Pole piece and coating system thereof, battery monomer, battery device and power utilization device

Abstract

The invention provides a pole piece and a coating system thereof, a battery monomer, a battery device and a power utilization device, and relates to the technical field of batteries, the pole piece comprises a current collector and an active material layer; the current collector extends along a first direction, the surface of the current collector is provided with a plurality of areas which are adjacently arranged along a second direction, the second direction is perpendicular to the first direction, and the active material layers are attached in each area; wherein in the second direction, the expansion coefficient of the active material layer in the first region is greater than that of the active material layer in the regions on the two sides of the first region, and the first region is the region where the current collector is located in the middle position in the second direction. According to the invention, the problem of non-uniform temperature change in the charging and discharging process of the existing battery can be solved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a pole piece and its coating system, a battery cell, a battery device and an electrical device. Background Art

[0002] With the rapid growth of the electric vehicle and portable electronic device markets, the demand for high-performance, long-life lithium batteries is increasing. However, ordinary lithium-ion batteries on the market today face many challenges, especially the uneven heat distribution inside the battery cell.

[0003] This uneven heat distribution causes the temperature in the middle of the cell to be too high, which in turn accelerates the chemical reaction rate in this area, which may cause structural damage, such as thinning of the pole piece or increasing the gap between the anode and cathode. When charging again, these changes will cause more complex polarization effects inside the battery, causing faster capacity decay and possibly causing problems such as lithium deposition, which seriously affects the service life and performance of the entire cell.

[0004] It should be noted that the above statements are only used to provide background technical information related to the present application and do not necessarily constitute prior art. Summary of the invention

[0005] In view of this, the purpose of this application is to propose a pole piece and its coating system, a battery cell, a battery device and an electrical device. This application can specifically solve the problem that the battery life and performance are affected by uneven temperature changes during the charging and discharging process of existing batteries.

[0006] Based on the above-mentioned purpose, in the first aspect, the present application proposes a pole piece, comprising: a current collector and an active material layer; the current collector extends along a first direction, and the surface of the current collector has a plurality of regions adjacently arranged along a second direction, the second direction is perpendicular to the first direction, and the active material layer is attached to each region; wherein, along the second direction, the expansion coefficient of the active material layer in the first region is greater than the expansion coefficient of the active material layer in the regions on both sides of the first region, and the first region is the region where the middle position of the current collector along the second direction is located.

[0007] The above embodiment provides a pole piece, the expansion coefficient of the active material layer corresponding to the middle position area of ​​the pole piece is greater than the expansion coefficient of the active material layer corresponding to the two side positions, so as to realize the gradient distribution of the expansion coefficient. In this way, when the pole piece is used as a cathode pole piece, lithium ions are embedded in the cathode pole piece during the discharge process, and the reaction rate of the cathode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the cathode pole piece fills the reduction of the anode pole piece caused by the deintercalation of the anode lithium ions, thereby reducing the interval between the positive and negative pole pieces; when the pole piece is used as an anode pole piece, lithium ions are deintercalated from the cathode pole piece and embedded in the anode pole piece during the charging process, and the reaction rate of the anode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the anode pole piece fills the reduction of the anode pole piece caused by the deintercalation of the cathode lithium ions, thereby reducing the interval between the positive and negative pole pieces, reducing the risk of lithium deposition of the battery, and improving the cycle performance of the battery cell.

[0008] In some embodiments, the active material layer includes a first active material and a second active material, the expansion coefficient of the first active material is smaller than the expansion coefficient of the second active material, and the specific gravity of the first active material in the active material layer in each region is greater than the specific gravity of the second active material; along the second direction, the content of the second active material in the active material layer in the first region is greater than the content of the second active material in the active material layers in the regions on both sides of the first region.

[0009] The above-mentioned embodiment sets the content of the first active material and the second active material, so that in a scenario where the first active material with a small expansion coefficient is the main system, more second active materials with a high expansion coefficient are used in the middle area to achieve that the expansion coefficient of the active material layer in the first area is greater than the expansion coefficient of the active material layers in the areas on both sides of the first area. This active material distribution scheme can achieve greater expansion in the middle area, thereby balancing the stress and volume change of the anode and cathode plates inside the battery, and improving the performance and safety of the battery.

[0010] In some embodiments, the active material layer includes a first active material and a second active material, the expansion coefficient of the first active material is smaller than the expansion coefficient of the second active material, and the specific gravity of the first active material in the active material layer in each region is smaller than the specific gravity of the second active material; along the second direction, the content of the first active material in the active material layer in the first region is smaller than the content of the first active material in the active material layers in regions on both sides of the first region.

[0011] The above-mentioned embodiment sets the content of the first active material and the second active material, so that in a scenario where the second active material with a large expansion coefficient is the main system, more second active material with a high expansion coefficient is used in the middle area to achieve that the expansion coefficient of the active material layer in the first area is greater than the expansion coefficient of the active material layers in the areas on both sides of the first area. This active material distribution scheme can achieve greater expansion in the middle area, thereby balancing the stress and volume change of the anode and cathode plates inside the battery, and improving the performance and safety of the battery.

[0012] In some embodiments, the first active material includes lithium iron phosphate, and the second active material includes a ternary material.

[0013] By using different proportions of LFP and NCM in different areas, this embodiment can make the battery better adapt to different operating conditions, such as high-rate charging and discharging, high-temperature operation, etc., thereby improving the overall performance and reliability of the battery cell made with the electrode sheet of this embodiment.

[0014] In some embodiments, the active material layer includes a binder, and along the second direction, a content of the binder in the active material layer in the first region is less than a content of the binder in the active material layers in regions on both sides of the first region.

[0015] The above-mentioned embodiment achieves the change of the expansion coefficient of different areas by changing the content of the binder in different areas of the electrode piece, so that the expansion of the first area is greater than that of the two side areas. The expansion of the middle part of the cathode electrode piece is used to fill the reduction of the middle part of the anode electrode piece caused by the deintercalation of anode lithium ions, thereby reducing the interval between the positive and negative electrode pieces, reducing the risk of lithium plating in the battery, and improving the cycle performance of the battery cell.

[0016] In some embodiments, the current collector has a first surface and a second surface that are oppositely disposed, the first surface and the second surface each have a plurality of regions that are adjacently disposed along the second direction, and the active material layer is attached to each region.

[0017] The above-mentioned embodiment can realize coating on both sides of the current collector to form a double-sided coated pole piece, which can improve the utilization rate of the pole piece and reduce the cost.

[0018] In some embodiments, the first region is divided according to historical temperature data, and the historical temperature data includes the temperature values ​​of the battery cells during the charging and discharging process; wherein the first region is the pole piece region corresponding to the position of the maximum temperature value in the historical temperature data, and the regions on both sides of the first region are partitioned to both sides of the first region based on a preset temperature difference as the division gradient of a region.

[0019] The above embodiment uses the position with the highest temperature of the battery cell to obtain the middle area of ​​the pole piece, so that the pole piece area division has more experimental basis, improves the reliability of the pole piece, and uses the preset temperature difference as the area division gradient to divide the area on both sides of the position of the maximum temperature value, reducing the risk of local overheating of the battery.

[0020] In some embodiments, the first region is divided according to historical power-withdrawal capacity data, and the historical power-withdrawal capacity data includes the gram capacity loss value of the battery cell; wherein, the first region is the electrode area corresponding to the position where the gram capacity loss value in the historical power-withdrawal capacity data is greater than a preset value, and the areas on both sides of the first region are partitioned to both sides of the first region with the preset gram capacity difference as the division gradient of a region.

[0021] The above embodiment uses the relationship between the gram capacity loss value of the battery cell and the preset value to obtain the middle area of ​​the electrode, so that the electrode area division is more targeted and the reliability of the electrode is improved. By using the preset gram capacity difference as the area division gradient, the area can be divided into two sides of the location where the gram capacity loss is larger, reducing the performance difference between different areas, thereby extending the service life of the battery.

[0022] In some embodiments, the plurality of regions include a first region, a second region, and a third region, and along the second direction, the second region and the third region are respectively located on both sides of the first region.

[0023] The pole piece obtained in the above embodiment has three regions, which can realize rapid zoning of the pole piece and improve the preparation efficiency of the pole piece.

[0024] In some embodiments, the surface of the current collector also has a fourth region for forming a pole ear, and the fourth region is adjacent to the second region; the expansion coefficient of the active material layer in the first region is greater than the expansion coefficient of the active material layer in the third region, and the expansion coefficient of the active material layer in the third region is greater than the expansion coefficient of the active material layer in the second region.

[0025] The above embodiments can better fit the temperature distribution of the battery cell in actual application, and perform gradient zoning according to the actual use of the battery cell, so that the middle area with high temperature has a larger expansion coefficient, followed by the lower area, and the upper area has the smallest expansion coefficient. This can optimize the battery design, improve battery performance, extend life, and enhance safety.

[0026] In the second aspect, a coating system is also provided, the system comprising: a plurality of coating dies arranged in parallel along a second direction, each coating die head being respectively connected to a slurry storage tank, the coating die head being used to coat the slurry in the slurry storage tank on a current collector, the current collector extending along a first direction, the surface of the current collector having a plurality of adjacent regions arranged along the second direction, the second direction being perpendicular to the first direction, the slurry storage tank, the coating die head and the regions on the surface of the current collector corresponding one to one; wherein the expansion coefficient of the slurry in the slurry storage tank corresponding to the first region is greater than the expansion coefficient of the slurry in the slurry storage tank corresponding to the regions on both sides of the first region; a conveying device, the conveying device being used to convey the current collector along the first direction; the coating die head being arranged at one end of the conveying device, for coating the slurry on the surface of the current collector; a controller being used to control the conveying device and the coating die head to form the pole piece.

[0027] The system of the above embodiment can accurately control the expansion coefficient of the slurry in different regions by separately setting a coating die head and a corresponding slurry storage tank for each region. In this way, the slurry expansion coefficient of the first region and the regions on both sides thereof are differentially controlled, wherein the slurry expansion coefficient of the first region is greater than the slurry expansion coefficient of the regions on both sides, thereby preparing a pole piece that can solve the problem of uneven temperature distribution of the battery.

[0028] In some embodiments, the coating die includes a first coating die, a second coating die and a third coating die, the second coating die, the first coating die and the third coating die are arranged in sequence along the second direction, the first coating die, the second coating die and the third coating die are respectively connected to the first slurry storage tank, the second slurry storage tank and the third slurry storage tank; the first coating die is arranged corresponding to the first area; the expansion coefficient of the slurry in the first slurry storage tank is greater than the expansion coefficient of the slurry in the third slurry storage tank, and the expansion coefficient of the slurry in the third slurry storage tank is greater than the expansion coefficient of the slurry in the second slurry storage tank.

[0029] The above-mentioned embodiment can be more in line with the temperature distribution of the battery cell in actual application, and gradient partitioning can be performed according to the actual use of the battery cell, so that the middle area with high temperature has a larger expansion coefficient, followed by the lower area, and the upper area has the smallest expansion coefficient. The battery made of the electrode can be optimized, the battery performance can be improved, the life can be extended, and the safety can be enhanced.

[0030] In the third aspect, a battery cell is also provided, which includes an electrode assembly, an electrolyte and a shell, wherein the electrode assembly and the electrolyte are accommodated in a accommodating space inside the shell; the electrode assembly includes a first pole piece, a second pole piece and a diaphragm, wherein the diaphragm is arranged between the first pole piece and the second pole piece, and at least one of the first pole piece and the second pole piece is the pole piece described in any one of the first aspect.

[0031] In a fourth aspect, a battery device is provided, comprising the battery cell as described in the third aspect.

[0032] In a fifth aspect, an electrical device is also provided, comprising the battery device as described in the fourth aspect, wherein the battery device is used to supply power to the electrical device.

[0033] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application. In addition, the same reference numerals are used to represent the same parts in all the drawings.

[0035] Figure 1 A schematic diagram showing the structure of a pole piece provided in some embodiments of the present application;

[0036] Figure 2 A schematic diagram showing changes in pole pieces during a discharge process provided by some embodiments of the present application is shown;

[0037] Figure 3 Another schematic diagram showing the structure of a pole piece provided in some embodiments of the present application;

[0038] Figure 4 A schematic diagram showing the structure of a battery cell formed according to pole pieces provided in some embodiments of the present application;

[0039] Figure 5 A comparison chart of cell parameter results under different material ratios provided in the embodiments of the present application is shown;

[0040] Figure 6 A schematic diagram of the structure of a coating system provided in an embodiment of the present application is shown;

[0041] Figure 7A schematic structural diagram of a battery cell provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0042] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0044] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0045] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0046] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0047] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0048] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0049] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0050] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0051] The battery cell is generally placed in a shell to form a battery cell, which makes the space in the middle of the battery cell small, and the heat dissipation performance in the middle position is lower than that at the edge of the battery cell, resulting in uneven heat distribution inside the battery cell. Therefore, in the charging and discharging conditions, the temperature in the middle of the battery cell is generally higher than the temperature of the upper and lower areas. If the middle of the battery is consistently in a high temperature state, the reaction rate in the middle of the battery cell will be accelerated, and the stored energy will be released first. The thickness of the middle of the anode will be reduced, and the middle of the battery cell will complete the discharge step first, while the upper and lower parts of the anode have not yet completed full discharge. However, the state of charge (SOC) of the battery cell has been reduced. At this time, the thickness of the anode electrode in the middle of the battery cell is the smallest, and the gap with the cathode is larger. Polarization increases during recharging, and defects such as lithium deposition occur, increasing battery cell loss. As the number of charge and discharge cycles increases, the irreversible capacity loss of the battery cell will also increase, resulting in battery cell performance degradation.

[0052] In order to solve the above problems, the present embodiment provides a pole piece, the expansion coefficient of the active material layer corresponding to the middle position area of ​​the pole piece is greater than the expansion coefficient of the active material layer corresponding to the two side positions, so that when the pole piece is used as a cathode pole piece, lithium ions are embedded in the cathode pole piece during the discharge process, and the reaction rate of the cathode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the cathode pole piece fills the reduction in the middle part of the anode pole piece caused by the deintercalation of the anode lithium ions, thereby reducing the interval between the positive and negative pole pieces. Similarly, when the pole piece is used as an anode pole piece, lithium ions are deintercalated from the cathode pole piece and embedded in the anode pole piece during the charging process, and the reaction rate of the anode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the anode pole piece fills the reduction in the middle part of the anode pole piece caused by the deintercalation of the cathode lithium ions, thereby reducing the interval between the positive and negative pole pieces, reducing the risk of lithium plating of the battery, and improving the cycle performance of the battery cell.

[0053] For the convenience of description, the following embodiments are described by taking an example in which a pole piece of an embodiment of the present application is used to form a battery cell, and the battery cell is used to form a battery cell.

[0054] Figure 1 For a schematic diagram of the structure of the pole piece provided in some embodiments of the present application, see Figure 1 The pole piece 10 of this embodiment includes: a current collector 11 and an active material layer 12; the current collector 11 extends along a first direction, and the surface of the current collector 11 has a plurality of regions adjacently arranged along a second direction, the second direction is perpendicular to the first direction, and the active material layer 12 is attached to each region; wherein, along the second direction, the expansion coefficient of the active material layer in the first region 111 is greater than the expansion coefficient of the active material layer in the regions on both sides of the first region, and the first region 111 is the region where the middle position of the current collector along the second direction is located.

[0055] The current collector 11 is a structure or component for collecting current, and may be copper foil, nickel foil or aluminum foil, etc. The current collector 11 has the function of conducting electrons and carrying the active material layer.

[0056] The first direction of this embodiment is the length direction of the current collector. In the process of making the pole piece, the current collector extends along the first direction, and then the active material slurry is coated on the current collector to form the pole piece. The second direction is perpendicular to the first direction, that is, the second direction is the width direction of the current collector. In this embodiment, the current collector is divided into multiple regions in the width direction of the current collector, which can be 3 regions, 4 regions, 5 regions, 6 regions, etc., which can be set according to the width of the pole piece and actual product requirements.

[0057] like Figure 1The multiple regions of the current collector include a first region 111, a second region 112, and a third region 113. The first region 111 is the region where the middle position of the current collector is located along the second direction. Figure 1 In the second direction shown, the second region 112, the first region 111, and the third region 113 are adjacent in sequence. The expansion coefficient of the active material layer in the first region 111 is greater than the expansion coefficient of the active material layer in the regions on both sides of the first region. Continuing with the above example, the expansion coefficient of the active material layer in the first region 111 is greater than the expansion coefficient of the active material layer in the second region 112 and the third region 113. In this way, after the slurry of the active material layer is coated and dried, it is compacted by a pressure roller to obtain a lithium battery pole piece with upper and middle different structures and expansion coefficients.

[0058] Figure 2 Schematic diagram of the change of the electrode during the discharge process provided by some embodiments of the present application. This embodiment takes the cathode electrode as an example. When the electrode of this embodiment is used as the cathode electrode, the cathode electrode is matched with the anode electrode and the diaphragm through a winding process to form a bare battery cell. See Figure 2 In the battery cell, the anode electrode 202, the separator 201 and the electrode 10 of this embodiment are adjacent. During the discharge process, lithium ions are separated from the active material layer of the anode electrode 202 and embedded into the active material layer of the cathode electrode 10 through the electrolyte. Figure 2 As shown, since the temperature in the middle of the battery is high, the reaction rate in the middle of the anode electrode 202 is fast, and the thickness of the lithium ions in the middle decreases quickly. In this embodiment, since the middle of the cathode electrode 10, as shown in FIG. Figure 2 The expansion coefficient of the first region 111 is greater than the expansion coefficient of the active material layer of the second region 112 and the third region 113. Therefore, in the process of lithium ion embedding into the first region 111, the expansion degree of the first region 111 is also greater than that of the second region 112 and the third region 113. In this way, the expansion degree of the first region increases, and the amount of expansion toward the anode also increases, which can fill the reduction of the anode electrode sheet, thereby reducing the interval between the positive and negative electrode sheets, reducing the risk of lithium plating of the battery, and improving the cycle performance of the battery cell.

[0059] In this embodiment, the active material layer is a slurry coating with micropores, which serves as a carrier for embedding lithium ions and electrons during the battery charging and discharging process, and plays a role in storing and releasing energy.

[0060] In this embodiment, the expansion coefficient is a key parameter that describes the degree of dimensional change of a material when the temperature changes. The larger the thermal expansion coefficient, the greater the dimensional change of the material when the temperature changes. In one example, the expansion coefficient of each region of the pole piece can be calculated by using static thermomechanical analysis technology by measuring the deformation of the sample at different temperatures; the thermal expansion coefficient of the material can also be calculated by using the interference phenomenon of light by measuring the moving distance of the interference fringes.

[0061] The above embodiment provides a pole piece, the expansion coefficient of the active material layer corresponding to the middle position area of ​​the pole piece is greater than the expansion coefficient of the active material layer corresponding to the position on both sides, so as to realize the gradient distribution of the expansion coefficient. In this way, when the pole piece is used as a cathode pole piece, lithium ions are embedded in the cathode pole piece during the discharge process, and the reaction rate of the cathode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the cathode pole piece fills the reduction of the anode pole piece caused by the deintercalation of the anode lithium ions, reduces the interval between the positive and negative pole pieces, reduces the risk of lithium plating in the battery, and improves the cycle performance of the battery cell. When the pole piece is used as an anode pole piece, lithium ions are deintercalated from the cathode pole piece and embedded in the anode pole piece during the charging process, and the reaction rate of the anode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the anode pole piece fills the reduction of the anode pole piece caused by the deintercalation of the cathode lithium ions, reduces the interval between the positive and negative pole pieces, reduces the risk of lithium plating in the battery, and improves the cycle performance of the battery cell.

[0062] In an embodiment of the present application, the active material layer includes a first active material and a second active material, the expansion coefficient of the first active material is smaller than the expansion coefficient of the second active material, and the specific gravity of the first active material in the active material layer in each region is greater than the specific gravity of the second active material; along the second direction, the content of the second active material in the active material layer in the first region is greater than the content of the second active material in the active material layers in the regions on both sides of the first region.

[0063] In this embodiment, the expansion coefficient of the first active material is smaller than that of the second active material, which means that at the same temperature or volume change, the second active material expands more. In each region, the specific gravity of the first active material is greater than that of the second active material, that is, the slurry used to prepare the electrode of this embodiment is a slurry with the first active material as the main component. Figure 1 The content of the second active material in the first area (of the battery) is greater than that in the areas on both sides. This means that the middle area has more high expansion coefficient material (second active material), resulting in a greater volume expansion during discharge. In addition, since the temperature in the middle area is also higher than that on both sides during discharge, the expansion effect caused by this temperature is more obvious due to the higher content of the second active material in the middle area.

[0064] The above-mentioned embodiment sets the content of the first active material and the second active material, so that in a scenario where the first active material with a small expansion coefficient is the main system, more second active materials with a high expansion coefficient are used in the middle area to achieve that the expansion coefficient of the active material layer in the first area is greater than the expansion coefficient of the active material layers in the areas on both sides of the first area. This active material distribution scheme can achieve greater expansion in the middle area, thereby balancing the stress and volume change of the anode and cathode plates inside the battery, and improving the performance and safety of the battery.

[0065] In an embodiment of the present application, the active material layer includes a first active material and a second active material, the expansion coefficient of the first active material is smaller than the expansion coefficient of the second active material, and the specific gravity of the first active material in the active material layer in each region is smaller than the specific gravity of the second active material; along the second direction, the content of the first active material in the active material layer in the first region is smaller than the content of the first active material in the active material layers in the regions on both sides of the first region.

[0066] In this embodiment, the expansion coefficient of the first active material is smaller than that of the second active material, which means that at the same temperature or volume change, the second active material expands more. In each region, the specific gravity of the first active material is smaller than that of the second active material, that is, the slurry used to prepare the electrode of this embodiment is a slurry with the second active material as the main component. Figure 1 The first active material content in the first region is less than that in the two side regions. This allows the middle region to have more high expansion coefficient material (second active material), resulting in greater volume expansion during discharge.

[0067] The above-mentioned embodiment sets the content of the first active material and the second active material, so that in a scenario where the second active material with a large expansion coefficient is the main system, more second active material with a high expansion coefficient is used in the middle area to achieve that the expansion coefficient of the active material layer in the first area is greater than the expansion coefficient of the active material layers in the areas on both sides of the first area. This active material distribution scheme can achieve greater expansion in the middle area, thereby balancing the stress and volume change of the anode and cathode plates inside the battery, and improving the performance and safety of the battery.

[0068] In addition, the method of increasing the expansion amount of the middle area of ​​the cathode in this embodiment can not only reduce lithium plating of the anode electrode, but also make the cathode electrode, the diaphragm and the anode squeeze each other, thereby reducing the ion passage rate and the reaction rate, thereby reducing the temperature of the middle area, improving the consistency of the reaction rate in each area, and alleviating the uneven temperature distribution of the battery cell during charging and discharging.

[0069] In the embodiment of the present application, the first active material includes lithium iron phosphate, and the second active material includes a ternary material.

[0070] Lithium iron phosphate (LiFePO4, hereinafter referred to as LFP) has good cycle stability and can maintain relatively stable electrochemical performance in multiple charge and discharge cycles. 2 , hereinafter referred to as NCM) has good electrochemical performance and long cycle life. In this embodiment, the ternary material mainly includes three elements: nickel, cobalt and manganese. The proportions of nickel, cobalt and manganese can be adjusted to meet different battery requirements. LFP has a stable structure and a low thermal decomposition temperature. Therefore, the expansion coefficient of LFP is smaller than that of NCM.

[0071] For example, in the LFP system, that is, LFP is used as the main material and NCM is doped in LFP. Because the expansion coefficient of NCM material is higher than that of LFP, in the LFP system, the NCM content in the first area of ​​the pole piece is greater than the NCM content in the second and third areas.

[0072] In an example, the first region contains 90% LFP, 3% NCM, 3% binder, 3% conductive agent, and 1% plasticizer; the second region contains 91% LFP, 2% NCM, 3% binder, 3% conductive agent, and 1% plasticizer; and the third region contains 90.5% LFP, 2.5% NCM, 3% binder, 3% conductive agent, and 1% plasticizer.

[0073] For example, in the NCM system, that is, NCM is used as the main material and LFP is doped in NCM. Because the expansion coefficient of NCM material is higher than that of LFP, in the NCM system, the LFP content in the middle area should be smaller than the content of LFP doped in the two side areas, so that the NCM proportion in the middle area is large.

[0074] In an example, the first region contains 90% NCM, 3% LFP, 3% binder, 3% conductive agent, and 1% plasticizer; the second region contains 91% NCM, 2% LFP, 3% binder, 3% conductive agent, and 1% plasticizer; and the third region contains 90.5% NCM, 2.5% LFP, 3% binder, 3% conductive agent, and 1% plasticizer.

[0075] Specifically, the content of each NCM and LFP can change the composition ratio of the coating slurry according to actual product requirements, which will not be described in detail here.

[0076] By using different proportions of LFP and NCM in different areas, this embodiment can make the battery better adapt to different operating conditions, such as high-rate charging and discharging, high-temperature operation, etc., thereby improving the overall performance and reliability of the battery cell made with the electrode sheet of this embodiment.

[0077] In the embodiment of the present application, the active material layer includes a binder, and along the second direction, the content of the binder in the active material layer in the first region is less than the content of the binder in the active material layer in regions on both sides of the first region.

[0078] The main function of the binder is to bond the active material, conductive agent and current collector together and maintain the stability of the conductive network structure.

[0079] The distribution of the binder will affect the electrochemical properties of the electrode. It can be seen from the above embodiments that the active material layer is a slurry coating with micropores, that is, there are gaps in the active material and a certain porosity, and the binder will reduce the porosity of the active material. In this embodiment, by setting less binder in the first region, the porosity of the active material in the first region can be greater than the porosity of the active material in the regions on both sides of the first region, that is, the porosity in the first region is higher, thereby providing more space when the active material expands, further increasing the expansion, so that the expansion of the first region is greater than that of the regions on both sides. During the discharge process, the expansion of the middle part of the cathode pole piece is used to fill the reduction in the middle part of the anode pole piece caused by the deintercalation of the anode lithium ions. During the charging process, the expansion of the middle part of the anode pole piece is used to fill the reduction in the middle part of the cathode pole piece caused by the deintercalation of the cathode lithium ions, thereby reducing the interval between the positive and negative pole pieces, reducing the risk of lithium deposition in the battery, and improving the cycle performance of the battery cell.

[0080] In an example, assuming that the first region contains 1% of the adhesive, the third region may contain 2% of the adhesive, and the third region may contain 3% of the adhesive.

[0081] The above-mentioned embodiment achieves the change of the expansion coefficient of different areas by changing the content of the binder in different areas of the electrode piece, so that the expansion of the first area is greater than that of the two side areas. During the discharge process, the expansion of the middle part of the cathode electrode piece is used to make up for the reduction in the middle part of the anode electrode piece caused by the deintercalation of lithium ions from the anode. During the charging process, the expansion of the middle part of the anode electrode piece is used to make up for the reduction in the middle part of the cathode electrode piece caused by the deintercalation of lithium ions from the cathode, thereby reducing the distance between the positive and negative electrode pieces, reducing the risk of lithium plating of the battery, and improving the cycle performance of the battery cell.

[0082] In this embodiment, the above-mentioned method of controlling the content of the binder in the active material layer of the first region to be less than the content of the binder in the active material layer of the regions on both sides of the first region along the second direction can be applied to the scenario where the specific gravity of the first active material in the active material layer in each region is greater than the specific gravity of the second active material, and the content of the second active material in the active material layer of the first region is greater than the content of the second active material in the active material layers of the regions on both sides of the first region. Similarly, it can also be applied to the scenario where the specific gravity of the first active material in the active material layer in each region is less than the specific gravity of the second active material, and the content of the first active material in the active material layer of the first region is less than the content of the first active material in the active material layers of the regions on both sides of the first region.

[0083] In the embodiment of the present application, the current collector has a first surface and a second surface arranged oppositely, and the first surface and the second surface both have a plurality of regions arranged adjacent to each other along the second direction, and the active material layer is attached to each region.

[0084] It can be understood that the first surface and the second surface are two surfaces in the thickness direction of the current collector, and the first surface and the second surface have the same area and opposite positions. The first region 111, the second region 112, and the third region 113 of the first surface correspond to the positions of the first region 111, the second region 112, and the third region 113 of the second surface, respectively, and the expansion coefficient of the active material layer of the first region 111 of the first surface and the second surface is greater than the expansion coefficient of the active material layer of the regions on both sides of the first region. Since both can achieve the purpose of this application, they should be within the scope of protection of this application.

[0085] The above-mentioned embodiment can realize coating on both sides of the current collector to form a double-sided coated pole piece, which can improve the utilization rate of the pole piece and reduce the cost.

[0086] In an embodiment of the present application, the first region is divided according to historical temperature data, and the historical temperature data includes the temperature values ​​of the battery cells during the charging and discharging process; wherein the first region is the electrode region corresponding to the position of the maximum temperature value in the historical temperature data, and the regions on both sides of the first region are partitioned to both sides of the first region based on a preset temperature difference as the division gradient of a region.

[0087] In this embodiment, the charge and discharge test monitoring data of the existing battery cell can be obtained as the data basis of the historical temperature data, and a number of temperature sampling points can be arranged on the battery cell to obtain the temperature distribution of the battery cell during the charge and discharge process, and identify the area with the highest temperature of the battery during the charge and discharge process. Before preparing the electrode of the present application, the current collector can be divided into regions, and the electrode area corresponding to the position of the maximum temperature value in the historical temperature data can be used as the first area. That is to say, the first area of ​​the electrode in the embodiment of the present application corresponds to the area with the highest temperature of the battery cell in actual application, and the expansion coefficient of the active material layer in the first area is greater than the expansion coefficient of the active material layer in the areas on both sides of the first area. In this way, it can be seen from the principle of the electrode in the above embodiment that the risk of lithium plating in the new battery cell made using the electrode of the present application is reduced, and the cycle performance of the battery cell is improved.

[0088] As can be seen from the above, after the first area is determined, the first area can be used as a reference position, and the preset temperature difference can be used as a division gradient of a region to partition the first area on both sides to obtain other areas. For example, if the temperature corresponding to the first area is 50°C, and the change of 1°C is used as the preset temperature difference, it will expand to both sides of the first area, and each time the temperature drops by 1°C, it will be regarded as a region. In this way, the first area can be partitioned on both sides to obtain multiple areas.

[0089] In this embodiment, the middle area of ​​the electrode is obtained based on the position with the highest temperature of the battery cell, so that the division of the electrode area is more experimentally based, and the reliability of the electrode is improved. By using the preset temperature difference as the area division gradient, the area can be divided into two sides of the position where the maximum temperature value is located, thereby reducing the risk of local overheating of the battery.

[0090] In an embodiment of the present application, the first region is divided according to historical power-withdrawal capacity data, and the historical power-withdrawal capacity data includes the gram capacity loss value of the battery cell; wherein the first region is the electrode region corresponding to the position where the gram capacity loss value in the historical power-withdrawal capacity data is greater than a preset value, and the regions on both sides of the first region are partitioned to both sides of the first region using the preset gram capacity difference as the division gradient of a region.

[0091] Among them, the gram capacity loss value of a battery cell refers to the loss of its reversible capacity relative to the initial capacity after a certain number of cycles.

[0092] The historical capacity data of this embodiment can be obtained through laboratory testing, such as charging and discharging the battery and recording the gram capacity loss value in each cycle. It can also be collected online through a battery management system (BMS) during the use of the battery cell.

[0093] In this embodiment, the preset value can be set according to indicators such as the rated capacity, electrochemical characteristics and safety margin of the battery cell.

[0094] The gram capacity loss value at a certain position is greater than a preset value, indicating that the gram capacity loss at the position is too large. Therefore, the electrode area corresponding to the position where the gram capacity loss value is greater than the preset value is taken as the first area. The active material layer with a high expansion coefficient in the first area can be used to alleviate the gram capacity loss and improve the electrochemical performance of the first area.

[0095] The first region is partitioned on both sides with a preset gram capacity difference as a division gradient to obtain regions on both sides of the first region. This partition optimization helps to balance the electrochemical reaction inside the battery, reduce the performance difference between different regions, and thus extend the service life of the battery.

[0096] In this embodiment, the relationship between the gram capacity loss value of the battery cell and the preset value is used to obtain the middle area of ​​the electrode, so that the electrode area division is more targeted and the reliability of the electrode is improved. By using the preset gram capacity difference as the area division gradient, the area can be divided into two sides of the location where the gram capacity loss is larger, reducing the performance difference between different areas, thereby extending the service life of the battery.

[0097] In the embodiment of the present application, the multiple regions include a first region, a second region and a third region. Along the second direction, the second region and the third region are respectively located on both sides of the first region.

[0098] like Figure 1 As shown, the multiple regions of the current collector include a first region 111, a second region 112, and a third region 113. The first region 111 is the region where the middle position of the current collector is located along the second direction. Figure 1 In the second direction shown, the second area 112 , the first area 111 , and the third area 113 are adjacent to each other in sequence.

[0099] The pole piece obtained in this embodiment has three regions, which can realize rapid zoning of the pole piece and improve the preparation efficiency of the pole piece.

[0100] In the embodiment of the present application, Figure 3 Another schematic diagram of the structure of the pole piece provided in some embodiments of the present application, Figure 4 A schematic diagram of the structure of a battery cell formed based on pole pieces provided in some embodiments of the present application.

[0101] like Figure 3 As shown, the surface of the current collector also has a fourth region 114 for forming a pole ear, and the fourth region 114 is adjacent to the second region 112; the expansion coefficient of the active material layer in the first region 111 is greater than the expansion coefficient of the active material layer in the third region 113, and the expansion coefficient of the active material layer in the third region 113 is greater than the expansion coefficient of the active material layer in the second region 112.

[0102] The fourth region 114 forms a tab 40 such as Figure 4 As shown, the fourth region 114 is adjacent to the second region 112, that is, the second region 112 is located in the upper part of the battery, and since the upper part of the battery cell near the pole ear is located at the edge of the battery, the heat dissipation performance is better. The first region 111 is located in the middle area of ​​the battery cell, so the third region 113 is located in the lower part of the battery cell away from the pole ear 40. The lower part of the battery cell is surrounded by the shell, so the heat dissipation of the third region is less than that of the second region. Therefore, in this embodiment, the expansion coefficient of the active material layer of the first region 111 is greater than the expansion coefficient of the active material layer of the third region 113, and the expansion coefficient of the active material layer of the third region 113 is greater than the expansion coefficient of the active material layer of the second region 112.

[0103] This embodiment can better fit the temperature distribution of the battery cell in actual application, and perform gradient zoning according to the actual use of the battery cell, so that the middle area with high temperature has a larger expansion coefficient, followed by the lower area, and the upper area has the smallest expansion coefficient. This can optimize the battery design, improve battery performance, extend life, and enhance safety.

[0104] The following is a specific example to illustrate the electrode provided in the embodiment of the present application.

[0105] like Figure 4 As shown, the pole piece 10 includes a current collector 11 and an active material layer 12. The current collector 11 extends along a first direction. The surface of the current collector 11 has a fourth region 114, a second region 112, a first region 111, and a third region 113 which are arranged adjacent to each other in sequence along a second direction. The fourth region 114 is used to form a pole ear.

[0106] The expansion coefficient of the first region 111 is greater than the expansion coefficient of the active material layer of the second region 112, and the expansion coefficient of the active material layer of the second region 112 is greater than the expansion coefficient of the active material layer of the third region 113. Therefore, in the process of lithium ion embedding into the first region 111, the expansion degree of the first region 111 is also greater than that of the second region 112 and the third region 113. In this way, the expansion degree of the first region increases, and during the discharge process, the expansion of the middle part of the cathode electrode piece can be used to make up for the reduction in the middle part of the anode electrode piece caused by the deintercalation of anode lithium ions. During the charging process, the expansion of the middle part of the anode electrode piece can be used to make up for the reduction in the middle part of the cathode electrode piece caused by the deintercalation of cathode lithium ions, thereby reducing the distance between the positive and negative electrode pieces, reducing the risk of lithium plating of the battery, and improving the cycle performance of the battery cell.

[0107] Among them, the number of regions on the current collector coated with the active material layer can be greater than 3. The specific number of regions can be based on the pole piece region corresponding to the location of the maximum temperature value in the historical temperature data as the first region. After obtaining the first region, the preset temperature difference is used as the division gradient of a region to obtain other regions by partitioning on both sides of the first region. For example, if the temperature corresponding to the first region is 50°C, and the change of 1°C is used as the preset temperature difference, it will expand to both sides of the first region, and each time the temperature drops by 1°C, it will be regarded as a region. In this way, the first region is partitioned on both sides to obtain multiple regions.

[0108] The specific number of regions can also be that the electrode region corresponding to the position where the gram capacity loss value is greater than the preset value is taken as the first region, and after the first region is obtained, the preset gram capacity difference is used as a division gradient of a region to divide the two sides of the first region to obtain other regions. For example, the preset gram capacity difference is 10% of the initial gram capacity as a division gradient.

[0109] Figure 5A comparison chart of cell parameter results under different material ratios provided in the embodiments of the present application is shown. Figure 5 The serial numbers represent different groups. The reduction in the proportion of high expansion coefficient materials or Binder (binder) refers to the proportion of high expansion coefficient materials or Binder in the upper, middle and lower regions of the pole piece, taking the three-region pole piece as an example.

[0110] Specifically, in one example, taking the LFP system as an example, if the NCM contained in the second area, the first area, and the third area is 0%, the corresponding temperatures of the upper, middle, and lower areas are 42°C, 58°C, and 50°C, respectively, and the 200cls capacity retention rate is 80%. It can be seen that the temperature difference between the three areas is large, and the capacity retention rate is not high.

[0111] If the second area contains NCM0%, the first area contains NCM3%, and the third area contains NCM1%, the corresponding temperatures of upper, middle and lower are 46°C, 50°C and 46°C respectively, and the corresponding capacity retention rate is 88%. Compared with the first group of data, the temperature difference between the three areas is reduced, and the performance is better.

[0112] If the second area contains NCM0%, the first area contains NCM5%, and the third area contains NCM3%, the corresponding temperatures of the upper, middle and lower parts are 47°C, 49°C and 47°C respectively, and the corresponding capacity retention rate is 92%. Compared with the first and second groups of data, the temperature difference between the three areas is further reduced, which can solve the problem of uneven battery temperature distribution.

[0113] in, Figure 5 The reduction in Binder refers to the amount of binder reduced in each area compared to the original material. Taking the second group of data as an example, it means that when the binder is used as the control variable, the binder in the upper part remains unchanged, that is, the reduction is 0, the binder in the middle area is reduced by 3%, and the binder in the lower area is reduced by 1%. In this way, the binder in the middle area is less than that in the lower area and less than that in the upper area, thereby realizing the function of the pole piece in the above embodiment.

[0114] The embodiment of the present application provides a pole piece, the expansion coefficient of the active material layer corresponding to the middle position area of ​​the pole piece is greater than the expansion coefficient of the active material layer corresponding to the position on both sides, so that when the pole piece is used as a cathode pole piece, lithium ions are embedded in the cathode pole piece during the discharge process, and the reaction rate of the cathode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the cathode pole piece fills the reduction of the middle part of the anode pole piece caused by the deintercalation of the anode lithium ions, thereby reducing the gap between the positive and negative pole pieces. When the pole piece is used as an anode pole piece, lithium ions are deintercalated from the cathode pole piece and embedded in the anode pole piece during the charging process, and the reaction rate of the anode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the anode pole piece fills the reduction of the middle part of the anode pole piece caused by the deintercalation of the cathode lithium ions, thereby reducing the gap between the positive and negative pole pieces, reducing the risk of lithium plating of the battery, and improving the cycle performance of the battery cell.

[0115] Figure 6 The schematic diagram of the structure of the electrode coating system provided in the embodiment of the present application is shown. The embodiment of the present application provides a electrode coating system, which is used to prepare the electrode of the above embodiment. The system includes: a plurality of coating die heads (such as Figure 6 The second coating die head 602, the first coating die head 601, and the third coating die head 603 in the embodiment of the present invention are connected to a slurry storage tank (such as Figure 6 The second slurry storage tank 612, the first slurry storage tank 611, and the third slurry storage tank 613 are arranged in the coating process, the collector extends along the first direction, and the surface of the collector has a plurality of adjacent regions arranged along the second direction, the second direction is perpendicular to the first direction, and the slurry storage tanks, the coating die head, and the regions on the surface of the collector correspond one to one; wherein the expansion coefficient of the slurry in the slurry storage tank corresponding to the first region is greater than the expansion coefficient of the slurry in the slurry storage tanks corresponding to the regions on both sides of the first region.

[0116] like Figure 6 As shown, the coating die includes a first coating die 601, a second coating die 602, and a third coating die 603. The second coating die 602, the first coating die 601, and the third coating die 603 correspond to the second slurry storage tank 612, the first slurry storage tank 611, and the third slurry storage tank 613, respectively. The second coating die 602, the first coating die 601, and the third coating die 603 correspond to the second area 112, the first area 111, and the third area 113, respectively.

[0117] The expansion coefficient of the slurry in the slurry storage tank (first slurry storage tank 611) corresponding to the first region 111 is greater than the expansion coefficient of the slurry in the slurry storage tanks corresponding to the regions on both sides of the first region. In other words, the expansion coefficient of the slurry in the first slurry storage tank 611 is greater than the expansion coefficient of the slurry in the second slurry storage tank 612 and the third slurry storage tank 613. In this way, when the current collector is coated, the expansion coefficient of the active material layer in the first region 111 can be made greater than the expansion coefficient of the active material layer in the regions on both sides of the first region.

[0118] Conveyor( Figure 6 The conveying device is used to convey the current collector along the first direction; the coating die head is arranged at one end of the conveying device, and is used to coat the slurry on the surface of the current collector. In this embodiment, the conveying device can be a conveying assembly composed of a conveyor belt and a gear, such as Figure 6 As shown, the coating die is arranged at one end of the current collector. When the current collector is transported along a first direction, the slurry in the coating die is coated on the current collector, thereby preparing a pole piece.

[0119] Controller( Figure 6 The controller is used to control the conveying device and the coating die head, and the coating die head is used to coat the slurry in the slurry storage tank on the current collector to form the above-mentioned pole piece. For example, the controller can control the start and stop of the conveying device, control the opening and closing of the coating die head, etc.

[0120] The system of this embodiment can accurately control the expansion coefficient of the slurry in different regions by separately setting a coating die head and a corresponding slurry storage tank for each region. In this way, the slurry expansion coefficient of the first region and the regions on both sides thereof are differentially controlled, wherein the slurry expansion coefficient of the first region is greater than the slurry expansion coefficient of the regions on both sides, thereby preparing a pole piece that can solve the problem of uneven temperature distribution of the battery.

[0121] In the present application embodiment, Figure 6 As shown, the coating die includes a first coating die 601, a second coating die 602, and a third coating die 603. The second coating die 602, the first coating die, and the third coating die 603 are arranged in sequence along the second direction. The second coating die 602, the first coating die 601, and the third coating die 603 are respectively connected to the second slurry storage tank 612, the first slurry storage tank 611, and the third slurry storage tank 613; the first coating die 601 is arranged corresponding to the first area 111; the expansion coefficient of the slurry in the first slurry storage tank 611 is greater than the expansion coefficient of the slurry in the third slurry storage tank 613, and the expansion coefficient of the slurry in the third slurry storage tank 613 is greater than the expansion coefficient of the slurry in the second slurry storage tank 612.

[0122] That is, the second coating die 602, the first coating die 601, and the third coating die 603 correspond to the second slurry storage tank 612, the first slurry storage tank 611, and the third slurry storage tank 613, respectively, and the second coating die 602, the first coating die 601, and the third coating die 603 correspond to the second area 112, the first area 111, and the third area 113, respectively.

[0123] The expansion coefficient of the slurry in the first slurry storage tank 611 is greater than the expansion coefficient of the slurry in the third slurry storage tank 613 , and the expansion coefficient of the slurry in the third slurry storage tank 613 is greater than the expansion coefficient of the slurry in the second slurry storage tank 612 .

[0124] Thus, on the pole piece coated by the system, the expansion coefficient of the active material layer in the first region 111 is greater than the expansion coefficient of the active material layer in the third region 113, and the expansion coefficient of the active material layer in the third region 113 is greater than the expansion coefficient of the active material layer in the second region 112. In this way, it can be more in line with the temperature distribution of the battery cell in actual application, and gradient partitioning can be performed according to the actual use of the battery cell, so that the middle area with high temperature has a larger expansion coefficient, the lower area has the second largest expansion coefficient, and the upper area has the smallest expansion coefficient, which can achieve the optimization of the battery made of the pole piece, improve the battery performance, extend the life, and enhance the safety.

[0125] An embodiment of the present application provides a battery cell, which includes an electrode assembly, an electrolyte and a shell, wherein the electrode assembly and the electrolyte are contained in a accommodating space inside the shell; the electrode assembly includes a first pole piece, a second pole piece and a diaphragm, wherein the diaphragm is arranged between the first pole piece and the second pole piece, and at least one of the first pole piece and the second pole piece is the pole piece provided in the above embodiment.

[0126] Specifically, the battery cell 20 refers to the smallest unit constituting the battery. Figure 7, the battery cell 20 includes an end cap 21, a shell 22, an electrode assembly 23 and other functional components. The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The end cover 21 may also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0127] In some embodiments, an insulating member may be provided on the inner side of the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. Exemplarily, the insulating member may be plastic, rubber, etc. The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment may be used to accommodate the electrolyte of the electrode assembly 23 and other components. The housing 22 and the end cap 21 may be independent components, and an opening may be provided on the housing 22, and the internal environment of the battery cell 20 may be formed by covering the opening with the end cap 21 at the opening. Without limitation, the end cap 21 and the housing 22 may be integrated, specifically, the end cap 21 and the housing 22 may form a common connection surface before other components are put into the housing, and when the interior of the housing 22 needs to be encapsulated, the end cap 21 covers the housing 22. The housing 22 may be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 22 may be determined according to the specific shape and size of the electrode assembly 23. The shell 22 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0128] The electrode assembly 23 in this embodiment is a component in the battery cell where an electrochemical reaction occurs. Figure 4The electrode structure shown. One or more electrode assemblies 23 may be included in the shell. The electrode assembly 23 is mainly formed by winding or stacking an anode electrode sheet and a cathode electrode sheet 10, that is, the first electrode sheet and the second electrode sheet mentioned above, and a diaphragm is usually provided between the anode electrode sheet and the cathode electrode sheet 10. The portion of the anode electrode sheet and the cathode electrode sheet 10 having an active material layer constitutes the main body of the electrode assembly 23, and the portion of the anode electrode sheet and the cathode electrode sheet 10 not having an active material layer each constitutes a tab 23a. The anode tab and the cathode tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the anode active material and the cathode active material react with the electrolyte, and the tab 23a connects the electrode terminal to form a current loop.

[0129] Among them, the first pole piece and the second pole piece are the pole pieces described in any of the above embodiments. The expansion coefficient of the active material layer corresponding to the middle position area of ​​the pole piece is greater than the expansion coefficient of the active material layer corresponding to the position on both sides. In this way, when the pole piece is used as a cathode pole piece, lithium ions are embedded in the cathode pole piece during the discharge process, and the reaction rate of the cathode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the cathode pole piece fills the reduction of the middle part of the anode pole piece caused by the deintercalation of the anode lithium ions, thereby reducing the interval between the positive and negative pole pieces. Similarly, when the pole piece is used as an anode pole piece, lithium ions are deintercalated from the cathode pole piece and embedded in the anode pole piece during the charging process, and the reaction rate of the anode pole piece is accelerated. Since the expansion coefficient of the middle part of the pole piece is greater than that of the two sides, the expansion degree of the middle part becomes larger, and the expansion amount of the middle part of the anode pole piece fills the reduction of the middle part of the anode pole piece caused by the deintercalation of the cathode lithium ions, thereby reducing the interval between the positive and negative pole pieces, reducing the risk of lithium deposition of the battery, and improving the cycle performance of the battery cell.

[0130] The embodiment of the present application provides a battery device, including the above-mentioned battery cell. The battery device (Battery Apparatus) mentioned in the embodiment of the present application may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly (Battery Cell Assembly) may include one or more battery cells, and multiple battery cells are connected in series, parallel or mixed through a busbar component.

[0131] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of battery cells; as an example, a battery cell assembly may be a battery module, which is formed by arranging and fixing a plurality of battery cells to form an independent module. As an example, a battery module may be formed by bundling a plurality of battery cells by a cable tie.

[0132] In some embodiments, the battery device may be a battery pack, which includes a case and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the case.

[0133] As an example, the battery cell assembly may be a battery module, and the battery cell assembly may be accommodated in the box by fixing the battery module in the box.

[0134] As an example, the battery cell assembly may also be housed in the case by directly fixing a plurality of battery cells to the case.

[0135] As an example, the box may include a first box and a second box. The first box and the second box are buckled together to form a closed space inside the box to accommodate the battery cell assembly. The closed here means covered or closed, which can be sealed or unsealed. The first box can be a top cover or a bottom plate.

[0136] As an example, the box body may include a top cover, a frame and a bottom plate. The top cover and the bottom plate are respectively connected to the frame, so that a closed space is formed inside the box body to accommodate the battery cell assembly.

[0137] As an example, the box body can be used as a part of the chassis structure of the vehicle. For example, the top cover of the box body can become at least a part of the floor of the vehicle, or the frame of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0138] In some embodiments, the battery device refers to an energy storage device, which includes a box body, at least one side of which is provided with a door. The energy storage device includes an energy storage container, an energy storage cabinet, and the like.

[0139] An embodiment of the present application provides an electrical device, comprising the above-mentioned battery device, wherein the battery device is used to supply power to the electrical device.

[0140] The technical solutions described in the embodiments of the present application are applicable to various electrical devices using battery cells and battery devices, such as mobile phones, portable devices, laptop computers, electric vehicles, electric toys, electric tools, vehicles, ships and spacecraft, for example, spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.

[0141] It should be noted that:

[0142] In the above text, the term "comprises", "includes" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be noted that the scope of the method and device in the embodiment of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0143] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0144] The embodiments of the present application are described above in conjunction with the accompanying drawings, which are only specific implementation modes of the present application. However, the present application is not limited to the above-mentioned specific implementation modes. The above-mentioned specific implementation modes are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A pole piece, characterized in that: include: Current collector and active material layer; The current collector extends along a first direction, the surface of the current collector has a plurality of regions adjacently arranged along a second direction, the second direction is perpendicular to the first direction, and the active material layer is attached to each region; Among them, along the second direction, the expansion coefficient of the active material layer in the first region is greater than the expansion coefficient of the active material layers in the regions on both sides of the first region, and the first region is the middle region of the current collector along the second direction.

2. The pole piece according to claim 1, characterized in that: The active material layer includes a first active material and a second active material, the expansion coefficient of the first active material is smaller than the expansion coefficient of the second active material, and the specific gravity of the first active material in each region of the active material layer is greater than the specific gravity of the second active material; Along the second direction, the content of the second active material in the active material layer in the first region is greater than the content of the second active material in the active material layers in regions on both sides of the first region.

3. The pole piece according to claim 1, characterized in that: The active material layer includes a first active material and a second active material, the expansion coefficient of the first active material is smaller than the expansion coefficient of the second active material, and the specific gravity of the first active material in each region of the active material layer is smaller than the specific gravity of the second active material; Along the second direction, the content of the first active material in the active material layer in the first region is smaller than the content of the first active material in the active material layers in regions on both sides of the first region.

4. The pole piece according to claim 3, characterized in that: The first active material includes lithium iron phosphate, and the second active material includes a ternary material.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The active material layer includes a binder, and along the second direction, a content of the binder in the active material layer in the first region is smaller than a content of the binder in the active material layers in regions on both sides of the first region.

6. The pole piece according to any one of claims 1 to 4, characterized in that: The current collector has a first surface and a second surface that are opposite to each other, the first surface and the second surface each have a plurality of regions that are adjacent to each other along the second direction, and the active material layer is attached to each region.

7. The pole piece according to claim 5, characterized in that: The first area is divided according to historical temperature data, and the historical temperature data includes temperature values ​​of battery cells during charging and discharging; Among them, the first area is the pole piece area corresponding to the position of the maximum temperature value in the historical temperature data, and the areas on both sides of the first area are partitioned to both sides of the first area based on the preset temperature difference as the division gradient of an area.

8. The pole piece according to claim 5, characterized in that: The first area is divided according to historical power-withdrawing capacity data, and the historical power-withdrawing capacity data includes a gram capacity loss value of a battery cell; Among them, the first area is the electrode area corresponding to the position where the gram capacity loss value in the historical withholding capacity data is greater than the preset value, and the areas on both sides of the first area are partitioned to both sides of the first area with the preset gram capacity difference as the division gradient of an area.

9. The pole piece according to claim 5, characterized in that: The plurality of regions include a first region, a second region and a third region. Along the second direction, the second region and the third region are respectively located at two sides of the first region.

10. The pole piece according to claim 9, characterized in that: The surface of the current collector further has a fourth region for forming a pole ear, and the fourth region is adjacent to the second region; The expansion coefficient of the active material layer in the first region is greater than the expansion coefficient of the active material layer in the third region, and the expansion coefficient of the active material layer in the third region is greater than the expansion coefficient of the active material layer in the second region.

11. A coating system, characterized in that: The system comprises: A plurality of coating die heads are arranged in parallel along a second direction, each coating die head is respectively connected to a slurry storage tank, the coating die head is used to coat the slurry in the slurry storage tank on a current collector, the current collector extends along a first direction, the surface of the current collector has a plurality of regions arranged adjacently along the second direction, the second direction is perpendicular to the first direction, the slurry storage tank, the coating die head and the regions on the surface of the current collector correspond one to one; wherein the expansion coefficient of the slurry in the slurry storage tank corresponding to the first region is greater than the expansion coefficient of the slurry in the slurry storage tank corresponding to the regions on both sides of the first region; A conveying device, the conveying device is used to convey the current collector along the first direction; the coating die head is arranged at one end of the conveying device, and is used to coat the slurry on the surface of the current collector; A controller is used to control the conveying device and the coating die to form the pole piece.

12. The coating system according to claim 11, characterized in that: The coating die head comprises a first coating die head, a second coating die head and a third coating die head, the second coating die head, the first coating die head and the third coating die head are sequentially arranged along the second direction, the first coating die head, the second coating die head and the third coating die head are respectively connected to a first slurry storage tank, a second slurry storage tank and a third slurry storage tank; the first coating die head is arranged corresponding to the first area; The expansion coefficient of the slurry in the first slurry storage tank is greater than the expansion coefficient of the slurry in the third slurry storage tank, and the expansion coefficient of the slurry in the third slurry storage tank is greater than the expansion coefficient of the slurry in the second slurry storage tank.

13. A battery cell, characterized in that: The battery cell comprises an electrode assembly, an electrolyte and a shell, wherein the electrode assembly and the electrolyte are contained in a containing space inside the shell; The electrode assembly includes a first pole piece, a second pole piece, and a diaphragm, wherein the diaphragm is disposed between the first pole piece and the second pole piece, and at least one of the first pole piece and the second pole piece is the pole piece described in any one of claim 110.

14. A battery device, characterized in that: Comprising the battery cell as claimed in claim 13.

15. An electrical device, characterized in that: It comprises the battery device as claimed in claim 14, wherein the battery device is used to supply power to the electrical device.

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