess can be: 1.1, 1.2, 1.3, 1.4, 1.5, etc.; the ratio of the outer diameter of the first recess to the outer diameter of the second recess can be: 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, etc.; the ratio of the groove spacing of the first recess to the groove spacing of the second recess can be: 0.6, 0.7, 0.8, 0.9, 1, etc.

[0084] It should be noted that the outer diameter of the first recess and the second recess refers to the outer diameter of the notches of the first recess and the second recess. When the notch is circular, the outer diameter is the diameter of the notch; when the notch is non-circular such as elliptical, polygonal or irregular, the outer diameter is the diameter of the circumscribed circle of the notch.

[0085] In some embodiments, the groove spacing T between adjacent first recesses satisfies: 50μm≤T≤1000μm, and the groove spacing U between adjacent second recesses satisfies: 50μm≤U≤5000μm; and the groove spacing between adjacent first recesses is ensured to be smaller than the groove spacing between adjacent second recesses.

[0086] In some embodiments, the depth of the first recess is E and satisfies: 3μm≤E≤35μm; and the depth of the second recess is F and satisfies: 5μm≤F≤35μm; and the depth of the first recess is greater than the depth of the second recess; and the depth of the first recess is greater than the depth of the second recess. And the distance between the bottom of the second recess and the negative electrode collector 21 is greater than 0, and the distance between the bottom of the first recess and the positive electrode collector 11 is greater than 0. Such a configuration can avoid damage to the positive electrode collector 11 and the negative electrode collector 21.

[0087] In some embodiments, the maximum distance between the first concave portion near the edge of the positive electrode sheet 1 and the edge of the positive electrode sheet 1 is 50 μm to 970 μm, and the minimum distance between the first concave portion near the edge of the positive electrode sheet 1 and the edge of the positive electrode sheet 1 is 10 μm to 630 μm; wherein the maximum distance between the first concave portion near the edge of the positive electrode sheet 1 and the edge of the positive electrode sheet 1 is Figure 8 The distance shown by D in the figure is the minimum distance between the first concave portion close to the edge of the positive electrode sheet 1 and the edge of the positive electrode sheet 1. Figure 8 The distance shown by G in the figure. The maximum distance between the second concave portion near the edge of the negative electrode sheet 2 and the edge of the negative electrode sheet 2 is 50 μm to 970 μm, and the minimum distance between the second concave portion near the edge of the negative electrode sheet 2 and the edge of the negative electrode sheet 2 is 10 μm to 630 μm. Fig.10 The distance shown in I in the figure is the minimum distance between the second concave portion close to the edge of the negative electrode sheet 2 and the edge of the negative electrode sheet 2. Fig.10 The distance shown by J in the figure. Ensuring that the maximum distance and the minimum distance between the first recess and the second recess and the edge of the pole piece are within the above range can prevent the first recess and the second recess from being opened outside the active layer, improve the accuracy of setting the first recess and the second recess in the active layer, and improve the product yield.

[0088] In some embodiments, the inner diameter of the bottom of the first recess and the second recess is smaller than the outer diameter of the notch, that is, the first recess and the second recess are both tapered recesses with the inner diameter of the bottom smaller than the outer diameter of the notch. Such a configuration can make it easier for the electrolyte to enter the first recess and the second recess, improve the efficiency of the electrolyte infiltrating the winding structure, and improve the mobility efficiency of lithium ions and the charging and discharging efficiency.

[0089] It should be noted that if Figure 8 and Fig. 9As shown, the outer diameter of the first recess is H, and the inner diameter of the first recess is H1; Fig.10 and Fig.11 As shown, the outer diameter of the second recess is K, and the inner diameter of the second recess is K1.

[0090] In some embodiments, the first negative electrode active layer 23, the second negative electrode active layer 24 and the third negative electrode active layer 25 are not provided with recesses in the remaining negative electrode bends of the negative electrode sheet 2. It should be noted that the remaining negative electrode bends of the negative electrode sheet 2 refer to the remaining bends of the negative electrode sheet 2 other than the first negative electrode bend 3 and the second negative electrode bend 4. Moreover, the first positive electrode active layer 13, the second positive electrode active layer 14 and the third positive electrode active layer 15 are not provided with recesses in the remaining positive electrode bends of the positive electrode sheet 1. It should be noted that the remaining positive electrode bends of the positive electrode sheet 1 refer to the remaining bends of the positive electrode sheet 1 other than the first positive electrode bend 5 and the second positive electrode bend 6. With such a configuration, compared with the scheme in which recesses are provided in each bend, this scheme effectively alleviates the lithium precipitation of the negative electrode active layer 22 while avoiding excessive reduction in the energy density of the battery cell.

[0091] A battery includes the above-mentioned battery cell. Since the battery includes the above-mentioned battery cell, the beneficial effects brought by the battery cell can be found in the above content and will not be repeated here.

[0092] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0093] The block diagrams of the devices, apparatuses, equipment, and systems involved in this application are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The words "such as" used here refer to the phrase "such as but not limited to", and can be used interchangeably with them.

[0094] It should also be noted that in the apparatus, device and method of the present application, each component or each step can be decomposed and / or recombined. Such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0095] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0096] It should be understood that the qualifiers "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present application are only used to more clearly explain the technical solutions and cannot be used to limit the scope of protection of the present application.

[0097] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A battery cell, characterized in that: A winding structure comprising a negative electrode sheet, a separator and a positive electrode sheet, wherein: The negative electrode sheet comprises a negative electrode current collector, along the length direction of the negative electrode current collector, a first negative electrode active layer and a second negative electrode active layer are provided on one side surface of the negative electrode current collector adjacent to each other, and a third negative electrode active layer is provided on the other side surface of the negative electrode current collector; in the orthographic projection of the plane where the negative electrode current collector is located, the second negative electrode active layer at least partially overlaps with the third negative electrode active layer, and the first negative electrode active layer is located outside the projection of the third negative electrode active layer; the third negative electrode active layer faces the center of the winding structure; The positive electrode sheet comprises a positive electrode current collector, wherein along the length direction of the positive electrode current collector, a first positive electrode active layer and a second positive electrode active layer are provided on one side surface of the positive electrode current collector adjacent to each other, and a third positive electrode active layer is provided on the other side surface of the positive electrode current collector; in the orthographic projection of the plane where the positive electrode current collector is located, the second positive electrode active layer at least partially overlaps with the third positive electrode active layer, and the first positive electrode active layer is located outside the projection of the third positive electrode active layer; the first positive electrode active layer and the second positive electrode active layer face the center of the winding structure; The negative electrode sheet has a second negative electrode bend portion close to the end of the first negative electrode active layer, the positive electrode sheet has a second positive electrode bend portion corresponding to the second negative electrode bend portion, the second positive electrode active layer is located in a first area of ​​the second positive electrode bend portion and a first recess is set, the end area of ​​the second negative electrode active layer is close to the first negative electrode active layer, the end area is located in the second negative electrode bend portion, or the end area is close to the second negative electrode bend portion.

2. The battery cell according to claim 1, characterized in that: The negative electrode sheet has a first negative electrode bending portion, the positive electrode sheet has a first positive electrode bending portion corresponding to the first negative electrode bending portion, and the second positive electrode active layer is located in a second region of the first positive electrode bending portion to provide a first recess.

3. The battery cell according to claim 2, characterized in that: In the length direction of the positive electrode current collector, the width of the first region is W; the arc length of the outermost bend of the winding structure is M; wherein W and M satisfy: M≤W≤M+10mm; and / or, In the width direction of the positive electrode current collector, the length of the first region is equal to the width of the positive electrode plate; and or, In the length direction of the positive electrode current collector, the width of the second region is P, and the arc length of the outermost bending portion of the winding structure is M, wherein P and M satisfy: M≤P≤M+10mm; and / or, In the width direction of the positive electrode current collector, the length of the second region is equal to the width of the positive electrode sheet.

4. The battery cell according to claim 1, characterized in that: The third positive electrode active layer includes a third region where a first recess is disposed, and a difference between the projection dimensions of the first region and the third region in the length direction of the positive electrode sheet is N, where N≤5 mm.

5. The battery cell according to claim 3, characterized in that: The first negative electrode active layer is provided with a second recess in a fourth region of the first negative electrode bending portion; Wherein, in the length direction of the negative electrode current collector, the width of the fourth region is R, wherein: R and P satisfy: P-2mm≤R≤P; and / or, In the width direction of the negative electrode current collector, the length of the fourth region is not greater than the length of the second region.

6. The battery cell according to claim 1, characterized in that: A second recess is formed in the fifth region of the second negative electrode active layer and the first negative electrode active layer; Wherein, in the length direction of the negative electrode current collector, the width of the fifth region is S, and the width of the first region is W, wherein: S and W satisfy: W-2mm≤S≤W; and / or, In the width direction of the negative electrode current collector, the length of the fifth region is not greater than the length of the first region.

7. The battery cell according to claim 1, characterized in that: A second recess is provided in a sixth region of the third negative electrode active layer close to the first negative electrode active layer, in the length direction of the negative electrode current collector: The width of the sixth region is not less than 3 mm, and the overlapping width of the fifth region and the third negative electrode active layer is not less than 3 mm.

8. The battery cell according to any one of claims 5 to 7, characterized in that: In a direction perpendicular to the positive electrode current collector, the depth of the first recess is E; in a direction perpendicular to the negative electrode current collector, the depth of the second recess is F; wherein E and F satisfy: 1<E:F≤2; and / or, The outer diameter of the first recess is H, and the outer diameter of the second recess is K, wherein H and K satisfy: 1<H:K≤2; and / or, A plurality of the first recesses and a plurality of the second recesses are provided; wherein a groove spacing between adjacent first recesses is T, a groove spacing between adjacent second recesses is U, and T and U satisfy: 0.5≤T:U≤1.

9. The battery cell according to claim 8, characterized in that: A groove pitch T between adjacent first recesses satisfies: 50 μm ≤ T ≤ 5000 μm, and a groove pitch U between adjacent second recesses satisfies: 50 μm ≤ U ≤ 5000 μm; and / or, The depth of the first recess is E satisfying: 3μm≤E≤35μm, and the distance between the bottom of the first recess and the positive electrode collector is greater than 0; and the depth of the second recess is F satisfying: 3μm≤F≤35μm, and the distance between the bottom of the second recess and the negative electrode collector is greater than 0; and or, The maximum distance between the first recess near the edge of the positive electrode sheet and the edge of the positive electrode sheet is 50μm to 970μm, and / or the minimum distance between the first recess near the edge of the positive electrode sheet and the edge of the positive electrode sheet is 10μm to 630μm; and the maximum distance between the second recess near the edge of the negative electrode sheet and the edge of the negative electrode sheet is 50μm to 970μm, and the minimum distance between the second recess near the edge of the negative electrode sheet and the edge of the negative electrode sheet is 10μm to 630μm.

10. The battery cell according to any one of claims 5 to 7, characterized in that: The inner diameters of the groove bottoms of the first recess and the second recess are smaller than the outer diameters of the groove openings.

11. The battery cell according to claim 2, characterized in that: The first negative electrode active layer, the second negative electrode active layer and the third negative electrode active layer have no recesses on the remaining negative electrode bends of the negative electrode sheet, and the first positive electrode active layer, the second positive electrode active layer and the third positive electrode active layer have no recesses on the remaining positive electrode bends of the positive electrode sheet.

12. A battery, characterized in that: Comprising a battery cell as described in any one of claims 1 to 11.

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