Pole piece, battery cell and battery

Abstract

The application relates to the technical field of batteries, and discloses a pole piece, a battery cell and a battery. The pole piece comprises a current collector, a first active material layer and a second active material layer. In the thickness direction, the current collector comprises opposite first and second sides. The second side comprises a first empty foil area and a second empty foil area. In the length direction of the current collector, the first empty foil area and the second empty foil area are arranged in sequence, and the second empty foil area is arranged at one end of the second side. The first active material layer is coated on the first side. The second active material layer is coated on the first empty foil area. A liquid retention coating is coated on the second empty foil area. The battery cell comprises a separator, a positive pole piece and a negative pole piece. At least one of the positive pole piece and the negative pole piece adopts the pole piece. The separator is arranged between the positive pole piece and the negative pole piece. The battery comprises an aluminum plastic film and the battery cell. The pole piece, the battery cell and the battery can improve the liquid retention amount of the battery, thereby improving the cycle performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to an electrode, a cell, and a battery. Background Technology

[0002] In battery manufacturing technology, electrodes are typically compacted to increase the density of the active material layer, thereby improving the battery's energy density. However, increased compaction density can make it difficult for the electrolyte to wet the electrodes, resulting in poor electrolyte retention and consequently reduced battery cycle performance. Utility Model Content

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an electrode that can increase the liquid retention capacity of the battery, thereby improving the battery's cycle performance.

[0004] This application also proposes a battery cell having the aforementioned electrodes.

[0005] This application also proposes a battery having the above-mentioned cells.

[0006] The electrode sheet according to an embodiment of this application includes a current collector, a first active material layer, and a second active material layer; The current collector, along the thickness direction, includes a first side and a second side opposite to each other; The second side includes a first empty foil area and a second empty foil area. Along the length direction of the current collector, the first empty foil area and the second empty foil area are arranged in sequence, and the second empty foil area is located at one end of the second side. The first active material layer is coated on the first side; The second active material layer is coated on the first empty foil area; A liquid-retaining coating is applied to the second empty foil area.

[0007] The electrode sheet according to the embodiments of this application has at least the following beneficial effects: along the length direction of the current collector, by setting a second empty foil area at one end of the second side of the current collector and coating the second empty foil area with a liquid-retaining coating, the wetting ability of the electrolyte in the local area of ​​the electrode sheet can be enhanced, and the electrolyte can be more smoothly penetrated into the active material layer. At the same time, by taking advantage of the liquid-retaining coating's liquid storage characteristics, the amount of electrolyte retained by the battery can be increased, and the electrolyte loss can be reduced, thereby helping to improve the cycle performance of the battery.

[0008] According to some embodiments of this application, the second side also includes a third empty foil region, which is located between the liquid-retaining coating and the second active material layer along the length direction of the current collector.

[0009] According to some embodiments of this application, the size of the third empty foil region is 0 to 2 mm along the length direction of the current collector.

[0010] According to some embodiments of this application, the coating thickness of the liquid-retaining coating is 2µm to 5µm along the thickness direction.

[0011] According to some embodiments of this application, the coating density of the liquid-retaining coating is 0.2 g / m³. 2 Up to 1g / m 2 .

[0012] According to some embodiments of this application, the second side further includes a fourth empty foil region, which is located on the side of the second active material layer away from the liquid-retaining coating along the length direction of the current collector.

[0013] The battery cell according to an embodiment of this application includes a separator, a positive electrode plate, and a negative electrode plate; At least one of the positive electrode and the negative electrode is the electrode in any of the above embodiments, and the separator is located between the positive electrode and the negative electrode. Along the length direction of the current collector, the positive electrode, the separator and the negative electrode are wound to form a battery cell.

[0014] The battery cell according to the embodiments of this application has at least the following beneficial effects: by adopting the electrode sheet in any of the above embodiments, its own liquid retention can be effectively improved, providing a more sufficient and stable electrolyte environment for battery cell circulation, thereby improving the cycle performance of the battery cell and helping to extend the service life of the battery cell.

[0015] The battery according to the embodiments of this application includes an aluminum-plastic film and the battery cell in the above embodiments; The aluminum-plastic film includes a covering area and a sealing area. The sealing area surrounds and connects to the outer periphery of the covering area, and the covering area and the sealing area together enclose a receiving cavity. The battery cell is located in the receiving cavity, and the covering area and the battery cell are stacked together along the thickness direction; The thickness of the edge sealing area is greater than the thickness of the covering area.

[0016] The battery according to the embodiments of this application has at least the following beneficial effects: by reducing the thickness of the covering area, it is possible to reduce the overall space occupied by the battery while ensuring a reliable seal for the battery cell. Combined with the liquid retention performance of the battery cell, it is possible to balance the liquid retention performance and energy density of the battery.

[0017] According to some embodiments of this application, the edge sealing area includes a nylon layer, an aluminum layer, and a PP layer, with the aluminum layer located between the nylon layer and the PP layer, and the thickness of the aluminum layer being 20µm to 40µm.

[0018] According to some embodiments of this application, the covered area includes a nylon layer, an aluminum layer, and a PP layer, with the aluminum layer located between the nylon layer and the PP layer, and the thickness of the aluminum layer being 10 to 30 µm.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the structure of the first type of electrode in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the second type of electrode in the embodiments of this application; Figure 3 for Figure 1 Sectional view at point AA; Figure 4 This is a schematic diagram of the structure of the aluminum-plastic film-coated battery cell according to an embodiment of this application; Figure 5 This is a thickness rebound curve for the comparative examples and embodiments under room temperature conditions.

[0021] Reference numerals: current collector 110, first side 111, second side 112, first empty foil area 1121, second empty foil area 1122, third empty foil area 1123, fourth empty foil area 1124; First active material layer 210, second active material layer 220, liquid-retaining coating 230; Aluminum-plastic film 300, coverage area 310, edge sealing area 320. Detailed Implementation

[0022] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0023] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are 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.

[0024] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0025] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0026] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] The embodiments of this application are described below with reference to the accompanying drawings: refer to Figures 1 to 3 According to an embodiment of this application, the electrode includes a current collector 110, a first active material layer 210, and a second active material layer 220. Along the thickness direction, the current collector 110 includes a first side 111 and a second side 112 opposite to each other. The second side 112 includes a first empty foil region 1121 and a second empty foil region 1122. Along the length direction of the current collector, the first empty foil region 1121 and the second empty foil region 1122 are arranged sequentially, with the second empty foil region 1122 located at one end of the second side 112. The length direction of the current collector is perpendicular to the thickness direction. The first active material layer 210 is coated on the first side 111, the second active material layer 220 is coated on the first empty foil region 1121, and a liquid-retaining coating 230 is coated on the second empty foil region 1122. By providing the liquid-retaining coating 230, the wetting effect of the electrolyte can be improved while ensuring the compaction density of the first active material layer 210 and the second active material layer 220, increasing the amount of electrolyte retained by the battery, thereby improving the battery's cycle performance and extending its service life.

[0028] Specifically, the raw materials of the electrolyte retention coating 230 include boehmite microsphere powder, N-methylpyrrolidone, sodium carboxymethyl cellulose, linear crystalline polyvinylidene fluoride polymer, and γ-methacryloyloxypropyltrimethoxysilane. The mass ratio of the above five raw materials is 7.7:5.8:0.8:9.3:0.03. Among them, boehmite microsphere powder has good hydrophilicity and can enhance compatibility with electrolyte. N-methylpyrrolidone, as a solvent, can ensure uniform dispersion of each component. Sodium carboxymethyl cellulose and linear crystalline polyvinylidene fluoride polymer can form a stable network structure. γ-methacryloyloxypropyltrimethoxysilane is used to improve the binding force of the current collector 110, so that the electrolyte retention coating 230 can promote electrolyte wetting, increase the amount of electrolyte retained by the battery, reduce electrolyte loss during cycling, and thus help improve the cycle performance of the battery.

[0029] Meanwhile, by setting a second empty foil area 1122 in the edge region of the second side 112 of the current collector 110 along the length direction of the current collector, and coating the second empty foil area 1122 with a liquid-retaining coating 230, the end edge of the second side 112 is the edge of the liquid-retaining coating 230. Furthermore, the liquid-retaining coating 230 can serve as the starting end of winding. Compared with the electrode structure in which one side is coated with active material and the other side is empty foil along the thickness direction, the liquid-retaining coating 230 of this application can also alleviate the wrinkling of the feed material caused by uneven coating on both sides of the electrode, which is beneficial to ensuring the flatness of the electrode during processing.

[0030] It should be noted that the term "end" in this application is not limited to the edge, but refers to the boundary area that borders the edge along the length of the current collector. That is, the end is not a point, but a spatial area with a certain range.

[0031] in addition, Figure 2 The dashed boxes in the text are only used to represent the first empty foil area 1121 and the second empty foil area 1122, and should not be interpreted as solid structures.

[0032] refer to Figures 1 to 3 In other embodiments, the thickness of the liquid-retaining coating 230 is less than or equal to the thickness of the second active material layer 220 along the thickness direction, so as to avoid the liquid-retaining coating 230 protruding relative to the second active material layer 220 in the thickness direction, thereby facilitating full utilization of space and ensuring the energy density of the battery.

[0033] The thickness of the second active material layer 220 should be understood as the thickness after compaction.

[0034] refer to Figures 1 to 3In some embodiments, the second side 112 further includes a third empty foil region 1123. Along the length direction of the current collector, the third empty foil region 1123 is located between the liquid-retaining coating 230 and the second active material layer 220. That is, the first empty foil region 1121, the third empty foil region 1123, and the second empty foil region 1122 are arranged in sequence. The surface of the third empty foil region 1123 is not covered by a coating. Thus, an electrolyte permeation channel can be formed at the third empty foil region 1123. Compared with other locations, the electrolyte can more easily pass through the permeation channel, which is beneficial to improving the wetting and diffusion rate of the electrolyte. Combined with the liquid-retaining coating 230, it is beneficial to further increase the liquid retention and improve the cycle performance of the battery.

[0035] Specifically, the third empty foil region 1123 does not contain the second active material and the liquid-retaining coating 230, which can prevent the liquid-retaining coating 230 from directly contacting the second active material layer 220. This prevents the liquid-retaining coating 230 and the second active material layer 220 from interfering with each other when they are coated. In addition, during subsequent charge and discharge cycles, the second active material layer 220 will expand and contract due to lithium ion insertion and extraction. The third empty foil region 1123 can provide a buffer space to prevent the expansion of the second active material layer 220 or the liquid-retaining coating 230 from squeezing each other, thereby reducing the risk of damage caused by the liquid-retaining coating 230 and the second active material layer 220 squeezing each other.

[0036] refer to Figures 1 to 3 In some embodiments, the size of the third empty foil region 1123 along the length direction of the current collector is 0 (excluding) to 2 mm. For example, the size of the third empty foil region 1123 can be 0.5 mm, 1 mm, 1.5 mm, or 2 mm, or it can be any two of the above values ​​as endpoints (such as 1 mm to 2 mm). Limiting the size of the third empty foil region 1123 to be greater than 0 can form an effective gap between the second active material layer 220 and the electrolyte retention coating 230, avoiding direct contact between the two, reducing the interference of the expansion and contraction of the second active material layer 220 on the electrolyte retention coating 230 during charge and discharge cycles, which is beneficial to maintaining the structural stability and electrolyte retention function of the electrolyte retention coating 230, and ensuring the wetting and diffusion of the electrolyte. Limiting the upper limit of the size of the third empty foil region 1123 can avoid the waste of space caused by the third empty foil region 1123 being too long. While ensuring the spacing and penetration function, it is beneficial to make fuller use of space, thereby helping to ensure the energy density of the battery.

[0037] refer to Figures 1 to 3In some embodiments, the coating thickness of the electrolyte-retaining coating 230 is 2µm to 5µm along the thickness direction. For example, the coating thickness of the electrolyte-retaining coating 230 can be 2µm, 3µm, 4µm, or 5µm, or it can be a range of any two of the above values ​​as endpoints (e.g., 3µm to 4µm). Limiting the lower limit of the electrolyte-retaining coating 230's thickness ensures the structural stability and electrolyte retention of the coating 230, allowing it to fully exert its function of adsorbing and locking in the electrolyte, ensuring sufficient electrolyte retention, and thus alleviating the problem of insufficient electrolyte wetting after electrode compaction. Limiting the upper limit of the electrolyte-retaining coating 230's thickness prevents the coating 230 from being too thick, causing the electrode to occupy additional space in the thickness direction, preventing wasted space from affecting the capacity of active materials inside the battery, thereby helping to ensure the battery's energy density.

[0038] refer to Figures 1 to 3 In some embodiments, the coating density of the liquid-retaining coating 230 is 0.2 g / m³. 2 Up to 1g / m 2 For example, the coating density of the liquid-retaining coating 230 can be 0.2 g / m³. 2 0.3g / m 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 0.9g / m 2 or 1g / m 2 It can also be any two of the above values ​​as endpoints, such as 0.5g / m 2 Up to 0.6g / m 2 The lower limit of the coating density of the electrolyte-retaining coating 230 is set to ensure the formation of an effective electrolyte storage structure, thereby fully adsorbing and retaining the electrolyte and ensuring the retention of electrolyte. The upper limit of the coating density of the electrolyte-retaining coating 230 is set to prevent the structure of the electrolyte-retaining coating 230 from being too dense, which facilitates the wetting of the electrolyte. At the same time, it also helps to reduce the consumption of electrolyte-retaining materials and reduce costs.

[0039] refer to Figures 1 to 3 In some embodiments, the second side 112 further includes a fourth empty foil region 1124. Along the length direction of the current collector, the fourth empty foil region 1124 is located on the side of the second active material layer 220 away from the liquid retention coating 230. That is, along the length direction of the current collector, the fourth empty foil region 1124, the first empty foil region 1121 and the second empty foil region 1122 are arranged in sequence. The fourth empty foil region 1124 can correspond to the winding end of the electrode sheet, so as to reduce the space occupied by the electrode sheet through the empty foil, which is beneficial to improving the volumetric energy density of the battery.

[0040] Specifically, in this embodiment, the electrode can be a positive electrode. The position of the fourth empty foil region 1124 corresponds to the winding end of the positive electrode, and the fourth empty foil region 1124 is provided on the side of the positive electrode away from the negative electrode. For a cell structure in which the positive electrode is wrapped around the negative electrode, the fourth empty foil region 1124 is located on the outermost side of the cell and has no corresponding anode active material. Therefore, providing the fourth empty foil region 1124 can avoid occupying extra space and help improve the utilization rate of the internal space of the battery. At the same time, it can also reduce the consumption of active material, thereby helping to reduce the production cost of the electrode.

[0041] refer to Figures 1 to 4 According to the embodiments of this application, the battery cell includes a separator, a positive electrode plate and a negative electrode plate. At least one of the positive electrode plate and the negative electrode plate is an electrode plate in any of the above embodiments. The separator is located between the positive electrode plate and the negative electrode plate. The positive electrode plate, the separator and the negative electrode plate are wound together to form the battery cell along the length direction of the current collector.

[0042] Specifically, along the thickness direction, the positive electrode sheet, separator, and negative electrode sheet are stacked. After stacking, the positive electrode sheet, separator, and negative electrode sheet are simultaneously wound along the length direction of the current collector. The winding starts from the winding needle, making the layers tightly adhered and wound to form the battery cell. A electrolyte-retaining coating 230 is provided on the positive electrode sheet and / or negative electrode sheet. The electrolyte-retaining coating 230 can absorb and retain electrolyte, thereby increasing the electrolyte retention of the battery cell and improving its cycle performance.

[0043] For example, along the length of the current collector, a liquid-retaining coating 230 is provided at the starting end of the winding of the positive electrode sheet. After the positive electrode sheet, separator and negative electrode sheet are wound to form a battery cell, the starting end of the winding is located in the central region of the battery cell. Thus, the liquid-retaining coating 230 can promote the wetting of electrolyte in the central region of the battery cell and the amount of liquid retained. In turn, it is beneficial to alleviate the problems of lithium plating and cycle failure of the battery cell, and make the cycle performance of the battery cell better.

[0044] If the positive electrode is provided with a third empty foil area 1123, along the length direction of the current collector, the third empty foil area 1123 is located between the liquid-retaining coating 230 and the second active material layer 220. A gap can be formed at the third empty foil area 1123 to provide a channel for electrolyte flow, which facilitates smoother diffusion of electrolyte inside the cell, further improves the uniformity of electrolyte wetting, and helps to extend the service life of the cell.

[0045] For example, if both the positive and negative electrodes use the aforementioned electrodes, the electrolyte-retaining coating 230 on the positive and negative electrodes can further improve the degree of electrolyte wetting of the battery cell and the amount of electrolyte retained in the battery cell.

[0046] It should be noted that the position of the electrolyte-retaining coating 230 is not limited to the starting end of winding. Specifically, the battery cell can have a structure in which the positive electrode sheet is wrapped with a negative electrode sheet. In this case, the electrolyte-retaining coating 230 can absorb and retain the electrolyte at the winding end of the positive electrode sheet. At this time, the third empty foil area 1123 can be wound by contacting the winding needle at the winding start end.

[0047] refer to Figures 1 to 4 The battery according to the embodiments of this application includes an aluminum-plastic film 300 and a battery cell as described in the above embodiments. The aluminum-plastic film 300 includes a covering area 310 and a sealing area 320. The sealing area 320 surrounds and connects to the outer periphery of the covering area 310, and the covering area 310 and the sealing area 320 together form a receiving cavity. The battery cell is located in the receiving cavity. The aluminum-plastic film 300 is used to encapsulate the battery cell. Along the thickness direction, the covering area 310 and the battery cell are stacked. The thickness of the sealing area 320 is greater than the thickness of the covering area 310. Therefore, by reducing the thickness of the covering area 310, the increased thickness of the liquid-retaining coating 230 can be balanced. While ensuring the liquid-retaining performance of the battery, the thickness of the battery is avoided from being increased. This balances the liquid-retaining performance and energy density of the battery.

[0048] Specifically, the aluminum-plastic film 300 deforms through perforation to form a covering area 310 and a sealing area 320. The covering area 310 and the sealing area 320 together enclose a receiving cavity, in which the battery cell is located and the electrolyte is also encapsulated. Along the thickness direction, the covering area 310 is stacked with the battery cell and adheres to the opposite sides of the battery cell, meaning the covering area 310 is a planar structure perpendicular to the thickness direction. The sealing area 320 surrounds and connects to the outer periphery of the covering area 310. The sealing area 320 includes the side cavity wall surrounding the receiving cavity connecting the four edges of the covering area 310, and the sealing edge sealing the four sides of the receiving cavity. The thickness of the sealing area 320 is greater than the thickness of the covering area 310. For example, the covering area 310 is thinned while ensuring the sealing performance of the sealing area 320.

[0049] When the aluminum-plastic film 300 is perforated to form the receiving cavity, the surrounding walls of the cavity will undergo greater deformation (e.g., at the corners of the cavity). The deformation of the covering area 310 is less than that of the sealing area 320. Therefore, the thickness of the sealing area 320 needs to be ensured to achieve a good seal for the battery cell. Based on this, this application sets the thickness of the covering area 310 to be less than the thickness of the sealing area 320. While ensuring that the sealing area 320 can reliably seal the battery cell and electrolyte, the overall thickness of the battery is reduced by thinning the covering area 310. This balances the increased thickness of the battery cell due to the coating of the electrolyte-retaining coating 230, allowing the battery to maintain its electrolyte level and improve its electrolyte retention performance without increasing its thickness. This helps to balance the battery's electrolyte retention performance and energy density.

[0050] It should be noted that the aluminum-plastic film 300 includes a nylon layer, an aluminum layer and a PP layer (Polypropylene) arranged in sequence. The thickness of the covering layer is less than that of the edge sealing layer. It can be at least one of the nylon layer, aluminum layer and PP layer that is less than the corresponding layer of the edge sealing layer. For example, the thickness of the aluminum layer in the covering area 310 is less than the thickness of the aluminum layer in the edge sealing area 320.

[0051] For example, referring to the table below, Base is the comparative example, and liquid-retaining coating 230 with thicknesses of 1µm, 2µm and 3µm are used as three sets of examples, and the liquid injection coefficient of the control group and examples is kept consistent.

[0052] It can be seen that as the coating thickness of the liquid-retaining coating 230 increases, the liquid-retaining coefficient gradually increases, and correspondingly, the cell thickness also gradually increases. However, by reducing the thickness of the covering area 310, the cell thickness in each group of embodiments is smaller than that in the Base group, thus achieving a balance between liquid retention and energy density.

[0053]

[0054] in addition, Figure 5 The image shows the RT Thickness rebound curve (thickness rebound curve at room temperature) for comparison and examples, where the horizontal axis Cycle represents the number of cycles and the vertical axis Thickness rebound represents the thickness rebound.

[0055] Reference Figure 5 It can be seen that when the number of cycles is 0, the thickness springback rate of the comparative example and each embodiment is close to 0; When the number of cycles reaches 200, with the horizontal axis fixed and the values ​​on the vertical axis compared, it can be seen that the thickness rebound rate from largest to smallest is: Base group, Example 1, Example 2, and Example 3. That is, Example 3, which has the highest liquid retention coefficient, has a lower thickness rebound rate. It should be noted that the more cycles a battery has, the closer its thickness is to the initial thickness, and the better its cycle performance. Therefore, the cycle performance gradually increases from Base group to Example 1, Example 2, and Example 3.

[0056] Similarly, comparing the thickness rebound of batteries with 400, 600, 800 and 1000 cycles, the thickness rebound from largest to smallest is Base group, Example 1, Example 2 and Example 3. It can be seen that the method of setting the liquid-retaining coating 230 and reducing the thickness of the coverage area 310 in this application has better cycle performance.

[0057] It should be noted that the determination of the liquid injection coefficient usually requires first determining the theoretical liquid injection volume of the battery. During actual liquid injection, the actual mass of electrolyte injected into the battery is recorded. The liquid injection coefficient is the ratio of the actual liquid injection volume to the theoretical liquid injection volume.

[0058] The electrolyte retention coefficient is generally determined after electrolyte injection and a period of settling. First, the battery's mass at this point is measured. Then, the battery is packaged and undergoes formation and capacity testing. Afterward, the battery is disassembled, excess electrolyte is removed from the surface, and the mass of the remaining electrolyte is weighed. The electrolyte retention coefficient is the ratio of the remaining electrolyte mass to the initial injected electrolyte mass.

[0059] Thickness rebound determination after cycling requires measuring the battery thickness before cycling. The battery is then cycled under preset conditions (such as specific charge / discharge rates, temperature, and pressure). After cycling, the battery thickness is measured again under the same environmental conditions. The thickness rebound rate is the ratio of the change in battery thickness after cycling to the thickness before cycling.

[0060] refer to Figures 1 to 4 In some embodiments, the sealing region 320 includes a nylon layer, an aluminum layer, and a PP layer, with the aluminum layer located between the nylon layer and the PP layer. The thickness of the aluminum layer is 20µm to 40µm. For example, the thickness of the aluminum layer in the sealing region 320 can be 20µm, 21µm, 22µm, 23µm, 24µm, 25µm, 26µm, 27µm, 28µm, 29µm, 30µm, 31µm, 32µm, 33µm, 34µm, 35µm, 36µm, 37µm, 38µm, 39µm, or 40µm, or it can be a range of any two of the above values ​​as endpoints (e.g., 23µm to 25µm). Limiting the lower limit of the aluminum layer thickness in the sealing region 320 ensures the structural strength and barrier performance of the sealing region 320, effectively preventing gas and moisture from passing through the sealing region 320, thereby maintaining the battery's sealing performance and chemical stability. Limiting the upper limit of the thickness of the 320 aluminum layer in the sealing area is to prevent the overall volume of the battery from increasing due to an excessively thick 320 aluminum layer, thereby improving the volumetric energy density of the battery. Therefore, limiting the thickness range of the 320 aluminum layer in the sealing area can balance the battery's sealing performance and energy density.

[0061] refer to Figures 1 to 4In some embodiments, the coverage area 310 includes a nylon layer, an aluminum layer, and a PP layer, with the aluminum layer located between the nylon layer and the PP layer. The thickness of the aluminum layer is 10µm to 30µm. For example, the thickness of the aluminum layer in the coverage area 310 can be 10µm, 11µm, 12µm, 13µm, 14µm, 15µm, 16µm, 17µm, 18µm, 19µm, 20µm, 21µm, 22µm, 23µm, 24µm, 25µm, 26µm, 27µm, 28µm, 29µm, or 30µm, or it can be an interval value (e.g., 5µm to 6µm) where any two of the above values ​​are used as endpoints. The lower limit of the thickness of the aluminum layer in the coverage area 310 is limited to ensure the structural support and barrier performance of the coverage area 310 and maintain the sealing of the cavity. The upper limit of the aluminum layer in the coverage area 310 is limited to reduce the overall thickness of the coverage area 310 to the greatest extent while ensuring the barrier performance. This more effectively balances the increased thickness due to the coating of the cell with the liquid-retaining coating 230, resulting in a thinner battery and improving the energy density of the battery.

[0062] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. An electrode sheet, characterized in that, include: A current collector, along its thickness direction, includes opposing first and second sides; The second side includes a first empty foil area and a second empty foil area. Along the length direction of the current collector, the first empty foil area and the second empty foil area are arranged sequentially, and the second empty foil area is located at one end of the second side. A first active material layer is coated on the first side; A second active material layer is coated on the first empty foil area; A liquid-retaining coating is applied to the second empty foil area.

2. The electrode sheet according to claim 1, characterized in that, The second side also includes a third empty foil area, which is located between the liquid-retaining coating and the second active material layer along the length direction of the current collector.

3. The electrode sheet according to claim 2, characterized in that, Along the length of the current collector, the size of the third empty foil region is 0 to 2 mm.

4. The electrode sheet according to claim 1, characterized in that, Along the thickness direction, the coating thickness of the liquid-retaining coating is 2µm to 5µm.

5. The electrode sheet according to claim 1, characterized in that, The coating density of the liquid-retaining coating is 0.2 g / m³. 2 Up to 1g / m 2 .

6. The electrode sheet according to claim 1, characterized in that, The second side also includes a fourth empty foil region, which is located on the side of the second active material layer away from the liquid-retaining coating along the length direction of the current collector.

7. A battery cell, characterized in that, include: Diaphragm; The positive electrode and the negative electrode, at least one of which is the electrode according to any one of claims 1 to 6, the separator is located between the positive electrode and the negative electrode, and the positive electrode, the separator and the negative electrode are wound together to form the battery cell along the length direction of the current collector.

8. A battery, characterized in that, include: An aluminum-plastic film includes a covering area and a sealing area, wherein the sealing area surrounds and connects the outer periphery of the covering area, and the covering area and the sealing area together enclose a receiving cavity; The battery cell of claim 7 is located in the receiving cavity, and the covering area is stacked with the battery cell along the thickness direction; The thickness of the edge sealing area is greater than the thickness of the covering area.

9. The battery according to claim 8, characterized in that, The edge sealing area includes a nylon layer, an aluminum layer, and a PP layer, with the aluminum layer located between the nylon layer and the PP layer, and the thickness of the aluminum layer being 20µm to 40µm.

10. The battery according to claim 8, characterized in that, The coverage area includes a nylon layer, an aluminum layer, and a PP layer, with the aluminum layer located between the nylon layer and the PP layer, and the thickness of the aluminum layer being 10 to 30 µm.

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