Negative electrode plate and battery

Abstract

The present invention relates to the technical field of batteries, and particularly relates to a negative electrode plate and a battery. The provided negative electrode plate includes: a current collector, the current collector includes a plurality of straight portions; the straight portion includes a first region and a plurality of second regions, and the plurality of second regions are respectively located at the four corners of the straight portion; a first active coating, the first active coating is disposed on the first region and the second regions on at least one side of the straight portion; a second active coating, the second active coating is disposed on the first active coating located in the first region; a third active coating, the third active coating is disposed on the first active coating located in the second region; wherein, the porosity of the first active coating is A1, the porosity of the second active coating is A2, and the porosity of the third active coating is A3; A1, A2, and A3 satisfy: A3 < A1 < A2. The negative electrode plate provided by the present invention can enhance the structural stability of the four-corner part to reduce the risk of physical damage; at the same time, it ensures that the electrolyte can fully penetrate the main body part to improve the battery performance.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular, to a negative electrode sheet and a battery. Background Art

[0002] The electrode sheet of a lithium battery is designed by a coating method, and the microscopic design of the electrode sheet coating can effectively improve the overall performance of the battery. For example, through the design of double-layer coating on the negative electrode, with a high binder content in the lower layer coating and a low binder content in the upper layer coating, the fast charging ability and rate performance of the battery can be improved.

[0003] However, during the use of the battery, due to the low strength of the upper layer coating, problems such as easy powder falling may occur. In addition, as the requirement for the space utilization rate of the battery cell is higher, the design of the electrode sheet is getting larger and larger. During the winding process of the electrode sheet, the stress borne by the edge position of the bent part will also increase, causing wrinkles and deformation in the wound core, and further affecting the charge and discharge performance and cycle performance of the battery. Summary of the Invention

[0004] In view of this, the present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, the present invention provides a negative electrode sheet and a battery, which can enhance the mechanical strength of the corners of the electrode sheet and the four corners of the straight part of the electrode sheet, prevent wrinkles and deformation, reduce the physical damage of the electrode sheet, and make the active material on the electrode sheet not easy to fall off, thereby improving the cycle performance and charge and discharge performance of the battery.

[0005] In order to solve the above technical problems, the present invention is implemented as follows:

[0006] According to one aspect of the present invention, an embodiment of the present invention provides a negative electrode sheet, including:

[0007] A current collector, the current collector includes a plurality of straight parts; the straight part includes a first region and a plurality of second regions, and the plurality of second regions are respectively located at the four corners of the straight part;

[0008] A first active coating, the first active coating is provided on the first region and the second regions on at least one side of the straight part;

[0009] A second active coating, the second active coating is provided on the first active coating located in the first region;

[0010] A third active coating, the third active coating is provided on the first active coating located in the second region;

[0011] Wherein, the porosity of the first active coating is A1, the porosity of the second active coating is A2, the porosity of the third active coating is A3, and A1, A2, and A3 satisfy:

[0012] A3 < A1 < A2.

[0013] In some embodiments, A1 is 15% - 45%;

[0014] and / or, A2 is 20% - 50%;

[0015] and / or, A3 is 10% - 30%.

[0016] In some embodiments, the length of the straight part in the x-axis direction is L, and the length in the y-axis direction is H; the length of any one of the second regions in the x-axis direction is L1, and the length in the y-axis direction is H1. A1, A2, A3, L, H, L1, and H1 satisfy:

[0017] A3 * 2L1 * H1 / (L * H) + A2 * (1 - 2L1 * H1 / (L * H)) ≥ A1.

[0018] In some embodiments, the ratio L1 / L of the length L1 of the second region in the x-axis direction to the length L of the straight part in the x-axis direction is 0.1 - 0.5;

[0019] and / or, the ratio H1 / H of the length H1 of the second region in the y-axis direction to the length H of the straight part in the y-axis direction is 0.1 - 0.5.

[0020] In some embodiments, the current collector further includes at least one bent part;

[0021] At least one side of the bent part is provided with the first active coating, and is on the same side as the first active coating on the straight part;

[0022] On the first active coating located at the bent part, at least the third active coating is further provided.

[0023] In some embodiments, the bent part includes a third region and a fourth region;

[0024] The third region is located between the second regions of the adjacent straight parts, and the fourth region is located between the first regions of the adjacent straight parts; the first active coating is provided on the third region and the fourth region;

[0025] The third active coating is provided on the first active coating located in the third region, and the second active coating is provided on the first active coating located in the fourth region;

[0026] Alternatively, the third active coating is provided on both the first active coating located in the third region and the first active coating located in the fourth region.

[0027] In some of these embodiments, the first active coating, the second active coating, and the third active coating each include a negative electrode active material, a conductive agent, and a binder;

[0028] wherein the negative electrode active material includes a carbon-based material and / or a silicon-based material; and / or,

[0029] the conductive agent includes at least one of conductive carbon black, carbon nanotubes, or graphene; and / or,

[0030] the binder includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, or polyacrylic acid.

[0031] In some of these embodiments, the third active coating further includes a thermosetting polymer; the thermosetting polymer includes a resin.

[0032] In some of these embodiments, the thermosetting polymer includes at least one of phenolic resin, urea-formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, or polyurethane;

[0033] and / or, the mass content of the thermosetting polymer in the third active coating is 0.5% - 3%.

[0034] According to another aspect of the present invention, an embodiment of the present invention provides a battery, including: a positive electrode sheet, a separator, and the negative electrode sheet according to any one of the embodiments in one aspect of the embodiments of the present invention.

[0035] Implementing the technical solution of the present invention has at least the following beneficial effects:

[0036] 1. In the embodiment of the present invention, for the provided negative electrode sheet, by providing a first region on the straight portion of the current collector and second regions at the four corners of the straight portion, providing a second active coating on the first region, and providing a third active coating on the third region, and the porosity A1 of the first active coating, the porosity A2 of the second active coating, and the porosity A3 of the third active coating satisfy A3 < A1 < A2; the negative electrode sheet provided by the embodiment of the present application enhances the mechanical strength at the corners and the four corners of the straight portion, prevents wrinkles and deformation, reduces physical damage to the electrode sheet, and thus improves the cycle performance and charge-discharge performance of the battery.

[0037] 2. In a preferred embodiment of the present invention, by using a thermosetting material disposed in the third active coating of the electrode, a hard protective layer is formed outside the battery core, which is more conducive to resisting physical stress during battery use, reducing physical deformation of the battery during long-term cycling, and further slowing down the attenuation of the comprehensive performance of the battery.

[0038] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings are incorporated herein and constitute a part of this specification, showing embodiments consistent with the present invention and, together with the specification, are used to explain the principles of the present invention.

[0040] Figure 1 Shown is a schematic diagram of a negative electrode structure provided by an embodiment of the present invention Figure 1 .

[0041] Figure 2 Shown is a schematic cross-sectional structure diagram of a negative electrode provided by an embodiment of the present invention.

[0042] Figure 3 Shown is a schematic diagram of a negative electrode structure provided by an embodiment of the present invention Figure 2 .

[0043] Figure 4 Shown is a schematic diagram of a negative electrode structure provided by an embodiment of the present invention Figure 3 .

[0044] Figure 5 Shown is a schematic diagram of a negative electrode structure provided by an embodiment of the present invention Figure 4 .

[0045] Figure 6 Shown is a schematic diagram of a negative electrode structure provided by an embodiment of the present invention Figure 5 .

[0046] Figure 7 Shown is a schematic diagram of a negative electrode structure provided by an embodiment of the present invention Figure 6 .

[0047] Figure 8 Shown is a schematic diagram of a battery cell structure provided by an embodiment of the present invention.

[0048] STRUCTURAL DESCRIPTION OF THE DRAWINGS:

[0049] 100 - current collector; 110 - straight part; 120 - bent part;

[0050] 111 - First region; 112 - Second region; 121 - Third region; 122 - Fourth region;

[0051] 200 - First active coating; 300 - Second active coating; 400 - Third active coating.

[0052] Through the above - mentioned drawings, specific embodiments of the present invention have been shown, and there will be a more detailed description hereinafter. These drawings and textual descriptions are not intended to limit the scope of the inventive concept in any way, but to illustrate the concept of the present invention to those skilled in the art by reference to specific embodiments. Detailed embodiments

[0053] The following further elaborates the present application in combination with specific embodiments. It should be understood that these embodiments of the present application are only used to illustrate the present application and not to limit the scope of the present application.

[0054] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range or individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0055] If there is no special instruction, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0056] If there is no special instruction, all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0057] If there is no special instruction, all steps of the present invention can be carried out in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0058] If there is no special instruction, the "including" and "comprising" mentioned in the present invention mean open - ended or closed - ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or only the listed components are included or comprised.

[0059] Reference Figure 8 During the winding process of a battery cell, the electrode tab is usually obtained by winding the electrode sheet and the separator. During the winding process, the stress borne by the straight part of the electrode sheet at the four corner positions becomes greater and greater, resulting in wrinkles and deformations at the four corners of the straight part of the electrode sheet in the battery cell, which easily affects the battery capacity, charge and discharge performance, and cycle performance, etc.

[0060] Based on this, the embodiments of the present invention provide a negative electrode sheet. By dividing a first region and a plurality of second regions on the current collector, and arranging the second regions at the four corner positions of the current collector, and then by arranging different active coatings on the first region and the second regions, when the electrode sheet is wound, the coating structure at the four corner positions of the straight part of the electrode sheet is stable, reducing the physical damage to the electrode sheet, and further enabling the obtained battery cell in the battery to be fully permeated with the electrolyte, improving the cycle performance and charge and discharge performance of the battery.

[0061] As Figure 1 shown, the embodiments of the present invention provide a negative electrode sheet. The negative electrode sheet includes: a current collector 100, and the current collector 100 includes a plurality of straight parts 110; the straight part 110 includes a first region 111 and a plurality of second regions 112, and the plurality of second regions 112 are respectively located at the four corners of the straight part 110.

[0062] Reference Figure 1 On the current collector 100, a plurality of straight parts 110 are provided. The straight part 110 is divided into a first region 111, and a plurality of second regions 112 are divided at the four corners of the straight part 110. The first region 111 is located between the plurality of second regions 112, and the first region 111 is the main region; preferably, the area of the first region 111 can be larger than the areas of the plurality of second regions 112. Exemplarily, the shape of the second region 112 can be a right triangle, where the two right sides respectively coincide with the long side and the wide side of the straight part 110, and the hypotenuse corresponding to the right angle of the second region 112 can be a straight line or a curve.

[0063] Reference Figure 2 and Figure 3 shown, the negative electrode sheet further includes a first active coating 200, and the first active coating 200 is provided on the first region 111 and the second regions 112 on at least one side of the straight part 110. The first active coating 200 can be provided on a single surface of the current collector 100 along the thickness direction, or can be provided on both surfaces of the current collector 100 along the thickness direction, that is, the first active coating 200 can be provided on a single surface or both surfaces of the straight part 110.

[0064] The above-mentioned first active coating 200 is disposed on both side surfaces of the current collector 100. For example, the first active coating 200 is provided on both surfaces of the current collector 100 in the thickness direction, that is, the first active coating 200 is disposed on two opposite surfaces of the current collector 100. The first active coating 200 includes a negative electrode active material, such as graphite, a silicon-based material, or lithium titanate, etc.

[0065] Continue to refer to Figure 2 and Figure 3 , the negative electrode plate further includes a second active coating 300 and a third active coating 400. The second active coating 300 is disposed on the first active coating 200 located in the first region 111, and the third active coating 400 is disposed on the first active coating 200 located in the second region 112. Similarly, if the above-mentioned first active coating 200 is disposed on one side surface of the current collector 100, the second active coating 300 and the third active coating 400 are disposed on the first active coating 200. If the above-mentioned first active coating 200 is oppositely disposed on two surfaces of the current collector 100 in the thickness direction, the second active coating 300 and the third active coating 400 are disposed on two opposite surfaces of the current collector 100 and the first active coating 200.

[0066] The above-mentioned second active coating 300 includes a negative electrode active material, such as graphite, a silicon-based material, etc., and the third active coating 400 includes a negative electrode active material, such as graphite, a silicon-based material, etc. Exemplarily, such as Figure 2 and Figure 3 , the first active coating 200 is disposed on one side surface of the straight portion 110, and the second active coating 300 and the third active coating 400 are disposed on the first active coating 200. Among them, the second active coating 300 is located in the first region 111 of the straight portion 110, and the third active coating 400 is located in the second region 112 of the straight portion 110. The differences in the active materials of the first active coating 200, the second active coating 300, and the third active coating 400 can be the different particle sizes of the active materials; it can also be the different specific components of the active materials, such as the component content ratio; or the different coating densities and porosities between the respective coatings, etc. Exemplarily, the particle sizes of the active materials in the first active coating 200, the second active coating 300, and the third active coating 400 are different, and the particle size of the active material in the third active coating 400 is smaller than that in the first active coating 200 and the second active coating 300, so that during the winding process of the negative electrode plate, the third active coating 400 at the four corners of the straight portion 110 is less physically damaged, such as wrinkles and coating peeling, etc., so that the battery has a higher battery capacity, cycle performance, etc.

[0067] Further, in some embodiments, the porosity of the first active coating 200 is A1, the porosity of the second active coating 300 is A2, and the porosity of the third active coating 400 is A3; A1, A2, and A3 satisfy: A3 < A1 < A2.

[0068] The difference between the first active coating 200, the second active coating 300, and the third active coating 400 can also be the different porosities between the coatings. For example, the porosity of the first active coating 200 is A1, the porosity of the second active coating 300 is A2, and the porosity of the third active coating 400 is A3; wherein, A1, A2, and A3 satisfy: A3 < A1 < A2. In this way, it can ensure that the second active coating 300 located on the second region 112 has better structural stability and avoid physical damage to the electrode sheet during the winding process. Based on the above settings, the porosity A2 of the second active coating 300 is greater than the porosity A1 of the first active coating 200, which can ensure that when the electrode sheet contacts the electrolyte, the electrolyte can quickly and fully penetrate into the second active coating 300 and quickly and fully penetrate from the second active coating 300 to the first active coating 200, thereby improving the capacity, charge-discharge performance, and cycle performance of the battery. At the same time, A3 < A1, so that the four corners of the straight part 110 of the electrode sheet have excellent mechanical strength and are not damaged physically during bending or winding. If A1 is not less than A2, after the electrolyte contacts the second active coating 300, it cannot quickly penetrate to the first active coating 200 close to the current collector 100, thereby affecting the capacity of the battery; if A3 is not less than A2, the mechanical strength of the third active coating 400 at the four corners of the straight part 110 is too low and is easily damaged physically during bending or winding, which also affects the comprehensive performance of the battery.

[0069] An embodiment of the present invention provides a negative electrode sheet, which includes a current collector 100. The current collector 100 includes a plurality of straight parts 110; by dividing the straight part 110 into a first region 111 and a plurality of second regions 112, wherein the plurality of second regions 112 are respectively located at the four corners of the straight part 110; and a first active coating 200 is provided on at least one side of the first region 111 and the second region 112 of the straight part 110, a second active coating 300 is provided on the first active coating 200 located in the first region 111, and a third active coating 400 is provided on the first active coating 200 located in the second region 112; wherein, the porosity of the first active coating 200 is A1, the porosity of the second active coating 300 is A2, and the porosity of the third active coating 400 is A3, and A1, A2, and A3 satisfy: A3 < A1 < A2. The negative electrode sheet provided by the present invention can enhance the structural stability of the four-corner part to reduce the risk of physical damage; at the same time, ensure that the electrolyte can fully penetrate the main body part to improve the battery performance.

[0070] In some embodiments, A1 is 15% to 45%.

[0071] Specifically, A1 can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44% or 45%, etc.; within this range, A1 can ensure the contact between the electrolyte and the active material, enabling the electrolyte to diffuse sufficiently and having an excellent ion migration rate. If A1 is greater than this range, it will cause excessive aggregation of the electrolyte and reduce the contact with the active material; if A1 is less than this range, it will limit the diffusion of the electrolyte and reduce the ion migration speed.

[0072] In some embodiments, A2 is 20% to 50%.

[0073] Specifically, A2 can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%, etc.; within this range, A2 can strengthen the structure of the coating, reduce the risk of shedding of the active coating material; at the same time, it can also ensure the effective diffusion of the electrolyte and improve the charge and discharge performance of the battery. If A2 is greater than this range, it may lead to weakening of the active coating structure and increase the risk of shedding of the active material; if A2 is less than this range, it may reduce the effective diffusion of the electrolyte and affect the charge and discharge performance.

[0074] In some embodiments, A3 is 10% to 30%.

[0075] Specifically, A3 can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, etc.; within this range, A3 can make the active coating more solid, not easily damaged under mechanical stress, and provide an effective penetration channel for the electrolyte to ensure the performance of the battery. If A3 is greater than this range, it may lead to the structure being too fragile and easily damaged under mechanical stress; if A3 is less than this range, it may not be sufficient to provide the necessary channels for the electrolyte to effectively penetrate and affect the battery performance.

[0076] In some embodiments, the length of the straight portion 110 in the x-axis direction is L, and the length in the y-axis direction is H; the length of any second region 112 in the x-axis direction is L1, and the length in the y-axis direction is H1. A1, A2, A3, L, H, L1, and H1 satisfy: A3 * 2L1 * H1 / (L * H) + A2 * (1 - 2L1 * H1 / (L * H)) ≥ A1.

[0077] Reference Figure 1 Let the long side of the straight portion 110 along the current collector 100 be the x-axis, and the wide side of the straight portion 110 be the y-axis; then the length of the straight portion 110 in the x-axis direction is L, and the length in the y-axis direction is H; for the second region 112 at any one of the four corners of the straight portion 110, the length on the x-axis is L1, and the length in the y-axis direction is H1, that is, the two right-angled sides of the second region 112 have a length of L1 on the x-axis and a length of H1 in the y-axis direction. A1, A2, A3, L, H, L1, and H1 satisfy: A3 * 2L1 * H1 / (L * H) + A2 * (1 - 2L1 * H1 / (L * H)) ≥ A1, which can make the porosity of the active coating near the current collector 100 less than that of the active coating far from the current collector 100, thereby ensuring the active coating in the second region 112, that is, the four corners of the straight portion 110, enhancing the toughness of the active material in the active coating, enabling the active coating to provide sufficient support under mechanical stress without affecting the overall porosity, ensuring the effective penetration of the electrolyte, and improving the comprehensive performance of the battery. If A1, A2, A3, L, H, L1, and H1 are not within this range, such as the average porosity of the upper layer is too small, there will not be large enough voids for lithium ions to reach the current collector smoothly, or it is prone to powdering and collapse during overcharge and discharge, which will affect the comprehensive performance of the battery.

[0078] In some embodiments, the ratio L1 / L of the length L1 of the second region 112 in the x-axis direction to the length L of the straight portion 110 in the x-axis direction is 0.1 to 0.5.

[0079] The ratio of L1 / L can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5; within this range of the ratio of L1 / L, the active coating at the four corners of the straight portion 110 can have a certain mechanical strength, and the mechanical strength will not be too strong to affect the flexibility of the electrode sheet, allowing the electrode sheet to be wound. If the ratio of L1 / L is greater than this range, the mechanical strength at the four corners of the straight portion 110 will be overly strengthened, affecting the overall flexibility of the battery; if the ratio of L1 / L is less than this range, the enhancement effect at the four corners of the straight portion 110 is insufficient, and it cannot effectively resist mechanical stress.

[0080] In some embodiments, the ratio H1 / H of the length H1 of the second region 112 in the y-axis direction to the length H of the straight portion 110 in the y-axis direction is 0.1 to 0.5.

[0081] The ratio of H1 / H can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.; within this range of the ratio of H1 / H, the four corners of the straight portion 110 have sufficient mechanical strength and flexibility, without affecting the curling of the electrode sheet. If the ratio of H1 / H is greater than this range, it will also cause excessive strengthening of the four-corner area, which may affect the flexibility of the battery curling or shape adjustment; if the ratio of H1 / H is less than this range, it is not sufficient to protect the structural integrity of the edge when subjected to external forces.

[0082] In some embodiments, the current collector 100 further includes at least one bent portion 120; at least one side of the bent portion 120 is provided with a first active coating 200, and it is on the same side as the first active coating 200 on the straight portion 110; on the first active coating 200 located at the bent portion 120, at least a third active coating 400 is further provided.

[0083] Reference Figure 1 and Figure 4 , the current collector 100 further includes a bent portion 120, the bent portion 120 is located between any two straight portions 110, on the single-side surface of the bent portion 120 on the same side as the first active coating 200 on the straight portion 110, the first active coating 200 is provided, and on this first active coating 200, a third active coating 400, or a second active coating 300 and a third active coating 400 are provided, wherein the third active coating 400 is provided at the upper and lower edge positions of the bent portion 120, and the second active coating 300 is provided between the third active coatings 400; the middle second active coating 300 has an A2 porosity, providing necessary active materials and electrolyte channels for the battery; while the third active coatings 400 at the upper and lower two edges have an A3 porosity, enhancing the mechanical strength and structural stability of the bent portion.

[0084] In some embodiments, the bent portion 120 includes a third region 121 and a fourth region 122; the third region 121 is located between the second regions 112 of adjacent straight portions 110, and the fourth region 122 is located between the first regions 111 of adjacent straight portions 110; the first active coating 200 is provided on the third region 121 and the fourth region 122; the third active coating 400 is provided on the first active coating 200 located in the third region 121, and the second active coating 300 is provided on the first active coating 200 located in the fourth region 122. In the upward direction along the y-axis, the width and length of the third region 121 can be the same as those of the second region 112, or different, and correspondingly, the length of the third active coating 400 in the y-axis direction located on the third region 121 can be the same as or different from the length of the third active coating 400 located on the second region 112. Similarly, in the upward direction along the y-axis, the width and length of the fourth region 122 can be the same as or different from the length of the first region 111.

[0085] Reference Figures 4 to 6 , the bent portion 120 is divided into a third region 121 and a fourth region 122; the third region 121 is located between two second regions 112 of adjacent straight portions 110, and the fourth region 122 is located between two first regions 111 of adjacent straight portions 110. Among them, the boundary line between the third region 121 and the fourth region 122 can be a straight line or a curve. On the single-sided surface of the current collector 100 of the bent portion 120 in the third region 121 and the fourth region 122, a first active coating 200 is provided. A third active coating 400 is provided on the first active coating 200 in the third region 121, and a second active coating 300 is provided on the first active coating 200 in the fourth region 122. The negative electrode sheet in this embodiment can not only endow the sheet at the edge of the bent region with certain mechanical strength, but also has a certain flexibility, ensuring that the bent portion 120 of the sheet can be bent arbitrarily during bending and winding, and the materials in the active coating will not fall off, improving the comprehensive performance of the battery.

[0086] In some embodiments, a third active coating 400 is provided on both the first active coating 200 in the third region 121 and the first active coating 200 in the fourth region 122.

[0087] Reference Figure 7 , a first active coating 200 is provided on the single-sided surface of the bent portion 120, and a third active coating 400 is provided on the first active coating 200. The sheet in this embodiment has good and appropriate strength, flexibility, and can also make the electrolyte fully penetrate, improving the comprehensive performance of the battery.

[0088] In some embodiments, the first active coating 200, the second active coating 300, and the third active coating 400 all include a negative electrode active material, a conductive agent, and a binder; among them, the negative electrode active material includes a carbon-based material and / or a silicon-based material.

[0089] The proportions of the negative electrode active material, the conductive agent, and the binder in the first active coating 200, the second active coating 300, and the third active coating 400 can adopt the proportions known to those skilled in the art and will not be elaborated in detail here.

[0090] The negative electrode active materials in the first active coating 200, the second active coating 300, and the third active coating 400 can be the same or different; preferably, the same type of negative electrode active material, conductive agent, and binder can make the preparation process of the negative electrode sheet simpler and faster. At the same time, it can better control the porosity of each active coating, enabling the electrolyte to fully penetrate and improving the performance of the battery.

[0091] The negative electrode active material includes carbon-based materials such as graphite, amorphous carbon, carbon nanotubes, etc.; or silicon-based materials such as single-crystalline silicon, polycrystalline silicon or silicon oxide, etc. In a preferred embodiment, the carbon-based materials include artificial graphite, natural graphite, soft carbon or hard carbon. Among them, the negative electrode active material can be one or several of the carbon-based materials in any proportion, or one or several of the silicon-based materials in any proportion; it can also be a carbon-based material and a silicon-based material in any proportion.

[0092] Further, the conductive agent includes, but is not limited to, any one or several of conductive carbon black, carbon nanotubes or graphene in any proportion.

[0093] Further, the binder includes, but is not limited to, any one or several of polyvinylidene fluoride, styrene-butadiene rubber or polyacrylic acid in any proportion.

[0094] In an embodiment of the present invention, the third active coating 400 further includes a thermosetting polymer; the thermosetting polymer includes a resin.

[0095] Further, the thermosetting polymer includes at least one of, but is not limited to, phenolic resin, urea-formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin or polyurethane.

[0096] Adding a thermosetting polymer to the third active coating 400, the thermosetting polymer will undergo a cross-linking reaction to cure when heated. For example, in the battery manufacturing process, after the electrode sheet is coated, rolled and paired with the anode and cathode diaphragms, there is a step of hot pressing, that is, through pressure and high temperature, the positive and negative electrode sheets are more closely combined together, which helps to shape the battery cell and improve the uniformity. After the hot pressing process is combined, the adhesion between the electrode sheets of the battery cell is enhanced, playing a role in curing the battery cell, further enhancing the mechanical strength of the negative electrode sheet, and then improving the comprehensive performance of the battery.

[0097] In another embodiment of the present invention, the mass content of the thermosetting polymer in the third active coating 400 is 0.5% - 3%.

[0098] Specifically, the mass content of the thermosetting polymer in the third active coating 400 is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.7%, 2.8%, 2.9% or 3%; within this range, the thermosetting polymer can enhance the mechanical strength of the negative electrode plate to a certain extent, enabling the positive and negative electrode plates to be better bonded together. If it is less than this range, it cannot meet the requirement of enhancing the mechanical strength of the electrode plate; if it is greater than this range, it will cause too high mechanical strength, which is not conducive to the curling and bending of the electrode plate.

[0099] An embodiment of the present invention further provides a battery, which includes: a positive electrode plate, a separator, and the negative electrode plate in any of the above embodiments.

[0100] The positive electrode plate in the embodiment of the present invention includes a current collector and a positive electrode active material, where the positive electrode active material includes but is not limited to one or any proportion of several of LiCoO2 (lithium cobalt oxide), LiNiO2 (lithium nickel oxide), LiMnO2 (lithium manganate), LiFePO4 (lithium iron phosphate), NMC (lithium nickel cobalt manganate), NCA (lithium nickel cobalt aluminate), LiMn2O4 (lithium manganate), LiNi0.5Mn1.5O4 (lithium nickel manganate), LiFePO4 (lithium iron phosphate), LiMnPO4 (lithium manganese phosphate), Li3V2(PO4)3 (lithium tri-vanadium phosphate) or LiTi2(PO4)3 (lithium titanium phosphate).

[0101] The separator in this embodiment is a separator used in the art and is not particularly limited herein. All solvents and substances in the present invention can be obtained through market purchase.

[0102] Since the battery provided by the embodiment of the present invention adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated herein one by one.

[0103] The following specifically describes the present application in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. The following examples are only partial examples of the present application and do not limit the present application.

[0104] Example 1

[0105] 1. Preparation of raw materials:

[0106] (1) Negative electrode slurry A1: 400 g of artificial graphite, 8 g of styrene-butadiene rubber, 4 g of sodium carboxymethyl cellulose, and 4 g of carbon black are mixed in 60 g of deionized water.

[0107] (2) Anode Slurry A2: 400 g of artificial graphite (with more small particles), 8 g of styrene-butadiene rubber, 4 g of sodium carboxymethyl cellulose, and 4 g of carbon black are mixed in 60 g of deionized water. Note: Increasing the processing time of graphite can result in smaller graphite particles, thus reducing the porosity of graphite, and vice versa.

[0108] (3) Anode Slurry A3: 400 g of artificial graphite (with more large particles), 8 g of styrene-butadiene rubber, 4 g of sodium carboxymethyl cellulose, and 4 g of carbon black are mixed in 60 g of deionized water.

[0109] (4) Cathode Slurry: 950 g of lithium iron phosphate, 20 g of conductive agent, and 30 g of binder are mixed in 600 g of NMP solution and stirred to form the cathode slurry.

[0110] (5) 250 g of Electrolyte: Lithium hexafluorophosphate (LiPF6) is dissolved in a mixed solvent composed of ethylene carbonate (EC), dimethyl carbonate (DEC), and ethyl methyl carbonate (EMC) (the mass ratio of the three is 1:1:1) to obtain the electrolyte.

[0111] (6) Separator: A 7-μm thick PE separator (polyethylene) is coated with a 3-μm ceramic layer and a 3-μm polyvinylidene fluoride (PVDF) layer on both sides.

[0112] 2. Battery Assembly:

[0113] (1) Preparation of the Cathode Plate:

[0114] The obtained cathode slurry is coated on the current collector to form the cathode plate.

[0115] (2) Preparation of the Anode Plate:

[0116] The anode slurry A1 is coated on the current collector to obtain the first active coating, and the porosity A1 of the first active coating is 20%; the second and third active coatings are respectively coated on the first active coating corresponding to the first and second regions, and A2 is 30% and A3 is 15% to form the anode plate.

[0117] In this Example 1, the length L of the straight part of the current collector along the x-axis is 100 mm, and the length H along the y-axis is 50 mm; among them, the length L1 of the second region along the x-axis is 20 mm, and the length H1 along the y-axis is 10 mm.

[0118] The above-mentioned cathode plate, anode plate, and separator are assembled, and the electrolyte is injected to make the battery.

[0119] Example 2

[0120] The battery of Example 2 is prepared according to the above Example 1, with the only difference being:

[0121] In the preparation of the negative electrode plate, 4 g of urea-formaldehyde resin is further added to the negative electrode slurry A3.

[0122] Example 3

[0123] The battery of Example 3 was prepared according to Example 1 above, with the only difference being that:

[0124] In the preparation of the negative electrode plate, the porosity A1 of the first active coating was adjusted to 35%.

[0125] Example 4

[0126] The battery of Example 4 was prepared according to Example 1 above, with the only difference being that:

[0127] In the preparation of the negative electrode plate, the porosity A1 of the first active coating was adjusted to 15%.

[0128] Example 5

[0129] The battery of Example 5 was prepared according to Example 1 above, with the only difference being that:

[0130] In the preparation of the negative electrode plate, the porosity A3 of the third active coating was adjusted to 30%.

[0131] Example 6

[0132] The battery of Example 6 was prepared according to Example 1 above, with the only difference being that:

[0133] In the preparation of the negative electrode plate, the porosity A3 of the third active coating was adjusted to 10%.

[0134] Example 7

[0135] The battery of Example 7 was prepared according to Example 1 above, with the only difference being that:

[0136] In the preparation of the negative electrode plate, the porosity A2 of the second active coating was adjusted to 50%.

[0137] Example 8

[0138] The battery of Example 8 was prepared according to Example 1 above, with the only difference being that:

[0139] In the preparation of the negative electrode plate, the porosity A2 of the second active coating was adjusted to 20%.

[0140] Example 9

[0141] The battery of Example 9 was prepared according to Example 1 above, with the only difference being that:

[0142] In the preparation of the negative electrode plate, the length L1 of the second region along the x-axis direction was adjusted to 40 mm.

[0143] Example 10

[0144] The battery of Example 10 was prepared according to Example 1 above, with the only difference being that:

[0145] During the preparation of the negative electrode sheet, the length L1 of the second region along the x-axis was adjusted to 10 mm.

[0146] Example 11

[0147] The battery of Example 11 was prepared according to Example 1 above, with the only difference being that:

[0148] During the preparation of the negative electrode sheet, the length H1 of the second region along the y-axis was adjusted to 20 mm.

[0149] Example 12

[0150] The battery of Example 12 was prepared according to Example 1 above, with the only difference being that:

[0151] During the preparation of the negative electrode sheet, the length H1 of the second region along the y-axis was adjusted to 5 mm.

[0152] Comparative Example 1

[0153] The battery of Comparative Example 1 was prepared according to Example 1 above, with the only difference being that:

[0154] During the preparation of the negative electrode sheet, the porosity A1 of the first active coating was adjusted to 50%.

[0155] Comparative Example 2

[0156] The battery of Comparative Example 2 was prepared according to Example 1 above, with the only difference being that:

[0157] During the preparation of the negative electrode sheet, the porosity A1 of the first active coating was adjusted to 10%, and the length H1 of the second region along the y-axis was adjusted to 11 mm.

[0158] Comparative Example 3

[0159] The battery of Comparative Example 3 was prepared according to Example 1 above, with the only difference being that:

[0160] During the preparation of the negative electrode sheet, the porosity A2 of the second active coating was adjusted to 55%, and the length H1 of the second region along the y-axis was adjusted to 11 mm.

[0161] Comparative Example 4

[0162] The battery of Comparative Example 4 was prepared according to Example 1 above, with the only difference being that:

[0163] In the preparation of the negative electrode sheet, adjust the porosity A2 of the second active coating to 10%, and adjust the length H1 of the second region along the y-axis to 11 mm.

[0164] Comparative Example 5

[0165] The battery of Comparative Example 5 was prepared according to Example 1 above, with the only difference being that:

[0166] In the preparation of the negative electrode sheet, adjust the porosity A3 of the third active coating to 40%, and adjust the length H1 of the second region along the y-axis to 11 mm.

[0167] Comparative Example 6

[0168] The battery of Comparative Example 6 was prepared according to Example 1 above, with the only difference being that:

[0169] In the preparation of the negative electrode sheet, adjust the porosity A3 of the third active coating to 5%, and adjust the length H1 of the second region along the y-axis to 11 mm.

[0170] Performance Test

[0171] Test 1: 25°C Cycling Test

[0172] Place the battery in an environment at 25°C and charge it at a current rate of 1C to the charging cut-off voltage, then let it stand for 30 min. Discharge it at a current rate of 1C to the discharging cut-off voltage and let it stand for 30 min. This process is one cycle. Repeat this process and record the discharge capacity Cn of each cycle, the initial discharge capacity C0. The capacity retention rate of the nth cycle is Cn / C0, and record the number of cycles to reach 80% capacity retention rate.

[0173] Test 2. The test method for porosity is the gas adsorption method: Place the sample in a vacuum environment and gradually introduce an inert gas (such as nitrogen) with a known volume and pressure. The gas molecules will gradually fill the pores of the material. By monitoring the gas adsorption amount at different pressures, the pore volume can be calculated. Combining the total mass and volume information of the sample, the porosity is calculated. This method usually requires a special instrument such as a BET analyzer to complete.

[0174] Test 3. Ultimate Extrusion Safety Test:

[0175] 1) Extrude the large surface: Charge the finished battery at 25°C, use a cylinder with a radius of 75 mm, and extrude it towards the large surface at a speed of 5 mm / s. Keep it for 1 min for every 1% of the deformation until the voltage reaches 0V and stop extruding. Record the deformation amount when the final battery core fails.

[0176] 2) Extrusion on the top: Fully charge the finished battery at 25°C, use a cylinder with a radius of 75 mm, extrude towards the top at a speed of 5 mm / s, maintain for 1 minute for every 1% of deformation, and stop extrusion until the voltage reaches 0V. Record the deformation at which the final battery core fails.

[0177] The test results are shown in Table 1.

[0178] Table 1. Test Results

[0179]

[0180] Continued Table 1.

[0181] Note: In Continued Table 1, "large surface" means that the battery core is located in the xy-axis plane as shown in Figure 8 where the battery core is located in the xy-axis plane, and the extreme extrusion deformation of the large surface represents the deformation along the z-axis direction when extruded in the plane of the xy-axis; "top" means that the battery core is located in the xz-axis plane as shown in Figure 8 where the battery core is located in the xz-axis plane, and "the extreme extrusion deformation of the large surface" represents the deformation along the y-axis direction when extruded in the plane of the xz-axis.

[0182] It can be seen from Table 1 that if a thermosetting polymer is added, the extreme deformation of the large surface and the top is greater, and the compressive resistance is stronger; if the porosity formula is not satisfied, it will affect the number of cycles of the battery core, and at the same time, the compressive resistance of the large surface and the top is weaker; when the porosity of A1 is larger, the extreme deformation of the large surface is smaller, and the compressive resistance of the large surface is weaker; when the porosity of A1 is smaller, the influence on the number of cycles of the battery core is smaller; when the porosity of A2 is larger, the extreme deformation of the large surface is smaller, and the compressive resistance of the large surface is weaker; when the porosity of A2 is smaller, the influence on the number of cycles of the battery core is smaller; when the porosity of A3 is larger, the extreme deformation of the top is smaller, and the compressive resistance of the top is weaker; when the porosity of A3 is smaller, the extreme deformation of the top is larger, and the compressive resistance of the top is stronger, but the number of cycles of the battery core is smaller; when the area of the four-corner region is larger, the compressive resistance of the large surface and the top is stronger; when the area of the four-corner region is smaller, the compressive resistance of the large surface and the top is weaker.

[0183] The parts not detailed in the present invention are well-known technologies to those skilled in the art.

[0184] The basic principles of the present invention have been described above in combination with specific embodiments. However, it should be noted that the advantages, advantages, effects, etc. mentioned in the present invention are only examples and not limitations. It cannot be considered that these advantages, advantages, effects, etc. are essential for each embodiment of the present invention. In addition, the above-disclosed specific details are only for the purpose of illustration and facilitation of understanding, and not for limitation. The above details do not limit the present invention to necessarily adopt the above specific details to implement.

[0185] It should be noted that the term "and / or" or " / " used in this text is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0186] In the specific embodiments and the claims, a list of items connected by the terms "at least one of", "at least one in", "at least one kind in", or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0187] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A negative electrode plate, characterized in that, Comprising: A current collector (100), the current collector (100) comprising a plurality of straight portions (110); the straight portions (110) comprising a first region (111) and a plurality of second regions (112), the plurality of second regions (112) being respectively located at the four corners of the straight portions (110); A first active coating (200), the first active coating (200) being disposed on the first region (111) and the second regions (112) on at least one side of the straight portions (110); A second active coating (300), the second active coating (300) being disposed on the first active coating (200) located in the first region (111); A third active coating (400), the third active coating (400) being disposed on the first active coating (200) located in the second regions (112); Wherein, the porosity of the first active coating (200) is A1, the porosity of the second active coating (300) is A2, the porosity of the third active coating (400) is A3, and A1, A2, and A3 satisfy: A3 < A1 < A2; A1 is 15% - 45%; A2 is 20% - 50%; A3 is 10% - 30%; The length of the straight portion (110) in the x-axis direction is L, and the length in the y-axis direction is H; the length of any one of the second regions (112) in the x-axis direction is L1, and the length in the y-axis direction is H1, and A1, A2, A3, and L, H, L1, H1 satisfy: A3 * 2L1 * H1 / (L * H) + A2 * (1 - 2L1 * H1 / (L * H)) ≥ A1.

2. The negative electrode sheet according to claim 1, wherein The ratio L1 / L of the length L1 of the second region (112) in the x-axis direction to the length L of the straight portion (110) in the x-axis direction is 0.1 - 0.5; And / or, the ratio H1 / H of the length H1 of the second region (112) in the y-axis direction to the length H of the straight portion (110) in the y-axis direction is 0.1 - 0.

5.

3. The negative electrode sheet according to claim 1, characterized in that, The current collector (100) further comprises at least one bent portion (120); At least one side of the bent portion (120) is provided with the first active coating (200), and is on the same side as the first active coating (200) on the straight portion (110); On the first active coating (200) located in the bent portion (120), at least the third active coating (400) is further provided.

4. The negative electrode sheet according to claim 3, wherein The bent portion (120) comprises a third region (121) and a fourth region (122); The third region (121) is located between the second regions (112) of the adjacent straight portions (110), and the fourth region (122) is located between the first regions (111) of the adjacent straight portions (110); the third region (121) and the fourth region (122) are provided with the first active coating (200); The third active coating (400) is provided on the first active coating (200) located in the third region (121), and the second active coating (300) is provided on the first active coating (200) located in the fourth region (122); Alternatively, the third active coating (400) is provided on both the first active coating (200) located in the third region (121) and the first active coating (200) located in the fourth region (122).

5. The negative electrode sheet according to any one of claims 1 to 4, characterized in that, The first active coating (200), the second active coating (300) and the third active coating (400) all include a negative electrode active material, a conductive agent and a binder; wherein, the negative electrode active material includes a carbon-based material and / or a silicon-based material; and / or, the conductive agent includes at least one of conductive carbon black, carbon nanotubes or graphene; and / or, the binder includes at least one of polyvinylidene fluoride, styrene-butadiene rubber or polyacrylic acid.

6. The negative electrode sheet according to claim 5, wherein The third active coating (400) further includes a thermosetting polymer; the thermosetting polymer includes a resin.

7. The negative electrode sheet according to claim 6, characterized in that, The thermosetting polymer includes at least one of phenolic resin, urea-formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin or polyurethane; and / or, the mass content of the thermosetting polymer in the third active coating (400) is 0.5% - 3%.

8. A battery, characterized in that, Comprising: a positive electrode sheet, a separator, and a negative electrode sheet according to any one of claims 1 to 7.

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