Negative plate and battery comprising same

Abstract

The utility model relates to the technical field of batteries, and particularly provides a negative plate and a battery comprising the same. The negative plate comprises a current collector and an active substance layer, and the current collector comprises a first region and a second region along the length direction; the current collector is coated with a first active material layer on any surface of the first region along the thickness direction; the current collector is coated with second active material layers on the two opposite surfaces of the second region in the thickness direction of the second region respectively; the first active material layer contains a first hole, and the second active material layer and the current collector are provided with a second hole and / or a third hole. According to the lithium ion battery, the pore passages are used as channels for rapid diffusion of lithium ions in the negative plate, so that the diffusion speed of the lithium ions is effectively accelerated, and lithium precipitation of the negative plate is avoided, and therefore, the cycle life of the battery under rapid charge is remarkably prolonged; and the pore channel structure can reserve a space for volume expansion of the silicon material, so that the influence of the volume effect of the silicon material on the negative plate is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and specifically provides a negative electrode sheet and a battery comprising the negative electrode sheet. Background Art

[0002] In the relevant technology, the electrode is one of the key factors that determine the performance of the battery. Among them, the active material layer on the negative electrode sheet is generally graphite or silicon-doped graphite, which will cause the diffusion distance of lithium ions to the lithium insertion position to be longer, that is, the void tortuosity coefficient is large, then the resistance to lithium ion diffusion will also increase, which is not conducive to the performance of the battery. At the same time, the diffusion speed of lithium ions in the graphite solid is slower than the embedding speed, and the positions on the graphite surface that can be embedded with lithium ions are gradually saturated, and the further embedding of lithium ions will be hindered, resulting in lithium deposition, leading to lithium precipitation on the surface of the negative electrode sheet. Among them, the lithium precipitation reaction will cause problems such as increased internal resistance of lithium-ion batteries, capacity attenuation, and decreased battery rate performance and cycle life.

[0003] In addition, the silicon-doped graphite negative electrode sheet produces expansion / contraction stress during repeated lithium insertion / delithiation processes, resulting in large volume changes, which can easily lead to severe fracture of the silicon material, thereby forming an unstable solid electrolyte interface film on the silicon surface and starting to continuously consume the electrolyte, resulting in irreversible capacity loss and low initial coulombic efficiency of the battery. Utility Model Content

[0004] The purpose of the present invention is to solve at least part of the technical problems mentioned above, and this purpose is achieved through the following technical solutions:

[0005] In the first aspect, the utility model proposes a negative electrode sheet, which includes a current collector, a first active material layer and a second active material layer, the current collector includes a connected first region and a second region along its length direction; the current collector is provided with a first active material layer on any side of the first region along its thickness direction; the current collector is provided with a second active material layer on two opposite sides along its thickness direction; the first active material layer contains a first hole, and the second active material layer and the current collector contain a second hole and / or a third hole; wherein, the thickness of the current collector is d1, the thickness of the first active material layer and the second active material layer is d2, the pore depth of the first hole is h1, the pore depth of the second hole is h2, and the pore depth of the third hole is h3, then h1<h2<h3, and h1<d2, d2≤h2<d1+2*d2, and the third hole penetrates the current collector and the two layers of the second active material layer.

[0006] In some embodiments, 1 μm≤d1≤60 μm, 10 μm≤d2≤200 μm, 1 μm≤h1≤200 μm, 10 μm≤h2≤406 μm, and 21 μm≤h3≤406 μm.

[0007] In some embodiments, the second pores on the two second active material layers are staggered in distribution.

[0008] In some embodiments, the first active material layer includes a first retention area, a first opening area, and a second retention area connected in sequence along its length direction, and the first pore is located in the first opening area.

[0009] In some embodiments, the size of the first reserved area along the length direction of the current collector is S1, and the size of the second reserved area along the length direction of the current collector is S2, then 0.5 mm ≤ S1 ≤ 20 mm, 0.5 mm ≤ S2 ≤ 20 mm.

[0010] In some embodiments, the distance between two adjacent first holes on the first active material layer is δ1, the distance between two adjacent second holes on the second active material layer is δ2, and the distance between two adjacent third holes on the second active material layer is δ3, then δ1≤δ2≤δ3.

[0011] In some embodiments, 0.02 mm ≤ δ1 ≤ 2 mm, 0.05 mm ≤ δ2 ≤ 5 mm, and 0.1 mm ≤ δ3 ≤ 10 mm.

[0012] In some embodiments, the dimension of the first active material layer along the length direction is S11, and the dimension of the second active material layer along the length direction is S22, then δ1≤1 / 5*S11, δ2≤1 / 10*S22, and δ3≤1 / 10*S22.

[0013] In some embodiments, 5mm≤S11≤30mm, 30mm≤S22≤300mm.

[0014] In some embodiments, the second active material layer includes a connected third retained area and a second open area along its length direction, the third retained area is close to the first active material layer relative to the second open area, the second hole and the third hole are located in the second open area, and the size of the third retained area along the length direction of the current collector is S3, then 1mm≤S3≤20mm, and 1mm≤S1≤20mm, 5mm≤S11≤500mm.

[0015] In some embodiments, the CB value of the first active material layer is P1, and the CB value of the second active material layer is P2, then P1≥P2, and 0.01≤P1-P2≤0.5.

[0016] In some embodiments, the aperture of the first hole is D1, the aperture of the second hole is D2, and the aperture of the third hole is D3, then 40 μm≤D1≤80 μm, 70 μm≤D2≤100 μm, and 80 μm≤D3≤120 μm.

[0017] In some embodiments, the tensile strength of the current collector is σ, then σ≥400 MPa.

[0018] In some embodiments, the second active material layer includes a tab connection area, the tab connection area is covered with tab protection tape, and the tab protection tape covers the second hole and / or the third hole.

[0019] In some embodiments, the third hole has a first end and a second end along the thickness direction of the current collector, the pore diameter of the first end is D31, the pore diameter of the second end is D32, and D32≤1 / 2*D31.

[0020] In some embodiments, the current collector has a protruding structure at the second hole and / or the third hole, and the height of the protruding structure is g, then g≤1 / 20*h3.

[0021] In a second aspect, the present invention provides a battery comprising the negative electrode sheet according to the first aspect.

[0022] In some embodiments, the battery further includes a positive electrode sheet and a separator, and the negative electrode sheet, the positive electrode sheet, and the separator are wound to form a roll core, and the first hole on the negative electrode sheet faces the middle of the roll core.

[0023] The technical solution proposed by the utility model has at least the following technical effects:

[0024] In the present invention, for the negative electrode sheet of graphite or silicon-doped graphite, the current collector and the first active material layer and the second active material layer form a single-sided area and a double-sided area respectively, and a first hole is constructed on the first active material layer, and a second hole and / or a third hole are constructed on the second active material layer and the current collector. These serve as channels for the rapid diffusion of lithium ions in the negative electrode sheet, effectively accelerating the diffusion rate of lithium ions and avoiding the occurrence of lithium precipitation in the negative electrode sheet, thereby significantly improving the cycle life of the battery under fast charging; at the same time, the above-mentioned pore structure can also accelerate the infiltration of the electrolyte and improve the infiltration effect. Moreover, for the negative electrode sheet of silicon-doped graphite, the pore structure can also reserve space for the volume expansion of the silicon material, reducing the impact of the silicon material volume effect on the negative electrode sheet.

[0025] Therefore, the present invention is applicable to both the negative electrode sheets of pure graphite systems and the negative electrode sheets of silicon-doped graphite systems, and has a more unique beneficial effect on the negative electrode sheets of silicon-doped graphite systems.

[0026] In addition, under high-rate charge and discharge of the battery, the first active material layer on the negative electrode sheet is located in the single-sided area, which has a larger current density and potential difference than the double-sided area, and is more prone to lithium plating. The utility model constructs a first hole in the first active material layer of the negative electrode sheet, thereby increasing the CB value of the first active material layer and preventing lithium plating in the first active material layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to better integrate the contents shown in the drawings with the contents described in the specific embodiments, a brief introduction to the drawings is given below. It is understood that the drawings mentioned below are only schematic illustrations of the relevant technical solutions and some embodiments of the technical solutions of the present utility model. Without making any creative efforts, those skilled in the art can also create drawings showing other embodiments.

[0028] Specifically, the annotations to the drawings of the specification are as follows:

[0029] Figure 1 This is a schematic structural diagram of the winding core described in some embodiments of the present invention;

[0030] Figure 2 A cross-sectional view of a negative electrode sheet according to some embodiments of the present invention;

[0031] Figure 3 A top view of the negative electrode sheet according to some embodiments of the present invention;

[0032] Figure 4 This is a schematic structural diagram of the negative electrode sheet described in Example 1 of the present utility model;

[0033] Figure 5 This is a schematic diagram of the first structure of the negative electrode sheet described in Example 2 of the present utility model;

[0034] Figure 6 This is a second structural schematic diagram of the negative electrode sheet described in Example 2 of the present utility model;

[0035] Figure 7 This is a schematic structural diagram of the negative electrode sheet described in Example 3 of the present utility model;

[0036] Figure 8 This is a schematic structural diagram of the negative electrode sheet described in Example 4 of the present utility model.

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

[0038] 100, negative electrode sheet; 110, current collector; 120, active material layer; A, first active material layer; B, second active material layer; C, tab connection area; H, pore; H1, first pore; H2, second pore; H3, third pore; I, first end; O, second end; 200, tab; a1, positive electrode sheet; a2, double-sided area of ​​negative electrode sheet; a3, separator; a4, single-sided area of ​​negative electrode sheet; X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

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

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

[0041] It should be understood that the terms "include," "comprising," and "having" are open-ended, indicating the presence of the stated features but not excluding the possibility of additional features in the embodiment. Similarly, when terms such as first, second, etc. are used herein to describe multiple features, they are merely used to distinguish one feature from another and do not imply a sequence or order unless the context clearly indicates otherwise.

[0042] It should be understood that, unless the context clearly indicates otherwise, the terms "disposed," "connected," and "installed" should be interpreted broadly. For example, they may refer to fixed, detachable, or integral connections; they may be directly connected or indirectly connected through a medium. Those skilled in the art will understand the specific meanings of these terms in the context of the text based on the specific circumstances.

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

[0044] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0045] First, refer to Figure 2The present invention proposes a negative electrode sheet 100, which includes a current collector 110 and an active material layer 120. The current collector 110 includes a first region and a second region connected along its length direction X, and the active material layer 120 includes a first active material layer A and a second active material layer B; the current collector 110 is coated with the first active material layer A on any side along its thickness direction Z in the first region, and constitutes a single-sided region a4 of the negative electrode sheet; the current collector 110 is coated with the second active material layer B on two opposite sides along its thickness direction Z in the second region, and constitutes a negative electrode sheet. The double-sided area a2 of the sheet; the first active material layer A is provided with first holes H1 arranged in an array, and the second active material layer B is provided with second holes H2 and / or third holes H3 arranged in an array; wherein, the thickness of the current collector 110 is d1, the thickness of the active material layer 120 is d2, the hole depth of the first hole H1 is h1, the hole depth of the second hole H2 is h2, and the hole depth of the third hole H3 is h3, then h1<h2<h3, and h1<d2, d2≤h2<d1+2*d2, and the third hole H3 passes through the current collector 110 and the two layers of the second active material layer B.

[0046] It should be noted that, referring to Figure 1 Because the inner side of the negative electrode sheet single-sided area a4 does not face the positive electrode sheet a1 in the winding core, it does not need to be coated with the active material layer 120 on both sides, avoiding increasing the ineffective thickness and causing energy density loss.

[0047] In addition, the first hole H1 is a blind hole, which does not penetrate the active material layer 120; the second hole H2 is a semi-through hole, which penetrates the single-layer active material layer 120 but does not penetrate the entire negative electrode double-sided area a2; the third hole H3 is a through hole, which penetrates the negative electrode double-sided area a2.

[0048] In some embodiments, 1 μm≤d1≤60 μm, 10 μm≤d2≤200 μm, 1 μm≤h1≤200 μm, 10 μm≤h2≤406 μm, and 21 μm≤h3≤406 μm.

[0049] In the present invention, for a negative electrode sheet 100 made of graphite or silicon-doped graphite, the current collector 110 and the first active material layer A and the second active material layer B respectively form a single-sided negative electrode sheet area a4 and a double-sided negative electrode sheet area a2. A first hole H1 is constructed on the first active material layer A, and a second hole H2 and / or a third hole H3 are constructed on the second active material layer B and the current collector 110. These serve as channels for the rapid diffusion of lithium ions in the negative electrode sheet 100, effectively accelerating the diffusion rate of lithium ions and avoiding the occurrence of lithium deposition in the negative electrode sheet 100, thereby significantly improving the cycle life of the battery under fast charging. At the same time, the above-mentioned hole H can also accelerate the infiltration of the electrolyte and improve the infiltration effect. Moreover, for the negative electrode sheet 100 made of silicon-doped graphite, the hole H structure can also reserve space for the volume expansion of the silicon material, reducing the impact of the silicon material volume effect on the negative electrode sheet 100.

[0050] Therefore, the present invention is applicable to both the negative electrode sheet 100 of a pure graphite system and the negative electrode sheet 100 of a silicon-doped graphite system, and has a more unique beneficial effect on the negative electrode sheet 100 of the silicon-doped graphite system.

[0051] In addition, under high-rate charge and discharge of the battery, the first active material layer A on the negative electrode sheet 100 is located in the single-sided area a4 of the negative electrode sheet, which has a larger current density and potential difference than the double-sided area a2 of the negative electrode sheet, and is more prone to lithium deposition. The utility model constructs a first hole H1 in the first active material layer A of the negative electrode sheet 100, thereby increasing the CB value of the first active material layer A and preventing lithium deposition in the first active material layer A.

[0052] It can be understood that the current collector 110 has a length direction X, a width direction Y, and a thickness direction Z, and the length direction X, the width direction Y, and the thickness direction Z are perpendicular to each other.

[0053] It should be noted that the pores H can be prepared by any one of laser drilling and mechanical punching, or by a combination of the two methods. Preferably, the pores H are prepared by laser drilling to ensure the accuracy of the size of the pores H. The current collector 110 can be punched first, or the entire structure can be punched after the active material layer 120 is coated thereon.

[0054] Specifically, refer to Figures 6 to 8 The first hole H1 is formed in the first active material layer A, and the second hole H2 extends from one of the two second active material layers B to the other. In some embodiments, the second holes H2 in the two second active material layers B are staggered. This structure can prevent problems such as broken strips in the negative electrode sheet 100 during manufacturing, improving process capabilities.

[0055] In particular, the CB value, or Cell Balance value, is an important parameter in battery design. It refers to the excess ratio of the negative electrode capacity per unit area to the positive electrode capacity. This parameter is crucial to ensuring that the battery avoids the precipitation of lithium metal during the charge and discharge process and improving the safety and cycle life of the battery. The calculation method of the CB value is: CB = gram capacity of negative electrode active material × negative electrode surface density × negative electrode active material content ratio ÷ (gram capacity of positive electrode active material × positive electrode surface density × positive electrode active material content ratio). When designing a lithium battery, the CB value is usually required to be greater than 1 to ensure that the negative electrode has sufficient capacity relative to the positive electrode to accommodate the embedded and deintercalated lithium ions, thereby avoiding the precipitation of lithium dendrites on the negative electrode surface, which can significantly improve the safety performance of the battery.

[0056] In actual design, the CB value needs to take into account a variety of factors, including the initial efficiency of the positive and negative electrode materials, coating accuracy, and the decay rate of the positive and negative electrode cycles. For example, if the initial efficiency of the positive electrode material is lower than that of the negative electrode material, the CB value may need to be increased to ensure that the lithium ions generated by the positive electrode can be fully absorbed by the negative electrode during the first charge. Furthermore, the design of the CB value also needs to consider the battery's rate capability and cycle life, as well as the battery's performance under different usage conditions.

[0057] In some embodiments, reference Figure 2 The first active material layer A includes a first reserved area, a first opening area, and a second reserved area connected in sequence along its length direction X. The first hole H1 is located in the first opening area, that is, the first hole H1 is not opened in the first reserved area and the second reserved area. In some embodiments, the size of the first reserved area along the length direction X of the current collector 110 is S1, and the size of the second reserved area along the length direction X of the current collector 110 is S2. Then, 0.5 mm ≤ S1 ≤ 20 mm, 0.5 mm ≤ S2 ≤ 20 mm; In addition, for a clearer explanation, in Figure 2 The dimension of the first opening area in the length direction X is marked as S4.

[0058] In the above embodiment, the end of the first active material layer A is retained and not punched. This prevents the negative electrode sheet 100 from shedding powder, breaking, or wrinkling due to drilling in this area, which can lead to problems such as poor K value and lithium deposition, thereby improving the yield and efficiency of the process. The size of the reserved area should not be too short, otherwise the protection effect will be poor, nor too long, otherwise excessive space will be wasted. It should be kept moderate. For example, S1 can be 0.5 mm, 10 mm, or 20 mm, and S2 can be 0.5 mm, 10 mm, or 20 mm.

[0059] Similarly, in some embodiments, the second active material layer B includes a third reserved area and a second open area connected along its length direction X. The third reserved area is close to the first active material layer A relative to the second open area, and the second hole H2 and the third hole H3 are located in the second open area, that is, the third reserved area does not have the second hole H2 and the third hole H3; the size of the third reserved area along the length direction X of the current collector 110 is S3, then 1mm≤S3≤20mm, and 1mm≤S1≤20mm, 5mm≤S11≤500mm. Among them, S3 can be 1mm, 10mm, 20mm; S1 can be 1mm, 10mm, 20mm; S11 can be 5mm, 250mm, 500mm; for more clear explanation, in Figure 2 The dimension of the second opening area in the length direction X is marked as S5.

[0060] In some embodiments, the distance between two adjacent first holes H1 in the first active material layer A is δ1, the distance between two adjacent second holes H2 in the second active material layer B is δ2, and the distance between two adjacent third holes H3 in the second active material layer B is δ3, then δ1≤δ2≤δ3. In some embodiments, 0.02mm≤δ1≤2mm, 0.05mm≤δ2≤5mm, and 0.1mm≤δ3≤10mm. δ1 can be 0.02mm, 0.5mm, or 2mm; δ2 can be 0.05mm, 0.5mm, or 5mm; and δ3 can be 0.1mm, 0.5mm, or 10mm.

[0061] In some embodiments, reference Figure 1 , the dimension of the first active material layer A along the length direction X is S11, and the dimension of the second active material layer B along the length direction X is S22, then δ1 ≤ 1 / 5*S11, δ2 ≤ 1 / 10*S22, and δ3 ≤ 1 / 10*S22. In some embodiments, 5 mm ≤ S11 ≤ 30 mm, and 30 mm ≤ S22 ≤ 300 mm. S11 can be 5 mm, 10 mm, or 30 mm; S22 can be 30 mm, 100 mm, or 300 mm.

[0062] In some embodiments, the CB value of the first active material layer A is P1, and the CB value of the second active material layer B is P2, then P1 ≥ P2, and 0.01 ≤ P1-P2 ≤ 0.5. In some embodiments, the pore size of the first hole H1 is D1, the pore size of the second hole H2 is D2, and the pore size of the third hole H3 is D3, then

[0063] 40μm≤D1≤80μm, 70μm≤D2≤100μm, 80μm≤D3≤120μm.

[0064] In the above embodiment, preferably, the pore depth on the first active material layer A is smaller than the pore depth on the second active material layer B, and the pore diameter on the first active material layer A is smaller than the pore diameter on the second active material layer B, and the pore spacing on the first active material layer A is smaller than the pore spacing on the second active material layer B. Because the battery has a larger current density and potential difference in the first active material layer A of the negative electrode sheet 100 under high-rate charge and discharge, lithium plating is more likely to occur. The above setting method reduces the powder loss of the first active material layer A, and at the same time can improve the CB value of the first active material layer A, and ensures sufficient lithium ion diffusion channels to prevent lithium plating in the first active material layer A.

[0065] In some embodiments, reference Figure 3 The second active material layer B includes a tab connection area C, and the tab connection area C is covered with tab protection tape, which covers the second hole H2 and / or the third hole H3.

[0066] It should be noted that the tab connection area C has a tab 200 cleaning groove, which is used to clean dust and weld with the tab 200. The tab protection tape at least covers the tab connection area C, thereby protecting the tab 200; the tab connection area C is provided with a channel H to increase the roughness here, thereby increasing the bonding area with the tab protection tape and enhancing the firmness of the bonding.

[0067] In addition, the utility model is suitable for the solution of placing the pole tab in the middle, and is also suitable for the structure of multiple pole tabs, and the first active material layer A and the second active material layer B can be artificial graphite, natural graphite, silicon-doped graphite; they can also be at least one of soft carbon, hard carbon, carbon fiber, silicon-based material, tin-based material, and lithium titanate, wherein the silicon content of the silicon-doped graphite can be 1% to 90%.

[0068] In some embodiments, the third hole H3 has a first end I and a second end O along the thickness direction Z of the current collector 110 . The pore diameter of the first end I is D31 , and the pore diameter of the second end O is D32 . Then, D32 ≤ 1 / 2*D31 .

[0069] In some embodiments, the current collector 110 is a high-strength copper foil, and the tensile strength of the high-strength copper foil is σ, where σ ≥ 400 MPa. In some embodiments, the current collector 110 has a protrusion structure at the second hole H2 and / or the third hole H3, where the protrusion height of the protrusion structure is g, where g ≤ 1 / 20*h3.

[0070] It should be noted that while constructing multiple third holes H3 on the negative electrode sheet 100 is beneficial for electrolyte infiltration, it also poses a risk of tape breakage during the manufacturing process. Using high-strength copper foil can effectively avoid tape breakage during hole formation and can also prevent corner cracking. In addition, when laser drilling is used, the laser will burn the high-strength copper foil and generate copper oxide, thereby preventing the electrolyte from corroding the perforated areas of the high-strength copper foil, which is beneficial to battery stability. On the other hand, the perforated areas will also produce burnt residues, that is, protruding structures left by the perforations. The protrusion height cannot be too high, otherwise it will affect the electrolyte infiltration effect.

[0071] In a second aspect, the present invention provides a battery comprising the negative electrode sheet 100 of the first aspect. In some embodiments, referring to Figure 1 The battery also includes a positive electrode sheet a1 and a separator a3. The negative electrode sheet 100, the positive electrode sheet a1 and the separator a3 are wound to form a core. The first hole H1 on the negative electrode sheet 100 faces the middle of the core. Compared with the second hole H2 or the third hole H3 facing the middle of the core, this structure does not cause serious powder loss and has little impact on the battery K value.

[0072] The K value is a particularly important parameter in the battery industry, often used to measure a battery's self-discharge rate. Self-discharge refers to the loss of charge due to internal chemical reactions when the battery is not in use. The K value is calculated by measuring the change in the battery's open-circuit voltage over a certain time interval. Therefore, the K value has a significant impact on battery performance. A smaller K value means a battery has a lower self-discharge rate and better ability to retain a charge.

[0073] In the above embodiment, the battery of the second aspect includes the negative electrode sheet 100 of the first aspect. Therefore, the battery of the second aspect has at least all the technical effects of the negative electrode sheet 100 of the first aspect, and its specific technical effects are not repeated here.

[0074] The embodiments of the present invention only illustrate the structure of the battery of the second aspect related to the improvement points of the present application, but do not mean that it does not have other structures. For example, the battery of the second aspect also includes an end cover, a shell, etc. Other structures will not be described one by one here.

[0075] Specifically, some detailed embodiments are listed below to illustrate the utility model:

[0076] Example 1

[0077] 1. Preparation of positive electrode sheet a1: Lithium cobalt oxide, a conductive agent (a mixture of conductive carbon black and carbon nanotubes), and PVDF are placed in NMP at a mass ratio of 98.20:1.00:0.80 and stirred evenly to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the front and back sides of an aluminum foil, and the positive electrode sheet a1 is obtained after drying, rolling, slitting, cleaning, and sheeting.

[0078] 2. Reference Figure 4 , prepare the negative electrode sheet 100: put graphite, Si, conductive carbon black, binder, and CMC in deionized water according to a mass ratio of 93:7:0.05:2.4:0.35, stir evenly, and prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the current collector 110 of the negative electrode sheet 100, and the current collector 110 has a tensile strength σ=400MPa, and is dried, rolled, and cut in sequence. After the cut negative electrode sheet 100, a third hole H3 is laser-drilled on the second active material layer B. The hole depth h3 = 2*d2 + d1 = 406 μm, the spacing δ3 = 400 μm, and the hole diameter D3 = 120 μm were laser-drilled in the first active material layer A of the negative electrode sheet 100. The hole depth h1 = 1 μm, the spacing δ1 = 500 μm, and the hole diameter D1 = 90 μm were laser-drilled. The power of the laser drilling in the second active material layer B of the negative electrode sheet 100 was set to 30%, and the power of the laser drilling in the first active material layer A of the negative electrode sheet 100 was set to 12%. The laser-drilled negative electrode sheet 100 was then cleaned to obtain the product.

[0079] 3. Battery Preparation: The separator a3 has a total thickness of 7 μm and is made of a substrate + ceramic + adhesive coating. The electrolyte includes a lithium salt and a solvent. The solvent includes ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), with a molar ratio of DEC:EC:EMC = 1:1:1. The above-cut positive electrode sheet a1, separator a3, and negative electrode sheet 100 are stacked in sequence and wound into a core. After packaging, injection, formation, and secondary sealing, a lithium-ion battery is produced.

[0080] In addition, in this embodiment, d1=60μm, d2=200μm, S1=0.5mm, S2=0.5mm, S11=5mm, S22=30mm, S3=1mm, P1=1.05, P2=1.04, D31=120μm, D32=60μm, g=1.5μm.

[0081] Example 2

[0082] Reference Figure 5 and Figure 6 By adjusting the laser power, the second active material layer B of the negative electrode sheet 100 is set to have a second hole H2 drilled on both sides to the copper foil, with a hole depth h2 = d2 = 10 μm, a hole spacing δ2 = 400 μm, a hole diameter D2 = 100 μm, and a laser drilling power set to 18%; the first active material layer A of the negative electrode sheet 100 is set to have a first hole H1, with a hole depth h1 = 1 μm, a hole spacing δ1 = 500 μm, a hole diameter D1 = 90 μm, and a laser drilling power set to 12%; in addition, in this embodiment, S1 = 20 mm, S2 = 20 mm, S11 = 30 mm, S22 = 300 mm, and S3 = 20 mm, and the silicon doping rate in the graphite of the negative electrode sheet 100 is 1%. The rest is the same as in Example 1.

[0083] Example 3

[0084] Reference Figure 7 By adjusting the laser power, the second active material layer B of the negative electrode sheet 100 is set to have second holes H2 drilled on both sides until the copper foil is just broken, with a hole depth h2 = 100 μm, a hole spacing δ2 = 400 μm, and a hole diameter D2 = 108 μm. The laser drilling power is set to 21%; the first active material layer A of the negative electrode sheet 100 is set to have first holes H1, with a hole depth h1 = 20 μm, a hole spacing δ1 = 500 μm, and a hole diameter D1 = 90 μm. The laser drilling power is set to 12%; the silicon doping rate in the graphite of the negative electrode sheet 100 is 90%, and the rest is the same as in Example 1.

[0085] Example 4

[0086] Reference Figure 8By adjusting the laser power, the second active material layer B of the negative electrode sheet 100 is set to have a double-sided second hole H2 drilled through the negative electrode active material layer 120 and the current collector 110 on one side to 1 / 3 of the negative electrode active layer on the other side, with a hole depth of h2 = d2 + d1 = 130 μm, a hole spacing δ2 = 400 μm, a hole diameter D2 = 115 μm, and a laser drilling power set to 24%; the first active material layer A of the negative electrode sheet 100 is set to have a first hole H1, with a hole depth of h1 = 20 μm, a hole spacing δ1 = 500 μm, a hole diameter D1 = 90 μm, and a laser drilling power set to 12%; the rest is the same as in Example 1.

[0087] Example 5

[0088] Reference Figure 4 By adjusting the laser power, the power of laser drilling of the second active material layer B of the negative electrode sheet 100 is set to 30%, and a third hole H3 is set in the second active material layer B of the negative electrode sheet 100, with a hole depth h3 = 21 μm, a hole spacing δ3 = 21 μm, and a hole diameter D3 = 80 μm. A first hole H1 is laser-drilled in the first active material layer A of the negative electrode sheet 100, and the power of laser drilling is set to 12%, with a hole depth h1 = 10 μm, a hole spacing δ1 = 50 μm, and a hole diameter D1 = 40 μm. The rest is the same as in Example 1.

[0089] Example 6

[0090] Reference Figure 4 By adjusting the laser power, a third hole H3 is set in the second active material layer B of the negative electrode sheet 100, with a hole depth h3 = 406 μm, a hole spacing δ3 = 10 mm, and a hole diameter D3 = 120 μm. A first hole H1 is laser-drilled in the first active material layer A of the negative electrode sheet 100, with a hole depth h1 = 20 μm, a hole spacing δ1 = 2 mm, and a hole diameter D1 = 90 μm. The power of the laser drilling of the second active material layer B of the negative electrode sheet 100 is set to 30%; the power of the laser drilling of the first active material layer A of the negative electrode sheet 100 is set to 12%. The rest is the same as in Example 1.

[0091] Comparative Example 1

[0092] The positive electrode sheet a1 and the negative electrode sheet 100 are not punched, and the rest is the same as in Example 1.

[0093] Comparative Example 2

[0094] By adjusting the laser power, the third hole H3 is opened in both the second active material layer B and the first active material layer A of the negative electrode sheet 100. The laser drilling power is set to 30%, and the rest is the same as in Example 1.

[0095] Comparative Example 3

[0096] By adjusting the laser power, the first holes H1 are opened in both the second active material layer B and the first active material layer A of the negative electrode sheet 100. The laser drilling power is set to 12%, and the rest is the same as in Example 1.

[0097] The capacity, internal resistance, capacity decay and edge lithium deposition of the battery cells obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated, as shown in the following table.

[0098] Compared to Comparative Example 1, Examples 1 to 4 exhibited increased capacity, and capacity decay exhibited an increasing trend with increasing pore depth in the second active material layer B of the negative electrode sheet 100. Furthermore, increasing pore depth in the second active material layer B of the negative electrode sheet 100 further reduced internal resistance in Examples 1 to 4. Comparing Examples 1 to 4 with Comparative Example 1, the formation of second pores H2 and / or third pores H3 in the second active material layer B increased battery capacity, reduced internal resistance, widened the lithium plating window, and improved battery cycling performance.

[0099] Comparing Example 5 with Comparative Example 1, since the pore spacing between the negative electrode sheet single-sided area a4 and the negative electrode sheet double-sided area a2 in Example 5 is smaller, more negative electrode active material is lost, resulting in a lower overall CB value, so the lithium plating situation is slightly improved.

[0100] Comparing Example 6 with Comparative Example 1, since the pore spacing between the single-sided area a4 of the negative electrode sheet and the double-sided area a2 of the negative electrode sheet in Example 5 is larger, the pore H area on the negative electrode sheet 100 accounts for a smaller proportion, and a small part of the area reduces the pore tortuosity of the electrode, thereby slightly improving the lithium plating situation.

[0101] Comparing Example 1 with Comparative Example 2, the pore H areas of the first active material layer A and the second active material layer B of Comparative Example 2 are both third pores H3. Since the third pores H3 are constructed in the single-sided area of ​​Comparative Example 2, the surface of the negative electrode sheet 100 will fall off and peel, which will increase the internal resistance of the battery cell and affect the K value. At the same time, at a high rate, there is a greater current density and potential difference in the first active material layer A of the electrode sheet, which is more prone to lithium deposition. The construction of the first pore H1 in the single-sided area of ​​the electrode sheet in Example 1 accelerates the infiltration of the electrolyte, improves the infiltration effect, and increases the CB value of the edge area, thereby preventing lithium deposition in the single-sided area.

[0102] Overall, compared to Comparative Example 3, Examples 1 to 4 show improvements in internal resistance, capacity retention, and lithium plating window. This is primarily because the second pore H2 / third pore H3 structure of the negative electrode sheet 100 in Examples 1 to 4 significantly reduces the electrode's pore tortuosity, serving as a channel for the rapid diffusion of lithium ions within the electrode sheet. This facilitates rapid lithium ion diffusion within the electrode, improves the lithium ion diffusion coefficient, enhances mass transfer between the positive and negative electrodes, and reduces ionic impedance. Furthermore, this improves the electrolyte infiltration effect and speed, as well as the electrolyte storage capacity, thereby mitigating lithium plating at the edge of the negative electrode sheet 100 and improving the battery's capacity retention.

[0103] Group Capacity / mAh Internal resistance / mΩ Cycle times when capacity is less than 80% / T Edge lithium deposition at 400T cycle Example 1 4963.54 0.59 730 No lithium plating Example 2 4923.35 0.68 721 No lithium plating Example 3 4955.56 0.65 723 No lithium plating Example 4 4903.23 0.62 709 No lithium plating Example 5 4863.37 0.69 673 Slight lithium deposition on the edge Example 6 4829.79 0.70 659 Slight lithium deposition on the edge Comparative Example 1 4562.35 0.74 611 Severe lithium deposition at the edge Comparative Example 2 4792.56 0.79 642 Slight lithium deposition on the edge Comparative Example 3 4792.56 0.73 642 Severe lithium deposition at the edge

[0104] In particular, the first hole H1, the second hole H2 and the third hole H3 can all have a gradually decreasing pore size from the first end I to the second end O, or can have a consistent pore size from the first end I to the second end O; the second holes H2 on the two layers of the second active material layer B can be arranged correspondingly along the thickness direction Z, or can be staggered.

[0105] In addition, the term "and / or" in this utility model should be understood as follows:

[0106] In the first case, the term “and / or” located between a first subject and a second subject includes any one of the following meanings: (1) only the first subject; (2) only the second subject; and (3) the first subject and the second subject.

[0107] In the second case, the term "and / or" between the last two entities in three or more entities means including at least any one of the entities. For example, "the first entity, the second entity and / or the third entity" has the same meaning as "the first entity and / or the second entity and / or the third entity", specifically including the following combinations: (1) only the first entity; (2) only the second entity; (3) only the third entity; (4) the first entity and the second entity without the third entity; (5) the first entity and the third entity without the second entity; (6) the second entity and the third entity without the first entity; and (7) the first entity, the second entity, and the third entity.

[0108] In addition, although the above content describes the embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art can also make various modifications and variations without departing from the concept of the present invention, and such modifications and variations will fall within the scope of protection of the present invention.

Claims

1. A negative electrode sheet, characterized in that: The device comprises a current collector (110), a first active material layer (A) and a second active material layer (B), wherein the current collector (110) comprises a first region and a second region connected along a length direction (X) thereof; The current collector (110) is provided with the first active material layer (A) on any surface of the first region along the thickness direction (Z) thereof; The current collector (110) is provided with the second active material layer (B) on two opposite sides of the second region along the thickness direction (Z) thereof. The first active material layer (A) contains a first hole (H1), and the second active material layer (B) and the current collector (110) contain a second hole (H2) and / or a third hole (H3); The thickness of the current collector (110) is d1, the thickness of the first active material layer (A) and the second active material layer (B) is d2, the depth of the first hole (H1) is h1, the depth of the second hole (H2) is h2, and the depth of the third hole (H3) is h3, then h1<h2<h3, and h1<d2, d2≤h2<d1+2*d2; the third hole (H3) passes through the current collector (110) and the two layers of the second active material layer (B).

2. The negative electrode sheet (100) according to claim 1, characterized in that: 1μm≤d1≤60μm, 10μm≤d2≤200μm, 1μm≤h1≤200μm, 10μm≤h2≤406μm, 21μm≤h3≤406μm.

3. The negative electrode sheet according to claim 1, characterized in that: The second holes (H2) on the two second active material layers (B) are staggered in distribution.

4. The negative electrode sheet according to claim 1, characterized in that: The first active material layer (A) includes a first reserved area, a first opening area, and a second reserved area connected in sequence along its length direction (X), and the first hole (H1) is located in the first opening area.

5. The negative electrode sheet according to claim 4, characterized in that: The size of the first reserved area along the length direction (X) of the current collector (110) is S1, and the size of the second reserved area along the length direction (X) of the current collector (110) is S2, then 0.5mm≤S1≤20mm, 0.5mm≤S2≤20mm.

6. The negative electrode sheet according to claim 5, characterized in that: The distance between two adjacent first holes (H1) on the first active material layer (A) is δ1, the distance between two adjacent second holes (H2) on the second active material layer (B) is δ2, and the distance between two adjacent third holes (H3) on the second active material layer (B) is δ3, then δ1≤δ2≤δ3.

7. The negative electrode sheet according to claim 6, characterized in that: 0.02mm≤δ1≤2mm, 0.05mm≤δ2≤5mm, 0.1mm≤δ3≤10mm.

8. The negative electrode sheet according to claim 6, characterized in that: The size of the first active material layer (A) along the length direction (X) is S11, and the size of the second active material layer (B) along the length direction (X) is S22, then δ1≤1 / 5*S11, δ2≤1 / 10*S22, δ3≤1 / 10*S22.

9. The negative electrode sheet according to claim 8, characterized in that: 5mm≤S11≤30mm, 30mm≤S22≤300mm.

10. The negative electrode sheet according to claim 8, characterized in that: The second active material layer (B) includes a third reserved area and a second open area connected along its length direction (X), the third reserved area is close to the first active material layer (A) relative to the second open area, the second hole (H2) and the third hole (H3) are located in the second open area, and the size of the third reserved area along the length direction (X) of the current collector (110) is S3, then 1mm≤S3≤20mm, and 1mm≤S1≤20mm, 5mm≤S11≤500mm.

11. The negative electrode sheet according to claim 1, characterized in that: The CB value of the first active material layer (A) is P1, and the CB value of the second active material layer (B) is P2, then P1≥P2, and 0.01≤P1-P2≤0.

5.

12. The negative electrode sheet according to claim 1, characterized in that: The aperture of the first hole (H1) is D1, the aperture of the second hole (H2) is D2, and the aperture of the third hole (H3) is D3, then 40μm≤D1≤80μm, 70μm≤D2≤100μm, 80μm≤D3≤120μm.

13. The negative electrode sheet according to claim 1, characterized in that: The tensile strength of the current collector (110) is σ, σ≥400MPa.

14. The negative electrode sheet according to claim 1, characterized in that: The second active material layer (B) includes a tab connection area (C), and the tab connection area (C) is covered with tab protection tape, and the tab protection tape covers the second hole (H2) and / or the third hole (H3).

15. The negative electrode sheet according to claim 1, characterized in that: The third hole (H3) has a first end (I) and a second end (O) along the thickness direction (Z) of the current collector (110), the aperture of the first end (I) is D31, the aperture of the second end (O) is D32, and D32≤1 / 2*D31.

16. The negative electrode sheet according to claim 1, characterized in that: The current collector (110) has a convex structure at the second hole (H2) and / or the third hole (H3), and the height of the convex structure is g, then g≤1 / 20*h3.

17. A battery, characterized in that: A negative electrode sheet (100) comprising the negative electrode sheet (100) according to any one of claims 1 to 16.

18. The battery according to claim 17, characterized in that The battery further comprises a positive electrode sheet (a1) and a separator (a3); the negative electrode sheet (100), the positive electrode sheet (a1) and the separator (a3) ​​are wound to form a winding core; the first hole (H1) on the negative electrode sheet (100) faces the middle of the winding core.

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