Pole piece, electrode assembly, battery cell, and coating device

Abstract

The application relates to a pole piece, an electrode assembly, a battery monomer and a coating device. The pole piece comprises a coating layer. The coating layer is divided into a first coating area and a second coating area along the width direction of the pole piece, and the two sides of the first coating area are provided with the second coating area. Along the extension direction of the pole piece, the first coating area comprises at least one low-density area, the compaction density of the low-density area is lower than that of the second coating area, and the compaction densities of all the low-density areas change according to the rule of first decreasing and then increasing along the extension direction of the pole piece. The design of the low-density area in the application can guarantee that the middle region of the pole piece still maintains effective porosity under the pressure working condition, ensures the smoothness of the ion transmission channel, and further improves the cycle performance of the battery monomer.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, and in particular to electrode sheets, electrode assemblies, battery cells and coating apparatus. Background Technology

[0002] During the cycle of a battery cell, the SEI film formation side reaction leads to a large loss of active lithium and an increase in impedance. The spacing between the negative electrode layer and the positive electrode cell will continue to increase, resulting in a continuous increase in the internal stress of the battery cell. This further leads to severe local pressure on the electrode, resulting in excessively low electrode porosity, ineffective electrolyte wetting, obstructed ion transport, accelerated cycle decay, and a significant impact on the cycle performance of the battery cell. Summary of the Invention

[0003] Based on this, in order to improve the cycle performance of a battery cell, an electrode sheet, an electrode assembly, a battery cell, and a coating apparatus are provided.

[0004] Firstly, this application proposes an electrode sheet comprising: The coating is divided into a first coating area and a second coating area along the width direction of the electrode sheet, and the second coating area is provided on both sides of the first coating area; Along the extension direction of the electrode, the first coating area includes at least one low-density area, the compaction density of the low-density area is lower than the compaction density of the second coating area, and the compaction density of all the low-density areas varies along the extension direction of the electrode according to the law of first decreasing and then increasing.

[0005] In some embodiments, the first coating region includes a low-density region, and the compaction density of the low-density region changes continuously along the extension direction of the electrode in a pattern of first decreasing and then increasing.

[0006] In some embodiments, the first coating area includes a plurality of adjacent low-density areas, and the compaction density of each low-density area changes sequentially along the extension direction of the electrode in a pattern of first decreasing and then increasing.

[0007] In some embodiments, the first coating region includes a high-pressure dense region, and the low-pressure dense region and the high-pressure dense region are arranged alternately along the extension direction of the electrode. The compaction density of the high-pressure dense region is equal to the compaction density of the second coating region, and the compaction density of all the low-pressure dense regions varies stepwise along the extension direction of the electrode according to a pattern of first decreasing and then increasing.

[0008] In some embodiments, the first coating area and its two adjacent second coating areas constitute a coating unit, the centerline of the coating unit in the width direction being located in the first coating area.

[0009] In some embodiments, the width of the coating unit is W, and the width of the low-density zone is W1, satisfying: W1=d4*W, 5%≤d4≤50%; and / or, the two second coating zones in the coating unit are set with equal width.

[0010] In some embodiments, the width of all the low-pressure dense regions varies along the extension direction according to a pattern of first increasing and then decreasing.

[0011] In some embodiments, the width W1 of the low-pressure dense region and the length L1 of the electrode sheet satisfy: W1=d1+d2*L1-d3*L1^2, 5≤d1≤100, 0<d2≤0.5, 0<d3≤0.1, 5m≤L1≤50m, and the unit of W1 is mm.

[0012] In some embodiments, a plurality of low pressure density regions are arranged sequentially along the extension direction of the electrode, and the width W1 of each low pressure density region varies stepwise along the extension direction of the electrode according to a pattern of first increasing and then decreasing.

[0013] In some embodiments, along the width direction of the electrode, the compaction density E of the low-density zone and the width W1 of the low-density zone follow a pattern of first increasing and then decreasing, or satisfying E=d6+d7*W1-d8*W1^2, 1.0≤d6≤5.0, 0<d7≤0.5, 0<d8≤0.1, and the unit of E is g / cc.

[0014] In some embodiments, the low-density area is recessed relative to the second coating areas on both sides.

[0015] In some embodiments, the porosity of the low-density zone is higher than that of the second coating zone.

[0016] In some embodiments, the thickness of the second coating region is T1, and the thickness difference between the low-density region and the second coating region is T3, where T3 = d5 * T1, 0 ≤ d5 ≤ 20%, and 50 μm ≤ T1 ≤ 500 μm.

[0017] In some embodiments, the electrode is a negative electrode, the compaction density of the second coating region is E1 = 1.5 to 1.7 g / cc, and the maximum compaction density of the low-density region is E2 = d9 * E1, 70% ≤ d9 ≤ 95%.

[0018] In some embodiments, the electrode is a positive electrode, the compaction density of the second coating region is E3 = 3.3 to 3.7 g / cc, and the maximum compaction density of the low-density region is E4 = d10 * E3, 60% ≤ d10 ≤ 95%.

[0019] Secondly, this application proposes an electrode assembly, comprising: A positive electrode sheet, a negative electrode sheet, and a separator are wound together, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, and at least one of the positive electrode sheet and the negative electrode sheet is the electrode sheet described in the first aspect; The compaction density of all the low-density zones varies along the winding direction of the electrode from the beginning of the winding to the end of the winding, following a pattern of first decreasing and then increasing.

[0020] In some embodiments, both the positive electrode and the negative electrode are the electrodes described in the first aspect, and the low-pressure density region of the negative electrode is completely offset from or at least partially overlaps with the low-pressure density region of the positive electrode along the width direction of the electrode.

[0021] In some embodiments, along the width direction of the electrode, the low-pressure dense region of the positive electrode completely covers the low-pressure dense region of the negative electrode; The minimum width W1 of the low-pressure dense region of the positive electrode is... min-1 The maximum width W1 of the low pressure density region of the negative electrode sheet max-2 Satisfy: W1 min-1 -W1 max-2 =W4, where W4 is the overhang dimension of the electrode assembly.

[0022] In some embodiments, the first coating area of ​​the electrode includes the high-pressure dense area, and a high-pressure dense area is disposed between every two adjacent low-pressure dense areas. The length of the high-pressure dense area in the winding direction of the electrode is L2, and the number of layers of the electrode in which the high-pressure dense area is located is m, satisfying: L2 = d11 + d12 * m, 0 < d11 ≤ 300, 0 < d12 ≤ 10, and the unit of L2 is mm.

[0023] In some embodiments, the electrode assembly includes a flat region and a corner region, with the corner region arranged on both sides of the flat region, the low-pressure dense region being at least partially located in the corner region, and the high-pressure dense region being located in the flat region.

[0024] In some embodiments, at least one end of the low-pressure dense region in the winding direction is an extended end, the extended end is provided beyond the corner region and the extended length is t, and the length L2 of the high-pressure dense region adjacent to the extended end satisfies: t=d13*L2, 0<d13≤50%.

[0025] Thirdly, this application proposes a battery cell including the electrode assembly described in the second aspect.

[0026] Fourthly, this application provides a coating apparatus, comprising: A coating die head includes a die head body and a gasket, wherein the die head body has a slit and the gasket is located within the slit; The gasket includes a main body and a thinning member. The main body encloses and forms a discharge groove, which is disposed through the thickness direction of the main body and is open at one end in the width direction of the main body. The thinning member is disposed on the main body and located in the discharge groove, and is spaced apart from the main body along the extension direction of the slit. The dimensions of the thinning component along the width direction of the main body are adjustable to adjust the distance D between the thinning component and the open end of the discharge trough.

[0027] In some embodiments, the thinning member moves periodically relative to the body along the width direction of the body, first extending and then retracting.

[0028] In some embodiments, a turbulence-dissipating portion is provided at one end of the thinned member near the open end of the discharge chute; The end face of the turbulence-dissipating part is either a flat surface or an arc surface that protrudes toward the open end of the discharge trough.

[0029] In some embodiments, the dimension of the discharge trough along the extension direction of the slit is S, the dimension of the thinned part along the extension direction of the slit is S1, the sum of the dimensions S1 of all the thinned parts is S1', S1'=a1*S, 5%≤a1≤50%.

[0030] In some embodiments, the main body forms at least one discharge trough, and at most two thinning members are disposed in each discharge trough. The at most two thinning members are separated in the discharge trough to form a plurality of first discharge areas. The plurality of first discharge areas are arranged sequentially along the extension direction of the slit. The dimensions S2 of two first discharge areas located on both sides of the same thinning member are equal or twice that of each other in the extension direction of the slit.

[0031] Compared with the prior art, this application has the following beneficial effects: The aforementioned electrode sheet, electrode assembly, battery cell, and coating apparatus exhibit a decreasing-then-increasing compaction density in the low-density region of the electrode sheet from the beginning to the end of winding. On one hand, the first coating region, located in the middle of the electrode sheet's width, has a lower average compaction density than the second coating regions on either side. The higher compaction density of the second coating regions enhances the adhesion between the coating and the current collector, reduces the risk of electrode delamination and detachment, and ensures the loading of active material, thus guaranteeing the electrode's energy density. On the other hand, the compaction density of the low-density region in the first coating region, exhibiting a distribution characteristic of high at both ends and low in the middle along the winding direction of the electrode sheet, allows the first coating region located in the center of the core to reserve sufficient porosity to offset the compression loss of pores during winding and compression. This ensures that the central region of the electrode sheet maintains effective porosity under pressure, guaranteeing the unobstructed ion transport channels and thereby improving the cycle performance of the battery cell. Attached Figure Description

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the external shape of a battery cell in some embodiments; Figure 2 For some Figure 1 The diagram shows an exploded view of a single battery cell. Figures 3 to 6 These are schematic diagrams of the electrode structure in different embodiments; Figure 7 This is a cross-sectional schematic diagram of the electrode portion where the coating unit is located in some embodiments; Figure 8 This is a schematic diagram of the winding of an electrode assembly according to some embodiments; Figure 9 This is a partial structural diagram of the core in some embodiments; Figure 10 This is a schematic diagram illustrating the composition of a coating die head in some embodiments; Figure 11 and Figure 12 These are schematic diagrams of the gaskets in different embodiments; Figure 13 This is a schematic diagram of the structure of a thinned component in some embodiments.

[0033] The reference numerals in the detailed embodiments are as follows: 1000, Battery cell; 100, Electrode assembly; 101, Positive electrode; 102, Negative electrode; 103, Separator; Q1, Straight region; Q2, Corner region; 10, Electrode; F1, Extension direction; X1, Width direction of electrode; 10A, Coating unit; Y1, Thickness direction of electrode; 11, Coating layer; 11a, First coating area; a1, Low-pressure dense area; r1, Extended end; a2, High-pressure dense area; 11b, Second coating area; 11c, Blank area; 12, current collector; 200, shell; 300, top cover assembly; 2000, coating die head; 2100, die head body; f, slit; r2, discharge end; F2, slit extension direction; 2200, gasket; 2210, main body; X2, width direction of the main body; C, discharge groove; C1, first discharge area; C2, second discharge area; 2211, longitudinal piece; 2212, transverse piece; 2220, thinning part; 2221, turbulence section. Detailed Implementation

[0034] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0035] In the description of this application, it should be understood that, where they appear, the terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0036] Furthermore, where applicable, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," "fixing," etc., shall be interpreted broadly. For example, they may refer to a fixed connection, a detachable connection, or an integral part; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; they may refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] It should be noted that, if an element is described as "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is described as "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0040] To improve the cycle performance of a single battery cell, embodiments of this application propose an electrode sheet, an electrode assembly, a single battery cell, and a coating apparatus.

[0041] Figure 1 This is a schematic diagram of the external shape of a battery cell 1000 according to some embodiments. Figure 2 For some Figure 1 The diagram shows an exploded view of the battery cell 1000.

[0042] The battery cell 1000 in this embodiment can be a primary battery or a secondary battery. Please refer to... Figure 1 and Figure 2 In some embodiments, the battery cell 1000 includes a housing 200, a top cover assembly 300, and an electrode assembly 100. The top cover assembly 300 and the housing 200 together form an internal space for accommodating the electrode assembly 100. Specifically, the housing 200 may have a receiving cavity formed therein, with at least one end open. The top cover assembly 300 closes to the open end of the housing 200 to seal the receiving cavity, and the electrode assembly 100 is mounted within the receiving cavity. The housing 200 may be, but is not limited to, a metal housing 200, such as an aluminum housing or a steel housing.

[0043] The electrode assembly 100 in this embodiment is a wound structure, i.e., a core. The core typically consists of a positive electrode 101, a negative electrode 102, and a separator 103 separating the positive and negative electrode 101. The separator 103 can be a membrane. The battery cell 1000 can be a liquid battery or a solid-state battery. If the battery cell 1000 is a liquid battery, an electrolyte can be injected into it. The electrolyte wets the interior of the electrode assembly 100, providing an ion migration pathway for the electrochemical reaction and acting as a conductor. If the battery cell 1000 is a solid-state battery, compared to a liquid battery, its electrolyte is solid-state and disposed between the positive and negative electrode 101.

[0044] The electrode 10 in the embodiments of this application is described below.

[0045] Figures 3 to 6 This is a schematic diagram of the structure of the electrode 10 in different embodiments. Please refer to... Figures 3 to 6 In this embodiment, the electrode 10 includes a coating 11. The coating 11 is divided into a first coating area 11a and a second coating area 11b along the width direction X1 of the electrode 10, and the second coating area 11b is provided on both sides of the first coating area 11a. Along the extension direction F1 of the electrode 10, the first coating area 11a includes at least one low-density area a1, the compaction density of the low-density area a1 is lower than the compaction density of the second coating area 11b, and the compaction density of all low-density areas a1 varies along the extension direction F1 of the electrode 10 according to the law of first decreasing and then increasing.

[0046] Understandably, the electrode 10 includes a current collector 12, and an active material is coated on the current collector 12 and cured to obtain a coating 11. The current collector 12 is used to collect current and has conductivity. Specifically, the current collector 12 can be a copper layer, an aluminum layer, a stainless steel layer, etc. The electrode 10 is a positive electrode 101 or a negative electrode 102, and the specific composition of the coating 11 depends on the type of electrode 10.

[0047] Electrode 10 is typically strip-shaped along its extension direction F1. Figures 3 to 6 The length of the electrode 10 structure shown in its extension direction F1 is only schematic and is not a limitation on its extension length.

[0048] The electrode 10 is divided into multiple coating areas along its width direction. The multiple coating areas include at least one first coating area 11a and two second coating areas 11b. The second coating areas 11b are distributed on both sides of the first coating area 11a.

[0049] The first coating region 11a includes a low-density region a1, the compaction density of which is lower than that of the low-density region a1 in the second coating region 11b. Compaction density characterizes the mass of active material contained in a unit volume of coating 11, directly reflecting the degree of compaction of the active material within coating 11. Since the proportion of active material per unit volume increases with increasing compaction density, the porosity of coating 11 decreases accordingly.

[0050] The first coating region 11a contains at least one low-density region a1. All low-density regions a1 are considered as a whole, and their compaction density exhibits an evolutionary characteristic of first decreasing and then increasing along the extension direction F1 of the electrode 10.

[0051] As the battery cell undergoes 1000 charge-discharge cycles, the spacing between the negative electrode layers and the positive electrode cells continues to increase, and the thickness of the electrode 10 increases. In the wound electrode assembly 100, the increased thickness of the core leads to increased lateral pressure from the restraint of the electrode 10, resulting in severe local pressure on the electrode 10 (especially in the middle region of the electrode 10), causing excessively low porosity and interrupting the ion transport channels, thus accelerating cycle decay.

[0052] In this embodiment, when the electrode 10 is applied to the winding core, the compaction density of its low compaction zone a1 shows a trend of first decreasing and then increasing along the winding start end to winding end. On the one hand, the first coating area 11a is located in the middle region of the electrode 10 in the width direction, and its average compaction density is lower than that of the second coating areas 11b on both sides. The second coating areas 11b with high compaction density can enhance the bonding force between the coating 11 and the current collector 12, reduce the risk of delamination and peeling of the electrode 10, and ensure the loading of active material to ensure the energy density of the electrode 10. On the other hand, the compaction density of the low compaction area a1 of the first coating area 11a has a distribution characteristic of high at both ends and low in the middle along the winding direction of the electrode 10. This allows the first coating area 11a located in the center region of the core to reserve sufficient pore margin to offset the compression loss of pores during winding and pressing, ensuring that the middle region of the electrode 10 still maintains effective porosity under pressure conditions, ensuring the smoothness of the ion transport channel, and thus improving the cycle performance of the battery cell 1000.

[0053] In some embodiments, refer to Figure 3 and Figure 4 The first coating region 11a includes a low-density region a1, the compaction density of which changes continuously along the extension direction F1 of the electrode 10 according to the law of first decreasing and then increasing.

[0054] The first coating area 11a can form a low-density area a1. The compaction density of this low-density area exhibits a distribution characteristic of being high at both ends and low in the middle, following a linear or nonlinear pattern.

[0055] Because the low-pressure dense area a1 is continuously set, during high-current charging and discharging, the low-pressure dense area a1 forms a continuous electrolyte wetting channel, and the electrolyte can quickly wet along the extension direction F1 of the electrode 10, thereby improving the electrolyte wetting uniformity and wetting amount.

[0056] In some embodiments, the first coating region 11a includes a plurality of adjacent low-density regions a1 (not shown), and the compaction density of each low-density region changes sequentially along the extension direction F1 of the electrode 10 in a pattern of first decreasing and then increasing.

[0057] The compaction density is the same at all points in each low-density zone a1. The compaction density of different low-density zones a1 can be equal or unequal, as long as the density of any two adjacent low-density zones a1 is different, so that the overall low-density zones a1 show a trend of first decreasing and then increasing.

[0058] The length of the low-pressure dense region a1 is the dimension of F1 along the extension direction of the electrode 10, and the lengths of each low-pressure dense region a1 may be equal or unequal.

[0059] At this point, the first coating area 11a is divided into multiple low-pressure dense areas a1 connected sequentially. The electrolyte wetting channels formed by each low-pressure dense area a1 are continuous, allowing the electrolyte to quickly wet along the extension direction F1 of the electrode 10, thus improving the uniformity and amount of electrolyte wetting. Moreover, within a certain rolling length, the same rolling parameters can be used to form a low-pressure dense area a1, simplifying the electrode 10 processing process.

[0060] In some embodiments, refer to Figure 5 and Figure 6 The first coating area 11a includes a high-pressure dense area a2, a low-pressure dense area a1 and a high-pressure dense area a2 arranged alternately along the extension direction F1 of the electrode 10. The compaction density of the high-pressure dense area a2 is equal to the compaction density of the second coating area 11b. The compaction density of all low-pressure dense areas a1 changes stepwise along the extension direction F1 of the electrode 10, first decreasing and then increasing.

[0061] The high-pressure dense zone a2 has the same compaction density as the second coating zone 11b. As a rigid support unit, it enhances the overall mechanical strength of the electrode 10, effectively offsetting the weakening of the electrode 10's structural strength by the low-pressure dense zone a1. This reduces the risk of deformation and breakage of the electrode 10 during production, assembly, and cycling, ensuring the structural integrity of the electrode 10. Simultaneously, the high-pressure dense zone a2 can increase the loading of active material in the electrode 10, thereby increasing its energy density.

[0062] In addition, during charge and discharge cycles, the electrode 10 undergoes volume changes due to lithium delithiation / lithiation. The high-pressure dense area a2, which is spaced apart, can disperse the stress generated by the low-pressure dense area a1, avoid stress concentration, alleviate local strain of the electrode 10, reduce the risk of pulverization and detachment of the low-pressure dense area a1, and improve the cycle life of the battery cell 1000.

[0063] The compaction density of all low-density zones a1 varies stepwise along the extension direction F1 of the electrode 10, first decreasing and then increasing. This includes two scenarios: First, the compaction density of each low-density zone a1 changes individually. Second, all low-density zones a1 are divided into multiple groups along the extension direction F1 of the electrode 10. Multiple low-density zones a1 within the same group are adjacent and have equal compaction densities. The compaction densities of low-density zones a1 in different groups are unequal, and the compaction density of each group of low-density zones a1 varies along the extension direction F1 of the electrode 10, first decreasing and then increasing.

[0064] At this point, the combination of high-pressure dense zone a2 and low-pressure dense zone a1 can be achieved through segmented pressure control of existing roller pressing equipment, without the need for large-scale modification of the production line. The step-like compaction density change achieves discrete control, reducing process complexity and implementation costs.

[0065] In some embodiments, such as Figure 4 and Figure 6 As shown, the first coating area 11a and its two adjacent second coating areas 11b constitute a coating unit 10A, and the center line of the coating unit 10A in the width direction is located in the first coating area 11a.

[0066] When the electrode 10 is applied to a winding core, it typically includes a coating unit 10A. The electrode 10 also includes a blank area 11c located on one side of the coating unit 10A. The blank area 11c is not coated with active material and is used to form tabs. The center line of the coating unit 10A is aligned with the center line of the electrode 10 in the wound state. At this time, the first coating area 11a in the coating unit 10A is centrally located. In the wound state, the first coating area 11a is located in the middle of the winding core, ensuring the electrolyte wetting effect in the middle area of ​​the winding core and improving the cycle performance of the battery cell 1000.

[0067] In some embodiments, continue to refer to Figure 4 and Figure 6 The width of the coating unit 10A is W, and the width of the low-pressure dense area a1 is W1, satisfying: W1=d4*W, 5%≤d4≤50%.

[0068] Specifically, d4 can take values ​​of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and any values ​​between adjacent values.

[0069] The size of d4 determines the total width of the second coating areas 11b on both sides. If d4 is too large, the total width of the second coating areas 11b on both sides will be too small, resulting in insufficient loading of active material on the electrode 10. If d4 is too small, the width of the low-pressure dense area a1 will be too narrow, the reserved pore margin will be insufficient, the pore compression loss that the electrode 10 can not offset under pressure will be insufficient, the ion transport channel will be easily interrupted, and the improvement effect on the core circulation performance will not be obvious.

[0070] When d4 is within the range of 5% to 50%, it can not only ensure that the second coating area 11b on both sides occupies 50% to 95% of the width of the electrode 10, thus guaranteeing the loading of active material in the electrode 10, but also take into account the ability of the low pressure density area a1 to offset the pore compression loss, so that the core energy density and cycle performance are in a better balance.

[0071] In some embodiments, the two second coating regions 11b in the coating unit 10A are arranged with equal width.

[0072] The width of the second coating area 11b refers to the dimension of the second coating area 11b in the width direction of the electrode 10.

[0073] At this point, the equal-width second coating area 11b not only simplifies the processing technology, unifies coating parameters, and reduces equipment debugging complexity, but also ensures a symmetrical distribution of force along the width of the electrode 10, guaranteeing uniform tension in each radial layer of the core and preventing local deformation. Furthermore, it optimizes the alignment reference of the electrode 10, reducing the risk of misalignment, and evenly distributes electrolyte wetting, preventing local capacity decay. Simultaneously, as a high-density area, the second coating area 11b is a crucial current conduction channel. The equal-width arrangement of the second coating areas 11b on both sides ensures consistent current path lengths along the width of the electrode 10, reducing local impedance and extending the 1000-cycle life of the battery cell.

[0074] In some embodiments, the width of all low-pressure dense regions a1 varies along the extension direction F1 according to a pattern of first increasing and then decreasing.

[0075] The radial pressure of the core exhibits a gradient characteristic of "low at both ends and high in the middle" along the winding direction, which can easily lead to excessive porosity compression of the middle electrode 10. The width of the low-pressure-density zone a1 changes according to a "first increases and then decreases" pattern, resulting in a wider low-pressure-density zone a1 in the middle of the core. This wider zone allows for sufficient porosity margin, offsetting the porosity compression loss caused by high pressure. The two ends of the core correspond to narrower low-pressure-density zones a1, avoiding insufficient loading of active material due to excessive width.

[0076] Specifically, in the embodiment, the width W1 of the low-pressure dense area a1 and the length L1 of the electrode 10 satisfy: W1=d1+d2*L1-d3*L1^2, 5≤d1≤100, 0<d2≤0.5, 0<d3≤0.1, 5m≤L1≤50m, and the unit of W1 is mm.

[0077] W1 = d1 + d2 * L1 - d3 * L1^2 is denoted as the first formula. The first formula shows that W1 has a distribution state of "low at both ends and high in the middle" as the length of the electrode 10 increases. This is consistent with the gradient characteristic of the radial pressure of the core along the winding direction of "low at both ends and high in the middle". This allows the electrode 10 in the middle of the core to reserve sufficient pore margin, which can offset the pore compression caused by high pressure stress and improve the circulation performance of the core.

[0078] d1 determines the base value of W1, ensuring that the width of the low-pressure dense zone a1 is maintained within a reasonable range, avoiding insufficient stress compensation due to a width that is too small (<5mm), or a sudden drop in the loading of active material and insufficient energy density due to a width that is too large (>100mm).

[0079] The role of d2 is to counteract the attenuation effect of the quadratic term in the first formula, ensuring that the low-pressure dense region a1 exhibits a slow growth trend in the initial stage of the electrode 10 length, rather than a direct attenuation. A larger d2 results in a faster initial growth rate of W1, allowing the width of the low-pressure dense region a1 to reach the appropriate width more quickly. Conversely, a smaller d2 results in a slower initial growth rate of W1, requiring the width of the low-pressure dense region a1 to reach the target width only at a longer L1 position. This leads to an excessively narrow low-pressure dense region a1 at the front of the core, insufficient stress compensation from pore compression deformation, and excessive porosity compression. Limiting d2 to the range of 0 to 0.5 ensures that W1 increases first and then decreases with the change in electrode 10 length, while preventing the low-pressure dense region a1 width from growing too rapidly, resulting in an excessively wide low-pressure dense region a1 in the middle of the electrode 10 and insufficient loading of active material.

[0080] When d3 takes a value in the range of 0 to 0.1, it works in conjunction with d2 to ensure that W1 takes a value within a reasonable range, avoiding W1 from increasing or decreasing too quickly. This makes W1 change gradually as the length L1 of electrode 10 increases, reducing the difficulty of coating.

[0081] 5m≤L1≤50m means that the first formula applies to the range from the 5th to the 50th meter of electrode 10. The beginning of the winding of electrode 10 is a tension transition zone with irregular stress distribution, making formula compensation meaningless. A fixed narrow width can be used to determine the width of the low-density zone a1 located at the beginning of the winding. After the winding enters a stable stage, the first formula can be used to accurately compensate for the stress. The end of the winding of electrode 10 is a stress release zone, requiring no additional stress compensation. Calculation using the first formula is prone to redundancy. A fixed narrow width can be used to determine the width of the low-density zone a1 at the end of the winding. The range from the 5th to the 50th meter of electrode 10 is usually located between the beginning and end of the winding. Using the first formula to determine the width of the low-density zone a1 within this range can well match the stress distribution characteristics of the core.

[0082] It is worth noting that W1 = d1 + d2*L1 - d3*L1^2, which can accommodate the following scenarios: the first coating region 11a includes only one low-density region a1; the first coating region 11a includes multiple adjacent low-density regions a1, with unequal compaction densities between any two adjacent low-density regions a1; and the first coating region 11a includes the aforementioned high-density region a2. In summary, regardless of the arrangement of the low-density region a1, its width can be determined based on the length position of the electrode 10 where the low-density region a1 is located.

[0083] In other embodiments, a plurality of low-pressure dense regions a1 are arranged sequentially along the extension direction F1 of the electrode 10, and the width W1 of each low-pressure dense region a1 changes sequentially along the extension direction F1 of the electrode 10 in a pattern of first increasing and then decreasing.

[0084] The width of each low-pressure dense zone a1 is equal at all points.

[0085] The width W1 varies stepwise along the extension direction F1 of the electrode 10, first increasing and then decreasing. This includes the fact that the widths of any two adjacent low-pressure dense regions a1 are not equal, and also that the widths of multiple adjacent low-pressure dense regions a1 are equal and form a comparison group. The widths of different comparison groups vary along the extension direction F1 of the electrode 10, first increasing and then decreasing.

[0086] For example, when electrode 10 is applied to the winding core, in turns 1 to h, the width of the low-pressure dense region a1 is W1 = e1 * W; in turns h to i, the width of the low-pressure dense region a1 is W1 = e2 * W; in turns i to j, the width of the low-pressure dense region a1 is W1 = e3 * W; in turns j to k, the width of the low-pressure dense region a1 is W1 = e4 * W, e1 < e2, e2 > e3, e3 > e4.

[0087] At this point, the width variation of each low-pressure dense zone a1 not only conforms to the gradient characteristic of radial stress of the core being "low at both ends and high in the middle", but also has better production adaptability.

[0088] In some embodiments, along the width direction X1 of the electrode 10, the compaction density E of the low-density region a1 and the width W1 of the low-density region a1 follow a pattern of first increasing and then decreasing.

[0089] At this time, along the width direction X1 of the electrode 10, the compaction density of the low-density zone a1 is high in the middle and low at both ends.

[0090] The axial stress of the core exhibits a distribution pattern of "low at both ends and high in the middle." After the core is wound, the central region of the low-density zone a1 is uniformly compressed, making electrolyte wetting more difficult than at the edges, and there is no risk of edge stress concentration. Setting a higher compaction density in the central region maximizes the loading of active material, improves battery energy density, and prevents local capacity imbalances from disrupting the NP ratio. In contrast, the edge region of the low-density zone a1 is prone to edge stress, resulting in more pronounced expansion and contraction during charge-discharge cycles. Furthermore, the edges are the main channels for electrolyte wetting; a lower compaction density retains more voids, alleviating stress, ensuring unobstructed electrolyte channels, and preventing cracking and lithium plating.

[0091] In the specific implementation example, E = d6 + d7 * W1 - d8 * W1^2, 1.0 ≤ d6 ≤ 5.0, 0 < d7 ≤ 0.5, 0 < d8 ≤ 0.1, and the unit of E is g / cc.

[0092] Let E = d6 + d7*W1 - d8*W1^2 be denoted as the second formula. Along the width of the electrode 10, the compaction density E of the low-density region a1 and the width W1 of the low-density region a1 satisfy the second formula. The second formula indicates that the compaction density E of the low-density region a1 exhibits a gradient change along the width direction X1 of the electrode 10, which is "low at both ends and high in the middle". Specifically, in the second formula, W1 can be understood as the coordinate value of any position in the width direction X1 of the low-density region a1, starting from one end point of the low-density region a1.

[0093] d6, as a constant term in the second formula, determines the basic compaction density of the low-density zone a1, expressed in g / cc. If d6 is too small, the overall porosity is too high, leading to insufficient active material loading and a severely insufficient battery energy density. If d6 is too large, the overall porosity is too low, resulting in insufficient stress buffering capacity for pore deformation and an inability to effectively prevent the interruption of ion transport channels. A design with 1.0 ≤ d6 ≤ 5.0 balances porosity and active material content, taking into account both energy density and cycle performance.

[0094] d7, as a linear term in the second formula, is used to control the variation of compaction density along the width direction, determining the slope of the gradient. d8, as a quadratic coefficient in the second formula, with d8 > 0, determines the concave curvature of the compaction density gradient, which is key to forming the "high in the middle and low at both ends" trend.

[0095] d7 > 0, working in conjunction with d8 to limit the rate of decrease in compaction density. Limiting d7 to 0.5 prevents excessively rapid changes in compaction density, which could lead to uneven stress on electrode 10 and warping during processing. Controlling d8 to 0.1 aims to avoid excessively large differences in compaction density between the middle and end regions of the low-density zone a1 in the width direction. Excessive difference results in high edge porosity, leading to insufficient capacity and reduced strength of electrode 10.

[0096] Figure 7 This is a cross-sectional schematic diagram of the electrode 10 where the coating unit 10A is located in some embodiments, excluding the blank area 11c.

[0097] In some embodiments, the low-pressure dense area a1 is provided relative to the second coating recesses on both sides.

[0098] Specifically, the outer surface of the low-pressure dense region a1 is a concave surface, which can be an arc-shaped concave surface, a triangular concave surface, or a trapezoidal concave surface.

[0099] When the low-pressure dense zone a1 is recessed compared to the second coating zones 11b on both sides, the recessed shape guides the flow path of the slurry during coating, allowing the slurry to transition more smoothly in the low-pressure dense zone a1, reducing turbulence and bubble generation, and improving the density and surface smoothness of the coating 11. Simultaneously, the recessed structure increases the space between the core electrodes 10, providing greater expansion space for the core and preventing deformation and cracking due to stress concentration in the core's center. Furthermore, the additional space created by the recessed structure increases the electrolyte storage and wetting channels, allowing the electrolyte to penetrate more fully into the core and optimizing ion transport efficiency. Moreover, the recessed structure increases the heat dissipation area inside the core, reducing the risk of localized overheating.

[0100] In some embodiments, the porosity of the low-pressure dense region a1 is higher than that of the second coating region 11b.

[0101] Typically, the active material in the low-density region a1 is the same as that in the second coating region 11b. When the compaction density of the low-density region a1 is less than that of the second coating region 11b, the porosity of the low-density region a1 is greater than that of the second coating region 11b. Thus, the low-density region a1 can reserve pores to buffer deformation and resist stress generated during the use of the core, avoiding pore compression loss that interrupts ion transport channels and improving the cycle performance of the battery cell 1000.

[0102] In some embodiments, refer to Figure 7 Understand that the thickness of the second coating region 11b is T1, and the thickness difference between the low-density region a1 and the second coating region 11b is T3, where T3 = d5 * T1, and 0 ≤ d5 ≤ 20%.

[0103] Specifically, T3 refers to the thickness difference between the thinnest point of the low-pressure dense area a1 and the thickest point of the second coating area 11b. Specifically, d5 can take values ​​of 0, 1%, 5%, 10%, 15%, 20%, and any values ​​between adjacent values.

[0104] When d5=0, the thickness of the low-pressure dense region a1 and the second coating region 11b are equal. At this time, the thickness of the electrode 10 is uniform throughout, which not only simplifies the coating process but also avoids stress concentration caused by thickness differences, improving the structural stability of the electrode 10 during rolling and assembly. At the same time, the uniform coating thickness 11 can optimize the current conduction path, reduce local polarization, and improve the cycle life and rate performance of the battery cell 1000.

[0105] When 0 < d5 ≤ 20%, the low-pressure density region a1 is recessed relative to the second coating region 11b. The space formed by the recess increases the electrolyte wetting channel and heat dissipation space inside the core. At the same time, T3 does not exceed 20% of the thickness of the second coating region 11b, which can avoid stress concentration problems caused by excessive recess, and ensure the amount of active material retained in the low-pressure density region a1, thereby improving the energy density of the battery cell 1000.

[0106] In some embodiments, 50μm≤T1≤500μm. Specifically, T1 can take values ​​of 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 400μm, 500μm, and any values ​​between adjacent values.

[0107] The thickness of the coating 11 on the electrode 10 should not be too thick or too thin. If the coating 11 is too thick, the active material loading will be excessive, resulting in waste of active material and a reduction in battery energy density. Moreover, the longer ion transport path and increased internal resistance of the core will reduce the 1000-cycle performance and rate performance of the battery cell. An excessively thick coating 11 will also increase the manufacturing difficulty of the electrode 10, making it prone to quality problems such as drying difficulties and cracking. If the coating 11 is too thin, the active material loading will be insufficient, leading to insufficient battery capacity and a risk of exposing the current collector 12, which could cause an internal short circuit.

[0108] At this point, the thickness T1 of the second coating area 11b is limited to the range of 50μm to 500μm. The coating 11 thickness of the second coating area 11b is reasonable, taking into account battery capacity, battery cycle performance, and processing difficulty. At the same time, it matches the coating 11 thickness of the electrode sheet 10 of most battery products on the market, without the need for major modifications to the production line, thereby reducing production switchover costs and improving process adaptability and mass production efficiency.

[0109] When the low-density zone a1 is recessed relative to the second coating zone 11b, the maximum compaction density of the low-density zone a1 is usually located at its most concave position in the middle. When the thickness of the low-density zone a1 is the same as that of the second coating zone 11, the compaction density at all points in the low-density zone a1 is usually equal to simplify the processing.

[0110] In some embodiments, the electrode 10 is a negative electrode 102, the compaction density of the second coating region 11b is E1=1.5~1.7g / cc, and the maximum compaction density of the low compaction region a1 is E2=d9*E1, 70%≤d9≤95%.

[0111] Designing E1 within the range of 1.5–1.7 g / cc represents the mainstream and mature mass-production compaction density range for artificial graphite anodes currently in the industry. This range effectively balances energy density, rate performance, cycle life, and expansion rate.

[0112] Specifically, d9 can take values ​​of 70%, 75%, 80%, 85%, 90%, 95%, and any values ​​between adjacent values.

[0113] If d9 is too large, the maximum compaction density of the low-pressure-density region a1 will be too high, which will weaken its pore buffering capacity and electrolyte wetting ability, hinder lithium-ion diffusion, increase interfacial polarization, and increase the risk of lithium plating on the negative electrode 102. If d9 is too small, the maximum compaction density of the low-pressure-density region a1 will be too low, which will reduce the structural strength of the low-pressure-density region a1, leading to a decrease in electronic conductivity and an increase in local impedance in this region, affecting the capacity and rate performance of the 1000 battery cell.

[0114] By controlling d9 within the range of 70% to 95%, the porosity buffering and wetting capacity of the low-pressure dense region a1 can be guaranteed, while balancing the requirements of structural strength and energy density, thus achieving a good match between the performance and process of the negative electrode 102.

[0115] In some embodiments, the electrode 10 is a positive electrode 101, the compaction density of the second coating region 11b is E3=3.3~3.7g / cc, and the maximum compaction density of the low compaction region a1 is E4=d10*E3, 60%≤d10≤95%.

[0116] The E3 design is in the range of 3.3 to 3.7 g / cc, which is the high density range currently pursued by the lithium iron phosphate cathode industry. It significantly improves the volumetric energy density of the battery by increasing the volume ratio of active material.

[0117] Specifically, d10 takes values ​​of 60%, 65%, 70%, 75%, 80%, 85%, 95%, and any values ​​between adjacent values.

[0118] If d10 is too large, the maximum compaction density of the low-density zone a1 will be too high, and the compaction difference between the low-density zone a1 and the main zone will be too small, failing to effectively form sufficient pores to buffer expansion stress and promote electrolyte wetting. If d10 is too small, the maximum compaction density of the low-density zone a1 will be too small, making the low-density zone a1 too loose, which may lead to a decrease in electronic conductivity and an increase in local impedance in this area, and the risk of powder shedding during the rolling process.

[0119] By controlling d10 within the range of 60% to 95%, the necessary structural integrity can be maintained while ensuring the pore buffering and wetting capacity of the low-pressure dense region a1, thus achieving a good match between the performance and process of the positive electrode 101.

[0120] In one embodiment of this application, the electrode 10 includes the aforementioned first coating region 11a and second coating region 11b. The first coating region 11a includes a low-density region a1, which extends from one end of the first coating region 11a to the other end, and the compaction density E of the low-density region a1 continuously varies along the extension direction F1 of the electrode 10 according to a pattern of first decreasing and then increasing. The width of the low-density region a1 continuously varies along the extension direction F1 of the electrode 10 according to a pattern of first increasing and then decreasing.

[0121] In another embodiment of this application, the electrode 10 includes the aforementioned first coating region 11a and second coating region 11b. The first coating region 11a includes a low-density region a1 and a high-density region a2, which are alternately arranged along the extension direction F1 of the electrode 10. The compaction density of the high-density region a2 is equal to the compaction density of the second coating region 11b. The compaction density of the low-density region a1 varies stepwise along the extension direction F1 of the electrode 10, first decreasing and then increasing. The width of the low-density region a1 varies stepwise along the extension direction F1 of the electrode 10, first increasing and then decreasing.

[0122] The electrode assembly 100 of this application is described below.

[0123] Figure 8 This is a schematic diagram of the winding of an electrode assembly 100 according to some embodiments.

[0124] The electrode assembly 100 in this embodiment is referred to... Figure 8 The electrode includes a positive electrode 101, a negative electrode 102, and a separator 103 wound together. The separator 103 is disposed between the positive electrode 101 and the negative electrode 102. At least one of the positive electrode 101 and the negative electrode 102 is the electrode 10 in any of the above embodiments. The compaction density of the entire low-density region a1 varies along the winding direction of the electrode 10 from its winding beginning to its winding end in a pattern of first decreasing and then increasing.

[0125] As described above, when at least one of the positive electrode 101 and the negative electrode 102 includes the first coating region 11a and the second coating region 11b, the compaction density of the low-density region a1 of the first coating region 11a shows a trend of first decreasing and then increasing from the beginning to the end of the winding. On the one hand, the second coating areas 11b on both sides of the first coating area 11a, with high compaction density, can enhance the bonding force between the coating 11 and the current collector 12, reduce the risk of coating 11 delamination and peeling, and ensure the loading of active material in the positive electrode 101 and / or negative electrode 102, thus ensuring the energy density of the electrode 10. On the other hand, the compaction density of the low compaction area a1 of the first coating area 11a has a distribution characteristic of high at both ends and low in the middle along the winding direction of the electrode 10. This allows the first coating area 11a located in the center of the core to reserve sufficient porosity to offset the compression loss of pores during winding and compression, ensuring that the middle area of ​​the positive electrode 101 and / or negative electrode 102 maintains effective porosity under pressure conditions, ensuring the smoothness of the ion transport channel, and thus improving the cycle performance of the battery cell 1000.

[0126] In some embodiments, the positive electrode 101 and the negative electrode 102 are both electrode 10 of the above embodiments, and the low pressure density region a1 of the negative electrode 102 is completely offset from or at least partially overlaps with the low pressure density region a1 of the positive electrode 101 along the width direction X1 of the electrode 10.

[0127] At this time, both the positive electrode 101 and the negative electrode 102 have a low pressure density region a1 with sufficient reserved pore space, which can effectively offset the stress generated during winding and expansion, ensure the normality of the ion transport channel, and help improve the cycle performance of the battery cell 1000.

[0128] In some embodiments, along the width direction X1 of the electrode 10, the low-pressure dense region a1 of the positive electrode 101 completely covers the low-pressure dense region a1 of the negative electrode 102.

[0129] That is, the minimum width W1 of the low-density region a1 of the positive electrode 101. min-1 The maximum width W1 of the low-density region a1 of the negative electrode 102 is greater than or equal to the maximum width W1 of the low-density region a1. max-2 That is, W1 min-1 ≥W1 max-2 Can it be that, along the width direction X1 of the electrode 10, the center of the low-pressure dense region a1 of the negative electrode 102 coincides with the center of the low-pressure dense region a1 of the positive electrode 101.

[0130] During cycling, the negative electrode 102 (especially when the active material is graphite) undergoes significant volume expansion. The low-density region a1 of the positive electrode 101 acts as a buffer, providing space for the expansion of the low-density region a1 of the negative electrode 102 and effectively absorbing mechanical stress. Moreover, the edge region of the low-density region a1 of the negative electrode 102 corresponds to the low-density region a1 of the positive electrode 101. The active material content of the low-density region a1 of the positive electrode 101 is lower than that of the second coating region 11b, resulting in a lower content of released lithium ions and thus avoiding lithium plating at the edge region of the low-density region a1 of the negative electrode 102.

[0131] In a specific embodiment, W1 min-1 -W1 max-2 =W4, where W4 is the overhang dimension of electrode assembly 100.

[0132] It is worth noting that, in order to reserve expansion space for the negative electrode 102 in the width direction X1 of the electrode 10 and avoid lithium deposition in the edge area of ​​the negative electrode 102, the conventional practice is to set the negative electrode 102 beyond the positive electrode 101 along the width direction X1 of the electrode 10, with the overhang dimensions being the same at both ends. W4 refers to the single-sided dimension (i.e., overhang) of the negative electrode 102 exceeding the positive electrode 101 along the thickness direction Y1 of the electrode 10.

[0133] W4 is set according to the edge expansion requirements of the negative electrode 102. For batteries with different systems or processes, W4 can be adaptively adjusted according to actual needs. Based on experimental simulation and testing of the edge expansion behavior of negative electrode active materials (such as graphite) during cycling, in order to effectively prevent lithium plating while taking energy density into account, W4 can be designed as: 0.5mm≤W4≤3mm. Specifically, W4 can be designed as 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, and any value between adjacent values.

[0134] When W1 min-1 With W1 max-2 The difference is equal to W4. W4 serves as a unified design benchmark, allowing the portion of the negative electrode 102 that extends beyond the edge and the portion of the positive electrode 101 that extends beyond the low-pressure dense region a1 to form a synergistic protection. This not only prevents lithium absorption at the edge of the negative electrode 102, but also allows the portion of the positive electrode 101 that extends beyond the low-pressure dense region a1 to absorb the expansion stress of the negative electrode 102 that extends beyond the low-pressure dense region a1, thereby improving the structural stability and cycle life of the battery cell 1000.

[0135] In some embodiments, combined with Figure 6 It is understood that the first coating region 11a of the electrode 10 includes a high-pressure dense region a2, and a high-pressure dense region a2 is provided between every two adjacent low-pressure dense regions a1. The length of the high-pressure dense region a2 in the winding direction of the electrode 10 is L2, and the number of layers of the electrode 10 in which the high-pressure dense region a2 is located is m, satisfying: L2 = d11 + d12 * m, 0 < d11 ≤ 300, 0 < d12 ≤ 10, and the unit of L2 is mm.

[0136] Let L2=d11+d12*m be denoted as the third formula. The third formula shows that the length of the high-pressure dense region a2 increases linearly with the increase of the number of 10 layers of the electrode in which it is located.

[0137] Compared to the low-pressure dense zone a1, the high-pressure dense zone a2 has higher structural strength. As the number of winding layers m of the electrode 10 increases, the accumulated expansion stress inside the core increases significantly. Through the dynamic design of the third formula, the length of the high-pressure dense zone a2 increases synchronously with the number of layers. Utilizing its high structural strength, the high-pressure dense zone a2 provides stronger radial support for the core, effectively resisting the compressive stress caused by multi-layer expansion and preventing deformation and collapse in the middle of the core.

[0138] d11, as a constant term in the third formula, is 0 < d11 to ensure that the high-pressure dense zone a2 can maintain a certain length even at lower layer counts, thereby enhancing the mechanical strength of the 10th zone of the low-layer electrode. d11 ≤ 300 is used to prevent excessive design of the foundation length, avoid the high-pressure dense zone a2 encroaching on the low-pressure dense zone a1, and ensure that each layer can reserve sufficient porosity to resist stress.

[0139] d12 serves as a layer compensation coefficient, with 0 < d12, ensuring that the length of the high-pressure dense zone a2 increases with the number of layers m, thus matching the displacement requirements of multi-layer cumulative expansion. d12 ≤ 10 is used to avoid an excessively large compensation system that would cause the length of the high-pressure dense zone a2 to grow too quickly, resulting in redundant support structures, which would not only waste materials but also hinder electrolyte wetting in the central region of electrode 10.

[0140] In one embodiment, 10 ≤ m ≤ 100 indicates that the third formula is applicable only to layers 10 to 100. 10 ≤ m ≤ 100 means that the length of the high-pressure dense zone a2 increases with the number of layers from layer 10 to layer 100. This is mainly because the cumulative expansion stress of the core is relatively small in the low-layer region (<10), and a fixed-length high-pressure dense zone a2 is sufficient. When the number of layers reaches 10 or more, the radial pressure and cumulative expansion effect inside the core begin to increase significantly. At this point, activating the third formula to dynamically design the length of the high-pressure dense zone a2 allows the support capacity of the high-pressure dense zone a2 to accurately match the stress growth. m ≤ 100 covers the mainstream winding layer range for both consumer and power cores, ensuring the universality of the formula in mass production scenarios while avoiding uncontrolled compensation due to excessive layers, thus maintaining the stability and safety of the design.

[0141] Figure 9 This is a partial structural diagram of the core in some embodiments.

[0142] In some embodiments, combined with Figure 8 and Figure 9 It is understood that the electrode assembly 100 includes a straight region Q1 and a corner region Q2, with the corner region Q2 arranged on both sides of the straight region Q1. The low-pressure dense region a1 is at least partially located in the corner region Q2, and the high-pressure dense region a2 is located in the straight region Q1.

[0143] In the winding process, the corner region Q2 is a core area of ​​stress concentration. The expansion / contraction of the battery cell during 1000 cycles generates greater mechanical stress here, easily leading to cracking of the electrode sheet 10. Placing the low-pressure dense region a1 in the corner region Q2 utilizes its high porosity to buffer and absorb expansion stress, preventing damage to the corner region Q2. The straight region Q1 is the main active area of ​​the core, playing a crucial role in energy storage. Placing the high-pressure dense region a2 in the straight region Q1 utilizes the high strength of the high-pressure dense region a2 to support the morphological stability of the straight region Q1 in the middle of the core, preventing deformation, while also providing a higher content of active material, reducing energy density loss in the straight region Q1.

[0144] In some embodiments, refer to Figure 9 At least one end of the low-pressure dense area a1 in the winding direction is the overhanging end r1. The overhanging end r1 extends beyond the corner area Q2 and the overhanging length is t. The length L2 of the high-pressure dense area a2 adjacent to the overhanging end r1 satisfies: t=d13*L2, 0<d13≤50%.

[0145] Typically, the corner area Q2 is a circular arc area, and the straight area Q1 is a planar area. The boundary between the two is the position where the circular arc area and the planar area are tangent. The overhanging end r1 of the low-pressure dense area a1 extends beyond this boundary position and into the straight area Q1.

[0146] The overhanging end r1 and its adjacent high-pressure dense area a2 are located in the same straight area Q1. The length t of the overhanging end r1 beyond the boundary position and the length L2 of the high-pressure dense area a2 in the same straight area Q1 satisfy the fourth formula: t=d13*L2, 0<d13≤50%.

[0147] On the one hand, the extended end r1 of the low-pressure dense region a1 extends to the straight region Q1, which can form a transition buffer zone at the junction of the corner region Q2 and the straight region Q1, absorbing the stress concentration in this area and avoiding the sudden change of expansion stress at the junction position from causing the electrode 10 to crack.

[0148] On the other hand, by binding t to L2, and controlling t to not exceed 50% of the length of L2 through d13, the low-pressure dense area a1 is prevented from excessively encroaching on the high-pressure dense area a2 space of the flat area Q1, thus ensuring the structural strength and energy density of the flat area Q1.

[0149] The following describes the 1000 battery cell of this application.

[0150] The battery cell 1000 in this embodiment includes the electrode assembly 100 in the above embodiments. The battery cell 1000 can be a pouch battery or a hard-case battery. When the battery cell 1000 is a hard-case battery, in some embodiments, the battery cell 1000 includes the housing 200 and the top cover assembly 300 mentioned above.

[0151] The battery cell 1000 includes all the beneficial effects described in the above embodiments, which will not be repeated here.

[0152] The coating apparatus of this application is described below.

[0153] Figure 10 This is a schematic diagram of the composition of a coating die head 2000 in some embodiments. Figure 11 and Figure 12 This is a schematic diagram of the structure of the gasket 2200 in different embodiments.

[0154] Please combine Figures 10 to 11 Understood, the coating apparatus in this embodiment includes a coating die 2000, which includes a die body 2100 and a gasket 2200. The die body 2100 has a slit f, and the gasket 2200 is located within the slit f. The gasket 2200 includes a main body 2210 and a thinning member 2220. The main body 2210 encloses a discharge groove C, which extends through the thickness direction of the main body 2210 and is open at one end in the width direction X2. The thinning member 2220 is disposed on the main body 2210 and located in the discharge groove C, spaced apart from the main body 2210 along the extension direction F2 of the slit f. The size of the thinning member 2220 in the width direction X2 of the main body is adjustable to adjust the distance D between the thinning member 2220 and the open end of the discharge groove C.

[0155] The die head body 2210 forms a slit f. A gasket 2200 is disposed in the slit f, and the thickness of the gasket 2200 matches the size of the slit f to prevent slurry leakage from the die head body 2210. The gasket 2200, disposed within the slit f, provides physical isolation or sealing, allowing the slurry to be transferred uniformly and stably to the substrate surface. In one example, the die head body 2100 includes a first die head and a second die head. After the first and second die heads are closed, they together form the slit f. The size of the slit f is adjusted by adjusting the distance between the first and second die heads, and gaskets 2200 of different thicknesses are matched to adjust the discharge flow rate of the coating die head 2000.

[0156] The main body 2210 of the gasket 2200 forms a discharge groove C. The discharge groove C opens towards the outlet of the slit f along the width direction X2 of the main body. Its open end extends a certain width along the extension direction F2 of the slit f, which is adapted to the coating width of the substrate.

[0157] Notably, the discharge channel C is arranged to extend through the thickness direction of the main body 2210. When the gasket 2200 is installed in the slit f, the two ends of the discharge channel C in the thickness direction of the main body 2210 are connected to the feeding channel in the die head body 2100. The feeding channel is typically arranged continuously or intermittently along the extension direction F2 of the slit f.

[0158] The thinning member 2220 is disposed within the discharge trough C, with one end connected to the main body 2210 and the other end extending toward the open end of the discharge trough C, and spaced apart from the open end of the discharge trough C along the width direction X2 of the main body. The thinning member 2220 is spaced apart from the main body 2210 along the extension direction F2 of the slit f, and divides the discharge trough C into a first discharge area C1. The thinning member 2220 has a first discharge area C1 on both sides of the slit f extension direction F1.

[0159] The dimension of the thinning component 2220 along the width direction of the main body 2210 is the length of the thinning component 2220. The length of the thinning component 2220 is adjustable to adjust the distance D between the thinning component 2220 and the open end of the discharge trough C. The space containing this distance forms a second discharge zone C2 within the discharge trough C. The smaller the distance D, the smaller the discharge flow rate of the second discharge zone C2.

[0160] In practical applications, the slurry delivered from the slurry feeding channel of the die head body 2100 flows to the discharge trough C and is diverted by the thinning member 2220. A portion of the slurry flows through the first discharge zone C1 between the thinning member 2220 and the main body 2210 to the open end of the discharge trough C, while the other portion of the slurry flows through the second discharge zone C2 where the spacing D is located to the open end. The open end of the first discharge zone C1 is used to form a second coating zone 11b on the surface of the current collector 12 of the electrode 10, and the open end of the second discharge zone C2 is used to form a first coating zone 11a on the surface of the current collector 12 of the electrode 10. Because the discharge flow rate of the second discharge zone C2 is less than that of the first discharge zone C1, the active material content of the second coating zone 11b is higher than that of the first coating zone 11a. After the electrode 10 coating 11 is subsequently rolled, a low-density zone a1 with a compaction density lower than that of the second coating zone 11b is easily formed in the first coating zone 11a.

[0161] The length of the thinning component 2220 is adjustable to adjust the size of the spacing D, which determines the discharge flow rate of the second discharge zone C2. In practical applications, during the coating process, the length of the thinning component 2220 is adjusted synchronously, so that the size of the spacing D dynamically adjusts the discharge flow rate of the second discharge zone C2, thereby dynamically matching the required active material content of the first coating zone 11a. This results in a low-density zone a1 on the electrode 10 after rolling, where the compaction density first decreases and then increases, thus preparing the electrode 10 in the above embodiment.

[0162] The electrode 10 of the above embodiment is prepared using the coating apparatus in this application. Only the length of the thinning member 2220 needs to be adjusted to achieve the partitioning of the coating 11 and the adjustment of the active material content in the first coating area 11a. In practical applications, existing roller pressing equipment can be used, and only the gasket 2200 of the coating apparatus needs to be adapted. The process improvement is simple and the cost is low.

[0163] Understandably, during the process of adjusting the length of the thinning part 2220, the length of the thinning part 2220 can be adjusted to 0, the spacing D reaches its maximum, and the discharge flow rate per unit volume of the second discharge zone C2 is equivalent to that of the first discharge zone C1, so as to form a high-density zone a2 in the first coating zone 11a with the same compaction density as the second coating zone 11b.

[0164] In some embodiments, the thinning member 2220 moves periodically relative to the body 2210 along the width direction X2 of the body, first extending and then retracting.

[0165] When the thinning part 2220 extends, the distance D between it and the open end of the discharge trough C decreases, the discharge flow rate of the second discharge zone C2 decreases, and the active material content of the corresponding coating area decreases. When the thinning part 2220 retracts, the distance D between it and the open end of the discharge trough C increases, the discharge flow rate of the second discharge zone C2 increases, and the active material content of the corresponding coating area increases.

[0166] In practical applications, when controlling the movement of the thinning part 2220 to extend and then retract, the coating die 2000 first decreases and then increases the coating of active material in the first coating area 11a. After rolling, a low-density area a1 with a compaction density that first decreases and then increases with the extension direction F1 of the electrode 10 can be obtained in the first coating area 11a.

[0167] If the low-pressure density is continuously set and changes continuously according to a pattern of first decreasing and then increasing, the extension and retraction of the thinning component 2220 are continuously adjusted according to the corresponding pattern. If the low-pressure density is set intermittently, the extension and retraction of the thinning component 2220 are intermittently adjusted according to the corresponding pattern.

[0168] In some embodiments, such as Figure 11 and Figure 12 As shown, a flow-deflecting section 2221 is provided at one end of the thinned part 2220 near the open end of the discharge trough C. The distance between the flow-deflecting section 2221 and the open end along the width direction of the main body 2210 is D. The flow-deflecting section 2221 is used to guide the flow direction of the slurry to control the compaction density distribution of the low-density zone a1.

[0169] Figure 13 This is a schematic diagram of the structure of the thinning member 2220 in some embodiments.

[0170] In one embodiment, such as Figure 13As shown, the end face of the turbulence-dissipating part 2221 is an arc-shaped surface that protrudes toward the open end of the discharge trough C. Specifically, in a cross-section perpendicular to the thickness direction of the main body 2210, the turbulence-dissipating part 2221 has an arc-shaped shape that protrudes toward the open end of the discharge trough C.

[0171] In practical applications, the slurry flows through the turbulence section 2221 on the arc surface and is guided to flow towards both sides of the slurry, making the coating thickness of the coating area corresponding to the convex part of the arc surface thinner, so that the low compaction zone a1 has a wider compaction density gradient and porosity gradient, leaving more pores, which is suitable for use in batteries with large expansion stress.

[0172] In another embodiment, such as Figure 11 and Figure 12 As shown, the end face of the turbulence-disrupting section 2221 is planar. The planar turbulence-disrupting section 2221 has a weak guiding effect on the slurry flow, and the gradient change of compaction density and porosity in the low-density zone a1 is gentle or unchanged, making it suitable for use in batteries with low expansion stress.

[0173] In some embodiments, combined with Figure 11 and Figure 12 Understand that the dimension of the discharge trough C along the extension direction F2 of the slit f is S, the dimension of each thinned part 2220 along the extension direction F2 of the slit f is S1, and the sum of the dimensions S1 of all thinned parts 2220 is S1', S1'=a1*S, 5%≤a1≤50%.

[0174] S1 in each thinned part 2220 represents the coating width of each first coating zone 11a, and S represents the coating width of the discharge trough C. For example... Figure 11 As shown, a thinning component 2220 is installed in a discharge trough C, and each discharge trough C can be coated to obtain a coating unit 10A. For example... Figure 12 As shown, two thinning elements 2220 are installed in one discharge trough C. Without the discharge trough C, two coating units 10A can be obtained. If there are multiple thinning elements 2220, the S1 of each thinning element 2220 is usually equal.

[0175] Specifically, a1 can take values ​​of 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and any value between adjacent values.

[0176] At this point, S1' is a constant value, and the total width of the first coating area 11a obtained by the coating die 2000 is consistent. If a1 is too small, the width of each first coating area 11a is too small, and the width of the low-density area a1 is too small. The reserved pores are insufficient to offset the influence of the internal stress of the core, resulting in excessive pore compression loss. This can easily lead to interruption of ion transport paths, insufficient electrolyte wetting, and poor core cycle performance. If a2 is too large, the loss of active material in the electrode 10 is greater, the core energy density is insufficient, and it is not conducive to the range of the battery cell 1000.

[0177] When a1 is within the above range, the cycle performance and energy density of the core can be balanced.

[0178] In some embodiments, the main body 2210 forms at least one discharge trough C, and at least two thinning members 2220 are provided in each discharge trough C. The at least two thinning members 2220 are separated in the discharge trough C to form a plurality of first discharge areas C1. The plurality of first discharge areas C1 are arranged sequentially along the extension direction F2 of the slit f. The dimensions S2 of the two first discharge areas C1 located on both sides of the same thinning member 2220 in the extension direction F2 of the slit f are equal or have a relationship of twice.

[0179] Specifically, when one thinning member 2220 is provided, the dimensions S2 of the first discharge areas C1 on both sides of the thinning member 2220 are equal. If two thinning members 2220 are provided, the dimension S2 of the first discharge area C1 located between the two thinning members 2220 is twice the S2 of the other two first discharge areas C1.

[0180] At this time, each discharge trough C can be coated once on the same current collector 12 to obtain two coating units 10A. After subsequent slitting, multiple electrode sheets 10 are obtained, each consisting of only one coating unit 10A and a blank area 11c. Then, electrode tabs are die-cut in the blank area 11c of the electrode sheet 10 to obtain an electrode sheet 10 containing multiple electrode tabs.

[0181] Specifically, in this embodiment, the main body 2210 includes a main sheet and at least two horizontal sheets 2212. All the horizontal sheets 2212 are arranged on the same side of the vertical sheet 2211 along the width direction X2 of the main body, and the horizontal sheets 2212 are spaced apart along the extension direction F2 of the slit f. Each pair of adjacent horizontal sheets 2212 and the vertical sheet 2211 together form a discharge groove C. In this case, the number of discharge grooves C is one less than the number of horizontal sheets 2212. In practical applications, the horizontal sheets 2212 are not coated with slurry and are used to form a blank area 11c on the current collector 12. The horizontal sheets 2212 and the vertical sheets 2211 can be integrally formed.

[0182] It is worth noting that, in order to achieve dimensional adjustment of the thinning component 2220 relative to the main body 2210 along the width direction X2 of the main body, in one embodiment, the coating apparatus further includes a cylinder. The thinning component 2220 is a multi-section telescopic sleeve, and the telescopic end of the cylinder is connected to the last section of the multi-section telescopic sleeve. When the cylinder telescopically extends or retracts the sleeve, the thinning component 2220 extends or retracts. Specific methods for moving the thinning component 2220 are not limited to this.

[0183] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0184] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An electrode (10), characterized in that, include: The coating (11) is divided into a first coating area (11a) and a second coating area (11b) along the width direction (X1) of the electrode (10), and the second coating area (11b) is provided on both sides of the first coating area (11a). Along the extension direction (F1) of the electrode (10), the first coating area (11a) includes at least one low compaction area (a1), the compaction density of the low compaction area (a1) is lower than the compaction density of the second coating area (11b), and the compaction density of all the low compaction areas (a1) varies along the extension direction (F1) of the electrode (10) in a pattern of first decreasing and then increasing.

2. The electrode (10) according to claim 1, characterized in that, The first coating area (11a) includes a low-density region (a1), and the compaction density of the low-density region (a1) continuously varies along the extension direction (F1) of the electrode (10) according to a pattern of first decreasing and then increasing; or, The first coating area (11a) includes a plurality of adjacent low-density areas (a1), and the compaction density of each low-density area (a1) varies sequentially along the extension direction (F1) of the electrode (10) according to a pattern of first decreasing and then increasing; or, The first coating area (11a) includes a high-density area (a2), and the low-density area (a1) and the high-density area (a2) are arranged alternately along the extension direction (F1) of the electrode (10). The compaction density of the high-density area (a2) is equal to the compaction density of the second coating area (11b). The compaction density of all the low-density areas (a1) varies stepwise along the extension direction (F1) of the electrode (10) according to the rule of first decreasing and then increasing.

3. The electrode (10) according to claim 1, characterized in that, The first coating area (11a) and its two adjacent second coating areas (11b) constitute a coating unit (10A), and the center line of the coating unit (10A) in the width direction is located in the first coating area (11a).

4. The electrode (10) according to claim 3, characterized in that, The width of the coating unit (10A) is W, and the width of the low-pressure dense area (a1) is W1, satisfying: W1=d4*W, 5%≤d4≤50%; and / or, the two second coating areas (11b) in the coating unit (10A) are set with equal width.

5. The electrode (10) according to claim 1, characterized in that, The width of all the low-pressure dense regions (a1) varies along the extension direction (F1) according to the rule of first increasing and then decreasing.

6. The electrode (10) according to claim 5, characterized in that, The width W1 of the low-pressure dense region (a1) and the length L1 of the electrode (10) satisfy: W1=d1+d2*L1-d3*L1^2, 5≤d1≤100, 0<d2≤0.5, 0<d3≤0.1, 5m≤L1≤50m, and the unit of W1 is mm; or, Multiple low-pressure dense regions (a1) are arranged sequentially along the extension direction (F1) of the electrode (10), and the width W1 of each low-pressure dense region (a1) changes stepwise along the extension direction (F1) of the electrode (10) in a pattern of first increasing and then decreasing.

7. The electrode (10) according to claim 1, characterized in that, Along the width direction (X1) of the electrode (10), the compaction density E of the low-density zone (a1) and the width W1 of the low-density zone (a1) follow a pattern of first increasing and then decreasing, or, satisfying E=d6+d7*W1-d8*W1^2, 1.0≤d6≤5.0, 0<d7≤0.5, 0<d8≤0.1, and the unit of E is g / cc.

8. The electrode (10) according to claim 1, characterized in that, The low-pressure dense area (a1) is recessed relative to the second coating areas (11b) on both sides; and / or, The porosity of the low-pressure dense region (a1) is higher than that of the second coating region (11b); and / or, The thickness of the second coating area (11b) is T1, and the thickness difference between the low-density area (a1) and the second coating area (11b) is T3, where T3 = d5 * T1, 0 ≤ d5 ≤ 20%, and 50 μm ≤ T1 ≤ 500 μm.

9. The electrode (10) according to claim 1, characterized in that, The electrode (10) is a negative electrode (102), the compaction density of the second coating area (11b) is E1 = 1.5~1.7 g / cc, and the maximum compaction density of the low-density area (a1) is E2 = d9*E1, 70%≤d9≤95%; or, The electrode (10) is a positive electrode (101), the compaction density of the second coating area (11b) is E3=3.3~3.7g / cc, and the maximum compaction density of the low compaction area (a1) is E4=d10*E3, 60%≤d10≤95%.

10. An electrode assembly (100), characterized in that, include: A positive electrode (101), a negative electrode (102), and a separator (103) are wound together, wherein the separator (103) is disposed between the positive electrode (101) and the negative electrode (102), and at least one of the positive electrode (101) and the negative electrode (102) is an electrode (10) as described in any one of claims 1-9; The compaction density of all the low-density regions (a1) varies along the winding direction of the electrode (10) from its winding beginning to its winding end in a pattern of first decreasing and then increasing.

11. The electrode assembly (100) according to claim 10, characterized in that, The positive electrode (101) and the negative electrode (102) are both electrode (10) as described in any one of claims 1 to 9, wherein the low pressure density region (a1) of the negative electrode (102) is completely offset from or at least partially overlaps with the low pressure density region (a1) of the positive electrode (101) along the width direction (X1) of the electrode (10).

12. The electrode assembly (100) according to claim 10, characterized in that, Along the width direction (X1) of the electrode (10), the low pressure density region (a1) of the positive electrode (101) completely covers the low pressure density region (a1) of the negative electrode (102); The minimum width W1 of the low-pressure dense region (a1) of the positive electrode (101) min-1 The maximum width W1 of the low pressure density region (a1) of the negative electrode (102) max-2 Satisfy: W1 min-1 -W1 max-2 =W4, where W4 is the overhang dimension of the electrode assembly (100).

13. The electrode assembly (100) according to claim 11, characterized in that, The first coating area (11a) of the electrode (10) includes the high-pressure dense area (a2), and the high-pressure dense area (a2) is provided between every two adjacent low-pressure dense areas (a1). The length of the high-pressure dense area (a2) in the winding direction of the electrode (10) is L2, and the number of layers of the electrode (10) where the high-pressure dense area (a2) is located is m, satisfying: L2 = d11 + d12 * m, 0 < d11 ≤ 300, 0 < d12 ≤ 10, and the unit of L2 is mm.

14. The electrode assembly (100) according to claim 13, characterized in that, The electrode assembly (100) includes a straight region (Q1) and a corner region (Q2), with the corner region (Q2) arranged on both sides of the straight region (Q1). The low-pressure dense region (a1) is at least partially located in the corner region (Q2), and the high-pressure dense region (a2) is located in the straight region (Q1).

15. The electrode assembly (100) according to claim 14, characterized in that, The low-pressure dense area (a1) has at least one end of an extension end (r1) in the winding direction. The extension end (r1) extends beyond the corner area (Q2) by a length of t. The length L2 of the high-pressure dense area (a2) adjacent to the extension end (r1) satisfies: t = d13 * L2, 0 < d13 ≤ 50%.

16. A single battery cell (1000), characterized in that, Includes the electrode assembly (100) as described in any one of claims 1-15.

17. A coating apparatus, characterized in that, include: A coating die (2000) includes a die body (2100) and a gasket (2200), the die body (2100) having a slit (f) and the gasket (2200) being located within the slit (f); The gasket (2200) includes a main body (2210) and a thinning member (2220). The main body (2210) encloses and forms a discharge groove (C). The discharge groove (C) is disposed through the thickness direction of the main body (2210) and is open at one end in the width direction (X2) of the main body (2210). The thinning member (2220) is disposed on the main body (2210) and located in the discharge groove (C). The thinning member (2220) is spaced apart from the main body (2210) along the extension direction (F2) of the slit (f). The size of the thinning member (2220) is adjustable along the width direction (X2) of the main body (2210) to adjust the distance D between the thinning member (2220) and the open end of the discharge trough (C).

18. The coating apparatus according to claim 17, characterized in that, The thinning member (2220) moves periodically relative to the body (2210) along the width direction (X2) of the body (2210), first extending and then retracting.

19. The coating apparatus according to claim 17, characterized in that, The thinned part (2220) has a turbulence part (2221) at one end near the open end of the discharge trough (C); The end face of the turbulence section (2221) is either a plane or an arc surface protruding toward the open end of the discharge trough (C).

20. The coating apparatus according to claim 17, characterized in that, The dimension of the discharge trough (C) along the extension direction (F2) of the slit (f) is S, the dimension of the thinned part (2220) along the extension direction (F2) of the slit (f) is S1, the sum of the dimensions S1 of all the thinned parts (2220) is S1', S1'=a1*S, 5%≤a1≤50%; and / or, The main body (2210) forms at least one discharge trough (C), and at most two thinning members (2220) are provided in each discharge trough (C). The at most two thinning members (2220) are separated in the discharge trough (C) to form a plurality of first discharge areas (C1). The plurality of first discharge areas (C1) are arranged sequentially along the extension direction (F2) of the slit (f). The dimensions S2 of the two first discharge areas (C1) located on both sides of the same thinning member (2220) in the extension direction (F2) of the slit (f) are equal or have a relationship of twice.

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